Message 2 Repetition Using Transmit Beam Scanning and Associated Beam Refinement for Message 3 and Message 4

Abstract

The present disclosure provides methods, devices, and systems for random access procedures and beam refinement in wireless communication. A base station may repeatedly send a random access message 2 to a user equipment (UE) on multiple physical downlink control channel (PDCCH) candidates to improve the reception of the random access message 2 and provide a selection of a refined beam. The UE may receive the random access message 2 on multiple repeated PDCCH candidates during a random access response window. The UE may select an offset based on the strongest PDCCH candidate among the multiple PDCCH candidates. The UE may send a random access message 3 on a resource that is time-shifted by the offset and indicated by the random access message 2. The base station may select a beam for sending a random access message 4 based on the offset.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of priority to U.S. Provisional Application No. 62 / 980,029, filed on February 21, 2020, entitled "MESSAGE 2 REPETITION WITH TRANSMIT BEAM SWEEP AND ASSOCIATED BEAM REFINEMENT FOR MESSAGE 3 AND MESSAGE 4", and U.S. Patent Application No. 17 / 178,852, filed on February 18, 2021, entitled "MESSAGE 2 REPETITION WITH TRANSMIT BEAM SWEEP AND ASSOCIATED BEAM REFINEMENT FOR MESSAGE 3 AND MESSAGE 4", the entire disclosures of which are hereby incorporated by reference herein and assigned to the assignee of the present application. Field of the Disclosure

[0003] The present disclosure generally relates to wireless communication systems, and more particularly, to random access procedures and beam refinement for wireless communication. Background of the Disclosure

[0004] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasting. A typical wireless communication system may employ a multiple access technology capable of supporting 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 techniques have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at the urban, national, regional, and even global levels. An example telecommunication standard is 5G New Radio (NR). 5G NR is part of the continuous mobile broadband evolution promulgated by the 3rd Generation Partnership Project (3GPP) and is 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 communication (mMTC), and ultra-reliable low-latency communication (URLLC). Some aspects of 5G NR can be based on the 4G Long Term Evolution (LTE) standard. There is a need for further improvement in 5G NR technology.

[0006] Specifically, wireless communication can include a random access process that allows a user equipment (UE) to initiate or resume communication with a base station. Under certain channel conditions, various messages of the random access process may not be correctly received, which may delay or prevent the UE from connecting to the base station. Wireless communication can include a random access process. Improvements are proposed herein. These improvements can also be applied to other multiple access techniques and telecommunication standards that employ these techniques. Summary of the Invention

[0007] A simplified summary of one or more aspects is given below in order to provide a basic understanding of these aspects. This summary is not an extensive overview of all contemplated aspects, and is neither intended to identify key or critical elements of all aspects nor to delineate the scope of any or all aspects. The sole purpose of the summary 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 present disclosure, a method, computer-readable medium, and apparatus for wireless communication of a user equipment (UE) are provided. The method can include receiving, during a random access response window, multiple repeated physical downlink control channel (PDCCH) candidates for a single random access message 2 from a base station. The method can include transmitting a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted based on an offset of the strongest PDCCH candidate among the multiple repeated PDCCH candidates. The method can include receiving a random access message 4, which is transmitted using a beam selected by the base station based on the offset.

[0009] In one aspect, the present disclosure provides an apparatus for wireless communication. The apparatus may 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 may be configured to receive, during a random access response window, multiple repeated PDCCH candidates for a single random access message 2 from a base station. The at least one processor may be configured to transmit a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted based on an offset of the strongest PDCCH candidate among the multiple repeated PDCCH candidates. The at least one processor may be configured to receive a random access message 4, which is transmitted using a beam selected by the base station based on the offset.

[0010] In one aspect, the present disclosure provides another apparatus for wireless communication. The apparatus may include means for receiving, during a random access response window, multiple repeated PDCCH candidates for a single random access message 2 from a base station. The apparatus may include means for transmitting a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted based on an offset of the strongest PDCCH candidate among the multiple repeated PDCCH candidates. The apparatus may include means for receiving a random access message 4, which is transmitted using a beam selected by the base station based on the offset.

[0011] In one aspect, the present disclosure provides a non-transitory computer-readable medium storing computer-executable code. When executed by a processor, the code causes the processor to receive, during a random access response window, multiple repeated PDCCH candidates for a single random access message 2 from a base station. When executed by a processor, the code causes the processor to transmit a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted based on an offset of the strongest PDCCH candidate among the multiple repeated PDCCH candidates. When executed by a processor, the code causes the processor to receive a random access message 4, which is transmitted using a beam selected by the base station based on the offset.

[0012] In one aspect of the present disclosure, there are provided a method, a computer-readable medium, and an apparatus for wireless communication of a base station. The method may include transmitting, during a random access response window, multiple repeated PDCCH candidates for a single random access message 2. The method may include receiving a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted based on an offset of the strongest PDCCH candidate among the multiple repeated PDCCH candidates. The method may include selecting, based on the offset, a beam for transmitting a random access message 4. The method may include transmitting the random access message 4 using the selected beam.

[0013] In one aspect, the present disclosure provides an apparatus for wireless communication. The apparatus may 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 may be configured to send, during a random access response window, multiple repetitions of PDCCH candidates for a single random access message 2. The at least one processor may be configured to receive a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted by an offset indicating the strongest PDCCH candidate among the multiple repetitions of PDCCH candidates. The at least one processor may be configured to select a beam based on the offset. The at least one processor may be configured to use the selected beam to send a random access message 4.

[0014] In one aspect, the present disclosure provides another apparatus for wireless communication. The apparatus may include means for sending, during a random access response window, multiple repetitions of PDCCH candidates for a single random access message 2. The apparatus may include means for receiving a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted by an offset indicating the strongest PDCCH candidate among the multiple repetitions of PDCCH candidates. The apparatus may include means for selecting, based on the offset, a beam for sending a random access message 4. The apparatus may include means for using the selected beam to send a random access message 4.

[0015] In one aspect, the present disclosure provides a non-transitory computer-readable medium storing computer-executable code. When executed by a processor, the code causes the processor to send, during a random access response window, multiple repetitions of PDCCH candidates for a single random access message 2. When executed by a processor, the code causes the processor to receive a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted by an offset indicating the strongest PDCCH candidate among the multiple repetitions of PDCCH candidates. When executed by a processor, the code causes the processor to select, based on the offset, a beam for sending a random access message 4. When executed by a processor, the code causes the processor to use the selected beam to send a random access message 4.

[0016] To achieve the foregoing and related purposes, one or more aspects include the features that are fully described hereinafter and particularly pointed out in the claims. The following description and the drawings set forth in detail some illustrative features of one or more aspects. However, these features are only several of the various ways in which the principles of the various aspects may be employed, and this description is intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a diagram showing an example of a wireless communication system and an access network.

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

[0019] Figure 2B It is a diagram showing an example of a downlink (DL) channel within a 5G NR subframe.

[0020] Figure 2C It is a diagram showing an example of a second 5G NR frame.

[0021] Figure 2D It is a diagram showing an example of an uplink (UL) channel within a 5G NR subframe.

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

[0023] Figure 4 It is a diagram showing an example message exchange of a random access channel (RACH) process between a base station and a UE in an access network.

[0024] Figure 5 It is a diagram showing an example resource for the repetition of random access message 2.

[0025] Figure 6 It is a diagram showing an example part of a random access response window for the repetition of random access message 2.

[0026] Figure 7 It is a flowchart of an example method for transmitting random access message 2 during a RACH process.

[0027] Figure 8 It is a flowchart of an example method for receiving random access message 2 during a RACH process.

[0028] Figure 9 It is a block diagram of an example apparatus (such as a UE) for wireless communication.

[0029] Figure 10 It is a block diagram of an example apparatus (such as a base station) for wireless communication. Detailed Description

[0030] The detailed description set forth below in connection with the accompanying drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. For the purpose of providing a thorough understanding of the various concepts, the detailed description includes specific details. It will be apparent, however, to one of ordinary skill in the art that these concepts may be practiced without these specific details. In some instances, structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0031] Using a random access channel (RACH) procedure, a user equipment (UE) may initiate or resume communication with a base station based on an exchange of four messages between the UE and the base station. Messages used for the RACH procedure may be interchangeably referred to as numbered random access messages (such as random access message 1), numbered RACH messages (such as RACH message 1), or abbreviated as numbered "Msg" (e.g., Msg 1). Under some channel conditions, messages transmitted as part of the RACH procedure may not be correctly received. In particular, when using high carrier frequencies, transmissions may suffer from high path loss. Beamforming between the user equipment (UE) and the base station may overcome the path loss experienced at high carrier frequencies. However, during the RACH procedure, beamforming between the UE and the base station may not be established, for example because the UE has been inactive prior to the RACH procedure.

[0032] Aspects of the present disclosure generally relate to random access procedures and beam refinement. In some particular aspects, a base station may transmit multiple repetitions of RACH message 2, which may increase the likelihood that RACH message 2 is successfully received by the UE. Additionally, the base station may transmit multiple repetitions of RACH message 2 using different beams based on receiving RACH message 1. The UE may receive multiple repetitions of RACH message 2 on multiple PDCCH candidates. In some implementations, the UE may soft combine the multiple PDCCH candidates and decode RACH message 2 based on the combination. The UE may measure the received power of one or more of the multiple PDCCH candidates based on the decoded RACH message 2. The UE may select the strongest beam based on the respective measured received powers of the multiple PDCCH candidates. In some such implementations, the UE may select a time offset based on the strongest beam and transmit RACH message 3 at that time offset to indicate the strongest beam to the base station. For example, the UE may time shift RACH message 3 by that time offset. The base station may receive RACH message 3 at that time offset and select a refined beam for transmitting RACH message 4 based on that time offset. The refined beam may increase the likelihood of successfully receiving RACH message 4.

[0033] Specific implementations of the subject matter described in this disclosure can be realized to achieve one or more of the following potential advantages. In some implementations, the described techniques can be used to improve the reliability of the RACH process, thereby facilitating access to the wireless network and establishing a communication connection between the UE and the base station. For example, due to the repetition and use of different beams, the UE may be able to receive the RACH message 2 PDCCH more reliably. In some implementations, since the offset for the RACH message 3 indicates the best beam for the RACH message 2 PDCCH, the base station can select this best beam to send the RACH message 4, so that the reliability of the message 4 is also improved.

[0034] Several aspects of a telecommunications system will now be presented with reference to various apparatuses and methods. These apparatuses and methods will be described in the following detailed description and illustrated in the drawings by various boxes, components, circuits, processes, algorithms, and other examples (collectively referred to as "elements"). These elements can be implemented using electronic hardware, computer software, or any combination thereof. Whether these elements are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0035] By way of example, an element or any part of an element or any combination of elements can be implemented as a "processing system" including 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, system 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 functions described throughout this disclosure. One or more processors in the processing system can execute software. Whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise, software should be broadly interpreted to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, processes, functions, and other examples.

[0036] Thus, in one or more examples, the described functionality may be implemented in hardware, software, or any combination thereof. If implemented in software, the functionality may be stored 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 include random access memory (RAM), read only memory (ROM), electrically erasable programmable ROM (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that can be used to store instructions or data structures in a form that can be accessed by a computer executable code.

[0037] Figure 1 FIG. Figure 1 is a diagram illustrating an example of a wireless communication system and an access network 100. The wireless communication 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 may include macro cells (high-power cellular base stations) or small cells (low-power cellular base stations). Macro cells include base stations. Small cells include femto cells, pico cells, and micro cells.

[0038] In one aspect, one or more of the UEs 104 may include a UE RACH component 140 configured to perform a RACH procedure, including receiving multiple repetitions of PDCCH candidates for a random access message 2, also referred to as a random access response (RAR). The UE RACH component 140 may include: a RAR receiving component 141 configured to receive multiple repetitions of physical downlink control channel (PDCCH) candidates for a single random access message 2 during a random access response window; an offset component 142 configured to transmit a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted by an offset selected based on the strongest PDCCH candidate among the multiple repetitions of PDCCH candidates. The UE RACH component 140 may include a contention resolution component 143 configured to receive a random access message 4.

[0039] In one aspect, one or more of the base stations 102 may include a BS RACH component 198 configured to repeat the transmission of random access message 2 PDCCH candidates. The BS RACH component 198 may include: a repeating component 146 configured to transmit multiple repeated PDCCH candidates for a single random access message 2 during a random access response window; and a detection component 147 configured to receive random access message 3 on a resource indicated by random access message 2. The resource for random access message 3 is time-shifted by an offset selected based on the strongest PDCCH candidate among the multiple repeated PDCCH candidates. The BS RACH component 198 may include a beam selection component 148 configured to select a beam for transmitting random access message 4 based on the offset. The BS RACH component 198 may include a transmission component (not shown) configured to transmit random access message 4 using the selected beam.

[0040] The base stations 102 configured for 4G LTE (collectively, the evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN)) may interface with the EPC 160 via a first backhaul link 132 (e.g., the S1 interface). The base stations 102 configured for 5G NR (collectively, the next-generation RAN (NG-RAN)) may interface with the core network 190 via a second backhaul link 184. In addition to other functions, the base stations 102 may perform one or more of the following functions: user data transfer, radio channel encryption and decryption, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution of non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment tracking, radio access network information management (RIM), paging, positioning, and warning message delivery. The base stations 102 may communicate directly or indirectly with each other (e.g., via the EPC 160 or the core network 190) on a third backhaul link 134 (e.g., the X2 interface). The third backhaul link 134 may be wired or wireless.

[0041] Base station 102 can communicate wirelessly with UE 104. Each of the base stations 102 can provide communication coverage for a corresponding geographical coverage area 110. There can be overlapping geographical coverage areas 110. For example, small cell 102a can have a coverage area 110a that overlaps with the coverage areas 110 of one or more macro base stations 102. A network including both small cells and macro cells can be referred to as a heterogeneous network. The heterogeneous network can also include a Home evolved Node B (eNB) (HeNB), which can provide services to a restricted group known as a Closed Subscriber Group (CSG). The communication link 120 between the base station 102 and the UE 104 can include an uplink (UL) (also known as the reverse link) transmission from the UE 104 to the base station 102 or a downlink (DL) (also known as the forward link) transmission from the base station 102 to the UE 104. The communication link 120 can use multiple-input multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, or transmit diversity. The communication link can be through one or more carriers. The base station 102 / UE 104 can use a spectrum with a bandwidth of up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz and other examples) per carrier in carrier aggregation with a total of up to Yx (x component carriers) MHz for transmission in each direction. The carriers can or can not be adjacent to each other. The allocation of carriers can be asymmetric for the DL and UL (e.g., more or fewer carriers can be allocated for the DL than for the UL). The component carriers can include a primary component carrier and one or more secondary component carriers. The primary component carrier can be referred to as the Primary Cell (PCell) and the secondary component carriers can be referred to as Secondary Cells (SCells).

[0042] Some UEs 104 can communicate with each other using device-to-device (D2D) communication links 158. The D2D communication links 158 can use the DL / UL WWAN spectrum. The D2D communication links 158 can use one or more sidelink channels, such as the Physical Sidelink Broadcast Channel (PSBCH), Physical Sidelink Discovery Channel (PSDCH), Physical Sidelink Shared Channel (PSSCH), and Physical Sidelink Control Channel (PSCCH). D2D communication can be through various wireless D2D communication systems, such as, for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

[0043] The wireless communication system may also include a Wi-Fi access point (AP) 150 that communicates with a Wi-Fi station (STA) 152 via a communication link 154 in the 5 GHz unlicensed spectrum. When communicating in the unlicensed spectrum, the STA 152 / AP 150 may perform a clear channel assessment (CCA) before communication to determine whether the channel is available.

[0044] The small cell 102a may operate in licensed or unlicensed spectrum. When operating in the unlicensed spectrum, the small cell 102a may adopt NR and use the same 5 GHz unlicensed spectrum as that used by the Wi-Fi AP 150. The small cell 102a adopting NR in the unlicensed spectrum may improve the coverage of the access network or increase the capacity of the access network.

[0045] The electromagnetic spectrum is generally subdivided into various categories, frequency bands, channels, etc. based on frequency / wavelength. In 5G NR, two initial operating frequency 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 generally referred to as mid-band frequencies. Although a part of FR1 is greater than 6 GHz, in various documents and articles, FR1 is often (interchangeably) referred to as the "Sub-6GHz" band. A similar naming issue sometimes occurs for FR2. Although it is different from the extremely high frequency (EHF) band (30 GHz - 300 GHz) identified by the International Telecommunication Union (ITU) as the "millimeter wave (mmW)" band, in documents and articles, FR2 is generally (interchangeably) referred to as the "millimeter wave" band. Communications using the mmW radio frequency band have extremely high path loss and short distances. The mmW base station 180 may utilize beamforming 182 with the UE 104 to compensate for the path loss and short distances.

[0046] Considering the above aspects, unless otherwise specifically stated, it should be understood that terms such as "Sub-6GHz" etc., if used in this article, may generally represent frequencies below 6 GHz, within FR1, or may include mid-band frequencies. In addition, unless otherwise specifically stated, it should be understood that terms such as "millimeter wave" etc., if used in this article, may generally represent frequencies that may include mid-band frequencies, within FR2, or within the EHF band. Communications using the mmW radio frequency band have extremely high path loss and short distances. The mmW base station 180 may utilize beamforming 182 with the UE 104 to compensate for the path loss and short distances.

[0047] Base station 180 may transmit beamformed signals to UE 104 in one or more transmission directions 182a. UE 104 may receive beamformed signals from base station 180 in one or more reception directions 182b. UE 104 may also transmit beamformed signals to base station 180 in one or more transmission directions. Base station 180 may receive beamformed signals from UE 104 in one or more reception directions. Base station 180 / UE 104 may perform beam training to determine the optimal reception and transmission directions for each of base station 180 / UE 104. The transmission and reception directions of base station 180 may be the same or different. The transmission and reception directions of UE 104 may be the same or different.

[0048] EPC 160 may 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. MME 162 may communicate with a Home Subscriber Server (HSS) 174. MME 162 is a control node that processes signaling between UE 104 and EPC 160. Generally, MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are transported through Serving Gateway 166 which is itself connected to PDN Gateway 172. PDN Gateway 172 provides UE IP address allocation and other functions. PDN Gateway 172 and BM-SC 170 are connected to IP services 176. IP services 176 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS streaming service, or other IP services. BM-SC 170 may provide functions for MBMS user service provisioning and delivery. BM-SC 170 may serve as an entry point for content provider MBMS transmissions, may be used to authorize and initiate MBMS bearer services within a Public Land Mobile Network (PLMN), and may be used to schedule MBMS transmissions. MBMS Gateway 168 may be used to distribute MBMS traffic to base stations 102 for broadcast-specific services belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area, and may be responsible for session management (start / stop) and collecting charging information related to eMBMS.

[0049] The core network 190 may include an 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 may communicate with a Unified Data Management (UDM) 196. The AMF 192 is a control node that processes signaling between the UE 104 and the core network 190. Generally, the AMF 192 provides QoS flow and session management. All user Internet Protocol (IP) packets are transmitted through the UPF 195. The UPF 195 provides UE IP address allocation and other functions. The UPF 195 is connected to an IP service 197. The IP service 197 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS streaming service, or other IP services.

[0050] The base station may include or be referred to as a gNB, Node B, eNB, access point, base transceiver station, radio base station, radio transceiver, transceiver function, Basic Service Set (BSS), Extended Service Set (ESS), Transmission and Reception Point (TRP), or some other suitable term. The base station 102 provides an access point for the UE 104 to the EPC 160 or the core network 190. Examples of the UE 104 include cellular phones, smart phones, Session Initiation Protocol (SIP) phones, laptop computers, personal digital assistants (PDAs), satellite radios, global positioning systems, multimedia devices, video devices, digital audio players (e.g., MP3 players), cameras, gaming consoles, tablet computers, smart devices, wearable devices, vehicles, electricity meters, air pumps, large or small kitchen appliances, healthcare devices, implants, sensors / actuators, displays, or any other similar functional devices. Some of the UEs 104 may be referred to as IoT devices (e.g., parking meters, air pumps, toasters, vehicles, heart monitors, and other examples). The UE 104 may also be referred to as a station, mobile station, subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handheld device, user agent, mobile client, client, or some other suitable term.

[0051] Figure 2A FIG. 200 is an example showing a first subframe within the 5G / NR frame structure. Figure 2B FIG. 230 is an example showing DL channels within a 5G / NR subframe. Figure 2C FIG. 250 is an example showing a second subframe within the 5G / NR frame structure. Figure 2DFIG. 280 is an example showing UL channels within a 5G / NR subframe. The 5G / NR frame structure can be FDD, where for a particular subcarrier set (carrier system bandwidth), subframes within the subcarrier set are dedicated to DL or UL, or can be TDD, where for a particular subcarrier set (carrier system bandwidth), subframes within the subcarrier set are dedicated to both DL and UL. In the example provided by Figure 2A , Figure 2C , it is assumed that the 5G / NR frame structure is TDD, subframe 4 is configured with slot format 28 (mostly DL), where D is DL, U is UL, and X can be flexibly used between DL / UL, and subframe 3 is configured with slot format 34 (mostly UL). Although subframes 3 and 4 are shown with slot formats 34 and 28 respectively, any particular subframe can be configured with any one of the various available slot formats 0 - 61. Slot formats 0 and 1 are all DL and UL respectively. The other slot formats 2 - 61 include a mixture of DL, UL, and flexible symbols. The UE is configured with a slot format (dynamically via DL control information (DCI), or semi-statically / statically via radio resource control (RRC) signaling) by a received slot format indicator (SFI). Note that the description here also applies to the 5G / NR frame structure as TDD.

[0052] Other wireless communication technologies can have different frame structures or different channels. A frame (10 ms) can be divided into 10 subframes of equal size (1 ms). Each subframe can include one or more time slots. A subframe can also include mini time slots, which can include 7, 4, or 2 symbols. Each time slot can include 7 or 14 symbols, depending on the time slot configuration. For time slot configuration 0, each time slot can include 14 symbols, and for time slot configuration 1, each time slot can include 7 symbols. Symbols on the DL can be cyclic prefix (CP) OFDM (CP - OFDM) symbols. 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 time slots within a subframe is based on the time slot configuration and numerology. For time slot configuration 0, different numerologies μ0 to 5 respectively allow 1, 2, 4, 8, 16, and 32 time slots per subframe. For time slot configuration 1, different numerologies 0 to 2 respectively allow 2, 3, and 8 time slots per subframe. Thus, for time slot configuration 0 and numerology μ, there are 14 symbols / time slot and 2 μ time slots / subframe. The subcarrier spacing and symbol length / duration are functions of the numerology. The subcarrier spacing can be equal to 2 μ*15 kHz, where μ is a parameter set from 0 to 5. Thus, the parameter set μ = 0 has a subcarrier spacing of 15 kHz, and the parameter set 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 slot configuration 0 with 14 symbols per slot and parameter set μ = 0 with 1 slot per subframe is provided. The subcarrier spacing is 15 kHz, and the symbol duration is approximately 66.7 μs.

[0053] A resource grid can be used to represent the frame structure. Each slot includes resource blocks (RBs) (also known as physical RBs (PRBs)), which span 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.

[0054] As Figure 2A shown, some REs carry reference (pilot) signals (RSs) for the UE. The RSs can include demodulation RSs (DM-RSs) for channel estimation at the UE (denoted as Rx for a specific configuration, where 100x is the port number, but other DM-RS configurations are also possible) and channel state information reference signals (CSI-RSs). The RSs can also include beam measurement RSs (BRSs), beam refinement RSs (BRRSs), and phase tracking RSs (PT-RSs).

[0055] Figure 2B Examples of various DL channels within a subframe of a frame are shown. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs), each CCE including nine RE groups (REGs), each REG including four consecutive REs in one OFDM symbol. The primary synchronization signal (PSS) can be in symbol 2 of a specific subframe of the frame. The PSS is used by the UE104 to determine subframe / symbol timing and the physical layer identity. The secondary synchronization signal (SSS) can be in symbol 4 of a specific subframe of the frame. The SSS is used by the UE to determine the physical layer cell identity group number and the radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine the physical cell identifier (PCI). Based on the PCI, the UE can determine the location of the above DM-RS. The physical broadcast channel (PBCH) carrying the master information block (MIB) can be logically grouped with the PSS and SSS to form a synchronization signal (SS) / PBCH block. The MIB provides the number of RBs in the system bandwidth and the system frame number (SFN). The physical downlink shared channel (PDSCH) carries user data, broadcast system information not sent via the PBCH (such as system information blocks (SIBs)), and paging messages.

[0056] As Figure 2CAs shown, some REs carry DM-RS for channel estimation at the base station (denoted as R for a specific configuration, but other DM-RS configurations are also possible). The UE can send DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH). The PUSCH DM-RS can be transmitted in the previous one or two symbols of the PUSCH. The PUCCH DM-RS can be sent in different configurations depending on whether a short PUCCH or a long PUCCH is being sent and according to the specific PUCCH format used. Although not shown, the UE can send a sounding reference signal (SRS). The SRS can be used by the base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

[0057] Figure 2D Examples of various UL channels within a subframe of a frame are shown. The PUCCH can be located as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as a scheduling request, 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.

[0058] Figure 3It is a block diagram of the communication between the base station 310 and the UE 350 in the access network. In the DL, IP packets from the EPC 160 can be provided to the controller / processor 375. The controller / processor 375 implements the layer 3 and layer 2 functions. The layer 3 includes the radio resource control (RRC) layer, and the layer 2 includes the service data adaptation protocol (SDAP) layer, the packet data convergence protocol (PDCP) layer, the radio link control (RLC) layer, and the media access control (MAC) layer. The controller / processor 375 provides RRC layer functions associated with broadcast system information (such as MIB, SIB), 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 for UE measurement reporting; PDCP layer functions associated with header compression / decompression, security (encryption, decryption, integrity protection, integrity verification), and handover support functions; RLC layer functions associated with the transfer of upper layer packet data units (PDUs), error correction via ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and re-ordering of RLC data PDUs; and MAC layer functions associated with the 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 via HARQ, priority handling, and logical channel prioritization.

[0059] The transmit (TX) processor 316 and the receive (RX) processor 370 implement the layer 1 functions associated with various signal processing functions. The layer 1, which includes the physical (PHY) layer, may include error detection on the transport channel, forward error correction (FEC) coding / decoding of the transport channel, interleaving, rate matching, mapping to the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. The TX processor 316 processes the mapping to the signal constellation based on various modulation schemes such as binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase shift keying (M-PSK), and M-quadrature amplitude modulation (M-QAM). The coded and modulated symbols can then be split into parallel streams. Each stream can then be mapped to OFDM subcarriers, multiplexed with reference signals such as pilots in the time domain or frequency domain, and then combined together using the inverse fast Fourier transform (IFFT) to generate a physical channel carrying a time domain OFDM symbol stream. The OFDM symbol stream is space precoded to generate multiple spatial streams. Channel estimates from the channel estimator 374 can be used to determine the coding and modulation schemes, as well as for spatial processing. The channel estimates can be derived from reference signals transmitted by the UE 350 or channel condition feedback. Each spatial stream can then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX can modulate an RF carrier with the corresponding spatial stream for transmission.

[0060] At the UE 350, each receiver 354RX receives signals via its respective antenna 352. Each receiver 354RX recovers the information modulated onto the RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement the layer 1 functions 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 uses the fast Fourier transform (FFT) to convert the OFDM symbol stream from the time domain to the frequency domain. The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols and reference signals on each subcarrier 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 the channel estimates calculated by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals 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 the layer 3 and layer 2 functions.

[0061] The controller / processor 359 may be associated with a memory 360 that stores program code and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller / processor 359 provides demultiplexing between the transport channel and the logical channel, packet reassembly, decryption, 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 the ACK or NACK protocol to support HARQ operations.

[0062] Similar to the functions described in connection with DL transmissions performed by the base station 310, the controller / processor 359 provides RRC layer functions associated with system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; PDCP layer functions associated with header compression / decompression and security (encryption, decryption, integrity protection, integrity verification); RLC layer functions associated with the transmission of upper layer PDUs, error correction via ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and re-ordering of RLC data PDUs; and MAC layer functions associated with the mapping between the logical channel and the transport channel, multiplexing of MAC SDUs into TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction via HARQ, priority handling, and logical channel prioritization.

[0063] Channel estimates derived by the channel estimator 358 from reference signals or feedback transmitted by the base station 310 may be used by the TX processor 368 to select an appropriate coding and modulation scheme and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antennas 352 via separate transmitters 354TX. Each transmitter 354TX may modulate an RF carrier with a corresponding spatial stream for transmission.

[0064] UL transmissions are processed at the base station 310 in a manner similar to that described in connection with the receiver functions at the UE 350. Each receiver 318RX receives signals via its respective antenna 320. Each receiver 318RX recovers the information modulated onto the RF carrier and provides the information to the RX processor 370.

[0065] The controller / processor 375 may be associated with a memory 376 that stores program code and data. The memory 376 may be referred to as a computer-readable medium. In the UL, the controller / processor 375 provides demultiplexing between the transport channel and the logical channel, packet reassembly, decryption, header decompression, and control signal processing to recover IP packets from the UE 350. The IP packets from the controller / processor 375 may be provided to the EPC 160. The controller / processor 375 is also responsible for error detection using the ACK or NACK protocol to support HARQ operations.

[0066] At least one of TX processor 368, RX processor 356, and controller / processor 359 may be configured to perform aspects related to Figure 1 UE RACH component 140.

[0067] At least one of TX processor 316, RX processor 370, and controller / processor 375 may be configured to perform aspects related to Figure 1 BS RACH component 198.

[0068] Figure 4 FIG. 400 is a diagram that illustrates an example message exchange of a RACH procedure between base station 102 and UE 104 in an access network. UE 104 may be a NR-Light UE and includes UE RACH component 140. Base station 102 may include BS RACH component 198.

[0069] Additionally referring to Table 1 (below), during operation, due to the occurrence of one or more RACH trigger events 420, UE 104 may perform an implementation of NR RACH procedure 410 according to a 4-step NR RACH message flow. Suitable examples of RACH trigger events 420 may include, but are not limited to: (i) UE 104 performs initial access to transition from the RRC_IDLE (RRC idle) state to the RRC_CONNECTED ACTIVE (RRC connected active) state; (ii) when in the RRC_IDLE state or RRC_CONNECTED INACTIVE (RRC connected inactive) state, UE 104 detects downlink (DL) data arrival; (iii) UE 104 determines the arrival of UL data from a higher layer during the RRC_IDLE state or RRC_CONNECTED INACTIVE state; (iv) UE 104 performs a handover from another station to base station 102 during the connected operation mode; and (v) UE performs a connection reestablishment procedure, such as a beam failure recovery procedure.

[0070] 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 reestablishment. 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 the connected operation mode.

[0071] 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), where the UE 104 exchanges messages with one or more base stations 102 to obtain access to the wireless network and establish a communication connection. These messages can be referred to as random access messages 1 to 4, RACH messages 1 to 4, or alternatively, can be referred to by the PHY channel carrying the message, such as Msg 3 PUSCH.

[0072]

[0073] Table 1 : The NR RACH procedure, including messages and message content sent through corresponding physical (PHY) channels at 411. For example, the UE 104 can send a first message (Msg 1) to one or more base stations 102 via a physical channel (such as the physical random access channel (PRACH)), and this first message can be referred to as a random access request message. 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 sending Msg 1 based on the received synchronization signal block (SSB) sent by the base station 102.

[0074] At 412, one or more of base stations 102 may respond to Msg 1 by sending a second message (Msg 2) on a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH), and this second message may be referred to as a random access response (RAR) message. In one aspect, an RAR receiving component 141 may receive the RAR message. The RAR receiving component 141 may monitor the PDCCH during an RAR window based on Msg 1 to detect the PDCCH portion of the RAR message as a DCI format 1_0 with a CRC scrambled by a corresponding RA-RNTI, and receive the PDSCH portion of the RAR message as a transport block in the corresponding PDSCH within this window.

[0075] In one aspect, at 430, the base station 102 may repeat the PDCCH portion of Msg 2. That is, the base station 102 may repeat Msg 2 on consecutive time slots on corresponding PDCCH candidates within a random access search space. In one aspect, a BSRACH component 198 may determine whether to repeat the PDCCH portion of Msg 2 based on the detection of coverage enhancement conditions. For example, the BSRACH component 198 may determine to repeat Msg 2 based on the signal strength of Msg 1. For example, when the signal strength of Msg 1 is less than a threshold, the BS RACH component 198 may repeat Msg 2. The base station 102 may use different refined beams to repeat the PDCCH portion of Msg 2. That is, the base station 102 may scan the beams for the PDCCH portion of Msg 2. In one aspect, each of the different refined beams may be a sub-beam of the beam corresponding to Msg 1. A sub-beam may refer to a lower-level beam in a hierarchical beam set. For example, a layer 1 (L1) beam may cover multiple L2 beams, and each L2 beam may cover multiple L3 beams. In other words, a refined sub-beam may have a narrower aperture included within the wider aperture of a higher-level beam. In one implementation, the beam corresponding to Msg 1 is an L2 beam, and each of the different refined beams is an L3 beam. The repeated L3 refined beams for the PDCCH portion of Msg 2 may be based on the L2 beam for Msg 1. That is, the base station 102 may generate different sub-beams corresponding to the L2 beam to attempt to improve the reception of Msg 3.

[0076] The UE 104 or the RAR receiving component 141 may perform blind detection after soft combining of PDCCH candidates. That is, the UE 104 may receive signals corresponding to each of the PDCCH candidates, perform soft combining on the signals received for each PDCCH candidate, and perform blind detection of DCI on the combined signals. Therefore, the UE 104 is more likely to successfully detect the Msg2 PDCCH. The RAR receiving component 141 may use the successfully decoded Msg 2 as a reference signal to perform individual reference signal received power (RSRP) measurements on the PDCCH candidates. The RAR receiving component 141 may select a PDCCH candidate and a corresponding beam based on the RSRP (e.g., the PDCCH candidate with the strongest RSRP).

[0077] At 432, the RAR receiving component 141 may receive a transport block in a corresponding PDSCH indicated by a PDCCH within the RAR window. The RAR receiving component 141 may pass the transport block to a higher layer, which may parse the transport block to obtain a random access preamble identifier (RAPID) associated with Msg 1. For example, Msg 2 may 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 fallback indicator, a UL grant, and a DL grant. If the higher layer identifies the RAPID in the transport block, the higher layer indicates a UL grant to the RAR receiving component 141 at the physical layer. This is referred to as the RAR UL grant in the physical layer.

[0078] At 413, in response to receiving Msg 2, the UE 104 or the offset component 142 sends a third message (Msg 3) to the base station 102 via a physical uplink channel (such as PUSCH) based on the RAR UL authorization provided in Msg 2 of the serving base station 102, and the third message may be an RRC connection request or a scheduling request. In one aspect, in the case where the UE 104 has received a repeated Msg2 PDCCH, the UE 104 may time-shift the resources of Msg 3 based on the offset of the strongest PDCCH candidate. For example, the offset may be the number of symbols or time slots equal to the time slot number of the strongest PDCCH candidate. In another aspect, the UE 104 may select a refined beam for Msg 3. For example, the UE 104 may select a beam corresponding to the PDCCH candidate with the strongest RSRP.

[0079] At 414, in response to receiving Msg 3, base station 102 or beam selection component 148 may send a fourth message (Msg 4) to UE 104 via PDCCH and PDSCH, and this fourth message may be referred to as a contention resolution message. For example, Msg 4 may include a cell radio network temporary identifier (C-RNTI) for UE 104 to use in subsequent communications. Base station 102 may select a beam based on the offset at which it received Msg 3. The selected beam may correspond to the sub-beam used to send Msg 2 on the PDCCH candidate selected by UE 104 as the strongest. Base station 102 may use the selected beam to send Msg 4. Contention resolution component 143 may receive Msg 4.

[0080] In some example scenarios, a conflict may occur between two or more UEs 104 requesting access. For example, two or more UEs 104 may send Msg 1 with the same RACH preamble because the number of RACH preambles may be limited and may be randomly selected by each UE 104 during a contention-based NR RACH procedure. In this way, each conflicting UE 104 that selects the same RACH preamble will receive the same temporary C-RNTI and the same UL grant, so each UE 104 may send a similar Msg 3. In this case, base station 102 may resolve the conflict in one or more ways. In the first scenario, the respective Msg 3s from each conflicting UE 104 may interfere with the other Msg 3s, so base station 102 may not send Msg 4. Then, each UE 104 will retransmit Msg 1 using a different RACH preamble. In the second scenario, base station 102 may successfully decode only one Msg 3 and send an ACK message to the UE 104 corresponding to the successfully decoded Msg 3. In the third scenario, base station 102 may successfully decode Msg 3s from each conflicting UE 104 and then send Msg 4 with a contention resolution identifier (such as an identifier bound to one of the UEs) to each conflicting UE. Each conflicting UE 104 receives Msg 4, decodes Msg 4, and determines whether UE 104 is the correct UE by successfully matching or identifying the contention resolution identifier. This problem may not occur in a contention-free NR RACH procedure because in this case, base station 102 may notify UE 104 which RACH preamble to use.

[0081] Figure 5FIG. 500 is a diagram showing an example resource for repeating random access message 2. Resource 510 may be located within consecutive time slots 520, 522, 524, and 526, which may be during the RAR window. The base station 102 may use different refinement beams to transmit repetitions of Msg 2 on PDCCH candidates 530, 532, 534, and 536 for Msg 3 in each of the time slots 520, 522, 524, and 526. The PDCCH candidates 530, 532, 534, and 536 may be located within the random access search space portion of a control resource set (CORESET) 540. That is, each of the PDCCH candidates 530, 532, 534, and 536 may include the same data, but be transmitted with different beamforming parameters. For example, the base station 102 or the repetition component 146 may transmit each repetition of Msg 2 on the PDCCH candidates 530, 532, 534, and 536 in the respective time slots 520, 522, 524, and 526 using different L3 refinement beams. The L3 refinement beams may be based on the L2 beam for Msg 1. That is, the base station 102 may generate different sub-beams of the L2 beam to attempt to improve the reception of Msg 2.

[0082] In one aspect, the UE 104 may determine which of the received PDCCH candidates 530, 532, 534, and 536 is the strongest. For example, the UE 104 may perform soft combining of the signals corresponding to the multiple repeated PDCCH candidates. After soft combining, the UE 104 may perform blind detection of DCI format 1_0 on the combined signal. Thus, the likelihood of successful detection can be increased through soft combining. Then, the UE 104 may determine the RSRP of each of the PDCCH candidates 530, 532, 534, and 536 based on Msg 2 alone. That is, the UE 104 may use the decoded Msg 2 as a reference signal and compare each of the PDCCH candidates 530, 532, 534, and 536 with this reference signal to determine the corresponding RSRP of each of the PDCCH candidates 530, 532, 534, and 536. Thus, the RSRP may indicate the quality of each of the PDCCH candidates 530, 532, 534, and 536.

[0083] In one aspect, the base station 102 may determine whether to transmit a repeated random access Msg 2 for a particular UE 104 based on a request from that UE 104. For example, the UE 104 may indicate a request for coverage enhancement or beam enhancement based on one or a combination of the time resources of the PRACH Msg 1, the format of the PRACH Msg 1, or the sequence of the PRACH Msg 1. For example, a subset of available PRACH sequences may be associated with coverage enhancement.

[0084] Figure 6 FIG. is an example portion of a RAR window 600 for repetition of random access message 2. For example, the RAR window 600 may include a first portion 610 for a legacy procedure without PDCCH repetition for Msg 2, and a second portion 620 for a RACH procedure using PDCCH repetition with soft combining over a certain number of consecutive time slots. In one aspect, the base station 102 may send a master information block (MIB) or a remaining minimum system information (RMSI) that indicates the portion of the RAR window 600 configured for PDCCH repetition. For example, a bit field defining the length of the RAR window 600 may be extended to define the second portion 620. In another aspect, the base station 102 may send a MIB or RMSI indicating the number of PDCCH candidates for multiple repetitions (e.g., 4 consecutive time slots).

[0085] Figure 7 FIG. is a flow chart of an example method 700 for transmitting random access message 3 during a RACH procedure. The method 700 may be performed by a UE (such as UE 104, which may include a memory 360 and may be the entire UE 104 or a component of the UE 104, such as UE RACH component 140, TX processor 368, RX processor 356, or controller / processor 359). The method 700 may be performed by a UE RACH component 140 in communication with a BS RACH component 198 of the base station 102.

[0086] At block 710, the method 700 may include receiving multiple PDCCH candidates for a single random access message 2 during a random access response window. In one aspect, for example, the UE 104, RX processor 356, or controller / processor 359 may execute the UE RACH component 140 or RAR receiving component 141 to receive multiple PDCCH candidates 530, 532, 534, and 536 for a single random access message 2 during the RAR window 600. For example, the RAR receiving component 141 may perform soft combining of the multiple PDCCH candidates and perform blind detection of downlink control information after soft combining of the multiple PDCCH candidates. The RAR receiving component 141 may perform separate RSRP measurements for each of the multiple PDCCH candidates. The RAR receiving component 141 may determine the strongest PDCCH candidate among the multiple PDCCH candidates based on these measurements. Thus, the UE 104, RX processor 356, or controller / processor 359 that executes the UE RACH component 140 or RAR receiving component 141 may provide components for receiving multiple PDCCH candidates for a single random access message 2 during a random access response window.

[0087] At block 720, method 700 may include transmitting a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted based on an offset of the strongest PDCCH candidate among multiple repeated PDCCH candidates. In one aspect, for example, UE 104, controller / processor 359, or TX processor 368 may execute UE RACH component 140 or offset component 142 to transmit the random access message 3 on a resource that is time-shifted based on an offset of the strongest PDCCH candidate among multiple repeated PDCCH candidates and indicated by the random access message 2. In one aspect, offset component 142 may select an uplink beam for the random access message 3 based on the strongest PDCCH candidate among multiple repeated PDCCH candidates. Thus, UE 104, TX processor 368, or controller / processor 359 that executes UE RACH component 140 or offset component 142 may provide components for transmitting the random access message 3 on a resource that is time-shifted based on an offset of the strongest PDCCH candidate among multiple repeated PDCCH candidates and indicated by the random access message 2.

[0088] At block 730, method 700 may include receiving a random access message 4 that is transmitted using a beam selected by the base station based on the offset. In one aspect, for example, UE 104, RX processor 356, or controller / processor 359 may execute UE RACH component 140 or contention resolution component 143 to receive the random access message 4 that is transmitted using a beam selected based on the offset. Thus, UE 104, RX processor 356, or controller / processor 359 that executes UE RACH component 140 or contention resolution component 143 may provide components for receiving the random access message 4 that is transmitted using a beam selected by the base station based on the offset.

[0089] Method 700 may further include determining a coverage enhancement condition and transmitting a physical random access message 1 indicating a request for multiple repeated PDCCH candidates based on a time resource of the physical random access message 1, a format of the physical random access message 1, a sequence of the physical random access message 1, or any combination thereof.

[0090] Method 700 may further include determining a coverage enhancement condition and transmitting a Physical Random Access Message 1 during a portion of the random access response window configured for PDCCH repetitions (such as the second portion 620), where the Physical Random Access Message 1 indicates a request for multiple repeated PDCCH candidates. Method 700 may further include receiving a System Information Block or Remaining Minimum System Information that indicates a portion of the random access response window configured for PDCCH repetitions. Method 700 may further include receiving a System Information Block or Remaining Minimum System Information that indicates the number of multiple repeated PDCCH candidates.

[0091] Figure 8 is a flowchart of an example method 800 for transmitting a Random Access Message 2 during a RACH procedure. Method 800 may be performed by a base station (such as base station 102, which may include a memory 376 and may be the entire base station 102 or a component of base station 102, such as BS RACH component 198, TX processor 316, RX processor 370, or controller / processor 375). Method 800 may be performed by a BS RACH component 198 that communicates with a UE RACH component 140 of UE 104.

[0092] At block 810, method 800 may include transmitting multiple repeated PDCCH candidates for a single Random Access Message 2 during a random access response window. In one aspect, for example, base station 102, TX processor 316, or controller / processor 375 may execute BS RACH component 198 or repetition component 146 to transmit multiple repeated PDCCH candidates for a single Random Access Message 2 during RAR window 600. Thus, base station 102, TX processor 316, or controller / processor 375 that executes BS RACH component 198 or repetition component 146 may provide means for transmitting multiple repeated PDCCH candidates for a single Random Access Message 2 during a random access response window.

[0093] At block 820, method 800 may include receiving a Random Access Message 3 on a resource indicated by the Random Access Message 2. The resource for the Random Access Message 3 may be time-shifted by an offset that indicates the strongest PDCCH candidate among multiple repeated PDCCH candidates. In one aspect, for example, base station 102, RX processor 370, or controller / processor 375 may execute BS RACH component 198 or detection component 147 to receive a Random Access Message 3 on a resource indicated by the Random Access Message 2. Thus, base station 102, RX processor 370, or controller / processor 375 that executes BS RACH component 198 or detection component 147 may provide means for receiving a Random Access Message 3 on a resource indicated by the Random Access Message 2.

[0094] At block 830, method 800 may include selecting a beam for transmitting the random access message 4 based on an offset. In one aspect, for example, base station 102, TX processor 316, or controller / processor 375 may execute BS RACH component 198 or beam selection component 148 to select a beam for transmitting the random access message 4 based on the offset. Beam selection component 148 may determine the offset at which the random access message 3 was received and select a refinement beam corresponding to the offset. Thus, base station 102, RX processor 370, or controller / processor 375 that executes BS RACH component 198 or beam selection component 148 may provide means for selecting a beam for transmitting the random access message 4 based on the offset.

[0095] At block 840, method 800 may include transmitting the random access message 4 using the selected beam. In one aspect, for example, base station 102, TX processor 316, or controller / processor 375 may execute BS RACH component 198 to transmit the random access message 4 using the selected beam. Thus, base station 102, TX processor 316, or controller / processor 375 that executes BS RACH component 198 may provide means for transmitting the random access message 4 using the selected beam.

[0096] Figure 9 is a block diagram of an example apparatus 900 for wireless communication. Apparatus 900 may be a UE or a UE may include apparatus 900. In some aspects, apparatus 900 includes a receiving component 902, a communication manager 904, and a transmitting component 906, which may communicate with each other (e.g., via one or more buses). As shown, apparatus 900 may use receiving component 902 and transmitting component 906 to communicate with another apparatus 908 (e.g., a UE, a base station, or another wireless communication device).

[0097] In some aspects, apparatus 900 may be configured to perform one or more operations described herein in connection with Figures 4 - 6 Additional or alternatively, apparatus 900 may be configured to perform one or more processes described herein, such as Figure 7 method 700. In some aspects, apparatus 900 may include one or more components of the UE described above in connection with Figure 1 described.

[0098] The receiving component 902 may receive communications from the device 908, such as reference signals, control information, data communications, or combinations thereof. The receiving component 902 may provide the received communications to one or more other components of the device 900, such as the communication manager 904. In some aspects, the receiving component 902 may 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 may provide the processed signals to one or more other components. In some aspects, the receiving component 902 may include one or more antennas, demodulators, MIMO detectors, receiving processors, controllers / processors, memories, or combinations thereof of the UE described above in conjunction with Figure 1 A description of one or more antennas, demodulators, MIMO detectors, receiving processors, controllers / processors, memories, or combinations thereof of the UE.

[0099] The transmitting component 906 may transmit communications to the device 908, such as reference signals, control information, data communications, or combinations thereof. In some aspects, the communication manager 904 may generate communications and may send the generated communications to the transmitting component 906 for transmission to the device 908. In some aspects, the transmitting component 906 may perform signal processing on the generated communications (e.g., filtering, amplification, modulation, digital-to-analog conversion, multiplexing, interleaving, mapping, or encoding, etc.), and may send the processed signals to the device 908. In some aspects, the transmitting component 906 may include one or more antennas, modulators, transmitting MIMO processors, transmitting processors, controllers / processors, memories, or combinations thereof of the UE described above in conjunction with Figure 1 A description of one or more antennas, modulators, transmitting MIMO processors, transmitting processors, controllers / processors, memories, or combinations thereof of the UE. In some aspects, the transmitting component 906 may be collocated with the receiving component 902 in a transceiver.

[0100] The communication manager 904 may receive multiple repeated PDCCH candidates for a single random access message 2 during a random access response window; send a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted by an offset selected based on the strongest PDCCH candidate among the multiple repeated PDCCH candidates. The communication manager 904 may receive a random access message 4, which is transmitted using a beam selected based on the offset. In some aspects, the communication manager 904 may include a controller / processor, memory, or combinations thereof of the UE described above in conjunction with Figure 1 A description of the UE.

[0101] In some aspects, the communication manager 904 may include a set of components, such as an RAR receiving component 910, an offset component 912, a contention resolution component 914, or combinations thereof. Alternatively, the set of components may be separate and distinct from the communication manager 904. In some aspects, one or more components in the set of components may include the above in conjunction with Figure 1The controller / processor, memory, or combination thereof of the described UE may be implemented therein. Additionally or alternatively, one or more components of the component set may be at least partially implemented as software stored in the memory. For example, a component (or part of a component) 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 functions or operations of the component.

[0102] The RAR receiving component 910 may receive multiple repeated PDCCH candidates for a single random access message 2 during a random access response window. The offset component 912 may send a random access message 3 on a resource indicated by the random access message 2. The resource for the random access message 3 is time-shifted by an offset selected based on the strongest PDCCH candidate among the multiple repeated PDCCH candidates. The contention resolution component 914 may receive a random access message 4 that is sent using a beam selected based on the offset.

[0103] Figure 9 The number and arrangement of the components shown are provided as an example. In fact, there may be more components, fewer components, different components, or components with different arrangements than Figure 9 shown. Additionally, Figure 9 two or more of the components shown may be implemented within a single component, or Figure 9 a single component shown may be implemented as multiple distributed components. Additionally or alternatively, Figure 9 a set of the (one or more) components shown may perform one or more functions described as being performed by Figure 9 another set of components shown.

[0104] Figure 10 is a block diagram of an example apparatus 1000 for wireless communication. The apparatus 1000 may be a base station, or a base station may include the apparatus 1000. In some aspects, the apparatus 1000 includes a receiving component 1002, a communication manager 1004, and a transmitting component 1006, which may communicate with each other (e.g., via one or more buses). As shown, the apparatus 1000 may use the receiving component 1002 and the transmitting component 1006 to communicate with another apparatus 1008 (such as a UE, a base station, or another wireless communication device).

[0105] In some aspects, the apparatus 1000 may be configured to perform one or more operations described herein in connection with Figures 4 - 6 Additional or alternative, the apparatus 1000 may be configured to perform one or more processes described herein, such as Figure 8 method 800. In some aspects, the apparatus 1000 may include the above in connection with Figure 1One or more components of the described base station.

[0106] The receiving component 1002 may receive communications from the device 1008, such as reference signals, control information, data communications, or combinations thereof. The receiving component 1002 may provide the received communications to one or more other components of the device 1000, such as the communication manager 1004. In some aspects, the receiving component 1002 may 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 may provide the processed signals to one or more other components. In some aspects, the receiving component 1002 may include one or more antennas, demodulators, MIMO detectors, receiving processors, controllers / processors, memories, or combinations thereof of the base station described above in connection with Figure 1 One or more components of the described base station.

[0107] The transmitting component 1006 may transmit communications to the device 1008, such as reference signals, control information, data communications, or combinations thereof. In some aspects, the communication manager 1004 may generate the communications and may send the generated communications to the transmitting component 1006 for transmission to the device 1008. In some aspects, the transmitting component 1006 may perform signal processing on the generated communications (e.g., filtering, amplification, modulation, digital-to-analog conversion, multiplexing, interleaving, mapping, or encoding, etc.), and may transmit the processed signals to the device 1008. In some aspects, the transmitting component 1006 may include one or more antennas, modulators, transmit MIMO processors, transmit processors, controllers / processors, memories, or combinations thereof of the base station described above in connection with Figure 1 One or more components of the described base station. In some aspects, the transmitting component 1006 may be collocated with the receiving component 1002 in a transceiver.

[0108] The communication manager 1004 may send multiple repeated PDCCH candidates for a single random access message 2 during the random access response window; receive the random access message 3 on the resources indicated by the random access message 2. The resources for the random access message 3 are time-shifted by an offset selected based on the strongest PDCCH candidate among the multiple repeated PDCCH candidates. The communication manager 1004 may select a beam based on the offset; and use the selected beam to send the random access message 4. In some aspects, the communication manager 1004 may include a controller / processor, memory, scheduler, communication unit, or combinations thereof of the base station described above in connection with Figure 1 One or more components of the described base station.

[0109] In some aspects, the communication manager 1004 may include a set of components, such as a repetition component 1010, a detection component 1012, a beam selection component 1014, or a combination thereof. Alternatively, the set of components may be separate and distinct from the communication manager 1004. In some aspects, one or more components in the set of components may include, or may be implemented as, the controller / processor, memory, scheduler, communication unit, or a combination thereof, of the base station described above in connection with Figure 1 Additionally or alternatively, one or more components in the set of components may be at least partially implemented as software stored in a memory. For example, a component (or a portion of a component) 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 functions or operations of the component.

[0110] The repetition component 1010 may send multiple repeated PDCCH candidates for a single random access message 2 during a random access response window. The detection component 1012 may receive a random access message 3 on a resource indicated by the random access message 2. The beam selection component 1014 may select a beam based on an offset and receive a certain number of repetitions of the random access message 3, each repetition using a different refined beam. The transmission component 1006 may use the selected beam to transmit a random access message 4.

[0111] Figure 10 The number and arrangement of the components shown in Figure 10 are provided as an example. In fact, there may be more components, fewer components, different components, or components with a different arrangement than Figure 10 shown. Additionally, Figure 10 two or more of the components shown may be implemented within a single component, or Figure 10 a single component shown may be implemented as multiple distributed components. Additionally or alternatively, Figure 1 the set of (one or more) components shown may perform one or more functions described as being performed by

[0112] another set of components shown.

[0113] Some further example clauses

[0114] Implementation examples are described in the following numbered clauses:

[0115] 1. A method for wireless communication, comprising:

[0116] During a random access response window, receive multiple repeated physical downlink control channel (PDCCH) candidates for a single random access message 2 from a base station;

[0117] Transmit a random access message 3 on a resource indicated by the random access message 2, wherein the resource for the random access message 3 is time-shifted by an offset based on the strongest PDCCH candidate among the multiple repeated PDCCH candidates; and

[0118] Receive a random access message 4 that is transmitted using a beam selected by the base station based on the offset.

[0119] 2. The method according to clause 1, wherein receiving the multiple repeated PDCCH candidates includes:

[0120] Perform soft combining of the multiple repeated PDCCH candidates;

[0121] After soft combining of the multiple repeated PDCCH candidates, perform blind detection of downlink control information;

[0122] Perform individual reference signal received power (RSRP) measurements on each of the multiple repeated PDCCH candidates; and

[0123] Determine the strongest PDCCH candidate among the multiple repeated PDCCH candidates based on the RSRP measurements.

[0124] 3. The method according to clause 1 or 2, further comprising selecting an uplink beam for the random access message 3 based on the strongest PDCCH candidate among the multiple repeated PDCCH candidates.

[0125] 4. The method according to any one of clauses 1-3, further comprising transmitting a physical random access message 1 indicating a request for the multiple repeated PDCCH candidates based on the time resource of the physical random access message 1, the format of the physical random access message 1, the sequence of the physical random access message 1, or any combination thereof in response to a coverage enhancement condition.

[0126] 5. The method according to any one of clauses 1-3, the method further comprising transmitting a physical random access message 1 indicating a request for the multiple repeated PDCCH candidates during a portion of the random access response window configured for PDCCH repetition in response to a coverage enhancement condition.

[0127] 6. The method according to clause 5, further comprising receiving a system information block or remaining minimum system information that indicates a portion of the random access response window configured for PDCCH repetition.

[0128] 7. The method according to any one of clauses 1-6 further comprises receiving a management information block or remaining minimum system information indicating the number of repeated PDCCH candidates.

[0129] 8. A method for wireless communication, comprising:

[0130] During a random access response window, sending multiple repeated physical downlink control channel (PDCCH) candidates for a single random access message 2 to a user equipment (UE);

[0131] Receiving a random access message 3 from the UE on a resource indicated by the random access message 2, wherein the resource for the random access message 3 is time-shifted by an offset indicating the strongest PDCCH candidate among the multiple repeated PDCCH candidates;

[0132] Selecting a beam for sending a random access message 4 based on the offset; and

[0133] Sending the random access message 4 using the selected beam.

[0134] 9. The method according to clause 8 further comprises:

[0135] Receiving a physical random access message 1 from the UE; and

[0136] Determining that the physical random access message 1 indicates a request for multiple repeated PDCCH candidates based on the time resource of the physical random access message 1, the format of the physical random access message 1, the sequence of the physical random access message 1, or any combination thereof.

[0137] 10. The method according to clause 8 further comprises:

[0138] Receiving a physical random access message 1 from the UE; and

[0139] Determining that the physical random access message 1 indicates a request for multiple repeated PDCCH candidates based on a portion of the random access response window configured for PDCCH repetition.

[0140] 11. The method according to clause 10 further comprises sending a management information block or remaining minimum system information indicating the portion of the random access response window configured for PDCCH repetition.

[0141] 12. The method according to any one of clauses 8-11 further comprises sending a management information block or remaining minimum system information indicating the number of repeated PDCCH candidates.

[0142] 13. A method according to any one of clauses 8 - 12, wherein receiving a random access message 3 on a resource indicated by a random access message 2 includes scanning for refined beams for receiving the random access message 3 on multiple potential offsets of the resource indicated by the random access message 2, where different refined beams correspond to each potential offset.

[0143] 14. The method according to clause 13, wherein beam selection based on an offset includes:

[0144] determining the offset at which the random access message 3 is received; and

[0145] selecting the refined beam corresponding to the offset as the selected beam for transmitting the random access message 4.

[0146] 15. The method according to any one of clauses 8 - 14, wherein the beam for receiving message 3 corresponds to the beam for transmitting message 2.

[0147] 16. An apparatus for wireless communication, comprising:

[0148] a memory storing computer - executable instructions; and

[0149] at least one processor coupled to the memory and configured to execute the instructions to:

[0150] receive, during a random access response window, multiple repeated physical downlink control channel (PDCCH) candidates for a single random access message 2 from a base station;

[0151] transmit a random access message 3 on a resource indicated by the random access message 2, wherein the resource for the random access message 3 is time - shifted based on an offset of the strongest PDCCH candidate among the multiple repeated PDCCH candidates; and

[0152] receive a random access message 4, which is transmitted using a beam selected by the base station based on the offset.

[0153] 17. The apparatus according to clause 16, wherein the at least one processor is configured to:

[0154] perform soft combination of the multiple repeated PDCCH candidates;

[0155] perform blind detection of downlink control information after soft combination of the multiple repeated PDCCH candidates;

[0156] perform individual reference signal received power (RSRP) measurements on each of the multiple repeated PDCCH candidates; and

[0157] Determine the strongest PDCCH candidate among multiple repeated PDCCH candidates based on the measurement.

[0158] 18. The apparatus according to clause 16 or 17, wherein at least one processor is configured to select an uplink beam for random access message 3 based on the strongest PDCCH candidate among multiple repeated PDCCH candidates.

[0159] 19. The apparatus according to any one of clauses 16 - 18, wherein the at least one processor is configured to transmit physical random access message 1 indicating a request for multiple repeated PDCCH candidates based on the time resource of physical random access message 1, the format of physical random access message 1, the sequence of physical random access message 1, or any combination thereof in response to a coverage enhancement condition.

[0160] 20. The apparatus according to any one of clauses 16 - 18, wherein the at least one processor is configured to transmit physical random access message 1 indicating a request for multiple repeated PDCCH candidates during a portion of the random access response window configured for PDCCH repetition in response to a coverage enhancement condition.

[0161] 21. The apparatus according to clause 20, wherein the at least one processor is configured to receive a management information block or remaining minimum system information indicating a portion of the random access response window configured for PDCCH repetition.

[0162] 22. The apparatus according to any one of clauses 16 - 20, wherein the at least one processor is configured to receive a management information block or remaining minimum system information indicating the number of repeated PDCCH candidates.

[0163] 23. An apparatus for wireless communication, comprising:

[0164] A memory storing computer - executable instructions; and

[0165] At least one processor coupled to the memory and configured to execute the instructions to:

[0166] During a random access response window, transmit multiple repeated physical downlink control channel (PDCCH) candidates for a single random access message 2;

[0167] Receive random access message 3 on a resource indicated by random access message 2, wherein the resource for random access message 3 is time - shifted by an offset indicating the strongest PDCCH candidate among multiple repeated PDCCH candidates;

[0168] Select a beam based on the offset;

[0169] Use the selected beam to send the random access message 4.

[0170] 24. The apparatus according to clause 23, wherein the at least one processor is configured to:

[0171] Receive a physical random access message 1 from a user equipment; and

[0172] Determine that the physical random access message 1 indicates a request for multiple repeated PDCCH candidates based on the time resource of the physical random access message 1, the format of the physical random access message 1, the sequence of the physical random access message 1, or any combination thereof.

[0173] 25. The apparatus according to clause 23, wherein the at least one processor is configured to:

[0174] Receive a physical random access message 1 from a user equipment; and

[0175] Determine that the physical random access message 1 indicates a request for multiple repeated PDCCH candidates based on a portion of the random access response window configured for PDCCH repetition.

[0176] 26. The apparatus according to clause 25, wherein the at least one processor is configured to send a management information block or remaining minimum system information indicating the portion of the random access response window configured for PDCCH repetition.

[0177] 27. The apparatus according to any one of clauses 23 - 26, wherein the at least one processor is configured to send a management information block or remaining minimum system information indicating the number of repeated PDCCH candidates.

[0178] 28. The apparatus according to any one of clauses 23 - 26, wherein the at least one processor is configured to scan for a refined beam for receiving a random access message 3 on multiple potential offsets of the resource indicated by the random access message 2, where different refined beams correspond to each potential offset.

[0179] 29. The apparatus according to clause 28, wherein the at least one processor is configured to:

[0180] Determine the offset at which the random access message 3 is received; and

[0181] Select the refined beam corresponding to the offset.

[0182] 30. The apparatus according to any one of clauses 23 - 29, wherein the beam for receiving message 3 corresponds to the beam for sending message 2.

[0183] 31. A device for wireless communication, comprising:

[0184] means for receiving, during a random access response window, multiple repeated physical downlink control channel (PDCCH) candidates for a single random access message 2 from a base station;

[0185] means for transmitting a random access message 3 on a resource indicated by the random access message 2, wherein the resource for the random access message 3 is time-shifted by an offset based on the strongest PDCCH candidate among the multiple repeated PDCCH candidates; and

[0186] means for receiving a random access message 4, which is transmitted using a beam selected by the base station based on the offset.

[0187] 32. The device according to clause 31, wherein the means for receiving multiple repeated PDCCH candidates is configured to:

[0188] perform soft combining of the multiple repeated PDCCH candidates;

[0189] perform blind detection of downlink control information after soft combining of the multiple repeated PDCCH candidates; and

[0190] perform individual reference signal received power (RSRP) measurements on each of the multiple repeated PDCCH candidates; and

[0191] determine the strongest PDCCH candidate among the multiple repeated PDCCH candidates based on the RSRP measurements.

[0192] 33. The device according to clause 31 or 32, further comprising means for selecting an uplink beam for the random access message 3 based on the strongest PDCCH candidate among the multiple repeated PDCCH candidates.

[0193] 34. The device according to any one of clauses 31 - 33, further comprising means for transmitting a physical random access message 1 in response to a coverage enhancement condition based on a time resource of the physical random access message 1, a format of the physical random access message 1, a sequence of the physical random access message 1, or any combination thereof, the physical random access message 1 indicating a request for the multiple repeated PDCCH candidates.

[0194] 35. The device according to any one of clauses 31 - 33, further comprising means for transmitting a physical random access message 1 during a portion of the PDCCH repetition configured in the random access response window in response to a coverage enhancement condition, the physical random access message 1 indicating a request for the multiple repeated PDCCH candidates.

[0195] 36. The apparatus according to clause 35 further comprises a component for receiving a management information block or remaining minimum system information, which indicates a portion configured for PDCCH repetition in a random access response window.

[0196] 37. The apparatus according to any one of clauses 31 - 35 further comprises a component for receiving a management information block or remaining minimum system information, which indicates the number of PDCCH candidates for multiple repetitions.

[0197] 38. An apparatus for wireless communication comprises:

[0198] a component for transmitting, during a random access response window, multiple repeated physical downlink control channel (PDCCH) candidates for a single random access message 2 to a user equipment (UE);

[0199] a component for receiving a random access message 3 from the UE on a resource indicated by the random access message 2, wherein the resource for the random access message 3 is time - shifted by an offset indicating the strongest PDCCH candidate among the multiple repeated PDCCH candidates;

[0200] a component for selecting, based on the offset, a beam for transmitting a random access message 4; and

[0201] a component for transmitting the random access message 4 using the selected beam.

[0202] 39. The apparatus according to clause 38 further comprises:

[0203] a component for receiving a physical random access message 1 from the UE; and

[0204] a component for determining, based on the time resource of the physical random access message 1, the format of the physical random access message 1, the sequence of the physical random access message 1, or any combination thereof, that the physical random access message 1 indicates a request for multiple repeated PDCCH candidates.

[0205] 40. The apparatus according to clause 38 further comprises:

[0206] a component for receiving a physical random access message 1 from the UE; and

[0207] a component for determining, based on a portion configured for PDCCH repetition in a random access response window, that the physical random access message 1 indicates a request for multiple repeated PDCCH candidates.

[0208] 41. The apparatus according to clause 40 further comprises a component for transmitting a management information block or remaining minimum system information, which indicates a portion configured for PDCCH repetition in a random access response window.

[0209] The apparatus according to any one of clauses 38 - 41 further comprises a component for transmitting a management information block or remaining minimum system information indicating the number of multiple repeated PDCCH candidates.

[0210] The apparatus according to any one of clauses 38 - 42, wherein the component for receiving a random access message 3 on a resource indicated by a random access message 2 is configured to scan for a refined beam for receiving the random access message 3 on multiple potential offsets of the resource indicated by the random access message 2, where different refined beams correspond to each potential offset.

[0211] The apparatus according to clause 43, wherein the component for selecting a beam based on an offset is configured to:

[0212] determine an offset at which the random access message 3 is received; and

[0213] select the refined beam corresponding to the offset as the selected beam for transmitting the random access message 4.

[0214] The method according to any one of clauses 38 - 44, wherein the beam for receiving message 3 corresponds to the beam for transmitting message 2.

[0215] A non - transitory computer - readable medium storing computer - executable code which, when executed by a processor, causes the processor to:

[0216] receive, during a random access response window, multiple repeated physical downlink control channel (PDCCH) candidates for a single random access message 2 from a base station;

[0217] transmit a random access message 3 on a resource indicated by the random access message 2, wherein the resource for the random access message 3 is time - shifted based on an offset of the strongest PDCCH candidate among the multiple repeated PDCCH candidates; and

[0218] receive a random access message 4 which is transmitted using a beam selected by the base station based on the offset.

[0219] The non - transitory computer - readable medium according to clause 46 further comprises instructions for:

[0220] performing soft combination of multiple repeated PDCCH candidates;

[0221] performing blind detection of downlink control information after soft combination of multiple repeated PDCCH candidates;

[0222] Perform separate reference signal received power (RSRP) measurements for each of a plurality of repeated PDCCH candidates; and

[0223] Determine the strongest PDCCH candidate among the plurality of repeated PDCCH candidates based on the measurements.

[0224] The non - transitory computer - readable medium according to clause 46 or 47 further includes instructions for selecting an uplink beam for random access message 3 based on the strongest PDCCH candidate among the plurality of repeated PDCCH candidates.

[0225] The non - transitory computer - readable medium according to any one of clauses 46 - 48 further includes instructions for transmitting a physical random access message 1 in response to a coverage enhancement condition based on a time resource of the physical random access message 1, a format of the physical random access message 1, a sequence of the physical random access message 1, or any combination thereof, the physical random access message 1 indicating a request for a plurality of repeated PDCCH candidates.

[0226] The non - transitory computer - readable medium according to any one of clauses 46 - 48 further includes instructions for transmitting a physical random access message 1 during a portion of a random access response window configured for PDCCH repetition in response to a coverage enhancement condition, the physical random access message 1 indicating a request for a plurality of repeated PDCCH candidates.

[0227] The non - transitory computer - readable medium according to clause 48 further includes instructions for receiving a system information block or remaining minimum system information that indicates a portion of the random access response window configured for PDCCH repetition.

[0228] The non - transitory computer - readable medium according to any one of clauses 46 - 51 further includes instructions for receiving a system information block or remaining minimum system information that indicates the number of a plurality of repeated PDCCH candidates.

[0229] A non - transitory computer - readable medium storing computer - executable code that, when executed by a processor, causes the processor to:

[0230] During a random access response window, transmit a plurality of repeated physical downlink control channel (PDCCH) candidates for a single random access message 2;

[0231] Receive a random access message 3 on a resource indicated by the random access message 2, wherein the resource for the random access message 3 is time - shifted by an offset indicating the strongest PDCCH candidate among the plurality of repeated PDCCH candidates;

[0232] Select a beam for transmitting the random access message 4 based on the offset; and

[0233] Use the selected beam to transmit the random access message 4.

[0234] 54. The non-transitory computer-readable medium according to clause 53 further includes code for:

[0235] Receiving a physical random access message 1 from a user equipment; and

[0236] Determining that the physical random access message 1 indicates a request for multiple repeated PDCCH candidates based on the time resource of the physical random access message 1, the format of the physical random access message 1, the sequence of the physical random access message 1, or any combination thereof.

[0237] 55. The non-transitory computer-readable medium according to clause 53 further includes code for:

[0238] Receiving a physical random access message 1 from a user equipment; and

[0239] Determining that the physical random access message 1 indicates a request for multiple repeated PDCCH candidates based on a portion of the random access response window configured for PDCCH repetitions.

[0240] 56. The non-transitory computer-readable medium according to clause 55 further includes code for transmitting a management information block or remaining minimum system information indicating a portion of the random access response window configured for PDCCH repetitions.

[0241] 57. The non-transitory computer-readable medium according to any one of clauses 53-56 further includes transmitting a management information block or remaining minimum system information indicating the number of multiple repeated PDCCH candidates.

[0242] 58. The non-transitory computer-readable medium according to any one of clauses 53-57 further includes code for scanning for refined beams for receiving the random access message 3 on multiple potential offsets of the resources indicated by the random access message 2, wherein different refined beams correspond to each potential offset.

[0243] 59. The non-transitory computer-readable medium according to clause 58 further includes code for:

[0244] Determining the offset at which the random access message 3 is received; and

[0245] Selecting the refined beam corresponding to the offset as the selected beam for transmitting the random access message 4.

[0246] 60. A non-transitory computer-readable medium according to any one of clauses 53-59, wherein the beam for receiving message 3 corresponds to the beam for transmitting message 2.

[0247] The foregoing description is intended to enable a person of ordinary skill in the art to practice the various aspects described herein. Those of ordinary skill in the art will readily appreciate various modifications to these aspects, and the general principles defined herein can be applied to other aspects. The claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims, where the elements in the singular form are not intended to mean "one and only one" but rather "one or more" unless specifically stated otherwise. 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 "any combination of A, B, C, or combinations thereof" include any combination of A, B, or C and may include multiple A's, multiple B's, or multiple C's. Specifically, combinations 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 "any combination of A, B, C, or combinations thereof" can be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combination can include one or more of A, B, or C. All structural and functional equivalents of the elements of the various aspects described herein that are known to those of ordinary skill in the art or will later become known are hereby expressly incorporated by reference and are intended to be encompassed by the claims. Furthermore, nothing disclosed herein is intended for the public, whether or not such disclosure is explicitly recited in the claims. The words "module", "mechanism", "element", "device", etc. are not to be used in place of the word "component". Thus, no claim element is to be construed as a means-plus-function unless the element is expressly recited using the phrase "means for...".

Claims

1. A method for wireless communication by a user equipment (UE), the method comprising: During a random access response (RAR) window, receive multiple repeated physical downlink control channel (PDCCH) candidates for a single random access message 2 from a base station, where the RAR window includes a first part for a legacy procedure for message 2 without PDCCH repetition, and a second part configured for a random access procedure using PDCCH repetition over multiple consecutive time slots, and where each of the multiple repeated PDCCH candidates is located within a corresponding random access search space part of a control resource set (CORESET) of a corresponding one of the multiple consecutive time slots during the RAR window; Transmit a random access message 3 on a resource indicated by the random access message 2, where the resource for the random access message 3 is time-shifted based on an offset of the strongest PDCCH candidate among the multiple repeated PDCCH candidates; and Receive a random access message 4, where the random access message 4 is transmitted using a beam selected by the base station based on the offset.

2. The method according to claim 1, wherein, Receiving the multiple repeated PDCCH candidates includes: Performing soft combining of the multiple repeated PDCCH candidates; After soft combining of the multiple repeated PDCCH candidates, performing blind detection of downlink control information; Performing a separate reference signal received power (RSRP) measurement for each of the multiple repeated PDCCH candidates; and Determining the strongest PDCCH candidate among the multiple repeated PDCCH candidates based on the RSRP measurement.

3. The method according to claim 1, further comprising selecting an uplink beam for a random access message 3 based on the strongest PDCCH candidate among the plurality of repeated PDCCH candidates.

4. The method according to claim 1, further comprising transmitting a physical random access message 1 based on a time resource of the physical random access message 1, a format of the physical random access message 1, a sequence of the physical random access message 1, or any combination thereof, in response to a coverage enhancement condition, the physical random access message 1 indicating a request for the plurality of repeated PDCCH candidates.

5. The method according to claim 1, further comprising transmitting a physical random access message 1 during a portion of a random access response window configured for PDCCH repetition, in response to a coverage enhancement condition, the physical random access message 1 indicating a request for the plurality of repeated PDCCH candidates.

6. The method according to claim 5, further comprising receiving a system information block (SIB) or a remaining minimum system information (RMSI) indicating a portion of the random access response window configured for PDCCH repetition.

7. The method according to claim 1, further comprising receiving a system information block (SIB) or a remaining minimum system information (RMSI) indicating a number of the plurality of repeated PDCCH candidates.

8. A method for wireless communication, the method comprising: During a random access response (RAR) window, transmit multiple repeated physical downlink control channel (PDCCH) candidates for a single random access message 2 to a user equipment (UE), where the RAR window includes a first part for a legacy procedure for message 2 without PDCCH repetition, and a second part configured for a random access procedure using PDCCH repetition over multiple consecutive time slots, and where each of the multiple repeated PDCCH candidates is located within a corresponding random access search space part of a control resource set (CORESET) of a corresponding one of the multiple consecutive time slots during the RAR window; Receive a random access message 3 from the UE on a resource indicated by the random access message 2, where the resource for the random access message 3 is time-shifted by an offset indicating the strongest PDCCH candidate among the multiple repeated PDCCH candidates; Select a beam for transmitting the random access message 4 based on the offset; and Transmit the random access message 4 using the selected beam.

9. The method according to claim 8, further comprising: Receive a physical random access message 1 from the UE; and Determine that the physical random access message 1 indicates a request for the multiple repeated PDCCH candidates based on a time resource of the physical random access message 1, a format of the physical random access message 1, a sequence of the physical random access message 1, or any combination thereof.

10. The method according to claim 8 further comprises: Receive a physical random access message 1 from the UE; and Determine that the physical random access message 1 indicates a request for multiple repeated PDCCH candidates based on a part of the random access response window configured for PDCCH repetition.

11. The method according to claim 10 further comprises sending a management information block or remaining minimum system information, the management information block or remaining minimum system information indicating a portion of the random access response window that is configured for PDCCH repetition.

12. The method according to claim 8 further comprises sending a management information block or remaining minimum system information indicating the number of the plurality of repeated PDCCH candidates.

13. The method according to claim 8, wherein, Receiving a random access message 3 on a resource indicated by a random access message 2 includes scanning for refined beams for receiving the random access message 3 on a plurality of potential offsets of the resource indicated by the random access message 2, where different refined beams correspond to each potential offset.

14. The method according to claim 13, wherein, Selecting a beam based on the offset includes: Determining the offset at which the random access message 3 is received; and Selecting the refined beam corresponding to the offset as the selected beam for transmitting the random access message 4.

15. The method according to claim 8, wherein, The beam for receiving the random access message 3 corresponds to the beam for transmitting the random access message 2.

16. An apparatus for wireless communication, the apparatus comprising: A memory storing computer-executable instructions; and At least one processor coupled to the memory and configured to execute the instructions to: During a random access response (RAR) window, receive a plurality of repeated physical downlink control channel (PDCCH) candidates for a single random access message 2 from a base station, where the RAR window includes a first part for a legacy procedure without PDCCH repetition for message 2 and a second part configured for a random access procedure using PDCCH repetition over a plurality of consecutive time slots, and where each of the plurality of repeated PDCCH candidates is located within a corresponding random access search space part of a control resource set (CORESET) of a corresponding time slot of the plurality of consecutive time slots during the RAR window; Transmit a random access message 3 on a resource indicated by the random access message 2, where the resource for the random access message 3 is time-shifted based on an offset of the strongest PDCCH candidate among the plurality of repeated PDCCH candidates; and Receive a random access message 4, where the random access message 4 is transmitted using a beam selected by the base station based on the offset.

17. The apparatus according to claim 16, wherein, The at least one processor is configured to: Perform soft combining of the plurality of repeated PDCCH candidates; After the soft combining of the plurality of repeated PDCCH candidates, perform blind detection of downlink control information; Perform individual reference signal received power (RSRP) measurements on each of the plurality of repeated PDCCH candidates; and Determine the strongest PDCCH candidate among the plurality of repeated PDCCH candidates based on the measurements.

18. The apparatus according to claim 16, wherein, The at least one processor is configured to select an uplink beam for the random access message 3 based on the strongest PDCCH candidate among the plurality of repeated PDCCH candidates.

19. The apparatus according to claim 16, wherein, The at least one processor is configured to transmit a physical random access message 1 indicating a request for the plurality of repeated PDCCH candidates based on a time resource of the physical random access message 1, a format of the physical random access message 1, a sequence of the physical random access message 1, or any combination thereof in response to a coverage enhancement condition.

20. The apparatus according to claim 16, wherein, The at least one processor is configured to transmit a physical random access message 1 indicating a request for the plurality of repeated PDCCH candidates during a part of the random access response window configured for PDCCH repetition in response to a coverage enhancement condition.

21. The apparatus according to claim 20, wherein the at least one processor is configured to receive a management information block or remaining minimum system information, the management information block or remaining minimum system information indicating a portion of a random access response window configured for PDCCH repetition.

22. The apparatus according to claim 16, wherein, The at least one processor is configured to receive a management information block or remaining minimum system information indicating the number of the plurality of repeated PDCCH candidates.

23. An apparatus for wireless communication, the apparatus comprising: A memory storing computer-executable instructions; and at least one processor, coupled to the memory and configured to execute the instructions to: During a random access response (RAR) window, transmit a plurality of repeated physical downlink control channel (PDCCH) candidates for a single random access message 2, wherein the RAR window includes a first portion for a legacy procedure without PDCCH repetition for message 2 and a second portion configured for a random access procedure using PDCCH repetition over a plurality of consecutive time slots, and wherein each of the plurality of repeated PDCCH candidates is located within a respective random access search space portion of a control resource set (CORESET) of a respective one of the plurality of consecutive time slots during the RAR window; Receive a random access message 3 on a resource indicated by the random access message 2, wherein the resource for the random access message 3 is time-shifted by an offset indicating the strongest PDCCH candidate among the plurality of repeated PDCCH candidates; Select a beam for transmitting the random access message 4 based on the offset; and Transmit the random access message 4 using the selected beam.

24. The apparatus according to claim 23, wherein, The at least one processor is configured to: Receive a physical random access message 1 from a user equipment; and Determine that the physical random access message 1 indicates a request for the plurality of repeated PDCCH candidates based on a time resource of the physical random access message 1, a format of the physical random access message 1, a sequence of the physical random access message 1, or any combination thereof.

25. The apparatus according to claim 23, wherein, The at least one processor is configured to: Receive a physical random access message 1 from a user equipment; and Determine that the physical random access message 1 indicates a request for the plurality of repeated PDCCH candidates based on a portion of the random access response window configured for PDCCH repetition.

26. The apparatus according to claim 25, wherein, The at least one processor is configured to transmit a management information block or remaining minimum system information indicating a portion of the random access response window configured for PDCCH repetition.

27. The apparatus according to claim 23, wherein, The at least one processor is configured to transmit a management information block or remaining minimum system information indicating the number of the plurality of repeated PDCCH candidates.

28. The apparatus according to claim 23, wherein, The at least one processor is configured to scan for a refined beam for receiving the random access message 3 at a plurality of potential offsets of the resource indicated by the random access message 2, wherein different refined beams correspond to each potential offset.

29. The apparatus according to claim 28, wherein, The at least one processor is configured to: Determine an offset at which the random access message 3 is received; and Select the refined beam corresponding to the offset as the selected beam for transmitting the random access message 4.

30. The apparatus according to claim 23, wherein, A beam for receiving the random access message 3 corresponds to a beam for transmitting the random access message 2.

31. An apparatus for wireless communication, comprising components for performing the steps of the method according to any one of claims 1 - 15.

32. A non - transitory computer - readable medium storing computer - executable code, the computer - executable code, when executed by a processor, causing the processor to perform the method according to any one of claims 1 - 15.

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