Communication Systems

Abstract

A system is disclosed in which a user equipment (UE) in a radio resource control (RRC) inactive state performs a small data transmission procedure using a configured grant or random access. As part of this procedure, the UE receives configuration information for controlling subsequent small data transmissions. For example, the configuration information may be used to reactivate, reconfigure, or release a configured grant stored by the UE.

Description

[Technical field]

[0001] The present invention relates to communication systems. The present invention is particularly, but not exclusively, related to wireless communication systems and devices thereof operating in accordance with 3GPP (3rd Generation Partnership Project) standards or equivalents or derivatives thereof, including LTE-Advanced and next generation or 5G networks. The present invention is particularly, but not necessarily exclusively, related to the transmission of small data to user equipment in an inactive state. [Background technology]

[0002] The latest developments in 3GPP standards are also referred to as Evolved Packet Core (EPC) and Long Term Evolution (LTE) of Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), and are also commonly referred to as "4G". In addition, the terms "5G" and "new radio" (NR) refer to evolving communication technologies that are expected to support various applications and services. Various details of 5G networks are described, for example, in the "NGMN5G White Paper" V1.0 by the Next Generation Mobile Networks (NGMN) Alliance, which is available from Non-Patent Document 1. 3GPP intends to support 5G as the so-called 3GPP NextGen Radio Access Network (RAN) and 3GPP NextGen Core Network.

[0003] Under 3GPP standards, a NodeB (or "eNB" in LTE and "gNB" in 5G) is a base station through which communication devices (user equipment or "UE") connect to a core network and communicate to other communication devices or remote servers. For simplicity, this application uses the term base station to refer to any such base station.

[0004] For simplicity, this application uses the terms mobile device, user device, or UE to refer to any communication device capable of communicating with a core network via one or more base stations.

[0005] The communication devices may be, for example, mobile communication devices such as mobile phones, smartphones, user equipment, personal digital assistants, laptop / tablet computers, web browsers, and / or e-book readers. Such mobile (or, more generally, stationary) devices are typically operated by a user. However, 3GPP standards also allow so-called "Internet of Things" (IoT) devices (e.g., Narrowband IoT (NB-IoT) devices) to be connected to the network, where IoT devices typically include various measurement instruments, telemetry instruments, monitoring systems, tracking and tracing devices, in-vehicle safety systems, vehicle maintenance systems, road sensors, digital billboards, point-of-sale (POS) terminals, and automation equipment such as remote control systems. Effectively, the Internet of Things is a network of devices (or "things") equipped with appropriate electronics, software, sensors, and / or network connectivity, etc., enabling the devices to collect and exchange data with each other and with other communication devices. It will be appreciated that IoT devices are also referred to as Machine-Type Communication (MTC) communication devices or Machine-to-Machine (M2M) communication devices.

[0006] For simplicity, this application often refers to mobile devices in the description, however, the described techniques may be implemented on any communications device (mobile and / or generally stationary) that can connect to a communications network to transmit / receive data, whether controlled by human input or software instructions stored in memory.

[0007] The core network (i.e., "EPC" in the case of LTE and "5GC" in 5G) typically hosts functionality for subscriber management, mobility management, charging, security, and call / session management, among other things, and provides connectivity for communication devices to external networks such as the Internet.

[0008] Before a UE can communicate data via a base station, it needs to perform a so-called (contention-based) random access procedure with the base station serving the cell in which the UE is located. The random access procedure includes a two-step or four-step procedure (e.g., Release 15 and later), after which the UE enters a so-called Radio Resource Control (RRC) CONNECTED state and can start to transmit / receive data (both user plane data and control plane data) using resources allocated by the network (base station). The transition of the UE between RRC states is controlled by the network (using associated timers, etc.). Typically, when the UE has no more data to transmit / receive, in order to free up network resources and save battery on the UE side, the UE is instructed by the network to move to a so-called RRC IDLE state. Each time the UE has data to transmit or receive, the UE needs to re-enter the RRC CONNECTED state (after performing an appropriate random access procedure with the network). Generally, the RRC IDLE state is the most power efficient state, and some UEs may need to transition between RRC IDLE and RRC CONNECTED frequently, which may result in increased signaling and may also have a negative impact on the UE power consumption.

[0009] Typically, a base station provides scheduling information (or scheduling "grant") to a particular RRC Connected UE (or group of UEs) to enable them to communicate (i.e., transmit / receive data and control signaling) within the cellular communication system. However, some UEs may be configured to transmit (uplink) data without an associated, explicit scheduling grant. This is referred to as "configured grant type-1" and may be useful in the case of sporadic communication by a group of devices (e.g., MTC devices that do not transmit frequently) using a particular communication resource, where such sporadic communication is unlikely to interfere with regular communication (e.g., by conventional UEs or other devices with scheduled transmissions).

[0010] In addition to RRC IDLE and RRC CONNECTED, the 3GPP NR standard has also introduced the so-called RRC INACTIVE state. In the RRC INACTIVE state, all DRBs and Signalling Radio Bearers (SRBs) are suspended except for "SRB0". However, the UE's Ng-U and Ng-C connections are maintained (unlike when in RRC IDLE), which means that only the Common Control Channel (CCCH) is active (for SRB0). Thus, when new data arrives from higher layers, it cannot be transmitted immediately. Data can only be transmitted after performing an RRC resumption procedure, which causes the UE to reactivate (or reconfigure) all its DRBs and SRBs.

[0011] For a UE in RRC INACTIVE state, 3GPP intends to support certain communications (typically relatively small amounts of data) without the UE having to (re)activate / restart its RRC connection with the network. This feature is referred to as "small data transmission" and is applicable to several traffic types, such as infrequent transmissions, short data bursts, and low throughput transmissions. Some of the advantages associated with small data transmission include reduced signaling overhead associated with RRC state transitions (compared to when the UE needs to transition to an RRC connected state), lower battery consumption, and lower latency.

[0012] The motivation behind small data transmission for UEs in INACTIVE state is explained in Non-Patent Document 2. In short, the small data transmission feature allows the UE to remain in RRC_INACTIVE state for certain downlink (mobile terminated, "MT") and uplink (mobile originated, "MO") data transmissions. In other words, the UE does not need to resume its RRC connection (i.e., move to RRC CONNECTED state) for data transmission and then release the connection (return to RRC INACTIVE state) after data transmission, thereby allowing the UE to avoid some of the associated drawbacks (e.g., increased power consumption and signaling overhead).

[0013] As part of the Rel-15 and Rel-16 work, key enablers for small data transmissions (RRC INACTIVE state, 2-step, 4-step random access, and configured grant type-1) have been specified by 3GPP. In Rel-17, small and infrequent data traffic is enabled in the INACTIVE state, for the following uses: -Smartphone Applications: - Traffic from instant messaging services (e.g. WhatsApp, QQ, WeChat, etc.); -heartbeat / keep-alive traffic from instant messaging / email clients and similar applications, - Push notifications from various applications, Non-smartphone applications: -Traffic from wearables (such as periodic positioning information), -Sensors (Industrial Wireless Sensor Networks that transmit temperature, pressure readings periodically or in an event-triggered manner), and -Smart meters and smart meter networks that send periodic meter readings

[0014] However, some challenges still remain that need to be addressed. For example, it is still not clear whether small data transmissions should be carried using either random access or configured grant (CG) procedures. On the one hand, random access is more versatile, but on the other hand, CG is more suitable for static UEs with known discontinuous reception (DRX) cycles. CG is more efficient and allows for larger pre-established payload sizes, potentially avoiding segmentation. CG requires reserving resources at the base station side, which may go unutilized (if there is no data to transmit). Moreover, small data transmissions can be initiated using CG only while the so-called Time Alignment Timer (TAT) is valid.

[0015] However, it is not clear what happens when the TAT expires. The default behavior is assumed to be that the UE may fall back to small data transmission using a random access procedure or perform an RRC resumption procedure. There is no mechanism to reactivate / reconfigure the CG. To save battery and signaling overhead, it may be beneficial to avoid returning to the RRC_CONNECTED state. For static UEs, typically UEs that use CG for small data transmission, reactivating their previous CG is expected to be more efficient than returning to the RRC_CONNECTED state. [Prior art documents] [Non-patent literature]

[0016] [Non-Patent Document 1] 'NGMN 5G White Paper' V1.0[online], Next Generation Mobile Networks (NGMN) Alliance, Internet<URL: https: / / www.ngmn.org / 5g-white-paper.html> [Non-Patent Document 2] ZTE Corporation, Work Item on NR smalldata transmissions in INACTIVE state[online], 3GPP TSG RAN Meeting #86 RP-193252, Internet<URL: https: / / www.3gpp.org / ftp / tsg_ran / TSG_RAN / TSGR_86 / Docs / RP-193252.zip> [Non-Patent Document 3] 3GPP Technical Specification (TS) 22.368 V13.1.0, Annex B Summary of the Invention

[0017] Accordingly, preferred exemplary embodiments of the present invention aim to provide a method and apparatus that addresses, or at least partially addresses, one or more of the above problems.

[0018] To facilitate efficient understanding for those skilled in the art, the present invention will be described in detail in the context of 3GPP systems (UMTS, LTE, NR), however, the principles of the present invention may be applied to other systems in which communication devices or user equipment (UE) access a core network using radio access technologies.

[0019] In one example aspect, the present invention provides a method performed by a user equipment (UE), the method including initiating a procedure for small data transmission when the UE is in a Radio Resource Control (RRC) Inactive state, and receiving, as part of said procedure, configuration information related to resources allocated for a subsequent small data transmission.

[0020] In one exemplary aspect, the present invention provides a method performed by a communication device of a radio access network, the method including performing a small data transmission procedure with a user equipment (UE) when the UE is in a Radio Resource Control (RRC) Inactive state, and providing, as part of said procedure, configuration information related to allocated resources for a subsequent small data transmission.

[0021] In one example aspect, the present invention provides a user equipment (UE) for small data transmission in a Radio Resource Control (RRC) Inactive state, the UE including: means for initiating a procedure for small data transmission when the UE is in a Radio Resource Control (RRC) Inactive state; and means for receiving, as part of said procedure, configuration information relating to resources allocated for a subsequent small data transmission.

[0022] In one exemplary aspect, the present invention provides a communications apparatus for a radio access network, the communications apparatus including: means for performing a small data transmission procedure with a user equipment (UE) when the UE is in a Radio Resource Control (RRC) Inactive state; and means for providing configuration information relating to allocated resources for a subsequent small data transmission as part of said procedure.

[0023] In another exemplary aspect, the present invention provides a user equipment (UE) for small data transmission in a Radio Resource Control (RRC) Inactive state, the UE including a controller and a transceiver, the controller configured to initiate a procedure for small data transmission when the UE is in a Radio Resource Control (RRC) Inactive state, and to control the transceiver to receive, as part of said procedure, configuration information relating to resources allocated for a subsequent small data transmission.

[0024] In another exemplary aspect, the present invention provides a communication apparatus for a radio access network, the communication apparatus including a controller and a transceiver, the controller configured to control the transceiver to perform a small data transmission procedure with a user equipment (UE) when the UE is in a Radio Resource Control (RRC) Inactive state, and to provide configuration information related to allocated resources for a subsequent small data transmission as part of said procedure.

[0025] Exemplary aspects of the invention extend to corresponding systems, apparatus, and computer program products, such as computer-readable storage media, having instructions stored thereon operable to program a programmable processor to perform the methods described in the above-listed exemplary aspects and implementations or recited in the claims, and / or to program a computer suitably adapted to provide an apparatus as recited in any of the claims.

[0026] Each feature disclosed in this specification (including the claims) and / or illustrated in the drawings may be incorporated into the invention independently of (or in any combination with) any other disclosed and / or illustrated feature. Without particular limitation, any feature of a claim dependent on a particular independent claim may be incorporated into that independent claim in any combination or individually.

[0027] Exemplary embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0028] [Figure 1] 1 illustrates generally a mobile (cellular or wireless) telecommunications system in which exemplary embodiments of the present invention may be applied. [Diagram 2] FIG. 2 is a block diagram of a user equipment (UE) forming part of the system shown in FIG. 1. [Diagram 3] 2 is a block diagram of a base station forming part of the system shown in FIG. 1; [Figure 4] FIG. 2 is a block diagram of a core network node entity forming part of the system shown in FIG. 1; [Diagram 5] FIG. 1 is a schematic diagram of the layers involved in small data transmission. [Figure 6] FIG. 1 is a schematic signaling (timing) diagram illustrating some example ways in which a configured grant may be (re)configured / released using RRC messages. [Figure 7] 10 illustrates generally an exemplary random access response for configuring and activating a configured grant for small data transmission. [Figure 8] A schematic signaling (timing) diagram illustrating some example ways in which a configured grant may be implicitly (re)activated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] overview FIG. 1 illustrates generally a mobile (cellular or wireless) telecommunications system 1 in which exemplary embodiments of the present invention may be applied.

[0030] In this network, users of mobile devices 3 (UE) can communicate with each other and other users via respective base stations 5 and a core network 7 using an appropriate 3GPP radio access technology (RAT), e.g., E-UTRA and / or 5G RAT. It will be appreciated that several base stations 5 form a (radio) access network or (R)AN. As those skilled in the art will appreciate, while for illustrative purposes one mobile device 3 and one base station 5 are shown in FIG. 1, the system, when implemented, will typically include other base stations and mobile devices (UE).

[0031] Each base station 5 controls (either directly or via a home base station, a relay, a remote radio head, and / or a distributed unit, etc.) one or more associated cells. A base station 5 supporting E-UTRA / 4G protocols may be referred to as an "eNB" and a base station 5 supporting Next Generation / 5G protocols may be referred to as a "gNB". It will be appreciated that some base stations 5 may be configured to support both 4G and 5G and / or any other 3GPP or non-3GPP communication protocols.

[0032] The mobile device 3 and its serving base station 5 are connected via a suitable air interface (e.g., the so-called "Uu" interface and / or similar). The neighboring base stations 5 are connected to each other via suitable inter-base station interfaces (such as the so-called "X2" interface and / or "Xn" interface). The base stations 5 are also connected to core network nodes via suitable interfaces (such as the so-called "S1", "NG-C", and / or "NG-U" interfaces).

[0033] The core network 7 typically includes logical nodes (or "functions") for supporting communications within the telecommunications system 1. Typically, for example, the core network 7 of a "next generation" / 5G system includes, among other functions, a control plane function (CPF) 11 and a user plane function (UPF) 12. From the core network 7, connectivity to external IP networks 20 (such as the Internet) may also be provided.

[0034] In this system, uplink and downlink data transmissions and the specific time / frequency resources used for such transmissions are controlled by the base station 5. In particular, when the base station 5 has downlink data to send, the base station 5 informs the intended recipient (e.g., by sending appropriate downlink control information (DCI) over a control channel) as to the resources used for the transmission of the downlink data, so that the intended recipient knows which time / frequency resources will be monitored and decoded before transmitting the downlink data. Similarly, when the mobile device 3 has uplink data to send, the mobile device 3 requests the base station 5 (via appropriate DCI) to allocate uplink resources for the mobile device 3 to transmit the data. This approach is referred to as grant-based transmission.

[0035] The mobile device 3 may also be configured to communicate without such an explicit grant from the network using resources allocated for configured grant type-1 communication (which may also be referred to as grant-free transmission). It will be appreciated that the particular set of time / frequency resources available for such configured grant transmission may be allocated (by the base station 5) separately from any time / frequency resources normally used for grant-based transmission (although they may nevertheless overlap with each other in at least one of the time and frequency domains).

[0036] The system 1 supports both legacy (i.e., 4-step) random access procedures and 2-step random access procedures. In the case of the 4-step random access procedure, the UE (mobile device 3) transmits a Physical Random Access Channel (PRACH) preamble (referred to as "Msg1") as the first step. If the base station detects the preamble, the base station 5 responds with a random access response (RAR), also known as "Msg2". The RAR includes the detected preamble identifier, a time-advance command, a temporary C-RNTI (TC-RNTI), and an uplink (UL) grant for scheduling a Physical Uplink Shared Channel (PUSCH) transmission from the UE (referred to as "Msg3"). The UE 3 transmits Msg3 as scheduled and includes an identifier for contention resolution. Upon receiving Msg3, the network transmits a contention resolution message, also known as "Msg4", with a contention resolution identifier. If UE3 successfully receives Msg4 and if it finds the contention resolution identifier in the message, it sends an acknowledgement on the Physical Uplink Control Channel (PUCCH), completing the 4-step random access procedure. As can be seen, the 4-step random access procedure requires two round trip cycles between the UE and the base station.

[0037] The 2-step random access procedure aims to reduce latency and control signaling overhead by using a single round trip cycle between the UE 3 and the base station 5. Effectively, this is achieved by combining the UE's PRACH preamble (Msg1) transmission and the scheduled PUSCH transmission (Msg3) into a single message (referred to as "MsgA"). Similarly, the random access response (RAR / Msg2) and the contention resolution message (Msg4) from the base station 5 to the UE 3 are combined in the 2-step random access procedure (also referred to as "MsgB"). The 2-step random access is primarily intended to support, among other things, (Ultra) Low Latency Communication, 10 ms control plane latency, fast handover, efficient channel access in unlicensed spectrum, and transmission of small data packets.

[0038] This network 1 node is configured to support small data transmission service for UE3 in RRC INACTIVE state using configured grant (while the associated time alignment timer is valid). When the TAT expires and the UE3 still has data to transmit, the UE3 can initiate small data transmission through an appropriate random access procedure (either 2-step random access or 4-step random access). In this case, the network (base station 5) reactivates or (re)configures the CG for the UE3 as part of the handshake during the random access small data transmission (RACH SDT) procedure. It will be appreciated that CG reactivation can be applicable when the UE3 is still in the same serving cell in which the CG was initially / previously configured, whereas CG reconfiguration can be applicable both for the same or a different serving cell. CG reactivation / (re)configuration can be achieved by appropriate use of radio resource control signaling, medium access control signaling, or physical downlink control channel signaling.

[0039] Some advantages of the proposed approach are that there is no waste in signaling, since CG reactivation is part of the uplink small data transmission process. The UE does not need to switch to RRC_CONNECTED mode. Moreover, the network has total control over CG reactivation. The same (or similar) approach may be used to configure a new CG for a UE that frequently uses random access for small data transmission. In other words, the proposed technique may be used to control switching between random access small data transmission and CG small data transmission (or vice versa).

[0040] Mobile Devices FIG. 2 is a block diagram illustrating the main components of the mobile device 3 (e.g., a mobile phone or IoT device) shown in FIG. 1. As shown, the mobile device 3 has a transceiver circuit 31 operable to transmit signals to and receive signals from a base station 5 via one or more antennas 33. The mobile device 3 has a controller 37 for controlling the operation of the mobile device 3. The controller 37 is associated with a memory 39 and coupled to the transceiver circuit 31. Although not necessarily required for its operation, the mobile device 3 may of course have all the usual functions of a conventional mobile phone (such as a user interface 35), which may be provided by any one or any combination of hardware, software, and firmware, as appropriate. The software may be pre-installed in the memory 39 and / or may be downloaded, for example, via a telecommunications network or from a removable data storage device (RMD).

[0041] The controller 37, in this example, is configured to control the overall operation of the mobile device 3 by means of program or software instructions stored in memory 39. As shown, those software instructions include, among other things, an operating system 41, a communications control module 43, and a small data module 45.

[0042] The communications control module 43 is operable to control communications between the mobile device 3 and its serving base station 5 (and other communications devices connected to the serving base station 5, such as other user equipment, core network nodes, etc.).

[0043] The small data module 45 is responsible for communicating small data transmissions that the mobile device 3 can send (or receive) without having an active RRC connection (e.g., while the mobile device 3 is in an RRC INACTIVE state). The small data module 45 is also responsible for handling a Time Alignment Timer (TAT) associated with a configured grant for small data transmissions, and for initiating / performing CG reactivation / (re)configuration for small data transmissions when the TAT expires (or it is no longer valid).

[0044] Although not shown in FIG. 2, the mobile device 3 also typically includes respective modules corresponding to different communication layers. Those modules may be implemented as part of the communication control module 43 and include one or more of the following: a Non-Access Stratum (NAS) module, a Radio Resource Control (RRC) module, a Service Data Adaptation Protocol (SDAP) module, a Packet Data Convergence Protocol (PDCP) module, a Radio Link Control (RLC) module, a Medium Access Control (MAC) module, and a physical layer (PHY) module. Those communication layers for both the user plane (UP) and the control plane (CP) are illustrated in FIG. 5.

[0045] The RRC module is operable to generate, transmit, and receive signaling messages formatted according to the RRC standard. For example, such messages are exchanged between the mobile device 3 and its serving base station 5. The RRC messages may include, for example, messages conveying small data transmissions and / or messages related to the (reception of) small data transmissions including related information (e.g., information related to CG reactivation / (re)configuration for small data transmissions). The RRC module is also responsible for managing the mobile device's radio resource control connection with the network as well as its RRC modes (e.g., RRC IDLE, RRC CONNECTED, and RRC INACTIVE).

[0046] The NAS module is operable to generate, transmit and receive signaling messages formatted according to NAS standards. For example, such messages are exchanged between the mobile device 3 and a mobility management entity (MME) or an access and mobility function (AMF) via the serving base station 5 using the RRC module. NAS messages may include, for example, messages related to CG reactivation / (re)configuration for small data transmission.

[0047] base station FIG. 3 is a block diagram illustrating the main components of the base station 5 shown in FIG. 1. As shown, the base station 5 has a transceiver circuit 51 for transmitting signals to and receiving signals from user equipment (such as the mobile device 3) via one or more antennas 53, a core network interface 55 (such as an S1 interface and / or an NG-C interface) for transmitting signals to and receiving signals from the core network 7, and a base station interface 56 (such as an X2 interface and / or an Xn interface) for transmitting signals to and receiving signals from neighboring base stations. The base station 5 has a controller 57 for controlling the operation of the base station 5 according to software stored in a memory 59. The software may be pre-installed in the memory 59 and / or may be downloaded via the telecommunications network 1 or, for example, from a removable data storage device (RMD). The software includes, among other things, an operating system 61, at least a communication control module 63, and a small data module 65.

[0048] The communication control module 63 is responsible for handling (generating / sending / receiving) signaling between the base station 5 and other nodes, such as the UE 3 and core network nodes. Such signaling may include, for example, control data for managing the operation of the mobile device 3 (e.g., NAS, RRC, paging, and / or system information, etc.).

[0049] The small data module 65 is responsible for handling small data transmissions for the mobile device 3 (eg, while the mobile device 3 is in an RRC INACTIVE state).

[0050] Although not shown in FIG. 3, the base station 5 also typically includes an inter-base station interface module (e.g., an X2 / Xn module), an appropriate core network interface module (which may be implemented as part of the communication control module 43), and respective modules corresponding to the different communication layers (e.g., an RRC module, an SDAP module, a PDCP module, an RLC module, a MAC module, and a PHY module).

[0051] The inter-base station interface module is operable to generate, transmit, and receive signaling messages (X2 / Xn messages) formatted according to the X2AP (or XnAP) standard. The X2 / Xn messages may include messages related to paging of the mobile device 3, handover, data transfer, transfer / fetching of UE context (and other information related to the mobile device 3) between neighboring base stations.

[0052] The core network interface module is operable to generate, send and receive signaling messages formatted according to the NG-C standard (or the S1AP standard in LTE), including messages carrying small data transmissions for the UE 3. For example, such messages are exchanged between the base station 5 and the MME / AMF and / or Serving Gateway (S-GW).

[0053] The RRC module is operable to generate, transmit, and receive signaling messages formatted according to the RRC standard. For example, such messages are exchanged between the base station 5 and the mobile device 3 (and other user equipment within the cell of the base station 5). The RRC messages may include messages related to small data transmissions (or reception), including, for example, messages carrying small data transmissions and related information. The RRC module is also responsible for managing the mobile device's radio resource control connection with the network as well as its RRC modes (e.g., RRC IDLE, RRC CONNECTED, and RRC INACTIVE).

[0054] Core Network Node FIG. 4 is a block diagram illustrating the main components (or functions) of a typical core network node shown in FIG. 1, e.g., CPF 11 or UPF 12. As shown, the core network node includes a transceiver circuit 71 operable to transmit signals to and receive signals from other nodes (including UE 3 and (R)AN node 5) via a network interface 75. A controller 77 controls the operation of the core network node according to software stored in a memory 79. The software may be pre-installed in the memory 79 and / or downloaded via the telecommunications network 1 or, for example, from a removable data storage device. The software includes, among other things, an operating system 81 and at least a communication control module 83. The communication control module 83 is responsible for handling (generating / sending / receiving) signaling between the core network node and other nodes, such as UE 3, (R)AN node 5, and other core network nodes. The signaling may include, for example, signaling related to CG reactivation / (re)configuration for small data transmission between the mobile device 3 and a core network node.

[0055] Further detailed description is now given of several example manners in which CG reactivation / (re)configuration may be achieved using appropriate Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling, and / or Physical Downlink Control Channel (PDCCH) signaling.

[0056] As explained above, small data transmission may be performed while the UE 3 is operating in the RRC_INACTIVE state. The operation of the RRC_INACTIVE state is triggered based on control data of an appropriate format from the network. Specifically, when the network (base station 5) releases the UE's RRC connection, the UE transmits an RRC_Release message that may include a suspendConfig information element (IE). This IE causes the UE 3 to enter the RRC_INACTIVE state and take the following actions: -Resetting the MAC; -re-establishing an RLC entity for SRB1 (Signaling Radio Bearer #1); -UE inactive access stratum (AS) context with the latest K gNB and K. RRCint storing the key, the ROHC state, the stored Data Radio Bearer (DRB) to Quality of Service (QoS) flow mapping rule, the temporary identifier (C-RNTI) used in the source PCell, the cellIdentity and physical cell identifier of the source PCell, and all other parameters configured except those in the ReconfigurationWithSync IE and the servingCellConfigCommonSIB IE; -Suspend all SRBs and DRBs except SRB0; - instructing all DRB lower layers to suspend PDCP; - indicating to upper layers a suspension of an RRC connection; Entering RRC_INACTIVE and performing cell selection; Execute.

[0057] Thus, in RRC INACTIVE state, the UE 3 can perform small data transmission using its configured grant while the associated Time Alignment Timer (TAT) is valid. When the TAT expires, the UE 3 can initiate small data transmission through an appropriate random access procedure (either 2-step random access or 4-step random access). In this case, the network (base station 5) reactivates or (re)configures the CG for the UE 3 as part of the handshake during the Random Access Small Data Transmission (RACH SDT) procedure. Several possible ways of performing CG reactivation / (re)configuration (e.g. using RRC, MAC CE or PDCCH) are described below.

[0058] In a general sense, the network has various options for controlling the UE's SDT operation, including (re)configuring a CG for small data transmission (SDT), (re)activating a CG for SDT, releasing a CG for SDT, and switching between CG-based SDT and random access-based SDT.

[0059] (Re)configuration: When the UE 3 moves from RRC CONNECTED mode to RRC INACTIVE mode, the UE 3 may be initially configured with CG resources for the SDT. The term reconfiguration refers to the provision of a new CG configuration and follows the same procedure as the initial configuration (in this case any previous CG is released as a result of the reconfiguration). It will be appreciated that a special case of reconfiguration is the release of CG resources for the SDT (in this case the UE 3 may still be able to use random access).

[0060] (Re)activation: Activation refers to the process of activating an existing CG configuration (e.g., an initial CG configuration or a reconfigured CG configuration), for example after restarting the associated TAT. Thus, in this case, it would be assumed that the CG is implicitly deactivated (and not released) after the TAT expires. This approach allows for reactivating a CG as many times as necessary.

[0061] Both options allow small data to continue to be transmitted over CG resources without the need for excessive RRC signaling (such as when switching back to RRC_CONNECTED state) even after the TAT has expired and then restarted again.

[0062] Below is a more detailed description of different ways to configure or reconfigure a CG while remaining in RRC_INACTIVE state, and different ways to reactivate an expired CG while remaining in RRC_INACTIVE state. Examples of possible combinations between the different configuration and reactivation methods are provided, along with examples of practical implementations.

[0063] (Re)configuration options Option 1a: RRC level at (re)configuration In this case, the network (base station 5) configures resources for the CG through a suitably formatted RRC message (e.g., an "RRCRelease" message containing a SuspendConfig IE). This message is sent from the base station 5 to the UE 3 during a small data transmission procedure. An exemplary SuspendConfig information element content is shown below: [Table 1]

[0064] Further details and implementation options are shown in Figure 6. As can be seen, in step S1, the UE 3 / mobile device may be configured to obtain information identifying resources for random access from system information (SI) transmitted by the base station 5. It will be appreciated that there may be different random access resources assigned to (groups of) different UEs, and different resources may be assigned for 2-step random access and 4-step random access. When the UE 3 is in RRC CONNECTED mode, the UE 3 initiates the relevant TAT, as generally shown in step S2.

[0065] When the network first configures resources for small data transmission via a configured grant (CG), the UE3 receives such configuration via a message that suspends the UE's RRC connection. This corresponds to "Case 1" in FIG. 6. In particular, as shown in step S3, the network uses the configured grant (configured grant type-1) to transmit to the UE3 a "RRCRelease" message that includes a SuspendConfig IE, which includes a ConfigGrantforSmallDataTransmission IE (and / or the like) that informs the UE3 about the parameters / resources for small data transmission. This message, and more specifically the information contained in the SuspendConfig IE, causes the UE to enter RRC INACTIVE mode and leave the TAT running. The UE3 also stores (using its small data module 45) parameters that identify the CG resources that will be used (when there is small data to transmit). Thus, when the UE3 has small data to transmit, the UE3 triggers a small data transmission procedure and activates the stored CG. Thus, as generally shown in step S4, the UE 3 (using its small data module 45) performs an appropriate SDT procedure using the CG resources allocated for the small data transmission, and following the small data transmission the network releases the UE's RRC connection back to the RRC INACTIVE state (step S5). Alternatively, the UE 3 may perform the SDT procedure in step S4 using random access.

[0066] As part of suspending the RRC connection or completing the small data transmission procedure and remaining in RRC INACTIVE mode, the base station 5 transmits an appropriately formatted RRC message to the UE 3, including a ConfigGrantforSmallDataTransmission IE (in the SuspendConfig IE) that configures or reconfigures parameters / resources to be used for the UE's subsequent small data transmission. The RRC message may include an "RRCRelease" message (as shown in step S5 of FIG. 6) or a "Small Data Transmission Complete" message. Effectively, the message in step S5 may be used to configure new CG resources for the UE 3 (i.e., "case 1") or to reconfigure CG resources ("case 2"), which involves updating at least one parameter used for SDT.

[0067] Turning now to "Case 3" of Figure 6, the UE 3 may be configured to release (or deactivate) its stored CG parameters when changing cells (see step S6, cell reselection). Thus, it is possible to avoid the UE transmitting in the new cell using resources that may not be appropriate for the SDT in that cell, even if the TAT is still valid and the UE 3 has an initial or reconfigured CG for the SDT. Thus, when the CG is cell specific (when the ConfigGrantforSmallDataTransmission IE in step S3 or S5 is valid only for the current cell), the UE 3 will let the TAT expire upon cell reselection and release any CG for the SDT.

[0068] However, even in this case, the UE 3 may be able to beneficially perform an appropriate SDT procedure via a random access procedure, as generally shown in step S7, to obtain new CG parameters / resources for the UE's subsequent small data transmission using CG. This scenario is referred to as "Case 4" in FIG. 6, where a random access method small data procedure is used to configure CG resources for SDT. In other words, it is possible to instruct the UE 3 to switch from using random access to using CG for its subsequent small data transmission. As in the above case, the applicable CG parameters may be provided by the network as part of the small data procedure, for example in the "RRCRelease" message (as shown in step S8 of FIG. 6) or in the "Small Data Transmission Complete" message, by transmitting a properly formatted ConfigGrantforSmallDataTransmission IE (within the SuspendConfig IE).

[0069] Another advantageous use of RRC signalling is illustrated in steps S9 and S10 of FIG. 6, relating to a scenario in which the network (gNB 5) instructs the UE 3 to release its active CG for SDT (which generally involves expiry of the associated TAT).

[0070] This is the scenario designated "Case 5". In this case, as part of the small data procedure, the network transmits a properly formatted ConfigGrantforSmallDataTransmission IE command (in a SuspendConfig IE) to the UE 3 to release its stored CG information. It will be appreciated that the small data procedure may be a random access SDT or a CG SDT (as shown in step S9 of FIG. 6). The command to release / deactivate the CG parameters may be provided by the network, for example, in a "RRCRelease" message or a "Small Data Transmission Complete" message (as shown in step S10 of FIG. 6). It will be appreciated that as a result of this message, the UE 3 will not attempt to transmit small data via the CG, although it may still use random access.

[0071] In short, the CG is maintained / stored by the UE 3 until it is explicitly released by the base station 5 or until the UE 3 changes the serving cell.

[0072] Option 1b: (Re)configuration at the MAC level It will be appreciated that CG (re)configuration may also be performed at the MAC level.

[0073] As a first variant of this option, the applicable CG configuration may be provided within a Random Access Response (RAR) from the base station 5 to the UE 3. For example, as generally shown in Figure 7, the current RAR may be modified to indicate that the grant is a CG and not a one-shot grant using a so-called "R" bit. It will be appreciated that such a bit (or bits) may be included in any suitable position in the RAR signaling. Since it is assumed that RACH resources are separated for the RACH SDT, the RAR may be modified to include the optional CG configuration along with the configuration bit.

[0074] For example, the R bit may be set to "1" (or "0") to indicate that the UL grant in this RAR is for a reoccurring CG instead of being a one-time grant and that it is activated immediately. When the R bit is set to "0" (or alternatively, "1"), the UL grant in the RAR is for a one-time grant only. It will be appreciated that the R bit may be included in the RAR message (in 4-step random access) or in the fallback RAR (in 2-step random access that falls back to 4-step random access).

[0075] As a second variant of the MAC scheme option, the applicable CG configuration may be provided using a new MAC Control Element (CE), which is compatible with other RRC-less solutions.

[0076] Option 1c: (Re)configuration at PDCCH level In this case, the network configures the CG using the PDCCH, and some of the CG information, eg, periodicity, may be pre-configured via an appropriate RRC message (and / or the like).

[0077] Option 1d: Hybrid RRC / MAC (re)configuration The network (base station 5) may configure the UE 3 with multiple CG resources (grants) with different sizes / periodicities at the RRC level. For example, the CG resources may be configured using the "RRCRelease" message or the "Small Data Transmission Complete" message, as described above, or other suitable RRC messages. The CG resources may be provided in the form of a list, for example via a SuspendConfig IE. It will be appreciated that multiple RRC messages may also be used, if appropriate. An exemplary SuspendConfig IE content according to option 1d is as follows: [Table 2]

[0078] In this case, the base station 5 can rely on the MAC layer to indicate to the UE 3 which one of the stored (active) CG resources is to be used for SDT. Advantageously, this approach is more dynamic and involves less RRC overhead for reconfiguration than some of the other options. This option is also compatible with other RRC-based methods.

[0079] Reactivation Options Option 2a: Reactivation at the RRC level It will be appreciated that the network (base station 5) may instruct the UE 3 to reactivate its CG using a suitably formatted RRC message (e.g., an RRCRelease message with a SuspendConfig IE) sent during the small data transmission procedure. For example, the RRC message may be configured to indicate that the CG is to be reactivated using a single bit. Effectively, this causes the UE to restart its TAT ​​and activate the CG for subsequent small data transmissions.

[0080] Option 2b: Reactivation at the MAC level CG reactivation may be performed at the MAC level, in which case the Random Access Response (RAR) from the base station 5 to the UE 3 may be adapted to use the "R" bit to indicate CG reactivation for SDT (similar to the option illustrated in Figure 7).

[0081] Option 2c: Reactivation at the PDCCH level The network (base station 5) may reactivate the CG by transmitting downlink control information (DCI) in an appropriate format over the PDCCH.

[0082] Option 2d: Hybrid RRC / MAC Reactivation In this case, appropriate information in the MAC layer (e.g. 1, 2 or 3 bits of MAC CE / RAR) may be used to indicate which configuration (if any) is to be used and that the UE 3 activates the relevant CG (any other CGs are deactivated). This option can work with multiple CGs configured from the RRC CONNECTED state or in combination with option 1d. It will be appreciated that a default CG from the CG list may be defined for initial use.

[0083] Option 2e: Implicit reactivation A CG stored by the UE 3 may be automatically reactivated according to the TAT during the random access method SDT (at least until it is explicitly released by the network).

[0084] Figure 8 illustrates three possibilities (denoted as "Case 1" to "Case 3") for controlling the small data transmission operation of a UE by activating, reactivating, and deactivating a previous CG. These procedures may be performed in combination with any of the procedures shown in Figure 6.

[0085] It is assumed that a CG is (re)activated when the associated TAT is running and that the CG is deactivated when the TAT expires. When a CG is deactivated (or all CGs are deactivated, if there are multiple), small data transmission can only take place via either the 4-step random access procedure or the 2-step random access procedure. In the example shown in Figure 8, the 4-step random access procedure is used.

[0086] For example, it is possible to define a new TAT, e.g. SDT-TAT (or another suitable timer) for the purpose of small data transmission procedures in RRC INACTIVE mode, otherwise the same TAT used for RRC CONNECTED mode is reused for this purpose.

[0087] Case 1 illustrates the activation of a CG that is initially (re)configured for the purpose of a subsequent SDT. As generally shown in steps S1 and S2, when a small data transmission procedure is triggered and the UE 3 does not have a stored CG for the SDT, or has stored CGs for the SDT but they are not activated, in this case the small data transmission procedure is triggered and takes place via random access (step S1). Within step S1, the network transmits a random access response that includes a time advance command (TAC). This allows the UE 3 to restart its TAT, and after finishing the small data transmission, the UE 3 can keep the TAT running and can auto-activate the CG stored by the UE 3 (in its small data module 45), which is reconfigured via the RRC message in step S2. The UE 3 can then use the stored CG parameters / resources when there is small data to transmit. Thus, the UE 3 does not need to use random access for the SDT. Instead, the UE 3 triggers a small data transmission procedure based on the activated CG (eg, as in step S3 of FIG. 8).

[0088] Case 2 illustrates an exemplary manner of deactivating a stored CG for SDT purposes. In this case, the UE 3 may use the stored CG to execute SDT procedures (step S3) as long as it is activated (step S4), i.e., as long as the TAT (or "SDT-TAT") is running. However, at some point, the TAT / SDT-TAT may time out / expire, resulting in the CG being deactivated.

[0089] Case 3 illustrates an exemplary scheme for re-deactivating a CG stored for SDT purposes (as in Case 2), e.g., following deactivation by the network or following regular expiration of the associated TAT.

[0090] In particular, in this case, the small data transmission procedure is triggered via a random access (step S5). In step S6, the network transmits a random access response including a time advance command (TAC). This allows the UE3 to restart its TAT ​​and to reactivate the corresponding CG for small data transmission. In this example, the procedure ends with step S9 when the network did not include any CG for small data transmission in the UE3 (after the small data transmission is completed). In this case, the UE3 can keep the stored CG, if it exists. It will be appreciated, however, that the network may decide to reconfigure the CG, as in step S2. In this case, the UE3 replaces the stored CG with the newly reconfigured CG. In either case, the stored CG is reactivated after the UE3 restarts the TAT.

[0091] Combining different (re)configuration and reactivation options It will be appreciated that, where appropriate, the (re)configuration and reactivation options described above may be combined to provide further alternatives. Although various combinations of options for configuration and reactivation exist, some options are further matched with some of the reactivation options below: - Configuration via RRC messages (option 1a) and implicit reactivation (option 2e). This allows the network to configure the correct CG if the UE considers it necessary and if the network can tolerate it (e.g. after a learning period from the random access method SDT). This is an effective combination of the methods described above with reference to Figures 6 and 8. - Configuration via RRC messages (option 1a) and reactivation at the MAC layer (option 2b). This combination is similar to options 1d / 2d, but with only one CG that is either activated or deactivated. In this case, the CG is maintained / stored until it is explicitly released by the network or the UE changes the serving cell. The CG is first activated and then deactivated when the TAT expires. After expiration of the TAT, the base station 5 can use, for example, a bit in the appropriate MAC CE / RAR to reactivate the CG, otherwise the CG remains in the deactivated state. - Configuration and reactivation at the MAC level (options 1b and 2b). See FIG. - A combination of options 1c and 2c (PDCCH based solution). In this case, the RRC layer may pre-configure at least a part of the CG, e.g. periodicity, CS-RNTI (RNTI used for CG activation and deactivation). Thus, in this case, the PDCCH / DCI addressed by the CS-RNTI may be used to periodically activate / release the grants that appear. This combination is similar to configured grant type-2 used in RRC CONNECTED mode.

[0092] Modifications and Substitutions Detailed exemplary embodiments have been described above. As those skilled in the art will recognize, several modifications and alternatives may be made to the exemplary embodiments and still benefit from the invention embodied therein. By way of example, several of those modifications and alternatives are now described.

[0093] In the above example, the UE has used a specific timer (TAT) to control the activation of the CG for small data transmission. However, it will be appreciated that any other suitable timer may be used, such as a new type TAT (e.g., SDT-TAT) or any other timer (new or existing) adapted for the purpose of small data transmission procedure in RRC INACTIVE mode.

[0094] It will be appreciated that CG reactivation may be applicable when the UE is still in the same serving cell where the CG was initially / previously configured, and CG reconfiguration may be applicable both for the same serving cell or a different serving cell.

[0095] The UE may receive an explicit indication / configuration from the network to enable small data transmission via the control plane. The indication / configuration may be sent via an appropriate broadcast or unicast message (e.g., RRC Release or RRC Suspend message and / or the like). The UE may be configured to apply any relevant constraints (e.g., transport block size restrictions, allowable QoS flows, etc.) for the small data transmission service. If no specific constraints are configured, small data transmission may be allowed up to the maximum size of the message carrying the SDT or transport block (TB) size.

[0096] If small data arrives from a higher layer and the size of the data (optionally with necessary padding and information elements) does not exceed the maximum size defined for small data transmission (and passes any other constraints specified or configured), the UE can initiate a small data transmission procedure. In this case, the UE generates a small data transmission message at the RRC layer (using its RRC module) and sends it to the lower layers (i.e., the MAC layer and the PHY layer) for transmission. If the data from the higher layers cannot be sent as "small data" (e.g., due to its size or due to any other applicable constraints), the UE may be configured to generate an RRC resume request message of an appropriate format and send it to the lower layers for transmission so that the data can be transmitted in a standard format (in RRC CONNECTED mode).

[0097] In the above description, for ease of understanding, the UE, (R)AN node, and core network node have been described as having several discrete modules (such as a communication control module). As such, the modules may be provided for some applications, e.g., applications where existing systems have been modified to implement the invention, and for other applications, e.g., applications where the system was designed with inventive features in mind from the beginning, and the modules may be built into an overall operating system or code, and thus may not be identifiable as discrete entities. The modules may also be implemented in software, hardware, firmware, or a mixture thereof.

[0098] Each controller may include any suitable type of processing circuitry, including, but not limited to, one or more hardware-implemented computer processors, microprocessors, central processing units (CPUs), arithmetic logic units (ALUs), input / output (IO) circuitry, internal memory / cache (program and / or data), processing registers, communication buses (e.g., a control bus, a data bus, and / or an address bus), direct memory access (DMA) facilities, and / or hardware or software implemented counters, pointers, and / or timers, etc.

[0099] In the above exemplary embodiment, several software modules have been described. As those skilled in the art will appreciate, the software modules may be provided in compiled or uncompiled form and may be provided to the UE, the (R)AN node, and the core network node as a signal over a computer network or on a recording medium. Furthermore, the functionality performed by some or all of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred to facilitate the updating of the UE, the (R)AN node, and the core network node to update their functionality.

[0100] A user equipment (or "UE") in this disclosure is an entity connected to a network via a radio interface. A UE may also be referred to as a "mobile base station," a "mobile device," a "wireless device," or a "wireless transmit / receive unit" (WTRU).

[0101] It should be noted that the present disclosure is not limited to dedicated communication devices, but may apply to any device having communication capabilities as described in the following paragraphs.

[0102] The terms "user equipment" or "UE" (as the terms are used by 3GPP), "mobile base station," "mobile device," and "wireless device" are generally intended to be synonymous with each other and include terminals, mobile phones, smartphones, tablets, cellular IoT devices, IoT devices, and standalone mobile base stations such as machinery. It will be appreciated that the terms "mobile base station" and "mobile device" also encompass devices that remain stationary for extended periods of time.

[0103] The UE may be, for example, an item of equipment for production or manufacturing and / or an item of energy-related machinery (e.g., boilers, engines, turbines, solar panels, wind turbines, hydroelectric generators, thermal generators, nuclear generators, batteries, nuclear systems and / or related equipment, heavy electrical machinery, pumps including vacuum pumps, compressors, fans, blowers, hydraulic equipment, pneumatic equipment, metal processing machinery, manipulators, robots and / or application systems thereof, tools, moulds or dies, rolls, conveying equipment, lifting equipment, material handling equipment, textile machinery, sewing machines, printing and / or related machinery, paper converting machinery, chemical machinery, mining and / or construction machinery and / or related equipment, machinery and / or implements for agriculture, forestry, and / or fishing, safety and / or environmental protection equipment, tractors, precision bearings, chains, gears, power transmission equipment, lubrication equipment, valves, fittings, and / or application systems for any of the previously mentioned equipment or machinery, etc.).

[0104] A UE may be, for example, an item of transportation equipment (e.g., vehicles, automobiles, motorcycles, bicycles, trains, buses, carts, rickshaws, ships and other watercraft, aircraft, rockets, satellites, drones, balloons, and other transportation equipment).

[0105] A UE may be, for example, an item of information and communications equipment (eg, information and communications equipment such as electronic computers and related equipment, communications and related equipment, electronic components, etc.).

[0106] The UE may be, for example, a refrigeration machine, a refrigeration application product, an item of trade and / or service industry equipment, a vending machine, an automated service machine, an office machine or equipment, a consumer electronic device (e.g., consumer electronic devices such as audio equipment, video equipment, loudspeakers, radios, televisions, microwave ovens, rice cookers, coffee makers, dishwashers, washing machines, dryers, electric fans or related devices, vacuum cleaners, etc.).

[0107] The UE may be, for example, an electrical application system or equipment (eg, an electrical application system or equipment such as an x-ray system, a particle accelerator, a radioisotope equipment, an acoustic equipment, an electromagnetic application equipment, a power application equipment, etc.).

[0108] The UE may be, for example, an electronic lamp, a lighting fixture, a measuring instrument, an analyzer, a tester, or a survey or detector (e.g., a smoke alarm, a motion sensor, a radio tag, or the like survey or detector), a watch or clock, laboratory equipment, optical equipment, medical equipment and / or systems, a weapon, an item of cutlery, or a hand tool, etc.

[0109] The UE may be, for example, a radio-equipped personal digital assistant or related equipment, such as a wireless card or module designed for attachment or insertion into another electronic device (eg, a personal computer, an electrical measuring instrument).

[0110] The UE may be, for example, a device or part of a system that uses various wired and / or wireless communication technologies to provide the applications, services, and solutions described below for the “Internet of Things” (IoT).

[0111] Internet of Things devices (or "Things") may be equipped with appropriate electronics, software, sensors, and / or network connectivity that enable them to collect and exchange data with each other and with other communicating devices. IoT devices may include automated machines that follow software instructions stored in internal memory. IoT devices can operate without the need for human supervision or interaction. IoT devices may also remain stationary and / or inactive for long periods of time. IoT devices may be implemented as part of a (totally) stationary apparatus. IoT devices may also be incorporated into non-stationary apparatus (e.g., vehicles) or attached to animals or humans to be monitored / tracked.

[0112] It will be appreciated that IoT technologies may be implemented on any communication device capable of connecting to a communication network to transmit / receive data, regardless of whether any communication device is controlled by human input or by software instructions stored in memory.

[0113] It will be appreciated that an IoT device may also be referred to as a machine type communication (MTC) device or a machine-to-machine (M2M) communication device. It will be appreciated that a UE may support one or more IoT or MTC applications. Some examples of MTC applications are listed in the table below (Source: Non-Patent Document 3, the contents of which are incorporated herein by reference). This list is not comprehensive and is intended to illustrate some examples of machine type communication applications. [Table 3]

[0114] The applications, services, and solutions may be Mobile Virtual Network Operator (MVNO) emergency wireless communication systems, Private Branch eXchange (PBX) systems, PHS / digital cordless telecommunications systems, Point of Sales (POS) systems, advertising call systems, Multimedia Broadcast and Multicast Services (MBMS), Vehicle-to-Everything (V2X) systems, train radio systems, location-related services, disaster / emergency wireless communication services, community services, video streaming services, femtocell application services, Voice over LTE (VoLTE) services, billing services, radio on-demand services, roaming services, behavior monitoring services, carrier / network selection services, functional restriction services, Proof of Concept (PoC) services, personal information management services, ad hoc networks / Delay Tolerant Networking (DTN) services, and the like.

[0115] Furthermore, the above-described UE categories are merely examples of applications of the technical ideas and exemplary embodiments described herein, and it should be understood that the technical ideas and exemplary embodiments are not limited to the above-described UEs, and various modifications may be made thereto.

[0116] The configuration information may be adapted to identify at least one of: a current configuration to be used by the UE for the subsequent small data transmission, a new or updated configuration to be used by the UE for the subsequent small data transmission, one of a plurality of configurations to be used by the UE for the subsequent small data transmission, a stored configuration to be activated by the UE for the subsequent small data transmission, a stored configuration to be deactivated by the UE for the small data transmission, a stored configuration to be released by the UE for the small data transmission, and a current configuration to be maintained for the subsequent small data transmission after an associated timer expires.

[0117] The configuration information may include a SuspendConfig information element. The configuration information may identify a configured grant for small data transmission. The configuration information may include an information element (e.g., a ConfigGrantforSmallDataTransmission IE) related to the configured grant for small data transmission.

[0118] The UE may receive the configuration information using at least one of RRC signaling, Medium Access Control (MAC) signaling (e.g., in a MAC control element), a Random Access Response (RAR) message, and Physical Downlink Control Channel (PDCCH) signaling (e.g., in Downlink Control Information (DCI)).

[0119] The procedure for a small data transmission may include transmitting a message including the small data transmission using resources associated with "configured grant type-1". The procedure for a small data transmission may include transmitting the small data transmission via a message (e.g., "Msg3" or "MsgA") that forms part of a random access procedure.

[0120] The method performed by the UE may further include, upon receiving a time advance command (TAC), restarting a timer associated with the stored configuration for the small data transmission and reactivating the stored configuration for a subsequent small data transmission.

[0121] When the UE holds information identifying a configured grant for small data transmission, the method may include initiating a procedure for small data transmission using the configured grant if an associated time alignment timer (TAT) is running, and initiating a procedure for small data transmission via random access if the associated TAT is not running, and determining based on the received configuration information whether to activate the information identifying the configured grant for a subsequent small data transmission.

[0122] The method may further include receiving, by the UE, via RRC signaling or PDCCH signaling, information identifying a plurality of candidate resources for the small data transmission (e.g., a plurality of "configured grant type-1" configurations), and receiving, via MAC signaling, information identifying at least one of the candidate resources for performing the small data transmission.

[0123] Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0124] The whole or part of the above disclosed exemplary embodiments can be described as follows, but is not limited thereto.

[0125] (Appendix 1) 1. A method performed by a user equipment (UE), comprising: Initiating a procedure for small data transmission when the UE is in a radio resource control (RRC) Inactive state; receiving configuration information relating to allocated resources for subsequent small data transmissions as part of the procedure; A method comprising:

[0126] (Appendix 2) The configuration information is a current configuration to be used by the UE for a subsequent small data transmission; and a new or updated configuration to be used by the UE for subsequent small data transmissions; and one of a plurality of configurations to be used by the UE for a subsequent small data transmission; a stored configuration to be reactivated by the UE for a subsequent small data transmission; and a stored configuration to be deactivated by the UE for small data transmission; and a stored configuration to be released by the UE for small data transmission; and a current configuration that is to be maintained for subsequent small data transmissions after an associated timer expires; 2. The method of claim 1, adapted to identify at least one of:

[0127] (Appendix 3) 3. The method of claim 1, wherein the configuration information includes a SuspendConfig information element.

[0128] (Appendix 4) 4. A method according to any one of claims 1 to 3, wherein the configuration information identifies a configured grant for small data transmission.

[0129] 5. A method according to any one of claims 1 to 4, wherein the configuration information includes an information element (e.g., a ConfigGrantforSmallDataTransmission IE) related to a configured grant for small data transmission.

[0130] (Appendix 6) 6. The method of claim 1, wherein the UE receives the configuration information using at least one of RRC signaling, Medium Access Control (MAC) signaling (e.g., in a MAC control element), a Random Access Response (RAR) message, and Physical Downlink Control Channel (PDCCH) signaling (e.g., in Downlink Control Information (DCI)).

[0131] (Appendix 7) 7. The method of claim 1, wherein the procedure for small data transmission includes transmitting a message including the small data transmission using resources associated with "configured grant type-1."

[0132] (Appendix 8) A method as described in any one of appendix 1 to 7, wherein the procedure for small data transmission includes transmitting the small data transmission via a message (e.g., "Msg3" or "MsgA") forming part of a random access procedure.

[0133] (Appendix 9) 9. The method of any one of claims 1 to 8, further comprising, upon receiving a time advance command (TAC), restarting a timer associated with a stored configuration for small data transmission and reactivating the stored configuration for a subsequent small data transmission.

[0134] (Appendix 10) The UE maintains information identifying a configured grant for small data transmission, and the method includes: initiating the procedure for small data transmission using the configured grant if an associated time alignment timer (TAT) is running; and restarting the procedure for small data transmission via random access if the associated TAT is not running and determining whether to activate the information identifying a configured grant for a subsequent small data transmission based on the received configuration information; 10. The method of any one of claims 1 to 9, comprising:

[0135] (Appendix 11) Receiving information via RRC signaling or PDCCH signaling identifying a plurality of candidate resources for small data transmission (e.g., a plurality of "configured grant type-1" configurations); receiving information via MAC signaling identifying at least one of the candidate resources for performing the small data transmission; 11. The method of any one of claims 1 to 10, further comprising:

[0136] (Appendix 12) 1. A method performed by a communication device of a radio access network, comprising: performing a small data transmission procedure with a user equipment (UE) when the UE is in a radio resource control (RRC) inactive state; providing configuration information relating to allocated resources for subsequent small data transmissions as part of the procedure; A method comprising:

[0137] (Appendix 13) A user equipment (UE) for small data transmission in a radio resource control (RRC) Inactive state, means for initiating a procedure for small data transmission when the UE is in a Radio Resource Control (RRC) Inactive state; means for receiving configuration information relating to resources allocated for subsequent small data transmissions as part of said procedure; Including, UE.

[0138] (Appendix 14) A communication device for a radio access network, comprising: A means for performing a small data transmission procedure with a user equipment (UE) when the UE is in a radio resource control (RRC) inactive state; means for providing configuration information relating to allocated resources for subsequent small data transmissions as part of said procedure; 23. A communication device comprising:

[0139] This application claims the benefit of priority from UK Patent Application No. 2015341.7, filed September 28, 2020, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A User Equipment (UE) in a Radio Resource Control (RRC) Inactive state, means for initiating a procedure for small data transmission (SDT); means for receiving, as part of said procedure while said UE is in said RRC Inactive state, configuration information regarding at least one resource for a subsequent SDT at an RRC layer and at a Medium Access Control (MAC) layer, respectively; means for maintaining, in the UE, the configuration information from the MAC layer when a time alignment timer (TAT) for SDT expires; means for configuring the subsequent SDT using the configuration information maintained at the UE; A UE comprising:

2. means for performing a procedure for Small Data Transmission (SDT) with a User Equipment (UE); means for transmitting, as part of the procedure, configuration information for at least one resource for a subsequent SDT at a Radio Resource Control (RRC) layer and a Medium Access Control (MAC) layer, respectively, while the UE is in an RRC Inactive state; The subsequent SDT is configured using the configuration information from the MAC layer maintained in the UE when a time alignment timer (TAT) for the SDT expires in the UE. A wireless access control node.

3. 1. A method in a User Equipment (UE) in a Radio Resource Control (RRC) Inactive state, comprising: initiating a procedure for small data transmission (SDT); receiving, as part of said procedure while said UE is in said RRC Inactive state, configuration information regarding at least one resource for a subsequent SDT at an RRC layer and a Medium Access Control (MAC) layer, respectively; maintaining the configuration information from the MAC layer in the UE when a time alignment timer (TAT) for SDT expires; configuring the subsequent SDT using the configuration information maintained at the UE; and A method comprising:

4. performing a procedure for Small Data Transmission (SDT) with a User Equipment (UE); transmitting, as part of the procedure, configuration information regarding at least one resource for a subsequent SDT at a Radio Resource Control (RRC) layer and a Medium Access Control (MAC) layer, respectively, while the UE is in an RRC Inactive state; The subsequent SDT is configured using the configuration information from the MAC layer maintained in the UE when a time alignment timer (TAT) for the SDT expires in the UE. A method in a radio access control node.

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