Method and apparatus for reducing overhead in random access process

Abstract

A method and apparatus for reducing overhead in a random access process are disclosed. In one embodiment, the method performed by a wireless communication node includes: sending first information to a wireless communication device; receiving a first message from the wireless communication device to enable the wireless communication device to access the wireless communication node; and sending a second message to the wireless communication device in response to the first message. The first information includes information about a time offset of the wireless communication device so that monitoring for the second message begins after the time offset from the end of sending the first message.

Description

Technical Field

[0001] The present disclosure relates generally to wireless communications, and more particularly to methods and apparatus for reducing overhead in a random access procedure for wireless communications. Background Art

[0002] Over the past few decades, mobile communications have evolved from voice services to high-speed broadband data services. With the in-depth development of new services and applications such as enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable and low-latency communications (URLLC), the demand for high-performance data transmission on mobile networks will continue to grow exponentially. Based on the specific requirements of these emerging services, wireless communication systems should meet various requirements such as throughput, latency, data rate, capacity, reliability, link density, cost, energy consumption, complexity, and coverage. Summary of the invention

[0003] The exemplary embodiments disclosed herein are directed to solving problems associated with one or more problems existing in the prior art, and provide other features that are readily apparent when referring to the following detailed description in conjunction with the accompanying drawings. According to some embodiments, exemplary systems, methods, and computer program products are disclosed herein. However, it should be understood that these embodiments are presented in an illustrative and non-limiting manner, and it is apparent to a person of ordinary skill in the art that various modifications that are still within the scope of the present invention may be made to the disclosed embodiments.

[0004] In one embodiment, a method performed by a wireless communication node is disclosed. The method includes: sending first information to a wireless communication device; receiving a first message from the wireless communication device to enable the wireless communication device to access the wireless communication node; and sending a second message to the wireless communication device in response to the first message. The first information includes information about a time offset of the wireless communication device so as to start monitoring the second message after the time offset from the end of sending the first message.

[0005] In another embodiment, a method performed by a wireless communication device is provided. The method includes: receiving first information from a wireless communication node; sending a first message to the wireless communication node to enable the wireless communication device to access the wireless communication node; and receiving a second message from the wireless communication node in response to the first message. The first information includes information about a time offset of the wireless communication device so that monitoring for the second message starts after the time offset from the end of sending the first message.

[0006] In another embodiment, a computing device includes at least one processor and a memory coupled to the processor, wherein the at least one processor is configured to perform any method disclosed herein. In another embodiment, a non-transitory computer-readable medium stores computer-executable instructions, wherein the computer-executable instructions are used to perform any method disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] When read in conjunction with the accompanying drawings, various aspects of the present disclosure can be best understood by the following detailed description. Please note that the various features are not necessarily drawn to scale. In fact, the size and geometry of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0008] Figure 1A An exemplary wireless communication network is shown, showing achievable modulation as a function of distance from a BS, in accordance with some embodiments of the present disclosure.

[0009] Figure 1B A block diagram of an exemplary wireless communication system for slot structure information indication according to some embodiments of the present disclosure is shown.

[0010] Figure 2 A method of performing a contention-based two-step random access (RACH) procedure in a wireless communication system according to some embodiments of the present disclosure is shown.

[0011] Figure 3 A method of performing a contention-based four-step random access (RACH) procedure in a wireless communication system according to some embodiments of the present disclosure is shown.

[0012] Figure 4 An exemplary method for reducing overhead in a random access procedure according to some embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0013] Various exemplary embodiments of the present invention are described below with reference to the accompanying drawings to enable those of ordinary skill in the art to make and use the present invention. It is apparent to those of ordinary skill in the art that, after reading this disclosure, various changes or modifications may be made to the examples described herein without departing from the scope of the present invention. Therefore, the present invention is not limited to the exemplary embodiments and applications described or illustrated herein. In addition, the specific order or hierarchy of steps in the methods disclosed herein are merely exemplary methods. Based on design preferences, the specific order or hierarchy of steps of the disclosed methods or processes may be rearranged while remaining within the scope of the present invention. Therefore, it will be understood by those of ordinary skill in the art that the methods and techniques disclosed herein present various steps or actions in an example order, and unless otherwise expressly stated, the present invention is not limited to the specific order or hierarchy presented.

[0014] Embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. The same or similar components may be represented by the same or similar reference numerals, although they are shown in different drawings. Detailed descriptions of constructions or processes known in the art may be omitted to avoid blurring the subject matter of the present invention. In addition, in embodiments of the present invention, terms are defined in consideration of their functions and may vary according to the intention, use, etc. of a user or operator. Therefore, they should be defined based on the overall content of this specification.

[0015] Due to limited device capacity, high latency and high signaling overhead, traditional methods that rely on random access of user terminals and scheduled data transmission between base stations and user terminals cannot provide satisfactory performance for the above services. In order to meet these requirements in 5G / NR (New Radio) communications, a contention-based unlicensed data transmission method is being considered. The random access (RACH) procedure is very important for the following situations: namely, during initial access from RRC (Radio Resource Control) idle, when performing the RRC connection establishment procedure, for downlink or uplink data transmission when the wireless communication device is not synchronized, and during handover when uplink synchronization is required in the target cell, etc.

[0016] In order to access the unlicensed spectrum during the RACH procedure, a Listen Before Talk (LBT) procedure is required, in which a CCA (Clear Channel Assessment) is performed. CCA uses at least energy detection to determine if there are other signals on the channel in order to determine whether the channel is occupied or idle, respectively. If the channel is occupied, the node enters a backoff state. In this state, a backoff timer is started and the node waits until the backoff timer expires before performing another LBT check. The backoff timer is decremented each time there is an unoccupied slot on the medium. If the channel is clear, the node can perform a transmission. The duration of the transmission (also called the channel occupation time or COT) is limited and is controlled by the backoff parameters used to access the channel.

[0017] Such an LBT process is performed during each step of the RACH process when accessing unlicensed spectrum, resulting in increased latency and adversely affecting system performance. In addition, when transmitting a random access preamble, the UE will start the ra-ResponseWindow configured in RACH-ConfigCommon at the first physical downlink control channel (PDCCH) opportunity after the end of the random access preamble transmission. However, a random access response (RAR) may not be received before the ra-ResponseWindow expires, and RAR reception may not increase RACH attempts.

[0018] The same problem also arises when supporting larger cell sizes, such as in non-terrestrial networks (NTNs), where the beam footprint size can reach a diameter of 1000 km and result in a maximum intra-beam delay of up to 16 milliseconds (ms). Considering the larger round-trip delay (RTD) in NTNs, more RACH attempts will result in an increase in access delay. Since the RAR is not received, the authorized PUSCH will not be used, wasting both RACH resources and PUSCH resources. In addition, for some scenarios, the transmission and processing delays may be large. The present teachings provide some solutions to solve this problem.

[0019] The method disclosed in the present teachings can be implemented in a wireless communication network, where the BS and the UE can communicate with each other via a communication link, for example, via a downlink radio frame from the BS to the UE or via an uplink radio frame from the UE to the BS. In various embodiments, the BS in the present disclosure may be referred to as a network side, and may include or be implemented as a next generation node B (gNB), an E-UTRAN node B (eNB), a transmission / reception point (TRP), an access point (AP), etc.; and the UE in the present disclosure may be referred to as a terminal, and may include or be implemented as a mobile station (MS), a station (STA), etc. The BS and the UE may be described herein as non-limiting examples of a "wireless communication node" and a "wireless communication device", respectively; according to various embodiments of the present disclosure, the BS and the UE may practice the methods disclosed herein and be capable of wireless and / or wired communication.

[0020] Figure 1A An exemplary wireless communication network 100 according to some embodiments of the present disclosure is shown. In a wireless communication system, a network-side communication node or base station (BS) may be a Node B, an E-utran Node B (also referred to as an Evolved NodeB, an eNodeB or an eNB), a micro-base station, a femto-base station, etc. A terminal-side node or user equipment (UE) may be a long-range communication system, such as a mobile phone, a smart phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a short-range communication system, such as a wearable device, a vehicle with an onboard communication system, etc. The network-side communication node and the terminal-side communication node are represented by BS 102 and UE 104, respectively, and are collectively referred to as "communication nodes" in all embodiments of the present invention below. According to some embodiments of the present invention, such communication nodes are capable of wireless and / or wired communication. It should be noted that all embodiments are only preferred embodiments and are not intended to limit the present invention. Therefore, it should be understood that the system may include any desired combination of UE and BS while remaining within the scope of the present disclosure.

[0021] refer to Figure 1A, the wireless communication network 100 includes a BS 102 and UEs 104a and 104b (collectively referred to herein as UE 104). BS 102 and UE 104 are contained within the geographical boundaries of a cell 101. Wireless transmissions from the transmit antennas of UE 104 to the receive antennas of BS 102 are referred to as uplink transmissions, while wireless transmissions from the transmit antennas of BS 102 to the receive antennas of UE 104 are referred to as downlink transmissions. Although Figure 1A Only two UEs 104 are shown in the figure, but it should be noted that any number of UEs 104 may be included in the cell 101 and is within the scope of the present invention. In some embodiments, the coverage of the uplink communication 105b is greater than the coverage of the uplink communication 105a, as shown by the dashed circles 112 and 110, respectively. The BS 102 is located in the intercept area of ​​the coverage areas 110 and 112 so that the BS 102 performs uplink communication with the UEs 104a and 104b in the cell 101.

[0022] The direct communication channel 105 / 103 between the UE 104 and the BS 102 may be through an interface, such as a Uu interface, also known as a UMTS (Universal Mobile Telecommunications System (UMTS) air interface. The direct communication channel (side link transmission) 106 between the UEs may be through a PC5 interface, which is introduced to meet high mobility and high density applications such as vehicle-to-vehicle (V2V) communication. The BS 102 is connected to a core network (CN) 108 through an external interface 107 (e.g., an Iu interface).

[0023] UE 104a and 104b obtain their synchronization timing from BS 102, which obtains its own synchronization timing from core network 108 through an Internet time service such as a public time NTP (Network Time Protocol) server or an RNC (Radio Frequency Simulation System Network Controller) server. This is called network-based synchronization. Alternatively, BS 102 can also obtain synchronization timing from a global navigation satellite system (GNSS) (not shown) through satellite signals 106, especially for large BSs in large cells with direct line of sight to the sky, which is called satellite-based synchronization.

[0024] Figure 1B A block diagram of an exemplary wireless communication system 150 according to some embodiments of the present disclosure is shown. The system 150 may include components and elements configured to support known or conventional operating features that do not need to be described in detail herein. In an exemplary embodiment, the system 150 may be used to send and receive data symbols in a wireless communication environment such as the wireless communication network 100 of FIG. 1 described above.

[0025] The system 150 generally includes a BS 102 and two UEs 104a and 104b (hereinafter collectively referred to as UE 104 for ease of discussion). The BS 102 includes a BS transceiver module 152, a BS antenna array 154, a BS memory module 156, a BS processor module 158, and a network interface 160, each of which is coupled and interconnected to each other via a data communication bus 180 as needed. The UE 104 includes a UE transceiver module 162, a UE antenna 164, a UE memory module 166, a UE processor module 168, and an input / output (I / O) interface 169, each of which is coupled and interconnected to each other via a data communication bus 190 as needed. The BS 102 communicates with the UE 104 via a communication channel 192, which may be any wireless channel or other medium known in the art suitable for the above-mentioned data transmission.

[0026] Those skilled in the art will appreciate that the system 150 may further include Figure 1B Any number of blocks, modules, circuits, etc. other than those shown. It will be appreciated by those skilled in the art that the various illustrative blocks, modules, circuits, and processing logic described in conjunction with the embodiments disclosed herein can be implemented in hardware, computer-readable software, firmware, or any actual combination thereof. In order to clearly illustrate this interchangeability and compatibility of hardware, firmware, and software, various illustrative components, blocks, modules, circuits, and steps are generally described according to their functions. Whether such functions are implemented as hardware, firmware, or software depends on specific applications and the design constraints imposed on the entire system. People familiar with the concepts described herein can implement such functions in a suitable manner for each specific application, but such implementation decisions should not be interpreted as limiting the scope of the present invention.

[0027] Wireless transmissions from the transmit antenna of UE 104 to the receive antenna of BS 102 are referred to as uplink transmissions, and wireless transmissions from the transmit antenna of BS 102 to the receive antenna of UE 104 are referred to as downlink transmissions. According to some embodiments, UE transceiver 162 may be referred to herein as an "uplink" transceiver 162, which includes an RF transmitter and receiver circuit each coupled to UE antenna 164. A duplex switch (not shown) may optionally couple the uplink transmitter or receiver to the uplink antenna in a time duplex mode. Similarly, according to some embodiments, BS transceiver 152 may be referred to herein as a "downlink" transceiver 152, which includes an RF transmitter and receiver circuit each coupled to antenna array 154. The downlink duplex switch may alternatively couple the downlink transmitter or receiver to the downlink antenna array 154 in a time duplex mode. The operation of the two transceivers 152 and 162 is coordinated in time so that the uplink receiver is coupled to the uplink UE antenna 164 to receive transmissions on the wireless communication channel 192 while the downlink transmitter is coupled to the downlink antenna array 154. Preferably, there is tightly synchronized timing with only a minimum guard time between changes in duplex direction. The UE transceiver 162 communicates with the BS 102 via the wireless communication channel 192 through the UE antenna 164, or communicates with other UEs via the wireless communication channel 193. The wireless communication channel 193 can be any wireless channel or other medium known in the art suitable for sidelink transmission of data as described herein.

[0028] The UE transceiver 162 and the BS transceiver 152 are configured to communicate via a wireless data communication channel 192 and cooperate with an appropriately configured RF antenna arrangement 154 / 164 capable of supporting a specific wireless communication protocol and modulation scheme. In some embodiments, the BS transceiver 152 is configured to send a physical downlink control channel (PDCCH) and a configured slot structure related information (SFI) entry set to the UE transceiver 162. In some embodiments, the UE transceiver 162 is configured to receive a PDCCH containing at least one SFI field from the BS transceiver 152. In some exemplary embodiments, the UE transceiver 162 and the BS transceiver 152 are configured to support industry standards such as long-term evolution (LTE) and emerging 5G standards. However, it should be understood that the present invention is not necessarily limited to specific standards and related protocols in application. Instead, the UE transceiver 162 and the BS transceiver 152 can be configured to support alternative or additional wireless data communication protocols, including future standards or variations thereof.

[0029] The BS processor module 158 and the UE processor module 168 are implemented or realized by a general purpose processor, a content addressable memory, a digital signal processor, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. In this manner, the processor may be implemented as a microprocessor, a controller, a microcontroller, a state machine, etc. The processor may also be implemented as a combination of computing devices, such as a combination of a digital signal processor and a microprocessor, a plurality of microprocessors, a combination of one or more microprocessors and a digital signal processor core, or any other such configuration.

[0030] Then, the UE processor module 168 detects the PHR trigger message on the UE transceiver module 162, and the UE processor module 168 is further configured to determine at least one second SFI entry set based on at least one predefined algorithm and at least one second SFI entry set received and configured by the BS 102, wherein the at least one predefined algorithm is selected based on other parameters calculated or received messages. The UE processor module 168 is also configured to generate at least one second SFI entry set and monitor the PDCCH received on the UE transceiver module 162 to further receive at least one SFI field. As used herein, "SFI entry set" refers to an SFI table or an SFI entry.

[0031] In addition, the steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be directly embodied in hardware, in firmware, in software modules executed by the processor modules 158 and 168, respectively, or in any practical combination thereof. The memory modules 156 and 166 may be implemented as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. In this regard, the memory modules 156 and 166 may be coupled to the processor modules 158 and 168, respectively, so that the processor modules 158 and 168 can read information from and write information to the memory modules 156 and 166, respectively. The memory modules 156 and 166 may also be integrated into their respective processor modules 158 and 168. In some embodiments, the memory modules 156 and 166 may each include a cache memory for storing temporary variables or other intermediate information during the execution of instructions to be executed by the processor modules 158 and 168, respectively. The memory modules 156 and 166 may also each include non-volatile memory for storing instructions to be executed by the processor modules 158 and 168, respectively.

[0032] The network interface 160 generally represents the hardware, software, firmware, processing logic and / or other components of the base station 102 that enable the BS transceiver 152 to communicate bidirectionally with other network components and communication nodes configured to communicate with the BS 102. For example, the network interface 160 can be configured to support Internet or WiMAX traffic. In a typical deployment, without any limitation, the network interface 160 provides an 802.3 Ethernet interface so that the BS transceiver 152 can communicate with a conventional computer network based on Ethernet. In this way, the network interface 160 may include a physical interface for connecting to a computer network (e.g., a mobile switching center (MSC)). As used herein with respect to a specified operation or function, the term "configured for" or "configured to" refers to a device, component, circuit, structure, machine, signal, etc. that is physically constructed, programmed, formatted, and / or arranged to perform a specified operation or function. The network interface 160 may allow the BS 102 to communicate with other BSs or a core network via a wired or wireless connection.

[0033] Reference again Figure 1A As described above, BS 102 repeatedly broadcasts system information associated with BS 102 to one or more UEs (e.g., 104) to allow UE 104 to access the network within cell 101 where BS 102 is located and generally operate correctly within cell 101. Access may be associated with at least one of: a handover process; an uplink synchronization process; and a beam failure recovery process. A variety of information such as downlink and uplink cell bandwidths, downlink and uplink configurations, random access configurations, etc. may be included in the system information, which will be discussed in more detail below. Typically, BS 102 broadcasts a first signal carrying some main system information, such as the configuration of cell 101, via a PBCH (physical broadcast channel). For clarity of explanation, such a broadcasted first signal is referred to herein as a "first broadcast signal." It should be noted that BS 102 may then broadcast one or more signals carrying some other system information via a corresponding channel (e.g., a physical downlink shared channel (PDSCH)), which are referred to herein as a "second broadcast signal," a "third broadcast signal," and the like.

[0034] Reference again Figure 1BIn some embodiments, the primary system information carried by the first broadcast signal may be transmitted by the BS 102 in a symbol format via the communication channel 192. According to some embodiments, the original form of the primary system information may be presented as one or more digital bit sequences, and the one or more digital bit sequences may be processed through multiple steps (e.g., encoding, scrambling, modulation, mapping steps, etc.), all of which may be processed by the BS processor module 158 to become the first broadcast signal. Similarly, when the UE 104 receives the first broadcast signal (in symbol format) using the UE transceiver 162, according to some embodiments, the UE processor module 168 may perform multiple steps (demapping, demodulating, decoding steps, etc.) to estimate the primary system information, such as the bit position, number of bits of the primary system information, etc. The UE processor module 168 is also coupled to the I / O interface 169, which provides the UE 104 with the ability to connect to other devices such as computers. The I / O interface 169 is a communication path between these accessories and the UE processor module 168.

[0035] In some embodiments, UE 104 may operate in a hybrid communication network, where the UE communicates with BS 102 and other UEs, such as between 104a and 104b. As described in further detail below, UE 104 supports sidelink communications with other UEs and downlink / uplink communications between BS 102 and UE 104. As described above, sidelink communications allow UE 104a and 104b to establish direct communication links with each other, or with other UEs from different cells, without requiring BS 102 to relay data between UEs.

[0036] Figure 2 A method 200 for performing a contention-based two-step random access (RACH) procedure in a wireless communication system according to some embodiments of the present disclosure is shown. In the illustrated embodiment, the wireless communication system includes a BS 102 and a UE 104. It should be understood that the two-step random access (RACH) procedure may be performed in a contention-based two-step random access (RACH) procedure in a wireless communication system according to some embodiments of the present disclosure. Figure 2 Additional operations are provided before, during, and after the method 200, and some other operations may be omitted or only briefly described. It should be noted that Figure 2 are examples for illustration and discussion purposes.

[0037] According to some embodiments, method 200 begins at operation 212, where UE 104 receives first information from BS 102. Then at operation 214, UE 104 sends a first message including a random access preamble and a scheduled transmission to BS 102 to enable UE 104 to access BS 102. At operation 216, BS 102 sends a second message including a random access (RA) response and contention resolution to UE 104 in response to the first message. For two-step RACH, the first message may be referred to as msgA; the second message may be referred to as msgB.

[0038] In some embodiments, the first information includes information about a time offset for the UE 104 so as to start monitoring the second message after the time offset from the end of the transmission of the first message. In some embodiments, the first information also includes information about a time window, which is configured for the UE 104 to monitor the second message within the time window, and the time window starts after the time offset from the end of the transmission of the first message. In some embodiments, the first information is sent in at least one of the following: system information and a radio resource control (RRC) message. In some embodiments, the first information also includes at least one search space (SS) and at least one control resource set (CORESET). In some embodiments, at least one SS and at least one CORESET provide resource information in the time domain and the frequency domain so that the UE 104 receives downlink control information (DCI) on a physical downlink control channel (PDCCH) in the RA response from the BS 102. In some embodiments, the RACH configuration, such as a random access preamble format, transmission timing, and a PRACH index, is also configured to the UE 104 through the system information or RRC message. In some embodiments, the RA response includes a MAC random access response (RAR). In some embodiments, the DCI is transmitted on the PDCCH and the MAC RAR is transmitted on the PDSCH.

[0039] For example, the time offset 202-1 and the time window 202-2 may be configured to the UE 104 via system information or an RRC message. In some embodiments, the time window is a RA-ResponseWindow and is determined by the CORESET and the SS. In some embodiments, the BS 102 configures the time offset 202-1 for the UE 104 after determining that the expected time window is longer than a predetermined threshold. The expected time window may be a time window that is expected to be configured for the UE 104 so as to monitor the second message within an expected time window starting from the end of the transmission of the first message without configuring the time offset 202-1 (i.e., without the time offset 202-1). In some embodiments, the expected time window is determined at least in part based on at least one of: a first delay associated with the transmission of the first message; and a second delay associated with processing the first message. In some embodiments, the time offset 202-1 is determined at least in part based on at least one of: an expected time window; a first delay associated with the transmission of the first message; and a second delay associated with processing the first message.

[0040] Before sending the random access preamble to the BS 102 at operation 214, the UE 104 performs an LBT process at the selected at least one PRACH opportunity. In some embodiments, the LBT process includes sensing interference and burst arrival of packets through its transmitter to determine the interference level and traffic load on the uplink carrier. If the LBT process fails, the UE 104 restarts the LBT process at the next PRACH opportunity on the corresponding uplink carrier until the LBT process passes (i.e., the uplink carrier is available and not occupied). The UE 104 then starts sending the random access preamble to the BS 102 for the first time at the PRACH opportunity. The UE 104 starts a time offset 202-1 from t0 204-1 to t1 204-2 to stop monitoring the RA response from the BS 102 within the time offset 202-1. t0 204-1 can be at the end of the transmission of the first message, or at the beginning of the first PDCCH opportunity.

[0041] In some embodiments, UE 104 starts time window 202-2 (ie, RA-ResponseWindow) at time t1 204-2 (which is the end of time offset 202-1). UE 104 monitors for the second message from BS 102 within time window 202-2. Figure 2As shown, the second message including the MAC RAR is received before the time window (i.e., ra-ResponseWindow) 202-2 ends. In some other embodiments, the MAC RAR is not received before the time window (i.e., ra-ResponseWindow) 202-2 ends, and the random access of the UE 104 fails. In some embodiments, the size of the time window 202-2 in the time domain is preconfigured by the system and sent to the UE 104 through system information.

[0042] In some embodiments, a system frame number (SFN) of a RACH opportunity used to transmit a random access preamble in the first message may be used to indicate a time window to be distinguished from another time window of another UE. In some embodiments, the SFN of the RACH opportunity is determined by BS 102 based on the SFN of the received random access preamble. In some embodiments, the second message includes information related to the SFN used to send the first message by UE 104.

[0043] In some embodiments, the SFN may be sent in at least one of the following: a MAC RAR and a DCI. For example, 10 bits in a MAC RAR or a DCI may be used to indicate the SFN used to send the radio access preamble. However, in order to reduce overhead, not all of these 10 bits are used to indicate the SFN. In some embodiments, the second message includes only one or more least significant bits of the SFN to indicate the SFN used to send the first message. In some embodiments, the second message includes only the remainder of the SFN divided by N to indicate the SFN, where N is a positive integer. In some embodiments, N is equal to a positive power of 2, such as 2, 4, 8, etc. In some embodiments, after determining that the number of bits required to indicate the SFN is greater than a predetermined threshold, the BS 102 configures the time offset 202-1 for the UE 104. As described above, the number of bits required to indicate the SFN may depend on the length of the desired time window.

[0044] When UE 104 receives the MAC RAR or DCI, UE 104 compares the SFN in the MAC RAR or DCI with the SFN used to send the random access preamble. If the SFN in the MAC RAR or DCI received by UE 104 from BS 102 in time window 202-2 matches the SFN used by UE 104 to send the random access preamble, and if the received preamble matches the sent preamble in the first message, the random access response is successfully received by UE 104. If the SFN in the MAC RAR or DCI received by UE 104 from BS 102 in time window 202-2 does not match the SFN used by UE 104 to send the random access preamble, UE 104 can skip the response and continue to wait for the random access response until the timer or time window expires.

[0045] Figure 3 1 shows a method 300 for performing a contention-based four-step random access (RACH) procedure in a wireless communication system according to some embodiments of the present disclosure. In the illustrated embodiment, the wireless communication system includes a BS 102 and a UE 104. It should be understood that the contention-based four-step random access (RACH) procedure may be performed in a wireless communication system. Figure 3 Additional operations are provided before, during, and after the method 300, and some other operations may be omitted or only briefly described. It should be noted that Figure 3 are examples for illustration and discussion purposes.

[0046] According to some embodiments, method 300 begins at operation 302, where UE 104 receives first information from BS 102. Then, at operation 304, according to some embodiments, UE 104 sends a first message including a random access preamble to BS 102. At operation 306, BS 102 sends a second message including a random access (RA) response to UE 104 in response to the first message.

[0047] In some embodiments, the first information includes information about a time offset for the UE 104 so as to start monitoring the second message after the time offset from the end of the transmission of the first message. In some embodiments, the first information also includes information about a time window configured for the UE 104 to monitor the second message within the time window. The time window starts after the time offset from the end of the transmission of the first message. In some embodiments, the first information is sent via at least one of: system information and a radio resource control (RRC) message. In some embodiments, the first information also includes at least one search space (SS) and at least one control resource set (CORESET). In some embodiments, at least one SS and at least one CORESET provide resource information in the time domain and the frequency domain so that the UE 104 receives downlink control information (DCI) on a physical downlink control channel (PDCCH) in an RA response from the BS 102. In some embodiments, the RACH configuration, such as a random access preamble format, transmission timing, and a PRACH index, is also configured to the UE 104 via the system information or RRC message. In some embodiments, the RA response includes a MAC random access response (RAR). In some embodiments, the DCI is transmitted on the PDCCH and the MAC RAR is transmitted on the PDSCH.

[0048] For example, the time offset 202-1 and the time window 202-2 may be configured to the UE 104 via system information or an RRC message. In some embodiments, the time window 202-2 is a RA-ResponseWindow and is determined by the CORESET and the SS. In some embodiments, the BS 102 configures the time offset 202-1 for the UE 104 after determining that the expected time window is longer than a predetermined threshold. The expected time window may be a time window that is expected to be configured for the UE 104 so as to monitor the second message within the expected time window starting from the end of the transmission of the first message without configuring the time offset 202-1 (i.e., without the time offset 202-1). In some embodiments, the expected time window is determined at least in part based on at least one of: a first delay associated with the transmission of the first message; and a second delay associated with processing the first message. In some embodiments, the time offset 202-1 is determined at least in part based on at least one of: an expected time window; a first delay associated with the transmission of the first message; and a second delay associated with processing the first message.

[0049] Before sending the random access preamble to the BS 102 at operation 304, the UE 104 performs an LBT process at the selected at least one PRACH opportunity. In some embodiments, the LBT process includes sensing interference and burst arrival of packets through its transmitter to determine the interference level and traffic load on the uplink carrier. If the LBT process fails, the UE 104 restarts the LBT process at the next PRACH opportunity on the corresponding uplink carrier until the LBT process passes (i.e., the uplink carrier is available and not occupied) or the maximum number of preamble transmissions is reached. The maximum number of preamble transmissions can be preconfigured to the UE 104. If the maximum number of preamble transmissions is reached, the UE 104 can terminate the RACH process and switch to another process, such as a re-establishment process. The UE 104 then starts sending the random access preamble to the BS 102 for the first time at the PRACH opportunity. The UE 104 starts the time offset 202-1 from t0 204-1 to t1 204-2 to stop monitoring the RA response from the BS 102 within the time offset 202-1. t0 204-1 may be at the end of transmission of the first message, or at the beginning of the first PDCCH opportunity.

[0050] In some embodiments, UE 104 starts time window 202-2 (ie, RA-ResponseWindow) at time t1 204-2 (which is the end of time offset 202-1). UE 104 monitors for the second message from BS 102 within time window 202-2. Figure 3As shown, the second message including the MAC RAR is received before the time window (i.e., ra-ResponseWindow) 202-2 ends. In some other embodiments, the MAC RAR is not received before the time window (i.e., ra-ResponseWindow) 202-2 ends, and the random access response reception of the UE 104 fails. In some embodiments, the size of the time window 202-2 in the time domain is preconfigured by the system and sent to the UE 104 through system information.

[0051] In some embodiments, a system frame number (SFN) of a RACH opportunity used to transmit a random access preamble in the first message may be used to indicate a time window to be distinguished from another time window of another UE. In some embodiments, the SFN of the RACH opportunity is determined by BS 102 based on the SFN of the received random access preamble. In some embodiments, the second message includes information related to the SFN used to send the first message by UE 104.

[0052] In some embodiments, the SFN may be sent in at least one of the following: a MAC RAR and a DCI. For example, 10 bits in a MAC RAR or a DCI may be used to indicate the SFN used to send the radio access preamble. However, in order to reduce overhead, not all of these 10 bits are used to indicate the SFN. In some embodiments, the second message includes only one or more least significant bits of the SFN to indicate the SFN used to send the first message. In some embodiments, when the second message includes only the remainder of the SFN divided by N to indicate the SFN, where N is a positive integer. In some embodiments, N is equal to a positive power of 2, such as 2, 4, 8, etc. In some embodiments, after determining that the number of bits required to indicate the SFN is greater than a predetermined threshold, the BS 102 configures the time offset 202-1 for the UE 104. As described above, the number of bits required to indicate the SFN may depend on the length of the desired time window.

[0053] When UE 104 receives the MAC RAR or DCI, UE 104 compares the SFN in the MAC RAR or DCI with the SFN used to send the random access preamble. If the SFN in the MAC RAR or DCI received by UE 104 from BS 102 in time window 202-2 matches the SFN used by UE 104 to send the random access preamble, the random access response is successfully received by UE 104. If the SFN in the MAC RAR or DCI received by UE 104 from BS 102 in time window 202-2 does not match the SFN used by UE 104 to send the random access preamble, the random access response fails.

[0054] According to some embodiments, after UE 104 successfully receives the random access response at operation 306, method 300 proceeds to operation 308, where BS 102 receives a scheduled transmission from UE 104. In some embodiments, the scheduled transmission is received on the PUSCH by BS 102. In some embodiments, the scheduled transmission is received on resources in the time domain and the frequency domain indicated by the MAC RAR received by UE 104 from BS 102.

[0055] The method 300 continues to operation 310, where, according to some embodiments, a contention resolution message is generated and sent by the BS 102 to the UE 104. In some embodiments, the contention resolution message includes a random access connection establishment from the BS 102. In some embodiments, the BS 102 performs an LBT procedure to determine availability of a downlink carrier before sending the contention resolution message.

[0056] Different embodiments of the present disclosure will be described in detail below. It should be noted that the features of the embodiments and examples in the present disclosure can be combined with each other in any manner without conflict.

[0057] In some scenarios, for the RACH process, when the preamble is sent, a timer similar to the RAR window is started. Taking into account the preamble transmission delay and processing delay on the network side, the timer or RAR window may be configured too large. In this case, if the current RA-RNTI formula of the NR system is used, once the timer or RAR window is configured too large, a conflict will occur. In order to resolve the conflict, the SFN indication of the sent preamble can be given to the UE via DCI or MAC RAR. From the perspective of reducing overhead, one or more least significant bits (LSBs) of the SFN are sufficient to indicate the SFN. However, if the window extension is too large, more bits are required, which increases the overhead. Therefore, the present teaching provides a method for combining the SFN indication with a time offset before the start of the RAR window. Figure 4 An example 400 is shown in FIG.

[0058] In this example, the time offset is a constant and can be sent to the UE via system information or RRC message. For the SFN of the transmission preamble, only one or more LSBs may be required to indicate the SFN to reduce overhead. In an alternative approach, the remainder of SFN mod N can be indicated to the UE via DCI or MAC RAR, where N is a positive integer.

[0059] like Figure 4As shown, different UEs can start their preamble transmission at different SFNs. For example, UE1 starts to transmit the preamble in SFN N from time t1 401, and UE2 starts to transmit the preamble in SFN N+1 from time t3 403. Here, each system frame has 10 time slots, and the length of each time slot is 1 ms.

[0060] After UE1 sends its preamble, UE1 waits for a 5 ms time offset 410 and then starts a RAR window 412 (or timer) at time t2 402. The RAR window 412 has a size of 20 ms and ends at time t5 405. Similarly, UE2 sends its preamble, UE2 waits for a 5 ms time offset 420 and then starts a RAR window 422 (or timer) at time t4 404. The RAR window 422 has a size of 20 ms and ends at time t6 406. Figure 4 As shown, RAR window 412 and RAR window 422 have an overlapping area 430. Since the BS may send back an RA response within the overlapping area 430, this causes a conflict between the two RA processes of the two UEs. In this case, the BS can use one of the two SFNs N and N+1 to indicate which SFN the RA response is in response to and correspondingly which UE preamble it is in response to. Since a time offset is used here before each UE monitors the RA response in the RAR window, the RAR window becomes shorter, which reduces the probability and expected length of the overlapping area between the two RAR windows, thereby reducing the probability of the BS sending an RA response in the overlapping area, and also reduces the need for long SFN indication, thereby reducing the overhead in the random access process.

[0061] According to the first embodiment, in the four-step RACH, the RAR window needs to be extended because the preamble transmission and processing delays are taken into account and the MAC RAR transmission opportunities need to be increased. When the RAR window is extended, conflicts are likely to occur. To solve this problem, the SFN information about the transmitted preamble can be indicated to the UE. If the RAR window is extended larger, more bits will be indicated to the UE, which will increase the overhead. In this case, a time offset can be introduced so that the RAR window does not need to be extended too much. This means dividing the desired longer time window into two parts: a time offset and a shorter time window. Figure 4 As shown, the desired time window of 25 ms is divided into a time offset of 5 ms and a shorter time window of 20 ms.

[0062] The time offset can be sent to the UE via system information or RRC message. After sending the preamble, the UE should delay the time offset to start the RAR window at the end of the random access preamble transmission. The RAR window then starts at the first PDCCH opportunity from the end of the time offset. Therefore, there is no need to indicate the entire SFN. Only one or more LSBs of the SFN are sufficient to distinguish different time windows and different preambles. In other words, only one or more LSBs of the SFN are indicated to the UE via DCI or MAC RAR.

[0063] According to the second embodiment, in the two-step RACH, taking into account the msgA transmission and processing delay and the increase in msgB transmission opportunities, it is necessary to extend the timer or RAR window. It can be understood that for the two-step RACH, a timer is set to monitor msgB, and the message includes not only RAR but also contention resolution, although the term RAR window is still used here to refer to the timer. When the RAR window is extended, RA conflicts are likely to occur. To solve this problem, the SFN information about the transmission preamble can be indicated to the UE. If the RAR window is extended larger, more bits will be indicated to the UE, which increases the overhead. In this case, a time offset can be introduced so that the RAR window does not need to be extended too large. This means that the desired longer time window is divided into two parts: a time offset and a shorter time window. As Figure 4 As shown, the desired time window of 25 ms is divided into a time offset of 5 ms and a shorter time window of 20 ms.

[0064] The time offset can be sent to the UE via system information or RRC message. After sending the preamble, the UE should delay the time offset to start the RAR window at the end of msgA transmission. The RAR window then starts at the first PDCCH opportunity from the end of this time offset. Therefore, there is no need to indicate the entire SFN. Only one or more LSBs of the SFN are sufficient to distinguish different time windows and different preambles. In other words, only one or more LSBs of the SFN are indicated to the UE via DCI or msgB.

[0065] According to the third embodiment, in the four-step RACH, the RAR window needs to be extended in consideration of the preamble transmission and processing delays and the increase in MAC RAR transmission opportunities. When the RAR window is extended, conflicts are likely to occur. To solve this problem, the UE may be indicated with SFN information about the transmitted preamble. If the RAR window is extended larger, more bits will be indicated to the UE, which increases the overhead. In this case, a time offset may be introduced so that the RAR window does not need to be extended too large. This means dividing the desired longer time window into two parts: a time offset and a shorter time window. Figure 4 As shown, the desired time window of 25 ms is divided into a time offset of 5 ms and a shorter time window of 20 ms.

[0066] The time offset can be sent to the UE via system information or RRC message. After sending the preamble, the UE should delay the time offset to start the RAR window at the end of the random access preamble transmission. In other words, the RAR window will start at the first PDCCH opportunity from the end of the time offset.

[0067] For SFN, from the perspective of reducing overhead, the BS does not indicate the entire SFN of the transmitted preamble, but only indicates SFN mod N, which is sufficient to distinguish different time windows and different preambles. N can be a constant, such as a positive power of 2, such as 2, 4, 8. The calculated SFN mod N value is indicated to the UE via DCI or MAC RAR.

[0068] According to the fourth embodiment, in the two-step RACH, taking into account the delay in sending and processing MsgA and increasing the opportunity to send msgB, it is necessary to extend the timer or RAR window. It will be understood that for the two-step RACH, a timer is set to monitor msgB, which message includes not only RAR but also contention resolution, although the term RAR window is still used here to refer to the timer. When the RAR window is extended, RA conflicts are likely to occur. To solve this problem, the SFN information about the sending preamble can be indicated to the UE. If the RAR window is extended larger, more bits will be indicated to the UE, which increases the overhead. In this case, a time offset can be introduced so that the RAR window does not need to be extended too large. This means dividing the desired longer time window into two parts: a time offset and a shorter time window. As Figure 4 As shown, the desired time window of 25 ms is divided into a time offset of 5 ms and a shorter time window of 20 ms.

[0069] The time offset can be sent to the UE via system information or RRC message. After sending the preamble, the UE should delay the time offset to start the RAR window at the end of msgA transmission. In other words, the RAR window will start at the first PDCCH opportunity from the end of the time offset.

[0070] For SFN, from the perspective of reducing overhead, the BS does not indicate the entire SFN of the preamble that sends msgA, but only indicates SFN mod N, which is sufficient to distinguish different time windows and different preambles. N can be a constant, such as a positive power of 2, such as 2, 4, 8. The calculated SFN mod N value is indicated to the UE via DCI or msgB.

[0071] Although various embodiments of the present disclosure have been described above, it should be understood that they are presented only in an exemplary and not limiting manner. Similarly, various diagrams can depict example architectures or configurations, and these example architectures or configurations are provided so that those of ordinary skill in the art can understand the exemplary features and functions of the present invention. However, these personnel will understand that the present invention is not limited to the example architectures or configurations shown, but can be implemented using a variety of alternative architectures and configurations. In addition, those of ordinary skill in the art will understand that one or more features of an embodiment can be combined with one or more features of another embodiment described herein. Therefore, the breadth and scope of the present disclosure should not be limited by any of the above-mentioned exemplary embodiments.

[0072] It should also be understood that any reference to elements herein using designations such as "first," "second," etc. does not generally limit the number or order of these elements. Rather, these designations may be used herein as a convenient means of distinguishing between two or more elements or multiple instances of an element. Thus, a reference to a first and a second element does not mean that only two elements can be used, nor does it mean that the first element must be located before the second element in some manner.

[0073] In addition, those of ordinary skill in the art will appreciate that information and signals may be represented using any of a variety of different techniques. For example, data, instructions, commands, information, signals, bits, and symbols referenced in the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0074] It will be further understood by those of ordinary skill in the art that any of some of the illustrative logical blocks, modules, processors, devices, circuits, methods, and functions described in conjunction with the various aspects disclosed herein may be implemented by electronic hardware (e.g., digital implementation, analog implementation, or a combination of both, which may be designed using source code or some other technique), various forms of programs or design codes containing instructions (referred to herein as "software" or "software modules" for convenience), or a combination of both. In order to clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of functionality. Whether such functionality is implemented as hardware, firmware, or software or a combination of these technologies depends on the specific application and the design constraints imposed on the overall system. Technicians may implement the described functionality in various ways for each specific application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0075] In addition, it will be understood by those of ordinary skill in the art that the various exemplary logic blocks, modules, devices, components, and circuits described herein may be implemented or performed within an integrated circuit (IC) including a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, or any combination thereof. The logic blocks, modules, and circuits may further include antennas and / or transceivers to communicate with various components within a network or within a device. A general purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, or state machine. The processor 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 suitable configuration to perform the functions described herein.

[0076] If implemented in software, the functions may be stored as one or more instructions or codes on a computer-readable medium. Therefore, the steps of the method or algorithm disclosed herein may be implemented as software stored on a computer-readable medium. Computer-readable media include computer storage media and communication media, and communication media include any media that can transfer a computer program or code from one place to another. The storage medium can be any available medium that can be accessed by a computer. As an example and not limitation, such a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage device, or any other medium that can be used to store the desired program code in the form of an instruction or data structure and can be accessed by a computer.

[0077] In this article, the term "module" used herein refers to software, firmware, hardware, and any combination of these elements for performing the related functions described herein. In addition, for the purpose of discussion, various modules are described as discrete modules. However, it is obvious to those of ordinary skill in the art that two or more modules can be combined to form a single module that performs the related functions according to an embodiment of the present invention.

[0078] In addition, in embodiments of the present invention, memory or other storage devices and communication components may be used. It should be understood that, for the sake of clarity, the above description has described embodiments of the present invention with reference to different functional units and processors. However, it will be apparent that any appropriate functional distribution between different functional units, processing logic elements or domains may be used without departing from the present invention. For example, the functions illustrated as being performed by a separate processing logic element or controller may be performed by the same processing logic element or controller. Therefore, reference to a specific functional unit is only a reference to a suitable device for providing the described function, rather than indicating a strict logical or physical structure or organization.

[0079] Various modifications to the implementations described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the implementations shown herein, but is to be given the widest scope consistent with the novel features and principles disclosed herein as set forth in the following claims.

Claims

1. A method performed by a wireless communication node, comprising: Sending first information to a wireless communication device; receiving a first message from the wireless communication device to enable the wireless communication device to randomly access the wireless communication node; as well as sending a second message to the wireless communication device in response to the first message, wherein the first information includes information about a time offset of the wireless communication device so as to start monitoring the second message after the time offset from the end of the transmission of the first message, The second message includes information related to a system frame number (SFN) used by the wireless communication device to send the first message.

2. The method of claim 1, wherein the first information further comprises information about a time window, the time window being configured for the wireless communication device to monitor the second message within the time window, wherein the time window starts after the time offset from the end of the sending of the first message.

3. The method of claim 1, wherein the first information is sent in at least one of: system information and a radio resource control (RRC) message.

4. The method of claim 1, wherein the second message includes one or more least significant bits of the SFN to indicate the SFN used to send the first message. 5 . The method of claim 1 , wherein the second message includes a remainder of dividing the SFN by N to indicate the SFN, wherein N is a positive integer. The method of claim 5 , wherein N is equal to a positive power of 2.

7. The method of claim 1, wherein the SFN is indicated to the wireless communication device via at least one of: a medium access control (MAC) random access response and downlink control information (DCI) in the second message.

8. The method of claim 1, further comprising configuring the time offset for the wireless communication device after determining that the number of bits required to indicate the SFN is greater than a predetermined threshold.

9. The method of claim 1, further comprising configuring the time offset for the wireless communication device after determining that the expected time window is longer than a predetermined threshold.

10. The method of claim 9, wherein the expected time window is a time window expected to be configured for the wireless communication device so as to monitor the second message within the expected time window starting from the end of sending the first message without configuring the time offset.

11. The method of claim 9, wherein the desired time window is determined based at least in part on at least one of: a first delay associated with said sending of said first message; and A second delay associated with processing the first message.

12. The method of claim 9, wherein the time offset is determined based at least in part on at least one of: the desired time window; a first delay associated with said sending of said first message; and A second delay associated with processing the first message.

13. The method according to claim 1, wherein the second message indicates whether the second message is for two-step random access or for four-step random access.

14. A method performed by a wireless communication device, comprising: receiving first information from a wireless communication node; Sending a first message to the wireless communication node so that the wireless communication device accesses the wireless communication node; as well as receiving a second message from the wireless communication node in response to the first message, wherein the first information includes information about a time offset of the wireless communication device so as to start monitoring the second message after the time offset from the end of the transmission of the first message, The second message includes information related to a system frame number (SFN) used to send the first message to the wireless communication node.

15. The method according to claim 14, further comprising: The second message is monitored within a time window, wherein the time window is indicated in the first information and begins after the time offset from the end of sending of the first message.

16. The method of claim 14, wherein the first information is received in at least one of: system information and a radio resource control (RRC) message.

17. The method of claim 14, wherein the second message includes one or more least significant bits of the SFN to indicate the SFN.

18. The method of claim 14, wherein the second message includes a remainder of dividing the SFN by N to indicate the SFN, wherein N is a positive integer. The method of claim 18 , wherein N is equal to a positive power of 2.

20. The method of claim 14, wherein the SFN is indicated by at least one of: a medium access control (MAC) random access response and downlink control information (DCI) in the second message.

21. The method of claim 14, wherein the time offset is configured for the wireless communication device based on determining that a number of bits required to indicate the SFN is greater than a predetermined threshold.

22. The method of claim 14, wherein the time offset is configured for the wireless communication device based on a determination that a desired time window is longer than a predetermined threshold.

23. The method of claim 22, wherein the expected time window is a time window expected to be configured for the wireless communication device so as to monitor the second message within the expected time window starting from the end of sending the first message without configuring the time offset.

24. The method of claim 22, wherein the desired time window is determined based at least in part on at least one of: a first delay associated with said sending of said first message; and A second delay associated with processing the first message.

25. The method of claim 22, wherein the time offset is determined based at least in part on at least one of: the desired time window; a first delay associated with said sending of said first message; and A second delay associated with processing the first message.

26. The method according to claim 14, wherein the second message indicates whether the second message is for two-step random access or for four-step random access.

27. A computing device comprising at least one processor and a memory coupled to the processor, the at least one processor being configured to perform the method according to any one of claims 1 to 26.

28. A non-transitory computer readable medium having stored thereon computer executable instructions for performing the method of any one of claims 1 to 26.

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