WO2025211348A1

WO2025211348A1 - Method, mobile device, access network node

Info

Publication number: WO2025211348A1
Application number: PCT/JP2025/013316
Authority: WO
Inventors: Maxime GRAU; Pravjyot DEOGUN
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2024-04-04
Filing date: 2025-04-01
Publication date: 2025-10-09
Anticipated expiration: 2026-10-04

Abstract

A method performed by a mobile device includes receiving, from a network whose an access network node is in a network energy saving (NES) mode, information used for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node; and transmitting the WUS using the information.

Description

METHOD, MOBILE DEVICE, ACCESS NETWORK NODE

　　The present disclosure relates to a communication system. The disclosure has particular but not exclusive relevance to wireless communication systems and devices thereof operating according to the 3rd Generation Partnership Project (3GPP) standards or equivalents or derivatives thereof (including Long Term Evolution (LTE)-Advanced, Next Generation or 5G networks, future generations, and beyond). The disclosure has particular, although not necessarily exclusive, relevance to network energy saving (NES) cells and on-demand transmission of system information blocks in 'New Radio' systems (also referred to as 'Next Generation' systems), and similar systems.

　　Earlier developments of the 3GPP standards were referred to as the Long-Term Evolution (LTE) of Evolved Packet Core (EPC) network and Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN), also commonly referred as '4G'. More recently, the terms '5G' and 'new radio' (NR) are used to refer to an evolving communication technology that is expected to support a variety of applications and services. Various details of 5G networks are described in, for example, the 'NGMN 5G White Paper' V1.0 by the Next Generation Mobile Networks (NGMN) Alliance, which document is available from https://www.ngmn.org/5g-white-paper.html. 3GPP intends to support 5G by way of the so-called 3GPP Next Generation (NextGen) radio access network (RAN) and the 3GPP NextGen core network.

　　Under the 3GPP standards, a NodeB (or an eNB in LTE, and gNB in 5G) is the radio access network (RAN) node (or simply 'access node', 'access network node' or 'base station') via which communication devices (user equipments or 'UEs') connect to a core network and communicate with other communication devices or remote servers. For simplicity, the present application will use the term access network node, RAN node, or base station to refer to any such access nodes.

　　Also for simplicity, the present application will use the term mobile device, user device, or UE to refer to any communication device that is able to connect to the core network via one or more base stations. Although the present application may refer to mobile devices in the description, it will be appreciated that the technology described can be implemented on any communication devices (mobile and/or generally stationary) that can connect to a communication system for sending/receiving data, regardless of whether such communication devices are controlled by human input or software instructions stored in memory.

NPL 1: 'NGMN 5G White Paper' V1.0 by the Next Generation Mobile Networks (NGMN) Alliance, which document is available from https://www.ngmn.org/5g-white-paper.html.

　　There is a need for improved wireless communication networks having improved energy efficiency. A reduction in the amount of energy needed to operate a communication network beneficially reduces the environmental impact of operating the system, and also reduces the operational costs.

　　One method of achieving a more efficient communication network is to reduce the energy requirements needed to provide a cell. Network energy saving (NES) cells having a reduced number of transmissions may be provided. In a non-anchor NES cell, some types of transmission (e.g. some types of broadcast transmissions) may not be transmitted in the cell. For example, system information corresponding to one or more system information blocks (SIB) may not be transmitted in the non-anchor NES cell. Access for a UE to the non-anchor NES cell may be configured via communication using a corresponding anchor cell. However, when implementing NES cells, more efficient and reliable mechanisms for enabling the UE to obtain system information (SI) for accessing the NES cell are needed.

　　More generally, there is a need for more efficient and reliable methods and apparatus for providing a UE 3 with information for accessing and communicating via an NES cell.

　　The disclosure aims to provide apparatus and methods that at least partially address one or more of the above needs and/or issues.

　　A method performed by a mobile device according to a first exemplary aspect of the present disclosure, the method comprising:
　　receiving, from a network whose an access network node is in a network energy saving (NES) mode, information used for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node; and
　　transmitting the WUS using the information.

　　A method performed by an access network node in a network energy saving (NES) mode according to a second exemplary aspect of the present disclosure, the method comprising:
　　transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node;
　　receiving the WUS using the information by the mobile device; and
　　transmitting the SIB1 to the mobile device.

　　A method performed by an access network node in a network whose another access network node is in a network energy saving (NES) mode according to a third exemplary aspect of the present disclosure, the method comprising:
　　transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the another access network node;
　　transmitting the SIB1 upon the another access network node receiving the WUS using the information by the mobile device.

　　A mobile device according to a fourth exemplary aspect of the present disclosure comprising:
　　means for receiving, from a network whose an access network node is in a network energy saving (NES) mode, information used for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node; and
　　means for transmitting the WUS using the information.

　　An access network node in a network energy saving (NES) mode according to a fifth exemplary aspect of the present disclosure, the access network node comprising:
　　means for transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node;
　　means for receiving the WUS using the information by the mobile device; and
　　means for transmitting the SIB1 to the mobile device.

　　An access network node in a network whose another access network node is in a network energy saving (NES) mode according to a sixth exemplary aspect of the present disclosure, the access network node comprising:
　　means for transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the another access network node; and
　　means for transmitting the SIB1 upon the another access network node receiving the WUS using the information by the mobile device.

　　　　Detailed examples of the disclosure will now be described, by way of example, with reference to the accompanying drawings in which:
Fig. 1 schematically illustrates a mobile ('cellular' or 'wireless') communication system 1; Fig. 2 illustrates a typical frame structure that may be used in the communication system 1 of Fig. 1; Fig. 3 illustrates a user plane protocol stack; Fig. 4 illustrates a control plane protocol stack; Fig. 5 shows a flow diagram illustrating a random access procedure; Fig. 6 illustrates a further example of a random access procedure; Fig. 7 shows a simplified schematic illustration of an anchor cell and a corresponding non-anchor NES cell; Fig. 8 illustrates a method in which a UE determines than an NES cell is provided as part of a multiple-cell configuration; Fig. 9 illustrates a method in which a UE receives an indication of a cell that can be used to obtain WUS configuration information for the NES cell; Fig. 10 illustrates a method in a which a request for transmission of SIB1 is transmitted to the base station that provides the NES cell via the anchor cell; Fig. 11 illustrates an example in which the UE 3 is connected to (or camping on) a serving cell, and is provided with an indication that an NES cell is provided in the communication system; Fig. 12 is a schematic block diagram illustrating the main components of a UE 3 for the communication system 1 of Fig. 1; Fig. 13 is a schematic block diagram illustrating the main components of a base station of a distributed type for the communication system of Fig. 1; and Fig. 14 is a schematic block diagram illustrating the main components of a core network node or function for the communication system of Fig. 1.

　　Overview
　　An exemplary communication system will now be described in general terms, by way of example only, with reference to Figs. 1 to 4.

　　Fig. 1 schematically illustrates a mobile ('cellular' or 'wireless') communication system 1 to which examples of the present disclosure are applicable.

　　In the communication system 1, user equipments (UEs) 3-1, 3-2, 3-3 (e.g. mobile telephones and/or other mobile devices) can communicate with each other via a radio access network (RAN) 50 that operates according to one or more compatible radio access technologies (RATs). In the illustrated example, the RAN 50 comprises a distributed base station 5 or 'gNB' 5 operating one or more associated cells 9. Communication via the RAN 50 is typically routed through an associated core network 7 (e.g. a 5G and/or later generations core network or evolved packet core network (EPC)).

　　As those skilled in the art will appreciate, whilst three UEs 3 and one base station 5 are shown in Fig. 1 for illustration purposes, the system, when implemented, will typically include other base stations 5 and UEs 3.

　　Each base station 5 controls one or more associated cells 9 either directly, or indirectly via one or more other nodes (such as home base stations, relays, remote radio heads, distributed units, and/or the like). It will be appreciated that the base stations 5 may be configured to support 4G, 5G, 6G, and/or later generations and/or any other 3GPP or non-3GPP communication protocols.

　　In this example the illustrated RAN 50 comprises a distributed base station 5 comprising at least one distributed unit (DU) 5b (e.g., a gNB-DU or the like), and a central unit (CU) 5c (e.g., a gNB-CU or the like). It will be appreciated that the DU 5b, the CU 5c or the base station 5 may be referred to as RAN nodes. The CU 5c employs a separated control plane and user plane and so is, itself, split between a control plane function (CU-CP) and a user plane function (CU-UP) which respectively communicate, with the DU 5b via appropriate interfaces (e.g. an F1-C interface and an F1-U logical interface (together forming an F1 interface (or 'reference point'))), and with one another via appropriate interfaces (e.g. an E1 interface). It will be appreciated that while, in this example, the DU 5b includes the physical and virtual elements required to provide the functionality of the lower parts of the PHY layer and hence communicate with the UEs 3 over the air interface, the RAN 50 may alternatively (or additionally) include one or more separate radio units (RUs) (e.g., providing this functionality of the lower parts of the PHY layer). It will, nevertheless, be appreciated that whilst a distributed base station 5 is shown and described, the base station 5 may be provided in a non-distributed form, for example as an integrated station 5.

　　The UEs 3 and their serving base station 5 are connected via an appropriate air interface (for example the so-called 'Uu' interface and/or the like). Neighbouring base stations 5 may be connected to each other via an appropriate base station to base station interface (such as the so-called 'X2' interface, 'Xn' interface and/or the like). Since the Xn connection with neighbouring base stations 5 is via the gNB-CU, the gNB-CU can obtain information regarding neighbouring cells provided by the neighbouring base station 5.

　　The core network 7 includes a number of logical nodes (or 'functions') for supporting communication in the communication system 1. In this example, the core network 7 comprises control plane functions (CPFs) 10 and one or more network node entities for the communication of user data (e.g., user plane functions (UPFs) 11). The CPFs 10 include one or more network node entities for the communication of control signalling (e.g., Access and Mobility Management Functions (AMFs) 10-1), one or more network node entities for session management (e.g., Session Management Functions (SMFs) 10-2) and a number of other functions 10-n (such as, for example, an Authentication Server Function (AUSF) which facilitates security processes, a Unified Data Management (UDM) entity for managing user specific data (e.g., for access authorization, user registration, and data network profiles), a Policy Control Function (PCF), an Application Function (AF), and/or the like). It will be appreciated that the nodes or functions may have different names in different systems.

　　The base station 5 is connected to the core network nodes via appropriate interfaces (or 'reference points') such as an N2 reference point between the CU 5c (CU-CP) of the RAN 50 and the AMF 10-1 for the communication of control signalling, and an N3 reference point between the CU 5c (CU-UP) of the RAN 50 and each UPF 11 for the communication of user data. The UEs 3 are each connected to the AMF 10-1 via a non-access stratum (NAS) connection over an appropriate interface (e.g.an N1 reference point (analogous to the S1 reference point in LTE)). It will be appreciated that N1 communications are routed transparently via the RAN 50.

　　One or more UPFs 11 are connected to an external data network 20 (e.g., an IP network such as the Internet) via an appropriate interface (e.g. an N6 reference point) for communication of the user data.

　　The AMF 10-1 performs mobility management related functions, maintains the NAS connection with each UE 3 and manages UE registration. The AMF 10-1 is also responsible for managing paging. The SMF 10-2 provides session management functionality (that formed part of MME functionality in LTE) and additionally combines some control plane functions (provided by the serving gateway and packet data network gateway in LTE). The SMF 10-2 also allocates IP addresses to each UE 3.

　　The base station 5 of the communication system 1 may be configured to operate at least one cell 9 on an associated time-division duplex (TDD) carrier that operates in unpaired spectrum. It will be appreciated that the base station 5 may also operate at least one cell 9 on an associated frequency-division duplex (FDD) carrier that operates in paired spectrum.

　　The base station 5 is also configured for transmission of, and the UEs 3 are configured for the reception of, control information and user data via a number of downlink (DL) physical channels and for transmission of a number of physical signals. The DL physical channels correspond to resource elements (REs) carrying information originating from a higher layer, and the DL physical signals are used in the physical layer and correspond to REs which do not carry information originating from a higher layer.

　　The physical channels may include, for example, a physical downlink shared channel (PDSCH), a physical broadcast channel (PBCH), and a physical downlink control channel (PDCCH). The PDSCH carries data sharing the PDSCH's capacity on a time and frequency basis. The PDSCH can carry a variety of items of data including, for example, user data, UE-specific higher layer control messages mapped down from higher channels, system information blocks (SIBs), and paging. The PDCCH carries downlink control information (DCI) for supporting a number of functions including, for example, scheduling the downlink transmissions on the PDSCH and also the uplink data transmissions on a physical uplink shared channel (PUSCH). The PBCH provides UEs 3 with the Master Information Block(MIB). It also, in conjunction with the PDCCH, supports the synchronisation of time and frequency, which aids cell acquisition, selection and re-selection. The UE 3 may receive a Synchronization Signal / Physical Broadcast Channel (PBCH) Block (SSB), and the UE 3 may assume that reception occasions of a PBCH, primary synchronization signal (PSS) and secondary synchronization signal (SSS) are in consecutive symbols and form a SS/PBCH block. The base station 5 may transmit a number of synchronization signal (SS) blocks corresponding to different DL beams. The total number of SS blocks may be confined, for example, within a 5 ms duration as an SS burst. The periodicity of the SSB transmissions may be indicated to the UE using any suitable signalling (e.g. per serving cell using ssb-periodicityServingCell). The periodicity value for the SSB may be, for example, greater than or equal to 20 ms. For initial cell selection, the UE 3 may be configured to assume that an SS burst occurs with a periodicity of 2 frames. The UE 3 may also be provided with an indication of which SSBs within a 5 ms duration are transmitted (e.g. using ssb-PositionsInBurst).

　　The DL physical signals may include, for example, reference signals (RSs) and synchronization signals (SSs). A reference signal (sometimes known as a pilot signal) is a signal with a predefined special waveform known to both the UE 3 and the base station 5. The reference signals may include, for example, cell specific reference signals, UE-specific reference signal (UE-RS), downlink demodulation signals (DMRS), and channel state information reference signal (CSI-RS).

　　Similarly, the UEs 3 are configured for transmission of, and the base station 5 is configured for the reception of, control information and user data via a number of uplink (UL) physical channels corresponding to REs carrying information originating from a higher layer, and UL physical signals which are used in the physical layer and correspond to REs which do not carry information originating from a higher layer. The physical channels may include, for example, the PUSCH, a physical uplink control channel (PUCCH), and/or a physical random-access channel (PRACH). The UL physical signals may include, for example, demodulation reference signals (DMRS) for a UL control/data signal, and/or sounding reference signals (SRS) used for UL channel measurement.

　　When the UE 3 initially establishes a radio resource control (RRC) connection with a base station 5 via a cell 9 it registers with an appropriate core network node (e.g., AMF, MME). The UE 3 is in the so-called RRC connected state and an associated UE context is maintained by the network. When the UE 3 is in the so-called RRC idle state, or is in the RRC inactive state, it selects an appropriate cell for camping so that the network is aware of the approximate location of the UE 3 (although not necessarily on a cell level).

　　As mentioned above, the base station 5 in this example is a 'distributed' base station 5 that is split between one or more distributed units (DUs) 5b and a central unit (CU) 5c, with a CU 5c typically performing higher level functions and communication with the next generation core, and with the DU 5b performing lower level functions and communication over an air interface with UEs 3 in the vicinity (i.e. in a cell operated by the base station 5). A distributed base station 5 may, for example, include the following functional units hosting the following functions:

　　Central Unit (CU): a logical node hosting Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) layers of the base station 5 that controls the operation of one or more DUs. The gNB-CU terminates an appropriate interface (e.g. the so-called F1 interface) connected with the DU.
　　Distributed Unit (DU): a logical node hosting Radio Link Control (RLC), Medium Access Control (MAC) and Physical (PHY) layers of the base station, and its operation is partly controlled by the CU. One DU supports one or multiple cells. One cell is supported by only one DU. The DU terminates an appropriate interface (e.g. the F1 interface) connected with the CU.

　　Frame Structure
　　Referring to Fig. 2, which illustrates a typical frame structure that may be used in the communication system 1, the base station 5 and UEs 3 of the communication system 1 communicate with one another using resources that are organised, in the time domain, into frames of length 10 ms. Each frame comprises ten equally sized subframes of 1 ms length. Each subframe is divided into one or more slots comprising 14 orthogonal frequency-division multiplexing (OFDM) symbols of equal length.

　　As seen in Fig. 2, the communication system 1 supports multiple different numerologies (subcarrier spacing (SCS), slot lengths and hence OFDM symbol lengths). Specifically, each numerology is identified by a parameter, μ, where μ=0 represents 15 kHz (corresponding to the LTE SCS). Currently, the SCS for other values of μ can, in effect, be derived from μ = 0 by scaling up in powers of 2 (i.e. SCS = 15 x 2μ kHz). The relationship between the parameter, μ, and SCS (Δf) is as shown in Table 1:

　　Protocol Stacks
　　Fig. 3 illustrates a user plane protocol stack that can be used in the communication system 1 illustrated in Fig. 1. The protocol stack includes a number of protocol layers that are terminated at the UE 3 and at the base station 5. As shown in Fig. 3, the protocol stack includes a physical (PHY) layer, Medium Access Control (MAC) layer, Radio Link Control (RLC) layer, Packet Data Convergence Protocol (PDCP) layer, and Service Data Adaptation Protocol (SDAP) layer. Fig. 4 illustrates a control plane protocol stack that can be used in the communication system 1 illustrated in Fig. 1. As shown in Fig. 4, the control plane protocol stack includes the PHY, MAC, RLC and PDCP layers, as well as the radio resource control (RRC) layer.

　　As described above, the SDAP and PDCP layers may be hosted at a CU 5c. The RLC, MAC and PHY layers may be hosted at a DU 5b.

　　The MAC layer is a layer 2 (L2) sublayer. The MAC layer receives RLC PDUs (as MAC service data units (SDU)s) from the RLC sublayer and processes them to form MAC PDUs (which are packaged as transport blocks (TBs)) for transmission via the PHY sublayer. PDCP PDUs carrying data from the upper layers may also be referred to as PDCP data PDUs to distinguish them from a PDCP control PDU carrying control data. The MAC layer supports the Hybrid Automatic Repeat Request (HARQ) protocol. The PHY layer is a layer 1 (L1) layer that can apply segmentation to large TBs to maintain the transmitted packet size below the configured maximum packet size, and enables transmission and reception via the air interface. Cyclic redundancy check (CRC) bits can be included in each TB at the PHY layer, to enable the receiving device to check for errors in the received TBs.

　　The RLC layer is a L2 sublayer. The RLC sublayer provides a radio link protocol used over the air interfaces between a UE 3 and the base station 5 (i.e., Uu). The RLC sublayer provides a number of functions depending on requirements including, for example: transfer of upper layer (PDCP) PDUs in one of three modes including acknowledged mode (AM), unacknowledged mode (UM) and transparent mode (TM); error correction through automatic repeat requests (ARQ) for AM data transfer; concatenation, segmentation and reassembly of RLC SDUs (UM and AM); re-segmentation of RLC data PDUs when a complete RLC PDU cannot be transmitted (AM); reordering of RLC data PDUs (UM and AM); duplicate detection (UM and AM); RLC SDU discard (UM and AM); RLC re-establishment; protocol error detection and recovery. One or more RLC entities may be established in the RLC sublayer for receiving data from higher layers and for processing the RLC SDUs through the RLC layer to become RLC PDUs (and vice versa). Following the processing of the RLC SDUs to form RLC PDUs, the RLC entity transfers the RLC PDUs to the MAC sublayer (where they are received as MAC SDUs). A receiving RLC entity in one device (e.g., the base station 5 or UE 3) can generate an RLC status report indicating the receive status of packets (RLC SDUs) successfully received (or not received) from a transmitting RLC entity at a corresponding peer device (e.g., the base station 5, or UE 3) and send the RLC status report as an RLC status PDU to the peer device. An RLC status report/PDU will typically include the receive status for a plurality of received RLC SDUs (and possibly RLC SDU segments). On receipt of the RLC status report / PDU, the RLC entity at the peer (transmitting) device will iterate through the positively acknowledged packets in the RLC status report / PDU and notify the PDCP layer of each RLC SDU (and hence PDCP PDU) that has been positively acknowledged. Accordingly the base station 5 and remote UE 3 may operate data radio bearers (DRBs) in an RLC acknowledge mode (AM).

　　The PDCP sublayer is the L2 sublayer that sits below the SDAP sublayer for user plane data, and below the RRC sublayer for control plane data. The PDCP sublayer provides a number of functions depending on requirements including, for example: transfer of user plane data (to/from the SDAP sublayer); transfer of control plane data (to/from the RRC sublayer); maintenance of PDCP sequence numbers; header compression and decompression (e.g., using the robust header compression (ROHC) protocol); ciphering and deciphering; integrity protection and integrity verification; timer based discarding of packets (PDCP SDUs); routing (e.g., for split bearers); duplication; reordering and in-order delivery; out-of-order delivery; and/or duplicate discarding.

　　When a discard timer expires for a PDCP SDU, or the successful delivery of a PDCP SDU is confirmed by a PDCP status report, the transmitting PDCP entity may discard the PDCP SDU along with the corresponding PDCP Data PDU. If the corresponding PDCP Data PDU has already been submitted to lower layers, the discard is indicated to lower layers.

　　The SDAP layer is the highest L2 sublayer of the protocol stack. It is responsible for quality of service (QoS) flow handling across the air (Uu) interface and N3 interface. The SDAP sublayer can have multiple SDAP entities (e.g., one for each protocol data unit (PDU) session between the base station 5 and remote UE 3-4) where SDAP entity establishment / release is initiated by RRC. The SDAP layer is responsible for the transfer of user plane data between the remote UE 3 and the core network (UPF 11). An SDAP entity maps each QoS flow from higher layers, within a particular PDU session, to a respective data radio bearer (DRB) established, via lower layers (e.g., PDCP and RLC) with the appropriate level of QoS, over the air interface between the UE 3 and the base station 5. As those skilled in the art will appreciate, the QoS flow may be in either the downlink or in the uplink and there may be more than one such QoS flow within the PDU session. It will be appreciated that the SDAP layer is not present in some architectures (e.g., in a non-stand-alone (NSA) architecture).

　　The RRC layer is considered to be a layer 3 (L3) sublayer and is the highest layer in the control plane of the access stratum (AS). It is also responsible for transferring messages of the non-access stratum (NAS), which is located above the RRC layer. The RRC layer is responsible for handling many RAN-related control plane procedures such as: broadcasting system Information (SI); transmission of paging messages to notify a UE about incoming connection requests; connection management; handling UE capabilities; and measurement configuration and reporting.

CU-DU Information Exchange
　　In the communication system 1, various messages may be exchanged between the CU 5c and the DU 5b, for instance during a setup procedure for configuring communication between the DU and CU (e.g., an 'F1 setup procedure'). The purpose of the setup procedure is to exchange application level data needed for the DU 5b and the CU 5c to interoperate correctly (e.g., on the F1 interface). This procedure is the initial procedure triggered for control plane communication (e.g., over the F1-C interface) after a transport network layer (TNL) association has become operational. Typically, this procedure will use non-UE associated signalling.

　　During such a procedure, the DU 5b may transmit a setup request message (e.g., an F1 Setup Request) to the CU 5c. Where the setup request message is an F1 Setup Request it may, for example, include the following information:
-　　DU Served Cells List IE: Information about the cells supported by the DU and associated features (e.g., NR-U);
-　　DU System Information IE.
It will be appreciated that differently named information elements, having a similar purpose, may be used.

　　In response, the CU 5c typically transmits an F1 Setup Response message to the DU 5b. The following information may be included in the F1 Setup Response message:
-　　Cells to be Activated List IE: a list of cells that the CU 5c requests the DU 5b to activate.

　　Further to the above messages, other messages (with associated information elements) may be used to update the configuration between the CU 5c and the DU 5b. For example, Public Land Mobile Network (PLMN) list, served cell information, DU Configuration Update or CU Configuration Update messages may be used to exchange information between the CU 5c and the DU 5b.

　　Additional messaging may be used between the CU 5c and the DU 5b, for instance when establishing a UE's context during a UE Context Setup procedure. The purpose of the UE Context Setup procedure is to establish the UE Context including, signalling radio bearer (SRB), and data radio bearer (DRB). This procedure uses UE associated signalling.

　　During such a procedure, the CU 5c may transmit a UE Context Setup Request message to the DU 5b (this message may comprise an RRC container used to carry additional information, e.g. in an RRC information IE). The following information may be included in the UE Context Setup Request message:
-　　UE-CapabilityRAT-ContainerList: the DU 5b may take this information into account for UE specific configurations;
-　　DRX Cycle IE: the DU 5b may use the provided value from the CU 5c;
-　　RRC Information IE; in the case where the CU 5c receives a UEAssistanceInformation IE from the UE 3, the UEAssistanceInformation IE may be included in the RRC Information IE. The DU 5b may, if supported, take the UE's assistance information into account when configuring resources for the UE 3.
-　　SRB To Be Setup List;
-　　DRB To Be Setup List.

　　In response, the DU 5b transmits a UE Context Setup Response message to the CU 5c. The following information may be included in the UE Context Setup Response message:
-　　A list of DRBs (and SRBs) which are successfully established and DRBs (and SRBs) which failed to establish;
-　　When the DU 5b reports the unsuccessful establishment of a DRB or SRB, an associated cause value should be precise enough to enable the CU 5c to know the reason for the unsuccessful establishment. This may include the reason that a given feature is not supported by the DU 5b;
-　　CellGroupConfig: As an Octet string which is included by CU 5c transparently within an RRC reconfiguration message sent to UE 3;
-　　DRX Config: As an Octet string which is included by CU 5c transparently within the RRC reconfiguration message sent to UE 3.

　　Instead of the above messages, alternative messages (with associated information elements) may be used to update the UE's configuration between the CU 5c and the DU 5b.

　　For example, to further update the UE 3 configuration between CU 5c and DU 5b (e.g., DRB/SRB), UE Context Modification Request message (from CU 5c to DU 5b) or UE Context Modification Required (from DU 5b to CU 5c) messages may be used for information exchange between the CU 5c and the DU 5b.

Random Access
　　Fig. 5 shows a random access (RA) procedure that may be performed in the system of Fig. 1, for example to transmit a request for a SIB using MSG3. The RA procedure can be used, for example, for initial access by a UE 3 that is in the RRC idle mode, or for a transition from the RRC inactive mode to the RRC connected mode. The RA procedure may also be used, for example, during handover of the UE 3 from a source base station to a target base station (e.g. the handover procedure described above with reference to Fig. 5), for initial access to the target base station 5.

　　In step S501, the UE 3 transmits a random access preamble to the base station 5. The UE 3 may select the random access preamble to transmit from a group of random access preambles that are shared with other UEs 3. The transmission of step S501 may be referred to as message 1 (MSG1), and is transmitted using PRACH.

　　In step S502, the base station 5 transmits a random access response to the UE 3. The transmission of step S502 may be referred to as message 2 (MSG2). The random access response indicates time and/or frequency resources (e.g. resource blocks and/or symbols) for use by the UE 3 to transmit a subsequent transmission to the base station 5. The random access response may also include further information for use by the UE 3 for communication with the base station 5, such as a timing advance (TA) value.

　　In step S503, the UE 3 transmits a transmission to the base station 5 using the indicated time and/or frequency resources. The transmission of step S503 may be referred to as message 3 (MSG3). The transmission of step S503 may be a layer 2 (L2) or layer 3 (L3) message. The transmission of step S503 may comprise, for example, an RRC setup request, an RRC resume request, an RRC reestablishment request, or an RRC reconfiguration complete message.

　　If two UEs 3 selected and transmitted the same random access preamble in step S501, and receive and decode MSG2 transmitted by the base station 5 in step S502, then the two UEs may transmit MSG3 using the same time and/or frequency resources. This situation can be referred to as 'contention' or 'collision'. In order to resolve the contention, in step S504 the base station 5 transmits a contention resolution message to the UE 3. The transmission of step S604 may be referred to as message 4 (MSG4). MSG4 indicates to the UE 3 whether the MSG3 transmitted by the UE 3 in step S503 was received and successfully decoded by the base station. MSG3 transmitted in step S503 may not have been received or successfully decoded by the base station 5 if the base station 5 decoded a MSG3 transmitted by another UE 3 that is in contention with the UE 3, or if interference occurred between the MSG3 transmitted by the two UEs 3. If MSG3 transmitted by the UE 3 was not decoded by the base station 5 (which the UE 3 may determine if the UE 3 does not receive MSG4 from the base station 5), then the UE 3 returns to step S501 of the method and transmits another MSG1 to the base station 5 (e.g. after selecting a different random access preamble).

　　The procedure illustrated in Fig. 5 is an example of a contention based RA procedure in which the UE 3 selects the random access preamble from a group of preambles that could also be used by other UEs 3 (and therefore contention can occur if two of the UEs 3 select the same random access preamble). Alternatively, the base station 5 may transmit a random access preamble assignment to the UE 3 before the UE 3 transmits MSG 1 to the base station 5, in which case the RA procedure is contention free (and the contention resolution in step S504 need not be performed). The random access preamble assignment may be transmitted to the UE 3 using an RRC message or layer 1 (L1) signalling (e.g. using DCI carried by a PDCCH).

　　MSG1 and/or MSG 3 may be used by the UE 3 to request on-demand SI (for example, SIB1) from the base station 5.

SSB Beams and Reference Signals
　　A base station 5 may transmit signals over a plurality of different beam directions. Each beam may have a corresponding index for identifying the beam. For SSB transmissions, the identifying index may be an SSB index. Whilst each beam is transmitted in a generally different direction, it will be appreciated that there may be some spatial overlap between the beams. For SIB1/SI/paging transmission, there may be one or multiple beam sweeping cycles within a SIB1/SI/paging transmission window/transmission occasion.

　　SSB beams may be transmitted in the time domain as a group of SSB transmissions, which may be referred to as an 'SSB burst set'. Each SSB in the SSB burst set may be referred to as an 'SSB block'. For example, a 5 ms SSB burst set in which SSB beams are transmitted by the base station 5 sequentially within a 5 ms time period may be used, resulting in the 'beam sweeping' effect. However, the burst set need not necessarily be of 5 ms duration. Various other transmission configurations in the time domain may be used depending on the configuration of the base station 5 and the available communication resources.

　　The UE 3 and the base station 5 may perform the initial access procedure after the UE 3 has received one of the beamformed signals transmitted by the base station 5, and the UE 3 may be configured to transmit a corresponding measurement report to the base station 5. The UE 3 may perform measurements of, for example, synchronization signal RSRP (SS-RSRP), reference signal received quality (RSRQ), RSRP and signal to noise interference ratio (RSRP-SINR), or physical broadcast channel demodulation reference signal (PBCH DMRS).

　　The UE 3 may be configured to determine an SSB index corresponding to a beam by decoding the PBCH DMRS. The UE 3 may determine a particular beam (and/or corresponding time or frequency resource) to be used for communication with the base station 5 based on corresponding signal measurements performed by the UE 3. Alternatively, the UE 3 may report the measurements to the base station 5, and the base station 5 may determine the beam (and/or corresponding time or frequency resource) to be used for communication with the UE 3.

　　The base station 5 is operable to transmit reference signals (RSs) in the one or more cells 9 that it operates. These reference signals include channel state information RS (CSI-RS). The CSI-RS may be used by the UE 3 for a number of different purposes including, for example, CSI reporting in which the UE 3 derives channel state information (CSI) including one or more channel quality indicators (CQIs), rank indicators (RIs), and/or precoding matrix indicators (PMIs) from CSI-RS measurements and reports them to the base station 5 in a CSI report. The CQI is an index (typically 4 bits) value representing a signal to interference and noise ratio (SINR). The CQI value also corresponds to a modulation and coding scheme (MCS) to be used for each layer. The RI indicates a number of MIMO transmission layers requested by the UE 3 (albeit the base station 5 might not necessarily use the requested number of Multiple-Input Multiple-Output (MIMO) transmission layers). The PMI is used by the UE 3 to report parameters defining a preferred precoding matrix to be applied for downlink transmissions (albeit the base station 5 may not use the requested precoding). A layer indicator (LI) may also be included in the CSI report for identifying the strongest layer from the set of layers indicated by the RI.

　　The CSI-RS may also be used by the UE 3 for beam management, including the refinement of initial beam selection based on SSBs. For example, the base station 5 may use a set of relatively broad beams for transmission of the SSBs and a set of narrower (more directional) beams for the CSI-RS. The UE 3 can be configured, by the base station 5, to measure each CSI-RS transmission to identify the best CSI-RS beam and to report this to the base station 5 (e.g., by means of a CSI report including a CSI-RS indicator (CRI) identifying the strongest CSI-RS and hence CSI-RS beam). The UE 3 may also be configured to report the (Layer 1) RSRP which has been measured for the strongest CSI-RS.

　　CSI-RS may either be either zero power (ZP-CSI-RS) or non-zero power (NZP-CSI-RS). ZP-CSI-RS are empty resource elements, used primarily for interference measurement. NZP-CSI-RS are used for most of the procedures including channel measurement, beam management, beam measurement, connected mode mobility etc. A non-zero-power CSI-RS may be configured, for example, using a NZP-CSI-RS-Resource information element (IE), or using a CSI-RS-Resource-Mobility field in an CSI-RS-ResourceConfigMobility IE. NZP CSI-RS can be used for interference measurement (IM), for example as part of determining a Signal to Interference plus Noise Ratio (SINR). For cases in which interference is likely to be primarily due to inter-cell interference, CSI IM resources may be used. These resources may be used to measure background interference originating from neighbouring cells. The UE 3 may be provided a configuration for receiving (and measuring) the CSI-RS from the base station 5 (e.g. using a CSI Report Configuration, CSI-ReportConfig, transmitted from the base station 5 to the UE 3). The CSI Report Configuration includes an indication of resources for channel measurement, NZP-CSI-RS resources for interference management, and CSI-IM resources. There are also several other ways in which the CSI-RS may be used including, for example, for connected mode mobility, radio link failure detection, beam failure detection / recovery, and fine timing of time and/or frequency synchronisation.

System information and SIB
　　It will be appreciated that transmissions in a cell 9 of a base station 5 may include one or more broadcast transmissions and one or more unicast transmissions for reception by a UE 3. System information (SI) transmitted in a cell may include 'minimum SI' (MSI) and 'other SI' (OSI). The OSI may be broadcast on-demand, for example using a downlink shared channel (DL-SCH). The OSI may be broadcast upon request from a UE 3 that is in a radio resource control (RRC) idle or RRC inactive state. The OSI may also be requested by a UE 3 that is in the RRC connected state, for example via one or more dedicated RRC transmissions.

　　The SI may include information for enabling (e.g. configuring) the UE 3 to complete a cell selection procedure (e.g. for a non-anchor NES cell), may include information for enabling the UE 3 to complete a cell reselection procedure, or for enabling the UE 3 to receive one or more paging messages transmitted in a cell (e.g. the non-anchor NES cell). SI may be broadcast using a Master Information Block (MIB) and one or more System Information Blocks (SIB).

　　The MSI comprises the MIB and system information block 1 (SIB1). The MIB includes information for use by a UE 3 to receive SIB1, for example a subcarrier spacing for SIB1. The MIB provides information corresponding to a Control Resource Set (CORESET) and Search Space. SIB1 may be referred to as 'remaining MSI' (RMSI). SIB1 may be transmitted in a dedicated RRC message, and other SIB (e.g. SIB2 to SIB9) may be transmitting using one or more other suitable RRC transmissions. The MIB and SIB1 may provide the UE 3 with an indication of scheduling information for receiving and decoding the other SIB, such as SIB2 to SIB9, and may provide information for use by the UE 3 to receive one or more paging messages. The OSI may comprise, for example, SIB2 to SIB9 transmitted using a DL-SCH in SI messages. A mapping of SIB2 to SIB9 to corresponding SI messages may be provided to the UE 3 by the base station 5. MIB and SIB1 to SIB9 are described in more detail, for example, in 3GPP TS 38.331. For example, SIB2 provides information for intra-frequency, inter-frequency and inter-system cell reselection, SIB3 provides cell-specific information for intra-frequency cell reselection, and SIB4 provides information for inter-frequency cell reselection. SIB5 provides information regarding inter-system cell reselection towards 4G (LTE). SIB6 and SIB7 provide information for an earthquake and tsunami warning system (ETWS). SIB8 provides information for a commercial mobile alert service (CMAS) notification, for example to provide warning text messages to the UE 3. SIB9 includes information regarding coordinated universal time (UTC), global positioning system (GPS) time (e.g. for GPS initialisation) and local time.

　　SIB may be broadcast periodically (e.g. according to a predetermined periodic pattern), or alternatively may be provided 'on-demand', for example in response to a request from a UE 3. For example, MIB may be transmitted with a periodicity of 80 ms and repetitions made within 80 ms, and SIB1 may be transmitted with a periodicity of 160 ms and a variable transmission repetition periodicity within 160 ms (e.g. 20 ms). SIB1 can be used to indicate to a UE 3 which SIB are transmitted periodically and which SIB are available on-demand in response to a request from the UE 3. A UE 3 may be configured to request on-demand SIB using MSG1 (random access preamble (RA)), which may be referred to as a MSG1-based on-demand SI request, or MSG3 (RRC Connection Request), which may be referred to as a MSG3-based on-demand SI request. Fig. 6 shows an example of a request for SIB using MSG1. In step S601 the UE 3 transmits a random access preamble (MSG1) that includes the request for the on-demand SIB, to the base station 5. The transmission may include information identifying the one or more SIBs that the UE 3 is requesting (for example an explicit or implicit indication of the SIBs). In step S602 the base station 5 transmits a corresponding random access response (MSG2) to the UE 3. MSG2 may include an acknowledgement of the UE's 3 request for the on-demand SIB. Alternatively, for example, the UE 3 may transmit a request for SIB using MSG3. The UE 3 may transmit an RRC system information request, for example RRCSystemInfoRequest, (MSG3) to the base station 5 that includes the request for the on-demand SIB. MSG3 may include information identifying the one or more SIBs that the UE 3 is requesting (for example an explicit or implicit indication of the SIBs).

　　A physical broadcast channel (PBCH) can be used to broadcast the MIB. The base station 5 may transmit the PBCH with synchronisation signals (SS) (e.g. primary synchronisation signal (PSS) and secondary synchronisation signal (SSS)) in a SS/PBCH Block. The SS/PBCH block comprises four orthogonal frequency-division multiplexed (OFDM) symbols that are mapped to PSS, SSS and PBCH associated with a demodulation reference signal (DM-RS). In the frequency domain, an SS/PBCH block consists of 240 contiguous subcarriers. When the UE 3 is in an RRC connected mode, the base station 5 may provide the UE 3 with an indication of resources used for the SS/PBCH, for example using dedicated signalling (e.g. for an anchor NES cell or a non-anchor NES cell). SIB1 may be transmitted using a physical downlink shared channel (PDSCH). The OSI may be similarly transmitted, for example, using a PDSCH.

　　When one or more beamformed transmissions are transmitted in a cell provided by the base station 5, some of the SI (e.g. some of the SIB) may only be transmitted using particular beams, or using a particular transmission/reception point (TRP).

　　Methods of providing a UE 3 with configuration information for accessing a non-anchor NES cell are described below. It will be appreciated that these methods may be used to provide the UE 3 with any suitable information for accessing the non-anchor NES cell (e.g. to receive one or more transmissions via the non-anchor NES cell, or to transmit one or more transmissions to a base station that is providing the non-anchor NES cell). For example, the below-described methods may be used to enable the UE 3 to receive any of the above-described SI, SIBs, and/or broadcast transmissions.

Network energy saving (NES) cells
　　Fig. 7 shows an example of a non-anchor NES cell 30 and a corresponding anchor cell 31. The anchor cell 31 may alternatively be referred to as an "anchor NES cell" 31, and the non-anchor NES cell 30 may simply be referred to as an "NES cell" 30 or "non-anchor cell" 30. In this example the non-anchor NES cell 30 is provided by a first base station 5-1, and the anchor cell 31 is provided by a second base station 5-2. However, the anchor cell 31 and the non-anchor NES cell 30 could alternatively be provided using the same base station 5.

　　The non-anchor NES cell 30 may be configured without transmissions of synchronization signal / physical broadcast channel (PBCH) blocks (SSB), or particular system information blocks, for example SIB1 (or may be a cell in which SSB and/or SIB are not normally transmitted, or are not transmitted according to a default configuration of the non-anchor NES cell 30), in order to reduce the power requirements for operating the cell. More generally, the non-anchor NES cell 30 is configured with a reduced number of broadcast transmissions in order to reduce the amount of energy needed to operate the non-anchor NES cell 30, thereby improving the energy efficiency of the network. However, whilst a non-anchor NES cell 30 may be configured not to transmit a certain type of transmission (e.g. not to broadcast a particular broadcast transmission) at a particular time, the transmission may nevertheless be transmitted in the non-anchor NES cell 30, for example in response to a request from the UE 3 (e.g. a request for transmission of SIB1) or the base station 5-2 that is operating a corresponding anchor cell 31. In other words, some transmissions may be conditionally transmitted in the non-anchor NES cell 30.

　　Access (e.g. initial access) by the UE 3 to the non-anchor NES cell 30 may be configured via the anchor cell 31. Alternatively, access by the UE 3 of the non-anchor NES cell 30 may be configured directly via the non-anchor NES cell 30. If direct access to the non-anchor NES cell 30 is supported, then a SIB transmitted using the anchor cell 31 may include information for use by the UE 3 to access the non-anchor NES cell 30. The UE 3 is operable to receive a configuration for accessing the non-anchor NES cell 30 from the anchor cell 31. For example, when the UE 3 is in an RRC connected state, the UE 3 may receive UE-specific RRC signalling for configuring the UE 3 to receive one or more unicast transmissions in the non-anchor NES cell 30.

　　It will be appreciated that when an NES cell 30 is provided, there need not necessarily be a separate anchor cell 31. For example, in a single-cell scenario, only the NES cell 30 illustrated in Fig. 7 may be provided, in which case the UE 3 may receive information directly via the NES cell 30 (e.g. via an SSB transmitted in the NES cell 30) for initial access to the NES cell 30. This scenario may be referred to as a "single-cell" scenario, and the scenario in which both an anchor cell 31 and one or more corresponding NES cells 30 are provided may be referred to as a "multiple-cell" scenario. The UE 3 may then subsequently request transmission of an on-demand transmission provided in the NES cell 30.

Uplink WUS
　　A wake-up signal (WUS) may be transmitted from a UE 3 to the base station 5 in order to 'wake up' the base station 5 (e.g. to request a transition of a cell from no or reduced transmission/reception activity to an active transmission or reception of a channel/signal/SIB). This type of WUS may be referred to as an uplink WUS. The uplink WUS may be transmitted from the UE 3 to the base station 5-1 that provides the NES cell 30 in order to trigger or request, for example, the transmission of SSB, SIB1 and/or reference signals by the base station 5-1. For example, the base station 5-1 may be configured to perform discontinuous transmission (DTX) or discontinuous reception (DRX), and the uplink WUS may be used to request or trigger the transmission or reception of a signal that would not normally be transmitted/received by the base station 5-1 during the discontinuous transmission/reception.

　　The uplink WUS may be for triggering (or controlling, or requesting) a change in SSB transmission by the base station 5. For example, the base station 5 may be configured for SSB/SIB1-less operation for intra-band carrier aggregation, in which the UE 3 is configured to retrieve system information (and perform synchronisation based on) another intra-band cell that transmits SSB and SIB1. It will be appreciated that a UE 3 may be configured with multiple carriers, and that in carrier aggregation (CA) a set of allowed band combinations are specified. The carrier aggregation may be inter-band, may be contiguous intra-band, or may be non-contiguous intra-band.

　　A carrier aggregation method may include the operation of a primary cell (Pcell) and a secondary cell (Scell) by one or more base stations 5. An intra-band SSB-less Scell may be configured in the communication system. Inter-band carrier aggregation with SSB-less carriers may be supported, in which case synchronisation may be achieved using other cells that are configured for SSB transmission. Activation of inter-band SSB-less Scell operation may include a mechanism for the UE 3 or the base station 5 to trigger normal SSB transmission and/or reference signal transmission by the base station 5 (e.g. via an uplink triggering signal). The uplink triggering signal may be received at either the inter-band SSB-less cell, or at another carrier or cell. RACH transmission may also be supported in the SSB-less Scell. Dynamic Pcell switching may be configured in the communication system, in which a common Pcell is dynamically indicated for a group of UEs 3. Transmission of SSBs/SIB1 by the base station 5 may be on-demand (for example, in response to a request from the UE 5). The uplink WUS may be used to request (or trigger) transmission of a particular SSB or SIB by the base station 5 (e.g. SIB1).

On-Demand SIB1 and WUS Configuration
　　Particularly advantageous methods and apparatus related to on-demand SIB1 transmission and WUS will now be described, with reference to Figs. 8 to 11. In these examples, the NES cell is configured for on-demand transmission of SIB1, and methods of providing the UE 3 with the SIB1 of the NES cell are provided.
UE in Idle Mode

　　In this example the UE 3 receives, when the UE 3 is in the idle mode, an indication that a SIB1-less NES cell (an NES cell that is not transmitting SIB1) is provided in the communication system, and determines whether the NES cell is provided as part of a single-cell configuration without an anchor cell, or as part of a multi-cell configuration with a corresponding anchor cell.

　　The UE 3 is configured to determine whether an NES cell is provided in the system as part of the multiple-cell configuration, or as a single cell (in which case there is no corresponding anchor cell). As described above, a WUS can be used to request or trigger the transmission of an on demand SIB (e.g. SIB1), and a configuration for the WUS can be provided to the UE 3 via the anchor cell. The UE 3 may be configured determine that the NES cell is provided as part of a multiple-cell configuration (in other words, determine that there is a corresponding anchor cell), if the UE 3 determines that there is no configuration available for a WUS to request transmission of SIB1 by the NES cell. The UE 3 can determine that there is no WUS available for the NES cell (determine the absence of a WUS for the NES cell) based on an indication, transmitted in the NES cell, that a WUS cannot be transmitted for the NES cell.

　　Fig. 8 shows a flow diagram illustrating a method in which a UE 3 determines that an NES cell is provided as part of a multiple-cell configuration (in which a corresponding anchor cell is also provided, for example as illustrated in Fig. 7). In step S801, the UE 3 receives an indication, from the base station 5-1 that provides the NES cell, that a WUS cannot be transmitted for the NES cell. For example, the transmission of step S801 may indicate that communication resources for transmission of the WUS are not currently configured for the NES cell. The indication may be provided via the MIB transmitted in the NES cell, or using any other suitable broadcast transmission (e.g. using DCI).

　　In step S802, the UE 3 determines that the NES cell is provided as part of a multiple-cell configuration, based on the information received in step S801. In other words, the UE 3 determines that since a WUS is not available for transmission by the UE 3 to request SIB1 in the NES cell, there is a corresponding anchor cell. As will be described in more detail later, the UE 3 may then perform a search for the anchor cell, and communicate via the anchor cell to obtain a configuration for a WUS for the NES cell (or to receive the SIB1 for the NES cell directly from the anchor cell).

　　If the WUS for the NES cell is already available for transmission in the NES cell, then the base station 5-1 does not transmit the indication of step S801. Instead, the base station 5-1 that provides the NES cell may transmit an indication to the UE 3 that the WUS can be transmitted in the NES cell. The indication may be an explicit indication transmitted using the MIB, DCI, or using any other suitable signalling. Alternatively, the indication may be an implicit indication that the WUS for the NES cell can be transmitted. The UE 3 can then transmit the WUS to cause the base station 5-1 to transmit SIB1 in the NES cell.

　　If the base station 5-1 transmits, to the UE 3, an indication that the WUS is available for the SIB1-less cell, then the UE 3 may be configured to determine a configuration to use for the transmission of the WUS implicitly. For example, the UE 3 may be provided with pre-configured WUS resources (e.g. via the network). The UE 3 may be configured to determine one or more communication resources (e.g. time and/or frequency resources) of the pre-configured WUS resources to use to transmit the WUS based on the physical cell identity (PCI) of the NES cell. Advantageously, therefore, the UE 3 is able to determine the communication resources to use to transmit the WUS in the NES cell based on the preconfigured WUS resources and the PCI of the NES cell, and can then transmit the WUS to trigger the transmission of SIB1 in the NES cell.

　　The indication of step S801 may be an implicit indication. For example, if no explicit indication that communication resources are available for transmission of the WUS in the NES cell is provided to the UE 3 by the base station 5-1, then the UE 3 may implicitly determine that transmission of the WUS in the NES cell is not currently possible, determine that the NES cell is part of a multi-cell configuration comprising an anchor cell, and determine to search for the anchor cell.

　　A modified legacy cell ranking procedure can be used to perform the search for the anchor cell. In the legacy cell ranking procedure, a SIB1-less cell will not be deemed suitable for camping. In the present example, the cell ranking procedure is modified so that SIB1-less NES cells are considered for camping (and connecting). When performing a search for the anchor cell, the UE 3 may be configured to identify the next best ranked cell with an available SIB1 (which may also be referred to as the 'second-best cell'). It will be appreciated that there may be many small SIB1-less cells provided in the vicinity of the UE 3. Since in this example the legacy cell ranking procedure is modified to include SIB1-less cells, the SIB1-less NES cell may be the best ranked cell identified in the search. The UE 3 will then need to identify an anchor cell among the next best ranked cells (after the SIB1-less NES cell). If the identified next best ranked cell with an available SIB1 is the anchor cell for the NES cell, then the search is complete and configuration information for the WUS for the NES cell can be provided to the UE 3 via the anchor cell (or alternatively, the SIB1 of the NES cell can be provided to the UE 3 directly via the anchor cell). If the next best ranked cell with an available SIB1 identified in the cell search is not the anchor cell for the NES cell, then the non-anchor cell may be re-configured to provide an anchor cell for the NES cell, and the configuration information for the WUS for the NES cell can be similarly provided to the UE 3. Otherwise, if the next best ranked cell with an available SIB1 identified in the cell search cannot provide a configuration for the WUS for the NES cell, then the UE 3 determines to connect to the second-best cell instead of the NES cell (in other words, the UE 3 gives up attempting to connect to the NES cell). If, in the search for the anchor cell corresponding to the NES cell, the UE 3 determines that a neighbouring cell is an anchor cell but is not the anchor cell for the NES cell (i.e. the anchor cell identified in the search is an anchor cell for one or more neighbouring SIB1-less NES cells, but not for the target SIB1-less NES cell), then the UE may similarly stop attempting to obtain a configuration for transmission of the WUS in the NES cell.

　　If the UE 3 successfully identifies the anchor cell for the NES cell in the cell search, but transmission of SIB1 is not available in the NES cell (or the NES cell is otherwise unavailable), then the anchor cell may transmit an indication, to the UE 3, that the NES cell is unavailable. The UE 3 can then determine to stop attempting to connect to the NES cell.

　　Fig. 9 shows an alternative method, in which the base station 5-1 that provides the NES cell transmits, to the UE 3, an indication of a neighbour cell that can be used by the UE 3 to obtain a configuration for the WUS for the NES cell.

　　In step S901, the base station 5-1 that provides the NES cell transmits, to the UE 3, an indication of an identity of a neighbour cell that can be used to obtain WUS configuration information for the WUS of the NES cell. The indication of step S901 may be provided, for example, using the MIB in the NES cell, or using any other suitable broadcast signalling (e.g. using DCI). In this example, the indication of the identity of the neighbour cell comprises a PCI of the neighbour cell. However, another suitable cell identifier could alternatively be used. The neighbour cell may be the anchor cell for the NES cell.

　　In step S902, the UE 3 communicates with the cell indicated in the transmission of step S901 to obtain the configuration for the WUS for the NES cell. Alternatively, when the neighbour cell indicated in step S901 is the anchor cell for the NES cell, the UE may communicate with the anchor cell to request the transmission of the on-demand SIB1 by the NES cell. This alternative is illustrated in the flow diagram of Fig. 10. In step S101 the UE 3 transmits, to the base station 5-2 that provides the anchor cell, a request for transmission of SIB1 in the NES cell. The transmission of step S101 may comprise the PCI of the NES cell, to indicate which cell the UE 3 is attempting to connect to. In step S102 the base station 5-2 that provides the anchor cell transmits, to the base station 5-1 that provides the NES cell (e.g. via the Xn interface), and indication that SIB1 is to be transmitted in the NES cell. In other words, in the example of Fig. 10, a request for transmission of SIB1 is transmitted to the base station that provides the NES cell, from the UE 3, via the base station 5-2 that provides the anchor cell. In step S103, after receiving the indication of step S102, the base station 5-1 that provides the NES cell determines to transmit SIB1 in the NES cell. Advantageously, therefore, the UE 3 is able to receive the SIB1 in the NES cell.

　　Signalling from Neighbouring Serving Cell
　　Fig. 11 illustrates an example in which the UE 3 is connected to (or camping on) a serving cell, and is provided with an indication that an NES cell is provided in the communication system. The UE 3 is therefore advantageously able to determine that the NES cell is available for communication, even when the NES cell is not transmitting SIB1.

　　In step S111, The base station 5-2 that provides the serving cell (the anchor base station 5-2 for the NES cell) transmits, to the UE3, an indication of an identity of a SIB1-less cell in a neighbour cell list. The neighbour cell list could be transmitted to the UE 3 using a legacy SIB (e.g. SIB3 or SIB4), but modified to include an indication that the NES cell in the neighbour cell list transmits SIB1 on-demand (i.e., the NES cell is 'SIB1-less').

　　Alternatively, new SI (which could be on-demand SI transmitted in response to a request from the UE 3) could be broadcast in the anchor cell comprising communication resources for a WUS for the NES cell. The UE 3 is then able to determine that the NES cell is present in the communication system, and is able to transmit the WUS in the NES cell to request SIB 1. In a further alternative, the SI transmitted in the anchor cell could include the actual SIB1 content of the SIB1 for the NES cell. Therefore, the UE 3 is able to acquire SIB1 for the NES cell and communicate via the NES cell.

　　In a further alternative, in step S111 the anchor cell could provide an indication of the identity or existence of the SIB1-less NES cell to the UE 3 by providing a unicast in dedicating signalling for the UE 3. The dedicated signalling may be provided per NES cell. After receiving the unicast, the UE 3 is therefore able to determine that the NES cell is present in the communication system, and attempt to communicate via the NES cell.

　　In step S111 the base station 5-2 that provides the anchor cell can also provide an indication to the UE 3 of whether a WUS is available for the SIB1-less cell, and/or whether a WUS can be requested for the NES cell. For example, if a communication resources for a WUS are not currently configured for transmission of a WUS in the NES cell, then in step S111 the base station 5-2 may provide an indication to the UE 3 that the communication resources for transmission of the WUS are not currently configured, but that the UE 3 may request configuration of the communication resources for transmission of the WUS. The UE 3 could then transmit a request to the base station 5-2 that provides the anchor cell for the communication resources for transmission of the WUS to be configured for the NES cell (in which case base station 5-2 that provides the anchor cell communicates with the base station 5-1 that provides the NES cell, via the Xn interface, to configure the communication resources for transmission of the WUS). The request for the communication resources for transmission of the WUS to be configured for the NES cell, transmitted from the UE 3 to the base station 5-2 the provides the anchor cell, may be included in any suitable transmission between the UE 3 and the base station 5-2. For example, the UE 3 may transmit the request to the base station 5-2 when the UE 3 is in connected mode, or via, for example, PRACH using an RRC cause value.

　　In step S112, the UE 3 detects the SIB1-less NES cell via a cell reselection procedure, based on the information received in step S111. The UE 3 may then determine whether SIB1 information for the NES cell is accessible at the serving cell. If the SIB1 information for the NES cell is available at the serving cell then, UE 3 may transmit, in step S113, a request for NES Cell Information to the base station 5-2 that provides the serving cell. The request for NES Cell Information may comprise a request for the SIB1 of the NES cell. The transmission of step S113 may comprise the PCI of the NES cell, to indicate which cell the UE 3 is attempting to connect to. The request for the NES cell information may comprise NES cell specific information. In step S114, the base station 5-2 transmits the requested NES Cell information to the UE 3. The requested NES Cell information transmitted to the UE 3 may comprise a configuration for a WUS for the NES cell (enabling the UE 3 to obtain the SIB1 for the NES cell via the NES cell), or may comprise the SIB1 for the NES cell.

SIB1 for the NES cell transmitted at the Anchor Cell
　　In the examples illustrated in Fig. 8 and Fig. 9, after the UE 3 has identified the anchor cell for the NES cell, the UE 3 may receive the SIB1 for the NES cell directly from the anchor cell. For example, the SIB1 for the NES cell may be broadcast in the anchor cell. Alternatively, the SIB1 for the NES cell may be transmitted on-demand in the anchor cell, in response to a request from the UE 3. SIB1 for one specific NES cell may be broadcast at the anchor cell. On-demand transmission of SIB1 for one or more NES cells in the anchor cell may be performed using dedicated signalling per NES cell. Alternatively, SIB1 for all of the SIB1-less NES cells corresponding to the anchor cell may be broadcast in the anchor cell. The UE 3 is therefore able to obtain SIB1 for the NES cell and communicate via the NES cell.

　　When the SIB1 for an NES cell is broadcast in the anchor cell, the base station 5-2 that provides the anchor cell may obtain the SIB1 of the NES cell from the base station 5-1 that provides the NES cell via the Xn interface. Alternatively, the base station 5-2 that provides the anchor cell may obtain the SIB1 for the NES cell from the network, for example via the AMF 10-1.

SIB1 WUS Configuration
　　In the single-cell scenario in which there is no anchor cell for the SIB1-less NES cell, communication resources for transmission of the WUS for the NES cell (which may be referred to as a 'WUS configuration' or 'WUS resources') may be preconfigured. The preconfigured communication resources for the WUS may be configured in advance at the UE 3 (e.g. via the network), or could be provided to the UE 3 using the MIB in the NES cell. The UE 3 may be provided with an explicit or implicit indication of the pre-configured WUS resources. For example, default communication resources to use for transmission of the WUS may be configured at the UE 3, for use in the case where the NES cell provides an indication to the UE 3 that the NES cell is a SIB1-less cell. As will be described in more detail later, to avoid or reduce interference with neighbouring SIB1-less cells, the preconfigured WUS resources may be determined (in which case there is no need for additional signalling) as a function of the PCI of the cell. In other words, the UE 3 (and the base station 5-1 that provides the NES cell) may store information for determining communication resources to transmit the WUS in the NES cell, based on the PCI of the NES cell.

　　In the multiple-cell scenario in which an anchor cell is provided, the anchor cell can be used to transmit an indication of the communication resources available for use in the NES cell to transmit the WUS (e.g. in step S114 of Fig. 11). The base station 5-2 that provides the anchor cell may communicate with the base station 5-1 that provides the NES cell (e.g. via the Xn interface) to allocate communication resources for the WUS at the NES cell, using any suitable signalling between the base station 5-2 that provides the anchor cell and the base station 5-1 that provides the NES cell. The base station 5-2 that provides the anchor cell may also communicate with the base station 5-1 that provides the NES cell (e.g. via the Xn interface) to obtain communication resources for the WUS that have already been configured for the NES cell. In a further alternative, the base station 5-2 that provides the anchor cell may obtain the resources for the WUS for the NES cell from the network, for example from the AMF 10-1.

SIB1 for NES Cell Provided at Anchor Cell
　　As described above, in any of the above methods in the multiple-cell scenario, the SIB1 for the NES cell could be provided to the UE 3 directly via the anchor cell. The base station 5-2 that provides the anchor cell may be configured to transmit an indication of the NES cell for which the base station 5-2 is able to transmit the SIB1. The indication of the NES cell for which the base station 5-2 is able to transmit the SIB1 may be transmitted on-demand (e.g. in step S114 of Fig. 11) in response to a request from the UE 3 (e.g. the request of step S113 of Fig. 11). The SIB1 for targeted NES cells (one or more NES cells for which the UE 3 has acquired SIB1-less cell measurements) may be provided via the anchor cell.

　　When an indication that WUS can be transmitted in the NES cell is transmitted to the UE 3 via the anchor cell, or the SIB1 for the NES cell is provided to the UE via the anchor cell (e.g. using any suitable broadcast transmission in the anchor cell), then the UE 3 is subsequently able to access the SIB1-less cell.

　　If the WUS resources for the NES cell are not initially provided to the UE 3 via the anchor cell, and the SIB1 for the NES cell is transmitted by the anchor cell, then the UE 3 may determine to transmit (e.g. in step S113 of Fig. 11, optionally using dedicated signalling) an indication of the PCI of the target SIB1-less NES cell to the base station 5-2 that provides the anchor cell to request that the SIB1 of the NES cell be transmitted via the anchor cell. This request from the UE 3 may trigger the base station 5-2 that provides the serving cell to obtain the requested information for the NES cell, either directly via the Xn interface, or from the AMF 10-1. Alternatively, the request transmitted from the UE 3 to the base station that provides the serving cell 5-2 may be a request for the WUS resources for the NES cell, which may trigger the base station 5-2 that provides the serving cell to configure WUS resources for the NES cell (in which case the base station 5-2 that provides the serving cell communicates with the base station 5-1 that provides the NES cell to configure the resources for the WUS).

Use of NES Cell PCI to indicate available/unavailable cells
　　In the example of Figs. 8 to 11, the PCI of the NES cell can be used to determine whether the UE 3 can communicate via the NES cell. For example, the PCI of the NES cells can be included in information transmitted in the anchor cell, to indicate for which of the NES cells the SIB1 or WUS resources can be provided in the anchor cell (e.g., if the PCI for an NES cell is provided in the information transmitted in the anchor cell, for example in step S111 of Fig. 11, then the UE 3 may determine that the WUS resources or SIB1 for that NES cell are available via the anchor cell). If a PCI is not provided to the UE 3 via the anchor cell for an NES cell, then the UE 3 may determine that the UE 3 is barred from communication using that NES cell.

WUS UL Shared Resources and Interference
　　In the examples illustrated in Figs. 8 to 11, the WUS resources may comprise any suitable communication resources, e.g. PRACH resources. If a plurality of NES cells are provided, and default or pre-allocated resources are used for the WUS, then there may be a need for interference management. Advantageously, as described above, the PCI of the NES cells can be used for interference management for the WUS (e.g. PRACH interference management). The WUS resources to use for transmission of the WUS in a particular NES cell can be determined by the UE 3 based on the PCI of the NES cell (e.g. selected from the set of pre-configured WUS resources stored at the UE 3 based on the PCI of the NES cell). The communication resources to use for transmission of the WUS by the UE 3 may be mapped according to the PCI of the NES using a hash-function. Alternatively, to mitigate against interference, the anchor cell could allocate the WUS resources to use for each NES cell, for example by allocating dedicate WUS resources for each NES cell.

　　Whilst the examples illustrated in Figs. 8 to 11 have been described primarily with respect to a case where there is a single target SIB1-less NES cell, it will be appreciated that there may be a plurality of NES cells for which the UE 3 has performed measurements, or to which the UE 3 may attempt to connect. Therefore, in any of the examples in which the UE 3 obtains information regarding the NES cell from the anchor cell (e.g. to obtain the WUS configuration or the SIB1, or any other information regarding the NES cell transmitted in step S114 of Fig. 11), the UE 3 may obtain the information for each of a plurality of NES cells (either in separate transmissions for each NES cell, or in a single transmission in the anchor cell).

User Equipment
　　Fig. 12 is a schematic block diagram illustrating the main components of a UE 3 as shown in Fig. 1.

　　As shown, the UE 3 has a transceiver circuit 310 that is operable to transmit signals to and to receive signals from a base station 5 via one or more antenna 330 (e.g., comprising one or more antenna elements). The UE 3 has a controller 370 to control the operation of the UE 3. The controller 370 is associated with a memory 390 and is coupled to the transceiver circuit 310. Although not necessarily required for its operation, the UE 3 might, of course, have all the usual functionality of a conventional UE 3 (e.g. a user interface 35b, such as a touch screen / keypad / microphone / speaker and/or the like for, allowing direct control by and interaction with a user) and this may be provided by any one or any combination of hardware, software, and firmware, as appropriate. Software may be pre-installed in the memory 390 and/or may be downloaded via the communication system 1 or from a removable data storage device (RMD), for example.
The controller 370 is configured to control overall operation of the UE 3 by, in this example, program instructions or software instructions stored within memory 390. As shown, these software instructions include, among other things, an operating system 410, and a communication control module 430.

　　The communication control module 430 is operable to control the communication between the UE 3 and its one or more serving base stations 5 (and other communication devices connected to the base station 5, such as further UEs and/or core network nodes). The communication control module 430 is configured for the overall handling of uplink communication via associated uplink channels (e.g. via a physical uplink control channel (PUCCH), random access channel (RACH), and/or a physical uplink shared channel (PUSCH)) including both dynamic and semi-static signalling (e.g., SRS). The communication control module 430 is also configured for the overall handling of receipt of downlink communications via associated downlink channels (e.g. via a physical downlink control channel (PDCCH) and/or a physical downlink shared channel (PDSCH)) including both dynamic and semi-static signalling (e.g., CSI-RS). The communication control module 430 is responsible, for example: for determining where to monitor for downlink control information (e.g., the location of CSSs / USSs, CORESETs, and associated PDCCH candidates to monitor); for determining the resources to be used by the UE 3 for transmission/reception of UL/DL communications (including interleaved resources and resources subject to frequency hopping); for managing frequency hopping at the UE side; for determining how slots/symbols are configured (e.g., for UL, DL or SBFD communication, or the like); for determining which one or more bandwidth parts are configured for the UE 3; for determining how uplink transmissions should be encoded; for applying any SBFD specific communication configurations appropriately; and the like.

RAN (Distributed Type)
　　Fig. 13 is a simplified block schematic illustrating the main components of a distributed RAN 50 comprising a distributed type of base station for implementation in the communication system 1 of Fig. 1.

　　As shown, the RAN 50 includes a central unit 5c and a distributed unit 5b (although it may include other DUs as described above). Each unit 5c, 5b includes respective transceiver circuitry 51c, 51b.

　　The transceiver circuitry 51b of the distributed unit 5b is operable to transmit signals to and to receive signals from UEs 3 via an air interface 53b and one or more antennas and is also operable to transmit signals to and to receive signals from the central unit 5c via an interface, for example the distributed unit side of an F1 interface (which may be provided over a satellite radio interface).

　　The transceiver circuitry 51c of the central unit 5c is operable to transmit signals to and to receive signals from functions of the core network 7 and/or other RANs 50 via a network interface 55c. The network interface typically includes an N2 and/or N3 interfaces for communicating with the core network 7 and a base station to base station (e.g. Xn) interface for communicating with other RANs. The transceiver circuitry 51c of the central unit 5c is also operable to transmit signals to and to receive signals from one or more distributed units 5b, for example the central unit side of the F1 interface provided.

　　Each unit 5c, 5b includes a respective controller 57c, 57b which controls the operation of the corresponding transceiver circuitry 51c, 51b in accordance with software stored in the respective memories 59c and 59b of the distributed unit 5b and the central unit 5c. The software of each unit may be pre-installed in the memory 59c, 59b and/or may be downloaded via the communication system 1 or from a removable data storage device (RMD), for example. The software of each unit includes, among other things, a respective operating system 61c, 61b, a respective communication control module 63c, 63b and a respective NES module 65c, 65b.

　　Each communication control module 63c, 63b is operable to control the communication of its corresponding unit 5c, 5b including the communication from one unit to the other. The communication control module 63b of the distributed unit 5b controls communication between the distributed unit 5b and the UEs 3, and the communication control module 63c of the central unit 5c controls communication between the central unit 5c and other network entities that are connected to the distributed RAN 50.

　　The communication control modules 63c, 63b also respectively control the part played by the distributed unit 5b and central unit 5c in the flow of uplink and downlink user traffic and control data to be transmitted to the communication devices served by the RAN 50 including, for example, control data for managing operation of the UEs 3. Each communication control module 63c, 63b is responsible, for example, for controlling the respective part played by the distributed unit 5b and central unit 5c in the reception and decoding of uplink communications, via associated uplink channels (e.g. via a physical uplink control channel (PUCCH), a random-access channel (RACH), and/or a physical uplink shared channel (PUSCH)) including both dynamic and semi-static signalling (e.g., SRS). Each communication control module 63c, 63b is responsible for controlling the respective part played by the distributed unit 5b and central unit 5c in the transmission of downlink communications via associated downlink channels (e.g. via a physical downlink control channel (PDCCH) and/or a physical downlink shared channel (PDSCH)) including both dynamic and semi-static signalling (e.g., CSI-RS, SSBs etc.).

　　The NES module 65c, 65b is configured for performing control of communication in accordance with any of the methods described above (for example, to perform any of the NES methods described above, e.g. to transmit SIB1).

　　It will be appreciated that the communication control modules 63b, 63c may also include a number of sub-modules (or layers) to support specific functionalities for the corresponding unit 5c, 5b. The modules included will depend on how the corresponding unit 5c, 5b is configured (e.g., the precise CU-DU split). For example, the communication control modules 63b of the distributed unit 5b may include a PHY sub-module, a MAC sub-module, and an RLC sub-module, whereas the communication control modules 63c of the central unit 5c may include a PDCP sub-module, an SDAP sub-module, an IP sub-module, an RRC sub-module, etc. The communication control modules 63b, 63c, may perform control as part of any of the methods described above (for example to provide the air interface protocols, or methods of feedback-based retransmission, described above).

Core Network Node/Function
　　Fig. 14 is a block diagram illustrating the main components of a core network node or function, such as the AMF 10-1, CPF 10, the UPF 11, the SMF 10-2 or OAM. As shown, the core network function includes a transceiver circuit 710 which is operable to transmit signals to and to receive signals from other nodes (including the UE 3, the base station 5, and other core network nodes) via a network interface 720. A controller 730 controls the operation of the core network function in accordance with software stored in a memory 740. The software may be pre-installed in the memory 740 and/or may be downloaded via the communication system 1 or from a removable data storage device (RMD), for example. The software includes, among other things, an operating system 750, and a communication control module 760.

　　The communication control module 760 is responsible for handling (generating/sending/ receiving) signalling between the core network function and other nodes, such as the UE 3, the base station 5, and other core network nodes, and may perform control according to any of the methods described above.

Modifications and Alternatives
　　As those skilled in the art will appreciate, a number of modifications and alternatives can be made to the above examples whilst still benefiting from the disclosure therein.

　　It will be appreciated, for example, that whilst cellular communication generation (2G, 3G, 4G, 5G, 6G etc.) specific terminology may be used, in the interests of clarity, to refer to specific communication entities, the technical features described for a given entity are not limited to devices of that specific communication generation. The technical features may be implemented in any functionally equivalent communication entity regardless of any differences in the terminology used to refer to them.

　　In the above description, the UEs and the base station are described for ease of understanding as having a number of discrete functional components or modules. Whilst these modules may be provided in this way for certain applications, for example where an existing system has been modified to implement the disclosure, in other applications, for example in systems designed with the inventive features in mind from the outset, these modules may be built into the overall operating system or code and so these modules may not be discernible as discrete entities.

　　In the above detailed examples, a number of software modules were described. As those skilled in the art will appreciate, the software modules may be provided in compiled or un-compiled form and may be supplied as a signal over a computer network, or on a recording medium. Further, the functionality performed by part, or all of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred as it facilitates the updating of the base station or the UE in order to update their functionalities.

　　Each controller may comprise any suitable form of processing circuitry including (but not limited to), for example: one or more hardware implemented computer processors; microprocessors; central processing units (CPUs); arithmetic logic units (ALUs); input/output (IO) circuits; internal memories / caches (program and/or data); processing registers; communication buses (e.g. control, data and/or address buses); direct memory access (DMA) functions; hardware or software implemented counters, pointers and/or timers; and/or the like. Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

　　The User Equipment (or "UE", "mobile station", "mobile device" or "wireless device") in the present disclosure is an entity connected to a network via a wireless interface.
It should be noted that the present disclosure is not limited to a dedicated communication device and can be applied to any device having a communication function as explained in the following paragraphs.

　　The terms "User Equipment" or "UE" (as the term is used by 3GPP), "mobile station", "mobile device", and "wireless device" are generally intended to be synonymous with one another, and include standalone mobile stations, such as terminals, cell phones, smart phones, tablets, cellular IoT devices, IoT devices, and machinery. It will be appreciated that the terms "mobile station" and "mobile device" also encompass devices that remain stationary for a long period of time.

　　A UE may, for example, be an item of equipment for production or manufacture and/or an item of energy related machinery (for example equipment or machinery such as: boilers; engines; turbines; solar panels; wind turbines; hydroelectric generators; thermal power generators; nuclear electricity generators; batteries; nuclear systems and/or associated equipment; heavy electrical machinery; pumps including vacuum pumps; compressors; fans; blowers; oil hydraulic equipment; pneumatic equipment; metal working machinery; manipulators; robots and/or their application systems; tools; molds or dies; rolls; conveying equipment; elevating equipment; materials 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 fisheries; safety and/or environment preservation equipment; tractors; precision bearings; chains; gears; power transmission equipment; lubricating equipment; valves; pipe fittings; and/or application systems for any of the previously mentioned equipment or machinery etc.).

　　A UE may, for example, be an item of transport equipment (for example transport equipment such as: rolling stocks; motor vehicles; motorcycles; bicycles; trains; buses; carts; rickshaws; ships and other watercraft; aircraft; rockets; satellites; drones; balloons etc.). A UE may, for example, be an item of information and communication equipment (for example information and communication equipment such as: electronic computer and related equipment; communication and related equipment; electronic components etc.).

　　A UE may, for example, be a refrigerating machine, a refrigerating machine applied product, an item of trade and/or service industry equipment, a vending machine, an automatic service machine, an office machine or equipment, a consumer electronic and electronic appliance (for example a consumer electronic appliance such as: audio equipment; video equipment; a loud speaker; a radio; a television; a microwave oven; a rice cooker; a coffee machine; a dishwasher; a washing machine; a dryer; an electronic fan or related appliance; a cleaner etc.).

　　A UE may, for example, be an electrical application system or equipment (for example an electrical application system or equipment such as: an x-ray system; a particle accelerator; radio isotope equipment; sonic equipment; electromagnetic application equipment; electronic power application equipment etc.).

　　A UE may, for example, be an electronic lamp, a luminaire, a measuring instrument, an analyser, a tester, or a surveying or sensing instrument (for example a surveying or sensing instrument such as: a smoke alarm; a human alarm sensor; a motion sensor; a wireless tag etc.), a watch or clock, a laboratory instrument, optical apparatus, medical equipment and/or system, a weapon, an item of cutlery, a hand tool, or the like.

　　A UE may, for example, be a wireless-equipped personal digital assistant or related equipment (such as a wireless card or module designed for attachment to or for insertion into another electronic device (for example a personal computer, electrical measuring machine)).
A UE may be a device or a part of a system that provides applications, services, and solutions described below, as to "internet of things (IoT)", using a variety of wired and/or wireless communication technologies.

　　Internet of Things devices (or "things") may be equipped with appropriate electronics, software, sensors, network connectivity, and/or the like, which enable these devices to collect and exchange data with each other and with other communication devices. IoT devices may comprise automated equipment that follow software instructions stored in an internal memory. IoT devices may operate without requiring human supervision or interaction. IoT devices might also remain stationary and/or inactive for a long period of time. IoT devices may be implemented as a part of a (generally) stationary apparatus. IoT devices may also be embedded in non-stationary apparatus (e.g. vehicles) or attached to animals or persons to be monitored/tracked.

　　It will be appreciated that IoT technology can be implemented on any communication devices that can connect to a communication system for sending/receiving data, regardless of whether such communication devices are controlled by human input or software instructions stored in memory.

　　It will be appreciated that IoT devices are sometimes also referred to as Machine-Type Communication (MTC) devices or Machine-to-Machine (M2M) communication devices. 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 following table. This list is not exhaustive and is intended to be indicative of some examples of machine type communication applications.

　　Applications, services, and solutions may be an MVNO (Mobile Virtual Network Operator) service, an emergency radio communication system, a PBX (Private Branch eXchange) system, a PHS/Digital Cordless Telecommunication system, a POS (Point of sale) system, an advertise calling system, an MBMS (Multimedia Broadcast and Multicast Service), a V2X (Vehicle to Everything) system, a train radio system, a location related service, a Disaster/Emergency Wireless Communication Service, a community service, a video streaming service, a femto cell application service, a VoLTE (Voice over LTE) service, a charging service, a radio on demand service, a roaming service, an activity monitoring service, a telecom carrier/communication NW selection service, a functional restriction service, a PoC (Proof of Concept) service, a personal information management service, an ad-hoc network/DTN (Delay Tolerant Networking) service, etc.

　　Further, the above-described UE categories are merely examples of applications of the technical ideas described in the present document. Needless to say, these technical ideas are not limited to the above-described UE and various modifications can be made thereto.
Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

　　This application is based upon and claims the benefit of priority from British patent application No. 2404842.3, filed on April 4, 2024, the disclosure of which is incorporated herein in its entirety by reference.

　　The whole or part of the exemplary embodiments disclosed above can be described as, but not limited to, the following supplementary notes.
　　(Supplementary note 1)
　　A method performed by a mobile device, the method comprising:
　　receiving, from a network whose an access network node is in a network energy saving (NES) mode, information used for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node; and
　　transmitting the WUS using the information.
　　(Supplementary note 2)
　　The method according to supplementary note 1, wherein
　　the information includes at least one of:
　　　　a physical cell identity of the NES cell for determining the resource for the transmitting the WUS,
　　　　information indicating a resource for the transmitting the WUS,
　　　　information indicating that a resource for the transmitting the WUS is available at the NES cell,
　　　　information indicating whether the WUS is available at the NES cell, or
　　　　information indicating whether the WUS or the SIB1 can be requested at another cell than the NES cell.
　　(Supplementary note 3)
　　The method according to supplementary note 1 or 2, wherein
　　the information is transmitted from the access network node directly or via another access network node.
　　(Supplementary note 4)
　　The method according to any one of supplementary notes 1 to 3, wherein
　　the information is received upon transmitting a request.
　　(Supplementary note 5)
　　The method according to any one of supplementary notes 1 to 4, further comprising:
　　searching a cell whose neighbour cells has the NES cell,
　　wherein the receiving the information is performed by receiving from the cell.
　　(Supplementary note 6)
　　The method according to any one of supplementary notes 1 to 5, further comprising:
　　checking, on a serving cell, whether information of the on-demand SIB1 on the NES cell is available, and wherein
　　the transmitting the WUS is performed in a case where the information of the on-demand SIB1 on the NES cell is available on the serving cell.
　　(Supplementary note 7)
　　The method according to any one of supplementary notes 1 to 6, wherein
　　the receiving the information is performed by receiving from the access network node, and
　　the transmitting the WUS is performed by transmitting to the access network node.
　　(Supplementary note 8)
　　The method according to any one of supplementary notes 1 to 6, wherein
　　the receiving the information is performed by receiving from the another access node, and
　　the transmitting the WUS is performed by transmitting to the access network node.
　　(Supplementary note 9)
　　The method according to supplementary note 8, wherein
　　the information is transmitted from the another access network node to the access network node.
　　(Supplementary note 10)
　　The method according to any one of supplementary notes 1 to 6, wherein
　　the receiving the information is performed by receiving from the another access network node, and
　　the transmitting the WUS is performed by transmitting to the another network node.
　　(Supplementary note 11)
　　The method according to any one of supplementary notes 1 to 10, wherein
　　the SIB1 is received upon transmitting the WUS, from at least one of:
　　　　another access network node, or
　　　　the access network node via the another access network node.
　　(Supplementary note 12)
　　The method according to supplementary note 11, wherein
　　the SIB1 is received via a broadcast transmission, or a dedicated signaling.
　　(Supplementary note 13)
　　A method performed by an access network node in a network energy saving (NES) mode, the method comprising:
　　transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node;
　　receiving the WUS using the information by the mobile device; and
　　transmitting the SIB1 to the mobile device.
　　(Supplementary note 14)
　　A method performed by an access network node in a network whose another access network node is in a network energy saving (NES) mode, the method comprising:
　　transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the another access network node;
　　transmitting the SIB1 upon the another access network node receiving the WUS using the information by the mobile device.
　　(Supplementary note 15)
　　A mobile device comprising:
　　means for receiving, from a network whose an access network node is in a network energy saving (NES) mode, information used for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node; and
　　means for transmitting the WUS using the information.
　　(Supplementary note 16)
　　An access network node in a network energy saving (NES) mode, the access network node comprising:
　　means for transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node;
　　means for receiving the WUS using the information by the mobile device; and
　　means for transmitting the SIB1 to the mobile device.
　　(Supplementary note 17)
　　An access network node in a network whose another access network node is in a network energy saving (NES) mode, the access network node comprising:
　　means for transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the another access network node; and
　　means for transmitting the SIB1 upon the another access network node receiving the WUS using the information by the mobile device.

1　　COMMUNICATION SYSTEM
3-1, 3-2, 3-3　　USER EQUIPMENTS (UEs)
5　　BASE STATION
7　　CORE NETWORK
9　　ASSOCIATED CELLS
10　　CONTROL PLANE FUNCTIONS (CPFs)
10-1　　ACCESS AND MOBILITY MANAGEMENT FUNCTIONS (AMFs)
10-2　　SESSION MANAGEMENT FUNCTIONS (SMFs)
10-n 　　OTHER FUNCTIONS
11　　USER PLANE FUNCTIONS (UPFs)
20　　EXTERNAL DATA NETWORK
30　　NON-ANCHOR NES CELL
31　　ANCHOR CELL
50　　RAN
51B 　　TRANSCEIVER CIRCUIT (DU)
51C　　TRANSCEIVER CIRCUIT (CU)
55C　　NETWORK INTERFACE
57b　　DU CONTROLLER
57c　　CU CONTROLLER
59b 　　DU MEMORY
59c 　　CU MEMORY
61b　　DU OPERATING SYSTEM
61c　　CU OPERATING SYSTEM
63b　　DU COMMUNICATION CONTROL MODULE
63c　　CU COMMUNICATION CONTROL MODULE
65c, 65b　　NES MODULE
310　　TRANSCEIVER CIRCUIT
330　　ANTENNA
350　　USER INTERFACE
370　　CONTROLLER
390　　MEMORY
410　　OPERATING SYSTEM
430　　COMMUNICATION CONTROL MODULE
710　　TRANSCEIVER CIRCUIT
720　　NETWORK INTERFACE
730　　CONTROLLER
740　　MEMORY
750　　OPERATING SYSTEM
760　　COMMUNICATION CONTROL MODULE

Claims

　　A method performed by a mobile device, the method comprising:
　　receiving, from a network whose an access network node is in a network energy saving (NES) mode, information used for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node; and
　　transmitting the WUS using the information.
　　The method according to claim 1, wherein
　　the information includes at least one of:
　　　　a physical cell identity of the NES cell for determining the resource for the transmitting the WUS,
　　　　information indicating a resource for the transmitting the WUS,
　　　　information indicating that a resource for the transmitting the WUS is available at the NES cell,
　　　　information indicating whether the WUS is available at the NES cell, or
　　　　information indicating whether the WUS or the SIB1 can be requested at another cell than the NES cell.
　　The method according to claim 1 or 2, wherein
　　the information is transmitted from the access network node directly or via another access network node.
　　The method according to any one of claims 1 to 3, wherein
　　the information is received upon transmitting a request.
　　The method according to any one of claims 1 to 4, further comprising:
　　searching a cell whose neighbour cells has the NES cell,
　　wherein the receiving the information is performed by receiving from the cell.
　　The method according to any one of claims 1 to 5, further comprising:
　　checking, on a serving cell, whether information of the on-demand SIB1 on the NES cell is available, and wherein
　　the transmitting the WUS is performed in a case where the information of the on-demand SIB1 on the NES cell is available on the serving cell.
　　The method according to any one of claims 1 to 6, wherein
　　the receiving the information is performed by receiving from the access network node, and
　　the transmitting the WUS is performed by transmitting to the access network node.
　　The method according to any one of claims 1 to 6, wherein
　　the receiving the information is performed by receiving from the another access node, and
　　the transmitting the WUS is performed by transmitting to the access network node.
　　The method according to claim 8, wherein
　　the information is transmitted from the another access network node to the access network node.
　　The method according to any one of claims 1 to 6, wherein
　　the receiving the information is performed by receiving from the another access network node, and
　　the transmitting the WUS is performed by transmitting to the another network node.
　　The method according to any one of claims 1 to 10, wherein
　　the SIB1 is received upon transmitting the WUS, from at least one of:
　　　　another access network node, or
　　　　the access network node via the another access network node.
　　The method according to claim 11, wherein
　　the SIB1 is received via a broadcast transmission, or a dedicated signaling.
　　A method performed by an access network node in a network energy saving (NES) mode, the method comprising:
　　transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node;
　　receiving the WUS using the information by the mobile device; and
　　transmitting the SIB1 to the mobile device.
　　A method performed by an access network node in a network whose another access network node is in a network energy saving (NES) mode, the method comprising:
　　transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the another access network node;
　　transmitting the SIB1 upon the another access network node receiving the WUS using the information by the mobile device.
　　A mobile device comprising:
　　means for receiving, from a network whose an access network node is in a network energy saving (NES) mode, information used for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node; and
　　means for transmitting the WUS using the information.
　　An access network node in a network energy saving (NES) mode, the access network node comprising:
　　means for transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the access network node;
　　means for receiving the WUS using the information by the mobile device; and
　　means for transmitting the SIB1 to the mobile device.
　　An access network node in a network whose another access network node is in a network energy saving (NES) mode, the access network node comprising:
　　means for transmitting, to a mobile device, information used by the mobile device for determining a resource for transmitting a wake-up signal (WUS) for requesting a on-demand system information block 1 (SIB1) on a NES cell operated by the another access network node; and
　　means for transmitting the SIB1 upon the another access network node receiving the WUS using the information by the mobile device.