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

Abstract

To provide a method for handling LBT (listen before talk) failure in a wireless communication system.SOLUTION: A terminal identifies consistent LBT failure for active uplink (UL) bandwidth part (BWP) of a carrier in a serving cell; in the case that consistent LBT failure has been triggered in all UL BWPs configured with physical random access channel (PRACH) occasions on the carrier in the serving cell, indicates the consistent LBT failure from a MAC (media access control) entity to an upper layer; in the case that at least one UL BWP for which consistent LBT failure has not been triggered on the carrier in the serving cell and is configured with a PRACH occasion is identified, switches the active UL BWP to an UL BWP among the at least one UL BWP; and initiates a random access procedure using the switched UL BWP of the carrier.SELECTED DRAWING: Figure 31

Description

[Technical Field]

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

[0002] Efforts are underway to develop improved 5G (or pre-5G) communication systems to meet the increasing demand for wireless data traffic since the commercialization of fourth-generation (4G) communication systems. For this reason, 5G (or pre-5G) communication systems are also referred to as "Beyond 4G Network" or "Post-LTE" communication systems. To achieve high data rates, 5G communication systems are expected to be implemented in ultra-high frequency (mmWave) bands (e.g., the 60 GHz band). To reduce radio wave propagation loss and increase transmission distance, technologies such as beamforming, multiple-input multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large-scale antennas are being discussed for 5G communication systems. Furthermore, to improve the system's network, technologies such as advanced small cells, cloud Radio Access Networks (cloud RAN), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving networks, cooperative communication, Coordinated Multi-Points (CoMP), and reception-end interference cancellation are being developed for 5G communication systems.For 5G communication systems, advanced coding modulation (ACM) methods such as FQAM (Hybrid FSK and QAM Modulation) and SWSC (Sliding Window Superposition Coding) and advanced access technologies such as FBMC (Filter Bank Multi Carrier), NOMA (non-orthogonal multiple access), and SCMA (sparse code multiple access) are being developed.

[0003] The Internet, a human-centered network where humans generate and consume information, is evolving into the Internet of Things (IoT), where dispersed entities like things exchange and process information without human intervention. The Internet of Everything (IoE) technology, which combines IoT technology and big data processing technology through connections to cloud servers, is emerging. To realize the IoT, technological elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. Recently, research has focused on sensor networks, M2M (Machine to Machine), and MTC (Machine Type Communication) for connecting things. In an IoT environment, intelligent IT (Internet Technology) services can be provided that create new value in people's lives by collecting and analyzing data generated by connected things. Through the convergence and integration of existing IT (information technology) technologies and various industries, the IoT can be applied to areas such as smart homes, smart buildings, smart cities, smart or connected cars, smart grids, healthcare, smart home appliances, and advanced medical services.

[0004] As a result, various attempts are being made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, MTC (Machine Type Communication), and M2M (Machine to Machine) are being realized through 5G communication technologies such as beamforming, MIMO, and array antennas. The application of cloud radio access network (Cloud RAN) as a big data processing technology is also an example of the convergence between 5G and IoT technologies.

[0005] In recent years, many broadband wireless technologies have been developed to meet the increasing number of broadband subscribers and provide more applications and services. Second-generation (2G) wireless communication systems were developed to provide voice services while ensuring user mobility. Third-generation (3G) wireless communication systems support voice and data services. Fourth-generation (4G) wireless communication systems were developed to provide high-speed data services. However, 4G wireless communication systems currently suffer from a lack of resources to meet the increasing demand for high-speed data services. Therefore, fifth-generation wireless communication systems (also known as next generation radio (NR)) are being developed to meet the increasing demand for diverse services with diverse requirements, such as high-speed data services, and to support ultra-reliable and low-latency applications.

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

[0007] The current design of 5G wireless communication systems is to operate on licensed carriers. Research has recently been initiated to study enhancements to 5G wireless communication systems for operation on unlicensed carriers. The primary motivation for using unlicensed carriers is to address the increasing wireless traffic demands under limited available spectrum, and to allow cellular operators to reduce capital expenditures (CAPEX) by utilizing free spectrum access for intelligent data offloading; improved intelligent spectrum access and management, so that network operators without licensed spectrum can utilize wireless-efficient 3GPP (3rd Generation Partnership Project) radio access technologies. Various deployment scenarios are being considered for operation on unlicensed carriers, including:

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

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

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

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

[0012] The above scenario includes an NR cell with a downlink (DL) in an unlicensed spectrum and an uplink (UL) in a licensed spectrum.

[0013] One of the goals of the above-mentioned research is to identify improvements necessary to support the random access (RA) procedure in unlicensed spectrum. 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 unsynchronized user equipment (UE) in the RRC CONNECTED state during initial access, handover, radio resource control (RRC) connection reconfiguration procedures, scheduling request transmission, secondary cell group (SCG) addition / modification, and UL data or control information transmission. During the RA procedure, the UE first transmits an RA preamble (also known as message 1 (Msg1)) and then waits for an RA response (RAR) or message 2 (Msg2) in the RAR window corresponding to the RA preamble transmission. The next generation node B (gNB) transmits an RAR on the physical DL shared channel (PDSCH) addressed to the RA-radio network temporary identifier (RA-RNTI). The RA-RNTI identifies the time-frequency resource (also called physical RA channel (PRACH) occasion, PRACH transmission (TX) occasion, or RA channel (RACH) occasion) on 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: RA-RNTI = 1 + s_id + 14 * t_id + 14 * 80 * f_id + 14 * 80 * 8 * ul_carrier_id, where

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

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

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

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

[0018] Multiple 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). An RAR in a MAC PDU corresponds to a UE RA preamble transmission if the RAR includes the RAPID (RA preamble identifier) ​​of the RA preamble transmitted by the UE. If an RAR corresponding to an RA preamble transmission is not received within the RAR window and the UE has not yet transmitted the RA preamble to be configured (configured by the gNB in ​​RACH configuration), the UE retransmits the RA preamble.

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

[0020] The cell from which the UE transmits 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 must perform channel detection (i.e., listen-before-talk (LBT)) to determine whether the channel is free before transmitting Msg1 and Msg3 in the UL. Similarly, if the carrier used for DL ​​transmission is an unlicensed carrier, the gNB must perform channel detection (i.e., LBT) to determine whether the channel is free before transmitting Msg2 and Msg4 in the DL. The gNB may receive the RA preamble but be unable to transmit the RAR within the RAR window because the channel is not free. The UE will retransmit the PRACH when the RAR window expires. The retransmitted RA preamble may not be received by the gNB due to a collision, the UE may fail to retransmit the RA preamble, or the retransmission may be delayed because the UL channel is not free. This problem can be avoided by using a larger RAR window size. However, a large RAR window with a size greater than 10 ms results in RA-RNTI mimicry.

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

[0022] When UE1 and UE2 transmit PRACH using the same RA preamble on PRACH occasion X and PRACH occasion Y, respectively, the RARs received in the common slots between RAR window X and RAR window Y cannot be distinguished because the RA-RNTIs for PRACH occasion X and PRACH occasion Y are the same.

[0023] The above-mentioned RA-RNTI imitation problem can be solved by including information for the radio frame in which the PRACH occasion begins. An RAR MAC PDU contains one or more RAR MAC subPDUs, each consisting of a RAPID MAC subheader and an RAR MAC payload. If the RAPID in the MAC subheader matches the RA preamble transmitted by the UE and the frame information in the RAR MAC payload corresponds to the radio frame of the PRACH occasion in which the UE transmitted the RA preamble, the RAR belongs to the UE. However, this is not an efficient approach because the UE must process the RAR MAC payload even if the RAR is not its own. This process must be repeated for each and every RAR in the received RAR MAC PDU until the UE finds the RAR for itself or until there are no more RARs left to process. This approach also introduces overhead issues because frame information must be included in the RAR MAC payload of each RAR MAC PDU. This approach cannot provide frame information for MAC sub-PDUs that contain a RAPID MAC subheader but no RAR MAC payload. This type of MAC subPDU without an RAR MAC payload is included to indicate an SI request acknowledgment when the transmitted RA preamble is for an SI request.

[0024] Therefore, there is a need for an improved method for transmitting and receiving frame information in RAR.

[0025] The above information is provided solely for background information to aid in the understanding of the present disclosure, and no determination has been made or assertion made as to whether any of the above is applicable as prior art with respect to the present disclosure. Summary of the Invention [Problem to be solved by the invention]

[0026] What is needed is an improved method for sending and receiving frame information in RAR.

[0027] For uplink (UL) transmission on an unlicensed carrier, the user equipment (UE) selects the highest channel access priority class (CAPC) index (i.e., the lowest priority CAPC) of the logical channel (LCH) multiplexed with the media access control (MAC) protocol data unit (PDU). The listen before talk (LBT) parameter corresponding to the selected CAPC index is used to perform channel access (i.e., the LBT procedure) for UL transmission. The SRB data (i.e., the MAC SDU of the signaling radio bearer) corresponding to the lowest CAPC (i.e., the highest priority) index is deprioritized when multiplexed with the MAC SDU of the data radio bearer and MAC CE in the MAC PDU. Therefore, some method is needed to improve the current design.

[0028] In the case of an extended RAR window, one or more least significant bits (LSBs) of the system frame number (SFN) can be included in the downlink control information (DCI) transmitted on the physical downlink common control channel (PDCCH). Therefore, during the reconfiguration synchronization procedure, the UE must first acquire the SFN of the target SpCell and then initiate an RA toward the target SpCell. Because the six most significant bits (MSBs) of the SFN are included in the MIB and the four bits are included in the PBCH payload, the UE must decode the PBCH of the target SpCell, which can delay reconfiguration during the synchronization procedure. Therefore, a method to reduce this delay is needed.

[0029] Aspects of the present disclosure address at least the problems and / or shortcomings discussed above and provide at least the advantages described below. Accordingly, aspects of the present disclosure provide communication methods and systems that converge fifth generation (5G) communication systems to support higher data transmission rates beyond fourth generation (4G) systems.

[0030] Additional aspects will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the provided embodiments. [Means for solving the problem]

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

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

[0033] The frame identifier can be applied to both the MAC subPDU containing the RAR and the MAC subPDU containing the SI request acknowledgment. The frame identifier can also be applied to the MAC subPDU containing the BI. The overhead is reduced by adding the frame identifier only once per RAR MAC PDU.

[0034] An advantage of the method of the present disclosure is that the CAPC that occupies the largest portion of the UL grant will always prevail over the lowest priority CAPC for better channel access than the selected legacy scheme.An advantage of another method of the present disclosure is that the highest priority CAPC among those that occupy a portion of the UL grant above a threshold will prevail over channel access even if it does not occupy the largest portion of the UL grant.

[0035] Selecting CAPC for UL approved design improves design.

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

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

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

[0039] [Figure 1] 1 is an exemplary diagram 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] 1 is a diagram illustrating 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 one embodiment of the present disclosure. [Figure 3] 10 is a diagram illustrating an example of an RAR MAC PDU based on a second RAR MAC PDU format according to an embodiment of the present disclosure. [Figure 4]1 is a diagram illustrating a user equipment (UE) operation according to one embodiment of the present disclosure. [Figure 5] 1 is a diagram illustrating next generation node B (gNB) operation according to one embodiment of the present disclosure. [Figure 6] 1 is a diagram illustrating an example of an RAR MAC PDU based on a first RAR MAC PDU format according to an embodiment of the present disclosure. [Figure 7] 1 is a diagram illustrating a UE operation according to one embodiment of the present disclosure. [Figure 8] 1 is a diagram showing gNB operation according to one embodiment of the present disclosure. [Figure 9] 1 is a diagram illustrating an example of an RAR MAC PDU based on a first RAR MAC PDU format according to an embodiment of the present disclosure. [Figure 10] 1 is a diagram illustrating a UE operation according to one embodiment of the present disclosure. [Figure 11] 1 is a diagram showing gNB operation according to one embodiment of the present disclosure. [Figure 12] 1 is a diagram illustrating an example of an RAR MAC PDU based on a first RAR MAC PDU format according to an embodiment of the present disclosure. [Figure 13] 1 is a diagram illustrating a UE operation according to one embodiment of the present disclosure. [Figure 14] 1 is a diagram showing gNB operation according to one embodiment of the present disclosure. [Figure 15] FIG. 1 is an exemplary diagram of a design for selecting a channel access priority class (CAPC) for UL-configured authorization in the related art; [Figure 16] 1 is a diagram illustrating selection of a CAPC for uplink (UL) transmission according to one embodiment of the present disclosure. [Figure 17] 1 is an exemplary diagram of a MAC PDU transmitted with UL grant using LBT (listen before talk) type 1 channel access according to one embodiment of the present disclosure. [Figure 18] 1 is a diagram illustrating selection of a CAPC for UL transmission according to one embodiment of the present disclosure. [Figure 19]1 is a diagram illustrating selection of a CAPC for UL transmission according to one embodiment of the present disclosure. [Figure 20] 1 is an exemplary diagram of a MAC PDU transmitted with UL grant using LBT type 1 channel access according to one embodiment of the present disclosure. [Figure 21] 1 is a diagram illustrating selection of a CAPC for UL transmission according to one embodiment of the present disclosure. [Figure 22] 1 is a diagram illustrating selection of a CAPC for UL transmission according to one embodiment of the present disclosure. [Figure 23] FIG. 1 is an illustrative diagram according to one embodiment of the present disclosure. [Figure 24] FIG. 10 is another illustrative diagram according to an embodiment of the present disclosure. [Figure 25] 1 is a diagram illustrating a method in which a UE performs an RA procedure according to one embodiment of the present disclosure. [Figure 26] 1 is a diagram illustrating an absolute timing advance (TA) command MAC control element (CE) according to one embodiment of the present disclosure. [Figure 27] 1 is a diagram illustrating a TA command MAC CE according to an embodiment of the present disclosure. [Figure 28] 10 is a diagram illustrating another method for a UE to perform an RA procedure according to one embodiment of the present disclosure. [Figure 29] 10 is a diagram illustrating another method for a UE to perform an RA procedure according to one embodiment of the present disclosure. [Figure 30] 10 is a diagram illustrating another method for a UE to perform an RA procedure according to one embodiment of the present disclosure. [Figure 31] FIG. 2 is a block diagram of a terminal according to one embodiment of the present disclosure. [Figure 32] FIG. 2 is a block diagram of a base station according to one embodiment of the present disclosure.

[0040] It will be understood that throughout the drawings, like reference numerals refer to like parts, components and structures. DETAILED DESCRIPTION OF THE INVENTION

[0041] The following description, with reference to the accompanying drawings, is provided to facilitate a comprehensive understanding of various embodiments of the present disclosure, as defined in the claims and their equivalents. While the present disclosure includes various specific details to facilitate such understanding, these details should be considered merely as examples. Therefore, those skilled in the art will recognize that various changes and modifications to the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Furthermore, for the sake of clarity and conciseness, descriptions of well-known functions and configurations may be omitted.

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

[0043] The singular forms "a," "an," and "the" should be understood to 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.

[0044] The term "substantially" means that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, such as tolerances, measurement errors, measurement accuracy limits, and other factors known to those of ordinary skill in the art, occur to an extent that does not preclude the effect that the characteristic is intended to provide.

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

[0046] The blocks of the flowcharts may correspond to, or portions of, modules, segments, or code that include one or more executable instructions that embody one or more logical functions. In some cases, the functions illustrated by the blocks may be performed in a different order than the order listed. For example, two blocks listed in a sequence may be executed simultaneously or in reverse order.

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

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

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

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

[0051] How to send and receive frame information in Random Access Response (RAR)

[0052] Method 1:

[0053] A method of the present disclosure for transmitting and receiving frame information in RAR, wherein a UE / gNB transmits and receives an RAR media access control (MAC) protocol data unit (PDU), where the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0054] 1st RAR MAC PDU format:

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

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

[0057] -MAC subheader with only the frame identifier;

[0058] -MAC subheader with only backoff indicator;

[0059] -MAC subheader with only a Random Access (RA) Preamble Identifier (RAPID) (i.e., an acknowledgment to a System Information (SI) request);

[0060] -MAC subheader with RAPID and MAC RAR.

[0061] The Frame Identifier MAC subheader contains the 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:

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

[0063] -Frame identifier = SFN module (maximum RAR window size supported in radio frames)

[0064] -Frame identifier = SFN module (RAR window size set in radio frame)

[0065] Frame identifier = 'p' least significant bits of SFN, where 'p' may be predefined or may be equal to log2 (maximum RAR window size in the wireless frame) or log2 (RAR window size set in the wireless frame).

[0066] SFN is the system frame number of the radio frame of the physical RA channel (PRACH) occasion or the system frame number of the radio frame in which the PRACH occasion starts.

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

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

[0069] A MAC subheader with a backoff indicator consists of five header fields: Extended (E), Type (T), Reserved (R), R, and Backoff Indicator (BI). If a MAC subPDU with only a backoff indicator is included, it is included immediately after the MAC subPDU carrying the Frame Identifier MAC subheader, i.e., the backoff indication is included immediately after the MAC subPDU carrying the Frame Identifier MAC subheader. In other words, the backoff indication is included in the second MAC subPDU.

[0070] 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 padding is implied based on the transport block (TB) size and the size of the MAC subPDU. The type (T) field is set to a unique value for the BI MAC subheader and the RAPID subheader. An 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. An E field set to '1' in the MAC subheader of a MAC subPDU indicates that at least another MAC subPDU follows.

[0071] The 'MAC subPDU with only RAPID' 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 back-off indication is included in the MAC PDU. The 'MAC subPDU with only RAPID' and the 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the first MAC subPDU and the padding (if any) if a back-off indication is not included in the MAC PDU.

[0072] Second RAR MAC PDU format:

[0073] FIG. 3 illustrates an example of an RAR MAC PDU based on the second RAR MAC PDU format according to one embodiment of the present disclosure.

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

[0075] Each MAC subPDU consists of either:

[0076] -MAC subheader with only backoff indicator;

[0077] -MAC header with only RAPID (i.e., acknowledgment to SI request);

[0078] -MAC subheader with RAPID and MAC RAR.

[0079] The MAC subheader with backoff indicator consists of five header fields: E / T / R / R / BI. If included, the MAC subPDU with only backoff indicator is placed at the beginning of the MAC PDU.

[0080] 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 padding is implied based on the TB size and the size of the MAC subPDU. The Type (T) field is set to a unique value for the BI MAC subheader and the RAPID subheader. An 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. An E field set to '1' in the MAC subheader of a MAC subPDU indicates that at least another MAC subPDU follows.

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

[0082] UE behavior:

[0083] Example 1:

[0084] FIG. 4 illustrates UE operation according to one embodiment of the present disclosure.

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

[0086] UE processing according to the first MAC PDU format:

[0087] The UE processes the first MAC subPDU in operation 451 to obtain a frame identifier from the MAC subheader of the first MAC subPDU, and processes the remaining MAC subPDUs in the RAR MAC PDU in operation 452 until the RAR is successfully received or no more MAC subPDUs remain.

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

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

[0090] If a MAC subPDU (other than the first MAC subPDU) includes a MAC subheader with RAPID, the RAPID matches the RA preamble transmitted by the UE, and the frame identifier obtained from the first MAC subPDU corresponds to the radio frame of the PRACH occasion in which the RA preamble was transmitted by the UE (i.e., the radio frame of any PRACH occasion in which the RA preamble was transmitted by the UE), the UE considers the RAR to have been successfully received in operation 454.

[0091] If the RAR is deemed to have been successfully received and such MAC subPDU contains only RAPID, the UE shall consider this as an acknowledgment to the SI request.

[0092] UE processing with second MAC PDU format:

[0093] In operation 462, the UE processes the MAC subPDUs in the RAR MAC PDU until the RAR is successfully received or no more MAC subPDUs remain.

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

[0095] If the MAC subPDU contains a MAC subheader with RAPID and RAPID matches the RA preamble sent by the UE, the UE considers the RAR to have been successfully received in operation 464. If the RAR is considered to have been successfully received and such MAC subPDU contains only RAPID, the UE considers this as an acknowledgment to the SI request.

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

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

[0098] gNB operation:

[0099] FIG. 5 illustrates gNB operation according to one embodiment of the present disclosure.

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

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

[0102] To generate an RAR MAC PDU according to the second RAR MAC PDU format, if a backoff indication needs to be transmitted in the RAR MAC PDU, the gNB includes a first MAC subPDU, which is configured with a MAC subheader having only a BI in operation 542. The gNB includes one or more MAC subPDUs in operation 543, each of which includes a MAC subheader having only a RAPID or a MAC subheader having a RAPID and a MAC RAR.

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

[0104] In another embodiment, the gNB receives one or more RA preambles and determines whether an RAR window size greater than 10 ms is configured for the cell in which the RAR is to be transmitted. If the configured RAR window size is greater than 10 ms, the gNB generates an RAR MAC PDU for transmission according to a first RAR MAC PDU format. If the configured RAR window size is less than 10 ms, the gNB generates an RAR MAC PDU for transmission according to a second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU. In this embodiment, detailed gNB operations for generating an RAR MAC PDU after determining the first or second RAR MAC PDU format are as described in FIG. 5.

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

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

[0107] The advantage of the first RAR MAC PDU format as started in this way is that the frame identifier can be applied to both the MAC subPDU containing the RAR and the MAC subPDU containing the SI request acknowledgment. The frame identifier can also be applied to the MAC subPDU containing the BI. There is little overhead because the frame identifier is added only once per RAR MAC PDU. The disadvantage is that the frame identifier must always be included in the RAR MAC PDU.

[0108] Method 2:

[0109] In a second method of the present invention for transmitting and receiving frame information in RAR, a UE / gNB transmits and receives an RAR MAC PDU, where the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0110] 1st RAR MAC PDU format:

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

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

[0113] -MAC subheader with only the frame identifier;

[0114] -MAC subheader with only backoff indicator;

[0115] -MAC subheader with only RAPID (i.e., acknowledgment to SI request);

[0116] -MAC subheader with RAPID and MAC RAR.

[0117] The Frame Identifier MAC subheader contains E, T, R1, and a frame identifier (FRAME ID). It can also contain 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; if the frame identifier is 3 bits long, there are two R bits. The frame identifier can be one of the following:

[0118] -Frame Identifier = SFN

[0119] -Frame identifier = SFN module (maximum supported RAR window size in radio frames)

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

[0121] Frame identifier = 'p' least significant bits of SFN, where 'p' may be predefined or equal to log2 (maximum RAR window size in radio frame) or log2 (RAR window size set in radio frame).

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

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

[0124] A MAC subheader with a backoff indicator consists of five header fields: E / T / R1 / R / BI. A MAC subheader with a frame identifier consists of at least four header fields: E / T / R1 / FRAME ID. The T bit is set to the same value (e.g., T is set to 0) for a MAC subheader with a backoff indicator and a MAC subheader with a frame identifier. The R1 bit is set to a different value to distinguish between a MAC subheader with a backoff indicator and a MAC subheader with a frame identifier (e.g., R1 is set to 0 in a MAC subheader with a backoff indicator, and R1 is set to '1' in a MAC subheader with a frame identifier).

[0125] 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 padding is implied 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.

[0126] An 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. An E field set to '1' in the MAC subheader of a MAC subPDU indicates that at least another MAC subPDU follows.

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

[0128] Example 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. A 'MAC subPDU with only RAPID' and a 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the second MAC subPDU and padding (if any) if a backoff indication is included in the MAC PDU. A 'MAC subPDU with only RAPID' and a 'MAC subPDU with RAPID and MAC RAR' can be placed anywhere between the first MAC subPDU and padding (if any) if a backoff indication is not included in the MAC PDU. This has the advantage that the UE can acquire the frame identifier before processing any MAC subPDU, and the frame identifier can be applied to each MAC subPDU.

[0129] Example 3: A MAC subPDU containing only a backoff indicator, if included, is placed at the beginning of a MAC PDU. A MAC subPDU containing only a frame identifier is placed before the first MAC subPDU containing RAPID and MAC RAR. A 'MAC subPDU containing only RAPID' can be placed anywhere between the second MAC subPDU and padding (if present) if a backoff indication is included in the MAC PDU. A 'MAC subPDU containing only RAPID' can be placed anywhere between the first MAC subPDU and padding (if present) if a backoff indication is not included in the MAC PDU. A 'MAC subPDU containing RAPID and MAC RAR' is placed after the MAC subPDU carrying the frame identifier and before padding (if present). This has the advantages that the UE can acquire the frame identifier before processing the MAC subPDU carrying RAPID and MAC RAR; the UE can acquire the backoff indicator without further processing the frame identifier; and the UE can acquire the MAC subPDU containing only RAPID without further processing the frame identifier. The gNB may transmit a RAR MAC PDU having only a backoff indicator without including a MAC subPDU having a frame identifier; the gNB may transmit a MAC subPDU having only a RAR MAC PDU with a backoff indication and / or a RAPID without including a MAC subPDU having a frame identifier.

[0130] 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 containing the RAR and the MAC subPDU containing the SI request acknowledgment. Since the frame identifier is added to each RAR MAC PDU, overhead is reduced. The frame identifier does not always need to be included in the RAR MAC PDU. It can be skipped when only the RAR MAC PDU contains a BI. In one embodiment, it can also be skipped if the RAR MAC PDU does not contain any MAC RAR. Additionally, this approach is advantageous for UE implementation because the MAC subheader structures for the first and second RAR MAC PDU formats are similar, reducing implementation complexity.

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

[0132] UE behavior:

[0133] Example 1:

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

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

[0136] While processing the RAR MAC PDU according to the first 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 in operation 751. If the first MAC subPDU of the RAR MAC PDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to the backoff value indicated by the BI field of the MAC subPDU multiplied by SCALING_FACTOR_BI in operation 752. If the MAC subPDU of the RAR MAC PDU includes a frame identifier, the UE processes the MAC subPDU and obtains the frame identifier from the MAC subheader of the MAC subPDU in operation 753. If the MAC subPDU includes a MAC subheader with RAPID, and RAPID matches the RA preamble transmitted by the UE, and the frame identifier obtained from the other MAC subPDUs corresponds to the radio frame of the PRACH occasion in which the RA preamble was transmitted by the UE, the UE considers the RAR to be successfully received in operation 754. If the RAR is deemed to have been successfully received and such MAC subPDU contains only RAPID, the UE shall consider this as an acknowledgment to the SI request.

[0137] While processing the RAR MAC PDU according to the second 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 in operation 761. If the first MAC subPDU of the RAR MAC PDU contains a backoff indicator, the UE sets PREAMBLE_BACKOFF to the backoff value indicated by the BI field of the MAC subPDU multiplied by SCALING_FACTOR_BI in operation 762. If the MAC subPDU contains a MAC subheader with RAPID and RAPID matches the RA preamble sent by the UE, the UE considers the RAR to be successfully received in operation 764. If the RAR is considered to be successfully received and such MAC subPDU contains only RAPID, the UE considers this as an acknowledgment for the SI request.

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

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

[0140] According to the first RAR MAC PDU format, the T bit is set to the same value (e.g., T is set to 0) for the MAC subheader with a back-off indicator and the MAC subheader with a frame identifier. Therefore, while processing an RAR MAC PDU according to the first MAC PDU format, the UE checks the R1 bit to determine whether the MAC subheader includes a BI or a frame identifier. The R1 bit is set to different values ​​to distinguish between the MAC subheader with a back-off indicator and the MAC subheader with a frame identifier (e.g., R1 is set to 0 for the MAC subheader with a back-off indicator, and R1 is set to '1' for the MAC subheader with a frame identifier). In one embodiment, while processing the RAR MAC PDU according to the first RAR MAC PDU format, the UE determines whether the MAC subheader in the MAC subPDU is a BI subheader, a frame identifier subheader, or a RAPID subheader, where 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 one 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.

[0141] gNB operation:

[0142] FIG. 8 illustrates gNB operation according to another embodiment of the present disclosure.

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

[0144] While generating the RAR MAC PDU according to the first RAR MAC PDU format, if a backoff indication needs to be transmitted in the RAR MAC PDU, the gNB includes a first or second MAC subPDU in the RAR MAC PDU in operation 831, where the first or second MAC subPDU is configured with a MAC subheader having only a BI. The gNB includes a first or second MAC subPDU in the RAR MAC PDU in operation 832, where the first or second MAC subPDU is configured with a MAC subheader having only a frame identifier. The gNB includes one or more MAC subPDUs in the RAR MAC PDU in operation 833, where each MAC subPDU includes a MAC subheader having only RAPID or a MAC subheader having RAPID and MAC RAR. Each such MAC subPDU corresponds to an RA preamble received by the gNB on a PRACH occasion starting with the radio frame in which the frame identifier is included in the first MAC subPDU.

[0145] While generating the RAR MAC PDU according to the second RAR MAC PDU format, if a backoff indication needs to be transmitted in the RAR MAC PDU, the gNB includes a first MAC subPDU, which is configured with a MAC subheader having only BI in operation 841. The gNB includes one or more MAC subPDUs in operation 843, each MAC subPDU including a MAC subheader having only RAPID or a MAC subheader having RAPID and MAC RAR.

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

[0147] Alternatively, the detailed operation of this embodiment may be as shown in Figure 5. While generating an RAR MAC PDU according to the first MAC PDU format, the T bit is set to the same value (e.g., T is set to 0) for the MAC subheader with the back-off indicator and the MAC subheader with the frame identifier. The R1 bit is set to different values ​​to distinguish between the MAC subheader with the back-off indicator and the MAC subheader with the frame identifier (e.g., R1 is set to 0 for the MAC subheader with the back-off indicator and R1 is set to '1' for the MAC subheader with the frame identifier). In one embodiment, while generating an RAR MAC PDU according to the first RAR MAC PDU format, the gNB sets T=0 and R1=0 for the BI MAC subheader; sets T=0 and R1=1 for the frame identifier MAC subheader; and sets T=1 for the RAPID MAC subheader. In one embodiment, while generating an 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.

[0148] In another embodiment, the gNB receives one or more RA preambles and determines whether an RAR window size greater than 10 ms is configured for the cell in which the RAR is to be transmitted. If the configured RAR window size is greater than 10 ms, the gNB generates an RAR MAC PDU for transmission according to a first RAR MAC PDU format. If the configured RAR window size is less than 10 ms, the gNB generates an RAR MAC PDU for transmission according to a second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU. Detailed gNB operations for generating an RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described with reference to FIG. 8. Alternatively, detailed gNB operations for generating an RAR MAC PDU after determining the first or second RAR MAC PDU format in this embodiment are as described with reference to FIG. 5. When generating a 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 a back-off indicator and the MAC subheader with a frame identifier. The R1 bit is set to different values ​​to distinguish between the MAC subheader with a back-off indicator and the MAC subheader with a frame identifier (e.g., R1 is set to 0 in the MAC subheader with a back-off indicator and R1 is set to '1' in the MAC subheader with a frame identifier). In one embodiment, when generating a 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 one embodiment, when generating a 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.

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

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

[0151] Method 3:

[0152] A third method disclosed herein for transmitting and receiving frame information in RAR, in which a UE / gNB transmits and receives an RAR MAC PDU, where the RAR MAC PDU is one of a first RAR MAC PDU format and a second RAR MAC PDU format.

[0153] 1st RAR MAC PDU format :

[0154] 9 shows an example of an RAR MAC PDU based on the first RAR MAC PDU format according to another embodiment of the present disclosure. For illustrative purposes, the Frame ID is assumed to be 3 bits in FIG. 9, which corresponds to a maximum RAR window size of 80 ms.

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

[0156] -MAC subheader with only the frame identifier;

[0157] -MAC subheader with only backoff indicator;

[0158] -MAC subheader with only RAPID (i.e., acknowledgment to SI request);

[0159] -MAC subheader with RAPID and MAC RAR.

[0160] Frame Identifier The MAC subheader contains E, T, and a frame identifier (FRAME ID). It can also contain 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 can be one of the following:

[0161] -Frame Identifier = SFN

[0162] -Frame identifier = SFN module (maximum supported RAR window size in radio frames)

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

[0164] Frame identifier = 'p' least significant bits of SFN, where 'p' may be predefined or may be equal to log2 (maximum RAR window size in the wireless frame) or log2 (RAR window size set in the wireless frame).

[0165] SFN is the system frame number of the radio frame of the PRACH occasion or the system frame number of the radio frame in which the PRACH occasion begins.

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

[0167] A MAC subheader with a backoff indicator consists of five header fields: E / T / R / R / BI. A MAC subheader with a frame identifier consists of at least three header fields: E / T / FRAME ID. The T bit is set to the same value (e.g., T is equal to 0) for a MAC subheader with a backoff indicator and a MAC subheader with a frame identifier. If there is only one MAC subPDU containing a subheader with T=0 in an RAR MAC PDU, the subheader is a frame identifier subheader. If there are two MAC subPDUs containing a subheader with T=0, the first MAC subPDU is for the BI and the second MAC subPDU is for the frame identifier.

[0168] 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 padding is implied 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.

[0169] An 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. An E field set to '1' in the MAC subheader of a MAC subPDU indicates that at least another MAC subPDU follows.

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

[0171] The advantage of the first RAR MAC PDU format implemented in this way is that the frame identifier can be applied to both the MAC subPDU containing the RAR and the MAC subPDU containing the SI request acknowledgment. Since the frame identifier is added only to the RAR MAC PDU, overhead is reduced. The frame identifier does not always need to be included in the RAR MAC PDU. It can be skipped when only the RAR MAC PDU contains a BI. Additionally, this approach is advantageous for UE implementation because the MAC subheader structures for the first and second RAR MAC PDU formats are similar, reducing implementation complexity.

[0172] Second RAR MAC PDU format: In the method of the present disclosure, the RAR MAC PDU in the second (ie, regular) RAR MAC PDU format is the same as in Method 1.

[0173] UE behavior:

[0174] Example 1:

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

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

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

[0178] While processing the RAR MAC PDU according to the second 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 in operation 1061. If the first MAC subPDU of the RAR MAC PDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to the backoff value indicated by the BI field of the MAC subPDU multiplied by SCALING_FACTOR_BI in operation 1062. If the MAC subPDU includes a MAC subheader with RAPID and RAPID matches the RA preamble sent by the UE, the UE considers the RAR to be successfully received in operation 1064. If the RAR is considered to be successfully received and such MAC subPDU contains only RAPID, the UE considers this as an acknowledgment for 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 the MAC subheader is a BI subheader when T=0, and determines that the MAC subheader is a RAPID subheader when T=1.

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

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

[0181] gNB operation:

[0182] FIG. 11 illustrates gNB operation according to one embodiment of the present disclosure.

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

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

[0185] While generating the RAR MAC PDU according to the first RAR MAC PDU format, a MAC subPDU having only a back-off indicator, if included, is placed at the beginning of the MAC PDU, i.e., the first MAC subPDU includes a BI. A MAC subPDU having a frame identifier is a second MAC subPDU if the first MAC subPDU includes a BI. If a back-off indication needs to be transmitted in the RAR MAC PDU, the gNB includes the first MAC subPDU in the RAR MAC PDU in operation 1131, where the first MAC subPDU is configured with a MAC subheader having only a BI. The gNB further includes a second MAC subPDU in the RAR MAC PDU, where the second MAC subPDU is configured with a MAC subheader having only a frame identifier. If a back-off indication does not need to be transmitted in the RAR MAC PDU, the gNB includes the first MAC subPDU in the RAR MAC PDU in operation 1132, where the first MAC subPDU is configured with a MAC subheader having only a BI. The gNB includes one or more MAC subPDUs in the RAR MAC PDU in operation 1133, each MAC subPDU including a MAC subheader with only RAPID or a MAC subheader with RAPID and MAC RAR, each such MAC subPDU corresponding to an RA preamble received by the gNB on a PRACH occasion starting in a radio frame whose frame identifier is included in the first MAC subPDU.

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

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

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

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

[0190] Method 4:

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

[0192] 1st RAR MAC PDU format:

[0193] 12 illustrates an example of an RAR MAC PDU based on the first RAR MAC PDU format according to one embodiment of the present disclosure. For illustrative purposes, the Frame ID is assumed to be 3 bits in FIG. 12, which corresponds to a maximum RAR window size of 80 ms.

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

[0195] -MAC subheader with only backoff indicator;

[0196] -MAC subheader with only RAPID and FRAME ID (i.e., acknowledgment to SI request);

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

[0198] The RAPID MAC subheader contains E, T, RAPID, and a frame identifier (FRAME ID). It can also contain one or more R bits depending on the number of bits defined for the frame identifier. 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 can be one of the following:

[0199] -Frame Identifier = SFN

[0200] -Frame identifier = SFN module (maximum supported RAR window size in radio frames)

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

[0202] Frame identifier = 'p' least significant bits of SFN, where 'p' may be predefined or may be equal to log2 (maximum RAR window size in the wireless frame) or log2 (RAR window size set in the wireless frame).

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

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

[0205] The MAC subheader with backoff indicator consists of five header fields: E / T / R / R / BI.

[0206] A MAC subheader containing only RAPID and FRAME ID consists of at least four header fields: E / T / RAPID / FRAME ID. It can also contain one or more R bits depending on the number of bits defined for FRAME ID. Padding, if present, is placed at the end of the MAC PDU. The presence and length of padding is implied based on the TB size and the size of the MAC subPDU.

[0207] A MAC subPDU with only a back-off indicator, if included, is placed at the beginning of the MAC PDU. A 'MAC subPDU with only RAPID' and a 'MAC subPDU with RAID and MAC RAR' can be placed anywhere between the second MAC subPDU and padding (if any) if a back-off indication is included in the MAC PDU. A 'MAC subPDU with only RAPID' and a 'MAC subPDU with RAID and MAC RAR' can be placed anywhere between the first MAC subPDU and padding (if any) if a back-off indication is not included in the MAC PDU.

[0208] An 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. An E field set to '1' in the MAC subheader of a MAC subPDU indicates that at least another MAC subPDU follows.

[0209] This approach is advantageous for UE implementation because the MAC subheader structures for the first and second RAR MAC PDU formats are similar, reducing implementation complexity, and the number of MAC subheaders is not further increased with this approach.

[0210] Second RAR MAC PDU format: In the method of the present disclosure, the RAR MAC PDU in the second (ie, regular) RAR MAC PDU format is the same as in Method 1.

[0211] UE behavior:

[0212] Example 1:

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

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

[0215] While processing the RAR MAC PDU according to the first 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 in operation 1351. If the first MAC subPDU of the RAR MAC PDU includes a backoff indicator, the UE sets PREAMBLE_BACKOFF to the backoff value indicated by the BI field of the MAC subPDU multiplied by SCALING_FACTOR_BI in operation 1352. If the MAC subPDU includes a MAC subheader with RAPID and FRAME ID, where RAPID matches the RA preamble sent by the UE and the FRAME ID corresponds to the radio frame of the PRACH occasion in which the RA preamble was sent by the UE, the UE considers the RAR to be successfully received in operation 1353. If the RAR is considered to be successfully received and such MAC subPDU includes only RAPID, the UE considers it an acknowledgment for the SI request.

[0216] While processing the RAR MAC PDU according to the second 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 in operation 1361. If the first MAC subPDU of the RAR MAC PDU contains a backoff indicator, the UE sets PREAMBLE_BACKOFF to the backoff value indicated by the BI field of the MAC subPDU multiplied by SCALING_FACTOR_BI in operation 1362. If the MAC subPDU contains a MAC subheader with RAPID and RAPID matches the RA preamble sent by the UE, the UE considers the RAR to be successfully received in operation 1363. If the RAR is considered to be successfully received and such MAC subPDU contains only RAPID, the UE considers this as an acknowledgment for the SI request.

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

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

[0219] gNB operation:

[0220] FIG. 14 illustrates gNB operation according to one embodiment of the present disclosure.

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

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

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

[0224] While generating the RAR MAC PDU according to the second RAR MAC PDU format, if a backoff indication needs to be transmitted in the RAR MAC PDU, the gNB includes a first MAC subPDU, which is configured with a MAC subheader having only BI in operation 1441. The gNB includes one or more MAC subPDUs in operation 1442, each MAC subPDU including a MAC subheader having only RAPID or a MAC subheader having RAPID and MAC RAR.

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

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

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

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

[0229] Method 5:

[0230] In the present invention, a method for transmitting and receiving frame information in RAR is proposed that defines 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). It can further 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 three R bits. The frame identifier can be one of the following:

[0231] -Frame Identifier = SFN

[0232] -Frame identifier = SFN module (maximum supported RAR window size in radio frames)

[0233] -Frame identifier = SFN module (RAR window size set in radio frame)

[0234] Frame identifier = 'p' least significant bits of SFN, where 'p' may be predefined or may be equal to log2 (maximum RAR window size in the wireless frame) or log2 (RAR window size set in the wireless frame).

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

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

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

[0238] 1st RAR MAC PDU format:

[0239] In the disclosed method, a RAR MAC PDU is composed of one or more MAC subPDUs and, optionally, padding, where each MAC subPDU is composed of either:

[0240] -MAC subheader with only the frame identifier;

[0241] -MAC subheader with only backoff indicator;

[0242] -MAC subheader with only RAPID (i.e., acknowledgment to SI request);

[0243] -MAC subheader with RAPID and MAC RAR;

[0244] - MAC subheader indicating padding.

[0245] The MAC subheader with backoff indicator consists of four header fields: T / R / R / BI.

[0246] The MAC subheader with frame identifier consists of at least two header fields: T / FRAME ID.

[0247] 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 padding is implied based on the TB size and the size of the MAC subPDU.

[0248] The MAC subheader for padding consists of T / R / R / R / R / R / R. The 2-bit type field distinguishes between BI, frame identifier, RAPID, and padding subheaders.

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

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

[0251] Second RAR MAC PDU format: In the method of the present disclosure, the RAR MAC PDU in the second (ie, regular) RAR MAC PDU format is the same as in Method 1.

[0252] UE behavior: In one embodiment, the UE transmits an RA preamble, monitors the PDCCH to receive an RAR, and receives an RAR MAC PDU. The UE determines whether the cell for which the UE monitors the PDCCH to receive an 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 a licensed 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 band, the cell is an unlicensed cell. Otherwise, the cell is a licensed cell. In one embodiment, the UE operation is as shown in FIG. 7.

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

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

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

[0256] In another embodiment, the gNB receives one or more RA preambles and determines whether an RAR window size greater than 10 ms is configured for the cell in which the RAR is to be transmitted. If the configured RAR window size is greater than 10 ms, the gNB generates an RAR MAC PDU for transmission according to a first RAR MAC PDU format. If the configured RAR window size is less than 10 ms, the gNB generates an RAR MAC PDU for transmission according to a second RAR MAC PDU format. The gNB then transmits the generated RAR MAC PDU.

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

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

[0259] How to handle authorized transmissions configured on unlicensed carriers

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

[0261] Category 1: No LBT

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

[0263] Category 2: LBT without random backoff

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

[0265] Category 3: LBT with random backoff in a fixed-size contention window

[0266] The UE transmits after detecting the channel as idle for a slot period of the delay period (Td); then, the counter is 0 in step 4. The detailed procedure is as follows.

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

[0268] [Table 1]

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

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

[0271] Step 5: Detect the channel for an additional delay period Td slot period. The delay period (Td) is T f +m p ×Ts, where Tf is like 16us and Ts is like 9us.

[0272] Step 6: If the channel is detected to be idle for Td, proceed to step 2. Otherwise, proceed to step 5.

[0273] Category 4: LBT with random backoff in variable-sized contention windows

[0274] The LBT procedure has the following as one of its components: The transmitting entity draws a random number N within a contention window. The size of the contention window is specified by the minimum and maximum values ​​of N. The transmitting entity can change the size of the contention window when drawing the random number N. The random number N is used in the LBT procedure to determine the period of time that the channel is detected as idle before the transmitting entity transmits on the channel. The detailed procedure is identical to Category 3. The only difference is that in Category 3 the size of the contention window is fixed, but in Category 4 the transmitting entity can change the size of the contention window when drawing the random number N. For UL transmissions, Category 4 is also referred to as the Type 1 channel access procedure.

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

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

[0277] Type 1: RRC directly provides configured UL authorization (including period).

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

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

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

[0281] One problem with this design of selecting CAPCs for UL-established approval is that data corresponding to the lowest CAPC (ie, highest priority) will be given low priority.

[0282] FIG. 15 is an exemplary diagram of a design for selecting a CAPC for UL-established approval in the related art.

[0283] Referring to Figure 15, according to the related art, even if a very small amount of data corresponds to such a CAPC in the MAC PDU, CAPC4 is selected for channel access. Selecting the lowest CAPC index (i.e., the highest priority CAPC) of the LCHs multiplexed into the MAC PDU is not necessarily a good idea. A very small amount of data in the MAC PDU may belong to the lowest CAPC index. Therefore, some method is needed to improve the current design.

[0284] Method 1:

[0285] In NR, a MAC PDU consists of one or more MAC subPDUs. Each MAC subPDU consists of one of the following: a MAC subheader only (including padding); a MAC subheader and a MAC service data unit (SDU); a MAC subheader and a MAC CE; or a MAC subheader and padding. The size of a MAC SDU varies. Each MAC subheader corresponds to a MAC SDU, a MAC CE, or padding. Except for MAC SDUs with a fixed size that include a MAC CE, padding, and a UL common control channel (CCCH), a MAC subheader consists of four header fields: R / F / LCID / L. The MAC subheader for a MAC SDU with a fixed size that includes a MAC CE, padding, and a UL CCCH consists of two header fields: R / LCID.

[0286] 16 illustrates CAPC selection for UL transmission according to one embodiment of the present disclosure. In one embodiment, this method is applied for UL transmission with configured grants.

[0287] 16, to determine the CAPC to be used for UL transmission of a MAC PDU, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU in operation 1610. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU excluding the MAC subPDUs carrying padding. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU excluding the MAC subPDUs carrying padding, the MAC subPDUs carrying padding BSR, and the MAC subPDUs carrying the recommended bit rate MAC CE.

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

[0289] For a MAC subPDU that includes a MAC CE, the CAPC is the CAPC of the MAC CE included in that MAC subPDU. The MAC CE excluding the padding BSR and the recommended bit rate uses the highest priority CAPC (i.e., the lowest CAPC index). The padding BSR and the recommended bit rate MAC CE uses the lowest priority CAPC (i.e., the highest CAPC index).

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

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

[0292] FIG. 17 is an example diagram of a MAC PDU transmitted with UL grant upon channel access (using an LBT procedure with CAPC) according to one embodiment of the present disclosure.

[0293] 17, the values ​​of 'X' calculated by the above method are 0.3, 0.4, and 0.3 for CAPC2, 3, and CAPC4, respectively. Therefore, the UE selects CAPC3, which corresponds to the highest value of X, i.e., 0.4.

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

[0295] 18, to determine the CAPC to be used for UL transmission of a MAC PDU, the UE first determines the CAPC of the MAC SDUs and MAC CEs multiplexed in the MAC PDU in operation 1810. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC SDUs and MAC CEs multiplexed in the MAC PDU excluding 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 SDUs.

[0296] 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 the DRB. The LCHs corresponding to the signaling radio bearers SRB0, SRB1, and SRB3 use the highest priority CAPC, while the CAPC for SRB2 is configured by the gNB via an RRC message.

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

[0298] Operation 1820: The UE then calculates a 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, which may be bytes or bits in operation 1820.

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

[0300] The advantage of the first method is that the CAPC that occupies the largest portion of the UL authorization will have better channel access dominance than the legacy method in which the CAPC with the lowest priority is always selected.

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

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

[0303] In another embodiment, the specific LCHs are LCHs for signaling radio bearers SRB 0, SRB 1, and SRB 3. If any of the SRB 0, SRB 1, and SRB 3 MAC SDUs are included in the MAC PDU, the UE selects the lowest CAPC index (i.e., highest priority) of the LCHs / MAC CEs multiplexed in the MAC PDU.

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

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

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

[0307] In another embodiment, the specific LCH is one or more MAC CEs. The one or more MAC CEs to which the rule applies may be predefined.

[0308] Method 2:

[0309] In NR, a MAC PDU consists of one or more MAC subPDUs. Each MAC subPDU consists of one of the following: a MAC subheader only (including padding); a MAC subheader and a MAC SDU; a MAC subheader and a MAC CE; or a MAC subheader and padding. The size of the MAC SDU varies. Each MAC subheader corresponds to a MAC SDU, a MAC CE, or padding. Except for MAC SDUs with a fixed size that include a MAC CE, padding, and UL CCCH, a MAC subheader consists of four header fields: R / F / LCID / L. A MAC subheader for a MAC SDU with a fixed size that includes a MAC CE, padding, and UL CCCH consists of two header fields: R / LCID.

[0310] 19 illustrates CAPC selection for UL transmission according to one embodiment of the present disclosure. In one embodiment, this method is applied for UL transmission with a configured grant.

[0311] 19, to determine the CAPC to be used for UL transmission of a MAC PDU, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU in operation 1910. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU excluding the MAC subPDUs carrying padding. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC subPDUs multiplexed in the MAC PDU excluding the MAC subPDUs carrying padding, the MAC subPDUs carrying padding BSR, and the MAC subPDUs carrying the recommended bit rate.

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

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

[0314] Operation 1920: The UE then calculates a parameter 'X' for each determined CAPC, where 'X' is equal to the total size of the MAC sub-PDUs for that CAPC / total size of the MAC PDU, in operation 1920. The size may be in number of bytes or bits. In one embodiment, the size of the MAC sub-PDU may not include the size of the MAC sub-header.

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

[0316] The gNB signals the threshold to the UE. The threshold can be common to all UL configured grants or configured separately for each UL configured grant. If a threshold is not configured, the UE selects the CAPC with the highest 'X' value. Alternatively, if a threshold is not configured, the UE selects the CAPC with the highest CAPC index (i.e., lowest priority) and does not need to perform operation 1920. Alternatively, if a threshold is not configured, the UE selects the CAPC with the lowest CAPC index (i.e., highest priority) and does not need to perform operation 1920.

[0317] FIG. 20 is an example diagram of a MAC PDU transmitted with UL grant using LBT Type 1 channel access according to one embodiment of the present disclosure.

[0318] 20, the values ​​of 'X' calculated by the above method are 0.2, 0.5, and 0.3 for CAPC2, CAPC4, and CAPC3, respectively. When the threshold value is 0.25, the UE selects a CAPC from CAPC3 and CAPC4. Since the lowest CAPC index among CAPC3 and CAPC4 is 3, the UE selects CAPC3.

[0319] 21 illustrates CAPC selection for UL transmission according to one embodiment of the present disclosure. In one embodiment, this method is applied for UL transmission with configured grants.

[0320] Operation 2110: Referring to Figure 21, to determine the CAPC to be used for UL transmission of a MAC PDU, the UE first determines the CAPC of the MAC SDUs and MAC CEs multiplexed in the MAC PDU in operation 2110. Alternatively, in another embodiment, the UE first determines the CAPC of the MAC SDUs and MAC CEs multiplexed in the MAC PDU excluding the padding BSR MAC CE and the recommended bit rate MAC CE.

[0321] 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 the DRB. The LCHs corresponding to the signaling radio bearers SRB0, SRB1, and SRB3 use the highest priority CAPC, while the CAPC for SRB2 is configured by the gNB via an RRC message.

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

[0323] Operation 2120: The UE then calculates a parameter 'X' for each determined CAPC, where 'X' is equal to [total size of MAC SDUs and / or MAC CEs for that CAPC] / total size of MAC PDUs, where size may be in number of bytes or bits in operation 2120.

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

[0325] The gNB signals the threshold to the UE. The threshold can be common to all UL configured grants or configured separately for each UL configured grant. If a threshold is not configured, the UE selects the CAPC with the highest 'X' value. Alternatively, if a threshold is not configured, the UE selects the CAPC with the highest CAPC index (i.e., lowest priority) and does not need to perform operation 2120. Alternatively, if a threshold is not configured, the UE selects the CAPC with the lowest CAPC index (i.e., highest priority) and does not need to perform operation 2120.

[0326] The advantage of this method is that among CAPCs that occupy a portion of the UL grant above the threshold, the highest priority CAPC will preempt channel access even if it does not occupy the largest portion of the UL grant.

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

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

[0329] In another embodiment, the specific LCHs are LCHs for signaling radio bearers SRB 0, SRB 1, and SRB 3. If any of the SRB 0, SRB 1, and SRB 3 MAC SDUs are included in the MAC PDU, the UE selects the lowest CAPC index (i.e., highest priority) of the LCHs / MAC CEs multiplexed in the MAC PDU.

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

[0331] In another embodiment, the specific LCH is one or more LCHs signaled by the gNB.

[0332] In another embodiment, the specific LCH is a MAC CE other than the padding BSR. If any MAC CE (other than the padding BSR) is included in the MAC PDU, the UE applies the rule.

[0333] In another embodiment, the specific LCH is one or more MAC CEs. The one or more MAC CEs to which the rule applies may be predefined.

[0334] Method 3:

[0335] In NR, a MAC PDU consists of one or more MAC subPDUs. Each MAC subPDU consists of one of the following: a MAC subheader only (including padding); a MAC subheader and a MAC SDU; a MAC subheader and a MAC CE; or a MAC subheader and padding. The size of the MAC SDU varies. Each MAC subheader corresponds to a MAC SDU, a MAC CE, or padding. Except for MAC SDUs with a fixed size that include a MAC CE, padding, and UL CCCH, a MAC subheader consists of four header fields: R / F / LCID / L. A MAC subheader for a MAC SDU with a fixed size that includes a MAC CE, padding, and UL CCCH consists of two header fields: R / LCID.

[0336] 22 illustrates CAPC selection for UL transmission according to one embodiment of the present disclosure. In one embodiment, this method is applied for UL transmission with a configured grant.

[0337] 22, the UE determines whether a specific LCH is multiplexed in the MAC PDU in operation 2210. If so, the UE applies rule 1, i.e., the UE selects the lowest CAPC index (i.e., highest priority) of the LCH / MAC CE multiplexed in the MAC PDU in operation 2220. If not, the UE applies rule 2, i.e., the UE selects the highest CAPC index (i.e., lowest priority) of the LCH / MAC CE multiplexed in the MAC PDU in operation 2230.

[0338] In one embodiment, the specific LCH is an LCH for a signaling radio bearer. If any of the SRB MAC SDUs is included in the MAC PDU, the UE applies rule 1. In other words, if any of the SRB MAC SDUs is included in the MAC PDU, the UE selects the CAPC index of the SRB with the lowest CAPC index (or the lowest CAPC index among the CAPC indexes of the SRBs whose MAC SDUs are included in the MAC PDU).

[0339] In another embodiment, the specific LCH is the LCH for the signaling 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 rule 1.

[0340] In another embodiment, the specific LCH is one or more LCHs for a signaling radio bearer. The one or more signaling radio bearers to which Rule 1 applies may be predefined.

[0341] In another embodiment, the specific LCH is one or more LCHs signaled by the gNB. Assume that the gNB signals LCH X and LCH Y to which the UE should apply Rule 1. If any of LCH X and LCH Y MAC SDUs is included in the MAC PDU, the UE applies Rule 1.

[0342] In another embodiment, the specific LCH is a MAC CE other than the padding BSR. If any MAC CE (other than the padding BSR) is included in the MAC PDU, the UE applies rule 1.

[0343] In another embodiment, the specific LCH is one or more MAC CEs. The one or more MAC CEs to which Rule 1 applies may be predefined.

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

[0345] Method 4:

[0346] In the method of the present disclosure, an improved multiplexing operation for UL transmissions is proposed. In one embodiment, the method is applied for UL transmissions with configured grants.

[0347] Action 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 such UL grant.

[0348] Action 2: The UE has data available for transmission and includes MAC SDUs from any other LCHs with a lower priority than the highest priority LCH among the LCHs allowed to use such UL grants in the MAC PDU only if the remaining available space in the MAC PDU is greater than a threshold value. The threshold value can be predefined or signaled by the gNB.

[0349] An exemplary UL authorization size is 1000 bytes.

[0350] LCH1, LCH2, and LCH3 can use such UL grants and have data available for transmission. If LCH1 is the highest priority, the UE includes LCH1 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 a threshold, the UE multiplexes LCH2 and / or LCH3 in the MAC PDU via LCP (LCH prioritization). Otherwise, only padding and / or padding BSR are included.

[0351] Method 5:

[0352] Example 1:

[0353] In the method of the present disclosure, an improved multiplexing operation for UL transmissions is proposed. In one embodiment, the method is applied for UL transmissions with configured grants.

[0354] Action 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 such UL grant.

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

[0356] An exemplary UL authorization size is 1000 bytes.

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

[0358] Example 2:

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

[0360] A MAC entity must do the following when a new transmission is made:

[0361] Primary selection criteria:

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

[0363] 2> The set of allowed SCS (Subcarrier Spacing) index values ​​in allowedSCS-List includes the SCS index associated with UL approval, if set;

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

[0365] 2> configuredGrantType1Allowed is set to true if the UL authorization is of configured authorization type 1;

[0366] 2> allowedServingCells, if set, contains cell information associated with UL authorization. It does not apply to LCHs associated with DRBs with packet data convergence protocol (PDCP) duplication within the same MAC entity (i.e., CA duplication) where PDCP duplication is deactivated.

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

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

[0369] allowedServingCells: If present in the LCH configuration received from the gNB, the UL MAC SDU from such an LCH can only be mapped to the serving cells listed in this list. Otherwise, the UL MAC SDU from such an LCH can be mapped to any configured serving cell in the LCH's cell group.

[0370] configureGrantType1Allowed: If present, UL MAC SDUs from such LCHs can be sent on configured grant type 1.

[0371] maxPUSCH-Duration: If present in the LCH configuration received from the gNB, UL MAC SDUs from such LCH can only be transmitted using UL grants whose PUSCH duration is shorter than the duration indicated by such field or which result in the same. Otherwise, UL MAC SDUs from such LCH can be transmitted using UL grants which result in any PUSCH duration.

[0372] Secondary selection criteria:

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

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

[0375] (alternative)

[0376] 1> If a new transmission is made for a configured UL grant on an unlicensed carrier and the highest priority LCH among the LCHs selected as described above belongs to the SRB (or a specific SRB can be predefined).

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

[0378] (alternative)

[0379] 1> If the new transmission is on an unlicensed carrier:

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

[0381] (alternative)

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

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

[0384] Resource allocation:

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

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

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

[0388] 2> Decrease Bj by the total size of the MAC SDU provided to LCH j mentioned above;

[0389] 2> If any resources remain, LCHs with the same priority must be served equally. All LCHs selected (according to the selection criteria described above) are served in a strict decreasing priority order (regardless of the Bj value) until the data for that LCH or UL authorization, whichever comes first, is exhausted. LCHs with the same priority must be served equally.

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

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

[0392] 1> Every instance of the LCP procedure before increments Bj by the product PBR XT, where T is the time elapsed since Bj was last incremented;

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

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

[0395] PBR and BSD are set by the gNB for each logic.

[0396] Method 6:

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

[0398] 1> Select an LCH (or an LCH with data available for transmission) for each UL authorization that meets all of the following conditions:

[0399] 2> The set of allowed SCS index values ​​in allowedSCS-List includes the SCS index associated with UL approval, if set;

[0400] 2> maxPUSCH-Duration, if configured, is greater than or equal to the PUSCH transmission duration associated with the UL grant;

[0401] 2> configuredGrantType1Allowed is set to true if the UL authorization is configured for authorization type 1;

[0402] 2> allowedServingCells, if set, contains cell information associated with UL authorization. It does not apply to LCHs associated with DRBs with PDCP duplication within the same MAC entity (i.e., CA duplication) where PDCP duplication is deactivated.

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

[0404] allowedSCS-List: If present in the LCH configuration received from the gNB, UL MAC SDUs from such LCH can only be mapped to the indicated numerology. Otherwise, UL MAC SDUs from such LCH can be mapped to any configured numerology.

[0405] allowedServingCells: If present in the LCH configuration received from the gNB, the UL MAC SDU from such an LCH can only be mapped to the serving cells listed in this list. Otherwise, the UL MAC SDU from such an LCH can be mapped to any configured serving cell in the LCH's cell group.

[0406] configureGrantType1Allowed: If present, UL MAC SDUs from such LCHs can be sent on configured grant type 1.

[0407] maxPUSCH-Duration: If present in the LCH configuration received from the gNB, UL MAC SDUs from such LCH can only be transmitted using UL grants whose PUSCH duration is shorter than the duration indicated by such field or which result in the same. Otherwise, UL MAC SDUs from such LCH can be transmitted using UL grants which result in any PUSCH duration.

[0408] Resource allocation:

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

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

[0411] LCHs selected (by the selection criteria described above) for UL approval of 2 > Bj > 0 are allocated resources in decreasing priority order, where resources are allocated to LCH j if one of the following conditions is met:

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

[0413] 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 authorizations is greater than the amount of UL authorizations already allocated.

[0414] If none of the LCHs have been allocated resources yet, then Z = highest CAPC index, otherwise Z = MAX (the CAPC index of all LCHs that have already been allocated UL approved resources).

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

[0416] 2> Decrease Bj by the total size of the MAC SDU provided to LCH j mentioned above;

[0417] 2> If any resources remain, LCHs with the same priority must be served equally. All LCHs selected (according to the selection criteria described above) are served in a strict decreasing priority order (regardless of the Bj value) until the data for that LCH or UL authorization, whichever comes first, is exhausted, where resources are allocated to LCH j if one of the following conditions is met:

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

[0419] 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 authorizations are greater than the amount of UL authorizations already allocated

[0420] If none of the LCHs have been allocated resources yet, then Z = highest CAPC index, otherwise Z = MAX (the CAPC index of all LCHs that have already been allocated UL approved resources).

[0421] FIG. 23 is an illustrative diagram according to an embodiment of the present disclosure.

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

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

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

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

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

[0427] -If the amount of data that can be included for the LCH in the remaining UL approval is > L1, does the LCH have a CAPC index Y such that Y > Max(X,X1);

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

[0429] RA procedure method to support large RAR window sizes

[0430] In 5G wireless communication systems operating in higher frequency (mmWave) bands, UEs and gNBs communicate with each other using beamforming. Beamforming technology is used to mitigate propagation path loss and increase the propagation distance for communication in higher frequency bands. Beamforming improves transmission and reception performance using high-gain antennas. Beamforming can be classified into transmit (TX) beamforming, which is performed at the transmitting end, and receive (RX) beamforming, which is performed at the receiving end. Generally, TX beamforming increases directivity by using multiple antennas to densely position the area where radio waves reach in a specific direction. In this situation, the aggregation of multiple antennas can be referred to as an antenna array, and each antenna included in the array can be referred to as an array element. Antenna arrays can be configured in various shapes, such as linear arrays and planar arrays. TX beamforming increases signal directionality and increases propagation distance. Furthermore, because signals are rarely transmitted in directions other than the directional direction, signal interference at other receiving ends 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 concentrating propagation in a specific direction, and eliminates signals transmitted in directions other than the specific direction from the RX signal, thereby blocking interference signals. Using beamforming techniques, the transmitter can create multiple transmit (TX) beam patterns in different directions. Each of these TX beam patterns can be further referred to as a TX beam. Wireless communication systems operating at high frequencies use multiple narrow TX beams to transmit signals within a cell, with each narrow TX beam providing coverage to a portion of the cell. The narrower the TX beam, the higher the antenna gain, and therefore the greater the radio wave distance of signals transmitted using beamforming. The receiver can also create multiple receive (RX) beam patterns in different directions.Each such RX beam pattern may further be referred to as an RX beam.

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

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

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

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

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

[0436] In a 5G wireless communication system, the PDCCH is used to schedule DL transmissions on a Physical Downlink Shared Channel (PDSCH) and UL transmissions on a PUSCH, where DL Control Information (DCI) on the PDCCH includes a DL assignment including at least a modulation and coding format, a resource assignment, and hybrid-automatic repeat request (HARQ) information for the DL-SCH; or an UL scheduling grant including at least a modulation and coding format, a resource assignment, and HARQ information for the UL-SCH. In addition to scheduling, the PDCCH can be used to activate and deactivate PUSCH transmissions configured for configured grants; activate and deactivate PDSCH semi-persistent transmissions; inform one or more UEs of slot formats; inform one or more UEs of physical resource blocks (PRBs) and orthogonal frequency division multiplexing (OFDM) symbols for which the UE can assume no transmission is intended; transmit TX power control (TPC) commands for the physical UL control channel (PUCCH) and PUSCH; transmit one or more TPC commands for semi-persistent scheduling (SRS) transmissions by one or more UEs; switch the UE's active bandwidth part (BWP); or initiate an RA procedure. A UE monitors a set of PDCCH candidates at configured monitoring occasions in one or more configured control resource sets (CORESETs) according to the corresponding search space configuration. A CORESET consists of a PRB set with a duration of one to three OFDM symbols. Resource units REG (Resource Element Groups) and CCE (Control Channel Element) are defined within a CORESET, where each CCE is configured in a REG set. A control channel is formed by an aggregation of CCEs.Different code rates for the control channel are achieved by aggregating different numbers of CCEs. Interleaved and non-interleaved CCE-REG mapping is supported in CORESET. Polar coding is used for the PDCCH. Each REG carrying a PDCCH carries its own demodulation reference signal (DMRS). Quadrature phase shift keying (QPSK) modulation is used for the PDCCH.

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

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

[0439] For each slot with a PDCCH monitoring occasion, the start symbol of the PDCCH monitoring occasion is given by Monitoring-symbols-PDCCH-within-slot. The length (symbols) of the PDCCH monitoring occasion is provided in the CORESET associated with the search space. The search space configuration includes the identifier of the CORESET configuration associated with it. A CORESET configuration list 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 the radio frame and the slot duration vary depending on the SCS. The number of slots in the radio frame and the slot duration by 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. One DL reference signal (RS) ID (SSB or channel state information (CSI) RS) is configured per TCI state. A list of TCI states corresponding to the CORESET configuration is signaled by the gNB via radio resource control (RRC) signaling. One of the TCI states in the TCI state list is activated and indicated to the UE by the gNB. The TCI state indicates the DL TX beam used by the gNB for PDCCH transmission in the PDCCH monitoring occasion of the search space (the DL TX beam is quasi-colocated with the SSB / CSI RS of the TCI state).

[0440] In 5G wireless communication systems, bandwidth adaptation (BA) is supported. With BA, the UE's transmission and reception bandwidth can be adjusted without being as large as the cell's bandwidth: the width can be instructed to change (e.g., to reduce it during periods of low activity to save power); the location can be moved in the frequency domain (e.g., to increase scheduling flexibility); and the SCS can be instructed to change (e.g., to accommodate different services). A subset of the cell's entire cell bandwidth is referred to as a BWP. BA is achieved by configuring a BWP for an RRC-connected UE and notifying the UE which of the configured BWPs is currently active. 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 all DL frequencies of the serving cell. In an RRC-connected state, the UE is configured with one or more DL and UL BWPs for each configured serving cell (i.e., PCell or SCell). For an activated serving cell, there is always one active UL and DL BWP at any given time. BWP conversion for a serving cell is used to activate an inactive BWP and deactivate an active BWP at the same time. BWP conversion is controlled by the PDCCH indicating DL allocation or UL grant, the bwp-InactivityTimer, RRC signaling, or the MAC entity itself when initiating an RA procedure. When an SpCell is attached or an SCell is activated, the DL BWP and UL BWP indicated by firstActiveDownlinkBWP-Id and firstActiveUplinkBWP-Id, respectively, are activated without receiving a PDCCH indicating DL allocation or UL grant. The active BWP for a serving cell is indicated by RRC or PDCCH. In the case of unpaired spectrum, the DL BWP is paired with the UL BWP, and BWP conversion is common to both UL and DL.When the BWP inactivity timer expires, the UE replaces the active DL BWP with the default DL BWP or the initial DL BWP (if the default DL BWP is not configured).

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

[0442] CBRA (contention-based RA): This is also called four-stage CBRA. In this type of RA, the UE first transmits an RA preamble (also called Message 1 (Msg1)) and then waits for an RAR in the RAR window. The RAR is also called Message 2 (Msg2). The gNB transmits the RAR on the PDSCH. The PDCCH that schedules the PDSCH carrying the RAR is addressed by the RA-Radio Network Temporary Identifier (RA-RNTI). The RA-RNTI identifies the time-frequency resource (also called the PRACH occasion, PRACH TX occasion, or RA channel (RACH) occasion (RO)) on which the RA preamble is detected by the gNB. The RA-RNTI is calculated as follows: RA-RNTI = 1 + s_id + 14 * t_id + 14 * 80 * f_id + 14 * 80 * 8 * ul_carrier_id, where s_id is the index of the first OFDM symbol of the PRACH occasion in which the UE transmitted Msg1, i.e., the RA preamble; 0 < s_id < 14; t_id is the index of the first slot of the PRACH occasion (0 < t_id < 80); f_id is the index of the PRACH occasion within the slot in the frequency domain (0 < f_id < 8); and ul_carrier_id is the UL carrier used to transmit Msg1 (0 for normal UL (NUL) carrier, 1 for auxiliary UL (SUL) carrier). Many RARs for various RA preambles detected by the gNB can be multiplexed by the gNB into the same RAR MAC PDU. If the RAR in the MAC PDU contains the RAPID of the RA preamble transmitted by the UE, it corresponds to the UE's RA preamble transmission. If the RAR corresponding to the RA preamble transmission is not received during the RAR window and the UE has not yet transmitted the RA preamble for a configurable number of times (configured by the gNB in ​​the RACH configuration), the UE returns to the first stage, i.e., selects an RA resource (preamble / RO) and transmits the RA preamble. A backoff may be applied before returning to the first stage.

[0443] When an RAR corresponding to the RA preamble transmission is received, the UE transmits message 3 (Msg3) with the UL acknowledgment received in the RAR. Msg3 includes messages such as an RRC connection request, an RRC connection reconfiguration request, an RRC handover confirmation, a scheduling request, an SI request, etc. It may include a UE identity (i.e., a C-RNTI or an S-TMSI (system architecture evolution (SAE)-temporary mobile subscriber identity), or a random number). After transmitting Msg3, the UE starts a contention resolution timer. If the UE receives a PDCCH addressed to the C-RNTI included in Msg3 while the contention resolution timer is running, the contention resolution is considered successful, the contention resolution timer is stopped, and the RA procedure is completed. If the UE receives a contention resolution MAC CE including the UE's contention resolution identity (the first Xth bit of the CCCH SDU sent in Msg3) while the contention resolution timer is running, the contention resolution is considered successful, the contention resolution timer is stopped, and the RA procedure is completed. If the contention resolution timer expires and the UE has not yet transmitted the RA preamble for a configurable number of times, the UE returns to stage 1, i.e., selects an RA resource (preamble / RO) and transmits the RA preamble. A backoff may be applied before returning to stage 1.

[0444] CFRA (Contention-Free RA): This is also called legacy CFRA or four-stage CFRA. The CFRA procedure is used in scenarios such as handovers that require low latency and timing advance (TA) configuration for SCells. The eNB (or gNB) allocates a dedicated RA preamble to the UE. The UE transmits the dedicated RA preamble. The eNB (or gNB) transmits an RAR on a PDSCH addressed to the RA-RNTI. The RAR carries an RA preamble identifier and timing alignment information. The RAR may further include a UL grant. The RAR is transmitted in an RAR window similar to the CBRA procedure. CFRA is considered to have been successfully completed after receiving an RAR containing the RAPID of the RA preamble transmitted by the UE. If an RA is initiated for beam failure recovery, CFRA is considered to have been 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 completed successfully and the UE has not yet transmitted the RA preamble for a configurable number of times (configured by the gNB in ​​the RACH configuration), the UE retransmits the RA preamble.

[0445] For certain events such as handover and beam failure recovery, if a dedicated preamble is assigned to the UE, during the first stage of RA, i.e., during RA resource selection for Msg1 transmission, the UE decides whether to transmit a dedicated preamble or a non-dedicated preamble. Dedicated preambles are generally provided for a subset of SSB / CSI RSs. If there is no SSB / CSI RS with a DL reference signal received power (RSRP) higher than a threshold among the SSB / CSI RSs for which a CFRA resource (i.e., a dedicated preamble / RO) is provided by the gNB, the UE selects a non-dedicated preamble. Otherwise, the UE selects a dedicated preamble. Therefore, during the RA procedure, one RA attempt may be CFRA, while another RA attempt may be CBRA.

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

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

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

[0449] problem After transmitting the first stage of 4-stage CBRA or CFRA, i.e., the RA preamble, the UE monitors the RAR in the configured RAR window. For an RAR window of up to 10 ms, if the UE receives a PDCCH addressed to the RA-RNTI and a successfully decoded TB scheduled by such PDCCH contains a RAPID that matches the RA preamble index of the transmitted RA preamble, the RAR is considered successful.

[0450] The cell from which the UE transmits the RA preamble may be a licensed or unlicensed carrier. If the carrier used for UL transmission is an unlicensed carrier, the UE must perform channel detection (i.e., listen-before-talk (LBT)) to determine whether the channel is free before transmitting Msg1 and Msg3 in the UL. Similarly, if the carrier used for DL ​​transmission is an unlicensed carrier, the gNB must perform channel detection (i.e., LBT) to determine whether the channel is free before transmitting Msg2 and Msg4 in the DL. The gNB may receive the RA preamble but be unable to transmit the RAR within the RAR window because the channel is not free. The UE will retransmit the PRACH when the RAR window expires. The retransmitted RA preamble may not be received by the gNB due to a collision, the UE may fail to retransmit the RA preamble, or the transmission may be delayed because the UL channel is not free. These issues can be avoided by using a larger RAR window size. However, a large RAR window size greater than 10 ms results in RA-RNTI imitation as shown in Figure 1. If UE1 and UE2 transmit PRACHs using the same RA preamble in their respective PRACH occasions X and Y, the RARs received in the common slots between RAR window X and RAR window Y cannot be distinguished because the RA-RNTI is the same for PRACH occasion X and PRACH occasion Y.

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

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

[0453] In the case of an extended RAR window, X LSBs of the SFN can be included in the DCI. Therefore, during reconfiguration in the synchronization procedure, the UE must first acquire the SFN of the target SpCell and then initiate an RA toward the target SpCell. Because 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 reconfiguration in the synchronization procedure. Therefore, a method is needed to reduce this delay.

[0454] Criteria for successful RAR reception for 4-stage CBRA and CFRA when RAR window size > 10 ms

[0455] Method 1:

[0456] FIG. 25 illustrates a method for a UE to perform an RA procedure according to one embodiment of the present disclosure.

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

[0458] The UE then checks whether the RA preamble transmitted in operation 2520 is selected from the CBRA preamble.

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

[0460] If a 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 a successfully decoded TB scheduled by such PDCCH includes a RAPID that matches the RA preamble index of the RA preamble transmitted in operation 2540, the RAR is considered to have been successfully received.

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

[0462] TA command in RAR: During the RA procedure, the UE sends a TA command (TA A ) is received. 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 to which the RA preamble is transmitted. The fact that it is received in the RAR means that N TA is used to determine where N TA =T A 16 64 / 2 μ .2 μ 15kHz is the SCS for the first UL transmission from the UE after receiving the RA response.

[0463] If the transmitted RA preamble is not selected from the CB RA preambles (i.e., it is a CF RA preamble), the UE monitors the PDCCH addressed to the C-RNTI in the RAR window in operation 2550. A contention-free preamble is dedicatedly assigned to the UE using an RRC signaling message.

[0464] If the UE receives a PDCCH addressed to a C-RNTI scheduling a DL TB and such DL TB includes an absolute TA command in operation 2560, the RAR is considered to have been successfully received. The absolute TA command may be included in the MAC CE.

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

[0466] Absolute TA command in TA MAC CE: FIG. 26 illustrates an absolute TA command MAC CE according to one 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 to which the RA is sent. The TAR received in the RAR A is N TA is used to determine where N TA =T A 16 64 / 2 μ .2 μ 15kHz is SCS UL BWP.

[0467] TA command in TA MAC CE: FIG. 27 illustrates a TA command MAC CE according to one embodiment of the present disclosure. A) can also be received via the TA command MAC CE. The length of the TA command received at the TA command MAC CE is 6 bits. A is T A = 0, 1, 2, ..., 63 are the index values ​​of the current N TA Value N TA_old New N TA Value N TA_new where 2 μ For 15kHz SCS, N TA_new =N TA_old +(T A -31)·16·64 / 2 μ 2 μ 15.2 μ 15kHz is SCS UL BWP.

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

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

[0470] Method 2:

[0471] FIG. 28 illustrates another method for a UE to perform an RA procedure according to one embodiment of the present disclosure.

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

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

[0474] If a 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 a successfully decoded TB scheduled by such PDCCH includes a RAPID that matches the RA preamble index of the RA preamble transmitted in operation 2830, the RAR is considered to have been successfully received.

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

[0476] TA command in RAR: During the RA procedure, the UE sends a TA command (TA A) is received. 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 to which the RA preamble is transmitted. The fact that it is received in the RAR indicates N TA is used to determine where N TA =T A 16 64 / 2 μ .2 μ · 15kHz is the SCS of the first UL transmission from the UE after receiving the RAR.

[0477] If the transmitted RA preamble is not selected from the CB RA preambles (i.e., it is a CF RA preamble) and such an RA procedure was initiated for reconfiguration in a synchronization procedure, the UE monitors the PDCCH addressed to the C-RNTI in the RAR window in operation 2840. A contention-free preamble is dedicatedly assigned to the UE using an RRC signaling message.

[0478] If the UE receives a PDCCH addressed to a C-RNTI scheduling a DL TB, and such DL TB includes an absolute TA command in operation 2850, the RAR is considered to be successfully received. The absolute TA command may be included in the MAC CE.

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

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

[0481] TA command in TA MAC CE (see Figure 27): TA command for a specific TAG (T A ) can also be received via the TA command MAC CE. The length of the TA command received at the TA command MAC CE is 6 bits. A is T A = 0, 1, 2, ..., 63 are the index values ​​of the current N TA Value N TA_old New N TA Value N TA_new where 2 μ For 15kHz SCS, N TA_new =N TA_old +(T A -31)·16·64 / 2 μ 2 μ 15.2 μ 15kHz is SCS UL BWP.

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

[0483] Method 3:

[0484] FIG. 29 illustrates another method for a UE to perform an RA procedure according to one embodiment of the present disclosure.

[0485] 29, after transmitting an RA preamble (also referred to as Msg1), the UE waits for an RAR in the RAR window in operation 2910. The RAR is also referred to as Msg2.

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

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

[0488] If a 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 a successfully decoded TB scheduled by such PDCCH includes a RAPID that matches the RA preamble index of the RA preamble transmitted in operation 2930, the RAR is considered to have been successfully received.

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

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

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

[0492] In one embodiment, the 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.

[0493] Method 4:

[0494] FIG. 30 illustrates another method for a UE to perform an RA procedure according to one embodiment of the present disclosure.

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

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

[0497] If the transmitted RA preamble is selected from the CB RA preamble or such RA procedure is not initiated for reconfiguration at synchronization (e.g., handover):

[0498] If a 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 a successfully decoded TB scheduled by such PDCCH includes a RAPID that matches the RA preamble index of the RA preamble transmitted in operation 3030, the RAR is considered to have been successfully received.

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

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

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

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

[0503] Method 5:

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

[0505] The network (ie, gnB) indicates whether the UE should perform action 1 or action 2.

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

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

[0508] The RRCReconfiguration message for reconfiguration through synchronization may include an indication to perform action 2. If there is no such indication in the RRCReconfiguration message, the UE shall perform action 1.

[0509] Method 6:

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

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

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

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

[0514] Method 7:

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

[0516] CAPC and configured approval process

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

[0518] Category 1: No LBT

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

[0520] Category 2: LBT without random backoff

[0521] The period during which the channel is sensed as idle before the transmitting entity transmits is crucial. For example, the sensing interval may be 25 us, i.e., the UE can transmit after sensing the channel as idle for at least the sensing interval Td = 25 us. For UL transmission, Category 3 is also referred to as Type 2 channel access procedure.

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

[0523] The LBT procedure has the following steps as one of 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 procedure to determine the period of time that the channel is detected to be idle before the transmitting entity transmits on the channel. The detailed Category 3 LBT procedure is as follows:

[0524] The UE transmits after detecting the channel as idle for a slot period of the delay period (Td); then, the counter is 0 in step 4. The detailed procedure is as follows:

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

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

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

[0528] Step 4: If N=0, then transmit; otherwise, go to step 2.

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

[0530] Step 6: If the channel is detected to be idle for Td, proceed to step 2. Otherwise, proceed to step 5.

[0531] Category 4: LBT with random backoff in variable-sized contention windows

[0532] 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 period of time that the channel is detected as idle before the transmitting entity transmits on the channel. The detailed procedure is identical to Category 3. The only difference is that in Category 3 the size of the contention window is fixed, but in Category 4 the transmitting entity can change the size of the contention window when drawing the random number N. For UL transmissions, Category 4 is also referred to as the Type 1 channel access procedure.

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

[0534] Type 1: RRC directly provides configured UL authorization (including period).

[0535] Type 2: The RRC defines the period of the configured UL grant, but the PDCCH addressed to the CS-RNTI can signal and activate or deactivate the configured UL grant; i.e., the PDCCH addressed to the CS-RNTI may be implicitly reused with a period defined by the RRC until the UL grant is deactivated.

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

[0537] For UL channel access using an exemplary LBT type 1 (i.e., Category 4 LBT) of the CAPC-based LBT procedure for a configured grant or MsgA payload transmission on a PUSCH in the case of a two-stage RACH, or for any UL transmission where the DCI does not include a CAPC, the UE must determine the CAPC. To do this, the gNB signals the CAPC for each LCH of the DRB. The padding BSR and MAC CE excluding the recommended bit rate use the highest priority CAPC (i.e., the lowest CAPC index). The padding BSR and MAC CE excluding the recommended bit rate use the lowest priority CAPC (i.e., the highest CAPC index). SRB0, SRB1, and SRB3 use the highest priority CAPC (i.e., the lowest CAPC index in Table 1), while the CAPC for SRB2 is configurable. The UE selects the highest CAPC index (i.e., the lowest priority CAPC) of the LCH with a MAC SDU multiplexed in the MAC PDU.

[0538] One problem with this design of selecting a CAPC for a UL-configured acknowledgement is that when multiplexed with other LCH MAC SDUs in a MAC PDU, the SRB data corresponding to the lowest CAPC (i.e., the highest priority) is given low priority. Therefore, some way to improve the current design is needed.

[0539] Method 1:

[0540] For a configured UL grant or MsgA payload transmission on the PUSCH in the case of a two-stage RACH, or for any UL transmission in which the DCI does not include CAPC, if a MAC SDU of a DCCH LCH is included in a MAC PDU on an unlicensed carrier (i.e., a serving cell operating in an unlicensed spectrum or frequency band) and a CAPC-based LBT procedure (e.g., LBT based on Category 3 or 4) is performed for channel access, the UE must not include any other MAC SDU of the LCH with a CAPC index higher than the CAPC index of the DCCH (i.e., the CAPC of the DCCH LCH in which the MAC SDU is included in the MAC PDU). If multiple MAC SDUs of DCCHs belonging to SRBs 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 DCCHs included in the MAC PDU.

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

[0542] In an alternative embodiment, for a configured UL grant or MsgA payload transmission on a PUSCH in the case of a two-stage RACH, or for any UL transmission in which the DCI does not include CAPC, if a MAC SDU of a DCCH LCH is included in a MAC PDU on an unlicensed carrier (i.e., a serving cell operating in an unlicensed spectrum or frequency band) and a CAPC-based LBT procedure (e.g., LBT based on Category 3 or 4) is performed for channel access, the UE must not include any other MAC SDU of an LCH other than the DCCH that has a CAPC index higher than the CAPC index of the DCCH (i.e., the CAPC of the DCCH LCH in which the MAC SDU is included in the MAC PDU). If multiple MAC SDUs of DCCHs belonging to SRBs 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 DCCHs included in the MAC PDU. For example, assume that SRB1 and SRB2 have CAPC index 1 and CAPC index 3, respectively, and if MAC SDUs of both SRB1 and SRB2 are included in a MAC PDU, the UE must not include any other MAC SDUs of the LCH with a CAPC index higher than 3.

[0543] In an alternative embodiment, for a configured UL grant or MsgA payload transmission on a PUSCH in the case of a two-stage RACH, or for any UL transmission in which the DCI does not include CAPC, if a MAC SDU of a DCCH LCH is included in a MAC PDU on an unlicensed carrier (i.e., a serving cell operating in an unlicensed spectrum or frequency band) and a CAPC-based LBT procedure (e.g., LBT based on Category 3 or 4) is performed for channel access, the UE must not include any other MAC SDU of an LCH other than the DCCH with a CAPC index higher than the CAPC index of the DCCH (i.e., the CAPC of the DCCH LCH in which the MAC SDU is included in the MAC PDU), and the UE must not include any MAC CE with a CAPC index higher than the CAPC index of the DCCH (i.e., the CAPC of the DCCH LCH in which the MAC SDU is included in the MAC PDU). If multiple MAC SDUs of DCCHs belonging to SRBs 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 DCCHs included in the MAC PDU. For example, assume that SRB1 and SRB2 have CAPC index 1 and CAPC index 3, respectively, and if the MAC SDUs of both SRB1 and SRB2 are included in a MAC PDU, the UE must not include any other MAC SDUs of the LCH with a CAPC index higher than 3, and the UE must not include any MAC CE with a CAPC index higher than 3.

[0544] Just because a configured UL authorization is for an unlicensed carrier does not mean that a CAPC-based LBT is performed by accessing the channel for transmission for such an UL authorization. Therefore, it is important for the UE to check whether a CAPC-based LBT procedure (e.g., LBT Category 3 / 4) applies. Various cases in which a CAPC-based LBT procedure (e.g., LBT Category 3 or 4) applies are described in detail in TS 38.889 and TS 38.213.

[0545] Method 2:

[0546] For a configured UL grant or a two-stage RACH, for an MsgA payload transmission on a PUSCH or any UL transmission where the DCI does not include CAPC, a CAPC-based LBT procedure (e.g., when LBT is based on Category 3 or 4) is performed for channel access on an unlicensed carrier (i.e., a serving cell operating in an unlicensed spectrum or frequency band). If a MAC SDU of a DCCH LCH is included in a MAC PDU, the UE selects a CAPC index for 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 a 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, assume that SRB1 and SRB2 have CAPC indexes 1 and 3, respectively. The MAC SDUs of SRB1 and SRB3 are included in a MAC PDU. Therefore, CAPC index 1 is selected, which is the lowest value 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.

[0547] Just because a configured UL authorization is for an unlicensed carrier does not mean that a CAPC-based LBT is performed by accessing the channel for transmission for such an UL authorization. Therefore, it is important for the UE to check whether a CAPC-based LBT procedure (e.g., LBT Category 3 / 4) applies. Various cases in which a CAPC-based LBT procedure (e.g., LBT Category 3 or 4) applies are described in detail in TS 38.889 and TS 38.213.

[0548] LBT failure handling

[0549] For LBT failure handling, the gNB signals the LBT-FailureRecoveryConfig IE in the RRC Reconfiguration message. The RRC Reconfiguration message is sent to the UE in the RRC CONNECTED state. The LBT-FailureRecoveryConfig IE is configured separately for the serving cell. The LBT-FailureRecoveryConfig IE includes the LBT-FailureInstanceMaxCount and LBT-FailureDetectionTimer parameters for consistent LBT failure detection. The RRC Reconfiguration message from the gNB is processed by the RRC layer of the UE. When the LBT-FailureRecoveryConfig is received from the gNB for a serving cell, the MAC entity of the serving cell performs a consistent LBT failure recovery procedure using the parameters configured in the LBT-FailureRecoveryConfig IE of the serving cell.

[0550] Consistent LBT failure is detected per UL BWP by counting LBT failure indications for all UL transmissions to the MAC entity at the lower layer (ie, physical layer).

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

[0552] For each activated serving cell with lbt-FailureRecoveryConfig set, the MAC entity shall:

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

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

[0555] 2> Increase LBT_COUNTER by 1;

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

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

[0558] 4> Declaring a consistent LBT failure for an active UL BWP;

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

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

[0561] 4> Declaring a consistent LBT failure for an active UL BWP;

[0562] 4> If a consistent LBT failure is declared in all UL BWPs with PRACH occasions configured in such a serving cell:

[0563] 5> Indicate a consistent LBT failure to a higher hierarchy.

[0564] 4> Otherwise:

[0565] 5> In such a serving cell, switching the active UL BWP to a UL BWP for which a PRACH occasion is set and a consistent LBT failure is not declared;

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

[0567] 5> Initiate the RA procedure.

[0568] 1> The LBT-FailureDetectionTimer expires; or

[0569] 1> When LBT-FailureDetectionTimer or LBT-FailureInstanceMaxCount is reset by a higher layer:

[0570] 2> Set LBT_COUNTER to 0.

[0571] In the above procedure, when the LBT fails for the active UL BWP of the SpCell, the UE switches to a UL BWP where a PRACH occasion is set and consistent LBT failure is not declared. However, there are only two carriers in the UL: SUL and NUL. If the active UL BWP is on the SUL and the UE switches from NUL to the UL BWP, the UE may not be in the UL coverage of NUL, which may cause problems when UL transmission fails. If the active UL BWP is on NUL and the UE switches from SUL to the UL BWP, the UE may not be in the UL coverage of SUL, which may cause problems when UL transmission fails.

[0572] Additionally, there may be multiple UL BWPs in both the NUL and SUL. If an LBT failure occurs on all UL BWPs with a PRACH occasion, an LBT failure is declared to the upper layer, which will delay the radio link failure (RLF).

[0573] Method 1:

[0574] The method of this disclosure describes LBT failure handling for an SpCell. For LBT failure handling, the gNB signals the LBT-FailureRecoveryConfig IE in an RRC Reconfiguration message. The RRC Reconfiguration message is sent to the UE in the RRC CONNECTED state. The LBT-FailureRecoveryConfig IE is configured for the SpCell. The LBT-FailureRecoveryConfig IE includes the LBT-FailureInstanceMaxCount and LBT-FailureDetectionTimer parameters for consistent LBT failure detection. The RRC Reconfiguration message from the gNB is processed by the RRC layer of the UE. When the LBT-FailureRecoveryConfig is received from the gNB for the SpCell, the MAC entity of the SpCell performs a consistent LBT failure recovery procedure using the parameters configured in the LBT-FailureRecoveryConfig IE of the SpCell.

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

[0576] 1> If an LBT failure indication is received from a lower layer (here, the LBT failure indication from the lower layer is for a failure to transmit 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 procedure for UL channel access):

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

[0578] 2> Increase LBT_COUNTER by 1;

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

[0580] 3> Declaring a consistent LBT failure for an active UL BWP;

[0581] 3> If a consistent LBT failure is declared in all UL BWPs with PRACH occasions configured in the NULL of such a serving cell: or

[0582] 3> If a consistent LBT failure is declared in all UL BWPs with PRACH occasions configured in the SUL of such a serving cell: or

[0583] 4> Indicate a consistent LBT failure to higher layers (upon receiving such an indication, higher layers, i.e., RRC, will declare RLF);

[0584] 3> Otherwise:

[0585] 4> In this serving cell, switching the active UL BWP with a UL BWP of the same carrier as the active UL BWP for which a PRACH occasion is set and a consistent LBT failure is not declared;

[0586] 4> Initiate the RA procedure.

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

[0588] If SUL is configured and the RSRP of the DL path loss metric is less than rsrp-ThresholdSSB-SUL, the UE selects the SUL carrier to perform the RA procedure; otherwise, the UE selects the NUL carrier to perform the RA procedure.

[0589] The selected carrier may be different from the carrier used before initiating the RA procedure. To ensure that an active UL BWP has an additional RACH occasion after a carrier change, for a serving cell configured with SUL and NUL, if a UL BWP with BWP ID 'X' has an RACH occasion in NUL, a UL BWP with the same BWP ID 'X' in SUL must also have an RACH occasion. The above proposal is applicable to cells operating on unlicensed carriers in one embodiment.

[0590] Method 2:

[0591] The method of this disclosure describes LBT failure handling for an SpCell. For LBT failure handling, the gNB signals the LBT-FailureRecoveryConfig IE in an RRC Reconfiguration message. The RRC Reconfiguration message is sent to the UE in the RRC CONNECTED state. The LBT-FailureRecoveryConfig IE is configured for the SpCell. The LBT-FailureRecoveryConfig IE includes the LBT-FailureInstanceMaxCount and LBT-FailureDetectionTimer parameters for consistent LBT failure detection. The RRC Reconfiguration message from the gNB is processed by the RRC layer of the UE. When the LBT-FailureRecoveryConfig is received from the gNB for the SpCell, the MAC entity of the SpCell performs a consistent LBT failure recovery procedure using the parameters configured in the LBT-FailureRecoveryConfig IE of the SpCell.

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

[0593] 1> If an LBT failure indication is received from a lower layer (here, the LBT failure indication from the lower layer is for a failure to transmit 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 procedure for UL channel access):

[0594] 2> LBT-FailureDetectionTimer is started or restarted;

[0595] 2> Increase LBT_COUNTER by 1;

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

[0597] 3> Declaring a consistent LBT failure for an active UL BWP;

[0598] 3> If a consistent LBT failure is declared for all UL BWPs with PRACH occasions configured on the carriers of the active UL BWPs of such serving cell:

[0599] 4> Indicate a consistent LBT failure to higher layers (i.e., the higher layers, i.e., the RRC, upon receiving such an indication, declare RLF);

[0600] 3> Otherwise:

[0601] 4> In this serving cell, switching the active UL BWP with a UL BWP of the same carrier as the active UL BWP for which a PRACH occasion is set and a consistent LBT failure is not declared;

[0602] 4> Initiate an RA procedure on the same carrier as the active UL BWP (in this case, the UE does not choose between SUL and NUL based on the RSRP threshold when the random access procedure is initiated).

[0603] RA Carrier Selection:

[0604] 1> If RA procedure is initiated due to LBT failure recovery:

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

[0606] 2> Set PCMAX to PCMAX, f, and c for the selected carrier.

[0607] 1> Else if the carrier to be used for the RA procedure is explicitly signalled (by the gNB):

[0608] 2> Select the carrier to be signaled to perform the RA procedure;

[0609] 2> Set PCMAX to the signaled carrier's PCMAX, f, c.

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

[0611] 1> The serving cell for the RA procedure has a supplemental uplink configured as specified in TS 38.331; and

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

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

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

[0615] 1> Otherwise:

[0616] 2> Select the NUL carrier to perform the RA procedure;

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

[0618] FIG. 31 illustrates a block diagram of a terminal according to one embodiment of the present disclosure.

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

[0620] The transceiver 3110 can transmit and receive signals to and from other network entities, eg, base stations.

[0621] The controller 3120 can control the UE to perform functions according to the above-described embodiments. In an embodiment of the present disclosure, for UL transmission on a configured grant, the controller 3120 is configured to select the CAPC of the DCCH if a DCCH SDU is transmitted, or to select the lowest priority CAPC (i.e., the highest-numbered CAPC index) of the MAC CE multiplexed with the LCH and MAC PDU carrying the MAC SDU. In another embodiment of the present disclosure, the controller 3120 is configured to trigger a consistent LBT failure for an active UL BWP in the serving cell. If an LBT failure indication is identified from a lower layer, the controller 3120 can be configured to increment an LBT counter (i.e., LBT_COUNTER). If the LBT counter is greater than a preset threshold (i.e., FailureInstanceMaxCount), a consistent LBT failure for an active UL BWP in the serving cell is triggered. If consistent LBT failures are triggered in all UL BWPs with PRACH occasions set 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 an active UL BWP to a UL BWP on the same carrier as the serving cell with PRACH occasions set and consistent LBT failures not triggered in the serving cell, and to initiate an RA procedure triggered by the consistent UL LBT failure on the switched UL BWP.

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

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

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

[0625] The transceiver 3210 can transmit signals to and receive signals from other network entities, eg, terminals.

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

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

[0628] While this disclosure has been shown and described with reference to various embodiments, those of ordinary skill in the art will recognize that various changes in form and detail can be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and equivalents thereof. [Explanation of symbols]

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

Claims

1. A method performed by a terminal for handling a listen before talk (LBT) failure in a wireless communication system, comprising: Identifying consistent LBT failures for an active uplink (UL) bandwidth portion (BWP) in a serving cell; Identifying at least one UL BWP in which a consistent LBT failure is not triggered on the same carrier in the serving cell, where a physical random access channel (PRACH) occasion is configured in the at least one UL BWP; and and replacing the active UL BWP with one of the at least one UL BWPs.

2. The method performed by the terminal of claim 1 , further comprising initiating a random access procedure triggered by the consistent UL LBT failure on the converted UL BWP.

3. The method according to claim 1, further comprising determining that a radio link failure has been detected for the serving cell when consistent LBT failures are triggered in all UL BWPs for which a PRACH occasion is configured on the same carrier of the serving cell.

4. identifying an LBT failure indication; and and incrementing an LBT counter based on the identification of the LBT failure indication. The method performed by the terminal of claim 1 , wherein the consistent LBT failure is identified when the LBT counter is greater than a preset threshold.

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

6. A terminal in a wireless communication system, a transceiver, and at least one processor operably coupled to the transceiver, the at least one processor comprising: Identifying consistent LBT failures for an active uplink (UL) bandwidth portion (BWP) in a serving cell; Identifying at least one UL BWP in which a consistent LBT failure is not triggered on the same carrier in the serving cell, where a physical random access channel (PRACH) occasion is configured in the at least one UL BWP; A terminal in a wireless communication system, configured to switch the active UL BWP with one of the at least one UL BWP.

7. The at least one processor:

10. The terminal in the wireless communication system of claim 6, further configured to initiate a random access procedure triggered by the consistent UL LBT failure on the converted UL BWP.

8. The at least one processor: The terminal in the wireless communication system described in claim 6, further configured to determine that a radio link failure has been detected for the serving cell when consistent LBT failures are triggered in all UL BWPs for which PRACH occasions are configured on the same carrier of the serving cell.

9. The at least one processor: Identifying an LBT failure indication; further configured to increment an LBT counter based on identification of the LBT failure indication; 7. The terminal in a wireless communication system of claim 6, wherein the consistent LBT failure is identified when the LBT counter is greater than a preset threshold.

10. The terminal in the wireless communication system according to claim 6, wherein the serving cell is a primary cell or a primary secondary cell of a secondary cell group.

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