Random access procedure method for supporting a large random access response (RAR) window size

Abstract

Provided is a method performed by a terminal to handle LBT (listen before talk) failure in a wireless communication system. The present disclosure relates to a communication method and system for converging a fifth generation (5G) communication system that supports higher data rates than a fourth generation (4G) system using Internet of Things (IOT) technology. The present disclosure can be applied to intelligent services based on 5G communication technology and IoT-related technologies, such as smart homes, smart buildings, smart cities, smart cars, connected cars, healthcare, digital education, smart retail, and security and safety services.

Description

Technical Field

[0001] The present disclosure relates to a method for transmitting and receiving frame information in a random access response (RAR), a method for processing grant transmission configured on an unlicensed carrier, a random access (RA) procedure method for supporting a large RAR window size, and an LBT (listen before talk) processing method.

Background Art

[0002] In order to meet the increasing demand for wireless data traffic that has been on the rise since the commercialization of the 4th generation (4G) communication system, efforts have been made to develop an improved 5G or pre-5G communication system. For this reason, the 5G or pre-5G communication system is also referred to as the "Beyond 4G Network" communication system or the "Post LTE" communication system. To achieve a high data rate, the 5G communication system is considered to be implemented in the millimeter wave (mmWave) band (e.g., 60 GHz band). In order to reduce the propagation loss of radio waves and increase the transmission distance, in the 5G communication system, beamforming, MIMO (Multiple-Input Multiple-Output), FD-MIMO (Full Dimensional MIMO), array antenna, analog beam-forming, and large scale antenna technologies are being discussed. Furthermore, for the improvement of the system network, in the 5G communication system, the development of technologies such as advanced small cell, cloud Radio Access Network (cloud RAN), ultra-dense network, Device-to-Device (D2D) communication, wireless backhaul, moving network, cooperative communication, CoMP (Coordinated Multi-Points), and reception-end interference cancellation is being carried out.In the 5G communication system, advanced coding modulation (ACM) methods such as FQAM (Hybrid FSK and QAM Modulation) and SWSC (Sliding Window Superposition Coding), and advanced access technologies such as FBMC (Filter Bank Multi Carrier), NOMA (non-orthogonal multiple access), and SCMA (sparse code multiple access) have been developed.

[0003] The Internet, a human-centered network where humans generate and consume information, is evolving into the Internet of Things (IoT), a network of things where scattered entities such as things exchange and process information without human intervention. The Internet of Everything (IoE) technology, which combines IoT technology and big data processing technology through connection to a cloud server, has emerged. To implement IoT, technical elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. Recently, technologies such as sensor networks, M2M (Machine to Machine), and MTC (Machine Type Communication) for connecting things have been studied. In the IoT environment, intelligent IT (Internet Technology) services can be provided that collect and analyze data generated by connected things to create new value for human life. IoT can be applied to fields such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart home appliances, and advanced medical services through the convergence and integration between existing IT (information technology) technologies and various industries.

[0004] In this regard, various attempts have been made to apply the 5G communication system to the IoT network. For example, technologies such as sensor network, MTC (Machine Type Communication), and M2M (Machine to Machine) are realized by techniques such as beamforming, MIMO, and array antennas in 5G communication technology. The application of cloud RAN (cloud Radio Access Network) as the above-mentioned big data processing technology can also be regarded as an example of the convergence between 5G technology and IoT technology.

[0005] In recent years, many broadband wireless technologies have been developed to satisfy the increasing number of broadband subscribers and provide such more applications and services. The 2nd generation (2G) wireless communication system was developed to provide voice services while ensuring user mobility. The 3rd generation (3G) wireless communication system supports voice services and data services. The 4G wireless communication system was developed to provide high-speed data services. However, the 4G wireless communication system is currently troubled by the lack of resources to meet the increasing demand for high-speed data services. Therefore, the 5th generation wireless communication system (also referred to as NR (next generation radio)) has been developed to meet the increasing demand for various services with diverse requirements such as high-speed data services and support ultra-reliable and low-latency applications.

[0006] Furthermore, the 5G wireless communication system is expected to solve different use cases with diverse requirements in terms of data transmission rate, latency, stability, and mobility. However, the design of the radio interface of the 5G wireless communication system is expected to be flexible enough to serve user equipment (UE) with very different capabilities depending on the use case and market segment in which the UE provides services to the end customer. Exemplary use cases expected to be addressed by the 5G wireless communication system include eMBB (enhanced mobile broadband), m-MTC (massive MTC), and URLL (ultra-reliable low latency communication). eMBB requirements (e.g., several tens of Gbps data transmission rate, low latency, high mobility, etc.) address the market segment representing wireless broadband subscribers who require an Internet connection full-time anywhere. m-MTC requirements such as very high connection density, rare data transmission, long battery life, and low mobility address the market segment representing IoT / IoE that envisions the connection of billions of devices. URLL requirements such as very low latency, very high reliability, and variable mobility address the market segment representing vehicle-to-vehicle / vehicle-to-infrastructure communication, which is expected to be one of the enablers for industrial automation applications and autonomous vehicles.

[0007] The current design of 5G wireless communication systems is for operation on licensed carriers. Research has recently begun to study enhancements for 5G wireless communication systems to operate on unlicensed carriers. The main motivations for using unlicensed carriers are to address the increasing wireless traffic demand under limited available spectrum and to enable free spectrum access for intelligent data offloading so that network operators without licensed spectrum can utilize wirelessly efficient 3GPP (3rd generation partnership project) radio access technologies; and for cellular operators to reduce capital expenditures (CAPEX) by leveraging improved intelligent spectrum access and management. The following diverse deployment scenarios are being considered for operation on unlicensed carriers:

[0008] NR-U (new radio-unlicensed) LAA (licensed assisted access): Carrier aggregation between a licensed band NR (Pcell (primary cell)) and an unlicensed band NR-U (Scell (secondary cell))

[0009] NR-U stand-alone (SA): Stand-alone NR-U

[0010] ENU-DC (LTE NR unlicensed-dual connectivity): Dual connectivity between a licensed band LTE (PCell) and an unlicensed band NR-U (PSCell (primary SCell))

[0011] NR unlicensed-dual connectivity (NNU-DC): Dual connectivity between a licensed band NR (PCell) and an unlicensed band NR-U (PSCell).

[0012] The above-described scenario includes an NR cell having a downlink (DL) in an unlicensed band and an uplink (UL) in a licensed band.

[0013] One of the goals of the above-described study is to identify the improvements necessary to support random access (RA) procedures in the unlicensed band. In a 5G (also referred to as NR or New Radio) wireless communication system, the RA procedure is used to achieve UL time synchronization. The RA procedure is used by a non-synchronized user equipment (UE) in the RRC CONNECTED state during initial access, handover, radio resource control (RRC) connection reconfiguration procedure, scheduling request transmission, secondary cell group (SCG) addition / modification, and data or control information transmission on the UL. During the RA procedure, the UE first transmits an RA Preamble (also referred to as Message 1 (Msg1)), and then waits for an RA Response (RAR) or Message 2 (Msg2) in an RAR window corresponding to the RA Preamble transmission. The next generation node B (gNB) transmits the RAR on a physical DL shared channel (PDSCH) addressed to the RA-radio network temporary identifier (RA-RNTI). The RA-RNTI identifies the time-frequency resource (also referred to as a physical RA channel (PRACH) occasion or PRACH transmission (TX) occasion or RA channel (RACH) occasion) at which the RA preamble was detected by the gNB. The maximum size of the RAR-window is one radio frame, i.e., 10 ms. The RA-RNTI is calculated as follows: RA-RNTI = 1 + s_id + 14 * t_id + 14 * 80 * f_id + 14 * 80 * 8 * ul_carrier_id, where

[0014] The s_id is the index of the first OFDM (orthogonal frequency division multiplexing) symbol of the PRACH occasion in which the UE transmits Msg1, i.e., the RA preamble; 0 ≤ s_id < 14,

[0015] The t_id is the index of the first slot of the PRACH occasion (0 ≤ t_id < 80).

[0016] The f_id is the index of the PRACH occasion within the slot in the frequency domain (0 ≤ f_id < 8),

[0017] The ul_carrier_id is the UL carrier used for Msg1 transmission (0 for normal UL (NUL) carriers and 1 for supplementary UL (SUL) carriers).

[0018] Many RARs for various RA preambles detected by the gNB can be multiplexed by the gNB in the same RAR MAC (media access control) PDU (protocol data unit). The RAR of the MAC PDU corresponds to the UE's RA preamble transmission if the RAR contains the RAPID (RA preamble identifier) of the RA preamble transmitted by the UE. If the RAR corresponding to the RA preamble transmission is not received during the RAR window and the UE has not yet transmitted the RA preamble set by the UE (set by the gNB in the RACH configuration), the UE re-transmits the RA preamble.

[0019] If a RAR corresponding to the RA preamble transmission is received and the UE transmits a dedicated RA preamble, the RA procedure is considered successful. If the UE transmits a non-dedicated (i.e., contention-based) RA preamble, upon successful reception of the RAR, the UE transmits Message 3 (Msg3) with the UL grant received in the RAR. Msg3 includes messages such as RRC connection request, RRC connection reconfiguration request, RRC handover confirmation, scheduling request, etc. This further includes the UE identity (i.e., C-RNTI (cell-radio network temporary identifier) or S-TMSI (SAE (system architecture evolution)-temporary mobile subscriber identity) or a random number). After transmitting Msg3, the UE starts a contention resolution timer. While the contention resolution timer is running, if the UE receives a physical downlink control channel (PDCCH) addressed to the C-RNTI included in Msg3, the contention resolution is considered successful, the contention resolution timer is stopped, and the RA procedure is completed. While the contention resolution timer is running, if the UE receives a contention resolution MAC CE including the UE's Contention Resolution Identity (the first X bits of the CCCH (common control channel) SDU (service data unit) transmitted in Msg3), the contention resolution is considered successful, the contention resolution timer is stopped, and the RA procedure is completed. If the contention resolution timer expires and the UE has not yet transmitted the RA preamble for a configurable number of times, the UE re-transmits the RA preamble.

[0020] The cell where the UE transmits the RA preamble may be a licensed carrier or an unlicensed carrier. When the carrier used for UL transmission is an unlicensed carrier, the UE needs to perform channel detection (i.e., LBT (listen-before-talk)) to determine whether the channel is free before transmitting Msg1 and Msg3 in UL. Similarly, when the carrier used for DL transmission is an unlicensed carrier, the gNB needs to perform channel detection (i.e., LBT) to determine whether the channel is free before transmitting Msg2 and Msg4 in DL. There may be a situation where the gNB receives the RA preamble but cannot transmit the RAR within the RAR window because the channel is not free. When the RAR window expires, the UE will resend the PRACH. The retransmitted RA preamble may not be received by the gNB due to collision, or the UE may fail to resend the RA preamble, or the retransmission may be delayed because the channel is not free in UL. Such problems can be avoided by using a larger RAR window size. However, a large RAR window with a size larger than 10 ms results in RA-RNTI mimicry.

[0021] Figure 1 is an illustrative diagram of RA-RNTI mimicry due to a large RAR window size according to the related art.

[0022] When the PRACH is transmitted using the same RA preamble in PRACH occasion X and PRACH occasion Y by UE1 and UE2 respectively, since the RA-RNTIs for PRACH occasion X and PRACH occasion Y are the same, the RAR received in the common slot between RAR window X and RAR window Y cannot be distinguished.

[0023] The above-mentioned RA-RNTI emulation problem can be solved by including it in the information for the radio frame in which the PRACH occasion starts. The RAR MAC PDU includes one or more RAR MAC sub-PDUs, each of which is composed of a RAPID MAC sub-header and a RAR MAC payload. When the RAPID of the MAC sub-header matches the RA preamble transmitted by the UE and the frame information of the RAR MAC payload corresponds to the radio frame of the PRACH occasion in which the UE transmitted the RA preamble, the RAR belongs to the UE. However, this is not an efficient approach because the UE needs to process the RAR MAC payload even when the RAR is not for it. Such a process needs to be performed for each RAR and all RARs of the received RAR MAC PDUs until the UE finds the RAR for itself or there are no more RARs to process. Such an approach can also cause an overhead problem because the frame information needs to be included in each RAR MAC payload of the RAR MAC PDU. Such an approach cannot provide frame information for MAC sub-PDUs that include the RAPID MAC sub-header but do not include the RAR MAC payload. Such a type of MAC sub-PDU without the RAR MAC payload is included to indicate the SI request acknowledgment when the transmitted RA preamble is for the SI request.

[0024] Therefore, an improved method for transmitting and receiving frame information with the RAR is needed.

[0025] The above information is provided only as background information to assist in the understanding of the present disclosure. No determination has been made and no claim holds as to which of the above can be applied as prior art in relation to the present disclosure.

Summary of the Invention

Problems to be Solved by the Invention

[0026] There is a need for an improved method for transmitting and receiving frame information by RAR.

[0027] In the case of uplink (UL) transmission on an unlicensed carrier, the user equipment (UE) selects the highest CAPC (channel access priority class) index of the logical channels (LCH) multiplexed in the MAC (media access control) protocol data unit (PDU) (i.e., the lowest priority CAPC). The LBT (listen before talk) parameters corresponding to the selected CAPC index are used to perform channel access for UL transmission (i.e., the LBT procedure). When SRB data (i.e., the MAC SDU of the signaling radio bearer) corresponding to the lowest CAPC (i.e., the highest priority) index is multiplexed with the MAC SDUs of the data radio bearer and the MAC CE in the MAC PDU, it is deprioritized. Therefore, there is a need for several types of methods to improve the current design.

[0028] In the case of an extended RAR window, one or more least significant bits (LSBs) of the system frame number (SFN) can be included in the downlink control information (DCI) transmitted on the physical downlink common control channel (PDCCH). Therefore, during the resynchronization procedure, the UE first needs to obtain the SFN of the target SpCell and then start RA towards the target SpCell. Since the 6 most significant bits (MSBs) of the SFN are included in the MIB and 4 bits are included in the PBCH payload, the UE needs to decode the PBCH of the target SpCell where it can delay the resynchronization procedure. Therefore, a method to reduce such delay is needed.

[0029] Aspects of the present disclosure are to solve at least the above-described problems and / or disadvantages and to provide at least the advantages described below. Therefore, aspects of the present disclosure are to provide a communication method and system that converge a 5th generation (5G) communication system to support higher data transmission rates beyond a 4th generation (4G) system.

[0030] Additional aspects are partially described in the following description, partially apparent from the description, or can be learned by practicing the provided examples. Means for Solving the Problems

[0031] According to one aspect of the present disclosure, a method performed by a terminal for handling listen before talk (LBT) failure in a wireless communication system is provided. The method includes identifying a consistent LBT failure for an active uplink (UL) bandwidth part (BWP) in a serving cell, identifying at least one UL BWP on the same carrier in the serving cell where a consistent LBT failure is not triggered - a physical random access channel (PRACH) occasion is configured for the at least one UL BWP -, and switching the active UL BWP to one of the at least one UL BWP.

[0032] According to another aspect of the present disclosure, a terminal in a wireless communication system is provided. The terminal includes a transceiver and at least one processor operably coupled to the transceiver. The at least one processor is configured to identify a consistent LBT failure for an active UL BWP in a serving cell, identify at least one UL BWP on the same carrier in the serving cell where a consistent LBT failure is not triggered - a physical random access channel (PRACH) occasion is configured for the at least one UL BWP -, and switch the active UL BWP to one of the at least one UL BWP.

Advantages of the Invention

[0033] The frame identifier can be applied to both sides of a MAC subPDU including a RAR and a MAC subPDU including a SI request confirmation response. The frame identifier can further be applied to a MAC subPDU including a BI. The overhead is small because the frame identifier is added only once for each RAR MAC PDU.

[0034] The advantage of the method of the present disclosure is that the CAPC that occupies the largest part of the UL approval has better channel access than the legacy method in which the lowest-priority CAPC is always selected. Another advantage of the method of the present disclosure is that the highest-priority CAPC among the CAPCs that occupy a part of the UL approval beyond the threshold can have an advantage over channel access without occupying the largest part of the UL approval.

[0035] The design for selecting the CAPC for the UL-set approval is improved.

[0036] The delay for resetting in the synchronization procedure can be reduced.

[0037] Other aspects, advantages, and significant features of the present disclosure will become apparent to those of ordinary skill in the art from the following detailed description that discloses various embodiments of the present disclosure taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0038] The above-described and other aspects, features, and advantages of specific embodiments of the present disclosure will become more apparent from the following description taken in connection with the accompanying drawings.

[0039]

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[0040] It will be understood that throughout the drawings, the same reference numerals refer to the same parts, components, and structures.

DETAILED DESCRIPTION OF THE INVENTION

[0041] The following description, with reference to the accompanying drawings, is provided to assist in a comprehensive understanding of the various embodiments of the present disclosure as defined in the claims and their equivalents. This includes various specific details for the purpose of assisting such understanding, but these should be regarded as merely exemplary. Thus, those of ordinary skill in the art will recognize that various changes and modifications to the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Further, descriptions of well-known functions and configurations may be omitted for clarity and conciseness.

[0042] The terms and words used in the following description and claims are not limited to their dictionary meanings and are used to enable the inventor to have a clear and consistent understanding of the present disclosure. Thus, it will be clear to those of ordinary skill in the art that the following detailed description is provided for illustrative purposes only and is not provided to limit the present disclosure as defined by the appended claims and their equivalents.

[0043] It should be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to “a component surface” includes a reference to one or more of such surfaces.

[0044] The term “substantially” means that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations such as, for example, tolerances, measurement errors, measurement accuracy limitations, and other factors known to those of ordinary skill in the art may occur to the extent that they do not exclude the effect the characteristic is intended to provide.

[0045] As is known to those of ordinary skill in the art, the blocks of a flowchart (or sequence diagram) and combinations of flowcharts can be represented by and executed by computer program instructions that can be loaded onto a processor of a general purpose computer, a special purpose computer, or a programmable data processing apparatus. When the loaded program instructions are executed by the processor, this produces means for performing the functions described in the flowchart. Since the computer program instructions can be stored in a computer-readable memory usable in a special purpose computer or a programmable data processing apparatus, it is also possible to produce a product that performs the functions described in the flowchart. Since the computer program instructions can be loaded onto a computer or a programmable data processing apparatus, when executed as a process, this can perform the operations of the functions described in the flowchart.

[0046] The blocks of a flowchart can correspond to, or a portion of, a module, segment, or code that contains one or more executable instructions embodying one or more logical functions. In some cases, the functions represented by the blocks can be performed in an order different from the order listed. For example, two blocks listed in sequence can be executed concurrently or in reverse order.

[0047] In such an explanation, words such as "unit" and "module" can refer to software components or hardware components such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC) that can perform functions or operations. However, "unit" etc. are not limited to hardware or software. A unit etc. can reside in an addressable storage medium or can be configured to drive one or more processors. A unit etc. can refer to a software component, an object-oriented software component, a class component, a task component, a process, a function, an attribute, a procedure, a subroutine, a program code segment, a driver, firmware, microcode, a circuit, data, a database, a data structure, a table, an array or a variable. The functions provided by the components and units may be a combination of smaller components and units, and can be combined with other components to form larger components and units. The components and units can be configured to drive a device or one or more processors with a secure multimedia card.

[0048] Prior to the detailed description, terms or definitions necessary to understand the present disclosure are explained. However, such terms should be interpreted in a non-limiting manner.

[0049] A "base station (BS)" is an entity that communicates with a user equipment (UE), and can be referred to as a BS, a base transceiver station (BTS), a node B (NB), an evolved NB (eNB), an access point (AP), a fifth-generation (5G) NB (5G NB), or a next-generation NB (gNB).

[0050] "UE" is an entity that communicates with the BS, and can be referred to as UE, device, mobile station (MS), mobile equipment (ME), or terminal.

[0051] Method for transmitting and receiving frame information in a Random Access Response (RAR)

[0052] Method 1:

[0053] One method of the present disclosure for transmitting and receiving frame information in a RAR, wherein the UE / gNB transmits and receives a RAR Media Access Control (MAC) Protocol Data Unit (PDU), where the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0054] First RAR MAC PDU Format:

[0055] FIG. 2 shows an example of a RAR MAC PDU based on the first RAR MAC PDU format according to an embodiment of the present disclosure. For purposes of illustration, it is assumed that the FRAME ID is 3 bits corresponding to a maximum RAR window size of 80 ms (i.e., 8 radio frames) in FIG. 2. Other sizes of the FRAME ID are not excluded.

[0056] Referring to FIG. 2, a RAR MAC PDU according to the first (i.e., enhanced) RAR MAC PDU format is composed of one or more MAC subPDUs and optionally padding. Each MAC subPDU is composed of one of the following:

[0057] - A MAC subheader having only a frame identifier;

[0058] - A MAC subheader having only a backoff indicator;

[0059] -MAC sub-header having only a Random Access (RA) preamble identifier (RAPID) (i.e., confirmation response for System Information (SI) request);

[0060] -MAC sub-header having RAPID and MAC RAR.

[0061] The Frame Identifier MAC sub-header contains a Frame Identifier (FRAME ID). The size of the Frame Identifier is 'X' bits, and the remaining bits (if any) of the Frame Identifier MAC sub-header are Reserved (R) bits. The Frame Identifier is one of the following:

[0062] -Frame Identifier = System Sub-frame Number (SFN)

[0063] -Frame Identifier = SFN modulo (maximum RAR window size supported in a radio frame)

[0064] -Frame Identifier = SFN modulo (RAR window size set in a radio frame)

[0065] -Frame Identifier = 'p' least significant bits of SFN, where 'p' may be predefined or the same as log2(maximum RAR window size of a radio frame) or log2(RAR window size set in a radio frame).

[0066] -SFN is the system frame number of the radio frame of a Physical RA Channel (PRACH) occasion or the system frame number of the radio frame in which the PRACH occasion starts.

[0067] - The configured RAR window size is the size of the RAR window signaled by the gNB, where the gNB selects the size of the RAR window from a set of configurable RAR window sizes. The set of configurable RAR window sizes is predefined. The maximum supported RAR window size indicates the maximum value of the RAR window size in the set of configurable RAR window sizes.

[0068] The MAC subPDU having only the frame identifier is placed at the beginning of the MAC PDU. The frame identifier MAC sub-header is included in the first MAC subPDU of the RAR MAC PDU.

[0069] The MAC sub-header having the backoff indicator consists of five header fields which are extended (E) / type (T) / reserved (R) / R / backoff indicator (BI). The MAC subPDU having only the backoff indicator, if included, is included immediately after the MAC subPDU that carried the frame identifier MAC sub-header, i.e., the backoff indication is included immediately after the MAC subPDU that carries the frame identifier MAC sub-header. That is, the backoff indication is included in the second MAC subPDU.

[0070] The MAC sub-header with RAPID consists of three header fields: E / T / RAPID. If padding exists, it is placed at the end of the MAC PDU. The presence and length of the padding are implied based on the transport block (TB) size and the size of the MAC subPDU. The type (T) field is set to the unique value of the BI MAC sub-header and the RAPID sub-header. The extension (E) field set to '0' in the MAC sub-header of the MAC subPDU indicates that the MAC subPDU is the last MAC subPDU in the MAC PDU. The E field set to '1' in the MAC sub-header of the MAC subPDU indicates that at least another MAC subPDU follows.

[0071] 'MAC subPDU with only RAPID' and 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the second MAC subPDU and the padding (if any) when the backoff indication is included in the MAC PDU. 'MAC subPDU with only RAPID' and 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the first MAC subPDU and the padding (if any) when the backoff indication is not included in the MAC PDU.

[0072] Second RAR MAC PDU Format:

[0073] Figure 3 shows an example of a RAR MAC PDU based on the second RAR MAC PDU format according to an embodiment of the present disclosure.

[0074] Referring to Figure 3, the RAR MAC PDU according to the second (i.e., regular) RAR MAC PDU format is composed of one or more MAC subPDUs and optionally padding.

[0075] Each MAC subPDU is composed of one of the following:

[0076] -MAC sub-header having only a back-off indicator;

[0077] -MAC header having only RAPID (i.e., confirmation response to SI request);

[0078] -MAC sub-header having RAPID and MAC RAR.

[0079] The MAC sub-header having a back-off indicator is composed of 5 header fields which are E / T / R / R / BI. The MAC subPDU having only a back-off indicator, if included, is placed at the start of the MAC PDU.

[0080] The MAC sub-header having RAPID is composed of 3 header fields which are E / T / RAPID. Padding, if present, is placed at the end of the MAC PDU. The presence and length of the padding are implied based on the TB size and the size of the MAC subPDU. The type (T) field is set to the unique value of the BI MAC sub-header and the RAPID sub-header. The E field set to '0' in the MAC sub-header of the MAC subPDU indicates that the MAC subPDU is the last MAC subPDU in the MAC PDU. The E field set to '1' in the MAC sub-header of the MAC subPDU indicates that at least another MAC subPDU follows.

[0081] The 'MAC subPDU with only RAPID' and the 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the first MAC subPDU and the padding (if any) when the backoff indication is included in the MAC PDU. The 'MAC subPDU with only RAPID' and the 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the start of the MAC PDU and the padding (if any) when the backoff indication is not included in the MAC PDU.

[0082] UE operation:

[0083] Example 1:

[0084] Figure 4 shows UE operation according to an embodiment of the present disclosure.

[0085] Referring to Figure 4, the UE transmits a RA preamble in operation 410, the UE monitors a physical downlink control channel (PDCCH) for RAR reception in operation 420, and the UE receives a RAR MAC PDU in operation 430. The UE determines in operation 440 whether the cell in which the UE monitors the PDCCH to receive the RAR is an unlicensed cell. If the cell is an unlicensed cell, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format in operation 450. If the cell is a licensed cell, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format in operation 460. If the DL carrier frequency of the cell corresponds to an unlicensed band or an unlicensed carrier, the cell is an unlicensed cell. Otherwise, the cell is a licensed cell.

[0086] UE Processing According to the First MAC PDU Format:

[0087] The UE processes the first MAC sub-PDU in operation 451 to obtain a frame identifier from the MAC sub-header of the first MAC sub-PDU, and processes the remaining MAC sub-PDUs with the RAR MAC PDU in operation 452 until the RAR is successfully received or there are no more MAC sub-PDUs left.

[0088] If the second MAC sub-PDU of the RAR MAC PDU contains a backoff indicator, the UE sets PREAMBLE_BACKOFF with the backoff value indicated by the BI field of the MAC sub-PDU multiplied by SCALING_FACTOR_BI in operation 453. SCALING_FACTOR_BI can be 1 or can be signaled by the gNB via RRC signaling. The frame identifier is not checked to process the MAC sub-PDU with BI. The backoff value is arbitrarily selected between 0 and PREAMBLE_BACKOFF when the backoff during the RA procedure is applied. Alternatively, if the second MAC sub-PDU of the RAR MAC PDU contains a backoff indicator and the frame identifier obtained from the first MAC sub-PDU corresponds to the radio frame of the PRACH occasion in which the RA preamble was transmitted by the UE (i.e., any PRACH occasion radio frame in which the RA preamble was transmitted by UE initiation), the UE sets PREAMBLE_BACKOFF with the backoff value indicated by the BI field of the MAC sub-PDU multiplied by SCALING_FACTOR_BI. The backoff value is arbitrarily selected between 0 and PREAMBLE_BACKOFF when the backoff during the RA procedure is applied.

[0089] To determine whether the frame identifier obtained from the first MAC sub-PDU corresponds to the radio frame of the PRACH occasion in which the RA preamble was transmitted by the UE, the UE calculates a frame identifier corresponding to the radio frame of the PRACH occasion as described above and compares it with the value of the frame identifier received in the RAR MAC PDU. If they match, the frame identifier obtained from the first MAC sub-PDU corresponds to the radio frame of the PRACH occasion in which the RA preamble was transmitted by the UE.

[0090] (When) a MAC sub-PDU (other than the first MAC sub-PDU) includes a MAC sub-header having a RAPID, the RAPID matches the RA preamble transmitted by the UE, and the frame identifier obtained from the first MAC sub-PDU corresponds to the radio frame of the PRACH occasion in which the RA preamble was transmitted by the UE (i.e., the radio frame of any PRACH occasion in which the RA preamble was transmitted by the UE start), the UE regards that the RAR was successfully received in operation 454).

[0091] If it is regarded that the RAR was successfully received and such a MAC sub-PDU includes only the RAPID, the UE regards this as a confirmation response to the SI request.

[0092] UE Processing According to the Second MAC PDU Format:

[0093] In operation 462, the UE processes the MAC sub-PDUs in the RAR MAC PDU until the RAR is successfully received or there are no more MAC sub-PDUs left.

[0094] If the first MAC sub-PDU of the RAR MAC PDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF with the backoff value indicated by the BI field of the MAC sub-PDU multiplied by SCALING_FACTOR_BI in operation 463.

[0095] If the MAC subPDU contains a MAC sub-header with RAPID and the RAPID matches the RA preamble transmitted by the UE, the UE considers that the RAR has been successfully received in operation 464. If the RAR is considered to have been successfully received and such a MAC subPDU contains only RAPID, the UE considers this as an acknowledgement response to the SI request.

[0096] Example 2: In other examples, the UE transmits a RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives a RAR MAC PDU. The UE determines whether the configured RAR window size is greater than 10 ms. If the configured RAR window size is greater than 10 ms, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the configured RAR window size is less than 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operations for processing the RAR MAC PDU after determining the first or second RAR MAC PDU format in this example are as described in FIG. 4.

[0097] Example 3: In other examples, the UE transmits a RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives a RAR MAC PDU. The UE determines whether the maximum supported RAR window size is greater than 10 ms. If the maximum supported RAR window size is greater than 10 ms, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the maximum supported RAR window size is less than 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operations for processing the RAR MAC PDU after determining the first or second RAR MAC PDU format in this example are as described in FIG. 4.

[0098] gNB Operation:

[0099] Figure 5 shows gNB operation according to an embodiment of the present disclosure.

[0100] Referring to Figure 5, the gNB receives one or more RA preambles in operation 510 and determines in operation 520 whether the cell where the RAR is to be transmitted is an unlicensed cell. If the cell is an unlicensed cell, the gNB generates an RAR MAC PDU for transmission in operation 530 according to the first RAR MAC PDU format. If the cell is a licensed cell, the gNB generates an RAR MAC PDU for transmission in operation 540 according to the second RAR MAC PDU format. If the downlink (DL) carrier frequency of the cell corresponds to an unlicensed band, the cell is an unlicensed cell. Otherwise, the cell is a licensed cell.

[0101] To generate an RAR MAC PDU for transmission according to the first RAR MAC PDU format, the gNB includes a first MAC subPDU in the RAR MAC PDU in operation 531, and the first MAC subPDU is composed of a MAC subheader having only a frame identifier. If a backoff indication needs to be transmitted in the RAR MAC PDU, the gNB includes a second MAC subPDU in the RAR MAC PDU in operation 532, and the second MAC subPDU is composed of a MAC subheader having only a BI. The gNB includes one or more MAC subPDUs in the RAR MAC PDU in operation 533, and each MAC subPDU includes a MAC subheader having only a RAPID or a MAC subheader having both a RAPID and a MAC RAR. Each such MAC subPDU corresponds to the RA preamble received by the gNB in a PRACH occasion starting with a radio frame whose frame identifier is included in the first MAC subPDU.

[0102] To generate a RAR MAC PDU according to the 2nd RAR MAC PDU format, when a backoff indication needs to be sent in the RAR MAC PDU, the gNB includes a 1st MAC subPDU, and the 1st MAC subPDU is composed of a MAC subheader having only a BI in operation 542. The gNB includes one or more MAC subPDUs in operation 543, and each MAC subPDU includes a MAC subheader having only a RAPID or a MAC subheader having a RAPID and a MAC RAR.

[0103] The gNB transmits the RAR MAC PDU generated in operation 534 or 544.

[0104] In other embodiments, the gNB receives one or more RA preambles and determines whether a RAR window size greater than 10 ms is set for the cell where the RAR is transmitted. If the set RAR window size is greater than 10 ms, the gNB generates a RAR MAC PDU for transmission according to the 1st RAR MAC PDU format. If the set RAR window size is less than 10 ms, the gNB generates a RAR MAC PDU for transmission according to the 2nd RAR MAC PDU format. Then, the gNB transmits the generated RAR MAC PDU. The detailed gNB operations for generating the RAR MAC PDU after determining the 1st or 2nd RAR MAC PDU format in this embodiment are as described in FIG. 5.

[0105] In other embodiments, the gNB receives one or more RA preambles and determines whether the maximum supported RAR window size for the cell where the RAR is transmitted is greater than 10 ms.

[0106] If the maximum supported RAR window size is greater than 10 ms, the gNB generates the RAR MAC PDU for transmission according to the first RAR MAC PDU format. If the maximum supported RAR window size is less than 10 ms, the gNB generates the RAR MAC PDU for transmission according to the second RAR MAC PDU format. Then, the gNB transmits the generated RAR MAC PDU. The detailed gNB operations for generating the RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described in FIG. 5.

[0107] The advantage of the first RAR MAC PDU format as starting in this way is that the frame identifier can be applied to both sides of the MAC subPDU containing the RAR and the MAC subPDU containing the SI request confirmation response. The frame identifier can further be applied to the MAC subPDU containing the BI. Since the frame identifier is added only once for each RAR MAC PDU, the overhead is small. The disadvantage is that the frame identifier always needs to be included in the RAR MAC PDU.

[0108] Method 2:

[0109] The second method of this start for transmitting and receiving frame information with RAR, where the UE / gNB transmits and receives the RAR MAC PDU, and here the RAR MAC PDU is one of the first RAR MAC PDU format and the second RAR MAC PDU format.

[0110] First RAR MAC PDU Format:

[0111] FIG. 6 shows an example of the RAR MAC PDU based on the first RAR MAC PDU format according to another embodiment of the present disclosure. For illustration purposes, it is assumed that the FRAME ID is 3 bits corresponding to the maximum RAR window size of 80 ms in FIG. 6.

[0112] Referring to FIG. 6, the RAR MAC PDU according to the first (i.e., enhanced) RAR MAC PDU format is composed of one or more MAC subPDUs and padding selectively. Each MAC subPDU is composed of one of the following:

[0113] - A MAC sub-header having only a frame identifier;

[0114] - A MAC sub-header having only a backoff indicator;

[0115] - A MAC sub-header having only RAPID (i.e., a confirmation response to an SI request);

[0116] - A MAC sub-header having RAPID and MAC RAR.

[0117] The frame identifier MAC sub-header includes E, T, R1, and a frame identifier (FRAME ID). Also, it can include one or more R bits depending on the number of bits defined for the frame identifier. For example, when the length of the frame identifier is 5 bits, there are no R bits; when the length of the frame identifier is 3 bits, there are 2 R bits. The frame identifier is one of the following.

[0118] - Frame identifier = SFN

[0119] - Frame identifier = SFN modulo (the maximum supported RAR window size in a radio frame)

[0120] - Frame identifier = SFN modulo (the RAR window size set in a radio frame)

[0121] - Frame identifier = the 'p' least significant bits of SFN, where 'p' can be predefined or the same as log2 (the maximum RAR window size of a radio frame) or log2 (the RAR window size set in a radio frame).

[0122] - The SFN is the system frame number of the radio frame for the PRACH occasion or the system frame number of the radio frame in which the PRACH occasion starts.

[0123] - The set RAR window size is the size of the RAR window signaled by the gNB, where the gNB selects the size of the RAR window from a set of configurable RAR window sizes. The set of configurable RAR window sizes is predefined. The maximum supported RAR window size indicates the maximum value of the RAR window size in the set of configurable RAR window sizes.

[0124] The MAC sub-header with a backoff indicator consists of 5 header fields which are E / T / R1 / R / BI. The MAC sub-header with a frame identifier consists of at least 4 header fields which are E / T / R1 / FRAME ID. The T bit is set to the same value (e.g., T is the same as 0) for the MAC sub-header with a backoff indicator and the MAC sub-header with a frame identifier. The R1 bit is set to a different value to distinguish the MAC sub-header with a backoff indicator and the MAC sub-header with a frame identifier (e.g., R1 is set to 0 for the MAC sub-header with a backoff indicator and R1 is set to '1' for the MAC sub-header with a frame identifier).

[0125] The MAC sub-header with RAPID consists of 3 header fields which are E / T / RAPID. Padding, if present, is placed at the end of the MAC PDU. The presence and length of the padding are implied based on the TB size and the size of the MAC subPDU. The value of the T bit of the RAPID sub-header is different from the value of the T bit of the frame identifier sub-header and the BI sub-header.

[0126] The E field set to '0' in the MAC sub-header of the MAC subPDU indicates that the MAC subPDU is the last MAC subPDU in the MAC PDU. The E field set to '1' in the MAC sub-header of the MAC subPDU indicates that at least another MAC subPDU follows.

[0127] Example 1: Referring to FIG. 6, a MAC subPDU having only a backoff indicator, if included, is placed at the start of the MAC PDU. A MAC subPDU having only a frame identifier, if included, is placed at the start of the MAC PDU after the MAC subPDU having a backoff indicator. 'MAC subPDUs having only RAPID' and 'MAC subPDUs having RAPID and MAC RAR' can be placed anywhere between the second MAC subPDU and padding (if any) when a backoff indication is included in the MAC PDU. 'MAC subPDUs having only RAPID' and 'MAC subPDUs having RAPID and MAC RAR' can be placed anywhere between the first MAC subPDU and padding (if any) when a backoff indication is not included in the MAC PDU. This has the advantage that the UE can obtain the frame identifier before processing the MAC subPDU carrying the RAPID; the UE can obtain the backoff indicator without further processing the frame identifier; and the gNB can transmit a RAR MAC PDU having only a backoff indicator, which is not possible with method 1.

[0128] Example 2: The MAC subPDU having only a frame identifier is arranged at the start part of the MAC PDU. The MAC subPDU having only a backoff indication is arranged at the start part of the MAC PDU after the MAC subPDU having a frame identifier. The MAC subPDU having only ‘RAPID’ and the MAC subPDU having ‘RAPID and MAC RAR’ can be arranged at any place between the second MAC subPDU and padding (if any) when the backoff indication is included in the MAC PDU. The MAC subPDU having only ‘RAPID’ and the MAC subPDU having ‘RAPID and MAC RAR’ can be arranged at any place between the first MAC subPDU and padding (if any) when the backoff indication is not included in the MAC PDU. This has the advantage that the UE can acquire the frame identifier before processing any MAC subPDU, and the frame identifier can be applied to each MAC subPDU.

[0129] Example 3: The MAC subPDU having only the backoff indicator, if included, is placed at the start of the MAC PDU. The MAC subPDU having only the frame identifier is placed before the first MAC subPDU containing RAPID and MAC RAR. The 'MAC subPDU having only RAPID' can be placed anywhere between the second MAC subPDU and the padding (if any) when the backoff indication is included in the MAC PDU. The 'MAC subPDU having only RAPID' can be placed anywhere between the first MAC subPDU and the padding (if any) when the backoff indication is not included in the MAC PDU. The 'MAC subPDU having RAID and MAC RAR' is placed after the MAC subPDU carrying the frame identifier and before the padding (if any). This has the advantage that the UE can obtain the frame identifier before processing the MAC subPDU carrying RAPID and MAC RAR; the UE can obtain the backoff indicator without further processing the frame identifier; the UE can obtain the MAC subPDU having only RAPID without further processing the frame identifier. The gNB can transmit an RAR MAC PDU having only the backoff indicator without including the MAC subPDU having the frame identifier; the gNB can transmit an RAR MAC PDU having the backoff indication without including the MAC subPDU having the frame identifier and / or the MAC subPDU having only RAPID.

[0130] The advantage of the first RAR MAC PDU format as disclosed in this method is that the frame identifier can be applied to both the MAC subPDU containing the RAR and the MAC subPDU containing the SI request confirmation response. Since one frame identifier is added for each RAR MAC PDU, the overhead is small. The frame identifier does not always need to be included in the RAR MAC PDU. This can be skipped when only the RAR MAC PDU contains the BI. In one embodiment, this can also be skipped when the RAR MAC PDU does not contain any MAC RAR. Additionally, such an approach is advantageous for UE implementation as the MAC sub-header structure for the first and second RAR MAC PDU formats is similar, reducing implementation complexity.

[0131] Second RAR MAC PDU Format : In the method of the present disclosure, the RAR MAC PDU according to the second (i.e., regular) RAR MAC PDU format is the same as Method 1 for transmitting and receiving frame information with the RAR.

[0132] UE Operation:

[0133] Example 1:

[0134] FIG. 7 shows UE operation according to another embodiment of the present disclosure.

[0135] Referring to FIG. 7, the UE transmits a RA preamble in operation 710, the UE monitors a PDCCH for RAR reception in operation 720, and the UE receives a RAR MAC PDU in operation 730. The UE determines in operation 740 whether the cell in which the UE monitors the PDCCH to receive the RAR is an unlicensed cell. If the cell is an unlicensed cell, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format in operation 750. If the cell is a licensed cell, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format in operation 760. If the DL carrier frequency of the cell corresponds to an unlicensed band, the cell is an unlicensed cell. Otherwise, the cell is a licensed cell.

[0136] While processing the RAR MAC PDU according to the first MAC PDU format, the UE processes the MAC subPDUs with the RAR MAC PDU until the RAR is successfully received or there are no more MAC subPDUs left in operation 751. If the first MAC subPDU of the RAR MAC PDU contains a backoff indicator, the UE sets PREAMBLE_BACKOFF with the backoff value indicated by the BI field of the MAC subPDU multiplied by SCALING_FACTOR_BI in operation 752. If the MAC subPDU of the RAR MAC PDU contains a frame identifier, the UE processes the MAC subPDU to obtain the frame identifier from the MAC sub-header of the MAC subPDU in operation 753. If the MAC subPDU contains a MAC sub-header with RAPID and the RAPID matches the RA preamble transmitted by the UE and the frame identifier obtained from other MAC subPDUs corresponds to the radio frame of the PRACH occasion in which the RA preamble was transmitted by the UE, the UE considers that the RAR has been successfully received in operation 754. If it is considered that the RAR has been successfully received and such a MAC subPDU contains only RAPID, the UE considers this as an acknowledgement response to the SI request.

[0137] While processing the RAR MAC PDU according to the second MAC PDU format, the UE processes the MAC subPDUs with the RAR MAC PDU until the RAR is successfully received in operation 761 or there are no more MAC subPDUs remaining. If the first MAC subPDU of the RAR MAC PDU contains a backoff indicator, the UE sets PREAMBLE_BACKOFF with the backoff value indicated by the BI field of the MAC subPDU multiplied by SCALING_FACTOR_BI in operation 762. If the MAC subPDU contains a MAC sub-header with RAPID and the RAPID matches the RA preamble transmitted by the UE, the UE considers the RAR to be successfully received in operation 764. If the RAR is considered to be successfully received and such a MAC subPDU contains only RAPID, the UE considers this as an acknowledgment response to the SI request.

[0138] Example 2: In other examples, the UE transmits an RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives the RAR MAC PDU. The UE determines whether the configured RAR window size is greater than 10 ms. If the configured RAR window size is greater than 10 ms, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the configured RAR window size is less than 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operations for processing the RAR MAC PDU after determining the first or second RAR MAC PDU format in this example are as described in FIG. 7.

[0139] Example 3: In another example, the UE transmits a RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives a RAR MAC PDU. The UE determines whether the maximum supported RAR window size is greater than 10 ms. If the maximum supported RAR window size is greater than 10 ms, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the maximum supported RAR window size is less than 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operations for processing the RAR MAC PDU after determining the first or second RAR MAC PDU format in this example are as described in FIG. 7.

[0140] According to the first RAR MAC PDU format, the T bit is set to the same value (e.g., T is the same as 0) for the MAC sub-header with a backoff indicator and the MAC sub-header with a frame identifier. Therefore, while processing the RAR MAC PDU according to the first MAC PDU format, the UE checks the R1 bit to determine whether the MAC sub-header contains a BI or a frame identifier. The R1 bit is set to different values to distinguish between the MAC sub-header with a backoff indicator and the MAC sub-header with a frame identifier (e.g., R1 is set to 0 for the MAC sub-header with a backoff indicator and R1 is set to '1' for the MAC sub-header with a frame identifier). In one embodiment, while processing the RAR MAC PDU according to the first RAR MAC PDU format, the UE determines whether the MAC sub-header in the MAC subPDU is a BI sub-header, a frame identifier sub-header, or a RAPID sub-header. Here, the UE determines that when T = 0 and R1 = 0, the MAC sub-header is a BI sub-header; when T = 0 and R1 = 1, the MAC sub-header is a frame identifier sub-header; and when T = 1, the MAC sub-header is a RAPID sub-header. In one embodiment, while processing the RAR MAC PDU according to the second RAR MAC PDU format, the UE determines whether the MAC sub-header in the MAC subPDU is a BI sub-header or a RAPID sub-header. The UE determines that when T = 0, the MAC sub-header is a BI sub-header; and when T = 1, the MAC sub-header is a RAPID sub-header.

[0141] gNB Operation:

[0142] FIG. 8 shows gNB operations according to other embodiments of the present disclosure.

[0143] Referring to FIG. 8, the gNB receives one or more RA preambles in operation 810 and determines whether the cell where the RAR is to be transmitted in operation 820 is an unlicensed cell. If the cell is an unlicensed cell, the gNB generates a RAR MAC PDU for transmission by the first RAR MAC PDU format in operation 830. If the cell is a licensed cell, the gNB generates a RAR MAC PDU for transmission by the second RAR MAC PDU format in operation 840. If the DL carrier frequency of the cell corresponds to the unlicensed band, the cell is an unlicensed cell. Otherwise, the cell is a licensed cell.

[0144] When a backoff indication needs to be transmitted in the RAR MAC PDU while generating the RAR MAC PDU by the first RAR MAC PDU format, the gNB includes a first or second MAC sub-PDU in the RAR MAC PDU in operation 831, and the first or second MAC sub-PDU is composed of a MAC sub-header having only BI. The gNB includes a first or second MAC sub-PDU in the RAR MAC PDU in operation 832, and the first or second MAC sub-PDU is composed of a MAC sub-header having only a frame identifier. The gNB includes one or more MAC sub-PDUs in the RAR MAC PDU in operation 833, and each MAC sub-PDU includes a MAC sub-header having only RAPID or a MAC sub-header having RAPID and MAC RAR. Each of such MAC sub-PDUs corresponds to the RA preamble received by the gNB in a PRACH occasion starting with a radio frame in which the frame identifier is included in the first MAC sub-PDU.

[0145] When generating the RAR MAC PDU according to the 2nd RAR MAC PDU format, if a backoff indication needs to be sent in the RAR MAC PDU, the gNB includes the 1st MAC subPDU, and the 1st MAC subPDU is composed of a MAC sub-header having only BI in operation 841. The gNB includes one or more MAC subPDUs in operation 843, and each MAC subPDU includes a MAC sub-header having only RAPID or a MAC sub-header having RAPID and MAC RAR.

[0146] The gNB transmits the RAR MAC PDU generated in operation 834 or 844.

[0147] Alternatively, the detailed operations of this embodiment are by the operations as shown in FIG. 5. When generating the RAR MAC PDU according to the 1st MAC PDU format, the T bit is set to the same value (e.g., T is the same as 0) for the MAC sub-header having a backoff indicator and the MAC sub-header having a frame identifier. The R1 bit is set to different values to distinguish the MAC sub-header having a backoff indicator and the MAC sub-header having a frame identifier (e.g., R1 is set to 0 for the MAC sub-header having a backoff indicator, and R1 is set to '1' for the MAC sub-header having a frame identifier). In one embodiment, when generating the RAR MAC PDU according to the 1st RAR MAC PDU format, the gNB sets T = 0 and R1 = 0 in the BI MAC sub-header; sets T = 0 and R1 = 1 in the frame identifier MAC sub-header; and sets T = 1 in the RAPID MAC sub-header. In one embodiment, when generating the RAR MAC PDU according to the 2nd RAR MAC PDU format, the gNB sets T = 0 in the BI MAC sub-header; and sets T = 1 in the RAPID MAC sub-header.

[0148] In another embodiment, the gNB receives one or more RA preambles and determines whether to set an RAR window size greater than 10 ms for the cell where the RAR is to be transmitted. If the set RAR window size is greater than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the first RAR MAC PDU format. If the set RAR window size is less than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the second RAR MAC PDU format. Thereafter, the gNB transmits the generated RAR MAC PDU. The detailed gNB operations for generating the RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described in FIG. 8. Alternatively, the detailed gNB operations for generating the RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described in FIG. 5. During generating the RAR MAC PDU according to the first MAC PDU format, the T bit is set to the same value (e.g., T is the same as 0) for the MAC sub-header with a backoff indicator and the MAC sub-header with a frame identifier. The R1 bit is set to different values to distinguish the MAC sub-header with a backoff indicator and the MAC sub-header with a frame identifier (e.g., R1 is set to 0 in the MAC sub-header with a backoff indicator, and R1 is set to '1' in the MAC sub-header with a frame identifier). In one embodiment, during generating the RAR MAC PDU according to the first RAR MAC PDU format, the gNB sets T = 0 and R1 = 0 in the BI MAC sub-header; sets T = 0 and R1 = 1 in the frame identifier MAC sub-header; and sets T = 1 in the RAPID MAC sub-header. In one embodiment, during generating the RAR MAC PDU according to the second RAR MAC PDU format, the gNB sets T = 0 in the BI MAC sub-header; and sets T = 1 in the RAPID MAC sub-header.

[0149] In another embodiment, the gNB receives one or more RA preambles and determines whether the maximum supported RAR window size is greater than 10 ms for the cell in which the RAR is to be transmitted.

[0150] If the maximum supported RAR window size is greater than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the first RAR MAC PDU format. If the maximum supported RAR window size is less than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the second RAR MAC PDU format. Then, the gNB transmits the generated RAR MAC PDU. The detailed gNB operations for generating the RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described in FIG. 8. Alternatively, the detailed gNB operations for generating the RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described in FIG. 5. While generating the RAR MAC PDU according to the first MAC PDU format, the T bit is set to the same value (e.g., T is the same as 0) for the MAC sub-header with a backoff indicator and the MAC sub-header with a frame identifier. The R1 bit is set to different values to distinguish the MAC sub-header with a backoff indicator and the MAC sub-header with a frame identifier (e.g., R1 is set to 0 in the MAC sub-header with a backoff indicator and R1 is set to '1' in the MAC sub-header with a frame identifier). In one embodiment, while generating the RAR MAC PDU according to the first RAR MAC PDU format, the gNB sets T = 0 and R1 = 0 in the BI MAC sub-header; sets T = 0 and R1 = 1 in the frame identifier MAC sub-header; and sets T = 1 in the RAPID MAC sub-header. In one embodiment, while generating the RAR MAC PDU according to the second RAR MAC PDU format, the gNB sets T = 0 in the BI MAC sub-header; and sets T = 1 in the RAPID MAC sub-header.

[0151] Method 3:

[0152] A third method of the present disclosure for transmitting and receiving frame information by RAR, wherein the UE / gNB transmits and receives a RAR MAC PDU, and the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0153] First RAR MAC PDU Format :

[0154] FIG. 9 shows an example of a RAR MAC PDU based on a first RAR MAC PDU format according to another embodiment of the present disclosure. For purposes of illustration, it is assumed that the frame ID is 3 bits corresponding to a maximum RAR window size of 80 ms in FIG. 9.

[0155] Referring to FIG. 9, a RAR MAC PDU according to the first (i.e., enhanced) RAR MAC PDU format is composed of one or more MAC subPDUs and optionally padding. Each MAC subPDU is composed of one of the following:

[0156] - A MAC sub-header having only a frame identifier;

[0157] - A MAC sub-header having only a backoff indicator;

[0158] - A MAC sub-header having only RAPID (i.e., a confirmation response to an SI request);

[0159] - A MAC sub-header having RAPID and MAC RAR.

[0160] The frame identifier MAC sub-header includes E, T, and a frame identifier (FRAME ID). It can also include one or more R bits depending on the number of bits defined for the frame identifier. For example, if the frame identifier has a length of 6 bits, there are no R bits; if the frame identifier has a length of 3 bits, there are 3 R bits. The frame identifier can be any one of the following:

[0161] - Frame identifier = SFN

[0162] - Frame identifier = (Maximum supported RAR window size in a radio frame) in the SFN module

[0163] - Frame identifier = (Set RAR window size in a radio frame) in the SFN module

[0164] - Frame identifier = The 'p' least significant bits of the SFN, where 'p' can be predefined or the same as log2(maximum RAR window size of a radio frame) or log2(set RAR window size in a radio frame).

[0165] - SFN is the system frame number of the radio frame of the PRACH occasion or the system frame number of the radio frame where the PRACH occasion starts.

[0166] - The set RAR window size is the size of the RAR window signaled by the gNB, where the gNB selects the size of the RAR window from a set of configurable RAR window sizes. The set of configurable RAR window sizes is predefined. The maximum supported RAR window size indicates the maximum value of the RAR window size in the set of configurable RAR window sizes.

[0167] The MAC sub-header with a back-off indicator consists of 5 header fields which are E / T / R / R / BI. The MAC sub-header with a frame identifier consists of at least 3 header fields which are E / T / FRAME ID. The T bit is set to the same value (for example, T is the same as 0) for both the MAC sub-header with a back-off indicator and the MAC sub-header with a frame identifier. In the RAR MAC PDU, if there is only one MAC subPDU containing a sub-header with T = 0, the sub-header is a frame identifier sub-header. If there are two MAC subPDUs containing a sub-header with T = 0, the first MAC subPDU is for BI and the second MAC subPDU is for the frame identifier.

[0168] The MAC sub-header with RAPID consists of 3 header fields which are E / T / RAPID. If padding exists, it is placed at the end of the MAC PDU. The presence and length of the padding are implied based on the TB size and the size of the MAC subPDU. The value of the T bit in the RAPID sub-header is different from the value of the T bit in the frame identifier sub-header and the BI sub-header.

[0169] The E field set to '0' in the MAC sub-header of the MAC subPDU indicates that the MAC subPDU is the last MAC subPDU in the MAC PDU. The E field set to '1' in the MAC sub-header of the MAC subPDU indicates that at least another MAC subPDU follows.

[0170] A MAC subPDU having only a backoff indicator, if included, is placed at the start of the MAC PDU. A MAC subPDU having only a frame identifier, if included, is placed at the start of the MAC PDU after the MAC subPDU having only a backoff indicator. A MAC subPDU having only 'RAPID' and a MAC subPDU having 'RAID and MAC RAR' can be placed anywhere between the second MAC subPDU and padding (if any) when a backoff indication is included in the MAC PDU. A MAC subPDU having only 'RAPID' and a MAC subPDU having 'RAID and MAC RAR' can be placed anywhere between the first MAC subPDU and padding (if any) when a backoff indication is not included in the MAC PDU.

[0171] The advantage of the first RAR MAC PDU format as initiated in this way is that the frame identifier can be applied to both a MAC subPDU containing an RAR and a MAC subPDU containing an SI request confirmation response. Since the frame identifier is added only as many times as there are RAR MAC PDUs, the overhead is small. The frame identifier does not always need to be included in the RAR MAC PDU. This can be skipped when only the RAR MAC PDU contains a BI. Additionally, such an approach is advantageous for UE implementation as the MAC subheader structure for the first and second RAR MAC PDU formats is similar, reducing implementation complexity.

[0172] Second RAR MAC PDU Format: In the method of the present disclosure, the RAR MAC PDU according to the second (i.e., regular) RAR MAC PDU format is the same as Method 1.

[0173] UE Operation:

[0174] Example 1:

[0175] FIG. 10 shows UE operation according to another embodiment of the present disclosure.

[0176] Referring to FIG. 10, the UE transmits a RA preamble in operation 1010, the UE monitors a PDCCH for RAR reception in operation 1020, and the UE receives a RAR MAC PDU in operation 1030. The UE determines in operation 1040 whether the cell in which the UE monitors the PDCCH to receive the RAR is an unlicensed cell. If the cell is an unlicensed cell, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format in operation 1050. If the cell is a licensed cell, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format in operation 1060. If the DL carrier frequency of the cell corresponds to an unlicensed band, the cell is an unlicensed cell. Otherwise, the cell is a licensed cell.

[0177] While processing the RAR MAC PDU according to the first MAC PDU format, the UE processes the MAC subPDUs with the RAR MAC PDU until the RAR is successfully received in operation 1051 or there are no more MAC subPDUs left. If the first MAC subPDU of the RAR MAC PDU contains a backoff indicator, the UE sets PREAMBLE_BACKOFF with the backoff value indicated by the BI field of the MAC subPDU multiplied by SCALING_FACTOR_BI in operation 1052. If the MAC subPDU of the RAR MAC PDU contains a frame identifier, the UE processes the MAC subPDU in operation 1053 to obtain the frame identifier from the MAC sub-header of the MAC subPDU. If the MAC subPDU contains a MAC sub-header with RAPID and the RAPID matches the RA preamble transmitted by the UE and the frame identifier obtained from other MAC subPDUs corresponds to the radio frame of the PRACH occasion where the RA preamble was transmitted by the UE, the UE considers the RAR to have been successfully received in operation 1054. If the RAR is considered to have been successfully received and such a MAC subPDU contains only RAPID, the UE considers this as an acknowledgement response to the SI request. The UE determines whether the MAC sub-header is a BI sub-header or a frame identifier as follows: In the RAR MAC PDU, if there is only one MAC subPDU containing a sub-header with T = 0, the sub-header is a frame identifier sub-header and such a MAC subPDU contains only the frame identifier sub-header. If there are two MAC subPDUs containing sub-headers with T = 0, the first MAC subPDU contains BI and the second MAC subPDU contains a frame identifier. The UE determines that the MAC sub-header is a RAPID sub-header when T = 1.

[0178] While processing the RAR MAC PDU according to the 2nd MAC PDU format, the UE processes the MAC subPDUs with the RAR MAC PDU until the RAR is successfully received in operation 1061 or there are no more MAC subPDUs remaining. If the first MAC subPDU of the RAR MAC PDU contains a backoff indicator, the UE sets PREAMBLE_BACKOFF with the backoff value indicated by the BI field of the MAC subPDU multiplied by SCALING_FACTOR_BI in operation 1062. If the MAC subPDU contains a MAC sub-header with RAPID and the RAPID matches the RA preamble transmitted by the UE, the UE considers the RAR to have been successfully received in operation 1064. If the RAR is considered to have been successfully received and such a MAC subPDU contains only RAPID, the UE considers this as an acknowledgement response to the SI request. The UE determines whether the MAC sub-header in the MAC subPDU is a BI sub-header or a RAPID sub-header. The UE determines that the MAC sub-header is a BI sub-header when T = 0 and determines that the MAC sub-header is a RAPID sub-header when T = 1.

[0179] Example 2: In another example, the UE transmits a RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives a RAR MAC PDU. The UE determines whether the configured RAR window size is greater than 10 ms. If the configured RAR window size is greater than 10 ms, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the configured RAR window size is less than 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operations for processing the RAR MAC PDU after determining the first or second RAR MAC PDU format in this example are as described in FIG. 10. While processing the RAR MAC PDU according to the first MAC PDU format, the UE determines whether the MAC subheader in the RAR MAC PDU is a BI subheader or a frame identifier as follows: In the RAR MAC PDU, if there is only one MAC subPDU containing a subheader with T = 0, the subheader is a frame identifier subheader, and such a MAC subPDU contains only the frame identifier subheader. If there are two MAC subPDUs containing subheaders with T = 0, the first MAC subPDU contains BI, and the second MAC subPDU contains a frame identifier. The UE determines that the MAC subheader is a RAPID subheader when T = 1. While processing the RAR MAC PDU according to the second MAC PDU format, the UE determines whether the MAC subheader in the MAC subPDU is a BI subheader or a RAPID subheader. The UE determines that the MAC subheader is a BI subheader when T = 0 and determines that the MAC subheader is a RAPID subheader when T = 1.

[0180] Example 3: In other examples, the UE transmits a RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives a RAR MAC PDU. The UE determines whether the maximum supported RAR window size is greater than 10 ms. If the maximum supported RAR window size is greater than 10 ms, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the maximum supported RAR window size is less than 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operations for processing the RAR MAC PDU after determining the first or second RAR MAC PDU format in this example are as described in FIG. 10. While processing the RAR MAC PDU according to the first MAC PDU format, the UE determines whether the MAC subheader in the following manner is a BI subheader or a frame identifier: In the RAR MAC PDU, if there is only one MAC subPDU containing a subheader with T = 0, the subheader is a frame identifier subheader, and such a MAC subPDU contains only the frame identifier subheader. If there are two MAC subPDUs containing subheaders with T = 0, the first MAC subPDU contains BI, and the second MAC subPDU contains a frame identifier. The UE determines that the MAC subheader is a RAPID subheader when T = 1. While processing the RAR MAC PDU according to the second MAC PDU format, the UE determines whether the MAC subheader in the MAC subPDU is a BI subheader or a RAPID subheader. The UE determines that the MAC subheader is a BI subheader when T = 0 and determines that the MAC subheader is a RAPID subheader when T = 1.

[0181] gNB Operation:

[0182] FIG. 11 shows gNB operations according to an embodiment of the present disclosure.

[0183] Referring to FIG. 11, the gNB receives one or more RA preambles in operation 1110 and determines whether the cell where the RAR is to be transmitted in operation 1120 is an unlicensed cell. If the cell is an unlicensed cell, the gNB generates an RAR MAC PDU for transmission by the first RAR MAC PDU format in operation 1130. If the cell is a licensed cell, the gNB generates an RAR MAC PDU for transmission by the second RAR MAC PDU format in operation 1140. If the DL carrier frequency of the cell corresponds to an unlicensed band, the cell is an unlicensed cell.

[0184] Otherwise, the cell is a licensed cell.

[0185] When generating the RAR MAC PDU according to the first RAR MAC PDU format, if a MAC subPDU having only a backoff indicator is included, it is placed at the start of the MAC PDU, that is, the first MAC subPDU contains the BI. The MAC subPDU having a frame identifier is the second MAC subPDU when the first MAC subPDU contains the BI. If the backoff indication needs to be sent in the RAR MAC PDU, the gNB includes the first MAC subPDU in the RAR MAC PDU in operation 1131, and the first MAC subPDU is composed of a MAC subheader having only the BI. The gNB further includes the second MAC subPDU in the RAR MAC PDU, and the second MAC subPDU is composed of a MAC subheader having only the frame identifier. If the backoff indication does not need to be sent in the RAR MAC PDU, the gNB includes the first MAC subPDU in the RAR MAC PDU in operation 1132, and the first MAC subPDU is composed of a MAC subheader having only the BI. The gNB includes one or more MAC subPDUs in the RAR MAC PDU in operation 1133, and each MAC subPDU includes a MAC subheader having only the RAPID or a MAC subheader having the RAPID and the MAC RAR. Each such MAC subPDU corresponds to the RA preamble received by the gNB in a PRACH occasion starting with a radio frame in which the frame identifier is included in the first MAC subPDU.

[0186] When generating the RAR MAC PDU according to the second RAR MAC PDU format, if the backoff indication needs to be sent in the RAR MAC PDU, the gNB includes the first MAC subPDU, and the first MAC subPDU is composed of a MAC subheader having only the BI in operation 1141. The gNB includes one or more MAC subPDUs in operation 1143, and each MAC subPDU includes a MAC subheader having only the RAPID or a MAC subheader having the RAPID and the MAC RAR.

[0187] The gNB transmits the RAR MAC PDU generated in operation 1134 or 1144.

[0188] In other embodiments, the gNB receives one or more RA preambles and determines whether an RAR window size greater than 10 ms is set for the cell in which the RAR is to be transmitted. If the set RAR window size is greater than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the first RAR MAC PDU format. If the set RAR window size is less than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the second RAR MAC PDU format. Thereafter, the gNB transmits the generated RAR MAC PDU. The detailed gNB operations for generating the RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described in FIG. 11. During generating the RAR MAC PDU according to the first RAR MAC PDU format, if a MAC subPDU having only a backoff indicator is included, it is placed at the start of the MAC PDU, i.e., the first MAC subPDU includes the BI. The MAC subPDU having a frame identifier is the second MAC subPDU if the first MAC subPDU includes the BI.

[0189] In another embodiment, the gNB receives one or more RA preambles and determines whether the maximum supported RAR window size is greater than 10 ms for the cell to which the RAR is to be transmitted. If the maximum supported RAR window size is greater than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the first RAR MAC PDU format. If the maximum supported RAR window size is less than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the second RAR MAC PDU format. Thereafter, the gNB transmits the generated RAR MAC PDU. The detailed gNB operations for generating the RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described in FIG. 11. During generating the RAR MAC PDU according to the first RAR MAC PDU format, if a MAC subPDU having only a backoff indicator is included, it is placed at the start of the MAC PDU, that is, the first MAC subPDU includes the BI. The MAC subPDU having a frame identifier is the second MAC subPDU if the first MAC subPDU includes the BI.

[0190] Method 4:

[0191] A fourth method of this start for transmitting and receiving frame information in the RAR, wherein the UE / gNB transmits and receives an RAR MAC PDU, where the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0192] First RAR MAC PDU Format:

[0193] FIG. 12 shows an example of an RAR MAC PDU based on the first RAR MAC PDU format according to an embodiment of the present disclosure. For illustration purposes, it is assumed that the frame ID is 3 bits corresponding to a maximum RAR window size of 80 ms in FIG. 12.

[0194] Referring to FIG. 12, the RAR MAC PDU according to the first (i.e., enhanced) RAR MAC PDU format is composed of one or more MAC subPDUs and padding selectively. Each MAC subPDU is composed of one of the following:

[0195] - A MAC subheader having only a backoff indicator;

[0196] - A MAC subheader having only RAPID and FRAME ID (i.e., a confirmation response to an SI request);

[0197] - A MAC subheader having RAPID, FRAME ID, and MAC RAR.

[0198] The RAPID MAC subheader includes E, T, RAPID, and a frame identifier (FRAME ID). Also, it can include one or more R bits depending on the number of bits defined for the frame identifier. For example, when the length of the frame identifier is 8 bits, there are no R bits; when the length of the frame identifier is 3 bits, there are 5 R bits. The frame identifier is one of the following:

[0199] - Frame identifier = SFN

[0200] - Frame identifier = SFN modulo (the maximum supported RAR window size in a radio frame)

[0201] - Frame identifier = SFN modulo (the set RAR window size in a radio frame)

[0202] - Frame identifier = the 'p' least significant bits of SFN, where 'p' can be predefined or the same as log2 (the maximum RAR window size of a radio frame) or log2 (the set RAR window size in a radio frame).

[0203] - The SFN is the system frame number of the radio frame of the PRACH occasion or the system frame number of the radio frame in which the PRACH occasion starts.

[0204] - The set RAR window size is the size of the RAR window signaled by the gNB, where the gNB selects the size of the RAR window from a set of configurable RAR window sizes. The set of configurable RAR window sizes is predefined. The maximum supported RAR window size indicates the maximum value of the RAR window size in the set of configurable RAR window sizes.

[0205] The MAC subheader with a backoff indicator consists of 5 header fields which are E / T / R / R / BI.

[0206] The MAC subheader having only RAPID and FRAME ID consists of at least 4 header fields which are E / T / RAPID / FRAME ID. Also, this can include one or more R bits depending on the number of bits defined for the FRAME ID. Padding, if present, is placed at the end of the MAC PDU. The presence and length of the padding are implied based on the TB size and the size of the MAC subPDU.

[0207] The MAC subPDU having only a backoff indicator, if included, is placed at the start of the MAC PDU. The 'MAC subPDU having only RAPID' and the 'MAC subPDU having RAID and MAC RAR' can be placed anywhere between the second MAC subPDU and the padding (if any) when the backoff indication is included in the MAC PDU. The 'MAC subPDU having only RAPID' and the 'MAC subPDU having RAID and MAC RAR' can be placed anywhere from the first MAC subPDU and the padding (if any) when the backoff indication is not included in the MAC PDU.

[0208] The E field set to '0' in the MAC sub - header of the MAC subPDU indicates that the MAC subPDU is the last MAC subPDU in the MAC PDU. The E field set to '1' in the MAC sub - header of the MAC subPDU indicates that at least one other MAC subPDU follows.

[0209] Such an approach is advantageous for UE implementation in order to reduce the implementation complexity with a similar MAC sub - header structure for the first and second RAR MAC PDU formats. The number of MAC sub - headers is not further increased in such an approach.

[0210] Second RAR MAC PDU Format: In the method of the present disclosure, the RAR MAC PDU according to the second (i.e., normal) RAR MAC PDU format is the same as that of method 1.

[0211] UE Operation:

[0212] Example 1:

[0213] FIG. 13 shows the detailed UE operation according to another embodiment of the present disclosure.

[0214] Referring to FIG. 13, the UE transmits a RA preamble in operation 1310, the UE monitors a PDCCH for RAR reception in operation 1320, and the UE receives a RAR MAC PDU in operation 1330. The UE determines in operation 1340 whether the cell for which the UE monitors the PDCCH to receive the RAR is an unlicensed cell. If the cell is an unlicensed cell, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format in operation 1350. If the cell is a licensed cell, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format in operation 1360. If the DL carrier frequency of the cell corresponds to the unlicensed band, the cell is an unlicensed cell. Otherwise, the cell is a licensed cell.

[0215] While processing the RAR MAC PDU according to the first MAC PDU format, the UE processes the MAC sub-PDUs with the RAR MAC PDU until the RAR is successfully received in operation 1351 or there are no more MAC sub-PDUs remaining. If the first MAC sub-PDU of the RAR MAC PDU contains a backoff indicator, the UE sets PREAMBLE_BACKOFF with the backoff value indicated by the BI field of the MAC sub-PDU multiplied by SCALING_FACTOR_BI in operation 1352. If the MAC sub-PDU contains a MAC sub-header with RAPID and FRAME ID, and the RAPID matches the RA preamble transmitted by the UE and the FRAME ID corresponds to the radio frame of the PRACH occasion where the RA preamble was transmitted by the UE, the UE considers that the RAR was successfully received in operation 1353. If the RAR is considered to have been successfully received and such a MAC sub-PDU contains only RAPID, the UE considers this as an acknowledgment response to the SI request.

[0216] While processing the RAR MAC PDU according to the second MAC PDU format, the UE processes the MAC sub-PDUs with the RAR MAC PDU until the RAR is successfully received in operation 1361 or there are no more MAC sub-PDUs remaining. If the first MAC sub-PDU of the RAR MAC PDU contains a backoff indicator, the UE sets PREAMBLE_BACKOFF with the backoff value indicated by the BI field of the MAC sub-PDU multiplied by SCALING_FACTOR_BI in operation 1362. If the MAC sub-PDU contains a MAC sub-header with RAPID and the RAPID matches the RA preamble transmitted by the UE, the UE considers that the RAR was successfully received in operation 1363. If the RAR is considered to have been successfully received and such a MAC sub-PDU contains only RAPID, the UE considers this as an acknowledgment response to the SI request.

[0217] Example 2: In another example, the UE transmits a RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives a RAR MAC PDU. The UE determines whether the configured RAR window size is greater than 10 ms. If the configured RAR window size is greater than 10 ms, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the configured RAR window size is less than 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operations for processing the RAR MAC PDU after determining the first or second RAR MAC PDU format in this example are as described in FIG. 13.

[0218] Example 3: In another example, the UE transmits a RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives a RAR MAC PDU. The UE determines whether the maximum supported RAR window size is greater than 10 ms. If the maximum supported RAR window size is greater than 10 ms, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the maximum supported RAR window size is less than 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operations for processing the RAR MAC PDU after determining the first or second RAR MAC PDU format in this example are as described in FIG. 13.

[0219] gNB Operation:

[0220] FIG. 14 shows gNB operations according to an embodiment of the present disclosure.

[0221] Referring to FIG. 14, the gNB receives one or more RA preambles in operation 1410 and determines whether the cell where the RAR is to be transmitted in operation 1420 is an unlicensed cell. If the cell is an unlicensed cell, the gNB generates a RAR MAC PDU for transmission by the first RAR MAC PDU format in operation 1430. If the cell is a licensed cell, the gNB generates a RAR MAC PDU for transmission by the second RAR MAC PDU format in operation 1440. If the DL carrier frequency of the cell corresponds to the unlicensed band, the cell is an unlicensed cell.

[0222] Otherwise, the cell is a licensed cell.

[0223] When generating the RAR MAC PDU by the first RAR MAC PDU format, if a backoff indication needs to be transmitted in the RAR MAC PDU, the gNB includes a first MAC subPDU in the RAR MAC PDU in operation 1431, and the first MAC subPDU is composed of a MAC sub-header having only BI. The gNB includes one or more MAC subPDUs in the RAR MAC PDU in operation 1432), and each MAC subPDU includes a MAC sub-header having RAPID and FRAME ID or a MAC sub-header having RAPID, FRAME ID, and MAC RAR. Each such MAC subPDU corresponds to the RA preamble received by the gNB in a PRACH occasion starting with a radio frame in which the frame identifier (FRAME ID) is included in the first MAC subPDU.

[0224] When a backoff indication needs to be transmitted in the RAR MAC PDU during generation of the RAR MAC PDU according to the second RAR MAC PDU format, the gNB includes a first MAC subPDU, and the first MAC subPDU is composed of a MAC subheader having only BI in operation 1441. The gNB includes one or more MAC subPDUs in operation 1442, and each MAC subPDU includes a MAC subheader having only RAPID or a MAC subheader having RAPID and MAC RAR.

[0225] The gNB transmits the RAR MAC PDU generated in operation 1433 or 1443.

[0226] In other embodiments, the gNB receives one or more RA preambles and determines whether a RAR window size greater than 10 ms is set for the cell in which the RAR is transmitted. If the set RAR window size is greater than 10 ms, the gNB generates a RAR MAC PDU for transmission according to the first RAR MAC PDU format. If the set RAR window size is less than 10 ms, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format. Then, the gNB transmits the generated RAR MAC PDU. The detailed gNB operations for generating the RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described in FIG. 14.

[0227] In other embodiments, the gNB receives one or more RA preambles and determines whether the maximum supported RAR window size is greater than 10 ms for the cell in which the RAR is transmitted.

[0228] If the maximum supported RAR window size is greater than 10 ms, the gNB generates the RAR MAC PDU for transmission according to the first RAR MAC PDU format. If the maximum supported RAR window size is less than 10 ms, the gNB generates the RAR MAC PDU for transmission according to the second RAR MAC PDU format. Then, the gNB transmits the generated RAR MAC PDU. The detailed gNB operations for generating the RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described in FIG. 14.

[0229] Method 5:

[0230] A method for starting to transmit and receive frame information in RAR is proposed, which defines a new MAC sub-header (i.e., frame identifier MAC sub-header). The frame identifier MAC sub-header includes T and a frame identifier (FRAME ID). This can further include one or more R bits depending on the number of bits defined for the frame identifier. For example, if the length of the frame identifier is 6 bits, there are no R bits; if the length of the frame identifier is 3 bits, there are 3 R bits. The frame identifier is any one of the following:

[0231] - Frame identifier = SFN

[0232] - Frame identifier = SFN modulo (maximum supported RAR window size in a radio frame)

[0233] - Frame identifier = SFN modulo (configured RAR window size in a radio frame)

[0234] - Frame identifier = the 'p' least significant bits of SFN, where 'p' can be predefined or the same as log2(maximum RAR window size of a radio frame) or log2(configured RAR window size in a radio frame).

[0235] - The SFN is the system frame number of the radio frame of the PRACH occasion or the system frame number of the radio frame at which the PRACH occasion starts.

[0236] - The configured RAR window size is the size of the RAR window signaled by the gNB, where the gNB selects the size of the RAR window from a set of configurable RAR window sizes. The set of configurable RAR window sizes is predefined. The maximum supported RAR window size indicates the maximum value of the RAR window size in the set of configurable RAR window sizes.

[0237] In the present disclosure, the UE / gNB transmits and receives a RAR MAC PDU, where the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0238] First RAR MAC PDU Format:

[0239] In the method of the present disclosure, the RAR MAC PDU is selectively composed of one or more MAC subPDUs and padding. Each MAC subPDU is composed of one of the following:

[0240] - A MAC subheader having only a frame identifier;

[0241] - A MAC subheader having only a backoff indicator;

[0242] - A MAC subheader having only RAPID (i.e., a confirmation response to an SI request);

[0243] - A MAC subheader having RAPID and MAC RAR;

[0244] - A MAC subheader indicating padding.

[0245] The MAC sub-header with a back-off indicator consists of 4 header fields which are T / R / R / BI.

[0246] The MAC sub-header with a frame identifier consists of at least 2 header fields which are T / FRAME ID.

[0247] The MAC sub-header with RAPID consists of 2 header fields which are T / RAPID. Padding, if present, is placed at the end of the MAC PDU. The presence and length of the padding are implied based on the TB size and the size of the MAC subPDU.

[0248] The MAC sub-header for padding consists of T / R / R / R / R / R / R. A 2-bit type field differentiates BI, frame identifier, RAPID, and padding sub-headers.

[0249] A MAC subPDU with only a back-off indicator, if included, is placed at the start of the MAC PDU. A MAC subPDU with only a frame identifier, if included, is placed at the start of the MAC PDU after the MAC subPDU with a back-off indicator. A 'MAC subPDU with only RAPID' and a 'MAC subPDU with RAID and MAC RAR' can be placed anywhere between the second MAC subPDU and the padding (if any) when a back-off indication is included in the MAC PDU. A 'MAC subPDU with only RAPID' and a 'MAC subPDU with RAID and MAC RAR' can be placed anywhere between the first MAC subPDU and the padding (if any) when a back-off indication is not included in the MAC PDU.

[0250] (As an alternative) A MAC subPDU having only a backoff indicator, if included, is placed at the start of the MAC PDU. A MAC subPDU having only a frame identifier is placed before the first MAC subPDU containing RAPID and MAC RAR. A MAC subPDU having only 'RAPID' can be placed anywhere between the second MAC subPDU and padding (if any) when a backoff indication is included in the MAC PDU. A MAC subPDU having only 'RAPID' can be placed anywhere between the first MAC subPDU and padding (if any) when a backoff indication is not included in the MAC PDU. A MAC subPDU having 'RAID and MAC RAR' is placed after the MAC subPDU carrying the frame identifier and before padding (if any).

[0251] Second RAR MAC PDU Format: In the method of the present disclosure, the RAR MAC PDU according to the second (i.e., normal) RAR MAC PDU format is the same as that of method 1.

[0252] UE Operation: In one embodiment, the UE transmits a RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives a RAR MAC PDU. The UE determines whether the cell in which the UE monitors the PDCCH for RAR reception is an unlicensed cell. If the cell is an unlicensed cell, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the cell is a licensed cell, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. If the DL carrier frequency of the cell corresponds to an unlicensed band, the cell is an unlicensed cell. Otherwise, the cell is a licensed cell. In one embodiment, the UE operation is as illustrated in FIG. 7.

[0253] In another embodiment, the UE transmits a RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives a RAR MAC PDU. The UE determines whether the configured RAR window size is greater than 10 ms. If the configured RAR window size is greater than 10 ms, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the configured RAR window size is less than 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format.

[0254] In another embodiment, the UE transmits a RA preamble, the UE monitors the PDCCH for RAR reception, and the UE receives a RAR MAC PDU. The UE determines whether the maximum supported RAR window size is greater than 10 ms. If the maximum supported RAR window size is greater than 10 ms, the UE processes the received RAR MAC PDU according to the first RAR MAC PDU format. If the maximum supported RAR window size is less than 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format.

[0255] gNB Operation: In one embodiment, the gNB receives one or more RA access preambles and determines whether the cell where the RAR is to be transmitted is an unlicensed cell. If the cell is an unlicensed cell, the gNB generates a RAR MAC PDU for transmission according to the first RAR MAC PDU format. If the cell is a licensed cell, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format. If the DL carrier frequency of the cell corresponds to the unlicensed band, the cell is an unlicensed cell. Otherwise, the cell is a licensed cell. In one embodiment, the gNB operation is as illustrated in FIG. 8.

[0256] In other embodiments, the gNB receives one or more RA preambles and determines whether to set an RAR window size greater than 10 ms for the cell where the RAR is transmitted. If the set RAR window size is greater than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the first RAR MAC PDU format. If the set RAR window size is less than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the second RAR MAC PDU format. Then, the gNB transmits the generated RAR MAC PDU.

[0257] In other embodiments, the gNB receives one or more RA preambles and determines whether the maximum supported RAR window size for the cell where the RAR is transmitted is greater than 10 ms.

[0258] If the maximum supported RAR window size is greater than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the first RAR MAC PDU format. If the maximum supported RAR window size is less than 10 ms, the gNB generates an RAR MAC PDU for transmission according to the second RAR MAC PDU format. Then, the gNB transmits the generated RAR MAC PDU.

[0259] Method for processing authorized transmissions set on an unlicensed carrier

[0260] In the case of uplink (UL) transmission on an unlicensed carrier, the UE needs to perform channel detection (i.e., LBT (listen-before-talk)) to determine whether the channel is free before transmission. There are two types of LBT procedures defined for UL transmission as described below:

[0261] Category 1: No LBT

[0262] The LBT procedure is not performed by the transmitting entity.

[0263] Category 2: LBT without random backoff

[0264] The period during which the channel is detected to be idle before the transmitting entity transmits is crucial. For example, the detection interval could be 25 us, i.e., the UE can transmit after detecting that the channel has been idle for at least the detection interval Td = 25 us. In the case of UL transmission, Category 3 is further referred to as Type 2 channel access procedure.

[0265] Category 3: LBT with random backoff to a fixed - sized contention window

[0266] The UE transmits after detecting that the channel is idle during the slot period of the delay period (Td); then, the counter is 0 at Stage 4. The detailed procedure is as follows.

[0267] Stage 1: N = N init is set, where N init is a random number uniformly distributed between 0 and CWp. CWp is the contention window for a given channel access priority class 'p'. Various LBT parameters for different CAPC (channel access priority class) are listed in Table 1 below.

[0268]

Table 1

[0269] If the absence of any other technology sharing the carrier wave can be guaranteed long-term (e.g., by a regulatory level), the maximum channel occupancy time for LBT priority classes 3 and 4 is 10 msec. Otherwise, the maximum channel occupancy time for LBT priority classes 3 and 4 is 8 msec. Step 2: When N>0 and the UE chooses to decrease the counter, set N = N - 1. Step 3: Detect the channel during the additional slot period.

[0270] If the additional slot period is in the idle state, proceed to step 4; otherwise, proceed to step 5. Step 4: If N = 0, perform transmission. Otherwise, proceed to step 2.

[0271] Step 5: Detect the channel during the slot period of the additional delay period Td. The delay period (Td) is the same as T f +m p ×Ts, where Tf seems to be 16 us and Ts is the same as 9 us.

[0272] Step 6: When it is detected that the channel is idle during Td, proceed to step 2. Otherwise, proceed to step 5.

[0273] Category 4: LBT with random backoff in a variable-size contention window

[0274] The LBT procedure, as one of these components, has the following. The transmitting entity draws a random number N within a contention window. The size of the contention window is specified by the minimum and maximum values of N. The transmitting entity can change the size of the contention window when drawing the random number N. The random number N is used to determine the period of time during which the channel is detected to be in an idle state before the transmitting entity transmits on the channel in the LBT procedure. The detailed procedure is the same as Category 3. The only difference is that in Category 3 the size of the contention window is fixed, while in Category 4 the transmitting entity can change the size of the contention window when drawing the random number N. In the case of UL transmission, Category 4 is further referred to as Type 1 channel access procedure.

[0275] In the NR (new radio) system design, the gNB in UL can dynamically allocate resources to the UE via the C-RNTI (cell-radio network temporary identifier) on the PDCCH. The UE always monitors the PDCCH to find possible grants for UL transmission when DL reception is activated (the activity is managed by discontinuous reception (DRX) when the setting is configured). When carrier aggregation (CA) is configured, the same C-RNTI is applied to all serving cells.

[0276] Also, using the configured grant, the gNB can allocate periodic UL resources for UL transmission to the UE. Two types of configured UL grants are defined:

[0277] Type 1, RRC directly provides the configured UL grant (including the period).

[0278] For Type 2, RRC defines the configured UL grant period, and the PDCCH addressed to the CS-RNTI (configured scheduling-RNTI) can signal and activate or deactivate the configured UL grant; that is, it indicates that the PDCCH addressed to the CS-RNTI can be implicitly reused according to the period defined by RRC until the UL grant is deactivated.

[0279] In the case of dynamic grants, the LBT type / category used for channel access is signaled by the gNB on the PDCCH. The CAPC value used is further signaled by the gNB on the PDCCH.

[0280] For UL channel access for configured grants, the gNB signals the CAPC for each logical channel (LCH). MAC control elements (CEs) except for the padding buffer state report (BSR) MAC CE and the recommended bitrate MAC CE use the highest priority CAPC (i.e., the lowest CAPC index). Signaling radio bearer 0 (SRB0), signaling radio bearer 1 (SRB1), and signaling radio bearer 3 (SRB3) use the highest priority CAPC (i.e., the lowest CAPC index), but the CAPC for SRB2 is configurable. The UE selects the highest CAPC index (i.e., the lowest priority CAPC) among the LCHs multiplexed in the MAC PDU.

[0281] One problem with such a design for selecting CAPC for UL configured grants is that the data corresponding to the lowest CAPC (i.e., the highest priority) has a lower priority.

[0282] FIG. 15 is an illustrative diagram of a design for selecting CAPC for UL configured grants in the related art.

[0283] Referring to FIG. 15, according to the related art, even if a very small amount of data in the MAC PDU is suitable for such a CAPC, CAPC4 is selected for channel access. It is not always good to select the lowest CAPC index (i.e., the highest priority CAPC) of the LCH multiplexed in the MAC PDU. A very small amount of data in the MAC PDU can belong to the lowest CAPC index. Therefore, some methods to improve the current design are needed.

[0284] Method 1:

[0285] In NR, a MAC PDU is composed of one or more MAC subPDUs. Each MAC subPDU is composed of only a MAC subheader (including padding); a MAC subheader and a MAC service data unit (SDU); a MAC subheader and a MAC CE; or a MAC subheader and padding. The size of the MAC SDU is diverse. Each MAC subheader corresponds to a MAC SDU, a MAC CE, or padding. The MAC subheader excluding the MAC CE, padding, and MAC SDU including the UL CCCH (common control channel) with a fixed size is composed of 4 header fields of R / F / LCID / L. The MAC subheader for the MAC SDU including the fixed-size MAC CE, padding, and UL CCCH is composed of 2 header fields of R / LCID.

[0286] FIG. 16 shows the selection of CAPC for UL transmission according to an embodiment of the present disclosure. In one embodiment, this method is applied for UL transmission with a set approval.

[0287] Operation 1610: Referring to FIG. 16, to determine the CAPC used for UL transmission of the MAC PDU, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU in operation 1610. Alternatively, in other embodiments, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU excluding the MAC subPDUs carrying padding. Optionally, in other embodiments, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU excluding the MAC subPDUs carrying padding, the MAC subPDUs carrying padding BSR, and the MAC subPDUs carrying the recommended bitrate MAC CE.

[0288] For a MAC subPDU containing a MAC SDU, the CAPC is the CAPC of the LCH of the MAC SDU contained in the MAC subPDU. The gNB signals the CAPC for each LCH of the data radio bearer (DRB). The LCHs corresponding to the signaling radio bearers SRB0, SRB1, and SRB3 use the highest priority CAPC (i.e., the lowest CAPC index), while the CAPC for SRB2 is set by the gNB in the RRC message. Padding uses the lowest priority CAPC (i.e., the highest CAPC index).

[0289] For a MAC subPDU containing a MAC CE, the CAPC is the CAPC of the MAC CE contained in the MAC subPDU. MAC CEs excluding padding BSR and the recommended bitrate use the highest priority CAPC (i.e., the lowest CAPC index). Padding BSR and the recommended bitrate MAC CE use the lowest priority CAPC (i.e., the highest CAPC index).

[0290] Operation 1620:Next, at operation 1620, the UE calculates for each determined CAPC a parameter 'X' where 'X' is equal to the total size of the MAC subPDUs for the given CAPC / the total size of the MAC PDU. The size can be in number of bytes or bits. In one embodiment, the size of the MAC subPDU may not include the size of the MAC sub-header.

[0291] Operation 1630: At operation 1630, the UE selects the CAPC with the highest value of 'X'. The UE applies the parameters corresponding to the selected CAPC to access the channel for UL transmission.

[0292] Figure 17 is an illustration of a MAC PDU transmitted with UL grant during channel access (using the LBT procedure with CAPC) according to an embodiment of the present disclosure.

[0293] Referring to Figure 17, the values of 'X' calculated by the method described above are 0.3, 0.4, and 0.3 respectively for CAPC2, CAPC3, and CAPC4. Therefore, the UE selects CAPC3 corresponding to the highest value of X, i.e., 0.4.

[0294] Figure 18 shows the selection of CAPC for UL transmission according to another embodiment of the present disclosure. In one embodiment, this method is applied for UL transmission with a configured grant.

[0295] Operation 1810: Referring to Figure 18, to determine the CAPC used for UL transmission of the MAC PDU, the UE first determines at operation 1810 the CAPCs of the MAC SDUs and MAC CEs multiplexed in the MAC PDU. Alternatively, in other embodiments, the UE first determines the CAPCs of the MAC SDUs and MAC CEs multiplexed in the MAC PDU excluding the padding BSR MAC CE and the recommended bitrate MAC CE. Alternatively, in other embodiments, the UE first determines the CAPC of the MAC SDU.

[0296] In the case of a MAC SDU, the CAPC is the CAPC of the LCH of the MAC SDU. The gNB signals the CAPC for each LCH of the DRB. The LCHs corresponding to the signaling radio bearers SRB0, SRB1, and SRB3 use the highest-priority CAPC, while the CAPC for SRB2 is set by the gNB in the RRC message.

[0297] In the case of a MAC CE, the CAPC is the CAPC of the MAC CE. MAC CEs excluding the padding BSR and the recommended bit rate use the highest-priority CAPC (i.e., the lowest CAPC index). The padding BSR and the recommended bit rate MAC CEs use the lowest-priority CAPC (i.e., the highest CAPC index).

[0298] Operation 1820: Next, the UE calculates the parameter 'X' for each determined CAPC where 'X' is the same as [the total size of the MAC SDU and / or MAC CE for the corresponding CAPC of the MAC PDU] / the total size of the MAC PDU. The size may be in bytes or bits in Operation 1820.

[0299] Operation 1830: The UE selects the CAPC with the highest value of 'X'. The UE applies the parameters corresponding to the selected CAPC to access the channel for UL transmission in Operation 1830.

[0300] The advantage of the first method is that it has better channel access than the legacy method where the CAPC that occupies the largest part of the UL grant always selects the lowest-priority CAPC.

[0301] In other embodiments, the method described above is applied when a specific LCH is not multiplexed in the MAC PDU. When a specific LCH is multiplexed in the MAC PDU, the UE applies the rule, i.e., the UE selects the lowest CAPC index (i.e., the highest priority) among the LCH / MAC CEs multiplexed in the MAC PDU.

[0302] In one embodiment, the specific LCH is an LCH for a signaling radio bearer. When any SRB MAC SDU is included in the MAC PDU, the UE applies the rule, i.e., the UE selects the lowest CAPC index (i.e., the highest priority) among the LCH / MAC CEs multiplexed in the MAC PDU. In other words, when any SRB MAC SDU is included in the MAC PDU, the UE selects the CAPC index of the SRB when the CAPC index of the SRB is the lowest (or the lowest CAPC index among the CAPC indexes of the SRBs whose MAC SDUs are included in the MAC PDU).

[0303] In other embodiments, the specific LCH is an LCH for signaling radio bearers SRB0, SRB1, and SRB3. When any of the SRB0, SRB1, and SRB3 MAC SDUs is included in the MAC PDU, the UE selects the lowest CAPC index (i.e., the highest priority) of the LCH / MAC CEs multiplexed in the MAC PDU.

[0304] In other embodiments, the specific LCH is one or more LCHs for signaling radio bearers. One or more signaling radio bearers for which the UE selects the lowest CAPC index (i.e., the highest priority) of the LCH / MAC CEs multiplexed in the MAC PDU can be predefined.

[0305] In other embodiments, the specific LCH is one or more LCHs signaled by the gNB.

[0306] In other embodiments, the specific LCH is a MAC CE other than the padding BSR. When any MAC CE (other than the padding BSR) is included in the MAC PDU, the UE applies the rule.

[0307] In other embodiments, the specific LCH is one or more MAC CEs. One or more MAC CEs to which the rule is applied can be predefined.

[0308] Method 2:

[0309] In NR, a MAC PDU is composed of one or more MAC sub-PDUs. Each MAC sub-PDU consists of only a MAC sub-header (including padding); a MAC sub-header and a MAC SDU; a MAC sub-header and a MAC CE; or a MAC sub-header and padding. The size of the MAC SDU varies. Each MAC sub-header corresponds to a MAC SDU, a MAC CE, or padding. The MAC sub-header excluding the MAC CE, padding, and MAC SDU including UL CCCH with a fixed size is composed of 4 header fields of R / F / LCID / L. The MAC sub-header for the MAC SDU including the MAC CE, padding, and UL CCCH with a fixed size is composed of 2 header fields of R / LCID.

[0310] FIG. 19 shows the selection of a CAPC for UL transmission according to an embodiment of the present disclosure. In one embodiment, this method is applied for UL transmission with a set approval.

[0311] Operation 1910: Referring to FIG. 19, to determine the CAPC for UL transmission of a MAC PDU, the UE first determines the CAPC of the MAC sub-PDUs multiplexed in the MAC PDU in operation 1910. Alternatively, in other embodiments, the UE first determines the CAPC of the MAC sub-PDUs multiplexed in the MAC PDU excluding the MAC sub-PDUs carrying padding. Alternatively, in other embodiments, the UE first determines the CAPC of the MAC sub-PDUs multiplexed in the MAC PDU excluding the MAC sub-PDUs carrying padding, the MAC sub-PDUs carrying padding BSR, and the MAC sub-PDUs carrying the recommended bit rate.

[0312] In the case of a MAC subPDU containing a MAC SDU, the CAPC is the CAPC of the LCH of the MAC SDU contained in the MAC subPDU. The gNB signals the CAPC for each LCH of the DRB. The LCHs corresponding to the signaling radio bearers SRB0, SRB1, and SRB3 use the highest priority CAPC (i.e., the lowest CAPC index), while the CAPC for SRB2 is set by the gNB in the RRC message. Padding uses the lowest priority CAPC (i.e., the highest CAPC index).

[0313] In the case of a MAC subPDU containing a MAC CE, the CAPC is the CAPC of the MAC CE contained in the MAC subPDU. MAC CEs excluding the padding BSR use the highest priority CAPC (i.e., the lowest CAPC index). The padding BSR and the recommended bit rate use the lowest priority CAPC (i.e., the highest CAPC index).

[0314] Operation 1920: Next, the UE calculates, in operation 1920, for each determined CAPC for which 'X' is the same as the total size of the MAC subPDU for the CAPC / total size of the MAC PDU. The size may be in number of bytes or bits. In one embodiment, the size of the MAC subPDU may not include the size of the MAC subheader.

[0315] Operation 1930: Among the CAPCs for which 'X' is greater than the threshold, the UE selects, in operation 1930, the CAPC with the lowest CAPC index (i.e., the highest priority). If there is no CAPC for which 'X' is greater than the threshold, the UE selects the CAPC with the highest 'X' value. The UE applies the parameters corresponding to the selected CAPC to access the channel for UL transmission.

[0316] The gNB signals a threshold to the UE. The threshold can be common to all UL configured grants or can be set separately for each UL configured grant. If no threshold is set, the UE selects the CAPC with the highest 'X' value. Alternatively, if no threshold is set, the UE selects the CAPC with the highest CAPC index (i.e., the lowest priority) and does not need to perform operation 1920. Alternatively, if no threshold is set, the UE selects the CAPC with the lowest CAPC index (i.e., the highest priority) and does not need to perform operation 1920.

[0317] Figure 20 is an exemplary diagram of a MAC PDU transmitted in a UL grant using LBT type 1 channel access according to an embodiment of the present disclosure.

[0318] Referring to Figure 20, the values of 'X' calculated by the method described above are 0.2, 0.5, and 0.3 for CAPC2, 4, and CAPC3, respectively. If the threshold is 0.25, the UE selects the CAPC from CAPC3 and CAPC4. Since the lowest CAPC index among CAPC3 and CAPC4 is 3, the UE selects CAPC3.

[0319] Figure 21 shows the selection of a CAPC for UL transmission according to an embodiment of the present disclosure. In one embodiment, this method is applied for UL transmission with a configured grant.

[0320] Operation 2110: Referring to Figure 21, to determine the CAPC used for UL transmission of the MAC PDU, the UE first determines the CAPC of the MAC SDU and MAC CE multiplexed in the MAC PDU in operation 2110. Alternatively, in other embodiments, the UE first determines the CAPC of the MAC SDU and MAC CE multiplexed in the MAC PDU excluding the padding BSR MAC CE and the recommended bitrate MAC CE.

[0321] In the case of a MAC SDU, the CAPC is the CAPC of the LCH of the MAC SDU. The gNB signals the CAPC for each LCH of the DRB. The LCHs corresponding to the signaling radio bearers SRB0, SRB1, and SRB3 use the highest priority CAPC, while the CAPC for SRB2 is set by the gNB in the RRC message.

[0322] In the case of a MAC CE, the CAPC is the CAPC of the MAC CE. MAC CEs excluding the padding BSR and the recommended bit rate use the highest priority CAPC (i.e., the lowest CAPC index). The padding BSR uses the lowest priority CAPC (i.e., the highest CAPC index).

[0323] Operation 2120: Next, the UE calculates the parameter 'X' for each determined CAPC where 'X' is the same as [the total size of the MAC SDU and / or MAC CE for the said CAPC] / the total size of the MAC PDU. The size may be in number of bytes or bits in Operation 2120.

[0324] Operation 2130: Among the CAPCs where 'X' is greater than the threshold, the UE selects the CAPC with the lowest CAPC index (i.e., the highest priority) in Operation 2130. If there is no CAPC where 'X' is greater than the threshold, the UE selects the CAPC with the highest 'X' value. The UE applies the parameters corresponding to the selected CAPC to access the channel for UL transmission.

[0325] The gNB signals the threshold to the UE. The threshold can be common to all UL-configured grants or can be set separately for each UL-configured grant. If no threshold is set, the UE selects the CAPC with the highest 'X' value. Alternatively, if no threshold is set, the UE selects the CAPC with the highest CAPC index (i.e., the lowest priority) and does not need to perform operation 2120. Alternatively, if no threshold is set, the UE selects the CAPC with the lowest CAPC index (i.e., the highest priority) and does not need to perform operation 2120.

[0326] The advantage of this method is that among the CAPCs that occupy a part of the UL grant beyond the threshold, the CAPC with the highest priority can take precedence over channel access even if it does not occupy the largest part of the UL grant.

[0327] In other embodiments, the method described above is applied when a specific LCH is not multiplexed in the MAC PDU. When a specific LCH is multiplexed in the MAC PDU, the UE applies the rule, i.e., the UE selects the lowest CAPC index (i.e., the highest priority) among the LCH / MAC CEs multiplexed in the MAC PDU.

[0328] In one embodiment, the specific LCH is an LCH for a signaling radio bearer. If any SRB MAC SDU is included in the MAC PDU, the UE applies the rule, i.e., the UE selects the lowest CAPC index (i.e., the highest priority) among the LCH / MAC CEs multiplexed in the MAC PDU. In other words, if any SRB MAC SDU is included in the MAC PDU, the UE selects the CAPC index of the SRB when the CAPC index of the SRB is the lowest (or the lowest CAPC index among the CAPC indexes of the SRBs whose MAC SDUs are included in the MAC PDU).

[0329] In other embodiments, a particular LCH is an LCH for signaling radio bearers SRB 0, SRB1, and SRB3. When any of the SRB 0, SRB1, and SRB3 MAC SDUs are included in a MAC PDU, the UE selects the lowest CAPC index (i.e., the highest priority) of the LCH / MAC CE multiplexed in the MAC PDU.

[0330] In other embodiments, a particular LCH is one or more LCHs for signaling radio bearers. One or more signaling radio bearers for which the UE selects the lowest CAPC index (i.e., the highest priority) of the LCH / MAC CE multiplexed in the MAC PDU can be predefined.

[0331] In other embodiments, a particular LCH is one or more LCHs signaled by a gNB.

[0332] In other embodiments, a particular LCH is a MAC CE other than a padding BSR. When any MAC CE (other than a padding BSR) is included in a MAC PDU, the UE applies the rules.

[0333] In other embodiments, a particular LCH is one or more MAC CEs. One or more MAC CEs to which the rules are applied can be predefined.

[0334] Method 3:

[0335] In NR, a MAC PDU is composed of one or more MAC sub-PDUs. Each MAC sub-PDU consists of only a MAC sub-header (including padding); a MAC sub-header and a MAC SDU; a MAC sub-header and a MAC CE; or a MAC sub-header and padding. The size of the MAC SDU varies. Each MAC sub-header corresponds to a MAC SDU, a MAC CE, or padding. Excluding the MAC sub-header for the MAC CE, padding, and the MAC SDU including the UL CCCH with a fixed size, the MAC sub-header is composed of 4 header fields, namely R / F / LCID / L. The MAC sub-header for the MAC SDU including the fixed-size MAC CE, padding, and UL CCCH is composed of 2 header fields, R / LCID.

[0336] Figure 22 shows the selection of the CAPC for UL transmission according to an embodiment of the present disclosure. In one embodiment, this method is applied for UL transmission with a set approval.

[0337] Referring to Figure 22, the UE determines at operation 2210 whether a specific LCH is multiplexed in the MAC PDU. If so, the UE applies the first rule, i.e., the UE selects at operation 2220 the lowest CAPC index (i.e., the highest priority) of the LCH / MAC CE multiplexed in the MAC PDU. Otherwise, the UE applies the second rule, i.e., the UE selects at operation 2230 the highest CAPC index (i.e., the lowest priority) of the LCH / MAC CE multiplexed in the MAC PDU.

[0338] In one embodiment, a specific LCH is an LCH for a signaling radio bearer. When any of the SRB MAC SDUs is included in the MAC PDU, the UE applies the first rule. In other words, when any of the SRB MAC SDUs is included in the MAC PDU, the UE selects the CAPC index of the SRB when the CAPC index of the SRB is the lowest (or the lowest CAPC index among the CAPC indexes of the SRBs whose MAC SDUs are included in the MAC PDU).

[0339] In other embodiments, a specific LCH is an LCH for signaling radio bearers SRB0, SRB1, and SRB3. When any of the SRB0, SRB1, and SRB3 MAC SDUs is included in the MAC PDU, the UE applies the first rule.

[0340] In other embodiments, a specific LCH is one or more LCHs for signaling radio bearers. One or more signaling radio bearers to which the first rule applies can be predefined.

[0341] In other embodiments, a specific LCH is one or more LCHs signaled by the gNB. Assume that the gNB signals LCH X and LCH Y for which the UE needs to apply the first rule. When any of the LCH X, LCH Y MAC SDUs is included in the MAC PDU, the UE applies the first rule.

[0342] In other embodiments, a specific LCH is a MAC CE other than the padding BSR. When any (MAC CE other than the padding BSR) MAC CE is included in the MAC PDU, the UE applies the first rule.

[0343] In other embodiments, a specific LCH is one or more MAC CEs. One or more MAC CEs to which the first rule applies can be predefined.

[0344] One or more of the above-described embodiments can be used to determine the application of the first and second rules.

[0345] Method 4:

[0346] In the method of the present disclosure, an improved multiplexing operation for UL transmission is proposed. In one embodiment, this method is applied for UL transmission with a set approval.

[0347] Operation 1: The UE is allowed to use such UL approval with the MAC SDU from the highest priority LCH among the LCHs allowed to use such UL approval having data available for transmission.

[0348] Operation 2: The UE is allowed to use such UL approval in the MAC PDU with the MAC SDU from any other LCH having a lower priority than the highest priority LCH among the LCHs allowed to use such UL approval only when the remaining available space in the MAC PDU with the data available for transmission is greater than a threshold. The threshold can be predefined or signaled by the gNB.

[0349] - An exemplary UL approval size is 1000 bytes.

[0350] LCH1, LCH2, and LCH3 can use such UL approval and have data available for transmission. If LCH1 has the highest priority, the UE includes LCH1 data in the MAC PDU. If the amount of remaining available data including the highest priority LCH is 200 bytes and 200 bytes is greater than the threshold, the UE multiplexes LCH2 and / or LCH3 in the MAC PDU by LCP (LCH prioritization). Otherwise, it includes only padding and / or padding BSR.

[0351] Method 5:

[0352] Example 1:

[0353] In the method of the present disclosure, an improved multiplexing operation for UL transmission is proposed. In one embodiment, this method is applied for UL transmission with a set approval.

[0354] Operation 1: The UE includes a MAC SDU from the highest priority LCH among the LCHs allowed to use such UL approval with data available for transmission.

[0355] Operation 2: The UE includes a MAC SDU from any other LCH having a lower priority than the highest priority LCH among the LCHs allowed to use such UL approval with a MAC PDU only if it has the same CAPC as the highest priority LCH and has data available for transmission.

[0356] - An exemplary UL approval size is 1000 bytes.

[0357] LCH1, LCH2, and LCH3 can use such UL approval and have data available for transmission. If LCH1 has the highest priority (P1), LCH2 has priority (P2), LCH3 has priority (P4), the CAPC for LCH1 is CAPC1, the CAPC for LCH2 is CAPC1, and the CAPC for LCH3 is CAPC3, the MAC SDU for LCH1 is first included in the MAC PDU because of the highest priority. If the UL approval after adding the MAC SDU of LCH1 is not yet consumed, the MAC SDU for LCH2 is included because it has the same CAPC as LCH1. Even though the UL approval is still not consumed after adding the MAC SDU of LCH2, the MAC SDU for LCH3 is not included because it does not have the same CAPC as LCH1 and LCH2. If available, data from LCH1 and LCH2 can be included in a lower priority procedure.

[0358] Example 2:

[0359] The UE applies the first and second selection criteria to select the LCH that can be multiplexed in the MAC PDU.

[0360] When a new transmission is performed, the MAC entity must do the following:

[0361] First selection criterion:

[0362] 1> Select the LCH (or the LCH with data available for transmission) for each UL grant that satisfies all of the following conditions:

[0363] 2> If the set of SCS (Subcarrier Spacing) index values allowed in the allowedSCS-List is set, it includes the SCS index associated with the UL grant;

[0364] 2> If maxPUSCH-Duration is set, it is greater than or equal to the physical UL shared channel (PUSCH) transmission period associated with the UL grant;

[0365] 2> If configuredGrantType1Allowed is set, it is set to true if the UL grant is of the configured grant type 1;

[0366] 2> If allowedServingCells is set, it includes the cell information associated with the UL grant. It does not apply to the LCH associated with the DRB for which the packet data convergence protocol (PDCP) replication is set in the same MAC entity where the PDCP replication is deactivated (i.e., CA replication).

[0367] allowedSCS-List, maxPUSCH-Duration, ConfiguredGrantType1Allowed, and allowedServingCells are selectively set by the gNB in the LCH configuration.

[0368] allowedSCS-List: If present in the LCH configuration received from the gNB, UL MAC SDUs from such an LCH can only be mapped to the indicated numerology. Otherwise, UL MAC SDUs from such an LCH can be mapped to any configured numerology.

[0369] allowedServingCells: If present in the LCH configuration received from the gNB, UL MAC SDUs from such an LCH can only be mapped to the serving cells indicated in such a list. Otherwise, UL MAC SDUs from such an LCH can be mapped to any configured serving cell of the cell group of the LCH.

[0370] configureGrantType1Allowed: If present, UL MAC SDUs from such an LCH can be transmitted on the configured grant type 1.

[0371] maxPUSCH-Duration: If present in the LCH configuration received from the gNB, UL MAC SDUs from such an LCH can only be transmitted using a UL grant that results in a PUSCH duration shorter than or equal to the duration indicated by such a field. Otherwise, UL MAC SDUs from such an LCH can be transmitted using a UL grant that results in any PUSCH duration.

[0372] Second selection criterion:

[0373] 1> When a new transmission is made for a UL grant configured on an unlicensed carrier:

[0374] 2> Select an LCH that has the same CAPC as the CAPC of the highest priority LCH among the LCHs selected as described above (by the first selection criterion).

[0375] (Instead)

[0376] 1> When a new transmission is made for the UL approval set on the unlicensed carrier wave and the highest priority LCH among the selected LCHs as described above belongs to the SRB (or when a specific SRB can be predefined)

[0377] 2> Select an LCH having the same CAPC as the CAPC of the highest priority LCH among the LCHs selected as described above (by the first selection criterion).

[0378] (Instead)

[0379] 1> When a new transmission is made on the unlicensed carrier wave:

[0380] 2> Select an LCH having the same CAPC as the CAPC of the highest priority LCH among the LCHs selected as described above (by the first selection criterion).

[0381] (Instead)

[0382] 1> When a new transmission is made on the unlicensed carrier wave and the highest priority LCH among the selected LCHs as described above belongs to the SRB (or when a specific SRB can be predefined)

[0383] 2> Select an LCH having the same CAPC as the CAPC of the highest priority LCH among the LCHs selected as described above (by the first selection criterion).

[0384] Resource Allocation:

[0385] The MAC entity must do the following when a new transmission is made:

[0386] 1> Allocate resources to the LCH as follows:

[0387] For UL approval with 2 > Bj > 0, the LCHs selected (by the selection criteria described above) are allocated resources in decreasing order of priority. When the prioritized bit rate (PBR) of an LCH is set to infinity, the MAC entity must allocate resources for all data available for transmission on the LCH before satisfying the PBR of lower priority LCHs.

[0388] 2> Decrease Bj by up to the total size of the MAC SDUs provided to the above-described LCH j;

[0389] 2> If any resources remain, LCHs configured with the same priority must be provided equally. All LCHs selected (by the selection criteria described above) are provided in a strictly decreasing priority order until all data for that LCH or any data for UL approval comes first and is consumed (regardless of the Bj value). LCHs configured with the same priority must be provided equally.

[0390] The MAC entity must initialize Bj of an LCH to 0 when the LCH is configured.

[0391] For each LCH j, the MAC entity must do the following:

[0392] 1> Increase Bj by PBR × T prior to all instances of the LCP procedure, where T is the elapsed time since Bj was last increased;

[0393] 1> If the Bj value is greater than the bucket size (i.e., PBR × bucket size duration (BSD)):

[0394] 1> Set Bj to the bucket size.

[0395] PBR and BSD are set by the gNB for their respective logics.

[0396] Method 6:

[0397] In the current design, the UE selects the LCH for multiplexing as follows:

[0398] 1> Selects the LCH for each UL grant (or the LCH with data available for transmission) that satisfies all of the following conditions:

[0399] 2> If the set of SCS index values allowed in the allowedSCS-List is set, it includes the SCS index associated with the UL grant;

[0400] 2> If maxPUSCH-Duration is set, it is greater than or equal to the PUSCH transmission period associated with the UL grant;

[0401] 2> If configuredGrantType1Allowed is set, it is set to true if the UL grant is of the configured grant type 1;

[0402] 2> If allowedServingCells is set, it includes the cell information associated with the UL grant. It does not apply to the LCH associated with the DRB for which PDCP duplication is set within the same MAC entity where PDCP duplication is deactivated (i.e., CA duplication).

[0403] allowedSCS-List, maxPUSCH-Duration, ConfiguredGrantType1Allowed, and allowedServingCells are selectively set by the gNB in the LCH configuration.

[0404] allowedSCS-List: If it exists in the LCH configuration received from the gNB, UL MAC SDUs from such LCHs can only be mapped to the indicated cryptographic algorithms. Otherwise, UL MAC SDUs from such LCHs can be mapped to any configured cryptographic algorithm.

[0405] allowedServingCells: If it exists in the LCH configuration received from the gNB, UL MAC SDUs from such LCHs can only be mapped to the serving cells indicated in such list. Otherwise, UL MAC SDUs from such LCHs can be mapped to any configured serving cell of the LCH's cell group.

[0406] configureGrantType1Allowed: If it exists, UL MAC SDUs from such LCHs can be transmitted on the configured grant type 1.

[0407] maxPUSCH-Duration: If it exists in the LCH configuration received from the gNB, UL MAC SDUs from such LCHs can only be transmitted using a UL grant that results in a PUSCH duration shorter than or equal to the duration indicated by such field. Otherwise, UL MAC SDUs from such LCHs can be transmitted using a UL grant that results in any PUSCH duration.

[0408] Resource Allocation:

[0409] The MAC entity must do the following when a new transmission is made:

[0410] 1> Allocate resources to LCHs as follows:

[0411] 2> The LCHs selected for UL approval (by the selection criteria described as above) are allocated resources in decreasing order of priority, where the resources are allocated to LCH j when one of the following conditions is satisfied:

[0412] 3> Condition 1: The CAPC index of LCH j <= Z

[0413] 3> Condition 2: The CAPC index of LCH j > Z and the amount of data that can be included from LCH j in the remaining UL approvals is greater than the amount of UL approvals already allocated

[0414] If none of the LCHs have been allocated resources yet, Z = the highest CAPC index. Otherwise, Z = MAX (the CAPC indices of all LCHs for which UL approval resources have already been allocated).

[0415] When the PBR of an LCH is set to infinity, the MAC entity must allocate resources for all data available for transmission on the LCH before satisfying the PBR of lower priority LCHs;

[0416] 2> Decrease Bj by the total size of the MAC SDUs provided to LCH j as described above;

[0417] 2> If any resources remain, LCHs set to the same priority must be provided equally. All LCHs selected (by the selection criteria described as above) are provided in a strict decreasing priority order until all data for that LCH or UL approval has been consumed (regardless of the Bj value), where resources are allocated to LCH j when one of the following conditions is satisfied.

[0418] 3> Condition 1: The CAPC index of LCH j <= Z

[0419] 3> Condition 2: When the CAPC index of LCH j > Z and the amount of data that can be included from LCH j with the remaining UL approvals is greater than the amount of UL approvals already allocated

[0420] If none of the LCHs have had resources allocated yet, Z = the highest CAPC index. Otherwise, Z = MAX(CAPC indices of all LCHs for which UL-approved resources have already been allocated).

[0421] Figure 23 is an exemplary diagram according to an embodiment of the present disclosure.

[0422] Referring to Figure 23, resources have already been allocated to SDU1 corresponding to LCH with UL approval. To schedule the next LCH, the candidate LCHs among the 'LCHs that can use such UL approvals with data available for transmission' must satisfy one of the following conditions:

[0423] - When the amount of data that can be included for the LCH with the remaining UL approvals > L1, does the LCH have a CAPC index Y where Y > X?

[0424] - The LCH has a CAPC index Y <= X.

[0425] Figure 24 is another exemplary diagram according to an embodiment of the present disclosure.

[0426] Referring to Figure 24, resources have already been allocated to SDU1 and SDU2 corresponding to LCH with UL approval. To schedule the next LCH, the candidate LCHs among the 'LCHs that can use such UL approvals with data available for transmission' must satisfy one of the following conditions:

[0427] - When the amount of data that can be included for the LCH with the remaining UL approvals > L1, does the LCH have a CAPC index Y where Y > Max(X, X1)?

[0428] -LCH has the CAPC index Y <= MAX(X, X1).

[0429] RA procedure method for supporting a large RAR window size

[0430] In a 5G wireless communication system operating in a higher frequency (mmWave) band, the UE and the gNB communicate with each other using beamforming. Beamforming technology is used to mitigate propagation path loss and increase the propagation distance for communication in a higher frequency band. Beamforming improves transmission and reception performance using high-gain antennas. Beamforming can be classified into transmission (TX) beamforming performed at the transmitter side and reception (RX) beamforming performed at the receiver side. Generally, TX beamforming enhances directivity by concentrating the area where radio waves arrive in a specific direction by using a number of antennas. In such a situation, the aggregation of multiple antennas can be referred to as an antenna array, and each antenna included in the array can be referred to as an array element. The antenna array can be configured in various forms such as a linear array, a planar array, etc. When TX beamforming is used, the directivity of the signal increases and the propagation distance increases. Also, since the signal is hardly transmitted in directions other than the directive direction, the signal interference acting on other receivers is considerably reduced. The receiver can perform beamforming on the RX signal by using an RX antenna array. RX beamforming provides the effect of increasing the intensity of the RX signal transmitted in a specific direction by concentrating the propagation in a specific direction, excluding signals transmitted in directions other than the specific direction from the RX signal, and blocking interference signals. By using beamforming techniques, the transmitter can create multiple transmission (TX) beam patterns in different directions. Each of such TX beam patterns can be further referred to as a TX beam. A wireless communication system operating at a high frequency uses a plurality of narrow TX beams to transmit signals within the cell by each narrow TX beam providing coverage to a part of the cell. The narrower the TX beam, the higher the antenna gain, and thus the radio wave distance of the signal transmitted using beamforming becomes even larger. The receiver can further create multiple reception (RX) beam patterns in different directions.Each of such RX beam patterns can further be referred to as an RX beam.

[0431] The 5G wireless communication system supports a stand-alone operation mode and dual connectivity (DC). In DC, a multi-Rx / Tx UE can be configured to utilize resources provided by two different nodes (or NBs) connected via a non-ideal backhaul. One node serves as the MN (Master Node), and the other node serves as the SN (Secondary Node). The MN and the SN are connected via a network interface, and at least the MN is connected to the core network. NR further supports a multi-radio access technology (RAT) DC (Multi-radio access technology (RAT) DC; MR-DC) operation in which a UE in the RRC_CONNECTED state located at two different nodes connected via a non-ideal backhaul utilizes radio resources provided by two separate schedulers that provide either E-UTRA (i.e., when the node is an ng-eNB) or NR access (i.e., when the node is a gNB). For an NR UE in the RRC_CONNECTED state where CA / DC is not configured, there is only one serving cell including the PCell (primary cell). For an RRC_CONNECTED UE where CA / DC is configured, the term'serving cell' is used to indicate a set of cells including the SpCell (Special Cell) and all SCells (secondary cells). In NR, the term Master Cell Group (MCG) refers to a group of serving cells associated with the MN that includes the PCell and optionally one or more SCells. In NR, the term Secondary Cell Group (SCG) refers to a group of serving cells associated with the SN that includes the PSCell (primary SCell) and optionally one or more SCells. In NR, the PCell refers to the serving cell of the MCG that operates on the primary frequency on which the UE performs an initial connection setup procedure or starts a connection reconfiguration procedure.In NR for a UE with CA configured, an SCell is a cell that provides additional radio resources on top of the SpCell. A PSCell refers to the serving cell in the SCG where the UE performs RA when performing Reconfiguration in the synchronization procedure. In the case of DC operation, the term SpCell refers to the PCell of the MCG or the PSCell of the SCG; otherwise (e.g., when DC is not configured), the term SpCell refers to the PCell.

[0432] In a 5G wireless communication system, a gNB or BS in a cell broadcast SSB (Synchronization Signal and physical broadcast channel (PBCH) block) is composed of a PSS (primary synchronization signal), an SSS (secondary synchronization signal), and an SI. The SI contains common parameters necessary for communication in the cell. In a 5G wireless communication system, the SI is divided into a master information block (MIB) and a number of SI blocks (SIBs).

[0433] The MIB is always transmitted on the PBCH with a period of 80 ms and a repetition within 80 ms, which contains the parameters necessary to obtain SIB1 from the cell.

[0434] SIB1 is transmitted on the DL shared channel (SCH) with a period of 160 ms and a variable transmission repetition. The default transmission repetition period of SIB1 is 20 ms, but the actual transmission repetition period follows the network implementation. SIB1 contains information regarding the availability and scheduling of other SIBs (e.g., the mapping of SIBs to SI messages, the period, the SI-window size) indicating whether one or more SIBs are provided only on demand, and in this case, the configuration necessary for the UE to make an SI request. SIB1 is a cell-specific SIB.

[0435] SIBs other than SIB1 are carried in SystemInformation messages transmitted on the DL-SCH. Only SIBs with the same period can be mapped to the same SI message.

[0436] In a 5G wireless communication system, the PDCCH is used to schedule DL transmissions on the physical DL shared channel (PDSCH) and UL transmissions on the PUSCH. Here, the DL control information (DCI) on the PDCCH includes at least a DL allocation including modulation and coding formats, a resource allocation, and HARQ (hybrid-automatic repeat request) information related to the DL-SCH; or a UL scheduling grant including at least modulation and coding formats, a resource allocation, and HARQ information related to the UL-SCH. In addition to scheduling, the PDCCH can be used for activating and deactivating PUSCH transmissions set for a set approval; activating and deactivating semi-permanent PDSCH transmissions; notifying one or more UEs of a slot format; notifying one or more UEs of physical resource blocks (PRBs) and orthogonal frequency division multiplexing (OFDM) symbols for which a UE can assume that no transmission is intended for the UE; transmitting TX power control (TPC) commands for the physical UL control channel (PUCCH) and the PUSCH; transmitting one or more TPC commands for SRS (semi-persistent scheduling) transmissions by one or more UEs; switching the active bandwidth part (BWP) of a UE; or starting an RA procedure. A UE monitors a set of PDCCH candidates in a monitoring occasion set by one or more configured control resource sets (CORESETs) according to corresponding search space configurations. A CORESET is composed of a set of PRBs having a period of 1 to 3 OFDM symbols. Resource units REG (Resource Element Groups) and CCE (Control Channel Element) are defined within a CORESET in which each CCE is composed of a set of REGs. The control channel is formed by the aggregation of CCEs.Different code rates for the control channel are achieved by aggregating different numbers of CCEs. Interleaved and non-interleaved CCE-REG mappings are supported in the CORESET. Polar coding is used for the PDCCH. Each REG that carries the PDCCH also carries its own demodulation reference signal (DMRS). Quadrature phase shift keying (QPSK) modulation is used for the PDCCH.

[0437] In a 5G wireless communication system, the list of search space configurations is signaled by the gNB for each configured BWP, where each search configuration is identified by an identifier to be unique. The identifiers of the search space configurations used for specific purposes such as paging reception, SI reception, and RAR reception are explicitly signaled by the gNB. In NR, the search space configuration consists of the parameters Monitoring-periodicity-PDCCH-slot, Monitoring-offset-PDCCH-slot, Monitoring-symbols-PDCCH-in-slot, and duration. The UE determines the PDCCH monitoring occasion within the slot using the parameters PDCCH monitoring period (Monitoring-periodicity-PDCCH-slot), PDCCH monitoring offset (Monitoring-offset-PDCCH-slot), and PDCCH monitoring pattern (Monitoring-symbols-PDCCH-within-slot). The PDCCH monitoring occasion exists in slot 'x' up to x + duration, where the slot with number 'x' in a radio frame with number 'y' satisfies the following equation:

[0438] (y * (number of slots in a radio frame) + x - Monitoring-offset-PDCCH-slot) mod (Monitoring-periodicity-PDCCH-slot) = 0;

[0439] In each slot having a PDCCH monitoring occasion, the starting symbol of the PDCCH monitoring occasion is given by Monitoring-symbols-PDCCH-within-slot. The length (symbols) of the PDCCH monitoring occasion is provided in the CORESET associated with the search space. The search space configuration includes the identifier of the CORESET configuration associated therewith. The CORESET configuration list is signaled by the gNB for each configured BWP, where each CORESET configuration is identified to be unique by an identifier. The period of each radio frame is 10 ms. The radio frame is identified by a radio frame number or SFN. Each radio frame is composed of a number of slots in which the number of slots in the radio frame and the slot period vary depending on the SCS. The number of slots in the radio frame and the slot period by the radio frame for each supported SCS are predefined in NR. Each CORESET configuration is associated with a list of TCI (transmission configuration indicator) states. One DL reference signal (RS) ID (SSB or channel state information (CSI) RS) is set per TCI state. The list of TCI states corresponding to the CORESET configuration is signaled by the gNB via radio resource control (RRC) signaling. One of the TCI states in the TCI state list is activated and indicated to the UE by the gNB. The TCI state is used by the gNB for the transmission of the PDCCH in the PDCCH monitoring occasion of the search space (the DL TX beam used by the gNB for the transmission of the PDCCH in the PDCCH monitoring occasion of the search space indicates that it is QCLed (quasi co-located) with the SSB / CSI RS of the TCI state.

[0440] In a 5G wireless communication system, BA (bandwidth adaptation) is supported. Using BA, the transmission and reception bandwidth of the UE can be adjusted without being as large as the cell bandwidth: the width can be instructed to change (e.g., to shrink during periods of low activity to save power); the position can move in the frequency domain (e.g., to increase scheduling flexibility); the SCS can be instructed to change (e.g., to accommodate different services). A subset of the overall cell bandwidth of the cell is referred to as the BWP. BA is achieved by notifying the UE which of the configured BWPs for the RRC-connected UE is currently active. When BA is configured, the UE must monitor only the PDCCH on one active BWP, i.e., it does not need to monitor the PDCCH over the entire DL frequency of the serving cell. In the RRC-connected state, one or more DL and UL BWPs are configured for each serving cell (i.e., PCell or SCell) set for the UE. For an activated serving cell, there is always one active UL and DL BWP at any given time. BWP transition for a serving cell is used to activate an inactive BWP and deactivate the active BWP at once. BWP transition is controlled by the PDCCH indicating a DL assignment or UL grant, the bwp-InactivityTimer, the RRC signaling, or the MAC entity itself when starting an RA procedure. When a SpCell is added or an SCell is activated, the indicated DL BWP and UL BWP by the firstActiveDownlinkBWP-Id and firstActiveUplinkBWP-Id are activated without receiving the PDCCH indicating a DL assignment or UL grant. The active BWP for a serving cell is indicated by the RRC or PDCCH. In the case of unpaired spectrum, the DL BWP is paired with the UL BWP, and the BWP transition is common to both UL and DL.When the BWP inactivity timer expires, the UE switches the active DL BWP to the default DL BWP or the initial DL BWP (if the default DL BWP is not configured).

[0441] In a 5G radio communication system, RA is supported. RA is used to achieve UL time synchronization. RA is used during initial access, handover, RRC connection reconfiguration procedure, scheduling request transmission, SCG addition / modification, beam failure recovery, and UL data or control information transmission by a UE not synchronized in the RRC CONNECTED state. Many types of RA procedures are supported.

[0442] CBRA (Contention Based RA): This is also referred to as four - step CBRA. In such a type of RA, the UE first transmits a RA preamble (also known as Message 1 (Msg1)), and then waits for the RAR within the RAR window. The RAR is also known as Message 2 (Msg2). The gNB transmits the RAR on the PDSCH. The PDCCH that schedules the PDSCH carrying the RAR is addressed to the RA - Radio Network Temporary Identifier (RA - RNTI). The RA - RNTI identifies the time - frequency resource (also known as the PRACH occasion or PRACH TX occasion or RA channel (RACH) occasion (RO)) at which the RA preamble was detected by the gNB. The RA - RNTI is calculated as follows: RA - RNTI = 1 + s_id+14*t_id + 14*80*f_id+14*80*8*ul_carrier_id, where s_id is the index of the first OFDM symbol of the PRACH occasion on which the UE transmitted Msg1, i.e., the RA preamble; 0 ≤ s_id < 14; t_id is the index of the first slot of the PRACH occasion (0 ≤ t_id < 80); f_id is the index of the PRACH occasion within the slot in the frequency domain (0 ≤ f_id < 8), and ul_carrier_id is the UL carrier used for Msg1 transmission (0 for the normal UL (NUL) carrier and 1 for the supplementary UL (SUL) carrier). Multiple RARs for various RA preambles detected by the gNB can be multiplexed by the gNB in the same RAR MAC PDU. The RAR within the MAC PDU corresponds to the UE's RA preamble transmission if the RAR contains the RAPID of the RA preamble transmitted by the UE. If the RAR corresponding to the RA preamble transmission is not received during the RAR window and the UE has not yet transmitted the RA preamble for the number of times that can still be set (set by the gNB in the RACH configuration), the UE returns to the first step, i.e., selects a RA resource (preamble / RO) and transmits the RA preamble. Back - off can be applied before returning to the first step.

[0443] When a RAR corresponding to the RA preamble transmission is received, the UE transmits Message 3 (Msg3) with the UL grant received in the RAR. Msg3 includes messages such as RRC connection request, RRC connection reconfiguration request, RRC handover confirmation, scheduling request, SI request, etc. This can include the UE identity (i.e., C-RNTI or S-TMSI (system architecture evolution (SAE)-temporary mobile subscriber identity) or a random number). After transmitting Msg3, the UE starts a contention resolution timer. While the contention resolution timer is running, if the UE receives a PDCCH addressed to the C-RNTI included in Msg3, the contention resolution is considered successful, the contention resolution timer is stopped, and the RA procedure is completed. While the contention resolution timer is running, if the UE receives a contention resolution MAC CE including the UE's contention resolution identity (the first X bits of the CCCH SDU transmitted in Msg3), the contention resolution is considered successful, the contention resolution timer is stopped, and the RA procedure is completed. If the contention resolution timer expires and the UE has not yet transmitted the RA preamble for a configurable number of times, the UE returns to the first step, i.e., selects an RA resource (preamble / RO) and transmits the RA preamble. Backoff can be applied before returning to the first step.

[0444] CFRA (Contention Free RA): This can also be either legacy CFRA or 4-step CFRA. The CFRA procedure is used in scenarios such as handovers that require low latency, TA (timing advance) setting for SCell, etc. The eNB (or gNB) allocates a UE-specific RA preamble. The UE transmits the dedicated RA preamble. The eNB (or gNB) transmits the RAR on the PDSCH addressed with the RA-RNTI. The RAR conveys the RA preamble identifier and the timing alignment information. The RAR can further include UL grant. The RAR is transmitted in an RAR window similar to the CBRA procedure. CFRA is considered to be successfully completed after receiving an RAR that includes the RAPID of the RA preamble transmitted by the UE. When RA is initiated for beam failure recovery, CFRA is considered to be successfully completed when a PDCCH addressed with the C-RNTI is received in the search space for beam failure recovery. If the RAR window expires and the RA is not successfully completed and the UE has not yet transmitted the RA preamble for a configurable number of times (configured by the gNB in the RACH configuration), the UE retransmits the RA preamble.

[0445] For a specific event with handover and beam failure recovery, when a dedicated preamble is allocated to the UE, during the first stage of RA, i.e., during the RA resource selection for Msg1 transmission, the UE decides whether to transmit the dedicated preamble or the non-dedicated preamble. The dedicated preamble is generally provided for a subset of SSB / CSI RS. If there is no SSB / CSI RS with a DL RSRP (reference signal received power) higher than the threshold among the SSB / CSI RS provided by the gNB for the CFRA resources (i.e., dedicated preamble / RO), the UE selects the non-dedicated preamble. Otherwise, the UE selects the dedicated preamble. Therefore, during the RA procedure, one RA attempt can be CFRA, while another RA attempt can be CBRA.

[0446] Two-stage CBRA: In the first stage, the UE transmits an RA preamble on the PRACH and a payload on the PUSCH. The RA preamble and payload transmission also serve as Message A (MsgA). In the second stage, after transmitting MsgA, the UE monitors for a response from the network (i.e., gNB) within a configured window. The response also serves as Message B (MsgB). If a CCCH SDU is transmitted in the MsgA payload, the UE performs contention resolution using the contention resolution information in MsgB. If a C-RNTI is transmitted in the MsgA payload, contention resolution is successful if the UE receives a PDCCH addressed to the C-RNTI. If contention resolution is successful, the RA procedure is considered to have completed successfully. Instead of the contention resolution information corresponding to the transmitted MsgA, MsgB can include fallback information corresponding to the RA preamble transmitted in MsgA. When the fallback information is received, the UE transmits Msg3 as in the CBRA procedure and performs contention resolution using Msg4. If contention resolution is successful, the RA procedure is considered to have completed successfully. If contention resolution fails during fallback (i.e., when transmitting Msg3), the UE retransmits MsgA. If the configured window for monitoring the network response after the UE transmits MsgA expires and the UE cannot receive MsgB containing the contention resolution information or fallback information as described above, the UE retransmits MsgA. If the RA procedure is not successfully completed even after transmitting MsgA the configurable number of times, the UE falls back to a four-stage RA procedure, i.e., the UE transmits only the RA preamble.

[0447] The MsgA payload can include one or more of a CCCH SDU, a dedicated control channel (DCCH) SDU, a dedicated traffic channel (DTCH) SDU, a BSR MAC CE, a PHR (power headroom report) MAC CE, SSB information, a C-RNTI MAC CE, or padding. MsgA can include a UE ID (e.g., a random ID, S-TMSI, C-RNTI, resume ID, etc.) together with a first-stage preamble. The UE ID can be included in the MAC PDU of MsgA. A UE ID such as a C-RNTI can be carried in a MAC CE included in the MAC CE included in the MAC PDU. Other UE IDs (e.g., a random ID, S-TMSI, C-RNTI, resume ID, etc.) can be carried in the CCCH SDU. The UE ID can be any one of a random ID, S-TMSI, C-RNTI, resume ID, IMSI (international mobile subscriber identity), an idle mode ID, an inactive mode ID, etc. The UE ID can be different in different scenarios where the UE performs RA procedures. When the UE performs RA after power-on (before connecting to the network), the UE ID is a random ID. When the UE performs RA in the IDLE state after connecting to the network, the UE ID is an S-TMSI. When the UE has an assigned C-RNTI (e.g., in the connected state), the UE ID is a C-RNTI. When the UE is in the INACTIVE state, the UE ID is a resume ID. In addition to the UE ID, some additional control information can be transmitted in MsgA. The control information can be included in the MAC PDU of MsgA.The control information can include one or more of a connection request indication, a connection resume request indication, an SI request indication, a buffer status indication, beam information (e.g., one or more DL TX beam IDs or SSB IDs), a beam failure recovery indication / information, a data indicator, a cell / BS / TRP (transmit-receive point) conversion indication, a connection reconfiguration indication, a reconfiguration complete or handover complete message, etc.

[0448] 2-step CFRA: In this case, the gNB allocates a dedicated RA preamble and PUSCH resources for MsgA transmission to the UE. The RO used for preamble transmission can be further indicated. In the first step, the UE transmits an RA preamble on the PRACH using contention-free RA resources (i.e., dedicated preamble / PUSCH resource / RO) and transmits the payload on the PUSCH. In the second step, after MsgA transmission, the UE monitors for responses from the network (i.e., gNB) within a configured window. When the UE receives a PDCCH addressed to the C-RNTI, the RA procedure is considered to have completed successfully.

[0449] Problem : In the first step of the 4-step CBRA or CFRA, i.e., after transmitting the RA preamble, the UE monitors for the RAR within a configured RAR window. For a maximum 10 ms RAR window, if the UE receives a PDCCH addressed to the RA-RNTI and the transmitted TB successfully decoded and scheduled by such PDCCH contains a RAPID that matches the RA preamble index of the RA preamble for which the RAR is being considered, the RAR is considered successful.

[0450] The cell where the UE transmits the RA preamble may be either a licensed carrier or an unlicensed carrier. When the carrier used for UL transmission is an unlicensed carrier, the UE needs to perform channel detection (i.e., LBT (listen-before-talk)) to determine whether the channel is free before transmitting Msg1 and Msg3 in UL. Similarly, when the carrier used for DL transmission is an unlicensed carrier, the gNB needs to perform channel detection (i.e., LBT) to determine whether the channel is free before transmitting Msg2 and Msg4 in DL. There may be a situation where the gNB receives the RA preamble but cannot transmit the RAR within the RAR window because the channel is not free. The UE will retransmit the PRACH if the RAR window expires. The retransmitted RA preamble may not be received by the gNB due to collision or the UE may fail to retransmit the RA preamble or the transmission may be delayed because the channel is not free in UL. Such problems can be avoided by having a larger RAR window size. However, a large RAR window with a size larger than 10 ms results in RA-RNTI ambiguity as shown in FIG. 1. When PRACH is transmitted using the same RA preamble at respective PRACH occasions X and PRACH occasion Y by UE1 and UE2, the RAR received in the common slot between RAR window X and RAR window Y cannot be distinguished because the RA-RNTI is the same for PRACH occasion X and PRACH occasion Y.

[0451] The above-mentioned RA-RNTI emulation problem can be solved by including it in the information for the radio frame in which the PRACH occasion is started by DCI. In the case of an extended RAR window (>10 ms), when the UE receives a PDCCH addressed to the RA-RNTI and the frame information in the DCI of the received PDCCH is such that the RA preamble is transmitted, and the successfully decoded TB scheduled by such a PDCCH contains a RAPID that matches the RA preamble index of the RA preamble transmitted, the RAR is considered successful if it matches the frame information corresponding to the SFN. The frame information is the 'X' least significant bits (LSB) of the SFN. When the RAR window size is 40 ms, X is 2.

[0452] In NR, when the UE receives an RRCReconfiguration message with the CellGroupConfig information element (IE) including spCellConfig along with reconfigurationWithSync, the UE performs reconfiguration in the synchronization procedure. During such a procedure, the UE synchronizes with the DL of the target SpCell and starts RA towards the target SpCell. The UE does not always need to decode the PBCH. For example, if the frequency band of the target SpCell is less than 3 GHz and the PRACH association period is not greater than one radio frame, the UE does not need to decode the PBCH before performing RA.

[0453] In the case of an extended RAR window, the X LSB of the SFN can be included in the DCI. Therefore, during the reconfiguration to the synchronization procedure, the UE first needs to obtain the SFN of the target SpCell and then start RA towards the target SpCell. Since the 6 most significant bits (MSB) of the SFN are included in the MIB and 4 bits are included in the PBCH payload, the UE needs to decode the PBCH of the target SpCell, which can delay the reconfiguration in the synchronization procedure. Therefore, a method is needed to reduce such a delay.

[0454] Criteria for Successful RAR Reception for Four-Stage CBRA and CFRA When the RAR Window Size > 10 ms

[0455] Method 1:

[0456] FIG. 25 shows a method by which a UE performs a RA procedure according to an embodiment of the present disclosure.

[0457] Referring to FIG. 25, after transmitting a RA preamble (also referred to as Msg1), the UE waits for a RAR in a RAR window in operation 2510. The RAR is also referred to as Msg2.

[0458] Thereafter, the UE checks in operation 2520 whether the transmitted RA preamble is selected from the CBRA preambles.

[0459] When the transmitted RA preamble is selected from the CBRA preambles, the UE monitors, in operation 2530, a PDCCH addressed to a RA-RNTI in the RAR window.

[0460] When the UE receives a PDCCH addressed to a RA-RNTI, the frame information in the DCI of the received PDCCH matches the frame information corresponding to the SFN in which the RA preamble was transmitted, and the successfully decoded TB scheduled by such a PDCCH contains a RAPID that matches the RA preamble index of the RA preamble transmitted in operation 2540, the RAR is considered to have been successfully received.

[0461] Upon receiving the CBRA preamble, the gNB transmits the RAR on the PDSCH. The PDCCH that schedules the PDSCH carrying the RAR is addressed to the RA-RNTI. The RA-RNTI identifies the time-frequency resource (also referred to as a PRACH occasion or a PRACH TX occasion or an RO) where the RA preamble was detected by the gNB. The RA-RNTI is calculated as follows: RA-RNTI = 1 + s_id + 14 * t_id + 14 * 80 * f_id + 14 * 80 * 8 * ul_carrier_id, where s_id is the index of the first OFDM symbol of the PRACH occasion on which the UE transmitted Msg1, i.e., the RA preamble; 0 ≤ s_id < 14; t_id is the index of the first slot of the PRACH occasion (0 ≤ t_id < 80); f_id is the index of the PRACH occasion within the slot in the frequency domain (0 ≤ f_id < 8), and ul_carrier_id is the UL carrier used for Msg1 transmission (0 for the NUL carrier and 1 for the SUL carrier). The frame information corresponding to the SFN in which the RA preamble is received is included in the DCI of the PDCCH addressed to the RA-RNTI. The frame information is the 'X' LSB of the SFN. X can be predefined or determined by the RAR window size. For example, X can be 2 bits for a 40 ms RAR window size.

[0462] TA command in the RAR: During the RA procedure, the UE receives a TA command (T A ) in the RAR. The RAR is included in the DL TB scheduled by the PDCCH addressed to the RA-RNTI. The length of the TA command received in the RAR is 12 bits. The TA command corresponds to the TA group (TAG) of the serving cell where the RA preamble was transmitted. Receiving the RAR is used to determine N TA , where N TA = T A ·16·64 / 2 μ . 2 μ ·15 kHz is the SCS of the first UL transmission from the UE after receiving the RA response.

[0463] If the transmitted RA preamble is not selected from the CBRA preambles (i.e., this is a CFRA preamble), the UE monitors the PDCCH addressed to the C-RNTI in the RAR window in operation 2550. The non-competitive preambles are dedicatedly assigned to the UE using RRC signaling messages.

[0464] When the UE receives a PDCCH addressed to the C-RNTI that schedules the DL TB, and if such DL TB contains an absolute TA command in operation 2560, the RAR is considered to be successfully received. The absolute TA command can be included in the MAC CE.

[0465] Upon receiving a CFRA preamble, the gNB transmits a response on the PDSCH. The PDCCH that schedules the PDSCH is addressed to the C-RNTI. Since the CFRA preamble is assigned by the gNB to the UE, the gNB can identify the UE when receiving the CFRA preamble, and thus, the C-RNTI is assigned to the UE. The gNB includes an absolute TA command in the DL TB transmitted on the PDSCH.

[0466] Absolute TA Command in TA MAC CE: FIG. 26 illustrates an absolute TA command MAC CE according to an embodiment of the present disclosure. The length of the received TA command is 12 bits. The TA command corresponds to the TAG of the serving cell where the RA is transmitted. T received in the RAR A is used to determine N TA where N TA = T A ·16·64 / 2 μ 2 μ ·15 kHz is the SCS UL BWP.

[0467] TA Command in TA MAC CE: FIG. 27 illustrates a TA command MAC CE according to an embodiment of the present disclosure. The TA command (T) for a specific TAG A) can also be received via the TA command MAC CE. The length of the TA command received in the TA command MAC CE is 6 bits. The T received in the TA MAC CE A is T A = 0, 1, 2,..., 63 index values indicates that the current N TA value N TA_old to the new N TA value N TA_new to the adjustment, where 2 μ · 15 kHz SCS, N TA_new = N TA_old +(T A - 31) · 16 · 64 / 2 μ · 2 μ · 15. 2 μ · 15 kHz is the SCS UL BWP.

[0468] In FIGS. 26 and 27, different LCIDs are used in the MAC subheader of the MAC CE for the TA command MAC CE.

[0469] In one embodiment, the method described above is applicable only when the RAR window size is greater than 10 ms. In other embodiments, the method described above is applicable to RAR window sizes of any size.

[0470] Method 2:

[0471] FIG. 28 shows another method by which a UE performs a RA procedure according to an embodiment of the present disclosure.

[0472] Referring to FIG. 28, after transmitting a RA preamble (also referred to as Msg1), the UE waits for a RAR in a RAR window at operation 2810. The RAR is also referred to as Msg2.

[0473] If the transmitted RA preamble is selected from a CBRA preamble or such a RA procedure is not started for reconfiguration in synchronization (e.g., handover), the UE monitors a PDCCH addressed to a RA-RNTI in the RAR window at operation 2820.

[0474] If the UE receives a PDCCH addressed with a RA-RNTI, and the frame information in the DCI of the received PDCCH matches the frame information corresponding to the SFN in which the RA preamble was transmitted, and the successfully decoded TB scheduled by such a PDCCH contains a RAPID that matches the RA preamble index of the RA preamble transmitted in operation 2830, the RAR is considered to have been successfully received.

[0475] Upon receiving a CBRA preamble, the gNB transmits a RAR on the PDSCH. The PDCCH that schedules the PDSCH carrying the RAR is addressed with a RA-RNTI. The RA-RNTI identifies the time-frequency resource (also referred to as a PRACH occasion or a PRACH TX occasion or an RO) in which the RA preamble was detected by the gNB. The RA-RNTI is calculated as follows: RA-RNTI = 1 + s_id + 14 * t_id + 14 * 80 * f_id + 14 * 80 * 8 * ul_carrier_id, where s_id is the index of the first OFDM symbol of the PRACH occasion on which the UE transmitted Msg1, i.e., the RA preamble; 0 ≤ s_id < 14; t_id is the index of the first slot of the PRACH occasion (0 ≤ t_id < 80); f_id is the index of the PRACH occasion within the slot in the frequency domain (0 ≤ f_id < 8), and ul_carrier_id is the UL carrier used for Msg1 transmission (0 for the NUL carrier and 1 for the SUL carrier). The frame information corresponding to the SFN in which the RA preamble is received is included in the DCI of the PDCCH addressed with the RA-RNTI. The frame information is the 'X' LSBs of the SFN. X can be predefined or determined by the RAR window size. For example, X can be 2 bits for a 40 ms RAR window size.

[0476] TA command in RAR: During the RA procedure, the UE receives a TA command (T A) is received. The RAR is included in the DL TB scheduled by the PDCCH addressed with the RA-RNTI. The length of the TA command received in the RAR is 12 bits. The TA command corresponds to the TAG of the serving cell where the RA preamble is transmitted. Receiving the RAR is used to determine N TA and is used to determine N TA = T A · 16 · 64 / 2 μ . 2 μ · 15 kHz is the SCS of the first UL transmission from the UE after receiving the RAR.

[0477] If the transmitted RA preamble is not selected from the CBRA preambles (i.e., this is a CFRA preamble) and such an RA procedure is initiated for reconfiguration in the synchronization procedure, the UE monitors the PDCCH addressed with the C-RNTI in the RAR window in operation 2840. The non-competitive preambles are dedicatedly assigned to the UE using RRC signaling messages.

[0478] The RAR is considered to be successfully received when the UE receives the PDCCH addressed with the C-RNTI that schedules the DL TB and such a DL TB contains the absolute TA command in operation 2850. The absolute TA command can be included in the MAC CE.

[0479] Upon receiving the CFRA preamble, the gNB transmits a response on the PDSCH. The PDCCH that schedules the PDSCH is addressed with the C-RNTI. Since the CFRA preamble is assigned to the UE by the gNB, the gNB can identify the UE when receiving the CFRA preamble, and thus, the C-RNTI is assigned to the UE. The gNB includes the absolute TA command in the DL TB transmitted on the PDSCH.

[0480] Absolute TA Command in TA MAC CE (see Figure 26):The length of the received TA command is 12 bits. The TA command corresponds to the TAG of the serving cell where the RA preamble is transmitted. T received in the RAR A is N TA used to determine, where N TA = T A · 16 · 64 / 2 μ . 2 μ · 15 kHz is the SCS UL BWP.

[0481] TA Command in TA MAC CE (see Figure 27): The TA command (T A ) for a specific TAG can be further received via the TA command MAC CE. The length of the TA command received in the TA command MAC CE is 6 bits. T received in the TA MAC CE A is T A = an index value of 0, 1, 2,..., 63 such that the current N TA value N TA_old is adjusted to the new N TA value N TA_new , where for the SCS of 2 μ · 15 kHz, N TA_new = N TA_old + (T A - 31) · 16 · 64 / 2 μ · 2 μ · 15. 2 μ · 15 kHz is the SCS UL BWP.

[0482] In one embodiment, the method described above is applicable only when the RAR window size is greater than 10 ms. In other embodiments, the method described above is applicable to RAR window sizes of any size.

[0483] Method 3:

[0484] FIG. 29 shows another method by which a UE performs the RA procedure according to an embodiment of the present disclosure.

[0485] Referring to FIG. 29, after the UE transmits a RA preamble (also referred to as Msg1), it waits for a RAR in the RAR window at operation 2910. The RAR is also called Msg2.

[0486] At operation 2920, the UE monitors the PDCCH addressed to the RA-RNTI in the RAR window.

[0487] If the transmitted RA preamble is selected from the CBRA preambles:

[0488] If the UE receives a PDCCH addressed to the RA-RNTI, the frame information in the DCI of the received PDCCH matches the frame information corresponding to the SFN in which the RA preamble was transmitted, and the successfully decoded TB scheduled by such a PDCCH contains a RAPID that matches the RA preamble index of the RA preamble transmitted at operation 2930, the RAR is considered to have been successfully received.

[0489] Upon receiving a CBRA preamble, the gNB transmits the RAR on the PDSCH. The PDCCH that schedules the PDSCH carrying the RAR is addressed to the RA-RNTI. The RA-RNTI identifies the time-frequency resource (also referred to as a PRACH occasion or a PRACH TX occasion or an RO) at which the RA preamble was detected by the gNB. The RA-RNTI is calculated as follows: RA-RNTI = 1 + s_id + 14 * t_id + 14 * 80 * f_id + 14 * 80 * 8 * ul_carrier_id, where s_id is the index of the first OFDM symbol of the PRACH occasion on which the UE transmitted Msg1, i.e., the RA preamble; 0 ≤ s_id < 14; t_id is the index of the first slot of the PRACH occasion (0 ≤ t_id < 80); f_id is the index of the PRACH occasion within the slot in the frequency domain (0 ≤ f_id < 8), and ul_carrier_id is the UL carrier used for Msg1 transmission (0 for the NUL carrier and 1 for the SUL carrier). The frame information corresponding to the SFN in which the RA preamble is received is included in the DCI of the PDCCH addressed to the RA-RNTI. The frame information is the 'X' LSB of the SFN. X can be predefined or determined by the RAR window size. For example, X can be 2 bits for a 40 ms RAR window size.

[0490] If the transmitted RA preamble is not selected from the CBRA preambles (i.e., if this is a CFRA preamble):

[0491] If the UE receives a PDCCH addressed to the RA-RNTI and the successfully decoded TB scheduled by such PDCCH contains a RAPID that matches the RA preamble index of the RA preamble transmitted in operation 2940, the RAR is considered to have been successfully received.

[0492] In one embodiment, the method described above is applicable only when the RAR window size is greater than 10 ms. In other embodiments, the method described above is applicable to RAR window sizes of any size.

[0493] Method 4:

[0494] FIG. 30 shows another method by which a UE performs an RA procedure according to an embodiment of the present disclosure.

[0495] Referring to FIG. 30, after transmitting an RA preamble (also referred to as Msg1), the UE waits for an RAR in the RAR window in operation 3010. The RAR is also referred to as Msg2.

[0496] In operation 3020, the UE monitors a PDCCH addressed to the RA-RNTI in the RAR window.

[0497] If the transmitted RA preamble is selected from the CBRA preambles or such an RA procedure is not started for reconfiguration in synchronization (e.g., handover):

[0498] If the UE receives a PDCCH addressed to the RA-RNTI, the frame information in the DCI of the received PDCCH matches the frame information corresponding to the SFN in which the RA preamble was transmitted, and the successfully decoded TB scheduled by such a PDCCH contains a RAPID that matches the RA preamble index of the RA preamble transmitted in operation 3030, the RAR is considered to have been successfully received.

[0499] Upon receiving the CBRA preamble, the gNB transmits the RAR on the PDSCH. The PDCCH that schedules the PDSCH carrying the RAR is addressed with the RA-RNTI. The RA-RNTI identifies the time-frequency resource (also referred to as the PRACH occasion or PRACH TX occasion or RO) at which the RA preamble was detected by the gNB. The RA-RNTI is calculated as follows: RA-RNTI = 1 + s_id + 14 * t_id + 14 * 80 * f_id + 14 * 80 * 8 * ul_carrier_id, where s_id is the index of the first OFDM symbol of the PRACH occasion on which the UE transmitted Msg1, i.e., the RA preamble; 0 ≤ s_id < 14; t_id is the index of the first slot of the PRACH occasion (0 ≤ t_id < 80); f_id is the index of the PRACH occasion within the slot in the frequency domain (0 ≤ f_id < 8), and ul_carrier_id is the UL carrier used for Msg1 transmission (0 for the NUL carrier, 1 for the SUL carrier). The frame information corresponding to the SFN in which the RA preamble is received is included in the DCI of the PDCCH addressed with the RA-RNTI. The frame information is the 'X' LSB of the SFN. X can be predefined or determined by the RAR window size. For example, X can be 2 bits for a 40 ms RAR window size.

[0500] If the transmitted RA preamble is not selected from the CBRA preambles (i.e., it is a CFRA preamble) and such an RA procedure is started for synchronization or reset:

[0501] If the UE receives a PDCCH addressed with the RA-RNTI and the successfully decoded TB scheduled by such a PDCCH contains a RAPID that matches the RA preamble index of the RA preamble transmitted in operation 3040, the RAR is considered to be successfully received.

[0502] In one embodiment, the method described above is applicable only when the RAR window size is greater than 10 ms. In other embodiments, the method described above is applicable to RAR window sizes of any size.

[0503] Method 5:

[0504] In one method of the present disclosure, the UE performs the RA procedure as follows:

[0505] The network (i.e., gNB) indicates whether the UE should perform operation 1 or operation 2.

[0506] Operation 1: Before starting RA on the target SpCell, the UE decodes the PBCH of the SpCell to derive two LSBs. After transmitting the RA preamble, the UE monitors the PDCCH addressed to the RA-RNTI. If the UE receives a PDCCH addressed to the RA-RNTI, the DCI contains frame information corresponding to the SFN in which the preamble was transmitted, and the TB scheduled by such a PDCCH contains the RAPID of the preamble transmitted, the RAR is considered to have been successfully received.

[0507] Operation 2: In one embodiment of the present disclosure, such an operation is the same as defined in Method 1. In an alternative embodiment of the present disclosure, such an operation is the same as defined in Method 2. In an alternative embodiment of the present disclosure, such an operation is the same as defined in Method 3. In an alternative embodiment of the present disclosure, such an operation is the same as defined in Method 4.

[0508] The RRCReconfiguration message for resetting through synchronization may include an indication for performing operation 2. If there is no such indication in the RRCReconfiguration message, the UE performs operation 1.

[0509] Method 6:

[0510] In one method of the present disclosure, the UE performs the RA procedure as follows:

[0511] While reconfiguring via synchronization, if the UE decodes the PBCH before accessing the target cell or if the UE already has the timing information of the target cell, the UE performs Operation 1; otherwise, it performs Operation 2. If the UE does not have the timing of the target cell in advance, the UE can decode the PBCH for the half-frame timing (the half-frame timing exists in the PBCH when > 3 GHz), and if the RA association period of the UE is > 10 ms, the UE can decode the PBCH for the SFN timing.

[0512] Operation 1: Before starting RA on the target SpCell, the UE decodes the PBCH of the SpCell to derive two LSBs. After transmitting the RA preamble, the UE monitors the PDCCH addressed to the RA-RNTI. If the UE receives the PDCCH addressed to the RA-RNTI, and the DCI contains the frame information corresponding to the SFN in which the preamble was transmitted, and the TB scheduled by such PDCCH contains the RAPID of the preamble transmitted, the RAR is considered to have been successfully received.

[0513] Operation 2: In one embodiment of the present disclosure, such operation is the same as defined in Method 1. In an alternative embodiment of the present disclosure, such operation is the same as defined in Method 2. In an alternative embodiment of the present disclosure, such operation is the same as defined in Method 3. In an alternative embodiment of the present disclosure, such operation is the same as defined in Method 4.

[0514] Method 7:

[0515] In one method of the present disclosure, the UE receives an RRC reconfiguration message with reconfiguration via a synchronization IE. In the received reconfiguration message, the UE receives first and second RAR window size settings for a first active UL BWP. The first RAR window size is <= 10 ms. The second RAR window size may be <= 10 ms or > 10 ms. The first RAR window size is set in the RACHConfigCommon IE, and the second RAR window size is set in the RACHConfigDedicated IE. In the case of RA towards the target SpCell when receiving reconfiguration via synchronization, the UE uses the RAR window size set in the RACHConfigDedicated IE. The UE does not monitor the LSB of the SFN in the DCI of the PDCCH addressed to each RA-RNTI / MSGB-RNTI in the case of 4-step RA / 2-step RA. After the RA procedure is completed, for subsequent RA procedures started on the target SpCell, the UE uses the RAR window size set in the RACHConfigCommon. The advantage of such operation is that the UE does not need to obtain the SFN for RAR reception during handover.

[0516] CAPC and configured approval processing

[0517] The LBT procedure is essential for fair and friendly coexistence for devices and technologies operating in unlicensed spectrum. The LBT procedure on a node attempting to transmit on a carrier in unlicensed spectrum requires the node to perform a clear channel assessment to determine if the channel is available. The various types or categories of LBT procedures used for transmission are as follows:

[0518] Category 1: No LBT

[0519] The LBT procedure is not performed by the transmission entity.

[0520] Category 2: LBT without random backoff

[0521] The period during which the channel is detected to be in the idle state before transmission by the transmitting entity is crucial. For example, the detection interval could be 25 us, that is, the UE can transmit after detecting that the channel has been in the idle state for at least the detection interval Td = 25 us. In the case of UL transmission, Category 3 is further referred to as Type 2 channel access procedure.

[0522] Category 3: LBT with random backoff in a fixed - size contention window

[0523] The LBT procedure has the following steps as one of these components. The transmitting entity draws a random number N within the contention window. The size of the contention window is specified by the minimum and maximum values of N. The size of the contention window is fixed. The random number N is used to determine the period of time during which the transmitting entity detects that the channel is in the idle state before transmitting on the channel in the LBT procedure. The detailed Category 3 LBT procedure is as follows:

[0524] The UE transmits after detecting that the channel is in the idle state during the slot period of the delay period (Td); then, the counter is 0 in stage 4. The detailed procedure is the same as follows.

[0525] Stage 1: N = N init is set, where N init is a random number uniformly distributed between 0 and CWp. CWp is the contention window for a given channel access priority class 'p'. Diverse LBT parameters for different CAPCs are listed in Table 1.

[0526] Stage 2: If N > 0 and the UE chooses to decrease the counter, then set N = N - 1.

[0527] Step 3: Detect the channel during the additional slot period (Ts). If the additional slot period is in the idle state, proceed to Step 4; otherwise, proceed to Step 5.

[0528] Step 4: If N = 0, perform transmission. Otherwise, proceed to Step 2.

[0529] Step 5: Detect the channel during the slot period of the additional delay period Td. The delay period (Td) is the same as T f +m p ×Ts, where T f seems to be 16 us and Ts is the same as 9 us.

[0530] Step 6: When it is detected that the channel is in the idle state during Td, proceed to Step 2. Otherwise, proceed to Step 5.

[0531] Category 4: LBT with random backoff in a variable-size contention window

[0532] The LBT procedure has the following as one of these components. The transmitting entity draws a random number N within the contention window. The size of the contention window is specified by the minimum and maximum values of N. The transmitting entity can change the size of the contention window when drawing the random number N. The random number N is used to determine the period of time during which it is detected that the channel is in the idle state before the transmitting entity transmits on the channel in the LBT procedure. The detailed procedure is the same as that in Category 3. The only difference is that in Category 3, the size of the contention window is fixed, while in Category 4, the transmitting entity can change the size of the contention window when drawing the random number N. In the case of UL transmission, Category 4 is further referred to as Type 1 channel access procedure.

[0533] In the NR system design, the gNB in UL can dynamically allocate resources to the UE via the C-RNTI on the PDCCH. The UE always monitors the PDCCH to find possible grants for UL transmission when DL reception is activated (the activity is managed by DRX when configured). When CA is configured, the same C-RNTI is applied to all serving cells. Also, using the configured grants, the gNB can allocate periodic UL resources for UL transmission to the UE. Two types of configured UL grants are defined:

[0534] Type 1, the RRC directly provides the configured UL grant (including the period).

[0535] Type 2, the RRC defines the period of the configured UL grant, but the PDCCH addressed to the CS-RNTI can signal and activate or deactivate the configured UL grant; that is, it indicates that the PDCCH addressed to the CS-RNTI may be implicitly reused according to the period defined by the RRC until the UL grant is deactivated.

[0536] In the case of dynamic grants, the gNB indicates that the LBT type / category used for channel access is signaled by the gNB on the PDCCH. The CAPC value used is also signaled by the gNB on the PDCCH.

[0537] For UL channel access using an exemplary LBT type 1 (i.e., category 4 LBT) of the CAPC-based LBT procedure for MsgA payload transmission on PUSCH or any UL transmission where the DCI does not contain CAPC in the case of set approval or two-step RACH, the UE needs to determine the CAPC. For this purpose, the gNB signals the CAPC for each LCH of the DRB. The MAC CE excluding the padding BSR and the recommended bitrate uses the highest priority CAPC (i.e., the lowest CAPC index). The padding BSR and the recommended bitrate MAC CE use the lowest priority CAPC (i.e., the highest CAPC index). SRB0, SRB1, and SRB3 use the highest priority CAPC (i.e., the lowest CAPC index in Table 1), but the CAPC for SRB2 is configurable. The UE selects the highest CAPC index (i.e., the lowest priority CAPC) of the LCH with the MAC SDU multiplexed in the MAC PDU.

[0538] One problem with such a design for selecting CAPC for UL set approval is that when the SRB data corresponding to the lowest CAPC (i.e., the highest priority) has a lower priority when multiplexed with other LCH MAC SDUs in the MAC PDU. Therefore, some ways to improve the current design are needed.

[0539] Method 1:

[0540] For MsgA payload transmission on PUSCH or any UL transmission where DCI does not include CAPC, in the case of configured UL approval or two-step RACH, on an unlicensed carrier (i.e., a serving cell operating in an unlicensed spectrum or frequency band), when the MAC SDU of DCCH LCH is included in the MAC PDU and a CAPC-based LBT procedure (e.g., LBT based on category 3 or 4) is performed for channel access, the UE shall not include any other MAC SDU of an LCH having a CAPC index higher than the CAPC index of the DCCH (i.e., the CAPC of the DCCH LCH whose MAC SDU is included in the MAC PDU). When multiple MAC SDUs of DCCHs belonging to SRBs with different CAPC indices are included in the MAC PDU, the CAPC index of the DCCH is the highest index among the CAPC indices of the DCCHs included in the MAC PDU.

[0541] In an alternative embodiment, for MsgA payload transmission on PUSCH or any UL transmission where the DCI does not include CAPC, in the case of configured UL approval or two-step RACH, on an unlicensed carrier (i.e., a serving cell operating in an unlicensed spectrum or frequency band), if the MAC SDU of the DCCH LCH is included in the MAC PDU and a CAPC-based LBT procedure (e.g., LBT based on category 3 or 4) is performed for channel access, the UE shall not include any other MAC SDU of an LCH having a CAPC index higher than the CAPC index of the DCCH (i.e., the CAPC of the DCCH LCH whose MAC SDU is included in the MAC PDU), and the UE shall not include any MAC CE having a CAPC index higher than the CAPC index of the DCCH (i.e., the CAPC of the DCCH LCH whose MAC SDU is included in the MAC PDU). If multiple MAC SDUs of DCCHs belonging to SRBs with different CAPC indexes are included in the MAC PDU, the CAPC index of the DCCH is the highest index among the CAPC indexes of the DCCHs included in the MAC PDU. For example, assuming that SRB1 and SRB2 have CAPC indexes 1 and 3 respectively, and if the MAC SDUs of both SRB1 and SRB are included in the MAC PDU, the UE shall not include any other MAC SDU of an LCH having a CAPC index higher than 3, and the UE shall not include any MAC CE having a CAPC index higher than 3.

[0542] In an alternative embodiment, for MsgA payload transmission on PUSCH or any UL transmission where the DCI does not contain CAPC, in the case of configured UL approval or two-step RACH, on an unlicensed carrier (i.e., a serving cell operating in the unlicensed spectrum or frequency band), when the MAC SDU of the DCCH LCH is included in the MAC PDU and a CAPC-based LBT procedure (e.g., LBT based on category 3 or 4) is performed for channel access, the UE shall not include any other MAC SDU of an 'LCH other than DCCH' having a CAPC index higher than the CAPC index of the DCCH (i.e., the CAPC of the DCCH LCH whose MAC SDU is included in the MAC PDU). When multiple MAC SDUs of DCCHs belonging to SRBs with different CAPC indices are included in the MAC PDU, the CAPC index of the DCCH is the highest index among the CAPC indices of the DCCHs included in the MAC PDU. For example, assuming SRB1 and SRB2 have CAPC indices 1 and 3 respectively, and the MAC SDUs of both SRB1 and SRB2 are included in the MAC PDU, the UE shall not include any other MAC SDU of an LCH having a CAPC index higher than 3.

[0543] In an alternative embodiment, for MsgA payload transmission on PUSCH or any UL transmission where DCI does not include CAPC, for a configured UL approval or two-step RACH case, on an unlicensed carrier (i.e., a serving cell operating in an unlicensed spectrum or frequency band), when the MAC SDU of DCCH LCH is included in the MAC PDU and a CAPC-based LBT procedure (e.g., LBT based on category 3 or 4) is performed for channel access, the UE shall not include any other MAC SDU of an LCH other than DCCH having a CAPC index higher than the CAPC index of the DCCH (i.e., the CAPC of the DCCH LCH whose MAC SDU is included in the MAC PDU), and the UE shall not include any MAC CE having a CAPC index higher than the CAPC index of the DCCH (i.e., the CAPC of the DCCH LCH whose MAC SDU is included in the MAC PDU). When multiple MAC SDUs of DCCHs belonging to SRBs with different CAPC indices are included in the MAC PDU, the CAPC index of the DCCH is the highest index among the CAPC indices of the DCCHs included in the MAC PDU. For example, assuming SRB1 and SRB2 have CAPC indices 1 and 3 respectively, and the MAC SDUs of both SRB1 and SRB2 are included in the MAC PDU, the UE shall not include any other MAC SDU of an LCH having a CAPC index higher than 3, and the UE shall not include any MAC CE having a CAPC index higher than 3.

[0544] Saying that the configured UL approval is for an unlicensed carrier does not mean that channel access for transmission for such UL approval and CAPC-based LBT are performed. Therefore, it is important for the UE to check whether a CAPC-based LBT procedure (e.g., LBT category 3 / 4) is applied. Various cases where a CAPC-based LBT procedure (e.g., LBT category 3 or 4) is applied are described in detail in TS38.889 and TS38.213.

[0545] Method 2:

[0546] For MsgA payload transmission on PUSCH or any UL transmission where DCI does not contain CAPC, in the case of configured UL approval or two-step RACH, on an unlicensed carrier (i.e., a serving cell operating in the unlicensed spectrum or frequency band), the CAPC-based LBT procedure (e.g., when LBT is based on category 3 or 4) is performed for channel access. When the MAC SDU of the DCCH LCH is included in the MAC PDU, the UE selects the CAPC index of the DCCH. The MAC SDUs of SRB1, SRB2, and SRB3 are mapped to the DCCH. When multiple MAC SDUs belonging to different DCCHs (or DCCH LCHs) are included in the MAC PDU, the UE selects the lowest CAPC index (i.e., the highest priority) of the DCCH on which the MAC SDUs are multiplexed in the MAC PDU. For example, assume that SRB1 and SRB2 have CAPC indices 1 and 3 respectively. The MAC SDUs of SRB1 and SRB3 are included in the MAC PDU. Therefore, the CAPC index 1 is selected as the lowest value among CAPC index 1 and CAPC index 3. If the MAC SDU of an LCH other than the DCCH is included in the MAC PDU, the UE selects the highest CAPC index (lowest priority) of the LCH multiplexed in the MAC PDU (alternatively, the UE selects the highest CAPC index (lowest priority) of the LCH / MAC CE multiplexed in the MAC PDU). When only the MAC CE is included in the MAC PDU, the UE selects the lowest CAPC index (i.e., the highest priority) of the MAC CE included in the MAC PDU.

[0547] It does not mean that the configured UL approval is for an unlicensed carrier, and that channel access for transmission with such UL approval is performed with CAPC-based LBT. Therefore, it is important for the UE to check whether the CAPC-based LBT procedure (e.g., LBT category 3 / 4) is applicable. The various cases where the CAPC-based LBT procedure (e.g., LBT category 3 or 4) is applicable are described in detail in TS38.889 and TS38.213.

[0548] LBT Failure Handling

[0549] In the case of LBT failure handling, the gNB signals the LBT-FailureRecoveryConfig IE in the RRCReconfiguration message. The RRCReconfiguration message is sent to the UE in RRC CONNECTED. The LBT-FailureRecoveryConfig IE is configured separately for the serving cell. The LBT-FailureRecoveryConfig IE includes the LBT-FailureInstanceMaxCount and LBT-FailureDetectionTimer parameters for consistent LBT failure detection. The RRCReconfiguration message from the gNB is processed by the UE's RRC layer. When the LBT-FailureRecoveryConfig is received from the gNB for the serving cell, the MAC entity of the serving cell performs consistent LBT failure recovery procedures using the parameters set in the LBT-FailureRecoveryConfig IE of the serving cell.

[0550] Consistent LBT failures are detected for each UL BWP by counting LBT failure indications for all UL transmissions to the MAC entity at the lower layer (i.e., the physical layer).

[0551] The UE variable LBT_COUNTER, i.e., the counter for LBT failure indication initially set to 0, is used in the consistent LBT failure detection procedure and is maintained separately for each activated serving cell for which lbt-FailureRecoveryConfig is configured.

[0552] For each activated serving cell for which lbt-FailureRecoveryConfig is configured, the MAC entity shall:

[0553] 1> If an LBT failure indication is received from the lower layer:

[0554] 2> Start or restart the LBT-FailureDetectionTimer;

[0555] 2> Increment LBT_COUNTER by 1;

[0556] 2> If LBT_COUNTER >= LBT-FailureInstanceMaxCount:

[0557] 3> If such a serving cell is an SCell:

[0558] 4> Declare a consistent LBT failure for the active UL BWP;

[0559] 4> Indicate to the multiplexing and assembly entity to include an LBT failure MAC CE in subsequent UL transmissions.

[0560] 3> Otherwise (i.e., SpCell):

[0561] 4> Declare a consistent LBT failure for the active UL BWP;

[0562] 4> If consistent LBT failures are declared in all UL BWPs in which PRACH occasions are configured in such a serving cell:

[0563] 5> Indicate the consistent LBT failures to the upper layer.

[0564] 4> Otherwise:

[0565] 5> In such a serving cell, switch the active UL BWP in a UL BWP in which PRACH occasions are configured and consistent LBT failures are not declared;

[0566] 5> Perform BWP operations as specified in Section 5.15 of TS38.321;

[0567] 5> Start the RA procedure.

[0568] 1> If the LBT-FailureDetectionTimer expires; or

[0569] 1> If the LBT-FailureDetectionTimer or LBT-FailureInstanceMaxCount is reset by the upper layer:

[0570] 2> Set the LBT_COUNTER to 0.

[0571] In the procedures described above, when there is an LBT failure for the active UL BWP of the SpCell, the UE switches to a UL BWP in which PRACH occasions are configured and consistent LBT failures are not declared. However, it is sufficient to have two carrier waves, SUL and NUL, in the UL. If the active UL BWP is on the SUL and the UE switches the UL BWP from the NUL, there is a possibility that the UE is not within the UL coverage of the NUL, and problems may occur when UL transmission fails. If the active UL BWP is on the NUL and the UE switches the UL BWP from the SUL, there is a possibility that the UE is not within the UL coverage of the SUL, and problems may occur when UL transmission fails

[0572] Additionally, there may be multiple UL BWPs for both NUL and SUL. Declaring LBT failure to the upper layer when LBT fails on all UL BWPs where there is a PRACH occasion will delay the delay radio link failure (RLF).

[0573] Method 1:

[0574] In the method of this disclosure, the LBT failure handling for the SpCell is described. In the case of LBT failure handling, the gNB signals the LBT-FailureRecoveryConfig IE in the RRCReconfiguration message. The RRCReconfiguration message is sent to the UE in RRC CONNECTED. The LBT-FailureRecoveryConfig IE is configured for the SpCell. The LBT-FailureRecoveryConfig IE includes the LBT-FailureInstanceMaxCount and LBT-FailureDetectionTimer parameters for consistent LBT failure detection. The RRCReconfiguration message from the gNB is processed by the RRC layer of the UE. When the LBT-FailureRecoveryConfig is received from the gNB for the SpCell, the MAC entity of the SpCell performs consistent LBT failure recovery procedures using the parameters set in the LBT-FailureRecoveryConfig IE of the SpCell.

[0575] Consistent LBT failure is detected for each UL BWP by counting the LBT failure indication for all UL transmissions to the MAC entity at the lower layer (i.e., the physical layer). The UE variable LBT_COUNTER, i.e., the counter for the LBT failure indication initially set to 0, is used in the consistent LBT failure detection procedure. For the LBT failure handling of the SpCell, the UE operation is as follows:

[0576] 1> If receiving a LBT failure indication from the lower layer (where the LBT failure indication from the lower layer is for the failure of transmitting on the UL of the SpCell due to LBT failure, that is, it is determined that UL transmission cannot be performed based on the LBT procedure for UL channel access):

[0577] 2> Start or restart the LBT-FailureDetectionTimer;

[0578] 2> Increment LBT_COUNTER by 1;

[0579] 2> When LBT_COUNTER >= LBT-FailureInstanceMaxCount:

[0580] 3> Declare a consistent LBT failure for the active UL BWP;

[0581] 3> When a consistent LBT failure is declared for all UL BWPs where PRACH occasion is configured in the NUL of such a serving cell: Or

[0582] 3> When a consistent LBT failure is declared for all UL BWPs where PRACH occasion is configured in the SUL of such a serving cell: Or

[0583] 4> Indicate the consistent LBT failure to the upper layer (the upper layer, that is, RRC will declare RLF when receiving such an indication);

[0584] 3> Otherwise:

[0585] 4> In such a serving cell, switch the active UL BWP to the UL BWP of the same carrier as the active UL BWP where PRACH occasion is configured and a consistent LBT failure is not declared;

[0586] 4> Start the RA procedure.

[0587] When the RA procedure is started, the UE will select between SUL and NUL based on the RSRP threshold.

[0588] If SUL is configured and the RSRP of the DL path loss reference is less than rsrp-ThresholdSSB-SUL, the UE selects the SUL carrier for the RA procedure. Otherwise, the UE selects the NUL carrier for the RA procedure.

[0589] The selected carrier can be different from the carrier used before starting the RA procedure. Since the active UL BWP after carrier conversion must surely have a RACH occasion, for the serving cell with SUL and NUL configured, if the UL BWP with BWP ID ‘X’ in NUL has a RACH occasion, the UL BWP with the same BWP ID ‘X’ in SUL must also be configured with a RACH occasion. The above-described proposal can be applied to cells operating on unlicensed carriers in one embodiment.

[0590] Method 2:

[0591] The method of the present disclosure describes the LBT failure handling for the SpCell. In the case of LBT failure handling, the gNB signals the LBT-FailureRecoveryConfig IE in the RRCReconfiguration message. The RRCReconfiguration message is sent to the UE in RRC CONNECTED. The LBT-FailureRecoveryConfig IE is configured for the SpCell. The LBT-FailureRecoveryConfig IE includes the LBT-FailureInstanceMaxCount and LBT-FailureDetectionTimer parameters for consistent LBT failure detection. The RRCReconfiguration message from the gNB is processed by the RRC layer of the UE. When the LBT-FailureRecoveryConfig is received from the gNB for the SpCell, the MAC entity of the SpCell performs consistent LBT failure recovery procedures using the parameters set in the LBT-FailureRecoveryConfig IE of the SpCell.

[0592] Consistent LBT failures are detected for each UL BWP by counting LBT failure indications for all UL transmissions to the MAC entity at the lower layer (i.e., the physical layer). The UE variable LBT_COUNTER, i.e., the counter for LBT failure indications initially set to 0, is used for the consistent LBT failure detection procedure. For the LBT failure handling of the SpCell, the UE operation is as follows:

[0593] 1> If a LBT failure indication is received from the lower layer (where the LBT failure indication from the lower layer is for the failure of transmission on the UL of the SpCell due to LBT failure, i.e., it is determined that UL transmission cannot be performed based on the LBT procedure for UL channel access):

[0594] 2> Start or restart the LBT-FailureDetectionTimer;

[0595] 2> Increment the LBT_COUNTER by 1;

[0596] 2> If LBT_COUNTER >= LBT-FailureInstanceMaxCount:

[0597] 3> Declare a consistent LBT failure for the active UL BWP;

[0598] 3> If a consistent LBT failure is declared for all UL BWPs where a PRACH occasion is configured on the carrier of the active UL BWP of such a serving cell:

[0599] 4> Indicate the consistent LBT failure to the upper layer (the upper layer, i.e., RRC, declares an RLF when receiving such an indication);

[0600] 3> Otherwise:

[0601] 4> In such a serving cell, switch the active UL BWP to a UL BWP on the same carrier as the active UL BWP where a PRACH occasion is configured and a consistent LBT failure is not declared;

[0602] 4> Start a RA procedure on the same carrier as the active UL BWP. (In this case, when the random access procedure is started, the UE does not select between SUL and NUL based on the RSRP threshold).

[0603] RA Carrier Selection:

[0604] 1> If a RA procedure is started for LBT failure recovery:

[0605] 2> Select the carrier for the current active UL BWP to perform the RA procedure;

[0606] 2> Set PCMAX with the PCMAX, f, and c of the selected carrier wave.

[0607] 1> Otherwise, if the carrier wave used for the RA procedure is explicitly signaled (by the gNB):

[0608] 2> Select the carrier wave signaled for performing the RA procedure;

[0609] 2> Set PCMAX with the PCMAX, f, and c of the signaled carrier wave.

[0610] 1> Otherwise, if the carrier wave used for the RA procedure is not explicitly signaled; and

[0611] 1> If supplementary uplink is configured for the serving cell for the RA procedure as specified in TS38.331; and

[0612] 1> If the RSRP of the downlink path loss criterion is less than rsrp - ThresholdSSB - SUL:

[0613] 2> Select the SUL carrier wave for performing the RA procedure;

[0614] 2> Set PCMAX with the PCMAX, f, and c of the SUL carrier wave.

[0615] 1> Otherwise:

[0616] 2> Select the NUL carrier wave for performing the RA procedure;

[0617] 2> Set PCMAX with the PCMAX, f, and c of the NUL carrier wave.

[0618] Figure 31 shows a block diagram of a terminal according to an embodiment of the present disclosure.

[0619] Referring to FIG. 31, the terminal includes a transceiver 3110, a control unit 3120, and a memory 3130. The control unit 3120 can refer to a circuit, an ASIC, an FPGA, or at least one processor. The transceiver 3110, the control unit 3120, and the memory 3130 are configured to perform the operations of the UE shown in the drawings, for example, FIGS. 4, 7, 10, 13, 16, 18, 19, 21, 22, 25, 28, 29, and 30 or as described above. Although the transceiver 3110, the control unit 3120, and the memory 3130 are shown as separate entities, they can be integrated on a single chip. The transceiver 3110, the control unit 3120, and the memory 3130 can further be electrically connected or coupled to each other.

[0620] The transceiver 3110 can transmit and receive signals with other network entities, such as a base station.

[0621] The control unit 3120 can control the UE to perform the functions according to the above-described embodiments. In an embodiment of the present disclosure, for UL transmission on the basis of the set approval, when a DCCH SDU is to be transmitted, the control unit 3120 selects the CAPC of the DCCH, or otherwise selects the lowest-priority CAPC (i.e., the highest number of CAPC indexes) of the MAC CE multiplexed with the LCH having the MAC SDU and the MAC PDU. In another embodiment of the present disclosure, the control unit 3120 is configured to trigger a consistent LBT failure for the active UL BWP in the serving cell. When an LBT failure indication is identified from the lower layer, the control unit 3120 can be configured to increment an LBT counter (i.e., LBT_COUNTER). When the LBT counter is greater than a preset threshold (i.e., FailureInstanceMaxCount), a consistent LBT failure for the active UL BWP in the serving cell is triggered. When a consistent LBT failure is triggered for all UL BWPs in which a PRACH occasion is set on the same carrier in the serving cell, the control unit 3120 is configured to determine that an RLF has been detected for the serving cell. Otherwise, the control unit 3120 converts the active UL BWP to another UL BWP on the same carrier as the serving cell in which the PRACH occasion is set and no consistent LBT failure is triggered, and starts a RA procedure triggered by a consistent UL LBT failure on the converted UL BWP.

[0622] In one embodiment, the operation of the terminal can be implemented using a memory 3130 that stores corresponding program code. Specifically, the terminal can be equipped with a memory 3130 for storing program code for implementing a desired operation. To perform the desired operation, the control unit 3120 can read and interpret the program code stored in the memory 3130 by using a processor or a central processing unit (CPU).

[0623] Figure 32 is a block diagram of a base station according to an embodiment of the present disclosure.

[0624] Referring to Figure 32, the base station includes a transceiver 3210, a control unit 3220, and a memory 3230. The control unit 3220 can refer to a circuit, an ASIC, an FPGA, or at least one processor. The transceiver 3210, the control unit 3220, and the memory 3230 are configured to perform the operations of the gNB illustrated in the drawings, for example, Figures 5, 8, 11, and 14 or as described above. Although the transceiver 3210, the control unit 3220, and the memory 3230 are illustrated as separate entities, they can be integrated on a single chip. The transceiver 3210, the control unit 3220, and the memory 3230 can also be electrically connected or coupled to each other.

[0625] The transceiver 3210 can transmit and receive signals with other network entities, for example, terminals.

[0626] The control unit 3220 can control the gNB to perform functions according to embodiments of the present disclosure.

[0627] In one embodiment, the operation of the base station can be implemented using the memory 3230 that stores corresponding program code. Specifically, the base station can be equipped with the memory 3230 for storing the program code that implements the desired operation. To perform the desired operation, the control unit 3220 can read and execute the program code stored in the memory 3230 by using a processor or a CPU.

[0628] Although illustrated and described with reference to various embodiments of the present disclosure, those of ordinary skill in the art will understand that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Description of Reference Numerals

[0629] 3110 Transceiver 3120 Control Unit 3130 Memory 3210 Transceiver 3220 Control Unit 3230 Memory

Claims

1. A method performed by a terminal that transmits uplink data in a serving cell operating in an unlicensed band in a wireless communication system, comprising: confirming a MAC (medium access control) PDU (protocol data unit) of the uplink data; confirming whether the MAC PDU includes a dedicated control channel (DCCH) service data unit (SDU); when the MAC PDU includes the DCCH SDU, selecting a CAPC (channel access priority class) of the DCCH as a CAPC index for the MAC PDU; when the MAC PDU does not include the DCCH SDU, selecting, as the CAPC index for the MAC PDU, the lowest priority CAPC among at least one logical channel for a MAC SDU multiplexed with the MAC PDU; transmitting, in the serving cell, uplink data including the MAC PDU to a base station using a channel connection procedure based on the selected CAPC index; A method performed by a terminal, comprising the above steps.

2. The lower the value of the CAPC, the higher the priority. The method performed by the terminal according to claim 1, wherein the uplink data including the MAC PDU is transmitted in the serving cell when it is confirmed that a channel for the serving cell is in an idle state.

3. confirming a contention window corresponding to the selected CAPC index; determining whether a channel is in an idle state based on the confirmed contention window; The method performed by the terminal according to claim 1, comprising the above steps.

4. The method performed by the terminal according to claim 1, wherein the MAC PDU is for a configured grant.

5. When the MAC PDU is for a dynamic grant, the method performed by the terminal according to claim 1, wherein the CPC index is selected for the MAC PDU based on the fact that the CAPC is not indicated by DCI (Downlink Control Information).

6. A terminal that transmits uplink data in a serving cell operating in an unlicensed band in a wireless communication system, a transceiver, checks the MAC (medium access control) PDU (protocol data unit) of the uplink data, checks whether the MAC PDU includes a dedicated control channel (DCCH) service data unit (SDU), and if the MAC PDU includes the DCCH SDU, selects the CAPC of the DCCH as the CAPC (channel access priority class) index for the MAC PDU, and if the MAC PDU does not include the DCCH SDU, selects the lowest priority CAPC of the logical channels among at least one logical channel for the MAC SDU multiplexed with the MAC PDU as the CAPC index for the MAC PDU, and controls the transceiver to transmit uplink data including the MAC PDU in the serving cell using a channel connection procedure based on the selected CAPC index, A terminal in a wireless communication system, characterized by including the above.

7. The lower the value of the CAPC index, the higher the priority, The terminal in the wireless communication system according to claim 6, wherein the uplink data including the MAC PDU is transmitted in the serving cell when it is confirmed that the channel for the serving cell is in an idle state.

8. The control unit Check a contention window corresponding to the selected CAPC index, and determine whether a channel is in an idle state based on the checked contention window. The terminal in the wireless communication system according to claim 6 is characterized by this.

9. The MAC PDU is for a configured grant. The terminal in the wireless communication system according to claim 6 is characterized by this.

10. When the MAC PDU is for a dynamic grant, the CAPC index is selected for the MAC PDU based on the fact that CAPC is not indicated by DCI (Downlink Control Information). The terminal in the wireless communication system according to claim 6 is characterized by this.

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