Radio terminal equipment, radio access network nodes, and communication methods.

Abstract

The invention relates to a radio terminal (1) that performs a first random access step using a random access resource associated with a feature combination. If the first random access step fails, the radio terminal (1) retreats to a second random access step using a random access resource associated with a feature subset included in the feature combination. This helps, for example, to make redundancy in case the random access procedure using the random access resource associated with the feature combination fails.

Description

Wireless terminal and method

[0001] TECHNICAL FIELD The present disclosure relates to wireless communication networks, and more particularly to random access.

[0002] The 3rd Generation Partnership Project (3GPP®) Radio Access Network (RAN) Working Group is currently considering additional random access resource partitioning support. This functionality is expected to be introduced in 3GPP Release 17 (see, for example, non-patent documents 1-4). Random access resource partitioning partitions the random access resources used for random access preamble transmission. Random access resource partitioning enables a wireless terminal (e.g., User Equipment (UE)) to inform a radio access network node (e.g., gNB, eNB) of the resources used for random access preamble transmission.

[0003] In this specification, random access resources refer to random access preambles or combinations of random access occasions and random access preambles. Random access resource partitioning is also called Random Access Channel (RACH) resource partitioning or RACH partitioning. Random access opportunities are also called RACH occasions (ROs), and random access preambles are also called RACH preambles. One RACH occasion is a time and frequency resource for RACH preamble transmission. According to the current 3GPP Release 15 and Release 16 specifications, one RACH occasion has 64 RACH preambles available for transmission.

[0004] In 3GPP Release 16 RACH partitioning, the UE can inform the gNB of the following information depending on which RACH preamble it uses: - Selected Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) (or selected beam) - Contention-Free Random Access (CFRA) or Contention-Based RA (CBRA) cause - Payload size (preamble group B configured or not) - Random access type (2-Step or 4-step RA)

[0005] To enable the network (e.g., gNB) to identify features early, additional RACH partitioning is being considered for some Release 17 features. These features include, for example, Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CE or CovEnh), and Slicing. All RACH resource partitions resulting from possible feature combinations or combinations of features need to be configured. Possible feature combinations include, for example, RedCap+SDT, RedCap+CovEnh, RedCap+Slicing, RedCap+SDT+CovEnh, RedCap+SDT+Slicing, RedCap+CovEnh+Slicing, etc. Features may also be referred to as functional features.

[0006] The RedCap indication on the RACH is used to indicate reduced capabilities to the network in the first RACH message (MSG1 in 4-step RA, MSGA in 2-step RA), allowing the network to adapt subsequent transmissions.

[0007] The SDT indication on the RACH is used to indicate the SDT to the network and request a larger third RACH message (MSG3) size, or to indicate a larger MSGA size (the size of the data portion of the MSGA) in the case of a 2-step RA.

[0008] The CovEnh indication in the RACH is used to indicate the need for coverage enhancement, for example, to request repetition of the third RACH message (MSG3 in 4-step RA). The CovEnh indication may be binary information to indicate whether Msg3 PUSCH repetition is required or not.

[0009] The slicing indication on the RACH indicates a prioritized slice to the network and is used to achieve slice isolation for the RACH as well. The slicing indication may be binary information to distinguish between prioritized and non-prioritized network slices. Alternatively, the slicing indication may indicate multi-level slice priority, a selected or intended network slice, or a selected or intended network slice group, which would further increase the number of partitions.

[0010] ZTE Corporation, "RRC and MAC related aspects of common RACH configuration", R2-2107484, 3GPP TSG-RAN WG2 #115e Electronic meeting, August 16 - 27, 2021NEC, "General aspects of RACH indication and partitioning", R2-2108138, 3GPP TSG-RAN WG2 #115e Electronic meeting, August 16 - 27, 2021Ericsson, "RACH partitioning for Rel-17 features", R2-2108253, 3GPP TSG-RAN WG2 #115e Electronic meeting, August 16 - 27, 2021InterDigital, "Report for Rel-17 Small data and URLLC / IIoT", R2-2108834, 3GPP TSG-RAN WG2 #115e Electronic meeting, August 16 - 27, 2021

[0011] The inventors have investigated random access resource partitioning for Release 17 features and feature combinations and have found various challenges.

[0012] One of these issues concerns the fallback behavior when the random access procedure fails. For example, if a UE attempts random access using a resource selected from a set of random access resources associated with a Release 17 feature combination, but this random access fails, it is unclear how the UE should behave. Furthermore, if a UE-initiated contention-free random access (CFRA) fails, the UE may fall back to contention-based random access (CBRA). In this case, it is unclear how the UE selects the random access resource for CBRA.

[0013] Another of these issues concerns the behavior of a UE after initiating a random access procedure for Small Data Transmission (SDT). When a UE is in Radio Resource Control (RRC)_INACTIVE state, SDT is only permitted for a specific Data Radio Bearer (DRB) (hereinafter referred to as an SDT DRB). For uplink data transmissions of other DRBs (hereinafter referred to as non-SDT DRBs), the UE performs a normal RRC resume procedure. If uplink data transmission for a non-SDT DRB becomes necessary during SDT, the UE is expected to perform an RRC resume procedure slightly different from that in Release 15 and Release 16, which is currently under discussion in 3GPP. In this case, random access may be required, for example, when radio resources for uplink transmission are not allocated. The UE selects random access resources for a 4-step RA. However, when a first random access based on a feature combination including SDT and other features is in progress (or has been performed), it is unclear how the UE will handle a subsequent random access triggered for uplink data transmission of a non-SDT DRB.

[0014] Yet another of these challenges relates to reporting random access-related information from a UE to a network. UEs in 3GPP Release 15 and Release 16 can store a random access report (RA-Report) containing information on random access failures and transmit it to a network (e.g., gNB) in response to a network request. The RA-Report includes a cell ID (cellId), common RA-related information (ra-InformationCommon), and RA purpose (raPurpose). However, the current random access report (RA-Report) does not include information related to new features or feature combinations introduced in 3GPP Release 17.

[0015] One of the objectives to be achieved by the embodiments disclosed in this specification is to provide an apparatus, a method, and a program that contribute to solving at least one of multiple problems related to random access resource partitioning, including the above-mentioned problems. It should be noted that this objective is only one of multiple objectives to be achieved by the multiple embodiments disclosed in this specification. Other objectives or objectives and novel features will be apparent from the description of this specification or the accompanying drawings.

[0016] In a first aspect, a wireless terminal includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to perform a first random access using a random access resource associated with a feature combination, and the at least one processor configured to fall back to a second random access using a random access resource associated with a feature subset included in the feature combination if the first random access fails.

[0017] In a second aspect, a method performed by a wireless terminal includes: (a) performing a first random access using a random access resource associated with a feature combination; and (b) if the first random access fails, falling back to a second random access using a random access resource associated with a feature subset included in the feature combination.

[0018] In a third aspect, a wireless terminal includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to perform contention-free random access (CFRA), and if the CFRA fails, the at least one processor configured to fall back to contention-based random access (CBRA) using a random access resource associated with a feature or feature combination.

[0019] In a fourth aspect, a method performed by a wireless terminal includes (a) performing contention-free random access (CFRA); and (b) if the CFRA fails, falling back to contention-based random access (CBRA) using a random access resource associated with a feature or feature combination.

[0020] In a fifth aspect, a wireless terminal includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to initiate random access for initiating Small Data Transmission (SDT), and when a need arises to transmit uplink data not related to the SDT during execution of the SDT, the at least one processor configured to perform random access using a random access resource associated with one or more combinations of features excluding the SDT.

[0021] In a sixth aspect, a method performed by a wireless terminal includes: (a) initiating random access to initiate an SDT; and (b) when a need arises to transmit uplink data not related to the SDT while the SDT is being performed, performing random access using a random access resource associated with a combination of one or more features excluding the SDT.

[0022] In a seventh aspect, a wireless terminal includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to perform random access using a random access resource selected from a set of random access resources associated with a feature or a combination of features. The at least one processor is configured to, if the random access fails, include information about the feature or combination of features in a random access report regarding the failed random access. The at least one processor is configured to store the random access report. The at least one processor is configured to transmit the random access report to a network.

[0023] In an eighth aspect, a method performed by a wireless terminal includes the following steps: (a) performing a random access using a random access resource selected from a set of random access resources associated with a feature or a combination of features; (b) if the random access fails, including information about the feature or combination of features in a random access report regarding the failed random access; (c) storing the random access report; and (d) transmitting the random access report to a network.

[0024] A ninth aspect is directed to a program, which includes a set of instructions (software code) that, when loaded into a computer, causes the computer to perform the method according to the second, fourth, sixth, or eighth aspect.

[0025] According to the above-described aspects, it is possible to provide an apparatus, a method, and a program that contribute to solving at least one of a plurality of problems related to random access resource partitioning.

[0026] FIG. 1 is a diagram showing an example of a configuration of a wireless communication system according to an embodiment. FIG. 2 is a diagram showing an example of a protocol stack of a control plane of a wireless terminal according to an embodiment. FIG. 3 is a flowchart showing an example of an operation of a wireless terminal according to an embodiment. FIG. 4 is a flowchart showing an example of an operation of a wireless terminal according to an embodiment. FIG. 5 is a flowchart showing an example of an operation of a wireless terminal according to an embodiment. FIG. 6 is a sequence diagram showing an example of an operation of a wireless terminal and a radio access network node according to an embodiment. FIG. 7 is a diagram showing an example of a message between RAN nodes according to an embodiment. FIG. 8 is a block diagram showing an example of a configuration of a wireless terminal according to an embodiment. FIG. 9 is a block diagram showing an example of a configuration of a radio access network node according to an embodiment.

[0027] Hereinafter, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and for clarity of explanation, duplicate explanations will be omitted as necessary.

[0028] The multiple embodiments described below can be implemented independently or in appropriate combination. These multiple embodiments have different novel features. Therefore, these multiple embodiments contribute to solving different purposes or problems and to achieving different effects.

[0029] Although the following embodiments will be described mainly with respect to the 3GPP fifth generation mobile communication system (5G system), these embodiments may also be applied to other wireless communication systems.

[0030] As used herein, depending on the context, "if" may be interpreted to mean "when," "at or around the time," "after," "upon," "in response to determining," "in accordance with a determination," or "in response to detecting." These expressions may be interpreted to have the same meaning, depending on the context.

[0031] First, the configurations and operations of several network elements common to several embodiments will be described. Figure 1 shows an example configuration of a wireless communication system according to several embodiments. In the example of Figure 1, the wireless communication system includes a wireless terminal (i.e., UE) 1 and a radio access network (RAN) node (e.g., gNB) 2. Each element (network function) shown in Figure 1 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on the dedicated hardware, or as a virtualized function instantiated on an application platform.

[0032] The UE 1 has at least one radio transceiver and is configured to perform cellular communication with the RAN node 2. The RAN node 2 is configured to manage a cell 21 and perform cellular communication with multiple UEs including the UE 1 using a cellular communication technology (e.g., NR Radio Access Technology (RAT)).

[0033] The RAN node 2 may be a Central Unit (e.g., gNB-CU) in a cloud RAN (C-RAN) deployment, or a combination of a CU and one or more Distributed Units (e.g., gNB-DUs). C-RAN is also referred to as a CU / DU split. Furthermore, a CU may include a Control Plane (CP) Unit (e.g., gNB-CU-CP) and one or more User Plane (UP) Units (e.g., gNB-CU-UP). Thus, the RAN node 2 may be a CU-CP or a combination of a CU-CP and a CU-UP. The CU may be a logical node that hosts the Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP), and Packet Data Convergence Protocol (PDCP) protocols of the gNB (or the RRC and PDCP protocols of the gNB). The DU may be a logical node that hosts the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of the gNB.

[0034] The RAN node 2 transmits signals including system information (SI) 101 and other signals within the cell 21. The system information 101 includes a master information block (MIB) and many system information blocks (SIBs). The system information 101 is divided into a minimum SI and other SI. The minimum SI is always broadcast periodically and includes basic information required for initial access and information required to acquire other SI. Other SI includes all SIBs that are not broadcast within the minimum SI. More specifically, the minimum SI includes the MIB and SIB type 1 (SIB1), and the other SI includes SIB types from SIB type 2 (SIB2) onwards. Each SIB included in the Other SI is broadcast periodically at all times, broadcast on demand based on a request from UEs in RRC_IDLE or RRC_INACTIVE, or sent to UEs in RRC_CONNECTED via dedicated RRC signaling. When the RAN node 2 is a C-RAN deployment, a DU (e.g., gNB-DU) may generate at least a part of the system information (e.g., MIB, SIB1). The DU may transmit the generated system information directly to the UE 1, or may transmit it to a CU (e.g., gNB-CU) so that the CU can transmit it to the UE 1 (via the DU).

[0035] In the example of FIG. 1 , UE 1 selects or reselects cell 21 of RAN node 2 and is camped on cell 21. In other words, cell 21 is the serving cell of UE 1. The serving cell of UE 1 can be referred to as the cell on which UE 1 is camped. The serving cell may also be called a camped cell. A UE in RRC_IDLE or RRC_INACTIVE camps on a cell once it can select a suitable cell to camp on according to cell selection criteria or cell reselection criteria. Camping on a cell means that the UE has completed the cell selection or reselection process and selected the cell. In other words, the term "camping" means a state in which the UE is staying on a cell and is ready to start a potential dedicated service in the cell.

[0036] 2 shows an example of a control plane protocol stack for UE 1. The control plane protocol stack 200 for UE 1 includes an application (APP) layer 201, a non-access stratum (NAS) layer 202, and an access stratum (AS) layer 208. The AS layer 208 includes an RRC layer 203, a PDCP layer 204, an RLC layer 205, a MAC layer 206, and a PHY layer 207.

[0037] The NAS layer 202 utilizes data communication over the air interface and management of the air interface provided by the AS layer 208 to communicate with the core network (i.e., 5G Core (5GC)) via the RAN node 2 according to the 5G System (5GS) Mobility Management (5GMM) protocol and the 5GS Session Management (5GSM) protocol. The 5GMM protocol runs between the UE 1 and the Access and Mobility Management Function (AMF) in the 5GC and is used for UE registration, mobility, and transport of 5GSM protocol messages. The 5GSM protocol runs between the UE 1 and the Session Management Function (SMF) in the 5GC via the AMF and supports management of PDU session connectivity.

[0038] The NAS layer 202 communicates with the RRC layer 203 to utilize the services provided by the AS layer 208 (i.e., data communication over the air interface between the UE 1 and the RAN node 2 and management of the air interface). The RRC layer 203 is a lower layer of the NAS layer 202, provides radio resource control (RRC), and manages the RRC states of the UE 1 (i.e., RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED).

[0039] The AS layer 208 initiates an RRC connection establishment procedure or an RRC connection resumption procedure in response to a request from the NAS layer 202 or spontaneously. For example, in response to receiving a PDU session establishment request from an upper layer (i.e., application layer 201), if the 5GS mobility management (5GMM) mode of UE1 is 5GMM-IDLE, the NAS layer 202 initiates a registration procedure or a service request procedure to transition to 5GMM-CONNECTED mode and attempts to send an initial NAS message (e.g., a registration request message or a service request message) to the AMF. The initial NAS message from the NAS layer 202 triggers the AS layer 208 to establish an RRC connection between UE1 and RAN node 2. If the 5GMM mode is 5GMM-CONNECTED or 5GMM-CONNECTED with RRC inactive indication, the NAS layer 202 attempts to send a NAS message (e.g., a PDU SESSION ESTABLISHMENT REQUEST message, a UL NAS TRANSPORT message, a PDU SESSION MODIFICATION REQUEST, or a SERVICE REQUEST message) depending on the event that triggered the access attempt. Alternatively, if the 5GMM mode is 5GMM-CONNECTED or 5GMM-CONNECTED with RRC inactive indication and the access attempt is "an uplink user data packet is to be sent for a PDU session with suspended user-plane resources," the NAS layer 202 requests the AS layer 208 to transition to RRC_CONNETED in order to send an uplink user data packet (Mobile Originated (MO) data).

[0040] In response to receiving the initial NAS message or the request to transition to RRC_CONNETED, the RRC layer 203 requests or triggers the MAC layer 206 to initiate a random access procedure to send an RRC message (i.e., an RRC Setup Request message or an RRC Resume Request message) for establishing or resuming an RRC connection. Prior to this, the RRC layer 203 may perform one or more access barring checks. If the access barring checks are passed, the RRC layer 203 may request the MAC layer 206 to initiate a random access procedure. Techniques for access barring include, for example, Access Class Barring (ACB), Extended Access Barring (EAB), Application Specific Congestion Control for Data Communication (ACDC), and Unified Access Control (UAC). The RRC layer 203 may perform barring checks for one or more of these access barring techniques.

[0041] The MAC layer 206 receives triggers for the random access procedure based on events such as re-establishment and resumption of an RRC connection from the RRC layer 203, and initiates the random access procedure accordingly. The MAC layer 206 may initiate the random access procedure by itself or by Physical Downlink Control Channel (PDCCH) order.

[0042] In the random access procedure, the MAC layer 206 selects one RACH resource from a set of partitioned random access resources (RACH resources) to be used for RACH preamble transmission. The set of RACH resources includes RACH preambles or combinations of RACH occasions and RACH preambles. A RACH occasion is a time and frequency resource for RACH preamble transmission. According to the current 3GPP Release 15 and Release 16 specifications, there are 64 RACH preambles available for transmission in one RACH occasion.

[0043] The MAC layer 206 requests the PHY layer 207 to transmit a random access preamble (RACH preamble) on the selected RACH resource. The random access procedure further includes a Random Access Response (RAR) reception and contention resolution.

[0044] The MAC layer 206 may follow the RACH partitioning of 3GPP Release 16. In 3GPP Release 16 RACH partitioning, the UE can inform the gNB of the following information depending on which RACH preamble to use: - Selected Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) (or selected beam) - Contention-Free Random Access (CFRA) or Contention-Based RA (CBRA) cause - Payload size (preamble group B configured or not) - Random access type (2-Step or 4-step RA)

[0045] In addition, the MAC layer 206 supports additional RACH partitioning for Release 17 features. This allows the RAN node 2 to early identify the Release 17 features or feature combinations selected, desired, or intended by the UE 1. For example, a RACH resource partition is configured for each of all or a subset of the Release 17 features, and a RACH resource partition is configured for each possible feature combination or combination of features. Each Release 17 feature may be, for example, Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CE or CovEnh), or Slicing. A feature combination may include, for example, at least two of RedCap, SDT, CovEnh, and Slicing. As used hereinafter in this specification, the term "feature" refers to any of these Release 17 features unless otherwise specified. Similarly, the term "feature combination" means a combination of at least two of these Release 17 features, unless otherwise specified. A "feature combination" may also be referred to as a "feature set" or "set of features."

[0046] The RedCap indication on the RACH is used to indicate reduced capabilities to the network in the first RACH message (MSG1 in 4-step RA, MSGA in 2-step RA), allowing the network to adapt subsequent transmissions. The 3GPP RAN Working Group is currently considering New Radio (NR) support for RedCap UEs, which is expected to be introduced in 3GPP Release 17. The introduction of RedCap NR devices will enable the addressing of use cases not yet optimally served by current NR standards. Use cases motivating the standardization of NR RedCap include wearables (e.g., smart watches, wearable medical devices, Augmented Reality (AR) / Virtual Reality (VR) goggles), industrial wireless sensors, and video surveillance. These use cases have less stringent data rate requirements than enhanced mobile broadband (eMBB) use cases, and do not require the tight or deterministic latency requirements of time-critical communications use cases. Therefore, there is room to trade off device functionality for complexity or cost reduction compared to a baseline Release 15 NR device. According to currently envisioned RedCap device capabilities, the maximum device bandwidth, minimum number of device receive branches, maximum number of downlink MIMO layers, and maximum downlink modulation order may be reduced or relaxed compared to those of a Release 15 NR device.

[0047] The SDT indication on the RACH indicates the SDT to the network and is used to request a larger third RACH message (MSG3) size. Alternatively, the SDT indication is used to indicate a larger MSGA size (the size of the data portion of the MSGA) in the case of 2-step RA. Furthermore, similar to the RACH in 3GPP Release 15 / 16, two sizes of MSG3 or MSGA may be possible. In this case, the SDT indication on the RACH may further indicate the size of MSG3 or MSGA. SDT, also known as SDT in inactive state, is one of the new features introduced in 3GPP Release 17. It enables UEs in RRC_INACTIVE to send infrequent and small data without requiring RRC state transitions.

[0048] The CovEnh indicator on the RACH is used to indicate the need for coverage enhancement, for example, to request repetition of the third RACH message (MSG3 in 4-step RA). The CovEnh indicator may be binary information to indicate whether Msg3 PUSCH repetition is required. Alternatively, the CovEnh indicator may indicate one of multiple coverage enhancement (CE) levels. The CovEnh indicator may indicate one of two or more CE level groups (or CE modes). One CE level group or CE mode includes one or more CE levels. For example, the CE specified in 3GPP Release 14 supports up to four CE levels (i.e., CE levels 0 to 3). The UE determines the CE level based on the measured RSRP level. CE level 0 is associated with the highest RSRP threshold, and CE level 3 is associated with the lowest RSRP threshold. In other words, a UE in CE level 0 enjoys a relatively low path loss and a high downlink received power, and a UE in CE level 3 enjoys a relatively high path loss and a low downlink received power.

[0049] The slicing indication on the RACH indicates a high-priority slice to the network and is used to achieve slice isolation for the RACH as well. The slicing indication may be binary information for distinguishing between prioritized and non-prioritized network slices. Alternatively, the slicing indication may be information indicating one of three or more multi-level slice priorities. The slicing indication may indicate a network slice selected or intended by UE1, or a selected or intended network slice group. A network slice group includes one or more network slices.

[0050] Network slicing uses Network Function Virtualization (NFV) and software-defined networking (SDN) technologies to create multiple virtualized logical networks on a physical network. Each virtualized logical network is called a network slice or network slice instance, and includes logical nodes and functions. It is used for specific traffic and signaling. A network slice may be provided by a core network (e.g., 5GC). Multiple network slices are distinguished by the services or use cases provided to UEs on each network slice. Use cases include, for example, enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low Latency Communication (URLLC), and massive Machine Type Communication (mMTC). These are called slice types (e.g., Slice / Service Type (SST)). The RAN node 2 may assign to the UE 1 a RAN slice and a radio slice associated with the network slice of the core network selected for the UE 1, in order to provide end-to-end network slicing to the UE 1. From the above, the Slicing indication on the RACH may be information about the network slice of the core network, information about the RAN or radio slice, or information about the end-to-end network slice.

[0051] The network slice may be indicated by Network Slice Selection Assistance Information (NSSAI) or Single NSSAI (S-NSSAI). This may be notified, for example, from a core network (e.g., 5GC) to the NAS layer 202 of UE1, and then from the NAS layer 202 of UE1 to the AS layer 208 (e.g., RRC). The network slice selected and the intended network slice by UE1 may be referred to as a selected NSSAI and an intended NSSAI, respectively. The selected network slice (selected NSSAI) may also be referred to as an allowed NSSAI, meaning a network slice permitted for use by the core network. The SST may be included in the S-NSSAI (i.e., the S-NSSAI includes information about the SST).

[0052] More specifically, each network slice selected or intended by UE1 may be identified by an identifier known as Single Network Slice Selection Assistance Information (S-NSSAI). The selected or intended network slice may be the S-NSSAI(s) included in the Configured NSSAI or the S-NSSAI(s) included in the Allowed NSSAI. Note that the S-NSSAIs in the Requested NSSAI included in the NAS Registration Request message must be part of the Configured NSSAI and / or the Allowed NSSAI. Therefore, the intended network slice may be the S-NSSAI(s) included in the Requested NSSAI.

[0053] The Configured NSSAI includes one or more S-NSSAIs, each applicable to one or more Public Land Mobile Networks (PLMNs). The Configured NSSAI is configured by, for example, a Serving PLMN and applies to the Serving PLMN. The Allowed NSSAI is provided to UE1 by the Serving PLMN and indicates one or more S-NSSAIs that UE1 can use in the current Registration Area of ​​the Serving PLMN. The Configured NSSAI may be the Default Configured NSSAI. The Default Configured NSSAI is configured by the Home PLMN (HPLMN) and applies to any PLMNs for which a specific Configured NSSAI is not provided. The UE1 may be pre-configured with the Default Configured NSSAI. The UE1 may be provisioned or updated with the Default Configured NSSAI determined by the Unified Data Management (UDM) of the HPLMN. The Allowed NSSAI is determined by the AMF of the Serving PLMN, for example, during a registration procedure. The Allowed NSSAI is signaled to the UE 1 by the network (i.e., the AMF) and stored in the (non-volatile) memory of the AMF and the UE 1, respectively.

[0054] In some implementations, the AS layer 208 may determine or select the feature combination. In one example, the RRC layer 203 of UE1 may determine or select the feature combination. Specifically, the RRC layer 203 of UE1 may determine the feature combination and indicate the determined feature combination to the MAC layer 206 of UE1. Alternatively, the final determination or selection of the feature combination may be made by the MAC layer 206 of UE1. Specifically, the RRC layer 203 of UE1 may determine one or more features to be included in the feature combination and indicate the determined one or more features to the MAC layer 206 of UE1. The MAC layer 206 may further determine required features and determine the feature combination.

[0055] In other implementations, the NAS layer 202 may determine or select the feature combination, and the NAS layer 208 may indicate the feature combination to the AS layer 208 (eg, the RRC layer 203).

[0056] <First Embodiment> A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in Fig. 1. The protocol stack of the control plane of UE1 may be the same as the example shown in Fig. 2.

[0057] 3 shows an example of the operation of UE1 in a random access procedure. In step 301, UE1 performs random access (hereinafter referred to as first random access) using a random access resource associated with a feature combination selected, desired, or intended by UE1. The feature combination may include two or more of RedCap, SDT, CovEnh, and Slicing.

[0058] As described above, in one example, the RRC layer 203 of UE1 may determine a feature combination and indicate the determined feature combination to the MAC layer 206 of UE1. The MAC layer 206 may select one resource for transmitting a random access preamble from a set of random access resources associated with the feature combination. The MAC layer 206 may then request the PHY layer 207 to transmit the random access preamble on the selected preamble resource. Alternatively, the RRC layer 203 of UE1 may determine one or more features to be included in the feature combination and indicate the determined one or more features to the MAC layer 206 of UE1. The MAC layer 206 may further determine the required features, determine a feature combination, and select one resource for transmitting a random access preamble from the set of random access resources associated with the feature combination.

[0059] In step 302, if the first random access fails, UE1 falls back to random access (hereinafter referred to as second random access) using a random access resource associated with a feature subset included in the feature combination. The feature subset may also be referred to as a feature subset, a feature subcombination, or a subcombination of features. The feature subset includes one or more features. The feature subset may include one or more of RedCap, SDT, CovEnh, and Slicing.

[0060] A first random access failure may mean that the number of preamble transmissions reaches a predetermined number (i.e., the maximum number of preamble transmissions) but the random access is not completed. A first random access failure may mean that the initiated random access procedure has not yet completed successfully or unsuccessfully. A first random access failure may be caused by consecutive failures to receive a random access response (i.e., MSG2 in 4-step RA or MSGB in 2-step RA), consecutive failures to resolve contention, or both. In other words, a first random access failure may be caused by consecutive failures to transmit a random access preamble (MSG1 in 4-step RA or MSGA in 2-step RA), consecutive failures to transmit a third RACH message (MSG3 in 4-step RA), or both. The maximum number of preamble transmissions may be configured for each feature combination. Additionally or alternatively, a maximum number of transmissions may be set for each feature, and the UE 1 may apply the maximum value of multiple maximum transmissions associated with multiple features included in the feature combination. Additionally or alternatively, a maximum number of transmissions may be set for each feature, and the UE 1 may apply the value of the maximum transmission number set for the most prioritized feature among the multiple features included in the feature combination.

[0061] For example, when the feature combination considered in the first random access is SDT+Slicing, the feature subset considered in the second random access may be SDT or Slicing. When the feature combination considered in the first random access is RedCap+SDT+Slicing, the feature subset considered in the second random access may be RedCap, RedCap+SDT, or RedCap+Slicing.

[0062] In general, the set (or partition) of random access resources reserved for a feature subset is considered to be larger than the set (or partition) of random access resources reserved for a feature combination, and therefore the operations described with reference to FIG. 3 can contribute to improving the probability of successful random access.

[0063] When selecting the feature subset in step 302, UE 1 may preferably select one or more features that are preferred or important over other features, allowing RAN node 2 to identify the preferred or important features early.

[0064] In one example, if the feature combination considered for the first random access includes slicing and one or more other features, UE1 (MAC layer 206) selects a feature subset consisting of only slicing and chooses a random access resource associated with that feature subset for the second random access. This operation enables RAN node 2 to early identify a feature (here, slicing) that is prioritized or important over other features.

[0065] In yet another example, if the feature combination considered for the first random access includes one or both of CovEnh and RedCap and one or more other features, UE1 (MAC layer 206) selects a feature subset consisting of only one or both of CovEnh and RedCap and chooses a random access resource associated with that feature subset for the second random access. This operation enables RAN node 2 to early identify features (here, one or both of CovEnh and RedCap) that are prioritized or important over other features.

[0066] Second Embodiment A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in Fig. 1. The protocol stack of the control plane of UE1 may be the same as the example shown in Fig. 2.

[0067] 4 shows an example of the operation of UE1 in a random access procedure. In step 401, UE1 (MAC layer 206) performs contention-free random access (CFRA). The CFRA uses contention-free random access resources explicitly provided to UE1 by RAN node 2 via dedicated RRC signaling. UE1 may also perform the CFRA in step 401 during handover, i.e., when accessing a target cell during handover.

[0068] In step 402, if CFRA fails, UE1 falls back to contention-based random access (CBRA). In CBRA, the MAC layer 206 selects one resource for preamble transmission from a set of random access resources associated with a feature combination selected, desired, or intended by UE1. Specifically, the RRC layer 203 of UE1 may determine the feature or feature combination and indicate the determined feature or feature combination to the MAC layer 206 of UE1. The MAC layer 206 may select one resource for random access preamble transmission from the set of random access resources associated with the feature or feature combination indicated by the RRC layer 203. The MAC layer 206 may request the PHY layer 207 to transmit the random access preamble on the selected preamble resource. Note that information regarding the set of random access resources associated with the feature or feature combination in the handover target cell may be transmitted from the target RAN node (e.g., gNB) to UE1 via the source RAN node.

[0069] The feature may be RedCap, SDT, CovEnh, or Slicing. The feature combination may include two or more of RedCap, SDT, CovEnh, and Slicing.

[0070] A CFRA failure may mean unsuccessful completion of the CFRA procedure. A CFRA failure may be caused by consecutive failures to receive a random access response (i.e., MSG2 in 4-step RA or MSGB in 2-step RA). In other words, a CFRA failure may be caused by consecutive failures to transmit a random access preamble (MSG1 in 4-step RA, MSGA in 2-step RA). Alternatively, if a CFRA is performed during handover, a CFRA failure may mean that the handover has not been successful within a predetermined period of time.

[0071] According to the operation described with reference to FIG. 4, UE1 can inform RAN node 2 early of the features or feature combinations selected, desired, or intended by UE1 during CBRA after CFRA failure.

[0072] <Third Embodiment> A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in Fig. 1. The protocol stack of the control plane of UE1 may be the same as the example shown in Fig. 2.

[0073] FIG. 5 illustrates an example of the operation of UE1 in a random access procedure. In step 501, UE1 initiates random access to initiate SDT. During this random access, UE1 may transmit a random access preamble on a random access resource associated with a feature combination including the feature "SDT." Specifically, the RRC layer 203 of UE1 may determine a feature combination including the feature "SDT" and indicate this to the MAC layer 206 of UE1. The MAC layer 206 may select one resource for transmitting the random access preamble from a set of random access resources associated with the feature combination including the feature "SDT." The MAC layer 206 may then request the PHY layer 207 to transmit the random access preamble on the selected preamble resource. The feature combination including the feature "SDT" may include at least one of RedCap, CovEnh, and Slicing in addition to SDT.

[0074] In step 502, when it becomes necessary to transmit uplink data not related to the SDT during execution of the SDT, UE1 performs random access using a random access resource associated with one or more feature combinations excluding the SDT. The uplink data not related to the SDT is uplink data of other DRBs (non-SDT DRBs) for which SDT is not permitted. The one or more feature combinations excluding the SDT may be one or more remaining features excluding the SDT from the feature combinations considered in step 501. Alternatively, the one or more feature combinations excluding the SDT may be features or feature combinations corresponding to non-SDT DRBs.

[0075] According to the operation described with reference to Figure 5, when the first random access based on a feature combination including SDT and one or more other features is being performed (or has been performed), UE1 can appropriately perform the next random access for uplink data transmission of a non-SDT DRB. For example, if UE1 is not allocated radio resources for uplink transmission to perform an RRC resume procedure (e.g., transmitting information required for RRC resume on a DCCH), which is slightly different from Release 15 and Release 16, UE1 may perform step 502 of this embodiment, thereby allowing the network (e.g., RAN node 2) to identify features related to the non-SDT DRB early.

[0076] <Fourth embodiment> A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in Fig. 1. The protocol stack of the control plane of UE1 may be the same as the example shown in Fig. 2.

[0077] Figure 6 shows an example of the operation of UE1. The operation of Figure 6 relates to reporting random access related information from UE1 to the network (e.g., RAN node 2). In step 601, UE1 performs random access using a random access resource selected from a set of random access resources associated with a feature or feature combination. The feature is RedCap, SDT, CovEnh, or Slicing. The feature combination includes two or more of RedCap, SDT, CovEnh, and Slicing.

[0078] As described above, in one example, the RRC layer 203 of UE1 may determine a feature or feature combination and indicate the determined feature or feature combination to the MAC layer 206 of UE1. The MAC layer 206 may select one resource for transmitting the random access preamble from a set of random access resources associated with the feature or feature combination indicated by the RRC layer 203. The MAC layer 206 may request the PHY layer 207 to transmit the random access preamble on the selected preamble resource. Alternatively, the RRC layer 203 of UE1 may determine one or more features to be included in the feature combination and indicate the determined one or more features to the MAC layer 206 of UE1. The MAC layer 206 may further determine the required features, determine the feature combination, and select one resource for transmitting the random access preamble from the set of random access resources associated with the feature combination.

[0079] In step 602, if the random access in step 601 fails, information about the feature or feature combination is included in a random access report (e.g., RA-Report) related to the random access failure. Specifically, the MAC layer 206 may indicate the random access failure or problem to the RRC layer 203 in response to the random access failure. The RRC layer 203 may include information about the feature or feature combination in a memory (e.g., VarRA-Report) for the random access report (e.g., RA-Report) related to the random access failure based on the random access failure or problem indicated by the MAC layer 206.

[0080] A random access failure may refer to an unsuccessful completion of the random access procedure. A random access failure may be caused by consecutive failures to receive a random access response (i.e., MSG2 in 4-step RA or MSGB in 2-step RA), consecutive failures to resolve contention, or both. In other words, a random access failure may be caused by consecutive failures to transmit a random access preamble (MSG1 in 4-step RA, MSGA in 2-step RA), consecutive failures to transmit a third RACH message (MSG3 in 4-step RA), or both.

[0081] In one implementation, UE1 (e.g., RRC layer 203) may set the raPurpose field included in the random access report to indicate the purpose of the random access to indicate feature or feature combination information, which may be an extension of the raPurpose field in Release 15 and / or Release 16 (e.g., raPurpose-v17xy or raPurpose-v18xy).

[0082] In another implementation, UE1 (eg, RRC layer 203) may set a new field (eg, raFeatureCombination, or raFC) included in the random access report to indicate feature or feature combination information.

[0083] In step 603, UE1 stores in memory the random access report generated in step 602. Step 603 may be performed by the RRC layer 203.

[0084] In step 604, UE1 transmits the stored random access report to the network (e.g., RAN node 2). Step 604 may be performed by the RRC layer 203. The RRC layer 203 may transmit the random access report to RAN node 2 in response to a request from RAN node 2. More specifically, UE1 and RAN node 2 may operate as shown in FIG. 7. RAN node 2 transmits a UE Information Request message to UE1 (step 701). The UE Information Request message is an RRC message used by the network to retrieve information from UE1. In step 701, the UE Information Request message includes the ra-ReportReq field set to true. In response to this message, UE1 sets the stored random access report in a predetermined field (e.g., the ra-Report field) of a UE Information Response message and transmits the UE Information Response message to RAN node 2 (step 702).

[0085] According to the operations described with reference to Figures 6 and 7, the UE 1 can provide a random access report to the RAN node 2 that includes information related to a new feature or feature combination introduced in 3GPP Release 17. This can be used by the RAN node 2, Operation, Administration and Maintenance (OAM), or a network operator, for example, to optimize random access resource partitioning.

[0086] By way of example and not limitation, the operations shown in Figure 6 may be modified or elaborated as follows: These modifications allow the network to be informed of the details of random access failures based on a feature or combination of features.

[0087] In step 601, UE1 may perform a fallback (hereinafter referred to as a first fallback) from transmitting a preamble using a random access resource associated with a feature combination to transmitting a preamble using a random access resource associated with a feature subset included in the feature combination. The feature subset includes one or more features. It may also be referred to as a feature subset, a feature subcombination, or a feature subcombination. For example, when the feature combination is RedCap+Slicing, the feature subset may be RedCap. When the feature combination is RedCap+CovEnh+Slicing, the feature subset may be RedCap+CovEnh, RedCap, or CovEnh. If the first fallback was performed in step 601, UE1 may include information about the first fallback in the random access report in step 602.

[0088] Additionally or alternatively, in step 601, UE1 may perform a fallback from transmitting preambles using random access resources associated with a feature or feature combination to transmitting preambles using random access resources not associated with a feature or feature combination (hereinafter referred to as a second fallback). In the second fallback, UE1 may perform random access resource selection in the same manner as in the random access procedure of 3GPP Release 15 and / or Release 16. If the second fallback was performed in step 601, UE1 may include information of the second fallback in the random access report in step 602.

[0089] The RAN node 2 may transmit the random access report received from the UE 1 to a surrounding (neighboring) RAN node 2, for example, by including it in a RACH Report Container IE of an ACCESS AND MOBILITY INDICATION message of Xn.

[0090] Fifth Embodiment A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in FIG.

[0091] FIG. 8 shows an example of information about random access (e.g., Physical RACH (PRACH)) resources transmitted in an Xn message between the RAN node 2 and a surrounding (or neighboring) RAN node in this embodiment. The Xn message may be, for example, an Xn SETUP, an Xn SETUP RESPONSE, an NG-RAN NODE CONFIGURATION UPDATE, or an NG-RAN NODE CONFIGURATION UPDATE ACKNOWLEDGE. The RAN node 2 may include information about support for RACH resources associated with feature combinations in PRACH configuration information (NR PRACH Configuration) in the served cell information it manages. The information about support for RACH resources associated with feature combinations may be, for example, but not limited to, a Feature Set Combination information element (IE), a Feature Set Combination-based PRACH IE, or a PRACH per Feature Set Combination IE.

[0092] As shown as Option 1 in Fig. 8, the information regarding support of RACH resources associated with feature combinations (e.g., Feature Set Combination IE) may be, for example, information indicating that the feature is supported (or that it is configured in the cell) (e.g., ENUMERATED (true, ...)). Alternatively, as shown as Option 2 in Fig. 8, the information may be in the form of a bitmap (e.g., BITSTRING (SIZE(32))) indicating each feature combination. In this case, what each bit indicates (i.e., which feature combination it corresponds to) may be specified in advance in a specification or the like.

[0093] This allows the RAN node 2 to know whether the RACH resources associated with the feature combination are supported by neighboring (or adjacent) RAN nodes. The RAN node 2 can use this information, for example, to determine a target cell for UE1 handover or to configure radio parameters (e.g., Qoffset, frequency priority) used by UE1 for cell (re)selection. This can contribute to optimizing UE1's mobility. Note that similar information may be included in an F1 message between a CU (e.g., gNB-CU) and a DU (e.g., gNB-DU) in a C-RAN configuration. The F1 message may be, for example, an F1 SETUP REQUEST, an F1 SETUP RESPONSE, a GNB-DU CONFIGURATION UPDATE, or a GNB-DU CONFIGURATION UPDATE ACKNOWLEDGE.

[0094] Sixth Embodiment A configuration example of a wireless communication system according to this embodiment may be the same as the example shown in Fig. 1. The protocol stack of the control plane of UE1 may be the same as the example shown in Fig. 2.

[0095] This embodiment relates to handling of features and feature combinations selected, desired, or intended by UE1. Features can be divided into at least two types. In the first type, the MAC layer 206 of UE1 determines whether or not a feature needs to be implemented (or whether or not the feature can be implemented) based on information or conditions predetermined by itself. Additionally or alternatively, the MAC layer 206 may determine the above based on information received from or specified by a higher layer (e.g., the RRC layer 203) of UE1. In this type, if the MAC layer 206 of UE1 determines that at least one feature of the selected, desired, or intended feature combination does not need to be implemented (or cannot be implemented), the MAC layer 206 may change the content of the feature combination (i.e., the included features) to select RACH resources for the remaining features or feature combinations excluding the selected feature. In other words, the MAC layer 206 may select a feature subset excluding the feature that does not need to be implemented (or cannot be implemented). In this case, the MAC layer 206 may notify the RRC layer 203 of the determination result (for example, information on the feature combination to be executed, information on the removed feature).

[0096] In the second type, the MAC layer 206 of UE1 does not or should not determine whether the feature needs to be implemented (or whether the feature can be implemented). In this type, the RRC layer 203 of UE1 determines whether the feature needs to be implemented (or whether the feature can be implemented) and notifies the MAC layer 206 of the necessary information. The determination by the RRC layer 203 may be based on one or both of the UE1's capabilities and predefined information held by the RRC layer 203. Additionally or alternatively, the RRC layer 203 may make the above determination based on information received or specified from a higher layer of UE1 (e.g., the NAS layer 202). The MAC layer 206 selects a RACH resource corresponding to the feature or a feature combination including the feature. If the MAC layer 206 determines that there is no RACH resource corresponding to the feature, it may report a RACH resource selection failure indication to the RRC layer 203. On the other hand, if the MAC layer 206 determines that there is no RACH resource corresponding to the feature combination including the feature, the MAC layer 206 may exclude one or more features of the first type from the feature combination and select a RACH resource corresponding to a feature subset including the feature of the second type and the remaining one or more features of the first type. Alternatively, the MAC layer 206 may select a RACH resource corresponding only to the feature of the second type. In other words, when selecting a feature subset from a feature combination, the MAC layer 206 may always include one or more features of the second type (e.g., RedCap) that were included in the feature combination. The MAC layer 206 may then adjust the number of features in the feature subset depending on whether or not the feature of the first type that was included in the feature combination is included in the feature subset.

[0097] The feature combination selected, desired, or intended by UE1 may include only one of the above two types, or may include both types. If the feature combination includes both types, the MAC layer 206 may preferentially consider the feature of the second type. For example, the MAC layer 206 may preferentially implement the feature of the second type. The MAC layer 206 may preferentially select RACH resources corresponding to the feature of the second type. For example, in step 302 of FIG. 3 described in the first embodiment, UE1 (MAC layer 206) may preferentially select the feature of the second type when determining the feature subset.

[0098] Next, exemplary configurations of a UE 1 and a RAN node 2 according to the above-described embodiments will be described. FIG. 9 is a block diagram illustrating an exemplary configuration of a UE 1. A radio frequency (RF) transceiver 901 performs analog RF signal processing for communication with a RAN node. The RF transceiver 901 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 901 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 901 is coupled to an antenna array 902 and a baseband processor 903. The RF transceiver 901 receives modulation symbol data (or OFDM symbol data) from the baseband processor 903, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 902. The RF transceiver 901 also generates a baseband receive signal based on the receive RF signal received by the antenna array 902 and provides the baseband receive signal to the baseband processor 903. The RF transceiver 901 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers.

[0099] The baseband processor 903 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) transmission format (transmission frame) generation / decomposition, (d) transmission path coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) using Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management for Layer 1 (e.g., transmit power control), Layer 2 (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and Layer 3 (e.g., signaling related to attachment, mobility, and call management).

[0100] For example, the digital baseband signal processing by the baseband processor 903 may include signal processing of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a Medium Access Control (MAC) layer, and a Physical (PHY) layer. Also, the control plane processing by the baseband processor 903 may include processing of a Non-Access Stratum (NAS) protocol, a Radio Resource Control (RRC) protocol, MAC Control Elements (CEs), and Downlink Control Information (DCIs).

[0101] The baseband processor 903 may perform Multiple Input Multiple Output (MIMO) encoding and precoding for beamforming.

[0102] The baseband processor 903 may include a modem processor (e.g., a Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., a Central Processing Unit (CPU) or a Micro Processing Unit (MPU)) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 904, which will be described later.

[0103] The application processor 904 is also referred to as a CPU, MPU, microprocessor, or processor core. The application processor 904 may include multiple processors (multiple processor cores). The application processor 904 executes a system software program (operating system (OS)) and various application programs (e.g., a calling application, a web browser, a mailer, a camera operation application, and a music playback application) read from the memory 906 or a memory not shown, thereby realizing various functions of the UE 1.

[0104] In some implementations, the baseband processor 903 and the application processor 904 may be integrated on a single chip, as indicated by the dashed line (905) in Figure 9. In other words, the baseband processor 903 and the application processor 904 may be implemented as a single System on Chip (SoC) device 905. An SoC device may also be called a system Large Scale Integration (LSI) or chipset.

[0105] The memory 906 is volatile memory, nonvolatile memory, or a combination thereof. The memory 906 may include multiple physically independent memory devices. The volatile memory may be, for example, static random access memory (SRAM), dynamic RAM (DRAM), or a combination thereof. The nonvolatile memory may be mask read only memory (MROM), electrically erasable programmable ROM (EEPROM), flash memory, a hard disk drive, or any combination thereof. For example, the memory 906 may include an external memory device accessible from the baseband processor 903, the application processor 904, and the SoC 905. The memory 906 may also include an internal memory device integrated within the baseband processor 903, the application processor 904, or the SoC 905. Furthermore, the memory 906 may include memory within a Universal Integrated Circuit Card (UICC).

[0106] The memory 906 may store one or more software modules (computer programs) 907 including instructions and data for performing the processes described in the above embodiments by the UE 1. In some implementations, the baseband processor 903 or the application processor 904 may be configured to read and execute the software modules 907 from the memory 906 to perform the processes by the UE 1 described in the above embodiments with reference to the drawings.

[0107] In addition, the control plane processing and operations performed by UE1 described in the above embodiment can be realized by elements other than the RF transceiver 901 and the antenna array 902, namely, at least one of the baseband processor 903 and the application processor 904, and the memory 906 storing the software module 907.

[0108] FIG. 10 is a block diagram showing an example configuration of a RAN node 2 according to the above embodiment. Referring to FIG. 10, the RAN node 2 includes a radio frequency transceiver 1001, a network interface 1003, a processor 1004, and a memory 1005. The RF transceiver 1001 performs analog RF signal processing for communication with UEs, including UE1. The RF transceiver 1001 may include multiple transceivers. The RF transceiver 1001 is coupled to an antenna array 1002 and the processor 1004. The RF transceiver 1001 receives modulation symbol data from the processor 1004, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1002. The RF transceiver 1001 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1002 and provides the baseband receive signal to the processor 1004. The RF transceiver 1001 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers.

[0109] The network interface 1003 is used to communicate with network nodes (e.g., SN2, and control and forwarding nodes of the core network), and may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0110] The processor 1004 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The processor 1004 may include multiple processors. For example, the processor 1004 may include a modem processor (e.g., a Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., a Central Processing Unit (CPU) or a Micro Processing Unit (MPU)) that performs control plane processing. The processor 1004 may include a digital beamformer module for beamforming. The digital beamformer module may include a Multiple Input Multiple Output (MIMO) encoder and precoder.

[0111] The memory 1005 is configured by a combination of volatile memory and non-volatile memory. The volatile memory is, for example, Static Random Access Memory (SRAM), Dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is, for example, Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or a hard disk drive, or any combination thereof. The memory 1005 may include storage located remotely from the processor 1004. In this case, the processor 1004 may access the memory 1005 via the network interface 1003 or an I / O interface (not shown).

[0112] The memory 1005 may store one or more software modules (computer programs) 1006 including instructions and data for performing the processes of the RAN node 2 described in the above embodiments. In some implementations, the processor 1004 may be configured to read and execute the software modules 1006 from the memory 1005 to perform the processes of the RAN node 2 described in the above embodiments.

[0113] Note that if the RAN node 2 is a CU (e.g., gNB-CU) or a CU-CP (e.g., gNB-CU-CP), the RAN node 2 may not include the RF transceiver 1001 (and the antenna array 1002).

[0114] As described with reference to Figures 9 and 10, each of the processors included in the UE 1 and the RAN node 2 according to the above-described embodiments may execute one or more programs including instructions for causing a computer to perform the algorithms described with reference to the drawings. The programs include instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The programs may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disk (DVD), Blu-ray disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The programs may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0115] <Other Embodiments> In the above-described embodiments, the "feature" may be a feature newly introduced in a future 3GPP Release 18 or later. Similarly, in the above-described embodiments, the "feature combination" may include a feature newly introduced in a future 3GPP Release 18 or later. For example, in addition to the Mobile Originated (MO) SDT introduced in Release 17, Mobile Terminated (MT) SDT is planned to be introduced in 3GPP Release 18. In one implementation, the feature MT-SDT may be distinguished from the feature MO-SDT, and a separate RACH resource set (or partition, or pool) may be configured for the feature MT-SDT. In this case, the feature combination may include MT-SDT. The RAN node 2 may inform the UE 1 via a broadcast (e.g., SIB) or dedicated RRC signaling whether the MO-SDT and MT-SDT are distinguished in the RACH resource partition. Specifically, the random access configuration (e.g., RACH-Config) sent from the RAN node 2 to the UE 1 may include a one-bit flag (e.g., "mt-SDT") as an optional element. If the random access configuration includes this flag, the UE 1 may use the RACH resource set for the feature (MO-)SDT for MT-SDT. On the other hand, if the random access configuration does not include this flag, the UE 1 checks whether a separate RACH resource set (or partition, or pool) is configured for MT-SDT, and if so, uses the separate RACH resource set for MT-SDT. If the random access configuration does not include this flag and a separate RACH resource set for MT-SDT is not configured, the UE 1 may understand that MT-SDT is not supported. In this case, if UE1 triggers MT-SDT, UE1 may use the RACH resource set for the feature (MO-)SDT for MT-SDT, or may use the same RACH resource set for MT-SDT as in Release 15 and / or Release 16.

[0116] In the above-described embodiment, if the configuration (e.g., random access configuration) received via RRC signaling (e.g., SIB) includes configuration, information, or fields related to features (e.g., Release 17 features) that UE1 does not support, UE1 may operate not to ignore the value (or code point) of the configuration, information, or field.

[0117] For example, UE1 may recognize the size of the RACH resource set (or partition) for a desired feature or feature combination based on the value of a first ra-PreambleStartIndex field for that feature or feature combination and the value of a second ra-PreambleStartIndex field for another feature or feature combination immediately following it. In this case, UE1 should not ignore the value of the second ra-PreambleStartIndex field, regardless of whether UE1 supports the feature or feature combination associated with the second ra-PreambleStartIndex field.

[0118] In some of the above-described embodiments, for a specific feature or a feature combination including the same, UE1 may perform an operation (or process) different from that of the above-described embodiment. For example, with respect to uplink carrier selection, for a specific feature (e.g., RedCap) or a feature combination including the same, the uplink carrier (e.g., NUL carrier) to be selected may be predetermined (or specified in a specification). This is useful for fully utilizing the functionality of the feature or taking into account limitations in the functionality of the feature.

[0119] In some of the above-described embodiments, for a specific feature or a feature combination including the specific feature, UE1 may perform an operation (or process) different from that in the above-described embodiments. For example, for a specific feature (e.g., Coverage Enhancement), UE1 may determine whether the feature is necessary (or whether to execute the feature) after selecting an uplink carrier. This is useful when the function of the feature depends on the result of uplink carrier selection.

[0120] Furthermore, the above-described embodiments are merely examples of application of the technical ideas obtained by the inventors of the present invention. In other words, the technical ideas are not limited to the above-described embodiments, and various modifications are possible.

[0121] For example, some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0122] (Supplementary Note 1) A wireless terminal comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to: perform a first random access using a random access resource associated with a feature combination; and, if the first random access fails, fall back to a second random access using a random access resource associated with a feature subset included in the feature combination. (Supplementary Note 2) The wireless terminal of Supplementary Note 1, wherein the feature combination includes two or more of Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CovEnh), and Slicing, and the feature subset includes one or more of RedCap, SDT, CovEnh, and Slicing. (Supplementary Note 3) The wireless terminal of Supplementary Note 2, wherein the feature combination includes Reduced Capability (RedCap) and another feature, and the feature subset includes only RedCap. (Supplementary Note 4) The wireless terminal of Supplementary Note 2, wherein the feature combination includes Coverage Enhancement (CovEnh) and other features, and the feature subset includes only CovEnh. (Supplementary Note 5) A method performed by a wireless terminal, comprising: performing a first random access using a random access resource associated with the feature combination, and if the first random access fails, falling back to a second random access using a random access resource associated with a feature subset included in the feature combination. (Supplementary Note 6) A program for causing a computer to perform a method for a wireless terminal, the method comprising: performing a first random access using a random access resource associated with the feature combination, and if the first random access fails, falling back to a second random access using a random access resource associated with a feature subset included in the feature combination.(Supplementary Note 7) A wireless terminal comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to perform contention-free random access (CFRA), and if the CFRA fails, fall back to contention-based random access (CBRA) using a random access resource associated with a feature or a feature combination. (Supplementary Note 8) The wireless terminal according to Supplementary Note 7, wherein the feature is Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CovEnh), or Slicing, and the feature combination includes at least two of RedCap, SDT, CovEnh, and Slicing. (Supplementary Note 9) The wireless terminal according to Supplementary Note 7 or 8, wherein the CFRA is performed during handover. (Supplementary Note 10) A method performed by a wireless terminal, comprising: performing contention-free random access (CFRA); and if the CFRA fails, falling back to contention-based random access (CBRA) using a random access resource associated with a feature or a combination of features. (Supplementary Note 11) A program for causing a computer to perform a method for a wireless terminal, the method comprising: performing contention-free random access (CFRA); and if the CFRA fails, falling back to contention-based random access (CBRA) using a random access resource associated with a feature or a combination of features.(Supplementary Note 12) A wireless terminal comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to: initiate random access to start a Small Data Transmission (SDT), and, when it becomes necessary to transmit uplink data not related to the SDT while the SDT is being executed, perform random access using a random access resource associated with one or more combinations of features excluding the SDT. (Supplementary Note 13) The wireless terminal according to Supplementary Note 12, wherein the combination of one or more features includes at least one of Reduced Capability (RedCap), Coverage Enhancement (CovEnh), and Slicing. (Supplementary Note 14) A method performed by a wireless terminal, comprising: initiating random access to start a Small Data Transmission (SDT), and, when it becomes necessary to transmit uplink data not related to the SDT while the SDT is being executed, performing random access using a random access resource associated with one or more combinations of features excluding the SDT. (Supplementary Note 15) A program for causing a computer to perform a method for a wireless terminal, the method comprising: initiating random access for initiating Small Data Transmission (SDT); and, when it becomes necessary to transmit uplink data not related to the SDT while the SDT is being executed, performing random access using a random access resource associated with a combination of one or more features excluding the SDT.and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to: perform random access using a random access resource selected from a set of random access resources associated with a feature or a combination of features; if the random access fails, include information of the feature or the combination of features in a random access report regarding the failure of the random access; store the random access report; and transmit the random access report to a network, wherein the feature is Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CovEnh), or Slicing, and the combination of features includes at least two of RedCap, SDT, CovEnh, and Slicing. (Supplementary Note 17) The wireless terminal according to Supplementary Note 16, wherein the at least one processor is configured to set a raPurpose field included in the random access report and for indicating a purpose of the random access to indicate the information. (Supplementary Note 18) The wireless terminal according to Supplementary Note 16, wherein the at least one processor is configured to set a new field included in the random access report to indicate the information. (Supplementary Note 19) The wireless terminal according to any one of Supplements 16 to 18, wherein if a first fallback from preamble transmission using a random access resource associated with the feature combination to preamble transmission using a random access resource associated with a feature subset included in the feature combination is performed in the random access, the at least one processor is configured to include information of the first fallback in the random access report.(Supplementary Note 20) The wireless terminal of any one of Supplementary Notes 16 to 19, wherein if a second fallback from preamble transmission using a random access resource associated with the feature or the combination of features to preamble transmission using a random access resource not associated with the feature or the combination of features is performed in the random access, the at least one processor is configured to include information of the second fallback in the random access report. (Supplementary Note 21) A method performed by a wireless terminal, comprising: performing random access using a random access resource selected from a set of random access resources associated with a feature or a feature combination; if the random access fails, including information of the feature or feature combination in a random access report regarding the random access failure; storing the random access report; and transmitting the random access report to a network, wherein the feature is Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CovEnh), or Slicing, and the feature combination includes at least two of RedCap, SDT, CovEnh, and Slicing.(Supplementary Note 22) A program for causing a computer to perform a method for a wireless terminal, the method comprising: performing random access using a random access resource selected from a set of random access resources associated with a feature or a combination of features; if the random access fails, including information of the feature or the combination of features in a random access report regarding the failure of the random access; storing the random access report; and transmitting the random access report to a network; wherein the feature is Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CovEnh), or Slicing; and the combination of features includes at least two of RedCap, SDT, CovEnh, and Slicing.

[0123] This application claims priority based on Japanese Patent Application No. 2021-171922, filed on October 20, 2021, the disclosure of which is incorporated herein in its entirety.

[0124] 1 UE 2 RAN node 21 cell 903 baseband processor 904 application processor 906 memory 907 modules 1004 processor 1005 memory 1006 modules

Claims

1. A wireless terminal comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to: perform a first random access using a random access resource associated with a feature combination; and, if the first random access fails, fall back to a second random access using a random access resource associated with a feature subset included in the feature combination.

2. The wireless terminal of claim 1, wherein the feature combination includes two or more of Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CovEnh), and Slicing, and the feature subset includes one or more of RedCap, SDT, CovEnh, and Slicing.

3. The wireless terminal of claim 2, wherein the feature combination includes Reduced Capability (RedCap) and other features, and the feature subset includes only RedCap.

4. The wireless terminal of claim 2, wherein the feature combination includes Coverage Enhancement (CovEnh) and other features, and the feature subset includes only CovEnh.

5. A method performed by a wireless terminal, comprising: performing a first random access using a random access resource associated with a feature combination; and, if the first random access fails, falling back to a second random access using a random access resource associated with a feature subset included in the feature combination.

6. A non-transitory computer-readable medium storing a program for causing a computer to perform a method for a wireless terminal, the method comprising: performing a first random access using a random access resource associated with a feature combination; and, if the first random access fails, falling back to a second random access using a random access resource associated with a feature subset included in the feature combination.

7. A wireless terminal comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to: perform contention-free random access (CFRA); and, if the CFRA fails, fall back to contention-based random access (CBRA) using a random access resource associated with a feature or feature combination.

8. The wireless terminal according to claim 7, wherein the feature is Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CovEnh), or Slicing, and the feature combination includes at least two of RedCap, SDT, CovEnh, and Slicing.

9. The wireless terminal according to claim 7 or 8, wherein the CFRA is performed during handover.

10. A method performed by a wireless terminal, comprising: performing contention-free random access (CFRA); and, if the CFRA fails, falling back to contention-based random access (CBRA) using random access resources associated with a feature or feature combination.

11. A non-transitory computer-readable medium storing a program for causing a computer to perform a method for a wireless terminal, the method comprising: performing contention-free random access (CFRA); and, if the CFRA fails, falling back to contention-based random access (CBRA) using a random access resource associated with a feature or combination of features.

12. A wireless terminal comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to initiate random access to start a Small Data Transmission (SDT); and, when a need arises to transmit uplink data not related to the SDT while the SDT is being executed, to perform random access using a random access resource associated with a combination of one or more features excluding the SDT.

13. The wireless terminal of claim 12, wherein the combination of one or more features includes at least one of Reduced Capability (RedCap), Coverage Enhancement (CovEnh), and Slicing.

14. A method performed by a wireless terminal, comprising: initiating random access to start Small Data Transmission (SDT); and, when it becomes necessary to transmit uplink data not related to the SDT during execution of the SDT, performing random access using a random access resource associated with a combination of one or more features excluding the SDT.

15. A non-transitory computer-readable medium storing a program for causing a computer to perform a method for a wireless terminal, the method comprising: initiating random access to initiate Small Data Transmission (SDT); and, when a need arises to transmit uplink data not related to the SDT while the SDT is being executed, performing random access using a random access resource associated with a combination of one or more features excluding the SDT.

16. A wireless terminal comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to: perform random access using a random access resource selected from a set of random access resources associated with a feature or a combination of features; if the random access fails, include information about the feature or combination of features in a random access report regarding the failure of the random access; store the random access report; and transmit the random access report to a network; wherein the feature is Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CovEnh), or Slicing; and the combination of features includes at least two of RedCap, SDT, CovEnh, and Slicing.

17. The wireless terminal of claim 16, wherein the at least one processor is configured to set a raPurpose field included in the random access report to indicate a purpose of the random access to indicate the information.

18. The wireless terminal of claim 16, wherein said at least one processor is configured to set a new field included in said random access report to indicate said information.

19. The wireless terminal according to any one of claims 16 to 18, wherein if a first fallback from preamble transmission using a random access resource associated with the feature combination to preamble transmission using a random access resource associated with a feature subset included in the feature combination is performed in the random access, the at least one processor is configured to include information of the first fallback in the random access report.

20. The wireless terminal of any one of claims 16 to 19, wherein if a second fallback is performed in the random access from preamble transmission using a random access resource associated with the feature or the combination of features to preamble transmission using a random access resource not associated with the feature or the combination of features, the at least one processor is configured to include information of the second fallback in the random access report.

21. A method performed by a wireless terminal, comprising: performing random access using a random access resource selected from a set of random access resources associated with a feature or a combination of features; if the random access fails, including information about the feature or combination of features in a random access report regarding the failure of the random access; storing the random access report; and transmitting the random access report to a network, wherein the feature is Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CovEnh), or Slicing, and the combination of features includes at least two of RedCap, SDT, CovEnh, and Slicing.

22. A non-transitory computer-readable medium storing a program for causing a computer to perform a method for a wireless terminal, the method comprising: performing random access using a random access resource selected from a set of random access resources associated with a feature or a combination of features; if the random access fails, including information about the feature or combination of features in a random access report regarding the failure of the random access; storing the random access report; and transmitting the random access report to a network, wherein the feature is Reduced Capability (RedCap), Small Data Transmission (SDT), Coverage Enhancement (CovEnh), or Slicing, and the combination of features includes at least two of RedCap, SDT, CovEnh, and Slicing.

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