Patent Publication Number: US-2021168574-A1

Title: Beamforming and grouping for nr v2x

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of U.S. Provisional Patent Applications No. 62/716,782, filed Aug. 9, 2018, 62/737,643, filed Sep. 27, 2018, 62/753,757, filed Oct. 31, 2018, 62/790,754, filed Jan. 10, 2019, 62/791,055, filed Jan. 11, 2019, which are hereby incorporated by reference in their entirety. 
    
    
     FIELD 
     The present application is directed to methods and systems for beamforming and grouping for new radio (NR) vehicle to anything (V2X). 
     BACKGROUND 
     V2X communications, such as PSCCH, PSSCH and PSDCH, in LTE are omni-directional. However, V2X communications in NR mmW frequency band are beamforming-based. Appropriate design solutions are desired to improve these technologies. 
     In NR V2X, use cases are generally directed to platooning, advanced driving, and enhanced sensors. Namely, these use cases have much higher requirements in terms of latency, data rates and reliability than LTE V2X. Therefore, new synchronization, discovery and beam management procedures and mechanisms are desired to support these new cases. 
     In NR, SSB/PBCH are packed as a single block that always moves together. Each SS/PBCH within a SS burst set (i.e., all the SS blocks within the 5 ms period of the SS burst set transmission) is assigned with a unique number starting from 0 and increasing by 1. This number is reset to 0 in the next SS burst set (i.e., next 5 ms span after SS/PBCH transmission cycle (e.g., 20 ms)). 
     NR SS/PBCH structure will require modification for sidelink synchronization structure due to the following factors. First, PSSS (Primary Sidelink Sync Signal) &amp; SSSS (Secondary Sidelink Sync Signal) need to convey sidelink synchronization ID, synchronization sources and in network coverage or out of network coverage. The number of symbols for PSSS, SSSS, DMRS and PSBCH need redesigning to support better detection performance and timing/frequency offset estimation. Second, NR Sidelink MIB (MIB-SL) may carry different essential system information from LTE sidelink MIB. NR radio interfaces also are significantly different from LTE radio interface. As a result, existing LTE sidelink MIB design and LTE PSBCH design cannot readily be re-used for NR V2X. Solutions for NR sidelink (or V2X) SS/PBCH structure design are needed to solve these problems. 
     In LTE, PSCCH and PSSCH are not beamformed transmitted. In NR, FR2 is support. Since NR PSCCH and PSSCH may be transmitted with beam forming, beam training and pairing for NR PSCCH and PSSCH is required. Higher layer and/or application level discovery in NR V2X is desired. 
     SUMMARY 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to limit the scope of the claimed subject matter. The foregoing needs are met, to a great extent, by the present application describing. 
     One aspect of the present application is directed to a method including a step of providing a sidelink (SL) synchronization signal (SS) burst over a time period, the SL SS burst including a slot including OFDM symbols. The method also includes a step of restricting, in a first OFDM symbol of the slot, transmission of a synchronization signal block (SSB) over resource blocks (RBs). The method further includes a step of transmitting, from a user equipment (UE) via plural symbols after the first symbol, the SSB over the RBs in a new radio (NR) SL SS and physical broadcast channel (PBCH) (NR SL SS/PBCH) to a gNB. 
     Another aspect of the present application is directed to a method for discovering a vehicle group in vehicle to anything (V2X) communication range including a step of transmitting, via a first vehicle, a to be discovered message on NR-PSDCH. The method also includes a step of receiving, from a vehicle in the vehicle group, information of members in the vehicle group. The method further includes a step of evaluating criteria including policy and terms of the vehicle group. The method even further includes a step of sending, based on the evaluation, a request to one of the members to join the vehicle group. The method yet even further includes a step of receiving, from one or more of the members, a decision based on the request to join. 
     There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to facilitate a more robust understanding of the application, reference is now made to the accompanying drawings, in which like elements are referenced with like numerals. These drawings should not be construed to limit the application and are intended only to be illustrative. 
         FIG. 1A  illustrates an exemplary communications system according to an aspect of the application. 
         FIG. 1B  illustrates an exemplary apparatus configured for wireless communication according to an aspect of the application. 
         FIG. 1C  illustrates a system diagram of a radio access network and a core network according to an aspect of the application. 
         FIG. 1D  illustrates a system diagram of a radio access network and a core network according to an aspect of the application. 
         FIG. 1E  illustrates a system diagram of a radio access network and a core network according to an aspect of the application. 
         FIG. 1F  illustrates a block diagram of an exemplary computing system in communication with one or more networks previously shown in  FIGS. 1A, 1C, 1D and 1E  according to an aspect of the application. 
         FIG. 1G  illustrates an exemplary communications system according to an embodiment. 
         FIG. 2  illustrates a side-link CSI-RS for beam training according to an aspect of the application. 
         FIG. 3  illustrates beam training NR-PSSB for indication of NR-PSDCH according to an aspect of the application. 
         FIG. 4  illustrates an exemplary scenario in accordance with an aspect of the application. 
         FIG. 5  illustrates another exemplary scenario in accordance with an aspect of the application. 
         FIG. 6  illustrates yet another exemplary scenario in accordance with an aspect of the application. 
         FIG. 7  illustrates an exemplary NR SL SS/PBCH burst set, burst and block design in accordance with an aspect of the application. 
         FIG. 8A  illustrates an exemplary transmission pattern of SL SS Block for SCS=30 kHz in NR in accordance with an aspect of the application. 
         FIG. 8B  illustrates an exemplary transmission pattern of SL SS Block for SCS=30 kHz in NR and two SL SS Block are punctured in accordance with an aspect of the application. 
         FIG. 9  illustrates a SL SS/PBCH aligned in Uu SS/PBCH synchronization raster and TDM in accordance with an aspect of the application. 
         FIG. 10  illustrates an aperiodic SL SS/PBCH transmission in accordance with an aspect of the application. 
         FIGS. 11A-B  illustrate enhanced SL SS/PBCH blocks in accordance with an aspect of the application. 
         FIG. 12A  illustrates DMRS for PSBCH where DMRS and PSBCG are multiplexing at the same resource in accordance with an aspect of the application. 
         FIG. 12B  illustrates DMRS for PSBCH where DMRS and PSBCH are TDM in accordance with an aspect of the application. 
         FIG. 13  illustrates a proposed sidelink beam training and pairing Step 1 before discovery in accordance with an aspect of the application. 
         FIG. 14A  illustrates a resource selection for common PSCCH (Type M) for beam pairing response before discovery in FDM in accordance with an aspect of the application. 
         FIG. 14B  illustrates a resource selection for common PSCCH (Type M) for beam pairing response before discovery in TDM in accordance with an aspect of the application. 
         FIG. 15  illustrates a proposed sidelink beam training step 2 (response) before discovery in accordance with an aspect of the application. 
         FIG. 16  illustrates a proposed sidelink beam training procedure in accordance with an aspect of the application. 
         FIG. 17A  illustrates a resource mapping for SL SS/PBCH, PSCCH Type 0 and PSSCH for SL RMSI (or PSDCH) in FDM in accordance with an aspect of the application. 
         FIG. 17B  illustrates a resource mapping for SL SS/PBCH, PSCCH Type 0 and PSSCH for SL RMSI (or PSDCH) in TDM in accordance with an aspect of the application. 
         FIG. 18A  illustrates a FDM resource mapping for SL SS/PBCH and PSSCH for SL RMSI (or PSDCH) in accordance with an aspect of the application. 
         FIG. 18B  illustrates a TDM resource mapping for SL SS/PBCH and PSSCH for SL RMSI (or PSDCH) in accordance with an aspect of the application. 
         FIG. 19  illustrates a broadcast burst configured with a transmission periodicity in accordance with an aspect of the application. 
         FIG. 20  illustrates a broadcast burst configured with a transmission periodicity in accordance with an aspect of the application. 
         FIG. 21  illustrates DM-RS symbols setup in front of PSSCH symbols in accordance with an aspect of the application. 
         FIG. 22  illustrates an example of built-in sensors sensing distance between vehicles in accordance with an aspect of the application. 
         FIG. 23  illustrates resources for PSSCH partitioned into two regions in accordance with an aspect of the application. 
         FIG. 24  illustrates a vehicle/UE broadcasting its discovery message in accordance with an aspect of the application. 
         FIG. 25  illustrates two vehicles competing for the same channel resource for discovery response at the slot in accordance with an aspect of the application. 
         FIG. 26  illustrates a LFSR sequence with the Fibonacci representation in accordance with an aspect of the application. 
         FIG. 27  illustrates SL PSS and SL SSS sequence mapping in the frequency domain in accordance with an aspect of the application. 
         FIG. 28  illustrates an exemplary SL SS block design and resource mapping for SL SS BW=20 RB in accordance with as aspect of the application. 
         FIG. 29  illustrates a SL PSS sequence mapping in the frequency domain when SL SS block BW=24 RB in accordance with an aspect of the application. 
         FIG. 30  illustrates an SL SS block design and exemplary mapping for SL SS BW=24 RB in accordance with an aspect of the application. 
         FIG. 31  illustrates a SL PSS sequence mapping in the frequency domain when SL SS block BW=24 RB and SL PSS sequence length=127 in accordance with an aspect of the application. 
         FIG. 32  illustrates an SL PSS sequence mapping in the frequency domain when SL SS block BW=24 RB and SL PSS sequence length=127 in accordance with an aspect of the application. 
         FIG. 33  illustrates a SL SSS sequence mapping in the frequency domain when SL SS block BW=24 RB and SL SSS sequence length=255 in accordance with an aspect of the application. 
         FIGS. 34A-B  illustrate an SL SS block and resource mapping for SL SS BW=24 RB when SL PSS length=127 and SL SSS length=255 in accordance with an aspect of the application. 
         FIGS. 35A-B  illustrate sidelink PSS mapping methods in frequency domain when SL SS Block BW is equal to 11 RBs. 
         FIG. 36  illustrates Sidelink SSB structure with SL PSS at the symbol 1 and 2 and SL SSS at symbol 3 and 4 in a slot. 
         FIG. 37  illustrates sidelink SSB structure with SL PSS at symbol 1 and 2 and SL SSS at symbol 6 and 7 in a slot. 
         FIG. 38  illustrates a sidelink SSB structure with SL PBCH at symbol 5 to 11 in a slot. 
         FIG. 39  illustrates SL SS block periodicity, where the periodicity of SL SS block can be based on each different transmit beam. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS 
     A detailed description of the illustrative embodiment will be discussed in reference to various figures, embodiments and aspects herein. Although this description provides detailed examples of possible implementations, it should be understood that the details are intended to be examples and thus do not limit the scope of the application. 
     Reference in this specification to “one embodiment,” “an embodiment,” “one or more embodiments,” or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Moreover, the term “embodiment” in various places in the specification is not necessarily referring to the same embodiment. That is, various features are described which may be exhibited by some embodiments and not by the other. Reference in this specification to “one aspect,” “an aspect,” or “one or more aspects,” or the like encompasses one or more embodiments listed thereunder. 
     Generally, the application describes methods and systems for beamforming and grouping for NR V2X. 
     Definitions/Acronyms 
     Provided below are definitions for terms and phrases commonly used in this application in Table 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Acronym 
                 Term or Phrase 
               
               
                   
                   
               
             
            
               
                   
                 A/N 
                 Ack/Nack 
               
               
                   
                 BRS 
                 Beam Reference Signal 
               
               
                   
                 CE 
                 Control Element 
               
               
                   
                 DL 
                 Downlink 
               
               
                   
                 DRX 
                 Discontinuous Reception 
               
               
                   
                 eMBB 
                 Enhanced Mobile Broadband 
               
               
                   
                 ETWS 
                 Earthquake and Tsunami Warning System 
               
               
                   
                 HARQ 
                 Hybrid Automatic Repeat Request 
               
               
                   
                 KPI 
                 Key Performance Indicators 
               
               
                   
                 LTE 
                 Long Term Evolution 
               
               
                   
                 MAC 
                 Medium Access Control 
               
               
                   
                 MIB 
                 Master Information Block 
               
               
                   
                 MTC 
                 Machine-Type Communications 
               
               
                   
                 mMTC 
                 Massive Machine Type Communication 
               
               
                   
                 NACK 
                 Non-Acknowledgment 
               
               
                   
                 NR 
                 New Radio 
               
               
                   
                 NR-PDSCH 
                 NR Physical Sidelink Discovery Channel 
               
               
                   
                 NR-PSSCH 
                 NR Physical Sidelink Shared Channel 
               
               
                   
                 PBCH 
                 Physical Broadcast Channel 
               
               
                   
                 PDCCH 
                 Physical Downlink Control Channel 
               
               
                   
                 PDSCH 
                 Physical Downlink Shared Data Channel 
               
               
                   
                 PSCCH 
                 Physical Sidelink Control Channel 
               
               
                   
                 PSDCH 
                 Physical Sidelink Discovery Channel 
               
               
                   
                 PRACH 
                 Physical Random Access Channel 
               
               
                   
                 PSDCH 
                 Physical Sidelink Discovery Channel 
               
               
                   
                 PRB 
                 Physical Resource Block 
               
               
                   
                 RAN 
                 Radio Access Network 
               
               
                   
                 RNTI 
                 Radio Network Temporary Identifier 
               
               
                   
                 RAT 
                 Radio Access Technology 
               
               
                   
                 RRC 
                 Radio Resource Control 
               
               
                   
                 SI 
                 System Information 
               
               
                   
                 SIB 
                 System Information Block 
               
               
                   
                 TDD 
                 Time Divisional Duplex 
               
               
                   
                 UE 
                 User Equipment 
               
               
                   
                 V2X 
                 Vehicle To Everything 
               
               
                   
                 UL 
                 Uplink 
               
               
                   
                 URLLC 
                 Ultra-Reliable and Low 
               
               
                   
                   
                 Latency Communications 
               
               
                   
                   
               
            
           
         
       
     
     General Architecture 
     The 3rd Generation Partnership Project (3GPP) develops technical standards for cellular telecommunications network technologies, including radio access, the core transport network, and service capabilities—including work on codecs, security, and quality of service. Recent radio access technology (RAT) standards include WCDMA (commonly referred as 3G), LTE (commonly referred as 4G), LTE-Advanced standards, and New Radio (NR), which is also referred to as “5G”. 3GPP NR standards development is expected to continue and include the definition of next generation radio access technology (new RAT), which is expected to include the provision of new flexible radio access below 7 GHz, and the provision of new ultra-mobile broadband radio access above 7 GHz. The flexible radio access is expected to consist of a new, non-backwards compatible radio access in new spectrum below 7 GHz, and it is expected to include different operating modes that may be multiplexed together in the same spectrum to address a broad set of 3GPP NR use cases with diverging requirements. The ultra-mobile broadband is expected to include cmWave and mmWave spectrum that will provide the opportunity for ultra-mobile broadband access for, e.g., indoor applications and hotspots. In particular, the ultra-mobile broadband is expected to share a common design framework with the flexible radio access below 7 GHz, with cmWave and mmWave specific design optimizations. 
     3GPP has identified a variety of use cases that NR is expected to support, resulting in a wide variety of user experience requirements for data rate, latency, and mobility. The use cases include the following general categories: enhanced mobile broadband (eMBB) ultra-reliable low-latency Communication (URLLC), massive machine type communications (mMTC), network operation (e.g., network slicing, routing, migration and interworking, energy savings), and enhanced vehicle-to-everything (eV2X) communications, which may include any of Vehicle-to-Vehicle Communication (V2V), Vehicle-to-Infrastructure Communication (V2I), Vehicle-to-Network Communication (V2N), Vehicle-to-Pedestrian Communication (V2P), and vehicle communications with other entities. Specific service and applications in these categories include, e.g., monitoring and sensor networks, device remote controlling, bi-directional remote controlling, personal cloud computing, video streaming, wireless cloud-based office, first responder connectivity, automotive ecall, disaster alerts, real-time gaming, multi-person video calls, autonomous driving, augmented reality, tactile internet, virtual reality, home automation, robotics, and aerial drones to name a few. All of these use cases and others are contemplated herein. 
       FIG. 1A  illustrates an example communications system  100  in which the systems, methods, and apparatuses described and claimed herein may be used. The communications system  100  may include wireless transmit/receive units (WTRUs)  102   a,    102   b,    102   c,    102   d,    102   e,    102   f,  and/or  102   g,  which generally or collectively may be referred to as WTRU  102  or WTRUs  102 . The communications system  100  may include, a radio access network (RAN)  103 / 104 / 105 / 103   b / 104   b / 105   b,  a core network  106 / 107 / 109 , a public switched telephone network (PSTN)  108 , the Internet  110 , other networks  112 , and Network Services  113 .  113 . Network Services  113  may include, for example, a V2X server, V2X functions, a ProSe server, ProSe functions, IoT services, video streaming, and/or edge computing, etc. 
     It will be appreciated that the concepts disclosed herein may be used with any number of WTRUs, base stations, networks, and/or network elements. Each of the WTRUs  102  may be any type of apparatus or device configured to operate and/or communicate in a wireless environment. In the example of  FIG. 1A , each of the WTRUs  102  is depicted in  FIGS. 1A-1E  as a hand-held wireless communications apparatus. It is understood that with the wide variety of use cases contemplated for wireless communications, each WTRU may comprise or be included in any type of apparatus or device configured to transmit and/or receive wireless signals, including, by way of example only, user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a tablet, a netbook, a notebook computer, a personal computer, a wireless sensor, consumer electronics, a wearable device such as a smart watch or smart clothing, a medical or eHealth device, a robot, industrial equipment, a drone, a vehicle such as a car, bus or truck, a train, or an airplane, and the like. 
     The communications system  100  may also include a base station  114   a  and a base station  114   b.  In the example of  FIG. 1A , each base stations  114   a  and  114   b  is depicted as a single element. In practice, the base stations  114   a  and  114   b  may include any number of interconnected base stations and/or network elements. Base stations  114   a  may be any type of device configured to wirelessly interface with at least one of the WTRUs  102   a,    102   b,  and  102   c  to facilitate access to one or more communication networks, such as the core network  106 / 107 / 109 , the Internet  110 , Network Services  113 , and/or the other networks  112 . Similarly, base station  114   b  may be any type of device configured to wiredly and/or wirelessly interface with at least one of the Remote Radio Heads (RRHs)  118   a,    118   b,  Transmission and Reception Points (TRPs)  119   a,    119   b,  and/or Roadside Units (RSUs)  120   a  and  120   b  to facilitate access to one or more communication networks, such as the core network  106 / 107 / 109 , the Internet  110 , other networks  112 , and/or Network Services  113 . RRHs  118   a,    118   b  may be any type of device configured to wirelessly interface with at least one of the WTRUs  102 , e.g., WTRU  102   c,  to facilitate access to one or more communication networks, such as the core network  106 / 107 / 109 , the Internet  110 , Network Services  113 , and/or other networks  112 . 
     TRPs  119   a,    119   b  may be any type of device configured to wirelessly interface with at least one of the WTRU  102   d,  to facilitate access to one or more communication networks, such as the core network  106 / 107 / 109 , the Internet  110 , Network Services  113 , and/or other networks  112 . RSUs  120   a  and  120   b  may be any type of device configured to wirelessly interface with at least one of the WTRU  102   e  or  102   f,  to facilitate access to one or more communication networks, such as the core network  106 / 107 / 109 , the Internet  110 , other networks  112 , and/or Network Services  113 . By way of example, the base stations  114   a,    114   b  may be a Base Transceiver Station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a Next Generation Node-B (gNode B), a satellite, a site controller, an access point (AP), a wireless router, and the like. 
     The base station  114   a  may be part of the RAN  103 / 104 / 105 , which may also include other base stations and/or network elements (not shown), such as a Base Station Controller (BSC), a Radio Network Controller (RNC), relay nodes, etc. Similarly, the base station  114   b  may be part of the RAN  103   b / 104   b / 105   b,  which may also include other base stations and/or network elements (not shown), such as a BSC, a RNC, relay nodes, etc. The base station  114   a  may be configured to transmit and/or receive wireless signals within a particular geographic region, which may be referred to as a cell (not shown). Similarly, the base station  114   b  may be configured to transmit and/or receive wired and/or wireless signals within a particular geographic region, which may be referred to as a cell (not shown). The cell may further be divided into cell sectors. For example, the cell associated with the base station  114   a  may be divided into three sectors. Thus, for example, the base station  114   a  may include three transceivers, e.g., one for each sector of the cell. The base station  114   a  may employ Multiple-Input Multiple Output (MIMO) technology and, therefore, may utilize multiple transceivers for each sector of the cell, for instance. 
     The base station  114   a  may communicate with one or more of the WTRUs  102   a,    102   b,    102   c,  and  102   g  over an air interface  115 / 116 / 117 , which may be any suitable wireless communication link (e.g., Radio Frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible light, cmWave, mmWave, etc.). The air interface  115 / 116 / 117  may be established using any suitable Radio Access Technology (RAT). 
     The base station  114   b  may communicate with one or more of the RRHs  118   a  and  118   b,  TRPs  119   a  and  119   b,  and/or RSUs  120   a  and  120   b,  over a wired or air interface  115   b / 116   b / 117   b,  which may be any suitable wired (e.g., cable, optical fiber, etc.) or wireless communication link (e.g., RF, microwave, IR, UV, visible light, cmWave, mmWave, etc.). The air interface  115   b / 116   b / 117   b  may be established using any suitable RAT. 
     The RRHs  118   a,    118   b,  TRPs  119   a,    119   b  and/or RSUs  120   a,    120   b,  may communicate with one or more of the WTRUs  102   c,    102   d,    102   e,    102   f  over an air interface  115   c / 116   c / 117   c,  which may be any suitable wireless communication link (e.g., RF, microwave, IR, ultraviolet UV, visible light, cmWave, mmWave, etc.) The air interface  115   c / 116   c / 117   c  may be established using any suitable RAT. 
     The WTRUs  102  may communicate with one another over a direct air interface  115   d / 116   d / 117   d,  such as Sidelink communication which may be any suitable wireless communication link (e.g., RF, microwave, IR, ultraviolet UV, visible light, cmWave, mmWave, etc.) The air interface  115   d / 116   d / 117   d  may be established using any suitable RAT. 
     The communications system  100  may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station  114   a  in the RAN  103 / 104 / 105  and the WTRUs  102   a,    102   b,    102   c,  or RRHs  118   a,    118   b,  TRPs  119   a,    119   b  and/or RSUs  120   a  and  120   b  in the RAN  103   b / 104   b / 105   b  and the WTRUs  102   c,    102   d,    102   e,  and  102   f,  may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface  115 / 116 / 117  and/or  115   c / 116   c / 117   c  respectively using Wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink Packet Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA). 
     The base station  114   a  in the RAN  103 / 104 / 105  and the WTRUs  102   a,    102   b,    102   c,  and  102   g,  or RRHs  118   a  and  118   b,  TRPs  119   a  and  119   b,  and/or RSUs  120   a  and  120   b  in the RAN  103   b / 104   b / 105   b  and the WTRUs  102   c,    102   d,  may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface  115 / 116 / 117  or  115   c / 116   c / 117   c  respectively using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A), for example. The air interface  115 / 116 / 117  or  115   c / 116   c / 117   c  may implement 3GPPPP NR technology. The LTE and LTE-A technology may include LTE D 2 D and/or V2X technologies and interfaces (such as Sidelink communications, etc.) Similarly, the 3GPP NR technology may include NR V2X technologies and interfaces (such as Sidelink communications, etc.) 
     The base station  114   a  in the RAN  103 / 104 / 105  and the WTRUs  102   a,    102   b,    102   c,  and  102   g  or RRHs  118   a  and  118   b,  TRPs  119   a  and  119   b,  and/or RSUs  120   a  and  120   b  in the RAN  103   b / 104   b / 105   b  and the WTRUs  102   c,    102   d,    102   e,  and  102   f  may implement radio technologies such as IEEE 802.16 (e.g., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like. 
     The base station  114   c  in  FIG. 1A  may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a train, an aerial, a satellite, a manufactory, a campus, and the like. The base station  114   c  and the WTRUs  102 , e.g., WTRU  102   e,  may implement a radio technology such as IEEE 802.11 to establish a Wireless Local Area Network (WLAN). Similarly, the base station  114   c  and the WTRUs  102 , e.g., WTRU  102   d,  may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). The base station  114   c  and the WTRUs  102 , e.g., WRTU  102   e,  may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, NR, etc.) to establish a picocell or femtocell. As shown in  FIG. 1A , the base station  114   c  may have a direct connection to the Internet  110 . Thus, the base station  114   c  may not be required to access the Internet  110  via the core network  106 / 107 / 109 . 
     The RAN  103 / 104 / 105  and/or RAN  103   b / 104   b / 105   b  may be in communication with the core network  106 / 107 / 109 , which may be any type of network configured to provide voice, data, messaging, authorization and authentication, applications, and/or Voice Over Internet Protocol (VoIP) services to one or more of the WTRUs  102 . For example, the core network  106 / 107 / 109  may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, packet data network connectivity, Ethernet connectivity, video distribution, etc., and/or perform high-level security functions, such as user authentication. 
     Although not shown in  FIG. 1A , it will be appreciated that the RAN  103 / 104 / 105  and/or RAN  103   b / 104   b / 105   b  and/or the core network  106 / 107 / 109  may be in direct or indirect communication with other RANs that employ the same RAT as the RAN  103 / 104 / 105  and/or RAN  103   b / 104   b / 105   b  or a different RAT. For example, in addition to being connected to the RAN  103 / 104 / 105  and/or RAN  103   b / 104   b / 105   b,  which may be utilizing an E-UTRA radio technology, the core network  106 / 107 / 109  may also be in communication with another RAN (not shown) employing a GSM or NR radio technology. 
     The core network  106 / 107 / 109  may also serve as a gateway for the WTRUs  102  to access the PSTN  108 , the Internet  110 , and/or other networks  112 . The PSTN  108  may include circuit-switched telephone networks that provide Plain Old Telephone Service (POTS). The Internet  110  may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and the internet protocol (IP) in the TCP/IP internet protocol suite. The other networks  112  may include wired or wireless communications networks owned and/or operated by other service providers. For example, the networks  112  may include any type of packet data network (e.g., an IEEE 802.3 Ethernet network) or another core network connected to one or more RANs, which may employ the same RAT as the RAN  103 / 104 / 105  and/or RAN  103   b / 104   b / 105   b  or a different RAT. 
     Some or all of the WTRUs  102   a,    102   b,    102   c,    102   d,    102   e,  and  102   f  in the communications system  100  may include multi-mode capabilities, e.g., the WTRUs  102   a,    102   b,    102   c,    102   d,    102   e,  and  102   f  may include multiple transceivers for communicating with different wireless networks over different wireless links. For example, the WTRU  102   g  shown in  FIG. 1A  may be configured to communicate with the base station  114   a,  which may employ a cellular-based radio technology, and with the base station  114   c,  which may employ an IEEE 802 radio technology. 
     Although not shown in  FIG. 1A , it will be appreciated that a User Equipment may make a wired connection to a gateway. The gateway maybe a Residential Gateway (RG). The RG may provide connectivity to a Core Network  106 / 107 / 109 . It will be appreciated that many of the ideas contained herein may equally apply to UEs that are WTRUs and UEs that use a wired connection to connect to a network. For example, the ideas that apply to the wireless interfaces  115 ,  116 ,  117  and  115   c / 116   c / 117   c  may equally apply to a wired connection. 
       FIG. 1B  is a system diagram of an example RAN  103  and core network  106 . As noted above, the RAN  103  may employ a UTRA radio technology to communicate with the WTRUs  102   a,    102   b,  and  102   c  over the air interface  115 . The RAN  103  may also be in communication with the core network  106 . As shown in  FIG. 1B , the RAN  103  may include Node-Bs  140   a,    140   b,  and  140   c,  which may each include one or more transceivers for communicating with the WTRUs  102   a,    102   b,  and  102   c  over the air interface  115 . The Node-Bs  140   a,    140   b,  and  140   c  may each be associated with a particular cell (not shown) within the RAN  103 . The RAN  103  may also include RNCs  142   a,    142   b.  It will be appreciated that the RAN  103  may include any number of Node-Bs and Radio Network Controllers (RNCs.) 
     As shown in  FIG. 1B , the Node-Bs  140   a,    140   b  may be in communication with the RNC  142   a.  Additionally, the Node-B  140   c  may be in communication with the RNC  142   b.  The Node-Bs  140   a,    140   b,  and  140   c  may communicate with the respective RNCs  142   a  and  142   b  via an Iub interface. The RNCs  142   a  and  142   b  may be in communication with one another via an Iur interface. Each of the RNCs  142   a  and  142   b  may be configured to control the respective Node-Bs  140   a,    140   b,  and  140   c  to which it is connected. In addition, each of the RNCs  142   a  and  142   b  may be configured to carry out or support other functionality, such as outer loop power control, load control, admission control, packet scheduling, handover control, macro-diversity, security functions, data encryption, and the like. 
     The core network  106  shown in  FIG. 1B  may include a media gateway (MGW)  144 , a Mobile Switching Center (MSC)  146 , a Serving GPRS Support Node (SGSN)  148 , and/or a Gateway GPRS Support Node (GGSN)  150 . While each of the foregoing elements are depicted as part of the core network  106 , it will be appreciated that any one of these elements may be owned and/or operated by an entity other than the core network operator. 
     The RNC  142   a  in the RAN  103  may be connected to the MSC  146  in the core network  106  via an IuCS interface. The MSC  146  may be connected to the MGW  144 . The MSC  146  and the MGW  144  may provide the WTRUs  102   a,    102   b,  and  102   c  with access to circuit-switched networks, such as the PSTN  108 , to facilitate communications between the WTRUs  102   a,    102   b,  and  102   c,  and traditional land-line communications devices. 
     The RNC  142   a  in the RAN  103  may also be connected to the SGSN  148  in the core network  106  via an IuPS interface. The SGSN  148  may be connected to the GGSN  150 . The SGSN  148  and the GGSN  150  may provide the WTRUs  102   a,    102   b,  and  102   c  with access to packet-switched networks, such as the Internet  110 , to facilitate communications between and the WTRUs  102   a,    102   b,  and  102   c,  and IP-enabled devices. 
     The core network  106  may also be connected to the other networks  112 , which may include other wired or wireless networks that are owned and/or operated by other service providers. 
       FIG. 1C  is a system diagram of an example RAN  104  and core network  107 . As noted above, the RAN  104  may employ an E-UTRA radio technology to communicate with the WTRUs  102   a,    102   b,  and  102   c  over the air interface  116 . The RAN  104  may also be in communication with the core network  107 . 
     The RAN  104  may include eNode-Bs  160   a,    160   b,  and  160   c,  though it will be appreciated that the RAN  104  may include any number of eNode-Bs. The eNode-Bs  160   a,    160   b,  and  160   c  may each include one or more transceivers for communicating with the WTRUs  102   a,    102   b,  and  102   c  over the air interface  116 . For example, the eNode-Bs  160   a,    160   b,  and  160   c  may implement MIMO technology. Thus, the eNode-B  160   a,  for example, may use multiple antennas to transmit wireless signals to, and receive wireless signals from, the WTRU  102   a.    
     Each of the eNode-Bs  160   a,    160   b,  and  160   c  may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the uplink and/or downlink, and the like. As shown in  FIG. 1C , the eNode-Bs  160   a,    160   b,  and  160   c  may communicate with one another over an X2 interface. 
     The core network  107  shown in  FIG. 1C  may include a Mobility Management Gateway (MME)  162 , a serving gateway  164 , and a Packet Data Network (PDN) gateway  166 . While each of the foregoing elements are depicted as part of the core network  107 , it will be appreciated that any one of these elements may be owned and/or operated by an entity other than the core network operator. 
     The MME  162  may be connected to each of the eNode-Bs  160   a,    160   b,  and  160   c  in the RAN  104  via an S1 interface and may serve as a control node. For example, the MME  162  may be responsible for authenticating users of the WTRUs  102   a,    102   b,  and  102   c,  bearer activation/deactivation, selecting a particular serving gateway during an initial attach of the WTRUs  102   a,    102   b,  and  102   c,  and the like. The MME  162  may also provide a control plane function for switching between the RAN  104  and other RANs (not shown) that employ other radio technologies, such as GSM or WCDMA. 
     The serving gateway  164  may be connected to each of the eNode-Bs  160   a,    160   b,  and  160   c  in the RAN  104  via the S1 interface. The serving gateway  164  may generally route and forward user data packets to/from the WTRUs  102   a,    102   b,  and  102   c.  The serving gateway  164  may also perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when downlink data is available for the WTRUs  102   a,    102   b,  and  102   c,  managing and storing contexts of the WTRUs  102   a,    102   b,  and  102   c,  and the like. 
     The serving gateway  164  may also be connected to the PDN gateway  166 , which may provide the WTRUs  102   a,    102   b,  and  102   c  with access to packet-switched networks, such as the Internet  110 , to facilitate communications between the WTRUs  102   a,    102   b,    102   c,  and IP-enabled devices. 
     The core network  107  may facilitate communications with other networks. For example, the core network  107  may provide the WTRUs  102   a,    102   b,  and  102   c  with access to circuit-switched networks, such as the PSTN  108 , to facilitate communications between the WTRUs  102   a,    102   b,  and  102   c  and traditional land-line communications devices. For example, the core network  107  may include, or may communicate with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the core network  107  and the PSTN  108 . In addition, the core network  107  may provide the WTRUs  102   a,    102   b,  and  102   c  with access to the networks  112 , which may include other wired or wireless networks that are owned and/or operated by other service providers. 
       FIG. 1D  is a system diagram of an example RAN  105  and core network  109 . The RAN  105  may employ an NR radio technology to communicate with the WTRUs  102   a  and  102   b  over the air interface  117 . The RAN  105  may also be in communication with the core network  109 . A Non-3GPP Interworking Function (N3IWF)  199  may employ a non-3GPP radio technology to communicate with the WTRU  102   c  over the air interface  198 . The N3IWF  199  may also be in communication with the core network  109 . 
     The RAN  105  may include gNode-Bs  180   a  and  180   b.  It will be appreciated that the RAN  105  may include any number of gNode-Bs. The gNode-Bs  180   a  and  180   b  may each include one or more transceivers for communicating with the WTRUs  102   a  and  102   b  over the air interface  117 . When integrated access and backhaul connection are used, the same air interface may be used between the WTRUs and gNode-Bs, which may be the core network  109  via one or multiple gNBs. The gNode-Bs  180   a  and  180   b  may implement MIMO, MU-MIMO, and/or digital beamforming technology. Thus, the gNode-B  180   a,  for example, may use multiple antennas to transmit wireless signals to, and receive wireless signals from, the WTRU  102   a.  It should be appreciated that the RAN  105  may employ of other types of base stations such as an eNode-B. It will also be appreciated the RAN  105  may employ more than one type of base station. For example, the RAN may employ eNode-Bs and gNode-Bs. 
     The N3IWF  199  may include a non-3GPP Access Point  180   c.  It will be appreciated that the N3IWF  199  may include any number of non-3GPP Access Points. The non-3GPP Access Point  180   c  may include one or more transceivers for communicating with the WTRUs  102   c  over the air interface  198 . The non-3GPP Access Point  180   c  may use the 802.11 protocol to communicate with the WTRU  102   c  over the air interface  198 . 
     Each of the gNode-Bs  180   a  and  180   b  may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the uplink and/or downlink, and the like. As shown in  FIG. 1D , the gNode-Bs  180   a  and  180   b  may communicate with one another over an Xn interface, for example. 
     The core network  109  shown in  FIG. 1D  may be a 5G core network (5GC). The core network  109  may offer numerous communication services to customers who are interconnected by the radio access network. The core network  109  comprises a number of entities that perform the functionality of the core network. As used herein, the term “core network entity” or “network function” refers to any entity that performs one or more functionalities of a core network. It is understood that such core network entities may be logical entities that are implemented in the form of computer-executable instructions (software) stored in a memory of, and executing on a processor of, an apparatus configured for wireless and/or network communications or a computer system, such as system  90  illustrated in  FIG. x1G . 
     In the example of  FIG. 1D , the 5G Core Network  109  may include an access and mobility management function (AMF)  172 , a Session Management Function (SMF)  174 , User Plane Functions (UPFs)  176   a  and  176   b,  a User Data Management Function (UDM)  197 , an Authentication Server Function (AUSF)  190 , a Network Exposure Function (NEF)  196 , a Policy Control Function (PCF)  184 , a Non-3GPP Interworking Function (N3IWF)  199 , a User Data Repository (UDR)  178 . While each of the foregoing elements are depicted as part of the 5G core network  109 , it will be appreciated that any one of these elements may be owned and/or operated by an entity other than the core network operator. It will also be appreciated that a 5G core network may not consist of all of these elements, may consist of additional elements, and may consist of multiple instances of each of these elements.  FIG. 1D  shows that network functions directly connect to one another, however, it should be appreciated that they may communicate via routing agents such as a diameter routing agent or message buses. 
     In the example of  FIG. 1D , connectivity between network functions is achieved via a set of interfaces, or reference points. It will be appreciated that network functions could be modeled, described, or implemented as a set of services that are invoked, or called, by other network functions or services. Invocation of a Network Function service may be achieved via a direct connection between network functions, an exchange of messaging on a message bus, calling a software function, etc. 
     The AMF  172  may be connected to the RAN  105  via an N2 interface and may serve as a control node. For example, the AMF  172  may be responsible for registration management, connection management, reachability management, access authentication, access authorization. The AMF may be responsible forwarding user plane tunnel configuration information to the RAN  105  via the N2 interface. The AMF  172  may receive the user plane tunnel configuration information from the SMF via an N11 interface. The AMF  172  may generally route and forward NAS packets to/from the WTRUs  102   a,    102   b,  and  102   c  via an N1 interface. The N1 interface is not shown in  FIG. 1D . 
     The SMF  174  may be connected to the AMF  172  via an N11 interface. Similarly the SMF may be connected to the PCF  184  via an N7 interface, and to the UPFs  176   a  and  176   b  via an N4 interface. The SMF  174  may serve as a control node. For example, the SMF  174  may be responsible for Session Management, IP address allocation for the WTRUs  102   a,    102   b,  and  102   c,  management and configuration of traffic steering rules in the UPF  176   a  and UPF  176   b,  and generation of downlink data notifications to the AMF  172 . 
     The UPF  176   a  and UPF 176   b  may provide the WTRUs  102   a,    102   b,  and  102   c  with access to a Packet Data Network (PDN), such as the Internet  110 , to facilitate communications between the WTRUs  102   a,    102   b,  and  102   c  and other devices. The UPF  176   a  and UPF  176   b  may also provide the WTRUs  102   a,    102   b,  and  102   c  with access to other types of packet data networks. For example, Other Networks  112  may be Ethernet Networks or any type of network that exchanges packets of data. The UPF  176   a  and UPF  176   b  may receive traffic steering rules from the SMF  174  via the N4 interface. The UPF  176   a  and UPF  176   b  may provide access to a packet data network by connecting a packet data network with an N6 interface or by connecting to each other and to other UPFs via an N9 interface. In addition to providing access to packet data networks, the UPF  176  may be responsible packet routing and forwarding, policy rule enforcement, quality of service handling for user plane traffic, downlink packet buffering. 
     The AMF  172  may also be connected to the N3IWF  199 , for example, via an N2 interface. The N3IWF facilitates a connection between the WTRU  102   c  and the 5G core network  170 , for example, via radio interface technologies that are not defined by 3GPP. The AMF may interact with the N3IWF  199  in the same, or similar, manner that it interacts with the RAN  105 . 
     The PCF  184  may be connected to the SMF  174  via an N7 interface, connected to the AMF  172  via an N15 interface, and to an Application Function (AF)  188  via an N5 interface. The N15 and N5 interfaces are not shown in  FIG. 1D . The PCF  184  may provide policy rules to control plane nodes such as the AMF  172  and SMF  174 , allowing the control plane nodes to enforce these rules. The PCF  184 , may send policies to the AMF  172  for the WTRUs  102   a,    102   b,  and  102   c  so that the AMF may deliver the policies to the WTRUs  102   a,    102   b,  and  102   c  via an N1 interface. Policies may then be enforced, or applied, at the WTRUs  102   a,    102   b,  and  102   c.    
     The UDR  178  may act as a repository for authentication credentials and subscription information. The UDR may connect to network functions, so that network function can add to, read from, and modify the data that is in the repository. For example, the UDR  178  may connect to the PCF  184  via an N36 interface. Similarly, the UDR  178  may connect to the NEF  196  via an N37 interface, and the UDR  178  may connect to the UDM  197  via an N35 interface. 
     The UDM  197  may serve as an interface between the UDR  178  and other network functions. The UDM  197  may authorize network functions to access of the UDR  178 . For example, the UDM  197  may connect to the AMF  172  via an N8 interface, the UDM  197  may connect to the SMF  174  via an N10 interface. Similarly, the UDM  197  may connect to the AUSF  190  via an N13 interface. The UDR  178  and UDM  197  may be tightly integrated. 
     The AUSF  190  performs authentication related operations and connects to the UDM  178  via an N13 interface and to the AMF  172  via an N12 interface. 
     The NEF  196  exposes capabilities and services in the 5G core network  109  to Application Functions (AF)  188 . Exposure may occur on the N33 API interface. The NEF may connect to an AF  188  via an N33 interface and it may connect to other network functions in order to expose the capabilities and services of the 5G core network  109 . 
     Application Functions  188  may interact with network functions in the 5G Core Network  109 . Interaction between the Application Functions  188  and network functions may be via a direct interface or may occur via the NEF  196 . The Application Functions  188  may be considered part of the 5G Core Network  109  or may be external to the 5G Core Network  109  and deployed by enterprises that have a business relationship with the mobile network operator. 
     Network Slicing is a mechanism that could be used by mobile network operators to support one or more ‘virtual’ core networks behind the operator&#39;s air interface. This involves ‘slicing’ the core network into one or more virtual networks to support different RANs or different service types running across a single RAN. Network slicing enables the operator to create networks customized to provide optimized solutions for different market scenarios which demands diverse requirements, e.g. in the areas of functionality, performance and isolation. 
     3GPP has designed the 5G core network to support Network Slicing. Network Slicing is a good tool that network operators can use to support the diverse set of 5G use cases (e.g., massive IoT, critical communications, V2X, and enhanced mobile broadband) which demand very diverse and sometimes extreme requirements. Without the use of network slicing techniques, it is likely that the network architecture would not be flexible and scalable enough to efficiently support a wider range of use cases need when each use case has its own specific set of performance, scalability, and availability requirements. Furthermore, introduction of new network services should be made more efficient. 
     Referring again to  FIG. 1D , in a network slicing scenario, a WTRU  102   a,    102   b,  or  102   c  may connect to an AMF  172 , via an N1 interface. The AMF may be logically part of one or more slices. The AMF may coordinate the connection or communication of WTRU  102   a,    102   b,  or  102   c  with one or more UPF  176   a  and  176   b,  SMF  174 , and other network functions. Each of the UPFs  176   a  and  176   b,  SMF  174 , and other network functions may be part of the same slice or different slices. When they are part of different slices, they may be isolated from each other in the sense that they may utilize different computing resources, security credentials, etc. 
     The core network  109  may facilitate communications with other networks. For example, the core network  109  may include, or may communicate with, an IP gateway, such as an IP Multimedia Subsystem (IMS) server, that serves as an interface between the 5G core network  109  and a PSTN  108 . For example, the core network  109  may include, or communicate with a short message service (SMS) service center that facilities communication via the short message service. For example, the 5G core network  109  may facilitate the exchange of non-IP data packets between the WTRUs  102   a,    102   b,  and  102   c  and servers or applications functions  188 . In addition, the core network  170  may provide the WTRUs  102   a,    102   b,  and  102   c  with access to the networks  112 , which may include other wired or wireless networks that are owned and/or operated by other service providers. 
     The core network entities described herein and illustrated in  FIGS. 1A, 1C, 1D, and 1E  are identified by the names given to those entities in certain existing 3GPP specifications, but it is understood that in the future those entities and functionalities may be identified by other names and certain entities or functions may be combined in future specifications published by 3GPP, including future 3GPP NR specifications. Thus, the particular network entities and functionalities described and illustrated in  FIGS. 1A, 1B, 1C, 1D, and 1E  are provided by way of example only, and it is understood that the subject matter disclosed and claimed herein may be embodied or implemented in any similar communication system, whether presently defined or defined in the future. 
       FIG. 1E  illustrates an example communications system  111  in which the systems, methods, apparatuses described herein may be used. Communications system  111  may include Wireless Transmit/Receive Units (WTRUs) A, B, C, D, E, F, a base station gNB  121 , a V2X server  124 , and Road Side Units (RSUs)  123   a  and  123   b.  In practice, the concepts presented herein may be applied to any number of WTRUs, base station gNBs, V2X networks, and/or other network elements. One or several or all WTRUs A, B, C, D, E, and F may be out of range of the access network coverage  131 . WTRUs A, B, and C form a V2X group, among which WTRU A is the group lead and WTRUs B and C are group members. 
     WTRUs A, B, C, D, E, and F may communicate with each other over a Uu interface  129  via the gNB  121  if they are within the access network coverage  131 . In the example of  FIG. 1E , WTRUs B and F are shown within access network coverage  131 . WTRUs A, B, C, D, E, and F may communicate with each other directly via a Sidelink interface (e.g., PC5 or NR PC 5 ) such as interface  125   a,    125   b,  or  128 , whether they are under the access network coverage  131  or out of the access network coverage  131 . For instance, in the example of  FIG. 1E , WRTU D, which is outside of the access network coverage  131 , communicates with WTRU F, which is inside the coverage  131 . 
     WTRUs A, B, C, D, E, and F may communicate with RSU  123   a  or  123   b  via a Vehicle-to-Network (V2N)  133  or Sidelink interface  125   b.  WTRUs A, B, C, D, E, and F may communicate to a V2X Server  124  via a Vehicle-to-Infrastructure (V2I) interface  127 . WTRUs A, B, C, D, E, and F may communicate to another UE via a Vehicle-to-Person (V2P) interface  128 . 
       FIG. 1F  is a block diagram of an example apparatus or device WTRU  102  that may be configured for wireless communications and operations in accordance with the systems, methods, and apparatuses described herein, such as a WTRU  102  of  FIG. 1A, 1B, 1C, 1D , or  1 E. As shown in  FIG. 1F , the example WTRU  102  may include a processor  118 , a transceiver  120 , a transmit/receive element  122 , a speaker/microphone  124 , a keypad  126 , a display/touchpad/indicators  128 , non-removable memory  130 , removable memory  132 , a power source  134 , a global positioning system (GPS) chipset  136 , and other peripherals  138 . It will be appreciated that the WTRU  102  may include any sub-combination of the foregoing elements. Also, the base stations  114   a  and  114   b,  and/or the nodes that base stations  114   a  and  114   b  may represent, such as but not limited to transceiver station (BTS), a Node-B, a site controller, an access point (AP), a home node-B, an evolved home node-B (eNodeB), a home evolved node-B (HeNB), a home evolved node-B gateway, a next generation node-B (gNode-B), and proxy nodes, among others, may include some or all of the elements depicted in  FIG. 1F  and described herein. 
     The processor  118  may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Array (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor  118  may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the WTRU  102  to operate in a wireless environment. The processor  118  may be coupled to the transceiver  120 , which may be coupled to the transmit/receive element  122 . While  FIG. 1F  depicts the processor  118  and the transceiver  120  as separate components, it will be appreciated that the processor  118  and the transceiver  120  may be integrated together in an electronic package or chip. 
     The transmit/receive element  122  of a UE may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station  114   a  of  FIG. 1A ) over the air interface  115 / 116 / 117  or another UE over the air interface  115   d / 116   d / 117   d.  For example, the transmit/receive element  122  may be an antenna configured to transmit and/or receive RF signals. The transmit/receive element  122  may be an emitter/detector configured to transmit and/or receive IR, UV, or visible light signals, for example. The transmit/receive element  122  may be configured to transmit and receive both RF and light signals. It will be appreciated that the transmit/receive element  122  may be configured to transmit and/or receive any combination of wireless or wired signals. 
     In addition, although the transmit/receive element  122  is depicted in  FIG. 1F  as a single element, the WTRU  102  may include any number of transmit/receive elements  122 . More specifically, the WTRU  102  may employ MIMO technology. Thus, the WTRU  102  may include two or more transmit/receive elements  122  (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface  115 / 116 / 117 . 
     The transceiver  120  may be configured to modulate the signals that are to be transmitted by the transmit/receive element  122  and to demodulate the signals that are received by the transmit/receive element  122 . As noted above, the WTRU  102  may have multi-mode capabilities. Thus, the transceiver  120  may include multiple transceivers for enabling the WTRU  102  to communicate via multiple RATs, for example NR and IEEE 802.11 or NR and E-UTRA, or to communicate with the same RAT via multiple beams to different RRHs, TRPs, RSUs, or nodes. 
     The processor  118  of the WTRU  102  may be coupled to, and may receive user input data from, the speaker/microphone  124 , the keypad  126 , and/or the display/touchpad/indicators  128  (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit. The processor  118  may also output user data to the speaker/microphone  124 , the keypad  126 , and/or the display/touchpad/indicators  128 . In addition, the processor  118  may access information from, and store data in, any type of suitable memory, such as the non-removable memory  130  and/or the removable memory  132 . The non-removable memory  130  may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory  132  may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. The processor  118  may access information from, and store data in, memory that is not physically located on the WTRU  102 , such as on a server that is hosted in the cloud or in an edge computing platform or in a home computer (not shown). 
     The processor  118  may receive power from the power source  134 , and may be configured to distribute and/or control the power to the other components in the WTRU  102 . The power source  134  may be any suitable device for powering the WTRU  102 . For example, the power source  134  may include one or more dry cell batteries, solar cells, fuel cells, and the like. 
     The processor  118  may also be coupled to the GPS chipset  136 , which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU  102 . In addition to, or in lieu of, the information from the GPS chipset  136 , the WTRU  102  may receive location information over the air interface  115 / 116 / 117  from a base station (e.g., base stations  114   a,    114   b ) and/or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU  102  may acquire location information by way of any suitable location-determination method. 
     The processor  118  may further be coupled to other peripherals  138 , which may include one or more software and/or hardware modules that provide additional features, functionality, and/or wired or wireless connectivity. For example, the peripherals  138  may include various sensors such as an accelerometer, biometrics (e.g., finger print) sensors, an e-compass, a satellite transceiver, a digital camera (for photographs or video), a universal serial bus (USB) port or other interconnect interfaces, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, and the like. 
     The WTRU  102  may be included in other apparatuses or devices, such as a sensor, consumer electronics, a wearable device such as a smart watch or smart clothing, a medical or eHealth device, a robot, industrial equipment, a drone, a vehicle such as a car, truck, train, or an airplane. The WTRU  102  may connect to other components, modules, or systems of such apparatuses or devices via one or more interconnect interfaces, such as an interconnect interface that may comprise one of the peripherals  138 . 
       FIG. 1G  is a block diagram of an exemplary computing system  90  in which one or more apparatuses of the communications networks illustrated in  FIGS. 1A, 1C, 1D and 1E  may be embodied, such as certain nodes or functional entities in the RAN  103 / 104 / 105 , Core Network  106 / 107 / 109 , PSTN  108 , Internet  110 , Other Networks  112 , or Network Services  113 . Computing system  90  may comprise a computer or server and may be controlled primarily by computer readable instructions, which may be in the form of software, wherever, or by whatever means such software is stored or accessed. Such computer readable instructions may be executed within a processor  91 , to cause computing system  90  to do work. The processor  91  may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Array (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor  91  may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the computing system  90  to operate in a communications network. Coprocessor  81  is an optional processor, distinct from main processor  91 , that may perform additional functions or assist processor  91 . Processor  91  and/or coprocessor  81  may receive, generate, and process data related to the methods and apparatuses disclosed herein. 
     In operation, processor  91  fetches, decodes, and executes instructions, and transfers information to and from other resources via the computing system&#39;s main data-transfer path, system bus  80 . Such a system bus connects the components in computing system  90  and defines the medium for data exchange. System bus  80  typically includes data lines for sending data, address lines for sending addresses, and control lines for sending interrupts and for operating the system bus. An example of such a system bus  80  is the PCI (Peripheral Component Interconnect) bus. 
     Memories coupled to system bus  80  include random access memory (RAM)  82  and read only memory (ROM)  93 . Such memories include circuitry that allows information to be stored and retrieved. ROMs  93  generally contain stored data that cannot easily be modified. Data stored in RAM  82  may be read or changed by processor  91  or other hardware devices. Access to RAM  82  and/or ROM  93  may be controlled by memory controller  92 . Memory controller  92  may provide an address translation function that translates virtual addresses into physical addresses as instructions are executed. Memory controller  92  may also provide a memory protection function that isolates processes within the system and isolates system processes from user processes. Thus, a program running in a first mode may access only memory mapped by its own process virtual address space; it cannot access memory within another process&#39;s virtual address space unless memory sharing between the processes has been set up. 
     In addition, computing system  90  may contain peripherals controller  83  responsible for communicating instructions from processor  91  to peripherals, such as printer  94 , keyboard  84 , mouse  95 , and disk drive  85 . 
     Display  86 , which is controlled by display controller  96 , is used to display visual output generated by computing system  90 . Such visual output may include text, graphics, animated graphics, and video. The visual output may be provided in the form of a graphical user interface (GUI). Display  86  may be implemented with a CRT-based video display, an LCD-based flat-panel display, gas plasma-based flat-panel display, or a touch-panel. Display controller  96  includes electronic components required to generate a video signal that is sent to display  86 . 
     Further, computing system  90  may contain communication circuitry, such as for example a wireless or wired network adapter  97 , that may be used to connect computing system  90  to an external communications network or devices, such as the RAN  103 / 104 / 105 , Core Network  106 / 107 / 109 , PSTN  108 , Internet  110 , WTRUs  102 , or Other Networks  112  of  FIGS. 1A, 1B, 1C, 1D, and 1E , to enable the computing system  90  to communicate with other nodes or functional entities of those networks. The communication circuitry, alone or in combination with the processor  91 , may be used to perform the transmitting and receiving steps of certain apparatuses, nodes, or functional entities described herein. 
     It is understood that any or all of the apparatuses, systems, methods and processes described herein may be embodied in the form of computer executable instructions (e.g., program code) stored on a computer-readable storage medium which instructions, when executed by a processor, such as processors  118  or  91 , cause the processor to perform and/or implement the systems, methods and processes described herein. Specifically, any of the steps, operations, or functions described herein may be implemented in the form of such computer executable instructions, executing on the processor of an apparatus or computing system configured for wireless and/or wired network communications. Computer readable storage media includes volatile and nonvolatile, removable and non-removable media implemented in any non-transitory (e.g., tangible or physical) method or technology for storage of information, but such computer readable storage media do not include signals. Computer readable storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other tangible or physical medium which may be used to store the desired information and which may be accessed by a computing system. 
     New Radio Requirements 
     3GPP TR 38.913 defines scenarios and requirements for New Radio (NR) technologies. The Key Performance Indicators (KPIs) for eMBB, URLLC and mMTC devices are summarized in Table 2 below. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Device 
                 KPI 
                 Description 
                 Requirement 
               
               
                   
               
             
            
               
                 eMBB 
                 Peak  
                 Peak data rate is the highest theoretical data rate 
                 20 Gbps for 
               
               
                   
                 data rate 
                 which is the received data bits assuming error-free 
                 downlink and 
               
               
                   
                   
                 conditions assignable to a single mobile station, 
                 10 Gbps for 
               
               
                   
                   
                 when all assignable radio resources for the 
                 uplink 
               
               
                   
                   
                 corresponding link direction are utilized (i.e., 
                   
               
               
                   
                   
                 excluding radio resources that are used for physical 
                   
               
               
                   
                   
                 layer synchronization, reference signals or pilots, 
                   
               
               
                   
                   
                 guard bands and guard times). 
                   
               
               
                   
                 Mobility 
                 Mobility interruption time means the shortest time 
                 0 ms for intra- 
               
               
                   
                 interruption 
                 duration supported by the system during which a user 
                 system 
               
               
                   
                 time 
                 terminal cannot exchange user plane packets with 
                 mobility 
               
               
                   
                   
                 any base station during transitions. 
                   
               
               
                   
                 Data Plane 
                 For eMBB value, the evaluation needs to consider all 
                 4 ms for UL, 
               
               
                   
                 Latency 
                 typical delays associated with the transfer of the data 
                 and 4 ms for 
               
               
                   
                   
                 packets in an efficient way (e.g. applicable 
                 DL 
               
               
                   
                   
                 procedural delay when resources are not pre- 
                   
               
               
                   
                   
                 allocated, averaged HARQ retransmission delay, 
                   
               
               
                   
                   
                 impacts of network architecture). 
                   
               
               
                 URLLC 
                 Control 
                 Control plane latency refers to the time to move from 
                 10 ms 
               
               
                   
                 Plane 
                 a battery efficient state (e.g., IDLE) to start of 
                   
               
               
                   
                 Latency 
                 continuous data transfer (e.g., ACTIVE). 
                   
               
               
                   
                 Data Plane 
                 For URLLC the target for user plane latency for UL 
                 0.5 ms 
               
               
                   
                 Latency 
                 and DL. Furthermore, if possible, the latency should 
                   
               
               
                   
                   
                 also be low enough to support the use of the next 
                   
               
               
                   
                   
                 generation access technologies as a wireless transport 
                   
               
               
                   
                   
                 technology that can be used within the next generation 
                   
               
               
                   
                   
                 access architecture. 
                   
               
               
                   
                 Reliability 
                 Reliability can be evaluated by the success 
                 1-10-5 
               
               
                   
                   
                 probability of transmitting X bytes (1) within 1 ms, 
                 within 1 ms 
               
               
                   
                   
                 which is the time it takes to deliver a small data 
                   
               
               
                   
                   
                 packet from the radio protocol layer 2/3 SDU ingress 
                   
               
               
                   
                   
                 point to the radio protocol layer 2/3 SDU point of the 
                   
               
               
                   
                   
                 radio interface, at a certain channel quality (e.g., 
                   
               
               
                   
                   
                 coverage-edge). 
                   
               
               
                   
                   
                 NOTE1: Specific value for X is FFS. 
                   
               
               
                 mMTC 
                 Coverage 
                 “Maximum coupling loss” (MCL) in uplink and 
                 164 dB 
               
               
                   
                   
                 downlink between device and Base Station site 
                   
               
               
                   
                   
                 (antenna connector(s)) for a data rate of [X bps], 
                   
               
               
                   
                   
                 where the data rate is observed at the egress/ingress 
                   
               
               
                   
                   
                 point of the radio protocol stack in uplink and 
                   
               
               
                   
                   
                 downlink. 
                   
               
               
                   
                 UE Battery 
                 User Equipment (UE) battery life can be evaluated 
                 15 years 
               
               
                   
                 Life 
                 by the battery life of the UE without recharge. For 
                   
               
               
                   
                   
                 mMTC, UE battery life in extreme coverage shall be 
                   
               
               
                   
                   
                 based on the activity of mobile originated data 
                   
               
               
                   
                   
                 transfer consisting of [200 bytes] Uplink (UL) per 
                   
               
               
                   
                   
                 day followed by [20 bytes] Downlink (DL) from 
                   
               
               
                   
                   
                 Maximum Coupling Loss (MCL) of [tbd] dB, 
                   
               
               
                   
                   
                 assuming a stored energy capacity of [5Wh]. 
                   
               
               
                   
                 Connection 
                 Connection density refers to total number of devices 
                 106 
               
               
                   
                 Density 
                 fulfilling specific Quality of Service (QoS) per unit 
                 devices/km2 
               
               
                   
                   
                 area (per km2). QoS definition should take into 
                   
               
               
                   
                   
                 account the amount of data or access request 
                   
               
               
                   
                   
                 generated within a time t_gen that can be sent or 
                   
               
               
                   
                   
                 received within a given time, t_sendrx, with x% 
                   
               
               
                   
                   
                 probability. 
               
               
                   
               
            
           
         
       
     
     LTE V2X 
     Vehicular communication services, represented by V2X services, can include the following: V2V, V2I, V2N and V2P. V2X services are provided by the PC5 interface and/or Uu interface. Support of V2X services via PC5 interface is provided by V2X sidelink. communication whereby UEs can communicate with each other directly over the PC5 interface. This communication mode is supported when the UE is served by E-UTRAN and when the UE is outside of E-UTRA coverage. Only the UEs authorized to be used for V2X services can perform V2X sidelink communication. 
     LTE-Uu can be unicast and/or MBMS. These two operation modes are used by a UE independently for transmission and reception, e.g. a UE can use MBMS for reception without using LTE-Uu for transmission. A UE may also receive V2X messages via LTE-Uu unicast downlink. 
     V2X in 5G NR 
     SA1 has identified 25 use cases for advanced V2X services with the consideration of desirable new applications in automotive industry. The 25 use cases for advanced V2X services are categorized into four use case groups. These include vehicle platooning, extended sensors, advanced driving, and remote driving. 
     Vehicle platooning enables the vehicles to dynamically form a platoon travelling together. All vehicles in the platoon obtain information from the leading vehicle to manage the platoon. This information allows vehicles to drive closer than normally performed in a coordinated and efficient manner, all going to the same direction, and travelling together. 
     Extended sensors enable the exchange of raw or processed data gathered through local sensors or live video images among vehicles, road site units, devices of pedestrian and V2X application servers. Vehicles can increase their perception of their environment beyond what their own sensors can detect. They also have a broader and holistic view of the local situation. High data rate is one of its key characteristics. 
     Advanced driving enables semi-automated or fully automated driving. Each vehicle and/or RSU shares its own perception data obtained from its local sensors with vehicles in proximity and that allows vehicles to synchronize and coordinate their trajectories or maneuvers. Each vehicle also shares its driving intention with vehicles in proximity. 
     Remote driving enables a remote driver or a V2X application to operate a remote vehicle for those passengers who cannot drive by themselves or remote vehicles located in dangerous environments. In situations where variation is limited and routes are predictable, such as public transportation, driving based on cloud computing may be employed. In these situations, high reliability and low latency are the main requirements. 
     In Rel-14 LTE V2X, a basic set of requirements for V2X service in TR 22.885 has been supported and considered sufficient for basic road safety service. Vehicles (i.e., UEs supporting V2X applications) can exchange their own status information through sidelink, such as position, speed and heading, with other nearby vehicles, infrastructure nodes and/or pedestrians. An ongoing work item for 3GPP V2X phase 2 in Rel-15 introduces a number of new features in sidelink, including: carrier aggregation, high order modulation, latency reduction, and feasibility study on both transmission diversity and short TTI in sidelink. All of these enhanced features in 3GPP V2X phase 2 are predominantly based on LTE and requires co-existence with Rel- 14  UE in same resource pool. 
     Synchronization and Sidelink Configuration Acquisition 
     According to an aspect of the application, there are three possible cases for NR V2X synchronization and sidelink configuration acquisition. Each will be discussed below. 
     Case 1: Network based synchronization and acquisition: gNB and RSU will transmit NR SSB and other system information (OSI) essential for V2X sidelink synchronization and discovery. This may include, for example, the synchronization configuration used for transmission/reception of SLSS on the given frequency. Examples of essential V2X sidelink synchronization and discovery parameters can be provided in OSI. 
     Case 2: UE relay base synchronization and acquisition: perform synchronization and provide essential system information of sidelink for out of coverage vehicle UEs. Some UEs will function as a synchronization source in V2X communication scenarios by transmitting a synchronization signal burst and NR-PSBCH (NR physical sidelink broadcast channel). The synchronization signal burst can be similar to NR-SSB, e.g., the synchronization source UE&#39;s ID or group ID or group lead ID is carried on the synchronization signal, as well as the time index of the SSBs of the UE&#39;s synchronization sweeping bursts. NR-PSBCH will carry most essential system information about V2X sidelink configuration. This may include, for example, the default V2X discovery resource and initial side link resource configuration and/or a point allocating a NR-PSSCH on sidelink which carries remaining detail information on numerology, sidelink resource configurations, etc. 
     Compared with NR PBCH, this NR-PSBCH for sidelink may have more content. This makes the structure of NR-PSBCH take more RBs in frequency and more symbols in time, e.g. wider bandwidth in frequency and more than 2 symbols in time, FDMed and TDMed with the NR-PSSS, and NR-SSSS within the NR sidelink synchronization signal block (NR-SSSB). Such a UE can either be a UE synchronized to a gNB or RSU (called as in-network-coverage UE), a V2X group lead (for example, the lead of a platooning group), or a UE that belongs to a V2X group and carries the synchronization signal burst and NR-PSBCH of the group lead node. 
     The synchronization signal burst and NR-PSBCH will be transmitted in beamforming manner swept across (all) different beams. When an out of coverage vehicle UE detects synchronization signal burst and NR-PSBCH transmitted by another vehicle UE, it acquires synchronization and essential system information of V2X sidelink channels and signals configuration. 
     Case 3: Ad hoc synchronization and acquisition: for the vehicle UEs of interest in a proximity, if all of them are out of network coverage and no V2X group is formed yet, then ad hoc synchronization and acquisition will be performed. Among vehicles of interest in a proximity, at least one vehicle UE will broadcast synchronization signal burst, which can be similar to NR-SSB, e.g., the synchronization source UE&#39;s ID or group ID is carried on the synchronization signal, as well as the time index of synchronization signal&#39;s block of the UE&#39;s synchronization sweeping bursts. When an out-of-coverage vehicle UE detects synchronization signal burst transmitted by such a UE, it acquires synchronization with that UE. Such a UE may also broadcast NR-PSBCH containing the most essential system information about V2X sidelink configuration, e.g., the default V2X discovery resource and initial side link resource configuration and/or a point allocating a NR-PSSCH on sidelink, which carries remaining detail information on numerology, sidelink resource configurations, etc. 
     Compared with NR PBCH, this NR-PSBCH for sidelink may have more content which may make the structure of NR-PSBCH take more RBs in frequency and more symbols in time, e.g. wider bandwidth in frequency and more than 2 symbols in time, FDMed and TDMed with the NR-PSSS and NR-SSSS within the NR sidelink synchronization signal block (NR-SSSB). When an out-of-coverage vehicle UE detects NR-PSBCH transmitted by such a UE, it acquires essential system information of V2X sidelink channels and signals configuration. If NR-PSBCH is not transmitted by such a UE, then those out of coverage vehicle UEs can use a default configuration of essential system information needed to receive V2X sidelink channels and signals. The synchronization signal burst and NR-PSBCH will be transmitted in beamforming manner swept across (all) different beams. 
     Beamforming for NR V2X 
     According to another aspect of the application, beamforming before discovery for NR V2X will be similar to beam forming at initial access of NR Release-15. In each of the synchronization and acquisition cases, after the UE detected the best NR-SSB on a beam or NR-PSSB (physical side-link SS block), it already found the best TX beam of source node. 
     In each of the synchronization and acquisition cases, the UE will also acquire the configuration of resource pools on the sidelink and the information to complete beam link pairing with the synchronization node, and use the information to complete beam link pairing with the synchronization node. 
     Upon higher layer signaling (for example, triggered by RADAR sensing results or a new UE join platooning message), the vehicle UE will start beamforming training process with one or several UEs. The higher layer signaling may provide a range of spatial directions or a selected subset of beams of other UEs to perform BF training. This will greatly reduce the beamforming overhead. During beamforming training procedures, beam-width selection can be decided based on speed (for example, the relative speed between two V2X nodes). The V2X node can configure side-link CSI-RS (SL-CSI-RS) for beam training. The UE may be configured with multiple SL-CSI-RS for beam management. The SL-CSI-RS resource may be periodic (i.e., configured at the slot level), semi-persistent (also at the slot level, but it can be activated or deactivated with messages from the V2X node) and aperiodic (the transmission is triggered by the V2X node signaling). An exemplary SL-CSI-RS configuration for beam training is shown in  FIG. 2 . 
     NR V2X Discovery 
     According to yet another aspect of the application, NR V2X discovery should be performed after beamforming training. NR-PSDCH is the physical sidelink discovery channel for NR V2X, which is exchanged between the pair of V2X nodes performing discovery. It should be transmitted in beamforming manner on the beam link pair established between the two V2X nodes. The best detected beam of NR-PSSB indicates the beam of NR-PDSCH. In this example as shown in  FIG. 3 , Block number  2  is the preferred beam for the UE and NR-PSSB block  2  indicates the beam of NR-PDSCH, e.g., the index of NR-PSSB block  2  point to the sidelink resource(s) for NR-PDSCH. 
     Procedures in Vehicle Grouping Scenarios 
     According to yet even another aspect of the application, procedures are described for vehicle grouping scenarios. In an embodiment of this aspect, Cooperative Short Distance Grouping (CoSdG) refers to the scenario where the distance between vehicles such as trucks is extremely small. This creates a desirable form of legal tailgating. 
     In an exemplary embodiment as shown in  FIG. 4 , several vehicles are V2X enabled, and they are traveling in close proximity and in V2X communication range. They will discover each other and form a group. Such a group can be a CoSdG or platooning group. Based on this architecture, the following procedures for group forming and maintenance are envisaged as follows: 
     Step 1: The vehicles in close proximity will discover each other. The discovery includes proximity discovery, beam link pairing (beamforming training), and higher layer V2X protocol discovery. Vehicles can use beamforming training methods as described above. The higher layer V2X protocol discovery channel carry information which can be similar to the LTE V2X discovery. Such a discovery can be periodic or event-triggered. For example, upon receiving a higher layer signaling or MAC-CE signaling, the vehicle can start the procedures of discovery. The higher layer signaling or MAC-CE signaling can be triggered by UE&#39;s RADAR or other sensors detect a vehicle in proximity. 
     Step 2: After beam discovery and beam link pair is established, those vehicles will form a group via the peer device discovery and association conducted by the higher layer or application with the decoded NR-PSDCH passed from physical layer. 
     Step 2a: A vehicle that wants to initiate the procedures to form a new V2X group will send a V2X grouping request to one or several other vehicles. A new signaling called V2X grouping request can be either a higher layer signaling or a MAC-CE signaling. It can be transmitted on NR-PSSCH (NR Physical Sidelink Shared Channel). It contains at least the following information: 
     (i) The type of V2X group the vehicle is capable or willing to establish: Platooning, SSMS (sensor and state map sharing), CoSdG and etc. One or several groups types can be signaled at the same time. 
     (ii) Key information of the vehicle: for example, vehicle size, speed, location, planned travel route/destination and etc. 
     Step 2b: A vehicle that received a V2X grouping request from the initiating vehicle will respond with a V2X grouping response. The new signaling V2X grouping response is envisaged to be the response to the V2X grouping request. It can be either a higher layer signaling or a MAC-CE signaling. It can be transmitted on NR-PSSCH (NR Physical Sidelink Shared Channel). It contains the following information (but not limited to them): 
     The type of V2X group the responding vehicle agrees to establish with the initiating vehicle includes: Platooning, SSMS (sensor and state map sharing), CoSdG, etc. One or several group types can be signaled at the same time. At least one codeword in the group type signaling can indicate “no group can be formed”. 
     Key information of the vehicle: for example, vehicle size, speed, location, planned travel route/destination and etc. 
     Step 2c: Subsequent V2X group establishment signaling are exchanged according to higher layer grouping protocol. If a group is established successfully, then a V2X grouping complete message is broadcast within the group. The V2X grouping complete message is a confirmation that the group is established. Carry group information may include the group ID, group size, speed, inter-vehicle distance policies, individual group member&#39;s index and position within the group, planned trajectory, etc. The communication link between any two members of the group can be either direct beam link pair or relay via other vehicles or even RSU. Each group member can be uniquely identified by its group ID and group member index. 
     Step 3: Group members (vehicles) will continuously exchange their on-board information, sensor data, speed, direction, maneuvers and etc. They utilize information in beam tracking after initial beam link pairing. This also includes the relay links. 
     According to another exemplary embodiment as illustrated in  FIG. 5 , procedures for joining the group are described. Here, several vehicles are V2X enabled, and they are traveling in close proximity and in V2X communication range. They have already formed a group. Such a group can be a CoSdG or platooning group. Another vehicle is traveling close to the group. The following procedures are provided for this embodiment: 
     Step 1: After several vehicles have formed a group, each group member will broadcast their group related information to non-group members. The group information may include the group ID, group size, speed, inter-vehicle distance policies, their positions in the group, planned trajectory, etc. Alternatively, group related information will be carried in group member&#39;s discovery channel/signal, such as NR-PSDCH. 
     Step 2: A vehicle that is traveling close to the group will perform discovery with a group member, which can be initiated by either this new vehicle or existing group member. The vehicle UE that initiates the peer device discovery will send out “To Be Discovered” message on NR-PSDCH. Then the other one will respond accordingly. The discovery includes proximity beam discovery, beam link pairing (beamforming training), and higher layer V2X protocol peer device or service discovery. Vehicles can use beamforming training methods as described above. The higher layer V2X protocol discovery channel carry information similar to the LTE V2X discovery. Such a discovery can be periodic or event-triggered. For example, upon receiving a higher layer signaling or MAC-CE signaling, the vehicle can start the procedures of discovery. The higher layer signaling or MAC-CE signaling can be triggered by UE&#39;s RADAR or other sensors detect a vehicle in proximity. 
     Step 3: The new vehicle receives group-related information from the group members (can be either broadcast message or NR-PSDCH during or after discovery). Then, this vehicle will evaluate whether this group policy and terms are acceptable to join. The criteria to join or not may include (but not limited to): group size, speed, inter-vehicle distance policies, planned ftrajectory, etc. If the vehicle decides to join the group, it will proceed to Step 4. 
     Step 4: In order to join the group, this vehicle sends a V2X group join request message to one or several members of the group. This new signaling called V2X group join request can be defined as either a higher layer signaling or a MAC-CE signaling. It contains the following information: (i) Indication of the request to join; (ii) Group ID; (iii) The intended position within the group when it joins; and (iv) Key information of the vehicle itself: for example, vehicle size, speed, location, planned travel route/destination and etc. 
     Step 5: Depending on the group type (platooning, CoSdG or others), the vehicle that received a V2X group join request may need to forward/relay the received V2X group join request to other group member(s) to make decision. For example, in the platooning case, the platooning lead vehicle may make the decision to allow the new vehicle to join or not. After group members decide to allow the new vehicle to join or not, the vehicle that received a V2X group join request will respond with a V2X group join response. 
     The new signaling V2X group join response is defined as the response to the V2X group join request. It can either be a higher layer signaling or a MAC-CE signaling. It can be transmitted on NR-PSSCH (NR Physical Sidelink Shared Channel). It contains the following information: (i) Indication of approve or rejection the request to join; (ii) Group ID; (iii) The allowed position within the group when it joins; and (iv) Other key information of the group. 
     Step 6: If the requesting vehicle receives a V2X group join response that approves its request to join, it will proceed to join the group. Then, it will send a V2X group join complete message to the group. Otherwise (the requesting vehicle receives a V2X group join response that rejects its request to join), it will not join the group. 
     Step 7: Upon receiving V2X group join complete message, other group members will update their group information. They may need to update their beam link pair and relay route among group members due to the group topology change caused by the newly joining member. 
     Step 8: Group members (vehicles) will continuously exchange their on-board information, sensor data, speed, direction, maneuvers, etc. They utilize this information in beam tracking after initial beam link pairing, which also includes the relay links. 
     A further embodiment of this aspect describes procedures for leaving the group. An exemplary illustration of this embodiment is depicted in  FIG. 6 . Here, several vehicles are V2X enabled, and they are traveling in close proximity and in V2X communication range. They already formed a group. Such a group can be a CoSdG or platooning group. Subsequently, one vehicle within the group leaves the group. The following procedures are described for leaving the group: 
     Step 1: A group member within a group decides to leave the group. It will send a V2X group leave message to all members of the group in a unicast or broadcast manner. The vehicle leaving the group may not have direct communication links to all group members. This message may be relayed to some group members. This new signaling, called V2X group leave, can be defined as either a higher layer signaling or a MAC-CE signaling. It contains the following information: (i) The vehicle&#39;s decision to leave the group; (ii) Group ID; (iii) The vehicle&#39;s position within the group; and (iv) Key information of the vehicle itself: for example, planned travel route/destination, etc. This V2X group leave message can be transmitted on NR-PSBCH, NR-PSSCH, NR-PSDCH. 
     Step 2: Upon receiving V2X group leave message, other group members will update their group information. They may need to update their beam link pair and relay route among group members due to the group topology change caused by the member that leaves the group. 
     Step 3: Group members (vehicles) will continuously exchange their on-board information, sensor data, speed, direction, maneuvers, etc. They utilize this information in beam tracking after initial beam link pairing, which also includes the relay links. 
     A further embodiment of this aspect describes sidelink synchronization channel design for NR V2X. NR sidelink synchronization signal (SS) and PBCH channel, i.e., NR SL SSB/PBCH is composed of four elements: The primary sidelink synchronization signal (NR PSSS), the secondary sidelink synchronization Signal (NR SSSS), the demodulation reference signals (DMRS), and the physical sidelink broadcast channel (PSBCH). The NR PSSS and NR SSSS are used for time and frequency reference; together they encode the sidelink synchronization signal identifier (SL-SSID), which identities the synchronization reference (SyncRef). There is a subset of SL-SSIDs reserved for identifying SyncRefs in-coverage (configured by the network) where in-coverage may further be differentiated into in-LTE-coverage, in-NR-coverage, in-GNSS-coverage, in both LTE and NR coverage, and another subset reserved for out of coverage use, where out of coverage may further be differentiated into out of LTE coverage, out of GNSS coverage or out of NR coverage. The NR PSBCH carries the sidelink master information block, i.e., MasterinformationBlock-SL (MIB-SL), which contains the basic system information such as system subframe number, SL SS/PBCH block index, SL subcarrier spacing (SCS), etc. The DMRSs may be used as a reference for channel estimation, demodulation of the PSBCH, and measurement of Sidelink Reference Signal Received Power (S-RSRP) in the receiving UE. Note: NR PSSS and SSSS may be used for S-RSRP calculation. In addition, DMRS sequence initialization (i.e., different gold sequences) may be used for the indication of in network coverage or out of network coverage. 
     A NR SL SS/PBCH burst set encompasses one or multiple SS burst(s) with transmission periodic (e.g. 80 ms, i.e., N=80 subframe, in  FIG. 7 ), and confined in 5 ms (5 subframes) window. This window time can be broadcast in SL OSI. A SL SS burst may be composite by one or multiple SL SS Block(s). A SL SS Block may include one symbol PSSS, one symbol SSSS and two symbols PSPBCH (including DMRS). NR SL SS burst set periodicity can be defined to vary with different numerology. For FR1, SCS={30 KHz, 60 KHz}, The default NR SL SS/PBCH burst set periodicity can be set as 80 ms or higher (e.g., 160 ms). For FR2, SCS={60 KHz, 120 KHz, 240 KHz} The default NR SL SS/PBCH burst set periodicity can be set as 20 ms or higher (60 ms). 
     SL SS/PBCH Transmission Condition 
     According to yet another aspect of this application, the following conditions for SL SS/PBCH transmission are met in one embodiment to trigger SL SS/PSBCH transmission: 
     Condition 1: UE transmit SL SS/PBCH under gNB instruction, the time-and-frequency resource for SL SS/PBCH transmission can be scheduled by gNB, 
     Condition 2: When UE-measured RSRP/S-RSRP is below certain threshold, 
     Condition 3: If the UE selects GNSS as synchronization reference, the UE may transmit SL SS/PSBCH at a pre-defined time and frequency resource 
     Condition 4: UE can decide when to transmit SL SS/PBCH at a pre-defined time and frequency resource. If UE is out of coverage, before sending SL SS/PBCH, it has to perform channel sensing on pre-defined SL SS/PBCH resource (the sensing time is depend on a random value in terms of ms), if channel is clean after sensing time is completed then it can start to transmit the SL SS/PBCH, otherwise, it indicates other UE has transmitted SL SS/SSPBCH. 
     In an alternative embodiment, the UE can stop transmitting NR SL SS/PBCH burst set when the following conditions are met: 
     Condition 1: gNB instruct UE to stop transmission of NR SL SS/PBCH via Uu DCI, 
     Condition 2: UE detect the synchronization priority has changed, 
     Condition 3: When a timer (SLSyncTxTimer) is expired. The SLSyncTxTimer value can be either pre-configured or from higher signaling such as SL OSI. 
     Condition 4: UE decides to stop SL SS/PBCH transmission when maximum number of transmission (window) is reached. 
     SL SS/PBCH burst, burst set structure 
     In yet another aspect of the application, NR sidelink synchronization signal/channel may use two symbols PSSS, two symbol SSSS and five symbols PSPBCH (includes DMRS) to enhance one-shot detection performance and to further enhance the timing and frequency offset estimation and one-shot PSPBCH demodulation performance. 
     For a half frame (5 ms) with NR SL SS/PBCH blocks, the first symbol indexes for candidate NR SL SS/PBCH blocks are determined according to the subcarrier spacing of NR SL SS/PBCH blocks as following example, where index 0 corresponds to the first symbol of the first slot in a half-frame. For example, 30 kHz subcarrier spacing: the first symbols of the candidate SL SS/PBCH blocks have indexes {1, 7}+14n. The first OFDM symbol is reserved for not used for SS/PBCH transmission. The value of n is varied with different frequency band. For example, for carrier frequencies smaller than or equal to 3 GHz, n=0, 1. For carrier frequencies larger than 3 GHz and smaller than or equal to 6 GHz, n=0, 1, 2, 3.  FIG. 8A  describes a transmission pattern of SL SS/PBCH for SCS=30 kHz for frequency band is 3 GHz. The first symbol in a SL SS slot reserves for AGC stable time. SyncRef UE (UE transmit SL SS/PBCH) can decide which SL SS/PBCK block can be disabled, i.e., some of SL SS/PBCH blocks may not transmit in an SL SS burst. For example, in mode 1, if a SyncRef UE is in gNB coverage then gNB can instruct the SyncRef UE to transmit SL SS/PBCH. In this case, gNB may know other proximity UEs&#39; position, hence, gNB can instruct a SyncRef UE to transmit certain of SL SS/PBCH beams instead of transmitting whole SL SS/PBCH blocks (beams). In mode 2, a SyncRef UE may be assisted with a sensor&#39;s (e.g., radar sensor) side information such as GPS position of proximity vehicles/UEs, speed, moving direction, etc. or gNB/gNB type RSU provide side information to estimate the directions of proximity UEs before it determines which SL SS/PBCH block need to be transmitted. 
     In  FIG. 8B , SL SS/PBCH block (index=1) starting at symbol index 7 in slot M and SL SS/PBCH block (index 2) starting at symbol index 1 in slot M+1 are not transmitted. 
     In mode 1, If a SyncRef UE is in gNB coverage then gNB may instruct the SyncRef UE to transmit SL SS/PBCH. The SL SS/PBCH transmission resource can be scheduled by gNB. In mode 2, a SyncRef UE may transmit SL SS/PBCH within a pre-configured time and frequency resource. To reduce or avoid the interference with Uu (cell) SS/PBCH, it is envisaged the SL SS/PBCH allocation methods are based on the following cases: 
     Case 1—Pair spectrum: 
     For mode 1, the time and frequency resource for SL SS/PBCH transmission can be scheduled by the network resource (gNB). The resource for SL SS/PBCH transmission can be scheduled in an UL frequency band. Therefore, Uu SS/PBCH won&#39;t cause timing and frequency offset detection ambiguity with DL Uu SS/PBCH. 
     For mode 2, UE can autonomously transmit SL SS/PBCH in a pre-configured time and frequency resource. Thus, pre-configured resource for SL SS/PBCH can be reserved at a sub band of UL frequency band. If SL SS/PBCH resources are scheduled in the DL sub band, then the scheduled resource for SL SS/PBCH transmission may be exact, partial, or non-overlapped with Uu SS/PBCH in frequency domain. When scheduled resource is exact or partial overlapped with Uu SS in frequency domain, Uu UE may falsely detect SL SS/PBCH. Here, three solutions are envisaged to solve this issue as described in the options below: 
     Option 1: SL UE can assume gNB won&#39;t schedule an SL SS/PBCH resource overlap with Uu SS/PBCH in a frequency domain. For pair spectrum, it can allocate SL SS/PBCH resource in UL frequency band. 
     Option 2: SL SPSS and SSSS use different initialization value for M-sequence than the value for Uu PSS and SSS M-sequence generation but keep the same polynomial coefficients for M-sequence generation. The initial value for SPSS/SSSS will have the minimum correlation with PSS/SSS of gNB. 
     Option 3: SL SPSS/SSSS use difference sequence than Uu PSS and SSS sequence. For example, SL SPSS/SSSS can use different M-sequence polynomial coefficients than Uu PSS/SSS. 
     Case 2—Unpair spectrum: 
     The above-proposed options for SS/PBCH resource allocation can be applied for unpair spectrum as well. For mode 1, the time and frequency resource for SL SS/PBCH transmission can be scheduled by network (gNB). For unpair spectrum, DL and UL are at a same frequency band. Therefore, it is impossible to allocate SL SS/PBCH in a dedicated UL frequency band. 
     In mode 2, UE can autonomously transmit SL SS/PBCH in a pre-configured time and frequency resource for SL SS/PBCH transmission. If the SL SS/PBCH resource(s) are non-overlapped with Uu SS/PBCH resource(s). It is noted the center of a Uu SS/PBCH resources is allocated at the synchronization raster and spans 20 RBs to avoid Uu UE false detected SL SS/PBCH. 
     In an embodiment as depicted in  FIG. 9 , SL SS/PBCH and Uu SS/PBCH are TDM and the center of SL SS/PBCH is aligned with a Uu SS/PBCH synchronization raster. In this case, vehicle UE doesn&#39;t have to tune its receiver to simultaneously monitor different sub bands to detect the SL SS/PBCH and Uu SS/PBCH. This may save switching time and potentially reduce complexity. However, SL synchronization signal (SPSS/SSSS) needs to use different sequences or different initial values for M-sequence generation than Uu PSS/SSS to reduce the correlation between Uu SS/PBCH and SL SS/PBCH and avoid the timing and frequency offset estimation ambiguity. 
     For mode 1 SL SS/PBCH transmission, UE may assume SL SS/PBCH is transmitted at the center of a scheduled SL band. For mode 2 SL SS/PBCH transmission, the resource(s) for SL SS/PBCH transmission is based on a pre-configured resource (or a SL band). UE may not assume the SL SS/PBCH is transmitted at the center of a pre-configured SL band. NR SL SS/PBCH Transmission Periodicity 
     According to yet another aspect of the application, transmission of NR SL SS/PBCH can have the following options: 
     Option 1: Periodical Transmission 
     In mode 1, when a SyncRef UE synchronization source is based on gNB, gNB can instruct SyncRef UE to transmit (a or multiple) SL SS/PBCH burst set(s) (e.g., different transmission periodicity of SL PSSS/SSS and SL PBCH) to out of coverage UEs. For example, the transmission of SL SS/PBCH burst set periodicity can support {5 ms, 10 ms, 20 ms, 40 ms, 80 ms, 160 ms, 200 ms}. 
     In mode 2, UE can determine SL SS/PBCH burst set transmission periodicity. The SL SS/PBCH burst set periodicity can be in {5 ms, 10 ms, 20 ms, 40 ms, 80 ms, 160 ms, 200 ms}. 
     NR PSBCH transmission periodicity can be different than NR SL PSSS/SSSS transmission periodicity. For example, the transmission periodicity of NR PSBCH can be set as 80 ms but the transmission periodicity of NR SPSS/SSSS can be set as 40 ms. 
     Option 2: Aperiodicity Transmission 
     In mode 1, gNB can instruct UE to transmit SL SS/PBCH burst set with a timing period. The SL SS/PBCH transmission window is set as multiple of 5 ms (or equivalent to number of transmission of a burst set). In mode 2, UE can determine the SL SS/PBCH transmission window as multiple of 5 ms. In  FIG. 10  two of SL SS/PBCH burst set are transmitted. 
     For mode 1 SL SS/PBCH transmission, UE may assume SL SS/PBCH is transmitted at the central of a scheduled SL band. For mode 2 SL SS/PBCH transmission, the resource(s) for SL SS/PBCH transmission is based on a pre-configured resource (or a SL band). Hence, UE may not assume the SL SS/PBCH transmit at the center of a pre-configured SL band. 
     NR SL SS/PBCH Transmission Periodicity 
     According to yet even another aspect, transmission of NR SL SS/PBCH can have the following options: 
     Option 1: Periodical Transmission 
     In mode 1, when a SyncRef UE synchronization source is based on gNB, gNB can instruct SyncRef UE to transmit (a or multiple) SL SS/PBCH burst set(s) (e.g.: different transmission periodicity of SL PSSS/SSS and SL PBCH) to out of coverage UEs. For example, the transmission of SL SS/PBCH burst set periodicity can support {5 ms, 10 ms, 20 ms, 40 ms, 80 ms, 160 ms, 200 ms}. 
     In mode 2, UE can determine SL SS/PBCH burst set transmission periodicity. The SL SS/PBCH burst set periodicity can be in {5 ms, 10 ms, 20 ms, 40 ms, 80 ms, 160 ms, 200 ms}. 
     NR PSBCH transmission periodicity can be different than NR SL PSSS/SSSS transmission periodicity. For example, the transmission periodicity of NR PSBCH can be set as 80 ms but the transmission periodicity of NR SPSS/SSSS can be set as 40 ms. 
     Option 2: Aperiodicity Transmission 
     In mode 1, gNB can instruct UE to transmit SL SS/PBCH burst set with a timing period. The SL SS/PBCH transmission window is set as multiple of 5 ms (or equivalent to number of transmission of a burst set). In mode 2, UE can determine the SL SS/PBCH transmission window as multiple of 5 ms. In  FIG. 10 , two of SL SS/PBCH burst set are transmitted. 
     Table 3 below illustrates an exemplary NR SL-SSID from a different source ID. Table 4 below illustrates an exemplary NR SL-SSID from different source ID. 
     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 SSID Set 
                 SSID Range 
                 Description 
               
               
                   
               
             
            
               
                 GNSS 
                 0, ..., M 1   
                 GNSS is the source of synchronization. 
               
               
                   
                   
                 The UE is synchronized  
               
               
                   
                   
                 to GNSS (direct) or to a 
               
               
                   
                   
                 nearby UE that achieves  
               
               
                   
                   
                 time and frequency synchronization  
               
               
                   
                   
                 from GNSS (indirect) 
               
               
                 gNB 
                 M1 + 1, ..., M 2   
                 gNB is the synchronization source. 
               
               
                   
                   
                 The UE is synchronized to an gNB  
               
               
                   
                   
                 (direct) or to a nearby UE that is  
               
               
                   
                   
                 synchronized to an gNB (indirect) 
               
               
                 eNB 
                 M 2  + 1, ..., M 3   
                 eNB is the synchronization source. 
               
               
                   
                   
                 The UE is synchronized to a LTE  
               
               
                   
                   
                 eNB (direct) or to a nearby  
               
               
                   
                   
                 UE that is synchronized  
               
               
                   
                   
                 to a LTE eNB (indirect) 
               
               
                 NR UE 
                 M 3  + 1, ... M 4   
                 A NR UE is the synchronization  
               
               
                   
                   
                 source. The UE is synchronized to  
               
               
                   
                   
                 a nearby NR UE that obtains 
               
               
                   
                   
                 no synchronization information 
               
               
                   
                   
                 either directly or indirectly  
               
               
                   
                   
                 from GNSS, gNB or eNB 
               
               
                 LTE UE 
                 M 4  + 1, ... N 
                 A LTE UE is the synchronization  
               
               
                   
                   
                 source. The UE is synchronized to  
               
               
                   
                   
                 a nearby LTE UE that obtains  
               
               
                   
                   
                 no synchronization information  
               
               
                   
                   
                 either directly or indirectly from  
               
               
                   
                   
                 GNSS, gNB, eNB, or NR UE. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 SSID Set 
                 SSID Range 
                 Description 
               
               
                   
               
             
            
               
                 GNSS 
                 0, ..., M 1   
                 GNSS is the source of synchronization. 
               
               
                   
                   
                 The UE is synchronized to  
               
               
                   
                   
                 GNSS (direct) or to a 
               
               
                   
                   
                 nearby UE that achieves time  
               
               
                   
                   
                 and frequency synchronization  
               
               
                   
                   
                 from GNSS (indirect) 
               
               
                 gNB 
                 M 1  + 1, ..., M 2   
                 gNB is the synchronization source. 
               
               
                   
                   
                 The UE is synchronized to an gNB  
               
               
                   
                   
                 (direct) or to a nearby UE that is  
               
               
                   
                   
                 synchronized to an gNB (indirect) 
               
               
                 gNB- 
                 M 2  + 1, ..., M 3   
                 gNB-type RSU: stationary 
               
               
                 RSU 
                   
                 infrastructure providing 
               
               
                   
                   
                 V2X message transmission  
               
               
                   
                   
                 to UEs through the NR 
               
               
                   
                   
                 Uu reference point. This type of RSU  
               
               
                   
                   
                 can be physically collocated  
               
               
                   
                   
                 with a common gNB 
               
               
                 eNB 
                 M 3  + 1, ..., M 4   
                 eNB is the synchronization source. 
               
               
                   
                   
                 The UE is synchronized to a LTE  
               
               
                   
                   
                 eNB (direct) or to 
               
               
                   
                   
                 a nearby UE that is synchronized  
               
               
                   
                   
                 to a LTE eNB (indirect) 
               
               
                 eNB- 
                 M 4  + 1 , ... M 5   
                 eNB-type RSU: stationary  
               
               
                 RSU 
                   
                 infrastructure providing 
               
               
                   
                   
                 V2X message transmission  
               
               
                   
                   
                 to UEs through the LTE 
               
               
                   
                   
                 Uu reference point. This type of RSU  
               
               
                   
                   
                 can be physically collocated  
               
               
                   
                   
                 with a common eNB 
               
               
                 NR UE 
                 M 5  + 1, ... M 6   
                 A NR UE is the synchronization source. 
               
               
                   
                   
                 The UE is synchronized  
               
               
                   
                   
                 to a nearby NR UE that 
               
               
                   
                   
                 obtains no synchronization information  
               
               
                   
                   
                 either directly or indirectly  
               
               
                   
                   
                 from GNSS, gNB or eNB 
               
               
                 LTE UE 
                 M 6  + 1, ... N 
                 A LTE UE is the synchronization  
               
               
                   
                   
                 source. The UE is synchronized  
               
               
                   
                   
                 to a nearby LTE UE that obtains  
               
               
                   
                   
                 no synchronization information  
               
               
                   
                   
                 either directly or indirectly from  
               
               
                   
                   
                 GNSS, gNB, eNB, or NR UE. 
               
               
                   
               
            
           
         
       
     
     In an embodiment, Whe the UE may be with the network control synchronization transmission not included in the resource assignment. In this scenario, the UE has to decide on its own whether to transmit the sidelink synchronization signals. The UE takes the threshold (from higher signaling) and compares the RSRP measurement of its cell to this value. If this RSRP measurement is below the threshold, it transmits its own sidelink synchronization signal and MIB-SL (i.e., SL SS/PBCH), along with the necessary parameters from the sidelink synchronization similar to the gNB as the synchronization source. However, when a UE is out of network coverage, it looks for another UE providing a synchronization reference. Such a UE, if found, is called a SyncRef UE. From this SyncRef UE, the UE obtains the time and frequency synchronization as well as the information provided by the MIB-SL. 
     Whether the SyncRef UE is in coverage (gNB, eNB or GNSS) or out of the coverage, both can include signaling by DMRS or by an indication flag in NR MIB-SL. The monitoring UE can use SyncRef UE SLSSID and in-coverage flag to determine synchronization priority. The highest synchronization priority of SLSSID is in GNSS or gNB with coverage being true. A next synchronization priority is those SyncRef UEs which have an SLSSID in the set of GNSS or gNB but with coverage being false. The lowest priority is SSSSID is in UE. In coverage or out of coverage indications are carried by the DMRS for SL PBCH demodulation. As a result, the monitoring UE does not have to decode the MIB-SL to determine the synchronization priority and enhance the synchronization priority selection performance. 
     Slide Link Master Information Block 
     According to yet even a further aspect of the application, NR V2X exploits sidelink synchronization signals on the PHY layer and the master information block MIB-SL-V2X message on the RLC sublayer to achieve time and frequency synchronization. A UE offering synchronization information to nearby UEs serves as a synchronization reference. Information provided by the SF number includes whether the UE is in coverage or out of coverage (if not carried by DMRS), and whether the control resource set for PSCCH and DMRS format for PSCCH. This information supports UEs in selecting the reference source according to the configured prioritization when seeking synchronization. Three options for sidelink MIB-SL designs are described below in Table 5, Table 6 and Table 7 below. 
     
       
         
           
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 Information Field 
                 Usage 
               
               
                   
               
             
            
               
                 directSystemFrameNumber 
                 Sidelink system frame number (Q bits), The 
               
               
                   
                 K most significant bit (MSB) of the Q bit 
               
               
                   
                 System Frame Number. The Q-K LSB of 
               
               
                   
                 the SFN are conveyed in the PBCH 
               
               
                   
                 transport block as part of channel coding 
               
               
                   
                 (i.e. outside the MIB-SL encoding). 
               
               
                   
                 When GNSS is the synchronization source, 
               
               
                   
                 the direct frame number (DFN) is used 
               
               
                   
                 instead of the system frame number (SFN) 
               
               
                 inCoverage 
                 UE is in network coverage (GNSS, gNB) or 
               
               
                   
                 not. Note: this field (bit) is not presented in 
               
               
                   
                 NR MIB-SL if it is carried by DMRS for SL 
               
               
                   
                 PBCH demodulation 
               
               
                 subCarrierSpacingCommon 
                 Common SCS for sidelink 
               
               
                   
                 If UE acquires MIB on carrier 
               
               
                   
                 frequency &lt;6 GHz (FR1), value 
               
               
                   
                 scs30or120 means 30 KHz. 
               
               
                   
                 Else if MIB is acquired on freq ≥6 
               
               
                   
                 GHz (FR2), value scs15or60 means 
               
               
                   
                 60 KHz and value scs30or120 
               
               
                   
                 means 120 KHz. 
               
               
                 ssb-SubcarrierOffset 
                 This is frequency offset between subcarrier 
               
               
                   
                 0 of SL SS/PBCH block to subcarrier 0 of 
               
               
                   
                 common resource block for SL SS/PBCH 
               
               
                   
                 block. (Note: This field is not present when 
               
               
                   
                 SL (sub)band is pre-configured) 
               
               
                 commonPSCCH-Config 
                 Determines a bandwidth for SL Control 
               
               
                   
                 Resource Set (CORESET), search space and 
               
               
                   
                 necessary sidelink control channel (PSCCH) 
               
               
                   
                 parameters for discovery data message. 
               
               
                   
                 (more details can refer Section 5.5) 
               
               
                 DMRS configuration 
                 DMRS port configuration (type) parameter 
               
               
                   
                 for SL common CORESET. The DMRS 
               
               
                   
                 port configuration for commonPSCCH- 
               
               
                   
                 Config can be assumed QCL with NR 
               
               
                   
                 SS/PBCH 
               
               
                   
                 (Note: this is field is not presented in MIB- 
               
               
                   
                 SL if pscch-discConfig is not presented) 
               
               
                 Spare 
                 Reserved bits 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 Information Element 
                 Usage 
               
               
                   
               
             
            
               
                 directSystemFrameNumber 
                 Sidelink system frame number (Q bits), The 
               
               
                   
                 K most significant bit (MSB) of the Q bit 
               
               
                   
                 System Frame Number. The Q-K LSB of 
               
               
                   
                 the SFN are conveyed in the PBCH 
               
               
                   
                 transport block as part of channel coding 
               
               
                   
                 (i.e. outside the MIB-SL encoding). 
               
               
                   
                 When GNSS is the synchronization source, 
               
               
                   
                 the direct frame number (DFN) is used 
               
               
                   
                 instead of the system frame number (SFN) 
               
               
                 inCoverage 
                 UE is in network coverage (GNSS, gNB) or 
               
               
                   
                 not. Note: this field (bit) is not presented in 
               
               
                   
                 NR MIB-SL if it is carried by DMRS for SL 
               
               
                   
                 PBCH demodulation 
               
               
                 subCarrierSpacingCommon 
                 Common SCS for sidelink 
               
               
                   
                 If UE acquires MD3 on carrier 
               
               
                   
                 frequency &lt;6 GHz (FR1), value 
               
               
                   
                 scs30or120 means 30 KHz. 
               
               
                   
                 Else if MIB is acquired on freq ≥6 
               
               
                   
                 GHz (FR2), value scs15or60 means 
               
               
                   
                 60 KHz and value scs30or120 
               
               
                   
                 means 120 KHz. 
               
               
                 commonPSSCH-Config 
                 Determines a bandwidth for SL sidelink 
               
               
                   
                 common (broadcast) data channel (common 
               
               
                   
                 PSSCH) resource parameters for discovery 
               
               
                   
                 data message and DMRS configuration for 
               
               
                   
                 common PSSCH. (more details can refer 
               
               
                   
                 Section 5.5) 
               
               
                 SL bandwidth 
                 The bandwidth allocates for SL 
               
               
                 Spare 
                 Reserved bits 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 7 
               
               
                   
               
               
                 Information Element 
                 Usage 
               
               
                   
               
             
            
               
                 directSystemFrameNumber 
                 Sidelink system frame number (Q bits), The 
               
               
                   
                 K most significant bit (MSB) of the Q bit 
               
               
                   
                 System Frame Number. The Q-K LSB of 
               
               
                   
                 the SFN are conveyed in the PBCH 
               
               
                   
                 transport block as part of channel coding 
               
               
                   
                 (i.e. outside the MIB-SL encoding). 
               
               
                   
                 When GNSS is the synchronization source, 
               
               
                   
                 the direct frame number (DFN) is used 
               
               
                   
                 instead of the system frame number (SFN) 
               
               
                 inCoverage 
                 UE is in network coverage (GNSS, gNB) or 
               
               
                   
                 not. Note: this field (bit) is not presented in 
               
               
                   
                 NR MIB-SL if it is carried by DMRS for SL 
               
               
                   
                 PBCH demodulation 
               
               
                 subCarrierSpacingCommon 
                 Common SCS for sidelink 
               
               
                   
                 If UE acquires MIB on carrier 
               
               
                   
                 frequency &lt;6 GHz (FR1), value 
               
               
                   
                 scs30or120 means 30 KHz. 
               
               
                   
                 Else if MIB is acquired on freq ≥6 
               
               
                   
                 GHz (FR2), value scs15or60 means 
               
               
                   
                 60 KHz and value scs30or120 
               
               
                   
                 means 120 KHz. 
               
               
                 SL bandwidth  
                 The bandwidth allocates 
               
               
                 Spare 
                 for SL Reserved bits 
               
               
                   
               
            
           
         
       
     
     SL SS/PBCH Block Structure 
     According to an aspect of the application, one-shot detection performance of SL SS/PBCH is enhanced by employing more DMRS, SPSS, SSSS symbols for SL SS/PBCH than PSS, SSS, DMRS symbols in NR Uu SS/PBCH. Accordign to the embodiment shown in  FIG. 11A , two enhanced SL SS/PBCH block structures are employed. The first proposed SL SS/PBCH block structure uses one-slot and encompass two SPSS, two SSSS and  8  DMRS+PSBCH symbols. The second proposed SL SS/PBCH block structure uses half-slot and encompass one SPSS, 1 SSSS and 5 DMRS+PSBCH symbols. The 1st OFDM symbol is reserved for not transmission (reserved for AGC) and the last symbol is reserved for guard symbol. For a half frame (5 ms) with NR SL SS/PBCH blocks, the first symbol indexes for candidate NR SL SS/PBCH blocks are determined by the subcarrier spacing as following, where index 0 corresponds to the first symbol of the first slot in a half-frame. 
     According to the embodiment in  FIG. 11B , with 60 kHz subcarrier spacing: the first symbols of the candidate SL SS/PBCH blocks have indexes {1}+14n, n=0,1,2,3. 
     DMRS Design for PSBCH Demodulation 
     According to a further aspect of the application, two design options for DMRS design for PSBCH demodulation are provided. The first option is DMRS multiplexing with PSBCH. The comb-type DMRS RE location varies with SL SSID. The relative RE location for comb-type DMRS can be formulated as 0+v, d+v, 2d+v, . . . , +(M−d)+v, where M denotes the maximum RE location for PSBCH, d is the distance between two DMRS RE and v is mod(SLSSID, d). The second option for DMRS design is PSBCH symbols are TDM with DMRS symbols. The relative RE location for comb-type DMRS can be formulated as 0+v, d+v,2d+v, . . . , +(M−d)+v in the DMRS symbols and other REs are set to zero.  FIG. 12A-B  illustrate two DMRS designs for SL PSBCH.  FIG. 12A  illustrates DMRS symbols are multiplexing with PSBCH symbols. In an exemplary embodiment as shown in  FIG. 12B  DMRS symbols are TDM with PSBCH symbols. 
     DRMS Sequence Construction 
     According to another aspect, the candidate SL SS/PBCH blocks in a half frame are indexed in ascending order from 0 to L−1. DMRS may carry a SL SS/PBCH block index (in terms of bits), and the MIB-SL carries the rest of the block index bits. A UE determines the Q 1  LSB bits, when L=P, or the Q 2  LSB bits, when L&gt;P, of an SS/PBCH block index per half frame from a one-to-one mapping with an index of the DMRS sequence transmitted in the SL PBCH. 
     The UE shall assume the reference-signal sequence r(m) for an NR SS/PSPBCH block is defined by: 
     
       
         
           
             
               r 
                
               
                 ( 
                 m 
                 ) 
               
             
             = 
             
               
                 
                   1 
                   
                     2 
                   
                 
                  
                 
                   ( 
                   
                     1 
                     - 
                     
                       2 
                        
                       
                         c 
                          
                         
                           ( 
                           
                             2 
                              
                             m 
                           
                           ) 
                         
                       
                     
                   
                   ) 
                 
               
               + 
               
                 
                   1 
                   
                     2 
                   
                 
                  
                 
                   ( 
                   
                     1 
                     - 
                     
                       2 
                        
                       
                         c 
                          
                         
                           ( 
                           
                             
                               2 
                                
                               m 
                             
                             + 
                             1 
                           
                           ) 
                         
                       
                     
                   
                   ) 
                 
               
             
           
         
       
     
     If DMRS for NR PSBCH is constructed by a gold sequence; the gold sequence g(n) can be specified as follows: 
         g ( n )=( x   1 ( n+N   c )+ x   2 ( n+N   c ))mod 2 
         x   1 ( n+ 31)=( x   1 ( n+ 3)+ x   1 ( n ))mod 2 
         x   2 ( n+ 31)=( x   2 ( n+ 3)+ x   2 ( n+ 2)+ x   2 ( n+ 1)+ x   2 ( n ))mod 2 
     where N c  is a constant (e.g=1600) and the operator “+” is the modulo-2 addition. The x 1  and x 2  are polynomial generator with length 31. Four options for sidelink SS/PBCH DMRS design are proposed as described in the option below. 
     Option 1: DMRS carry both SL SS/PBCH block index and in-coverage flag. In this option, the scrambling sequence generator shall be initialized at the start of each SS/PBCH block occasion with: 
         c   init =2 a (ī SsB +1)(└ N   ID   SL   /Z ┘+1)+2 b (ī SsB +1)+( N   UD   SL  mod  Z ),
 
     where N ID   SL  denotes the sidelink ID, a, b are integers, for example a=13 and b=7 respectively and blocks L=4, and set ī SsB =(i SSB ×2+B i )+4n hf  where n hf  is the number of the half-frame in which the NR PSBCH is transmitted in a frame with n hf =0 for the first half-frame in the frame and n hf =1 for the second half-frame in the frame, B i =0, 1, where B i  indicates in-coverage flag, Z=K+1+1=K+2 denotes the number of total bits for SSB (K least significant bits and in-coverage flag bit, where i SSB  is the first least significant bits of the SL SS/PBCH block index. For example, i SSB =1, B i =0 then (i SSB ×2+B i )=2. For L≥8, ī SSB =(i SSB ×2+ B   i ), where i SSB  is the K least significant bits of the SS/PBCH block index. 
     Option 2: The DMRS is only carried in the coverage flag and does not include the SL SS/PBCH index. In this option, the scrambling sequence generator shall be initialized at the start of each SS/PBCH block occasion with: 
         c   init =2 a ( B   i +2 n   hf +1)(└ N   ID   SL /3┘+1)+2 ┌a/2┐ ( B   i +1)+( N   ID   SL  mod 3),
 
     for any L. n hf =0, 1 denotes half frame indicator (n hf =0 denotes the first half-frame in the frame, n hf =1 is for the first half-frame in the frame). 
     Option 3: The DMRS carries the SSB index and the scrambling sequence generator shall be initialized at the start of each SS/PBCH block occasion with: 
         c   init =2 a (ī SsB +1)(└ N   ID   SL   /Z ┘+1)+2 b (ī SsB +1)+( N   ID   SL  mod  Z )
 
     For L=4, ī SsB =i SSB +4n hf  where n hf  is the number of the half-frame in which the NR PSBCH is transmitted in a frame with n hf =0 for the first half-frame in the frame and n hf =1 for the second half-frame in the frame, and i SSB  is the first least significant bits of the SL SS/PBCH block index. For L≥8, ī SsB =i SSB , where i SSB  is the Z=K+1 least significant bits of the SS/PBCH block index. 
     Option 4: The DMRS does not carry either SSB in coverage flag. In this case, the scrambling sequence generator shall be initialized at the start of each SS/PBCH block occasion with: 
         c   init =2 a ( n   hf +1)(└ N   ID   SL /2┘+1)+2 ┌a/2┐ ( n   hf +1)
 
     where n hf =0, 1 denotes half frame indicator (n hf =0 denotes the first half-frame in the frame, n hf =1 is for the first half-frame in the frame). 
     Sidelink Beam Training and Pairing for NR V2X 
     It is envisaged according to an aspect of this application to describe an SL beam training and pairing method for SL before discovery. The proposed SL beam training and pairing procedure includes three steps. 
     The first step incudes monitoring UEs to select the best beam from a SyncRef UE&#39;s SL SS/PBCH. At this stage, the SyncRef UE does not how many monitoring UEs are nearby or proximity as depicted in  FIG. 13 . In  FIG. 13 , vehicle A (UE A) is the SyncRef UE (i.e., initiating SL SS/PBCH burst transmission) and vehicle B (UE B) and vehicle C (UE C) are the monitoring UEs. UE A does not know how many proximity UEs (e.g., UEs B and C) are monitoring its SL SS/PBCH. 
     The second step includes monitoring UEs responses for the preferred SL SS/PBCH beam for beam paring. Monitoring UE(s) (UEs B and C in  FIG. 13 .  FIG. 13  performs S-RSRP measurements in SL sensing window (at least a SL SS/PBCH burst set) to determine the best SL SS/PBCH beam for beam paring. Once the best beam is identified. The monitoring UE select a PSCCH (hereafter, PSCCH is defined in Type 1) resource for beam response. The PSCCH Type 1 is beamformed with the best selected SL SS/PBCH beam (block) in a SS/PBCH burst set. The common PSCCH resources for the feedback/beam response can be obtained from the SL remaining system information (SL RMSI). More details of SL RMSI will be given in the later section. 
     The PSCCH Type 1 is based on a ZC sequence with length N. The root of the ZC sequence is dependent on the detected SL SSID. Furthermore, cyclic shift (denotes as C) applies on ZC sequence for supporting of multiple UEs transmitting on a same PSCCH Type M resource. The cyclic shift parameter is broadcast (or groupcast) in SL RMSI by SyncRef UE. The number of resources for PSCCH Type 1 are same as the number of L SL SS/PBCH. If a monitoring UE determine the best SL SS/PBCH block l, l∈{0, . . . , L−1}, then it will choose the l-th corresponding resource for PSSCH Type 1 transmission. The maximum number of UEs can simultaneously transmit on PSCCH Type 1 resources are equal to 
     
       
         
           
             L 
             × 
             
               
                 ⌊ 
                 
                   N 
                   C 
                 
                 ⌋ 
               
               . 
             
           
         
       
     
     The allocation of L (number of SL SS/PBCH block in a SL SS/PBCH burst set) PSCCH Type 1 resources can be based on FDM or TDM shown in  FIG. 14A  (i.e., FDM) and  FIG. 14B  (i.e., TDM). PSSCH Type 1 can be simultaneously transmit with PUCCH Type 1. PSSCH Type 1 carry some basic information for the monitoring UE such as UE ID, connection request, UE position (if available) etc. The default modulation order of PUSCH Type 1 can be set to QPSK or broadcast/groupcast by SyncRef UE SL RMSI. PUCCH Type 1 and PUSCH Type 1 can be setup with a Tx cycle or a window duration. PUCCH Type 1 may have different bandwidth (in terms of RBs) than PUCCH Type 2. The Tx cycle or window duration can be broadcast/groupcast by SyncRef UE SL RMSI. 
     The monitoring UE beamforms the PSCCH Type 1 with the best selected beam(s) from the detected SL SS/PBCH beam(s) for response. Once the (SyncRef) UE receives and can detect the beam response PSCCH Type M from monitoring UE(s), it will perform the following operation: (i) Demodulate and decode the PSSCH Type 1 for extraction of basic UE information, and (ii) Send out a PSCCH (implicit ACK) with a PSSCH to the monitoring UE. The PSCCH resource can be signaled by (SCI) PSCCH. The PSCCH resources can be implicitly indicated by the selected PSCCH Type 1 resource. Therefore, the monitoring UE can expect to receive the implicit ACK from the beam paring ACK sent by SyncRef UE. 
     The ACK is based on the implicit method, i.e., the monitoring UE receive a SCI (PSCCH) from the SyncRef UE within a window time, where the monitoring UE can assume the completion of beam training and beam-pairing. The window of time can be broadcast or groupcast by SyncRef UE&#39;s SL RMSI. Furthermore, the monitoring UE can assume the contention resolution is complete. If the monitoring UE cannot receive the implicit ACK, i.e., a PSCCH from SyncRef UE by the window time then the monitoring UE can perform the retransmission of PSCCH and PSSCH Type 1 at the next coming transmission cycle. If the retransmission reaches the maximum number of retransmission then the monitoring UE will restart the beam training. 
     The SL beam training and pairing procedure for before discovery is presented below according to the following steps: 
     Step 1: Beam training via SL NR PS SS/PBCH burst set. a monitoring UE performs the beam selection based on the SyncRef UE&#39;s (sender of SL SS/PBCH) SL SS/PBCH block l=0, . . . , L−1. At this stage, the monitoring UE selects the best SL SS/PBCH beam (ID l) from L blocks. 
     Step 2: The monitoring UE send out a PSCCH and PSSCH Type 1 to the SyncRef UE with the beamformed direction of the best selected SL SS/PBCH beam. 
     Step 3: If the SyncRef UE receive the monitoring UE PSCCH Type M, then it will send out an implicit ACK via a PSCCH to the monitoring UE. Once the monitoring UE receives the SyncRef UE&#39;s PSCCH by a setup window time, then the monitoring UE can assume the beam pairing being complete.  FIG. 15  illustrates a proposed sidelink beam training step 2 (response) before discovery.  FIG. 16  illustrates a proposed sidelink beam training procedure. 
     SL Beam Training and Paring using SL CSI-RS 
     According to another embodiment, in mode 1, gNB can instruct UE to send SL CSI-RS for SL beam training without using SL SS/PBCH. The SL CSI-RS can be configured a periodically or periodically for the monitoring UE(s). The SL CSI-RS resource (configured by gNB) may be periodic (i.e., configured at the slot level), semi-persistent (also at the slot level, but it can be activated or deactivated with messages from the UE) and aperiodic (the transmission is triggered by the UE signaling via SCI). Sidelink beam management operations can be based on the sidelink control (SCI) messages which are periodically or a periodically exchanged between the transmitter (SyncRef) and the receiver (monitoring) UEs. The resource of SL CSI-RS can be placed in PSSCH resource pools. The monitoring UE can response the channel state quality to the SyncRef UE via PSCCH. 
     In mode 2, after the monitoring UE performs the initial beam training and pairing. SyncRef UE can configure NR CSI-RS for further/finer beam training or alignment. The SL CSI-RS resource (configured by SyncRef UE) may be periodic (i.e., configured at the slot level), semi-persistent (also at the slot level, but it can be activated or deactivated with messages from the UE) and aperiodic (the transmission is triggered by UE&#39;s SCI). 
     SL Physical Channel for Discovery 
     According to yet another embodiment, two options for the PSSCH carrying SL RMSI (or PSDCH) configured by NR SL SS/PBCH are envisaged. 
     Option 1: The sidelink resource for the common PSCCH (hereafter PSCCH is referred to as Type 0) can be indicated by the NR sidelink MIB information field commonPSCCH-Config Table 4. PSCCH Type 0 can indicate the time and frequency for PSSCH-SL RMSI (or PSDCH). Upon detection of a SL SS/PBCH block, the UE determines that a control resource set (CORESET) for PSCCH Type 0 search space and the SL bandwidth. PSCCH Type 0 and PSSCH for SL RMSI can be either FDM, TDM or hybrid with NR SL SS/PBCH as depicted in  FIG. 17A  for FDM, and  FIG. 17B  for TDM. SL SS/PBCH block in a half frame (a SL SS/PBCH burst set) are indexed in an ascending order in time from 0 to L−1. The PSCCH Type 0 resources are one to one map with SL SS/PBCH block from 0 to L−1. The resource mapping rule between SL SS/PBCH and PSCCH Type 0 is dependent on multiplexing scheme. For FDM case, the frequency offset for PSCCH Type 0 resource is indicated by MIB-SL. A UE detect the best SL SS/PBCH block l and decode its MIB-SL. The commonPSCCH-Config can indicate the relative frequency offset from the l-th SS/PBCH. Hence, UE can search for the PSCCH Type 0 first and the corresponding PSSCH for SL RMSI. Furthermore, UE can assume QCL relationship between SL SS/PBCH block l and the l-th resources for PSCCH Type 0 and PSSCH for SL RMSI. Similarly, for TDM case, the timing offset between SL SS/PBCH block l and the l-th resources for PSCCH Type 0 can be indicated by commonPSCCH-Config. FDM and TDM resource mapping for SL SS/PBCH, PSCCH Type 0 and PSSCH for SL RMSI (or PSDCH) is depicted in  FIGS. 17A-B . 
     Option 2: The sidelink resource for PSCCH Type 0 can be indicated by the NR sidelink MIB information field commonPSSCH-Config Table 5. In this option, there is no PSCCH Type 0 to indicate the time and frequency for PSSCH-SL RMSI (or PSDCH). Instead, upon detection of a SL SS/PBCH block, the UE determines the time and frequency resource for PSSCH-SL RMSI. PSSCH for SL RMSI can be either FDM, TDM with NR SL SS/PBCH as depicted in (a) FDM (b) TDM. SL SS/PBCH block in a half frame (a SL SS/PBCH burst set) are indexed in an ascending order in time from 0 to L−1. The PSSCH for SL RMSI resources are one to one map with SL SS/PBCH block from 0 to L−1. The resource mapping rule between SL SS/PBCH and PSSCH for SL RMSI is dependent on multiplexing scheme. For FDM case, the frequency offset for PSSCH for SL RMSI resource is indicated by MIB-SL. A UE detect the best SL SS/PBCH block l and decode its MIB-SL. The commonPSSCH-Config can indicate the relative frequency offset from the l-th SS/PBCH. Hence, UE can directly find the PSSCH for SL RMSI when it successfully decode the l-th SS/PBCH MIB. Furthermore, UE can assume QCL relationship between SL SS/PBCH block l and the l-th resources for PSSCH for SL RMSI. Similarly, for TDM case, the timing offset between SL SS/PBCH block l and the l-th resources for PSSCH for SL RMSI can be indicated by commonPSSCH-Config. FDM and TDM resource mapping for SL SS/PBCH and PSSCH for SL RMSI (or PSDCH) is depicted in  FIG. 18A and 18B . 
     Side Information for Beam Alignment 
     According to even another aspect of the application, a vehicle/UE equipped with a DSRC unit designed on the IEEE 802.11p standard is configured to communicate with other vehicles. In so doing, messages such as for example warning messages are exchanged to avoid accidents and improve the traffic situation. Safety messages such as Cooperative Awareness Messages (CAMs) or Basic Safety Messages (BSMs) are periodically broadcasted to nearby vehicles. These messages contain key vehicle information (such as location, speed, heading, etc.) given by the on-board GPS. Other information such as for example, vehicle type and brake condition may also be included. Moreover, vehicles for advanced V2X applications exchange sensor data. The sensor data may contain distance, direction, angle, speed, relative speed, etc. 
     In NR, the higher layer, e.g., V2X application layer, extracts useful information, such as location, direction, angle, relative speed, etc., from BSM, CAM, or sensor data messages. These parameters may be used to augment beam training, beam fine alignment, beam tracking, etc. on side link with reduced overhead of beam sweeping. For example, the beams may be set with a very small range of angles augmented by the higher layer&#39;s parameters, and paired quickly without blindly sweeping through all the angles. UEs may use on-board sensors such as for example radar to estimate beam direction. The UE can determine SL CSI-RS for beam alignment with or without side information such as BSM or CAM. Table 8 lists an example of higher layer parameters, which may be used for augmenting beam training, beam fine alignment, beam tracking, etc. Table 8 below illustrates a higher layer parameters extracted from BSM, CAM and sensor data. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 8 
               
               
                   
                   
               
               
                   
                 Information Field 
                 Usage 
               
               
                   
                   
               
             
            
               
                   
                 UE position 
                 GSP location (Latitude, Longitude, 
               
               
                   
                   
                 Elevation) 
               
               
                   
                 Vehicle Motion Data 
                 Speed, Heading direction, 
               
               
                   
                   
                 Brake system status 
               
               
                   
                 Vehicle Path 
                 PH representation of recent vehicle 
               
               
                   
                 History (PH) 
                 movement over a certain distance 
               
               
                   
                   
               
            
           
         
       
     
     Broadcast and Multicast 
     In yet even a further aspect of the application, the communication phase relies on the discovery phase in V2X. Generally, there are two modes to perform discovery. The first mode includes broadcasting or multicasting its own information periodically without a request from a receiver. The second mode includes exchanging queries (i.e., request and response). The discovering vehicle/UE transmits a request containing information about what it is interested to discover. The discoveree vehicle/UE receives the request and responds with information related to discoverer&#39;s request. 
     In embodiments directed to this aspect, three methods are described with regard to sidelink physical channels carrying discovery messages. The first method is based on a physical sidelink discovery channel (PSDCH). For SL physical channels carrying discovery messages, the link adaptation mechanism is not required for the discovery phase and the sidelink PSSCH demodulation complexity can be reduced. PSCCH Type M can be used for indication of PSSCH for carrying discovery message. Broadcast discovery messages can be transmitted with a periodicity. The broadcast periodicity can be configured via sidelink remaining system information (RMSI), other system information (OSI) or a pre-defined rule. Furthermore, the time-and-frequency resource for sidelink broadcast channel to carry discovery message can be indicated by sidelink remaining system information (RMSI), other system information (OSI) or a pre-defined rule. 
     The second method is based on a physical shared channel via PSSCH where the resource of PSSCH can be indicated by physical sidelink control channel PSCCH. Sidelink broadcast physical channel for carrying discovery message can be a burst. The third method is based on PSCCH only. In each broadcast burst, it can transmit with a periodicity P (milliseconds). The broadcast burst can have L transmission blocks. Each transmission block consists of a PSSCH and PSCCH where PSCCH carry the indication of time-and-frequency resource for PSSCH. In  FIG. 19 , a broadcast burst is configured with a transmission periodicity P (slots, it can be converted to ms). Discovery message will be repeated across the different beam in the L transmission blocks. 
     The time-and-frequency resources of PSSCH for carrying discovery message can be transmitted within a sidelink resource pool. Within a specified SL resource pool, the broadcast PSSCH burst for carrying discovery message can adopt a frequency-hopping pattern. With the support of the frequency-hopping, the broadcast PSSCH block with frequency-hopping can reduce the collision probability thus many vehicle/UEs can avoid competing for the same time-and-frequency resources. In  FIG. 20 , a broadcast burst is configured with a transmission periodicity P (slots). In each broadcast block, it transmits a PSCCH to indicate the time-and-frequency of PSSCH for carrying discovery message and each PSSCH is frequency-hopping with a pre-defined pattern. 
     The DM-RS of PSSCH for carrying discovery messages can be assumed spatial QCL with the DM-RS of PSCCH which indicates the time-and-frequency of the PSSCH. An exemplary embodiment is depicted in  FIG. 21 . If the scheduling offset between PSCCH and PSSCH is smaller or equal to N symbols than the neighbor vehicle/UE should assume that the PSSCH transmission is QCL with the corresponding PSCCH transmission with a certain Transmission Configuration Indication (TCI) states. If the scheduling offset between PSCCH and PSSCH is larger than N symbols than the neighbor vehicle/UE should assume that the PSSCH transmission is QCL with the corresponding PSCCH transmission. The DM-RS of PSSCH can be based on front load DM-RS, i.e., DM-RS symbols are in front of PSSCH symbols. The number of DM-RS symbols configuration can be setup via sidelink remaining system information (RMSI), other system information (OSI) or a pre-defined rule. Zadoff-Chu sequences with cyclic-shift are used for generating DM-RS. The cyclic-shift can be configured via sidelink remaining system information (RMSI), sidelink other system information (OSI) or a pre-defined rule. PSSCH can be transmitted with a fixed modulation and coding scheme (MCS) and using one spatial stream, i.e., transmission rank one as default. 
     If SL physical channel resources carrying discovery message are allocated on a non-vehicle/UE specific basis, collision may occur because plural vehicles/UEs compete for the same time-and-frequency resource for discovery transmission. This occurs when many proximity vehicle/UEs try to broadcast their discovery messages over non-vehicle/UE specific basis resources. The non-vehicle/UE-specific resources for broadcast PSSCH burst can be allocated within a SL-BWP or a resource pool. gNB can broadcast the information about the SL-BWP or a vehicle/UE can use a pre-defined SL-BWP for SL physical channel carrying discovery message based on the non-vehicle/UE-specific resources. Collision can be avoided for a discovery procedure where resources are allocated for vehicle/UE-specific transmission instances of discovery messages. Groups or specific vehicle/UEs can be assigned by a dedicated time-and-frequency resources. Resource for physical channel carrying discovery message transmission can be semi-persistently allocated. 
     NR SL PBCH carries the MIB such as system frame number (SFN) when gNB or eNB is the synchronization source or direct frame number (DFN) when GMSS is the synchronization source, the in coverage or out of coverage indication (if this indication is not carried by DMRS), the synchronization reference source indication such as gNB, eNB or GNSS and resource-config which determines the bandwidth for SL sidelink, control and data channel resource parameters such as the slot format indication for V2X UE to identify the number of symbols for PSCCH, PSSCH and PFSCH in a slot, and DMRS formation/pattern for PSCCH and PSFCH demodulation. Tables 10 below describes the sidelink MIB for NR V2X. 
     
       
         
           
               
               
             
               
                 TABLE 10 
               
               
                   
               
               
                 Information Element 
                 Usage 
               
               
                   
               
             
            
               
                 directSystemFrameNumber 
                 Sidelink system frame number (Q bits). 
               
               
                   
                 When GNSS is the synchronization source, 
               
               
                   
                 the direct frame number (DFN) is used 
               
               
                   
                 instead of the system frame number (SFN) 
               
               
                 inCoverage 
                 UE is in network coverage (GNSS, gNB) or 
               
               
                   
                 not. Note: this field (bit) is not presented in 
               
               
                   
                 NR MIB-SL if it is carried by DMRS for SL 
               
               
                   
                 PBCH demodulation 
               
               
                 Synchronization source 
                 gNB, eNB or GNSS (If SL SSID carry the 
               
               
                   
                 synchronous source then this field is not 
               
               
                   
                 presented in SL MIB) 
               
               
                 SL-subCarrierSpacing 
                 SCS for sidelink 
               
               
                   
                 If UE acquires MIB on carrier 
               
               
                   
                 frequency &lt;6 GHz (FR1), value 
               
               
                   
                 scs30or120 means 30 KHz. 
               
               
                   
                 Else if MIB is acquired on freq ≥6 
               
               
                   
                 GHz (FR2), value scs15or60 means 
               
               
                   
                 60 KHz and value scs30or120 
               
               
                   
                 means 120 KHz. 
               
               
                 ssb-SubcarrierOffset 
                 This is frequency offset between subcarrier 
               
               
                   
                 0 of SL SS/PBCH block to subcarrier 0 of 
               
               
                   
                 common resource block for SL SS/PBCH 
               
               
                   
                 block. (Note: This field is not present when 
               
               
                   
                 SL (sub)band is pre-configured) 
               
               
                 SL-Resource-Config 
                 Determines a bandwidth for SL sidelink, 
               
               
                   
                 control and data channel resource 
               
               
                   
                 parameters such as including the slot format 
               
               
                   
                 indication for V2X UE to identify the 
               
               
                   
                 number of symbols for PSCCH, PSSCH and 
               
               
                   
                 PFSCH in a slot, which slots are available 
               
               
                   
                 for SL if share with a UL band, and DMRS 
               
               
                   
                 configuration for PSCCH and/or PSSCH. 
               
               
                 SL bandwidth 
                 The bandwidth allocates (or BWP) for SL 
               
               
                 Spare 
                 Reserved bits 
               
               
                   
               
            
           
         
       
     
     Another option for NR SL PBCH is carrying the following: the master system information such as (Direct)SF number, the in coverage or out of coverage indication (if this indication is not carried by DMRS), the synchronization reference source indication such as gNB, eNB or GNSS and resource-config which determines the bandwidth for SL sidelink, control channel resource parameters such as the slot format indication for V2X UE to identify the number of symbols for PSCCH in a slot, and DMRS formation/pattern for PSCCH demodulation. The actual PSSCH symbols formation can be indicated by PSCCH. Table 11 below describe the sidelink MIB for NR V2X. To reduce the overhead to signal sidelink slot information in the MIB, we further propose the allocated sidelink control channel (PSCCH) symbols in a sidelink slot is carried in the SL MIB shown in SL-Resource-Config Table 11. In this option, there is no need for MIB carrying allocated PSSCH and PFSCH symbols in a sidelink slot. PSSCH and PSFCH resource can be signaled by SCI carried by PSCCH. 
     
       
         
           
               
               
             
               
                 TABLE 11 
               
               
                   
               
               
                 Information Element 
                 Usage 
               
               
                   
               
             
            
               
                 directSystemFrameNumber 
                 Sidelink system frame number (Q bits. 
               
               
                   
                 When GNSS is the synchronization source, 
               
               
                   
                 the direct frame number (DFN) is used 
               
               
                   
                 instead of the system frame number (SFN) 
               
               
                 inCoverage 
                 UE is in network coverage (GNSS, gNB) or 
               
               
                   
                 not. Note: this field (bit) is not presented in 
               
               
                   
                 NR MIB-SL if it is carried by DMRS for SL 
               
               
                   
                 PBCH demodulation 
               
               
                 Synchronization source 
                 gNB, eNB or GNSS (If SL SSID carry the 
               
               
                   
                 synchronous source then this field is not 
               
               
                   
                 presented in SL MIB) 
               
               
                 ssb-SubcarrierOffset 
                 This is frequency offset between subcarrier 
               
               
                   
                 0 of SL SS/PBCH block to subcarrier 0 of 
               
               
                   
                 common resource block for SL SS/PBCH 
               
               
                   
                 block. (Note: This field is not present when 
               
               
                   
                 SL (sub)band is pre-configured) 
               
               
                 SL-Resource-Config 
                 Determines a bandwidth for SL sidelink, 
               
               
                   
                 control and data channel resource 
               
               
                   
                 parameters such as including the slot format 
               
               
                   
                 indication for V2X UE to identify the 
               
               
                   
                 number of symbols for PSCCH in a slot, 
               
               
                   
                 which slots are available for SL if share 
               
               
                   
                 with a UL band and DMRS configuration 
               
               
                   
                 for PSCCH. 
               
               
                 SL bandwidth 
                 The bandwidth allocates (or BWP) for SL 
               
               
                 Spare 
                 Reserved bits 
               
               
                   
               
            
           
         
       
     
     The sidelink resource for PSCCH can be specified by the NR sidelink MIB information field such as commonPSSCH-Config/SL-Resource-Config as shown in Table 5 and 10. Upon detection of a SL SS/PBCH block, the UE can determine the time and frequency resource to search PSCCH in a resource pool. The commonPSSCH-Config/SL-Resource-Config can be used for the indication of the time-frequency resource information for PSCCH, PSSCH and/or PSFCH. The time-frequency resource information includes number of available symbols allocated for PSCCH, PSSCH and PSFCH in a slot and which slots are available for SL transmission and reception. 
     In this option, UE can directly find the PSCCH, PSSCH and PSFCH time-frequency resource (e.g. for discovery message) when it successfully decodes the SL SS/PBCH MIB. For instance, the time resource (slot) mapping formats for PSCCH, PSSCH and PSFCH may be based on a pre-defined table (e.g., Table 12 below). The actual slot format can be indicated by the slot format indicator in the contents of commonPSSCH-Config/SL-Resource-Config information broadcast in the SL MIB. This is a useful case when out of coverage V2X UEs that have synchronized to SL SSB (transmitted by a in coverage V2X UE) for the first time can figure out sidelink resource configuration to use. The sidelink resource can be based on a shared carrier which sidelink resource is shared with a Uu uplink resource. As shown in Table, 12 below, ‘D’ presents the available symbols for sidelink data channel, i.e., PSSCH transmission and reception, ‘C’ presents the available control channel, i.e., PSCCH, ‘G’ presents the GAP symbol, ‘X’ means the symbols are not used for any sidelink transmission and ‘F’ presents the feedback channel. i.e., PSFCH. 
     
       
         
           
               
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                   
                 Symbol number in a slot 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Format 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
               
               
                   
               
               
                 0 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
               
               
                 1 
                 C 
                 C 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
               
               
                 2 
                 C 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 G 
                 F 
               
               
                 M 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 X 
                 X 
                 D 
                 D 
                 G 
                 F 
               
            
           
           
               
               
            
               
                 M + 1 − 
                 Reserved 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 N-1 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
            
           
           
               
               
            
               
                 N 
                 UE determines the slot format for the slot 
               
               
                   
                 based on SL-ResourceConfiguration 
               
               
                   
               
            
           
         
       
     
     The physical sidelink feedback channel PSFCH for feedback of the discovery message is based on a single or two symbol duration. Multiple V2X UEs may still contest at a same time slot for the SL feedback. Therefore, this application has defined the feedback for discovery message to be based on CDM. The single sidelink feedback channel can be constructed from a CAZAC sequence. The SL feedback channel sequence can be defined as r u,v   (α) (n)=e jαn   r   u,v   (α) (n), where 0≤n≤N is the length of SL feedback channel sequence. Multiple sequences can be derived from a single base sequence through different values of α. If the sequence length is greater than 3 PRBs. The base sequence is defined as the cyclic extension of the Zadoff-Chu sequence  r   u,v   (α) (n)=x q  (n mod N ZC ) where N ZC  is the length of Zadoff-Chu sequence that is given by the largest prime number such that 
     
       
         
           
             
               
                 
                   N 
                   
                     S 
                      
                     C 
                   
                 
                 &lt; 
                 
                   N 
                   · 
                   
                     
                       x 
                       q 
                     
                      
                     
                       ( 
                       m 
                       ) 
                     
                   
                 
               
               = 
               
                 e 
                 
                   
                     - 
                     j 
                   
                    
                   
                     
                       π 
                        
                       q 
                        
                       
                         m 
                          
                         
                           ( 
                           
                             m 
                             + 
                             1 
                           
                           ) 
                         
                       
                     
                     
                       N 
                       ZC 
                     
                   
                 
               
             
             , 
           
         
       
     
     where q is q-th root Zadoff-Chu sequence and N ZC  is the largest prime number which is less than N. The q=└ q +1/2┘+v(− 1 ) └2 q ┘ ,  q =N SC (u+1)/31, u∈{0,1 . . . , 29} is the PSSCH group number, v∈{0,1} is the base sequence number within the group. Such that each group contains one base sequence (v=0) of each length N=mN sc   RB , m≤5 and two base sequences (v=1) of each length, N=mN sc   RB , 6≤m≤N RB   max,SL , where N RB   max,SL  denotes the maximum RB can be allocated in a SL BWP. The setup of the cyclic shift 
     
       
         
           
             α 
             = 
             
               π 
               N 
             
           
         
       
     
     value is signaled by SCI carried by PSCCH. Proximity V2X UE can exchange geo-location information during discovery processes; thus V2X UE can estimate and determine the corresponding cyclic-shift value of sidelink feedback channel. If the sequence length is less than 3 PRB, i.e., 36 REs then the sequence can be generated by a pre-defined CAZAC or low-PAPR sequence. Short duration PSFCH (sequence length is less than 3PRB) can span 1 or 2 symbols within a slot and may carry either small (1-2 SL feedback bits) payload size. For example, short PSFCH length={12, 24} REs can span in the frequency domain. If two symbols are used for short PSFCH, then two symbols will be applied with the same sequence. 
     Extended DM-RS Sequences 
     In order to support a large number of vehicle/UEs in sidelink, a large number of different DM-RS sequences are needed. A DM-RS sequence r u,v   (α) (n)=e jαn   r   u,v   (α) (n), where 0≤n≤N is the length of DMRS sequence. Multiple DMRS sequences can be derived from a single base sequence through different values of α. The base sequence is defined as the cyclic extension of the Zadoff-Chu sequence  r   u,v   (α) (n)=x q (n mod N SC ) where N SC  is the length of Zadoff-Chu sequence that is given by the largest prime number such that 
     
       
         
           
             
               
                 N 
                 
                   S 
                    
                   C 
                 
               
               &lt; 
               
                 N 
                 · 
                 
                   
                     x 
                     q 
                   
                    
                   
                     ( 
                     m 
                     ) 
                   
                 
               
             
             = 
             
               
                 e 
                 
                   
                     - 
                     j 
                   
                    
                   
                     
                       π 
                        
                       q 
                        
                       
                         m 
                          
                         
                           ( 
                           
                             m 
                             + 
                             1 
                           
                           ) 
                         
                       
                     
                     
                       N 
                       SC 
                     
                   
                 
               
               . 
             
           
         
       
     
     where q is q-th root Zadoff-Chu sequence. The setup of the cyclic-shift α value can be dependent on the maximum delay spread between the transmitter and receiver. In practice, small cyclic-shift value can generate more orthogonal sequences for q-th root Zadoff-Chu sequence than larger cyclic-value. However, the smaller cyclic-shift value maintains orthogonality only for smaller delay spread. Proximity vehicle/UEs can exchange geo-location information during discovery processes, thus vehicle/UE can estimate the range (˜maximum delay spread) for the cyclic-shift value of DM-RS. In  FIG. 22 , vehicles A and C have larger distance/ranges than vehicles A and B. Vehicle/UEs can also estimate the proximity distance via build-in sensor such as radar if it is equipped. Proximity distance can either be exchanged via a discovery processes or it can be autonomously estimated via build-in sensor/radar. Therefore, the cyclic-shift value of DM-RS can be based on the proximity estimation result. Here, the sidelink resource pool can be partitioned into several resource regions. Each partitioned region can be mapped to a cyclic shift value. Different partitioned region may use different cyclic shift value for DM-RS. In this manner, more orthogonal DM-RS sequences can be generated based on the proximity property. In  FIG. 23 , resources for PSSCH are partitioned into two regions. The first and second region setup with cyclic-shift value with 2 and 3, respectively. The resource region partition with different cyclic-shift configuration can be setup via sidelink remaining system information (RMSI), other system information (OSI) or a pre-defined rule. 
     Multiple Feedbacks 
     According to yet even a further aspect of the application in regard to V2V, the multicast group or unicast is determined based on the reliably discovered vehicles. A vehicle/UE will successfully be discovered when a discovery response from a neighbor is received. A vehicle/UE may broadcast or multicast sidelink physical channels for carrying discovery message. The discovery response from a neighbor may compete for the same time-and-frequency resource. This is because neighbor vehicle/UEs may not know each other until discovery process is complete. To reduce the collision probability, the discovery response mechanism for sidelink physical channel carrying discovery message can be based on the following rules: 
     The sidelink control channel PSCCH can assign or indicate response timing for PSSCH carrying discovery message. If the discovery message is trying to discover the neighbor vehicle/UE, then the neighbor vehicle/UE may need to respond to this discovery query. The monitored vehicle/UE and decode the PSCCH to obtain the discovery response timing information (in SCI) during the discovery phase. For example, in  FIG. 24 , a vehicle/UE broadcasts its discovery message at slot Q, Q+1 and indicates the discovery response timing at slot Q+3, Q+4, respectively. The indication of discovery response timing by PSCCH (with its SCI), in this way, it allows multiple discovery response can be scheduled at a same slot or different slots. According to an embodiment of  FIG. 24 , PSCCH may or may not indicate the PSSCH resource. For implicit resource allocation, a mapping relation between PSCCH and PSSCH in predefined. For explicit resource allocation, PSCCH content (SCI) indicates where to receive data PSSCH. 
     Neighbor vehicle/UEs may transmit the discovery response information carried out by a PSCCH with sidelink response control information (SFCI). Not all neighbor vehicle/UEs will perform the discovery response. Higher layer (MAC) can decide whether to response the broadcasting discovery message or not. However, multiple neighbor vehicle/UEs may still contest at a same time slot for discovery response. It is envisaged the discoveree vehicle/UEs can transmit discovery messages on demand to discoverer vehicle/UEs. The on-demand discovery messages can be transmitted in a more efficient manner. For example, such a message can be transmitted in a certain direction (without beam swiping through all directions). The discoveree vehicle/UEs can use the location information from the discover vehicle/UE to determine the beam direction for discovery response. Hence, the discovery message can be repeated a few times however without the long periodicity as regular broadcast discovery. 
     This SFCI can be piggybacked on the PSSCH because the discover vehicle/UE can expect discoveree UEs may transmit the response at a specified slot. The following PSSCH resource allocation methods are employed: 
     1. Implicit resource allocation: mapping relationship between PSCCH and PSSCH is pre-defined. 
     2. Explicit resource allocation: PSCCH content (SCI) indicates where to receive data PSS. 
     If multiple vehicles/UEs are trying to feedback for a same broadcast physical channel. For example, two vehicle/UEs may want to feedback for the broadcast physical channel transmitted at slot Q as exemplary shown in  FIG. 25 . In this case, two vehicle/UEs may try to compete the same channel resource for discovery response at the same slot. To resolve this potential collision, it is envisaged the vehicle/UE sends broadcasts for carrying discovery messages an can monitor multiple PSCCHs at a slot for feedback. The resource blocks can be classified into a contention phase (i.e., multiple PSCCHs for feedback may compete at the) and a data transmission phase. In the contention phase, two different vehicle/UEs can transmit their PSCCH at different time-frequency resources. For example, the selection of feedback resource can base on its UE-ID or other parameters. 
     SL PSS sequence generation 
     According to even a further aspect of the application, a cyclic-shift property of m-sequence is employed for SL PSS sequence generation. The SL PSS m-sequence, s(n), can be generated from polynomial f(x)=x 7 +x 4 +1 which is same as NR Uu PSS but with different cyclic-shift. For a sequence of length 127, m-sequence, s={s(n)}n=0, . . . , 126, is generated from the primitive polynomial f(x)=x 7 +x 4 +1, and with initial state of [0 1 1 0 1 1 1]=[s(0) s(1) s(2) . . . s(6)]. The other presentation of m-sequence of s(n) can be provided in the following recursive form: 
         s ( n+ 7)=( s ( n+ 4)+ s ( n )) mod 2, 0≤n≤126
 
     s(0)=0, s(1)=1, s(2)=1, s(3)=0, s(4)=s(5)=s(6)=1, which results in the following binary m-sequence is BPSK modulated sequence s(n), n=0, . . . , 126: { 1 1 1 0 1 1 0 0 0 1 0 1 0 0 1 0 1 1 1 1 1 0 1 0 1 0 1 0 0 0 0 1 0 1 1 0 1 1 1 1 0 0 1 1 1 0 0 1 0 1 0 1 1 0 0 1 1 0 0 0 0 0 1 1 0 1 1 0 1 0 1 1 1 0 1 0 0 0 1 1 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0 0 1 0 0 1 1 0 1 0 0 1 1 1 1 0 1 1 1 0 0 0 0 1 1 1 1 1 1 1 0 0 0} 
     In an embodiment of this aspect, the LFSR sequence with the Fibonacci representation for the primitive polynomial f(x)=x 7 +x 4 +1 is depicted in  FIG. 26 . The sequence dSL-PSS(n) for the SL primary synchronization signal (SL PSS) is defined by: 
         d   SL-PSS ( n )=1-2 s ( m ), n=0, . . . , 126 
         m= ( n+ 43 N   SL-SSID   (2)   +z ) mod 127, 
     where z is an integer 0&lt;z&lt;43 and the side link ID part 2, i.e., N SL-SSID   (2) ∈{0, 1, 2}. For example, z=21 for N SL-SSID   (2) ∈{0, 1, 2}. Since a cyclic-shift (left-cyclic or right-cyclic) of an m-sequence is still an m-sequence, therefore, it can generate three different m-sequences for SL PSS for N SL-SSID   (2) ∈{0, 1, 2}. In this approach, each cyclic-shift m-sequence can have low aperiodic cross-correlation with the NR Uu PSS. To support larger SL-SSID, the side link ID N SL-ID   (2)  can be extended by taking more cyclic-shift of s(n) m-sequence. For example, the sequence dSL-PSS(n) for the SL primary synchronization signal is defined by: 
         d   SL-PSS ( n )=1-2 s ( m ), n=0, . . . , 126   Eq 1
 
         m= ( n+pN   SL-SSID   (2)   +z ) mod 127,   Eq 2
 
     where N SL-SSID   (2) ∈{0, 1, 2, . . . , Q−1}, Q&gt;3, z is an integer 0&lt;z&lt;p, and p=ceil(127/Q), where ceil(x) rounds each element of x to the nearest integer greater than or equal to that element. Mapping of N SL-SSID   (2)  to a cyclic-shift value can be based on finding the lower mean square aperiodic cross-correlation value (MSACC) with the NR Uu PSS sequences. MSACC value with the NR Uu PSS sequences can be defined by, 
     
       
         
           
             
               
                 
                   R 
                   
                     c 
                      
                     c 
                   
                 
                  
                 
                   ( 
                   j 
                   ) 
                 
               
               = 
               
                 
                   1 
                   
                     M 
                      
                     
                       ( 
                       
                         M 
                         - 
                         1 
                       
                       ) 
                     
                   
                 
                  
                 
                   1 
                   
                     N 
                     2 
                   
                 
                  
                 
                   
                     ∑ 
                     
                       i 
                       = 
                       1 
                     
                     M 
                   
                    
                   
                       
                   
                    
                   
                     
                       ∑ 
                       
                         τ 
                         = 
                         
                           1 
                           - 
                           N 
                         
                       
                       
                         N 
                         - 
                         1 
                       
                     
                      
                     
                         
                     
                      
                     
                       
                          
                         
                           
                             r 
                             
                               i 
                               , 
                               j 
                             
                           
                            
                           
                             ( 
                             τ 
                             ) 
                           
                         
                          
                       
                       2 
                     
                   
                 
               
             
             , 
           
         
       
     
     where M=3 denotes the total number of NR Uu PSS sequences, j denotes the j-th cyclic shift value for the m-sequence s(n), j∈{1, 2, . . . , 42, 44, . . . , 85, 87, . . . N−1} which excludes cyclic-shift {0, 43, 86}, and r i,j (τ) 
         r   i,j (τ)=Σ q=0   N−1−τ (1−2 {tilde over (s)} ( q )(1−2 s ( q+ 43 i+τ )) for 0≤τ≤N−1
 
         r   i,j (τ)=Σ q=0   N−1+τ (1−2 {tilde over (s)} ( q−τ )(1−2 s ( q+ 43 i )) for −N+1≤τ&lt;0
 
     denotes the aperiodic cross-correlation value for i-th NR Uu PSS sequence and j-th cyclic-shift m-sequence, i.e., {tilde over (s)}=Tj(s)=[s(N−j+1) . . . s(N) s(0) . . . s(N−j−1) s(N−j)]. 
     The other performance metric is mean square aperiodic auto-correlation (MSAAC). MSACC can be defined by: 
     
       
         
           
             
               
                 R 
                 
                   A 
                    
                   C 
                 
               
                
               
                 ( 
                 j 
                 ) 
               
             
             = 
             
               
                 1 
                 
                   N 
                   2 
                 
               
                
               
                 
                   ∑ 
                   
                     τ 
                     = 
                     
                       1 
                       - 
                       N 
                     
                   
                   
                     N 
                     - 
                     1 
                   
                 
                  
                 
                     
                 
                  
                 
                   
                      
                     
                       
                         r 
                         
                           j 
                           , 
                           j 
                         
                       
                        
                       
                         ( 
                         τ 
                         ) 
                       
                     
                      
                   
                   2 
                 
               
             
           
         
       
     
     The tradeoff for selecting sets with good CC properties is a degradation in the AC properties. In the end, it selects Q∈{0, 1, 2, . . . , Q−1} number of cyclic-shift values have lower mean square aperiodic cross-correlation with the NR Uu PSS sequences and auto-correlation values for mapping N SL-SSID   (2) ∈{0, 1, 2, . . . , Q−1} for SL PSS sequences. 
     One advantage for SL PSS to adopt Uu PSS sequences with different cyclic-shift values is simultaneous detection of Uu and SL PSS via fast Hadamard transform (FHWT). 
     The SL PSS m-sequence, s={s(n)} n=0, . . . , 126, is generated from distinct primitive polynomial, e.g., f(x)=x 7 +x 6 +1 other than using NR Uu PSS polynomial f(x)=x 7 +x 4 +1. The initial state can be set as any not zero vector such as [1 1 0 0 1 1 1]=[s(0) s(1) s(2) . . . s(6)]. The Q different cyclic-shift m-sequences are used for SL PSS sequences. The total number of SL PSS sequences is equal to Q. The sequence dSL-PSS(n) for the SL PSS can be generated according to Eq 1 and Eq 2 with N SL-SSID   (2) ∈{0, 1, 2, . . . , Q−1}, Q≥3, where z is an integer 0&lt;z&lt;p, and p=ceil(127/Q). 
     It is envisaged according to application to select primitive polynomials with less taps (weight) for the generation of the SL PSS m-sequence as the preferred SL PSS sequences. For example, as shown in Table 13 below (polynomial with order 7), the primitive polynomial with minimum taps is f(x)=x 7 +x 3 +1 and f(x)=x 7 +x 6 +1 (taps=2), respectively. The reason selects the primitive polynomial with minimum taps for the SL PSS sequence generation is illustrated as follow: any m-sequence can be generated by a cyclic linear code with coding rate r/N, where r (e.g. r=7) is the order of the polynomial. The parity check matrix of this code depends on the sequence&#39;s primitive polynomial. For example, the parity check matrix for the primitive polynomial f(x)=x 7 +x 6 +1 is written as follows: 
     
       
         
           
             A 
             = 
             
               [ 
               
                 
                   
                     1 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     … 
                   
                   
                     0 
                   
                 
                 
                   
                     0 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     … 
                   
                   
                     0 
                   
                 
                 
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     … 
                   
                 
                 
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     1 
                   
                   
                     … 
                   
                 
                 
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     … 
                   
                 
                 
                   
                     ⋮ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋮ 
                   
                 
                 
                   
                     ⋮ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋮ 
                   
                 
                 
                   
                     ⋮ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋮ 
                   
                 
                 
                   
                     ⋮ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋱ 
                   
                   
                     ⋮ 
                   
                 
                 
                   
                     0 
                   
                   
                     … 
                   
                   
                     … 
                   
                   
                     … 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     1 
                   
                 
               
               ] 
             
           
         
       
     
     The parity check matrix A is with size (N−r)×N. Each column of non-zero elements in the parity matrix A is equal to the taps of the polynomial. Therefore, number of taps in a primitive polynomial is equivalent to the sparsity level in the parity check matrix. The characteristic polynomial of an LFSR generating a maximum-length sequence is a primitive polynomial. However, there are several primitive polynomials for order r but not every primitive polynomial will have minimum taps/weight. In Table 13 below, the primitive polynomial of order 7 is listed. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 13 
               
               
                   
                   
               
               
                   
                   
                 Taps 
               
               
                   
                 Primitive Polynomial 
                 (weight) 
               
               
                   
                   
               
             
            
               
                   
                 ƒ(x) = x 7  + x 3  + 1 
                 2 
               
               
                   
                 ƒ(x) = x 7  + x 6  + 1 
                 2 
               
               
                   
                 ƒ(x) = x 7  + x 4  + x 3  + x 2  + 1 
                 4 
               
               
                   
                 ƒ(x) = x 7  + x 3  + x 2  + x 1  + 1 
                 4 
               
               
                   
                 ƒ(x) = x 7  + x 6  + x 4  + x 1  + 1 
                 4 
               
               
                   
                 ƒ(x) = x 7  + x 6  + x 4  + x 2  + 1 
                 4 
               
               
                   
                 ƒ(x) = x 7  + x 5  + x 4  + x 3  + x 2  + 1 
                 5 
               
               
                   
                 ƒ(x) = x 7  + x 6  + x 5  + x 3  + x 2  + 1 
                 5 
               
               
                   
                   
               
            
           
         
       
     
     It is also envisaged to use different primitive polynomials for SL PSS sequence generation. For example, W different SL PSS sequences are generated from W different primitive polynomial, i.e., f1(x), f2(x), . . . fW(x) and each initial state [s(0) s(1) s(2) . . . s(6)] of m-sequence can be set as any non-zero vector. The sequence dSL-PSS(n) for the SL PSS is defined by: 
         d   SL-PSS ( n )=1-2 s   w ( n ), n=0, . . . , 126,   Eq 3
 
     where w=N SL-SSID   (2) . For example, for W=3, three different primitive polynomials are chosen. These include: f1(x)=x7+x6+1, f2(x)=x7+x3+1, f3(x)=x7+x4+x3+x2+1 for N SL-SSID   (2) =0, N SL-SSID   (2) =1, and N SL-SSID   (2) =2, respectively. 
     Then, the decimation property of m-sequence is applied for SL PSS sequence generation. For example, W different SL PSS sequences are generated from a primitive polynomial f(x) with different decimated factor q w , w∈{0, 1, . . . , W−1}. The sequence d SL-PSS (n) for the SL PSS is defined by: 
         d   SL-PSS ( n )=1-2 s ( q   w   n  mod  N ), n=0, . . . , 126,   Eq 4
 
     where w=N SL-SSID   (2) ∈{0, 1, . . . , W−1} and qw is a positive integer. If q w ∈2i, i is an positive integer for all w then s(qwn mod N) is equivalent to a cyclic-shift of s(n). Therefore, a cyclic-shift of an m-sequence can be treated as an m-sequence when the decimation factor qw∈2i, for example, q w ∈{2, 4, . . . , 2i}. For another example, if qw∈2 i+1, i is an positive integer and gcd(i, r)=1 for all w then m-sequence s(q w n mod N) is a preferred pair with m-sequence s(n) and the periodic cross-correlation between s(q w n mod N) and s(n) are three-valued cross-correlation. 
     A m-sequence s(n) n=0, . . . , 254, i.e., length 255 (28-1) can be used for SL PSS sequence generation. Analog to m-sequence with length 127 (27-1), SL PSS sequence generation can use cyclic-shift of an m-sequences, different primitive polynomial of m-sequences and multiple distinct decimation of an m-sequence. For cyclic-shift of an m-sequence for SL PSS sequence generation, Eqs. 1 and 2 can be extended as: 
         d   SL-PSS ( n )=1-2 s ( m ), n=0, . . . , 254 
         m= ( n+pN   SL-SSID   (2)   +z ) mod 255, 
     where N SL-SSID   (2) ∈{0, 1, 2, . . . , Q−1}, Q≥3, z is an integer 0&lt;z&lt;p, and p=ceil(255/Q). For different primitive polynomial of m-sequences example, for support W=3 ID, three different primitive polynomials are chosen. These include: f 1 (x)=x 8 +x 4 +x 3 +x 2 +1, f 2 (x)= x   8 +x 6 +x 5 +x 3 +1, f 3 (x)=x 8 +x 6 +x 5 +x+1 for N SL-SSID   (2) =0, N SL-SSID   (2) =1, and N LS-SSID   (2) =2, respectively. In Table 14 below, the primitive polynomial of order 8 is listed. A polynomial of Different SL PSS sequences are generated from a primitive polynomial f(x) with different decimated factor qw, w∈{0, 1, . . . , W−1}. For example, length-255 sequence d SL-PSS (n) for the SL PSS is defined by: 
         d   SL-PSS ( n )=1-2 s ( q   w   n  mod  N ), n=0, . . . , 254, 
     where w=N SL-SSID   (2) ∈{0, 1, . . . , W−1} and qw is a positive integer. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 14 
               
               
                   
                   
               
               
                   
                   
                 Taps 
               
               
                   
                 Primitive Polynomial 
                 (weight) 
               
               
                   
                   
               
             
            
               
                   
                 ƒ(x) = x 8  + x 4  + x 3  + x 2  + 1 
                 4 
               
               
                   
                 ƒ(x) = x 8  + x 6  + x 5  + x 3  + 1 
                 4 
               
               
                   
                 ƒ(x) = x 8  + x 6  + x 5  + x + 1 
                 4 
               
               
                   
                 ƒ(x) = x 8  + x 7  + x 3  + x 2  + 1 
                 4 
               
               
                   
                 ƒ(x) = x 8  + x 6  + x 4  + x 3  + x 2  + x 1  + 1 
                 6 
               
               
                   
                 ƒ(x) = x 8  + x 7  + x 6  + x 5  + x 4  + x 2  + 1 
                 6 
               
               
                   
                   
               
            
           
         
       
     
     It is envisaged SL SSS sequence generation can based on Gold sequences or Gold-like sequences. The sequence d SL-SSS (n) for the SL SSS is defined by: 
         d   SL-SSS ( n )=1-2( s   0 ( n+m   0 )● s   1 ( n+m   1 )), n=0, . . . , N−1 N=127 or 255,
 
     where ● can be either modular  2  addition or multiplication operator. The sequence s0(n) and s1(n) are two m-sequences with length either 127 (order 7) or 254 (order 8), respectively. The construction of s0(n) and s1(n) can be based on the following rule: s0(n) and s1(n) are based on different primitive polynomials. For example, s 0 (n) can be based on primitive polynomial f 0 (x)=x 7 +x 6 +1 and s 1 (n) is based on polynomial f 1 (x)=x 7 +x 3 +1 for length 127. Any non-zero vector can be used for the initial value [s(0) s(1) s(2) . . . s(6)] for s0(n) and s1(n). s0(m)=s0((n+m0) mod N) and s1(m)=s1((n+m1) mod N), where 
     
       
         
           
             
               
                 m 
                  
                 0 
               
               = 
               
                 z 
                  
                 
                   ( 
                   
                     
                       Q 
                        
                       
                         ⌊ 
                         
                           
                             N 
                             
                               
                                 S 
                                  
                                 L 
                               
                               - 
                               
                                 S 
                                  
                                 S 
                                  
                                 I 
                                  
                                 D 
                               
                             
                             
                               ( 
                               1 
                               ) 
                             
                           
                           L 
                         
                         ⌋ 
                       
                     
                     + 
                     
                       N 
                       
                         
                           S 
                            
                           L 
                         
                         - 
                         
                           S 
                            
                           S 
                            
                           I 
                            
                           D 
                         
                       
                       
                         ( 
                         2 
                         ) 
                       
                     
                   
                   ) 
                 
               
             
             , 
           
         
       
     
     m1=t(N SL-SSID   (1)  mod L) and N SL-SSID   (1) ∈{0, 1, . . . , Z}. The Q denotes the number of N SL-SSID   (2) , t and z are an arbitrary positive integer. The maximum number of NSL-SSID is equal to Q×L. When s 0 (n) and s 1 (n) are based on current NR SSS polynomial f 0 (x)=x 7 +x 4 +1 and f 1 (x)=x 7 +x+1. In this case, UE can determine from the 
     The sequence dsL-sss(n) for the SL SSS is defined by : 
         d   SL-SSS ( n )=1-2( s   0 ( m   1   n )● s   1 ( m   2   n )), n=0, . . . , N−1 N=127 or 255,
 
     s 0 (n) and s 1 (n) are based on different primitive polynomials. For example, s 0 (n) can be based on primitive polynomial f 0 (x)=x 7 +x 6 +1, and s1(n) is based on polynomial f 1 (x)=x 7 +x 3 +1 for length 127. Any non-zero vector can be used for the initial value [s(0) s(1) s(2) . . . s(6)] for s 0 (n) and s 1 (n). s 0 (m)=s 0 (m 0 n)mod N) and s1(m)=s 1 ((m 1 n)mod N), where 
     
       
         
           
             
               
                 m 
                 0 
               
               = 
               
                 p 
                  
                 o 
                  
                 
                   w 
                    
                   
                     ( 
                     
                       
                         z 
                          
                         
                           ( 
                           
                             
                               Q 
                                
                               
                                 ⌊ 
                                 
                                   
                                     N 
                                     
                                       
                                         S 
                                          
                                         L 
                                       
                                       - 
                                       
                                         S 
                                          
                                         S 
                                          
                                         I 
                                          
                                         D 
                                       
                                     
                                     
                                       ( 
                                       1 
                                       ) 
                                     
                                   
                                   L 
                                 
                                 ⌋ 
                               
                             
                             + 
                             
                               N 
                               
                                 
                                   S 
                                    
                                   L 
                                 
                                 - 
                                 
                                   S 
                                    
                                   S 
                                    
                                   I 
                                    
                                   D 
                                 
                               
                               
                                 ( 
                                 2 
                                 ) 
                               
                             
                           
                           ) 
                         
                       
                       , 
                       2 
                     
                     ) 
                   
                 
               
             
             , 
             
               
 
             
              
             
               
                 m 
                 1 
               
               = 
               
                 po 
                  
                 
                   w 
                    
                   
                     ( 
                     
                       
                         
                           N 
                           
                             
                               S 
                                
                               L 
                             
                             - 
                             SSID 
                           
                           
                             ( 
                             1 
                             ) 
                           
                         
                          
                         
                             
                         
                          
                         mod 
                          
                         
                             
                         
                          
                         L 
                       
                       , 
                       2 
                     
                     ) 
                   
                 
               
             
             , 
             
               
 
             
              
             
               
                 
                   N 
                   
                     
                       S 
                        
                       L 
                     
                     - 
                     
                       S 
                        
                       S 
                        
                       I 
                        
                       D 
                     
                   
                   
                     ( 
                     1 
                     ) 
                   
                 
                 ∈ 
                 
                   
                     { 
                     
                       0 
                       , 
                       1 
                       , 
                       … 
                        
                       
                           
                       
                       , 
                       Z 
                     
                     } 
                   
                    
                   
                       
                   
                    
                   and 
                    
                   
                       
                   
                    
                   
                     pow 
                      
                     
                       ( 
                       
                         x 
                         , 
                         
                             
                         
                          
                         2 
                       
                       ) 
                     
                   
                 
               
               = 
               
                 
                   2 
                   x 
                 
                 . 
               
             
           
         
       
     
     The Q denotes the number of N SL-SSID   (2)  and z is an arbitrary integer. 
     The sequence d SL-SSS (n) n=0, . . . N−1 N=254 used for the SL second synchronization signal is an interleaved concatenation of two length-127 binary sequences, i.e., d SL-SSS (2n)=1−2s 0 (n+m0) and d SL-SSS (2n+1)=1−2s 1 (n+m1) for n=0, . . . , 126. s 0 (n) and s 1 (n) can be based on m-sequence or Gold-sequence. For m-sequence example, s 0 (n) and s 1 (n) can be based on primitive polynomial f 0 (x)=x 7 +x 6 +1, and s 1 (n) is based on primitive polynomial f 1 (x)=x 7 +x 3 +1. For Gold-sequence example, s 0 (n)=xor(g 0 (n), c 0 (n)) and s 1 (n)=xor(g 1 (n),c 1 (n)), where g 0 (n), g 1 (n) c 0 (n) and c_1(n) are m-sequences, respectively. For example, g 0 (n) and c 0 (n) can be constructed with polynomial f(x)=x 7 +x 6 +x 4 +x+1 and x 7 +x 4 +x 3 +x 2 +1. g 0 (n) and c 0 (n) are constructed with polynomial f(x)=x 7 +x 6 +x 4 +x 2  +1 and x 7 +x 3 +x2+x+1. 
     
       
         
           
             
               
                 m 
                 0 
               
               = 
               
                 z 
                  
                 
                   ( 
                   
                     
                       Q 
                        
                       
                         ⌊ 
                         
                           
                             N 
                             
                               
                                 S 
                                  
                                 L 
                               
                               - 
                               
                                 S 
                                  
                                 S 
                                  
                                 I 
                                  
                                 D 
                               
                             
                             
                               ( 
                               1 
                               ) 
                             
                           
                           L 
                         
                         ⌋ 
                       
                     
                     + 
                     
                       N 
                       
                         
                           S 
                            
                           L 
                         
                         - 
                         
                           S 
                            
                           S 
                            
                           I 
                            
                           D 
                         
                       
                       
                         ( 
                         2 
                         ) 
                       
                     
                   
                   ) 
                 
               
             
             , 
             
               
                 m 
                 1 
               
               = 
               
                 t 
                  
                 
                   ( 
                   
                     
                       N 
                       
                         
                           S 
                            
                           L 
                         
                         - 
                         
                           S 
                            
                           S 
                            
                           I 
                            
                           D 
                         
                       
                       
                         ( 
                         1 
                         ) 
                       
                     
                      
                     
                         
                     
                      
                     mod 
                      
                     
                         
                     
                      
                     L 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 N 
                 
                   
                     S 
                      
                     L 
                   
                   - 
                   
                     S 
                      
                     S 
                      
                     I 
                      
                     D 
                   
                 
                 
                   ( 
                   1 
                   ) 
                 
               
               ∈ 
               
                 
                   { 
                   
                     0 
                     , 
                     1 
                     , 
                     … 
                      
                     
                         
                     
                     , 
                     Z 
                   
                   } 
                 
                 . 
               
             
           
         
       
     
     The Q denotes the number of N SL-SSID   (2) , t and z are an arbitrary positive integers. 
     The SL PSS and SSS can be precoded by DFT to support DFT-s-OFDM waveform with size 20 or 24 RBs (or 240/288 Res). 
     Resource Mapping 
     According to even a further aspect of the application, in one embodiment thereof, where the SL PSS length=127 and SL SS block bandwidth is 20 RB, the SL primary synchronization signal can be mapped to the first symbol of the SL SS block. The sequence d SL-PSS (n) and d SL-SSS (n) are mapped to frequency domain depicted in  FIG. 27 . The subcarrier 0 is relative to the start of an SL SS block. SL SSS can be mapped to the last symbol of the SL SS block. The sequence dSL-SSS(n) is mapped to frequency domain is same as dSL-PSS(n). An example for SL SS block with bandwidth 20 RBs is shown in  FIG. 28 . 
     For SL PSS length 255 and SL SS block bandwidth is 24 RB, the SL primary synchronization signal can be mapped to the first symbol of the SL SS block. The sequence d SL-PSS (n) and d SL-SSS (n) are mapped to frequency domain as depicted in  FIG. 29 . 
     SL SSS can be mapped to the last symbol of the SL SS block. The sequence d SL-SSS (n) is mapped to frequency domain in the same way as d SL-PSS (n). An example for SL SS block with bandwidth 24 RBs is shown in  FIG. 30 . 
     For length=127 SL PSS and SL SS block with bandwidth of 24 RB, the SL primary synchronization signal can be mapped to the first symbol of the SL SS block. The sequence d SL-PSS (n) is mapped to frequency domain, as depicted in  FIG. 31 . 
     Another option for length-127 SL PSS and SL SS block with bandwidth of 24 RB, the SL primary synchronization signal can be mapped to the first symbol of the SL SS block. The sequence d SL-PSS (n)(n) is mapped to frequency domain, as depicted in  FIG. 32 . 
     In  FIGS. 31 and 32 , the SL PSS length=127 transmission power and can be doubled for SL PSS length=255 when SL SS block bandwidth=24 RBs. SL SSS can be mapped to the last symbol of the SL SS block. The sequence d SL-SSS (n) is mapped to frequency domain, as depicted in the following  FIG. 33 . An example for SL SS block with bandwidth 24 RBs and length-127 SL PSS and length-255 SL SSS is shown in  FIGS. 34A and 34B . Here, an SL SS block exemplary design and resource mapping for SL SS BW=24 RB when SL PSS length=127 and SL SSS length=255. Further,  FIGS. 34A-B  illustrate an SL block design and resource mapping for SL SS BW=24 RB when SL PSS length=127 and SL SSS length=255. 
     For length=127 SL PSS with SL SS bandwidth of 11 RBs, the SL primary synchronization signal can be mapped to the first and second symbol in an SL SS block as shown in  FIG. 36 . Same sequence d SL-PSS (n), n=0, . . . , 126 applies for both the 1 st  and 2 nd  symbols. The sequence d SL-PSS (n) is mapped to frequency domain, as depicted in  FIGS. 35( a ) and ( b ) . Here, sidelink PSS mapping methods depict a frequency domain when SL SS Block BW is equal to 11 RBs. In  FIG. 35( a ) , the subcarrier 0, 1, 2, 130 and 131 are zero padded. In  FIG. 35( b ) , subcarrier 0, 1, 129,130 and 131 are zero padded, respectively. 
     Similar to SL PSS with length 127 and SL SS bandwidth of 11 RBs for length=127 SL SSS, the SL secondary synchronization signal can be mapped to the first and second symbol in the SL SS block. Same sequence d SL-SSS (n), n=0, . . . , 126 applies for both the third and fourth symbols in the SL SSB as shown in  FIG. 35 . The sequence d SL-SSS (n) n=0, . . . , 126 is mapped to the frequency domain, as depicted in  FIGS. 35( a ) and ( b ) . In  FIG. 35( a ) , the subcarrier 0, 1, 2, 130 and 131 are zero padded. In  FIG. 35( b ) , subcarrier 0, 1, 129, 130 and 131 are zero padded, respectively. 
     In an embodiment, two SL SSS symbols can be placed at the 7th and 8th symbols in the SL SSB as shown in  FIG. 36 . The DMRS for SL PBCH can be placed at the symbol 5,6, 9 and 10 when SL PSS and SSS symbols are located in the 1, 2 and 3, 4 symbol location as shown in  FIG. 36  in SL SSB. The relative RE location for comb-type DMRS can be formulated as 0+v, d+v, 2d+v, . . . , +(M−d)+v, where M denotes the maximum RE location for SL PBCH (PSBCH), d=4 is the distance between two DMRS RE and v=0, . . . , d−1 is mod(SL SSID, d). The first two DMRS symbols are allocated at two continuous symbols as shown in  FIG. 36 . In  FIG. 36 , we assume v=1 for illustration. In this manner, it is facilitated for the frequency offset estimation. 
     In an alternative embodiment as exemplary shown in  FIG. 37 , the DMRS for SL PBCH can be placed at the symbol 3,4, 9 and 10 where the SL PSS is located at 1 and 2 symbol locations and SSS at 6, 7 symbol locations in a slot. The relative RE location for comb-type DMRS can be formulated as 0 +v, d+v, 2d+v, . . . ,+(M−d)+v, where M denotes the maximum RE location for SL PBCH (PSBCH), d=4 is the distance between two DMRS RE and v=0, . . . , d−1 is mod(SL SSID, d). The first two DMRS symbols are allocated at two continuous symbols as shown in  FIG. 37 . For illustrative purposes v=1 is assumed. 
     In an embodiment, the first symbol (symbol 0) in the slot carrying SL SSB can be used for automatic gain control (AGC) training. The symbol 0 can be used to carry extra DMRS or DMRS with SL PBCH symbol. If the symbol 0 is used to carry DMRS, then other RE leaves as blank in the SL SSB bandwidth, e.g., 11 RB. 
     SSB Time-Multiplexing with other SL Physical Channel 
     According to yet even a further aspect of the application of the application, SSB time-multiplexing with other SL physical channels is described. According to a first option, where a slot contains an SL SSB, the SL SSB slot is not time division multiplexed (TDM) with another SL physical channel (e.g., PSCCH, PSSCH and PSFCH). In this option, the V2X UE assume no other SL physical channels are multiplexing with the slot when it is transmitting a SL SSB. 
     According to a second option, where the number of used symbols for SL SSB in a slot are less or equal than 10 or 11 symbols, the last of one or two available symbols in the slot can be used for transmission of SL feedback channel (e.g.: for HARQ ACK/NACK) with time multiplexing (TDM) with SL SSB as shown in  FIG. 38 . In this case, the gap symbol for Tx-Rx switching can be placed at symbol  12  in the slot. The  1 st symbol can be reserved for AGC training. 
     SL SS Block Periodicity 
     Yet even another aspect of the application describes SL SS block periodicity. The Uu initial access procedure, i.e., multiple SS blocks is transmitted with a certain SSB periodicity and each SSB within the burst set is associated with different PRACH resources (e.g., PRACH occasions or preambles). In Uu, the gNB can obtain knowledge about the specific SSB transmissions received by a certain UE. V2X UE use SL SS/PBCH as a timing reference and doesn&#39;t use SL SSB to associate with any PRACH resource like in Uu since PRACH is not used in sidelink. Therefore, it may not need to define SL SS burst set as proposed in Uu. In this way, DMRS for SL PBCH is no need to carry SS block indication like in Uu, thus, it can reduce the blind search effort for monitoring SL SS block indication in DMRS. The scrambling sequence generator for DMRS shall be initialized at the start of each SS/PBCH block occasion with: 
         c   init =2 a ( n   hf +1)(└ N   ID   SL /2┘+1)+2 6 ( n   hf +1)
 
     where n hf =0, 1 denotes half frame indicator (n hf =0 denotes the first half-frame in the frame, n hf =1 is for the first half-frame in the frame). For instance, when a=11, the initialization for DMRS can be expressed as: 
         c   init =2 11 ( n   hf +1)(└N ID   SL /2′+1)+2 6 ( n   hf +1)
 
     The SL SS/PBCH block periodicity can be pre-defined. For example, the SL SS/PBCH block periodicity can be supported in {5 ms, 10 ms, 20 ms, 40 ms, 80 ms, 160 ms, 200 ms}. For example, longer SL SS/PBCH block periodicity such as 160 ms can be supported to reduce SL SS/PBCH overhead. To support of multiple beams transmission of SL SS/PBCH block, we can define the SS/PBCH block transmission periodicity is based on the beam transmission periodicity as shown in  FIG. 39 . Each (different) beam associated with the SL SS/PBCH block repeats with the same periodicity, .e.g. 160 ms. In this sequel, the number of different transmitting beams for SL SS block (SSB) is dependent on V2X UE implementation. In this method, there is no impaction for a V2X UE to detect a SL SSB within a SL SSB transmission periodicity. UE still assume to perform SL SSB detection within the transmission periodicity. 
     The sequence dSL-SSS(n) for the SL SSS can be reused from Uu SSS is defined by: 
         d   SL-SSS ( n )=1−2( s   0 ( n+m 0)● s   1 ( n+m   1 )), n=0, . . . , N−1 N=127,
 
     where ● can be either modular 2 addition or multiplication operator. The sequence s 0 (n) and s 1 (n) are two m-sequences with length either 127 (order 7). The construction of s 0 (n) and s 1 (n) can be based on the following rule: s 0 (n) and s 1 (n) are based on different primitive polynomials. For example, s 0 (n) can be based on primitive polynomial f0(x)=x 7 +x 4 +1 and s 1 (n) is based on polynomial f 1 (x)=x 7 +x+1 for length 127. See Tables 12a and 12b below. The initial value for s0(n) and s1(n) can be set as: 
       [ s   0 (6)  s   0 (5)  s   0 (4)  s   0 (3)  s   0 (2)  s   0 (1)  s   0 (0)]=[0 0 0 0 0 0 1] and 
       [ s   1 (6)  s   1 (5)  s   1 (4)  s   1 (3)  s   1 (2)  s   1 (1)  s   1 (0)]=[0 0 0 0 0 0 1], respectively. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 12-1 
               
               
                   
                   
               
             
            
               
                   
                 The same sequence d SL-SSS (n) shall be 
                 Cyclic shift value  
               
               
                   
                 repeated at symbol location either at symbol 
                 for d SL-PSS   
               
               
                   
                 {3, 4 }or {6, 7}in a slot transmitting the SL 
                 (n) for symbol  
               
               
                   
                 SSS. The sequence d SL-PSS (n) for the SL PSS 
                 1, 2 location in  
               
               
                   
                 can choose a cyclic-shift property of m- 
                 SL SSB slot 
               
               
                   
                 sequence The SL PSS m-sequence, s(n), can 
                   
               
               
                   
                 be generated from polynomial ƒ(x) = x 7  + 
                   
               
               
                   
                 x 4  + 1 which is same as NR Uu PSS but 
                   
               
               
                   
                 with different cyclic-shift. For a sequence of 
                   
               
               
                   
                 length 127 , m-sequence, s = {s(n)}n = 
                   
               
               
                   
                 0, ..., 126, is generated from the primitive 
                   
               
               
                   
                 polynomial ƒ(x) = x 7  + x 4  + 1 , and 
                   
               
               
                   
                 with initial state of [1 1 1 0 1 1 0] = 
                   
               
               
                   
                 [s(6) s(5) s(4) ... s(0)]. The sequence d SL-   
                   
               
               
                   
                   PSS (n) for the SL PSS symbol location 1 and 2 
                   
               
               
                   
                 in a slot can be either using a same or 
                   
               
               
                   
                 different cyclic shift value. The cyclic value 
                   
               
               
                   
                 for d SL-PSS  (n) can be choose from the 
                   
               
               
                   
                 following values {22, 65, 87}to have lower 
                   
               
               
                   
                 cross-correlation value with Uu PSS and SSS 
                   
               
               
                   
                 sequences. If two symbols of SL PSS apply 
                   
               
               
                   
                 with two different cyclic shift value 
                   
               
               
                   
                 respectively. The following table is suggested 
                   
               
               
                   
                 for N (2)   ID  mapping with the cyclic value for 
                   
               
               
                   
                 d SL-PSS  (n) at symbol 1 and 2 in a SL SSB slot. 
                   
               
               
                   
                 N (2)   ID   
                   
               
               
                   
                 0 
                 {22} 
               
               
                   
                 1 
                 {65} 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 12-2 
               
               
                   
                   
               
               
                   
                   
                 Cyclic shift value for d SL-PSS  (n) for 
               
               
                   
                 N (2)   ID   
                 symbol 1, 2 location in SL SSB slot 
               
               
                   
                   
               
             
            
               
                   
                 0 
                 {12, 65} 
               
               
                   
                 1 
                 {34, 87} 
               
               
                   
                   
               
            
           
         
       
     
     N ID   (1)  can choose from 0 to 335 for dSL-SSS(n). Therefore, total N ID   SL =2×336=672 SL SSID are supported. 
     While the systems and methods have been described in terms of what are presently considered to be specific aspects, the application need not be limited to the disclosed aspects. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures. The present disclosure includes any and all aspects of the following claims.