Communication device, base station, and communication method

Abstract

A communication device (100) according to an embodiment of the present invention comprises: a reception unit (112) that receives, from a network (10), first information indicating the number of subgroups per paging opportunity and second information concerning setting of the subgroups based on user equipment identity (UE_ID); and a control unit (120) that calculates the UE_ID using a specific calculation formula on the basis of the first information and the second information and that calculates a subgroup identifier on the basis of the UE_ID calculated using the specific calculation formula. The reception unit monitors the paging opportunity on the basis of the subgroup identifier.

Description

Cross-reference to related applications

[0001] This application is based on and claims the benefit of priority from patent application No. 2021-135156, filed on August 20, 2021, and all of the contents of that patent application are incorporated herein by reference.

Technical Field

[0002] The present disclosure relates to a communication device, a base station, and a communication method used in a mobile communication system.

Background Art

[0003] In 3GPP (registered trademark; the same shall apply hereinafter) (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, discussions have been held to reduce power consumption for communication devices in the RRC (Radio Resource Control) idle state or RRC inactive state (see Non-Patent Document 1). Specifically, it has been considered to introduce a mechanism for classifying each of a plurality of communication devices assigned to the same paging opportunity into any of a plurality of subgroups (hereinafter referred to as paging subgroups).

[0004] Before transmitting a paging message, the network notifies each communication device of the paging subgroup to which the communication device that is the destination of the paging message belongs. A communication device in the RRC idle state or RRC inactive state performs reception processing of the paging message (specifically, reception and decoding of a physical downlink shared channel) only when it determines that it belongs to the notified paging subgroup, and determines whether its own unique identifier is included in the paging message. On the other hand, when a communication device determines that it does not belong to the notified paging subgroup, it can skip the reception processing of the paging message in the paging opportunity, thereby reducing power consumption.

[0005] As a method for determining the paging subgroup to which a communication device belongs, a method has been proposed in which the communication device determines the paging subgroup based on its own unique identifier (e.g., 5G-S-TMSI). Specifically, the communication device calculates the user equipment identity (UE identity: UE ID) from its own unique identifier, and calculates the paging subgroup (specifically, the paging subgroup ID (UE subgroup ID)) to which it belongs from the calculated user equipment identity. As an equation for calculating the paging subgroup identifier from the user equipment identity, the equation "UE subgroup ID = floor(UE_ID / (N*Ns)) mod Nsg" has been proposed. N is the total number of paging frames (PF) within the discontinuous reception (DRX) cycle of the communication device, Ns is the number of paging opportunities per PF, and Nsg is the number of paging subgroups (specifically, the maximum number of paging subgroups per paging opportunity in the cell).

[0006] Here, when calculating the paging subgroup using the above equation from the user equipment identity calculated using the equation "UE_ID = 5G-S-TMSI mod 1024" defined in the current 3GPP technical specification, if the condition "N*Ns*Nsg > 1024" is satisfied, all communication devices assigned to the same paging opportunity will belong to the same paging subgroup. Therefore, Non-Patent Document 2 describes that the user equipment identity is calculated by the equation "UE identity = 5G-S-TMSI mod 1024*Nsg".

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

[0008] The communication device according to the first aspect includes a receiving unit that receives from a network first information indicating the number of subgroups per paging opportunity and second information regarding the setting of the subgroup based on a user equipment identity (UE_ID), and a control unit that calculates the UE_ID using a predetermined calculation formula based on the first information and the second information, and calculates a subgroup identifier based on the UE_ID calculated using the predetermined calculation formula. The receiving unit monitors a paging opportunity based on the subgroup identifier.

[0009] The base station according to the second aspect includes a transmitting unit that transmits to a communication device first information indicating the number of subgroups per paging opportunity and second information regarding the setting of the subgroup based on a user equipment identity (UE_ID), and a control unit that calculates the UE_ID using a predetermined calculation formula based on the first information and the second information, and calculates a subgroup identifier based on the UE_ID calculated using the predetermined calculation formula. The transmitting unit transmits downlink control information on a physical link control channel in a paging opportunity based on the subgroup identifier.

[0010] The 3 communication method according to the aspect includes steps of receiving from a network first information indicating the number of subgroups per paging opportunity and second information regarding the setting of the subgroup based on a user equipment identity (UE_ID), calculating the UE_ID using a predetermined calculation formula based on the first information and the second information, calculating a subgroup identifier based on the UE_ID calculated using the predetermined calculation formula, and monitoring a paging opportunity based on the subgroup identifier.

Brief Description of the Drawings

[0011] The objectives, features, advantages, etc. of the present disclosure will become clearer from the following detailed description with reference to the accompanying drawings.

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DETAILED DESCRIPTION OF THE INVENTION

[0012] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0013] When calculating the user equipment identity according to the formula described in Non-Patent Document 2, compared with the calculation method according to the formula defined in the current 3GPP technical specification, the number of user equipment identities increases, so the number of bits required to indicate the user equipment identity increases. As a result, for example, when transmitting the user equipment identity between base stations, there is a problem that the amount of information of the user equipment identity increases. Therefore, one of the objectives of the present disclosure is to provide a communication device, a base station, and a communication method that can suppress an increase in the amount of information of the user equipment identity in a mobile communication system in which each of a plurality of communication devices assigned to the same paging opportunity can be classified into any of a plurality of paging subgroups.

[0014] (Configuration of Mobile Communication System) With reference to FIG. 1, the configuration of the mobile communication system 1 according to the embodiment will be described. The mobile communication system 1 is, for example, a system compliant with 3GPP technical specifications (Technical Specification: TS). Hereinafter, the mobile communication system 1 will be described by taking, as an example, a 5th generation system (5th Generation System: 5GS) of the 3GPP standard, that is, a mobile communication system based on NR (New Radio).

[0015] The mobile communication system 1 includes a network 10 and a user equipment (UE) 100 that communicates with the network 10. The network 10 includes an NG-RAN (Next Generation Radio Access Network) 20 that is a 5G radio access network and a 5GC (5G Core Network) 30 that is a 5G core network.

[0016] UE100 is an example of a communication device. It is an example of a communication device. UE100 may be a mobile wireless communication device. UE100 may be a device used by a user. UE100 is, for example, a mobile device such as a mobile phone terminal like a smartphone, a tablet terminal, a notebook PC, a communication module, or a communication card. UE100 may be a vehicle (e.g., a car, a train, etc.) or a device provided thereon (e.g., a Vehicle UE). UE100 may be a transport aircraft other than a vehicle (e.g., a ship, an airplane, a flying object, etc.) or a device provided thereon. UE100 may be a sensor or a device provided thereon. Note that UE100 may be called by another name such as a mobile station, a mobile terminal, a mobile device, a mobile unit, a subscriber station, a subscriber terminal, a subscriber device, a subscriber unit, a wireless station, a wireless terminal, a wireless device, a wireless unit, a remote station, a remote terminal, a remote device, or a remote unit.

[0017] NG-RAN20 includes a plurality of base stations 200. Each base station 200 manages at least one cell. A cell constitutes the smallest unit of a communication area. For example, one cell belongs to one frequency (carrier frequency) and is composed of one component carrier. The term "cell" may represent a wireless communication resource and may also represent a communication target of UE100. Each base station 200 can perform wireless communication with UE100 present in its cell. The base station 200 communicates with UE100 using the RAN protocol stack. The base station 200 provides NR user plane and control plane protocol termination towards UE100 and is connected to 5GC30 via the NG interface. Such an NR base station 200 may be referred to as a gNodeB (gNB).

[0018] 5GC30 includes a core network device 300. The core network device 300 includes, for example, an AMF (Access and Mobility Management Function) and / or a UPF (User Plane Function). The AMF performs mobility management of the UE100. The UPF provides functions specialized for user plane processing. The AMF and the UPF are connected to the base station 200 via an NG interface.

[0019] Referring to FIG. 2, a configuration example of a protocol stack in the mobile communication system 1 according to the embodiment will be described.

[0020] The protocol for the radio section between the UE100 and the base station 200 has a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an RRC (Radio Resource Control) layer.

[0021] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Between the PHY layer of the UE100 and the PHY layer of the base station 200, data and control information are transmitted via a physical channel.

[0022] The physical channel is composed of a plurality of OFDM (Orthogonal Frequency Division Multiplexing) symbols in the time domain and a plurality of subcarriers in the frequency domain. One subframe is composed of a plurality of OFDM symbols in the time domain. A resource block is a resource allocation unit and is composed of a plurality of OFDM symbols and a plurality of subcarriers. A frame can be composed of 10 ms and can include 10 subframes composed of 1 ms. The number of slots corresponding to the subcarrier spacing can be included in the subframe.

[0023] Among physical channels, the Physical Downlink Control Channel (PDCCH) plays a central role, for example, for purposes such as downlink scheduling allocation, uplink scheduling grant, and transmission power control.

[0024] In NR, the UE 100 can use a bandwidth narrower than the system bandwidth (i.e., the cell bandwidth). The base station 200 sets a bandwidth part (BWP) consisting of consecutive PRBs for the UE 100. The UE 100 transmits and receives data and control signals in the active BWP. Up to, for example, four BWPs can be set for the UE 100. Each BWP may have a different subcarrier spacing or may have overlapping frequencies. When multiple BWPs are set for the UE 100, the base station 200 can specify which BWP to activate by means of control in the downlink. Thereby, the base station 200 can dynamically adjust the UE bandwidth according to, for example, the amount of UE data traffic, etc., and can reduce UE power consumption.

[0025] The base station 200 can set up to three control resource sets (CORESETs) for each of up to four BWPs on the serving cell, for example. A CORESET is a radio resource for control information that the UE 100 should receive. Up to 12 CORESETs can be set for the UE 100 on the serving cell. Each CORESET has an index from 0 to 11. For example, a CORESET is composed of six resource blocks (PRBs) and one, two, or three consecutive OFDM symbols in the time domain.

[0026] The MAC layer performs functions such as priority control of data, retransmission processing by Hybrid ARQ (HARQ), and random access procedures. Between the MAC layer of UE100 and the MAC layer of base station 200, data and control information are transmitted via transport channels. The MAC layer of base station 200 includes a scheduler. The scheduler determines the uplink and downlink transport formats (transport block size, modulation and coding scheme (MCS)) and the allocated resources for UE100.

[0027] The RLC layer transmits data to the RLC layer on the receiving side by utilizing the functions of the MAC layer and the PHY layer. Between the RLC layer of UE100 and the RLC layer of base station 200, data and control information are transmitted via logical channels.

[0028] The PDCP layer performs header compression / expansion and encryption / decryption.

[0029] An SDAP (Service Data Adaptation Protocol) layer may be provided as the upper layer of the PDCP layer. The SDAP (Service Data Adaptation Protocol) layer performs mapping between an IP flow, which is a unit for the core network to perform QoS (Quality of Service) control, and a radio bearer, which is a unit for the AS (Access Stratum) to perform QoS control.

[0030] The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re - establishment, and release of radio bearers. Between the RRC layer of the UE100 and the RRC layer of the base station 200, RRC signaling for various settings is transmitted. When there is an RRC connection between the RRC of the UE100 and the RRC of the base station 200, the UE100 is in the RRC connected state. When there is no RRC connection between the RRC of the UE100 and the RRC of the base station 200, the UE100 is in the RRC idle state. When the RRC connection between the RRC of the UE100 and the RRC of the base station 200 is suspended, the UE100 is in the RRC inactive state.

[0031] The NAS layer located above the RRC layer performs session management and mobility management of the UE100. Between the NAS layer of the UE100 and the NAS layer of the core network device 300 (AMF), NAS signaling is transmitted. Note that the UE100 has an application layer etc. in addition to the protocol of the radio interface.

[0032] (Assumed scenario) Referring to FIGS. 3 to 5, the assumed scenario in the mobile communication system 1 according to the embodiment will be described.

[0033] Regarding paging reception, the paging message transmitted by the network 10 (base station 200) includes the identifier of each UE100 called by the network 10.

[0034] UE 100 in the RRC idle state or the RRC inactive state intermittently monitors paging using discontinuous reception (DRX) to reduce power consumption. The period for monitoring such paging is referred to as the DRX cycle. Also, the frame in which UE 100 should monitor paging is called the paging frame (PF), and the subframe in which UE 100 should monitor paging within this PF is called the paging occasion (PO). In the PO, UE 100 may receive a paging message.

[0035] UE 100 in the RRC idle state or the RRC inactive state wakes up in the PO to monitor the paging message and performs reception processing of the paging message (specifically, reception and decoding of the physical downlink shared channel (PDSCH)). UE 100 that has performed the reception processing determines whether its own unique identifier is included in the paging message. If UE 100's identifier is included in the paging message, it is considered that there is an incoming call, and for example, it performs an operation to transition to the RRC connected state.

[0036] Thus, in the paging reception operation, all UE 100 to which the same PO is assigned wake up in the PO to monitor paging and perform reception processing of the paging message. A group of UEs to which the same PO is assigned is called a paging group. Here, actually, UE 100 that is not being called from the network 10 also wakes up and performs reception processing of the paging message, resulting in extra power consumption.

[0037] Therefore, each of the plurality of UEs 100 assigned to the same PO is classified (i.e., grouped) into any one of a plurality of sub - groups (hereinafter, paging sub - groups (PSGs)) that are smaller units than the paging group. In FIG. 3, an example of dividing the paging group into three paging sub - groups with paging sub - group IDs "#1" to "#3" is shown. An example where the number of UEs 100 belonging to each paging sub - group is three is shown, but the number of UEs 100 belonging to each paging sub - group may be one or two, or four or more.

[0038] As a method of grouping each UE 100 assigned to the same PO, a first grouping method (so - called CN - assigned subgrouping) in which the network 10 assigns a paging sub - group ID to each UE 100, and a second grouping method (so - called UE_ID based subgrouping) in which the UE 100 itself determines the paging sub - group are being considered.

[0039] In the first grouping method, the assignment of the paging sub - group ID to each UE 100 may be performed, for example, at the time of network registration of the UE 100. The network 10 assigns the paging sub - group ID according to the characteristics of the UE 100 (such as paging probability, power consumption profile, and / or mobility state, etc.).

[0040] In the second grouping method, UE 100 determines a paging subgroup based on its own unique identifier (e.g., 5G-S-TMSI (Temporary Mobile Subscriber Identifier)). Specifically, UE 100 calculates a user equipment identity (UE identity: UE ID) from its own unique identifier, and calculates the paging subgroup (specifically, paging subgroup ID (UE subgroup ID)) to which it belongs from the calculated user equipment identity. As an equation for calculating a paging subgroup identifier from a user equipment identity, the equation "UE subgroup ID = floor(UE_ID / (N*Ns)) mod Nsg" has been proposed. N is the total number of PFs within the DRX cycle of UE 100 in the cell, Ns is the number of POs per PF in the cell, and Nsg is the number of paging subgroups in the cell (specifically, the maximum number of paging subgroups per PO in the cell where UE 100 is located) (see Figure 5). Note that 5G-S-TMS is a temporary mobile subscription identifier.

[0041] Before transmitting a paging message, network 10 (base station 200) notifies each UE 100 of the paging subgroup to which the UE 100 that is the destination of the paging message belongs. For example, before a PO, network 10 (base station 200) notifies each UE 100 of the paging subgroup ID to which the UE 100 called by the paging message transmitted at the PO belongs (so-called paging early indication). Network 10 notifies each UE 100 of the paging subgroup ID using, for example, a reference signal / synchronization signal.

[0042] Each UE 100 in the RRC idle state or the RRC inactive state wakes up at the PO and performs paging monitoring only when it is notified of the paging subgroup ID to which it belongs (i.e., it belongs to the notified paging subgroup). Thereby, since the UE 100 belonging to some paging subgroups does not have to wake up at the PO, the occurrence of excessive power consumption is suppressed.

[0043] Also, in order to notify each UE 100 of the paging subgroup to which the UE 100 that is the destination of the paging message belongs, for example, the network 10 (base station 200) may transmit downlink control information (DCI) including the paging subgroup ID to which the UE 100 called by the paging message transmitted at the PO belongs, by means of the PDCCH. The UE 100 receives (decodes) the DCI with a CRC (Cyclic Redundancy Check) parity bit scrambled by a P-RNTI (Paging Radio Network Temporary Identifier) in the PDCCH. Here, the base station 200 may set the P-RNTI for the UE 100. Also, the DCI may be a DCI format used for scheduling of the physical downlink shared channel (PDSCH). The DCI with a CRC parity bit scrambled by the P-RNTI is also referred to as paging DCI.

[0044] When the UE 100 that has received (decoded) the PDCCH determines that the paging subgroup ID included in the DCI indicates the paging subgroup to which it belongs, it determines that it belongs to the notified paging subgroup. The UE 100 performs the reception process of the paging message (specifically, reception and decoding of the PDSCH) only when it belongs to the notified paging subgroup, and determines whether its own unique identifier is included in the paging message. When the UE 100 determines that it does not belong to the notified paging subgroup, it can skip the reception process of the paging message during the paging opportunity, thereby reducing power consumption.

[0045] FIG. 4 shows an operation example when the UE 100 in the RRC idle state or RRC inactive state determines a paging subgroup (the second grouping method described above). The UE 100 is camped on a cell managed by the base station 200. The cell may be a cell selected by the UE 100 by cell (re)selection and may be referred to as a camp-on cell.

[0046] In step S11, R The UE 100 in the RRC idle state or RRC inactive state determines a user equipment identity (UE identity: UE_ID) based on its own unique identifier.

[0047] In step S12, the UE 100 calculates (determines) a paging frame, a paging opportunity, and a paging subgroup.

[0048] As shown in FIG. 5, the UE 100 calculates a paging frame (specifically, a system frame number (SFN) which is a paging frame) based on the calculated user equipment identity using Equation E11. The UE 100 calculates a paging opportunity (specifically, an index (i_s) of the paging opportunity) based on the calculated user equipment identity using Equation E12. The UE 100 calculates a paging subgroup (PSG) based on the calculated user equipment identity using Equation E13. The calculated paging subgroup is the paging subgroup to which the UE 100 belongs.

[0049] In step S13, the network 10 (base station 200) notifies each UE 100 of the paging subgroup ID to which the UE 100, which is the destination of the paging message, belongs before transmitting the paging message. The UE 100 receives the paging subgroup ID from the base station 200 in the cell where the UE 100 is located.

[0050] The UE 100 determines whether it belongs to the notified paging subgroup. Specifically, the UE 100 determines whether it belongs to the notified paging subgroup when the calculated paging subgroup matches the notified paging subgroup ID. The UE 100 determines that it does not belong to the notified paging subgroup if not. The UE 100 performs the following processing only when it belongs to the notified paging subgroup. Therefore, the UE 100 maintains a wake-up state to receive the paging message from the base station 200. On the other hand, the UE 100 may transition to a sleep state without executing the following processing when it does not belong to the notified paging subgroup.

[0051] In step S14, the network 10 (base station 200) transmits a paging message. The UE 100 receives the paging message from the base station 200 in the cell. The UE 100 determines whether its own unique identifier is included in the paging message. If the UE 100's own unique identifier is included in the paging message, it is considered that there is a call, and for example, an operation to transition to the RRC connected state is performed. On the other hand, if the UE 100's own unique identifier is not included in the paging message, for example, it may transition to the sleep state.

[0052] Incidentally, in step S11 described above, assume a case where a paging subgroup is calculated using formula E13 from the UE_ID calculated using the formula "UE_ID = 5G - S - TMSI mod 1024" defined in the current 3GPP technical specification. Here, the maximum values of N, Ns, and Nsg that can be set as N defined in the current 3GPP technical specification are 256, 4, and 8, respectively. For this reason, the condition "N * Ns * Nsg > 1024" may be satisfied. When this condition is satisfied, for example, when N is 256 and Ns is 4, all user devices assigned to the same paging opportunity belong to the same paging subgroup, and an appropriate paging subgroup ID cannot be assigned to each UE 100.

[0053] Also, when the UE_ID is calculated by the formula "UE_ID = 5G - S - TMSI mod 1024 * Nsg", compared with the calculation method by "UE_ID = 5G - S - TMSI mod 1024" defined in the current 3GPP technical specification when calculating the UE_ID, the number of UE_IDs increases, and as a result, the number of bits required to indicate the UE_ID increases. Consequently, for example, when transmitting the UE_ID between base stations, there is a problem that the amount of information of the UE_ID increases. In an embodiment described later, an operation for suppressing an increase in the amount of information of the UE_ID will be described.

[0054] (Configuration of User Equipment) Referring to FIG. 6, the configuration of the UE 100 according to the embodiment will be described. The UE 100 includes a communication unit 110 and a control unit 120.

[0055] The communication unit 110 performs wireless communication with the base station 200 by transmitting and receiving wireless signals to and from the base station 200. The communication unit 110 includes at least one transmitter 111 and at least one receiver 112. The transmitter 111 and the receiver 112 may be configured to include a plurality of antennas and RF circuits. The antenna converts a signal into a radio wave and radiates the radio wave into space. Also, the antenna receives a radio wave in space and converts the radio wave into a signal. The RF circuit performs analog processing of signals transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, and the like.

[0056] The control unit 120 performs various controls in the UE 100. The control unit 120 controls communication with the base station 200 via the communication unit 110. The operations of the UE 100 described above and below may be operations under the control of the control unit 120. The control unit 120 may include at least one processor capable of executing a program and a memory for storing the program. The processor may execute the program to perform the operations of the control unit 120. The control unit 120 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of the RAN protocol stack. Note that the memory stores a program executed by the processor, parameters related to the program, and data related to the program. The memory may include at least one of ROM (Read Only Memory), EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), RAM (Random Access Memory), and flash memory. All or part of the memory may be included in the processor.

[0057] In the UE 100 configured as described above, when the UE 100 is in the RRC idle state or the RRC inactive state, the control unit 120 calculates a paging occasion (PO) where the UE 100 may receive a paging message based on the UE_ID. The receiving unit 112 receives a paging message from the base station 200 that manages the cell in the cell where the UE 100 is located at the calculated PO. The control unit 120 selects one of a first calculation formula and a second calculation formula based on whether a paging subgroup to which a part of a plurality of UEs 100 assigned to the same paging opportunity belongs is set for the UE 100, and calculates the UE_ID using the selected calculation formula. The number of bits required to indicate the UE_ID calculated by the second calculation formula is shorter than the number of bits required to indicate the UE_ID calculated by the first calculation formula. Thus, when the UE 100 (control unit 120) selects the second calculation formula, the number of bits required to transmit the UE_ID becomes smaller compared to the case where the first calculation formula is selected, and an increase in the amount of information of the UE_ID can be suppressed.

[0058] (Configuration of the base station) With reference to FIG. 7, the configuration of the base station 200 according to the embodiment will be described. The base station 200 includes a communication unit 210, a network interface 220, and a control unit 230.

[0059] The communication unit 210 receives, for example, a radio signal from the UE 100 and transmits a radio signal to the UE 100. The communication unit 210 includes at least one transmitting unit 211 and at least one receiving unit 212. The transmitting unit 211 and the receiving unit 212 may be configured to include an RF circuit. The RF circuit performs analog processing of signals transmitted and received via an antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, and the like.

[0060] The network interface 220 transmits and receives signals to and from the network. The network interface 220 receives signals from an adjacent base station connected via, for example, an Xn interface which is an interface between base stations, and transmits signals to the adjacent base station. Also, the network interface 220 receives signals from a core network device 300 connected via, for example, an NG interface, and transmits signals to the core network device 300.

[0061] The control unit 230 performs various controls in the base station 200. The control unit 230 controls, for example, communication with the UE 100 via the communication unit 210. Also, the control unit 230 controls communication with nodes (for example, an adjacent base station, the core network device 300) via, for example, the network interface 220. Operations of the base station 200 described above and below may be operations under the control of the control unit 230. The control unit 230 may include at least one processor capable of executing a program and a memory for storing the program. The processor may execute the program to perform the operations of the control unit 230. The control unit 230 may include a digital signal processor that performs digital processing of signals transmitted and received via an antenna and an RF circuit. The digital processing includes processing of the RAN protocol stack. Note that the memory stores a program executed by the processor, parameters related to the program, and data related to the program. All or part of the memory may be included in the processor.

[0062] The base station 200 configured as described above manages the cell in which the UE 100 is located. When the UE 100 is in the RRC idle state or the RRC inactive state, the control unit 230 calculates a PO at which the UE 100 may receive a paging message based on the UE_ID. The transmission unit 211 transmits a paging message to the UE 100 in the cell using the calculated PO. The control unit 230 selects one of a first calculation formula and a second calculation formula based on whether a paging subgroup to which a part of a plurality of UEs 100 assigned to the same PO belongs is set for the UE 100, and calculates the UE_ID using the selected calculation formula. The number of bits required to indicate the UE_ID calculated by the second calculation formula is shorter than the number of bits required to indicate the UE_ID calculated by the first calculation formula. Thereby, when the second calculation formula is selected, the number of bits required to transmit the UE_ID becomes smaller compared to the case where the first calculation formula is selected, and an increase in the amount of information of the UE_ID can be suppressed.

[0063] Note that the UE_ID is transmitted, for example, in a RAN paging message via the Xn interface from the base station 200 where RAN paging is triggered to another base station 200.

[0064] (Operation of the mobile communication system) (1) First operation example With reference to FIGS. 8 to 10, a first operation example of the mobile communication system 1 will be described. Note that the description will mainly focus on the differences from the above-described operation examples.

[0065] As shown in FIG. 8, in step S101, the base station 200 (transmission unit 211) transmits Nsg information indicating the number of paging subgroups (Nsg) in the cell managed by the base station 200 in the cell. The base station 200 (transmission unit 211) may transmit, for example, a system information block (SIB) including Nsg. The UE 100 (reception unit 112) receives the Nsg information in the cell in which the UE 100 is located.

[0066] In step S102, the UE 100 (control unit 120) calculates a user equipment identity (UE_ID). Specifically, the UE 100 (control unit 120) selects one of the following first calculation formula and second calculation formula based on whether a paging subgroup to which a part of a plurality of UEs 100 assigned to the same PO belongs is set for the UE 100. The UE 100 (control unit 120) calculates the UE_ID using the selected calculation formula. FIG. 9 shows an operation example of the UE 100.

[0067] As shown in FIG. 9, in step S121, the UE 100 (control unit 120) determines whether a paging subgroup (PSG) is set for the UE 100. The UE 100 (control unit 120) may determine that the PSG is set for the UE 100 in at least any of the following cases. Note that the setting of the paging subgroup may be a setting for the UE 100 (control unit 120) to monitor a PDCCH monitoring opportunity (i.e., monitor paging) (see FIG. 10).

[0068] First, when the UE 100 (control unit 120) is notified of Nsg from the network 10 (base station 200), the UE 100 may determine that the PSG is set for the UE 100. Therefore, when the UE 100 (control unit 120) receives Nsg information in the cell where the UE 100 is located, the UE 100 may determine that the PSG is set for the UE 100.

[0069] Second, when the UE 100 (control unit 120) receives information regarding the setting of the paging subgroup from the network 10 (base station 200), the UE 100 may determine that the PSG is set for the UE 100. For example, when the UE 100 (control unit 120) receives information indicating that the paging subgroup is determined by the second grouping method, the UE 100 may determine that the PSG is set for the UE 100.

[0070] When the UE 100 (control unit 120) determines that the PSG is set for the UE 100, it executes the process of step S122. On the other hand, when the UE 100 (control unit 120) determines that the PSG is not set for the UE 100, it executes the process of step S123.

[0071] In step S122, the UE 100 (control unit 120) selects the first calculation formula. The UE 100 (control unit 120) calculates the UE_ID using the selected first calculation formula.

[0072] For example, the first calculation formula is "UE_ID = unique identifier of the user equipment mod Y". The unique identifier of the user equipment is, for example, 5G-S-TMSI. Y may be a fixed value obtained by multiplying 1024 by the maximum value of the configurable PSG number defined in the technical specifications of the mobile communication system 1. In the current 3GPP technical specifications, the maximum value of the configurable PSG number is 8. For example, as shown in FIG. 10, the UE 100 (control unit 120) calculates the UE_ID using formula E21A as the first calculation formula. In formula E21A, the fixed value is 8192 (= 1024 × 8). Note that the fixed value may be any value larger than N * Ns * Nsg.

[0073] In step S123, the UE 100 (control unit 120) selects the second calculation formula. The UE 100 (control unit 120) calculates the UE_ID using the selected second calculation formula.

[0074] For example, as shown in FIG. 10, the second calculation formula is formula E21B which is "UE_ID = 5G-S-TMSI mod 1024" defined in the current 3GPP technical specifications.

[0075] The number of bits required to indicate the UE_ID calculated by the second calculation formula is shorter than the number of bits required to indicate the UE_ID calculated by the first calculation formula. In this operation example, the UE_ID calculated by the second calculation formula is represented by 10 bits (= log2(1024)), while the UE_ID calculated by the first calculation formula is represented by 13 bits (= log2(8192)).

[0076] Returning to FIG. 8, in step S103, the UE 100 (control unit 120) calculates PF, PO, and PSG. For example, the UE 100 (control unit 120) calculates PF using Equation E11, calculates PO using Equation E12, and calculates PSG using Equation E13.

[0077] Steps S104 and S105 are the same as steps S13 and S14. Note that the base station 200 (control unit 230) calculates the UE_ID, PF, PO, and PSG in the same manner as the UE 100. The base station 200 (control unit 230, transmission unit 211) performs a paging transmission operation based on the calculated UE_ID, PF, PO, and PSG.

[0078] Specifically, when paging for the UE 100 is triggered, the base station 200 (control unit 230) calculates the UE_ID of the UE 100 and calculates the PSG (paging subgroup ID) based on the calculated UE_ID. Before transmitting the paging message, the base station 200 (transmission unit 211) notifies each UE 100 of the calculated paging subgroup ID. Thereafter, the base station 200 (transmission unit 211) transmits a paging message including the unique identifier of the UE 100.

[0079] As described above, the UE100 (control unit 120) calculates the UE_ID using the formula E21A (UE_ID = 5G-S-TMSI mod 8192). Even when using the formula "UE subgroup ID = floor(UE_ID / (N*Ns)) mod Nsg" as the formula for calculating the paging subgroup ID from the UE_ID, since not all UE100s assigned to the same paging opportunity belong to the same PSG, an appropriate paging subgroup ID is assigned to each UE100.

[0080] When the PSG is not set for the UE100, the UE100 (control unit 120) selects the second calculation formula. Compared with the case where the first calculation formula is selected, the number of bits required to transmit the UE_ID becomes smaller, and an increase in the information amount of the UE_ID can be suppressed.

[0081] Also, the first calculation formula is "UE_ID = user equipment's unique identifier mod Y", and Y is a fixed value obtained by multiplying 1024 by the maximum value of the configurable number of PSGs defined in the technical specifications of the mobile communication system 1. Thus, compared with the case where Y is a variable value (for example, Nsg) that can be changed for each cell, the UE100 (control unit 120) can omit, for example, the management of the variable value, and the process for calculating the UE_ID becomes simpler.

[0082] (2) Second operation example Referring to FIGS. 11 and 12, the differences between the second operation example and the above-described operation example will be mainly described. In the second operation example, the UE100 selects the first calculation formula when the condition "N*Ns*Nsg > threshold" is satisfied, and selects the second calculation formula when the condition is not satisfied.

[0083] As shown in FIG. 11, step S221 is the same as step S121. When the UE100 (control unit 120) determines that the PSG is set for the UE100, it executes the process of step S222. On the other hand, when the UE100 (control unit 120) determines that the PSG is not set for the UE100, it executes the process of step S223.

[0084] In step S222, the UE100 (control unit 120) determines whether or not the condition "N * Ns * Nsg > threshold" is satisfied.

[0085] The threshold value is the value obtained by multiplying the maximum value of the total PF that can be set as N defined in the technical specifications of the mobile communication system 1 and the maximum value of the PO that can be set as Ns defined in the technical specifications of the mobile communication system 1. In the current 3GPP technical specifications, the maximum value of the total PF that can be set as N is 256, and the maximum value of the PO that can be set as Ns is 4. Therefore, as shown in FIG. 12, the threshold value is 1024 (= 256 × 4), and the condition is "N * Ns * Nsg > 1024".

[0086] When the condition is satisfied, the UE100 (control unit 120) executes the process of step S223. On the other hand, when the condition is not satisfied none the UE100 (control unit 120) executes the process of step S224.

[0087] In step S223, the UE100 (control unit 120) selects, for example, as the first calculation formula, formula E22A as shown in FIG. 12. In this operation example, formula E22A is the same as formula E21A.

[0088] In step S224, the UE100 (control unit 120) selects, for example, as the second calculation formula, formula E22B as shown in FIG. 12. In this operation example, formula E22B is the same as formula E21B.

[0089] As described above, when the condition "N * Ns * Nsg > 1024" is satisfied, the UE100 (control unit 120) calculates the UE_ID using the formula E22A (UE_ID = 5G - S - TMSI mod 8192). Even when using the formula "UE subgroup ID = floor(UE_ID / (N * Ns)) mod Nsg" as the formula for calculating the paging subgroup ID from the UE_ID, since not all UE100s assigned to the same paging opportunity belong to the same PSG, an appropriate paging subgroup ID is assigned to each UE100.

[0090] Also, when the condition "N * Ns * Nsg > 1024" is not satisfied, even if the PSG is set for the UE100, the UE100 (control unit 120) selects the second calculation formula. Therefore, compared with the case where the first calculation formula is selected, the number of bits required to transmit the UE_ID becomes smaller, and an increase in the information amount of the UE_ID can be suppressed.

[0091] (3) Third operation example Referring to FIG. 13, the differences between the third operation example and the above-described operation examples will be mainly described. In the third operation example, the UE100 (control unit 120) selects a formula different from the above-described operation examples as the first calculation formula. The flowchart of the UE100 (control unit 120) in this operation example is the same as that in the second operation example.

[0092] In step S223, the UE100 (control unit 120) selects, for example, formula E23A as the first calculation formula as shown in FIG. 13. In this operation example, formula E23A is "UE_ID = user equipment's unique identifier mod Z". Z is the value obtained by multiplying 1024 by Nsg.

[0093] In step S224, the UE100 (control unit 120) selects, for example, formula E23B as the second calculation formula as shown in FIG. 3 1. In this operation example, formula E23B is the same as formula E21B.

[0094] As described above, when the condition "N * Ns * Nsg > 1024" is satisfied, the UE100 (control unit 120) calculates the UE_ID using Equation E23A. Even when using the equation "UE subgroup ID = floor(UE_ID / (N * Ns)) mod Nsg" as the equation for calculating the paging subgroup ID from the UE_ID, since all UE100s assigned to the same paging opportunity do not belong to the same PSG, an appropriate paging subgroup ID is assigned to each UE100.

[0095] Also, when the UE100 (control unit 120) calculates the UE_ID using Equation E23A, if Nsg is less than 8, the number of bits required to transmit the UE_ID is smaller compared to the case of using Equation 21A or Equation 22A, and an increase in the information amount of the UE_ID can be suppressed.

[0096] Also, when the condition "N * Ns * Nsg > 1024" is not satisfied, even if the PSG is set for the UE100, since the second calculation formula is selected, the number of bits required to transmit the UE_ID is smaller compared to the case where the first calculation formula is selected, and an increase in the information amount of the UE_ID can be suppressed.

[0097] (Other Embodiments) In the above-described embodiment, the second calculation formula was "UE_ID = 5G - S - TMSI mod 1024" defined in the current 3GPP technical specification, but other calculation formulas may also be used.

[0098] The operation sequences (and operation flows) in the above-described embodiments do not necessarily have to be executed in chronological order along the order described in the flowcharts or sequence diagrams. For example, the steps in the operations may be executed in an order different from the order described as the flowchart or sequence diagram, or may be executed in parallel. Also, some of the steps in the operations may be deleted, and additional steps may be added to the processing. Further, the operation sequences (and operation flows) in the above-described embodiments may be implemented separately and independently, or may be implemented by combining two or more operation sequences (and operation flows). For example, some steps of one operation flow may be added to another operation flow, or some steps of one operation flow may be replaced with some steps of another operation flow.

[0099] In the above-described embodiment, the mobile communication system 1 has been described by taking a mobile communication system based on NR as an example. However, the mobile communication system 1 is not limited to this example. The mobile communication system 1 may be a system compliant with any one of LTE (Long Term Evolution) or other generation systems of the 3GPP standard (for example, the sixth generation). The base station 200 may be an eNB that provides E-UTRA user plane and control plane protocol termination to the UE 100 in LTE. The mobile communication system 1 may be a system compliant with a TS of a standard other than the 3GPP standard. The base station 200 may be an IAB (Integrated Access and Backhaul) donor or an IAB node.

[0100] A program may be provided that causes a computer to execute each process performed by the UE 100 or the base station 200. The program may be recorded on a computer-readable medium. By using a computer-readable medium, it is possible to install the program in a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM (Compact Disk Read Only Memory) or a DVD-ROM (Digital Versatile Disc Read Only Memory). Further, a circuit that executes each process performed by the UE 100 or the base station 200 may be integrated, and at least a part of the UE 100 or the base station 200 may be configured as a semiconductor integrated circuit (chip set, SoC (System On Chip)).

[0101] In the above embodiments, "transmit" may mean performing processing of at least one layer in a protocol stack used for transmission, or may mean physically transmitting a signal wirelessly or via wire. Alternatively, "transmit" may mean a combination of performing the processing of the at least one layer and physically transmitting a signal wirelessly or via wire. Similarly, "receive" may mean performing processing of at least one layer in a protocol stack used for reception, or may mean physically receiving a signal wirelessly or via wire. Alternatively, "receive" may mean a combination of performing the processing of the at least one layer and physically receiving a signal wirelessly or via wire. Similarly, "obtain / acquire" may mean obtaining information from stored information, may mean obtaining information from information received from other nodes, or may mean obtaining the information by generating the information. Similarly, the descriptions "based on" and "depending on / in response to" do not mean "only based on" and "only in response to" unless otherwise specified. The description "based on" means both "only based on" and "at least partially based on". Similarly, the description "depending on" means both "only depending on" and "at least partially depending on". Similarly, "include" and "comprise" do not mean including only the recited items, and may mean including only the recited items or may mean including additional items in addition to the recited items. Similarly, in the present disclosure, "or" does not mean exclusive disjunction and means disjunction. Further, any reference to elements using designations such as "first", "second", etc. used in the present disclosure does not generally limit the quantity or order of those elements. These designations may be used in the present disclosure as a convenient way to distinguish between two or more elements.Accordingly, references to the first and second elements do not mean that only two elements may be employed there, or that the first element must precede the second element in some form. In the present disclosure, for example, when articles are added by translation, such as a, an, and the in English, these articles shall be construed to include pluralities unless the context clearly indicates otherwise.

[0102] The present disclosure has been described with reference to embodiments, but it is understood that the present disclosure is not limited to such embodiments or structures. The present disclosure also encompasses various modifications and variations within the equivalent scope. In addition, various combinations and forms, and still other combinations and forms including only one element, more than one element, or less than one element thereof, fall within the scope and spirit of the present disclosure.

[0103] (Supplementary Note) The features regarding the above-described embodiments are supplemented as follows.

[0104] (Supplementary Note 1) A receiving unit that receives from a network first information indicating the number of subgroups per paging opportunity and second information regarding the setting of the subgroup based on a user equipment identity (UE_ID); A control unit that calculates the UE_ID using a predetermined calculation formula based on the first information and the second information, and calculates a subgroup identifier based on the UE_ID calculated using the predetermined calculation formula; The receiving unit monitors a paging opportunity based on the subgroup identifier Communication device.

[0105] (Supplementary Note 2) The predetermined calculation formula is a formula based on a 5G-S-TMSI which is a temporary mobile subscription identifier The communication device according to Supplementary Note 1.

[0106] (Supplementary Note 3) The predetermined calculation formula is a first calculation formula, The control unit calculates the UE_ID using a second calculation formula different from the first calculation formula based on the fact that the second information has not been received, and monitors a paging opportunity based on the UE_ID calculated using the second calculation formula. The communication device according to appendix 1 or 2.

[0107] (Appendix 4) The second calculation formula is a formula based on the 5G-S-TMSI which is a temporary mobile subscription identifier. The communication device according to appendix 3.

[0108] (Appendix 5) A transmission unit that transmits to a communication device first information indicating the number of subgroups per paging opportunity and second information regarding the setting of the subgroup based on a user equipment identity (UE_ID); a control unit that calculates the UE_ID using a predetermined calculation formula based on the first information and the second information, and calculates a subgroup identifier based on the UE_ID calculated using the predetermined calculation formula; wherein the transmission unit transmits downlink control information on a physical link control channel in a paging opportunity based on the subgroup identifier. Base station.

[0109] (Appendix 6) A communication method executed by a communication device, the method comprising: receiving from a network first information indicating the number of subgroups per paging opportunity and second information regarding the setting of the subgroup based on a user equipment identity (UE_ID); calculating the UE_ID using a predetermined calculation formula based on the first information and the second information, and calculating a subgroup identifier based on the UE_ID calculated using the predetermined calculation formula; monitoring a paging opportunity based on the subgroup identifier. Communication method.

Claims

1. A communication device (100), a receiving unit (112) that receives, from a base station (200), downlink control information including information for indicating a subgroup identifier of a paging opportunity on a physical downlink control channel; and a control unit (120) that calculates a user equipment identity (UE_ID). The control unit (120): Based on the communication device receiving first information for indicating the number of subgroups per paging opportunity and second information for setting UE_ID-based subgrouping, calculates a first UE_ID as the UE_ID using a first formula that performs a mod operation on a unique identifier of the communication device with a first value, and monitors the paging opportunity based on a subgroup identifier based on the first UE_ID calculated using the first formula and the subgroup identifier indicated by the information included in the downlink control information; Based on the communication device not receiving the second information, calculates a second UE_ID as the UE_ID using a second formula that performs a mod operation on a unique identifier of the communication device with a second value, and monitors the paging opportunity based on the second UE_ID calculated using the second formula; The first value is greater than the second value Communication device (100).

2. The receiving unit receives a paging message from the base station during the paging opportunity The communication device according to claim 1.

3. The unique identifier of the communication device is a 5G-S-TMSI (Temporary Mobile Subscriber Identifier), The subgroup identifier based on the UE_ID calculated using the first formula is based on the number of subgroups per paging opportunity, the number of paging opportunities for a paging frame, and the total number of paging frames within a discontinuous reception (DRX) cycle of the communication device The communication device according to claim 1 or claim 2.

4. The first value is 8192, The second value is 1024 The communication device according to claim 1 or claim 2.

5. A base station (200), a transmitting unit (211) that transmits, on a physical downlink control channel, downlink control information including information for indicating a subgroup identifier of a paging opportunity to a communication device A control unit (230) for calculating a user equipment identifier (UE_ID), and the control unit (230) is based on the base station having transmitted to the communication device first information for indicating the number of subgroups per paging opportunity and second information for setting UE_ID-based subgrouping, a subgroup identifier based on a first UE_ID calculated as the UE_ID using a first formula for performing a mod operation on the unique identifier of the communication device with a first value, and the subgroup identifier indicated by the information included in the downlink control information, controlling the communication device to monitor the paging opportunity, based on the base station not transmitting the second information to the communication device, controlling the communication device to monitor the paging opportunity according to a second UE_ID calculated as the UE_ID using a second formula for performing a mod operation on the unique identifier of the communication device with a second value, the first value is greater than the second value Base station. **Claim 6** The transmitting unit transmits a paging message to the communication device in the paging opportunity The base station according to claim 5. **Claim 7** The unique identifier of the communication device is 5G-S-TMSI (Temporary Mobile Subscriber Identifier), the subgroup identifier based on the first UE_ID calculated using the first formula is based on the number of subgroups per paging opportunity, the number of paging opportunities for a paging frame, and the total number of paging frames within the discontinuous reception (DRX) cycle of the communication device The base station according to claim 5 or claim 6. **Claim 8** the first value is 8192, the second value is 1024 The base station according to claim 5 or claim 6. **Claim 9** A communication method executed by a communication device (100), comprising receiving, on a physical downlink control channel, downlink control information including information for indicating a subgroup identifier of a paging opportunity from a base station (200), Based on receiving first information for indicating the number of subgroups per paging opportunity and second information for setting user equipment identity (UE_ID)-based subgrouping by the communication device, a first UE_ID is calculated as the UE_ID using a first formula that performs a mod operation on the unique identifier of the communication device with a first value, and based on the subgroup identifier based on the first UE_ID calculated using the first formula and the subgroup identifier indicated by the information included in the downlink control information, a step of monitoring the paging opportunity; Based on the communication device not receiving the second information, a second UE_ID is calculated as the UE_ID using a second formula that performs a mod operation on the unique identifier of the communication device with a second value, and based on the second UE_ID calculated using the second formula, a step of monitoring the paging opportunity, and comprising; The first value is greater than the second value Communication method.

10. Comprising a step of receiving a paging message from the base station in the paging opportunity The communication method according to claim 9.

11. The unique identifier of the communication device is 5G-S-TMSI (Temporary Mobile Subscriber Identifier), The subgroup identifier based on the first UE_ID calculated using the first formula is based on the number of subgroups per paging opportunity, the number of paging opportunities for a paging frame, and the total number of paging frames within a discontinuous reception (DRX) cycle of the communication device The communication method according to claim 9 or claim 10.

12. The first value is 8192, The second value is 1024 The communication method according to claim 9 or claim 10.

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