Method for supporting random access procedure of large random access response (RAR) window size

Abstract

A method for supporting a random access procedure of a large random access response (RAR) window size is provided. A communication method and system for converging a 5th-Generation (5G) communication system for supporting a higher data rate than a 4th-Generation (4G) system with a technology for Internet of Things (IoT) are provided. The communication method and system may be applied to intelligent services based on 5G communication technology and IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method performed by a terminal for handling a listen before talk (LBT) failure in a wireless communication system is provided.

Description

[0001] This application is a divisional application of a patent application with an application date of July 2, 2020, application number 2020800480587, and invention name “Method for supporting a random access process with a large random access response (RAR) window size”. Technical Field

[0002] The present disclosure relates to a method of transmitting and receiving frame information in a random access response (RAR), a method of processing a configured grant transmission in an unlicensed carrier, a method of a random access (RA) procedure for supporting a large RAR window size, and a method of listen-before-talk (LBT) processing. Background Art

[0003] In order to meet the demand for wireless data services that have increased since the deployment of the fourth generation (4G) communication system, efforts have been made to develop an improved fifth generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called "beyond 4G network" or "post-long term evolution (LTE) system". The 5G wireless communication system is considered to support not only lower frequency bands but also higher frequency (mmWave) bands, such as 10 GHz to 100 GHz bands, in order to achieve higher data rates. In order to mitigate the propagation loss of radio waves and increase the transmission distance, beamforming, massive multiple input multiple output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antenna technology are being considered in the design of the 5G wireless communication system. In addition, in the 5G communication system, development for system network improvement is underway based on advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, mobile networks, cooperative communication, coordinated multi-point (CoMP), receiving-end interference cancellation, etc. In the 5G system, frequency and quadrature amplitude modulation (FQAM), which is a combination of hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM), and sliding window superposition coding (SWSC), filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as advanced access technologies have also been developed.

[0004] In a similar vein, the Internet, which is a human-centered connected network in which humans generate and consume information, is now evolving into the Internet of Things (IoT), in which distributed entities such as things exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of IoT technology and big data processing technology through connection with a cloud server, has also emerged. As IoT implementations have required technical elements such as "sensing technology", "wired / wireless communication and network infrastructure", "service interface technology" and "security technology", sensor networks, machine-to-machine (M2M) communication, machine type communication (MTC), etc. have recently been studied. Such an IoT environment can provide intelligent Internet technology services that create new value for human life by collecting and analyzing data generated among networked things. In this case, IoT can be applied to various fields including smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, health care, smart appliances, and advanced medical services through the fusion and combination between existing information technology (IT) and various industrial applications.

[0005] In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, MTC, and M2M communications can be implemented through beamforming, MIMO, and array antennas. Cloud RAN as an application of the above-mentioned big data processing technology can also be considered as an example of the fusion between 5G technology and IoT technology.

[0006] In recent years, several broadband wireless technologies have been developed to meet the growing number of broadband subscribers and to provide more and better applications and services such as these. The second generation (2G) wireless communication system has been developed to provide voice services while ensuring the mobility of users. The third generation (3G) wireless communication system supports voice services and data services. The 4G wireless communication system has been developed to provide high-speed data services. However, 4G wireless communication system resources currently suffer from a lack of resources and cannot meet the growing demand for high-speed data services. Therefore, 5G wireless communication systems (also known as next-generation radio or NR) are being developed to meet the growing demand for various services (e.g., high-speed data services) with diverse requirements, supporting ultra-reliability and low-latency applications.

[0007] In addition, the 5G wireless communication system is expected to address different use cases with completely different requirements in terms of data rate, latency, reliability, mobility, etc. However, it is expected that the design of the air interface of the 5G wireless communication system will be flexible enough to serve user equipment (UE) with completely different efforts depending on the use case and market segment that the UE provides services to the end customer. Example use cases that the 5G wireless communication system is expected to address include enhanced mobile broadband (eMBB), massive machine type communication (m-MTC), ultra-reliable low latency communication (URLL), etc. The eMBB requirements (e.g., data rates of tens of Gbps, low latency, high mobility, etc.) address the market segment representing wireless broadband subscribers who need Internet connection anytime and anywhere. The m-MTC requirements (e.g., very high connection density, infrequent data transmission, very long battery life, low mobility address, etc.) address the market segment representing the connection of billions of devices envisioned by IoT / IoE. The URLL requirements (e.g., very low latency, very high reliability variable mobility, etc.) address the market segment representing industrial automation applications and vehicle-to-vehicle / vehicle-to-infrastructure communications that are foreseen as one of the enablers of autonomous cars.

[0008] The current design of 5G wireless communication systems is to operate on licensed carriers. A study has recently been initiated to investigate enhancements to 5G wireless communication systems to operate on unlicensed carriers. The main motivation for using unlicensed carriers is to reduce the capital expenditure (CAPEX) of cellular operators by leveraging free spectrum access for intelligent data offloading; improved and intelligent spectrum access and management to address the increased demand for wireless services under limited available spectrum, and to allow network operators without licensed spectrum to utilize radio-efficient Third Generation Partnership Project (3GPP) radio access technologies. Various deployment scenarios are being considered for operation on unlicensed carriers, such as: New Radio - Unlicensed (NR-U) Licensed Assisted Access (LAA): Carrier aggregation between licensed band NR (primary cell (PCell)) and unlicensed band NR-U (secondary cell (SCell)) NR-U Independent (SA): Independent NR-U LTE NR Unlicensed-Dual Connectivity (ENU-DC): Dual connectivity between licensed LTE (PCell) and unlicensed NR-U (Primary SCell (PSCell)) NR Unlicensed-Dual Connectivity (NNU-DC): Dual connectivity between licensed band NR (PCell) and unlicensed band NR-U (PSCell) Note that the above scenario includes NR cells with downlink (DL) in an unlicensed band and uplink (UL) in a licensed band.

[0009] One of the objectives of the above study is to determine the improvements required to the random access (RA) procedure to support unlicensed bands. In 5G (also known as NR or New Radio) wireless communication systems, the RA procedure is used to achieve UL time synchronization. The RA procedure is used by an unsynchronized user equipment (UE) in the RRC connected state in the UL during initial access, handover, radio resource control (RRC) connection re-establishment procedure, scheduling request transmission, secondary cell group (SCG) addition / modification, and data or control information transmission. During the RA procedure, the UE first transmits a RA preamble (also known as message 1 (Msg1)) and then waits for a RA response (RAR) or message 2 (Msg2) in the RAR window corresponding to its RA preamble transmission. The next generation Node B (gNB) transmits the RAR on the physical DL shared channel (PDSCH) addressed to the RA Radio Network Temporary Identifier (RA-RNTI). The RA-RNTI determines the time-frequency resource (also known as physical RA channel (PRACH) opportunity or PRACH transmission (TX) opportunity or RA channel (RACH) opportunity) in which the RA preamble is 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: , in s_id is the index of the first orthogonal frequency division multiplexing (OFDM) symbol of the PRACH opportunity in which the UE has sent Msg1 (ie, RA preamble); 0≤s_id<14, t_id is the index of the first time slot of the PRACH opportunity (0≤t_id<80).

[0010] f_id is the index of the PRACH opportunity 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 normal UL (NUL) carrier and 1 for supplementary UL (SUL) carrier).

[0011] Several RARs for various RA preambles detected by the gNB can be multiplexed by the gNB in ​​the same RAR Media Access Control (MAC) Protocol Data Unit (PDU). If the RAR includes the RA Preamble Identifier (RAPID) of the RA preamble transmitted by the UE, the RAR in the MAC PDU corresponds to the RA preamble transmission of the UE. The UE retransmits the RA preamble if the RAR corresponding to its RA preamble transmission is not received during the RAR window and the UE has not transmitted the RA preamble for a configurable number of times (configured by the gNB in ​​the RACH configuration).

[0012] The RA procedure is considered successful if the RAR corresponding to its RA preamble transmission is received and the UE has sent a dedicated RA preamble. If the UE has sent a non-dedicated (i.e., contention-based) RA preamble, upon successful reception of the RAR, the UE sends a message 3 (Msg3) in the UL grant received in the RAR. Msg3 includes messages such as RRC connection request, RRC connection reestablishment request, RRC handover confirmation, scheduling request, etc. It also includes a UE identifier (i.e., cell-radio network temporary identifier (C-RNTI) or system architecture evolution (SAE)-temporary mobile subscriber identifier (S-TMSI) or a random number). After sending 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, 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 identifier (the first X bits of the common control channel (CCCH) service data unit (SDU) sent 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 sent the RA preamble for a configurable number of times, the UE retransmits the RA preamble.

[0013] The cell on which the UE sends the RA preamble may be a licensed carrier or an unlicensed carrier. If the carrier used for UL transmission is an unlicensed carrier, the UE needs to perform channel sensing (i.e., listen before talk (LBT)) to determine whether the channel is idle before sending Msg1 and Msg3 in UL. Similarly, if the carrier used for DL ​​transmission is an unlicensed carrier, the gNB needs to perform channel sensing (i.e., LBT) to determine whether the channel is idle before sending Msg2 and Msg4 in DL. It is possible that the gNB has received the RA preamble but is not able to send the RAR in the RAR window when the channel is not idle. The UE will retransmit the PRACH when 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 retransmission may be delayed due to the channel not being idle in UL. This problem can be avoided by having a larger RAR window size. However, a large RAR window size greater than 10 ms leads to RA-RNTI ambiguity.

[0014] Figure 1 is an example illustration of RA-RNTI ambiguity due to a large RAR window size according to the related art.

[0015] If PRACH is transmitted by UE1 and UE2 using the same RA preamble in PRACH occasion X and PRACH occasion Y, respectively, RAR received in a common time slot between RAR window X and RAR window Y cannot be distinguished because RA-RNTI is the same for PRACH occasion X and PRACH occasion Y.

[0016] The aforementioned problem of RA-RNTI ambiguity can be solved by including information about the radio frame in which the PRACH opportunity starts. The RAR MAC PDU includes one or more RAR MAC subPDUs, each of which consists of a RAPID MAC subheader and a RAR MAC payload. If the RAPID in the MAC subheader matches the RA preamble sent by the UE and the frame information in the RAR MAC payload corresponds to the radio frame of the PRACH opportunity in which the UE has sent the RA preamble, the RAR belongs to the UE. However, this is not an efficient method because the UE needs to process the RAR MAC payload even if the RAR is not prepared for it. This process needs to be performed for each RAR in the received RAR MAC PDU until the UE finds the RAR for itself or until there are no more RARs left to be processed. This method may also cause overhead problems because frame information needs to be included for each RAR MAC payload in the RAR MAC PDU. This method cannot provide frame information for a MAC subPDU that includes a RAPID MAC subheader but does not include a RAR MAC payload. When the transmitted RA preamble is for an SI request, this type of MAC subPDU without a RAR MAC payload is included to indicate an SI request acknowledgment.

[0017] Therefore, there is a need for an enhanced method for sending and receiving frame information in RAR.

[0018] The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with respect to the present disclosure. Summary of the invention

[0019] Technical issues What is needed is an enhanced method for sending and receiving frame information in RAR.

[0020] For uplink (UL) transmission on an unlicensed carrier, the user equipment (UE) selects the highest channel access priority level (CAPC) index (i.e., lowest priority CAPC) of the logical channel (LCH) multiplexed in the media access control (MAC) protocol data unit (PDU). The listen-before-talk (LBT) parameters corresponding to the selected CAPC index are used to perform channel access (i.e., LBT procedure) for UL transmission. The SRB data (i.e., MAC SDU of signaling radio bearer) corresponding to the lowest CAPC (i.e., highest priority) index is de-prioritized in case of multiplexing with MAC CE in MAC SDU and MAC PDU of data radio bearer. Therefore, some methods are needed to enhance the current design.

[0021] For the 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) sent on the physical downlink common control channel (PDCCH). Therefore, during the reconfiguration with synchronization process, the UE needs to first obtain the SFN of the target SpCell and then initiate RA to 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, which can delay the reconfiguration with synchronization process. Therefore, a method to reduce the delay is needed.

[0022] Various aspects of the present disclosure are to address at least the above problems and / or disadvantages and to provide at least the advantages described below. Therefore, one aspect of the present disclosure is to provide a communication method and system for converging a fifth generation (5G) communication system to support a higher data rate than a fourth generation (4G) system.

[0023] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments.

[0024] Solution to the problem According to one aspect of the present disclosure, a method for handling a listen-before-talk (LBT) failure in a wireless communication system performed by a terminal is provided. The method includes: identifying a consistent LBT failure of an active uplink (UL) bandwidth part (BWP) in a serving cell; identifying at least one UL BWP, the at least one UL BWP is not triggered by a consistent LBT failure on the same carrier in the serving cell, wherein the at least one UL BWP is configured with a physical random access channel (PRACH) opportunity; and switching the active UL BWP to a UL BWP among the at least one UL BWP.

[0025] 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 of an active UL BWP in a serving cell; identify at least one UL BWP, the at least one UL BWP is not triggered with a consistent LBT failure on the same carrier in the serving cell, wherein the at least one UL BWP is configured with a PRACH opportunity; and switch the active UL BWP to a UL BWP among the at least one UL BWP.

[0026] Advantageous Effects of the Invention The frame identifier can be applied to both the MAC subPDU including the RAR and the MAC subPDU including the SI request positive acknowledgement. The frame identifier can also be applied to the MAC subPDU including the BI. Since the frame identifier is added only once per RAR MAC PDU, the overhead is less.

[0027] An advantage of the method of the present disclosure is that the CAPC that occupies the largest portion of the UL grant dominates the channel access, which is better than the conventional scheme in which the lowest priority CAPC is always selected. Another advantage of the method of the present disclosure is that among the CAPCs that occupy the portion of the UL grant exceeding a threshold, the highest priority CAPC dominates the channel access even if it does not occupy the largest portion of the UL grant.

[0028] The design of the CAPC for permission selection for UL configuration is enhanced.

[0029] The delay of reconfiguration with synchronization process can be reduced.

[0030] Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the accompanying drawings, discloses various embodiments of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other aspects, features and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: Figure 1 is an example illustration of random access (RA) radio network temporary identifier (RA-RNTI) ambiguity due to a large RAR window size according to the related art; Figure 2 An example of a random access response (RAR) media access control (MAC) protocol data unit (PDU) based on a first RAR MAC PDU format according to an embodiment of the present disclosure is shown; Figure 3 An example of a RAR MAC PDU based on a second RAR MAC PDU format according to an embodiment of the present disclosure is shown; Figure 4 illustrates a user equipment (UE) operation according to an embodiment of the present disclosure; Figure 5 Next generation Node B (gNB) operations according to embodiments of the present disclosure are illustrated; Figure 6 An example of a RAR MAC PDU based on a first RAR MAC PDU format according to an embodiment of the present disclosure is shown; Figure 7 UE operation according to an embodiment of the present disclosure is shown; Figure 8 illustrates gNB operations according to an embodiment of the present disclosure; Fig. 9 An example of a RAR MAC PDU based on a first RAR MAC PDU format according to an embodiment of the present disclosure is shown; Fig.10 UE operation according to an embodiment of the present disclosure is shown; Fig.11 illustrates gNB operations according to an embodiment of the present disclosure; Fig.12 An example of a RAR MAC PDU based on a first RAR MAC PDU format according to an embodiment of the present disclosure is shown; Fig.13 UE operation according to an embodiment of the present disclosure is shown; Fig.14 illustrates gNB operations according to an embodiment of the present disclosure; Fig.15 is an example diagram of a design of a grant selection channel access priority level (CAPC) for a UL configuration of the related art; Fig.16 illustrates the selection of a CAPC for uplink (UL) transmission according to an embodiment of the present disclosure; Fig.17 is an example illustration of a MAC PDU to be sent in a UL Grant using Listen Before Talk (LBT) Type 1 channel access according to an embodiment of the present disclosure; Fig.18 illustrates the selection of CAPC for UL transmission according to an embodiment of the present disclosure; Fig.19 illustrates the selection of CAPC for UL transmission according to an embodiment of the present disclosure; Fig. 20is an example illustration of a MAC PDU to be sent in a UL grant using LBT Type 1 channel access according to an embodiment of the present disclosure; Fig.21 illustrates the selection of CAPC for UL transmission according to an embodiment of the present disclosure; Fig. 22 illustrates the selection of CAPC for UL transmission according to an embodiment of the present disclosure; Fig.23 is an example illustration according to an embodiment of the present disclosure; Fig.24 is another example illustration according to an embodiment of the present disclosure; Fig.25 A method for a UE to perform an RA process according to an embodiment of the present disclosure is shown; Fig.26 An absolute timing advance (TA) command MAC control element (CE) according to an embodiment of the present disclosure is shown; Fig. 27 shows a TA command MAC CE according to an embodiment of the present disclosure; Fig.28 Another method for a UE to perform a RA process according to an embodiment of the present disclosure is shown; Fig.29 Another method for a UE to perform a RA process according to an embodiment of the present disclosure is shown; Fig.30 Another method for a UE to perform a RA process according to an embodiment of the present disclosure is shown; Fig.31 is a block diagram of a terminal according to an embodiment of the present disclosure; and Fig.32 is a block diagram of a base station according to an embodiment of the present disclosure.

[0032] Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures. DETAILED DESCRIPTION

[0033] 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 by the claims and their equivalents. It includes various specific details to assist in this understanding, but these should be considered as merely exemplary. Therefore, one of ordinary skill in the art will recognize that various changes and modifications can be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and configurations may be omitted for clarity and brevity.

[0034] The terms and words used in the following description and claims are not limited to the bibliographic meanings, but are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Therefore, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purposes only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

[0035] It should be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

[0036] By the term "substantially," it is meant that the recited characteristic, parameter or value need not be achieved exactly, but that deviations or variations, including, for example, tolerances, measurement errors, measurement accuracy limitations and other factors known to those skilled in the art, may not preclude the occurrence of the amount of the effect that the characteristic is intended to provide.

[0037] It is known to those skilled in the art that the blocks and combinations of flowcharts (or sequence diagrams) can be represented and executed by computer program instructions. These computer program instructions can be loaded on a processor of a general-purpose computer, a special-purpose computer, or a programmable data processing device. When the loaded program instructions are executed by the processor, they create means for performing the functions described in the flowchart. Because the computer program instructions can be stored in a computer-readable memory that can be used in a special-purpose computer or a programmable data processing device, it is also possible to create an article that performs the functions described in the flowchart. Because the computer program instructions can be loaded on a computer or a programmable data processing device, when executed as a process, they can perform the operations of the functions described in the flowchart.

[0038] The blocks of the flowchart may correspond to a module, segment or code containing one or more executable instructions that implement one or more logical functions, or may correspond to a portion thereof. In some cases, the functions described by the blocks may be performed in an order different from the order listed. For example, two blocks listed in order may be performed simultaneously or in reverse order.

[0039] In this specification, the words "unit", "module", etc. may refer to software components or hardware components, such as, for example, a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC) that can perform a function or operation. However, "unit", etc. are not limited to hardware or software. Units, etc. may be configured to reside in an addressable storage medium or drive one or more processors. Units, etc. may also refer to software components, object-oriented software components, class components, task components, processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays, or variables. The functions provided by components and units may be a combination of smaller components and units, and may be combined with other components and units to form larger components and units. Components and units may be configured to drive devices or one or more processors in a secure multimedia card.

[0040] Before the detailed description, terms or definitions necessary for understanding the present disclosure are described. However, these terms should be interpreted in a non-restrictive manner.

[0041] A base station (BS) is an entity that communicates with a user equipment (UE) and may be referred to as a BS, base transceiver station (BTS), Node B (NB), evolved NB (eNB), access point (AP), fifth generation (5G) NB (5GNB) or next generation NB (gNB).

[0042] The UE is an entity communicating with the BS and may be referred to as a UE, a device, a mobile station (MS), a mobile equipment (ME), or a terminal.

[0043] Method for sending and receiving frame information in random access response (RAR) Method 1: In a method for transmitting and receiving frame information in a RAR of the present disclosure, a UE / gNB transmits / receives a RAR medium access control (MAC) protocol data unit (PDU), wherein the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0044] The first RAR MAC PDU format: Figure 2 An example of a RAR MAC PDU based on the first RAR MAC PDU format according to an embodiment of the present disclosure is shown. For illustration, the frame ID is assumed to be the same as Figure 2 3 bits corresponding to the maximum RAR window size of 80 ms (i.e. 8 radio frames) in Frame ID 1. Other sizes of frame IDs are not excluded.

[0045] refer to Figure 2, a RAR MAC PDU according to the first (i.e. enhanced) RAR MAC PDU format consists of one or more MACsubPDUs and optionally padding. Each MAC subPDU consists of one of the following: - a MAC subheader with a frame identifier only; - a MAC subheader with backoff indicator only; - a MAC subheader with only the Random Access (RA) Preamble Identifier (RAPID) (i.e. a positive acknowledgement to a System Information (SI) request); - MAC subheader with RAPID and MAC RAR.

[0046] The Frame Identifier MAC subheader includes a Frame Identifier (Frame ID). The size of the Frame Identifier is "X" bits and the remaining bits (if any) in the Frame Identifier MAC subheader are Reserved (R) bits. The Frame Identifier is one of the following: - Frame Identifier = System Subframe Number (SFN) - Frame identifier = SFN modulo (maximum supported RAR window size in radio frames) - Frame identifier = SFN modulo (configured RAR window size in radio frames) - Frame Identifier = 'p' least significant bits of SFN, where 'p' can be predefined or equal to log 2 (maximum RAR window size in radio frames) or log 2 (Configured RAR window size in radio frames) - SFN is the system frame number of the radio frame of the physical RA channel (PRACH) opportunity or the system frame number of the radio frame where the PRACH opportunity starts.

[0047] - 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 refers to the maximum value of the RAR window sizes in the set of configurable RAR window sizes.

[0048] A MAC subPDU with only a frame identifier is placed at the beginning of the MAC PDU. A frame identifier MAC subheader is included in the first MAC subPDU of the RAR MAC PDU.

[0049] The MAC subheader with backoff indicator consists of five header fields Extension (E) / Type (T) / Reserved (R) / R / Backoff Indicator (BI). The MAC subPDU with only the backoff indicator is placed after the MAC subPDU with the frame identifier if included. If necessary, the backoff indication is included immediately after the MAC subPDU carrying the frame identifier MAC subheader, i.e. the backoff indication is included in the second MAC subPDU.

[0050] The MAC subheader with RAPID consists of three header fields E / T / RAPID. Padding, if present, is placed at the end of the MAC PDU. The presence and length of the padding is implicit based on the transport block (TB) size and the size of the MAC subPDU. The Type (T) field is set to fundamentally different values ​​in the BI MAC subheader and the RAPID subheader. The Extension (E) field set to '0' in the MAC subheader of a 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 subheader of a MAC subPDU indicates that at least another MAC subPDU follows.

[0051] If a backoff indication is included in the MAC PDU, the 'MAC subPDU with RAPID only' and the 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the second MAC subPDU and the padding (if any). If a backoff indication is not included in the MAC PDU, the 'MAC subPDU with RAPID only' and the 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the first MAC subPDU and the padding (if any).

[0052] Second RAR MAC PDU format: Figure 3 An example of a RAR MAC PDU based on the second RAR MAC PDU format according to an embodiment of the present disclosure is shown.

[0053] refer to Figure 3 , a RAR MAC PDU according to the second (i.e., conventional) RAR MAC PDU format consists of one or more MACsubPDUs and optionally padding. Each MAC subPDU consists of one of the following: - a MAC subheader with backoff indicator only; - a MAC sub-header with RAPID only (i.e. a positive response to a SI request); - MAC subheader with RAPID and MAC RAR.

[0054] The MAC subheader with backoff indicator consists of five header fields E / T / R / R / BI. A MAC subPDU with backoff indicator only is placed at the beginning of the MAC PDU if included.

[0055] The MAC subheader with RAPID consists of three header fields E / T / RAPID. Padding, if present, is placed at the end of the MAC PDU. The presence and length of the padding is implicit based on the TB size and the size of the MAC subPDU. The Type (T) field is set to fundamentally different values ​​in the BIMAC subheader and the RAPID subheader. The E field set to '0' in the MAC subheader of a 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 subheader of a MAC subPDU indicates that at least another MAC subPDU follows.

[0056] If a backoff indication is included in the MAC PDU, 'MAC subPDU with RAPID only' and 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the first MAC subPDU and the padding (if any). If a backoff indication is not included in the MAC PDU, 'MAC subPDU with RAPID only' and 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the beginning of the MAC PDU and the padding (if any).

[0057] UE operation: Embodiment 1: Figure 4 UE operation according to an embodiment of the present disclosure is shown.

[0058] refer to Figure 4, the UE sends a RA preamble at operation 410, the UE monitors a physical downlink control channel (PDCCH) for RAR reception at operation 420, and the UE receives a RAR MAC PDU at operation 430. The UE determines at operation 440 whether the cell on 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 at operation 450. If the cell is an authorized cell, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format at 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 an authorized cell.

[0059] UE processing according to the first MAC PDU format: The UE processes the first MAC subPDU and obtains a frame identifier from a MAC subheader of the first MAC subPDU at operation 451, and processes the remaining MAC subPDUs in the RAR MAC PDU at operation 452 until the RAR is successfully received or no more MAC subPDUs remain.

[0060] If the second MAC subPDU in the RAR MAC PDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to a backoff value indicated by multiplying the BI field of the MAC subPDU by the SCALING_FACTOR_BI at operation 453. The SCALING_FACTOR_BI may be 1 or may be signaled by the gNB in ​​RRC signaling. The frame identifier is not checked in order to process the MAC subPDU with the BI. When the backoff is applied during the RA procedure, the backoff value is randomly selected between 0 and PREAMBLE_BACKOFF. Alternatively, if the second MAC subPDU in the RAR MAC PDU includes a backoff indicator and the frame identifier obtained from the first MAC subPDU corresponds to a radio frame in which a PRACH opportunity of a RA preamble is sent by the UE (i.e., corresponds to a radio frame in which a PRACH opportunity of a RA preamble is sent by the UE), the UE sets PREAMBLE_BACKOFF to a backoff value indicated by multiplying the BI field of the MAC subPDU by the SCALING_FACTOR_BI. When backoff is applied during the RA procedure, the backoff value is randomly selected between 0 and PREAMBLE_BACKOFF.

[0061] To determine whether the frame identifier obtained from the first MAC subPDU corresponds to a radio frame of a PRACH opportunity in which the UE sends an RA preamble, the UE calculates the frame identifier corresponding to the radio frame of the PRACH opportunity as explained earlier 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 subPDU corresponds to a radio frame of a PRACH opportunity in which the UE sends an RA preamble.

[0062] If the MAC subPDU (other than the first MAC subPDU) includes a MAC subheader with a RAPID, where the RAPID matches the RA preamble sent by the UE and the frame identifier obtained from the first MAC subPDU corresponds to a radio frame of a PRACH opportunity in which the RA preamble is sent by the UE (i.e., corresponds to a radio frame starting with a PRACH opportunity in which the RA preamble is sent by the UE), the UE considers that the RAR is successfully received at operation 454.

[0063] If the RAR is deemed to be successfully received and this MAC subPDU only includes the RAPID, the UE shall consider this to be a positive acknowledgement of the SI request.

[0064] UE processing according to the second MAC PDU format: The UE processes the MAC subPDUs in the RAR MAC PDU at operation 462 until the RAR is successfully received or no more MAC subPDUs remain.

[0065] If the first MAC subPDU in the RAR MAC PDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to a backoff value indicated by multiplying the BI field of the MAC subPDU by SCALING_FACTOR_BI at operation 463 .

[0066] If the MAC subPDU includes a MAC subheader with a RAPID, where the RAPID matches the RA preamble sent by the UE, the UE considers the RAR to be successfully received at operation 464. If the RAR is considered to be successfully received and this MAC subPDU includes only the RAPID, the UE considers this to be a positive response to the SI request.

[0067] Embodiment 2: In another embodiment, the UE sends 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 or equal to 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operation and the processing of the RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment are as follows: Figure 4 Same as described in .

[0068] Embodiment 3: In another embodiment, the UE sends 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 or equal to 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operation and the method for processing the RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment are as follows: Figure 4 Same as described in .

[0069] gNB Operation: Figure 5 The gNB operation according to an embodiment of the present disclosure is shown.

[0070] refer to Figure 5 , the gNB receives one or more RA preambles at operation 510, and determines whether the cell on which the RAR is to be transmitted is an unlicensed cell at operation 520. If the cell is an unlicensed cell, the gNB generates a RAR MAC PDU for transmission according to a first RAR MAC PDU format at operation 530. If the cell is an authorized cell, the gNB generates a RAR MAC PDU for transmission according to a second RAR MAC PDU format at operation 540. If a downlink (DL) carrier frequency of the cell corresponds to an unlicensed band, the cell is an unlicensed cell. Otherwise, the cell is an authorized cell.

[0071] In order to generate a 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 at operation 531, wherein the first MAC subPDU is composed of a MAC subheader having only a frame identifier. If a backoff indication needs to be sent in the RAR MAC PDU, the gNB includes a second MAC subPDU in the RAR MAC PDU at operation 532, wherein 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 at operation 533, wherein each MAC subPDU includes a MAC subheader having only a RAPID or a MAC subheader having a RAPID and a MAC RAR. Each of these MAC subPDUs corresponds to a RA preamble received by the gNB in ​​a PRACH opportunity, the PRACH opportunity starting with a radio frame, and the frame identifier of the radio frame is included in the first MAC subPDU.

[0072] To generate the RAR MAC PDU according to the second RAR MAC PDU format, if a backoff indication needs to be sent in the RAR MAC PDU, the gNB includes a first MAC subPDU at operation 542, wherein the first MAC subPDU is composed of a MAC subheader having only a BI. The gNB includes one or more MAC subPDUs at operation 543, wherein each MAC subPDU includes a MAC subheader having only a RAPID or a MAC subheader having a RAPID and a MAC RAR.

[0073] The gNB sends the generated RAR MAC PDU at operation 534 or 544.

[0074] In another embodiment, the gNB receives one or more RA preambles and determines whether the cell on which the RAR is to be transmitted is configured with a RAR window size greater than 10 ms. If the configured 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 configured RAR window size is less than or equal to 10 ms, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU. The detailed gNB operation of generating a RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment is similar to Figure 5 Same as described in .

[0075] 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 on which the RAR is to be transmitted. If the maximum supported 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 maximum supported RAR window size is less than or equal to 10 ms, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU. The detailed gNB operation of generating a RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment is the same as Figure 5 Same as described in .

[0076] The advantage of the first RAR MAC PDU format disclosed in this method is that the frame identifier can be applied to both the MAC subPDU including the RAR and the MAC subPDU including the SI request positive acknowledgement. The frame identifier can also be applied to the MAC subPDU including the BI. Since the frame identifier is added only once per RAR MAC PDU, there is less overhead. The disadvantage is that the frame identifier needs to be always included in the RAR MAC PDU.

[0077] Method 2: In a second method for sending and receiving frame information in a RAR of the present disclosure, a UE / gNB sends / receives a RAR MAC PDU, wherein the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0078] The first RAR MAC PDU format: Figure 6 FIG. 4 shows an example of a RAR MAC PDU based on the first RAR MAC PDU format according to another embodiment of the present disclosure. For illustration, the frame ID is assumed to be the same as Figure 6 3 bits corresponding to the maximum RAR window size of 80 ms.

[0079] refer to Figure 6 , a RAR MAC PDU according to the first (i.e. enhanced) RAR MAC PDU format consists of one or more MACsubPDUs and optionally padding. Each MAC subPDU consists of one of the following: - a MAC subheader with a frame identifier only; - a MAC subheader with backoff indicator only; - a MAC sub-header with RAPID only (i.e. a positive response to a SI request); - MAC subheader with RAPID and MAC RAR.

[0080] The Frame Identifier MAC subheader includes E, T, R1 and a frame identifier (Frame ID). It may also include one or more R bits, depending on the number of bits defined for the frame identifier. For example, if the frame identifier is 5 bits long, there are no R bits; and if the frame identifier is 3 bits long, there are two R bits. The frame identifier is one of the following: - Frame Identifier = SFN - Frame identifier = SFN modulo (maximum supported RAR window size in radio frames) - Frame identifier = SFN modulo (configured RAR window size in radio frames) - Frame Identifier = 'p' least significant bits of SFN, where 'p' can be predefined or equal to log 2 (maximum RAR window size in radio frames) or log 2 (Configured RAR window size in radio frames) - SFN is the system frame number of the radio frame of the PRACH opportunity or the system frame number of the radio frame where the PRACH opportunity starts.

[0081] - 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 refers to the maximum value of the RAR window sizes in the set of configurable RAR window sizes.

[0082] The MAC subheader with backoff indicator consists of five header fields E / T / R1 / R / BI. The MAC subheader with frame identifier consists of at least four header fields E / T / R1 / Frame ID. For the MAC subheader with backoff indicator and the MAC subheader with frame identifier, the T bit is set to the same value (e.g., T is equal to 0). The R1 bit is set to different values ​​(e.g., R1 is set to zero in the MAC subheader with backoff indicator and R1 is set to '1' in the MAC subheader with frame identifier) ​​to distinguish the MAC subheader with backoff indicator and the MAC subheader with frame identifier.

[0083] The MAC subheader with RAPID consists of three header fields E / T / RAPID. Padding, if present, is placed at the end of the MAC PDU. The presence and length of the padding is implicit based on the TB size and the size of the MAC subPDU. The value of the T bit in the RAPID subheader is different from the value of the T bit in the frame identifier subheader and the BI subheader.

[0084] The E field set to '0' in the MAC subheader 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 subheader of the MAC subPDU indicates that at least another MAC subPDU follows.

[0085] Example 1: Reference Figure 6 , a MAC subPDU with only a backoff indicator is placed at the beginning of the MAC PDU if included. A MAC subPDU with only a frame identifier is placed at the beginning of the MAC PDU after the MAC subPDU with the backoff indicator if included. If 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 second MAC subPDU and the padding (if any). If the backoff indication is not 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). This has the following advantages: the UE can obtain the frame identifier before processing the MAC subPDU carrying RAPID; the UE can also obtain the backoff indicator without processing the frame identifier; and the gNB can send a RAR MAC PDU with only a backoff indicator, which is not possible in method 1.

[0086] Embodiment 2: A MAC subPDU with only a frame identifier is placed at the beginning of a MAC PDU. A MAC subPDU with only a backoff indication is placed at the beginning of a MAC PDU after a MAC subPDU with a frame identifier if included. If a 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 second MAC subPDU and the padding (if any). If a backoff indication is not 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). This has the following advantages: the UE can obtain the frame identifier before processing any MAC subPDU and the frame identifier can be applied to each MAC subPDU.

[0087] Embodiment 3: A MAC subPDU with only a backoff indicator is placed at the beginning of a MAC PDU if included. A MAC subPDU with only a frame identifier is placed before the first MAC subPDU including RAPID and MAC RAR. If a backoff indication is included in the MAC PDU, the 'MAC subPDU with only RAPID' can be placed anywhere between the second MAC subPDU and the padding (if any). If a backoff indication is not included in the MAC PDU, the 'MAC subPDU with only RAPID' can be placed anywhere between the first MAC subPDU and the padding (if any). The 'MAC subPDU with RAPID and MAC RAR' is placed after the MAC subPDU carrying the frame identifier and before the padding (if any). This has the following advantages: the UE can obtain the frame identifier before processing the MAC subPDU carrying RAPID and MAC RAR; the UE can also obtain the backoff indicator without processing the frame identifier; and the UE can also obtain the MAC subPDU with only RAPID without processing the frame identifier. The gNB may send a RAR MAC PDU with only a backoff indicator without including a MAC subPDU with a frame identifier; and the gNB may send a RAR MAC PDU with a backoff indication and / or a MAC subPDU with only a RAPID without including a MAC subPDU with a frame identifier.

[0088] The advantage of the first RAR MAC PDU format disclosed in this method is that the frame identifier can be applied to both the MAC subPDU including the RAR and the MAC subPDU including the SI request positive response. Since the frame identifier is added only once per RAR MAC PDU, there is less overhead. There is no need to always include the frame identifier in the RAR MAC PDU. If the RAR MAC PDU only includes the BI, it can be skipped. In an embodiment, if the RAR MAC PDU does not include any MAC RAR, it can also be skipped. Alternatively, this method is beneficial for UE implementation because the MAC subheader structure of the first RAR MAC PDU format and the second RAR MAC PDU format is similar and thus reduces the complexity of the implementation.

[0089] Second RAR MAC PDU format: In this method of the present disclosure, the RAR MAC PDU according to the second (ie, normal) RAR MAC PDU format is the same as described in method 1 for transmitting and receiving frame information in RAR.

[0090] UE operation: Embodiment 1: Figure 7 The UE operation according to another embodiment of the present disclosure is shown.

[0091] refer to Figure 7 , the UE sends a RA preamble at operation 710, the UE monitors the PDCCH for RAR reception at operation 720, and the UE receives a RAR MAC PDU at operation 730. The UE determines at operation 740 whether the cell on 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 at operation 750. If the cell is an authorized cell, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format at operation 760. If the DL carrier frequency of the cell corresponds to the unlicensed frequency band, the cell is an unlicensed cell. Otherwise, the cell is an authorized cell.

[0092] While processing the RAR MAC PDU according to the first MAC PDU format, the UE processes the MAC subPDUs in the RAR MACPDU until the RAR is successfully received or no more MAC subPDUs remain at operation 751. If the first MAC subPDU in the RAR MACPDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to a backoff value indicated by multiplying the BI field of the MAC subPDU by the SCALING_FACTOR_BI at operation 752. If the MACsubPDU in the RAR MAC PDU includes a frame identifier, the UE processes the MAC subPDU at operation 753 and obtains the frame identifier from the MAC subheader of the MAC subPDU. If the MAC subPDU includes a MAC subheader with a RAPID, wherein the RAPID matches the RA preamble transmitted by the UE and the frame identifier obtained from another MAC subPDU corresponds to a radio frame of a PRACH opportunity in which the RA preamble is transmitted by the UE, the UE considers that the RAR is successfully received at operation 754. If the RAR is deemed to be successfully received and this MACsubPDU only includes the RAPID, the UE considers this as a positive acknowledgement to the SI request.

[0093] While processing the RAR MAC PDU according to the second RAR MAC PDU format, the UE processes the MAC subPDUs in the RAR MAC PDU at operation 761 until the RAR is successfully received or no more MAC subPDUs remain. If the first MAC subPDU in the RAR MAC PDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to a backoff value indicated by multiplying the BI field of the MAC subPDU by the SCALING_FACTOR_BI at operation 762. If the MAC subPDU includes a MAC subheader with a RAPID, where the RAPID matches the RA preamble sent by the UE, the UE considers the RAR to be successfully received at operation 764. If the RAR is considered to be successfully received and this MAC subPDU only includes the RAPID, the UE considers this as a positive response to the SI request.

[0094] Embodiment 2: In another embodiment, the UE sends 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 or equal to 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operation and the processing of the RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment are as follows: Figure 7 Same as described in .

[0095] Embodiment 3: In another embodiment, the UE sends 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 or equal to 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operation and the method for processing the RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment are as follows: Figure 7 Same as described in .

[0096] According to the first RAR MAC PDU format, the T bit is set to the same value (e.g., T is equal to 0) for the MAC subheader with the backoff indicator and the MAC subheader with the frame identifier. So when processing the RAR MAC PDU according to the first MAC PDU format, the UE checks the R1 bit to determine whether the MAC subheader includes the BI or the frame identifier. The R1 bit is set to different values ​​(e.g., R1 is set to zero in the MAC subheader with the backoff indicator and R1 is set to '1' in the MAC subheader with the frame identifier) ​​to distinguish between the MAC subheader with the backoff indicator and the MAC subheader with the frame identifier. In an embodiment, while processing the RAR MAC PDU according to the first RAR MAC PDU format, the UE determines whether the MAC subheader in the MAC subPDU is a BI subheader or a frame identifier subheader or a RAPID subheader, wherein the UE determines that if T=0 and R1=0, the MAC subheader is a BI subheader; if T=0 and R1=1, the MAC subheader is a frame identifier subheader; and if T=1, the MAC subheader is a RAPID subheader. In an embodiment, while processing the RAR MAC PDU according to the second RAR 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 if T=0, the MAC subheader is a BI subheader; and if T=1, the MAC subheader is a RAPID subheader.

[0097] gNB Operation: Figure 8 A gNB operation according to another embodiment of the present disclosure is shown.

[0098] refer to Figure 8 , the gNB receives one or more RA preambles at operation 810, and determines whether the cell on which the RAR is to be transmitted is an unlicensed cell at operation 820. If the cell is an unlicensed cell, the gNB generates a RAR MAC PDU for transmission according to the first RAR MAC PDU format at operation 830. If the cell is an authorized cell, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format at 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 an authorized cell.

[0099] While generating the RAR MAC PDU according to the first RAR MAC PDU format, if a backoff indication needs to be sent in the RAR MAC PDU, the gNB includes a first MAC subPDU or a second MAC subPDU in the RAR MAC PDU at operation 831, wherein the first MAC subPDU or the second MAC subPDU is composed of a MAC subheader having only a BI. The gNB includes the first MAC subPDU or the second MAC subPDU in the RAR MAC PDU at operation 832, wherein the first MAC subPDU or the second MAC subPDU is composed of a MAC subheader having only a frame identifier. The gNB includes one or more MAC subPDUs in the RAR MAC PDU at operation 833, wherein each MAC subPDU includes a MAC subheader having only a RAPID or a MAC subheader having a RAPID and a MAC RAR. Each of these MAC subPDUs corresponds to a RA preamble received by the gNB in ​​a PRACH opportunity, the PRACH opportunity starting at a radio frame, and the frame identifier of the radio frame is included in the first MAC subPDU.

[0100] While generating the RAR MAC PDU according to the second RAR MAC PDU format, if a backoff indication needs to be sent in the RAR MAC PDU, the gNB includes a first MAC subPDU at operation 841, wherein the first MAC subPDU is composed of a MAC subheader having only a BI. The gNB includes one or more MAC subPDUs at operation 843, wherein each MAC subPDU includes a MAC subheader having only a RAPID or a MAC subheader having a RAPID and a MAC RAR.

[0101] The gNB sends the generated RAR MAC PDU at operation 834 or 844.

[0102] Alternatively, the detailed operations in this embodiment follow as follows: Figure 5The operation shown. 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 equal to 0) for the MAC subheader with the backoff indicator and the MAC subheader with the frame identifier. The R1 bit is set to different values ​​(e.g., R1 is set to zero in the MAC subheader with the backoff indicator and R1 is set to '1' in the MAC subheader with the frame identifier) ​​to distinguish the MAC subheader with the backoff indicator from the MAC subheader with the frame identifier. In an 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 subheader; sets T=0 and R1=1 in the frame identifier MAC subheader; and sets T=1 in the RAPID MAC subheader. In an embodiment, while generating the RAR MAC PDU according to the second RAR MAC PDU format, the gNB sets T=0 in the BI MAC subheader; and sets T=1 in the RAPID MAC subheader.

[0103] In another embodiment, the gNB receives one or more RA preambles and determines whether the cell on which the RAR is to be transmitted is configured with a RAR window size greater than 10 ms. If the configured 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 configured RAR window size is less than or equal to 10 ms, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU. The detailed gNB operation of generating a RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment is similar to Figure 8 Alternatively, the detailed gNB operation of generating the RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment is the same as described in Figure 5The same as described in . 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 equal to 0) for the MAC subheader with the backoff indicator and the MAC subheader with the frame identifier. The R1 bit is set to different values ​​(e.g., R1 is set to zero in the MAC subheader with the backoff indicator and R1 is set to '1' in the MAC subheader with the frame identifier) ​​to distinguish the MAC subheader with the backoff indicator and the MAC subheader with the frame identifier. In an 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 subheader; sets T=0 and R1=1 in the frame identifier MAC subheader; and sets T=1 in the RAPID MAC subheader. In an embodiment, while generating the RAR MAC PDU according to the second RAR MAC PDU format, the gNB sets T=0 in the BIMAC subheader; and sets T=1 in the RAPID MAC subheader.

[0104] 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 on which the RAR is to be transmitted. If the maximum supported 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 maximum supported RAR window size is less than or equal to 10 ms, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU. The detailed gNB operation of generating a RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment is similar to Figure 8 Alternatively, the detailed gNB operation of generating the RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment is the same as described in Figure 5The same as described in . 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 equal to 0) for the MAC subheader with the backoff indicator and the MAC subheader with the frame identifier. The R1 bit is set to different values ​​(e.g., R1 is set to zero in the MAC subheader with the backoff indicator and R1 is set to '1' in the MAC subheader with the frame identifier) ​​to distinguish the MAC subheader with the backoff indicator and the MAC subheader with the frame identifier. In an 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 subheader; sets T=0 and R1=1 in the frame identifier MAC subheader; and sets T=1 in the RAPID MAC subheader. In an embodiment, while generating the RAR MAC PDU according to the second RAR MAC PDU format, the gNB sets T=0 in the BI MAC subheader; and sets T=1 in the RAPID MAC subheader.

[0105] Method 3: In a third method for sending and receiving frame information in RAR of the present disclosure, the UE / gNB sends / receives a RAR MAC PDU, wherein the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0106] The first RAR MAC PDU format: Fig. 9 FIG. 4 shows an example of a RAR MAC PDU based on the first RAR MAC PDU format according to another embodiment of the present disclosure. For illustration, the frame ID is assumed to be the same as Fig. 9 3 bits corresponding to the maximum RAR window size of 80 ms.

[0107] refer to Fig. 9 , a RAR MAC PDU according to the first (i.e. enhanced) RAR MAC PDU format consists of one or more MACsubPDUs and optionally padding. Each MAC subPDU consists of one of the following: - a MAC subheader with a frame identifier only; - a MAC subheader with backoff indicator only; - a MAC sub-header with RAPID only (i.e. a positive response to a SI request); - MAC subheader with RAPID and MAC RAR.

[0108] The Frame Identifier MAC subheader includes E, T, and a frame identifier (Frame ID). It may also include one or more R bits, depending on the number of bits defined for the frame identifier. For example, if the frame identifier is 6 bits long, there are no R bits. If the frame identifier is 3 bits long, there are 3 R bits. The frame identifier is one of the following: - Frame Identifier = SFN - Frame identifier = SFN modulo (maximum supported RAR window size in radio frames) - Frame identifier = SFN modulo (configured RAR window size in radio frames) - Frame Identifier = 'p' least significant bits of SFN, where 'p' can be predefined or equal to log 2 (maximum RAR window size in radio frames) or log 2 (Configured RAR window size in radio frames) - SFN is the system frame number of the radio frame of the PRACH opportunity or the system frame number of the radio frame where the PRACH opportunity starts.

[0109] - 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 refers to the maximum value of the RAR window sizes in the set of configurable RAR window sizes.

[0110] The MAC subheader with backoff indicator consists of five header fields E / T / R / R / BI. The MAC subheader with frame identifier consists of at least three header fields E / T / Frame ID. For the MAC subheader with backoff indicator and the MAC subheader with frame identifier, the T bit is set to the same value (e.g., T equals 0). In a RAR MAC PDU, if there is only one MAC subPDU including a subheader with T=0, the subheader is a frame identifier subheader. If there are two MAC subPDUs including a subheader with T=0, the first MAC subPDU is used for the BI and the second MAC subPDU is used for the frame identifier.

[0111] The MAC subheader with RAPID consists of three header fields E / T / RAPID. Padding, if present, is placed at the end of the MAC PDU. The presence and length of the padding is implicit based on the TB size and the size of the MAC subPDU. The value of the T bit in the RAPID subheader is different from the value of the T bit in the frame identifier subheader and the BI subheader.

[0112] The E field set to '0' in the MAC subheader 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 subheader of the MAC subPDU indicates that at least another MAC subPDU follows.

[0113] A MAC subPDU with only a backoff indicator is placed at the beginning of the MAC PDU if included. A MAC subPDU with only a frame identifier is placed at the beginning of the MAC PDU after the MAC subPDU with the backoff indicator if included. If the backoff indication is included in the MAC PDU, then the 'MACsubPDU with RAPID only' and the 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the second MAC subPDU and the padding (if any). If the backoff indication is not included in the MAC PDU, then the 'MACsubPDU with RAPID only' and the 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the first MAC subPDU and the padding (if any).

[0114] The advantage of the first RAR MAC PDU format disclosed in this method is that the frame identifier can be applied to both the MAC subPDU including the RAR and the MAC subPDU including the SI request positive acknowledgement. Since the frame identifier is added only once per RAR MAC PDU, there is less overhead. There is no need to always include the frame identifier in the RAR MAC PDU. If the RAR MAC PDU only includes the BI, it can be skipped. Alternatively, this method is beneficial for UE implementation because the MAC subheader structure for the first RAR MAC PDU format and the second RAR MAC PDU format is similar and thus reduces the complexity of the implementation.

[0115] Second RAR MAC PDU format: In this method of the present disclosure, the RAR MAC PDU according to the second (ie, normal) RAR MAC PDU format is the same as described in Method 1.

[0116] UE operation: Embodiment 1: Fig.10 The UE operation according to another embodiment of the present disclosure is shown.

[0117] refer to Fig.10, the UE sends a RA preamble at operation 1010, the UE monitors the PDCCH for RAR reception at operation 1020, and the UE receives a RAR MAC PDU at operation 1030. The UE determines at operation 1040 whether the cell on 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 at operation 1050. If the cell is an authorized cell, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format at operation 1060. If the DL carrier frequency of the cell corresponds to the unlicensed frequency band, the cell is an unlicensed cell. Otherwise, the cell is an authorized cell.

[0118] While processing the RAR MAC PDU according to the first MAC PDU format, the UE processes the MAC subPDU in the RAR MACPDU until the RAR is successfully received or no more MAC subPDUs remain at operation 1051. If the MAC subPDU in the RAR MACPDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to a backoff value indicated by multiplying the BI field of the MACsubPDU by the SCALING_FACTOR_BI at operation 1052. If the MACsubPDU in the RAR MAC PDU includes a frame indicator, the UE processes the MAC subPDU at operation 1053 and obtains a frame identifier from a MAC subheader of the MAC subPDU. If the MAC subPDU includes a MAC subheader with a RAPID, wherein the RAPID matches the RA preamble sent by the UE and the frame identifier obtained from another MAC subPDU corresponds to a radio frame of a PRACH opportunity in which the RA preamble is sent by the UE, the UE considers that the RAR is successfully received at operation 1054. If the RAR is deemed to be successfully received and this MACsubPDU includes only RAPID, the UE considers this as a positive response to the SI request. The UE determines whether the MAC subheader is a BI subheader or a frame identifier as follows: In the RAR MAC PDU, if there is only one MACsubPDU including a subheader with T=0, the subheader is a frame identifier subheader and this MAC subPDU includes only a frame identifier subheader. If there are two MAC subPDUs including a subheader with T=0, the first MAC subPDU includes a BI and the second MAC subPDU includes a frame identifier. If T=1, the UE determines that the MAC subheader is a RAPID subheader.

[0119] While processing the RAR MAC PDU according to the second RAR MAC PDU format, the UE processes the MAC subPDUs in the RAR MAC PDU at operation 1061 until the RAR is successfully received or no more MAC subPDUs remain. If the first MAC subPDU in the RAR MAC PDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to a backoff value indicated by multiplying the BI field of the MAC subPDU by the SCALING_FACTOR_BI at operation 1062. If the MAC subPDU includes a MAC subheader with a RAPID, where the RAPID matches the RA preamble sent by the UE, the UE considers the RAR to be successfully received at operation 1064. If the RAR is considered to be successfully received and this MAC subPDU only includes the RAPID, the UE considers this to be a positive response to the SI request. The UE determines whether the MAC subheader in the MAC subPDU is a BI subheader or a RAPID subheader. The UE determines that if T=0, the MAC subheader is a BI subheader; and if T=1, the MAC subheader is a RAPID subheader.

[0120] Embodiment 2: In another embodiment, the UE sends 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 or equal to 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operation and the processing of the RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment are as follows: Fig.10The same as described in . While processing the RAR MAC PDU according to the first MAC PDU format, the UE determines whether the MAC subheader is a BI subheader or a frame identifier as follows: In the RAR MAC PDU, if there is only one MAC subPDU including a subheader with T=0, the subheader is a frame identifier subheader and this MAC subPDU includes only a frame identifier subheader. If there are two MAC subPDUs including a subheader with T=0, the first MAC subPDU includes a BI and the second MAC subPDU includes a frame identifier. The UE determines that the MAC subheader is a RAPID subheader if T=1. While processing the RAR MAC PDU according to the second RAR 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 if T=0; and the MAC subheader is a RAPID subheader if T=1.

[0121] Embodiment 3: In another embodiment, the UE sends 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 or equal to 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operation and the method for processing the RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment are as follows: Fig.10The same as described in . While processing the RAR MAC PDU according to the first MAC PDU format, the UE determines whether the MAC subheader is a BI subheader or a frame identifier as follows: In the RAR MAC PDU, if there is only one MAC subPDU including a subheader with T=0, the subheader is a frame identifier subheader and this MACsubPDU only includes a frame identifier subheader. If there are two MAC subPDUs including a subheader with T=0, the first MAC subPDU includes a BI and the second MAC subPDU includes a frame identifier. The UE determines that the MAC subheader is a RAPID subheader if T=1. While processing the RAR MAC PDU according to the second RAR 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 if T=0; and the MAC subheader is a RAPID subheader if T=1.

[0122] gNB Operation: Fig.11 The gNB operation according to an embodiment of the present disclosure is shown.

[0123] refer to Fig.11 , the gNB receives one or more RA preambles at operation 1110, and determines whether the cell on which the RAR is to be transmitted is an unlicensed cell at operation 1120. If the cell is an unlicensed cell, the gNB generates a RAR MAC PDU for transmission according to the first RAR MAC PDU format at operation 1130. If the cell is an authorized cell, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format at operation 1140. If the DL carrier frequency of the cell corresponds to the unlicensed band, the cell is an unlicensed cell. Otherwise, the cell is an authorized cell.

[0124] While generating the RAR MAC PDU according to the first RAR MAC PDU format, a MAC subPDU having only a backoff indicator is placed at the beginning of the MAC PDU if included, that is, the first MAC subPDU includes the BI. If the first MAC subPDU includes the BI, the MAC subPDU having the frame identifier is the second MAC subPDU. If it is necessary to send a backoff indication in the RAR MAC PDU, the gNB includes the first MAC subPDU in the RAR MAC PDU at operation 1131, wherein the first MAC subPDU is composed of a MAC subheader having only the BI. The gNB also includes the second MAC subPDU in the RAR MAC PDU, wherein the second MAC subPDU is composed of a MAC subheader having only the frame identifier. If it is not necessary to send a backoff indication in the RAR MAC PDU, the gNB includes the first MAC subPDU in the RAR MAC PDU at operation 1132, wherein 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 at operation 1133, wherein each MAC subPDU includes a MAC subheader with only RAPID or a MAC subheader with RAPID and MAC RAR. Each of these MAC subPDUs corresponds to a RA preamble received by the gNB in ​​a PRACH opportunity, the PRACH opportunity starting with a radio frame, a frame identifier of the radio frame being included in the first MAC subPDU.

[0125] While generating the RAR MAC PDU according to the second RAR MAC PDU format, if a backoff indication needs to be sent in the RAR MAC PDU, the gNB includes a first MAC subPDU at operation 1141, wherein the first MAC subPDU is composed of a MAC subheader having only a BI. The gNB includes one or more MAC subPDUs at operation 1143, wherein each MAC subPDU includes a MAC subheader having only a RAPID or a MAC subheader having a RAPID and a MAC RAR.

[0126] The gNB sends the generated RAR MAC PDU at operation 1134 or 1144.

[0127] In another embodiment, the gNB receives one or more RA preambles and determines whether the cell on which the RAR is to be transmitted is configured with a RAR window size greater than 10 ms. If the configured 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 configured RAR window size is less than or equal to 10 ms, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU. The detailed gNB operation of generating a RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment is similar to Fig.11 The same as described in. While generating the RAR MAC PDU according to the first RAR MAC PDU format, the MAC subPDU with only the backoff indicator is placed at the beginning of the MAC PDU if included, that is, the first MAC subPDU includes the BI. If the first MAC subPDU includes the BI, the MAC subPDU with the frame identifier is the second MAC subPDU.

[0128] 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 on which the RAR is to be transmitted. If the maximum supported 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 maximum supported RAR window size is less than or equal to 10 ms, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU. The detailed gNB operation of generating a RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment is the same as Fig.11 The same as described in. While generating the RAR MAC PDU according to the first RAR MAC PDU format, the MAC subPDU with only the backoff indicator is placed at the beginning of the MAC PDU if included, that is, the first MAC subPDU includes the BI. If the first MAC subPDU includes the BI, the MAC subPDU with the frame identifier is the second MAC subPDU.

[0129] Method 4: In a fourth method for sending and receiving frame information in a RAR of the present disclosure, a UE / gNB sends / receives a RAR MAC PDU, wherein the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0130] The first RAR MAC PDU format: Fig.12 An example of a RAR MAC PDU based on the first RAR MAC PDU format according to an embodiment of the present disclosure is shown. For illustration, the frame ID is assumed to be the same as Fig.12 3 bits corresponding to the maximum RAR window size of 80 ms.

[0131] refer to Fig.12 , a RAR MAC PDU according to the first (i.e. enhanced) RAR MAC PDU format consists of one or more MAC subPDUs and optionally padding. Each MAC subPDU consists of one of the following: - a MAC subheader with backoff indicator only; - a MAC sub-header with only RAPID and Frame ID (i.e. a positive response to the SI request); - MAC subheader with RAPID, Frame ID and MAC RAR.

[0132] The RAPID MAC subheader consists of E, T, RAPID and a frame identifier (Frame ID). Depending on the number of bits defined for the frame identifier, it may also include one or more R bits. For example, if the frame identifier is 8 bits long, there are no R bits. If the frame identifier is 3 bits long, there are 5 R bits. The frame identifier is one of the following: - Frame Identifier = SFN - Frame identifier = SFN modulo (maximum supported RAR window size in radio frames) - Frame identifier = SFN modulo (configured RAR window size in radio frames) - Frame Identifier = 'p' least significant bits of SFN, where 'p' can be predefined or equal to log 2 (maximum RAR window size in radio frames) or log 2 (Configured RAR window size in radio frames) - SFN is the system frame number of the radio frame of the PRACH opportunity or the system frame number of the radio frame where the PRACH opportunity starts - 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 refers to the maximum value of the RAR window sizes in the set of configurable RAR window sizes.

[0133] The MAC subheader with backoff indicator consists of five header fields E / T / R / R / BI.

[0134] The MAC subheader with RAPID and Frame ID consists of at least four header fields E / T / RAPID / Frame ID. Depending on the number of bits defined for the Frame ID, it may also include one or more R bits. Padding, if present, is placed at the end of the MAC PDU. The presence and length of the padding is implicit based on the TB size and the size of the MAC subPDU.

[0135] The MAC subPDU with only the backoff indicator is placed at the beginning of the MAC PDU if included. If the backoff indication is included in the MAC PDU, the 'MAC subPDU with RAPID only' and the 'MAC subPDU with RAPID and MAC RAR' may be placed anywhere between the second MAC subPDU and the padding (if any). If the backoff indication is not included in the MAC PDU, the 'MAC subPDU with RAPID only' and the 'MAC subPDU with RAPID and MACRAR' may be placed anywhere between the first MAC subPDU and the padding (if any).

[0136] The E field set to '0' in the MAC subheader of a 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 subheader of a MAC subPDU indicates that at least another MAC subPDU follows.

[0137] This method is beneficial for UE implementation because the MAC subheader structure of the first RAR MAC PDU format and the second RAR MAC PDU format is similar and thus reduces the complexity of the implementation. In this method, the number of MAC subheaders is also not increased.

[0138] Second RAR MAC PDU format: In this method of the proposed disclosure, the RAR MAC PDU according to the second (ie, normal) RAR MAC PDU format is the same as described in Method 1.

[0139] UE operation: Embodiment 1: Fig.13 Detailed UE operation according to another embodiment of the present disclosure is shown.

[0140] refer to Fig.13 , the UE sends a RA preamble at operation 1310, the UE monitors the PDCCH for RAR reception at operation 1320, and the UE receives a RAR MAC PDU at operation 1330. The UE determines at operation 1340 whether the cell on 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 at operation 1350. If the cell is an authorized cell, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format at operation 1360. If the DL carrier frequency of the cell corresponds to the unlicensed frequency band, the cell is an unlicensed cell. Otherwise, the cell is an authorized cell.

[0141] While processing the RAR MAC PDU according to the first MAC PDU format, the UE processes the MAC subPDUs in the RAR MACPDU until the RAR is successfully received or no more MAC subPDUs remain at operation 1351. If the MAC subPDU in the RAR MACPDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to a backoff value indicated by multiplying the BI field of the MACsubPDU by the SCALING_FACTOR_BI at operation 1352. If the MAC subPDU includes a MAC subheader having a RAPID and a frame ID, wherein the RAPID matches the RA preamble sent by the UE and the frame ID corresponds to a radio frame of a PRACH opportunity in which the RA preamble is sent by the UE, the UE considers the RAR to be successfully received at operation 1353. If the RAR is considered to be successfully received and this MAC subPDU includes only the RAPID, the UE considers this as a positive response to the SI request.

[0142] While processing the RAR MAC PDU according to the second RAR MAC PDU format, the UE processes the MAC subPDUs in the RAR MAC PDU until the RAR is successfully received or no more MAC subPDUs remain at operation 1361. If the first MAC subPDU in the RAR MAC PDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to a backoff value indicated by multiplying the BI field of the MAC subPDU by the SCALING_FACTOR_BI at operation 1362. If the MAC subPDU includes a MAC subheader with a RAPID, where the RAPID matches the RA preamble sent by the UE, the UE considers the RAR to be successfully received at operation 1363. If the RAR is considered to be successfully received and this MAC subPDU only includes the RAPID, the UE considers this as a positive response to the SI request.

[0143] Embodiment 2: In another embodiment, the UE sends 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 or equal to 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operation and the processing of the RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment are as follows: Fig.13 Same as described in .

[0144] Embodiment 3: In another embodiment, the UE sends 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 or equal to 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format. The detailed UE operation and the method for processing the RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment are as follows: Fig.13 Same as described in .

[0145] gNB Operation: Fig.14 The gNB operation according to an embodiment of the present disclosure is shown.

[0146] refer to Fig.14 , the gNB receives one or more RA preambles at operation 1410, and determines whether the cell on which the RAR is to be transmitted is an unlicensed cell at operation 1420. If the cell is an unlicensed cell, the gNB generates a RAR MAC PDU for transmission according to a first RAR MAC PDU format at operation 1430. If the cell is an authorized cell, the gNB generates a RAR MAC PDU for transmission according to a second RAR MAC PDU format at operation 1440. If the DL carrier frequency of the cell corresponds to an unlicensed band, the cell is an unlicensed cell. Otherwise, the cell is an authorized cell.

[0147] While generating the RAR MAC PDU according to the first RAR MAC PDU format, if a backoff indication needs to be sent in the RAR MAC PDU, the gNB includes a first MAC subPDU in the RAR MAC PDU at operation 1431, wherein the first MAC subPDU consists of a MAC subheader having only a BI. The gNB includes one or more MAC subPDUs in the RAR MAC PDU at operation 1432, wherein each MAC subPDU includes a MAC subheader having a RAPID and a frame ID or a MAC subheader having a RAPID, a frame ID, and a MAC RAR. Each of these MAC subPDUs corresponds to a RA preamble received by the gNB in ​​a PRACH opportunity, the PRACH opportunity starting with a radio frame, and a frame identifier (frame ID) of the radio frame is included in the first MAC subPDU.

[0148] When generating the RAR MAC PDU according to the second RAR MAC PDU format, if a backoff indication needs to be sent in the RAR MAC PDU, the gNB includes a first MAC subPDU at operation 1441, wherein the first MAC subPDU is composed of a MAC subheader having only a BI. The gNB includes one or more MAC subPDUs at operation 1442, wherein each MAC subPDU includes a MAC subheader having only a RAPID or a MAC subheader having a RAPID and a MAC RAR.

[0149] The gNB sends the generated RAR MAC PDU at operation 1433 or 1443.

[0150] In another embodiment, the gNB receives one or more RA preambles and determines whether the cell on which the RAR is to be transmitted is configured with a RAR window size greater than 10 ms. If the configured 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 configured RAR window size is less than or equal to 10 ms, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU. The detailed gNB operation of generating a RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment is similar to Fig.14 Same as described in .

[0151] 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 on which the RAR is to be transmitted. If the maximum supported 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 maximum supported RAR window size is less than or equal to 10 ms, the gNB generates a RAR MAC PDU for transmission according to the second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU. The detailed gNB operation of generating a RAR MAC PDU after determining the first RAR MAC PDU format or the second RAR MAC PDU format in this embodiment is the same as Fig.14 Same as described in .

[0152] Method 5: In this method for sending and receiving frame information in RAR of the present disclosure, it is proposed to define a new MAC subheader (i.e., a frame identifier MAC subheader). The frame identifier MAC subheader includes a T and a frame identifier (frame ID). Depending on the number of bits defined for the frame identifier, it may also include one or more R bits. For example, if the frame identifier is 6 bits long, there is no R bit. If the frame identifier is 3 bits long, there are 3 R bits. The frame identifier is one of the following: - Frame Identifier = SFN - Frame identifier = SFN modulo (maximum supported RAR window size in radio frames) - Frame identifier = SFN modulo (configured RAR window size in radio frames) - Frame Identifier = 'p' least significant bits of SFN, where 'p' can be predefined or equal to log2 (maximum RAR window size in radio frames) or log 2 (Configured RAR window size in radio frames) - SFN is the system frame number of the radio frame of the PRACH opportunity or the system frame number of the radio frame where the PRACH opportunity starts.

[0153] - 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 refers to the maximum value of the RAR window sizes in the set of configurable RAR window sizes.

[0154] In the present disclosure, the UE / gNB sends / receives a RAR MAC PDU, wherein the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0155] The first RAR MAC PDU format: In this method of the present disclosure, the RAR MAC PDU is composed of one or more MAC subPDUs and optional padding. Each MAC subPDU includes one of the following: - a MAC subheader with a frame identifier only; - a MAC subheader with backoff indicator only; - a MAC sub-header with RAPID only (i.e. a positive response to a SI request); - MAC subheader with RAPID and MAC RAR.

[0156] - Indicates the MAC subheader to be padded The MAC subheader with backoff indicator consists of four header fields T / R / R / BI.

[0157] The MAC subheader with frame identifier consists of at least two header fields T / Frame ID.

[0158] The MAC subheader with RAPID consists of two header fields T / RAPID. Padding, if present, is placed at the end of the MAC PDU. The presence and length of the padding is implicit based on the TB size and the size of the MAC subPDU.

[0159] The MAC subheader used for padding consists of T / R / R / R / R / R / R. The 2-bit type field distinguishes the BI, frame identifier, RAPID, and padding subheader.

[0160] A MAC subPDU with only a backoff indicator is placed at the beginning of the MAC PDU if included. A MAC subPDU with only a frame identifier is placed at the beginning of the MAC PDU after the MAC subPDU with the backoff indicator if included. If the backoff indication is included in the MAC PDU, then the 'MACsubPDU with RAPID only' and the 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the second MAC subPDU and the padding (if any). If the backoff indication is not included in the MAC PDU, then the 'MACsubPDU with RAPID only' and the 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the first MAC subPDU and the padding (if any).

[0161] (Alternative) A MAC subPDU with only a backoff indicator is placed at the beginning of the MAC PDU if included. A MAC subPDU with only a frame identifier is placed before the first MAC subPDU including RAPID and MAC RAR. If a backoff indication is included in the MAC PDU, the 'MAC subPDU with only RAPID' may be placed anywhere between the second MAC subPDU and the padding (if any). If a backoff indication is not included in the MAC PDU, the 'MAC subPDU with only RAPID' may be placed anywhere between the first MAC subPDU and the padding (if any). The 'MAC subPDU with RAPID and MAC RAR' is placed after the MAC subPDU carrying the frame identifier and before the padding (if any).

[0162] Second RAR MAC PDU format: In this method of the present disclosure, the RAR MAC PDU according to the second (ie, normal) RAR MAC PDU format is the same as described in Method 1.

[0163] UE operation:In an embodiment, the UE sends 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 on 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 a first RAR MAC PDU format. If the cell is an authorized cell, the UE processes the received RAR MAC PDU according to a second RAR MAC PDU format. If the DL carrier frequency of the cell corresponds to an unlicensed frequency band, the cell is an unlicensed cell. Otherwise, the cell is an authorized cell. In an embodiment, the UE operates as follows Figure 7 shown.

[0164] In another embodiment, the UE sends 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 or equal to 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format.

[0165] In another embodiment, the UE sends 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 or equal to 10 ms, the UE processes the received RAR MAC PDU according to the second RAR MAC PDU format.

[0166] gNB Operation: In an embodiment, the gNB receives one or more RA access preambles and determines whether the cell on which the RAR is to be sent is an unlicensed cell. If the cell is an unlicensed cell, the gNB generates a RAR MAC PDU for transmission according to a first RAR MAC PDU format. If the cell is an authorized cell, the gNB generates a RAR MAC PDU for transmission according to a 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 an authorized cell. In an embodiment, the gNB operates as follows Figure 8 shown.

[0167] In another embodiment, the gNB receives one or more RA preambles and determines whether the cell on which the RAR is to be transmitted is configured with a RAR window size greater than 10 ms. If the configured RAR window size is greater than 10 ms, the gNB generates a RAR MAC PDU for transmission according to a first RAR MAC PDU format. If the configured RAR window size is less than or equal to 10 ms, the gNB generates a RAR MAC PDU for transmission according to a second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU.

[0168] 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 on which the RAR is to be transmitted. If the maximum supported RAR window size is greater than 10 ms, the gNB generates a RAR MAC PDU for transmission according to a first RAR MAC PDU format. If the maximum supported RAR window size is less than or equal to 10 ms, the gNB generates a RAR MAC PDU for transmission according to a second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU.

[0169] Method for processing configured license transmission in unlicensed carrier For uplink (UL) transmissions on unlicensed carriers, the UE needs to perform channel sensing (i.e., listen before talk (LBT)) before transmission to determine whether the channel is idle. There are two types of LBT procedures defined for UL transmissions as explained below: Category 1: No LBT No LBT procedure is performed by the sending entity.

[0170] Category 2: LBT without random backoff The duration of the channel being sensed to be idle before the transmitting entity transmits is deterministic. In the example, the sensing interval may be 25 us, i.e., the UE may sense that the channel is idle for at least the sensing interval T. d =Sent after 25 us. For UL transmission, Category 3 is also known as Type 2 channel access procedure.

[0171] Category 3: LBT with random backoff and fixed contention window size UE delays for a period of time (T d ) after sensing that the channel is idle during the time slot duration of the 2nd ... Step 1: Set N=N init , where N initis evenly distributed between 0 and CW p A random number between . CW p is the contention window for a given channel access priority level 'p'. The various LBT parameters for different channel access priority levels (CAPC) are listed in Table 1 below.

[0172] [Table 1]

[0173] If the absence of any other technology sharing the carrier can be guaranteed on a long-term basis (e.g. by regulatory levels), the maximum channel occupancy time for LBT priority levels 3 and 4 lasts for 10 milliseconds. Otherwise, the maximum channel occupancy time for LBT priority levels 3 and 4 lasts for 8 milliseconds. Step 2: If N>0, and the UE chooses to decrement the counter, set N=N-1. Step 3: Sense the channel for the additional time slot duration. If the additional time slot duration is idle, proceed to step 4; otherwise, proceed to step 5. Step 4: If N=0, perform a transmission. Otherwise, proceed to step 2.

[0174] Step 5: Add a deferral duration T d The channel is sensed during the time slot duration. The delay duration (T d ) is equal to T f + m p x T s , where T f is equal to 16 us and T s Equal to 9 us.

[0175] Step 6: If in T d If the channel is idle during the period, the process goes to step 2. Otherwise, the process goes to step 5.

[0176] Category 4: LBT with random backoff and variable contention window size The LBT procedure has the following as one of its 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 in the LBT procedure to determine the duration of time that the channel is sensed to be idle before the transmitting entity transmits on the channel. 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, whereas in Category 4 the transmitting entity can change the size of the contention window when drawing the random number N. Category 4 is also known as Type 1 channel access procedure for UL transmission.

[0177] In the New Radio (NR) system design, in the UL, the gNB can dynamically allocate resources to the UE via the Cell Radio Network Temporary Identifier (C-RNTI) on the PDCCH. The UE always monitors the PDCCH to find possible grants for UL transmission when its DL reception is enabled (an activity governed by discontinuous reception (DRX) when configured). When carrier aggregation (CA) is configured, the same C-RNTI applies to all serving cells.

[0178] Additionally, using the configured grant, the gNB is able to allocate periodic UL resources for UL transmission to the UE. Two types of configured UL grants are defined: In the Type 1 case, RRC directly provides the configured UL grant (including periodicity).

[0179] In the Type 2 case, RRC defines the periodicity of the configured UL grant, however a PDCCH addressed to the configured Scheduling-RNTI (CS-RNTI) may signal and activate the configured UL grant, or deactivate it; i.e., a PDCCH addressed to the CS-RNTI indicates that the UL grant may be implicitly reused according to the periodicity defined by RRC until it is deactivated.

[0180] In case of dynamic grant, the LBT type / category to be used for channel access is signaled by the gNB in ​​the PDCCH. The CAPC value to be used is also signaled by the gNB in ​​the PDCCH.

[0181] For UL channel access for configured grants, the gNB signals the CAPC for each logical channel (LCH). MAC Control Elements (CEs) other than Fill Buffer Status Report (BSR) MAC CE and Recommended Bit Rate MAC CE use the highest priority CAPC (i.e. lowest CAPC index). Signalling Radio Bearer 0 (SRB0), Signalling Radio Bearer 1 (SRB1) and Signalling Radio Bearer 3 (SRB3) use the highest priority CAPC (i.e. lowest CAPC index), however the CAPC for SRB2 is configurable. The UE selects the highest CAPC index (i.e. lowest priority CAPC) for the LCH multiplexed in the MAC PDU.

[0182] One problem with this design of selecting the CAPC for the grant configured for the UL is that data corresponding to the lowest CAPC (ie, highest priority) is de-prioritized.

[0183] Fig.15 is an example illustration of a design of a related art permission selection CAPC configured for UL.

[0184] refer to Fig.15According to the related art, CAPC4 is selected for channel access even if a very small amount of data in the MAC PDU corresponds to this CAPC. It may not always be good to select the lowest CAPC index (i.e., the highest priority CAPC) of the LCH multiplexed in the MAC PDU. It is possible that a very small amount of data in the MAC PDU belongs to the lowest CAPC index. So some methods are needed to enhance the current design.

[0185] Method 1: In NR, the MAC PDU consists of one or more MAC subPDUs. Each MAC subPDU consists of one of the following: MAC subheader only (including padding); MAC subheader and MAC service data unit (SDU); MAC subheader and MAC CE; or MAC subheader and padding. The MAC SDU is of variable size. Each MAC subheader corresponds to a MAC SDU, MAC CE, or padding. The MAC subheader except for the fixed-size MAC CE, padding, and MAC SDU containing the UL common control channel (CCCH) consists of four header fields R / F / LCID / L. The MAC subheader for the fixed-size MAC CE, padding, and MAC SDU containing the UL CCCH consists of two header fields R / LCID.

[0186] Fig.16 The selection of CAPC for UL transmission according to an embodiment of the present disclosure is shown. In an embodiment, this method is applied to UL transmission in a configured grant.

[0187] Operation 1610: Reference Fig.16 , in order to determine the CAPC to be used for UL transmission of the MAC PDU, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU at operation 1610. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU except the MAC subPDUs carrying padding. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU except the MAC subPDUs carrying padding and the MAC subPDUs carrying the padding BSR and the MAC subPDUs carrying the recommended bit rate MAC CE.

[0188] For a MAC subPDU including a MAC SDU, the CAPC is the CAPC of the LCH of the MAC SDU included in the MAC subPDU. The gNB signals the CAPC for each LCH of a data radio bearer (DRB). The LCHs corresponding to signaling radio bearers SRB0, SRB1, and SRB3 use the highest priority CAPC (i.e., lowest CAPC index), whereas the CAPC for SRB2 is configured by the gNB in ​​the RRC message. Padding uses the lowest priority CAPC (i.e., highest CAPC index).

[0189] For a MAC subPDU including a MAC CE, the CAPC is the CAPC of the MAC CE included in the MAC subPDU. MAC CEs other than padding BSR and recommended bit rate use the highest priority CAPC (i.e., lowest CAPC index). Padding BSR and recommended bit rate MAC CE use the lowest priority CAPC (i.e., highest CAPC index).

[0190] Operation 1620: The UE then calculates parameter 'X' for each determined CAPC at operation 1620, where 'X' is equal to the total size of the MAC subPDU / total size of the MAC PDU for that CAPC. The size may be the number of bytes or the number of bits. In an embodiment, the size of the MAC subPDU may not include the size of the MAC subheader.

[0191] Operation 1630: The UE selects a CAPC having a highest value of 'X' at operation 1630. The UE applies parameters corresponding to the selected CAPC for accessing a channel for UL transmission.

[0192] Fig.17 is an example illustration of a MAC PDU to be sent in a UL grant upon channel access (utilizing an LBT procedure using CAPC) according to an embodiment of the present disclosure.

[0193] refer to Fig.17 , the 'X' values ​​calculated according to the method described above are 0.3, 0.4 and 0.3 for CAPC 2, 3 and CAPC 4 respectively. So the UE selects CAPC 3 corresponding to the highest value of X, i.e. 0.4.

[0194] Fig.18 The selection of CAPC for UL transmission according to another embodiment of the present disclosure is shown. In an embodiment, this method is applied to UL transmission in a configured grant.

[0195] Operation 1810: Reference Fig.18In order to determine the CAPC to be 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 at operation 1810. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC SDU and MAC CE multiplexed in the MAC PDU except for the padding BSR MAC CE and the recommended bit rate MAC CE. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC SDU.

[0196] For a MAC SDU, the CAPC is the CAPC of the LCH of the MAC SDU. The gNB signals the CAPC for each LCH of a DRB. For LCHs corresponding to signalling radio bearers SRB0, SRB1 and SRB3, the highest priority CAPC is used, whereas the CAPC for SRB2 is configured by the gNB in ​​the RRC message.

[0197] For MAC CE, CAPC is the CAPC of the MAC CE. MAC CEs other than filling BSR and recommended bit rate use the highest priority CAPC (i.e., lowest CAPC index). Filling BSR and recommended bit rate MAC CE use the lowest priority CAPC (i.e., highest CAPC index).

[0198] Operation 1820: The UE then calculates parameter 'X' for each determined CAPC, where 'X' is equal to [total size of MAC SDUs and / or MAC CEs for that CAPC in the MAC PDU] / total size of the MAC PDU. At operation 1820, the size may be the number of bytes or the number of bits.

[0199] Operation 1830: The UE selects a CAPC having a highest value of 'X.' The UE applies parameters corresponding to the selected CAPC at operation 1830 for accessing a channel for UL transmission.

[0200] The advantage of the first method is that the CAPC that occupies the largest portion of the UL grant dominates the channel access, which is better than the traditional scheme that always selects the lowest priority CAPC.

[0201] In another embodiment, if some LCHs are not multiplexed in the MAC PDU, the method described above is applied. If some LCHs are multiplexed in the MAC PDU, the UE applies a rule that the UE selects the lowest CAPC index (i.e., highest priority) of the LCH / MAC CE multiplexed in the MAC PDU.

[0202] In an embodiment, some of the LCHs are LCHs for signaling radio bearers. If any of the SRBs MAC SDUs are included in the MAC PDU, the UE applies the rule that the UE selects the lowest CAPC index (i.e., highest priority) of the LCH / MAC CE multiplexed in the MAC PDU. In other words, if any of the SRBs MAC SDUs are included in the MAC PDU, the UE selects the CAPC index of the SRB (or the lowest CAPC index of the SRB whose MAC SDU is included in the MAC PDU) because the CAPC index of the SRB is the lowest.

[0203] In another embodiment, some of the LCHs are LCHs for signaling radio bearers SRB0, SRB1 and SRB3. If SRB0, SRB1 and SRB3 MAC SDUs are included in a MAC PDU, the UE selects the lowest CAPC index (ie, highest priority) of the LCH / MAC CE multiplexed in the MAC PDU.

[0204] In another embodiment, certain LCHs are one or more LCHs for signaling radio bearers.One or more signaling radio bearers with the lowest CAPC index (ie highest priority) for which the UE selects LCH / MAC CE multiplexed in a MAC PDU may be predefined.

[0205] In another embodiment, certain LCHs are one or more LCHs signaled by the gNB.

[0206] In another embodiment, some of the LCHs are MAC CEs other than padding BSRs.If any MAC CE (other than padding BSRs) is included in a MAC PDU, the UE applies the rules.

[0207] In another embodiment, some of the LCHs are one or more MAC CEs.One or more MAC CEs for which the rules apply may be predefined.

[0208] Method 2: In NR, the MAC PDU consists of one or more MAC subPDUs. Each MAC subPDU consists of one of the following: MAC subheader only (including padding); MAC subheader and MAC SDU; MAC subheader and MAC CE; or MAC subheader and padding. The MAC SDU is of variable size. Each MAC subheader corresponds to a MAC SDU, MAC CE, or padding. The MAC subheader except for the fixed-size MAC CE, padding, and MAC SDU containing UL CCCH consists of four header fields R / F / LCID / L. The MAC subheader for the fixed-size MAC CE, padding, and MAC SDU containing UL CCCH consists of two header fields R / LCID.

[0209] Fig.19 The selection of CAPC for UL transmission according to an embodiment of the present disclosure is shown. In an embodiment, this method is applied to UL transmission in a configured grant.

[0210] Operation 1910: Reference Fig.19 , in order to determine the CAPC to be used for UL transmission of the MAC PDU, the UE first determines the CAPC of the MAC subPDU multiplexed in the MAC PDU at operation 1910. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC subPDU multiplexed in the MAC PDU except the MAC subPDU carrying padding. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC subPDU multiplexed in the MAC PDU except the MAC subPDU carrying padding and the MAC subPDU carrying the padding BSR and the MAC subPDU carrying the recommended bit rate.

[0211] For a MAC subPDU including a MAC SDU, the CAPC is the CAPC of the LCH of the MAC SDU included in the MAC subPDU. The gNB signals the CAPC for each LCH of the DRB. The highest priority CAPC (i.e., lowest CAPC index) is used for the LCHs corresponding to signaling radio bearers SRB0, SRB1, and SRB3, whereas the CAPC for SRB2 is configured by the gNB in ​​the RRC message. The lowest priority CAPC (i.e., highest CAPC index) is used for padding.

[0212] For a MAC subPDU including a MAC CE, the CAPC is the CAPC of the MAC CE included in the MAC subPDU. MAC CEs other than the padding BSR use the highest priority CAPC (i.e., the lowest CAPC index). Padding BSR and recommended bit rate use the lowest priority CAPC (i.e., the highest CAPC index).

[0213] Operation 1920: The UE then calculates parameter 'X' for each determined CAPC at operation 1920, where 'X' is equal to the total size of the MAC subPDU / total size of the MAC PDU for that CAPC. The size may be the number of bytes or the number of bits. In an embodiment, the size of the MAC subPDU may not include the size of the MAC subheader.

[0214] Operation 1930: Among the CAPCs whose 'X' is greater than the threshold, the UE selects the CAPC with the lowest CAPC index (i.e., the highest priority) at operation 1930. If there is no CAPC whose 'X' is greater than the threshold, the UE selects the CAPC with the highest value of 'X'. The UE applies the parameters corresponding to the selected CAPC for accessing the channel for UL transmission.

[0215] The gNB signals the threshold to the UE. The threshold may be common for all UL configured grants, or it may be configured individually for each UL configured grant. If the threshold is not configured, the UE selects the CAPC with the highest value of 'X'. Alternatively, if the threshold is not configured, the UE selects the CAPC with the highest CAPC index (i.e., lowest priority) without performing operation 1920. Alternatively, if the threshold is not configured, the UE selects the CAPC with the lowest CAPC index (i.e., highest priority) without performing operation 1920.

[0216] Fig. 20 is an example illustration of a MAC PDU to be sent in a UL grant using LBT Type 1 channel access according to an embodiment of the present disclosure.

[0217] refer to Fig. 20 , the 'X' values ​​calculated according to the method described above are 0.2, 0.5 and 0.3 for CAPC 2, 4 and CAPC 3 respectively. If the threshold is 0.25, the UE selects CAPC from CAPC 3 and CAPC 4. The lowest CAPC index among CAPC 3 and CAPC 4 is 3, so the UE selects CAPC 3.

[0218] Fig.21 The selection of CAPC for UL transmission according to an embodiment of the present disclosure is shown. In an embodiment, this method is applied to UL transmission in a configured grant.

[0219] Operation 2110: Reference Fig.21 , in order to determine the CAPC to be 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 at operation 2110. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC SDU and MAC CE multiplexed in the MAC PDU except for the padding BSR MAC CE and the recommended bit rate MAC CE.

[0220] For a MAC SDU, the CAPC is the CAPC of the LCH of the MAC SDU. The gNB signals the CAPC for each LCH of a DRB. The highest priority CAPC is used for the LCHs corresponding to signalling radio bearers SRB0, SRB1 and SRB3, whereas the CAPC for SRB2 is configured by the gNB in ​​the RRC message.

[0221] For MAC CE, CAPC is the CAPC of MAC CE. MAC CE except for padding BSR and recommended bit rate uses the highest priority CAPC (i.e., lowest CAPC index). Padding BSR uses the lowest priority CAPC (i.e., highest CAPC index).

[0222] Operation 2120: The UE then calculates parameter 'X' for each determined CAPC, where 'X' is equal to [total size of MAC SDU and MAC CE for that CAPC] / total size of MAC PDU. At operation 2120, the size may be the number of bytes or the number of bits.

[0223] Operation 2130: Among the CAPCs whose 'X' is greater than the threshold, the UE selects the CAPC with the lowest CAPC index (i.e., the highest priority) at operation 2130. If there is no CAPC whose 'X' is greater than the threshold, the UE selects the CAPC with the highest value of 'X'. The UE applies the parameters corresponding to the selected CAPC for accessing the channel for UL transmission.

[0224] The gNB signals the threshold to the UE. The threshold may be common for all UL configured grants or it may be configured individually for each UL configured grant. If the threshold is not configured, the UE selects the CAPC with the highest value of 'X'. Alternatively, if the threshold is not configured, the UE selects the CAPC with the highest CAPC index (i.e., lowest priority) without performing operation 2120. Alternatively, if the threshold is not configured, the UE selects the CAPC with the lowest CAPC index (i.e., highest priority) without performing operation 2120.

[0225] The advantage of this method is that among the CAPCs that occupy the portion of the UL grant exceeding the threshold, the highest priority CAPC dominates the channel access even if it does not occupy the largest portion of the UL grant.

[0226] In another embodiment, if some LCHs are not multiplexed in the MAC PDU, the method described above is applied. If some LCHs are multiplexed in the MAC PDU, the UE applies a rule that the UE selects the lowest CAPC index (i.e., highest priority) of the LCH / MAC CE multiplexed in the MAC PDU.

[0227] In an embodiment, some of the LCHs are LCHs for signaling radio bearers. If any of the SRBs MAC SDUs are included in the MAC PDU, the UE applies the rule that the UE selects the lowest CAPC index (i.e., highest priority) of the LCH / MAC CE multiplexed in the MAC PDU. In other words, if any of the SRBs MAC SDUs are included in the MAC PDU, the UE selects the CAPC index of the SRB (or the lowest CAPC index of the SRB whose MAC SDU is included in the MAC PDU) because the CAPC index of the SRB is the lowest.

[0228] In another embodiment, some of the LCHs are LCHs for signaling radio bearers SRB0, SRB1 and SRB3. If any of the SRB0, SRB1 and SRB3 MAC SDUs are included in the MAC PDU, the UE selects the lowest CAPC index (i.e., highest priority) of the LCH / MAC CE multiplexed in the MAC PDU.

[0229] In another embodiment, certain LCHs are one or more LCHs for signaling radio bearers.One or more signaling radio bearers with the lowest CAPC index (ie highest priority) for which the UE selects LCH / MAC CE multiplexed in a MAC PDU may be predefined.

[0230] In another embodiment, certain LCHs are one or more LCHs signaled by the gNB.

[0231] In another embodiment, some of the LCHs are MAC CEs other than padding BSRs.If any MAC CE (other than padding BSRs) is included in a MAC PDU, the UE applies the rules.

[0232] In another embodiment, some of the LCHs are one or more MAC CEs.One or more MAC CEs for which the rules apply may be predefined.

[0233] Method 3: In NR, the MAC PDU consists of one or more MAC subPDUs. Each MAC subPDU consists of one of the following: MAC subheader only (including padding); MAC subheader and MAC SDU; MAC subheader and MAC CE; or MAC subheader and padding. The MAC SDU is of variable size. Each MAC subheader corresponds to a MAC SDU, MAC CE, or padding. The MAC subheader except for the fixed-size MAC CE, padding, and MAC SDU containing UL CCCH consists of four header fields R / F / LCID / L. The MAC subheader for the fixed-size MAC CE, padding, and MAC SDU containing UL CCCH consists of two header fields R / LCID.

[0234] Fig. 22 The selection of CAPC for UL transmission according to an embodiment of the present disclosure is shown. In an embodiment, this method is applied to UL transmission in a configured grant.

[0235] refer to Fig. 22 , the UE determines whether some LCHs are multiplexed in the MAC PDU at operation 2210. If yes, the UE applies a first rule at operation 2220, i.e., the UE selects the lowest CAPC index (i.e., the highest priority) of the LCH / MAC CE multiplexed in the MAC PDU. Otherwise, the UE applies a second rule at operation 2230, i.e., the UE selects the highest CAPC index (i.e., the lowest priority) of the LCH / MAC CE multiplexed in the MAC PDU.

[0236] In an embodiment, some of the LCHs are LCHs for signaling radio bearers. If any of the SRBs MAC SDUs are included in the MAC PDU, the UE applies the first rule. In other words, if any of the SRBs MAC SDUs are included in the MAC PDU, the UE selects the CAPC index of the SRB (or the lowest CAPC index of the SRB whose MAC SDU is included in the MAC PDU) because the CAPC index of the SRB is the lowest.

[0237] In another embodiment, some of the LCHs are LCHs for signalling radio bearers SRB0, SRB1 and SRB3.If any of the SRB0, SRB1 and SRB3 MAC SDUs is included in the MAC PDU, the UE applies the first rule.

[0238] In another embodiment, the certain LCHs are one or more LCHs for signalling radio bearers.One or more signalling radio bearers for which the first rule applies may be predefined.

[0239] In another embodiment, the certain LCHs are one or more LCHs signaled by the gNB. Assume that the gNB signals the UE to which the first rule needs to be applied, LCH X and LCH Y. If any one of LCH X, LCH Y MAC SDU is included in the MAC PDU, the UE applies the first rule.

[0240] In another embodiment, some of the LCHs are MAC CEs other than padding BSRs.If any MAC CE (other than padding BSRs) is included in the MAC PDU, the UE applies the first rule.

[0241] In another embodiment, some of the LCHs are one or more MAC CEs.One or more MAC CEs for which the first rule is applied may be predefined.

[0242] One or more of the above embodiments may be used to determine application of the first rule and the second rule.

[0243] Method 4: In this method disclosed, an enhanced multiplexing operation for UL transmission is proposed. In an embodiment, this method is applied to UL transmission in a configured grant.

[0244] Operation 1: The UE includes a MAC SDU from the highest priority LCH among the LCHs that have data available for transmission and are allowed to use this UL grant.

[0245] Action 2: The UE includes a MAC SDU from any other LCH with the lowest priority except the highest priority LCH among the LCHs that have data available for transmission and is allowed to use this UL grant in the MAC PDU only if the remaining available space in the MAC PDU is greater than a threshold. The threshold may be predefined or signaled by the gNB.

[0246] - Example UL grant size is 1000 bytes LCH 1, LCH 2 and LCH 3 are allowed to use this UL grant and have data available for transmission. If LCH 1 is the highest priority, the UE includes LCH 1 data in the MAC PDU. If the amount of data available after including the highest priority LCH is 200 bytes, and 200 bytes is greater than the threshold, the UE multiplexes LCH 2 and / or LCH 3 in the MAC PDU according to LCH prioritization (LCP). Otherwise only padding and / or padding BSR is included.

[0247] Method 5: Embodiment 1: In this method disclosed, an enhanced multiplexing operation for UL transmission is proposed. In an embodiment, this method is applied to UL transmission in a configured grant.

[0248] Operation 1: The UE includes a MAC SDU from the highest priority LCH among the LCHs that have data available for transmission and are allowed to use this UL grant.

[0249] Action 2: The UE includes the MAC SDU from any other LCH with the lowest priority except the highest priority LCH among the LCHs that have data available for transmission and are allowed to use this UL grant in the MAC PDU only if they have the same CAPC as the highest priority LCH.

[0250] - Example UL grant size is 1000 bytes LCH 1, LCH 2, and LCH 3 are allowed to use this UL grant and have data available for transmission. If LCH 1 is the highest priority (P1), LCH 2 has priority (P2), and LCH 3 has priority (P4), the CAPC for LCH 1 is CAPC 1, the CAPC for LCH 2 is CAPC 1, and the CAPC for LCH 3 is CAPC 3, and the MAC SDU for LCH 1 is included first in the MAC PDU because it has the highest priority. If the UL grant is not used up after the MAC SDU for LCH 1 is added, the MAC SDU for LCH 2 is included because it has the same CAPC as LCH 1. Although the UL grant is not used up after the MAC SDU for LCH 2 is added, the MAC SDU for LCH 3 is not included because it does not have the same CAPC as LCH 1 and LCH 2. If available, data from LCH 1 and LCH 2 can be included in descending order of priority.

[0251] Embodiment 2: The UE applies the first selection criterion and the second selection criterion in order to select an LCH that can be multiplexed in the MAC PDU.

[0252] When performing a new transmission, the MAC entity shall: First selection criteria: 1> For each UL grant, select an LCH that meets all of the following conditions (or an LCH that has data available for transmission): 2> allowedSCS-List The set of allowed subcarrier spacing (SCS) index values ​​in , if configured, includes the SCS index associated with the UL grant; and 2> maxPUSCH-DurationIf configured, greater than or equal to the physical UL shared channel (PUSCH) transmission duration associated with the UL grant; and 2> configuredGrantType1Allowed If configured, it is set to UL Grant Type 1 if the UL Grant is configured. ture (true); and 2> allowedServingCells Includes cell information associated with UL grant, if configured. Not applicable to LCH associated with DRBs for which Packet Data Convergence Protocol (PDCP) repetition is configured within the same MAC entity (i.e. CA repetition), for which PDCP repetition is disabled.

[0253] allowedSCS-List , maxPUSCH-Duration , ConfiguredGrantType1Allowed and allowedServingCells Optionally configured by gNB in ​​LCH configuration.

[0254] allowedSCS-List : If present in the LCH configuration received from the gNB, UL MAC SDUs from this LCH can only be mapped to the indicated parameter set. Otherwise, UL MAC SDUs from this LCH can be mapped to any configured parameter set.

[0255] allowedServingCells : If present in the LCH configuration received from the gNB, the UL MAC SDU from this LCH can only be mapped to the serving cells indicated in this list. Otherwise, the UL MAC SDU from this LCH can be mapped to any configured serving cell of the cell group of the LCH.

[0256] configureGrantType1Allowed : If present, UL MAC SDUs from this LCH may be sent on configured grant type 1.

[0257] maxPUSCH-Duration : If present in the LCH configuration received from the gNB, UL MACSDUs from this LCH can only be sent with UL grants that result in a PUSCH duration shorter than or equal to the duration indicated by this field. Otherwise, UL MAC SDUs from this LCH can be sent with UL grants that result in any PUSCH duration.

[0258] Second selection criteria: 1> If a new transmission is performed on an unlicensed carrier for a configured UL grant: 2> (according to the first selection criterion) select the LCH having the same CAPC as the highest priority LCH among the LCHs selected above.

[0259] (or) 1> If a new transmission is performed on the unlicensed carrier for the configured UL grant and the highest priority LCH among the LCHs selected above belongs to an SRB (or a specific SRB, which can be predefined) 2> (according to the first selection criterion) select the LCH having the same CAPC as the highest priority LCH among the LCHs selected above.

[0260] (or) 1> If a new transmission is performed on an unlicensed carrier: 2> (according to the first selection criterion) select the LCH having the same CAPC as the highest priority LCH among the LCHs selected above.

[0261] (or) 1> If a new transmission is performed on an unlicensed carrier, and the highest priority LCH among the LCHs selected above belongs to an SRB (or a specific SRB, which can be predefined) 2> (according to the first selection criterion) select the LCH having the same CAPC as the highest priority LCH among the LCHs selected above.

[0262] Allocation of resources: When performing a new transmission, the MAC entity shall: 1> Allocate resources to LCH as follows: 2> (according to the selection criteria described above) is to have Bj >0 UL grant selected LCHs are allocated resources in descending priority order. If the Priority Bit Rate (PBR) of the LCH is set to infinity (infinity), the MAC entity shall allocate resources for all data available for transmission on the LCH before satisfying the PBR of the lower priority LCH; 2> Bj Decreasing supply to the above LCH j The total size of the MAC SDU; 2> If any resources remain, all LCHs selected (according to the selection criteria described above) are provided in a strictly descending priority order (regardless of Bj The LCHs configured with equal priority shall be served equally.

[0263] When LCH is established, the MAC entity shall Bj Initialized to zero.

[0264] For each LCH j , the MAC entity should: 1> Before each instance of the LCP process Bj Incremental product PBR×T, where T is the Bj The time that has passed since it was last incremented; 1>If Bj The value is greater than the bucket size (i.e. PBR × bucket size duration (BSD)): 2> Bj Set to the bucket size.

[0265] The PBR and BSD are configured by the gNB for each logic.

[0266] Method 6: In the current design, the UE selects LCH for multiplexing as follows: 1> For each UL grant, select an LCH that satisfies all of the following conditions (or an LCH that has data available for transmission): 2> allowedSCS-List The set of allowed SCS index values ​​in includes the SCS index associated with the UL grant if configured; and 2> maxPUSCH-Duration If configured, greater than or equal to the PUSCH transmission duration associated with the UL grant; and 2> configuredGrantType1Allowed If configured, it is set to UL Grant Type 1 if the UL Grant is configured. true (true); and 2> allowedServingCells Includes cell information associated with UL grant, if configured. Not applicable to LCH associated with DRBs for which PDCP repetition is configured within the same MAC entity (i.e. CA repetition), for which PDCP repetition is disabled.

[0267] allowedSCS-List , maxPUSCH-Duration , ConfiguredGrantType1Allowed and allowedServingCells Optionally configured by gNB in ​​LCH configuration.

[0268] allowedSCS-List : If present in the LCH configuration received from the gNB, UL MAC SDUs from this LCH can only be mapped to the indicated parameter set. Otherwise, UL MAC SDUs from this LCH can be mapped to any configured parameter set.

[0269] allowedServingCells: If present in the LCH configuration received from the gNB, the UL MAC SDU from this LCH can only be mapped to the serving cells represented in this list. Otherwise, the UL MAC SDU from this LCH can be mapped to any configured serving cell of the cell group of the LCH.

[0270] configureGrantType1Allowed : If present, UL MAC SDUs from this LCH may be sent on configured grant type 1.

[0271] maxPUSCH-Duration : If present in the LCH configuration received from the gNB, UL MAC SDUs from this LCH can only be sent with UL grants that result in a PUSCH duration shorter than or equal to the duration indicated by this field. Otherwise, UL MACSDUs from this LCH can be sent with UL grants that result in any PUSCH duration.

[0272] Allocation of resources: When performing a new transmission, the MAC entity shall: 1> Allocate resources to LCH as follows: 2> (according to the selection criteria described above) is to have Bj The LCHs selected by UL grant > 0 are allocated resources in descending priority order, where resources are allocated to LCH j if one of the following conditions is met: 3> Condition 1: CAPC index of LCH j ≤ Z 3> Condition 2: If the CAPC index of LCH j > Z and the amount of data that can be included from LCH j in the remaining UL grant is greater than the amount of UL grant that has been allocated If resources have not been allocated for the LCH, then Z = the highest CAPC index. Otherwise Z = MAX (CAPC indexes of all LCHs that have been allocated resources for UL grants).

[0273] If the PBR of LCH is set to infinity (infinity), the MAC entity shall allocate resources for all data available for transmission on the LCH before satisfying the PBR of the lower priority LCH; 2> Bj Decreasing supply to the above LCH j The total size of the MAC SDU; 2> If there are any resources left, then all LCHs selected (according to the selection criteria described above) are sorted in strict descending priority order (regardless of BjThe resource is allocated to LCH j if one of the following conditions is met: 3> Condition 1: CAPC index of LCH j ≤ Z 3> Condition 2: If the CAPC index of LCH j > Z and the amount of data that can be included from LCH j in the remaining UL grant is greater than the amount of UL grant that has been allocated If resources have not been allocated for the LCH, then Z = the highest CAPC index. Otherwise Z = MAX (CAPC indexes of all LCHs that have been allocated resources for UL grants).

[0274] Fig.23 is an example illustration according to an embodiment of the present disclosure.

[0275] refer to Fig.23 , SDU 1 corresponding to the LCH has been allocated resources in the UL grant. In order to schedule the next LCH, the candidate LCHs among the 'LCHs that have data available for transmission and are allowed to use this UL grant' should meet one of the following conditions: - the LCH has a CAPC index Y, where Y>X if the amount of data that can be included in the remaining UL grant for that LCH>L1; or - LCH has CAPC index Y ≤ X Fig.24 is another example illustration according to an embodiment of the present disclosure.

[0276] refer to Fig.24 , SDU 1 and SDU 2 corresponding to the LCH have been allocated resources in the UL grant. In order to schedule the next LCH, the candidate LCH among the 'LCHs that have data available for transmission and are allowed to use this UL grant' should meet one of the following conditions: - the LCH has a CAPC index Y, where Y>Max(X, X1) if the amount of data that can be included in the remaining UL grant for that LCH>L1; or - LCH has CAPC index Y≤MAX (X, X1) Method for RA process supporting large RAR window size In a 5G wireless communication system operating in a higher frequency (mmWave) band, UE and gNB communicate with each other using beamforming. Beamforming technology is used to mitigate propagation path loss and increase propagation distance in order to communicate in a higher frequency band. Beamforming uses a high-gain antenna to enhance transmission and reception performance. Beamforming can be classified into transmit (TX) beamforming performed in a transmitting end and receive (RX) beamforming performed in a receiving end. Generally, TX beamforming increases directivity by allowing the area reached by propagation to be densely located in a specific direction by using multiple antennas. In this case, 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, and the like. The use of TX beamforming results in an increase in the directivity of the signal, thereby increasing the propagation distance. In addition, since the signal is hardly transmitted in a direction other than the directional direction, the signal interference acting on the other receiving end is significantly reduced. The receiving end can perform beamforming on the RX signal by using an RX antenna array. RX beamforming increases the strength of the RX signal transmitted in a specific direction by allowing propagation to be concentrated in a specific direction, and excludes signals transmitted in directions other than the specific direction from the RX signal, thereby providing the effect of blocking interference signals. By using beamforming technology, the transmitter can make multiple transmit (TX) beam patterns in different directions. Each of these TX beam patterns can also be referred to as a TX beam. Wireless communication systems operating at high frequencies use multiple narrow TX beams to transmit signals in a cell because each narrow TX beam provides coverage to a portion of the cell. The narrower the TX beam, the higher the antenna gain, and therefore the greater the propagation distance of the signal transmitted using beamforming. The receiver can also make multiple receive (RX) beam patterns in different directions. Each of these RX beam patterns can also be referred to as an RX beam.

[0277] The 5G wireless communication system supports independent operation mode as well as dual connectivity (DC). In DC, multiple Rx / Tx UEs can be configured to utilize resources provided by two different nodes (or NBs) connected via a non-ideal backhaul. One node acts as a master node (MN) and the other node acts as a secondary node (SN). The MN and the SN are connected via a network interface and at least the MN is connected to the core network. NR also supports multi-radio access technology (RAT) DC (MR-DC) operation, whereby the UE in RRC_CONNECTED is configured to utilize radio resources provided by two fundamentally different schedulers located in two different nodes connected via a non-ideal backhaul and providing E-UTRA (ie if the node is an ng-eNB) or NR access (ie if the node is a gNB). In NR, for UEs in RRC_CONNECTED that are not configured with CA / DC, there is only one serving cell consisting of a primary cell (PCell). For UEs in RRC_CONNECTED that are configured with CA / DC, the term 'serving cell' is used to refer to a collection of cells consisting of a special cell (SpCell) and all secondary cells (SCells). In NR, the term Master Cell Group (MCG) refers to the group of serving cells associated with a MN consisting of a PCell and optionally one or more SCells. In NR, the term Secondary Cell Group (SCG) refers to the group of serving cells associated with a SN consisting of a primary SCell (PSCell) and optionally one or more SCells. In NR, PCell refers to a serving cell in an MCG operating on the primary frequency, where the UE performs an initial connection establishment procedure or initiates a connection re-establishment procedure. In NR, for UEs configured with CA, an SCell is a cell that provides additional radio resources on top of the SpCell. PSCell refers to a serving cell in an SCG, where the UE performs RA when performing a reconfiguration with a synchronization procedure. For DC operation, the term SpCell refers to the PCell of an MCG or the PSCell of an SCG, otherwise (e.g., when DC is not configured) the term SpCell refers to the PCell.

[0278] In the 5G wireless communication system, the gNB or BS in the cell broadcasts a synchronization signal and the physical broadcast channel (PBCH) block (SSB) consists of a primary synchronization signal (PSS), a secondary synchronization signal (SSS) and SI. SI includes common parameters required for communication in the cell. In the 5G wireless communication system, SI is divided into a master information block (MIB) and multiple SI blocks (SIBs).

[0279] The MIB is always sent on the PBCH with a periodicity of 80 ms and is repeated every 80 ms, and it includes the parameters required to obtain SIB1 from the cell.

[0280] SIB1 is sent on the DL Shared Channel (SCH) with a periodicity of 160 ms and variable transmission repetition. The default transmission repetition period of SIB1 is 20 ms, but the actual transmission repetition period is determined by the network implementation. SIB1 includes information about the availability and scheduling of other SIBs (e.g. mapping of SIBs to SI messages, periodicity, SI window size) with an indication whether one or more SIBs are provided only on demand, and the configuration required by the UE to perform the SI request in that case. SIB1 is a cell-specific SIB.

[0281] SIBs other than SIB1 are carried in the SystemInformation message transmitted on DL-SCH. Only SIBs with the same periodicity can be mapped to the same SI message.

[0282] In the 5G wireless communication system, PDCCH is used to schedule DL transmission on the physical DL shared channel (PDSCH) and UL transmission on the PUSCH, wherein the DL control information (DCI) on the PDCCH includes: DL allocation including at least the modulation and coding format, resource allocation and hybrid automatic repeat request (HARQ) information related to the DL-SCH; or UL scheduling permission including at least the modulation and coding format, resource allocation and HARQ information related to the UL-SCH. In addition to scheduling, the PDCCH can also be used for: activation and deactivation of configured PUSCH transmissions with configured grants; activation and deactivation of PDSCH semi-persistent transmissions; notification of the slot format to one or more UEs; notification of physical resource blocks (PRBs) and orthogonal frequency division multiplexing (OFDM) symbols to one or more UEs, where the UE can assume that there is no transmission to the UE; transmission of TX power control (TPC) commands for physical UL control channel (PUCCH) and PUSCH; transmission of one or more TPC commands for semi-persistent scheduling (SRS) transmission by one or more UEs; switching the active bandwidth part (BWP) of the UE; or initiating an RA procedure. The UE monitors the PDCCH candidate set in the configured monitoring opportunities in one or more configured control resource sets (CORESETs) according to the corresponding search space configuration. A CORESET consists of a set of PRBs with a duration of 1 to 3 OFDM symbols. Resource units Resource element groups (REGs) and control channel elements (CCEs) are defined within a CORESET, where each CCE consists 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 to REG mapping is supported in CORESET. Polarity coding is used for PDCCH. Each REG carrying PDCCH carries its own demodulation reference signal (DMRS). Quadrature Phase Shift Keying (QPSK) modulation is used for PDCCH.

[0283] In a 5G wireless communication system, a list of search space configurations is signaled by the gNB for each configured BWP, where each search configuration is uniquely identified by an identifier. The search space configuration identifier to be used for a specific purpose such as paging reception, SI reception, and RAR reception is 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-within-slot, and duration. The UE uses 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) to determine the PDCCH monitoring timing within a time slot. The PDCCH monitoring opportunity exists in slots 'x' to x+duration, where the slot numbered 'x' in the radio frame numbered 'y' satisfies the following equation: ; The starting symbol of the PDCCH monitoring opportunity in each slot with a PDCCH monitoring opportunity is given by Monitoring-symbols-PDCCH-in-slot. The length of the PDCCH monitoring opportunity (in symbols) is given in the CORESET associated with the search space. The search space configuration includes an identifier of the CORESET configuration associated with it. A list of CORESET configurations is signaled by the gNB for each configured BWP, where each CORESET configuration is uniquely identified by an identifier. The duration of each radio frame is 10 ms. A radio frame is identified by a radio frame number or SFN. Each radio frame consists of a number of slots, where the number of slots in a radio frame and the duration of a slot depend on the SCS. The number of slots in a radio frame and the duration of a slot depending on the radio frame for each supported SCS are predefined in NR. Each CORESET configuration is associated with a list of transmission configuration indicator (TCI) states. Each TCI state is configured with one DL reference signal (RS) ID (SSB or channel state information (CSI) RS). 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 by the gNB and indicated to the UE. The TCI state indicates the DL TX beam used by the gNB to transmit PDCCH in the PDCCH monitoring occasions of the search space (the DL TX beam is quasi-co-located (QCLed) with the SSB / CSI RS of the TCI state).

[0284] In 5G wireless communication systems, bandwidth adaptation (BA) is supported. With BA, the reception and transmission bandwidth of the UE does not need to be as large as the bandwidth of the cell and can be adjusted: the width can be commanded to change (for example, to shrink during periods of low activity to save power); the position can be moved in the frequency domain (for example, to increase scheduling flexibility); and the SCS can be commanded to change (for example, to allow different services). A subset of the total cell bandwidth of a cell is called a BWP. BA is implemented by configuring a BWP for an RRC-connected UE and telling the UE which configured BWP is the current active BWP. When BA is configured, the UE only needs to monitor the PDCCH on one active BWP, that is, it does not need to monitor the PDCCH on the entire DL frequency of the serving cell. In the RRC connected state, for each configured serving cell (i.e., PCell or SCell), the UE is configured with one or more DL and UL BWPs. For an activated serving cell, there is always one active UL and DL BWP at any point in time. BWP switching of a serving cell is used to activate one inactive BWP and deactivate one active BWP at a time. BWP switching is initiated by a PDCCH indicating a DL allocation or UL grant, bwp-InactivityTimer, RRC signaling or when starting the RA process. firstActiveDownlinkBWP-Id and firstActiveUplinkBWP-Id The DL BWP and UL BWP indicated are active without receiving a PDCCH indicating a DL allocation or UL grant. The active BWP for the serving cell is indicated by RRC or PDCCH. For unpaired spectrum, the DL BWP is paired with the UL BWP and the BWP switching is common for both UL and DL. Upon expiration of the BWP inactivity timer, the UE switches the active DL BWP to the default DL BWP or the initial DL BWP (if no default DL BWP is configured).

[0285] In the 5G wireless communication system, RA is supported. RA is used to achieve UL time synchronization. RA is used by non-synchronized UEs in the RRC connected state in the UL during initial access, handover, RRC connection reestablishment process, scheduling request transmission, SCG addition / modification, beam failure recovery, and data or control information transmission. Several types of RA procedures are supported.

[0286] Contention-based RA (CBRA): This is also known as 4-step CBRA. In this type of RA, the UE first sends a RA preamble (also known as Message 1 (Msg1)) and then waits for the RAR in the RAR window. The RAR is also known as Message 2 (Msg2). The gNB sends the RAR on the PDSCH. The PDCCH scheduling 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 PRACH opportunity or PRACH TX opportunity or RA channel (RACH) opportunity (RO)) in which the RA preamble is detected by the gNB. The RA-RNTI is calculated as follows: , where s_id is the index of the first OFDM symbol of the PRACH opportunity in which the UE has transmitted Msg1, i.e., RA preamble; 0≤s_id<14; t_id is the index of the first slot of the PRACH opportunity (0≤t_id<80); f_id is the index of the PRACH opportunity 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). Several RARs for various RA preambles detected by the gNB can be multiplexed by the gNB in ​​the same RAR MAC PDU. If the RAR includes the RAPID of the RA preamble transmitted by the UE, the RAR in the MAC PDU corresponds to the RA preamble transmission of the UE. If no RAR corresponding to its RA preamble transmission is received during the RAR window and the UE has not sent a RA preamble for a configurable (configured by the gNB in ​​the RACH configuration) number of times, the UE returns to the first step, i.e. selecting RA resources (preamble / RO) and sending a RA preamble. A backoff may be applied before returning to the first step.

[0287] If a RAR corresponding to its RA preamble transmission is received, the UE sends a message 3 (Msg3) in the UL grant received in the RAR. Msg3 includes messages such as RRC connection request, RRC connection reestablishment request, RRC handover confirmation, scheduling request, SI request, etc. It may include a UE identifier (i.e., C-RNTI or System Architecture Evolution (SAE)-Temporary Mobile Subscriber Identifier (S-TMSI) or a random number). After sending 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, 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 identifier (the first X bits of the CCCH SDU sent in Msg3), 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 sent a RA preamble for a configurable number of times, the UE returns to the first step, i.e. selecting RA resources (preamble / RO) and sending a RA preamble. A backoff may be applied before returning to the first step.

[0288] Contention-Free RA (CFRA): This is also known as legacy CFRA or 4-step CFRA. The CFRA procedure is used for scenarios such as handovers requiring low latency, timing advance (TA) establishment for SCells, etc. The eNB (or gNB) allocates a dedicated RA preamble to the UE. The UE sends a dedicated RA preamble. The eNB (or gNB) sends a RAR on the PDSCH addressed to the RA-RNTI. The RAR conveys the RA preamble identifier and timing alignment information. The RAR may also include an UL grant. The RAR is sent in the RAR window similar to the CBRA procedure. The CFRA is considered to be successfully completed after receiving the RAR including the RAPID of the RA preamble sent by the UE. In case of RA initiated for beam failure recovery, the CFRA is considered to be successfully completed if a PDCCH addressed to 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 sent the RA preamble for a configurable number of times (configured by the gNB in ​​the RACH configuration), the UE retransmits the RA preamble.

[0289] For certain events such as handover and beam failure recovery, if a dedicated preamble is assigned to the UE, during the first step of RA, i.e., during RA resource selection for Msg1 transmission, the UE determines whether to send a dedicated preamble or a non-dedicated preamble. A dedicated preamble is usually provided for a subset of SSB / CSI RS. If there is no SSB / CSI RS with a DL reference signal received power (RSRP) higher than a threshold among the SSB / CSI RS for which CFRA resources (i.e., dedicated preamble / RO) are provided by the gNB, the UE selects a non-dedicated preamble. Otherwise the UE selects a dedicated preamble. So during the RA procedure, one RA attempt can be CFRA, while the other RA attempts can be CBRA.

[0290] 2-step CBRA: In the first step, the UE sends a RA preamble on the PRACH and a payload on the PUSCH. The RA preamble and payload transmission is also referred to as Message A (MsgA). In the second step, after the MsgA transmission, the UE monitors for a response from the network (i.e., gNB) within a configured window. The response is also referred to as Message B (MsgB). If a CCCH SDU is sent in the MsgA payload, the UE performs contention resolution using the contention resolution information in the MsgB. If the C-RNTI is sent 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 be successfully completed. Instead of the contention resolution information corresponding to the transmitted MsgA, the MsgB may include backoff information corresponding to the RA preamble sent in the MsgA. If the backoff information is received, the UE sends Msg3 and performs contention resolution using Msg4 as in the CBRA procedure. If contention resolution is successful, the RA procedure is considered to be successfully completed. If contention resolution fails at fallback (i.e., at the time of sending Msg3), the UE retransmits MsgA. If the configured window for the UE to monitor the network response after sending MsgA expires and the UE has not received MsgB including contention resolution information or fallback information as explained above, the UE retransmits MsgA. If the RA procedure is not successfully completed even after sending MsgA a configurable number of times, the UE falls back to the 4-step RA procedure, i.e., the UE only sends the RA preamble.

[0291] The MsgA payload may 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 power headroom report (PHR) MAC CE, SSB information, a C-RNTI MAC CE, or padding. MsgA may include a UE ID (e.g., a random ID, S-TMSI, C-RNTI, recovery ID, etc.) and a preamble in the first step. The UE ID may be included in the MAC PDU of MsgA. A UE ID such as a C-RNTI may be carried in a MAC CE, where the MACCE is included in the MAC PDU. Other UE IDs (such as a random ID, S-TMSI, C-RNTI, recovery ID, etc.) may be carried in a CCCH SDU. The UE ID may be one of a random ID, S-TMSI, C-RNTI, recovery ID, an international mobile subscriber identifier (IMSI), an idle mode ID, an inactive mode ID, etc. The UE ID may be different in different scenarios where the UE performs a RA procedure. If the UE performs RA after power-on (before it attaches to the network), the UE ID is a random ID. If the UE performs RA in the IDLE state after it attaches to the network, the UE ID is the S-TMSI. If the UE has an assigned C-RNTI (for example, in a connected state), the UE ID is the C-RNTI. If the UE is in an inactive state, the UE ID is a recovery ID. In addition to the UE ID, some additional control information may also be sent in the MsgA. The control information may be included in the MAC PDU of the MsgA. The control information may include one or more of the following: a connection request indication, a connection recovery request indication, an SI request indication, a buffer status indication, beam information (for example, one or more DL TX beam IDs or SSB IDs), a beam failure recovery indication / information, a data indicator, a cell / BS / transmitting receiving point (TRP) switching indication, a connection reconstruction indication, a reconfiguration completion or switching completion message, etc.

[0292] 2 Operation CFRA: In this case, the gNB allocates dedicated RA preamble and PUSCH resources to the UE for MsgA transmission. The RO to be used for preamble transmission may also be indicated. In the first step, the UE uses contention-free RA resources (i.e. dedicated preamble / PUSCH resources / RO) to send the RA preamble on PRACH and the payload on PUSCH. In the second step, after the MsgA transmission, the UE monitors the response from the network (i.e. gNB) within the configured window. If the UE receives a PDCCH addressed to the C-RNTI, the RA procedure is considered to be successfully completed.

[0293] question:After sending the first step of a 4-step CBRA or CFRA, i.e. the RA preamble, the UE monitors the RAR in the configured RAR window. For a RAR window of up to 10 ms, the RAR is considered successful if the UE receives a PDCCH addressed to the RA-RNTI and a successfully decoded TB scheduled by this PDCCH includes a RAPID matching the RA preamble index of the sent RA preamble.

[0294] The cell on which the UE sends the RA preamble can be a licensed carrier or an unlicensed carrier. If the carrier used for UL transmission is an unlicensed carrier, the UE needs to perform channel sensing (i.e., listen before talk (LBT)) to determine whether the channel is idle before sending Msg1 and Msg3 in UL. Similarly, if the carrier used for DL ​​transmission is an unlicensed carrier, the gNB needs to perform channel sensing (i.e., LBT) to determine whether the channel is idle before sending Msg2 and Msg4 in DL. It is possible that the gNB has received the RA preamble but is unable to send the RAR in the RAR window because the channel is not idle. The UE will retransmit the PRACH when the RAR window expires. The retransmitted RA preamble may not be received by the gNB due to collision or the UE may not be able to retransmit the RA preamble or the retransmission may be delayed because the channel is not idle in UL. This problem can be avoided by a larger RAR window size. However, a large RAR window size greater than 10 ms leads to problems such as Figure 1 RA-RNTI ambiguity shown. If PRACH is sent by UE 1 and UE 2 using the same RA preamble in PRACH opportunity X and PRACH opportunity Y, respectively, the RAR received in the common time slot between RAR window X and RAR window Y cannot be distinguished because the RA-RNTI is the same for PRACH opportunity X and PRACH opportunity Y.

[0295] The aforementioned problem of RA-RNTI ambiguity can be resolved by including information about the radio frame in which the PRACH opportunity starts in the DCI. For an extended RAR window (>10 ms), the RAR is considered successful if the UE receives a PDCCH addressed to the 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 this PDCCH includes a RAPID that matches the RA preamble index of the transmitted RA preamble. The frame information is the 'X' least significant bits (LSBs) of the SFN. For a RAR window size of 40 ms, X is 2.

[0296] In NR, if the UE receives an RRCReconfiguration message, where CellGroupConfigInformation Elements (IEs) contain reconfigurationWithSync of spCellConfig , the UE performs a reconfiguration with a synchronization procedure. During this procedure, the UE synchronizes with the DL of the target SpCell and then initiates a RA to the target SpCell. The UE is not required to always decode the PBCH. For example, if the frequency band of the target SpCell is <3 GHz and the PRACH association period is not greater than one radio frame, the UE is not required to decode the PBCH before performing a RA.

[0297] For extended RAR window, X LSBs of SFN may be included in DCI. So during reconfiguration with synchronization procedure, UE needs to first obtain SFN of target SpCell and then initiate RA to target SpCell. Since 6 most significant bits (MSBs) of SFN are included in MIB and 4 bits are included in PBCH payload, UE needs to decode PBCH of target SpCell, which may delay reconfiguration with synchronization procedure. So a method is needed to reduce this delay.

[0298] Criteria for successful RAR reception for 4-step CBRA and CFRA when RAR window size > 10 ms Method 1: Fig.25 A method for a UE to perform a RA process according to an embodiment of the present disclosure is shown.

[0299] refer to Fig.25 , the UE sends a RA preamble (also referred to as Msg1) at operation 2510 and then waits for a RAR in the RAR window. The RAR is also referred to as Msg2.

[0300] The UE then checks at operation 2520 whether the transmitted RA preamble is selected from the CBRA preamble.

[0301] If the transmitted RA preamble is selected from the CBRA preamble, the UE monitors the PDCCH addressed to the RA-RNTI in the RAR window at operation 2530 .

[0302] If the UE receives a PDCCH addressed to the RA-RNTI at operation 2540 and the frame information in the DCI of the received PDCCH matches the frame information corresponding to the SFN in which the RA preamble is transmitted and the successfully decoded TB scheduled by this PDCCH includes a RAPID matching the RA preamble index of the transmitted RA preamble, then the RAR is considered to be successfully received.

[0303] Upon receiving a CBRA preamble, the gNB sends a RAR on the PDSCH. The PDCCH scheduling the PDSCH carrying the RAR is addressed to the RA-RNTI. The RA-RNTI identifies the time-frequency resource (also called PRACH opportunity or PRACH TX opportunity or RO) in which the RA preamble was detected by the gNB. The RA-RNTI is calculated as follows: , where s_id is the index of the first OFDM symbol of the PRACH opportunity in which the UE has sent Msg1, i.e., the RA preamble; 0≤s_id<14; t_id is the index of the first time slot of the PRACH opportunity (0≤t_id<80); f_id is the index of the PRACH opportunity within the time 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 'X' LSBs of the SFN. X can be predefined or determined based on the RAR window size. For example, X can be 2 bits for a RAR window size of 40 ms.

[0304] TA command in RAR: During the RA procedure, the UE receives the TA command (T A ). 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 on which the RA preamble is transmitted. A To determine N TA , where N TA= T A ·16·64 / 2 μ . 2 μ • 15 kHz is the SCS for the first UL transmission from the UE after receiving a RA response.

[0305] If the transmitted RA preamble is not selected from the CBRA preambles (ie, it is a CFRA preamble), the UE monitors the PDCCH addressed to the C-RNTI in the RAR window at operation 2550. The contention-free preamble is exclusively allocated to the UE using an RRC signaling message.

[0306] If the UE receives a PDCCH addressed to the C-RNTI that schedules a DL TB and this DL TB includes an absolute TA command at operation 2560, the RAR is considered to be successfully received. The absolute TA command may be included in the MAC CE.

[0307] After receiving the CFRA preamble, the gNB sends a response on the PDSCH. The PDCCH that schedules the PDSCH is addressed to the C-RNTI. Since the CFRA preamble is assigned to the UE by the gNB, the gNB can identify the UE upon receiving the CFRA preamble and therefore the C-RNTI assigned to the UE. The gNB includes the absolute TA command in the DL TB sent on the PDSCH.

[0308] Absolute TA command in TA MAC CE: Fig.26 FIG. 4 shows an absolute TA command MACCE 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 on which the RA is sent. The TAG received in the RAR A To determine N TA , where N TA= T A ·16·64 / 2 μ . 2 μ 15 kHz is the SCS UL BWP.

[0309] TA command in TA MAC CE: Fig. 27 FIG. 4 shows a TA command MAC CE according to an embodiment of the present disclosure. A TA command (TAG) for a specific TAG may also be received via the TA command MAC CE. A ). The length of the TA command received in the TA command MAC CE is 6 bits. A Indicates the value of index T A =0, 1, 2, ..., 63 Set the current N TA Value N TA_old Adjust to new N TA Value N TA_new , where for 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.

[0310] exist Fig.26 and Fig. 27 For TA command MAC CE, a different LCID is used in the MAC subheader of MAC CE.

[0311] In an embodiment, the above method is applicable only when the RAR window size is greater than 10 ms. In another embodiment, the above method is applicable to any RAR window size.

[0312] Method 2: Fig.28 Another method for a UE to perform a RA process according to an embodiment of the present disclosure is shown.

[0313] refer to Fig.28 , the UE sends a RA preamble (also referred to as Msg1) at operation 2810 and then waits for a RAR in the RAR window. The RAR is also referred to as Msg2.

[0314] If the transmitted RA preamble is selected from the CBRA preamble or if this RA procedure is not initiated for reconfiguration with synchronization (eg, handover), the UE monitors the PDCCH addressed to the RA-RNTI in the RAR window at operation 2820 .

[0315] If the UE receives a PDCCH addressed to the RA-RNTI at operation 2830 and the frame information in the DCI of the received PDCCH matches the frame information corresponding to the SFN in which the RA preamble is transmitted and the successfully decoded TB scheduled by this PDCCH includes a RAPID matching the RA preamble index of the transmitted RA preamble, then the RAR is considered to be successfully received.

[0316] Upon receiving a CBRA preamble, the gNB sends a RAR on the PDSCH. The PDCCH scheduling the PDSCH carrying the RAR is addressed to the RA-RNTI. The RA-RNTI identifies the time-frequency resource (also called PRACH opportunity or PRACH TX opportunity or RO) in which the RA preamble was detected by the gNB. The RA-RNTI is calculated as follows: , where s_id is the index of the first OFDM symbol of the PRACH opportunity in which the UE has sent Msg1, i.e., the RA preamble; 0≤s_id<14; t_id is the index of the first time slot of the PRACH opportunity (0≤t_id<80); f_id is the index of the PRACH opportunity within the time 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 'X' LSBs of the SFN. X can be predefined or determined based on the RAR window size. For example, X can be 2 bits for a RAR window size of 40ms.

[0317] TA command in RAR: During the RA procedure, the UE receives the TA command (T A). 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 TAG of the serving cell on which the RA preamble is transmitted. The T A To determine N TA , where N TA =T A ·16·64 / 2 μ . 2 μ • 15 kHz is the SCS for the first UL transmission from the UE after receiving the RAR.

[0318] If the transmitted RA preamble is not selected from the CBRA preamble (ie, it is a CRFA preamble) and this RA procedure is initiated for reconfiguration with synchronization procedure, the UE monitors the PDCCH addressed to the C-RNTI in the RAR window at operation 2840. The contention-free preamble is exclusively allocated to the UE using an RRC signaling message.

[0319] If the UE receives a PDCCH addressed to the C-RNTI that schedules a DL TB and this DL TB includes an absolute TA command at operation 2850, the RAR is considered to be successfully received. The absolute TA command may be included in the MAC CE.

[0320] After receiving the CFRA preamble, the gNB sends a response on the PDSCH. The PDCCH that schedules the PDSCH is addressed to the C-RNTI. Since the CFRA preamble is assigned to the UE by the gNB, the gNB can identify the UE upon receiving the CFRA preamble and therefore the C-RNTI assigned to the UE. The gNB includes the absolute TA command in the DL TB sent on the PDSCH.

[0321] Absolute TA command in TA MAC CE (see Fig.26 ) : The length of the received TA command is 12 bits. The TA command corresponds to the TAG of the serving cell on which the RA preamble is sent. The T A To determine N TA , where N TA =T A ·16·64 / 2 μ . 2 μ 15 kHz is the SCS UL BWP.

[0322] TA MAC CE in the TA command (see Fig. 27 ) : A TA command for a specific TAG can also be received via the TA command MAC CE (T A ). The length of the TA command received in the TA command MAC CE is 6 bits. AIndicates the value of index T A =0,1,2,...,63 Set the current N TA Value N TA_old Adjust to new N TA Value N TA_new , where for 2 μ 15kHz SCS, N TA_new =N TA_old +(T A -31)·16·64 / 2 μ 2 μ 15.2 μ 15kHz is the SCS UL BWP.

[0323] In an embodiment, the above method is applicable only when the RAR window size is greater than 10 ms. In another embodiment, the above method is applicable to any RAR window size.

[0324] Method 3: Fig.29 Another method for a UE to perform a RA process according to an embodiment of the present disclosure is shown.

[0325] refer to Fig.29 , the UE sends a RA preamble (also referred to as Msg1) at operation 2910 and then waits for a RAR in the RAR window. The RAR is also referred to as Msg2.

[0326] The UE monitors the PDCCH addressed to the RA-RNTI in the RAR window at operation 2920 .

[0327] If the RA preamble sent is selected from the CBRA preambles: If the UE receives a PDCCH addressed to the RA-RNTI at operation 2930 and the frame information in the DCI of the received PDCCH matches the frame information corresponding to the SFN in which the RA preamble is transmitted and the successfully decoded TB scheduled by this PDCCH includes a RAPID matching the RA preamble index of the transmitted RA preamble, then the RAR is considered to be successfully received.

[0328] Upon receiving a CBRA preamble, the gNB sends a RAR on the PDSCH. The PDCCH scheduling the PDSCH carrying the RAR is addressed to the RA-RNTI. The RA-RNTI identifies the time-frequency resource (also called PRACH opportunity or PRACH TX opportunity or RO) in which the RA preamble was detected by the gNB. The RA-RNTI is calculated as follows: , where s_id is the index of the first OFDM symbol of the PRACH opportunity in which the UE has sent Msg1, i.e., the RA preamble; 0≤s_id<14; t_id is the index of the first time slot of the PRACH opportunity (0≤t_id<80); f_id is the index of the PRACH opportunity within the time 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 'X' LSBs of the SFN. X can be predefined or determined based on the RAR window size. For example, X can be 2 bits for a RAR window size of 40ms.

[0329] If the RA preamble sent was not selected from the CBRA preambles (i.e. it was a CFRA preamble): If the UE receives a PDCCH addressed to the RA-RNTI at operation 2940 and a successfully decoded TB scheduled by this PDCCH includes a RAPID matching the RA preamble index of the transmitted RA preamble, the RAR is considered to be successfully received.

[0330] In an embodiment, the above method is applicable only when the RAR window size is greater than 10 ms. In another embodiment, the above method is applicable to any RAR window size.

[0331] Method 4: Fig.30 Another method for a UE to perform a RA process according to an embodiment of the present disclosure is shown.

[0332] refer to Fig.30 , the UE sends a RA preamble (also referred to as Msg1) at operation 3010 and then waits for a RAR in the RAR window. The RAR is also referred to as Msg2.

[0333] The UE monitors the PDCCH addressed to the RA-RNTI in the RAR window at operation 3020 .

[0334] If the RA preamble sent is selected from the CBRA preamble or this RA procedure is not initiated for a reconfiguration with synchronization (e.g. handover): If the UE receives a PDCCH addressed to the RA-RNTI at operation 3030 and the frame information in the DCI of the received PDCCH matches the frame information corresponding to the SFN in which the RA preamble is transmitted and the successfully decoded TB scheduled by this PDCCH includes a RAPID matching the RA preamble index of the transmitted RA preamble, then the RAR is considered to be successfully received.

[0335] Upon receiving a CBRA preamble, the gNB sends a RAR on the PDSCH. The PDCCH scheduling the PDSCH carrying the RAR is addressed to the RA-RNTI. The RA-RNTI identifies the time-frequency resource (also called PRACH opportunity or PRACH TX opportunity or RO) in which the RA preamble was detected by the gNB. The RA-RNTI is calculated as follows: , where s_id is the index of the first OFDM symbol of the PRACH opportunity in which the UE has sent Msg1, i.e., the RA preamble; 0≤s_id<14; t_id is the index of the first time slot of the PRACH opportunity (0≤t_id<80); f_id is the index of the PRACH opportunity within the time 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 'X' LSBs of the SFN. X can be predefined or determined based on the RAR window size. For example, X can be 2 bits for a RAR window size of 40ms.

[0336] If the sent RA preamble is not selected from the CBRA preambles (i.e. it is a CFRA preamble) and this RA procedure is initiated for a reconfiguration with synchronization: If the UE receives a PDCCH addressed to the RA-RNTI at operation 3040 and a successfully decoded TB scheduled by this PDCCH includes a RAPID matching the RA preamble index of the transmitted RA preamble, the RAR is considered to be successfully received.

[0337] In an embodiment, the above method is applicable only when the RAR window size is greater than 10 ms. In another embodiment, the above method is applicable to any RAR window size.

[0338] Method 5: In one method of the present disclosure, the UE performs the RA process as follows: The network (ie, gnB) indicates whether the UE should perform operation 1 or operation 2.

[0339] Operation 1: Before initiating RA in the target SpCell, the UE decodes the PBCH of the SpCell to derive 2 LSBs. After sending the RA preamble, the UE monitors the PDCCH addressed to the RA-RNTI. If the UE receives a PDCCH addressed to the RA-RNTI and the DCI includes frame information corresponding to the SFN in which the preamble is sent and the TB scheduled by this PDCCH includes the RAPID of the sent preamble, the RAR is considered to be successfully received.

[0340] Operation 2: In one embodiment of the present disclosure, this operation is the same as defined in Method 1. In an alternative embodiment of the present disclosure, this operation is the same as defined in Method 2. In an alternative embodiment of the present disclosure, this operation is the same as defined in Method 3. In an alternative embodiment of the present disclosure, this operation is the same as defined in Method 4.

[0341] The RRCReconfiguration message for reconfiguration with synchronization may include an indication to perform operation 2. In the absence of such indication in the RRCReconfiguration message, the UE performs operation 1.

[0342] Method 6: In one method of the present disclosure, the UE performs the RA process as follows: During reconfiguration with 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 to obtain the half-frame timing (for greater than 3GHz, the half-frame timing is in the PBCH); and if the RA association period is greater than 10 ms, the UE can decode the PBCH to obtain the SFN timing.

[0343] Operation 1: Before initiating RA in the target SpCell, the UE decodes the PBCH of the SpCell to derive 2 LSBs. After sending the RA preamble, the UE monitors the PDCCH addressed to the RA-RNTI. If the UE receives a PDCCH addressed to the RA-RNTI and the DCI includes frame information corresponding to the SFN in which the preamble is sent and the TB scheduled by this PDCCH includes the RAPID of the sent preamble, the RAR is considered to be successfully received.

[0344] Operation 2: In one embodiment of the present disclosure, this operation is the same as defined in Method 1. In an alternative embodiment of the present disclosure, this operation is the same as defined in Method 2. In an alternative embodiment of the present disclosure, this operation is the same as defined in Method 3. In an alternative embodiment of the present disclosure, this operation is the same as defined in Method 4.

[0345] Method 7: In one method of the present disclosure, a UE receives an RRC reconfiguration message with a reconfiguration of a synchronization IE. In the received reconfiguration message, the UE receives a first window size configuration and a second RAR window size configuration for a first active UL BWP. The first RAR window size is less than or equal to 10 ms. The second RAR window size may be less than or equal to 10 ms or greater than or equal to 10 ms. The first RAR window size is configured in the RACHConfigCommon IE and the second RAR window size is configured in the RACHConfigDedicated IE. For RA to a target SpCell upon receiving a reconfiguration with synchronization, the UE uses the RAR window size configured in the RACHConfigDedicated IE. The UE does not monitor the LSB of the SFN in the DCI of the PDCCH addressed to the RA-RNTI / MSGB-RNTI in the case of a 4-step RA / 2-step RA, respectively. When the RA procedure is completed, for subsequent RA procedures initiated on the target SpCell, the UE uses the RAR window size configured in the RACHConfigCommon. The advantage of this operation is that during handover, the UE is not required to acquire the SFN for RAR reception.

[0346] CAPC and configured license handling The LBT process is essential for fair and friendly coexistence of devices and technologies operating in unlicensed spectrum. The LBT process on a node attempting to transmit on a carrier in the unlicensed spectrum requires the node to perform a clear channel assessment to determine if the channel is free for use. The various types or categories of LBT processes for transmission are as follows: Category 1: No LBT No LBT procedure is performed by the sending entity.

[0347] Category 2: LBT without random backoff The duration of the channel being sensed to be idle before the transmitting entity transmits is deterministic. In the example, the sensing interval may be 25 us, i.e., the UE may sense that the channel is idle for at least the sensing interval T. d =Sent after 25 us. For UL transmission, Category 3 is also known as Type 2 channel access procedure.

[0348] Category 3: LBT with random backoff and fixed contention window size The LBT process has the following process as one of its 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 in the LBT process to determine the duration of time that the channel is sensed to be idle before the transmitting entity transmits on the channel. The detailed Category 3 LBT process is as follows: UE delays for a period of time (T d ) after sensing that the channel is idle within the time slot duration of the 10000 time slot and after the counter reaches zero in step 4, the detailed process is as follows: Step 1: Set N=N init , where N init is evenly distributed between 0 and CW p A random number between . CW p is the contention window for a given channel access priority level 'p'. Various LBT parameters for different CAPCs are listed in Table 1.

[0349] Step 2: If N>0, and the UE chooses to decrement the counter, set N=N-1.

[0350] Step 3: During the additional time slot duration (T s ) within the additional time slot duration. If the additional time slot duration is idle, proceed to step 4; otherwise, proceed to step 5.

[0351] Step 4: If N=0, perform the transmission. Otherwise, proceed to step 2.

[0352] Step 5: Add a deferral duration T d The channel is sensed during the time slot duration. The delay duration (T d ) is equal to T f +m p x T s , where T f is equal to 16 us and T s Equal to 9 us.

[0353] Step 6: If in T d If the channel is idle during the period, the process goes to step 2. Otherwise, the process goes to step 5.

[0354] Category 4: LBT with random backoff and variable contention window size The LBT procedure has the following as one of its 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 in the LBT procedure to determine the duration of time that the channel is sensed to be idle before the transmitting entity transmits on the channel. 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, whereas in Category 4 the transmitting entity can change the size of the contention window when drawing the random number N. UL transmission Category 4 is also known as Type 1 channel access procedure.

[0355] In the NR system design, in the UL, the gNB 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 transmissions when its DL reception is enabled (active via DRX control when configured). When CA is configured, the same C-RNTI applies to all serving cells. In addition, with the configured grants, the gNB can allocate periodic UL resources for UL transmissions to the UE. Two types of configured UL grants are defined: In the Type 1 case, RRC directly provides the configured UL grant (including period).

[0356] In the type 2 case, RRC defines the period of the configured UL grant, and the PDCCH addressed to the CS-RNTI can signal and activate the configured UL grant or deactivate it; that is, the PDCCH addressed to the CS-RNTI indicates that the UL grant can be implicitly reused according to the period defined by RRC until it is deactivated.

[0357] In case of dynamic grant, the gNB indicates that the LBT type / category to be used for channel access is signaled by the gNB in ​​the PDCCH. The CAPC value to be used is also signaled by the gNB in ​​the PDCCH.

[0358] For UL channel access using CAPC-based LBT procedure example LBT type 1 (i.e. Category 4 LBT) for a configured grant or for MsgA payload transmission on PUSCH in case of 2-step RACH or for any UL transmission where the DCI does not include a CAPC, the UE needs to determine the CAPC. To do this, the gNB signals the CAPC for each LCH of the DRB. MAC CEs other than padding BSR and recommended bit rate use the highest priority CAPC (i.e. lowest CAPC index). Padding BSR and recommended bit rate MAC CEs use the lowest priority CAPC (i.e. highest CAPC index). SRB0, SRB1 and SRB3 use the highest priority CAPC (i.e. lowest CAPC index in Table 1), while the CAPC for SRB2 is configurable. The UE selects the highest CAPC index (i.e. lowest priority CAPC) for the LCH with the MAC SDU multiplexed in the MAC PDU.

[0359] One problem with this design of selecting CAPC for UL configured grants is that if the SRB data corresponding to the lowest CAPC (ie, highest priority) is de-prioritized if multiplexed with other LCH MAC SDUs in a MAC PDU, some method is needed to enhance the current design.

[0360] Method 1: For a configured UL grant or for MsgA payload transmission on PUSCH in case of 2-step RACH or for any UL transmission where the DCI does not include a CAPC, on an unlicensed carrier (i.e., a serving cell operating on an unlicensed spectrum or band), if a MAC SDU of a DCCH LCH is included in a 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). In case a plurality of MAC SDUs of a DCCH belonging to an SRB with different CAPC indices are included in a MAC PDU, the CAPC index of the DCCH is the highest index among the CAPC indices of the DCCH included in the MAC PDU.

[0361] In an alternative embodiment, for a configured UL grant or for MsgA payload transmission on PUSCH in case of a 2-step RACH or for any UL transmission where the DCI does not include a CAPC, on an unlicensed carrier (i.e., a serving cell operating on an unlicensed spectrum or band), if a MAC SDU for a DCCH LCH is included in a 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 for a 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). In case a plurality of MAC SDUs belonging to a DCCH of an SRB with different CAPC indices are included in a MAC PDU, the CAPC index of the DCCH is the highest index among the CAPC indices of the DCCH included in the MAC PDU. For example, let us assume that SRB1 and SRB2 have CAPC index 1 and CAPC index 3 respectively, if the MAC SDUs of both SRB1 and SRB2 are included in the MAC PDU, the UE should not include any other MAC SDU of LCH with a CAPC index higher than 3 and the UE should not include any MAC CE with a CAPC index higher than 3.

[0362] In an alternative embodiment, for a configured UL grant or for MsgA payload transmission on PUSCH in case of 2-step RACH or for any UL transmission where the DCI does not include a CAPC, on an unlicensed carrier (i.e., a serving cell operating on an unlicensed spectrum or band), if a MAC SDU of a DCCH LCH is included in a 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 'LCH other than DCCH' having a CAPC index higher than the CAPC index of the DCCH (i.e., its MAC SDU is included in the CAPC of the DCCH LCH in the MAC PDU). In case a plurality of MAC SDUs of a DCCH belonging to an SRB with different CAPC indices are included in a MAC PDU, the CAPC index of the DCCH is the highest index among the CAPC indices of the DCCH included in the MAC PDU. For example, let us assume that SRB1 and SRB2 have CAPC index 1 and CAPC index 3 respectively, if the MAC SDUs of both SRB1 and SRB2 are included in the MAC PDU, the UE should not include any other MAC SDU of the LCH with a CAPC index higher than 3.

[0363] In an alternative embodiment, for a configured UL grant or for MsgA payload transmission on PUSCH in case of 2-step RACH or for any UL transmission where DCI does not include CAPC, on an unlicensed carrier (i.e., a serving cell operating on an unlicensed spectrum or band), if a MAC SDU for a DCCH LCH is included in a 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 for '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). In case a plurality of MAC SDUs of a DCCH belonging to an SRB with different CAPC indices are included in a MAC PDU, the CAPC index of the DCCH is the highest index among the CAPC indices of the DCCH included in the MAC PDU. For example, let us assume that SRB1 and SRB2 have CAPC index 1 and CAPC index 3 respectively, if the MAC SDUs of both SRB1 and SRB2 are included in the MAC PDU, the UE should not include any other MAC SDU of LCH with a CAPC index higher than 3 and the UE should not include any MAC CE with a CAPC index higher than 3.

[0364] Just because the configured UL grant is for an unlicensed carrier does not mean that CAPC-based LBT is performed to access the channel to transmit on this UL grant. So it is important that the UE checks whether a CAPC-based LBT procedure (e.g., LBT Category 3 / 4) is applied. Various cases in which a CAPC-based LBT procedure (e.g., LBT Category 3 or 4) is applied are detailed in TS 38.889 and TS 38.213.

[0365] Method 2: For a configured UL grant or for a MsgA payload transmission on PUSCH in the case of a 2-step RACH or for any UL transmission where the DCI does not include a CAPC, a CAPC-based LBT procedure (e.g., if it is a category 3 or 4-based LBT) is performed for channel access on an unlicensed carrier (i.e., a serving cell operating on an unlicensed spectrum or band), and if a MAC SDU of a 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. If 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 whose MAC SDUs are multiplexed in the MAC PDU. For example, let us assume that SRB1 and SRB2 have CAPC indexes 1 and 3, respectively. The MAC SDUs of SRB1 and SRB3 are included in the MAC PDU. So CAPC index 1 is selected because it is the lowest of CAPC index 1 and CAPC index 3. If a MAC SDU of an LCH other than a DCCH is included in the MAC PDU, the UE selects the highest CAPC index (lowest priority) of the LCH multiplexed in the MAC PDU (or alternatively the UE selects the highest CAPC index (lowest priority) of the LCH / MAC CE multiplexed in the MAC PDU). If only a MAC CE is included in the MAC PDU, the UE selects the lowest CAPC index (i.e., highest priority) of the MAC CE included in the MAC PDU.

[0366] Just because the configured UL grant is for an unlicensed carrier does not mean that CAPC-based LBT is performed to access the channel to transmit on this UL grant. So it is important that the UE checks whether a CAPC-based LBT procedure (e.g., LBT Category 3 / 4) is applied. Various cases in which a CAPC-based LBT procedure (e.g., LBT Category 3 or 4) is applied are detailed in TS 38.889 and TS 38.213.

[0367] LBT Troubleshooting For LBT failure handling, the gNB signals in the RRCReconfiguration message lbt- FailureRecoveryConfig IE. The RRCReconfiguration message is sent to the UE in the RRC connection. lbt- FailureRecoveryConfig The IE is configured individually for the serving cell. lbt-FailureRecoveryConfig IE includes parameters for consistent LBT failure detection lbt-FailureInstanceMaxCount and lbt- FailureDetectionTimer The RRCReconfiguration message from the gNB is processed by the RRC layer in the UE. If the serving cell receives lbt-FailureRecoveryConfig , the MAC entity of the serving cell uses the lbt-FailureRecoveryConfig IE to perform consistent LBT failure recovery procedures.

[0368] Consistent LBT failure is detected per UL BWP by counting LBT failure indications for all UL transmissions from lower layers (ie, physical layer) to the MAC entity.

[0369] UE variables LBT_COUNTER , i.e., the counter for LBT fault indication, which is initially set to 0, is used for consistent LBT fault detection process and is for a configured lbt-FailureRecoveryConfig Each activated serving cell is maintained individually.

[0370] For configuration lbt-FailureRecoveryConfig For each activated serving cell, the MAC entity shall: 1> If an LBT fault indication has been received from the lower layer: 2> Start or restart lbt-FailureDetectionTimer ; 2> LBT_COUNTER Increment by 1; 2>If LBT_COUNTER >= lbt-FailureInstanceMaxCount : *3> If the serving cell is SCell: 4> For active UL BWP, declare consistent LBT failure; 4> Indicate to the multiplexing and assembly entity to include the LBT failure MAC CE in subsequent UL transmissions.

[0371] 3> Otherwise (i.e. SpCell): 4> For active UL BWP, declare consistent LBT failure; 4> If a consistent LBT failure has been declared in all UL BWPs configured with PRACH opportunities in this serving cell: 5>Indicate consistent LBT failure to higher layers.

[0372] 4> Otherwise: 5> Switch the active UL BWP to a UL BWP for which a PRACH opportunity is configured in this serving cell and for which a consistent LBT failure has not been declared; 5>Perform BWP operations as specified in clause 5.15 of TS 38.321; 5>Initiate RA process.

[0373] 1>If lbt-FailureDetectionTimer expires; or 1>If lbt-FailureDetectionTimer or lbt-FailureInstanceMaxCount Reconfiguration from a high level: 2> LBT_COUNTER Set to 0.

[0374] In the above process, upon LBT failure of the active UL BWP of the SpCell, the UE switches to a UL BWP configured with a PRACH opportunity and for which a consistent LBT failure has not been declared. However, in the UL, there may be two carriers, SUL and NUL. If the active UL BWP is on SUL and the UE switches to a UL BWP on NUL, there may be a problem because the UE may not be in the UL coverage of NUL and the UL transmission will fail. If the active UL BWP is on NUL and the UE switches to a UL BWP on SUL, there may be a problem because the UE may not be in the UL coverage of SUL and the UL transmission will fail.

[0375] Additionally, there may be multiple UL BWPs on both NUL and SUL.Declaring LBT failure to higher layers when LBT fails on all UL BWPs with PRACH opportunities will delay Radio Link Failure (RLF).

[0376] Method 1: In the method of the present disclosure, LBT failure handling for SpCell is described. For LBT failure handling, the gNB signals the lbt-FailureRecoveryConfig IE. The RRCReconfiguration message is sent to the UE in the RRC connection. lbt-FailureRecoveryConfig IE is configured for SpCell. lbt-FailureRecoveryConfig IE includes parameters for consistent LBT failure detection lbt- FailureInstanceMaxCount and lbt-FailureDetectionTimer The RRCReconfiguration message from the gNB is processed by the RRC layer in the UE. If the RRCReconfiguration message is received from the gNB for the SpCell lbt- FailureRecoveryConfig , then the MAC entity of SpCell is used in SpCell lbt- FailureRecoveryConfig IE to perform consistent LBT failure recovery procedures.

[0377] Consistent LBT failure is detected per UL BWP by counting LBT failure indications for all UL transmissions from lower layers (i.e. physical layer) to the MAC entity. UE variables LBT_COUNTER , that is, the counter for LBT fault indication that is initially set to 0 is used for consistent LBT fault detection process. The UE operation for LBT fault handling of SpCell is as follows: 1> Upon receiving an LBT failure indication from a lower layer (here, the LBT failure indication from a lower layer fails to be sent in the UL of the SpCell due to an LBT failure, i.e., it is determined that UL transmission cannot be performed based on the LBT process for UL channel access): 2> Start or restart lbt-FailureDetectionTimer ; 2> LBT_COUNTER Increment by 1; 2>If LBT_COUNTER >= lbt-FailureInstanceMaxCount : 3> For active UL BWP, declare consistent LBT failure; 3> If consistent LBT failure is declared in all UL BWPs configured with PRACH opportunities in the NUL of this serving cell; or 3> If consistent LBT failure is declared in all UL BWPs configured with PRACH opportunities in the SUL of this serving cell; 4> Indicate consistent LBT failure to the upper layer (the upper layer, i.e., RRC will declare RLF upon receiving this indication) 3> Otherwise: 4> Switch the active UL BWP to the UL BWP of the same carrier as the active UL BWP for which a PRACH opportunity is configured in this serving cell and for which a consistent LBT failure has not been declared; 4>Initiate RA process.

[0378] When initiating the RA procedure, the UE will select between SUL and NUL based on the RSRP threshold.

[0379] If SUL is configured and if the DL path loss reference RSRP is less than rsrp-ThresholdSSB-SUL , the UE selects the SUL carrier to perform the RA process. Otherwise, the UE selects the NUL carrier to perform the RA process.

[0380] It is possible that the selected carrier is different from the carrier used before initiating the RA procedure. In order to ensure that the active UL BWP after carrier switching also has a RACH opportunity, it is proposed that for a serving cell configured with SUL and NUL, if the UL BWP with BWP ID 'X' in NUL has a RACH opportunity, the UL BWP with the same BWP ID 'X' in SUL should also be configured with a RACH opportunity. The above proposal can be applied to cells operating on unlicensed carriers in an embodiment.

[0381] Method 2: In the method of the present disclosure, LBT failure handling for SpCell is described. For LBT failure handling, the gNB signals the lbt-FailureRecoveryConfig IE. The RRCReconfiguration message is sent to the UE in the RRC connection. lbt-FailureRecoveryConfig IE is configured for SpCell. lbt-FailureRecoveryConfig IE includes parameters for consistent LBT failure detection lbt- FailureInstanceMaxCount and lbt-FailureDetectionTimer The RRCReconfiguration message from the gNB is processed by the RRC layer in the UE. If the RRCReconfiguration message is received from the gNB for the SpCell lbt- FailureRecoveryConfig , then the MAC entity of SpCell is used in SpCell lbt- FailureRecoveryConfig IE to perform consistent LBT failure recovery procedures.

[0382] Consistent LBT failure is detected per UL BWP by counting LBT failure indications for all UL transmissions from lower layers (i.e. physical layer) to the MAC entity. UE variables LBT_COUNTER , that is, the counter for LBT fault indication that is initially set to 0 is used for consistent LBT fault detection process. The UE operation for LBT fault handling of SpCell is as follows: 1> Upon receiving an LBT failure indication from a lower layer (here, the LBT failure indication from a lower layer fails to be sent in the UL of the SpCell due to an LBT failure, i.e., it is determined that UL transmission cannot be performed based on the LBT process for UL channel access): 2> Start or restart lbt-FailureDetectionTimer ; 2> LBT_COUNTER Increment by 1; 2>If LBT_COUNTER >= lbt-FailureInstanceMaxCount : 3> For active UL BWP, declare consistent LBT failure; 3> If consistent LBT failure is declared in all UL BWPs that have been configured with PRACH opportunities on the carrier of the active UL BWP in this serving cell; 4> Indicate consistent LBT failure to the upper layer (the upper layer, i.e., RRC will declare RLF upon receiving this indication) 3> Otherwise: 4> Switch the active UL BWP to the UL BWP of the same carrier as the active UL BWP for which a PRACH opportunity is configured in this serving cell and for which a consistent LBT failure has not been declared; 4> Initiate a RA procedure on the same carrier as the active UL BWP. (In this case the UE will not choose between SUL and NUL based on the RSRP threshold when initiating the random access procedure) RA carrier selection: 1> If the RA process is initiated for LBT failure recovery: 2> Select the carrier of the currently active UL BWP for performing the RA process; 2> PCMAX Set to the P of the selected carrier CMAX,f,c .

[0383] 1> Otherwise if the carrier to be used for the RA procedure is explicitly signalled (by the gNB): 2> Select the signaled carrier for performing the RA procedure; 2> PCMAX Set to the signaled carrier's P CMAX,f,c .

[0384] 1> else if the carrier to be used for the RA procedure is not explicitly signaled; and 1> if the serving cell for the RA procedure is configured with a supplementary uplink as specified in TS 38.331; and 1> If the RSRP of the downlink path loss benchmark is less than rsrp-ThresholdSSB-SUL : 2> Select the SUL carrier for performing the RA process; 2> PCMAX Set to SUL carrier’s P CMAX,f,c .

[0385] 1> Otherwise: 2> Select the NUL carrier for performing the RA process; 2> PCMAX Set to NUL carrier's P CMAX,f,c .

[0386] Fig.31 is a block diagram of a terminal according to an embodiment of the present disclosure.

[0387] refer to Fig.31 The terminal includes a transceiver 3110, a controller 3120, and a memory 3130. The controller 3120 may refer to a circuit system, an ASIC, an FPGA, or at least one processor. The transceiver 3110, the controller 3120, and the memory 3130 are configured to execute various diagrams. Figure 4 , Figure 7 , Fig.10 , Fig.13 , Fig.16 , Fig.18 , Fig.19 , Fig.21 , Fig. 22 , Fig.25 , Fig.28 , Fig.29 and Fig.30 Operation of the UE as illustrated in or as otherwise described above. Although the transceiver 3110, the controller 3120, and the memory 3130 are shown as separate entities, they can be integrated into a single chip. The transceiver 3110, the controller 3120, and the memory 3130 can also be electrically connected or coupled to each other.

[0388] The transceiver 3110 may transmit and receive signals to and from other network entities (eg, base stations).

[0389] The controller 3120 may control the UE to perform the functions according to the above-mentioned embodiments. In an embodiment of the present disclosure, for UL transmission on a configured grant, the controller 3120 is configured to select a CAPC of a DCCH in the case of transmitting a DCCH SDU, otherwise select a lowest priority CAPC (i.e., a highest number of CAPC indexes) of an LCH with a MAC SDU and a MAC CE multiplexed in a MAC PDU. In another embodiment of the present disclosure, the controller 3120 is configured to trigger a consistent LBT failure of an active ULBWP in a serving cell. If an LBT failure indication has been identified from a lower layer, the controller 3120 may be configured to increment an LBT counter (i.e., LBT_COUNTER If the LBT counter is greater than the preconfigured threshold (i.e. FailureInstanceMaxCount), a consistent LBT failure of the active UL BWP in the serving cell is triggered. If a consistent LBT failure is triggered in all UL BWPs configured with PRACH opportunities on the same carrier in the serving cell, the controller 3120 is configured to determine that RLF is detected for the serving cell. Otherwise, the controller 3120 is configured to switch the active UL BWP to a UL BWP configured with PRACH opportunities on the same carrier in the serving cell and for which a consistent LBT failure has not been triggered, and to initiate a RA procedure triggered by a consistent UL LBT failure on the switched UL BWP.

[0390] In an embodiment, the operation of the terminal can be implemented using a memory 3130 storing a corresponding program code. Specifically, the terminal can be equipped with a memory 3130 to store a program code that implements the desired operation. In order to perform the desired operation, the controller 3120 can read and execute the program code stored in the memory 3130 by using a processor or a central processing unit (CPU).

[0391] Fig.32 is a block diagram of a base station according to an embodiment of the present disclosure.

[0392] refer to Fig.32 The base station includes a transceiver 3210, a controller 3220, and a memory 3230. The controller 3220 may refer to a circuit system, an ASIC, an FPGA, or at least one processor. The transceiver 3210, the controller 3220, and the memory 3230 are configured to execute various operations such as Figure 5 , Figure 8 , Fig.11 and Fig.14 Operation of the gNB as illustrated in or otherwise described above. Although the transceiver 3210, the controller 3220, and the memory 3230 are shown as separate entities, they may be integrated onto a single chip. The transceiver 3210, the controller 3220, and the memory 3230 may also be electrically connected or coupled to each other.

[0393] The transceiver 3210 may transmit and receive signals to and from other network entities (eg, terminals).

[0394] The controller 3220 may control the gNB to perform functions according to an embodiment of the present disclosure.

[0395] In an embodiment, the operation of the base station can be implemented using a memory 3230 storing corresponding program codes. Specifically, the base station can be equipped with a memory 3230 to store program codes that implement the desired operation. In order to perform the desired operation, the controller 3220 can read and execute the program code stored in the memory 3230 by using a processor or CPU.

[0396] While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

1. A method for handling a listen-before-talk (LBT) failure in a wireless communication system performed by a terminal, the method comprising: Identifying whether there is a consistent LBT failure of the active uplink UL bandwidth part BWP of the carriers in the serving cell; If the consistent LBT failure of the active UL BWP of the carrier in the serving cell is identified, identifying whether a consistent LBT failure has been triggered in all UL BWPs configured with physical random access channel PRACH opportunities on the carrier in the serving cell, wherein the carrier configured with all UL BWPs is one of a normal uplink carrier NUL of the serving cell or a supplementary uplink carrier SUL of the serving cell; If the consistent LBT failure is triggered in all UL BWPs that have been configured with the PRACH opportunity on the carrier in the serving cell, the media access control MAC entity indicates the consistent LBT failure to the upper layer; as well as If there is at least one UL BWP configured with a PRACH opportunity on the carrier in the serving cell and a consistent LBT failure is not triggered, the active UL BWP is switched to a UL BWP among the at least one UL BWP, and a random access procedure is initiated on the switched UL BWP of the carrier.

2. The method according to claim 1, further comprising: identifying, at the MAC entity, an LBT failure indication received from a lower layer; as well as Based on the LBT fault indication, an LBT counter is incremented.

3. The method according to claim 2, in, The consistent LBT failure is identified when the LBT counter is greater than a preconfigured threshold.

4. The method according to claim 1, in, A radio link failure RLF of the serving cell is determined based on the indication of the consistent LBT failure.

5. The method according to claim 1, in, The serving cell is a primary cell or a primary or secondary cell of a secondary cell group.

6. A terminal in a wireless communication system, the terminal comprising: Transceiver; as well as at least one processor operably coupled to the transceiver and configured to: Identify whether there is a consistent listen-before-talk (LBT) failure of the active uplink UL bandwidth part (BWP) of the carrier in the serving cell; If it is identified that the consistent LBT failure exists in the active UL BWP of the carrier in the serving cell, identifying whether a consistent LBT failure has been triggered in all UL BWPs configured with physical random access channel PRACH opportunities on the carrier in the serving cell, wherein the carrier configured with all the UL BWPs is one of a normal uplink carrier NUL of the serving cell or a supplementary uplink carrier SUL of the serving cell; If the consistent LBT failure is triggered in all UL BWPs that have been configured with the PRACH opportunity on the carrier in the serving cell, the media access control MAC entity indicates the consistent LBT failure to a higher layer; as well as If there is at least one UL BWP configured with a PRACH opportunity on the carrier in the serving cell and a consistent LBT failure is not triggered, the active UL BWP is switched to a UL BWP among the at least one UL BWP, and a random access procedure is initiated on the switched UL BWP of the carrier.

7. The terminal according to claim 6, wherein: The at least one processor is further configured to: identifying, at the MAC entity, an LBT failure indication received from a lower layer; and Based on the LBT fault indication, an LBT counter is incremented.

8. The terminal according to claim 7, in, The consistent LBT failure is identified when the LBT counter is greater than a preconfigured threshold.

9. The terminal according to claim 6, in, A radio link failure RLF of the serving cell is determined based on the indication of the consistent LBT failure.

10. The terminal according to claim 6, in, The serving cell is a primary cell or a primary or secondary cell of a secondary cell group.

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