Patent Publication Number: US-2022225431-A1

Title: Method and apparatus for random access

Description:
FIELD OF THE INVENTION 
     The present disclosure generally relates to communication networks, and more specifically, to method and apparatus for random access. 
     BACKGROUND 
     This section introduces aspects that may facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art. 
     Communication service providers and network operators have been continually facing challenges to deliver value and convenience to consumers by, for example, providing compelling network services and performance. With the rapid development of networking and communication technologies, wireless communication networks such as long-term evolution (LTE) and new radio (NR) networks are expected to achieve high traffic capacity and end-user data rate with lower latency. In order to connect to a network node, a random access (RA) procedure may be initiated for a terminal device. In the RA procedure, system information (SI) and synchronization signals (SS) as well as the related radio resource and transmission configuration can be informed to the terminal device by control information from the network node. The RA procedure can enable the terminal device to establish a session for a specific service with the network node. Thus, it is desirable to enhance the configuration and performance of the RA procedure. 
     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 identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
     A wireless communication network such as a NR/5G network may be able to support flexible network configuration. Various signaling approaches (e.g., a four-step approach, a two-step approach, etc.) may be used for a RA procedure of a terminal device to set up a connection with a network node. For the RA procedures using different signaling approaches, separate radio resources need to be configured so that a terminal device performing a RA procedure such as a four-step RA procedure can be distinguished from a terminal device performing another RA procedure such as a two-step RA procedure. For a RA procedure, there may be a specific association of signaling transmissions, for example, an association between a synchronization signal and physical broadcast channel block (which is also known as a SS/PBCH block or SSB for short) and a time-frequency physical random access channel (PRACH) occasion (which is also known as a RA occasion). It may be desirable to configure the association between signaling transmissions more flexibly and efficiently for different RA procedures. 
     Various embodiments of the present disclosure propose a solution for RA, which can support a flexible configuration for a RA procedure such as a two-step RA procedure, for example, by providing flexibility for the SSB to RA occasion and preamble mapping, so as to save signaling overhead while avoiding significant impact on other RA procedure such as a four-step RA procedure. 
     It can be realized that the terms “random access occasion (RO)”, “random access channel (RACH) occasion” or “PRACH occasion” mentioned herein may refer to a time-frequency resource usable for the preamble transmission in a RA procedure, which may also be referred to as “RA occasion”. These terms may be used interchangeably in this document. 
     According to a first aspect of the present disclosure, there is provided a method performed by a network node. The method comprises determining an association between an SSB and a RA occasion in a two-step RA procedure, based at least in part on whether RA resource is shared by the two-step RA procedure and a four-step RA procedure. In the two-step RA procedure, a preamble and a physical uplink shared channel (PUSCH) may be transmitted respectively at the RA occasion and a PUSCH occasion in one message. The method further comprises transmitting information indicating the association to a terminal device. 
     According to a second aspect of the present disclosure, there is provided an apparatus which may be implemented as a network node. The apparatus comprises one or more processors and one or more memories comprising computer program codes. The one or more memories and the computer program codes are configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the first aspect of the present disclosure. 
     According to a third aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the first aspect of the present disclosure. 
     According to a fourth aspect of the present disclosure, there is provided an apparatus which may be implemented as a network node. The apparatus comprises a determining unit and a transmitting unit. In accordance with some exemplary embodiments, the determining unit is operable to carry out at least the determining step of the method according to the first aspect of the present disclosure. The transmitting unit is operable to carry out at least the transmitting step of the method according to the first aspect of the present disclosure. 
     According to a fifth aspect of the present disclosure, there is provided a method performed by a terminal device such as a user equipment (UE). The method comprises receiving, from a network node, information indicating an association between an SSB and a RA occasion in a two-step RA procedure. The association may be based at least in part on whether RA resource is shared by the two-step RA procedure and a four-step RA procedure. Optionally, the method may further comprise performing the two-step RA procedure, according to the information received from the network node. 
     According to a sixth aspect of the present disclosure, there is provided an apparatus which may be implemented as a terminal device. The apparatus comprises one or more processors and one or more memories comprising computer program codes. The one or more memories and the computer program codes are configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the fifth aspect of the present disclosure. 
     According to a seventh aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the fifth aspect of the present disclosure. 
     According to an eighth aspect of the present disclosure, there is provided an apparatus which may be implemented as a terminal device. The apparatus comprises a receiving unit, and optionally a performing unit. In accordance with some exemplary embodiments, the receiving unit is operable to carry out at least the receiving step of the method according to the fifth aspect of the present disclosure. The performing unit is operable to carry out at least the performing step of the method according to the fifth aspect of the present disclosure. 
     In accordance with an exemplary embodiment, the association between the SSB and the RA occasion in the two-step RA procedure may be further based on RA resource configuration for a four-step RA procedure. 
     In accordance with an exemplary embodiment, the association between the SSB and the RA occasion may comprise mapping of the SSB to one or more preambles in the RA occasion. 
     In accordance with an exemplary embodiment, the RA occasion for the two-step RA procedure may be separate from a RA occasion for a four-step RA procedure. 
     In accordance with an exemplary embodiment, the association between the SSB and the RA occasion in the two-step RA procedure may be the same as an association between an SSB and a RA occasion in the four-step RA procedure. 
     In accordance with an exemplary embodiment, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may also indicate: the association between the SSB and the RA occasion in the four-step RA procedure. 
     In accordance with an exemplary embodiment, the association between the SSB and the RA occasion in the two-step RA procedure may be different from the association between the SSB and the RA occasion in the four-step RA procedure. 
     In accordance with an exemplary embodiment, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may comprise a first parameter to indicate:
         a number of SSBs mapped to a RA occasion for the two-step RA procedure; and   a number of preambles mapped to an SSB for the two-step RA procedure.       

     In accordance with an exemplary embodiment, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may further comprise a second parameter to indicate:
         a number of preambles in the RA occasion for the two-step RA procedure, where the preambles in the RA occasion for the two-step RA procedure may comprise contention based preambles.       

     In accordance with an exemplary embodiment, the preambles in the RA occasion for the two-step RA procedure may further comprise contention free preambles. 
     In accordance with an exemplary embodiment, a RA occasion may be shared by the two-step RA procedure and the four-step RA procedure. 
     In accordance with an exemplary embodiment, the shared RA occasion may be configured with separate preambles for the two-step RA procedure and the four-step RA procedure. Optionally, the shared RA occasion may be configured with at least one reserved preamble. 
     In accordance with an exemplary embodiment, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may comprise a third parameter to indicate:
         a number of SSBs mapped, for the two-step RA procedure, to the shared RA occasion.       

     In accordance with an exemplary embodiment, the third parameter may be usable to determine a number of preambles mapped to an SSB for the two-step RA procedure. 
     In accordance with an exemplary embodiment, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may comprise a fourth parameter to indicate:
         a number of preambles for the two-step RA procedure configured in the shared RA occasion.       

     In accordance with an exemplary embodiment, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may comprise a fifth parameter to indicate:
         a number of preambles mapped to an SSB for the two-step RA procedure.       

     In accordance with an exemplary embodiment, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may further comprise a sixth parameter to indicate:
         a total number of preambles for the two-step RA procedure and the four-step RA procedure in the shared RA occasion.       

     In accordance with an exemplary embodiment, the preambles mapped to the SSB for the two-step RA procedure may be configured by using at least a part of contention free preambles initially configured for the four-step RA procedure. 
     In accordance with an exemplary embodiment, the two-step RA procedure and the four-step RA procedure may be configured with the same association between an SSB and the shared RA occasion. 
     According to a ninth aspect of the present disclosure, there is provided a method implemented in a communication system which may include a host computer, a base station and a UE. The method may comprise providing user data at the host computer. Optionally, the method may comprise, at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station which may perform any step of the method according to the first aspect of the present disclosure. 
     According to a tenth aspect of the present disclosure, there is provided a communication system including a host computer. The host computer may comprise processing circuitry configured to provide user data, and a communication interface configured to forward the user data to a cellular network for transmission to a UE. The cellular network may comprise a base station having a radio interface and processing circuitry. The base station&#39;s processing circuitry may be configured to perform any step of the method according to the first aspect of the present disclosure. 
     According to an eleventh aspect of the present disclosure, there is provided a method implemented in a communication system which may include a host computer, a base station and a UE. The method may comprise providing user data at the host computer. Optionally, the method may comprise, at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station. The UE may perform any step of the method according to the fifth aspect of the present disclosure. 
     According to a twelfth aspect of the present disclosure, there is provided a communication system including a host computer. The host computer may comprise processing circuitry configured to provide user data, and a communication interface configured to forward user data to a cellular network for transmission to a UE. The UE may comprise a radio interface and processing circuitry. The UE&#39;s processing circuitry may be configured to perform any step of the method according to the fifth aspect of the present disclosure. 
     According to a thirteenth aspect of the present disclosure, there is provided a method implemented in a communication system which may include a host computer, a base station and a UE. The method may comprise, at the host computer, receiving user data transmitted to the base station from the UE which may perform any step of the method according to the fifth aspect of the present disclosure. 
     According to a fourteenth aspect of the present disclosure, there is provided a communication system including a host computer. The host computer may comprise a communication interface configured to receive user data originating from a transmission from a UE to a base station. The UE may comprise a radio interface and processing circuitry. The UE&#39;s processing circuitry may be configured to perform any step of the method according to the fifth aspect of the present disclosure. 
     According to a fifteenth aspect of the present disclosure, there is provided a method implemented in a communication system which may include a host computer, a base station and a UE. The method may comprise, at the host computer, receiving, from the base station, user data originating from a transmission which the base station has received from the UE. The base station may perform any step of the method according to the first aspect of the present disclosure. 
     According to a sixteenth aspect of the present disclosure, there is provided a communication system which may include a host computer. The host computer may comprise a communication interface configured to receive user data originating from a transmission from a UE to a base station. The base station may comprise a radio interface and processing circuitry. The base station&#39;s processing circuitry may be configured to perform any step of the method according to the first aspect of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure itself, the preferable mode of use and further objectives are best understood by reference to the following detailed description of the embodiments when read in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a diagram illustrating an exemplary four-step RA procedure according to an embodiment of the present disclosure; 
         FIG. 1B  is a diagram illustrating an exemplary PRACH configuration according to an embodiment of the present disclosure; 
         FIGS. 1C-1D  are diagrams illustrating examples of an association between an SSB and a PRACH occasion according to some embodiments of the present disclosure; 
         FIG. 1E  is a diagram illustrating an example of mapping between an SSB and RA preambles according to an embodiment of the present disclosure; 
         FIG. 1F  is a diagram illustrating exemplary preambles per SSB per PRACH occasion according to an embodiment of the present disclosure; 
         FIG. 2  is a diagram illustrating an exemplary two-step RA procedure according to an embodiment of the present disclosure; 
         FIGS. 3A-3C  are diagrams illustrating examples of preamble configuration for Option I according to some embodiments of the present disclosure; 
         FIGS. 3D-3F  are diagrams illustrating examples of preamble configuration for Option II according to some embodiments of the present disclosure; 
         FIG. 4  is a flowchart illustrating a method according to some embodiments of the present disclosure; 
         FIG. 5  is a flowchart illustrating another method according to some embodiments of the present disclosure; 
         FIG. 6  is a block diagram illustrating an apparatus according to some embodiments of the present disclosure; 
         FIG. 7  is a block diagram illustrating another apparatus according to some embodiments of the present disclosure; 
         FIG. 8  is a block diagram illustrating yet another apparatus according to some embodiments of the present disclosure; 
         FIG. 9  is a block diagram illustrating a telecommunication network connected via an intermediate network to a host computer in accordance with some embodiments of the present disclosure; 
         FIG. 10  is a block diagram illustrating a host computer communicating via a base station with a UE over a partially wireless connection in accordance with some embodiments of the present disclosure; 
         FIG. 11  is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment of the present disclosure; 
         FIG. 12  is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment of the present disclosure; 
         FIG. 13  is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment of the present disclosure; and 
         FIG. 14  is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the present disclosure, rather than suggesting any limitations on the scope of the present disclosure. Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present disclosure should be or are in any single embodiment of the disclosure. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Furthermore, the described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the disclosure. 
     As used herein, the term “communication network” refers to a network following any suitable communication standards, such as new radio (NR), long term evolution (LTE), LTE-Advanced, wideband code division multiple access (WCDMA), high-speed packet access (HSPA), and so on. Furthermore, the communications between a terminal device and a network node in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), 4G, 4.5G, 5G communication protocols, and/or any other protocols either currently known or to be developed in the future. 
     The term “network node” refers to a network device in a communication network via which a terminal device accesses to the network and receives services therefrom. The network node may refer to a base station (BS), an access point (AP), a multi-cell/multicast coordination entity (MCE), a controller or any other suitable device in a wireless communication network. The BS may be, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a next generation NodeB (gNodeB or gNB), a remote radio unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto, a pico, and so forth. 
     Yet further examples of the network node comprise multi-standard radio (MSR) radio equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, positioning nodes and/or the like. More generally, however, the network node may represent any suitable device (or group of devices) capable, configured, arranged, and/or operable to enable and/or provide a terminal device access to a wireless communication network or to provide some service to a terminal device that has accessed to the wireless communication network. 
     The term “terminal device” refers to any end device that can access a communication network and receive services therefrom. By way of example and not limitation, the terminal device may refer to a mobile terminal, a user equipment (UE), or other suitable devices. The UE may be, for example, a subscriber station, a portable subscriber station, a mobile station (MS) or an access terminal (AT). The terminal device may include, but not limited to, portable computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, a mobile phone, a cellular phone, a smart phone, a tablet, a wearable device, a personal digital assistant (PDA), a vehicle, and the like. 
     As yet another specific example, in an Internet of things (IoT) scenario, a terminal device may also be called an IoT device and represent a machine or other device that performs monitoring, sensing and/or measurements etc., and transmits the results of such monitoring, sensing and/or measurements etc. to another terminal device and/or a network equipment. The terminal device may in this case be a machine-to-machine (M2M) device, which may in a 3rd generation partnership project (3GPP) context be referred to as a machine-type communication (MTC) device. 
     As one particular example, the terminal device may be a UE implementing the 3GPP narrow band Internet of things (NB-IoT) standard. Particular examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, or home or personal appliances, e.g. refrigerators, televisions, personal wearables such as watches etc. In other scenarios, a terminal device may represent a vehicle or other equipment, for example, a medical instrument that is capable of monitoring, sensing and/or reporting etc. on its operational status or other functions associated with its operation. 
     As used herein, the terms “first”, “second” and so forth refer to different elements. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises”, “comprising”, “has”, “having”, “includes” and/or “including” as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. The term “based on” is to be read as “based at least in part on”. The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment”. The term “another embodiment” is to be read as “at least one other embodiment”. Other definitions, explicit and implicit, may be included below. 
     Wireless communication networks are widely deployed to provide various telecommunication services such as voice, video, data, messaging and broadcasts. As described previously, in order to connect to a network node such as a gNB in a wireless communication network, a terminal device such as a UE may need to perform a RA procedure to exchange essential information and messages for communication link establishment with the network node. 
       FIG. 1A  is a diagram illustrating an exemplary four-step RA procedure according to an embodiment of the present disclosure. As shown in  FIG. 1A , a UE can detect a synchronization signal (SS) by receiving  101  an SSB (e.g., a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and physical broadcast channel (PBCH)) from a gNB. The UE can decode  102  some system information (e.g., remaining minimum system information (RMSI) and other system information (OSI)) broadcasted in the downlink (DL). Then the UE can transmit  103  a PRACH preamble (message1/msg1) in the uplink (UL). The gNB can reply  104  with a random access response (RAR, message2/msg2). In response to the RAR, the UE can transmit  105  the UE&#39;s identification information (message3/msg3) on physical uplink shared channel (PUSCH). Then the gNB can send  106  a contention resolution message (CRM, message4/msg4) to the UE. 
     In this exemplary procedure, the UE transmits message3/msg3 on PUSCH after receiving a timing advance command in the RAR, allowing message3/msg3 on PUSCH to be received with timing accuracy within a cyclic prefix (CP). Without this timing advance, a very large CP may be needed in order to be able to demodulate and detect message3/msg3 on PUSCH, unless the communication system is applied in a cell with very small distance between the UE and the gNB. Since a NR system can also support larger cells with a need for providing a timing advance command to the UE, the four-step approach is needed for the RA procedure. 
     In the NR system, the time and frequency resource on which a PRACH preamble is transmitted can be defined as a PRACH occasion. Different PRACH configuration schemes may be specified for FR1 (Frequency Range 1) paired spectrum, FR1 unpaired spectrum and FR2 (Frequency Range 2) with unpaired spectrum, respectively. The specified PRACH configuration can be maintained in a PRACH configuration table. The time resource and preamble format for PRACH transmission can be configured by a PRACH configuration index, which indicates a row in a PRACH configuration table. For example, at least part of PRACH configuration for preamble format 0 for FR1 unpaired spectrum is shown in Table 1. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 N t   RA.slot , 
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 number of 
                   
               
               
                   
                   
                   
                   
                   
                   
                 Number of 
                 time-domain 
                   
               
               
                   
                   
                   
                   
                   
                   
                 PRACH 
                 PRACH 
                   
               
               
                 PRACH 
                   
                   
                   
                   
                   
                 slots 
                 occasions 
                 N dur   RA , 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Configuration 
                 Preamble 
                 n SFN  mod x = y 
                 Subframe 
                 Starting 
                 within a 
                 within a 
                 PRACH 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Index 
                 format 
                 x 
                 y 
                 number 
                 symbol 
                 subframe 
                 PRACH slot 
                 duration 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 0 
                 0 
                 16 
                 1 
                 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 1 
                 0 
                 8 
                 1 
                 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 2 
                 0 
                 4 
                 1 
                 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 3 
                 0 
                 2 
                 0 
                 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 4 
                 0 
                 2 
                 1 
                 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 5 
                 0 
                 2 
                 0 
                 4 
                 0 
                 — 
                 — 
                 0 
               
               
                 6 
                 0 
                 2 
                 1 
                 4 
                 0 
                 — 
                 — 
                 0 
               
               
                 7 
                 0 
                 1 
                 0 
                 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 8 
                 0 
                 1 
                 0 
                 8 
                 0 
                 — 
                 — 
                 0 
               
               
                 9 
                 0 
                 1 
                 0 
                 7 
                 0 
                 — 
                 — 
                 0 
               
               
                 10 
                 0 
                 1 
                 0 
                 6 
                 0 
                 — 
                 — 
                 0 
               
               
                 11 
                 0 
                 1 
                 0 
                 5 
                 0 
                 — 
                 — 
                 0 
               
               
                 12 
                 0 
                 1 
                 0 
                 4 
                 0 
                 — 
                 — 
                 0 
               
               
                 13 
                 0 
                 1 
                 0 
                 3 
                 0 
                 — 
                 — 
                 0 
               
               
                 14 
                 0 
                 1 
                 0 
                 2 
                 0 
                 — 
                 — 
                 0 
               
               
                 15 
                 0 
                 1 
                 0 
                 1, 6 
                 0 
                   
                   
                 0 
               
               
                 16 
                 0 
                 1 
                 0 
                 1, 6 
                 7 
                 — 
                 — 
                 0 
               
               
                 17 
                 0 
                 1 
                 0 
                 4, 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 18 
                 0 
                 1 
                 0 
                 3, 8 
                 0 
                 — 
                 — 
                 0 
               
               
                 19 
                 0 
                 1 
                 0 
                 2, 7 
                 0 
                 — 
                 — 
                 0 
               
               
                 20 
                 0 
                 1 
                 0 
                 8, 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 21 
                 0 
                 1 
                 0 
                 4, 8, 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 22 
                 0 
                 1 
                 0 
                 3, 4, 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 23 
                 0 
                 1 
                 0 
                 7, 8, 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 24 
                 0 
                 1 
                 0 
                 3, 4, 8, 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 25 
                 0 
                 1 
                 0 
                 6, 7, 8, 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 26 
                 0 
                 1 
                 0 
                 1, 4, 6, 9 
                 0 
                 — 
                 — 
                 0 
               
               
                 27 
                 0 
                 1 
                 0 
                 1, 3, 5, 7, 9 
                 0 
                 — 
                 — 
                 0 
               
               
                   
               
            
           
         
       
     
     In Table 1, the value of x indicates the PRACH configuration period in number of system frames, and the value of y indicates the system frame within each PRACH configuration period on which the PRACH occasions are configured. For instance, if y is set to 0, then it means that PRACH occasions are only configured in the first frame of each PRACH configuration period. The value in the column “Subframe number” tells on which subframes PRACH occasions are configured. The value in the column “Starting symbol” is the symbol index. 
     In the case of time division duplexing (TDD), semi-statically configured DL parts and/or actually transmitted SSBs can override and invalidate some time-domain PRACH occasions defined in the PRACH configuration table. More specifically, PRACH occasions in the UL part are always valid, and a PRACH occasion within a certain part (e.g., a part with flexible symbols within a NR slot) is valid as long as it does not precede or collide with an SSB in the RACH slot and there are at least N symbols after the DL part and the last symbol of an SSB. For example, N may be set as 0 or 2, depending on the PRACH format and subcarrier spacing. 
       FIG. 1B  is a diagram illustrating an exemplary PRACH configuration according to an embodiment of the present disclosure. In the frequency domain, a NR system can support multiple frequency-multiplexed PRACH occasions on the same time-domain PRACH occasion. This is mainly motivated by the support of analog beam sweeping in the NR system such that the PRACH occasions associated to one SSB are configured at the same time instance but different frequency locations. As shown in  FIG. 1B , the number of PRACH occasions frequency-division multiplexed (FDMed) in one time domain PRACH occasion may be 1, 2, 4, or 8, and the PRACH configuration period may be 10 ms, 20 ms, 40 ms, 80 ms or 160 ms. As mentioned previously, a row in a PRACH/RACH configuration table can specify the time-domain PRACH occasion pattern for one PRACH configuration period. 
     In accordance with an exemplary embodiment, there are up to 64 sequences that can be used as RA preambles per PRACH occasion in each cell. The radio resource control (RRC) parameter such as totalNumberOfRA-Preambles can be used to determine how many of these 64 sequences are used as RA preambles per PRACH occasion in each cell. The 64 sequences may be configured by including firstly all the available cyclic shifts of a root Zadoff-Chu sequence, and secondly in the order of increasing root index, until 64 preambles have been generated for the PRACH occasion. 
     According to some exemplary embodiments, there may be an association between an SSB and a PRACH occasion. For example, one-to-one association between an SSB and a PRACH occasion (e.g., one SSB per PRACH occasion) can be supported in the NR system. Similarly, one-to-many and/or many-to-one association between SSB(s) and PRACH occasion(s) can also be supported in the NR system. 
       FIGS. 1C-1D  are diagrams illustrating examples of an association between an SSB and a PRACH occasion according to some embodiments of the present disclosure. In the example of one SSB per PRACH occasion as shown in  FIG. 1C , SSB0, SSB1, SSB2 and SSB3 are associated with four different PRACH occasions, respectively. In the example of two SSBs per PRACH occasion as shown in  FIG. 1D , SSB0 and SSB1 are associated with a PRACH occasion, and SSB2 and SSB3 are associated with another PRACH occasion. It can be appreciated that the association between an SSB and a PRACH occasion as shown in  FIG. 1C  or  FIG. 1D  is just as an example, and other suitable association between an SSB and a PRACH occasion with a proper PRACH preamble format may also be implemented. 
     In accordance with an exemplary embodiment, a gNB can use different transmission beams to transmit the respective SSBs to a UE. In response to reception of the SSBs from the gNB, the UE can send PRACH preambles to the gNB in an associated PRACH occasion. According to the association between an SSB and a PRACH occasion and the mapping from an SSB to a transmission beam, the gNB can use the PRACH preambles received from the UE to determine its transmission beam preferred by the UE. The gNB can use the determined transmission beam in the DL transmission and optionally in the UL reception. 
     In accordance with some exemplary embodiments, the preambles associated to each SSB can be configured by two RRC parameters ssb-perRACH-OccasionAndCB-PreamblesPerSSB and totalNumberOfRA-Preambles, which may be indicated by an information element (IE) such as RACH-ConfigCommon in a system information block (e.g., SIB1). A specific rule may be defined for mapping an SSB to RA preambles. For example, a UE may be provided with a number N of SSBs associated to one PRACH occasion and a number R of contention based (CB) preambles per SSB per valid PRACH occasion by parameter ssb-perRACH-OccasionAndCB-PrearnblesPerSSB. If N&lt;1, one SSB is mapped to 1/N consecutive valid PRACH occasions and R contention based preambles with consecutive indexes associated with the SSB per valid PRACH occasion start from preamble index 0. If N≥1, R contention based preambles with consecutive indexes associated with SSB n, 0≤n≤N−1, per valid PRACH occasion start from preamble index n·N preamble   total N, where N preamble   total  is provided by parameter totalNumberOfRA-Preambles and is an integer multiple of N. 
       FIG. 1E  is a diagram illustrating an example of mapping between an SSB and RA preambles according to an embodiment of the present disclosure. In this example, the number of PRACH slots in one PRACH configuration period is 2, the number of PRACH occasions in one PRACH slot is 4, and the number of SSBs in one PRACH occasion is 2. As shown in  FIG. 1E , the mapping between an SSB and PRACH preambles may be done by consecutively associating M preambles to each SSB, where M=N preamble   total /N. For instance, the preambles can be taken as follows:
         first, in increasing order of preamble indexes within a single PRACH occasion;   second, in increasing order of frequency resource indexes for frequency multiplexed PRACH occasions; and   third, in increasing order of time.       

       FIG. 1F  is a diagram illustrating exemplary preambles per SSB per PRACH occasion according to an embodiment of the present disclosure. In this embodiment, for each SSB, the associated preambles per PRACH occasion are further divided into two sets for contention based random access (CBRA) and contention free random access (CFRA). The number of contention based (CB) preambles per SSB per PRACH occasion may be signaled by a RRC parameter such as CB-preambles-per-SSB. Preamble indices for CBRA and CFRA are mapped consecutively for one SSB in one PRACH occasion, as shown in  FIG. 1F . 
       FIG. 2  is a diagram illustrating an exemplary two-step RA procedure according to an embodiment of the present disclosure. Similar to the procedure as shown in  FIG. 1A , in the procedure shown in  FIG. 2 , a UE can detect a SS by receiving  201  an SSB (e.g., comprising a PSS, a SSS and PBCH) from a gNB, and decode  202  system information (e.g., remaining minimum system information (RMSI) and other system information (OSI)) broadcasted in the DL. Compared to the four-step approach as shown in  FIG. 1A , the UE performing the procedure in  FIG. 2  can complete random access in only two steps. Firstly, the UE sends  203   a / 203   b  to the gNB a message A (msgA) including RA preamble together with higher layer data such as a RRC connection request possibly with some payload on PUSCH. Secondly, the gNB sends  204  to the UE a RAR (also called message B or msgB) including UE identifier assignment, timing advance information, a contention resolution message, and etc. 
     In the two-step RA procedure, the preamble and msgA PUSCH can be transmitted by the UE in one message called message A. Separate PRACH resources (defined by PRACH occasions and preamble sequences) can be configured for the two-step RA procedure and the four-step RA procedure so that the network can distinguish the legacy UEs performing the four-step RA procedure from the UEs performing the two-step RA procedure. 
     Some agreement may be made regarding PRACH configuration for two-step RA. Considering the relation of PRACH resources between two-step RA and four-step RA, the network may have the flexibility to configure the following options: 
     Option I: separate PRACH occasions for two-step RA and four-step RA; and 
     Option II: shared PRACH occasion but separate preambles for two-step RA and four-step RA. 
     For the four-step RA procedure, the SSB to PRACH occasion and preamble mapping is described in connection with  FIGS. 1C-1F . For the two-step RA procedure, it may be desirable to map an SSB to a PRACH occasion and the corresponding preambles adaptively, according to the selected option (e.g., Option I or Option II) for PRACH configuration. 
     In the proposed solution according to some exemplary embodiments, a network node can indicate an association between signaling transmissions for a two-step RA procedure to a terminal device. In accordance with an exemplary embodiment, the proposed solution may allow a gNB to inform a UE of the SSB to PRACH occasion mapping for a two-step RA procedure. Optionally, the legacy SSB to PRACH occasion and preamble mapping for the four-step RA procedure can be utilized, reused or simply revised for the two-step RA procedure, so as to minimize signaling overhead while providing the flexibility for the SSB to PRACH occasion and preamble mapping without impact on the legacy four-step RA procedure. 
     In accordance with some exemplary embodiments, an association between DL and UL transmissions may be adaptive to a relation between RA occasion configuration schemes for different RA procedures. For example, in the case of Option I where separate PRACH occasions are configured for two-step RA and four-step RA, the SSB to PRACH occasion and preamble mapping rule used for two-step RA can also be used for four-step RA. Alternatively, separate configuration rules for the SSB to PRACH occasion and preamble mapping may be introduced for two-step RA and four-step RA. Alternatively, in the case of Option II where a shared PRACH occasion is configured for two-step RA and four-step RA, the SSB to PRACH occasion and preamble mapping rule used for two-step RA may be defined based at least in part on the rule used for four-step RA. 
       FIGS. 3A-3C  are diagrams illustrating examples of preamble configuration for Option I according to some embodiments of the present disclosure. In the case of Option I, PRACH occasions are separately configured for two-step RA and four-step RA. In accordance with some exemplary embodiments, the same preamble configuration may be used for two-step RA and four-step RA. For example, the preamble configuration may indicate that 16 out of the total 64 preambles are configured for CBRA, where the number of SSBs mapped to a PRACH occasion is 4, as shown in  FIG. 3A . According to an exemplary embodiment, some configuration parameters such as ssb-perRACH-OccasionAndCB-PreamblesPerSSB and totalNumberOfRA-Preambles may be used for both of two-step RA and four-step RA. In this case, no extra signaling is needed by the network to additionally indicate the preamble configuration for two-step RA. Optionally, the parameter totalNumberOfRA-Preambles can be ignored or skipped if no CFRA is supported for two-step RA. 
     In accordance with some exemplary embodiments, separate preamble configuration may be introduced for two-step RA, as shown in  FIG. 3B  and  FIG. 3C . According to an exemplary embodiment, the preamble configuration for two-step RA may be indicated by one or more predefined parameters. For example, a parameter ssb-perRACH-OccasionAndCB-PreamblesPerSSB-2Step can be defined to indicate the number of SSBs mapped to a PRACH occasion for two-step RA and the number of CB preambles for two-step RA mapped to an SSB. In the example of  FIG. 3B , 16 preambles are separately configured for CBRA in a PRACH occasion for two-step RA. 
     Optionally, another parameter totalNumberOfRA-Preambles-2Step can be defined to indicate the total number of preambles used for both CBRA and CFRA in two-step RA. In the example of  FIG. 3C , 16 out of the total 64 preambles are configured for CBRA for two-step RA, and the rest can be used for CFRA if supported. 
     In accordance with some exemplary embodiments, the CFRA may not be expected to be supported for two-step RA. In this case, the parameter totalNumberOfRA-Preambles-2Step can be used for CBRA via making sure that the total number of preambles for the CBRA is the same as the value of the parameter totalNumberOfRA-Preambles-2Step. Optionally, the parameter totalNumberOfRA-Preambles-2Step may not be necessary, and the parameter ssb-perRACH-OccasionAndCB-PreamblesPerSSB-2Step can be used to determine the total number of preambles used for two-step RA. 
     It will be realized that parameters, variables and settings related to the signaling transmission and resource allocation described herein are just examples. Other suitable message settings, the associated configuration parameters and the specific values thereof may also be applicable to implement the proposed methods. 
       FIGS. 3D-3F  are diagrams illustrating examples of preamble configuration for Option II according to some embodiments of the present disclosure. In the case of Option II, a PRACH occasion can be shared by two-step RA and four-step RA. According to some exemplary embodiments, separate preambles may be configured for two-step RA and four-step RA. For example, the preambles for four-step RA per PRACH occasion may be configured such that the value of the four-step RA parameter totalNumberOfRA-Preambles is less than the maximum number of preambles per PRACH occasion (e.g., MaxNumberOfRA-Preambles=64), and the rest preambles (e.g., 64−totalNumberOfRA-Preambles) may be used as the preambles for 2-step RA per PRACH occasion. Optionally, configuration of the SSB to PRACH occasion mapping may be provisioned separately for two-step RA and four-step RA. In this case, the number of SSBs mapped to a PRACH occasion for two-step RA (which may be indicated by a parameter such as ssb-perRACH-Occasion-2Step) may be the same as or different from the number of SSBs mapped to a PRACH occasion for four-step RA. In the example of  FIG. 3D , the preambles per PRACH occasion are divided for two-step RA and four-step RA, where the number of preambles configured for four-step RA is indicated by the parameter totalNumberOfRA-Preambles=56, and the rest 8 preambles are used for two-step RA, with 2 preambles per SSB. 
     In accordance with some exemplary embodiments, a separate parameter for two-step RA (e.g., totalNumberOfRA-Preambles-2step) may be introduced to indicate the number of preambles for two-step RA in a PRACH occasion. Optionally, the preambles for four-step RA per PRACH occasion may be configured such that totalNumberOfRA-Preambles&lt;MaxNumberOfRA-Preambles, and the preambles for two-step RA per PRACH occasion may be configured such that totalNumberOfRA-Preambles-2step&lt;MaxNumberOfRA-Preambles totalNumberOfRA-Preambles. In this case, a subset of the rest preambles (MaxNumberOfRA-Preambles−totalNumberOfRA-Preambles) are used as the preambles for two-step RA per PRACH occasion, and the remaining preamble(s) may be reserved and not used for RA. Thus, some preambles per PRACH occasion may be used for four-step RA, some may be used for two-step RA, and some may be reserved. In the example of  FIG. 3E , the number of preambles configured in a PRACH occasion is MaxNumberOfRA-Preambles=64, the number of preambles configured for four-step RA is totalNumberOfRA-Preambles=56, the number of preambles configured for two-step RA is totalNumberOfRA-Preambles-2step=4, and the rest 4 preambles are reserved and not used for RA. 
     In accordance with some exemplary embodiments, the number of preambles used for both two-step RA and four-step RA per PRACH occasion may be indicated by a parameter such as totalNumberOfRA-Preambles if it is configured. A separate parameter such as CB-preambles-per-SSB-2step may be introduced to indicate the number of CB preambles per SSB for two-step RA, such that the sum of the CB preambles configured for both two-step RA and four-step RA per PRACH occasion is less than or equal to the value of the parameter MaxNumberOfRA-Preambles, or is less than or equal to the value of the parameter totalNumberOfRA-Preambles if it is configured. 
     Optionally, a part of the CFRA preambles initially usable for four-step RA may be configured as the preambles for two-step RA. In this case, a network node such as a gNB needs to avoid using these preambles for four-step CFRA. This can be done, for example via network implementation, or by specifying a rule that the preambles configured or reused for two-step RA (e.g., by defining a parameter such as CB-preambles-per-SSB-2step) are not valid for four-step CFRA. In the example of  FIG. 3F , the number of preambles configured for both two-step RA and four-step RA per PRACH occasion is 64, the number of CBRA preambles configured for four-step RA per SSB per PRACH occasion is CB-preambles-per-SSB=4, the number of CBRA preambles configured for two-step RA per SSB per PRACH occasion is CB-preambles-per-SSB-2step=2, and the rest preambles are for CFRA. 
     It is noted that some embodiments of the present disclosure are mainly described in relation to 5G or NR specifications being used as non-limiting examples for certain exemplary network configurations and system deployments. As such, the description of exemplary embodiments given herein specifically refers to terminology which is directly related thereto. Such terminology is only used in the context of the presented non-limiting examples and embodiments, and does naturally not limit the present disclosure in any way. Rather, any other system configuration or radio technologies may equally be utilized as long as exemplary embodiments described herein are applicable. 
       FIG. 4  is a flowchart illustrating a method  400  according to some embodiments of the present disclosure. The method  400  illustrated in  FIG. 4  may be performed by a network node or an apparatus communicatively coupled to the network node. In accordance with an exemplary embodiment, the network node may comprise a base station such as gNB. The network node can be configured to communicate with one or more terminal devices such as UEs which may be able to support one or more RA approaches such as two-step RA and/or four-step RA. 
     According to the exemplary method  400  illustrated in  FIG. 4 , the network node can determine an association between a DL transmission and an UL transmission (e.g., an association between an SSB and a RA occasion, etc.) in a two-step RA procedure, based at least in part on RA resource configuration for the two-step RA procedure (e.g., based at least in part on whether RA resource is shared by the two-step RA procedure and a four-step RA procedure), as shown in block  402 . As described with respect to  FIG. 2 , in the two-step RA procedure, a preamble and a PUSCH may be transmitted respectively at the RA occasion and a PUSCH occasion in one message (e.g. msgA, etc.). Then the network node can transmit information indicating the association to a terminal device, as shown in block  404 . For example, the information indicating the association may be carried in a broadcast information block (such as SIB1) transmitted to the terminal device from the network node. Optionally, the terminal device may use the information indicating the association between the SSB and the RA occasion in the two-step RA procedure to implement accessing to the network node. 
     In accordance with some exemplary embodiments, the association between the DL transmission and the UL transmission may comprise an association between an SSB and a RA occasion, and/or other association reflecting signaling transmission/resource allocation for the two-step RA procedure. In an exemplary embodiment, the association between the SSB and the RA occasion may comprise mapping of the SSB to one or more preambles in the RA occasion. 
       FIG. 5  is a flowchart illustrating a method  500  according to some embodiments of the present disclosure. The method  500  illustrated in  FIG. 5  may be performed by a terminal device or an apparatus communicatively coupled to the terminal device. In accordance with an exemplary embodiment, the terminal device such as a UE can be configured to communicate with a network node such as a gNB by supporting one or more RA approaches such as two-step RA and/or four-step RA. 
     According to the exemplary method  500  illustrated in  FIG. 5 , the terminal device may receive, from a network node (such as the network node described with respect to  FIG. 4 ), information indicating an association between a DL transmission and an UL transmission (e.g., an association between an SSB and a RA occasion) in a two-step RA procedure, as shown in block  502 . The association may be based at least in part on RA resource configuration for the two-step RA procedure (e.g., based at least in part on whether RA resource is shared by the two-step RA procedure and a four-step RA procedure). Optionally, the terminal device may perform the two-step RA procedure, according to the information received from the network node, as shown in block  504 . 
     In accordance with some exemplary embodiments, the association between the SSB and the RA occasion in the two-step RA procedure may be further based on RA resource configuration (e.g. RA occasion configuration and optionally RA preamble configuration, etc.) for a four-step RA procedure. In an embodiment, the RA resource may comprise a RA occasion and/or one or more associated RA preambles. 
     In accordance with some exemplary embodiments, the RA resource available for the two-step RA procedure may be separate from the RA resource available for the four-step RA procedure. In this case, the two-step RA procedure and the four-step RA procedure may not share the RA resource. In an embodiment, the RA occasion for the two-step RA procedure may be separate from a RA occasion for the four-step RA procedure. According to an exemplary embodiment, the association between the SSB and the RA occasion in the two-step RA procedure may be the same as an association between an SSB and an RA occasion in the four-step RA procedure (e.g., the SSB to RA occasion mapping applicable for both two-step RA and four-step RA as shown in  FIG. 3A ). In an embodiment, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure can also indicate the association between the SSB and the RA occasion in the four-step RA procedure. Thus, some existing parameters defined for the four-step RA procedure can also be used for the two-step RA procedure. 
     In accordance with some exemplary embodiments, the association between the SSB and the RA occasion in the two-step RA procedure may be different from an association between the SSB and the RA occasion in the four-step RA procedure. In this case, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may comprise a first parameter (such as ssb-perRACH-OccasionAndCB-PreamblesPerSSB-2Step described with respect to  FIG. 3B ) to indicate:
         a number of SSBs mapped to a RA occasion for the two-step RA procedure; and   a number of preambles mapped to an SSB for the two-step RA procedure.       

     According to an exemplary embodiment, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may further comprise a second parameter (such as totalNumberOfRA-Preambles-2Step described with respect to  FIG. 3C ) to indicate:
         a number of preambles in the RA occasion for the two-step RA procedure.       

     The preambles in the RA occasion for the two-step RA procedure may comprise CB preambles (e.g., CBRA preambles as shown in  FIG. 3C ). Optionally, the preambles in the RA occasion for the two-step RA procedure may further comprise CF preambles (e.g., CFRA preambles as shown in  FIG. 3C ). 
     In accordance with some exemplary embodiments, the RA resource available for the two-step RA procedure may be shared by the four-step RA procedure. In an embodiment, a RA occasion may be shared by the two-step RA procedure and the four-step RA procedure. In this case, the shared RA occasion may be configured with separate preambles for the two-step RA procedure and the four-step RA procedure (e.g., the preamble configuration as shown in  FIG. 3D - FIG. 3F ). In an embodiment, the shared RA occasion may be configured with at least one reserved preamble (e.g., the preamble configuration as shown in  FIG. 3E ). 
     In accordance with some exemplary embodiments, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may comprise a third parameter (such as ssb-perRACH-Occasion-2Step described with respect to  FIG. 3D ) to indicate:
         a number of SSBs mapped, for the two-step RA procedure, to the shared RA occasion.       

     According to an exemplary embodiment, the third parameter may be usable to determine a number of preambles mapped to an SSB for the two-step RA procedure. For example, the number of preambles mapped to an SSB for the two-step RA procedure can be determined by (MaxNumberOfRA-Preambles−totalNumberOfRA-Preambles)/ssb-perRACH-Occasion-2Step, as described in connection with  FIG. 3D . 
     In accordance with some exemplary embodiments, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may comprise a fourth parameter (such as totalNumberOfRA-Preambles-2step described with respect to  FIG. 3E ) to indicate:
         a number of preambles for the two-step RA procedure configured in the shared RA occasion.       

     In accordance with some exemplary embodiments, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may comprise a fifth parameter (such as CB-preambles-per-SSB-2step described with respect to  FIG. 3E  and  FIG. 3F ) to indicate:
         a number of preambles mapped to an SSB for the two-step RA procedure.       

     In accordance with some exemplary embodiments, the information indicating the association between the SSB and the RA occasion in the two-step RA procedure may further comprise a sixth parameter (such as totalNumberOfRA-Preambles described with respect to  FIG. 3F ) to indicate:
         a total number of preambles for the two-step RA procedure and the four-step RA procedure in the shared RA occasion.       

     In accordance with some exemplary embodiments, the preambles mapped to the SSB for the two-step RA procedure may be configured by using at least a part of CF preambles initially configured for the four-step RA procedure. In this way, some of preambles initially configured for the four-step RA procedure may be reused for the two-step RA procedure. Optionally, the two-step RA procedure and the four-step RA procedure may be configured with the same association between an SSB and the shared RA occasion (e.g., the preamble configuration as shown in  FIG. 3F ). 
     The proposed solution according to one or more exemplary embodiments can enable an UL transmission to be associated with a DL transmission based at least in part on a specified configuration rule for a RA procedure such as a two-step RA procedure. In accordance with some exemplary embodiments, the association between the SSB and the RA occasion (e.g., the SSB to RA occasion and msgA preamble mapping) for the two-step RA procedure can be determined according to a relation between RA resource (e.g., RA occasion) configuration for the two-step RA procedure and RA resource configuration for a four-step procedure (e.g., according to whether the RA resource is shared by the two-step RA procedure and the four-step RA procedure). The configuration rule and parameters of the SSB to RA occasion mapping for the four-step RA procedure may be utilized at least partly to form the configuration rule and parameters of the SSB to RA occasion mapping for the two-step RA procedure, so as to improve flexibility of transmission configuration and enhance resource utilization. 
     The various blocks shown in  FIGS. 4-5  may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). The schematic flow chart diagrams described above are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of specific embodiments of the presented methods. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated methods. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown. 
       FIG. 6  is a block diagram illustrating an apparatus  600  according to various embodiments of the present disclosure. As shown in  FIG. 6 , the apparatus  600  may comprise one or more processors such as processor  601  and one or more memories such as memory  602  storing computer program codes  603 . The memory  602  may be non-transitory machine/processor/computer readable storage medium. In accordance with some exemplary embodiments, the apparatus  600  may be implemented as an integrated circuit chip or module that can be plugged or installed into a network node as described with respect to  FIG. 4 , or a terminal device as described with respect to  FIG. 5 . In such case, the apparatus  600  may be implemented as a network node as described with respect to  FIG. 4 , or a terminal device as described with respect to  FIG. 5 . 
     In some implementations, the one or more memories  602  and the computer program codes  603  may be configured to, with the one or more processors  601 , cause the apparatus  600  at least to perform any operation of the method as described in connection with  FIG. 4 . In other implementations, the one or more memories  602  and the computer program codes  603  may be configured to, with the one or more processors  601 , cause the apparatus  600  at least to perform any operation of the method as described in connection with  FIG. 5 . Alternatively or additionally, the one or more memories  602  and the computer program codes  603  may be configured to, with the one or more processors  601 , cause the apparatus  600  at least to perform more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure. 
       FIG. 7  is a block diagram illustrating an apparatus  700  according to some embodiments of the present disclosure. As shown in  FIG. 7 , the apparatus  700  may comprise a determining unit  701  and a transmitting unit  702 . In an exemplary embodiment, the apparatus  700  may be implemented in a network node such as a gNB. The determining unit  701  may be operable to carry out the operation in block  402 , and the transmitting unit  702  may be operable to carry out the operation in block  404 . Optionally, the determining unit  701  and/or the transmitting unit  702  may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure. 
       FIG. 8  is a block diagram illustrating an apparatus  800  according to some embodiments of the present disclosure. As shown in  FIG. 8 , the apparatus  800  may comprise a receiving unit  801 , and optionally a performing unit  802 . In an exemplary embodiment, the apparatus  800  may be implemented in a terminal device such as a UE. The receiving unit  801  may be operable to carry out the operation in block  502 , and the performing unit  802  may be operable to carry out the operation in block  504 . Optionally, the receiving unit  801  and/or the performing unit  802  may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure. 
       FIG. 9  is a block diagram illustrating a telecommunication network connected via an intermediate network to a host computer in accordance with some embodiments of the present disclosure. 
     With reference to  FIG. 9 , in accordance with an embodiment, a communication system includes a telecommunication network  910 , such as a 3GPP-type cellular network, which comprises an access network  911 , such as a radio access network, and a core network  914 . The access network  911  comprises a plurality of base stations  912   a ,  912   b ,  912   c , such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area  913   a ,  913   b ,  913   c . Each base station  912   a ,  912   b ,  912   c  is connectable to the core network  914  over a wired or wireless connection  915 . A first UE  991  located in a coverage area  913   c  is configured to wirelessly connect to, or be paged by, the corresponding base station  912   c . A second UE  992  in a coverage area  913   a  is wirelessly connectable to the corresponding base station  912   a . While a plurality of UEs  991 ,  992  are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station  912 . 
     The telecommunication network  910  is itself connected to a host computer  930 , which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer  930  may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. Connections  921  and  922  between the telecommunication network  910  and the host computer  930  may extend directly from the core network  914  to the host computer  930  or may go via an optional intermediate network  920 . An intermediate network  920  may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network  920 , if any, may be a backbone network or the Internet; in particular, the intermediate network  920  may comprise two or more sub-networks (not shown). 
     The communication system of  FIG. 9  as a whole enables connectivity between the connected UEs  991 ,  992  and the host computer  930 . The connectivity may be described as an over-the-top (OTT) connection  950 . The host computer  930  and the connected UEs  991 ,  992  are configured to communicate data and/or signaling via the OTT connection  950 , using the access network  911 , the core network  914 , any intermediate network  920  and possible further infrastructure (not shown) as intermediaries. The OTT connection  950  may be transparent in the sense that the participating communication devices through which the OTT connection  950  passes are unaware of routing of uplink and downlink communications. For example, the base station  912  may not or need not be informed about the past routing of an incoming downlink communication with data originating from the host computer  930  to be forwarded (e.g., handed over) to a connected UE  991 . Similarly, the base station  912  need not be aware of the future routing of an outgoing uplink communication originating from the UE  991  towards the host computer  930 . 
       FIG. 10  is a block diagram illustrating a host computer communicating via a base station with a UE over a partially wireless connection in accordance with some embodiments of the present disclosure. 
     Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to  FIG. 10 . In a communication system  1000 , a host computer  1010  comprises hardware  1015  including a communication interface  1016  configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system  1000 . The host computer  1010  further comprises a processing circuitry  1018 , which may have storage and/or processing capabilities. In particular, the processing circuitry  1018  may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer  1010  further comprises software  1011 , which is stored in or accessible by the host computer  1010  and executable by the processing circuitry  1018 . The software  1011  includes a host application  1012 . The host application  1012  may be operable to provide a service to a remote user, such as UE  1030  connecting via an OTT connection  1050  terminating at the UE  1030  and the host computer  1010 . In providing the service to the remote user, the host application  1012  may provide user data which is transmitted using the OTT connection  1050 . 
     The communication system  1000  further includes a base station  1020  provided in a telecommunication system and comprising hardware  1025  enabling it to communicate with the host computer  1010  and with the UE  1030 . The hardware  1025  may include a communication interface  1026  for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system  1000 , as well as a radio interface  1027  for setting up and maintaining at least a wireless connection  1070  with the UE  1030  located in a coverage area (not shown in  FIG. 10 ) served by the base station  1020 . The communication interface  1026  may be configured to facilitate a connection  1060  to the host computer  1010 . The connection  1060  may be direct or it may pass through a core network (not shown in  FIG. 10 ) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware  1025  of the base station  1020  further includes a processing circuitry  1028 , which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station  1020  further has software  1021  stored internally or accessible via an external connection. 
     The communication system  1000  further includes the UE  1030  already referred to. Its hardware  1035  may include a radio interface  1037  configured to set up and maintain a wireless connection  1070  with a base station serving a coverage area in which the UE  1030  is currently located. The hardware  1035  of the UE  1030  further includes a processing circuitry  1038 , which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE  1030  further comprises software  1031 , which is stored in or accessible by the UE  1030  and executable by the processing circuitry  1038 . The software  1031  includes a client application  1032 . The client application  1032  may be operable to provide a service to a human or non-human user via the UE  1030 , with the support of the host computer  1010 . In the host computer  1010 , an executing host application  1012  may communicate with the executing client application  1032  via the OTT connection  1050  terminating at the UE  1030  and the host computer  1010 . In providing the service to the user, the client application  1032  may receive request data from the host application  1012  and provide user data in response to the request data. The OTT connection  1050  may transfer both the request data and the user data. The client application  1032  may interact with the user to generate the user data that it provides. 
     It is noted that the host computer  1010 , the base station  1020  and the UE  1030  illustrated in  FIG. 10  may be similar or identical to the host computer  930 , one of base stations  912   a ,  912   b ,  912   c  and one of UEs  991 ,  992  of  FIG. 9 , respectively. This is to say, the inner workings of these entities may be as shown in  FIG. 10  and independently, the surrounding network topology may be that of  FIG. 9 . 
     In  FIG. 10 , the OTT connection  1050  has been drawn abstractly to illustrate the communication between the host computer  1010  and the UE  1030  via the base station  1020 , without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE  1030  or from the service provider operating the host computer  1010 , or both. While the OTT connection  1050  is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network). 
     Wireless connection  1070  between the UE  1030  and the base station  1020  is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE  1030  using the OTT connection  1050 , in which the wireless connection  1070  forms the last segment. More precisely, the teachings of these embodiments may improve the latency and the power consumption, and thereby provide benefits such as lower complexity, reduced time required to access a cell, better responsiveness, extended battery lifetime, etc. 
     A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection  1050  between the host computer  1010  and the UE  1030 , in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection  1050  may be implemented in software  1011  and hardware  1015  of the host computer  1010  or in software  1031  and hardware  1035  of the UE  1030 , or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection  1050  passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which the software  1011 ,  1031  may compute or estimate the monitored quantities. The reconfiguring of the OTT connection  1050  may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station  1020 , and it may be unknown or imperceptible to the base station  1020 . Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer  1010 &#39;s measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software  1011  and  1031  causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection  1050  while it monitors propagation times, errors etc. 
       FIG. 11  is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to  FIG. 9  and  FIG. 10 . For simplicity of the present disclosure, only drawing references to  FIG. 11  will be included in this section. In step  1110 , the host computer provides user data. In substep  1111  (which may be optional) of step  1110 , the host computer provides the user data by executing a host application. In step  1120 , the host computer initiates a transmission carrying the user data to the UE. In step  1130  (which may be optional), the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step  1140  (which may also be optional), the UE executes a client application associated with the host application executed by the host computer. 
       FIG. 12  is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to  FIG. 9  and  FIG. 10 . For simplicity of the present disclosure, only drawing references to  FIG. 12  will be included in this section. In step  1210  of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In step  1220 , the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In step  1230  (which may be optional), the UE receives the user data carried in the transmission. 
       FIG. 13  is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to  FIG. 9  and  FIG. 10 . For simplicity of the present disclosure, only drawing references to  FIG. 13  will be included in this section. In step  1310  (which may be optional), the UE receives input data provided by the host computer. Additionally or alternatively, in step  1320 , the UE provides user data. In substep  1321  (which may be optional) of step  1320 , the UE provides the user data by executing a client application. In substep  1311  (which may be optional) of step  1310 , the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in substep  1330  (which may be optional), transmission of the user data to the host computer. In step  1340  of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure. 
       FIG. 14  is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to  FIG. 9  and  FIG. 10 . For simplicity of the present disclosure, only drawing references to  FIG. 14  will be included in this section. In step  1410  (which may be optional), in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In step  1420  (which may be optional), the base station initiates transmission of the received user data to the host computer. In step  1430  (which may be optional), the host computer receives the user data carried in the transmission initiated by the base station. 
     In general, the various exemplary embodiments may be implemented in hardware or special purpose chips, circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. 
     As such, it should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be practiced in various components such as integrated circuit chips and modules. It should thus be appreciated that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, where the integrated circuit may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor, a digital signal processor, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this disclosure. 
     It should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be embodied in computer-executable instructions, such as in one or more program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer executable instructions may be stored on a computer readable medium such as a hard disk, optical disk, removable storage media, solid state memory, random access memory (RAM), etc. As will be appreciated by one of skill in the art, the function of the program modules may be combined or distributed as desired in various embodiments. In addition, the function may be embodied in whole or partly in firmware or hardware equivalents such as integrated circuits, field programmable gate arrays (FPGA), and the like. 
     The present disclosure includes any novel feature or combination of features disclosed herein either explicitly or any generalization thereof. Various modifications and adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure.