Message 3 is repeated using the received beam scan and associated beam refinement is used for message 4.

Abstract

The random access procedure between a user equipment (UE) and a base station may include repetition of random access message 3 to improve reception and provide selection of a refined beam. The UE may use a first receive beam to receive random access message 2 transmitted by the base station using a first transmit beam. Random access message 2 instructs the UE to transmit multiple repetitions of random access message 3. The UE may transmit multiple repetitions based on random access message 2. The UE may receive random access message 4 transmitted by the base station using a second transmit beam that is a sub-beam of the first transmit beam, based on the transmission of multiple repetitions. The base station may select the second transmit beam based on at least one of the multiple repetitions.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 980,004, filed February 21, 2020, entitled “MESSAGE 3 REPETITION WITH RECEIVE BEAM SWEEP AND ASSOCIATED BEAM REFINEMENT FOR MESSAGE,” and U.S. Patent Application No. 17 / 178,915, filed February 18, 2021, entitled “MESSAGE 3 REPETITION WITH RECEIVE BEAMSWEEP AND ASSOCIATED BEAM REFINEMENT FOR MESSAGE 4,” which have been assigned to the assignee of this application and are incorporated herein by reference in their entirety. Technical Field

[0003] This disclosure generally relates to wireless communication systems, and more specifically, to random access procedures for establishing wireless communication. Background Technology

[0004] Wireless communication systems are widely deployed to provide a variety of telecommunications services, such as telephone, video, data, messaging, and broadcasting. Typical wireless communication systems employ multiple access technologies that enable communication with multiple users by sharing available system resources. Examples of such multiple access technologies include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single Carrier Frequency Division Multiple Access (SC-FDMA) systems, and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems.

[0005] These multiple access technologies have been adopted in various telecommunications standards to provide a common protocol enabling different wireless devices to communicate at the city, country, region, and even global levels. An example telecommunications standard is 5G New Radio (NR). 5G NR is part of the Continuous Evolution of Mobile Broadband program issued by the 3rd Generation Partnership Project (3GPP), designed to meet new requirements associated with latency, reliability, security, scalability (such as with the Internet of Things (IoT), and other requirements). 5G NR includes services associated with enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communications (URLLC). Some aspects of 5G NR can be based on the 4G Long Term Evolution (LTE) standard. There is a need for further improvements to 5G NR technology.

[0006] In particular, wireless communications can include random access procedures that allow a user equipment (UE) to initiate or resume communications with a base station. Under certain channel conditions, various messages of the random access procedure can not be received correctly, which can delay or prevent the UE from connecting to the base station. Improvements are presented herein. The improvements can also be applied to other multiple access technologies and telecommunication standards that employ these technologies. SUMMARY

[0007] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0008] In one aspect of the disclosure, a method, a computer readable medium, and an apparatus for wireless communications for a user equipment (UE) are provided. The method can include receiving, using a first receive beam, a random access message 2 transmitted by a base station using a first transmit beam, the random access message 2 indicating to the UE to transmit a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions. The method can include transmitting the plurality of repetitions of the random access message 3 based on the random access message 2. The method can include receiving, based on transmitting the plurality of repetitions of the random access message 3, a random access message 4 transmitted by the base station using a second transmit beam that is a sub-beam of the first transmit beam.

[0009] In one aspect, the disclosure provides an apparatus for wireless communication. The apparatus can include a memory that stores computer-executable instructions and at least one processor coupled to the memory and configured to execute the instructions. The at least one processor can be configured to receive, using a first receive beam, a random access message 2 transmitted by a base station using a first transmit beam, the random access message 2 indicating to the UE to transmit a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions. The at least one processor can be configured to transmit the plurality of repetitions of the random access message 3 based on the random access message 2. The at least one processor can be configured to receive, based on transmitting the plurality of repetitions of the random access message 3, a random access message 4 transmitted by the base station using a second transmit beam that is a sub-beam of the first transmit beam.

[0010] In one aspect, the disclosure provides another apparatus for wireless communication. The apparatus can include means for receiving, using a first receive beam, a random access message 2 transmitted by a base station using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions. The apparatus can include means for transmitting the plurality of repetitions of the random access message 3 based on the random access message 2. The apparatus can include means for receiving, based on transmitting the plurality of repetitions of the random access message 3, a random access message 4 transmitted by the base station using a second transmit beam that is a sub-beam of the first transmit beam.

[0011] In one aspect, the disclosure provides a non-transitory computer-readable medium storing computer-executable code. When executed by a processor, the code causes the processor to receive, using a first receive beam, a random access message 2 transmitted by a base station using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions. When executed by the processor, the code causes the processor to transmit the plurality of repetitions of the random access message 3 based on the random access message 2. When executed by the processor, the code causes the processor to receive, based on transmitting the plurality of repetitions of the random access message 3, a random access message 4 transmitted by the base station using a second transmit beam that is a sub-beam of the first transmit beam.

[0012] In one aspect of the disclosure, a method, a computer-readable medium, and an apparatus for wireless communication for a base station are provided. The method can include transmitting, to a UE, a random access message 2 using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions. The method can include receiving, based on the random access message 2, a number of repetitions of the random access message 3 using a different refined beam for each repetition. The method can include transmitting, based on at least one of the plurality of repetitions of the random access message 3, a random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam.

[0013] In one aspect, the disclosure provides an apparatus for wireless communication. The apparatus can include a memory storing computer-executable instructions and at least one processor coupled to the memory and configured to execute the instructions. The at least one processor can be configured to transmit, to a UE, a random access message 2 using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions. The at least one processor can be configured to receive, based on the random access message 2, a number of repetitions of the random access message 3 using a different refined beam for each repetition. The at least one processor can be configured to transmit, based on at least one of the plurality of repetitions of the random access message 3, a random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam.

[0014] In one aspect, the disclosure provides another apparatus for wireless communication. The apparatus can include means for transmitting, to a UE, a random access message 2 using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions. The apparatus can include means for receiving, based on the random access message 2, a number of repetitions of the random access message 3 using a different refined beam for each repetition. The apparatus can include means for transmitting, based on at least one of the plurality of repetitions of the random access message 3, a random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam.

[0015] In one aspect, the disclosure provides a non-transitory computer-readable medium storing computer-executable code that, when executed by a processor, causes the processor to transmit, to a UE, a random access message 2 using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions. The code, when executed by the processor, causes the processor to receive, based on the random access message 2, a number of repetitions of the random access message 3 using a different refined beam for each repetition. The code, when executed by the processor, causes the processor to transmit, based on at least one of the plurality of repetitions of the random access message 3, a random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam.

[0016] To the accomplishment of the foregoing and related aspects, one or more aspects comprise the features recited in the following description and illustrated in the accompanying drawings. The following description and accompanying drawings provide illustrative aspects of one or more aspects. However, the aspects are indicative of but a few of the various ways in which one or more aspects can be employed, and this description is intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network.

[0018] Figure 2A FIG. 2 is a diagram illustrating an example of a first 5G New Radio (NR) frame.

[0019] Figure 2B FIG. 3 is a diagram illustrating an example of downlink (DL) channels within a 5G NR subframe.

[0020] Figure 2C FIG. 4 is a diagram illustrating an example of a second 5G NR frame.

[0021] Figure 2D FIG. 5 is a diagram illustrating an example of uplink (UL) channels within a 5G NR subframe.

[0022] Figure 3 FIG. 6 is a diagram illustrating an example of a base station and a user equipment (UE) in an access network.

[0023] Figure 4 FIG. 7 is a diagram illustrating an example message exchange for a random access channel (RACH) procedure between a base station and a UE in an access network.

[0024] Figure 5 FIG. 8 is a diagram illustrating example resources for repetition of a random access message 3.

[0025] Figure 6 FIG. 9 is a flow diagram of an example method for transmitting a random access message 3 during a RACH procedure.

[0026] Figure 7 FIG. 10 is a flow diagram of an example method for receiving a random access message 3 during a RACH procedure.

[0027] Figure 8 FIG. 11 is a block diagram of an example apparatus for wireless communication, such as a UE.

[0028] Figure 9 FIG. 12 is a block diagram of an example apparatus for wireless communication, such as a base station. DETAILED DESCRIPTION

[0029] The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein can be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts can be practiced without these specific details. In some instances, structures and components are shown in block diagram form in order to avoid obscuring the concepts.

[0030] During a random access channel (RACH) procedure, a transmitted message can not be correctly received under some channel conditions. In particular, when utilizing a high carrier frequency, transmissions can suffer from high path loss. Beamforming between a user equipment (UE) and a base station can overcome the path loss experienced at high carrier frequencies. However, during the RACH procedure, beamforming between the UE and the base station can not be established, for example because the UE has been inactive prior to the RACH procedure.

[0031] The present disclosure addresses this issue of the RACH procedure by utilizing multiple repetitions of a RACH message 3 (also referred to herein as “Msg 3”) that increase the likelihood of correctly receiving the RACH message 3. In some implementations, a base station can transmit a random access message 2 (also referred to herein as “Msg 2”) indicating that the UE is to repeat a random access message 3 using a first transmit beam. Based on the indication, the base station can utilize different beams to receive each of the repetitions of the message 3. For each of the repetitions of the RACH message 3, the base station can measure channel conditions using a respective receive beam associated with receiving the repetition and select one of the receive beams as a refined beam for receiving uplink transmissions from the UE. Further, in some examples, the base station can select a sub-beam of the transmit beam used for the RACH message 2 as a refined beam for transmitting a RACH message 4 (also referred to herein as “Msg 4”). For example, the base station can select the sub-beam within an aperture of the transmit beam that corresponds to the selected receive beam. Selection of the refined beam can increase the likelihood of successfully receiving subsequent messages.

[0032] Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. In some implementations, the described techniques can be used to improve the reliability of a RACH procedure, thereby ensuring establishment of a communication connection between a UE and a base station. For example, by transmitting multiple repetitions of a RACH message 3, a UE can increase the likelihood that a base station successfully receives the RACH message 3, even when the UE is operating near a cell edge of the base station. Further, by selecting a refined beam for transmitting a RACH message 4, the base station can increase the likelihood that the UE successfully receives the RACH message 4. The base station can conserve transmission resources by indicating when or how many repetitions the UE is to transmit.

[0033] Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, among other examples (collectively referred to as "elements"). These elements can be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends on the particular application and design constraints imposed on the overall system.

[0034] By way of example, an element, or any portion of an element, or any combination of elements can be implemented as a "processing system" that includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on a chip (SoC), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system can execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, among other examples, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0035] Accordingly, in one or more examples, the functions described can be implemented in hardware, software, or any combination thereof. If implemented in software, the functions can be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise a random-access memory (RAM), a read-only memory (ROM), an electrically erasable programmable ROM (EEPROM), compact disk ROM (CD-ROM), diskette, hard disk, flash memory, other non-transitory computer-readable medium, a

[0036] Figure 1is a diagram illustrating an example of a wireless communications system and an access network 100. The wireless communications system (also referred to as a wireless wide area network (WWAN)) includes base stations 102, UEs 104, an Evolved Packet Core (EPC) 160, and another core network 190 (e.g., a 5G Core (5GC)). The base stations 102 can include macro cells (high power cellular base stations) or small cells (low power cellular base stations). The macro cells include base stations. The small cells include femtocells, picocells, and microcells.

[0037] In one aspect, one or more of the UEs 104 can include a UE RACH component 140 configured to perform a RACH procedure, including transmitting a random access message 3. The UE RACH component 140 can include a random access response (RAR) reception component 142 configured to receive a random access message 2 indicating a number of repetitions of a random access message 3 using a first receive beam, a repetition component 144 configured to transmit the number of repetitions of the random access message 3, and a contention resolution component 145 configured to receive a random access message 4 transmitted on a refined transmit beam corresponding to a sub-beam of the first receive beam.

[0038] In one aspect, one or more of the base stations 102 can include a base station (BS) RACH component 198 configured to receive repetitions of a random access message 3. The BS RACH component 198 can include a RAR transmission component 146 configured to transmit, via a first transmit beam, a random access message 2 indicating a number of repetitions of a random access message 3 based on an indication in the random access message 2, a beam selection component 148 configured to receive the number of repetitions of the random access message 3 using a different refined beam for each of the repetitions, and a refined transmission component 149 configured to transmit, based on at least one of the number of repetitions of the random access message 3, a random access message 4 via a second transmit beam corresponding to a sub-beam of the first transmit beam.

[0039] The base stations 102 configured for 4G LTE (collectively referred to as the Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) can interface with the EPC 160 through the first backhaul links 132 (e.g., S I interface). The base stations 102 configured for 5G R (collectively referred to as Next Generation RAN (NG-RAN)) can interface with the core network 190 through the second backhaul links 184. In addition to other functions, the base stations 102 can perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment trace, RAN information management (RIM), paging, positioning, and warning message transmission. The base stations 102 can communicate directly or indirectly (e.g., through the EPC 160 or core network 190) with each other over the third backhaul links 134 (e.g., X2 interface). The third backhaul links 134 can be wired or wireless.

[0040] The base stations 102 can wirelessly communicate with the UEs 104. Each of the base stations 102 can provide communication coverage for a respective geographic coverage area 110. There can be overlapping geographic coverage areas 110. For example, a small cell 102a can have a coverage area 110a that overlaps with one or more macrocells 102. The network that includes both small cell and macrocells can be known as a heterogeneous network. A heterogeneous network can also include Home Evolved Node Bs (eNBs) (HeNBs), which can provide service to a restricted group known as a closed subscriber group (CSG). The communication links 120 between the base stations 102 and the UEs 104 can include uplink (UL) (also referred to as reverse link) transmissions from a UE 104 to a base station 102 or downlink (DL) (also referred to as forward link) transmissions from a base station 102 to a UE 104. The communication links 120 can use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, or transmit diversity. The communication links can be through one or more carriers, and each carrier can be a band of frequency waves having a predetermined width and can be used to transmit information. The base stations 102 / UEs 104 can use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz, and others) bandwidth per carrier allocated in the spectrum for each direction of transmission (e.g., data, control information, etc.). The carriers can or can not be adjacent to each other. The allocation of carriers can be asymmetric with respect to DL and UL (e.g., more or less carriers can be allocated for DL than for UL). The component carriers can include a primary component carrier and one or more secondary component carriers. A primary component carrier can be referred to as a primary cell (PCell) and a secondary component carrier can be referred to as a secondary cell (SCell).

[0041] Some UEs 104 can communicate using device-to-device (D2D) communication link 158. The D2D communication link 158 can use a DL / UL WWAN spectrum. The D2D communication link 158 can use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). D2D communication can be through a variety of wireless D2D communications systems, such as for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on IEEE 802.11 standards, LTE, or NR.

[0042] The wireless communications system can also include a Wi-Fi access point (AP) 150 in communication with Wi-Fi stations (STAs) 152 via communication links 154 in a 5 GHz unlicensed frequency spectrum. When communicating in an unlicensed frequency spectrum, the STAs 152 / AP 150 can perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available.

[0043] The small cells 102a can operate in a licensed or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cells 102a can employ NR and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP 150. The small cells 102a employing NR in an unlicensed frequency spectrum can improve coverage to the access network or increase capacity of the access network.

[0044] The electromagnetic spectrum is often subdivided based on frequency / wavelength into various classes, bands, channels, etc. In 5G NR, two initial operating bands have been identified as frequency range designations FR1 (410 MHz - 7. 125 GHz) and FR2 (24.25 GHz - 52.6 GHz). The frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Although a portion of FR1 is greater than 6 GHz, FR1 is often referred to (interchangeably) as a “Sub-6 GHz” band in various documents and articles. A similar nomenclature issue sometimes occurs with respect to FR2, which is often (interchangeably) referred to as a “millimeter wave” band in documents and articles, despite its frequencies being different from the extremely high frequency (EHF) band (30 GHz - 300 GHz) which is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band.

[0045] With the above in mind, unless specifically stated otherwise, it should be understood that the term “Sub-6 GHz” or the like if used herein can broadly represent frequencies that are below 6 GHz, can be within FR1, or can include mid-band frequencies. Further, unless specifically stated otherwise, it should be understood that the term “millimeter wave” or the like if used herein can broadly represent frequencies that can include mid-band frequencies, can be within FR2, or can be within an EHF band. Communications using the mmW radio band have extremely high path loss and a short range. The mmW base stations 180 can utilize beamforming 182 with the UEs 104 to compensate for the path loss and the short range.

[0046] The base stations 180 can transmit to the UEs 104 in one or more transmit directions 182a. The UEs 104 can receive from the base stations 180 in one or more receive directions 182b. The UEs 104 can also transmit to the base stations 180 in one or more transmit directions. The base stations 180 can receive from the UEs 104 in one or more receive directions. The base stations 180 / UEs 104 can perform beam training to determine the best receive and transmit directions for each of the base stations 180 / UEs 104. The transmit and receive directions for the base stations 180 can or can not be the same. The transmit and receive directions for the UEs 104 can or can not be the same.

[0047] The EPC 160 can include a mobility management entity (MME) 162, other MMEs 164, a serving gateway 166, a multimedia broadcast multicast service (MBMS) gateway 168, a broadcast multicast service center (BM-SC) 170, and a packet data network (PDN) gateway 172. The MME 162 can be in communication with a home subscriber server (HSS) 174. The MME 162 is the control node that processes the signaling between the UEs 104 and the EPC 160. Generally, the MME 162 provides bearer and connection management. All user Internet protocol (IP) packets are transferred through the serving gateway 166, which is itself connected to the PDN gateway 172. The PDN gateway 172 provides UE IP address allocation as well as other functions. The PDN gateway 172 and the BM-SC 170 are connected to the IP services 176. The IP services 176 can include the Internet, an intranet, an IP multimedia subsystem (IMS), a PS streaming service, or other IP services. The BM-SC 170 can provide functions for MBMS user service provisioning and

[0048] The core network 190 can include a Access and Mobility Management Function (AMF) 192, other AMFs 193, a Session Management Function (SMF) 194, and a User Plane Function (UPF) 195. The AMF 192 can be in communication with a Unified Data Management (UDM) 196. The AMF 192 is the control node that processes the signaling between the UEs 104 and the core network 190. Generally, the AMF 192 provides QoS flow and session management. All user Internet Protocol (IP) packets are transferred

[0049] Base stations can include or be referred to as gNBs, NodeBs, eNBs, access points, base transceiver stations, radio base stations, radio transceivers, transceiver functions, basic service sets (BSSs), extended service sets (ESSs), transmission and reception points (TRPs), or some other suitable terminology. The base station 102 provides wireless access to the EPC 160 or core network 190 for the UEs 104. Examples of UEs 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop computer, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitch appliance, a healthcare device, an implant, a sensor / actuator, a display, or any other similar functional device. Some of the UEs 104 can be referred to as IoT devices (e.g., parking meter, gas pump, toaster, vehicle, heart monitor, and other examples). The UE 104 can also be referred to as a station, a mobile, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

[0050] Figure 2A FIG. 200 is an example of a first subframe within a 5G / NR frame structure. Figure 2B FIG. 230 is an example of DL channels within a 5G / NR subframe. Figure 2C FIG. 250 is an example of a second subframe within a 5G / NR frame structure. Figure 2Dis a diagram 280 illustrating an example of UL channels within a 5G / NR subframe. The 5G / NR frame structure can be FDD in which, for a particular subcarrier set (carrier system bandwidth), subframes within the subcarrier set are dedicated to either DL or UL, or can be TDD in which, for a particular subcarrier set (carrier system bandwidth), subframes within the subcarrier set are dedicated to both DL and UL. In the examples provided, it is assumed that the 5G / NR frame structure is TDD, and subframe 4 is configured with slot format 28 (mostly DL) in which D is DL, U is UL, and X is flexible for use between DL / UL, and subframe 3 is configured with slot format 34 (mostly UL). Although subframes 3, 4 are illustrated with slot formats 34, 28, respectively, any particular subframe can be configured with any of the various available slot formats 0-61. Slot formats 0, 1 are all DL, UL, respectively. Other slot formats 2-61 include a mix of DL, UL, and flexible symbols. A UE is configured with a slot format by receiving a slot format indicator (SFI) dynamically (through DL control information (DCI)), or semi- statically / statically through radio resource control (RRC) signaling. Note that the description here also applies for 5G / NR frame structures that are TDD. Figure 2A 、 Figure 2C In the examples provided, it is assumed that the 5G / NR frame structure is TDD, and subframe 4 is configured with slot format 28 (mostly DL) in which D is DL, U is UL, and X is flexible for use between DL / UL, and subframe 3 is configured with slot format 34 (mostly UL). Although subframes 3, 4 are illustrated with slot formats 34, 28, respectively, any particular subframe can be configured with any of the various available slot formats 0-61. Slot formats 0, 1 are all DL, UL, respectively. Other slot formats 2-61 include a mix of DL, UL, and flexible symbols. A UE is configured with a slot format by receiving a slot format indicator (SFI) dynamically (through DL control information (DCI)), or semi- statically / statically through radio resource control (RRC) signaling. Note that the description here also applies for 5G / NR frame structures that are TDD.

[0051] Other wireless communication technologies can have different frame structures or different channels. A frame (10 ms) can be divided into 10 equally sized subframes (1 ms). Each subframe can include one or more time slots. A subframe can also include a mini-slot, which can include 7, 4, or 2 symbols. Each slot can include 7 or 14 symbols depending on the slot configuration. For a slot configuration 0, each slot can include 14 symbols, and for a slot configuration 1, each slot can include 7 symbols. The symbols on the DL can be cyclic prefix (CP) OFDM (CP-OFDM) symbols. The symbols on the UL can be CP-OFDM symbols (for high throughput scenarios) or discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (also known as single carrier frequency division multiple access (SC-FDMA) symbols) (for power limited scenarios; limited to single stream transmission). The number of slots within a subframe is based on the slot configuration and the numerology. For slot configuration 0, different numerologies m0to 5 allow for 1, 2, 4, 8, 16, and 32 slots per subframe, respectively. For slot configuration 1, different numerologies 0 to 2 allow for 2, 3, and 8 slots per subframe, respectively. Thus, for slot configuration 0 and numerology m, there are 14 symbols / slot and 2 μ The subcarrier spacing and symbol length / duration are a function of the numerology. The subcarrier spacing can equal 2 μ* 15 kHz, where μ is the numerology 0 through 5. In this way, the numerology μ = 0 has a subcarrier spacing of 15 kHz, and the numerology μ = 5 has a subcarrier spacing of 480 kHz. The symbol length / duration is inversely proportional to the subcarrier spacing. Figures 2A-2D An example of a slot configuration 0 with 14 symbols per slot and numerology μ = 0 with 1 slot per subframe is provided. The subcarrier spacing is 15 kHz, and the symbol duration is approximately 66.7 μβ.

[0052] A resource grid can be used to represent the frame structure. Each time slot includes a resource block (RB) (also referred to as a physical RB (PRB)) that extends over 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

[0053] As illustrated in Figure 2A Some of the REs carry reference (pilot) signals (RS) for the UE. The RS can include demodulation RS (DM-RS) (indicated as Rx for one particular configuration, where 100x is the port number, but other DM-RS configurations are possible) and channel state information reference signals (CSI-RS) for channel estimation at the UE. The RS can also include beam measurement RS (BRS), beam refinement RS (BRRS), and phase tracking RS (PT-RS).

[0054] Figure 2B An example of various DL channels are illustrated. The physical downlink control channel (PDCCH) carries DCI within one or multiple control channel elements (CCEs), each CCE including nine RE groups (REGs), each REG including four consecutive REs in one OFDM symbol. A primary synchronization signal (PSS) can be within symbol 2 of particular subframes of a frame. The PSS is used by a UE 104 to determine subframe / symbol timing and physical layer identity. A secondary synchronization signal (SSS) can be within symbol 4 of particular subframes of a frame. The SSS is used by a UE to determine physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI). Based on the PCI, the UE can determine the locations of the aforementioned DM-RS. The physical broadcast channel (PBCH), which carries a master information block (MIB) that provides system bandwidth configuration and scheduling information, can be logically grouped with the PSS and SSS to form a synchronization signal (SS) / PBCH block. The physical downlink shared channel (PDSCH) carries user data, broadcast system information such as system information blocks (SIBs), and paging messages.

[0055] As illustrated in Figure 2CAs illustrated, some of the REs carry DM-RS (indicated as R for one particular configuration, but other DM-RS configurations are possible) for channel estimation at the base station. The UE can transmit DM-RS for channel estimation for the physical uplink control channel (PUCCH) and for the physical uplink shared channel (PUSCH). The PUSCH DM-RS can be transmitted in the first one or two symbols of a slot for the PUSCH. The PUCCH DM-RS can be transmitted in different configurations depending on whether short or long PUCCHs are transmitted and according to the particular PUCCH format used. Although not shown, the UE can transmit sounding reference signals (SRS). The SRS can be used by a base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

[0056] Figure 2D An example of various UL channels within a subframe of a frame is shown. The PUCCH can be positioned as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and HARQ ACK / NACK feedback. The PUSCH carries data, and can additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), or UCI.

[0057] Figure 3is a block diagram of the base station 310 in communication with the UE 350 in an access network. In the DL, IP packets from the EPC 160 can be provided to a controller / processor 375. The controller / processor 375 implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller / processor 375 provides RRC layer functionality associated with broadcasting of system information (such as MIB, SIBs), RRC connection control (such as RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter radio access technology (RAT) mobility, and measurement configuration; PDCP layer functionality associated with header compression / decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with the transfer of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

[0058] The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, can include error detection on the transport channels, forward error correction (FEC) coding / decoding of the transport channels, interleaving, rate matching, mapping to physical channels, modulation / demodulation of physical channels, and MIMO antenna processing. The TX processor 316 handles mapping to signal constellations based on various modulation schemes (such as binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols are then split into parallel streams. Each stream can then be mapped to an OFDM subcarrier, multiplexed with a reference signal (such as pilot) in the time or frequency domain, and then combined together using an inverse fast Fourier transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM symbol stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 374 can be used to determine the coding and modulation schemes, as well as for spatial processing. The channel estimate can be derived from a reference signal or channel condition feedback transmitted by the UE 350. Each spatial stream can then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX can modulate a respective spatial stream onto an RF carrier that is transmitted on a different antenna 320.

[0059] At the UE 350, each receiver 354RX receives a signal through its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functionality associated with various signal processing functions. The RX processor 356 can perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they can be combined by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then converts the OFDM symbol stream from the time-domain to the frequency domain using a fast Fourier transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the base station 310. These soft decisions can be based on channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the base station 310 on the physical channel. The data and control signals are then provided to the controller / processor 359, which implements layer 3 and layer 2 functionality.

[0060] The controller / processor 359 can be associated with a memory 360 that stores program codes and data. The memory 360 can be referred to as a computer-readable medium. In the UL, the controller / processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the EPC 160. The controller / processor 359 is also responsible for error detection using an ACK or NACK protocol to support HARQ operations.

[0061] Similar to the functionality described in connection with the DL transmission by the base station 310, the controller / processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression / decompression, and security (ciphering, deciphering, integrity protection, integrity verification); RLC layer functionality associated with the transfer of upper layer PDUs, error correction using ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs into TBs, demultiplexing of TBs to MAC SDUs, scheduling information reporting, error correction using HARQ, priority handling, and logical channel prioritization.

[0062] Channel estimates derived by the channel estimator 358 from a reference signal or feedback transmitted by the base station 310 can be used by the TX processor 368 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 368 can be provided to different antenna 352 via separate transmitters 354TX. Each transmitter 354TX can modulate an RF carrier with a respective spatial stream for transmission.

[0063] The UL transmission is processed at the base station 310 in a manner similar to that described in connection with the receiver function at the UE 350. Each receiver 318RX receives a signal through its respective antenna 320. Each receiver 318RX recovers information modulated onto an RF carrier and provides the information to a RX processor 370.

[0064] The controller / processor 375 can be associated with a memory 376 that stores program codes and data. The memory 376 can be referred to as a computer-readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the UE 350. IP packets from the controller / processor 375 can be provided to the EPC 160. The controller / processor 375 is also responsible for error detection using an ACK or NACK protocol to support HARQ operations.

[0065] At least one of the TX processor 368, the RX processor 356, and the controller / processor 359 can be configured to perform aspects related to the UE RACH component 140 of FIG. 2. Figure 1

[0066] At least one of the TX processor 316, the RX processor 370, and the controller / processor 375 can be configured to perform aspects related to the BS RACH component 198 of FIG. 2. Figure 1

[0067] Figure 4 FIG. 4 is a diagram 400 illustrating an example message exchange showing a RACH procedure between a base station 102 and a UE 104 in an access network. The UE 104 can be a NR-Light UE and include a UE RACH component 140. The base station 102 can include a BS RACH component 198.

[0068] With additional reference to Table 1 (below), during operation, the UE 104 can perform an implementation of a NR RACH procedure 410 in accordance with a 4-step NR RACH message flow as a result of occurrence of one or more RACH trigger events 420. Suitable examples of RACH trigger events 420 can include, but are not limited to: (i) the UE 104 performs initial access to transition from an RRC IDLE state to an RRC CONNECTED ACTIVE state; (ii) the UE 104 detects downlink (DL) data arrival while in an RRC IDLE state or an RRC CONNECTED INACTIVE state; (iii) the UE 104 determines UL data arrival from a higher layer during an RRC IDLE state or an RRC CONNECTED INACTIVE state; (iv) the UE 104 performs a handover from another station to the base station 102 during a connected mode of operation; and (v) the UE performs a connection reestablishment procedure, such as a beam failure recovery procedure.

[0069] ​​The NR RACH procedure 410 can be associated with a contention-based random access procedure or a contention-free random access procedure. In one implementation, the contention-based NR RACH procedure corresponds to the following RACH trigger events 420: initial access from RRC IDLE to RRC CONNECTED ACTIVE; UL data arrival during RRC IDLE or RRC CONNECTED INACTIVE; and connection re-establishment. In one implementation, the contention-free NR RACH procedure corresponds to the following RACH trigger events 420: downlink (DL) data arrival during RRC IDLE or RRC CONNECTED INACTIVE; and handover during connected mode of operation.

[0070] Upon occurrence of any of the above RACH trigger events 420, the execution of the NR RACH procedure 410 can include a 4-step NR RACH message flow (see Figure 4 and Table 1), in which the UE 104 exchanges messages with one or more base stations 102 to gain access to the wireless network and establish a communication connection. These messages can be referred to as random access messages 1-4, RACH messages 1-4, or can alternatively be referred to by the PHY channel carrying the message, such as message 3 PUSCH.

[0071]

[0072]

[0073] Table 1 : NR RACH procedure, including messages and message content sent over corresponding physical (PHY) channels at 411, for example, the UE 104 can transmit a first message (Msg 1), which can be referred to as a random access request message, to one or more base stations 102 via a physical channel, such as a physical random access channel (PRACH). For example, Msg 1 can include one or more of a RACH preamble and resource requirements. In one aspect, the RACH preamble can be a relatively long preamble sequence that is more easily received by the base station 102 than an OFDM symbol. In one aspect, the UE RACH component 140 can select a beam for transmitting Msg 1 based on a received synchronization signal block (SSB) transmitted by the base station 102.

[0074] At 412, one or more of the base stations 102 can respond to Msg 1 by transmitting a second message (Msg 2), which can be referred to as a random access response (RAR) message, on a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH). For example, Msg 2 can include one or more of a detected preamble identifier (ID), a timing advance (TA) value, a temporary cell radio network temporary identifier (TC-RNTI), a backoff indicator, a UL grant, or a DL grant. The base stations 102 can select a beam for Msg 2 based on the preamble sequence of Msg 1. In one aspect, the RAR reception component 142 can receive the RAR message. The RAR reception component 142 can monitor the PDCCH during a monitoring window based on Msg 1 to detect a PDCCH portion of the RAR message as a DCI format 1 0 with CRC scrambled by a corresponding RA-RNTI and receive a PDSCH portion of the RAR message as a transport block in a corresponding PDSCH within the window. The RAR reception component 142 can pass the transport block to a higher layer, which can parse the transport block to obtain a random access preamble identity (RAPID) associated with Msg 1. If the higher layer identifies the RAPID in the transport block, the higher layer indicates an uplink grant to the RAR reception component 142 at the physical layer. This is referred to as a RAR UL grant in the physical layer.

[0075] At 413, in response to receiving Msg 2, the repetition component 144 transmits a third message (Msg 3), which can be an RRC connection request or a scheduling request, to the base stations 102 via a physical uplink channel, such as a PUSCH, based on the RAR UL grant provided in Msg 2 by the base stations 102. In one aspect, a UE that is experiencing conditions that can result in poor reception of Msg 3 by the base stations 102 can use repetition to enhance reception of Msg 3 and other RACH messages by the base stations 102. For example, if the UE is an NR-Light UE with relatively low transmission power, repetition of Msg 3 can improve reception of Msg 3 at the base stations 102. Other conditions that can result in poor reception of Msg 3 include use of high frequencies, such as carriers in millimeter wave bands, blocked line of sight, or interference.

[0076] At 430, the UE 104 can transmit up to n Msg 3 repetitions. In one aspect, each repetition can be received at the base station 102 using a different receive beam. The beams can be sub-beams of the previously determined beams. Thus, the beams can refine the previously determined beams and one or more of the repetitions can be received with greater power or better quality. In one aspect, the BS RACH component 198 can determine whether the UE 104 is to repeat the Msg 3 PUSCH based on detection of a beam enhancement condition. For example, the BS RACH component 198 can determine whether the UE 104 is to repeat the Msg 3 based on a signal strength of the Msg 1. For example, when the signal strength of the Msg 1 is less than a threshold, the BS RACH component 198 can indicate repetition of the Msg 3.

[0077] At 414, in response to receiving the Msg 3, the BS RACH component 198 can transmit, via a PDCCH and a PDSCH, a fourth message (Msg 4) to the UE 104, which can be referred to as a contention resolution message. For example, the Msg 4 can include a cell radio network temporary identifier (C-RNTI) for the UE 104 to use in subsequent communications. In one aspect, the beam selection component 148 can select a beam for transmitting the Msg 4 based on which repetition of the Msg 3 was strongest.

[0078] In some example scenarios, collisions can occur between two or more UEs 104 requesting access. For example, two or more UEs 104 can transmit Msg 1 with the same RACH preamble, as the number of RACH preambles can be limited and can be randomly selected by each UE 104 in a contention-based NR RACH procedure. As such, each colliding UE 104 that selects the same RACH preamble will receive the same temporary C-RNTI and the same UL grant, and thus each UE 104 can transmit a similar Msg 3. In this case, the base station 102 can resolve the collision in one or more ways. In a first scenario, the respective Msg 3 from each colliding UE 104 can interfere with the other Msg 3, so the base station 102 can not transmit Msg 4. Each UE 104 will then retransmit Msg 1 using a different RACH preamble. In a second scenario, the base station 102 can successfully decode only one Msg 3, and transmit an ACK message to the UE 104 corresponding to the successfully decoded Msg 3. In a third scenario, the base station 102 can successfully decode the Msg 3 from each colliding UE 104, and then transmit Msg 4 with a contention resolution identifier (such as an identifier tied to one of the UEs) to each colliding UE. Each colliding UE 104 receives the Msg 4, decodes the Msg 4, and determines whether the UE 104 is the correct UE by successfully matching or recognizing the contention resolution identifier. This problem can not occur in a contention-free NR RACH procedure, as in this case the base station 102 can inform the UE 104 which RACH preamble to use.

[0079] Figure 5is a diagram 500 illustrating example resources for repetition of a random access message 3. Resources 510 can be located within consecutive time slots 520, 522, 524, and 526. The UE 104 can transmit repetitions 530, 532, 534, 536 of the Msg 3 in each time slot 520, 522, 524, and 526. That is, each repetition 530, 532, 534, and 536 can include the same data. Each repetition 530, 532, 534, and 536 can use the same transmit beam from the UE 104. The base station 102 can receive each repetition 530, 532, 534, and 536 in the respective time slot 520, 522, 524, and 526 with a different refined sub-beam. A refined sub-beam can refer to a lower level beam in a hierarchical set of beams. For example, a layer 1 (LI) beam can cover multiple L2 beams, each of which can cover multiple L3 beams. In other words, a refined sub-beam can have a narrower aperture included within a wider aperture of a higher level beam. In one implementation, the beams corresponding to Msg 1 and Msg 2 are L2 beams, and each of the different refined sub-beams is an L3 beam. The L3 refined beams can be based on the L2 beams used for Msg 1 and Msg 2. That is, the base station 102 can generate different sub-beams of the L2 beams to attempt to improve reception of the Msg 3.

[0080] In one aspect, the base station 102 can select one of the received repetitions 530, 532, 534, and 536 based on one or more criteria. For example, the base station 102 can determine which of the received repetitions 530, 532, 534, and 536 is the strongest and select that repetition. In a first implementation, for each repetition, the base station 102 can use the corresponding refined beam to detect each repetition of the Msg 3 separately. That is, the base station 102 can receive a signal for each repetition 530, 532, 534, and 536 using the respective refined beam and attempt to decode the Msg 3 based only on the signal received with the respective refined beam. The base station 102 can determine a signal power, such as a received signal strength indicator (RSSI), for each repetition 530, 532, 534, and 536.

[0081] In the second implementation, the base station 102 can improve the likelihood of detection by soft combining the signals received via each of the different refined beams. That is, the base station 102 can soft combine the received signals of the repetitions 530, 532, 534, and 536 to determine the Msg 3. The base station 102 can then determine a reference signal received power (RSRP) for each repetition 530, 532, 534, and 536 based on the Msg 3. For example, the base station 102 can use the decoded Msg 3 as a reference signal and compare each repetition 530, 532, 534, and 536 to the reference signal. Thus, the RSRP can indicate the quality of each reference signal. In the first implementation or the second implementation, the base station 102 can select the beam corresponding to one of the repetitions 530, 532, 534, and 536 (e.g., the repetition with the strongest RSSI or RSRP) for the Msg 4.

[0082] In one aspect, the base station 102 can indicate the repetition parameters in the Msg 2. For example, an indication to use Msg 3 repetition and an indication of the number of repetitions to use can be indicated in the Msg 2 PDCCH. The Msg 2 PDSCH can additionally or alternatively provide an indication to use Msg 3 repetition and an indication of the number of repetitions to use or an indication of the related resources for the repetitions. For example, the resources can utilize frequency hopping to improve diversity. The Msg 2 PDSCH can indicate a frequency hopping pattern or specific frequency domain resources.

[0083] Figure 6 is a flow diagram of an example method 600 for transmitting a random access message 3 during a RACH procedure. The method 600 can be performed by a UE, such as the UE 104, which can include the memory 360 and can be the entire UE 104 or a component of the UE 104, such as the UE RACH component 140, the TX processor 368, the RX processor 356, or the controller / processor 359. The method 600 can be performed by the UE RACH component 140 in communication with the BS RACH component 198 of the base station 102.

[0084] At block 610, the method 600 can include receiving, using the first receive beam, a random access message 2 transmitted by the base station using the first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of transmitting a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions. In one aspect, for example, the UE 104, the RX processor 356, or the controller / processor 359 can execute the UE RACH component 140 or the RAR reception component 142 to receive, using the first receive beam, a random access message 2 indicating to the UE a plurality of repetitions of transmitting a random access message 3. The random access message 2 can further include an indication of a number of repetitions in the plurality of repetitions. For example, the RAR reception component 142 can receive a PDCCH portion of the random access message 2, determine that a CRC of a DCI on the PDCCH is scrambled by a RA-RNTI, determine a corresponding PDSCH transport block, pass the transport block to a higher layer, and receive, from the higher layer, a PDSCH portion of the random access message 2. In one aspect, the random access message 2 can indicate to the UE a plurality of repetitions of transmitting a random access message 3. The PDCCH can indicate a number of the plurality of repetitions. In another aspect, the random access message 2 indicates to the UE a plurality of repetitions of transmitting a random access message 3 in a PDSCH. The PDSCH can indicate a number of the plurality of repetitions or resources for the repetitions. Accordingly, the UE 104, the RX processor 356, or the controller / processor 359 executing the UE RACH component 140 or the RAR reception component 142 can provide means for receiving, using the first receive beam, a random access message 2 transmitted by the base station using the first transmit beam.

[0085] At block 620, the method 600 can include transmitting a plurality of repetitions of the random access message 3 based on the random access message 2. In one aspect, for example, the UE 104, the controller / processor 359, or the TX processor 368 can execute the UE RACH component 140 or the repetition component 144 to transmit a plurality of repetitions of the random access message 3 based on the random access message 2. The repetition component 144 can repeat the message 3 based on the number of the plurality of repetitions. In one aspect, transmitting the plurality of repetitions of the random access message 3 can include transmitting the plurality of repetitions using a frequency hopping pattern. Accordingly, the UE 104, the TX processor 368, or the controller / processor 359 executing the UE RACH component 140 or the repetition component 144 can provide means for transmitting a plurality of repetitions of the random access message 3 based on the random access message 2.

[0086] At block 630, the method 600 can include receiving, based on transmitting the multiple repetitions of the random access message 3, a random access message 4 transmitted by the base station using a second transmission beam that is a sub-beam of the first transmission beam. In one aspect, for example, the UE 104, the RX processor 356, or the controller / processor 359 can execute the UE RACH component 140 or the contention resolution component 145 to receive, based on transmitting the multiple repetitions of the random access message 3, a random access message 4 transmitted by the base station 102 on a second transmission beam that is a sub-beam of the first transmission beam. In one aspect, the second transmission beam is a refined beam having a narrower aperture included within a wider aperture of the first transmission beam. In one aspect, the first reception beam is a level 2 beam of a set of hierarchical beams, and the second transmission beam is a level 3 beam of the set of hierarchical beams. Thus, the UE 104, the RX processor 356, or the controller / processor 359 executing the UE RACH component 140 or the contention resolution component 145 can provide means for receiving, based on transmitting the multiple repetitions of the random access message 3, a random access message 4 transmitted by the base station using a second transmission beam that is a sub-beam of the first transmission beam.

[0087] Figure 7 is a flowchart representation of an example method 700 for receiving a random access message 3 during a RACH procedure. The method 700 can be performed by a base station, such as the base station 102, which can include the memory 376 and can be the entire base station 102 or a component of the base station 102, such as the BS RACH component 198, the TX processor 316, the RX processor 370, or the controller / processor 375. The method 700 can be performed by the BS RACH component 198 in communication with the UE RACH component 140 of the UE 104.

[0088] At block 710, the method 700 can include transmitting, to the UE using a first transmission beam, a random access message 2 that indicates to the UE to transmit a number of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the number of repetitions. In one aspect, for example, the base station 102, the TX processor 316, or the controller / processor 375 can execute the BS RACH component 198 or the RAR transmission component 146 to transmit, to the UE 104 using a first transmission beam, a random access message 2 that indicates to the UE to transmit a number of repetitions of a random access message 3. The random access message 2 can further include an indication of a number of repetitions in the number of repetitions. Thus, the base station 102, the TX processor 316, or the controller / processor 375 executing the BS RACH component 198 or the RAR transmission component 146 can provide means for transmitting, to the UE using a first transmission beam, a random access message 2 that indicates to the UE to transmit a number of repetitions of a random access message 3.

[0089] At block 720, the method 700 can include receiving a number of repetitions of a random access message 3, using a different refined beam for each repetition based on the random access message 2. In one aspect, for example, the base station 102, the RX processor 370, or the controller / processor 375 can execute the BS RACH component 198 or the beam selection component 148 to receive the number of repetitions of the random access message 3, using a different refined beam for each repetition based on the random access message 2. In one aspect, receiving the number of repetitions of the random access message 3 can include receiving the repetitions using a frequency hopping pattern. Thus, the base station 102, the RX processor 370, or the controller / processor 375 executing the BS RACH component 198 or the beam selection component 148 can provide means for receiving a number of repetitions of a random access message 3, using a different refined beam for each repetition based on the random access message 2.

[0090] At block 730, the method 700 can include transmitting a random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam based on at least one of the multiple repetitions of the random access message 3. In one aspect, for example, the base station 102, the TX processor 316, or the controller / processor 375 can execute the BS RACH component 198 or the refined transmission component 149 to transmit the random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam based on at least one of the multiple repetitions of the random access message 3. Thus, the base station 102, the TX processor 316, or the controller / processor 375 executing the BS RACH component 198 or the refined transmission component 149 can provide means for transmitting a random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam based on at least one of the multiple repetitions of the random access message 3.

[0091] Figure 8 FIG. 8 is a block diagram of an example apparatus 800 for wireless communication. The apparatus 800 can be a UE or a UE can include the apparatus 800. In some aspects, the apparatus 800 includes a reception component 802, a communication manager 804, and a transmission component 806, which can be in communication with one another (for example, via one or more buses). As shown, the apparatus 800 can communicate with another apparatus 808 (such as a UE, a base station, or another wireless communication device) using the reception component 802 and the transmission component 806.

[0092] In some aspects, the apparatus 800 can be configured to perform one or more operations described herein with Figure 4 and Figure 5 one or more processes described herein. Additionally, or alternatively, the apparatus 800 can be configured to perform one or more operations described herein with Figure 6 the method 600 of FIG. 6. In some aspects, the apparatus 800 can include the reception component 802, the transmission component 806, and / or the communication manager 804, which can be in communication with one another (for example, via one or more buses). Additionally, or alternatively, the apparatus 800 can include one or more other components (for example, one or more processors, memory, or one or more user interfaces).Figure 1 one or more components of the described UE.

[0093] The reception component 802 can receive communications, such as reference signals, control information, data communications, or a combination thereof, from the apparatus 808. The reception component 802 can provide received communications to one or more other components of the apparatus 800, such as the communication manager 804. In some aspects, the reception component 802 can perform signal processing on the received communications (such as filtering, amplification, demodulation, analog-to-digital conversion, demultiplexing, deinterleaving, de-mapping, equalization, interference cancellation, or decoding, among other examples), and can provide the processed signals to the one or more other components. In some aspects, the reception component 802 can include one or more antennas, a demodulator, a MIMO detector, a receive processor, a controller / processor, a memory, or a combination thereof, of the UE described above in connection with Fig. 2. Figure 1 one or more components of the described UE.

[0094] The transmission component 806 can transmit communications, such as reference signals, control information, data communications, or a combination thereof, to the apparatus 808. In some aspects, the communication manager 804 can generate communications and can transmit the generated communications to the transmission component 806 for transmission to the apparatus 808. In some aspects, the transmission component 806 can perform signal processing on the generated communications (such as filtering, amplification, modulation, digital-to-analog conversion, multiplexing, interleaving, mapping, or encoding, among other examples), and can transmit the processed signals to the apparatus 808. In some aspects, the transmission component 806 can include one or more antennas, a modulator, a transmit MIMO processor, a transmit processor, a controller / processor, a memory, or a combination thereof, of the UE described above in connection with Fig. 2. In some aspects, the transmission component 806 can be co-located with the reception component 802 in a transceiver. Figure 1 one or more components of the described UE.

[0095] The communication manager 804 can receive, using a first receive beam, a random access message 2 indicating a number of repetitions of a random access message 3; transmit the number of repetitions of the random access message 3; and receive a random access message 4, the random access message 4 being transmitted on a refined transmit beam corresponding to a sub-beam of the first receive beam. In some aspects, the communication manager 804 can include a set of components, such as a RAR reception component 810, a repetition component 812, and a contention resolution component 814, or a combination thereof. Alternatively, the set of components can be separate and distinct from the communication manager 804. In some aspects, one or more components of the set of components can include the above-described components of the UE described above in connection with Fig. 2. Figure 1 one or more components of the described UE.

[0096] In some aspects, the communication manager 804 can include a set of components, such as a RAR reception component 810, a repetition component 812, and a contention resolution component 814, or a combination thereof. Alternatively, the set of components can be separate and distinct from the communication manager 804. In some aspects, one or more components of the set of components can include the above-described components of the UE described above in connection with Fig. 2. Figure 1The controller / processor, memory, or combinations thereof, of the described UEs can be used to implement or realize the processes, blocks, and / or components (or portions thereof) described herein. Additionally or alternatively, one or more components of the described UEs can be implemented or realized in software. For example, one or more components (or portions thereof) can be implemented as instructions or code stored in the memory and executable by the controller or processor to perform the functions or operations of the components.

[0097] The RAR receiving component 810 can receive a random access message 2 indicating a plurality of repetitions of a random access message 3 using a first receive beam. The repetition component 812 can transmit a number of repetitions of the random access message 3. The contention resolution component 814 can receive a random access message 4 transmitted on a refined transmit beam corresponding to a sub-beam of the first receive beam.

[0098] Figure 8 The number and arrangement of components shown is provided as an example. In practice, there can be additional components, fewer components, different components, or differently arranged components than those shown. Additionally or alternatively, two or more components shown can be implemented within a single component, or a single component shown can be implemented as multiple, distributed components. Further, a component shown as an internal component of another component can be implemented as a standalone component. Figure 8 Similarly, a component shown as an external component to one component can be implemented as a standalone component or can be incorporated as an internal component of another component. Further, components shown in Figure 8 two or more components shown can be implemented within a single component, or a single component shown can be implemented as multiple, distributed components. Further, a component shown as an internal component of another component can be implemented as a standalone component. Figure 8 Similarly, a component shown as an external component to one component can be implemented as a standalone component or can be incorporated as an internal component of another component. Further, components shown in Figure 8 the set of components shown can perform one or more functions described as being performed by another set of components shown. Figure 8 Similarly, a component shown as an external component to one component can be implemented as a standalone component or can be incorporated as an internal component of another component. Further, components shown in

[0099] Figure 9 is a block diagram of an example apparatus 900 for wireless communication. The apparatus 900 can be a base station or the base station can include the apparatus 900. In some aspects, the apparatus 900 includes a reception component 902, a communication manager 904, and a transmission component 906, which can be in communication with one another (for example, via one or more buses). As shown, the apparatus 900 can communicate with another apparatus 908 (such as a UE, a base station, or another wireless communication device) using the reception component 902 and the transmission component 906.

[0100] In some aspects, the apparatus 900 can be configured to perform one or more operations described herein in connection with the method 700. Additionally or alternatively, the apparatus 900 can be configured to perform one or more processes described herein, such as process 800. In some aspects, the apparatus 900 can include one or more components of the base station described above in connection with Figure 4 and Figure 5 In some aspects, the apparatus 900 can be configured to perform one or more operations described herein in connection with the method 700. Additionally or alternatively, the apparatus 900 can be configured to perform one or more processes described herein, such as process 800. In some aspects, the apparatus 900 can include one or more components of the base station described above in connection with Figure 7 In some aspects, the apparatus 900 can include one or more components of the base station described above in connection with Figure 1 In some aspects, the apparatus 900 can include one or more components of the base station described above in connection with

[0101] Receiver 902 can receive communications from device 908, such as reference signals, control information, data communications, or combinations thereof. Receiver 902 can provide the received communications to one or more other components of device 900, such as communication manager 904. In some aspects, receiver 902 can perform signal processing on the received communications (e.g., filtering, amplification, demodulation, analog-to-digital conversion, demultiplexing, deinterleaving, demapping, equalization, interference cancellation, or decoding, etc.) and can provide the processed signal to one or more other components. In some aspects, receiver 902 can include the above-described combinations... Figure 1 The described base station includes one or more antennas, demodulators, MIMO detectors, receiver processors, controllers / processors, memory, or combinations thereof.

[0102] Transmitting component 906 can transmit communications, such as reference signals, control information, data communications, or combinations thereof, to device 908. In some aspects, communication manager 904 can generate communications and send the generated communications to transmitting component 906 for transmission to device 908. In some aspects, transmitting component 906 can perform signal processing (e.g., filtering, amplification, modulation, digital-to-analog conversion, multiplexing, interleaving, mapping, or encoding) on ​​the generated communications and can transmit the processed signals to device 908. In some aspects, transmitting component 906 can include the combinations described above. Figure 1 The described base station includes one or more antennas, a modulator, a transmit MIMO processor, a transmit processor, a controller / processor, a memory, or a combination thereof. In some aspects, the transmit component 906 may be co-located with the receive component 902 in a transceiver.

[0103] The communication manager 904 can send multiple repeated random access messages 2 indicating random access messages 3; and receive a certain number of repetitions of random access messages 3, using a different refined beam for each repetition. In some aspects, the communication manager 904 may include the combination described above. Figure 1 The described base station's controller / processor, memory, scheduler, communication unit, or a combination thereof.

[0104] In some aspects, the communication manager 904 may include a set of components, such as a RAR transmission component 910, a beam selection component 912, a refinement transmission component 914, or a combination thereof. Alternatively, this set of components may be separate from and distinct from the communication manager 904. In some aspects, one or more components in this set may include combinations of the above. Figure 1The described base station may include a controller / processor, memory, scheduler, communication unit, or a combination thereof, or may be implemented in these components. Additionally or alternatively, one or more components in this set may be implemented at least partially as software stored in memory. For example, a component (or a portion thereof) may be implemented as instructions or code stored in a non-transitory computer-readable medium and executable by a controller or processor to perform the component's function or operation.

[0105] RAR transmission component 910 can transmit multiple repeated random access messages 2 indicating random access message 3. Beam selection component 912 can receive a certain number of repetitions of random access message 3, using a different refined beam for each repetition. Refined transmission component 914 can transmit random access message 4 via a second transmission beam corresponding to a sub-beam of the first transmission beam, based on at least one of the said number of repetitions of random access message 3.

[0106] Figure 9 The number and arrangement of components shown are provided as an example. In reality, there may be more. Figure 9 This shows more components, fewer components, different components, or components arranged differently. Furthermore, Figure 9 The two or more components shown can be implemented within a single component, or Figure 9 The single component shown can be implemented as multiple distributed components. Additionally or alternatively, Figure 9 The collection of (one or more) components shown can perform actions described as being performed by Figure 1 The other set of components shown performs one or more functions.

[0107] The specific order or hierarchy of boxes in the disclosed process / flowchart is an illustration of the illustrative method. The specific order or hierarchy of boxes in the process / flowchart may be rearranged based on design preferences. Furthermore, some boxes may be combined or omitted. The appended method claims present the elements of various boxes in an illustrative order, but are not intended to limit one to the specific order or hierarchy presented.

[0108] Some further example terms

[0109] Examples of implementation methods are described in the following numbered clauses:

[0110] 1. A method for wireless communication, comprising:

[0111] The first receive beam is used to receive a random access message 2 transmitted by the base station using the first transmit beam. The random access message 2 instructs the UE to transmit multiple repetitions of the random access message 3. The random access message 2 also includes an indication of the number of repetitions among the multiple repetitions.

[0112] transmitting a plurality of repetitions of the random access message 3 based on the random access message 2;

[0113] receiving a random access message 4 transmitted by the base station using a second transmit beam based on the transmitting the plurality of repetitions of the random access message 3, the second transmit beam being a sub-beam of the first transmit beam.

[0114] 2. The method of clause 1, wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam.

[0115] 3. The method of clause 1 or 2, wherein the random access message 2 indicates to the UE that the plurality of repetitions of the random access message 3 are transmitted in a physical downlink control channel (PDCCH).

[0116] 4. The method of clause 3, wherein the PDCCH indicates a number of repetitions in the plurality of repetitions.

[0117] 5. The method of clause 1 or 2, wherein the random access message 2 indicates to the UE that the plurality of repetitions of the random access message 3 are transmitted in a physical downlink shared channel (PDSCH).

[0118] 6. The method of clause 5, wherein the PDSCH indicates a number of repetitions in the plurality of repetitions or resources for the plurality of repetitions.

[0119] 7. The method of any of clauses 1-6, wherein the transmitting the plurality of repetitions of the random access message 3 includes transmitting the plurality of repetitions using a frequency hopping pattern.

[0120] 8. The method of any of clauses 1-7, wherein the first transmit beam is a level 2 beam in a hierarchical beam set and the second transmit beam is a level 3 beam in the hierarchical beam set.

[0121] 9. A method of wireless communication, comprising:

[0122] transmitting, to a user equipment (UE), a random access message 2 using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions;

[0123] receiving the plurality of repetitions of the random access message 3 based on the random access message 2, using a different refined beam for each repetition; and

[0124] transmitting a random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam based on at least one of the plurality of repetitions of the random access message 3.

[0125] 10. The method of clause 9, the random access message 2 indicating to the UE a number of repetitions in which the random access message 3 is transmitted in a physical downlink control channel (PDCCH).

[0126] 11. The method of clause 10, wherein the PDCCH indicates a number of repetitions in the number of repetitions.

[0127] 12. The method of clause 9, wherein the random access message 2 indicates to the UE a number of repetitions in which the random access message 3 is transmitted in a physical downlink shared channel (PDSCH).

[0128] 13. The method of clause 12, wherein the PDSCH indicates a number of repetitions in the number of repetitions or resources for the number of repetitions.

[0129] 14. The method of any of clauses 9-13, wherein receiving the number of repetitions of the random access message 3 comprises receiving the number of repetitions using a frequency hopping pattern.

[0130] 15. The method of any of clauses 9-14, wherein each of the different refined beams is a sub-beam of a beam used for the random access message 1 and the random access message 2.

[0131] 16. The method of any of clauses 9-15, further comprising:

[0132] receiving each of the number of repetitions of the random access message 3, respectively; and

[0133] selecting, based on a strongest signal strength of the number of repetitions, a second transmit beam for transmitting a random access message 4.

[0134] 17. The method of any of clauses 9-15, further comprising:

[0135] performing a soft combining of the number of repetitions to determine a received message 3;

[0136] determining, based on the received message 3, a respective reference signal received power (RSRP) for each of the number of repetitions; and

[0137] selecting, based on a strongest respective RSRP of the number of repetitions, a second transmit beam for transmitting a random access message 4.

[0138] 18. The method of any of clauses 9-17, wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam.

[0139] 19. An apparatus for wireless communication, comprising:

[0140] a memory storing computer-executable instructions; and

[0141] at least one processor coupled to the memory and configured to execute instructions to:

[0142] receive, using a first receive beam, a random access message 2 transmitted by the base station using a first transmit beam, the random access message 2 indicating to the UE a number of repetitions for transmitting a random access message 3, the random access message 2 further including an indication of the number of repetitions;

[0143] transmit the number of repetitions of the random access message 3 based on the random access message 2; and

[0144] receive, based on transmitting the number of repetitions of the random access message 3, a random access message 4 transmitted by the base station using a second transmit beam that is a sub-beam of the first transmit beam.

[0145] 20. The apparatus of clause 19, wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam.

[0146] 21. The apparatus of clause 19 or 20, wherein the random access message 2 indicates to the UE that the number of repetitions of the random access message 3 are transmitted in a physical downlink control channel (PDCCH).

[0147] 22. The apparatus of clause 21, wherein the PDCCH indicates the number of repetitions.

[0148] 23. The apparatus of clause 19 or 20, wherein the random access message 2 indicates to the UE that the number of repetitions of the random access message 3 are transmitted in a physical downlink shared channel (PDSCH).

[0149] 24. The apparatus of clause 23, wherein the PDSCH indicates the number of repetitions or resources for the number of repetitions.

[0150] 25. The apparatus of any of clauses 19-24, wherein the at least one processor is configured to transmit the number of repetitions using a frequency hopping pattern.

[0151] 26. The apparatus of any of clauses 19-25, wherein the first transmit beam is a level 2 beam of a set of hierarchical beams and the second transmit beam is a level 3 beam of the set of hierarchical beams.

[0152] 27. An apparatus for wireless communication, comprising:

[0153] a memory storing computer-executable instructions; and

[0154] at least one processor coupled to the memory and configured to execute instructions to:

[0155] transmitting a random access message 2 to a user equipment (UE) using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions to transmit a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions;

[0156] receiving a number of repetitions of the random access message 3 using a different refined beam for each repetition based on the indication in the random access message 2; and

[0157] transmitting a random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam based on at least one of the number of repetitions of the random access message 3.

[0158] 28. The apparatus of clause 27, the random access message 2 indicating to the UE a plurality of repetitions to transmit the random access message 3 in a physical downlink control channel (PDCCH).

[0159] 29. The apparatus of clause 28, wherein the PDCCH indicates a number of repetitions in the plurality of repetitions.

[0160] 30. The apparatus of clause 27, wherein the random access message 2 indicates to the UE a plurality of repetitions to transmit the random access message 3 in a physical downlink shared channel (PDSCH).

[0161] 31. The apparatus of clause 30, wherein the PDSCH indicates a number of repetitions or resources for the repetitions.

[0162] 32. The apparatus of any of clauses 27-31, wherein the at least one processor is configured to receive the repetitions using a frequency hopping pattern.

[0163] 33. The apparatus of any of clauses 27-32, wherein each of the different refined beams is a sub-beam of a beam used for the random access message 1 and the random access message 2.

[0164] 34. The apparatus of any of clauses 27-33, wherein the at least one processor is configured to:

[0165] receive each of the plurality of repetitions of the random access message 3, respectively; and

[0166] select the second transmit beam for transmitting the random access message 4 based on a strongest signal strength of the plurality of repetitions.

[0167] 35. The apparatus of any of clauses 27-33, wherein the at least one processor is configured to:

[0168] perform soft combining on the plurality of repetitions to determine a received message 3;

[0169] determine, based on the received message 3, a respective reference signal received power (RSRP) for each of the plurality of repetitions; and

[0170] select, based on a strongest respective RSRP of the plurality of repetitions, a second transmit beam for transmitting a random access message 4.

[0171] 36. The apparatus of any of clauses 27-35, wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam.

[0172] 37. An apparatus for wireless communication, comprising:

[0173] means for receiving, using a first receive beam, a random access message 2 transmitted by a base station using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of transmitting a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions;

[0174] means for transmitting, based on the random access message 2, the plurality of repetitions of the random access message 3; and

[0175] means for receiving, based on transmitting the plurality of repetitions of the random access message 3, a random access message 4 transmitted by the base station using a second transmit beam, the second transmit beam being a sub-beam of the first transmit beam.

[0176] 38. The apparatus of clause 37, wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam.

[0177] 39. The apparatus of clause 37 or 38, wherein the random access message 2 indicates to the UE that the plurality of repetitions of the random access message 3 are transmitted in a physical downlink control channel (PDCCH).

[0178] 40. The apparatus of clause 39, wherein the PDCCH indicates the number of repetitions in the plurality of repetitions.

[0179] 41. The apparatus of clause 37 or 38, wherein the random access message 2 indicates to the UE that the plurality of repetitions of the random access message 3 are transmitted in a physical downlink shared channel (PDSCH).

[0180] 42. The apparatus of clause 41, wherein the PDSCH indicates the number of repetitions in the plurality of repetitions or resources for the plurality of repetitions.

[0181] 43. The apparatus of any of clauses 37-42, wherein the means for transmitting the number of repetitions of the random access message 3 is configured to transmit the repetitions using a frequency hopping pattern.

[0182] 44. The apparatus of any of clauses 37-43, wherein the first receive beam is a tier-2 refined beam of a tiered set of beams and the second transmit beam is a tier-3 beam of the tiered set of beams.

[0183] 45. An apparatus for wireless communication, comprising:

[0184] means for transmitting, to a user equipment (UE), a random access message 2 using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions to transmit a random access message 3, the random access message 2 further including an indication of a number of repetitions;

[0185] means for receiving, based on the random access message 2, a number of repetitions of the random access message 3 using a different refined beam for each repetition; and

[0186] means for transmitting, based on at least one of the plurality of repetitions of the random access message 3, a random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam.

[0187] 46. The apparatus of clause 45, wherein the random access message 2 indicates to the UE that the plurality of repetitions of the random access message 3 are transmitted in a physical downlink control channel (PDCCH).

[0188] 47. The apparatus of clause 46, wherein the PDCCH indicates the number of repetitions in the plurality of repetitions.

[0189] 48. The apparatus of clause 45, wherein the random access message 2 indicates to the UE that the plurality of repetitions of the random access message 3 are transmitted in a physical downlink shared channel (PDSCH).

[0190] 49. The apparatus of clause 48, wherein the PDSCH indicates the number of repetitions in the plurality of repetitions or resources for the plurality of repetitions.

[0191] 50. The apparatus of any of clauses 45-49, wherein the means for receiving a number of repetitions of the random access message 3 is configured to receive the repetitions using a frequency hopping pattern.

[0192] 51. The apparatus of any of clauses 45-50, wherein each of the different refined beams is a sub-beam of a beam used for the random access message 1 and the random access message 2.

[0193] 52. The apparatus of any of clauses 45-51, wherein the means for receiving is configured to receive each of a plurality of repetitions of a random access message 3, respectively, and select the second transmit beam for transmitting a random access message 4 based on a strongest signal strength of the plurality of repetitions.

[0194] 53. The apparatus of any of clauses 45-51, wherein the means for receiving is configured to perform soft combining on the plurality of repetitions to determine a received message 3, determine a respective reference signal received power (RSRP) of each of the plurality of repetitions based on the received message 3, and select the second transmit beam for transmitting a random access message 4 based on a strongest respective RSRP of the plurality of repetitions.

[0195] 54. The apparatus of any of clauses 45-53, wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam.

[0196] 55. A non-transitory computer-readable medium storing computer-executable code that, when executed by a processor, causes the processor to:

[0197] receive, using a first receive beam, a random access message 2 transmitted by a base station using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of transmitting a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions;

[0198] transmit the plurality of repetitions of the random access message 3 based on the random access message 2; and

[0199] receive, based on transmitting the plurality of repetitions of the random access message 3, a random access message 4 transmitted by the base station using a second transmit beam that is a sub-beam of the first transmit beam.

[0200] 56. The non-transitory computer-readable medium of clause 55, wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam.

[0201] 57. The non-transitory computer-readable medium of clause 55 or 56, wherein the random access message 2 indicates to the UE that the plurality of repetitions of the random access message 3 are transmitted in a physical downlink control channel (PDCCH).

[0202] 58. The non-transitory computer-readable medium of clause 57, wherein the PDCCH indicates the number of repetitions in the plurality of repetitions.

[0203] 59. A non-transitory computer-readable medium pursuant to clauses 55 or 56, wherein random access message 2 instructs the UE to transmit multiple repetitions of random access message 3 in the physical downlink shared channel (PDSCH).

[0204] 60. A non-transitory computer-readable medium pursuant to Clause 59, wherein the PDSCH indicates the number of repetitions in a plurality of repetitions or the resources used for a plurality of repetitions.

[0205] 61. A non-transitory computer-readable medium pursuant to any of clauses 55-60, wherein the code for transmission includes transmitting multiple repeated codes using a frequency hopping mode.

[0206] 62. A non-transitory computer-readable medium according to any one of clauses 55-60, wherein the first transmitting beam is a level 2 beam in a hierarchical beamset and the second transmitting beam is a level 3 beam in the hierarchical beamset.

[0207] 63. A non-transitory computer-readable medium storing computer-executable code, which, when executed by a processor, causes the processor to:

[0208] Random access message 2 is sent to user equipment (UE) using a first transmit beam. Random access message 2 instructs the UE to send multiple repetitions of random access message 3. Random access message 2 also includes an indication of the number of repetitions among the multiple repetitions.

[0209] Based on the indication in random access message 2, for each reuse of a different refined beam, a certain number of repetitions of random access message 3 are received; and

[0210] Random access message 4 is transmitted via a second transmission beam that is a sub-beam of the first transmission beam, based on at least one of the number of repetitions of random access message 3.

[0211] 64. A non-transitory computer-readable medium pursuant to Clause 63, wherein random access message 2 instructs the UE to transmit multiple repetitions of random access message 3 in the physical downlink control channel (PDCCH).

[0212] 65. A non-transitory computer-readable medium pursuant to Clause 64, wherein the PDCCH indicates the number of repetitions in a plurality of repetitions.

[0213] 66. A non-transitory computer-readable medium pursuant to Clause 64, wherein random access message 2 instructs the UE to transmit multiple repetitions of random access message 3 in the Physical Downlink Shared Channel (PDSCH).

[0214] 67. A non-transitory computer-readable medium pursuant to Clause 66, wherein the PDSCH indicates the number of repetitions in a plurality of repetitions or the resources used for a plurality of repetitions.

[0215] 68. The non-transitory computer-readable medium pursuant to any of clauses 63-67 also includes receiving multiple repeated codes using frequency hopping mode.

[0216] 69. A non-transitory computer-readable medium pursuant to any of clauses 63-68, wherein each of the different refined beams is a sub-beam of the beam used for random access message 1 and random access message 2.

[0217] 70. The non-transitory computer-readable medium pursuant to any of clauses 63-69 also includes code for the following operations:

[0218] Receive each of the multiple repetitions of random access message 3 respectively; and

[0219] Based on the strongest repeated signal strength, a second transmission beam is selected for transmitting random access message 4.

[0220] 71. The non-transitory computer-readable medium pursuant to any of clauses 63-69 also includes code for the following operations:

[0221] Perform soft combination on multiple repetitions to determine the received message 3;

[0222] Based on received message 3, determine the corresponding Reference Signal Received Power (RSRP) for each of the multiple repetitions; and

[0223] Based on the strongest response RSRP among multiple repetitions, the second transmission beam is selected for transmitting random access message 4.

[0224] 72. A non-transitory computer-readable medium according to any one of clauses 63-71, wherein the second transmit beam is a thinned beam having a narrower aperture included within the wider aperture of the first transmit beam.

[0225] The foregoing description is intended to enable those skilled in the art to practice the various aspects described herein. Various modifications to these aspects will readily be apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. The claims are not intended to limit us to the aspects shown herein, but are to be consistent with the full scope of the language claims, wherein, unless specifically stated otherwise, the singular form element is not intended to mean “one and only one,” but rather “one or more.” The word “exemplary” as used herein means “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or more advantageous than other aspects. Unless specifically stated otherwise, the term “some” means one or more. Combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof” include any combination of A, B, or C, and may include multiple A, multiple B, or multiple C. Specifically, phrases such as "at least one of A, B, or C," "A, B, or C," "at least one of A, B, and C," "one or more of A, B, and C," and "A, B, C, or any combination thereof" can be A only, B only, C only, A and B, A and C, B and C, or A and B and C, wherein any such combination may contain one or more A, B, or C. All structural and functional equivalents of the elements of the various aspects described in this disclosure that are known to or will be known thereafter by those skilled in the art are expressly incorporated herein by reference and are intended to be included in the claims. Furthermore, nothing disclosed herein is intended for the general public, whether or not such disclosure is expressly stated in the claims. The words "module," "mechanism," "element," "device," etc., cannot replace the word "component." Therefore, unless an element is explicitly stated using the phrase "component for...", no claim element is interpreted as a device plus a function.

Claims

1. A method of wireless communication by a user equipment (UE), comprising: receiving, using a first receive beam, a random access message 2 transmitted by a base station using a first transmit beam, the random access message 2 indicating to the UE a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions; in association with receiving the random access message 2, transmitting the plurality of repetitions of the random access message 3 so that the base station can perform soft combining on the plurality of repetitions to determine a received message 3; and in association with transmitting the plurality of repetitions of the random access message 3, receiving a random access message 4 transmitted by the base station using a second transmit beam that is a sub-beam of the first transmit beam, wherein the first transmit beam is a layer 2 beam in a set of hierarchical beams within a layer 1 beam, wherein the second transmit beam is a layer 3 beam in the set of hierarchical beams within the first transmit beam, and wherein the second transmit beam corresponds to one of the plurality of repetitions of the random access message 3 associated with a strongest corresponding reference signal received power (RSRP), wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam, and wherein the refined beam for the layer 2 beam used to receive each of the repetitions of the random access message 3 is different. the random access message 2 indicates to the UE the plurality of repetitions of the random access message 3 are transmitted in a physical downlink control channel (PDCCH) portion of the random access message 2.

2. The method of claim 1, wherein, the PDCCH portion indicates the number of repetitions in the plurality of repetitions.

3. The method of claim 2, wherein, the random access message 2 indicates to the UE the plurality of repetitions of the random access message 3 are transmitted in a physical downlink shared channel (PDSCH) portion of the random access message 2.

4. The method of claim 1, wherein, the PDSCH portion indicates the number of repetitions in the plurality of repetitions or resources for the plurality of repetitions.

5. The method of claim 4, wherein, transmitting the plurality of repetitions of the random access message 3 includes transmitting the plurality of repetitions using a frequency hopping pattern.

6. The method of claim 1, wherein, 7. A method of wireless communication, comprising: transmitting, using a first transmit beam, a random access message 2 to a user equipment (UE), the random access message 2 indicating to the UE a plurality of repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions in the plurality of repetitions; in association with transmitting the random access message 2, receiving the plurality of repetitions of the random access message 3 using a different respective refined beam for each of the plurality of repetitions, wherein the refined beam for the layer 2 beam used to receive each of the repetitions of the random access message 3 is different; performing soft combining on the plurality of repetitions to determine a received message 3; based on the received message 3, determining a respective reference signal received power (RSRP) for each of the plurality of repetitions; for one of the plurality of repetitions associated with a strongest respective RSRP, selecting a refined second transmit beam associated with the respective refined beam; and ​ transmitting a random access message 4 via a second transmit beam, wherein the first transmit beam is the layer 2 beam of the set of hierarchical beams within the layer 1 beam, wherein the second transmit beam is a layer 3 beam of the set of hierarchical beams within the first transmit beam, and wherein the second transmit beam corresponds to one of the multiple repetitions of the random access message 3 associated with the strongest respective RSRP, wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam.

8. The method of claim 7, wherein, The random access message 2 indicates to the UE that the multiple repetitions of the random access message 3 are transmitted in a physical downlink control channel (PDCCH) portion of the random access message 2.

9. The method of claim 8, wherein, The PDCCH portion indicates a number of repetitions of the multiple repetitions.

10. The method of claim 7, wherein, The random access message 2 indicates to the UE that the multiple repetitions of the random access message 3 are transmitted in a physical downlink shared channel (PDSCH) portion of the random access message 2.

11. The method of claim 10, wherein, The PDSCH portion indicates a number of repetitions of the multiple repetitions or resources for the multiple repetitions.

12. The method of claim 7, wherein, Receiving the multiple repetitions of the random access message 3 includes receiving the multiple repetitions using a frequency hopping pattern.

13. The method of claim 7, wherein, A different respective refined beam for each of the multiple repetitions is a sub-beam of a beam used for the random access message 1 and the random access message 2.

14. An apparatus of a user equipment (UE) for wireless communication, comprising: a memory that stores computer-executable instructions; and at least one processor coupled to the memory and configured to execute the instructions to: receive, using a first receive beam, a random access message 2 transmitted by a base station using a first transmit beam, the random access message 2 indicating to the UE to transmit multiple repetitions of a random access message 3, the random access message 2 further including an indication of a number of repetitions of the multiple repetitions; in association with receiving the random access message 2, transmit the multiple repetitions of the random access message 3 so that the base station is able to perform soft combining on the multiple repetitions to determine a received message 3; and in association with transmitting the multiple repetitions of the random access message 3, receive a random access message 4 transmitted by the base station using a second transmit beam that is a sub-beam of the first transmit beam, wherein the first transmit beam is a layer 2 beam of a set of hierarchical beams within a layer 1 beam, wherein the second transmit beam is a layer 3 beam of the set of hierarchical beams within the first transmit beam, and wherein the second transmit beam corresponds to one of the multiple repetitions of the random access message 3 associated with the strongest respective reference signal received power (RSRP), wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam, and wherein the refined beam for the layer 2 beam for receiving each of the multiple repetitions of the random access message 3 is different.

15. The apparatus of claim 14, wherein, The random access message 2 indicates to the UE that the multiple repetitions of the random access message 3 are transmitted in a physical downlink control channel (PDCCH) portion of the random access message 2.

16. The apparatus of claim 15, wherein, The PDCCH portion indicates a number of repetitions of the multiple repetitions. The random access message 2 indicates to the UE that the multiple repetitions of the random access message 3 are transmitted in a physical downlink shared channel (PDSCH) portion of the random access message 2.

17. The apparatus of claim 14, wherein, The random access message 2 indicates to the UE that a plurality of repetitions of a random access message 3 are transmitted in a physical downlink shared channel, PDSCH, portion of the random access message 2.

18. The apparatus of claim 17, wherein, The PDSCH portion indicates a number of repetitions of the plurality of repetitions or resources for the plurality of repetitions.

19. The apparatus of claim 14, wherein, The at least one processor is configured to transmit the plurality of repetitions using a frequency hopping pattern.

20. An apparatus for wireless communication, comprising: a memory storing computer executable instructions; and at least one processor coupled to the memory and configured to execute the instructions to: transmit, using a first transmit beam, a random access message 2 to a user equipment, UE, the random access message 2 indicating to the UE that a plurality of repetitions of a random access message 3 are transmitted, the random access message 2 further including an indication of a number of repetitions of the plurality of repetitions; receive, in association with transmitting the random access message 2, the plurality of repetitions of the random access message 3 using a different respective refined beam for each repetition of the plurality of repetitions, wherein a refined beam of a layer 2 beam used to receive each repetition of the random access message 3 is different; perform soft combining on the plurality of repetitions to determine a received message 3; determine a respective reference signal received power, RSRP, for each of the plurality of repetitions based on the received message 3; select a refined second transmit beam associated with the respective refined beam for one of the plurality of repetitions associated with a strongest respective RSRP; and transmit, based on at least one of the number of repetitions of the random access message 3, a random access message 4 via a second transmit beam that is a sub-beam of the first transmit beam, wherein the first transmit beam is a layer 2 beam of a set of hierarchical beams within a layer 1 beam, wherein the second transmit beam is a layer 3 beam of the set of hierarchical beams within the first transmit beam, and wherein the second transmit beam corresponds to the one of the plurality of repetitions of the random access message 3 associated with the strongest respective RSRP, wherein the second transmit beam is a refined beam having a narrower aperture included within a wider aperture of the first transmit beam.

21. The apparatus of claim 20, wherein, The random access message 2 indicates to the UE that a plurality of repetitions of a random access message 3 are transmitted in a physical downlink control channel, PDCCH, portion of the random access message 2.

22. The apparatus of claim 21, wherein, The PDCCH portion indicates a number of repetitions of the plurality of repetitions.

23. The apparatus of claim 20, wherein, The random access message 2 indicates to the UE that a plurality of repetitions of a random access message 3 are transmitted in a physical downlink shared channel, PDSCH, portion of the random access message 2.

24. A computer-readable medium having program code recorded thereon, wherein the program code is executable by one or more processors of a user equipment, UE, to cause the one or more processors to perform the method of any of claims 1-6.

25. A computer-readable medium having program code recorded thereon, wherein the program code is executable by one or more processors of a network node to cause the one or more processors to perform the method of any of claims 7-13.

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