Systems and methods for latency reduction for 2-step random access channel (RACH) hybrid automatic repeat requests (HARQ)

Abstract

A radio communication system and method are provided related to the timing arrangement and transmission gap configuration in a two-step random access channel (RACH) procedure to improve system latency and reliability of the RACH HARQ procedure. The UE transmits a first message including a random access preamble and a payload, and subsequently monitors a second message responding to the first message during a random access response (RAR) window. In response to a decision that the UE did not receive the second message from the BS or received a shift indicator within the RAR window, the UE retransmits the preamble and payload of the first message after the RAR window has passed. In response to a decision that the second message received within the RAR window carries a shifted RAR or a successful RAR, the UE then decides whether to retransmit the payload of the first message based on the shifted RAR, or to transmit an acknowledgment message based on the successful RAR.

Description

Technical Field

[0001] This patent application claims priority to PCT / CN2019 / 109800, a co-pending and co-owned Patent Cooperation Treaty (PCT) international application filed on October 2, 2019, which is hereby expressly incorporated herein by reference in its entirety.

[0002] The technology discussed below relates to wireless communication systems, and more specifically, to reducing latency in retransmission schemes using two-step random access channel (RACH) hybrid automatic repeat request (HARQ) that can be used in fifth-generation (5G) new radio (NR) networks. Prior Technology

[0003] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, and broadcasting. These systems can support communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Wireless multiplexing access communication systems may include multiple base stations (BSs), each simultaneously supporting communication with multiple communication devices (which may also be referred to as user equipment (UE)).

[0004] In a wireless system, the BS can broadcast synchronization signals (such as the primary synchronization signal (PSS), secondary synchronization signal (SSS), and extended synchronization signal (ESS)), beam reference signals (BRS), and system information in multiple directional beams. Additionally, the BS can transmit other reference signals (such as channel state information reference signals (CSI-RS)) on the beams to enable the UE to measure the channel between the BS and the corresponding UE. The UE can perform initial cell acquisition by listening to the broadcast signals and perform signal measurements based on the synchronization signals, BRS, and / or other signals. The UE can determine the received signal strength based on the received signals and select a cell and the beam within the selected cell for performing access procedures.

[0005] To execute the access procedure, the UE can initiate the Random Access Channel (RACH) procedure by sending a Random Access Preamble signal using the same subarray and beam direction as the selected beam, and monitor the RAR in the Random Access Response (RAR) window. When the BS detects the Random Access Preamble signal, the BS sends the RAR to the UE in the same beam direction as the received Random Access Preamble signal. The RAR may include a transmission opportunity for the UE to send the next random access message. Due to beam correspondence, user mobility, rotation, and / or signal congestion, beam characteristics may vary over time or differ between the uplink and downlink at the UE or BS. Therefore, the UE may fail to receive the RAR. After failing to receive the RAR within the RAR window, the UE can choose to retry the RACH procedure after the RAR window expires. However, each time a retransmission is performed, the UE may need to wait a significant amount of time (e.g., at least until the RAR window expires plus additional backoff time). Therefore, retransmissions can lead to significant system latency.

[0006] Therefore, it is necessary to improve the latency performance of the RACH procedure in wireless communication systems. Summary of the Invention

[0007] To provide a basic understanding of the technology discussed, some aspects of the subject matter are summarized below. This summary is not a general overview of all anticipated features of the subject matter, nor is it intended to identify key or essential elements of all aspects of the subject matter, nor to illustrate the scope of any or all aspects of the subject matter. Its sole purpose is to present some concepts of one or more aspects of the subject matter in a generalized form as a prelude to the more detailed description provided later.

[0008] For example, in one embodiment of this case, a wireless communication method includes the following steps: a user equipment (UE) receiving system information from a base station (BS) for initiating a random access channel (RACH) procedure. The method also includes the following steps: the UE transmitting a first message to the BS including a first payload comprising a random access preamble signal and a connection request; and the UE monitoring a second message from the BS responding to the first message during a random access response (RAR) window. The method further includes the following steps: in response to determining, based on the monitoring, that the UE has not received the second message from the BS within the RAR window, retransmitting the first message to the BS. The method also includes the following steps: in response to determining that the UE has received the second message from the BS within the RAR window, the UE deciding whether to retransmit the first payload or transmit an acknowledgment message to the BS based on the type of the second payload decoded from the second message.

[0009] In another embodiment of this case, a wireless communication method includes the following steps: a BS broadcasts system information to a UE for initiating a random access channel procedure. The method also includes the following steps: the BS receives from the UE a first message including a random access preamble signal and a connection request first payload; and the BS determines whether at least a portion of the first message is decodable. The method further includes the following steps: in response to a decoding failure of the first message, avoiding transmission of any message to the UE within a Random Access Response (RAR) window. The method also includes the following steps: in response to a successful decoding of at least that portion of the first message, the BS transmits a RAR message to the UE containing a second payload, the second payload being determined based on the type of that portion of the first message.

[0010] In another embodiment of this case, a wireless communication UE includes a transceiver configured to: receive system information for initiating a Random Access Channel (RACH) procedure; transmit a first message including a first payload comprising a random access preamble signal and a connection request; monitor a second message responding to the first message during a Random Access Response (RAR) window; and, in response to determining, based on the monitoring, that the UE has not received the second message from the BS within the RAR window, retransmit the first message. The UE also includes a processor configured to: in response to determining that the UE has received the second message from the BS within the RAR window, decide, based on the type of a second payload decoded from the second message, whether to retransmit the first payload to the BS or transmit an acknowledgment message to the BS.

[0011] In another embodiment of this case, a wireless communication BS includes a transceiver configured to: broadcast system information for initiating a random access channel procedure; and receive a first message including a random access preamble signal and a first payload of a connection request. The BS also includes a processor configured to: determine whether at least a portion of the first message is decodable; and, in response to a decoding failure of the first message, avoid transmitting any message to the UE within a Random Access Response (RAR) window. The transceiver is also configured to: in response to successful decoding of at least that portion of the first message, transmit a RAR message containing a second payload, the second payload being determined based on the type of that portion of the first message.

[0012] After reviewing the following description of specific exemplary aspects of the invention in conjunction with the accompanying drawings, other aspects, features, and variations of the invention will become apparent to those skilled in the art. Although features of the invention may be discussed below with respect to certain aspects and drawings, all aspects of the invention may include one or more of the advantageous features discussed herein. In other words, although one or more aspects may be discussed as having certain advantageous features, one or more of these features may also be used according to the various aspects of the invention discussed herein. Similarly, although exemplary aspects may be discussed below as apparatus, system, or method aspects, it should be understood that such exemplary aspects can be implemented using various apparatuses, systems, and methods. Simple Explanation of the Diagram

[0013] Figure 1 illustrates some types of wireless communication networks according to the content of this case.

[0014] Figure 2 illustrates various random access schemes in the wireless communication network shown in Figure 1, based on the contents of this case.

[0015] Figures 3A-3C illustrate various transmission scenarios of the two-step RACH scheme between the UE and BS that can be implemented in the wireless communication network shown in Figures 1-2, according to some of the contents of this case.

[0016] Figure 4 is a block diagram of some types of user equipment (UE) according to the content of this case.

[0017] Figure 5 is a block diagram of an exemplary base station (BS) based on some of the features described in this case.

[0018] Figures 6A-6C illustrate the retransmission isochronous line design in different scenarios of the two-step RACH procedure between the UE and BS, based on some of the states described in this case.

[0019] Figures 7A and 7B illustrate the logical flow executed by the UE in some states according to the content of this case, corresponding to the retransmission isochronous line design in different scenarios of the two-step RACH procedure shown in Figures 6A and 6B.

[0020] Figure 8 illustrates the logical flow executed by the BS in some states according to the content of this case, corresponding to the retransmission isochronous line design in different scenarios of the two-step RACH procedure shown in Figures 6A-6B.

[0021] Figure 9 illustrates the logical flow of configuring the Random Access Response (RAR) window length in a two-step RACH procedure, based on some aspects of the case.

[0022] Figure 10 illustrates the logical flow of configuring the starting point of the Random Access Response (RAR) window in a two-step RACH procedure, based on some of the states described in this case. Implementation

[0023] The detailed descriptions following, taken in conjunction with the accompanying drawings, are intended as descriptions of various configurations, and not as representations of only configurations in which the concepts described herein can be implemented. For a thorough understanding of the various concepts, the detailed descriptions include specific details. However, it will be apparent to those skilled in the art that these concepts can be implemented without using such specific details. In some cases, to avoid ambiguity regarding these concepts, well-known structures and components are illustrated in block diagram form.

[0024] In summary, this case pertains to wireless communication systems (also known as wireless communication networks). In various forms, these technologies and apparatuses can be used in wireless communication networks and other communication networks such as: Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, Single Carrier FDMA (SC-FDMA) networks, LTE networks, Global System for Mobile Communications (GSM) networks, and 5G or New Radio (NR) networks. As described herein, the terms "network" and "system" are used interchangeably.

[0025] OFDMA networks can implement radio technologies such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, and Flash OFDM. UTRA, E-UTRA, and GSM are part of the Universal Mobile Telecommunications System (UMTS). Specifically, Long Term Evolution (LTE) is a version of UMTS using E-UTRA. UTRA, E-UTRA, GSM, UMTS, and LTE are described in documents from an organization called the 3rd Generation Partnership Project (3GPP), and cdma 2000 is described in documents from an organization called 3rd Generation Partnership Project 2 (3GPP2). These various radio technologies and standards are either known or under development. For example, the 3rd Generation Partnership Project (3GPP) is a collaboration between telecommunications associations aimed at defining a globally applicable third-generation (3G) mobile phone specification. 3GPP Long Term Evolution (LTE) is a 3GPP project aimed at improving the UMTS mobile phone standard. 3GPP defines specifications for next-generation mobile networks, mobile systems, and mobile devices. This case concerns the evolution of wireless technologies from LTE, 4G, 5G, NR, and beyond, which features shared access to the radio spectrum between networks using new and different radio access technologies or radio space interfaces.

[0026] Specifically, 5G networks are expected to enable diverse deployments, diverse spectrum, and diverse services and devices using a unified OFDM-based air interface. To achieve these goals, in addition to developing new radio technologies for 5G NR networks, further enhancements to LTE and LTE-A are also being considered. 5G NR will be able to scale to provide coverage for: (1) massive Internet of Things (IoT) networks with ultra-high density (e.g., ~1M nodes / km2), ultra-low complexity (e.g., ~10 s bits / second), ultra-low energy (e.g., ~10+ years of battery life), and deep coverage with the ability to reach challenging locations; (2) mission-critical control with strong security for protecting sensitive personal, financial, or confidential information, ultra-high reliability (e.g., ~99.9999% reliability), ultra-low latency (e.g., ~1 ms), and a wide range of mobile or inactive users; and (3) enhanced mobile broadband with ultra-high capacity (e.g., ~10 Tbps / km2), extreme data rates (e.g., multi-Gbps rates, 100+ Mbps user experience rates), and deep sensing with advanced exploration and optimization.

[0027] 5G NR can be implemented using optimized OFDM-based waveforms with scalable parameter sets (numerology) and transmission time intervals (TTI); a common, flexible framework to efficiently multiplex services and features using dynamic, low-latency time-division duplex (TDD) / frequency-division duplex (FDD) designs; and advanced wireless technologies such as massive MIMO, robust millimeter-wave (mm-wave) transmission, advanced channel coding, and device-centric mobility. The scalability of the parameter set in 5G NR (with scaling of subcarrier spacing) efficiently addresses the operation of diverse services across diverse spectrum and deployments. For example, in various outdoor and macro coverage deployments using FDD / TDD implementations below 3 GHz, subcarrier spacing can exist, for example, at 15 kHz over bandwidths (BW) of 5, 10, and 20 MHz. For various other outdoor and small-cell coverage deployments using TDD above 3 GHz, the subcarrier spacing can exist at 30 kHz over an 80 / 100 MHz BW. For various other indoor broadband implementations using TDD in the unlicensed portion of the 5 GHz band, the subcarrier spacing can exist at 60 kHz over a 160 MHz BW. Finally, for various deployments utilizing the mm-wave component of TDD at 28 GHz, the subcarrier spacing can exist at 120 kHz over a 500 MHz BW.

[0028] 5G NR's scalable parameter set facilitates scalable TTIs for different latency and Quality of Service (QoS) requirements. For example, shorter TTIs can be used for low latency and high reliability, while longer TTIs can be used for higher spectral efficiency. Efficient multiplexing for both long and short TTIs allows transmissions to begin at symbol boundaries. 5G NR also anticipates self-contained integrated subframe designs, where uplink / downlink scheduling information, data, and acknowledgments are within the same subframe. Self-contained integrated subframes support communication in unlicensed or contention-based shared spectrum, and self-adjusting uplink / downlink (which can be flexibly configured on a per-cell basis to dynamically switch between uplink and downlink to meet current traffic demands).

[0029] The following further describes various other aspects and features of the subject matter. It should be apparent that the teachings herein can be embodied in a wide variety of forms, and any particular structure, function, or both disclosed herein are merely representative and not limiting. Based on the teachings herein, it should be understood by those skilled in the art that the aspects disclosed herein can be implemented independently of any other aspects, and two or more of such aspects can be combined in various ways. For example, an apparatus or a method can be implemented using any number of the aspects described herein. Furthermore, such an apparatus or method can be implemented using structures, functions, or structures and functions other than or different from one or more of the aspects described herein. For example, a method can be implemented as part of a system, device, apparatus, and / or as instructions stored on a computer-readable medium for execution on a processor or computer. Additionally, an aspect may include at least one element of a claim.

[0030] In a wireless system, when a UE wants to access the network, it may attempt to attach to or synchronize with a BS. To synchronize with the network, a RACH procedure is used. For example, traditionally, a four-step RACH procedure is used for the UE to establish a synchronization connection with the BS. Specifically, in the System Information Block (SIB2), a BS such as a Next Generation Node B (gNB) periodically broadcasts several parameters, such as the root sequence ID, RACH configuration index, power offset, and initial power. In a contention-based RACH procedure, the UE randomly selects a preceding signal from 54 orthogonal zadoff-chu (ZC) sequences generated via cyclic shifting of the root sequence. This preceding signal is transmitted as Msg 1 in time on the random access subframe and in frequency on the resource block (RB), implicitly defining the RA Radio Network Temporary Identifier (RA-RNTI). After a successful Msg 1, the gNB responds with a Random Access Response (RAR) in Msg 2. The Msg 2 RAR contains a Temporary Cellular RNTI (C-RNTI), Timing Advance (TA), and uplink resource allowance. After decoding the RB assignment from Msg 2, in Msg 3, the UE transmits a Radio Resource Control (RRC) connection request including a randomly selected initial device identity. Multiple UEs can choose the same preamble, RAR-RNTI, and corresponding C-RNTI from Msg 1, and transmit their own Msg 3 on uplink resources; the gNB detects this as a conflict. In Msg 4, the gNB sends an RRC connection establishment with a permanent C-RNTI and a repeat of the initial identity transmitted in Msg 3 (echo). If the identities match, the RACH procedure is considered successful; otherwise, the device retrys the procedure after a shift interval. The successful UE is ready to transmit uplink data.

[0031] To reduce access latency in a four-step RACH access procedure, a two-step RACH procedure can be used, in which the UE combines Msg1 and Msg3 into an initial message, and the BS then responds using a conventional combined message of Msg2 and Msg4. Depending on the specifics of this application, as further described with respect to Figures 3A-3C, the two-step RACH procedure may include an isochronous mechanism for implementing Hybrid Automatic Repeat Request (HARQ) to avoid excessive latency both during and when the UE performs a retransmission.

[0032] To reduce the overall latency in two-step RACH procedures, this paper describes various isochronous designs with improved system latency for retransmission schemes in two-step RACH procedures. Specifically, as further described with respect to Figures 6A-10, various timing parameters are employed to align message transmission and / or retransmission in the two-step RACH procedure. The defined isochronous arrangement improves the overall latency of the two-step RACH procedure.

[0033] Figure 1 illustrates a wireless communication network 100 of some forms according to the content of this case. Network 100 may be a 5G network. Network 100 includes multiple base stations (BS) 105 (labeled as 105a, 105b, 105c, 105d, 105e, and 105f, respectively) and other network entities. BS 105 may be a station communicating with UE 115, and may also be referred to as an evolved Node B (eNB), a next-generation eNB (gNB), an access point, etc. Each BS 105 may provide communication coverage for a specific geographic area. In 3GPP, the term "cell" may represent the specific geographic coverage area of ​​BS 105 and / or the BS subsystem serving that coverage area, depending on the context in which the term is used.

[0034] BS 105 can provide communication coverage for macrocells or small cells (e.g., picocells or femtocells) and / or other types of cells. Macrocells typically cover a relatively large geographic area (e.g., a radius of several kilometers) and can allow unrestricted access by UEs with service subscriptions to a network provider. Small cells (e.g., picocells) will typically cover a relatively small geographic area and can allow unrestricted access by UEs with service subscriptions to a network provider. Small cells (e.g., femtocells) will also typically cover a relatively small geographic area (e.g., a residential area) and, in addition to unrestricted access, can provide restricted access by UEs associated with that femtocell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for users in a residential area, etc.). A BS used for macrocells may be referred to as a macro BS. A BS used for small cells may be referred to as a small cell BS, pico BS, femto BS, or home BS. In the examples illustrated in Figure 1, BS 105d and 105e can be general macro BSs, while BS 105a-105c can be macro BSs implemented using one of three-dimensional (3D), full-dimensional (FD), or large-scale MIMO. BS 105a-105c can utilize its higher-dimensional MIMO capabilities to employ 3D beamforming in both elevation and azimuth beamforming to increase coverage and capacity. BS 105f can be a small-cell BS, which can be a family node or a portable access point. BS 105 can support one or more (e.g., two, three, four, etc.) cells.

[0035] Network 100 can support synchronous or asynchronous operation. For synchronous operation, BSs can have similar frame timings, and transmissions from different BSs can be approximately aligned in time. For asynchronous operation, BSs can have different frame timings, and transmissions from different BSs may not be aligned in time.

[0036] UE 115 is distributed throughout the wireless network 100, and each UE 115 can be stationary or mobile. UE 115 can also be referred to as a terminal, mobile station, user unit, station, etc. UE 115 can be a cellular phone, personal digital assistant (PDA), wireless modem, wireless communication device, handheld device, tablet computer, laptop computer, wireless phone, wireless loopback (WLL) station, etc. In one configuration, UE 115 can be a device including a Universal Integrated Circuit Card (UICC). In another configuration, UE 115 can be a device without a UICC. In some configurations, UEs without a UICC can also be referred to as IoT devices or Internet of Things (IoE) devices. UE 115a-115d are examples of mobile smartphone-type devices accessing network 100. UE 115 can also be a machine specifically configured for connected communications (including Machine Type Communication (MTC), Enhanced MTC (eMTC), Narrowband IoT (NB-IoT), etc.). UE 115e-115k are examples of various machines configured for communication to access network 100. UE 115 can communicate with any type of BS (whether macro BS, small cell, etc.). In Figure 1, lightning (e.g., communication link) indicates radio transmissions between UE 115 and serving BS 105 (which is designated to serve UE 115 on the downlink and / or uplink), or expected transmissions between BSs and backhaul transmissions between BSs.

[0037] In operation, BS 105a-105c can use 3D beamforming and coordinated spatial technologies (e.g., Coordinated Multipoint (CoMP) or Multi-Connection) to service UEs 115a and 115b. Macro BS 105d can perform backhaul communications with BS 105a-105c and small cells (BS 105f). Macro BS 105d can also transmit multicast services subscribed to and received by UEs 115c and 115d. Such multicast services may include mobile TV or streaming video, or may include other services for providing cell information, such as weather emergencies or alerts (e.g., Amber Alert or Grey Alert).

[0038] BS 105 can also communicate with the core network. The core network provides user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. At least some of the BS 105s (e.g., instances of gNBs or Access Node Controllers (ANCs)) can interface with the core network via a backhaul link (e.g., NG-C, NG-U, etc.) and can perform radio configuration and scheduling for communication with the UE 115. In various instances, the BS 105s can communicate directly or indirectly (e.g., via the core network) with each other on a backhaul link (e.g., X1, X2, etc.), which can be a wired or wireless communication link.

[0039] Network 100 can also support mission-critical communication using highly reliable and redundant links for mission-critical devices (e.g., UE 115e, which could be a drone). Redundant communication links with UE 115e can include links from macro BSs 105d and 105e and links from small cell BS 105f. Other machine-type devices (e.g., UE 115f (e.g., a thermometer), UE 115g (e.g., a smart instrument), and UE 115h (e.g., a wearable device)) can communicate directly with the BSs (e.g., small cell BS 105f and macro BS 105e) via Network 100, or via another user device relaying its information to the network (e.g., UE 115f transmits temperature measurement information to a smart instrument (UE 115g), and the temperature measurement information is subsequently reported to the network via small cell BS 105f) in a multi-hop configuration. Network 100 can also provide additional network efficiency through dynamic, low-latency TDD / FDD communication, such as in vehicle-to-vehicle (V2V) communication.

[0040] In some implementations, Network 100 uses OFDM-based waveforms for communication. OFDM-based systems can divide the system BW into multiple (K) orthogonal subcarriers, which are often referred to as subcarriers, tones, bands, etc. Data can be used to modulate each subcarrier. In some cases, the spacing between adjacent subcarriers can be fixed, and the total number of subcarriers (K) can depend on the system BW. The system BW can also be divided into subbands. In other cases, the subcarrier spacing and / or the duration of the time interval (TTI) can be scalable.

[0041] BS 105 can assign or schedule transmission resources (e.g., in the form of time-frequency resource blocks (RBs)) for downlink (DL) and uplink (UL) transmissions in network 100. DL refers to the transmission direction from BS 105 to UE 115, while UL refers to the transmission direction from UE 115 to BS 105. Communication can be in the form of wireless frames. A wireless frame can be divided into multiple subframes or time slots, for example, approximately 10. Each time slot can be further divided into micro-time slots. In FDD mode, simultaneous UL and DL transmissions can occur in different frequency bands. For example, each subframe includes UL subframes in the UL band and DL subframes in the DL band. In TDD mode, UL and DL transmissions occur using the same frequency band at different time periods. For example, a subset of subframes in a wireless frame (e.g., DL subframes) can be used for DL ​​transmissions, while another subset of subframes in the wireless frame (e.g., UL subframes) can be used for UL transmissions.

[0042] The DL subframe and UL subframe can be further divided into several regions. For example, each DL or UL subframe can have a predefined region for the transmission of reference signals, control information, and data. The reference signal is a predetermined signal that facilitates communication between BS 105 and UE 115. For example, the reference signal can have a specific pilot frequency pattern or structure, where the pilot frequency tone can span the operating BW or frequency band, and each pilot frequency tone is located at a predefined time and predefined frequency. For example, BS 105 can transmit a cell-specific reference signal (CRS) and / or channel status information-reference signal (CSI-RS) to enable UE 115 to estimate the DL channel. Similarly, UE 115 can transmit a probe reference signal (SRS) to enable BS 105 to estimate the UL channel. Control information may include resource allocation and protocol control. Data may include protocol data and / or operational data. In some cases, BS 105 and UE 115 can communicate using self-contained subframes. A self-contained subframe may include portions for DL ​​communication and portions for UL communication. Self-contained subframes can be DL-centric or UL-centric. DL-centric subframes can include a longer duration for DL ​​communication (compared to UL communication). UL-centric subframes can include a longer duration for UL communication (compared to UL communication).

[0043] In some configurations, network 100 may be an NR network deployed on licensed spectrum. BS 105 may transmit synchronization signals (e.g., including primary synchronization signal (PSS) and secondary synchronization signal (SSS)) in network 100 to facilitate synchronization. BS 105 may broadcast system information associated with network 100 (e.g., including primary information block (MIB), residual system information (RMSI), and other system information (OSI)) to facilitate initial network access. In some cases, BS 105 may broadcast PSS, SSS, and / or MIB in the form of synchronization signal blocks (SSB) on the physical broadcast channel (PBCH), and may broadcast RMSI and / or OSI on the physical downlink shared channel (PDSCH).

[0044] In some configurations, UE 115 attempting to access network 100 can perform an initial cell search by detecting a PSS from BS 105. The PSS can synchronize time-of-use data and indicate a physical layer identity value. Subsequently, UE 115 can receive an SSS. The SSS can synchronize radio frames and provide a cell identity value, which can be combined with the physical layer identity value to identify the cell. The PSS and SSS can be located in the center portion of the carrier or at any suitable frequency within the carrier.

[0045] After receiving the PSS and SSS, UE 115 can receive the MIB. The MIB may include system information for initial network access and scheduling information for RMSI and / or OSI. After decoding the MIB, UE 115 can receive the RMSI and / or OSI. The RMSI and / or OSI may include radio resource control (RRC) information related to random access channel (RACH) procedures, paging, control resource set (CORESET) for physical downlink control channel (PDCCH) monitoring, physical uplink control channel (PUCCH), physical uplink shared channel (PUSCH), power control, and SRS.

[0046] After obtaining the MIB, RMSI, and / or OSI, UE 115 can execute a random access procedure to establish a connection with BS 105. In some instances, the random access procedure can be a four-step random access procedure. For example, UE 115 can transmit a random access preamble, and BS 105 can respond with a random access response. The random access response (RAR) may include a detected random access preamble identifier (ID) corresponding to the random access preamble, timing advance (TA) information, UL permission, temporary cellular radio network temporary identifier (C-RNTI), and / or shift indicator. Upon receiving the random access response, UE 115 can transmit a connection request to BS 105, and BS 105 can respond with a connection response. The connection response may indicate contention resolution. In some instances, the random access preamble, RAR, connection request, and connection response can be referred to as Message 1 (MSG1), Message 2 (MSG2), Message 3 (MSG3), and Message 4 (MSG4), respectively. In some instances, the random access procedure can be a two-step random access procedure, where UE 115 can transmit the random access preamble and connection request in a single transmission, and BS 105 can respond by transmitting the random access response and connection response in a single transmission.

[0047] After the connection is established, UE 115 and BS 105 can enter the normal operation phase, during which they can exchange operational data. For example, BS 105 can schedule UL and / or DL ​​communication for UE 115. BS 105 can transmit UL and / or DL ​​scheduling permissions to UE 115 via PDCCH. BS 105 can transmit DL communication signals to UE 115 via PDSCH according to DL scheduling permissions. UE 115 can transmit UL communication signals to BS 105 via PUSCH and / or PUCCH according to UL scheduling permissions.

[0048] In some cases, BS 105 can use Hybrid Automatic Request (HARQ) to transmit data with UE 115 to improve communication reliability. BS 105 can schedule PDSCH communication with UE 115 by transmitting DL permission in the PDSCH. BS 105 can transmit DL data packets to UE 115 according to the schedule in the PDSCH. DL data packets can be transmitted in transport blocks (TBs). If UE 115 successfully receives the DL data packet, UE 115 can transmit a HARQ ACK to BS 105. Conversely, if UE 115 fails to receive the DL transmission, UE 115 can transmit a HARQ NACK to BS 105. After receiving a HARQ NACK from UE 115, BS 105 can retransmit the DL data packet to UE 115. The retransmission may include the same encoded version of the DL data as the initial transmission. Alternatively, the retransmission may include a different encoded version of the DL data than the initial transmission. UE 115 can apply soft combining to combine encoded data received from the initial transmission and retransmissions for decoding. BS 105 and UE 115 can also use a mechanism essentially similar to DL HARQ to apply HARQ to UL communications.

[0049] In some configurations, network 100 can operate on a system BW or a component carrier BW. Network 100 can divide the system BW into multiple BWPs (e.g., portions). BS 105 can dynamically assign UE 115 to operate on a particular BWP (e.g., a portion of the system BW). The assigned BWP can be referred to as the active BWP. UE 115 can monitor the active BWP based on signaling information from BS 105. BS 105 can schedule UE 115 to perform UL or DL ​​communication on the active BWP. In some configurations, BS 105 can assign a pair of BWPs within a component carrier to UE 115 for UL and DL communication. For example, a BWP pair may include one BWP for UL communication and one BWP for DL ​​communication. Additionally, BS 105 can configure UE 115 to have one or more CORESETs among the BWPs. A CORESET may include a set of frequency resources spanning multiple symbols in time. BS 105 can configure UE 115 to have one or more search spaces for PDCCH monitoring based on CORESET. UE 115 can perform blind decoding in the search space to search for DL ​​control information (e.g., UL and / or DL ​​scheduling permissions) from BS. In one instance, BS 105 can configure UE 115 to have BWP, CORESET, and / or PDCCH search spaces via RRC configuration.

[0050] In some configurations, Network 100 may operate on a shared or unlicensed frequency band (e.g., at approximately 3.5 GHz, below 6 GHz, or higher in the mm-wave band). Network 100 may divide the frequency band into multiple channels, for example, each occupying approximately 20 MHz. BS 105 and UE 115 may be operated by multiple network operating entities sharing resources in a shared communication medium and may employ an LBT procedure to acquire Channel Occupancy Time (COT) in the shared medium for communication. COT may be discontinuous in time and may refer to the amount of time a radio node can transmit frames after it has won contention for the radio medium. Each COT may include multiple transmission slots. COT may also be referred to as Transmission Opportunity (TXOP). BS 105 or UE 115 may perform LBT in the frequency band before transmitting. LBT may be based on power detection or signal detection. For energy detection, when the signal energy measured from a channel exceeds a certain signal energy threshold, BS 105 or UE 115 can determine whether the channel is busy or occupied. For signal detection, when a reserved signal (e.g., a preceding signal sequence) is detected in a channel, BS 105 or UE 115 can determine whether the channel is busy or occupied.

[0051] Furthermore, BS 105 can configure UE 115 to have narrowband operation capability (e.g., where transmission and / or reception are limited to a BW of 20 MHz or less) to perform BWP transitions for channel monitoring and communication. The mechanism for performing BWP transitions is described in more detail herein.

[0052] Figure 2 illustrates a random access scheme in a wireless communication network 200 according to various embodiments of the present invention. Network 200 corresponds to a portion of network 100. For the purpose of simplification, Figure 2 illustrates one BS 204 and one UE 202, but it will be appreciated that the embodiments of the present invention can be extended to more UEs 202 and / or BS 204. BS 204 corresponds to one of BS 104. UE 202 corresponds to one of UE 102. UE 202 and BS 204 can communicate with each other at any suitable frequency.

[0053] In Figure 2, as shown by the dashed ellipse 220, BS 204 transmits synchronization signals, BRS, and system information on multiple directional beams 211 in multiple directions. To access network 200, UE 202 listens for the synchronization signals and / or BRS and selects the beam for performing a random access procedure (RAR). For example, UE 202 may receive beams 211a, 211b, and 211c and select beam 211b for RAR. UE 202 transmits a RAR preamble on beam 221 in the beam direction of beam 211b and monitors for the RAR from BS 204. After detecting the RAR preamble, BS 204 transmits the RAR on beam 211b in the same beam direction as the received RAR. BS 204 uses the entire subframe to transmit the RAR on beam 211b. This can lead to resource inefficiency when large bandwidths are available. Additionally, by the time BS 204 transmits the RAR, UE 202 may have moved to a different location away from beam 211b, as indicated by the dashed arrow. Therefore, UE 202 may fail to receive the RAR from beam 211b. An additional reason for RAR failure could be beam correspondence. Although UE 202 can retry another random access attempt after a waiting period (e.g., a delayed period), retrying adds additional latency. Therefore, transmitting a single random access preamble signal in a single beam direction for each random access attempt may not be robust enough to successfully complete the RACH procedure.

[0054] Figures 3A-3C illustrate various transmission scenarios of the two-step RACH scheme between UE 202 and BS 204 that can be implemented in the wireless communication network shown in Figures 1-2, according to some of the contents of this case.

[0055] Figure 300a in Figure 3A illustrates a two-step RACH procedure, which reduces access latency in the control plane compared to the conventional four-step RACH. At 315, the system information block (e.g., SIB2) and RRC signal are transmitted from BS 204 to UE 202, and after UE 202 decodes the system information and RRC signal at 320, at 340, UE 202 transmits Msg A carrying standard four-step LTE RACH Msg 1 and Msg 3, for example, including random access preamble signals followed by a payload for random access messages (connection request, device ID, buffer status report, etc.). Subsequently, UE 202 monitors Msg B from BS 204 at 345, while BS 204 processes and decodes Msg A at 350. Msg B is transmitted from BS 204, corresponding to Msg 2 and Msg 4 of the standard four-step LTE RACH (e.g., RAR, timing advance), and the connection is finally completed at 355 using an RRC response message. Therefore, the two-step RACH can establish a connection between UE 202 and BS 204 for UE 202 with reduced access latency (e.g., 2 message exchanges compared to the traditional 4 message exchanges) to begin uplink data transmission.

[0056] Figure 300b in Figure 3B illustrates a retransmission scenario when BS 204 fails to receive the preceding signal or payload of MsgA. For example, MsgA transmission 340 may fail due to channel collision, channel fading, or interference. BS 204 may monitor MsgA at 375 but fail to receive anything. Alternatively, BS 204 may receive a corrupted MsgA but fail to decode the preceding signal or payload from the corrupted version. In this case, BS 204 may not respond to UE 202 using MsgB. UE 202 may monitor MsgB 345 for a period of time and attempt to retransmit MsgA at 380. Since the two-step RACH does not specify a waiting time or retransmission scheme for UE 202 to monitor MsgB 345, additional delay 310 may occur during the retransmission process.

[0057] Figure 300c in Figure 3B illustrates another retransmission scenario when UE 202 fails to receive MsgB from BS 204. For example, even if BS 204 successfully receives and decodes MsgA at 350, and subsequently responds with MsgA at 355 to transmit MsgB to UE 202, the transmission of MsgB at 355 may fail due to channel corruption, receiver failure at UE 202, etc. In this case, UE 202 may monitor MsgB 345 for a period of time but fail to receive any content, or only receive an undecipherable corrupted version of MsgB. When UE 202 fails to receive MsgB in response to the transmitted MsgA or decode a RAR response from it, similar to the scenario in Figure 300b, UE 202 can retry retransmitting MsgA at 380, and BS 204 can subsequently retransmit MsgB at 385. Since the retransmission isochrones for MsgA or MsgB are not defined in the two-step RACH, if UE 202 waits for an indefinite period of time to retransmit, it may result in an additional delay of 310.

[0058] Given the need to reduce overall latency in two-step RACH procedures, the various forms described herein provide isochronous designs with improved system latency for retransmission schemes in two-step RACH procedures. Specifically, as further described with respect to Figures 6A-10, MsgA or MsgB can be retransmitted based on a specific scenario of decoding failure at UE 202 or BS 204, and various timing parameters are employed to align the transmission or retransmission of MsgA and MsgB in the two-step RACH procedure. The overall latency of the two-step RACH procedure is improved by utilizing the isochronous arrangement defined in the retransmission.

[0059] Figure 4 is a block diagram of an exemplary UE 400 according to some of the contents of this case. For example, UE 400 may be UE 115 discussed above in Figure 1 or UE 202 illustrated in other figures. As shown, UE 400 may include a processor 402, memory 404, BWP transition module 408, communication interface 409, transceiver 410 including data machine subsystem 412 and radio frequency (RF) unit 414, and one or more antennas 416. These components may communicate directly or indirectly with each other, for example, via one or more buses.

[0060] Processor 402 may include a central processing unit (CPU), digital signal processor (DSP), application-specific integrated circuit (ASIC), controller, field-programmable gate array (FPGA) device, another hardware device, firmware device, or any combination thereof configured to perform the operations described herein. Processor 402 may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, a combination of one or more microprocessors and a DSP core, or any other such configuration.

[0061] Memory 404 may include cache memory (e.g., the cache memory of processor 402), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electronically erasable programmable read-only memory (EEPROM), flash memory, solid-state memory devices, hard disks, other forms of volatile and non-volatile memory, or combinations of different types of memory. In one configuration, memory 404 includes a non-transitory computer-readable medium. Memory 404 may store or have instructions 406 recorded thereon. Instructions 406 may include, when executed by processor 402, causing processor 402 to perform the operations described herein in accordance with the configurations (e.g., the configurations of Figures 3A-3C and 6A-10), referring to UE 115. Instructions 406 may also be referred to as program code. Program code can be used to cause wireless communication devices to perform such operations, for example, by causing one or more processors (such as processor 402) to control or command the wireless communication devices to do so. The terms "instruction" and "code" should be interpreted broadly to include any type of computer-readable statement. For example, the terms "instruction" and "code" can represent one or more programs, routines, subroutines, functions, procedures, etc. "Instruction" and "code" can include a single computer-readable statement or multiple computer-readable statements.

[0062] The two-step RACH module 408 can communicate with the communication interface 409 to receive messages from or transmit messages to another device. Each of the two-step RACH module 408 and the communication interface 409 can be implemented via hardware, software, or a combination thereof. For example, each of the two-step RACH module 408 and the communication interface 409 can be implemented as a processor, circuitry, and / or instructions 406 stored in memory 404 and executed by processor 402. In some instances, the two-step RACH module 408 and the communication interface 409 can be integrated within the data center subsystem 412. For example, the two-step RACH module 408 and the communication interface 409 can be implemented via a combination of software components (e.g., executed by a DSP or general-purpose processor) and hardware components (e.g., logic gates and circuitry) within the data center subsystem 412. In some instances, the UE may include one of the two-step RACH module 408 and the communication interface 409. In other instances, the UE may include both a two-step RACH module 408 and a communication interface 409.

[0063] The two-step RACH module 408 and communication interface 409 can be used in various configurations of this invention, such as those shown in Figures 2-3 and 6-17. The two-step RACH module 408 is configured to receive system information from the BS (e.g., 204) for initiating the RACH procedure. The two-step RACH module 408 is also configured to transmit MsgA, including a random access preamble and a payload containing a connection request, to the BS. The two-step RACH module 408 is also configured to monitor for MsgB responses to MsgA from the BS during the Random Access Response (RAR) window. The two-step RACH module 408 is also configured to retransmit MsgA if MsgB is not received from the BS within the RAR window. Alternatively, the two-step RACH module 408 is also configured to: if MsgB is received from the BS within the RAR window, determine whether to retransmit the connection request in Msg 3 as a shift to the standard four-step RACH or transmit an acknowledgment message, based on the type of payload decoded from the received MsgB.

[0064] Communication interface 409 is configured to coordinate with two-step RACH module 408 to receive system information, MsgB and / or other DL scheduling permissions from BS, and / or communicate with BS according to UL and / or DL ​​scheduling permissions. Communication interface 409 is also configured to transmit MsgA and / or other UL data to BS.

[0065] As shown in the figure, transceiver 410 may include a data exchange subsystem 412 and an RF unit 414. Transceiver 410 may be configured to communicate bidirectionally with other devices (such as BS 105). Data exchange subsystem 412 may be configured to modulate and / or encode data from memory 404, two-step RACH module 408, and / or communication interface 409 according to a modulation and coding scheme (MCS) (e.g., low-density parity checking (LDPC) coding scheme, turbo coding scheme, cyclotron coding scheme, digital beamforming scheme, etc.). RF unit 414 may be configured to process modulated / encoded data (e.g., PUCCH, PUSCH, channel report, ACK / NACK) from data exchange subsystem 412 (regarding outbound transmissions) or modulated / encoded data transmitted from another source (such as UE 115 or BS 105) (e.g., performing analog-to-digital conversion or digital-to-analog conversion, etc.). RF unit 414 can also be configured to perform analog beamforming in conjunction with digital beamforming. Although shown as being integrated with transceiver 410, data unit subsystem 412 and RF unit 414 can be separate devices coupled together at UE 115 to enable UE 115 to communicate with other devices.

[0066] RF unit 414 can provide modulated and / or processed data (e.g., data packets (or more generally, data messages that may contain one or more data packets and other information)) to antenna 416 for transmission to one or more other devices. Antenna 416 can also receive data messages transmitted from other devices. Antenna 416 can provide the received data messages for processing and / or demodulation at transceiver 410. Transceiver 410 can provide demodulated and decoded data (e.g., DL data blocks, PDSCH, PUSCH, BWP transition configuration, and / or commands) to two-step RACH module 408 and / or communication interface 409 for processing. Antenna 416 may include multiple antennas with similar or different designs to maintain multiple transmission links. RF unit 414 can configure antenna 416.

[0067] In one configuration, UE 400 may include multiple transceivers 410 implementing different RATs (e.g., NR and LTE). In one configuration, UE 400 may include a single transceiver 410 implementing multiple RATs (e.g., NR and LTE). In one configuration, transceiver 410 may include various components, wherein different combinations of components can implement different RATs.

[0068] Figure 5 is a block diagram of an exemplary BS 500 according to some of the contents of this case. For example, BS 500 may be BS 105 as discussed above in Figure 1 and BS 204 as described in other figures. As shown, BS 500 may include a processor 502, memory 504, a two-step RACH module 508, a communication interface 509, a transceiver 510 including a data machine subsystem 512 and an RF unit 514, and one or more antennas 516. These components may communicate directly or indirectly with each other, for example, via one or more buses.

[0069] Processor 502 may have various features as a type-specific processor. For example, such processors may include a CPU, DSP, ASIC, controller, FPGA device, another hardware device, firmware device, or any combination thereof configured to perform the operations described herein. Processor 502 may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0070] Memory 504 may include cache memory (e.g., the cache memory of processor 502), RAM, MRAM, ROM, PROM, EPROM, EEPROM, flash memory, solid-state memory devices, one or more hard disks, memristor-based arrays, other forms of volatile and non-volatile memory, or combinations of different types of memory. In some embodiments, memory 504 may include non-transitory computer-readable media. Memory 504 may store instructions 506. Instructions 506 may include instructions that, when executed by processor 502, cause processor 502 to perform the operations described herein (e.g., the embodiments of Figures 2-3 and 6-16 and 18). Instructions 506 may also be referred to as code, which can be broadly interpreted to include any type of computer-readable statement, as discussed above with respect to Figure 4.

[0071] The two-step RACH module 408 can communicate with the communication interface 409 to receive or transmit messages to another device. Each of the two-step RACH module 508 and the communication interface 509 can be implemented via hardware, software, or a combination thereof. For example, each of the two-step RACH module 508 and the communication interface 509 can be implemented as a processor, circuitry, and / or instructions 506 stored in memory 504 and executed by processor 502. In some instances, the two-step RACH module 508 and the communication interface 509 can be integrated within the data center subsystem 512. For example, the two-step RACH module 508 and the communication interface 509 can be implemented via a combination of software components (e.g., executed by a DSP or general-purpose processor) and hardware components (e.g., logic gates and circuitry) within the data center subsystem 512. In some instances, the UE may include one of the two-step RACH module 508 and the communication interface 509. In other instances, the UE may include both a two-step RACH module 508 and a communication interface 509.

[0072] The two-step RACH module 508 and communication interface 509 can be used in various configurations of this invention, such as those shown in Figures 3A-3C and 6A-10. The two-step RACH module 508 is configured to broadcast system information for initiating a random access channel procedure. The two-step RACH module 508 is also configured to receive a MsgA including a random access preamble signal and a payload containing a connection request. The two-step RACH module 508 is also configured to determine whether at least a portion of the MsgA is decodeable. In response to a decoding failure of the MsgA, the two-step RACH module 508 is also configured to avoid transmitting any message to the UE 202 within the RAR window. In response to successful decoding of at least a portion of the first message, the two-step RACH module 508 is also configured to transmit a RAR message containing a payload determined based on the type of the successfully decoded portion of the MsgA.

[0073] Communication interface 509 is configured to coordinate with two-step RACH module 508 to broadcast system information or transmit MsgB to the UE. Communication interface 509 is also configured to receive MsgA or other UL data from the UE.

[0074] As shown in the figure, transceiver 510 may include a data exchange subsystem 512 and an RF unit 514. Transceiver 510 may be configured to communicate bidirectionally with other devices (such as UE 115 and / or 400 and / or another core network element). Data exchange subsystem 512 may be configured to modulate and / or encode data according to an MCS (e.g., LDPC coding scheme, turbo coding scheme, cyclotron coding scheme, digital beamforming scheme, etc.). RF unit 514 may be configured to process modulated / encoded data (e.g., BWP transition configuration and commands, PDCCH, PDSCH) from data exchange subsystem 512 (regarding outbound transmissions) or modulated / encoded data transmitted from another source (such as UE 115 and 400) (e.g., performing analog-to-digital conversion or digital-to-analog conversion, etc.). RF unit 514 may also be configured to perform analog beamforming in conjunction with digital beamforming. Although shown as being integrated with transceiver 510, data interface subsystem 512 and / or RF unit 514 may be separate devices, coupled together at BS 105 to enable BS 105 to communicate with other devices.

[0075] RF unit 514 can provide modulated and / or processed data (e.g., data packets (or more generally, data messages containing one or more data packets and other information)) to antenna 516 for transmission to one or more other devices. For example, depending on various aspects of this invention, this may include transmitting information to complete attachment to a network and communication with a resident UE 115 or 400. Antenna 516 can also receive data messages transmitted from other devices and provide the received data messages for processing and / or demodulation at transceiver 510. Transceiver 510 can provide demodulated and decoded data (e.g., channel reports, PUSCH, PUCCH, HARQ ACK / NACK) to two-step RACH module 508 and / or communication interface 509 for processing. Antenna 516 may include multiple antennas with similar or different designs to maintain multiple transmission links.

[0076] In one configuration, the BS 500 may include multiple transceivers 510 implementing different RATs (e.g., NR and LTE). In one configuration, the BS 500 may include a single transceiver 510 implementing multiple RATs (e.g., NR and LTE). In one configuration, the transceiver 510 may include various components, wherein different combinations of components can implement different RATs.

[0077] Figures 6A-6C illustrate retransmission isochronous line designs for different scenarios of the two-step RACH procedure between the UE and BS, based on some of the features described in this case. In Figures 6A-6C, schemes 600a-c can be adopted by BSs (such as BS 105 in Figure 1, BS 204 in Figure 2, and / or 500 in Figure 5) and UEs (such as UE 115 in Figure 1, UE 202 in Figure 2, and / or 400 in Figure 4) in a network such as network 100 operating on a shared or unlicensed frequency band. UE 202 can be a low-cost UE device operating on a narrow frequency band of approximately 20 MHz or less. Additionally, in Figures 6A-6C, the horizontal axis represents time in a constant unit.

[0078] Figure 600a illustrates a scenario where a two-step RACH procedure between UE 202 and BS 204 successfully establishes a connection. BS 204 can broadcast a downlink channel or signal 605 to multiple UEs within the communication range. For example, the downlink channel or signal 605 may include a system information block containing a root sequence identifier, cyclic shift, RA subframe, uplink allow, etc. After receiving downlink data 605, UE 202 can wait for a time interval T0 after the last downlink data symbol before transmitting MsgA (610a-b, which are also collectively referred to as 610) to BS 204.

[0079] In some configurations, time gap T0 facilitates the transition from downlink to uplink transmission and may have a lower bound. The lower bound of T0 can be predetermined based on a variety of factors, including but not limited to the duplex mode between BS 202 and UE 204 (e.g., time-domain duplex or frequency-domain duplex), the tuning time for the parameter set or bandwidth portion (BWP) handover between the last downlink data symbol and the first uplink data symbol of MsgA 610, the preparation time required for UE 202 to prepare MsgA payload 610b, and the processing time required for the downlink channel to transmit downlink channel information 610 from BS 204 to UE 202, etc.

[0080] In some configurations, after time gap T0, UE 202 transmits MsgA preamble 610a and MsgA payload 610b to BS 204. For example, MsgA payload 610b may include an RRC connection request with BS 204 (e.g., RA-RNTI, uplink information, initial device identity, etc.). To transmit MsgA, UE 202 may wait for time gap Tg between the transmission of MsgA preamble 610a and MsgA payload 610b, which facilitates BS 204's detection of the start of MsgA payload 610b. The time gap Tg is greater than the lower bound, which can be predetermined by a variety of factors, including but not limited to the physical random access channel (PRACH) format of MsgA 610, the time domain resource allocation for MsgA 610, the time slot format, the tuning time for parameter set switching between MsgA preamble signal 610a and MsgA payload 610b, the listen-before-tell (LBT) mechanism between BS 204 and UE 202, the channel occupancy time between BS 204 and UE 202, the frequency band for RACH procedure, and the physical uplink shared channel (PUSCH) mapping type for MsgA 610.

[0081] In some cases, timing parameters T0 and Tg can be pre-stored in a lookup table. For example, the parameter values ​​of T0 and Tg can be determined empirically based on various combinations of the factors mentioned above and stored in the lookup table. UE 202 can retrieve the corresponding timing parameters T0 and Tg from the predefined lookup table based on system factors.

[0082] After MsgA 610 is transmitted, UE 202 can start a timer for the RAR window to monitor MsgB from BS 204. The start point 615a of the RAR window 615 is aligned with the first PDCCH symbol in the PDCCH search space of MsgB. The determination of the start point 615a of the RAR window 615 is further discussed with reference to Figure 10. UE 202 executes the timer within the length of the RAR window until the end of the RAR window 615b. BS 204 can provide the length of the RAR window to UE 202, which will be further described with reference to Figure 9.

[0083] During RAR window 615, BS 204 can receive and decode MsgA 610 and prepare for MsgB (including MsgB PDCCH 620a and MsgB payload 620b, which are collectively referred to as 620), while UE 202 can monitor MsgB. If BS 204 successfully decodes MsgA payload 610b and obtains information from it, BS 205 can include a RAR response represented by "Successful RAR" 620b in the payload of MsgB 620. Subsequently, BS 204 transmits MsgB 620 to UE 202.

[0084] Upon receiving MsgB 620, UE 202 can decode MsgB 620. If a successful RAR 620b is decoded from the payload of MsgB 620, UE 202 transmits an acknowledgment message 625 to BS 204 to notify that an RRC connection has been established. UE 202 may wait for a time gap T1 after the last data symbol of the PDSCH of MsgB 620 before transmitting the acknowledgment message 625. For example, time gap T1 provides processing time for UE 202 to decode the received MsgB 620 and for TA-based uplink timing adjustments for UE 202. Time gap T1 is also determined such that the acknowledgment message 625 is transmitted using RAR window 615, but is also greater than a lower bound. The lower bound value for T1 can be predetermined based on various factors, including but not limited to PDSCH processing time, time slot format (whether TDD is used), whether the approval message 625 is carried on the PUSCH, etc.

[0085] In some cases, similar to time intervals T0 and Tg, T1 can be obtained from a pre-stored lookup table that lists empirically determined values ​​for T1 corresponding to various combinations of factors. In some cases, the time interval T1 can be dynamically determined based on the RAR window 615, allowing sufficient time for the approval message 625 before the RAR window ends 615b.

[0086] Figure 600b illustrates a scenario where the two-step RACH procedure between UE 202 and BS 204 is shifted to a traditional four-step RACH procedure due to decoding failure of the MsgA payload 610b. Similar to Figure 600a, BS 204 broadcasts a downlink channel or signal 605 to multiple UEs within the communication range, and then UE 202 transmits MsgA 610 to BS 204. UE 202 can start a timer for the RAR window to monitor MsgB from BS 204.

[0087] Unlike Figure 600a, in Figure 600b, if BS 204 fails to decode the MsgA payload 610b—for example, if the received MsgA 610 is corrupted due to channel fading or collision, and only the MsgA preamble signal 610a can be detected from the received message—BS 204 cannot respond using connection establishment due to the lack of a connection request from the MsgA payload 610b. In this case, BS 204 can include a shift indication represented by "Shift-Back RAR" 620c in the MsgB 620 payload and transmit MsgB 620 to UE 202 to indicate that the RRC connection establishment was unsuccessful and the two-step RACH will be shifted to a four-step mode.

[0088] After receiving MsgB 620 from BS 204, UE 202 decodes the received MsgB 620. If a shifted RAR 620c is decoded from the payload of MsgB 620, UE 202 transmits Msg3 630 on the PUSCH to notify BS 204 that the RACH procedure will be shifted to a four-step RACH. In some cases, Msg3 630 may be a retransmission version of the MsgA payload 610b that was not successfully decoded at BS 204. In some cases, Msg3 630 may differ from the MsgA payload 610b, for example, to initiate a new RRC connection request. When Msg3 630 has a different length than the MsgA payload 610b, UE 202 may add padding bits or truncate Msg3 to ensure that the transmission of Msg3 can be completed at the end of the RAR window 615b.

[0089] UE 202 may wait for time gap T2 after the last data symbol of MsgB 620 before retransmitting the MsgA payload 610b. For example, time gap T2 provides processing time for UE 202 to decode the received MsgB 620 and for TA-based uplink timing adjustments for UE 202. Time gap T2 is also determined to allow sufficient time for transmitting Msg3 630 in RAR window 615, but also greater than a lower bound. The lower bound for T1 can be predetermined based on various factors, including but not limited to PDSCH processing time, slot format, PUSCH preparation time, etc.

[0090] In some cases, similar to time gaps T0 and Tg, T2 can be obtained from a pre-stored lookup table listing empirically determined values ​​for T2 corresponding to various combinations of factors. In some cases, time gap T2 can be dynamically determined based on the RAR window 615, allowing sufficient time for Msg3 630 before the end of the RAR window 615b. In some cases, time gap T2 can be shorter than time gap T1 because Msg3 630 may require more transmission time compared to the approval message 625.

[0091] Figure 600c illustrates a scenario where a two-step RACH procedure between UE 202 and BS 204 requires a complete retransmission of MsgA when BS 204 fails to decode or receive MsgA at all. Similar to Figures 600a-b, BS 204 broadcasts a downlink channel or signal 605 to multiple UEs within the communication range, and then UE 202 transmits MsgA 610 to BS 204. UE 202 can start a timer for the RAR window to monitor for MsgB from BS 204.

[0092] Unlike Figures 600a-b, in Figure 600c, BS 204 may not receive any message from UE 202 due to channel corruption, or may receive a largely undecodeable corrupted MsgA 610. If BS 204 fails to detect either the MsgA preamble signal 610a or the MsgA payload 610b due to decoding failure at 613 during RAR window 615, BS 204 may take no action and transmit no content during RAR window 615. Meanwhile, UE 202 may monitor during RAR window 615, but will not receive any content from BS 204.

[0093] In this scenario, if UE 202 does not receive MsgB 620 from BS 204 during RAR window 615, UE 202 can request a retransmission of MsgA 610. After shifting and MAC protocol processing at 623, UE 202 can retransmit MsgA containing MsgA preamble 635a and MsgA payload 635b. In some cases, MsgA preamble 635a and MsgA payload 635b can be the same as MsgA preamble 610a and MsgA payload 610b, respectively. In some cases, UE 202 can reselect MsgA preamble 635a or PUSCH timing in the time or frequency domain, or reselect the demodulation reference signal source for retransmission. In some configurations, UE 202 can reconstruct the MsgA payload 635b for the retransmitted MsgA using content different from the MsgA payload 610b, a different modulation and coding scheme (MCS), and a different transport block size (TBS). In some configurations, the retransmitted MsgA preamble signal 635a or MsgA payload 635b can be configured with power ramping or transmitter beam switching.

[0094] As shown in Figures 6A-6C, UE 202 does not always transmit HARQ feedback signals (e.g., acknowledgment or non-acknowledgment messages) for MsgB to BS 204 to notify whether the RRC connection has been successfully established. As shown in Figure 600b, if UE 202 successfully decodes the shifted RAR 620b from MsgB 620, UE 202 does not transmit "ACK" or "NACK" to BS 204. As shown in Figure 600c, if UE 202 does not receive a successful RAR 620b or shifted RAR 620c, UE 202 also does not transmit any "ACK" or "NACK" to BS 204.

[0095] As shown in Figure 600a, UE 202 only transmits an "ACK" to BS 204 if UE 202 can decode the successful RAR 620b from MsgB 620. Before UE 202 transmits the acknowledgment message 625, UE 202 can apply "timing advance" to adjust the timing offset on the uplink. For example, the Media Access Control (MAC) control element used for the timing advance command can be included in the successful RAR 620b.

[0096] In some configurations, the acknowledgment message 625 can be transmitted on the PUCCH, uplink control information (UCI) carried on the PUSCH, or uplink reference signals. In some configurations, UE 202 can configure a resource allocation indicator for the acknowledgment message 625 at the index of the MAC control element, MAC sub-header, or sub-protocol data unit (PDU) corresponding to the payload 620b. Alternatively, UE 202 can configure the resource allocation indicator for the acknowledgment message 625 at a sub-field of the downlink control information (DCI) or at the resource mapping mode of the CCE on the PDCCH. Alternatively, UE 202 can configure the resource allocation indicator for the acknowledgment message 625 using a joint indication via MsgB PDCCH and MsgB PDSCH. Alternatively, UE 202 can configure the resource allocation indicator for the acknowledgment message 625 via RRC and preceding signal resource index.

[0097] Figures 7A-7B illustrate the logic flow of some states executed by the UE according to the present invention, corresponding to the retransmission isochronous design in different scenarios of the two-step RACH procedure shown in Figures 6A-6C. The steps of method 700 can be performed by the computing device of the wireless communication device (e.g., processor, processing circuitry, and / or other suitable components) or other suitable components for performing such steps. For example, the wireless communication device (such as UE 115, UE 202, or UE 400) can utilize one or more components (such as processor 402, memory 404, two-step RACH module 408, communication interface 409, transceiver 410, data transmitter 412, and one or more antennas 416) to perform the steps of method 700. Method 700 can be used in conjunction with Figures 600a-c described above with respect to Figures 6A-6C. As shown, method 700 includes multiple enumerated steps, but various states of method 700 include additional steps before, after, and between the enumerated steps. In some cases, one or more of the listed steps may be omitted or performed in a different order.

[0098] At step 702, UE 202 receives, for example, system information or RRC signaling for configuring the RACH procedure from BS 204. For example, the system information or RRC signaling can be transmitted via the downlink channel or signaling 605 shown in Figures 6A-6C.

[0099] At step 704, UE 202 waits for a time gap after the last downlink symbol from the BS (e.g., the last symbol of system information, control, or reference signals) before transmitting the first message to the BS. For example, as shown in FIG6A, UE 202 waits for a time period T0 before transmitting the MsgA preamble signal 610a. In some embodiments, the value of T0 can be predetermined based on a variety of factors, including but not limited to the duplex mode between BS 202 and UE 204 (e.g., time-domain duplex or frequency-domain duplex), the tuning time for switching parameter sets or bandwidth portions (BWP) between the last symbol and the first uplink symbol of the random access preamble signal of the first message MsgA 610, the preparation time required for UE 202 to prepare the MsgA payload 610b, the processing delay for the Media Access Control (MAC) protocol, the processing time required for the downlink channel to transmit downlink channel information 610 from BS 204 to UE 202, etc.

[0100] At step 706, UE 204 begins uplink transmission of the first message (e.g., MsgA 610 in FIG. 6A) to BS. Specifically, at step 708, UE 202 waits for a time gap Tg (as shown in FIG. 6A) between the transmission of the MsgA preamble signal (e.g., 610a in FIG. 6A) and the transmission of the MsgA payload (e.g., 610b in FIG. 6A). In some embodiments, the value of Tg is greater than a lower bound, which can be predetermined by a variety of factors, including but not limited to the format of the preamble signal for the PRACH format, the time-domain resource allocation for the MsgA preamble signal 610a, the time slot format used in time-division duplex (TDD) mode, the tuning time for parameter set switching between the MsgA preamble signal 610a and the PUSCH carrying the MsgA payload 610b, the LBT mechanism between BS 204 and UE 202 when the RACH procedure is operating on shared or unlicensed spectrum, the channel occupancy time for UE 202 when the RACH procedure is operating on shared or unlicensed spectrum, the frequency band for the RACH procedure, and the PUSCH mapping type for the MsgA payload 610b.

[0101] At step 710, UE 202 starts a timer for the MsgB RAR window (e.g., 615 in FIG. 6A). For example, the starting point of the MsgB RAR window is determined via method 1000 in FIG. 10.

[0102] At step 712, UE 202 monitors the second message responding to the first message during the RAR window. For example, UE 202 may search for MsgB responding to MsgA in the MsgB PDCCH search space during the RAR window (e.g., 620 in FIG. 6A).

[0103] At step 714, UE 202 determines whether a second message (e.g., MsgB 620) has been received. If MsgB is not received, method 700 proceeds to step 716, where UE 202 determines whether the RAR window has expired. If the RAR window has not expired, method 700 proceeds to step 712, allowing UE 202 to continue monitoring MsgB.

[0104] If the RAR window has expired at step 716, UE 202 stops the timer for the MsgB RAR window at step 718. At step 720, UE 202 waits for a time shift to perform uplink timing adjustments, and then at step 722, UE 202 retransmits the first message. For example, UE 202 may retransmit MsgA, see, for example, 635a-b in FIG6C. In some embodiments, UE 202 may reconstruct the message payload for the retransmitted MsgA. Returning to step 714, if UE 202 determines that the second message (e.g., MsgB 620) has been received, method 700 continues to step 724, where UE 202 processes and decodes MsgB. At step 726, UE 202 determines whether it can decode MsgB and which part of MsgB it can decode. If the preceding signals of MsgB cannot be decoded at all, method 700 continues to step 718. For example, if only the shift indicator (BI) is decoded from MsgB at step 726 but the payload is not decoded, then UE 202 performs a shift at step 720 based on the shift indicator decoded from MsgB and the MAC protocol processing delay after the RAR window has passed. Subsequently, UE 202 retransmits MsgA at step 722.

[0105] In some embodiments, at step 722, UE 202 reselects a random access prequence signal resource or a PUSCH resource in the code domain, spatial domain, time domain, or frequency domain for retransmission of MsgA.

[0106] In some embodiments, UE 202 reconstructs the payload for the retransmitted MsgA using content different from the MsgA payload 610b, and applies power ramp to the retransmission of MsgA.

[0107] If at least a portion of MsgB (e.g., MsgB preamble 620a or payload 620b) is decoded, method 700 proceeds to step 728, where UE 202 determines what type of MsgB payload can be decoded from MsgB, for example, whether it is a successful RAR 620b or a delayed RAR 620c. If the decoded MsgB payload indicates that the MsgA payload was successfully decoded at BS 204, for example, a successful RAR 620b was decoded, method 700 proceeds to step 730, where UE 202 waits for a time gap T1 (e.g., as shown in FIG. 6A) after the last symbol of MsgB before any uplink transmission. For example, time gap T1 provides processing time for UE 202 to decode the received MsgB 620 and for TA-based uplink timing adjustments for UE 202. The time gap T1 is also determined to ensure that the acknowledgment message 625 is transmitted using the RAR window 615, but it is also greater than the lower bound. The lower bound for T1 can be predetermined based on various factors, including but not limited to PDSCH processing time, time slot format (whether TDD is used), MAC protocol processing latency, whether the acknowledgment message 625 is carried on the PUSCH, etc.

[0108] In some embodiments, after decoding the successful RAR at step 728, UE 202 decodes the resource allocation configured by the network in order for UE to prepare an acknowledgment message in response to the successful RAR.

[0109] At step 732, UE 202 transmits an acknowledgment message indicating successful completion of the random access procedure before the RAR window expires (e.g., 625 in FIG. 6A). For example, the acknowledgment message can be transmitted on the PUCCH, the UCI on the PUSCH, or the uplink reference signal.

[0110] In some embodiments, UE 202 applies a timing advance command to adjust the timing offset on the uplink from UE to BS before transmitting an acknowledgment message. The timing advance command is included in the random access response from the MsgB payload.

[0111] Returning to step 728, if UE 202 determines that the type of payload decoded from MsgB is a failed decoding of the MsgA payload at BS, for example, the delayed RAR 620c is decoded, then method 700 continues to step 731. In step 731, UE 202 waits for a time gap T2 (e.g., as shown in FIG. 6A) after the last symbol of MsgB before any uplink transmission. For example, the value of T2 is determined to allow sufficient time for the transmission of Msg3 630 in RAR window 615. The value of T2 can be predetermined based on various factors, including but not limited to PDSCH processing time, MAC protocol processing delay, TDD slot format, PUSCH preparation time, etc. In step 733, UE 202 retransmits the MsgA payload in Msg3 (e.g., 630 in FIG. 6B) on the PUSCH based on the uplink allowance included in the delayed RAR.

[0112] Figure 8 illustrates the logic flow of some states of the present invention executed by the BS, corresponding to the retransmission isochronous line design in different scenarios of the two-step RACH procedure shown in Figures 6A-6C. The steps of method 800 can be executed by the computing device of the wireless communication device (e.g., processor, processing circuitry, and / or other suitable components) or other suitable components for executing such steps. For example, the wireless communication device (such as BS 105, BS 204, or BS 500) can utilize one or more components (such as processor 502, memory 504, two-step RACH module 508, communication interface 509, transceiver 510, data transmitter 512, and one or more antennas 516) to execute the steps of method 800. Method 800 can be used in conjunction with Figures 600a-c described above with respect to Figures 6A-6C. As shown, method 800 includes multiple enumerated steps, but various states of method 800 include additional steps before, after, and between the enumerated steps. In some cases, one or more of the listed steps may be omitted or performed in a different order.

[0113] At step 802, BS 204 transmits system information and RRC signal transmissions to multiple UEs via the downlink. For example, the system information and RRC signal transmissions can be transmitted via the downlink channel or signal 605 shown in FIG. 6A.

[0114] At step 804, BS 204 receives the uplink transmission of the first message. For example, BS 204 receives MsgA from UE 202 (e.g., 610 in FIG. 6A).

[0115] At step 806, BS 204 decodes the received first message. For example, as shown in FIG6A, BS 204 processes and decodes MsgA during RAR window 615.

[0116] At step 808, BS 204 determines whether the first message can be decoded. If the first message cannot be decoded, method 800 continues to step 810, where BS 204 avoids transmitting any downlink during the RAR window. For example, if the MsgA preamble signal cannot be decoded from MsgA at step 808, BS 204 transmits a shift indicator to UE 202.

[0117] At step 812, BS 204 monitors for MsgA retransmission after the RAR window expires. At step 814, BS 204 receives the first retransmitted message. For example, the retransmitted message (e.g., 635a-b in FIG. 6C) may have the same MsgA payload 610b, or it may have a reconstructed payload (e.g., with a new connection request).

[0118] Returning to step 808, if BS 204 determines that at least a portion of the first message can be decoded, for example, the MsgA payload (e.g., 610b in FIG. 6A) can be decoded, then method 800 continues to step 818. In step 818, BS 204 decodes the MsgA payload to obtain the unique identification code of UE 202 and prepares a second message with a payload indicating successful decoding. For example, BS 204 prepares MsgB (e.g., 620b in FIG. 6A) with a successful RAR payload to indicate a successful connection. BS 204 also prepares MsgB with PDCCH and PDSCH and configures scheduling information for the PSDCH used for MsgB. In another instance, BS 204 also prepares MsgB by scrambling the cyclic redundancy check of the PDCCH using a Cellular Radio Network Temporary Identifier (C-RNTI) or a group RNT and mapping the payload of MsgB to the PDSCH. The MsgB payload must include at least a shift indicator (BI).

[0119] In some embodiments, BS 204 detects the MsgA preceding signal from MsgA to obtain the timing advance of UE 202, and then prepares MsgB, which includes a timing advance command, a unique identifier of UE 202, and resource allocation for UE in MsgB.

[0120] At step 820, BS 204 transmits a second message to UE, for example, MsgB with successful RAR 620b. At step 822, BS 204 receives from UE an acknowledgment message indicating successful completion of the random access procedure (e.g., 625 in FIG. 6A).

[0121] Returning to step 808, if BS 204 determines that only the preceding signal of the first message (e.g., MsgA preceding signal 610a in FIG. 6B) can be decoded, then method 800 continues to step 819, where BS 204 prepares a second message with a payload indicating decoding failure. For example, BS 204 prepares MsgB (e.g., 620c in FIG. 6B) with a payload shifted back to RAR to indicate decoding failure of the MsgA payload, and therefore needs to shift back to four steps of RACH.

[0122] In some embodiments, BS 204 includes a timing advance command, an index of the random access prequel sequence (RAPID), and an uplink permission for UE 202 to retransmit the MsgA payload in MsgB.

[0123] At step 821, BS 204 transmits a second message, for example, MsgB with MsgB shifted back to RAR (e.g., 620b in FIG. 6B). At step 823, BS 204 receives a third message that informs the UE that it will shift back to four-step RACH. For example, the MsgA payload can be retransmitted to BS 204 in the form of Msg3 for four-step RACH. In this way, BS 204 is notified that four-step RACH is being implemented after receiving Msg3.

[0124] Figure 9 illustrates the logical flow of configuring the Random Access Response (RAR) window length in a two-step RACH procedure according to some states of the present invention. The steps of method 900 can be performed by the computing device of a wireless communication device (e.g., a processor, processing circuitry, and / or other suitable components) or other suitable components for performing such steps. For example, a wireless communication device (such as BS 105, BS 204, or BS 500) can utilize one or more components (such as processor 502, memory 504, two-step RACH module 508, communication interface 509, transceiver 510, data transmitter 512, and one or more antennas 516) to perform the steps of method 800. Method 900 can be used in conjunction with Figures 600a-c described above with respect to Figures 6A-6C. As shown, method 900 includes multiple enumerated steps, but various states of method 900 include additional steps before, after, and between the enumerated steps. In some states, one or more of the enumerated steps can be omitted or performed in a different order.

[0125] At step 902, BS 204 obtains the length of the MsgB RAR window, which can be predetermined by the network. In some embodiments, the RAR window length can be determined based on factors such as, but not limited to, the following: MsgA priority, the density of resource allocation for MsgA preceding signals / payloads, the timing-related periodicity of synchronization signal blocks (SSBs), UE capabilities, etc. For example, the RAR window length can be inversely proportional to the MsgA priority level; for instance, a shorter window length can be assigned to MsgA with a higher priority. In another instance, the RAR window length can be increased when resource allocation for MsgA decreases.

[0126] At step 904, BS 204 determines whether any UE is in an RRC connection state. If UE 202 is not in an RRC connection state, for example, in an idle state, then BS 204 can send the RAR window length to the UE in a system information broadcast at step 906. If UE 202 is in an RRC connection state at step 904, then BS 204 sends the RAR window length to UE 202 via RRC signal transmission at step 908. At step 910, UE 202 can dynamically update the RAR window length via RRC signal transmission from BS 204.

[0127] Figure 10 illustrates the logical flow of configuring the starting point of the Random Access Response (RAR) window in a two-step RACH procedure according to some states of the present invention. The steps of method 1000 can be performed by the computing device of a wireless communication device (e.g., a processor, processing circuitry, and / or other suitable components) or other suitable components for performing such steps. For example, a wireless communication device (such as UE 115, UE 202, or UE 400) can utilize one or more components (such as processor 402, memory 404, two-step RACH module 408, communication interface 409, transceiver 410, data transmitter 412, and one or more antennas 416) to perform the steps of method 1000. Method 1000 can be used in conjunction with Figures 600a-c described above with respect to Figures 6A-6C. As shown, method 1000 includes multiple enumerated steps, but various states of method 1000 include additional steps before, after, and between the enumerated steps. In some cases, one or more of the listed steps may be omitted or performed in a different order.

[0128] At step 1002, UE 202 completes the PUSCH timing. At step 1004, UE 202 determines whether the UE is in an RRC connection state, for example, whether it is connected to the BS. If UE 202 is not in an RRC connection state, for example, in an idle state, then method 1000 continues to step 1006, at which step 1006, UE 202 starts a timer for the RAR window at the first PDCCH symbol of the earliest shared search space (CSS) for the MsgB PDCCH. In this case, UE 202 searches for the first PDCCH symbol of MsgB within the CSS configured by system information.

[0129] Otherwise, if UE 202 is in an RRC connection, UE 202 further determines at step 1008 whether random access is contention-based (CBRA) or contention-free (CFRA). Under the CBRA scheme at step 1008, UE 202 starts a timer for the MsgB RAR window at step 1010 at the earliest CSS or the first PDCCH symbol in the UE-specific search space (USS) for the MsgB PDCCH. In this case, UE 202 searches for the first PDCCH symbol of MsgB within the CSS configured by system information or within the USS configured by RRC signaling.

[0130] Otherwise, under the CFBA scheme at step 1008, the method continues to step 1012, where UE 202 starts a timer for the MsgB RAR window at the first PDCCH symbol of the earliest USS used for the MsgB PDCCH. In this case, the search space for the MsgB PDCCH is only the USS.

[0131] Information and signals can be represented using any of a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips mentioned throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

[0132] The various illustrative blocks and modules described in connection with the disclosure herein can be implemented or executed using a general-purpose processor, DSP, ASIC, FPGA or other programmable logic device, individual gate or transistor logic, individual hardware element or any combination thereof designed to perform the functions described herein. The general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller or state machine. The processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, a combination of one or more microprocessors with a DSP core, or any other such configuration).

[0133] The functions described herein can be implemented using hardware, processor-executed software, firmware, or any combination thereof. If implemented using processor-executed software, such functions can be stored as one or more instructions or code on or transmitted via a computer-readable medium. Other examples and implementations are within the scope of this document and the appended claims. For example, due to the nature of software, the functions described above can be implemented using processor-executed software, hardware, firmware, hardwiring, or any combination thereof. Features implementing the functions can also be located at various physical locations, including being distributed such that different parts of the functions are implemented at different physical locations. Furthermore, as used herein (including in the claims), "or" as used in a list of projects (e.g., a list of projects ending with phrases such as "at least one of" or "one or more of") indicates an inclusive list, such that a list such as [at least one of A, B, or C] means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

[0134] As a person skilled in the art would have understood up to now and in light of the specific application at the time, numerous modifications, substitutions, and alterations could be made to the materials, apparatus, configuration, and methods of use of the equipment described herein, without departing from the spirit and scope of this case. Therefore, the scope of this case should not be limited to the specific forms described herein (as they are only described through some examples), but should be fully commensurate with the claims appended below and their functional equivalents.

[0135] 100: Wireless communication network 105a:BS 105b:BS 105c:BS 105d:BS 105e:BS 105f:BS 115a:UE 115b:UE 115c:UE 115d:UE 115e:UE 115f:UE 115g:UE 115h:UE 115i:UE 115j:UE 115k:UE 200: Wireless communication network 202:UE 204:BS 211: Directional Beam 211a: Beam 211b: Beam 211c: Beam 221: Beam 300a: Figure 300b: Figure 300c: Image 310: Delay 315: Component Symbols 320: Component Symbol 340: Component Symbol 345: Component Symbol 350: Component Symbol 355: Component Symbol 375: Component Symbol 380: Component Symbol 385: Component Symbol 400:UE 402: Processor 404: Memory error 406: Instruction 408: BWP Jump Module 409: Communication Interface 410: Transceiver 412: Data Subsystem 414: Radio Frequency (RF) Unit 416: Antenna 500:BS 502: Processor 504: Memory error 506: Instruction 508: Two-step RACH module 509: Communication Interface 510: Transceiver 512: Data Subsystem 514: RF Unit 516: Antenna 600a: Solution 600b: Solution 600c: Solution 605: Signal 610a:MsgA 610b:MsgA 613: Component Symbol 615: RAR Window 615a: Starting point 615b: End of RAR message window 620a:MsgB PDCCH 620b:MsgB effective load 620c: Rear-shifted RAR 623: Component Symbol 625: Recognition Message 630:Msg3 635a: MsgA Preceding Signal 635b:MsgA effective load 700: Method 702: Steps 704: Steps 706: Steps 708: Steps 710: Steps 712: Steps 714: Steps 716: Steps 718: Steps 720: Steps 722: Steps 724: Steps 726: Steps 728: Steps 730: Steps 731: Steps 732: Steps 733: Steps 800: Method 802: Steps 804: Steps 806: Steps 808: Steps 810: Steps 812: Steps 814: Steps 816: Steps 818: Steps 819: Steps 820: Steps 821: Steps 822: Steps 823: Steps 900: Method 902: Steps 904: Steps 906: Steps 908: Steps 910: Steps 1000: Method 1002: Steps 1004: Steps 1006: Steps 1008: Steps 1010: Steps 1012: Steps

Claims

1. A method for wireless communication, comprising: A user equipment (UE) receives system information from a base station (BS) for initiating a random access channel (RACH) procedure; The UE transmits a first message to the BS, the first message representing a connection request; the UE monitors a second message from the BS in response to the first message, the monitoring occurring during a Random Access Response (RAR) window; when the second message received by the UE from the BS within the RAR window contains a shift response, the UE transmits one or more retransmissions of the first payload to the BS; or when the second message received within the RAR window contains a success response, the UE transmits an acknowledgment message to the BS.

2. The method as described in claim 1, further comprising: If the UE does not receive the second message from the BS after monitoring within the RAR window, the UE will retransmit the first message to the BS.

3. The method as described in claim 1, further comprising: Before transmitting the first message to the BS, the UE waits for a time gap after the BS receives the last data symbol of the system information; wherein the time gap is determined by at least one of the following: a duplex mode between the BS and the UE; a tuning time for numerical adjustment or a bandwidth portion (BWP) switch between the last data symbol and the first data symbol of the first message; a preparation time for the first payload; or a processing time for a downlink channel for transmitting the system information from the BS to the UE.

4. The method as described in claim 1, further comprising: The UE waits for a time gap between the transmission of the random access preamble signal and the transmission of the first payload; wherein the time gap is determined by at least one of the following: a physical random access channel (PRACH) format; a time domain resource allocation; a time slot format; a tuning time for the numerical switching between the random access preamble signal and the first payload; a listen-before-tell (LBT) mechanism between the BS and the UE; a channel occupancy time between the BS and the UE; a frequency band for the RACH procedure; or a physical uplink shared channel (PUSCH) mapping type for the first message.

5. The method as described in claim 1, further comprising: When the RAR window expires, and the second message received within the RAR window is not decoded into a payload, the UE retransmits a payload of the first message to the BS.

6. The method as described in claim 5, further comprising: The UE may reselect a first preamble signal or a PUSCH timing for the first preamble signal in the time or frequency domain for the first payload of the retransmitted first message, or reconstruct the first payload for the retransmission of a different content.

7. The method as described in claim 1, further comprising: After the UE receives the second message from the BS through the monitoring in the RAR window, it decodes the second payload of the second message; when the decoded second payload indicates that the first payload has been successfully decoded at the base station (BS), it constructs the confirmation message to respond to the connection request in the RAR window and indicates a connection setting.

8. The method as described in claim 7, further comprising: Waiting for a time gap after the last data symbol of the second message and before transmitting the acknowledgment message, wherein the time gap is determined by at least one of the following: a physical downlink shared channel (PDSCH) processing time; a time slot format; or whether the acknowledgment message is transmitted on the PUSCH.

9. The method as described in claim 7, further comprising: Before transmitting the confirmation message, the UE applies a time advance offset to adjust the time offset on an uplink from the UE to the BS.

10. The method as described in claim 7, wherein the acknowledgment message is transmitted via one of the following: a physical uplink control channel (PUCCH); uplink control information (UCI) carried on the PUSCH; or an uplink reference signal.

11. A user equipment (UE) for wireless communication, comprising: A communication interface is configured to: receive system information from a base station (BS) for initiating a random access channel (RACH) procedure; and transmit a first message to the BS indicating a connection request; and one or more processors configured to: monitor a second message in response to the first message from the BS, the monitoring occurring during a random access response (RAR) window; wherein, when the second message is received by the UE from the base station (BS) within the RAR window, the communication interface transmits one or more retransmissions of the first payload to the BS, and when the second message is received within the RAR window, the communication interface transmits an acknowledgment message to the BS.

12. The UE as described in claim 1, wherein when the UE does not receive the second message from the base station (BS) after monitoring within a random access response (RAR) window, it retransmits the first message to the BS.

13. The UE as described in request item 11, wherein, After receiving a last data symbol of the system information from the BS and before transmitting the first message to the BS, the one or more processors further wait for a time gap; wherein the time gap is determined by at least one of: a duplex mode between the BS and the UE; a tuning time for numerical adjustment or a bandwidth portion (BWP) switch between the last data symbol and a first data symbol of the first message; a preparation time for the first payload; or a processing time for a downlink channel for transmitting the system information from the BS to the UE.

14. The UE as described in claim 11, wherein one or more processors further wait for a time gap, the time gap being between the transmission of the random access preamble signal and the transmission of the first payload; wherein, The time slot is determined by at least one of the following: a physical random access channel (RACH) format; a time-domain resource allocation; a time slot format; a tuning time for the numerical switching between the random access preamble signal and the first payload; a listen-before-tell (LBT) mechanism between the BS and the UE; a channel occupancy time between the BS and the UE; a frequency band for the RACH procedure; or a physical uplink shared channel (PUSCH) mapping type for the first message.

15. The UE as described in claim 1, wherein when the communication interface fails to decode the second message received within the RAR window into a payload after the RAR window expires, the UE retransmits a payload of the first message to the BS.

16. The UE as claimed in claim 15, wherein one or more processors further: reselect a first preamble signal or a PUSCH timing for the first preamble signal in the time or frequency domain for the first payload of the retransmitted first message; or reconstruct the first payload for the retransmission of a different content.

17. The UE as described in claim 11, wherein one or more processors further: after the UE receives the second message from the BS via the monitoring in the RAR window, decodes the second payload of the second message; when the decoded second payload indicates that the first payload has been successfully decoded at the base station (BS), constructs the confirmation message to respond to the connection request in the RAR window and indicates a connection setting.

18. The UE as described in claim 17, wherein one or more processors further wait for a time gap, the time gap being after a last data symbol of the second message and before transmitting the acknowledgment message; wherein, The time gap is determined by at least one of the following: the processing time of an entity downlink shared channel (PDSCH); a time slot format; or whether the acknowledgment message is transmitted on the PUSCH.

19. The UE as described in claim 17, wherein one or more processors further apply a time advance offset to adjust a time offset on an uplink from the UE to the BS before transmitting an acknowledgment message.

20. The UE as described in claim 17, wherein the acknowledgment message is transmitted via one of the following: a physical uplink control channel (PUCCH); uplink control information (UCI) carried on the PUSCH; or an uplink reference signal.

Images