Communication system

Abstract

To provide a system in which user equipment (UE) performs small data transmissions in an RRC (Radio Resource Control) inactive state.SOLUTION: In a portable telecommunication system, mobile equipment (UE) receives information configuring small data transmissions via a control-plane. When there is uplink data to be transmitted as a small data transmission, the UE generates an RRC message comprising the small data transmission using an SRB (Signaling Radio Bearer) provided via a CCCH (Common Control Channel) and transmits the RRC message to a base station 5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a communication system. The present invention is particularly related to, but not limited to, a wireless communication system and its devices operating according to 3GPP (3rd Generation Partnership Project) standards or their equivalents or derivatives (including LTE-Advanced and Next Generation or 5G networks). The present disclosure is particularly related to, but not limited to, the small data transmission of an inactive user equipment.

Background Art

[0002] Recent developments of 3GPP standards are called Long Term Evolution (LTE) of the evolved packet core (EPC) network and evolved UMTS terrestrial radio access network (E-UTRAN), and are generally also called "4G". Also, the terms "5G" and "New Radio" (NR) refer to evolving communication technologies expected to support various applications and services. Various details of 5G networks are described, for example, in the "NGMN 5G White Paper: NGMN 5G White Paper" V1.0 by the NGMN (Next Generation Mobile Networks) Alliance, and that document is available from https: / / www.ngmn.org / 5g-white-paper.html. 3GPP intends to support 5G through the so-called 3GPP's NextGen (Next Generation) RAN (radio access network) and 3GPP's NGC (NextGen core) network.

[0003] Under the 3GPP specifications, a NodeB (or "eNB" in LTE and "gNB" in 5G) is a base station for a communication device (user equipment or "UE") to connect to the core network and communicate with other communication devices or remote servers. For clarity, in this application, the term "base station" is used to refer to such a base station.

[0004] For simplicity, in this application, the terms "mobile device", "user equipment", or "UE" are used to refer to a communication device that can be connected to the core network via one or more base stations.

[0005] A communication device may be, for example, a mobile communication device such as a mobile phone, smartphone, user equipment, personal digital assistant, notebook computer / tablet computer, web browser, e-book reader, and / or the like. These portable (or generally fixed) devices are usually operated by a user. However, according to the 3GPP specifications, various measuring instruments, remote measuring instruments, monitoring systems, tracking / detection devices, in-vehicle safety systems, vehicle maintenance systems, road surface sensors, digital billboards, POS (point of sale) terminals, remote control systems, and the like. So-called "IoT (Internet of Things)" devices (e.g., NB-IoT (Narrow-Band IoT) devices), which usually include automation devices, can also be connected to the network. In fact, the IoT is a network of devices (i.e., "things") equipped with appropriate electronic devices, software, sensors, network connection functions, and / or the like, and through the IoT, these devices can collect or exchange data with each other or with other communication devices. It will be understood that IoT devices are sometimes also referred to as MTC (Machine-Type Communication) communication devices or M2M (Machine-to-Machine) communication devices.

[0006] For simplicity, this application generally refers to mobile devices within this specification, but it will be understood that the described technology is implementable for any communication device (portable and / or generally fixed) capable of connecting to a communication network to send and receive data, regardless of whether these communication devices are controlled by human input or by software instructions stored in memory.

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

[0008] Before data communication via a base station becomes possible, the UE needs to perform so-called (contention-based) random access procedures with the base station serving the cell in which the UE is located. Currently, in Release 15, the random access procedure is a four-step procedure. In the first step (referred to as "Msg1"), the UE transmits a PRACH (Physical Random Access Channel) preamble. When the base station detects the preamble, the base station responds with a RAR (random access response), also known as "Msg2". The RAR includes the detected preamble identifier, a timing advance command, a TC-RNTI (temporary C-RNTI), and a UL (uplink) grant for scheduling a PUSCH (Physical Uplink Shared Channel) transmission from the UE (referred to as "Msg3"). The UE transmits Msg3 as scheduled, including an identifier for contention resolution. When the network receives Msg3, it transmits a contention resolution message (also known as "Msg4") together with the contention resolution identifier. When the UE successfully receives Msg4 and finds the contention resolution identifier, it transmits an acknowledgment on the PUCCH (Physical Uplink Control Channel), thereby completing the four-step random access procedure.

[0009] Since Release 16 of the 3GPP specifications, a two-step random access procedure has been proposed (in addition to the currently used four-step random access procedure). The two-step random access mainly aims to support, among other things, (ultra) low-latency communication, 10-millisecond CP (control-plane) latency, fast handover, efficient channel access in unlicensed frequency bands, and the transmission of small data packets. As described above, in the four-step random access procedure, a two-round trip cycle is required between the UE and the base station. The two-step random access procedure aims to reduce latency and control signal overhead by performing a one-round trip cycle between the UE and the base station. In practice, this objective is achieved by combining the UE's PRACH preamble (Msg1) transmission and the scheduled PUSCH transmission (Msg3) into one message (referred to as "MsgA"). Similarly, the random access response (RAR / Msg2) from the base station to the UE and the contention resolution message (Msg4) are combined in the two-step random access procedure (and it is referred to as "MsgB").

[0010] After the random access procedure, the UE enters the so-called RRC (Radio Resource Control) CONNECTED state and can start transmitting / receiving data (both user plane data and control plane data) using the resources allocated by the network (base station). The transition between the RRC states of the UE is controlled by the network (using related timers, etc.). Usually, when there is no more data for the UE to transmit / receive, the network instructs the UE to transition to the so-called RRC IDLE state in order to release network resources and save the battery on the UE side. Whenever the UE has data to transmit or receive, it needs to enter the RRC CONNECTED state again (after performing an appropriate random access procedure with the network). Generally, although the RRC IDLE state is the most power-efficient state, some UEs may need to frequently transition between RRC IDLE and RRC CONNECTED, resulting in increased signaling and potentially adverse effects on power consumption.

[0011] In LTE, the 3GPP is attempting to address this issue in various ways such as CP-EDT (Control-Plane Earlier Data Transmission) and UP-EDT (User-Plane Earlier Data Transmission) available to UEs in the RRC IDLE state.

[0012] In the case of CP-EDT, the data is contained in the NAS (Non-Access Stratum) container and is put into the appropriate CCCH (Common Control Channel) RRC message. The NAS container is transferred by the MME to the S-GW. When the data is transmitted via the control plane, no DRB (Data Radio Bearer) is used. Therefore, the UE is maintained in RRC IDLE (except when the network instructs the UE to transition to RRC CONNECTED). CP-EDT does not use AS (Access Stratum) security, so the PDCP (Packet Data Convergence Protocol) layer and the RLC (Radio Link Control) layer are not involved in the transmission of the data (NAS container).

[0013] In the case of UP-EDT, the data is transmitted via the user plane after the appropriate DRB is resumed. The data is multiplexed with the RRCConnectionResumeRequest of the CCCH on the MAC (Medium Access Control) layer and is encrypted and transmitted on the DTCH (Dedicated Traffic Channel). In this case, the base station restarts the S1-U bearer for the UE and transfers the data directly to the S-GW.

[0014] In the 3GPP NR specification, in addition to RRC IDLE and RRC CONNECTED, a so-called RRC INACTIVE (inactive) state has been introduced. In the RRC INACTIVE state, all DRBs and SRBs (Signalling Radio Bearers) except "SRB0" are suspended. However, the UE's Ng-U connection and Ng-C connection are maintained (different from RRC IDLE), which means that only the CCCH channel is active (for SRB0). Therefore, when new data arrives from the upper layer, it cannot be transmitted immediately. The data can only be transmitted after executing the RRC resume procedure, which causes the UE to resume (or reset) all DRBs and SRBs. The difference from UP-EDT is that the DRB is resumed immediately after the data arrives, and the data can be properly transmitted via DRB / DTCH / PUSCH.

[0015] For a UE in the RRC INACTIVE state, 3GPP intends to support specific (usually a relatively small amount of data) communication so that the UE does not need to (re)activate / resume the RRC connection with the network. This function is called "small data transmission" and is applicable to many traffic types, such as sporadic transmission, short data bursts, low-throughput transmission, etc. The merits associated with small data transmission include reduction of signalling overhead associated with RRC state transitions, reduction of battery consumption, reduction of latency, etc. (compared to the case where the UE needs to transition to the RRC CONNECTED state).

[0016] The motivation behind small data transmission to an inactive UE is described in 3GPP work item RP-193252. In summary, with the small data transmission function, a UE can maintain the RRC_INACTIVE state in specific downlink (MT (mobile terminated)) data transmission and uplink (MO (mobile originated)) data transmission. In other words, the UE does not need to resume the RRC connection (i.e., transition to the RRC CONNECTED state) for data transmission, and after data transmission, it does not need to release the connection (return to the RRC INACTIVE state) subsequently. Therefore, UE3 can avoid some of the associated drawbacks (such as increased power consumption and signaling overhead).

[0017] In Rel-17, small and irregular data traffic in the INACTIVE state will be permitted in (among others) the following use cases. - Smartphone applications: · Traffic from instant messaging services (such as WhatsApp®, QQ, WeChat® etc.), · Heartbeat / keep-alive traffic from instant messaging / email clients and similar applications, · Push notifications from various applications, - Applications other than smartphones: · Traffic from wearables (such as periodic location information etc.), · Sensors (such as Industrial Wireless Sensor Networks that transmit temperature and pressure measurement values periodically or in an event-triggered manner), · Smart meters and smart meter networks that periodically transmit meter measurement values

[0018] The signaling overhead from an INACTIVE state UE for small data packets is a common issue and will be a significant problem for many UEs in NR, not only for network performance and efficiency but also for UE battery performance. Generally, any device with intermittent small data packets in the INACTIVE state will benefit from enabling small data transmission in the INACTIVE state.

[0019] Regarding the key to the success of small data transmission in NR, although some have already been identified in Rel-15 and Rel-16 (e.g., RRC INACTIVE state, two-step / four-step random access, configured grant type-1), there are still many issues and goals that need to be addressed. For example: · In the case of UL small data transmission using two-step or four-step random access: · There is no procedure to enable UP (user-plane) data transmission of small data packets from a UE in the RRC INACTIVE state (e.g., using MsgA in the two-step random access procedure or Msg3 in the four-step random access procedure), · To support UP data transmission in the UL, it is necessary to enable a flexible payload size larger than the Rel-16 CCCH message size currently defined for the RRC INACTIVE state for MsgA and Msg3, · It is necessary to define context fetch and data transfer procedures in the RRC INACTIVE state for random access-based solutions (with or without anchor relocation), · When transmitting UL data on a pre-configured PUSCH resource (using the so-called "configured grant type 1"): · There is no procedure to execute small data transmission via the configured grant type 1 resource in the RRC INACTIVE state, · The configured grant type 1 resource is not set for UL small data transmission in the RRC INACTIVE state.

Summary of the Invention

Problems to be Solved by the Invention

[0020] Therefore, a preferred exemplary embodiment of the present invention aims to provide a method and apparatus that correspond to or at least partially address one or more of the above problems.

[0021] For those skilled in the art to understand efficiently, the present invention will be described in detail from the perspective of 3GPP systems (UMTS, LTE, NR). However, the essence of the present invention can also be applied to other systems in which a communication device or UE (User Equipment) accesses a core network using radio access technology.

Means for Solving the Problems

[0022] In an exemplary aspect, the present invention provides a method performed by a UE (User Equipment) for small data transmission in the RRC (Radio Resource Control) inactive state, including receiving, via a control plane, information configuring the small data transmission, determining whether there is uplink data to be transmitted as small data while the UE is in the RRC inactive state, generating an RRC message including the small data transmission, and transmitting the RRC message including the small data transmission using an SRB (Signalling Radio Bearer) provided via a CCCH (Common Control Channel).

[0023] In another exemplary aspect, the present invention provides a method performed by a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, the method comprising: receiving information configuring the small data transmission in the RRC inactive state; determining whether there is uplink data to be transmitted as small data transmission when the UE is in the RRC inactive state; processing the uplink data to form small data transmission and adding information identifying the UE; and transmitting the small data transmission and the information identifying the UE using a DRB (Data Radio Bearer) based on the received information.

[0024] In an exemplary aspect, the present invention provides a method performed by a communication device of a radio access network for communicating with a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, the method comprising: transmitting, via a control plane, information configuring the small data transmission; and receiving, from the UE via an SRB (Signalling Radio Bearer) provided via a CCCH (Common Control Channel) while the UE is in the RRC inactive state, an RRC message including the small data transmission.

[0025] In an exemplary aspect, the present invention is a method performed by a communication device of a radio access network for communicating with a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, the method comprising: transmitting information configuring the small data transmission in the RRC inactive state; and receiving, from the UE while the UE is in the RRC inactive state, small data transmission and information for identifying the UE using a DRB (Data Radio Bearer) based on the transmitted information.

[0026] In an exemplary aspect, the present invention is a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, comprising: means for receiving, via a control plane, information configuring the small data transmission; means for determining whether there is uplink data to be transmitted as small data transmission while the UE is in the RRC inactive state; means for generating an RRC message including the small data transmission; and means for transmitting the RRC message including the small data transmission using an SRB (Signalling Radio Bearer) provided via a CCCH (Common Control Channel).

[0027] In an exemplary aspect, the present invention provides a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, comprising means for receiving information configuring the small data transmission in the RRC inactive state; means for determining whether there is uplink data to be transmitted as small data transmission when the UE is in the RRC inactive state; means for processing the uplink data to form small data transmission and adding information for identifying the UE; and means for transmitting the small data transmission and the information for identifying the UE using a DRB (Data Radio Bearer) based on the received information.

[0028] In another exemplary aspect, the present invention provides a communication apparatus of a radio access network for communicating with a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, comprising means for transmitting information configuring the small data transmission via a control plane; and means for receiving an RRC message including small data transmission using an SRB (Signalling Radio Bearer) provided via a CCCH (Common Control Channel) from the UE while the UE is in the RRC inactive state.

[0029] In yet another exemplary aspect, the present invention provides a communication apparatus of a radio access network for communicating with a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, the communication apparatus comprising means for transmitting information configuring the small data transmission in the RRC inactive state, and means for receiving, from the UE while the UE is in the RRC inactive state, small data transmission and information for identifying the UE using a DRB (Data Radio Bearer) based on the transmitted information.

[0030] Exemplary aspects of the present invention extend to corresponding systems, apparatuses, and computer program products, for example, a computer-readable storage medium storing instructions that program a programmable processor to perform the methods described in the exemplary aspects and the implementation means recited above and / or below in the claims, and / or program a suitably configured computer to provide the apparatuses recited in any of the claims.

[0031] Each feature disclosed and / or shown in the specification (which term includes the claims) can be incorporated into the present invention independently of (or in combination with) other disclosed and / or shown features. Without particular limitation, the features of any claim dependent on a particular independent claim can also be introduced into that independent claim in any combination or individually.

Brief Description of the Drawings

[0032] Exemplary embodiments of the present invention will be described by way of example with reference to the following accompanying drawings.

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[0033] Overview FIG. 1 schematically shows a mobile (cellular or wireless) communication system 1 to which an exemplary embodiment of the present invention is applicable.

[0034] In this network, users of mobile device 3 (UE) can communicate with each other and with other users via each base station 5 and core network 7 using an appropriate 3GPP radio access technology (RAT), such as E-UTRA and / or 5G RAT. It is understood that a number of base stations 5 form a (radio) access network or (R)AN. As will be understood by those skilled in the art, although one mobile device 3 and one base station 5 are shown in FIG. 1 for illustrative purposes, the system will typically include other base stations and mobile devices (UE) when implemented.

[0035] Each base station 5 controls one or more associated cells (either directly or via other nodes such as home base stations, repeaters, remote radio heads, and / or distributed units). A base station 5 that supports the E-UTRA / 4G protocol may be referred to as an "eNB", and a base station 5 that supports the Next Generation / 5G protocol may be referred to as a "gNB". It is understood that some base stations 5 may be configured to support both 4G and 5G, and / or any other 3GPP or non-3GPP communication protocol.

[0036] The mobile device 3 and its serving base station 5 are connected via an appropriate air interface (such as the so-called "Uu" interface). Adjacent base stations 5 are connected to each other via an inter-base station interface (such as the so-called "X2" interface and / or "Xn" interface). The base station 5 is also connected to core network nodes via an appropriate interface (such as the so-called "S1", "N1", "N2", and / or "N3" interfaces).

[0037] The core network 7 typically includes logical nodes (or "functions") to support communications in the communication system 1. Typically, for example, the core network 7 of a "Next Generation" / 5G system includes, among other functions, a control plane function (CPF) and a user plane function (UPF). The core network 7 may include, among other things, a mobility management entity (MME) 11 and a serving gateway (S-GW) 12. It will be understood that in an NR network, instead of or in addition to the MME 11, a so-called access and mobility management function (AMF) may be provided. A connection from the core network 7 to an external IP network 20 (such as the Internet) may also be provided.

[0038] This system supports both legacy (i.e., four-step) and two-step random access procedures. A particular UE3 may be configured to communicate using resources assigned to configured grant type-1 communications without using an explicit grant from the network.

[0039] The nodes of this network 1 are configured to support a small data transmission service to a UE3 in the RRC INACTIVE state. This small data transmission can be realized via either the control plane (first option) or the user plane (second option).

[0040] In the case of the first option, UE3 is (by the network) configured to perform small data transmission via the control plane. UE3 may be configured using an RRC release message or an RRC suspend message (and / or the like). If there is uplink data that can be transmitted as small data, UE3 generates an RRC message (e.g., a "smallDataTransmission" message and / or the like), and transmits this message within a properly formatted CCCH message (via the signaling radio bearer "SRB0" that maintains activity during RRC INACTIVE mode). The CCCH message containing small data transmission (within the RRC message) may be transmitted via a pre-configured PUSCH resource (if available), or using an appropriate (two-step or four-step) random access procedure. When using a random access procedure, the above CCCH message may be transmitted to the network (i.e., base station 5) either within MsgA or within Msg3.

[0041] In the case of the second option, UE3 can configure a DRB for small data transmission. In the case of RRC INACTIVE mode, UE3 suspends all other DRBs and SRBs. Thus, any uplink data can be processed through the appropriate user plane protocol of the DRB configured for small data transmission. This data may be transmitted via a pre-configured PUSCH resource (if available), or by triggering an appropriate (two-step / four-step) random access procedure. In this case, the MAC layer is configured to add appropriate information identifying UE3 (i.e., "UE ID") to the uplink transmission.

[0042] In summary, the above system has many advantages. For example, - Efficiency and flexibility for low-throughput, short data bursts, - Supports an efficient signaling mechanism (e.g., signaling is below the payload), - Completely reduce signaling overhead.

[0043] Mobile device FIG. 2 is a block diagram illustrating the main components of the mobile device 3 (e.g., a mobile phone or an 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 the base station 5 via one or more antennas 33. The mobile device 3 has a controller 37 that controls the operation of the mobile device 3. The controller 37 is associated with a memory 39 and is connected to the transceiver circuit 31. Although not necessarily required for the operation of the mobile device 3, the mobile device 3 may of course have all the normal functions of a normal mobile phone (e.g., a user interface 35), which can be appropriately realized by any one or any combination of hardware, software, and firmware. The software may be pre-installed in the memory 39 and / or downloaded via a telecommunications network or from a RMD (removable data storage device) or the like.

[0044] The controller 37 is configured to control the overall operation of the mobile device 3 by program instructions or software instructions stored in the memory 39 in the case of this embodiment. As shown, these software instructions include, among others, an operating system 41, a communication control module 43, and a small data module 45.

[0045] The communication control module 43 is operable to control the communication between the mobile device 3 and the serving base station 5 (and other communication devices connected to the serving base station 5, such as other user equipment, core network nodes, etc.).

[0046] The small data module 45 is involved in the transmission of small data, and can transmit (or receive) small data without using the active RRC connection of the mobile device 3 (for example, while the mobile device 3 is in the RRC INACTIVE state).

[0047] Although not shown in FIG. 2, the mobile device 3 will generally further include individual modules corresponding to different communication layers. These modules may be implemented as part of the communication control module 43 and may include one or more of the following modules. That is, a NAS module, an RRC module, an SDAP (Service Data Adaptation Protocol) module, a PDCP module, an RLC module, a MAC module, and a PHY (physical layer) module.

[0048] The RRC module is operable to generate / transmit / receive signaling messages formatted according to the RRC standard. For example, this message is exchanged between the mobile device 3 and the serving base station 5. The RRC message may include, for example, a message related to small data transmission (or reception) that includes a message for transmitting small data and related information. The RRC module is further involved in the management of the RRC connection and the RRC mode (for example, RRC IDLE, RRC CONNECTED, RRC INACTIVE) between the mobile device and the network.

[0049] The NAS module is operable to generate / transmit / receive signaling messages formatted according to the NAS standard. For example, this message is exchanged between the mobile device 3 and the MME / AMF 11 (via the serving base station 5 and using the RRC module). The NAS message may include, for example, a message related to the registration and / or update of the tracking area (or cell) where the mobile device 3 is currently located. The NAS message may further include small data transmission.

[0050] Base station FIG. 3 is a block diagram for explaining the main components of the base station 5 shown in FIG. 1. As shown in the figure, the base station 5 includes a transceiver circuit 51 that transmits and receives signals to and from a user device (for example, the mobile device 3) via one or more antennas 53, a core network interface 55 (for example, an S1 interface, an NG-C interface, and / or the like) that transmits and receives signals to and from the core network 7, and a base station interface 56 (for example, an X2 interface, an Xn interface, and / or the like) that transmits and receives signals to and from an adjacent base station. The base station 5 has a controller 57 that controls the operation of the base station 5 according to software stored in the memory 59. The software may be pre-installed in the memory 59 and / or may be downloaded via the telecommunications network 1 or from an RMD or the like. The software includes, among others, an operating system 61, at least a communication control module 63, and a small data module 65.

[0051] The communication control module 63 is involved in the processing (generation / transmission / reception) of signaling between the base station 5 and other nodes, for example, between the UE 3 and the core network nodes. This signaling may include, for example, control data for managing the operation of the mobile device 3 (such as NAS, RRC, paging, system information, and / or the like).

[0052] The small data module 65 is involved in the processing of small data transmission to the mobile device 3 (for example, while the mobile device 3 is in the RRC INACTIVE state).

[0053] Although not shown in FIG. 3, the base station 5 further generally includes an inter-base station interface module (e.g., an X2 / Xn module), a suitable core network interface module (which may be implemented as part of the communication control module 43), and individual modules corresponding to different communication layers (e.g., an RRC module, an SDAP module, a PDCP module, an RLC module, a MAC module, a PHY module).

[0054] The inter-base station interface module is operable to generate / transmit / receive signaling messages (X2 / Xn messages) formatted according to the X2AP (or XnAP) standard. The X2 / Xn messages may include, for example, messages related to paging of the mobile device 3, handover, data transfer, and transmission / fetching of UE context (and other information related to the mobile device 3) between adjacent base stations.

[0055] The core network interface module is operable to generate / transmit / receive signaling messages formatted according to the NG-C standard (or the S1AP standard in LTE), including messages that convey small data transmissions to the UE 3. For example, this message is exchanged between the base station 5 and the MME / AMF 11 and / or the S-GW 12.

[0056] The RRC module is operable to generate / transmit / receive signaling messages formatted according to the RRC standard. For example, this message is 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 message may include, for example, messages related to small data transmission (or reception) that include messages conveying small data transmission and related information. The RRC module is further involved in managing the RRC connection and RRC mode (e.g., RRC IDLE, RRC CONNECTED, RRC INACTIVE) of the mobile device with the network.

[0057] Core network node FIG. 4 is a block diagram illustrating the main components of a general core network node (i.e., function) shown in FIG. 1, such as MME 11 or S-GW 12. As shown, the core network node includes a transceiver circuit 71 operable to transmit and receive signals via a network interface 75 to other nodes (including UE 3 and (R)AN node 5). 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 may be downloaded via a telecommunication network 1 or from an RMD or the like. The software includes, among other things, an operating system 81 and at least a communication control module 83. The communication control module 83 is involved in the processing (generation / transmission / reception) of signaling between the core network node and other nodes, such as UE 3, (R)AN node 5, other core network nodes. This signaling may include, for example, NAS signaling and / or small data transmission between the mobile device 3 and the MME / AMF 11.

[0058] Detailed description A more detailed description will be given of an exemplary method by which small data transmission can be made possible by a UE in the RRC INACTIVE state.

[0059] FIG. 5 is an overview of the layers involved in small data transmission according to a first exemplary method using control plane signaling.

[0060] More specifically, the UE3 is configured to perform small data transmission via the CCCH channel using an appropriately formatted RRC message. The RRC message may be a dedicated (e.g., newly defined) RRC message or an RRC message suitable for this purpose. To smoothly proceed with small data transmission, when the UE3 transmits small data, the RRC layer (RRC module) adapts to add an appropriate UE-ID. In this embodiment, the UE-ID is added as part of an RRC Resume Request message (e.g., "UE-ID" or "Resume ID" information element and / or the like). However, other messages or information elements can also be used.

[0061] SRB0 does not use PDCP, is configured in TM (Transparent Mode) in RLC, and uses the CCCH logical channel. Therefore, there is no PDCP / RLC header for the packets transmitted via SRB0 (i.e., functions such as security / header compression, reordering, ARQ, and segmentation associated with PDCP / RLC are not available for such packets).

[0062] Furthermore, the sizes of CCCH and CCCH1 are fixed at 48 bits and 64 bits respectively. To permit small data transmission of other sizes (e.g., larger than 64 bits), a new CCCH message is defined to accommodate the small data to be transmitted, the necessary RRC message, and / or IE (Information Element). It will be understood that this new CCCH message may have a variable size (however, the size may be limited to multiples of, for example, 48 bits or 64 bits).

[0063] An exemplary CCCH called "UL-CCCH2-Message" (which may use other names) is shown below. - UL-CCCH2-Message The UL-CCCH2-Message class is a series of RRC messages that can be sent from UE3 to the network (e.g., base station 5) on the uplink CCCH2 logical channel.

Table 1

[0064] As shown in the table, in this embodiment, the content of small data transmission (i.e., the RRC IE related to data from the upper layer) is included within the appropriate element of UL-CCCH2-Message (in this case, the "UL-CCCH2-MessageType" element). In fact, the "smallDataTransmission" part of this message is an RRC message that includes (small) data from the upper layer and the appropriate information ("UE-ID") to identify UE3. In this embodiment, while using a new RRC message ("SmallDataTransmission"), it will be understood that existing RRC messages can be adapted for the purpose of small data transmission where appropriate.

[0065] The information elements of the RRC message may include, for example, the IEs currently defined for the RRCResumeRequest message. In one example, the RRC message includes data from UE3, the related UE-ID (to identify UE3 and facilitate smooth UE context search), and one or more security-related IEs (e.g., resume MAC-I and / or the like). Based on this message, the network (base station 5 in this example) can determine whether to resume the RRC connection for UE3.

[0066] Further details of this exemplary RRC message are shown below: - SmallDataTransmission The SmallDataTransmission message is used for uplink transmission of small data when UE3 is in the RRC INACTIVE mode. Signaling radio bearer: SRB0 RLC-SAP:TM Logical Channel: CCCH2 Direction: From UE to Network

Table 2

[0067] FIG. 6 is a schematic flowchart illustrating the main steps of small data transmission according to the first exemplary method.

[0068] In step 1, UE3 receives an explicit indication / configuration from the network that permits small data transmission via the control plane. This indication / configuration may be transmitted via an appropriate broadcast message or unicast message (e.g., an RRC release message or an RRC suspension message and / or the like). Upon receiving this message, UE3 sets the applicable restrictions (e.g., transport block size restrictions, permitted QoS flows, etc.) for the small data transmission service. If no specific restrictions are set, small data transmission may be permitted up to the maximum size of the CCCH message (or Msg3 / MsgA), e.g., the PUSCH TB (transport block) size.

[0069] Step 2: When the small data arrives from the upper layer, if the size of the data (and optionally the necessary padding and information elements) does not exceed the maximum size defined for small data transmission (and also passes any other specific or set restrictions), UE3 starts the small data transmission procedure. Specifically, UE3 generates a small data transmission message in the RRC layer (using its RRC module) and sends that message to the lower layers for transmission (i.e., the MAC and PHY layers). Although not shown in FIG. 6, if the data from the upper layer cannot be transmitted as "small data" (e.g., due to its size or any other applicable restrictions), UE3 generates a properly formatted RRC resume request message and sends that message to the lower layers for transmission so that the data can be transmitted in a normal manner (in RRC CONNECTED mode).

[0070] Step 3: In the MAC layer, the CCCH message transmission triggers an appropriate random access procedure, i.e., either a two-step or a four-step random access procedure. The above CCCH message is transmitted to the network (base station 5) using either MsgA or Msg3. It will be understood that if a pre-configured PUSCH resource is available, the CCCH message may be transmitted via that pre-configured PUSCH resource instead of using the random access procedure.

[0071] Step 4: When a response to the message in Step 3 is received (e.g., when MsgB / Msg4 is detected), the MAC layer reports to the RRC layer on the success of the CCCH message transmission. It will be understood that if the network wants to resume the RRC connection in response to the small data transmission, the network may also send an RRC resume message along with MsgB / Msg4.

[0072] It is beneficial that the method corresponds to a relatively small change as seen from the procedures currently specified by 3GPP. The RRC INACTIVE mode, as before, permits the suspension of all configurations (except SRB0). In this method, there is no need to change the behavior of the MAC layer at all (however, the grant size set for MsgA and / or additional preamble splitting for small data transmission may increase).

[0073] Figure 7 is an overview of the layers involved in small data transmission according to a second exemplary method. As shown, in this embodiment, user plane signaling is used.

[0074] To smoothly proceed with small data transmission, the MAC layer (MAC module) recognizes that UE3 is in the RRC INACTIVE mode and also recognizes the associated UE-ID. The MAC layer is configured to add the UE-ID to the MAC PDU (Protocol Data Unit) (for example, using a "UE-ID" MAC CE (Control Element)) and transmit the UE-ID together with the data. Here, it will be understood that other appropriate information for identifying UE3 may also be used. However, it will be understood that the MAC layer does not need to recognize the UE-ID. Instead, the UE-ID (or other appropriate information for identifying UE3) may be included in an RRC message (for example, RRC resumeRequest or the like), and the MAC layer may be configured to multiplex the processed small data and the RRC message and transmit them together to the network. In this case, the UE-ID may be included in the information element of the RRC message instead of the MAC CE.

[0075] Figure 8 is a schematic flowchart illustrating the main steps of small data transmission according to a second exemplary method.

[0076] Step 1: An RRC release (or RRC suspension) message is sent by the network (base station 5) to the UE, and a new DRB for small data transmission may be set up (or an existing DRB may be kept alive). Further, the network may set further restrictions on the small data transmission service. For example, a QFI (QoS (Quality of Service) Flow Identifier) can be mapped to this DRB and / or, if applicable, the associated data size / frequency limit. Predetermined (e.g., default) settings may be used for the DRB, whereby it will be understood that UE3 can continue to use that DRB after subsequent cell (re)selection. In other words, the DRB settings may be common for a plurality of base stations, e.g., base stations within a specific tracking area.

[0077] Step 2: The RRC layer suspends all other DRBs and SRBs and holds (or sets up) the user plane protocol of the DRB that is configured to remain active while UE3 is in the RRC INACTIVE mode. At the end of this step, UE3 enters the RRC INACTIVE mode.

[0078] Step 3: While in the RRC INACTIVE mode, UE3 monitors the upper layers for data. When data arrives, if the data conforms to the "small data" settings and belongs to the QFI mapped to the active DRB, UE3 processes the data via the appropriate user plane protocol of the associated DRB. If the data from the upper layer does not belong to any QFI mapped to the active DRB, or if the data is larger than the maximum size permitted by the current small data transmission settings, it will be understood that UE3 triggers the appropriate RRC resume procedure (or random access procedure) so that the data can be transmitted in the normal way (in the RRC CONNECTED mode).

[0079] Step 4: At the MAC layer, the data may be transmitted via a preconfigured PUSCH resource (if available) or by triggering an appropriate (two-step / four-step) random access procedure for uplink transmission. The MAC layer is further configured to add appropriate information (e.g., "UE ID") for identifying UE3 to the first uplink transmission. The information for identifying UE3 may be included in a MAC CE or an RRC information element. It will also be understood that if the size limit for small data transmission is exceeded and segmentation may be required at the RLC layer, multiple uplink transmissions may be used (without restarting the RRC connection) to transmit the data.

[0080] It is beneficial that UE3 can encrypt / compress data by this method. In this case, the RRC INACTIVE mode is similar to the RRC CONNECTED mode, but compared to the RRC CONNECTED mode, it leads to a reduction in the user plane and overhead.

[0081] Amendments and Alternatives The details of the exemplary embodiments have been described above. Those skilled in the art will understand that they can obtain benefits from the invention embodied in this specification and at the same time make many modifications and alternatives to the above exemplary embodiments. As an example, some of such amendments and alternatives are described below.

[0082] FIGS. 9 and 10 are diagrams illustrating some of the possible amendments to the first exemplary method described with reference to FIGS. 5 and 6. Specifically, AS security protection may be provided using the PDCP layer (as shown in FIG. 9) or an upper layer (e.g., a dedicated security layer as shown in FIG. 10). In this case, the security operation may be applied to the data portion using the PDCP layer or the upper layer.

[0083] The bearer used for small data transmission through the control plane is called "SRB0", but it will be understood that the SRB used for small data transmission may have a different name in order to distinguish it from the legacy "SRB0".

[0084] The following table shows an overview of possible limitations / changes to the user plane configuration that shorten the header for small data transmission and reduce the overall signaling overhead in the case of the second method.

[0085] [Table 3]

[0086] In the above description, the UE, (R)AN node, and core network node are described as having several individual modules (such as communication control modules) for ease of understanding. These modules may be provided in this way, for example, for a specific application in which an existing system is modified to implement the present invention, or for other applications in a system designed from the beginning with the features of the present invention in mind. On the other hand, these modules may be incorporated into the operating system or the entire code, and thus these modules may not be distinguishable as separate entities.

[0087] Each controller may include, for example, a computer processor implemented by one or more hardware, a microprocessor, a CPU (central processing unit), an ALU (arithmetic logic unit), an IO (input / output) circuit, an internal memory / cache (program and / or data), a processing register, a communication bus (e.g., control, data, and / or address bus), a DMA (direct memory access) function, and any suitable form of processing circuit including, but not limited to, a counter, a pointer, and / or a timer implemented by hardware or software.

[0088] In the above exemplary embodiments, many software modules have been described. As will be understood by those skilled in the art, the software modules may be provided in compiled form or non-compiled form, and may be supplied to the UE, (R)AN node, and core network node as signals on a computer network or on a recording medium. Further, the functions executed by some or all of this software may be executed using one or more dedicated hardware circuits. However, the use of software modules is preferred as it facilitates the updates of the UE, (R)AN node, and core network node in order to update their functions.

[0089] In the latest 5G architecture, the internal structure of the gNB can be divided into two parts connected by the F1 interface, namely the CU (Central Unit) and the DU (Distributed Unit). It will be understood that one CU may be connected to (and control) multiple DUs. This enables the use of a "split" architecture, as a result of which the usually "upper" CU layer (e.g., PDCP is an example, but it is not necessarily PDCP, or not limited to PDCP) and the usually "lower" DU layer (e.g., RLC / MAC / PHY is an example, but it is not necessarily RLC / MAC / PHY, or not limited to RLC / MAC / PHY) are implemented separately. Therefore, for example, the functions of the upper layer CU for a large number of gNBs may be implemented centrally (e.g., by a single processing unit, or in a cloud-based or virtual system), while on the other hand, the functions of the lower layer DU are maintained locally at each gNB. It will be understood that the CU may communicate with the next-generation core, and the DU may communicate with the surrounding UEs (i.e., within the cells operated by the gNB) through the air interface.

[0090] More specifically, the distributed gNB includes the following functional units. gNB Central Unit (gNB-CU): A logical node that hosts the RRC layer, SDAP layer, PDCP layer of the gNB, or the RRC and PDCP layers of the En-gNB that controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected to the gNB-DU. gNB Distributed Unit (gNB-DU): A logical node that hosts the RLC layer, MAC layer, PHY layer of the gNB or En-gNB, and its operation is partially controlled by the gNB-CU. One gNB-DU supports one or more cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU. gNB-CU-CP (gNB-CU-Control Plane: gNB-CU control plane): A logical node that hosts the RRC and control plane parts of the PDCP protocol of the gNB-CU for an en-gNB or gNB. The gNB-CU-CP terminates the E1 interface connected to the gNB-CU-UP and the F1-C interface connected to the gNB-DU. gNB-CU-UP (gNB-CU-User Plane: gNB-CU user plane): A logical node that hosts the user plane part of the PDCP protocol of the gNB-CU for an en-gNB and the user plane parts of the SDAP protocol and PDCP protocol of the gNB-CU for a gNB. The gNB-CU-UP terminates the E1 interface connected to the gNB-CU-CP and the F1-U interface connected to the gNB-DU.

[0091] A user equipment (or "UE") in the present disclosure is an entity connected to a network via a wireless interface. A UE may also be referred to as a "mobile station", "mobile device", "wireless device", or "wireless transmit / receive unit" (WTRU).

[0092] Note that the present disclosure is not limited to dedicated communication devices and can be applied to any device having the communication functions described in the following paragraphs.

[0093] The terms "user equipment" or "UE" (terms used in 3GPP), "mobile station", "mobile device", and "wireless device" are generally intended to be synonymous with each other and include stand-alone mobile stations such as terminals, mobile phones, smartphones, tablets, cellular IoT devices, IoT devices, machines, etc. It will be understood that the terms "mobile station" and "mobile device" also include devices that remain stationary for a long period of time.

[0094] The UE can be, for example, an item of equipment for production or manufacturing, and / or an item of energy-related machinery (such as boilers, engines, turbines, solar panels, wind turbines, hydroelectric generators, thermal generators, nuclear power generators, batteries, nuclear systems and / or related equipment, heavy electrical machinery, pumps including vacuum pumps, compressors, fans, blowers, hydraulic equipment, pneumatic equipment, metalworking machinery, manipulators, robots and / or their application systems, tools, dies or molds, rolls, conveying equipment, lifting equipment, material handling equipment, textile machinery, sewing machines, printing and / or related machinery, paper-making machinery, chemical machinery, mining and / or construction machinery and / or related equipment, machinery and / or appliances for agriculture, forestry and / or fisheries, safety and / or environmental protection equipment, tractors, precision bearings, chains, gears, power transmission equipment, lubrication equipment, valves, pipe fittings, etc., and / or application systems of any of the aforementioned equipment or machinery).

[0095] The UE can be, for example, an item of transportation equipment (such as transportation equipment like rolling stock, automobiles, motorcycles, bicycles, trains, buses, carts, rickshaws, ships, other vessels, aircraft, rockets, satellites, drones, balloons, etc.).

[0096] The UE can be, for example, an item of information and communication equipment (such as information and communication equipment like electronic computers and related equipment, communication and related equipment, electronic components, etc.).

[0097] The UE can be, for example, an item of refrigerators, refrigerator-applied products, equipment for the trade and / or service industries, vending machines, self-service machines, office machinery or equipment, consumer electronics and electrical appliances (such as consumer electrical appliances like audio equipment, video equipment, speakers, radios, TVs, microwave ovens, rice cookers, coffee machines, dishwashers, washing machines, dryers, electric fans or related electrical appliances, vacuum cleaners, etc.).

[0098] The UE can be, for example, an electrical application system or device (such as an electrical application system or device like an X-ray system, a particle accelerator, a radioisotope device, an acoustic device, an electromagnetic application device, an electric power application device, etc.).

[0099] The UE can be, for example, an electronic lamp, a lighting fixture, a measuring device, an analyzer, a tester, or a surveying or sensing device (such as a surveying or sensing device like a smoke detector, a human alarm sensor, a motion sensor, a wireless tag, etc.), a wristwatch or a table clock, a laboratory instrument, an optical device, a medical device and / or system, a weapon, a blade, a hand tool, etc.

[0100] The UE can be, for example, a mobile information terminal or a related device with wireless (such as a wireless card or module designed for attachment or insertion to other electronic devices (such as a personal computer, an electrical measuring instrument)).

[0101] The UE can be part of a device or system that uses various wired and / or wireless communication technologies to provide the applications, services, and solutions described below with respect to the "Internet of Things" (IoT).

[0102] Internet of Things devices (or "things") may be equipped with appropriate electronic devices, software, sensors, and / or network connections, etc., which enable these devices to collect and exchange data with each other and with other communication devices. IoT devices can be composed of automated devices that follow the instructions of software stored in internal memory. IoT devices can operate without the need for human monitoring or interaction. IoT devices can remain stationary or inactive for long periods. IoT devices can be implemented as part of (generally) stationary devices. IoT devices can be incorporated into non-stationary devices (such as vehicles) or attached to animals or people being monitored / tracked.

[0103] IoT technology can be implemented in any communication device that can be connected to a communication network to send and receive data, and it will be understood that such a device can be implemented regardless of whether the communication device is controlled by human input or software instructions stored in memory.

[0104] It will be understood that IoT devices may also be referred to as MTC (Machine-Type Communication) devices or M2M (Machine-to-Machine) communication devices. It will be understood that a UE may support one or more IoT or MTC applications. Some examples of MTC applications are shown in the following table (Source: 3GPP TS 22.368 V13.1.0, Annex B, the content of which is incorporated herein by reference). This list is not exhaustive and is intended to show some examples of machine-type communication applications.

[0105] [Table 4] Applications, services, and solutions can be, for example, MVNO (Mobile Virtual Network Operator) services, emergency wireless communication systems, PBX (Private Branch eXchange) systems, PHS / digital cordless telecommunication systems, POS (Point of sale) systems, advertising call systems, MBMS (Multimedia Broadcast and Multicast Service), V2X (Vehicle to Everything) systems, train wireless systems, location-based services, disaster / emergency wireless communication services, community services, video streaming services, femtocell application services, VoLTE (Voice over LTE) services, charging services, wireless on-demand services, roaming services, activity monitoring services, communication carrier / communication NW selection services, function-limited services, PoC (Proof of Concept) services, personal information management services, ad hoc network / DTN (Delay Tolerant Networking) services, and the like.

[0106] Furthermore, the above UE categories are only examples of the application of the technical ideas and exemplary embodiments described in this document. Needless to say, these technical ideas and exemplary embodiments are not limited to the above UEs and can be variously modified with respect to the above UEs.

[0107] The RRC message may include small data transmission and one or more RRC information elements. The RRC message may include information for identifying the UE (for example, the "UE-ID" information element). The SRB may be "SRB0".

[0108] RRC messages including small data transmission may be transmitted using resources associated with "configured grant type-1". As another method, RRC messages including small data transmission may be transmitted via a message (e.g., "Msg3" or "MsgA") that forms part of a random access procedure.

[0109] Access stratum security may be provided for small data transmission via layers other than the RRC layer (e.g., the PDCP layer and / or the dedicated security layer).

[0110] Determining by the UE may include determining whether a QFI associated with small data transmission can be mapped to an SRB, and the method may include transmitting an RRC message including small data transmission based on the result of the determination.

[0111] The information constituting small data transmission may include information for identifying the size limit of the CCCH, and determining by the UE may include determining that the small data transmission does not exceed the size limit.

[0112] The information for identifying the UE may include a MAC CE (e.g., "UE-ID" MAC CE) or an RRC information element.

[0113] Processing by the UE may include segmenting uplink data to form a plurality of small data transmissions and adding information for identifying the UE to at least one of the plurality of small data transmissions.

[0114] Determining by the UE may include determining whether a QFI associated with small data transmission can be mapped to a DRB, and the method may include transmitting the small data transmission and the information for identifying the UE based on the result of the determination.

[0115] Processing uplink data to form small data transmissions may include configuring at least one layer of a DRB for small data transmissions. For example, this configuring may include configuring the SDAP layer without an SDAP header, using a shortened PDCP sequence number (e.g., 7 bits), and / or using a 1-byte PDCP header size, using a TM for small data transmissions using a DRB, configuring the MAC layer without using an LCID (Logical Channel Identifier) and / or a length field, and configuring a fixed-size MAC PDU for small data transmissions, and may include at least one of these.

[0116] Various other variations will be apparent to those skilled in the art and are not described in further detail herein.

[0117] (Appendix 1) A method performed by a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, receiving, via a control plane, information configuring small data transmission; determining whether there is uplink data to be transmitted as small data transmission while the UE is in the RRC inactive state; generating an RRC message including the small data transmission; transmitting the RRC message including the small data transmission using an SRB (Signalling Radio Bearer) provided via a CCCH (Common Control Channel); A method comprising the above.

[0118] (Appendix 2) The RRC message includes the small data transmission and one or more RRC information elements, and is the method described in Appendix 1.

[0119] (Appendix 3) The RRC message includes information for identifying the UE (e.g., "UE-ID" information element), and is the method described in Appendix 1 or 2.

[0120] (Appendix 4) The SRB is "SRB0", and is the method described in any one of Appendices 1 to 3.

[0121] (Appendix 5) The RRC message including the small data transmission is transmitted using a resource associated with "configured grant type-1", and is the method described in any one of Appendices 1 to 4.

[0122] (Appendix 6) The RRC message including the small data transmission is transmitted via a message (e.g., "Msg3" or "MsgA") that forms part of a random access procedure, and is the method described in any one of Appendices 1 to 4.

[0123] (Appendix 7) Access stratum security is provided for the small data transmission via layers other than the RRC layer (e.g., the PDCP (Packet Data Convergence Protocol) layer and / or the dedicated security layer), and is the method described in any one of Appendices 1 to 6.

[0124] (Appendix 8) The determining includes determining whether a QFI (QoS (Quality of Service) Flow Identifier) associated with the small data transmission can be mapped to the SRB, and the method includes transmitting the RRC message including the small data transmission based on the result of the determination, and is the method described in any one of Appendices 1 to 7.

[0125] (Appendix 9) The information constituting the small data transmission includes information for identifying the size limit of the CCCH, and the determining includes determining that the small data transmission does not exceed the size limit. The method according to any one of Appendices 1 to 8.

[0126] (Appendix 10) A method performed by a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, receiving information constituting the small data transmission in the RRC inactive state; when the UE is in the RRC inactive state, determining whether there is uplink data to be transmitted as small data transmission; processing the uplink data to form small data transmission and adding information for identifying the UE; transmitting the small data transmission and the information for identifying the UE using a DRB (Data Radio Bearer) based on the received information; A method comprising the above.

[0127] (Appendix 11) The small data transmission is transmitted using a resource associated with "configured grant type-1". The method according to Appendix 10.

[0128] (Appendix 12) The small data transmission is transmitted via a message (e.g., "Msg3" or "MsgA") forming part of a random access procedure. The method according to Appendix 10.

[0129] (Appendix 13) The method according to any one of Appendices 10 to 12, wherein the information for identifying the UE includes a MAC (Medium Access Control) CE (Control Element) (e.g., a "UE-ID" MAC CE) or an RRC information element.

[0130] (Appendix 14) The method according to any one of Appendices 10 to 13, wherein the processing includes segmenting the uplink data to form a plurality of small data transmissions, and adding the information for identifying the UE to at least one of the plurality of small data transmissions.

[0131] (Appendix 15) The method according to any one of Appendices 10 to 14, wherein the determining includes determining whether a QFI (QoS (Quality of Service) Flow Identifier) associated with the small data transmission can be mapped to the DRB, and the method includes transmitting the small data transmission and the information for identifying the UE based on the result of the determination.

[0132] (Appendix 16) The method according to any one of Appendices 10 to 15, wherein forming the small data transmission by processing the uplink data includes configuring at least one layer of the DRB for the small data transmission.

[0133] (Appendix 17) Configuring at least one layer of the DRB for the small data transmission includes configuring the SDAP (Service Data Adaptation Protocol) layer without an SDAP header, Using a shortened PDCP (Packet Data Convergence Protocol) sequence number (e.g., 7 bits) and / or using a 1-byte PDCP header size, Using TM (Transparent Mode) for small data transmission using the DRB, Configuring the MAC (Medium Access Control) layer without using an LCID (Logical Channel Identifier) and / or a length field, Configuring a fixed-size MAC PDU (Protocol Data Unit) for small data transmission, The method according to Appendix 16, comprising at least one of the above.

[0134] (Appendix 18) A method performed by a communication device of a radio access network for communicating with a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, comprising: Transmitting information configuring small data transmission via a control plane; Receiving, from the UE via a CCCH (Common Control Channel), an RRC message including small data transmission using an SRB (Signalling Radio Bearer) provided while the UE is in the RRC inactive state; The method comprising the above.

[0135] (Appendix 19) A method performed by a communication device of a radio access network for communicating with a UE (User Equipment) for small data transmission in the RRC (Radio Resource Control) inactive state, comprising: transmitting information configuring the small data transmission in the RRC inactive state; receiving, from the UE while the UE is in the RRC inactive state, small data transmission and information identifying the UE using a DRB (Data Radio Bearer) based on the transmitted information; A method comprising the above.

[0136] (Appendix 20) A UE (User Equipment) for small data transmission in the RRC (Radio Resource Control) inactive state, comprising: means for receiving, via a control plane, information configuring small data transmission; means for determining whether there is uplink data to be transmitted as small data transmission while the UE is in the RRC inactive state; means for generating an RRC message including the small data transmission; means for transmitting the RRC message including the small data transmission using an SRB (Signalling Radio Bearer) provided via a CCCH (Common Control Channel); A UE comprising the above.

[0137] (Appendix 21) A UE (User Equipment) for small data transmission in the RRC (Radio Resource Control) inactive state, comprising: means for receiving information configuring the small data transmission in the RRC inactive state; means for determining whether there is uplink data to be transmitted as small data transmission when the UE is in the RRC inactive state; means for processing the uplink data to form small data transmission and adding information for identifying the UE; means for transmitting the small data transmission and the information for identifying the UE using a DRB (Data Radio Bearer) based on the received information; A UE comprising the above.

[0138] (Appendix 22) A communication device of a radio access network for communicating with a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, means for transmitting information constituting small data transmission via a control plane; means for receiving, from the UE via a CCCH (Common Control Channel), an RRC message including small data transmission using an SRB (Signalling Radio Bearer) provided while the UE is in the RRC inactive state; A communication device comprising the above.

[0139] (Appendix 23) A communication device of a radio access network for communicating with a UE (User Equipment) for small data transmission in an RRC (Radio Resource Control) inactive state, means for transmitting information constituting small data transmission in the RRC inactive state; means for receiving, from the UE while the UE is in the RRC inactive state, small data transmission and information for identifying the UE using a DRB (Data Radio Bearer) based on the transmitted information; A communication apparatus comprising the same.

[0140] This application claims the benefit of priority based on UK Patent Application No. 2004520.9 filed on Mar. 27, 2020, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A user equipment (UE) for small data transmission in a radio resource control (RRC) inactive state, comprising: A means for receiving information indicating a condition for restricting the small data transmission; A means for receiving an RRC release message used to set up a radio bearer (RB) configured for small data transmission in the RRC inactive state; A means for transmitting the small data using the RB when the UE is in the RRC inactive state and satisfies a condition indicated in information indicating a condition for restricting the small data transmission; A UE comprising:

2. The UE according to claim 1 , wherein the information indicating the conditions for restricting the small data transmission is transmitted by broadcast transmission.

3. 1. An access network node for communicating with a user equipment (UE) for small data transmission in a Radio Resource Control (RRC) inactive state, comprising: A means for transmitting information indicating a condition for restricting the transmission of the small data; means for transmitting an RRC release message used to set up a radio bearer (RB) configured for small data transmission in the RRC inactive state; A means for receiving the small data from the UE using the RB when the UE is in the RRC inactive state and satisfies a condition indicated in information indicating a condition for restricting the small data transmission; An access network node comprising:

4. The access network node according to claim 3 , wherein the information indicating the conditions for restricting the small data transmission is transmitted by broadcast transmission.

5. A method in a user equipment (UE) for small data transmission in a Radio Resource Control (RRC) inactive state, comprising: Receiving information indicating a condition for restricting the small data transmission; receiving an RRC release message used to set up a radio bearer (RB) configured for small data transmission in the RRC inactive state; When the UE is in the RRC inactive state and satisfies a condition indicated in the information indicating a condition for restricting the small data transmission, transmitting the small data using the RB; A method comprising:

6. 1. A method in an access network node for communicating with a User Equipment (UE) for small data transmission in a Radio Resource Control (RRC) inactive state, comprising: Transmitting information indicating a condition for restricting the small data transmission; Sending an RRC release message used to set up a radio bearer (DRB) configured for small data transmission in the RRC inactive state; When the UE is in the RRC inactive state and satisfies a condition indicated in the information indicating a condition for restricting the small data transmission, receiving the small data from the UE using the RB; A method comprising:

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