Methods and apparatus to perform multiple rach procedures

Abstract

A method and apparatus for performing random access (RACH) procedures are disclosed. In one embodiment, a method performed by a wireless communication node includes performing a plurality of random access (RACH) procedures with a wireless communication device on a first set of frequency resources and a second set of frequency resources, wherein the plurality of RACH procedures each include receiving a first message from the wireless communication device on a first frequency resource, wherein the first frequency resource is selected from the first set of frequency resources, transmitting a second message to the wireless communication device on a second frequency resource within a predetermined time window, wherein the second frequency resource is selected from the second set of frequency resources, receiving a third message from the wireless communication device on the first frequency resource, and transmitting a fourth message to the wireless communication device on the second frequency resource, and terminating a remainder of the plurality of RACH procedures based on the wireless communication device successfully receiving the fourth message of one of the plurality of RACH procedures.

Description

[0001] This application is a divisional application of Chinese patent application No. 201880091268.7, filed on April 4, 2018, entitled “Method and apparatus for performing multiple RACH procedures”. Technical Field

[0002] This disclosure generally relates to wireless communication, and more specifically, to methods and apparatus for performing multiple random access (RACH) procedures in a communication system. Background Technology

[0003] Over the past few decades, mobile communications have evolved from voice services to high-speed broadband data services. With the further development of new services and applications such as enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communications (URLLC), the demand for high-performance data transmission over mobile networks will continue to grow exponentially. Based on the specific requirements of these emerging services, wireless communication systems must meet various demands, such as throughput, latency, data rate, capacity, reliability, link density, cost, energy consumption, complexity, and coverage. Summary of the Invention

[0004] The exemplary embodiments disclosed herein are intended to address problems related to one or more issues existing in the prior art, and provide additional features that will become apparent when taken in conjunction with the accompanying drawings and referred to in the following detailed description. Exemplary systems, methods, and computer program products are disclosed herein according to some embodiments. However, it should be understood that these embodiments are presented by way of example and not limitation, and it will be apparent to those skilled in the art who have read this disclosure that various modifications can be made to the disclosed embodiments while remaining within the scope of the invention.

[0005] Traditional methods relying on random access from user terminals and scheduled data transmission between base stations and user terminals cannot provide satisfactory performance for the aforementioned services due to limited equipment capacity, high latency, and high signaling overhead. To meet these requirements in 5G / NR (New Radio) communications, contention-based unlicensed data transmission methods are being considered. The Random Access (RACH) procedure is important in the following situations: during initial access from Radio Resource Control (RRC) idle periods, during the execution of the RRC connection establishment procedure, for downlink or uplink data transmission when wireless communication devices are not synchronized, and during handover when uplink synchronization is required in the target cell.

[0006] To access unlicensed spectrum during the RACH procedure, a Listen-Before-Speak (LBT) process is required, during which Net Channel Assessment (CCA) is performed. CCA determines channel availability by detecting the presence of any existing signals on the channel. If a signal is detected and the channel is occupied, the next LBT process can be performed after a certain period until an unoccupied channel is detected, after which data transmission occurs. When accessing unlicensed spectrum, such an LBT process is performed during each step of the RACH procedure, leading to increased latency and adversely affecting system performance. Therefore, a new method is needed to reduce latency during the RACH procedure when accessing unlicensed spectrum.

[0007] In one embodiment, a method performed by a wireless communication node includes: executing a plurality of random access (RACH) procedures using a wireless communication device on a first frequency resource set and a second frequency resource set, wherein each of the plurality of RACH procedures includes: receiving a first message from the wireless communication device on a first frequency resource, wherein the first frequency resource is selected from the first frequency resource set; sending a second message to the wireless communication device on a second frequency resource within a predetermined time window, wherein the second frequency resource is selected from the second frequency resource set; receiving a third message from the wireless communication device on the first frequency resource; and sending a fourth message to the wireless communication device on the second frequency resource; and terminating the remainder of the plurality of RACH procedures based on the wireless communication device successfully receiving the fourth message of one of the plurality of RACH procedures.

[0008] In another embodiment, a method performed by a wireless communication device includes: executing a plurality of random access (RACH) procedures using a wireless communication node on a first frequency resource set and a second frequency resource set, wherein each of the plurality of RACH procedures includes: sending a first message to the wireless communication node on a first frequency resource, wherein the first frequency resource is selected from the first frequency resource set; receiving a second message from the wireless communication node on a second frequency resource within a predetermined time window, wherein the second frequency resource is selected from the plurality of second frequency resources; sending the third message to the wireless communication node on the first frequency resource; and receiving a fourth message from the wireless communication node on the second frequency resource; and terminating the remainder of the plurality of RACH procedures based on the successful receipt of the fourth message from one of the plurality of RACH procedures by the wireless communication node.

[0009] However, in another embodiment, a method performed by a wireless communication node includes: executing a plurality of random access (RACH) procedures using a wireless communication device on a first frequency resource set and a second frequency resource set, wherein each of the plurality of RACH procedures includes: receiving a first message from the wireless communication device on a first frequency resource, wherein the first frequency resource is selected from the first frequency resource set; sending a second message to the wireless communication device on a second frequency resource within a predetermined time window, wherein the second frequency resource is selected from the second frequency resource set; and terminating the remainder of the plurality of RACH procedures based on the wireless communication device successfully receiving the second message of one of the plurality of RACH procedures.

[0010] However, in another embodiment, a method performed by a wireless communication device includes: executing a plurality of random access (RACH) procedures using a wireless communication node on a first frequency resource set and a second frequency resource set, wherein each of the plurality of RACH procedures includes: sending a first message to the wireless communication node on a first frequency resource, wherein the first frequency resource is selected from the first frequency resource set; receiving a second message from the wireless communication node on a second frequency resource within a predetermined time window, wherein the second frequency resource is selected from the plurality of second frequency resources; and terminating the remainder of the plurality of RACH procedures based on the successful receipt of the second message from one of the plurality of RACH procedures by the wireless communication node. Attached Figure Description

[0011] When read in conjunction with the accompanying drawings, various aspects of this disclosure are best understood in the following detailed description. Note that the features are not necessarily drawn to scale. In fact, for clarity of discussion, the dimensions and geometries of the features may be increased or decreased at will.

[0012] Figure 1A An exemplary wireless communication network according to some embodiments of the present disclosure is shown, illustrating feasible modulation based on the distance from the BS.

[0013] Figure 1B A block diagram of an exemplary wireless communication system for indicating time slot structure information is shown according to some embodiments of the present disclosure.

[0014] Figure 2 A method for performing multiple four-step competition-based RACH procedures on multiple carriers is illustrated according to some embodiments of the present disclosure.

[0015] Figure 3 A method for performing multiple two-step competition-based RACH procedures on multiple carriers is illustrated according to some embodiments of the present disclosure.

[0016] Figure 4 A method for performing multiple two-step contention-free RACH procedures on multiple carriers is illustrated according to some embodiments of the present disclosure.

[0017] Figure 5 A method for performing multiple four-step competition-based RACH procedures on multiple bandwidth portions is illustrated according to some embodiments of the present disclosure.

[0018] Figure 6 A method for performing multiple two-step competition-based RACH procedures on multiple bandwidth portions is illustrated according to some embodiments of the present disclosure.

[0019] Figure 7 A method for performing multiple two-step contention-free RACH procedures on multiple bandwidth portions is illustrated according to some embodiments of the present disclosure. Detailed Implementation

[0020] Various exemplary embodiments of the invention are described below with reference to the accompanying drawings to enable those skilled in the art to make and use the invention. It will be apparent to those skilled in the art that various changes or modifications can be made to the examples described herein without departing from the scope of the invention after reading this disclosure. Therefore, the invention is not limited to the exemplary embodiments and applications described or shown herein. Furthermore, the specific order or hierarchy of steps in the methods disclosed herein is merely exemplary. Based on design preferences, the specific order or hierarchy of steps in the disclosed methods or processes can be rearranged while remaining within the scope of the invention. Therefore, those skilled in the art will understand that the methods and techniques disclosed herein present various steps or actions in a sample order, and unless otherwise expressly stated, the invention is not limited to the specific order or hierarchy presented.

[0021] Embodiments of the present invention are described in detail with reference to the accompanying drawings. Although the same or similar components are shown in different drawings, they may be designated by the same or similar reference numerals. Detailed descriptions of structures or processes well known in the art may be omitted to avoid obscuring the subject matter of the invention. Furthermore, terminology is defined in the embodiments of the invention with regard to their function, and terminology may be changed according to the intent, usage, etc., of the user or operator. Therefore, definitions should be based on the entire contents of this specification.

[0022] Figure 1AAn exemplary wireless communication network 100 according to some embodiments of the present disclosure is illustrated. In the wireless communication system, the network-side communication node or base station (BS) can be a Node B, an E-UTRAN Node B (also known as an evolved Node B, eNodeB, or eNB), a picocell, or a femtocell, etc. The terminal-side node or user equipment (UE) can be a remote communication system, such as a mobile phone, smartphone, personal digital assistant (PDA), tablet computer, laptop computer, or a short-range communication system, such as, for example, wearable devices and vehicles with vehicle communication systems. The network and terminal-side communication nodes are represented by BS 102 and UE 104, respectively, and are generally referred to as "communication nodes" hereinafter in all embodiments of the present disclosure. According to some embodiments of the present invention, such communication nodes may be capable of wireless and / or wired communication. Note that all embodiments are merely preferred examples and are not intended to limit the present disclosure. 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.

[0023] Reference Figure 1A Wireless communication network 100 includes BS 102 and UE 104a and UE 104b (collectively referred to herein as UE 104). BS 102 and UE 104 are contained within the geographical boundary of cell 101. Wireless transmission from the transmit antenna of UE 104 to the receive antenna of BS 102 is referred to as uplink transmission, while wireless transmission from the transmit antenna of BS 102 to the receive antenna of UE 104 is referred to as downlink transmission. UE 104a has a direct communication channel with BS 102 to operate on a first frequency f1 for downlink communication 103 and a second frequency resource f2 for uplink communication 105a. Similarly, UE 104b also has a direct communication channel with BS 102 to operate on a first frequency resource f1 (e.g., a carrier or bandwidth portion) for downlink communication 103 and a third frequency resource f3 for uplink communication. In some embodiments, the second frequency resource f2 and the third frequency resource f3 are different from the first frequency resource f1. In some embodiments, the second frequency resource f2 and the third frequency resource f3 are different from each other. Therefore, the second frequency resource f2 and the third frequency resource f3 have different transmission characteristics, such as path loss, coverage, maximum transmission power, etc. In some embodiments, the bandwidths of the first frequency resource f1, the second frequency resource f2, and the third frequency resource f3 may also be different. In some embodiments, the second frequency resource f2 and the third frequency resource f3 may have different transmission characteristics, such as path loss, coverage, maximum transmission power, etc., in different bandwidth portions. Although in Figure 1AOnly two UEs 104 are shown, but it should be noted that any number of UEs 104 can be included in cell 101 and are within the scope of this invention. In some embodiments, as indicated by dotted circles 112 and 110 respectively, the coverage area of ​​uplink communication 105b is greater than the coverage area of ​​uplink communication 105a. BS 102 is located at the intercept area of ​​coverage areas 110 and 112 so that BS 102 performs uplink communication with UEs 104a and UE 104b in cell 101.

[0024] When UE 104b is located at an extreme cell edge 101, for example, when there is a longer distance between BS 102 and UE 104b, path loss becomes significant. Therefore, UE 104b will transmit at maximum power over the long distance on the third frequency resource f3. As a result, the data rate between BS 102 and UE 104b is relatively low in this situation. As UE 104b moves closer to BS 102 (i.e., UE 104a), path loss decreases and the signal level at BS 102 increases, thus improving the SNR. In response, BS 102 instructs UE 104b to reduce its power on the second frequency resource f2 to minimize interference to other UEs and / or BS 102.

[0025] The direct communication channel 105 / 103 between UE 104 and BS 102 can be via an interface such as the Uu interface, also known as the Universal Mobile Telecommunications System (UMTS) air interface. The direct communication channel (sidelink transmission) 106 between UEs can be via the PC5 interface, which was introduced to address high-mobility and high-density applications such as vehicle-to-vehicle (V2V) communication. BS 102 is connected to the core network (CN) 108 via an external interface 107 (e.g., the Iu interface).

[0026] UEs 104a and 104b obtain their synchronization timing from BS 102, which obtains its own synchronization timing from the core network 108 via an Internet time service such as a Common Time NTP (Network Time Protocol) server or a Radio Frequency Emulation System Network Controller (RNC) server. This is referred to as network-based synchronization. Alternatively, BS 102 can also obtain synchronization timing from a Global Navigation Satellite System (GNSS) (not shown) via satellite signal 106, particularly for large BSs in large cells with direct line of sight to the sky; this is referred to as satellite-based synchronization.

[0027] Figure 1BA block diagram of an exemplary wireless communication system 150 according to some embodiments of the present disclosure is shown. 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 one exemplary embodiment, as described above, system 150 may be used in applications such as... Figure 1A The wireless communication network 100 transmits and receives data symbols in a wireless communication environment.

[0028] System 150 typically includes a BS 102 and two UEs 104a and 104b, which, for ease of discussion, will be collectively referred to as UE 104 below. 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 module being coupled and interconnected with each other as needed via a data communication bus 180. 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 module being coupled and interconnected with each other as needed via a data communication bus 190. BS 102 communicates with UE 104 via a communication channel 192, which can be any wireless channel or other medium known in the art suitable for data transmission as described herein.

[0029] As will be understood by those skilled in the art, in addition to Figure 1B In addition to those shown herein, system 150 may also include any number of blocks, modules, circuits, etc. Those skilled in the art will understand 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 practical combination thereof. To clearly illustrate this interchangeability and compatibility of hardware, firmware, and software, the various illustrative components, blocks, modules, circuits, and steps are described generally according to their functionality. Whether such functionality is implemented as hardware, firmware, or software depends on the specific application and the design constraints imposed on the system as a whole. Those skilled in the art can implement such functionality in a suitable manner for each specific application, but such implementation decisions should not be construed as limiting the scope of the invention.

[0030] The wireless transmission from the transmit antenna of UE 104 to the receive antenna of BS 102 is referred to as uplink transmission, and the wireless transmission from the transmit antenna of BS 102 to the receive antenna of UE 104 is referred to as downlink transmission. According to some embodiments, UE transceiver 162 may be referred to herein as "uplink" transceiver 162, which includes RF transmitter and receiver circuitry coupled to each UE antenna 164. A duplex switch (not shown) may alternatively couple the uplink transmitter or receiver to the uplink antenna in a time-duplex manner. Similarly, according to some embodiments, BS transceiver 152 may be referred to herein as "downlink" transceiver 152, which includes RF transmitter and receiver circuitry coupled to each antenna array 154. A downlink duplex switch may alternatively couple the downlink transmitter or receiver to the downlink antenna array 154 in a time-division duplex manner. The operation of the two transceivers 152 and 162 is time-coordinated, such that the uplink receiver is coupled to the uplink UE antenna 164 to receive transmissions via the wireless communication channel 192 simultaneously with the downlink transmitter being coupled to the downlink antenna array 154. Preferably, there is tight synchronization timing with only a minimum guard time between changes in the duplex direction. The UE transceiver 162 communicates with the BS 102 via the UE antenna 164 via the wireless communication channel 192, or 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 sidechain transmission of data as described herein.

[0031] UE transceiver 162 and BS transceiver 152 are configured to communicate via radio data communication channel 192 and cooperate with RF antenna arrangements 154 / 164 appropriately configured to support specific wireless communication protocols and modulation schemes. In some embodiments, BS transceiver 152 is configured to transmit a Physical Downlink Control Channel (PDCCH) and a configured set of Slot Structure Related Information (SFI) entries to UE transceiver 162. In some embodiments, UE transceiver 162 is configured to receive a PDCCH from BS transceiver 152 containing at least one SFI field. In some exemplary embodiments, UE transceiver 162 and 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 invention is not necessarily limited to specific standards and associated protocols. Rather, UE transceiver 162 and BS transceiver 152 can be configured to support alternative or additional radio data communication protocols, including future standards or variations thereof.

[0032] The BS processor module 158 and UE processor module 168 are implemented or constructed using a general-purpose processor, content-addressable memory, digital signal processor, application-specific integrated circuit, 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 way, the processor can be implemented as a microprocessor, controller, microcontroller, or state machine, etc. The processor can also be implemented as a combination of computing devices, such as a combination of a digital signal processor and a microprocessor, multiple microprocessors, one or more microprocessors combined with a digital signal processor core, or any other such configuration.

[0033] Then, the UE processor module 168 detects a PHR trigger message on the UE transceiver module 162. The UE processor module 168 is also configured to determine at least one second SFI entry set based on at least one predefined algorithm and at least one received first SFI entry set configured by the BS 102, wherein at least one predefined algorithm is selected based on other calculated parameters 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" means an SFI table or SFI entry.

[0034] Furthermore, the steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be directly embodied in hardware, firmware, software modules executed by processor modules 158 and 168 respectively, or any actual combination thereof. Memory modules 156 and 166 can 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, memory modules 156 and 166 can be coupled to processor modules 158 and 168 respectively, such that processor modules 158 and 168 can read information from and write information to memory modules 156 and 166 respectively. Memory modules 156 and 166 can also be integrated into their respective processor modules 158 and 168. In some embodiments, memory modules 156 and 166 may each include a cache memory for storing temporary variables or other intermediate information during the execution of instructions executed by processor modules 158 and 168 respectively. Memory modules 156 and 166 may each include non-volatile memory for storing instructions executed by processor modules 158 and 168, respectively.

[0035] Network interface 160 typically represents the hardware, software, firmware, processing logic, and / or other components of base station 102 that enable bidirectional communication between BS transceiver 152 and communication nodes and other network components configured to communicate with BS 102. For example, network interface 160 may be configured to support Internet or WiMAX traffic. In a typical deployment, without limitation, network interface 160 provides an 802.3 Ethernet interface, allowing BS transceiver 152 to communicate with a conventional Ethernet-based computer network. In this way, 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 particular operation or function, the terms "configured for" or "configured to" mean a device, component, circuit, structure, machine, signal, etc., physically constructed, programmed, formatted, and / or arranged to perform a specified operation or function. Network interface 160 may allow BS 102 to communicate with other BSs or core networks via wired or wireless connections.

[0036] Refer again Figure 1A As mentioned 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 resides, and typically operates normally within cell 101. Various pieces of information, such as downlink and uplink cell bandwidth, downlink and uplink configurations, and configurations for random access, can be included in the system information, which will be discussed in further detail below. Typically, BS 102 broadcasts a first signal carrying some key system information (e.g., the configuration of cell 101) via the Physical Broadcast Channel (PBCH). For clarity, this first broadcast signal is referred to herein as the "first broadcast signal." Note that BS 102 may subsequently broadcast one or more signals carrying other system information via a corresponding channel (e.g., the Physical Downlink Shared Channel (PDSCH)), referred herein as the "second broadcast signal," "third broadcast signal," and so on.

[0037] Refer again Figure 1BIn some embodiments, the primary system information carried by the first broadcast signal can be transmitted by BS102 in symbolic format via communication channel 192. According to some embodiments, the primary system information can be represented in its raw form as one or more sequences of digital bits, and these sequences can be processed through multiple steps (e.g., encoding, scrambling, modulation, mapping, etc.), all of which can be performed by BS processor module 158 to form the first broadcast signal. Similarly, according to some embodiments, when UE 104 receives the first broadcast signal (in symbolic format) using UE transceiver 162, UE processor module 168 can perform multiple steps (demapping, demodulation, decoding, etc.) to estimate the primary system information, such as, for example, the bit positions and number of bits of the primary system information. UE processor module 168 is also coupled to I / O interface 169, which provides UE 104 with the ability to connect to other devices such as a computer. I / O interface 169 is the communication path between these accessories and UE processor module 168.

[0038] In some embodiments, UE 104 can operate in a hybrid communication network in which the UE communicates with BS 102 and with other UEs (e.g., between 104a and 104b). As described in further detail below, UE 104 supports sidelink communication with other UEs and downlink / uplink communication between BS 102 and UE 104. As discussed above, sidelink communication allows UEs 104a and 104b to establish direct communication links with each other or with other UEs from different cells without BS 102 relaying data between UEs.

[0039] Figure 2 A method 200 for performing multiple four-step contention-based RACH procedures on multiple carriers is illustrated according to some embodiments of the present disclosure. It should be understood that... Figure 2Additional operations are provided before, during, and after method 200, and some other operations may be omitted or only briefly described herein. In the illustrated embodiment, there are three uplink carriers (i.e., F1 202, F2 204, and F4 206) and two downlink carriers (i.e., F3 208 and F5 210), which are configured to UE 104 via system information or Radio Resource Control (RRC) messages. Uplink carriers F1 202 and F2 204 correspond to downlink carrier F3 208, while uplink carrier F4 206 corresponds to downlink carrier F5 210. Furthermore, the RACH configuration (e.g., random access preamble format, transmission timing, and PRACH index) corresponding to each uplink carrier is configured to UE 104 via system information or RRC messages. Although only three uplink carriers and two downlink carriers are shown, any desired number of uplink and downlink carriers may be included in the system while remaining within the scope of this disclosure.

[0040] Method 200 begins with operation 212, in which UE 104 transmits a random access preamble to BS 102 on each of three uplink carriers (i.e., F1202, F2204, and F4206) according to some embodiments. In some embodiments, UE 104 selects at least one SS (synchronization signal) block for transmitting the random access preamble on the uplink carrier. This at least one SS block is selected from a plurality of SS blocks received by UE 104 from BS 102 on the corresponding downlink carrier based on its SS-RSRP (synchronization signal-reference signal received power) value. If the SS-RSRP value is greater than a predefined threshold, the SS block is selected. UE 104 also selects at least one PRACH timing based on the mapping between PRACH (physical random access channel) timing (i.e., frequency resources) and the SS blocks received in the system information. Then, UE 104 selects a random access preamble for each of the corresponding uplink carriers based on the received RACH configuration. Before sending the random access preamble to BS 102, UE 104 performs an LBT procedure on each of the uplink carriers at at least one selected PRACH timing. In some embodiments, the LBT procedure includes sensing burst arrivals and interference of packets through its transmitter to determine the traffic load and interference level on the uplink carrier. If the LBT procedure fails, UE 104 restarts the LBT on the corresponding uplink carrier until the LBT procedure succeeds (i.e., the uplink carrier is available and not occupied).

[0041] Then, UE 104 initiates a first transmission of a random access preamble to BS 102 on the corresponding uplink carrier at the PRACH timing and on the PRACH channel, wherein the random access preamble may include a cyclic prefix (CP) and a PRACH sequence. In some embodiments, the PRACH sequence includes mutually orthogonal Zadd-off Chu sequences. In some embodiments, each uplink carrier uses a random access preamble with a different or the same PRACH sequence. In some embodiments, UE 104 selects a preamble for each uplink carrier from a plurality of preamble sequences, which are configured or reserved by BS 102 accordingly for use in contention-based or contention-free RACH procedures. In some embodiments, the aforementioned process, including determining the SS block, performing the LBT procedure on the PRACH timing, and transmitting the random access preamble, is performed separately and independently on each of the three uplink carriers F1 202, F2 204, and F4 206. Although the transmission of the random access preamble of F1 202 is shown to begin before the transmission on F2 204 and F4 206, the start time of transmitting the random access preamble on the corresponding uplink carrier depends on the PRACH timing of the corresponding uplink carrier and any delays in their corresponding LBT process. Figure 2 The relative timing shown is exemplary and not intended to be limiting. It should be noted that any relative timing during the transmission of random access preambles on an uplink carrier is within the scope of this disclosure.

[0042] After a fixed duration of m symbols following the end of the first transmission of the random access preamble, UE 104 starts a re-ResponseWindow timer at the beginning of the PDCCH (Physical Downlink Control Channel) timing on each of the corresponding uplink carriers, where m is a non-negative integer. In some embodiments, for each of the three uplink carriers F1202, F2204, and F4206, there is an independent re-ResponseWindow timer, which can be started and restarted separately and independently.

[0043] In some embodiments, to ensure the reliability of the uplink carrier when it is determined to be unoccupied after the LBT procedure, UE 104 transmits a random access preamble with a preamble power having a Ra-offset value, which is determined by the following:

[0044] PREAMBLE_RECEIVED_TARGET_POWER=

[0045] ra-PreambleInitialReceivedTargetPower+DELTA_PREAMBLE+

[0046] (PREAMBLE_POWER_RAMPING_COUNTER–1)*powerRampingStep+

[0047] Ra-offset, where ra-PreambleInitialReceivedTargetPower is the initial preamble power.

[0048] DELTA_PREAMBLE is an offset based on the preamble format.

[0049] PREAMBLE_POWER_RAMPING_COUNTER is a counter used for preamble transmission. This counter increments by 1 each time the preamble is transmitted. powerRampingStep is the power ramp factor, and Ra-offset is a non-negative value configured by system information and can be included in the RACH configuration information. In some embodiments, the Ra-offset value can be 1 dB, 2 dB, 3 dB, and 4 dB, and other Ra-offset values ​​may be included within the scope of this invention.

[0050] According to some embodiments, method 200 continues with operation 214, wherein BS 102 generates and transmits a random access response on a downlink carrier corresponding to three uplink carriers on which a random access preamble has been received. In some embodiments, BS 102 performs an LBT procedure on the corresponding downlink carrier to determine availability. BS 102 also calculates a RA-RNTI (Random Access-Radio Network Temporary Identifier) ​​value based on the time and frequency resources on which the random access preamble has been transmitted. In some embodiments, there is one RA-RNTI value for each corresponding uplink carrier, which may be determined by:

[0051] RA-RNTI = 1 + s_id + 14*t_id + 14*X*f_id + 14*X*Y*ul_carrier_id, where s_id is the index of the first OFDM symbol of the PRACH occasion (0 ≤ s_id < 14), t_id is the index of the first time slot of the PRACH occasion in the system frame (0 ≤ t_id < X), f_id is the index of the first frequency of the PRACH occasion in the frequency domain (0 ≤ f_id < Y), and ul_carrier_id is the index of the uplink carrier for the random access preamble. The values of X and Y are 80 and 8 respectively. In some embodiments, for the first uplink carrier F1 202, ul_carrier_id = 0; for the second uplink carrier F2 204, ul_carrier_id = 1; and for the third uplink carrier F1 206, ul_carrier_id = 2.

[0052] BS 102 sends a random access response (RAR) to UE 104 on the downlink carrier until the LBT process passes (i.e., the downlink carrier is available and not occupied). In some embodiments, the random access response includes a PDCCH (Physical Downlink Control Channel) scrambled with the corresponding RA-RNTI value. In some embodiments, the random access response is sent on the downlink carrier corresponding to the uplink carrier on which the random access preamble was received. Specifically, in response to the random access preambles received on the uplink carriers F1 202 and F2 204, BS 102 sends a first random access response and a second random access response to UE 104 on the downlink carrier F3 208; and in response to the random access preamble received on the uplink carrier F4 206, sends a third random access response on the downlink carrier F5 210. In some embodiments, although it is the uplink carrier on which the random access preamble was obtained, BS 102 also sends a random access response to UE 104 on one of the downlink carriers F3 208 or F5 210.

[0053] In some embodiments, random access responses can be delayed due to opportunity occupancy characteristics, potentially causing the ra-ResponseWindow timer to expire. When the ra-ResponseWindow timer expires, UE 104 cannot receive a random access response from BS 102, resulting in RACH procedure failure on the uplink carrier. In some embodiments, the ra-ResponseWindow timer can be increased to prevent frequent RACH procedure failures caused by time delays during the LBT process. In some embodiments, the ra-ResponseWindow timer can be selected from a predefined matrix, wherein the matrix includes [sl1,sl2,sl4,sl8,sl10,sl20,sl40,sl80,sl88]. In some other embodiments, the matrix includes [sl1,sl2,sl4,sl8,sl10,sl20,sl40,sl80,sl96], where each element in the matrix indicates the number of time slots covered by the ra-ResponseWindow timer. For example, sl 1 indicates one time slot of ra-responseWindow, which can be equal to 1 millisecond (ms), while sl 96 indicates 96 time slots of ra-ResponseWindow timer, which is equal to 12 ms.

[0054] According to some embodiments, method 200 continues with operation 216, where UE 104 performs a scheduling transmission on the corresponding uplink carrier used to transmit the random access preamble. In some embodiments, the scheduling transmission is an RRC connection request. In some embodiments, this occurs when a random access response is received from BS 102 on a downlink carrier within the corresponding ra-ResponseWindow. UE 104 can distinguish the random access response and its corresponding random access preamble based on the RA-RNTI value in the random access response received from BS 102. UE 104 also determines whether each of the random access responses includes a random access preamble identifier that matches the index (PREAMBLE_INDEX) of the random access preamble generated in operation 212. If the random access preamble identifier in the random access response received from BS 102 on the downlink carrier matches PREAMBLE_INDEX, then UE 104 terminates the ra-ResponseWindow timer for the corresponding uplink carrier. If UE 104 fails to detect a random access preamble identifier in the random access response received from BS 102 on the downlink carrier that matches the PREAMBLE_INDEX generated in operation 212 before the ra-ResponseWindow timer expires, this causes the RACH procedure on the uplink carrier to fail. In some embodiments, UE 104 then determines the number of times to transmit the random access preamble on the uplink carrier. If the number of times the random access preamble is transmitted on the uplink carrier is less than N+1, where N is a predefined maximum number of random access preambles that can be transmitted, UE 104 continues with operation 502 and restarts the RACH procedure on the uplink carrier again.

[0055] When the random access preamble identifier in the random access response received from BS 102 on the downlink carrier matches PREAMBLE_INDEX and the ra-ResponseWindow timer terminates, UE 104 performs the LBT procedure until an unoccupied uplink carrier is identified. The UE then performs scheduled transmissions on the uplink carrier on which it transmitted the random access preamble. After the scheduled transmissions are completed, UE 104 initiates or restarts the ra-ContentionResolutionTimer corresponding to each of the three uplink carriers F1 202, F2 204, and F6 206 at each point in the HARQ (Hybrid Automatic Repeat Request) retransmission. In some embodiments, the ra-ContentionResolutionTimer for each corresponding uplink carrier can be initiated or restarted independently.

[0056] In some embodiments, time-slot aggregation can be used to ensure reliability, wherein scheduled transmissions are sent multiple times on different resources in the time domain. In some embodiments, parameters for time-slot aggregation, including repetition (repK) and repetition redundancy version (repK-RV), can be added to the UL (uplink) grant sent in the random access response from BS 102. In some embodiments, repK indicates the number of repetitions, and repK-RV indicates the sequence to be used if repetition is used. In some embodiments, repK and repK-RV comprise 2 bits. In some embodiments, repK comprises four positive values, including 1, 2, 4, and 8. In some other embodiments, different values ​​for repK can be included and are within the scope of the invention. In some embodiments, repK and repK-RV can be configured to UE 104 by system information. UE 104 uses repK and repK-RV to send scheduled transmissions.

[0057] According to some embodiments, method 200 continues with operation 218, wherein BS 102 generates a contention resolution message and sends it back to UE 104 on the corresponding downlink carrier. In some embodiments, the contention resolution message includes a random access connection establishment from BS 102. In some embodiments, BS 102 performs an LBT procedure to determine the availability of the downlink carrier before sending the contention resolution message. If UE 104 receives the contention resolution message within the corresponding ra-ContentionResolutionTimer on the corresponding uplink carrier, UE 104 stops the ra-ContentionResolutionTimer on the corresponding uplink carrier, and simultaneously, subsequently terminates other ongoing RACH procedures on other carriers. If UE 104 does not receive a contention resolution message from BS 102 within the corresponding ra-ContentionResolutionTimer for the corresponding uplink carrier, and if the number of times a random access preamble is sent on the uplink carrier is less than N+1, where N is the predefined maximum number of random access preambles that can be sent, then UE 104 continues operation 502 and restarts the RACH procedure on the uplink carrier again.

[0058] In some embodiments, when the number of times the random access preamble is transmitted on the uplink carrier is greater than N+1 (i.e., after multiple failed RACH procedures), a random access problem is reported to an upper layer, such as the RRC layer. Upon receiving it, the upper layer triggers a radio link failure (RLF) and executes an RRC reconstruction procedure. To reduce access latency, UE 104 may trigger the RACH procedure at least once more before indicating a random access problem to the upper layer to trigger an RRC reconstruction procedure.

[0059] In some embodiments, carriers can be divided into different groups with different priorities. For example, a cell may include six uplink carriers F1 to F6 that can be configured for UE 104. Uplink carriers F1, F2, and F3 are in group 1, while group 2 includes uplink carriers F4, F5, and F6. In some embodiments, group 1 may have a higher priority than group 2. When RACH is triggered, UE 104 can initiate a RACH procedure on all uplink carriers in group 1. When all RACH procedures on all carriers in group 1 fail, i.e., the preamble transmission time exceeds the maximum number of random access preambles that can be transmitted, UE 104 can then initiate a RACH procedure on all uplink carriers in group 2.

[0060] It should be noted that Figure 2 These are examples for illustrative and discussion purposes. All RACH procedures (i.e., operations 212-218 on each of the uplink / downlink carrier pairs) are operated independently, and any type of relative timing for each operation on each of the uplink or downlink carriers is within the scope of this invention. For example, the transmission of the random access response from BS 102 to UE 104 on downlink carrier F5 208 in operation 214 may occur before the transmission of the random access preamble from UE 104 to BS 102 on uplink carrier F4 206 in operation 212.

[0061] Figure 3 A method 300 for performing multiple two-step contention-based RACH procedures on multiple carriers is illustrated according to some embodiments of the present disclosure. It should be understood that... Figure 3Additional operations are provided before, during, and after method 300, and some other operations may be omitted or only briefly described herein. In the illustrated embodiment, there are three uplink carriers (i.e., F1 202, F2 204, and F4 206) and two downlink carriers (i.e., F3 208 and F5 210), which are configured to UE 104 via system information or Radio Resource Control (RRC) messages. Uplink carriers F1 202 and F2 204 correspond to downlink carrier F3 208, and uplink carrier F4 206 corresponds to downlink carrier F5 210. RACH configuration (e.g., random access preamble format, transmission timing, and PRACH index) corresponding to each uplink carrier is also configured to UE 104 via system information or RRC messages. Although only three uplink carriers and two downlink carriers are shown, any desired number of uplink and downlink carriers may be included in the system while remaining within the scope of this disclosure.

[0062] Method 300 begins with operation 302, in which UE 104 transmits random access preamble and scheduled transmissions to BS 102 on each of three uplink carriers (i.e., F1 202, F2 204, and F4 206) according to some embodiments. In some embodiments, UE 104 selects at least one SS (synchronization signal) block for transmitting the random access preamble on the first uplink carrier F1 202. This at least one SS block is selected from multiple SS blocks received by UE 104 from BS 102 on the corresponding downlink carrier based on its SS-RSRP (synchronization signal-reference signal received power) value. If the SS-RSRP value is greater than a predefined threshold, an SS block is selected. UE 104 also selects at least one PRACH timing based on the mapping between PRACH (physical random access channel) timing (i.e., frequency resources) and the SS blocks received in the system information. Then, UE 104 selects a random access preamble for each of the corresponding uplink carriers based on the received RACH configuration. Before sending the random access preamble to BS 102, UE 104 performs an LBT procedure on each of the uplink carriers at at least one selected PRACH timing. In some embodiments, the LBT procedure includes determining the traffic load and interference level on the uplink carrier by sensing burst arrivals and interference of packets through its transmitter. If the LBT procedure fails, UE 104 restarts the LBT procedure on the corresponding uplink carrier at a subsequent PRACH timing until the LBT procedure succeeds (i.e., the uplink carrier is available and not occupied).

[0063] Then, UE 104 initiates the first transmission of the random access preamble to BS 102 on the PRACH timing and the corresponding uplink carrier. In some embodiments, the aforementioned process, including determining the SS block, performing the LBT procedure on the PRACH timing, and transmitting the random access preamble, is performed separately and independently on each of the three uplink carriers F1 202, F2 204, and F4 206. Although the transmission of the random access preamble of F1 202 is shown to begin before the transmission on F2 204 and F4 206, the start time of transmitting the random access preamble on the corresponding uplink carrier depends on the PRACH timing of the corresponding uplink carrier and any delays in their corresponding LBT procedures. Figure 2 The relative timing shown is an example and is not intended to be limiting. It should be noted that any relative timing during the transmission of random access preambles on an uplink carrier is within the scope of this disclosure.

[0064] After a fixed duration of m symbols following the end of the first transmission of the random access preamble, UE 104 starts timer T1 at the beginning of the PDCCH (Physical Downlink Control Channel) timing on each of the corresponding uplink carriers, where m is a non-negative integer. In some embodiments, for each of the three uplink carriers F1 202, F2 204, and F4 206, there is an independent timer that can be started and restarted separately and independently.

[0065] In some embodiments, to ensure the reliability of the uplink carrier when it is determined to be unoccupied after the LBT procedure, UE 104 transmits a random access preamble with a preamble power having a Ra-offset value, which is determined by the following:

[0066] PREAMBLE_RECEIVED_TARGET_POWER = ra - PreambleInitialReceivedTargetPower + DELTA_PREAMBLE + (PREAMBLE_POWER_RAMPING_COUNTER – 1) * powerRampingStep + Ra-offset, where ra - PreambleInitialReceivedTargetPower is the initial preamble power, DELTA_PREAMBLE is the offset based on the preamble format, PREAMBLE_POWER_RAMPING_COUNTER is a preamble transmission counter that increments by 1 each time the preamble is transmitted, powerRampingStep is the power ramp factor, and Ra-offset is a non-negative value configured by system information and can be included in the RACH configuration information. In some embodiments, the Ra-offset value can be 1 dB, 2 dB, 3 dB, and 4 dB, and other Ra-offset values ​​can be included and are within the scope of this invention.

[0067] According to some embodiments, method 300 continues to operation 304, wherein BS 102 generates and transmits a random access response and contention resolution on a downlink carrier corresponding to three uplink carriers on which a random access preamble has been received. In some embodiments, BS 102 performs an LBT procedure on the corresponding downlink carrier to determine availability. BS 102 also calculates an RN-RNTI (Random Access-Radio Network Temporary Identifier) ​​value based on the time and frequency resources on which the random access preamble has been transmitted. In some embodiments, each corresponding uplink carrier has an RA-RNTI value, which may be determined by:

[0068] RA-RNTI = 1 + s_id + 14*t_id + 14*X*f_id + 14*X*Y*ul_carrier_id, where s_id is the index of the first OFDM symbol of the PRACH occasion (0 ≤ s_id < 14), t_id is the index of the first time slot of the PRACH occasion in the system frame (0 ≤ t_id < X), f_id is the index of the PRACH occasion in the frequency domain (0 ≤ f_id < Y), and ul_carrier_id is the index of the uplink carrier used for random access preamble transmission. The values of X and Y are 80 and 8 respectively. In some embodiments, for the first uplink carrier F1 202, ul_carrier_id = 0; for the second uplink carrier F2 204, ul_carrier_id = 1; and for the third uplink carrier F1 206, ul_carrier_id = 2.

[0069] The BS 102 sends a random access response to the UE 104 until the LBT process passes (i.e., the downlink carrier is available and not occupied). In some embodiments, the random access response includes a PDCCH (Physical Downlink Control Channel) scrambled with the corresponding RA-RNTI value. In some embodiments, the random access response is sent on the downlink carrier corresponding to the uplink carrier on which the random access preamble is received. Specifically, in response to the random access preambles received on the uplink carriers F1 202 and F2 204, the BS 102 sends a first random access response and a second random access response to the UE 104 on the downlink carrier F3 208; and in response to the random access preamble received on the uplink carrier F4 206, sends a third random access response on the downlink carrier F5 210. In some embodiments, despite the uplink carrier on which the random access preamble is obtained, the BS 102 also sends a random access response to the UE 104 on one of the downlink carriers F3 208 or F5 210.

[0070] In some embodiments, when a random access response and contention resolution are received from BS 102 on a downlink carrier within the corresponding timer T1, UE 104 can distinguish the random access response and its corresponding random access preamble based on the RA-RNTI value in the random access response received from BS 102. UE 104 also determines whether each random access response includes a random access preamble identifier that matches the index (PREAMBLE_INDEX) of the random access preamble generated in operation 212. If the random access preamble identifier in the random access response received from BS 102 on the downlink carrier matches PREAMBLE_INDEX, UE 104 terminates timer t1 on the corresponding uplink carrier, and simultaneously, subsequently terminates other ongoing RACH procedures on other uplink carriers. If UE 104 fails to detect the random access preamble identifier in the random access response received from BS 102 on the downlink carrier that matches the PREAMBLE_INDEX generated in operation 212 before timer T1 expires, this causes the RACH procedure on the uplink carrier to fail. In some embodiments, UE 104 then determines the number of times to transmit the random access preamble on the uplink carrier. If the number of times the random access preamble is transmitted on the uplink carrier is less than N+1, where N is a predefined maximum number of random access preambles that can be transmitted, UE 104 continues with operation 302 and restarts the RACH procedure on the uplink carrier again.

[0071] In some embodiments, when the number of times the random access preamble is transmitted on the uplink carrier is greater than N+1 (i.e., after multiple failed RACH procedures), a random access problem is reported to an upper layer, such as the RRC layer. Upon receiving it, the upper layer triggers a radio link failure (RLF) and executes an RRC reconstruction procedure. To reduce access latency, UE 104 may trigger the RACH procedure at least once more before indicating a random access problem to the upper layer to trigger an RRC reconstruction procedure.

[0072] In some embodiments, carriers can be divided into different groups with different priorities. For example, a cell may include six uplink carriers F1 to F6 that can be configured for UE 104. Uplink carriers F1, F2, and F3 are in group 1, while group 2 includes uplink carriers F4, F5, and F6. In some embodiments, group 1 may have a higher priority than group 2. When RACH is triggered, UE 104 can initiate a RACH procedure on all uplink carriers in group 1. When all RACH procedures on all carriers in group 1 fail, i.e., the preamble transmission time exceeds the maximum number of random access preambles that can be transmitted, UE 104 can then initiate a RACH procedure on all uplink carriers in group 2.

[0073] It should be noted that Figure 3 These are examples for illustrative and discussion purposes. All RACH procedures (i.e., operations 302 and 304 on each of the uplink / downlink carrier pairs) are operated independently, and any type of relative timing for each operation on each of the uplink or downlink carriers is within the scope of this invention. For example, the transmission of a random access response / contention resolution from BS 102 to UE 104 on F5 208 in operation 304 may occur before the transmission of a random access preamble from UE 104 to BS 102 on uplink carrier F4 206 in operation 302.

[0074] Figure 4 A method 400 for performing multiple two-step contention-free RACH procedures on multiple carriers according to some embodiments of the present disclosure is illustrated. It should be understood that... Figure 4 Additional operations are provided before, during, and after method 400, and some other operations may be omitted or only briefly described herein. In the illustrated embodiment, there are three uplink carriers (i.e., F1 202, F2 204, and F4 206) and two downlink carriers (i.e., F3 208 and F5 210), which are configured to UE 104 via system information or Radio Resource Control (RRC) messages. Uplink carriers F1 202 and F2 204 correspond to downlink carrier F3 208, and uplink carrier F4 206 corresponds to downlink carrier F5 210. RACH configuration (e.g., random access preamble format, transmission timing, and PRACH index) corresponding to each uplink carrier is also configured to UE 104 via system information or RRC messages. Although only three uplink carriers and two downlink carriers are shown, any desired number of uplink and downlink carriers may be included in the system while remaining within the scope of this disclosure.

[0075] Method 400 begins with operation 402, in which UE 104 transmits a random access preamble to BS 102 on each of three uplink carriers (i.e., F1202, F2204, and F4206) according to some embodiments. In some embodiments, the random access preamble for the uplink carriers is dedicated to BS 102. In some embodiments, UE 104 selects at least one SS (synchronization signal) block for transmitting the random access preamble on the uplink carrier. The at least one SS block is selected from a plurality of SS blocks received by UE 104 from BS 102 on the corresponding downlink carrier based on its SS-RSRP (synchronization signal-reference signal received power) value. If the SS-RSRP value of an SS block is greater than a predefined threshold, the SS block is selected. In some embodiments, UE 104 selects at least one CSI-RS (channel state information-reference signal) for transmitting the random access preamble on the uplink carrier. At least one CSI-RS is selected from multiple CSI-RS received by UE 104 from BS 102 on the corresponding downlink carrier based on its CSI-RSRP value. If the CSI-RSRP of a CSI-RS is greater than a predefined threshold, then the CSI-RS is selected. UE 104 also selects at least one PRACH timing based on the mapping relationship between PRACH (Physical Random Access Channel) timing (i.e., frequency resources) and the SS blocks or CSI-RS received in the system information.

[0076] Then, UE 104 selects a random access preamble for each of the corresponding uplink carriers based on the RACH received from BS 102. Before sending the random access preamble to BS 102, UE 104 performs an LBT procedure at at least one selected PRACH timing on each of the uplink carriers. In some embodiments, the LBT procedure includes determining the traffic load and interference level on the uplink carrier by sensing burst arrivals and interference of packets through its transmitter. If the LBT procedure fails, UE 104 restarts the LBT procedure at a subsequent PRACH timing on the corresponding uplink carrier until the LBT procedure succeeds (i.e., the uplink carrier is available and not occupied).

[0077] Then, UE 104 initiates the first transmission of the random access preamble to BS 102 on the PRACH timing and the corresponding uplink carrier. In some embodiments, the aforementioned process, including determining the SS block, determining the CSI-RS, performing the LBT procedure on the PRACH timing, and transmitting the random access preamble, is performed separately and independently on each of the three uplink carriers F1 202, F2 204, and F4 206. Although the transmission of the random access preamble of F1 202 is shown to begin before the transmission on F2 204 and F4 206, the start time of transmitting the random access preamble on the corresponding uplink carrier depends on the PRACH timing of the corresponding uplink carrier and any delays in their corresponding LBT procedures. Figure 4 The relative timing shown is an example and is not intended to be limiting. It should be noted that any relative timing between each in a transmission is within the scope of this disclosure.

[0078] After a fixed duration of m symbols following the end of the first transmission of the random access preamble, UE 104 starts a re-ResponseWindow timer at the beginning of the PDCCH (Physical Downlink Control Channel) timing on each of the corresponding uplink carriers, where m is a non-negative integer. In some embodiments, for each of the three uplink carriers F1202, F2204, and F4206, there is an independent re-ResponseWindow timer, which can be started and restarted separately and independently.

[0079] In some embodiments, to ensure the reliability of the uplink carrier when it is determined to be unoccupied after the LBT procedure, UE 104 transmits a random access preamble with a preamble power having a Ra-offset value, which is determined by the following:

[0080] PREAMBLE_RECEIVED_TARGET_POWER = ra - PreambleInitialReceivedTargetPower + DELTA_PREAMBLE + (PREAMBLE_POWER_RAMPING_COUNTER – 1) * powerRampingStep + Ra-offset, where ra - PreambleInitialReceivedTargetPower is the initial preamble power, DELTA_PREAMBLE is the offset based on the preamble format, PREAMBLE_POWER_RAMPING_COUNTER is a preamble transmission counter that increments by 1 each time the preamble is transmitted, powerRampingStep is the power ramp factor, and Ra-offset is a non-negative value configured by system information and included in the RACH configuration information. In some embodiments, the Ra-offset value can be 1 dB, 2 dB, 3 dB, and 4 dB, and other Ra-offset values ​​may be included and are within the scope of this invention.

[0081] According to some embodiments, method 400 continues to operation 404, wherein BS 102 generates and transmits a random access response on a downlink carrier corresponding to three uplink carriers on which a random access preamble has been received. In some embodiments, BS 102 performs an LBT procedure on the corresponding downlink carrier to determine availability. BS 102 also calculates a RA-RNTI (Random Access-Radio Network Temporary Identifier) ​​value based on the time and frequency resources on which the random access preamble has been transmitted. In some embodiments, there is one RA-RNTI value for each corresponding uplink carrier, which may be determined by:

[0082] RA-RNTI = 1 + s_id + 14*t_id + 14*X*f_id + 14*X*Y*ul_carrier_id, where s_id is the index of the first OFDM symbol of the PRACH occasion (0 ≤ s_id < 14), t_id is the index of the first time slot of the PRACH occasion in the system frame (0 ≤ t_id < X), f_id is the index of the PRACH occasion in the frequency domain (0 ≤ f_id < Y), and ul_carrier_id is the index of the uplink carrier used for random access preamble transmission. The values of X and Y are 80 and 8 respectively. In some embodiments, for the first uplink carrier F1 202, ul_carrier_id = 0; for the second uplink carrier F2 204, ul_carrier_id = 1; and for the third uplink carrier F1 206, ul_carrier_id = 2.

[0083] BS 102 sends a random access response to UE 104 until the LBT process passes (i.e., the downlink carrier is available and not occupied). In some embodiments, the random access response includes a PDCCH (Physical Downlink Control Channel) scrambled with the corresponding RA-RNTI value. In some embodiments, the random access response is sent on the downlink carrier corresponding to the uplink carrier on which the random access preamble is received. Specifically, in response to the random access preambles received on the uplink carriers F1 202 and F2 204, BS 102 sends a first random access response and a second random access response to UE 104 on the downlink carrier F3 208; and in response to the random access preamble received on the uplink carrier F4 206, sends a third random access response on the downlink carrier F5 210. In some embodiments, even though the uplink carrier on which the random access preamble is obtained, BS 102 also sends a random access response to UE 104 on one of the downlink carriers F3 208 or F5 210.

[0084] In some embodiments, when a random access response and contention resolution are received from BS 102 on a downlink carrier within the corresponding ra-ResponseWindow, UE 104 can distinguish the random access response and its corresponding random access preamble based on the RA-RNTI value in the random access response received from BS 102. UE 104 also determines whether each random access response includes a random access preamble identifier that matches the index (PREAMBLE_INDEX) of the random access preamble generated in operation 212. If the random access preamble identifier in the random access response received from BS 102 on the downlink carrier matches PREAMBLE_INDEX, UE 104 terminates the ra-ResponseWindow timer for the corresponding uplink carrier, and simultaneously, subsequently terminates other ongoing RACH procedures on other uplink carriers. If UE 104 cannot detect the random access preamble identifier in the random access response received from BS 102 on the downlink carrier that matches the PREAMBLE_INDEX generated in operation 212 before the ra-ResponseWindow timer expires, this causes the RACH procedure on the uplink carrier to fail. In some embodiments, UE 104 then determines the number of times to transmit the random access preamble on the uplink carrier. If the number of times the random access preamble is transmitted on the uplink carrier is less than N+1, where N is a predefined maximum number of random access preambles that can be transmitted, UE 104 continues with operation 402 and restarts the RACH procedure again on the corresponding uplink carrier.

[0085] In some embodiments, when the number of times the random access preamble is transmitted on the uplink carrier is greater than N+1 (i.e., after multiple failed RACH procedures), a random access problem is reported to an upper layer, such as the RRC layer. Upon receiving it, the upper layer triggers a radio link failure (RLF) and executes an RRC reconstruction procedure. To reduce access latency, UE 104 may trigger the RACH procedure at least once more before indicating a random access problem to the upper layer to trigger an RRC reconstruction procedure.

[0086] In some embodiments, carriers can be divided into different groups with different priorities. For example, a cell may include six uplink carriers F1 to F6 that can be configured for UE 104. Uplink carriers F1, F2, and F3 are in group 1, while group 2 includes uplink carriers F4, F5, and F6. In some embodiments, group 1 may have a higher priority than group 2. When RACH is triggered, UE 104 can initiate a RACH procedure on all uplink carriers in group 1. When all RACH procedures on all carriers in group 1 fail, i.e., the preamble transmission time exceeds the maximum number of random access preambles that can be transmitted, UE 104 can then initiate a RACH procedure on all uplink carriers in group 2.

[0087] It should be noted that Figure 4 These are examples for illustrative and discussion purposes. All RACH procedures (i.e., operations 212-218 on each of the uplink / downlink pairs) are operated independently, and any type of relative timing for each operation on each of the uplink or downlink carriers is within the scope of this invention. For example, the transmission of a random access response from BS 102 to UE 104 on downlink carrier F5 208 in operation 404 may occur before the transmission of a random access preamble from UE 104 to BS 102 on uplink carrier F4 206 in operation 402.

[0088] Figure 5 A method 500 for performing multiple four-step competition-based RACH procedures over multiple bandwidth portions is illustrated according to some embodiments of the present disclosure. It should be understood that... Figure 5 Additional operations are provided before, during, and after method 500, and some other operations may be omitted or only briefly described herein. In the illustrated embodiment, there are three uplink bandwidth portions (i.e., BWP1 502, BWP2 504, and BWP3 506) and three downlink BWPs (i.e., BWP4 508, BWP5 510, and BWP6 512), which are configured to UE 104 via system information or Radio Resource Control (RRC) messages. Uplink BWP1 502, BWP2 504, and BWP3 506 correspond to downlink BWP4 508, BWP 510, and BWP 512, respectively. Furthermore, the RACH configuration (e.g., random access preamble format, transmission timing, and PRACH index) corresponding to each uplink carrier is configured to UE 104 via system information or RRC messages. Although only three uplink BWPs and three downlink BWPs are shown, any desired number of uplink and downlink carriers may be included in the system while remaining within the scope of this disclosure.

[0089] Method 500 begins with operation 520, in which UE 104 transmits a random access preamble to BS 102 for each of the three uplink BWPs (i.e., BWP1 502, BWP2 504, and BWP3 506) according to some embodiments. In some embodiments, UE 104 selects at least one SS (synchronization signal) block for transmitting the random access preamble on the uplink BWP. The at least one SS block is selected from a plurality of SS blocks received by UE 104 from BS 102 on the corresponding downlink carrier based on its SS-RSRP (synchronization signal-reference signal received power) value. If the SS-RSRP value is greater than a predefined threshold, an SS block is selected. UE 104 also selects at least one PRACH (physical random access channel) timing (i.e., i.e., frequency resource) based on the mapping between PRACH timing and the SS blocks received in the system information. Then, UE 104 is configured to select a random access preamble for each of the corresponding uplink carriers based on the received RACH. Before sending the random access preamble to BS 102, UE 104 performs an LBT procedure at at least one selected PRACH timing on each of the uplink carriers. In some embodiments, the LBT procedure includes: sensing burst arrivals and interference of packets through its transmitter to determine the traffic load and interference level on the uplink carrier. If the LBT procedure fails, UE 104 restarts the LBT procedure at a subsequent PRACH timing on the corresponding uplink carrier until the LBT procedure succeeds (i.e., the uplink carrier is available and not occupied).

[0090] Then, UE 104 initiates the first transmission of the random access preamble to BS 102 on the PRACH timing and the corresponding uplink carrier. In some embodiments, the aforementioned process, including determining the SS block, performing the LBT procedure on the PRACH timing, and transmitting the random access preamble, is performed separately and independently on each of the three uplink BWPs (i.e., BWP1 502, BWP2 504, and BWP3 506). Although it is shown that the transmission of its random access preamble on the first BWP1 502 starts before the transmission on the second BWP2 504 and the third BWP3 506, the start time of transmitting the random access preamble on the corresponding uplink BWP depends on the PRACH timing of the corresponding uplink carrier and any delay in their corresponding LBT procedures before transmission. Figure 2 The relative timing shown is an example and is not intended to be limiting. It should be noted that any relative timing during the transmission of random access preambles on an uplink carrier is within the scope of this disclosure.

[0091] After a fixed duration of m symbols following the end of the first transmission of the random access preamble, UE 104 starts a re-ResponseWindow timer at the beginning of the PDCCH (Physical Downlink Control Channel) timing on each of the corresponding uplink carriers, where m is a non-negative integer. In some embodiments, for each of the three uplink BWPs (i.e., BWP1 502, BWP2 504, and BWP3 506), there is an independent re-ResponseWindow timer, which can be started and restarted separately and independently.

[0092] In some embodiments, to ensure the reliability of the uplink BWP when it is determined that the uplink BWP is not occupied after the LBT procedure, UE 104 transmits a random access preamble with a preamble power having a Ra-offset value, which is determined by the following:

[0093] PREAMBLE_RECEIVED_TARGET_POWER = ra - PreambleInitialReceivedTargetPower + DELTA_PREAMBLE + (PREAMBLE_POWER_RAMPING_COUNTER – 1) * powerRampingStep + Ra-offset, where ra - PreambleInitialReceivedTargetPower is the initial preamble power, DELTA_PREAMBLE is the offset based on the preamble format, PREAMBLE_POWER_RAMPING_COUNTER is a preamble transmission counter that increments by 1 each time the preamble is transmitted, powerRampingStep is the power ramp factor, and Ra-offset is a non-negative value configured by system information and included in the RACH configuration information. In some embodiments, the Ra-offset value can be 1 dB, 2 dB, 3 dB, and 4 dB, and other Ra-offset values ​​may be included and are within the scope of this invention.

[0094] According to some embodiments, method 500 proceeds to operation 522, where BS 102 generates and transmits a random access response on the downlink BWP corresponding to the three uplink BWPs on which the random access preamble was received. In some embodiments, BS 102 performs a LBT process on the corresponding downlink carrier to determine availability. BS 102 also calculates a RA-RNTI (Random Access - Radio Network Temporary Identifier) value based on the time and frequency resources on which the random access preamble was transmitted. In some embodiments, there is one RA-RNTI value for each corresponding uplink carrier, which can be determined by:

[0095] RA-RNTI = 1 + s_id + 14 * t_id + 14 * X * f_id + 14 * X * Y * ul_carrier_id + Z * BWP index, where s_id is the index of the first OFDM symbol of the PRACH occasion (0 ≤ s_id < 14), t_id is the index of the first slot of the PRACH occasion in the system frame (0 ≤ t_id < X), f_id is the index of the PRACH occasion in the frequency domain (0 ≤ f_id < Y), and the values of X and Y are 80 and 8, respectively. In some embodiments, Z is equal to 1. In some embodiments, Z is equal to 14 * X * Y. In some embodiments, ul-carrier_id is the index of the uplink carrier on which the uplink BWP is located, and the BWP index is the BWP index of the uplink BWP in the corresponding uplink carrier for random access preamble transmission. For example, there may be three uplink carriers, and each of them includes three uplink BWPs. In some embodiments, for the first uplink carrier, ul_carrier_id = 0; for the second uplink carrier, ul_carrier_id = 1; and for the third uplink carrier, ul_carrier_id = 2. In each of the uplink carriers, for the first uplink BWP, second uplink BWP, and third uplink BWP (e.g., BWP1 502, BWP2 504, and BWP3 506) of the corresponding uplink carrier, the BWP index = 0, 1, and 2.

[0096] BS 102 sends a random access response to UE 104 until the LBT procedure is completed on the downlink BWP (i.e., the downlink BWP is available and not occupied). In some embodiments, the random access response includes a PDCCH (Physical Downlink Control Channel) scrambled with the corresponding RA-RNTI value. In some embodiments, the random access response is sent on a downlink carrier corresponding to the uplink carrier on which the random access preamble is received. Specifically, in response to a random access preamble received on uplink BWP1 502, BS 102 sends a first random access response to UE 104 on downlink BWP4 508; in response to a random access preamble received on uplink BWP2 504, sends a second random access response to UE 104 on downlink BWP5 510; and in response to a random access preamble received on uplink BWP3 508, sends a third random access response on downlink BWP 512. In some embodiments, although the uplink BWP on which the random access preamble is sent is on which the BS 102 also sends a random access response to the UE 104 on one of the downlink BWPs (i.e., BWP4 508, BWP5 510 and BWP6 512).

[0097] In some embodiments, random access responses may be delayed due to opportunity occupancy characteristics, potentially causing the ra-ResponseWindow timer to expire. When the ra-ResponseWindow timer expires, UE104 cannot receive a random access response from BS102, resulting in RACH procedure failure. In some embodiments, the ra-ResponseWindow timer can be increased to prevent frequent RACH procedure failures due to time delays during LBT. In some embodiments, the ra-ResponseWindow timer can be selected from a predefined matrix, wherein the matrix includes [sl 1, sl 2, sl 4, sl 8, sl 10, sl 20, sl 40, sl 80, sl 88]. In some other embodiments, the matrix includes [sl 1, sl 2, sl 4, sl 8, sl 10, sl 20, sl 40, sl 80, sl 96], where each element in the matrix indicates the number of time slots covered by the ra-ResponseWindow timer. For example, sl 1 indicates one time slot of the ra-responseWindow timer, which is equal to 1 millisecond (ms), while sl 96 indicates 96 time slots of the ra-ResponseWindow timer, which is equal to 12 ms.

[0098] According to some embodiments, method 500 continues to operation 524, wherein UE 104 performs scheduled transmissions on the corresponding uplink carrier used to transmit the random access preamble. In some embodiments, when a random access response from BS 102 is received on the downlink BWP within the corresponding ra-ResponseWindow timer, UE 104 can distinguish the random access response and its corresponding random access preamble based on the RA-RNTI value in the random access response received from BS 102. UE 104 also determines whether each of the random access responses includes a random access preamble identifier that matches the index (PREAMBLE_INDEX) of the random access preamble generated in operation 520. If the random access preamble identifier in the random access response received from BS 102 on the downlink carrier matches PREAMBLE_INDEX, then UE 104 terminates the ra-ResponseWindow timer of the corresponding uplink BWP. If UE 104 fails to detect the random access preamble identifier in the random access response received from BS 102 on the downlink BWP that matches the PREAMBLE_INDEX generated in operation 520 before the ra-ResponseWindow timer expires, this causes the RACH procedure on the uplink BWP to fail. In some embodiments, UE 104 then determines the number of times to send the random access preamble on the uplink BWP. If the number of times the random access preamble is sent on the uplink BWP is less than N+1, where N is a predefined maximum number of random access preambles that can be sent on the uplink BWP, UE 104 continues with operation 520 and restarts the RACH procedure again on the corresponding uplink BWP.

[0099] When the random access preamble identifier in the random access response received from BS 102 on the downlink BWP matches PREAMBLE_INDEX and the ra-ResponseWindow timer terminates, UE 104 performs the LBT procedure until an unoccupied uplink BWP is identified. The UE then performs scheduled transmissions on the uplink BWP on which the random access preamble was transmitted. After the scheduled transmissions are completed, UE 104 starts or restarts the ra-ContentionResolutionTimer corresponding to each of the three uplink BWPs at each point in the HARQ (Hybrid Automatic Repeat Request) retransmission. In some embodiments, the ra-ContentionResolutionTimer for each corresponding uplink BWP can be started or restarted independently.

[0100] In some embodiments, time-slot aggregation can be used to ensure reliability, wherein scheduled transmissions are sent multiple times on different resources in the time domain. In some embodiments, parameters for time-slot aggregation, including repetition (repK) and repetition redundancy version (repK-RV), can be added to the UL (uplink) grant sent in the random access response from BS 102. In some embodiments, repK indicates the number of repetitions, and repK-RV indicates the sequence to be used if repetition is used. In some embodiments, repK and repK-RV comprise 2 bits. In some embodiments, repK comprises four positive values, including 1, 2, 4, and 8. In some other embodiments, different values ​​for repK can be included and are within the scope of the invention. In some embodiments, repK and repK-RV can be configured to UE 104 by system information. UE 104 uses repK and repK-RV to send scheduled transmissions.

[0101] According to some embodiments, method 500 continues with operation 526, where BS 102 generates a contention resolution message and sends it back to UE 104 on the corresponding downlink BWP. In some embodiments, BS 102 performs an LBT procedure to determine the availability of the downlink BWP before sending the contention resolution message. If UE 104 receives the contention resolution message within the corresponding ra-ContentionResolutionTimers of the corresponding uplink BWP, UE 104 stops the ra-ContentionResolutionTimers of the corresponding uplink carrier, and simultaneously terminates other ongoing RACH procedures on other BWPs. If UE 104 does not receive a contention resolution message from BS 102 within the corresponding ra-ContentionResolutionTimers of the corresponding uplink carrier, and if the number of times a random access preamble is sent on the uplink BWP is less than N+1, where N is a predefined maximum number of random access preambles that can be sent on the uplink BWP, UE 104 continues with operation 502 and restarts the RACH procedure on the uplink BWP again.

[0102] In some embodiments, when the number of times the random access preamble is transmitted on the uplink carrier is greater than N+1 (i.e., after multiple failed RACH procedures), a random access problem is reported to an upper layer, such as the RRC layer. Upon receiving it, the upper layer triggers a radio link failure (RLF) and executes an RRC reconstruction procedure. To reduce access latency, UE 104 may trigger the RACH procedure at least once more before indicating a random access problem to the upper layer to trigger an RRC reconstruction procedure.

[0103] In some embodiments, BWPs can be divided into different groups with different priorities. For example, a cell may include six uplink BWPs (i.e., BWP1 to BWP6) that can be configured for UE 104. Uplink BWP1, BWP2, and BWP3 are in group 1, while group 2 includes uplink BWPs BWP4, BWP5, and BWP6. In some embodiments, group 1 may have a higher priority than group 2. When RACH is triggered, UE 104 can initiate a RACH procedure in all uplink BWPs in group 1. When all RACH procedures on all uplink BWPs in group 1 fail, i.e., the preamble transmission time exceeds the maximum number of random access preambles that can be transmitted, UE 104 can then initiate a RACH procedure in all uplink BWPs in group 2.

[0104] It should be noted that Figure 5 These are examples for illustrative and discussion purposes. All RACH procedures (i.e., operations 520-526 on each of the uplink / downlink BWP pairs) are operated independently, and any type of relative timing for each operation on each of the uplink or downlink BWPs is within the scope of this invention. For example, the transmission of a random access response from BS 102 to UE 10 on downlink BWP4 508 in operation 522 may occur before the transmission of a random access preamble from UE 104 to BS 102 on uplink BWP1 502 in operation 520.

[0105] Figure 6 A method 600 for performing multiple two-step contention-based RACH procedures on multiple bandwidth portions is illustrated according to some embodiments of the present disclosure. In the illustrated embodiment, there are three uplink bandwidth portions (i.e., BWP1 502, BWP2 504, and BWP3 506) and three downlink BWPs (i.e., BWP4 508, BWP5 510, and BWP6 512), which are configured to UE 104 via system information or Radio Resource Control (RRC) messages. Uplink BWP1 502, BWP2 504, and BWP3 506 correspond to downlink BWP4 508, BWP 510, and BWP 512, respectively. Furthermore, RACH configurations (e.g., random access preamble format, transmission timing, and PRACH index) corresponding to each uplink carrier are configured to UE 104 via system information or RRC messages. Although only three uplink BWPs and three downlink BWPs are shown, any desired number of uplink and downlink carriers may be included in the system while remaining within the scope of this disclosure.

[0106] Method 600 begins with operation 602, in which UE 104 transmits random access preambles and scheduled transmissions to BS 102 in each of three uplink BWPs (i.e., BWP1 502, BWP2 504, and BWP3 506) according to some embodiments. In some embodiments, UE 104 selects at least one SS (synchronization signal) block for transmitting the random access preamble on the uplink BWP. The at least one SS block is selected from a plurality of SS blocks received by UE 104 from BS 102 on the corresponding downlink BWP based on its SS-RSRP (synchronization signal-reference signal received power) value. An SS block is selected if the SS-RSRP value is greater than a predefined threshold. UE 104 also determines at least one PRACH (physical random access channel) timing (i.e., i.e., frequency resources) based on the mapping between PRACH timing and the SS blocks received in the system information. Then, UE 104 configures to select a random access preamble for each of the corresponding uplink BWPs based on the received RACH. Before sending the random access preamble to BS 102, UE 104 performs an LBT procedure on each of the uplink BWPs. In some embodiments, the LBT procedure includes: sensing burst arrivals and interference of packets through its transmitter to determine the traffic load and interference levels on the uplink BWP. If the LBT procedure fails, UE 104 restarts the LBT procedure on the corresponding uplink BWP at a subsequent PRACH timing until the LBT procedure succeeds (i.e., the uplink BWP is available and not occupied).

[0107] Then, UE 104 initiates the first transmission of the random access preamble to BS 102 on the PRACH timing and the corresponding uplink carrier. In some embodiments, the aforementioned process, including determining the SS block, performing the LBT procedure, and transmitting the random access preamble, is performed separately and independently on each of the three uplink BWPs. Although it is shown that the transmission of the random access preamble and the scheduled transmission on the first uplink BWP1 502 in operation 602 are initiated before the transmission on the second uplink BWP2 504 and the third uplink BWP506, the start time of transmitting the random access preamble and the scheduled transmission on the corresponding uplink BWP depends on the PRACH timing of the corresponding uplink carrier and any delays in their corresponding LBT procedures. Figure 6 The relative timing shown is an example and is not intended to be limiting. It should be noted that any relative timing during the transmission of random access preambles and scheduling transmissions on the uplink BWP is within the scope of this disclosure.

[0108] After a fixed duration of m symbols following the end of the first transmission of the random access preamble, UE 104 starts a timer at the beginning of the PDCCH (Physical Downlink Control Channel) timing on each of the corresponding uplink carriers, where m is a non-negative integer. In some embodiments, for each of the three uplink BWPs, there is an independent timer that can be started and restarted separately and independently.

[0109] In some embodiments, to ensure the reliability of the uplink carrier when it is determined to be unoccupied after the LBT procedure, UE 104 transmits the random access preamble and scheduled transmission with a preamble power having a Ra-offset value, which is determined by the following:

[0110] PREAMBLE_RECEIVED_TARGET_POWER = ra - PreambleInitialReceivedTargetPower + DELTA_PREAMBLE + (PREAMBLE_POWER_RAMPING_COUNTER – 1) * powerRampingStep + Ra-offset, where ra - PreambleInitialReceivedTargetPower is the initial preamble power, DELTA_PREAMBLE is the offset based on the preamble format, PREAMBLE_POWER_RAMPING_COUNTER is a preamble transmission counter that increments by 1 each time the preamble is transmitted, powerRampingStep is the power ramp factor, and Ra-offset is a non-negative value configured by system information and included in the RACH configuration information. In some embodiments, the Ra-offset value can be 1 dB, 2 dB, 3 dB, and 4 dB, and other Ra-offset values ​​may be included and are within the scope of this invention.

[0111] According to some embodiments, method 600 continues to operation 604, wherein BS 102 generates and transmits a random access response and contention resolution on a downlink BWP, which corresponds to three uplink BWPs on which a random access preamble has been received. In some embodiments, BS 102 performs an LBT procedure on the corresponding downlink BWP to determine availability. BS 102 also calculates a RA-RNTI (Random Access-Radio Temporary Identifier) ​​value based on the time and frequency resources on which the random access preamble has been transmitted. In some embodiments, each corresponding uplink BWP has an RA-RNTI value, which may be determined by:

[0112] RA-RNTI = 1 + s_id + 14 * t_id + 14 * X * f_id + 14 * X * Y * ul_carrier_id + Z * BWP index, where s_id is the index of the first OFDM symbol of the PRACH occasion (0 ≤ s_id < 14), t_id is the index of the first time slot of the PRACH occasion in the system frame (0 ≤ t_id < X), and f_id is the index of the PRACH occasion in the frequency domain (0 ≤ f_id < Y). The values of X and Y are 80 and 8 respectively. In some embodiments, Z equals 1. In some embodiments, Z equals 14 * X * Y. In some embodiments, ul-carrier_id is the index of the uplink carrier where the uplink BWP is located, and the BWP index is the BWP index of the uplink BWP in the corresponding uplink carrier for random access preamble transmission. For example, there may be 3 uplink carriers, and each of them includes 3 uplink BWPs. In some embodiments, for the first uplink carrier, ul_carrier_id = 0; for the second uplink carrier, ul_carrier_id = 1; and for the third uplink carrier, ul_carrier_id = 2. In each of the uplink carriers, for the first uplink BWP, second uplink BWP, and third uplink BWP (e.g., BWP1 502, BWP2 504, and BWP3 506) of the corresponding uplink carrier, the BWP index = 0, 1, and 2.

[0113] BS 102 sends a random access response and contention resolution to UE 104 until the LBT procedure is complete (i.e., the downlink BWP is available and not occupied). In some embodiments, the random access response includes a PDCCH (Physical Downlink Control Channel) scrambled with the corresponding RA-RNTI value. In some embodiments, the random access response is transmitted on a downlink carrier corresponding to the uplink carrier on which the random access preamble was received. Specifically, in response to the transmission of the random access preamble and schedule received on the first uplink BWP1 502, BS 102 sends a first random access response and contention resolution to UE 104 on the first downlink BWP4 508; in response to the transmission of the random access preamble and schedule received on the second uplink BWP2 504, it sends a second random access response and contention resolution to UE 104 on the second downlink BWP5 510; and in response to the transmission of the random access preamble and schedule received on the third uplink BWP3 506, it sends a third random access response and contention resolution to UE 104 on the third downlink BWP6 512. In some embodiments, although the random access preamble is obtained on an uplink BWP, BS 102 also sends a random access response to UE 104 on one of the downlink BWPs.

[0114] In some embodiments, when a random access response and contention resolution are received from BS 102 on the downlink BWP within the corresponding timer T1, UE 104 can distinguish the random access response and its corresponding random access preamble based on the RA-RNTI value in the random access response received from BS 102. UE 104 also determines whether each random access response includes a random access preamble identifier that matches the index (PREAMBLE_INDEX) of the random access preamble generated in operation 602. If the random access preamble identifier in the random access response received from BS 102 on the downlink BWP matches PREAMBLE_INDEX, UE 104 terminates timer t1 on the corresponding uplink BWP, and simultaneously, subsequently terminates other ongoing RACH procedures on other uplink BWPs. If UE 104 fails to detect the random access preamble identifier in the random access response received from BS 102 on the downlink carrier that matches the PREAMBLE_INDEX generated in operation 602 before timer t1 expires, this causes the RACH procedure on the uplink BWP to fail. In some embodiments, UE 104 then determines the number of times to transmit the random access preamble on the uplink BWP. If the number of times the random access preamble is transmitted on the uplink BWP is less than N+1, where N is a predefined maximum number of random access preambles that can be transmitted on the uplink BWP, UE 104 continues with operation 602 and restarts the RACH procedure on the corresponding uplink BWP.

[0115] In some embodiments, when the number of times a random access preamble is transmitted on the uplink BWP is greater than N+1 (i.e., after multiple failed RACH procedures), a random access problem is reported to an upper layer, such as the RRC layer. Upon receiving it, the upper layer triggers a radio link failure (RLF) and executes an RRC reconstruction procedure. To reduce access latency, UE 104 may trigger the RACH procedure at least once more before indicating a random access problem to the upper layer to trigger an RRC reconstruction procedure.

[0116] In some embodiments, BWPs can be divided into different groups with different priorities. For example, a cell may include six uplink BWPs (i.e., BWP1 to BWP6) that can be configured for UE 104. Uplink BWPs BWP1, BWP2, and BWP3 are in group 1, while group 2 includes uplink BWPs BWP4, BWP5, and BWP6. In some embodiments, group 1 may have a higher priority than group 2. When RACH is triggered, UE 104 can initiate a RACH procedure on all uplink carriers in group 1. When all RACH procedures on all carriers in group 1 fail, i.e., the preamble transmission time exceeds the maximum number of random access preambles that can be transmitted, UE 104 can then initiate a RACH procedure on all uplink carriers in group 2.

[0117] It should be noted that Figure 6 This is an example for illustrative and discussion purposes. All RACH procedures (i.e., operations 602 and 604 on each of the uplink / downlink BWPs) are operated independently, and any type of relative timing for each operation on each of the uplink or downlink BWPs is within the scope of this invention. For example, the transmission of a random access response / contention resolution from BS 102 to UE 104 on BWP4508 in operation 604 may occur before the transmission of the random access preamble from UE 104 to BS 102 on uplink BWP3 in operation 602 and the transmission of the scheduled data.

[0118] Figure 7 A method 700 for performing multiple two-step contention-free RACH procedures on multiple bandwidth portions is illustrated according to some embodiments of the present disclosure. In the illustrated embodiment, there are three uplink bandwidth portions (i.e., BWP1 502, BWP2 504, and BWP3 506) and three downlink BWPs (i.e., BWP4 508, BWP5 510, and BWP6 512), which are configured to UE 104 via system information or Radio Resource Control (RRC) messages. Uplink BWP1 502, BWP2 504, and BWP3 506 correspond to downlink BWP4 508, BWP 510, and BWP 512, respectively. Furthermore, RACH configurations (e.g., random access preamble format, transmission timing, and PRACH index) corresponding to each uplink carrier are configured to UE 104 via system information or RRC messages. Although only three uplink BWPs and three downlink BWPs are shown, any desired number of uplink and downlink carriers may be included in the system while remaining within the scope of this disclosure.

[0119] Method 600 begins with operation 602, in which UE 104 transmits a random access preamble to BS 102 for each of three uplink BWPs (i.e., BWP1 502, BWP2 504, and BWP3 506) according to some embodiments. In some embodiments, the random access preamble for the uplink BWP is dedicated to BS 102. In some embodiments, UE 104 selects at least one SS (synchronization signal) block for transmitting the random access preamble on the uplink BWP. The at least one SS block is selected from a plurality of SS blocks received by UE 104 from BS 102 on the corresponding downlink BWP based on its SS-RSRP (synchronization signal-reference signal received power) value. If the SS-RSRP value of an SS block is greater than a predefined threshold, the SS block is selected. In some embodiments, UE 104 may select at least one CSI-RS (channel state information-reference signal) for transmitting the random access preamble on the uplink BWP. At least one CSI-RS is selected from multiple CSI-RS received by UE 104 from BS 102 on the corresponding downlink BWP based on its CSI-RSRP value. If the CSI-RSRP of a CSI-RS is greater than a predefined threshold, then the CSI-RS is selected. UE 104 also selects at least one PRACH (Physical Random Access Channel) timing (i.e., frequency resource) based on the mapping relationship between PRACH timing and the SS block or CSI-RS received in the system information.

[0120] Then, UE 104 configures itself to select a random access preamble for each of the corresponding uplink BWPs based on the received RACH. Before sending the random access preamble to BS 102, UE 104 performs an LBT procedure on each of the uplink carriers. In some embodiments, the LBT procedure includes: sensing burst arrivals and interference of packets through its transmitter to determine the traffic load and interference level on the uplink carrier. If the LBT procedure fails, UE 104 restarts the LBT procedure at the subsequent PRACH timing on the corresponding uplink BWP until the LBT procedure succeeds (i.e., the uplink BWP is available and not occupied).

[0121] Then, UE 104 initiates the first transmission of the random access preamble to BS 102 on the PRACH timing and the corresponding uplink BWP. In some embodiments, the aforementioned process is performed separately and independently on each of the three uplink BWPs, including determining the SS block, determining the CSI-RS, performing the LBT procedure, and transmitting the random access preamble on the PRACH timing. Although it is shown that the transmission of the random access preamble on the first uplink BWP1 502 is initiated before the transmission on the second BWP2 504 and the third BWP3 506, the start timing of transmitting the random access preamble on the corresponding uplink BWP depends on the PRACH timing of the corresponding uplink carrier and any delays in their corresponding LBT procedures. Figure 7 The relative timings shown are examples and are not intended to be limiting. It should be noted that any relative timing between each transmission in each operation on the uplink BWP is within the scope of this disclosure.

[0122] After a fixed duration of m symbols following the end of the first transmission of the random access preamble, UE 104 starts a re-ResponseWindow timer at the beginning of the PDCCH (Physical Downlink Control Channel) timing on each of the corresponding uplink carriers, where m is a non-negative integer. In some embodiments, for each of the three uplink BWPs, there is an independent re-ResponseWindow timer, which can be started and restarted separately and independently.

[0123] In some embodiments, to ensure the reliability of the uplink BWP when it is determined that the uplink BWP is not occupied after the LBT procedure, UE 104 transmits a random access preamble with a preamble power having a Ra-offset value, which is determined by the following:

[0124] PREAMBLE_RECEIVED_TARGET_POWER = ra - PreambleInitialReceivedTargetPower + DELTA_PREAMBLE + (PREAMBLE_POWER_RAMPING_COUNTER – 1) * powerRampingStep + Ra-offset, where ra - PreambleInitialReceivedTargetPower is the initial preamble power, DELTA_PREAMBLE is the offset based on the preamble format, PREAMBLE_POWER_RAMPING_COUNTER is a preamble transmission counter that increments by 1 each time the preamble is transmitted, powerRampingStep is the power ramp factor, and Ra-offset is a non-negative value configured by system information and included in the RACH configuration information. In some embodiments, the Ra-offset value can be 1 dB, 2 dB, 3 dB, and 4 dB, and other Ra-offset values ​​may be included and are within the scope of this invention.

[0125] According to some embodiments, method 700 continues to operation 704, wherein BS 102 generates and transmits a random access response on a downlink BWP, which corresponds to three uplink BWPs on which a random access preamble has been received. In some embodiments, BS 102 performs an LBT procedure on the corresponding downlink BWP to determine availability. BS 102 also calculates a RA-RNTI (Random Access-Radio Temporary Identifier) ​​value based on the time and frequency resources on which the random access preamble has been transmitted. In some embodiments, there is one RA-RNTI value for each corresponding uplink carrier, which may be determined by:

[0126] RA-RNTI = 1 + s_id + 14*t_id + 14*X*f_id + 14*X*Y*ul_carrier_id + Z*BWP index, where s_id is the index of the first OFDM symbol of the PRACH occasion (0 ≤ s_id < 14), t_id is the index of the first slot of the PRACH occasion in the system frame (0 ≤ t_id < X), and f_id is the index of the PRACH occasion in the frequency domain (0 ≤ f_id < Y). The values of X and Y are 80 and 8 respectively. In some embodiments, Z is equal to 1. In some embodiments, Z is equal to 14*X*Y. In some embodiments, ul-carrier_id is the index of the uplink carrier where the uplink BWP is located, and the BWP index is the BWP index of the uplink BWP in the corresponding uplink carrier for random access preamble transmission. For example, there may be 3 uplink carriers, and each of them includes 3 uplink BWPs. In some embodiments, for the first uplink carrier, ul_carrier_id = 0; for the second uplink carrier, ul_carrier_id = 1; and for the third uplink carrier, ul_carrier_id = 2. In each of the uplink carriers, for the first uplink BWP, the second uplink BWP, and the third uplink BWP (e.g., BWP1 502, BWP2 504, and BWP3 506) of the corresponding uplink carrier, the BWP index = 0, 1, and 2.

[0127] BS 102 sends a random access response to UE 104 until the LBT process passes (i.e., the downlink BWP is available and not occupied). In some embodiments, the random access response includes a PDCCH (Physical Downlink Control Channel) scrambled with the corresponding RA-RNTI value. In some embodiments, the random access response is sent on the downlink BWP corresponding to the uplink BWP on which the random access preamble is received. Specifically, in response to the random access preamble received on the first uplink BWP1502, BS 102 sends a first random access response to UE 104 on the first downlink BWP4 508; in response to the random access preamble received on the second uplink BWP2 504, a second random access response is sent to UE 104 on the second downlink BWP5 510; and in response to the random access preamble received on the third uplink BWP3 506, a third random access response is sent on the third downlink BWP6 512. In some embodiments, although it is the uplink BWP on which the random access preamble is obtained, BS 102 also sends a random access response to UE 104 on one of the downlink BWPs.

[0128] In some embodiments, when a random access response is received from BS102 on a downlink BWP within the corresponding ra-ResponseWindow timer, UE104 can distinguish the random access response and its corresponding random access preamble based on the RA-RNTI value in the random access response received from BS102. UE104 also determines whether each random access response includes a random access preamble identifier that matches the index (PREAMBLE_INDEX) of the random access preamble generated in operation 702. If the random access preamble identifier in the random access response received from BS102 on that downlink BWP matches PREAMBLE_INDEX, UE104 terminates the ra-ResponseWindow timer of the corresponding uplink BWP, and simultaneously, subsequently terminates other ongoing RACH procedures on other uplink BWPs. If UE 104 cannot detect the random access preamble identifier in the random access response received from BS 102 on the downlink BWP that matches the PREAMBLE_INDEX generated in operation 702 before the ra-ResponseWindow timer expires, this causes the RACH procedure on the uplink BWP to fail. In some embodiments, UE 104 then determines the number of times to send the random access preamble on the uplink BWP. If the number of times the random access preamble is sent on the uplink BWP is less than N+1, where N is a predefined maximum number of random access preambles that can be sent on the uplink BWP, UE 104 continues with operation 702 and restarts the RACH procedure again on the corresponding uplink BWP.

[0129] In some embodiments, when the number of times a random access preamble is transmitted on the uplink BWP is greater than N+1 (i.e., after multiple failed RACH procedures), a random access problem is reported to an upper layer, such as the RRC layer. Upon receiving it, the upper layer triggers a radio link failure (RLF) and executes an RRC reconstruction procedure. To reduce access latency, UE 104 may trigger the RACH procedure at least once more before indicating a random access problem to the upper layer to trigger an RRC reconstruction procedure.

[0130] In some embodiments, BWPs can be divided into different groups with different priorities. For example, a cell may include six uplink BWPs (i.e., BWP1 to BWP6) that can be configured for UE 104. Uplink BWPs BWP1, BWP2, and BWP3 are in group 1, while group 2 includes uplink BWPs BWP4, BWP5, and BWP6. In some embodiments, group 1 may have a higher priority than group 2. When RACH is triggered, UE 104 can initiate a RACH procedure on all uplink carriers in group 1. When all RACH procedures on all carriers in group 1 fail, i.e., the preamble transmission time exceeds the maximum number of random access preambles that can be transmitted, UE 104 can then initiate a RACH procedure on all uplink carriers in group 2.

[0131] It should be noted that Figure 7 These are examples for illustrative and discussion purposes. All RACH procedures (i.e., operations 702 and 704 on each of the uplink / downlink BWPs) are operated independently, and any type of relative timing for each operation on each of the uplink or downlink BWPs is within the scope of this invention. For example, the transmission of a random access response from BS 102 to UE 104 on downlink BWP4 508 in operation 704 may occur before the transmission of a random access preamble from UE 104 to BS 102 on uplink BWP3 506 in operation 702.

[0132] Although various embodiments of the invention have been described above, it should be understood that they are presented by way of example only and not by way of limitation. Similarly, various figures may depict exemplary architectures or configurations, provided to enable those skilled in the art to understand the exemplary features and functionality of the invention. However, those skilled in the art will understand that the invention is not limited to the exemplary architectures or configurations shown, but can be implemented using a variety of alternative architectures and configurations. Furthermore, as those skilled in the art will understand, one or more features of one embodiment may be combined with one or more features of another embodiment described herein. Therefore, the breadth and scope of this disclosure should not be limited to any of the exemplary embodiments described above.

[0133] It should also be understood that any reference to elements in this document using names such as "first," "second," etc., generally does not restrict the number or order of those elements. Rather, these names serve as a convenient means of distinguishing two or more elements or instances of elements. Therefore, a reference to the first element and the second element does not imply that only two elements can be used, or that the first element must somehow precede the second element.

[0134] Furthermore, those skilled in the art will understand that information and signals can be represented using any of a variety of different technologies and processes. For example, data, instructions, commands, information, signals, bits, and symbols referenced in the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

[0135] Those skilled in the art will further understand that any of the illustrative logic blocks, modules, processors, devices, circuits, methods, and functions described in connection with the aspects disclosed herein can be implemented by electronic hardware (e.g., a digital implementation, analog implementation, or a combination of both, designed using source code encoding or some other technique), various forms of program or design code incorporating instructions (which, for convenience, may be referred to herein as "software" or "software module"), or a combination of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally according to their functionality. Whether such functionality is implemented as hardware, firmware, or software, or a combination of these techniques, depends on the specific application and the design constraints imposed on the system as a whole. Those skilled in the art can implement the described functionality in various ways for each specific application, but such implementation decisions should not be construed as departing from the scope of this disclosure.

[0136] Furthermore, those skilled in the art will understand that the various illustrative logic blocks, modules, devices, components, and circuits described herein may be implemented within or executed by integrated circuits (ICs), including general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, or any combination thereof. Logic blocks, modules, and circuits may further include antennas and / or transceivers for communication with various components within a network or 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, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other suitable configuration to perform the functions described herein.

[0137] If implemented as software, the functionality can be stored as one or more instructions or code on a computer-readable medium. Therefore, the steps of the methods or algorithms disclosed herein can be implemented as software stored on a computer-readable medium. Computer-readable media include computer storage media and communication media, with communication media including any medium that enables the transfer of computer programs or code from one place to another. Storage media can be any available medium that is accessible to a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and is accessible to a computer.

[0138] In this document, the term "module" as used herein refers to software, firmware, hardware, and any combination of such elements for performing the related functions described herein. Furthermore, for the purposes of discussion, various modules are described as discrete modules; however, it will be apparent to those skilled in the art that two or more modules can be combined to form a single module that performs the associated functions according to embodiments of the invention.

[0139] Additionally, in embodiments of the present invention, memory or other memory and communication components may be employed. It should be understood that, for clarity, embodiments of the present invention have been described above with reference to different functional units and processors. However, it will be apparent that any suitable functional distribution among different functional units, processing logic elements, or domains may be used without departing from the present invention. For example, functions shown to be performed by a separate processing logic element or controller may be performed by the same processing logic element or controller. Therefore, references to specific functional units are merely references to suitable means for providing the described functions and not indications of a strict logical or physical structure or organization.

[0140] Various modifications to the embodiments described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the embodiments shown herein, but is to be endowed with the broadest scope consistent with the novel features and principles disclosed herein, as set forth in the following claims.

Claims

1. A wireless communication method, comprising: The wireless communication device determines that the first random access response (RAR) window has expired; The wireless communication device selects a second RAR window from a plurality of candidate RAR windows, wherein the second RAR window is expanded relative to the first RAR window, and the plurality of candidate RAR windows are configured as elements in a matrix. as well as The wireless communication device detects the RAR from the wireless communication node during the second RAR window.

2. The method according to claim 1, wherein, The second RAR window is longer than the first RAR window.

3. The method according to claim 1, further comprising: The wireless communication device applies the second RAR window to the Random Access Channel (RACH) procedure in an attempt to prevent the RACH procedure from failing.

4. The method according to claim 1, wherein, Each of the multiple candidate RAR windows corresponds to its respective number of time slots.

5. The method according to claim 1, further comprising: The RAR is received by the wireless communication device from the wireless communication node, wherein the RAR contains at least one parameter for time slot aggregation.

6. The method according to claim 5, wherein, At least one parameter used for time slot aggregation indicates a repetition value for scheduling transmissions.

7. The method according to claim 6, wherein, The at least one parameter is included in the uplink grant of the RAR.

8. The method according to claim 6, wherein, The repetition value is the number of times the transmission is repeated.

9. The method according to claim 6, wherein, The at least one parameter also indicates the repeating sequence used for the transmission.

10. A wireless communication device, comprising: At least one processor, said at least one processor being configured to: The first random access response RAR window has expired; A second RAR window is selected from a plurality of candidate RAR windows, wherein the second RAR window is expanded relative to the first RAR window, and the plurality of candidate RAR windows are configured as elements in a matrix; as well as Detect RAR from the wireless communication node during the second RAR window.

11. The wireless communication device according to claim 10, wherein, The second RAR window is longer than the first RAR window.

12. The wireless communication device according to claim 10, wherein, The at least one processor is further configured to: The second RAR window is applied to the Random Access Channel (RACH) procedure in an attempt to prevent the RACH procedure from failing.

13. The wireless communication device according to claim 10, wherein, Each of the multiple candidate RAR windows corresponds to its respective number of time slots.

14. The wireless communication device according to claim 10, wherein, The at least one processor is further configured to: The RAR is received from the wireless communication node via a receiver, wherein the RAR includes at least one parameter for time slot aggregation.

15. The wireless communication device according to claim 14, wherein, The at least one parameter indicates a repeating value used for scheduling transmissions.

16. The wireless communication device according to claim 15, wherein, The at least one parameter is included in the uplink grant of the RAR.

17. The wireless communication device according to claim 15, wherein, The repetition value is the number of times the transmission is repeated.

18. The wireless communication device according to claim 15, wherein, The at least one parameter also indicates the repeating sequence used for the transmission.

19. A non-transitory computer-readable medium having stored thereon computer-executable instructions for performing the method of any one of claims 1 to 9.

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