System and method for enhanced random access procedure

Abstract

Systems and methods for an enhanced random access procedure are provided. A wireless communication device may receive information indicating a value from a wireless communication node. The wireless communication device may compare a randomly generated value with the value. The wireless communication device may select a four-step random access procedure or a two-step random access procedure to access the wireless communication node based on the comparison. The wireless communication device may send a first message to access the wireless communication node, wherein the content of the first message is based on the selection of the four-step random access procedure or the two-step random access procedure.

Description

[0001] This application is a divisional application of a Chinese patent application with the application number "201980095874.0", the application date of "April 30, 2019", and the title of "System and Method for Enhanced Random Access Procedure". Technical Field

[0002] The present disclosure generally relates to wireless communication, and more particularly, to systems and methods for enhanced random access procedures. Background Art

[0003] In a fifth-generation (5G) new radio (NR) mobile network, before a user equipment (UE) transmits data to a base station (BS), the UE and the BS need to obtain uplink synchronization and downlink synchronization. Uplink timing synchronization can be achieved by performing a random access procedure. To meet faster and more efficient communication requirements, the random access procedure will be enhanced. Summary of the Invention

[0004] The exemplary embodiments disclosed herein are intended to solve problems related to one or more existing problems and to provide additional features that will become apparent when the following detailed description is read in conjunction with the accompanying drawings. According to various embodiments, exemplary systems, methods, devices, and computer program products are disclosed herein. However, it should be understood that these embodiments are given by way of example and not limitation, and it will be apparent to those of ordinary skill in the art who have read the present disclosure that various modifications can be made to the disclosed embodiments while remaining within the scope of the present disclosure.

[0005] In one embodiment, a method performed by a wireless communication device includes: receiving information indicating a value from a wireless communication node; comparing a randomly generated value with the value; selecting a four-step random access procedure or a two-step random access procedure to access the wireless communication node based on the comparison; and sending a first message to access the wireless communication node, wherein the content of the first message is based on the selection of the four-step random access procedure or the two-step random access procedure.

[0006] In another embodiment, a device includes a processor configured to implement the method. The method includes: receiving, by a wireless communication device, information indicating a value from a wireless communication node; comparing, by the wireless communication device, a randomly generated value with the value; selecting, by the wireless communication device, a four-step random access procedure or a two-step random access procedure to access the wireless communication node based on the comparison; and sending, by the wireless communication device, a first message to access the wireless communication node, wherein the content of the first message is based on the selection of the four-step random access procedure or the two-step random access procedure.

[0007] In yet another embodiment, a computer-readable medium storing code thereon, the code when executed by a processor causes the processor to implement a method. The method includes: receiving, by a wireless communication device, information indicating a value from a wireless communication node; comparing, by the wireless communication device, a randomly generated value with the value; selecting, by the wireless communication device, a four-step random access procedure or a two-step random access procedure to access the wireless communication node based on the comparison; and sending, by the wireless communication device, a first message to access the wireless communication node, wherein the content of the first message is based on the selection of the four-step random access procedure or the two-step random access procedure.

[0008] In one embodiment, a method performed by a wireless communication device includes: receiving, from a wireless communication node, information indicating a plurality of values, the plurality of values respectively corresponding to a plurality of parameters; selecting one of the plurality of parameters; comparing, by the wireless communication device, a randomly generated value with one of the plurality of values, the value being selected from the plurality of values according to a selected access control parameter; selecting, based on the comparison, a four-step random access procedure or a second two-step random access procedure to access the wireless communication node; and sending a first message to access the wireless communication node, wherein the content of the first message is based on the selection of the four-step random access procedure or the above two-step random access procedure.

[0009] In another embodiment, an apparatus includes a processor configured to implement a method. The method includes: receiving, by a wireless communication device, information indicating a plurality of values, the plurality of values respectively corresponding to a plurality of parameters; selecting, by the wireless communication device, one of the plurality of parameters; comparing, by the wireless communication device, a randomly generated value with one of the plurality of values, the value being selected from the plurality of values according to a selected access control parameter; selecting, by the wireless communication device, a four-step random access procedure or a second two-step random access procedure to access the wireless communication node based on the comparison; and sending, by the wireless communication device, a first message to access the wireless communication node, wherein the content of the first message is based on the selection of the four-step random access procedure or the two-step random access procedure.

[0010] In yet another embodiment, a computer-readable medium having code stored thereon, the code when executed by a processor causes the processor to implement a method. The method includes: receiving, by a wireless communication device, information indicating a plurality of values from a wireless communication node, the plurality of values respectively corresponding to a plurality of parameters; selecting, by the wireless communication device, one of the plurality of parameters; comparing, by the wireless communication device, a randomly generated value with one of the plurality of values, the value being selected from the plurality of values according to a selected access control parameter; selecting, by the wireless communication device, a four-step random access procedure or a second two-step random access procedure to access the wireless communication node based on the comparison; and sending, by the wireless communication device, a first message to access the wireless communication node, wherein the content of the first message is based on the selection of the four-step random access procedure or the two-step random access procedure.

[0011] In one embodiment, a method performed by a wireless communication device includes: receiving information indicating a timer from a wireless communication node; in response to determining that the timer is active, selecting a four-step random access procedure to access the wireless communication node; in response to determining that the timer is inactive, selecting the four-step random access procedure or the two-step random access procedure to access the wireless communication node; and sending a first message to access the wireless communication node, wherein the content of the first message is based on the selection of the four-step random access procedure or the two-step random access procedure.

[0012] In another embodiment, an apparatus includes a processor configured to implement a method. The method includes: receiving, by a wireless communication device, information indicating a timer from a wireless communication node; in response to determining that the timer is active, selecting a four-step random access procedure to access the wireless communication node by the wireless communication device; in response to determining that the timer is inactive, selecting the four-step random access procedure or the two-step random access procedure to access the wireless communication node by the wireless communication device; and sending, by the wireless communication device, a first message to access the wireless communication node, wherein the content of the first message is based on the selection of the four-step random access procedure or the two-step random access procedure.

[0013] In yet another embodiment, a computer-readable medium storing code thereon, the code causing a processor to implement a method when executed by the processor. The method includes: receiving, via a wireless communication device, information indicating a timer from a wireless communication node; selecting, via the wireless communication device, a four-step random access procedure to access the wireless communication node in response to determining that the timer is active; selecting, via the wireless communication device, the four-step random access procedure or the two-step random access procedure to access the wireless communication node in response to determining that the timer is inactive; and sending, via the wireless communication device, a first message to access the wireless communication node, wherein the content of the first message is based on the selection of the four-step random access procedure or the two-step random access procedure.

[0014] In one embodiment, a method performed by a wireless communication device includes: sending a first message to access a wireless communication node, wherein the content of the first message is based on a selection of a four-step random access procedure or a two-step random access procedure; receiving, in response to sending the first message, a second message from the wireless communication node indicating a first timer; and selecting, in response to determining that the timer is inactive, the four-step random access procedure or the two-step random access procedure to retransmit the first message.

[0015] In another embodiment, an apparatus includes a processor configured to implement a method. The method includes: sending, via a wireless communication device, a first message to access a wireless communication node, wherein the content of the first message is based on a selection of a four-step random access procedure or a two-step random access procedure; receiving, via the wireless communication device, in response to sending the first message, a second message from the wireless communication node indicating a first timer; and selecting, via the wireless communication device, the four-step random access procedure or the two-step random access procedure to retransmit the first message in response to determining that the timer is inactive.

[0016] In yet another embodiment, a computer-readable medium storing code thereon, the code causing a processor to implement a method when executed by the processor. The method includes: sending, via a wireless communication device, a first message to access a wireless communication node, wherein the content of the first message is based on a selection of a four-step random access procedure or a two-step random access procedure; receiving, via the wireless communication device, in response to sending the first message, a second message from the wireless communication node indicating a first timer; and selecting, via the wireless communication device, the four-step random access procedure or the two-step random access procedure to retransmit the first message in response to determining that the timer is in an inactive state.

[0017] The above and other aspects and their embodiments are described in more detail in the drawings, the description, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The various preferred embodiments of the present solution will be described in detail below with reference to the accompanying drawings. The accompanying drawings are provided for illustrative purposes only and depict exemplary embodiments of the present solution to facilitate the reader's understanding of the present solution. Therefore, the accompanying drawings should not be regarded as limiting the breadth, scope, or applicability of the present solution. It should be noted that these drawings are not necessarily drawn to scale for clarity and ease of illustration.

[0019] Figure 1 An example cellular communication network according to an embodiment of the present disclosure is shown, in which the techniques and other aspects disclosed herein can be implemented.

[0020] Figure 2 A block diagram of an example base station and an example user equipment device according to some embodiments of the present disclosure is shown.

[0021] Figure 3 An exemplary four-step random access procedure according to some embodiments of the present disclosure is shown.

[0022] Figure 4 An exemplary two-step random access procedure according to some embodiments of the present disclosure is shown.

[0023] Figure 5 is a flowchart showing an exemplary procedure of an enhanced random access procedure for using a RACH type selection factor according to some embodiments of the present disclosure.

[0024] Figure 6 is a flowchart showing another exemplary procedure of an enhanced random access procedure for using a RACH type selection factor according to some embodiments of the present disclosure.

[0025] Figure 7 is a flowchart showing an exemplary procedure of an enhanced random access procedure for using a RACH type selection timer according to some embodiments of the present disclosure.

[0026] Figure 8 is a flowchart showing an exemplary procedure of an enhanced random access procedure for having a fallback indicator according to some embodiments of the present disclosure. Detailed implementation manners

[0027] The following describes various exemplary embodiments of the present solution in conjunction with the accompanying drawings, so that those of ordinary skill in the art can implement and use the present solution. It will be apparent to those of ordinary skill in the art that various changes or modifications can be made to the examples described herein without departing from the scope of the present solution after reading this disclosure. Therefore, the present solution is not limited to the exemplary embodiments and applications described and illustrated herein. Additionally, the specific order or hierarchy of steps in the methods of the present solution herein is merely an exemplary method. Based on design preferences, the specific order or hierarchy of steps of the disclosed method or process can be rearranged while remaining within the scope of the present solution. Thus, those of ordinary skill in the art will understand that the methods and techniques disclosed herein present various steps or actions in an exemplary order, and the present solution is not limited to the specific order or hierarchy presented unless otherwise expressly stated.

[0028] A. Network Environment and Computing Environment

[0029] Figure 1 An exemplary wireless communication network and / or system 100 in accordance with an embodiment of the present disclosure is shown, in which the techniques disclosed herein may be implemented. In the following discussion, the wireless communication network 100 may be any wireless network, such as a cellular network or a NarrowBand Internet of Things (NB-IoT) network, and is referred to herein as "Network 100". Such an exemplary communication network 100 includes base stations 102 (hereinafter referred to as "BS 102") and user equipment 104 (hereinafter referred to as "UE 104") capable of communicating with each other via communication links 110 (e.g., wireless communication channels), and a set of cells 126, 130, 132, 134, 136, 138, and 140 that cover a geographical area 101. In Figure 1 which, the BS 102 and the UE 104 are contained within the geographical boundaries of the corresponding cell 126. Each of the other cells 130, 132, 134, 136, 138, and 140 may include at least one base station operating at its allocated bandwidth to provide sufficient wireless coverage to its intended users.

[0030] For example, BS 102 can operate on an allocated channel transmission bandwidth to provide sufficient coverage to UE 104. BS 102 and UE 104 can communicate via a downlink radio frame 118 and an uplink radio frame 124 respectively. Each radio frame 118 / 124 can be further divided into subframes 120 / 127 that can include data symbols 122 / 128. In the present disclosure, BS 102 and UE 104 are described herein as non-limiting examples of a general "communication node" (or "wireless communication node") and a "communication device" (or "wireless communication device") respectively, which can implement the methods disclosed herein. According to various embodiments of the present solution, such communication nodes and devices are capable of wireless and / or wired communication.

[0031] Figure 2 A block diagram of an exemplary wireless communication system 200 for transmitting and receiving wireless communication signals (such as OFDM / OFDMA signals) according to some embodiments of the present solution is illustrated. System 200 may include components and elements configured to support known or conventional operating features that need not be described in detail herein. In one illustrative embodiment, as described above, System 200 can be used to transmit (e.g., send and receive) data symbols in a wireless communication environment such as Figure 1 a wireless communication environment 100.

[0032] System 200 generally includes a base station 202 (hereinafter referred to as "BS 202") and a user equipment 204 (hereinafter referred to as "UE 204"). BS 202 includes a BS (base station) transceiver module 210, a BS antenna 212, a BS processor module 214, a BS memory module 216, and a network communication module 218, each of which is coupled and interconnected to each other via a data communication bus 220 as needed. UE 204 includes a UE (user equipment) transceiver module 230, a UE antenna 232, a UE memory module 234, and a UE processor module 236, each of which is coupled and interconnected to each other via a data communication bus 240 as needed. BS 202 communicates with UE 204 via a communication channel 250, which can be any wireless channel or other medium known in the art suitable for data transmission, as described herein.

[0033] As will be understood by those of ordinary skill in the art, System 200 may also include in addition to Figure 2Any number of modules outside the module shown. Those skilled in the art will understand that the various illustrative blocks, modules, circuits, and processing logics described in connection 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 generally described in terms of their functionality. Implementing this functionality as hardware, firmware, or software depends on the particular application and the design constraints imposed on the overall system. Those skilled in the art familiar with the concepts described herein can implement this functionality in a suitable manner for each particular application, but such implementation decisions should not be construed as limiting the scope of the present disclosure.

[0034] According to some embodiments, the UE transceiver 230 may be referred to herein as an “uplink” transceiver 230, which includes a radio frequency (RF) transmitter and an RF receiver, each including circuitry coupled to an antenna 232. A duplex switch (not shown) may alternatively couple the uplink transmitter or receiver to the uplink antenna in a time-division duplex manner. Similarly, according to some embodiments, the BS transceiver 210 may be referred to herein as a “downlink” transceiver 210, which includes an RF transmitter and an RF receiver, each including circuitry coupled to an antenna 212. A downlink duplex switch may alternatively couple the downlink transmitter or receiver to the downlink antenna 212 in a time-division duplex manner. The operations of the two transceiver modules 210 and 230 can be coordinated in time such that the uplink receiver circuitry is coupled to the uplink antenna 232 to receive transmissions via the wireless transmission link 250 while the downlink transmitter is coupled to the downlink antenna 212. In some embodiments, there is a tight time synchronization with a minimum guard time between changes in the duplex direction.

[0035] The UE transceiver 230 and the base station transceiver 210 are configured to communicate via a wireless data communication link 250 and cooperate with appropriately configured RF antenna devices 212 / 232 that can support a particular wireless communication protocol and modulation scheme. In some exemplary embodiments, the UE transceiver 210 and the base station transceiver 210 are configured to support industry standards such as Long-Term Evolution (LTE) and emerging 5G standards. However, it should be understood that the present disclosure need not be limited in application to a particular standard and related protocol. Instead, the UE transceiver 230 and the base station transceiver 210 can be configured to support alternative or additional wireless data communication protocols, including future standards or variants thereof.

[0036] According to various embodiments, the BS 202 can be, for example, a next-generation node B (gNodeB or gNB), an evolved node B (eNB), a serving eNB, a target eNB, a femto station, a pico station, or a transmit receive point (TRP). In some embodiments, the UE 204 can be embodied in various types of user equipment, such as a mobile phone, a smart phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, a wearable computing device, etc. The processor modules 214 and 236 can be implemented or realized using a general-purpose processor, a content addressable memory, a digital signal processor, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. In this way, the processor can be implemented as a microprocessor, a controller, a microcontroller, a 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, a combination of multiple microprocessors, the combination of one or more microprocessors and a digital signal processor core, or any other such configuration.

[0037] In addition, the steps of the processes, methods, or algorithms described in connection with the embodiments disclosed herein can be directly embodied in hardware, firmware, software modules executed respectively by the processor modules 214 and 236, or in any practical combination thereof. The memory modules 216 and 234 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, the memory modules 216 and 234 can be coupled respectively to the processor modules 214 and 236 such that the processor modules 214 and 236 can read information from and write information to the memory modules 216 and 234 respectively. The memory modules 216 and 234 can also be integrated into their respective processor modules 214 and 236. In some embodiments, the storage modules 216 and 234 can each include a cache memory for storing temporary variables or other intermediate information during the execution of instructions executed respectively by the processor modules 214 and 236. The memory modules 216 and 234 can also each include non-volatile memory for storing the instructions to be executed respectively by the processor modules 214 and 236.

[0038] The network communication interface 218 generally represents the hardware, software, firmware, processing logic, and / or other components of the base station 202, which enables two-way communication between the base station transceiver module 210 and other network components and communication nodes configured to communicate with the base station 202. For example, the network communication interface 218 can be configured to support Internet or WiMAX services. In a typical deployment without limitation, the network communication interface 218 provides an 802.3 Ethernet interface, enabling the base station transceiver 210 to communicate with a conventional Ethernet-based computer network. In this way, the network communication interface 218 can include a physical interface for connecting to a computer network (e.g., a mobile switching center (MSC)). As used herein, the terms "configured to" or "configured for" with respect to a particular operation or function, and their combinations, refer to a device, component, circuit, structure, machine, signal, etc. that is physically constructed, programmed, and / or formatted to perform the specified operation or function.

[0039] B. Exemplary Random Access Procedure

[0040] Figure 3 An exemplary four-step random access procedure 300 according to some embodiments of the present disclosure is shown. Referring Figure 3 , a four-step random access procedure (RACH) 300 is performed between the BS 302 (e.g., gNB) and the UE 304. The BS 302 and the UE 304 can be the same as or similar to the BS 202 and the UE 204 in Figure 2 . In some embodiments, in step 1 (306), the UE 304 sends a random access channel (RACH) preamble or a physical random access channel (PRACH) preamble 302 to the BS in message 1 (Msg1) via the uplink random access channel (RACH). In step 2 (308), once the preamble is successfully received by the BS 302, the BS 302 sends message 2 (Msg2) back to the UE 304, where the media access control (MAC) random access response (RAR) can be a response to the preamble. In step 3 (310), once the UE 304 receives the MAC RAR with the corresponding random access preamble (RAP) identifier (ID), the UE 304 sends message 3 (Msg3) to the BS 302 and carries the grant in the MAC RAR. In step 4 (312), once the BS 302 receives Msg3, the BS 302 sends message 4 (Msg4) back to the UE 304, where the contention resolution ID can be included for the purpose of contention resolution. In some embodiments, to reduce latency and accelerate the initial access process, a two-step random access procedure can be used, as described below with respect to Figure 4 .

[0041] Figure 4FIG. 0 illustrates an exemplary two-step random access procedure 400 according to some embodiments of the present disclosure. In some embodiments, the two-step random access procedure (RACH) 400 can be completed in two messages or two steps Figure 3 out of the four steps in. In some embodiments, at least some of the content of Msg1 and Msg3 in the four-step RACH is included in Msg1 of the two-step RACH, and at least some of the content of Msg2 and Msg4 (RAR and contention resolution) in the four-step RACH is included in Msg2 of the two-step RACH. Refer to Figure 4 , a two-step random access procedure 400 is performed between a BS 402 (e.g., a gNB) and a UE 404. The BS 402 and the UE 404 can be the same as or similar to the Figure 2 BS 202 and the UE 204 in. In some embodiments, at step 1 (406), the UE 404 sends a Msg1 including a preamble and a data payload to the BS 402 to access the BS 402. In some embodiments, the payload can be optional. In some embodiments, the preamble can be optional. At step 2 (408), the BS 402 sends a Msg2 to the UE 404 as a response to Msg1. Details of the two-step random access procedure are described below.

[0042] C. Random Access (RA) Type Selection between Two-Step RACH and Four-Step RACH

[0043] In some embodiments, when both a two-step RA configuration and a four-step RA configuration are broadcast in system information (e.g., system information block type 1 (SIB1)), RA type selection is performed, e.g., between a two-step random access procedure (two-step RACH) and a four-step random access procedure (four-step RACH). For example, in some embodiments, RA type selection can be performed for step 1 of the two-step random access procedure.

[0044] In some embodiments, the following alternatives or options can be considered or implemented in the RA type selection between two-step RACH and four-step RACH. These alternatives or options can be performed individually or in combination. Briefly, a solution based on a "RACH type selection factor" can be considered or implemented in a first alternative (ALT 1), a solution based on a "RACH type selection timer" can be considered or implemented in a second alternative (ALT 2), and a solution based on a fallback indicator can be considered or implemented in a third alternative (ALT 3), as described in more detail below.

[0045] ALT 1: Solution based on "RACH type selection factor"

[0046] In some embodiments, as the RACH type selection factor is configured, or when the RACH type selection factor is configured, or in response to the RACH type selection factor being configured, or after the RACH type selection factor is configured, or when the RACH type selection factor is configured (described in more detail below), a UE (e.g., UE 404) may draw, obtain, or determine a random number or randomly generated number "rand", e.g., in the range 0 ≤ rand < 1. In other embodiments, "rand" may be in other ranges. In some embodiments, "rand" may be randomly generated by the UE or another device. In some embodiments, the UE may compare "rand" with the value indicated by the RACH type selection factor. If "rand" is less than (or less than or equal to, or greater than, or greater than or equal to) the value indicated by the RACH type selection factor, the UE is allowed to select a two-step RACH. Otherwise, the UE selects a four-step RACH.

[0047] In some embodiments, as the RACH type selection factor is configured, or when the RACH type selection factor is configured, or in response to the RACH type selection factor being configured, or after the RACH type selection factor is configured, or when the RACH type selection factor is configured, a UE may draw, obtain, or determine a random number or randomly generated number "rand", e.g., in the range 0 ≤ rand < 1. In other embodiments, "rand" may be in other ranges. In some embodiments, "rand" may be randomly generated by the UE or another device. In some embodiments, the UE may compare "rand" with the value indicated by the RACH type selection factor. If "rand" is less than (or less than or equal to, or greater than, or greater than or equal to) the value indicated by the RACH type selection factor, the UE will select a two-step RACH. Otherwise, the UE will select a four-step RACH.

[0048] In some embodiments, in addition to the factor-based solution, some other criteria (e.g., an RSRP threshold, and a two-step RACH can only be selected if the measured RSRP is greater than the RSRP threshold) may also be considered in RA type selection. Thus, the factor-based RA type selection can be used in two ways: Alt1: The factor-based solution is used to determine whether a two-step RACH is allowed; and Alt2: The factor-based solution is used to determine whether a two-step RACH should be selected. In Alt1, the factor-based solution can be used together with other criteria, and a two-step RACH can only be selected if all criteria allow it. In Alt2, if a two-step RACH is allowed, the factor-based solution should be used, which can be determined by other criteria.

[0049] In some embodiments, the following alternatives or options may be considered or implemented for the configuration of the RACH type selection factor.

[0050] In alternative 1 of the RACH type selection factor configuration, the RACH type selection factor may be configured for each access category. By (based on, using) the "RACH type selection factor" configured for each access category, the UE can first determine the access category and then use the corresponding "RACH type selection factor" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0051] In alternative 2 of the RACH type selection factor configuration, the RACH type selection factor may be configured for each Unified Access Control (UAC)-BarringInfoSet. By (based on, using) the "RACH type selection factor" configured for each UAC-BarringInfoSet, the UE can first determine the UAC-BarringInfoSet and then use the corresponding "RACH type selection factor" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0052] In alternative 3 of the RACH type selection factor configuration, the RACH type selection factor may be configured for each access identifier. By (based on, using) the "RACH type selection factor" configured for each access identifier, the UE can first determine the access identifier and then use the corresponding "RACH type selection factor" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0053] In alternative 4 of the RACH type selection factor configuration, the RACH type selection factor may be configured for each Public Land Mobile Network (PLMN). By (based on, using) the "RACH type selection factor" configured for each PLMN, the UE can first determine the PLMN and then use the corresponding "RACH type selection factor" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0054] In alternative 5 of the RACH type selection factor configuration, the RACH type selection factor can be configured for different triggers or trigger events of the RACH procedure. In some embodiments, the following triggers or trigger events of the RACH procedure can be considered or implemented: (a) Initial access from Radio Resource Control (RRC)_IDLE; (b) RRC connection re-establishment procedure; (c) Handover; (d) During RRC_CONNECTED, when the UL synchronization state is "out of sync", downlink (DL) or uplink (UL) data arrival; (e) During RRC_CONNECTED, when there is no Physical Uplink Control Channel (PUCCH) resource available for Scheduling Request (SR), UL data arrival; (f) SR failure; (g) RRC requests during synchronous reconfiguration; (h) Transition from RRC_INACTIVE; (i) Establish (or will establish) time alignment during Secondary Cell (SCell) addition; (j) Request for other system information (sometimes may be referred to as remaining and other system information in the NR mobile network) or System Information message (SI); (k) Beam failure recovery. In some embodiments, by (based on, using) the "RACH type selection factor" specific to the trigger configuration, the UE can first determine the trigger and then use the corresponding "RACH type selection factor" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0055] In alternative 6 of the RACH type selection factor configuration, the RACH type selection factor can be configured for services with different Quality of Service (QoS) requirements, or for different logical channels, or for different logical channel groups. For each type of service with different QoS requirements, logical channels, or logical channel groups, the "RACH type selection factor" can be configured. Then, based on (using) the QoS requirements, logical channel, or logical channel group with data transmission, the UE uses the corresponding "RACH type selection factor" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0056] In alternative 7 of the RACH type selection factor configuration, the RACH type selection factor can be configured for each cell. By (based on, using) the "RACH type selection factor" configured for each cell, the UE can first determine the cell and then use the corresponding "RACH type selection factor" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0057] In alternative 8 of the RACH type selection factor configuration, the RACH type selection factor can be configured for each bandwidth part (BWP). By means of (based on, using) the "RACH type selection factor" configured for each BWP, the UE can first determine the BWP and then use the corresponding "RACH type selection factor" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0058] In some embodiments, a combination of the above alternatives for configuring the RACH type selection factor can be considered or implemented. For example, for each cell or BWP, different RACH type selection factors can be configured for different access categories, access identifiers, UAC-BarringInfoSet, triggers, or service types, etc.

[0059] In some embodiments, regarding the above alternatives for configuring the RACH type selection factor, in the case where the "RACH type selection factor" corresponding to the access category / access identifier / UAC-BarringInfoSet / trigger / cell / BWP / QoS requirement / logical channel / logical channel group is missing, the following additional alternatives can be considered or used: (a) additional alternative 1, where the UE uses a four-step random access procedure; (b) additional alternative 2, where a default value (e.g., configured by the network or BS, or fixed / specified in the specification) is used for the "RACH type selection factor"; (c) additional alternative 3, where the UE uses a two-step random access procedure.

[0060] Figure 5 is a flowchart showing an exemplary process 500 of an enhanced random access procedure for using a RACH type selection factor according to some embodiments of the present disclosure. In some embodiments, process 500 can be performed by a wireless communication device (e.g., UE 404). At operation 502, the wireless communication device receives information indicating a value from a wireless communication node (e.g., BS 402). In some embodiments, this information can be broadcast in system information or broadcast via RRC signaling. In some embodiments, the value can correspond to or be associated with the RACH type selection factor. In some embodiments, the value can be configured by the wireless communication node. For example, as described above, the value can be configured using the alternatives for configuring the RACH type selection factor.

[0061] In some embodiments, the value indicated by the information received in operation 502 can be configured based on an access category. In some embodiments, the value can be configured based on a UAC-BarringInfoSet. In some embodiments, the value can be configured based on an access identity. In some embodiments, the value can be configured based on a PLMN. In some embodiments, the value can be configured based on one or more triggers or trigger events of a four-step random access procedure or a two-step random access procedure to access a wireless communication node. In some embodiments, the value can be configured based on QoS requirements. In some embodiments, multiple values can be configured respectively based on multiple logical channels or logical channel groups. In some embodiments, the value can be configured based on the cell in which the wireless communication device is located. In some embodiments, the value can be configured based on a BWP.

[0062] Referring again to Figure 5 , in operation 504, the wireless communication device can compare the randomly generated value with the value received from the wireless communication node to determine whether the randomly generated value meets the value. In some embodiments, the wireless communication device can generate a random number as the randomly generated value. In other embodiments, the randomly generated value can be generated by another device and transmitted to the wireless communication device. In some embodiments, the randomly generated value can be in the range greater than or equal to 0 and less than 1 (0 ≤ randomly generated value < 1). In other embodiments, the randomly generated value can be in other ranges.

[0063] In some embodiments, in response to determining in operation 504 that the randomly generated value meets the value (e.g., the randomly generated value is less than, or less than or equal to, or greater than, or greater than or equal to the value), process 500 proceeds to operation 506. Otherwise, process 500 proceeds to operation 508.

[0064] In operation 506, the wireless communication device selects a two-step random access procedure to access the wireless communication node. In operation 508, the wireless communication device selects a four-step random access procedure to access the wireless communication node. If a two-step random access procedure is selected in operation 506, process 500 can proceed to operation 510. If a four-step random access procedure is selected in operation 508, process 500 can proceed to operation 512.

[0065] In operation 510, the wireless communication device sends a first message to access the wireless communication node. The content of the first message sent in operation 510 can be based on the selection of the two-step random access procedure. In some embodiments, when (in response to) the two-step random access procedure is selected, the content of the first message can include a random access preamble and a payload. In some embodiments, the payload can be optional. In some embodiments, the preamble can be optional.

[0066] At operation 512, the wireless communication device transmits a first message to access the wireless communication node. The content of the first message transmitted at operation 512 may be based on the selection of a four-step random access procedure. In some embodiments, when (in response to) the four-step random access procedure is selected, the content of the first message may include a random access preamble.

[0067] In some embodiments, the wireless communication node (e.g., BS 402) may convey information indicating a value to the wireless communication device (e.g., UE 404). In some embodiments, the value may correspond to or be associated with a RACH type selection factor. In some embodiments, the value may be configured by the wireless communication node. For example, as described above, an alternative for configuring the RACH type selection factor may be used to configure the value. In some embodiments, the wireless communication node may receive a first message from the wireless communication device to access the wireless communication node. In some embodiments, when (e.g., by the wireless communication device) the four-step random access procedure is selected, the first message may include a random access preamble. In some embodiments, when (e.g., by the wireless communication device) the two-step random access procedure is selected, the first message may include a random access preamble and a payload. In some embodiments, the payload may be optional. In some embodiments, the preamble may be optional. In some embodiments, the wireless communication node may transmit a second message in response to the first message.

[0068] Figure 6 is a flowchart illustrating an exemplary process 600 for an enhanced random access procedure using a RACH type selection factor in accordance with some embodiments of the present disclosure. In some embodiments, process 600 may be performed by a wireless communication device (e.g., UE 404). At operation 602, the wireless communication device receives information indicating a plurality of values from a wireless communication node (e.g., BS 402). In some embodiments, the information may be broadcast in system information or broadcast via RRC signaling. In some embodiments, the plurality of values respectively correspond to a plurality of parameters. In some embodiments, the plurality of parameters may be a plurality of access control parameters, such as a plurality of access categories, a plurality of UAC-BarringInfoSet, or a plurality of access identifiers. In some embodiments, the plurality of parameters may be a plurality of non-access control parameters, such as a plurality of PLMNs, a plurality of triggers or trigger events for a random access procedure, a plurality of QoS requirements, a plurality of logical channels or logical channel groups, a plurality of cell IDs, or a plurality of BWPs. In some embodiments, the plurality of values may be configured by the wireless communication node. For example, as described above, an alternative for configuring the RACH type selection factor may be used to configure the plurality of values.

[0069] In some embodiments, multiple values received in operation 602 can be configured based on multiple access categories. In some embodiments, multiple values can be configured based on multiple UAC-BarringInfoSet. In some embodiments, multiple values can be configured based on multiple access identifiers. In some embodiments, multiple values can be configured based on multiple PLMNs. In some embodiments, multiple values can be configured based on one or more triggers or triggering events of a four-step random access procedure or a two-step random access procedure to access a wireless communication node. In some embodiments, multiple values can be configured based on multiple QoS requirements. In some embodiments, multiple values can be configured based on multiple logical channels or logical channel groups. In some embodiments, multiple values can be configured based on multiple cells. In some embodiments, multiple values can be configured based on multiple BWPs.

[0070] For example, when the multiple parameters are multiple access categories (i.e., when the "RACH type selection factor" is configured according to each access category), the wireless communication node can configure factor 1 for access category 1, factor 2 for access category, factor 3 for access category 3, and so on. Continuing with this example, the wireless communication device can then determine or decide the access category, generate a randomly generated value, and compare the randomly generated value with the corresponding factor. For example, if the access category is category 2, the factor to be compared with is factor 2.

[0071] Referring again to Figure 6 , in operation 604, the wireless communication device selects one parameter from the multiple parameters. Continuing with the above example, when the multiple parameters are multiple access categories, the wireless communication device can select one category from the multiple access categories. In operation 606, the wireless communication device can compare the randomly generated value with the value selected from the multiple values to determine whether the randomly generated value satisfies the value. In some embodiments, in operation 604, the value is selected or determined from the multiple values according to the selected parameter. In some embodiments, the wireless communication device can generate a random number as the randomly generated value. In other embodiments, the randomly generated value can be generated by another device and transmitted to the wireless communication device. In some embodiments, the randomly generated value can be in a range greater than or equal to 0 and less than 1 (0 ≤ randomly generated value < 1). In other embodiments, the randomly generated value can be in other ranges.

[0072] In some embodiments, in response to determining in operation 606 that the randomly generated value satisfies the value selected from the multiple values (e.g., the randomly generated value is less than, or less than or equal to, or greater than, or greater than or equal to the value), process 600 proceeds to operation 608. Otherwise, process 600 proceeds to operation 610.

[0073] At operation 608, the wireless communication device selects a two-step random access procedure to access the wireless communication node. At operation 610, the wireless communication device selects a four-step random access procedure to access the wireless communication node. If the two-step random access procedure is selected at operation 608, process 600 can proceed to operation 612. If the four-step random access procedure is selected at operation 610, process 600 can proceed to operation 614.

[0074] At operation 612, the wireless communication device transmits a first message to access the wireless communication node. The content of the first message transmitted at operation 612 can be based on the selection of the two-step random access procedure. In some embodiments, when (in response to) the two-step random access procedure is selected, the content of the first message can include a random access preamble and a payload. In some embodiments, the payload can be optional. In some embodiments, the preamble can be optional.

[0075] At operation 614, the wireless communication device transmits a first message to access the wireless communication node. The content of the first message transmitted at operation 614 can be based on the selection of the four-step random access procedure. In some embodiments, when (in response to) the four-step random access procedure is selected, the content of the first message can include a random access preamble.

[0076] In some embodiments, the wireless communication node (e.g., BS 402) can transmit information indicating multiple values to the wireless communication device (e.g., UE 404). In some embodiments, the multiple values can respectively correspond to multiple parameters. In some embodiments, the multiple values respectively correspond to multiple parameters. In some embodiments, the multiple parameters can be multiple access control parameters, such as multiple access categories, multiple UAC-BarringInfoSet, or multiple access identifiers. In some embodiments, the multiple parameters can be multiple non-access control parameters, such as multiple PLMNs, multiple triggers or trigger events of the random access procedure, multiple QoS requirements, multiple logical channels, multiple logical channel groups, multiple cell IDs, or multiple BWPs. In some embodiments, the multiple values can be configured by the wireless communication node. For example, as described above, alternatives for configuring the RACH type selection factor can be used to configure the multiple values.

[0077] In some embodiments, a wireless communication node may receive a first message from a wireless communication device to access the wireless communication node. In some embodiments, when a four-step random access procedure is selected (e.g., by the wireless communication device), the first message may include a random access preamble. In some embodiments, when a two-step random access procedure is selected (e.g., by the wireless communication device), the first message may include a random access preamble and a payload. In some embodiments, the payload may be optional. In some embodiments, the preamble may be optional. In some embodiments, the wireless communication node may send a second message in response to the first message.

[0078] ALT 2: Solution based on "RACH type selection timer"

[0079] In some embodiments, a solution based on a "RACH type selection timer" may be considered or implemented for RACH type selection. In some embodiments, during each timer run, the corresponding UE (e.g., UE 404) is not allowed to initiate a two-step random access procedure, regardless of whether the conditions for selecting the two-step random access procedure are met (if configured). On the other hand, when the timer expires or stops, the UE is allowed to select a two-step random access procedure or a four-step random access procedure, or perform RACH type selection if other thresholds for type selection are configured.

[0080] In some embodiments, during each timer run, only the corresponding UE (e.g., UE 404) is allowed to initiate a two-step random access procedure, or allowed to initiate a two-step RACH, provided that the conditions for selecting the two-step random access procedure are met (if configured). On the other hand, when the timer expires or stops, the UE can only perform a four-step RACH.

[0081] In some embodiments, one or more times may be configured, having the same or different lengths. In some embodiments, the following alternatives or options may be used to configure the length of the timer. In the first alternative, the timer may be directly configured by the network or the BS and may be broadcast in the system information or notified by radio resource control (RRC) signaling. In the second alternative, a default length of the timer may be configured or predefined (predetermined), and a scaling factor may be used to configure the length of the timer. When the scaling factor is missing, the default length will be used.

[0082] In some embodiments, regarding the start of a timer, a "RACH type selection timer enable indicator" can be used to control the configured timer. In some embodiments, the "RACH type selection timer enable indicator" can be one bit in the case of a unified timer being configured, or a bit string if multiple timers are configured. In some embodiments, a "RACH type selection timer enable indicator" with a value of "1" means the timer is started, while "0" means the timer is stopped. In other embodiments, difficult values or formats of the "RACH type selection timer enable indicator" can be used. In some embodiments, the "RACH type selection timer enable indicator" can be transmitted or sent to the UE via system information or RRC signaling, or included in a RA response or Msg 2. In some embodiments, the UE can receive a "RACH type selection timer enable indicator" that can activate the timer. In some embodiments, the timer can be started at the first transmission of Msg1 in a two-step RACH (or after a certain duration after the first transmission), or at the first transmission of Msg1 in a four-step RACH (or after a certain duration after the first transmission).

[0083] In some embodiments, the configuration of the timer can be broadcast in system information or signaled by RRC signaling. In some embodiments, the following alternative solutions or options can be considered or implemented for the configuration of the RACH type selection timer.

[0084] In alternative 1 of the RACH type selection timer configuration, a timer can be configured for each access category. By (based on, using) the timer configured for each access category, the UE can first determine the access category and then use the corresponding "RACH type selection timer" to determine which random access procedure to select (e.g., a two-step random access procedure or a four-step random access procedure).

[0085] In alternative 2 of the RACH type selection timer configuration, a timer can be configured for each UAC-BarringInfoSet. By (based on, using) the timer configured for each UAC-BarringInfoSet, the UE can first determine the UAC-BarringInfoSet and then use the corresponding "RACH type selection timer" to determine which random access procedure to select (e.g., a two-step random access procedure or a four-step random access procedure).

[0086] In alternative 3 of the RACH type selection timer configuration, a timer can be configured for each access identifier. By (based on, using) the timer configured for each access identifier, the UE can first determine the access identifier and then use the corresponding "RACH type selection timer" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0087] In alternative 4 of the RACH type selection timer configuration, a timer can be configured for each PLMN. By (based on, using) the timer configured for each PLMN, the UE can first determine the PLMN and then use the corresponding "RACH type selection timer" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0088] In alternative 5 of the RACH type selection timer configuration, a timer can be configured for different triggers or trigger events of the RACH procedure. In some embodiments, the following triggers or trigger events of the RACH procedure can be considered or implemented: (a) initial access from RRC_IDLE; (b) RRC connection re-establishment procedure; (c) handover; (d) during RRC_CONNECTED, when the UL synchronization state is "out of sync", downlink (DL) or uplink (UL) data arrival; (e) during RRC_CONNECTED, when there is no PUCCH resource available for scheduling request (SR), UL data arrival; (f) SR failure; (g) RRC requests during synchronous reconfiguration; (h) transition from RRC_INACTIVE; (i) establishing (or to be established) time alignment when adding an SCell; (j) requesting other system information (sometimes may be referred to as remaining and other system information in the NR mobile network) or system information message (SI); (k) beam failure recovery. In some embodiments, by (based on, using) the timer specific to the trigger configuration, the UE can first determine the trigger and then use the corresponding timer to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0089] For example, if timers for different trigger events are configured and the "RACH type selection timer enable indicator" is set to "11111111110" and broadcast in the system information, the "RACH type selection timer" configured for trigger events other than beam failure recovery (BFR) can be run. During the running of each timer, the RACH triggered by the corresponding event can only follow the four-step random access procedure, except for the RACH triggered by BFR, where the UE can select the two-step random access procedure or the four-step random access procedure according to a specific threshold (if configured).

[0090] In alternative 6 of the RACH type selection timer configuration, the timer can be configured for services with different QoS requirements, or for different logical channels, or for different logical channel groups. For each type of service with different QoS requirements / logical channels / logical channel groups, the timer can be configured. Then, based on (using) the QoS requirements / logical channel / logical channel group, the UE uses the corresponding "RACH type selection timer" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0091] In alternative 7 of the RACH type selection timer configuration, the timer can be configured for each cell. Based on (using) the timer configured for each cell, the UE can first determine the PLMN and then use the corresponding "RACH type selection timer" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0092] In alternative 8 of the RACH type selection factor configuration, the RACH type selection factor can be configured for each BWP. Based on (using) the timer configured for each BWP, the UE can first determine the PLMN and then use the corresponding "RACH type selection timer" to determine which random access procedure to select (e.g., two-step random access procedure or four-step random access procedure).

[0093] In some embodiments, a combination of the above alternatives for configuring the RACH type selection timer can be considered or implemented. For example, for each cell or BWP, different RACH type selection timers can be configured for different access categories, access identifiers, UAC-BarringInfoSet, triggers, or service types, etc. In some embodiments, if the timer configuration does not exist, the UE can select the RACH type according to other configured or predefined criteria (if configured).

[0094] Figure 7 is a flowchart showing an exemplary process 700 of an enhanced random access procedure for using a RACH type selection timer according to some embodiments of the present disclosure. In some embodiments, process 700 can be performed by a wireless communication device (e.g., UE 404). At operation 702, the wireless communication device receives information indicating the timer from a wireless communication node (e.g., BS 402). In some embodiments, the information can be broadcast in system information or broadcast via RRC signaling. In some embodiments, the timer can be or correspond to a RACH type selection timer. In some embodiments, the timer can be configured by the wireless communication node. For example, as described above, the timer can be configured using the alternatives for configuring the RACH type selection timer.

[0095] In some embodiments, a timer (e.g., the duration of the timer) indicated by the information received in operation 702 may be configured based on an access category. In some embodiments, the timer (e.g., the duration of the timer) may be configured based on a UAC-BarringInfoSet. In some embodiments, the timer (e.g., the duration of the timer) may be configured based on an access flag. In some embodiments, the timer (e.g., the duration of the timer) may be configured based on a PLMN. In some embodiments, the timer (e.g., the duration of the timer) may be configured based on one or more triggers or triggering events of a four-step random access procedure or a two-step random access procedure. In some embodiments, the timer (e.g., the duration of the timer) may be configured based on QoS requirements / logical channels / logical channel groups. In some embodiments, the timer (e.g., the duration of the timer) may be configured based on the cell in which the wireless communication device is located. In some embodiments, the timer (e.g., the duration of the timer) may be configured based on a BWP.

[0096] In some embodiments, the duration of the timer may be configured by a communication network or a BS and broadcast in system information. In some embodiments, the duration of the timer may be configured by a communication network or a BS and notified by radio resource control (RRC) signaling. In some embodiments, the duration of the timer may be configured based on a scaling factor, and in the absence of a scaling factor, a default duration may be used.

[0097] In some embodiments, a wireless communication device may receive an enabling indicator (e.g., a RACH type selection timer enabling indicator) that may activate or start the timer. In some embodiments, the enabling indicator may be sent from a wireless communication node.

[0098] Referring again to Figure 7 , in operation 704, the wireless communication device may determine whether the timer is in an active state. In some embodiments, the timer is in an active state when the timer is running, and the timer is in an inactive state when the timer expires or stops. In some embodiments, in response to determining in operation 704 that the timer is in an active state, process 700 proceeds to operation 706, and in response to determining in operation 704 that the timer is in an inactive state, process 700 proceeds to operation 708.

[0099] At operation 706, in response to determining that the timer is in an active state, the wireless communication device selects a four-step random access procedure to access the wireless communication node. At operation 708, in response to determining that the timer is in an inactive state, the wireless communication device selects either a four-step random access procedure or a two-step random access procedure to access the wireless communication node. If a four-step random access procedure is selected at operation 706, process 700 may proceed to operation 710. If a four-step random access procedure or a two-step random access procedure is selected at operation 708, process 700 may proceed to operation 712.

[0100] At operation 710, the wireless communication device transmits a first message to access the wireless communication node. The content of the first message transmitted at operation 710 may be based on the selection of the four-step random access procedure. In some embodiments, when (in response to) the four-step random access procedure is selected, the content of the first message may include a random access preamble.

[0101] At operation 712, the wireless communication device transmits a first message to access the wireless communication node. The content of the first message transmitted at operation 712 may be based on the selection of the four-step random access procedure or the two-step random access procedure at operation 708. In some embodiments, when (in response to) the four-step random access procedure is selected at operation 708, the content of the first message may include a random access preamble. In some embodiments, when (in response to) the two-step random access procedure is selected at operation 708, the content of the first message may include a random access preamble and a payload. In some embodiments, the payload may be optional. In some embodiments, the preamble may be optional.

[0102] In some embodiments, the wireless communication node (e.g., BS 402) may convey information indicating the timer to the wireless communication device (e.g., UE 404). In some embodiments, the timer may be or correspond to a RACH type selection timer. In some embodiments, the timer may be configured by the wireless communication node. For example, as described above, alternative schemes for configuring the RACH type selection timer may be used to configure the value. In some embodiments, the wireless communication node may receive a first message from the wireless communication device to access the wireless communication node. In some embodiments, when (e.g., by the wireless communication device) the four-step random access procedure is selected, the first message may include a random access preamble. In some embodiments, when (e.g., by the wireless communication device) the two-step random access procedure is selected, the first message may include a random access preamble and a payload. In some embodiments, the payload may be optional. In some embodiments, the preamble may be optional. In some embodiments, the wireless communication node may transmit a second message in response to the first message.

[0103] ALT 3: Solution based on "fallback indicator"

[0104] In some embodiments, the backoff indicator may be included in Msg2 (e.g., Msg2 in a two-step random access procedure or a four-step random access procedure). When the UE receives the backoff indicator, the UE may determine the backoff time according to the backoff indicator. During the running of the backoff time, the UE is not allowed to retry the corresponding random access procedure or RACH.

[0105] In some embodiments, the backoff indicator may be configured according to the following alternatives: (a) In the first alternative, the same backoff indicator may be configured for two RACH types (e.g., a two-step random access procedure and a four-step random access procedure); (b) In the second alternative, a backoff indicator is configured for a two-step random access procedure or a four-step random access procedure; (c) In the third alternative, separate backoff indicators may be configured for the two-step random access procedure and the four-step random access procedure respectively, and may be included in Msg2. For example, during the backoff time of the two-step random access procedure and the four-step random access procedure, the UE cannot initiate a random access procedure. However, if the backoff time of the two-step random access procedure is running while the backoff time of the four-step random access procedure is not running, the UE can only initiate the four-step random access procedure. Similarly, if the backoff time of the four-step random access procedure is running while the backoff time of the two-step random access procedure is not running, the UE can only initiate the two-step random access procedure.

[0106] In some embodiments, a combination of the above alternatives may be considered or implemented. For example, different "RACH type selection factors" may be configured for different trigger events. In addition, different backoff times may be configured for the two-step random access procedure and the four-step random access procedure. An example is provided below, assuming that the backoff time of the two-step random access procedure is longer than that of the four-step random access procedure.

[0107] In step 1 of the example, the UE determines the RACH type selection factor based on the trigger event. The UE then selects the RACH type by comparing a randomly generated number with the RACH type selection factor.

[0108] In step 2 of the example, the UE selects the RACH resource and sends Msg1 on the selected RACH resource.

[0109] In step 3 of the example, the UE receives Msg2, which includes backoff indicators for the two-step random access procedure and the four-step random access procedure respectively.

[0110] In step 4 of the example, when the backoff time of the four-step random access procedure expires or stops, and the backoff time of the two-step random access procedure is still running, the UE reattempts the four-step random access procedure. If the UE still does not obtain access to the BS after the backoff time of the two-step random access procedure expires or stops, the UE reattempts the RACH by returning to step 1.

[0111] Figure 8 is a flowchart illustrating an exemplary process 800 for an enhanced random access procedure with a backoff indicator in accordance with some embodiments of the present disclosure. In some embodiments, process 800 may be performed by a wireless communication device (e.g., UE 404). At operation 802, the wireless communication device transmits a first message to access a wireless communication node (BS 402). In some embodiments, the content of the first message may be based on a selection between a four-step random access procedure or a two-step random access procedure. In some embodiments, the selection of the four-step random access procedure or the two-step random access procedure may be performed using the "RACH type selection factor" or "RACH type selection timer" procedures as described above. In some embodiments, when (in response to) the four-step random access procedure is selected, the content of the first message may include a random access preamble. When the two-step random access procedure is selected, the content of the first message may include a random access preamble and a payload. In some embodiments, the payload may be optional. In some embodiments, the preamble may be optional.

[0112] At operation 804, in response to transmitting the first message, the wireless communication device receives a second message from the wireless communication node indicating a first timer. In some embodiments, the first time may be a backoff timer or indicator, for example, as described above.

[0113] At operation 806, the wireless communication device determines that the first timer is inactive. In some embodiments, the wireless communication device may determine whether the first timer is in an active state (e.g., running). If the first timer is active or running, the wireless communication device is not allowed to retry the random access procedure or RACH. In this case, the wireless communication device may wait until the first timer expires or stops. On the other hand, if the first timer is inactive (e.g., not running, stopped, or expired within the duration of the timer), the wireless communication device may retry the random access procedure.

[0114] At operation 808, in response to determining in operation 806 that the first timer is in an inactive state, the wireless communication device selects a four-step random access procedure or a two-step random access procedure to retransmit the first message. In some embodiments, the first timer may be configured for both the four-step random access procedure and the two-step random access procedure. In such a case, the wireless communication device may retransmit the first message at operation 808 using the same random access procedure used in operation 802, or may select one of the four-step random access procedure or the two-step random access procedure according to the "RACH type selection factor" or "RACH type selection timer" procedure described above.

[0115] In some embodiments, the first timer may be configured for one of the four-step random access procedure or the two-step random access procedure. In such a case, the wireless communication device may retransmit the first message based on the random access procedure associated with the first timer (i.e., the four-step random access procedure or the two-step random access procedure).

[0116] In some embodiments, the first timer may include a first value and a second value. For example, the first value may be configured for the four-step random access procedure, and the second value may be configured for the two-step random access procedure. In such a case, the wireless communication device may retransmit the first message using the random access procedure associated with the value indicating the inactive timer. If both the first value and the second value indicate the inactive timer, the wireless communication device may retransmit the first message at operation 808 using the same random access procedure used in operation 802, or may select one of the four-step random access procedure or the two-step random access procedure according to the "RACH type selection factor" or "RACH type selection timer" procedure described above.

[0117] In some embodiments, a wireless communication node (e.g., BS 402) may receive the first message from a wireless communication device (e.g., UE404). In some embodiments, the content of the first message may be based on the selection of the four-step random access procedure or the two-step random access procedure. In some embodiments, the wireless communication node may send a second message indicating the first timer to the wireless communication device in response to receiving the first message. For example, the first timer may be a backoff time or an indication. In some embodiments, the wireless communication node may receive the first message sent from the wireless communication device.

[0118] D. Content in Msg1 of Two-step RACH

[0119] In some embodiments, in the two-step random access procedure, the payload of Msg1 may include at least one of the following information to implicitly or explicitly indicate the time-domain resource for transmitting the corresponding preamble. For example, the information may include: (a) a system frame number (SFN) index or the least significant bit (LSB) of the SFN index and a slot index; (b) absolute timing, which may at least include the coordinated universal time corresponding to the end boundary of the slot in which the preamble is transmitted or the SFN boundary immediately following it; (c) SFN mod N, where SFN is the index of the radio frame in which the preamble is transmitted and N is the period of consecutive random access occasions (ROs); (d) a random access radio network temporary identifier (RA-RNTI) value, which is determined by the RO in which the preamble is transmitted.

[0120] E. Transmission Control of Msg1 in Two-Step RACH

[0121] In some embodiments, a counter-based solution may be considered or implemented for the transmission control of Msg1 in the two-step random access procedure. In some embodiments, the UE may implement the counter in the MAC layer or the physical layer. For each Msg1 transmission, the UE may increment the counter by 1. When the counter exceeds the maximum allowed number of transmissions, the UE may report a RACH failure.

[0122] In some embodiments, the counter and the maximum allowed number of transmissions may be configured according to the following alternative solutions.

[0123] In the first alternative solution, a transmission counter and a maximum allowed number of transmissions are defined or configured (e.g., Transmax is defined for 2-step RACH and 4-step RACH). For each transmission of Msg1, whether it is Msg1 of 2-step RACH or 4-step RACH, the counter is incremented by 1. For example, if counter >= (Transmax + 1), the UE reports a RACH failure.

[0124] In a second alternative, a transmission counter and separate maximum allowed number of transmissions are defined or configured for two-step RACH and four-step RACH (e.g., transmax-2step for two-step RACH and transmax-4step for four-step RACH). In the case where transmax-2step is less than transmax-4step, if the transmission counter <= transmax-2step, the UE may initiate two-step RACH or four-step RACH; if transmax-2step < transmission counter <= transmax-4step, the UE is only allowed to initiate four-step RACH. Similarly, in the case where transmax-4step < transmax-2step, if the transmission counter <= transmax-4step, the UE may initiate two-step RACH or four-step RACH; if transmax-4step < transmission counter <= transmax-2step, the UE is only allowed to initiate two-step RACH. If the counter is greater than max{transmax-4step, transmax-2step}, the UE reports a RACH failure.

[0125] In a third alternative, separate counters and separate maximum allowed number of transmissions are defined or configured. A total maximum allowed number of transmissions transmax-total may be defined or configured. Separate counters and separate maximum allowed number of transmissions are maintained for two-step RACH and four-step RACH (e.g., counter-2stepRACH and transmax-2stepRACH for two-step RACH, and counter-4stepRACH and transmax-4stepRACH for four-step RACH). If the corresponding counter exceeds the configured corresponding maximum allowed number of transmissions, the UE is not allowed to select two-step RACH or four-step RACH. When (counter-2stepRACH + counter-4stepRACH) exceeds transmax-total, the UE reports a RACH failure.

[0126] In a fourth alternative, a counter for Msg1 transmission (whether it is for Msg1 of a four-step RACH or Msg1 of a two-step RACH) and a maximum allowed number of transmissions for a two-step RACH can be configured, such as TransCounter, and transmax-2stepRACH. For each two-step RACH attempt, the counter can be incremented by 1. After the first 2-step RACH attempt, if TransCounter <= transmax-2stepRACH, the UE can only re-attempt the two-step RACH. If TransCounter >= transmax-2stepRACH + 1, the UE is only allowed to perform a four-step RACH. Additionally, a maximum number of total allowed transmissions, such as transmax, can be configured. If TransCounter >= transmax + 1, the UE reports a RACH failure.

[0127] In a fifth alternative, a timer for reporting a RACH failure can be introduced. The timer is started at the first transmission of Msg1. During the running of the timer, the UE can re-attempt RACH if needed. The timer stops after the RACH procedure is successfully completed. After the timer expires, the UE reports a RACH failure.

[0128] In some embodiments, a combination of one or more of the above alternatives can also be considered or implemented. For example, a counter and a transmax can be configured; in addition, a timer can be additionally configured. If any threshold is met, the UE reports a RACH failure.

[0129] F. RA-RNTI for receiving Msg2 of a two-step RACH

[0130] In some embodiments, after sending Msg1, the UE can use a random access radio network temporary identifier (RA-RNTI) to monitor the corresponding search space, and the RA-RNTI is calculated based on the RO of the preamble part of the sent Msg1.

[0131] The RA-RNTI associated with the PRACH occasion for sending a random access preamble can be calculated as: RA-RNTI = 1 + s_id + 14×t_id + 14×80×f_id + 14×80×8×ul_carrier_id,

[0132] 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 < 80), f_id is the PRACH occasion in the index frequency domain (0 ≤ f_id < 8), and ul_carrier_id is the UL carrier used for random access preamble transmission (0 represents the NUL carrier, and 1 represents the SUL carrier).

[0133] In some embodiments of the present disclosure, the RNTI has a bit width of 16 bits. For cases where the cell size is very large (e.g., non-terrestrial network (NTN)) or the user density is very high (e.g., Internet of Things (IoT) services), the number of bits of the RNTI can be extended to meet the connection requirements. Therefore, some indicators can be introduced to enable long RNTI. For example, a one-bit indicator (e.g., long-RNTI-enabled) can be introduced. In some embodiments, if long-RNTI-enabled is set to "1", a long RNTI sequence can be used for scrambling; if long-RNTI-enabled is set to "0", a normal RNTI sequence can be used for scrambling. If there is no such indicator, it is interpreted that long-RNTI-enabled is set to "0", and a normal RNTI sequence can be used for scrambling.

[0134] In some embodiments, the indicator can be configured in the following alternative ways: (a) In the first alternative, the indicator is included in the master information block (MIB); (b) In the second alternative, the indicator is included in the system information block (SIB); (c) In the third alternative, the indicator is configured by frequency band (e.g., for transmissions using a band configured as "long-RNTI-enabled", a long RNTI sequence will be used for scrambling); (d) In the fourth alternative, the indicator is configured by PLMN.

[0135] In some embodiments, if long RNTI is used, the system frame information of the RO in which the preamble part of Msg1 is transmitted can be included in the formula of the RA-RNTI, which can be one of the following: (a) The LSB of the SFN index; (b) SFN_index; (c) SFN_index mod N, where the SFN index is equal to the system frame number index at the start of the PRACH occasion, and the PRACH occasion is where the preamble part of Msg1 is transmitted. N is the smallest integer greater than or equal to the RAR window size in the radio frame (e.g., if the RAR window size occupies 2.5 radio frames, then N is equal to 3).

[0136] An example is provided below:

[0137] RA-RNTI = 1 + s_id + 14 * t_id + 14 * 80 * f_id + 14 * 80 * 8 * ul_carrier_id + 14 * 80 * 8 * 2 * frame_id, where frame_id = SFN_index mod N; N is the smallest integer greater than or equal to the RAR window size in a radio frame, which can be written as CEIL(RAR window size in a radio frame); SFN_index is the system frame number index at which the PRACH occasion starts, and the PRACH occasion is where the preamble of Msg1 is transmitted.

[0138] G. Content and Format of Msg2 in Two-Step RACH

[0139] In some embodiments, the following alternative solutions may be considered or implemented regarding the content and format of Msg2 in the two-step random access procedure.

[0140] First alternative for the content and format of Msg2

[0141] MAC sub-protocol data unit subPDU in Msg2

[0142] In some embodiments, the Msg2 MAC protocol data unit (PDU) may include one or more MAC subPDUs and optional padding. Each MAC subPDU may include one of the following: (a) a MAC subheader with only a backoff indicator; (b) a MAC subheader and successRAR; (c) a MAC subheader and fallbackRAR.

[0143] Format of the MAC sub-header

[0144] In some embodiments, the MAC subheader of Msg2 includes the following fields: (a) E: The Extension field is a flag indicating whether the MAC subPDU containing this MAC subheader is the last MAC subPDU in the MAC PDU. In some embodiments, the size of the E field is 1 bit. (b) T: The Type field is a flag indicating whether there is a backoff indicator in the MAC subheader, whether there is a MAC RAR after the MAC subheader, and if so, the type of the corresponding MAC RAR (e.g., successRAR or fallbackRAR). In some embodiments, the size of the T field is 2 bits. (c) BI: The BackoffIndicator field identifies the overload situation in the cell. In some embodiments, the size of the BI field is 4 bits. (d) R: The reserved bit, which is set to "0" in some embodiments.

[0145] In some embodiments, the definition of the two-bit T field can be implemented as follows: (A) "00": indicates the presence of a backoff indicator field in the sub-header (BI); (b) "01": indicates the presence of a successRAR in the MAC subPDU; (c) "10": indicates the presence of a fallbackRAR in the MAC subPDU; (d) "11": reserved. In some embodiments, the T field can also be used to indicate the presence of a MAC sub-DU for the common configuration of the resources for transmitting the ACK for MsgB reception, and in this case, the value "11" of the T field can be used.

[0146] It should be understood that the values used in each of the above-listed cases are examples, and the mapping between the value and the case is not limited to the above examples. They are for illustrative purposes only and should not be considered restrictive.

[0147] In some embodiments, for the Msg1 response in two-step RACH, the following two MAC sub-headers can be supported in the MAC PDU: (a) A MAC sub-header with only a Backoff Indicator, including four header fields: E / T / R / BI; (b) A MAC sub-header with successRAR and fallback RAR, including seven header fields: E / T / R / R / R / R / R.

[0148] Format of successRAR

[0149] In some embodiments, successRAR has a fixed size and can include the following fields: (a) Contention resolution ID: This field contains the UL common control channel (CCCH) service data unit (SDU). In some embodiments, if the UL CCCH SDU is longer than 48 bits, this field contains the first 48 bits of the UL CCCH SDU. In some embodiments, the size of the contention resolution ID is 48 bits. (b) Timing Advance Command (TAC): The same as the TAC field in the MAC RAR of four-step RACH. In some embodiments, the size of the timing advance command field is 12 bits. (c) c-RNTI (Cell Radio Network Temporary Identifier): The c-RNTI assigned to the UE within the cell. In some embodiments, the size of the C-RNTI field is 16 bits. (d) R: Reserved bit, set to 0 in some embodiments. (e) In some embodiments, the UL grant can be included in successRAR or some fields to carry the resource configuration for the transmission of the ACK for MsgB reception.

[0150] Format of fallbackRAR

[0151] In some embodiments, the fallbackRAR has a fixed size and may include the following fields: (a) RAPID: The Random Access Preamble Identifier field identifies the transmitted random access preamble. In some embodiments, the size of the RAPID field is 6 bits. (b) Timing Advance Command (TAC): The same as the TAC field in the MAC RAR for the four-step RACH. In some embodiments, the size of the Timing Advance Command field is 12 bits. (c) UL Grant: The same as the UL Grant field in the MAC-RAR for the four-step RACH. In some embodiments, the size of the UL Grant field is 27 bits. (d) Temporary C-RNTI: The Temporary C-RNTI field represents the temporary identifier used by the MAC entity during random access. In some embodiments, the size of the Temporary C-RNTI field is 16 bits. (d) R: Reserved bit, set to 0 in some embodiments.

[0152] Second alternative for the content and format of Msg2

[0153] MAC sub-protocol data unit subPDU in Msg2

[0154] In some embodiments, the Msg2 MAC PDU includes one or more MAC subPDUs and optional padding. Each MAC subPDU may include one of the following: (a) a MAC sub-header with only a backoff indicator; and (b) a MAC sub-header with a RAPID and a MAC RAR, where the MAC RAR can be used to carry a successRAR or a fallbackRAR.

[0155] Format of the MAC sub-header

[0156] In some embodiments, the MAC sub-header of Msg2 may include the following fields: (a) E: The Extension field is a flag indicating whether the MAC subPDU containing this MAC sub-header is the last MAC subPDU in the MAC PDU. In some embodiments, the size of the E field is 1 bit. (b) T: The Type field is a flag indicating the presence of a Backoff Indicator in the MAC sub-header and a MAC RAR after the MAC sub-header. In some embodiments, the size of the T field is 1 bit. (c) BI: The Backoff Indicator field identifies the overload situation in the cell. In some embodiments, the size of the BI field is 4 bits. (d) RAPID: The Random Access Preamble Identifier field identifies the transmitted random access preamble. In some embodiments, the size of the RAPID field is 6 bits. (e) R: Reserved bit, set to 0 in some embodiments.

[0157] In some embodiments, the definition of a T field in the MAC sub-header can be implemented as follows: (a) "0": indicates the presence of a Backoff Indicator field in the sub-header (BI), "1": indicates the presence of a MAC RAR in the MAC subPDU; or (b) "1": indicates the presence of a Backoff Indicator field in the sub-header (BI), "0": indicates the presence of a MAC RAR in the MAC subPDU.

[0158] In some embodiments, the following two MAC sub-headers can be supported in the MAC PDU of the Msg1 response in the two-step RACH: (a) a MAC sub-header with only a Backoff Indicator, including four header fields: E / T / R / BI; (b) a MAC sub-header for successRAR and fallback RAR, including seven header fields: E / T / RAP ID.

[0159] Format of MAC RAR

[0160] In some embodiments, the MAC RAR has a flexible size and includes a T field and a field for successRAR or a field for fallback RAR. T: The Type field is a flag indicating whether the successRAR field or the fallbackRAR field is included in the MAC RAR.

[0161] In some embodiments, the definition of a T field in the MAC RAR is as follows: (a) "0": indicates that the MAC RAR contains a successRAR field, "1": indicates that the MAC RAR contains a fallbackRAR field; or (b) "1": indicates that the MAC RAR contains a successRAR field, "0": indicates that the MAC RAR contains a fallbackRAR field. In some embodiments, the size of the T field can also be greater than 1 bit. If the T field is greater than 1 bit, in addition to indicating that the value of the MAC RAR includes a successRAR or fallbackRAR field, other values can be reserved for further use or used for other purposes.

[0162] In some embodiments, the successRAR field includes the following information: (a) Contention resolution ID: This field contains the UL CCCH SDU. In some embodiments, if the UL CCCH SDU is longer than 48 bits, this field contains the first 48 bits of the UL CCCH SDU. In some embodiments, the size of the contention resolution ID is 48 bits. (b) Timing Advance Command (TAC): The same as the TAC field in the MAC RAR of the four-step RACH. In some embodiments, the size of the Timing Advance Command field is 12 bits. (c) c-RNTI: The c-RNTI assigned to the UE within the cell. In some embodiments, the size of the C-RNTI field is 16 bits. (d) R: Reserved bit, set to 0 in some embodiments. In some embodiments, the UL grant may be included in the successRAR or some fields to carry the resource configuration for the transmission of the ACK for MsgB reception.

[0163] In some embodiments, the fallbackRAR field includes the following information: (a) Timing Advance Command (TAC): The same as the TAC field in the MAC RAR of the four-step RACH. In some embodiments, the size of the Timing Advance Command field is 12 bits. (b) UL Grant: The same as the UL Grant field in the four-step RACH of the MAC-RAR. In some embodiments, the size of the UL Grant field is 27 bits. (c) Temporary C-RNTI: The Temporary C-RNTI field represents the temporary identifier used by the MAC entity during random access. In some embodiments, the size of the Temporary C-RNTI field is 16 bits. (d) R: Reserved bit, set to 0 in some embodiments.

[0164] H. Msg2 ACK Resource Configuration for Two-Step RACH

[0165] In some embodiments, for Solution 1 and Solution 2 (Alternative 1 and Alternative 2 below), the acknowledgement transmission feedback (ACK) resource information may also be included in Msg2. In the case of including the ACK resource information, the UE determines the resources for the ACK transmission of Msg2. In some embodiments, the configuration of the ACK resources may have the following schemes: (a) Alternative 1: A separate MAC subPDU is used to indicate the common resource configuration and another separate MAC subPDU explicitly indicates the UE-specific resource configuration; (b) Alternative 2: A separate MAC subPDU is used to indicate the configuration of the common resources and another separate MAC subPDU implicitly indicates the UE-specific resource configuration; (c) Alternative 3: The UE-specific ACK resources are indicated as part of the sucessRAR.

[0166] In some embodiments, the configuration of the common resource, or a portion of the common resource configuration, may also be included in the DCI used to schedule MsgB. In some embodiments, the ACK received for MsgB may be carried on the PUCCH, PUSCH, or some other physical channel specifically designed for transmitting feedback.

[0167] In some embodiments, for Alternative 1 and Alternative 2, the common MAC subPDU may be time, and / or frequency, and / or code domain resources that can be used by multiple UEs, for which corresponding successRARs can be found in the same Msg2. In some embodiments, the code domain resource refers to the code or sequence that will be used in the transmission of the ACK received at MsgB, including the generation of the ACK signal.

[0168] In some embodiments, for Alternative 1, a certain UE-specific resource configuration may be explicitly included in another separate MAC subPDU. In some embodiments, the explicitly configured resources may be at least one of the following: (a) the code domain resources that the UE can use in the ACK transmission, or some parameters that can be used to calculate or derive the code domain resources to be used by the UE; (b) the frequency domain resources that the UE can use in the ACK transmission, or some parameters that can be used to calculate or derive the frequency domain resources to be used by the UE; (c) the time domain resources that the UE can use in the ACK transmission, or some parameters that can be used to calculate or derive the time domain resources to be used by the UE; (d) the index of the resources configured for the common resources in the common MAC subPDU, where the resource pool may be configured as the common resource. For example, in the common resource pool, it indicates that the codes from X to Y are reserved for the transmission of the ACK, and in the UE-specific resource configuration, an index may be used to indicate that the nth code is used for the transmission of the ACK.

[0169] In some embodiments, for alternative 2, certain UE-specific resource configurations may be implicitly included in another separate MAC subPDU. In some embodiments, the implicitly configured resources may be at least one of the following: (a) The UE derives time-domain resources based on the RAP ID (e.g., the random access preamble identifier corresponding to the transmitted preamble index), or the sequence of MAC subPDUs in the entire MAC PDU in Msg2, or the sequence of MAC successRARs in the entire Msg2, or the sequence of MAC RARs in the entire MAC RAR included in Msg2; (b) The UE derives frequency-domain resources based on the RAP ID (e.g., the random access preamble identifier corresponding to the transmitted preamble index), or the sequence of MAC subPDUs in the entire MAC PDU in Msg2, or the sequence of MAC successRARs in the entire Msg2, or the sequence of MAC RARs in the entire MAC RAR included in Msg2; and (c) The UE derives code-domain resources based on the RAP ID (e.g., the random access preamble identifier corresponding to the transmitted preamble index), or the sequence of MAC subPDUs in the entire MAC PDU in Msg2, or the sequence of MAC successRARs in the entire Msg2, or the sequence of MAC RARs in the entire MAC RAR included in Msg2.

[0170] In some embodiments, for the above alternative 1 and alternative 2, the combination method of common resources and UE-specific resources may be as follows: (a) Alt1: The resources for ACK may include time-domain / frequency-domain / code-domain resources. Some of the resources may be configured as common resources, and the remaining resources may be configured as UE-specific resources. For example, the common resources may include frequency-domain and time-domain resources, and the UE-specific resources may include code-domain resources. Or, the common resources may include time-domain resources, and the UE-specific resources may include code-domain and frequency-domain resources. (b) Alt2: The common resources may include a resource pool (e.g., a resource list or a resource range), and the UE-specific resources may include an index indicating one of the resources in the pool. (c) Alt3: A combination of Alt1 and Alt2. For example, the common resources may include the configuration of time-frequency resources, as well as the range or list of code-domain resources. The UE may determine the code-domain resources according to a certain index derived based on the UE-specific resource configuration (in an explicit or implicit manner) and the range / list given in the common resources.

[0171] In some embodiments, to include a MAC subPDU for a common ACK resource, a new MAC subPDU that includes a MAC sub-header and an ACK resource will be supported. In some embodiments, the definition of the two-bit T field in the MAC sub-header can be implemented as follows: (A) "00": indicates the presence of a fallback indicator field in the sub-header (BI); (b) "01": indicates the presence of a successRAR in the MAC subPDU; (c) "10": indicates the presence of a fallbackRAR in the MAC subPDU; (d) "11": indicates the presence of an ACK resource in the MAC subPDU.

[0172] It should be understood that the values used in each of the above-listed cases are examples, and the mapping between the values and the cases is not limited to the above examples. They are for illustrative purposes only and should not be considered restrictive.

[0173] Although various embodiments of the present solution have been described above, it should be understood that they are presented by way of example and not limitation. Similarly, the various figures may depict exemplary architectures or configurations provided to enable those of ordinary skill in the art to understand the exemplary features and functions of the present solution. However, those skilled in the art will understand that the present solution is not limited to the exemplary architectures or configurations shown, but can be implemented using a variety of alternative architectures and configurations. Additionally, as will be understood by those of ordinary skill in the art, 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 the present disclosure should not be limited by any of the above-described illustrative embodiments.

[0174] It should also be understood that any reference to elements using names such as "first", "second", etc. generally does not limit the number or order of those elements. Instead, these names are used herein as a convenient means of distinguishing between two or more elements or instances of elements. Thus, the reference to a first and a second element does not mean that only two elements can be employed, or that the first element must be located before the second element in some manner.

[0175] In addition, those of ordinary skill in the art will understand that a variety of different technologies can be used to represent information and signals. For example, data, instructions, commands, information, signals, bits, and symbols, as referred to in the above description, can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0176] One of ordinary skill in the art will further appreciate that any of the various illustrative logical blocks, modules, processors, devices, circuits, methods, and functions described in connection with the aspects disclosed herein can be implemented by electronic hardware (e.g., digital implementation, analog implementation, or a combination of both), firmware, various forms of program or design code containing instructions (for convenience, herein may be referred to as "software" or "software modules"), or any combination of these techniques. To clearly illustrate this interchangeability of hardware, firmware, and software, various illustrative components, blocks, modules, circuits, and steps have been described generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware, or software, or a combination of these techniques, depends upon the particular application and design constraints imposed on the overall system. One of skill in the art may implement the described functionality in various ways for each particular application, but such implementation decisions do not result in a departure from the scope of the present disclosure.

[0177] In addition, one of ordinary skill in the art will understand that the various illustrative logical blocks, modules, devices, components, and circuits described herein can be implemented within or performed by an integrated circuit (IC), which may include a general-purpose processor, a digital signal processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device, or any combination thereof. The logical blocks, modules, and circuits may further include an antenna and / or a transceiver to communicate with various components within a network or within a device. A general-purpose processor may be a microprocessor, but optionally, the processor may be any conventional processor, controller, or state machine. The processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other suitable configuration to perform the functions described herein.

[0178] If implemented in software, the functionality may be stored as one or more instructions or code on a computer-readable medium. Accordingly, the steps of the methods or algorithms disclosed herein may be implemented as software stored on a computer-readable medium. Computer-readable media includes computer storage media and communication media, where communication media includes any medium that can convey a computer program or code from one place to another. Storage media may be any available medium accessible by a computer. By way of example and not limitation, such computer-readable media may 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 the desired program code in the form of instructions or data structures and that is accessible by a computer.

[0179] In this document, the term "module" as used herein refers to software, firmware, hardware, and any combination of these elements for performing the related functions described herein. Additionally, for the purposes of discussion, various modules are described as discrete modules; however, it will be apparent to one of ordinary skill in the art that two or more modules may be combined to form a single module that performs the related functions according to an embodiment of the present solution.

[0180] Furthermore, in an embodiment of the present solution, a memory or other memory and communication components may be employed. It should be understood that, for clarity, the embodiments of the present solution have been described above with reference to different functional units and processors. However, it will be apparent that any suitable functional distribution between different functional units, processing logic elements, or domains may be used without departing from the present solution. For example, functions illustrated as being performed by separate processing logic elements or controllers may be performed by the same processing logic element or controller. Thus, the reference to a particular functional unit is only a reference to the appropriate means for providing the described function, and does not indicate a strict logical or physical structure or organization.

[0181] Various modifications to the embodiments described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the scope of the disclosure. Accordingly, the disclosure is not limited to the embodiments shown herein, but will be accorded the widest scope consistent with the novel features and principles disclosed herein, as set forth in the following claims.

Claims

1. A random access method, comprising: A wireless communication device sends a first message to a network, the first message including a preamble and a data payload; And The wireless communication device receives a second message in response to the first message from the network, Wherein, the second message is a MAC protocol data unit PDU including one or more media access control MAC sub-protocol data units subPDU, at least one MAC subPDU of the one or more MAC subPDUs includes a first MAC sub-header and successRAR, and Wherein, the successRAR has a fixed size and includes: A contention resolution identifier, A timing advance command TAC, A cell radio network temporary identifier C-RNTI, Reserved bits, and Configuration of an acknowledgment resource for transmitting an acknowledgment of receiving the second message, Wherein, the configuration of the acknowledgment resource includes: Code domain resource information, Frequency domain resource information, and Time domain resource information.

2. The method according to claim 1, wherein, Each of the one or more MAC subPDUs includes one of the following: (a) the first MAC sub-header and the successRAR, (b) a second MAC sub-header only with a fallback indicator, (c) a third MAC sub-header and fallbackRAR.

3. The method according to claim 2, wherein, At least one of the first MAC sub-header, the second MAC sub-header, and the third MAC sub-header includes one of the following: (a) an extension field for indicating whether the MAC subPDU including the MAC sub-header is the last MAC subPDU in the MAC PDU, (b) a type field for indicating the presence of a fallback indicator in the MAC sub-header, the presence of a MAC random access response RAR after the MAC sub-header, and if the MAC RAR exists, indicating the type of the corresponding MAC RAR, (c) a fallback indicator field for identifying an overload situation in the cell, (d) reserved bits.

4. The method according to claim 3, wherein, The type field includes two bits, When the two bits are set to "00", the type field indicates the presence of a fallback indicator field in the sub-header, and When the two bits are set to "01", the type field indicates the presence of successRAR in the MAC subPDU.

5. The method according to claim 2, wherein The fallbackRAR has a fixed size and includes: A timing advance command TAC, An uplink UL grant, A temporary cell radio network temporary identifier C-RNTI, and Reserved bits.

6. The method according to claim 1, further comprising: Sending an acknowledgment of receiving the second message on a physical uplink control channel PUCCH.

7. The method according to claim 1, further comprising: The wireless communication device implements a counter, and the wireless communication device is configured with a first maximum number and a second maximum number, where the first maximum number specifies the maximum allowed number of transmissions of the first message during transmission in a two-step random access procedure RACH, and the second maximum number specifies the total maximum allowed number of transmissions of the first message during transmission in a two-step RACH and another first message during transmission in a four-step RACH.

8. The method according to claim 7, further comprising: Incrementing the counter by 1 for each two-step RACH attempt to transmit the first message; and If the counter is less than or equal to the first maximum number, performing another two-step RACH attempt; or If the counter is greater than or equal to the first maximum number + 1, performing a four-step RACH attempt.

9. The method according to claim 8, further comprising: Incrementing the counter by 1 for each four-step RACH attempt; and In response to determining that the counter is equal to the second maximum number + 1, reporting a RACH failure.

10. A wireless communication device, comprising: a processor; and a memory storing executable instructions that, when executed by the processor, cause the processor to: Send a first message to the network, the first message including a preamble and a data payload; and Receive a second message from the network in response to the first message, where the second message is a MAC protocol data unit PDU including one or more media access control MAC sub-protocol data units subPDU, and at least one of the one or more MAC subPDUs includes a first MAC sub-header and successRAR, and where the successRAR has a fixed size and includes: a contention resolution identifier, a timing advance command TAC, a cell radio network temporary identifier C-RNTI, reserved bits, and configuration of an acknowledgment resource for transmitting an acknowledgment of receiving the second message, where the configuration of the acknowledgment resource includes: code domain resource information, frequency domain resource information, and time domain resource information.

11. The wireless communication device according to claim 10, wherein, Each of the one or more MAC subPDUs includes one of the following: (a) the first MAC sub-header and the successRAR, (b) a second MAC sub-header only with a fallback indicator, (c) a third MAC sub-header and fallbackRAR.

12. The wireless communication device according to claim 11, wherein, At least one of the first MAC sub-header, the second MAC sub-header, and the third MAC sub-header includes one of the following: (a) an extension field for indicating whether the MAC sub-PDU including the MAC sub-header is the last MAC sub-PDU in the MAC PDU, (b) a type field for indicating the presence of a fallback indicator within the MAC sub-header, the presence of a MAC random access response (RAR) after the MAC sub-header, and, if a MAC RAR is present, indicating the type of the corresponding MAC RAR, (c) a fallback indicator field for identifying an overload situation in the cell, (d) reserved bits.

13. The wireless communication device according to claim 12, wherein, The type field includes two bits. When the two bits are set to "00", the type field indicates the presence of a fallback indicator field in the sub-header, and When the two bits are set to "01", the type field indicates the presence of a successRAR in the MAC sub-PDU.

14. The wireless communication device according to claim 11, wherein, The fallback RAR has a fixed size and includes: A timing advance command (TAC), An uplink (UL) grant, A temporary cell radio network temporary identifier (C-RNTI), and Reserved bits.

15. The wireless communication device according to claim 10, wherein, When executed by the processor, the executable instructions further cause the processor to send an acknowledgement of the received second message on a physical uplink control channel (PUCCH).

16. The wireless communication device according to claim 10, wherein, When executed by the processor, the executable instructions further cause the processor to implement a counter, and the wireless communication device is configured with a first maximum number and a second maximum number, where the first maximum number specifies the maximum allowed number of transmissions of the first message during transmission in a two-step random access procedure (RACH), and the second maximum number specifies the total maximum allowed number of transmissions of the first message during transmission in a two-step RACH and another first message during transmission in a four-step RACH.

17. The wireless communication device according to claim 16, wherein, When executed by the processor, the executable instructions further cause the processor to: Increment the counter by 1 for each two-step RACH attempt to send the first message; And If the counter is less than or equal to the first maximum number, perform another two-step RACH attempt; or If the counter is greater than or equal to the first maximum number + 1, perform a four-step RACH attempt.

18. The wireless communication device according to claim 16, wherein, When executed by the processor, the executable instructions further cause the processor to: Increment the counter by 1 for each four-step RACH attempt; and In response to determining that the counter is equal to the second maximum number + 1, report a RACH failure.

19. A computer-readable medium having code stored thereon, which when executed by a processor implements the method according to any one of claims 1 to 9.

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