Physical Random Access Channel Enhancements in New Radio

A UE may transmit a message comprising information regarding one or more physical random access channel (PRACH) capabilities of the UE to a base station (BS). The UE may then receive, from the BS, signaling comprising an indication of one or more configured PRACH formats supporting the one or more PRACH capabilities. Next, the UE may transmit, using the one or more configured PRACH formats, one or more preambles to the BS in a random access (RACH) procedure. Accordingly, the UE may receive a random access response (RAR) from the base station and further, in response to receiving the RAR, establish a connection with the BS.

FIELD

The present application relates to wireless devices, and more particularly to apparatus, systems, and methods for Physical Random Access Channel (PRACH) enhancements in New Radio.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage. In recent years, wireless devices such as smart phones and tablet computers have become increasingly sophisticated. In addition to supporting telephone calls, many mobile devices now provide access to the internet, email, text messaging, and navigation using the global positioning system (GPS), and are capable of operating sophisticated applications that utilize these functionalities. Additionally, there exist numerous different wireless communication technologies and standards. Some examples of wireless communication standards include GSM, UMTS (associated with, for example, WCDMA or TD-SCDMA air interfaces), LTE, LTE Advanced (LTE-A), HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), IEEE 802.11 (WLAN or Wi-Fi), BLUETOOTH™, etc.

The ever-increasing number of features and functionality introduced in wireless communication devices also creates a continuous need for improvement in both wireless communications and in wireless communication devices. To increase coverage and better  serve the increasing demand and range of envisioned uses of wireless communication, in addition to the communication standards mentioned above, there are further wireless communication technologies under development.

A proposed next telecommunications standard moving beyond the current International Mobile Telecommunications-Advanced (IMT-Advanced) Standards is called 5th generation mobile networks or 5th generation wireless systems, or 5G for short (otherwise known as 5G-NR for 5G New Radio, also simply referred to as NR). 5G-NR proposes a higher capacity for a higher density of mobile broadband users, also supporting device-to-device, ultra-reliable, and massive machine communications, as well as lower latency and lower battery consumption, than current LTE standards. Further, the 5G-NR standard may allow for less restrictive UE scheduling as compared to current LTE standards. Consequently, efforts are being made in ongoing developments of 5G-NR to take advantage of higher throughputs possible at higher frequencies. Accordingly, improvements in the field in support of such development and design are desired.

SUMMARY

Embodiments relate to apparatuses, systems, and methods for Physical Random Access Channel (PRACH) enhancements in New Radio.

According to some embodiments, a UE may transmit a message comprising information regarding one or more physical random access channel (PRACH) capabilities of the UE to a base station (BS). The UE may then receive, from the BS, signaling comprising an indication of one or more configured PRACH formats supporting the one or more PRACH capabilities. Next, the UE may transmit, using the one or more configured PRACH formats, one or more preambles to the BS in a random access (RACH) procedure. Accordingly, the UE may receive a random access response (RAR) from the base station and further, in response to receiving the RAR, establish a connection with the BS.

In some embodiments, the one or more PRACH capabilities may include at least one of PRACH repetition, PRACH frequency hopping, or PRACH beam sweeping. According to some embodiments, there may be a one to multiple or multiple to one mapping between synchronization signal blocks (SSBs) and RACH occasions (ROs). Additionally or alternatively, a first message (MsgA) may include the one or more preambles and one or more physical uplink shared channel (PUSCH) transmissions. According to some embodiments, the number of MsgA preambles may be configured separately from the MsgA PUSCH repetitions. Additionally or alternatively, the offset between a first MsgA PUSCH of the one or more PUSCH transmissions and a last MsgA preamble of the one or more preambles may be configured by the base station. According to some embodiments, the MsgA may be transmitted as a whole channel structure. In some embodiments, the UE may be further configured to determine a RAR window using one or more random access-radio network temporary identifiers (RA-RNTIs).

According to some embodiments, the one or more preambles may be transmitted at a maximum power level. Additionally or alternatively, the one or more preambles may be transmitted at increasing power levels. In some embodiments, a starting subframe periodicity of the one or more preambles may be greater than or equal to the number of the one or more preambles. Additionally or alternatively, the UE may configure a reference signal received power (RSRP) threshold for selecting PRACH resources for repetition. In some embodiments, the one or more PRACH formats may include PRACH format B4 and a predefined number of PRACH repetitions may be indicated by a system information block 1 (SIB1).

According to further embodiments, the UE may be configured for PRACH frequency hopping in at least one of a configured frequency region and configured bandwidth part (BWP), wherein a frequency hopping offset may be indicated in the one or more preambles. Additionally or alternatively, a frequency hopping time interval or pattern may be configured based on at least one of a per-slot basis, a per-subframe basis, a per-radio frame basis, and a per-half PRACH repetition basis.

In some embodiments, the UE may be configured to determine a number of beams to be swept based on one or more synchronization signal block (SSB) reference signal received power (RSRP) measurements. Additionally or alternatively, there may be a multiple to one mapping between synchronization signal blocks (SSBs) and RACH occasions (ROs) wherein one or more beams are swept in an associated period or an associated pattern period.

The techniques described herein may be implemented in and/or used with a number of different types of devices, including but not limited to cellular phones, tablet computers, wearable computing devices, portable media players, and any of various other computing devices.

This Summary is intended to provide a brief overview of some of the subject matter described in this document. Accordingly, it will be appreciated that the above-described

features are merely examples and should not be construed to narrow the scope or spirit of the subject matter described herein in any way. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following Detailed Description, Figures, and Claims.

DETAILED DESCRIPTION

Acronyms

Various acronyms are used throughout the present disclosure. Definitions of the most prominently used acronyms that may appear throughout the present disclosure are provided below:3GPP: Third Generation Partnership ProjectTS: Technical SpecificationRAN: Radio Access NetworkRAT: Radio Access TechnologyUE: User EquipmentRF: Radio FrequencyBS: Base StationDL: DownlinkUL: UplinkLTE: Long Term EvolutionNR: New Radio5GS: 5G System5GMM: 5GS Mobility Management5GC: 5G Core NetworkIE: Information ElementITS: Intelligent Transportation SystemRRC: Radio Resource ControlRACH: Random Access ChannelPRACH: Physical Random Access ChannelFR2: Frequency Range 2RAR: Random Access ResponseRA-RNTI: Random Access—Radio Network Temporary IdentifierRLC: Radio Link ControlRSRP: Reference Signal Received PowerNW: NetworkNAS: Non-Access StratumSIB1: System Information Block-1SSB: Synchronization Signal BlockRO: RACH OccasionTDM: Time Division MultiplexingFDM: Frequency Division MultiplexingSFN: System Frame NumberCFRA: Contention Free Random AccessPDCCH: Physical Downlink Control ChannelPUSCH: Physical Uplink Shared ChannelBWP: Bandwidth PartRB: Resource BlockCG: Configured GrantDG: Dynamic GrantPDCP: Packet Data Convergence Protocol

Terms

FIG.1illustrates a simplified example wireless communication system, according to some embodiments. It is noted that the system ofFIG.1is merely one example of a possible system, and that features of this disclosure may be implemented in any of various systems, as desired.

The base station (BS)102A may be a base transceiver station (BTS) or cell site (a “cellular base station”), and may include hardware that enables wireless communication with the UEs106A through106N.

As shown, the base station102A may also be equipped to communicate with a network100(e.g., a core network of a cellular service provider, a telecommunication network such as a public switched telephone network (PSTN), and/or the Internet, among various possibilities). Thus, the base station102A may facilitate communication between the user devices and/or between the user devices and the network100. In particular, the cellular base station102A may provide UEs106with various telecommunication capabilities, such as voice, SMS and/or data services.

In some embodiments, base station102A may be a next generation base station, e.g., a 5G New Radio (5G NR) base station, or “gNB”. In some embodiments, a gNB may be connected to a legacy evolved packet core (EPC) network and/or to a NR core (NRC) network. In addition, a gNB cell may include one or more transition and reception points (TRPs). In addition, a UE capable of operating according to 5G NR may be connected to one or more TRPs within one or more gNBs.

FIG.2illustrates user equipment106(e.g., one of the devices106A through106N) in communication with a base station102, according to some embodiments. The UE106may be a device with cellular communication capability such as a mobile phone, a hand-held device, a computer or a tablet, or virtually any type of wireless device.

FIG.3—Block Diagram of a UE

FIG.3illustrates an example simplified block diagram of a communication device106, according to some embodiments. It is noted that the block diagram of the communication device ofFIG.3is only one example of a possible communication device. According to embodiments, communication device106may be a user equipment (UE) device, a mobile device or mobile station, a wireless device or wireless station, a desktop computer or computing device, a mobile computing device (e.g., a laptop, notebook, or portable computing device), a tablet and/or a combination of devices, among other devices. As shown, the communication device106may include a set of components300configured to perform core functions. For example, this set of components may be implemented as a system on chip (SOC), which may include portions for various purposes. Alternatively, this set of components300may be implemented as separate components or groups of components for the various purposes. The set of components300may be coupled (e.g., communicatively; directly or indirectly) to various other circuits of the communication device106.

For example, the communication device106may include various types of memory (e.g., including NAND flash310), an input/output interface such as connector I/F320(e.g., for connecting to a computer system; dock; charging station; input devices, such as a microphone, camera, keyboard; output devices, such as speakers; etc.), the display360, which may be integrated with or external to the communication device106, and cellular communication circuitry330such as for 5G NR, LTE, GSM, etc., and short to medium range wireless communication circuitry329(e.g., Bluetooth™ and WLAN circuitry). In some embodiments, communication device106may include wired communication circuitry (not shown), such as a network interface card, e.g., for Ethernet.

The cellular communication circuitry330may couple (e.g., communicatively; directly or indirectly) to one or more antennas, such as antennas335and336as shown. The short to medium range wireless communication circuitry329may also couple (e.g., communicatively; directly or indirectly) to one or more antennas, such as antennas337and338as shown. Alternatively, the short to medium range wireless communication circuitry329may couple (e.g., communicatively; directly or indirectly) to the antennas335and336in addition to, or instead of, coupling (e.g., communicatively; directly or indirectly) to the antennas337and338. The short to medium range wireless communication circuitry329and/or cellular communication circuitry330may include multiple receive chains and/or multiple transmit chains for receiving and/or transmitting multiple spatial streams, such as in a multiple-input multiple output (MIMO) configuration.

The communication device106may further include one or more smart cards345that include SIM (Subscriber Identity Module) functionality, such as one or more UICC(s) (Universal Integrated Circuit Card(s)) cards345.

As shown, the SOC300may include processor(s)302, which may execute program instructions for the communication device106and display circuitry304, which may perform graphics processing and provide display signals to the display360. The processor(s)302may also be coupled to memory management unit (MMU)340, which may be configured to receive addresses from the processor(s)302and translate those addresses to locations in memory (e.g., memory306, read only memory (ROM)350, NAND flash memory310) and/or to other circuits or devices, such as the display circuitry304, short range wireless communication circuitry229, cellular communication circuitry330, connector I/F320, and/or display360. The MMU340may be configured to perform memory protection and page table translation or set up. In some embodiments, the MMU340may be included as a portion of the processor(s)302.

As noted above, the communication device106may be configured to communicate using wireless and/or wired communication circuitry. The communication device106may be configured to transmit a request to attach to a first network node operating according to the first RAT and transmit an indication that the wireless device is capable of maintaining substantially concurrent connections with the first network node and a second network node that operates according to the second RAT. The wireless device may also be configured transmit a request to attach to the second network node. The request may include an indication that the wireless device is capable of maintaining substantially concurrent connections with the first and second network nodes. Further, the wireless device may be configured to receive an indication that dual connectivity with the first and second network nodes has been established.

As described herein, the communication device106may include hardware and software components for implementing the above features for time division multiplexing UL data for NSA NR operations. The processor302of the communication device106may be configured to implement part or all of the features described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition), processor302may be configured as a programmable hardware element, such as an FPGA (Field Programmable Gate Array), or as an ASIC (Application Specific Integrated Circuit). Alternatively (or in addition) the processor302of the communication device106, in conjunction with one or more of the other components300,304,306,310,320,329,330,340,345,350,360may be configured to implement part or all of the features described herein.

Further, as described herein, cellular communication circuitry330and short range wireless communication circuitry329may each include one or more processing elements. In other words, one or more processing elements may be included in cellular communication circuitry330and, similarly, one or more processing elements may be included in short range wireless communication circuitry329. Thus, cellular communication circuitry330may include one or more integrated circuits (ICs) that are configured to perform the functions of cellular communication circuitry330. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of cellular communication circuitry230. Similarly, the short range wireless communication circuitry329may include one or more ICs that are configured to perform the functions of short range wireless communication circuitry32. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of short range wireless communication circuitry329.

FIG.4—Block Diagram of a Base Station

In addition, as described herein, processor(s)404may be comprised of one or more processing elements. In other words, one or more processing elements may be included in processor(s)404. Thus, processor(s)404may include one or more integrated circuits (ICs) that are configured to perform the functions of processor(s)404. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of processor(s)404.

Further, as described herein, radio430may be comprised of one or more processing elements. In other words, one or more processing elements may be included in radio430. Thus, radio430may include one or more integrated circuits (ICs) that are configured to perform the functions of radio430. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of radio430.

FIG.5: Block Diagram of Cellular Communication Circuitry

The cellular communication circuitry330may couple (e.g., communicatively; directly or indirectly) to one or more antennas, such as antennas335a-band336as shown (inFIG.3). In some embodiments, cellular communication circuitry330may include dedicated receive chains (including and/or coupled to, e.g., communicatively; directly or indirectly. dedicated processors and/or radios) for multiple RATs (e.g., a first receive chain for LTE and a second receive chain for 5G NR). For example, as shown inFIG.5, cellular communication circuitry330may include a modem510and a modem520. Modem510may be configured for communications according to a first RAT, e.g., such as LTE or LTE-A, and modem520may be configured for communications according to a second RAT, e.g., such as 5G NR.

In some embodiments, a switch570may couple transmit circuitry534to uplink (UL) front end572. In addition, switch570may couple transmit circuitry544to UL front end572. UL front end572may include circuitry for transmitting radio signals via antenna336. Thus, when cellular communication circuitry330receives instructions to transmit according to the first RAT (e.g., as supported via modem510), switch570may be switched to a first state that allows modem510to transmit signals according to the first RAT (e.g., via a transmit chain that includes transmit circuitry534and UL front end572). Similarly, when cellular communication circuitry330receives instructions to transmit according to the second RAT (e.g., as supported via modem520), switch570may be switched to a second state that allows modem520to transmit signals according to the second RAT (e.g., via a transmit chain that includes transmit circuitry544and UL front end572).

In some embodiments, the cellular communication circuitry330may be configured to establish a first wireless link with a first cell according to a first radio access technology (RAT), wherein the first cell operates in a first system bandwidth and establish a second wireless link with a second cell according to a second radio access technology (RAT), wherein the second cell operates in a second system bandwidth. Further, the cellular communication circuitry330may be configured to determine whether the cellular communication circuitry330has uplink activity scheduled according to both the first RAT and the second RAT and perform uplink activity for both the first RAT and the second RAT by time division multiplexing (TDM) uplink data for the first RAT and uplink data for the second RAT if uplink activity is scheduled according to both the first RAT and the second RAT. In some embodiments, to perform uplink activity for both the first RAT and the second RAT by time division multiplexing (TDM) uplink data for the first RAT and uplink data for the second RAT if uplink activity is scheduled according to both the first RAT and the second RAT, the cellular communication circuitry330may be configured to receive an allocation of a first UL subframe for transmissions according to the first RAT and an allocation of a second UL subframe for transmissions according to the second RAT. In some embodiments, the TDM of the uplink data may be performed at a physical layer of the cellular communication circuitry330. In some embodiments, the cellular communication circuitry330may be further configured to receive an allocation of a portion of each UL subframe for control signaling according to one of the first or second RATs.

As described herein, the modem510may include hardware and software components for implementing the above features or for time division multiplexing UL data for NSA NR operations, as well as the various other techniques described herein. The processors512may be configured to implement part or all of the features described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition), processor512may be configured as a programmable hardware element, such as an FPGA (Field Programmable Gate Array), or as an ASIC (Application Specific Integrated Circuit). Alternatively (or in addition) the processor512, in conjunction with one or more of the other components530,532,534,550,570,572,335and336may be configured to implement part or all of the features described herein.

In addition, as described herein, processors512may include one or more processing elements. Thus, processors512may include one or more integrated circuits (ICs) that are configured to perform the functions of processors512. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of processors512.

As described herein, the modem520may include hardware and software components for implementing the above features for time division multiplexing UL data for NSA NR operations, as well as the various other techniques described herein. The processors522may be configured to implement part or all of the features described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition), processor522may be configured as a programmable hardware element, such as an FPGA (Field Programmable Gate Array), or as an ASIC (Application Specific Integrated Circuit). Alternatively (or in addition) the processor522, in conjunction with one or more of the other components540,542,544,550,570,572,335and336may be configured to implement part or all of the features described herein.

In addition, as described herein, processors522may include one or more processing elements. Thus, processors522may include one or more integrated circuits (ICs) that are configured to perform the functions of processors522. In addition, each integrated circuit may include circuitry (e.g., first circuitry, second circuitry, etc.) configured to perform the functions of processors522.

In some implementations, fifth generation (5G) wireless communication will initially be deployed concurrently with current wireless communication standards (e.g., LTE). For example, dual connectivity between LTE and 5G new radio (5G NR or NR) has been specified as part of the initial deployment of NR. Thus, as illustrated inFIGS.6A-B, evolved packet core (EPC) network600may continue to communicate with current LTE base stations (e.g., eNB602). In addition, eNB602may be in communication with a 5G NR base station (e.g., gNB604) and may pass data between the EPC network600and gNB604. Thus, EPC network600may be used (or reused) and gNB604may serve as extra capacity for UEs, e.g., for providing increased downlink throughput to UEs. In other words, LTE may be used for control plane signaling and NR may be used for user plane signaling. Thus, LTE may be used to establish connections to the network and NR may be used for data services.

FIG.6Billustrates a proposed protocol stack for eNB602and gNB604. As shown, eNB602may include a medium access control (MAC) layer632that interfaces with radio link control (RLC) layers622a-b. RLC layer622amay also interface with packet data convergence protocol (PDCP) layer612aand RLC layer622bmay interface with PDCP layer612b. Similar to dual connectivity as specified in LTE-Advanced Release 12, PDCP layer612amay interface via a master cell group (MCG) bearer to EPC network600whereas PDCP layer612bmay interface via a split bearer with EPC network600.

Additionally, as shown, gNB604may include a MAC layer634that interfaces with RLC layers624a-b. RLC layer624amay interface with PDCP layer622bof eNB602via an X2interface for information exchange and/or coordination (e.g., scheduling of a UE) between eNB602and gNB604. In addition, RLC layer624bmay interface with PDCP layer614. Similar to dual connectivity as specified in LTE-Advanced Release 12, PDCP layer614may interface with EPC network600via a secondary cell group (SCG) bearer. Thus, eNB602may be considered a master node (MeNB) while gNB604may be considered a secondary node (SgNB). In some scenarios, a UE may be required to maintain a connection to both an MeNB and a SgNB. In such scenarios, the MeNB may be used to maintain a radio resource control (RRC) connection to an EPC while the SgNB may be used for capacity (e.g., additional downlink and/or uplink throughput).

NR Preamble

The physical random access channel (PRACH) may be used to carry random access preambles, which may be used for initiation of a random access procedure. In the frequency domain, several subcarriers at both ends of the, e.g., 6, physical resource blocks (PRBs) may not be used to avoid interference with adjacent channels (e.g., PUCCH and/or PUSCH). In the time domain, the cyclic prefix (CP) and guard time (GT) may be used to avoid interference with the previous and next subframes. In some embodiments, the GT may be related to the maximum cell radius. A random access preamble may include a sequence, a CP, and a GT. The sequence, CP, and GT may be defined in Ts (e.g., the basic time unit of the standard, which may be specified as a set number of nanoseconds, such as 32.552 ns) and/or in ms. NR supports scaled PRACH (physical random access channel) numerology. In addition, although increasing subcarrier spacing (SCS) can increase the peak power, it may also reduce the symbol/RACH duration, which may reduce the overall time of the signal transmission.

In some embodiments, the RACH preambles may be interlaced with sounding reference signals (e.g., SRS) in the frequency domain. Accordingly, RACH preambles and SRS may be FDM (frequency-domain multiplexed) together within the same allocation of time-frequency resources. Additionally, instead of using code domain multiplexing (e.g., applicable to the licensed frequency range), frequency domain multiplexing (FDM) may be used. Thus, different groups of PRACH resources may be frequency domain multiplexed. Moreover, within each group, PRACH resources can be further differentiated using CDM. For example, different sequences may be used according to CDM, e.g., cyclic shift of the same ZC sequence in frequency domain.

In some embodiments, the preamble may be transmitted a plurality of times to the base station. Note that this ability to transmit a plurality of times to the base station may be more than was possible using prior methods (e.g., only a single transmission may have been previously possible). For example, the repetition of the RACH preamble may be at a symbol-level, multiple-symbol-level, or segment-level (e.g., this segment could be 2 or 6 symbols). In some embodiments, the repetition factor could be similar order of the interlacing factor M. The overall RACH preamble (including repetition) length can be variable, targeting different cell sizes, and these parameters (including repetition factor) may be configured by the network (or BS) accordingly.

Note that the configuration of the preamble may be configured by the BS. For example, the BS may transmit configuration information that specifies the value of M, the value of u, (e.g., subcarrier spacing) and/or the number of repetitions of the preamble, among other parameters. In one embodiment, the UE may decode this information (e.g., from a broadcast channel, such as while decoding master information blocks (MIBs) or system information blocks (SIBs) prior to transmitting the preamble to the base station. The UE may then transmit the PRACH according to the parameters specified by the information.

In some embodiments, e.g., in NR, PRACH enhancements may include multiple PRACH transmissions using the same beam, multiple PRACH transmissions using different beams, and PRACH enhancements using one or more finer (e.g., narrower) beams. Additionally, further coverage enhancements including PRACH enhancement for frequency range 2 (FR2) involving PRACH repetition using the same or different beams are envisioned.

FIG.7—Method of Enhanced PRACH Procedures in New Radio (NR)

FIG.7illustrates an example flow chart corresponding to a method of enhanced PRACH procedures in New Radio (NR), according to some embodiments.

Aspects of the method ofFIG.7may be implemented by a wireless device, such as the UE(s)106, in communication with one or more base stations (e.g., BS102) as illustrated in and described with respect to the Figures, or more generally in conjunction with any of the computer systems or devices shown in the Figures, among other circuitry, systems, devices, elements, or components shown in the Figures, among other devices, as desired. For example, one or more processors (or processing elements) of the UE (e.g., processor(s)402, baseband processor(s), processor(s) associated with communication circuitry, etc., among various possibilities) may cause the UE to perform some or all of the illustrated method elements. Note that while at least some elements of the method are described in a manner relating to the use of communication techniques and/or features associated with 3GPP specification documents, such description is not intended to be limiting to the disclosure, and aspects of the method may be used in any suitable wireless communication system, as desired. In various embodiments, some of the elements of the methods shown may be performed concurrently, in a different order than shown, may be substituted for by other method elements, or may be omitted. Additional method elements may also be performed as desired. As shown, the method may operate as follows.

In702, the UE may transmit a message reporting a capability of PRACH repetition, frequency hopping, and/or beam sweeping to a base station. For example, the UE may indicate to the base station that it supports a PRACH repetition capability in which one or more preambles are transmitted at multiple RACH occasions (ROs). Additionally or alternatively, the UE may indicate that it supports capabilities of PRACH frequency hopping and/or PRACH beam sweeping. The UE may indicate these one or more enhanced PRACH capabilities via signaling including a report or indication. For example, the UE may indicate to the base station that it is configured to perform reference signal received power (RSRP) measurements for selecting PRACH resources for repetition, according to some embodiments. Additionally or alternatively, the UE may indicate to the base station that it supports PRACH beam sweeping in which it can use RSRP measurements to determine which uplink beams (and neighboring beams) are to be swept. According to some embodiments, the UE may indicate via the message that it supports performing PRACH frequency hopping corresponding to a frequency hopping time interval or pattern.

In704, the UE may receive a response from the base station indicating configured PRACH formats to support the UE's reported PRACH capabilities. In other words, the base station may utilize the information received in702from the UE in order to accommodate the UE's enhanced PRACH capabilities. For example, the base station may, in response to receiving the indication of the UE's PRACH capability, configure certain PRACH formats for the UE to utilize and transmit a response indicating said formats.

In706, the UE may transmit one or more preambles, using at least one of the one or more reported capabilities and one or more PRACH formats, to a base station as part of a random access (RACH) procedure. In some embodiments, the UE may transmit the one or more preambles as part of a random access procedure in a random access channel (RACH) (e.g., a physical RACH (PRACH)). Additionally or alternatively, the RACH procedure may involve combining the one or more preambles with one or more scheduled PUSCH transmissions into a single or first message (MsgA) from the UE. In other words, a first message (MsgA) may include a PRACH preamble and a PUSCH transmission (e.g., MsgA PRACH and MsgA PUSCH respectively). The MsgA PRACH preambles may be transmitted in RACH/PRACH Occasions (ROs) and the PUSCH transmissions may be transmitted in PUSCH Occasions (POs) which may span multiple symbols and physical resource blocks PRBs including optional guard periods and guard bands between consecutive POs, according to some embodiments. Accordingly, having received an indication of supported PRACH formats from the base station, the UE may be able to utilize this information in order to perform certain enhanced PRACH capabilities such as PRACH repetition, PRACH frequency hopping and/or PRACH beam sweeping as part of a RACH procedure.

In708, in response to transmitting the one or more preambles using enhanced PRACH capabilities, the UE may further receive a random access response (RAR) from the base station. In other words, after the UE transmits the one or more preambles (e.g., including MsgA), the UE may wait for a response from the base station (e.g., MsgB). For example, the base station may detect or receive the one or more preambles as part of the MsgA and upon successful decoding of the MsgA PUSCH, the base station may transmit back a random access response (RAR) to the UE indicating said successful reception and decoding of the MsgA. For example, if the base station detects the MsgA and successfully decodes the MsgA PUSCH from the UE, the base station may send back a “successRAR” message to the UE with a contention resolution ID of MsgA. In other words, the response from the base station (e.g., MsgB) may include the random-access response and the contention-resolution message.

In some embodiments, if the base station doesn't detect the MsgA PRACH, a response may not be sent back to the UE. Accordingly, the UE may optionally retransmit the MsgA or perform a fallback four-step RACH procedure. Additionally or alternatively, if the base station detects the MsgA preamble but fails to successfully decode the MsgA PUSCH from the UE, the base station may transmit back a response to the UE indicating the failed decoding attempt and further include a RAPID (random-access preamble ID) and an uplink grant for a MsgA PUSCH retransmission. Accordingly, upon receiving the fallbackRAR, the UE may fall back to four-step RACH with a transmission of Msg3(retransmission of the MsgA PUSCH).

In710, in response to receiving the random access response from the base station, the UE may establish a connection (e.g., an RRC connection) with the base station. Accordingly, the UE may be considered to be in an RRC_Connected state and perform further communications with the base station.

FIG.8A—PRACH Repetition Events Across Multiple RACH Occasions (ROs) for a Single Beam

FIG.8Aillustrates an example of PRACH repetition events across multiple RACH occasions (ROs), according to some embodiments. For example, initially the UE may report the capability of PRACH repetition and/or PRACH frequency hopping to the base station (e.g., gNB). Accordingly, the base station may then configure one or more PRACH formats to support said PRACH repetition.

According to some embodiments, the PRACH may repeated for the same SSB in a time division multiplexed (TDM) manner and the PRACH resource partition may be associated with a synchronization signal block—RACH occasion (SSB-RO). In some embodiments, PRACH may be repeated such that there is a one to multiple mapping between SSBs and ROs. For example, if mapping ROs are time division multiplexed (TDM), dedicated ROs (and associated preambles in the ROs) may be assigned for PRACH repetition, according to some embodiments. Additionally or alternatively, if mapping ROs are frequency division multiplexed (FDM), dedicated preambles in one RO (the RO which may be shared or dedicated) may be assigned for PRACH repetition. In some embodiments, PRACH may be repeated such that there is a multiple to one mapping between SSBs and ROs. For example, dedicated preambles may be utilized in a RO for PRACH repetition. Furthermore, PRACH repetition may be configured to support contention-based preambles as well as non-contention-based preambles, according to some embodiments.

FIG.8Aillustrates multiple ROs (R0#0, RO#1, RO#2, and RO#3) which may be utilized in performing PRACH repetition as part of a RACH procedure. For example, upon transmitting the one or more preambles as part of the MsgA PRACH, the base station may fail to detect or decode the MsgA PUSCH. Accordingly, the UE may attempt to retransmit (e.g., perform PRACH repetition) at the next RO such as RO#1. Moreover, if the base station fails to transmit a successful RAR message to the UE, the UE may subsequently use RO#2 and RO#3 to repeat the PRACH transmissions in order to successfully advance the RACH procedure. According to some embodiments, the UE may be able to utilize certain power control techniques for PRACH repetition. For example, if PRACH repetition is being utilized, a maximum transmission power may be applied for the PRACH such that the PRACH repetitions are transmitted at a specific or designated power. Additionally or alternatively, power ramping may be applied to the PRACH repetitions such that the power of the PRACH repetition transmissions are gradually increased from RO#0 to RO#3 (or subsequent ROs).

In some embodiments, the base station may configure the one or more PRACH formats to be PRACH format B4. Furthermore, a reference signal received power (RSRP) threshold may be configured for PRACH repetition selection, according to some embodiments. For example, if the UE measured synchronization signal block (SSB) RSRP is lower than a configured threshold, the UE may select the PRACH resources for repetition. In other words, due to a reduced signal strength the UE may utilize PRACH repetition in order to mitigate transmission issues or reception failures.

Furthermore, the number of PRACH repetitions may be indicated by a system information block (SIB) such as SIB1, according to some embodiments. Additionally or alternatively, a pre-defined set of number of repetitions may be characterized by a parameter such as prach-RepetitionNumber, according to some embodiments. For example, prach-RepetitionNumber may further characterize the number of repetitions to be a within a set of {1, 2, 4, 8, 16}. Additionally or alternatively, PRACH repetition may be configured such that repetitions may occur at predefined PRACH occasions using a parameter such as prach-ConfigurationIndex.

FIG.8B—PRACH Repetition Events Across Multiple System Frame Numbers (SFNs)

FIG.8Billustrates an example of PRACH repetition events across multiple system frame numbers (SFNs), according to some embodiments. For example,FIG.8Billustrates SFN=0, SFN=1, SFN=2, and SFN=3 being utilized for PRACH repetition. Additionally,FIG.8Billustrates ROs which are used for PRACH repetition as well as ROs which are not used for repetition. For example, for a repetition number of four,FIG.8Billustrates four PRACH ROs used for repetition (4, 6, 8, 0) between SFN=0 and SFN=1. Additionally,FIG.8illustrates a subframe offset of two which corresponds to SFN=1 ROs (2, 4, 6, and 8) which are not used for repetition. Accordingly, this PRACH repetition pattern may be continued through SFN=2 and SFN=3 according to these configured parameters. Furthermore, a starting subframe periodicity may be characterized by a parameter such as prach-StartingSubframePeriodicity which may specify the starting subframe as {1, 2, 4, 8, 16, 32, 64, 128, 256}. Additionally or alternatively, the PRACH starting subframe periodicity may be larger than or equal to the number of PRACH repetitions, according to some embodiments. For example, if there are two preambles in the first message (MsgA), then the corresponding starting subframe periodicity may be at least two.

In some embodiments, the starting subframe offset may be expressed in terms of PRACH opportunities and may be characterized by a parameter such as prach-StartingSubframeOffset, where prach-StartingSubframeOffset may be less than or equal to a parameter characterizing the number of PRACH repetitions such as prach-RepetitionNumber According to some embodiments, the PRACH starting subframe may be characterized by the equation Mprach-StartingSubframePeriodicity+prach-StartingSubframeOffset, where N={0, . . . }. According to some embodiments, a PRACH time-domain resource configuration may be characterized by a parameter such as prach-ConfigurationIndex. Additionally or alternatively, the PRACH repetition pattern may be re-started after 1024 radio frames, the PRACH occasion in the last starting subframe periodicity is transmitted, and/or if the repetition number is smaller than the configured number, according to some embodiments. As one example illustrated byFIG.8B, PRACH repetition has been configured with parameter prach-Configlndex equaling 25, preamble format B4, any SFN, slot numbers {0, 2, 4, 6, 8}, number of repetitions=4, starting subframe periodicity=8, and starting subframe offset=2.

FIG.9—Random Access Channel (RACH) Occasion and Associated Preambles

FIG.9illustrates an example RO and associated random access channel (RACH) preambles, according to some embodiments. More specifically,FIG.9illustrates an example of preamble allocation for repetition in which the RO is shared between contention based 4-step RACH and PRACH repetition.FIG.9also illustrates that two SSBs may be mapped into one RO according to the preamble allocation for PRACH repetition.

According to some embodiments and illustrated byFIG.9, an example RO may include 64 preambles. For example,FIG.9illustrates an RO containing preambles for SSB1 corresponding to a contention based (CB) 4-step RACH procedure, preambles for SSB1 corresponding PRACH repetition, and preambles for contention free RACH (CFRA). Additionally,FIG.9illustrates that the same RO may contain preambles for SSB2 corresponding to a contention based (CB) 4-step RACH procedure, preambles for SSB2 corresponding PRACH repetition, additional preambles for contention free RACH (CFRA), and preambles reserved for other usage for a total of 64 preambles in one RO. Accordingly, for PRACH repetition,FIG.9illustrates how preambles may be allocated such that two SSBs may be mapped into one RO.

For example, for a UE operating in the RRC_CONNECTED state, the preamble used for PRACH repetition (e.g., ra-PreambleIndex) may be provided by PDCCH order such that the RACH occasion used for repetition is indicated by parameter ra-ssb-OccasionMasklndex. Accordingly, the preamble repetition number of ra-Preamblelndex may be determined such that the repetition number is the same as contention based PRACH repetition, according to some embodiments. Additionally or alternatively, the repetition number may be provided by a contention free random access (CFRA) configuration.

According to some embodiments, a UE may support a PRACH frequency hopping capability characterized by a frequency hopping time interval or frequency hopping pattern for PRACH transmissions. For example, the UE may be configured to support PRACH frequency hopping patterns or intervals based on a per-slot, per-subframe, per-radio frame, or per-half-PRACH repetition basis. Additionally or alternatively, the UE may be configured to support PRACH frequency hopping patterns or intervals based on a combination of per-slot, per-subframe, per-radio frame, and per-half-PRACH repetition basis

In some embodiments, the hopping frequency offset for a UE supporting PRACH frequency hopping between two frequency locations may be determined according to the frequency hopping being in a configured PRACH frequency region. For example, a number of PRACH transmission occasions frequency division multiplexed (FDM) in one time instance or period may be msg1-FDM and further characterized by the parameter nRA={1, 2, 4, 8}. Additionally or alternatively, NRBRAmay be characterized as the PRACH allocation expressed in number of resource blocks (RBs) for a physical uplink shared channel (PUSCH). According to some embodiments, the msg1-frequencyStart may be the lowest PRACH transmission occasion in the frequency domain with respect to the lowest RB of the bandwidth part (BWP) and may be characterized by the parameter nRAstart. Accordingly, for a subframe, radio frame, or slot i: if i=0, RBstart=nRAstart+NRBRA*k where k=0, 1, 2, . . . nRA−1. Additionally or alternatively if

According to some embodiments, the hopping frequency offset for a UE supporting PRACH frequency hopping between two frequency locations may be determined according to the frequency hopping being in a configured bandwidth part (BWP). Accordingly, for a subframe, radio frame, or slot is i: if i=0, RBstart=nRAstart+NRBRA*k where k=0, 1, 2, . . . nRA−1. Additionally or alternatively, if i=1, RBstart=(nRAstart+NRBRA*k+RBoffset)mod(NNWPsize) where k=0, 1,2, . . . nRA−1, NZ, is the size of the BWP, and RBoffsetmay be characterized as

or be configured by the network.

According to some embodiments involving PRACH repetition and frequency hopping, the UE may determine the random access response (RAR) window. In some embodiments, the UE may start the ra-Response Window parameter at the first PDCCH occasion from the end of the last random access preamble transmission in the repetition. Accordingly, the random access—radio network temporary identifier (RA-RNTI) may be determined according each repetition. More specifically, the UE may attempt to use different RA-RNTIs from the first preamble transmission to the last preamble transmission in order to detect a RAR message. Accordingly, once the RAR has been detected, the UE may stop monitoring the RAR. Additionally or alternatively, the UE may start the ra-Response Window parameter at the first PDCCH occasion from the end of the first random access preamble transmission in the repetition. Accordingly, the RA-RNTI may be determined according to last preamble transmission

In some embodiments involving PRACH frequency hopping, the UE may determine the RA-RNTI by applying an identifier such as f_id to the respective PRACH occasion before the frequency hopping is initiated. Accordingly, the RA-RNTI may be calculated as RA−RNTI=1+sid+14*tid+14*80*fid+14*80*8* ulcarrieridwhere fidis the index of PRACH occasion in the frequency domain wherein 0≤fid<8, sidis the index of the first OFDM symbol of the PRACH occasion wherein 0≤sid<14, and tidis the index of the first slot of the PRACH occasion in a system frame wherein 0≤tid<80 and the subcarrier spacing configuration μ has a configured value used to determine tid.

FIG.10—PRACH Beam Sweeping for Multiple ROs

FIG.10illustrates an example of PRACH beam sweeping across multiple ROs, according to some embodiments. More specifically,FIG.10illustrates RO #0, RO #1, RO #2, and RO #3 which may correspond to different UL beams. As one example, when a UE performs beam sweeping as part of a RACH procedure, the UE may perform SSB RSRP measurements and determine that RO#2 and its associated beam has the strongest or highest RSRP signal. Accordingly, the number of beams to be swept may be determined by the uplink (UL) beam associated with the strongest measured SSB RSRP (e.g., RO#2) as well as two additional beams associated with RO#2′s neighboring SSBs. In other words, if the UE determines that RO#2 has the strongest RSRP, it may sweep the beams associated with RO#2 in addition to neighbors RO#1 and RO#3.

According to some embodiments, a RSPR threshold may be configured for PRACH beam sweeping. For example, if the UE measured SSB RSRP is lower than the threshold, the UE may select the PRACH resources for repetition. In other words, the UE may use the threshold to determine the strongest beam and its closest neighboring beams to perform the PRACH. Additionally or alternatively, the UE may determine that all UL beams are to be swept for the multiple ROs associated with the PRACH(s).

Accordingly, the PRACH may be repeated for the same SSB in a time division multiplexing (TDM) manner such that the PRACH resource partition is according to a SSB-RO association. In some embodiments, the SSB-RO association may be characterized by a one to multiple mapping between SSB and RO such that preambles in one RO may be assigned for PRACH beam sweeping and the RO can be shared or configured as a dedicated preamble. Additionally or alternatively, the SSB-RO association may be characterized by a multiple to one mapping between SSB and RO such the beam is swept in an association period, an association pattern period (e.g., 160 milliseconds). In some embodiments, PRACH beam sweeping may not be allowed and/or performed in a multiple to one mapping between an SSB and RO.

According to some embodiments involving PRACH beam sweeping, the UE may determine the random access response (RAR) window. For example, the UE may start the ra-ResponseWindow at the first PDCCH occasion from the end of the last random access preamble transmission in the repetition. Moreover, the RA-RNTI may be determined according to each beam swept in a different time instance. In other words, the UE may utilize different RA-RNTIs from the first preamble transmission to the last preamble transmission to detect the RAR message. Since only one RAR may be expected to be received by the UE via the specific RA-RNTI, the UE may be able to determine the strongest SSB and associated UL beam via the RA-RNTI.

Similarly to PRACH repetition and frequency hopping discussed above, the RA-RNTI may be calculated as RA−RNTI=1+sid+14*tid+14*80*fid+14*80*8ulcarrieridwhere fidwhere lid is the index of PRACH occasion in the frequency domain wherein 0≤fid<8 and tidis the index of the first slot of the PRACH occasion in a system frame wherein 0≤tid<80 and the subcarrier spacing configuration μ has a configured value used to determine tid.

ADDITIONAL INFORMATION

According to some embodiments, for PRACH repetition, frequency hopping, and beam sweeping as described above, MsgA repetition for a2-step RACH procedure may be characterized such that the Msg A includes the MagA preamble and MagA PUSCH. Accordingly, the MsgA preamble and MsgA PUSCH may perform repetition separately. For example, the number of MsgA preambles may be configured separately from the number of MsgA PUSCH repetitions. Accordingly, the MsgA preamble may only be transmitted in PRACH occasions and the offset between the first Msg PUSCH and the last MsgA preamble may be configured by the network, according to some embodiments.

In some embodiments, frequency hopping may be separately configured for the MsgA preamble(s) and MsgA PUSCH(s). For example, MsgA PUSCH repetition maybe configured with Type A PUSCH repetition or Type B PUSCH repetition. In some embodiments, if a MsgA PUSCH collides with another UL transmission or downlink DL reception, the UE may be configured such that existing configured grant (CG) or dynamic grant (DG) PUSCH collision dropping may be re-used for MsgA PUSCH repetition. Additionally or alternatively, other MsgA PUSCH configurations for repetition may re-use existing MsgA PUSCH configuration for a 2-step RACH procedure.

According to some embodiments, for PRACH repetition, frequency hopping, and beam sweeping as described above, MsgA repetition for a 2-step RACH procedure may be characterized such that the MsgA is characterized as a whole channel structure to perform repetition. For example, the repetition number of MsgA preambles and MsgA PUSCH(s) may be configured together such that the MsgA preamble repetition is only transmitted in PRACH occasions. Moreover, if a MsgA PUSCH experiences a collision with another UL transmission, that MsgA PUSCH may be dropped, according to some embodiments.

Note that while various embodiments described herein may relate to 5G/NR, they may be extended to any set of wireless communication, including LTE, GSM, CDMA, etc.