JP2023006096A - Base station and communication control method - Google Patents

Abstract

To provide a base station and a communication control method capable of suppressing increase in signaling due to handover of a user device.SOLUTION: In a mobile communication system having a user device 100 communicating with a first network 200A and a second network, a base station 210A1 of the first network includes a control unit that performs a pre-configuration procedure between the user device and the first network for configuring transition to the RRC inactive state before receiving a switching notification from the user device for transitioning from the RRC connected state in the first network and switching communication to the second network, and a network communication unit that, after performing the pre-configuration procedure, sends, to the neighboring base station 210A2, a handover request message requesting preparation of resources for handover of the user device. The handover request message contains pre-configuration information about the pre-configuration procedure.SELECTED DRAWING: Figure 5

Description

The present invention relates to a base station and communication control method used in a mobile communication system.

In Release 17 of 3GPP (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, a function for a user device equipped with multiple subscriber identification modules to perform data communication while being in the network of multiple carriers. A work item has been launched to formulate At present, there is no provision in the standard specifications for a mechanism for receiving paging by user devices that are present in multiple networks, and it depends on the implementation of the user device. Therefore, a method of receiving paging from a plurality of networks in cooperation with each network is being studied in the 3GPP standardization arena.

Here, in a case where a paging message is received from the other network (hereinafter, "second network") during communication in an RRC connected state in one network (hereinafter, "first network"), the first network If communication with the second network is prioritized over communication with the user equipment, the user equipment temporarily transitions from the RRC connected state in the first network in order to switch communication from the first network to the second network (i.e. , and leave) to the first network (for example, see Non-Patent Document 1). Unnecessary communication with the first network can be suppressed during communication with the second network by removing the user equipment from the RRC connected state in the first network.

In addition to the case of transitioning from the RRC connected state in the first network to the RRC idle state, a case of transitioning to the RRC inactive state in which the context information of the user equipment is held in the first network is also being considered. (For example, see Non-Patent Document 2).

3GPP contributions "R1-2100474" 3GPP contributions "R1-2104301"

For example, when the user equipment prioritizes communication with the second network over communication with the first network, the user equipment and the It is conceivable to perform a procedure (hereinafter referred to as a pre-configuration procedure) for configuring the transition to the RRC inactive state with the first network.

Now assume the case that the user equipment has performed a handover. A user equipment that has performed a pre-configuration procedure before handover can autonomously transition to the RRC inactive state even after handover by performing the pre-configuration procedure after handover.

However, the user equipment has to perform a pre-configuration procedure each time it performs a handover, which increases the signaling between the user equipment and the base station.

Therefore, the present invention provides a base station and communication system capable of suppressing an increase in signaling due to handover of a user equipment when a procedure for setting transition to an RRC inactive state before transmission of a switching notification is performed. The object is to provide a control method.

A base station according to a first aspect is a mobile communication system having user equipment that communicates with a first network using a first subscriber identity module and communicates with a second network using a second subscriber identity module. A base station of a first network, wherein, before receiving a switching notification from the user equipment for transitioning from the RRC connected state in the first network and switching communication to the second network, the user equipment and the A control unit that performs a pre-configuration procedure for configuring a transition to an RRC inactive state with a first network, and after performing the pre-configuration procedure, requests preparation of resources for handover of the user equipment. a network communication unit for sending a handover request message to a neighboring base station, said handover request message including pre-configured information regarding said pre-configured procedure.

A communication control method according to a second aspect is provided in a mobile communication system having a user equipment that communicates with a first network using a first subscriber identity module and communicates with a second network using a second subscriber identity module. A communication control method executed by a base station of the first network, before receiving from the user equipment a switching notification for transitioning from an RRC connected state in the first network and switching communication to the second network. a step of performing a pre-configuration procedure for configuring a transition to an RRC inactive state between the user equipment and the first network; sending a handover request message to a neighboring base station requesting resource preparation, said handover request message including pre-configured information regarding said pre-configured procedure.

According to one aspect of the present invention, a base capable of suppressing an increase in signaling due to a handover of a user equipment when a procedure for setting a transition to an RRC inactive state before transmitting a switching notification is performed. A station and communication control method can be provided.

1 is a diagram showing a configuration example of a mobile communication system according to an embodiment; FIG. It is a figure which shows the structural example of the protocol stack of the mobile communication system which concerns on embodiment. It is a figure which shows the structural example of UE (user apparatus) which concerns on embodiment. FIG. 3 is a diagram showing a configuration example of a base station of the first network according to the embodiment; FIG. 10 is a diagram (part 1) showing a first operation example of the embodiment; FIG. 11 is a diagram (part 2) showing a first operation example of the embodiment; It is a figure which shows the 2nd operation example of embodiment. It is a figure which shows the 3rd operation example of embodiment. It is a figure which shows the determination operation example of UE100 of embodiment.

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.

[Embodiment]
(System configuration)
A configuration of a mobile communication system 1 according to an embodiment will be described with reference to FIG. An example in which the mobile communication system 1 is a 3GPP standard fifth generation system (5G/NR: New Radio) will be mainly described below, but the mobile communication system 1 includes a fourth generation system (4G/LTE: Long Term Evolution) system and/or 6th generation system may be applied at least partially.

As shown in FIG. 1, the mobile communication system 1 according to the embodiment has a user equipment (UE) 100, a first network 200A, and a second network 200B.

UE 100 is a mobile wireless communication device. The UE 100 may be a device used by a user, but for example, the UE 100 may be a mobile phone terminal (including a smartphone), a tablet terminal, a notebook PC, a communication module (including a communication card or chipset), a sensor, or a sensor. a vehicle or a device installed in a vehicle (Vehicle UE); an aircraft or a device installed in an aircraft (Aerial UE).

The UE 100 is a multi-SIM device that supports multiple subscriber identity modules (SIMs). The UE 100 communicates with multiple networks using multiple SIMs. An example in which the UE 100 supports two SIMs will be mainly described below, but the UE 100 may support three or more SIMs. “Supporting multiple SIMs” means that the UE 100 has the ability to handle multiple SIMs, and the UE 100 does not necessarily have to be equipped with multiple SIMs. Such a UE 100 is sometimes called a "UE that supports multiple SIMs". Note that the SIM is not limited to a card-type SIM (so-called SIM card), and may be an embedded SIM (so-called eSIM) pre-installed in the UE 100 . The SIM is sometimes called a USIM (Universal Subscriber Identity Module).

A first network 200A is a network associated with one SIM of the UE 100 . A second network 200B is a network associated with the other SIM of the UE 100 . It is assumed that UE 100 performs location registration with first network 200A using one SIM, and performs location registration with second network 200B using the other SIM. That is, UE 100 is located in each of first network 200A and second network 200B. The first network 200A and the second network 200B may be networks of different carriers. However, the first network 200A and the second network 200B may be networks of the same carrier. Different PLMN (Public Land Mobile Network) IDs may be assigned to the first network 200A and the second network 200B.

The first network 200A has a base station 210A and a core network 220A that constitute a radio access network. The core network 220A has a mobility management device 221A and a gateway device 222A as core network devices. Similarly, the second network 200B has a base station 210B and a core network 220B forming a radio access network. The core network 220B has a mobility management device 221B and a gateway device 222B as core network devices. Hereinafter, when the base stations 210A and 200B are not distinguished, they are simply referred to as the base station 210; when the mobility management devices 221A and 221B are not distinguished, they are simply referred to as the mobility management device 221; It is called gateway device 222 .

The base station 210 is a radio communication device that performs radio communication with the UE 100 . A base station 210 manages one or more cells. The base station 210 performs radio communication with the UE 100 that has established a connection in the radio resource control (RRC) layer with its own cell. The base station 210 has a radio resource management (RRM) function, a user data (hereinafter simply referred to as “data”) routing function, a measurement control function for mobility control/scheduling, and the like. A "cell" is used as a term indicating the minimum unit of a wireless communication area. A “cell” is also used as a term indicating a function or resource for radio communication with the UE 100 . One cell belongs to one carrier frequency. FIG. 1 shows an example in which the base station 210A manages the cell C1 and the base station 210B manages the cell C2. The UE 100 is located in the overlapping area of cell C1 and cell C2.

The base station 210 may be a gNB, which is a 5G/NR base station, or an eNB, which is a 4G/LTE base station. In the following, an example in which the base station 210 is a gNB will be mainly described. The base station 210 may be functionally divided into a CU (Central Unit) and a DU (Distributed Unit). Base station 210 may be a relay node such as an IAB (Integrated Access and Backhaul) node.

The mobility management device 221 is a device that supports the control plane and performs various types of mobility management for the UE 100 . The mobility management device 221 communicates with the UE 100 using NAS (Non-Access Stratum) signaling and manages information on the tracking area in which the UE 100 is located. The mobility management device 221 performs paging through the base station 210 to notify the UE 100 of the incoming call. The mobility management device 221 may be a 5G/NR AMF (Access and Mobility Management Function) or a 4G/LTE MME (Mobility Management Entity).

The gateway device 222 is a device compatible with the user plane, and is a device that performs data transfer control of the UE 100 . The gateway device 222 may be a 5G/NR UPF (User Plane Function) or a 4G/LTE S-GW (Serving Gateway).

(Example of protocol stack configuration)
A configuration example of the protocol stack of the mobile communication system 1 will be described with reference to FIG. As shown in FIG. 2, the protocol of the radio section between the UE 100 and the base station 210 includes a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, and a PDCP (Packet Data Convergence Protocol) layer and RRC (Radio Resource Control) layer.

The PHY layer performs encoding/decoding, modulation/demodulation, antenna mapping/demapping, and resource mapping/demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the base station 210 via physical channels.

The MAC layer performs data priority control, hybrid ARQ (HARQ) retransmission processing, random access procedures, and the like. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the base station 210 via transport channels. The MAC layer of base station 210 includes a scheduler. The scheduler determines uplink and downlink transport formats (transport block size, modulation and coding scheme (MCS)) and allocation resources to the UE 100 .

The RLC layer uses functions of the MAC layer and the PHY layer to transmit data to the RLC layer of the receiving side. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the base station 210 via logical channels.

The PDCP layer performs header compression/decompression and encryption/decryption.

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

The RRC layer controls logical, transport and physical channels according to establishment, re-establishment and release of radio bearers. RRC signaling for various settings is transmitted between the RRC layer of the UE 100 and the RRC layer of the base station 210 . If there is an RRC connection between the RRC of UE 100 and the RRC of base station 210, UE 100 is in the RRC connected state. If there is no RRC connection between the RRC of the UE 100 and the RRC of the base station 210, the UE 100 is in RRC idle state. When the RRC connection between the RRC of UE 100 and the RRC of base station 210 is suspended, UE 100 is in RRC inactive state.

The NAS layer located above the RRC layer performs session management and mobility management for the UE 100 . NAS signaling is transmitted between the NAS layer of UE 100 and the NAS layer of mobility management device 221 .

A mode (NAS state) in the NAS layer of the UE 100 includes an idle mode and a connected mode. In the connected mode, the network holds the context information of the UE 100, and in the idle mode, the network does not hold the context information of the UE 100. When UE 100 is in connected mode, UE 100 is in RRC connected state or RRC inactive state. When the UE 100 is in idle mode, the UE 100 is in RRC idle state.

The mode in the NAS layer may be 5GMM (5G Mobility Management) mode. In this mode, the connected mode may be 5GMM-connected mode and the idle mode may be 5GMM-idle mode.

Note that the UE 100 has an application layer and the like in addition to the radio interface protocol.

(UE configuration example)
A configuration example of the UE 100 will be described with reference to FIG. As shown in FIG. 3, UE 100 has antenna 101, SIM 111, SIM 112, communication section 120, and control section . The antenna 101 may be provided outside the UE 100 . SIM 111 and SIM 112 are SIM cards or eSIMs.

The SIM 111 stores subscriber information and setting information necessary for the UE 100 to communicate with the first network 200A. The SIM 111 stores identification information of the UE 100 in the first network 200A, such as a telephone number and an IMSI (International Mobile Subscriber Identity). SIM 111 corresponds to the first subscriber information module. UE 100 uses SIM 111 to communicate with first network 200A.

The SIM 112 stores subscriber information and setting information necessary for the UE 100 to communicate with the second network 200B. The SIM 112 stores identification information of the UE 100 in the second network 200B, such as telephone number and IMSI. SIM 112 corresponds to the second subscriber information module. UE 100 uses SIM 112 to communicate with second network 200B.

The communication unit 120 performs wireless communication with the first network 200A and wireless communication with the second network 200B via the antenna 101 under the control of the control unit 130 . The communication unit 120 may have only one receiver (RX: Receiver) 121 . In this case, the communication unit 120 cannot receive from the first network 200A and receive from the second network 200B at the same time. However, the communication section 120 may have a plurality of reception sections 121 . Also, the communication unit 120 may have only one transmission unit (TX: Transmitter) 122 . In this case, the communication unit 120 cannot perform transmission to the first network 200A and transmission to the second network 200B at the same time. However, the communication section 120 may have a plurality of transmission sections 122 . Receiving section 121 converts a radio signal received by antenna 101 into a received signal that is a baseband signal, performs signal processing on the received signal, and outputs the received signal to control section 130 . Transmitter 122 performs signal processing on a transmission signal, which is a baseband signal output from controller 130 , converts the signal into a radio signal, and transmits the radio signal from antenna 101 .

The control unit 130 controls the communication unit 120 and performs various controls in the UE 100 . Control unit 130 uses SIM 111 to control communication with first network 200A and uses SIM 112 to control communication with second network 200B. Control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The memory may include at least one of ROM, EPROM, EEPROM, RAM and flash memory. The processor may include a digital signal processor (DSP), which performs digital processing of digital signals, and a central processing unit (CPU), which executes programs. Note that part of the memory may be provided in the communication unit 120 . Also, the DSP may be provided in the communication unit 120 .

Control unit 130 includes an RRC processing unit 131 and a NAS processing unit 132 . The RRC processing unit 131 performs processing in the RRC layer processing. The NAS processing unit 132 performs processing in the NAS layer, which is a higher layer than the RRC layer. Note that the RRC processing unit 131 and the NAS processing unit 132 may be configured by one processor, or may be configured by a plurality of processors.

Note that the operation of the functional units provided in the UE 100 (specifically, at least one of the antenna 101, the SIM 111, the SIM 112, the communication unit 120, and the control unit 130 (RRC processing unit 131 and NAS processing unit 132)) may be described as the operation of the UE 100.

(Base station configuration example)
A configuration example of the base station 210A of the first network 200A will be described with reference to FIG. Note that the base station 210B of the second network 200B has the same configuration as the base station 210A, so description thereof will be omitted. As shown in FIG. 4, the base station 210A has an antenna 211, a radio communication section 212, a network communication section 213, and a control section 214.

The wireless communication unit 212 communicates with the UE 100 via the antenna 211 under the control of the control unit 214 . The wireless communication unit 212 has a receiving unit 212a and a transmitting unit 212b. The receiving unit 212 a converts a radio signal received by the antenna 211 into a received signal that is a baseband signal, performs signal processing on the received signal, and outputs the received signal to the control unit 214 . The transmission unit 212 b performs signal processing on a transmission signal, which is a baseband signal output from the control unit 214 , converts the signal into a radio signal, and transmits the radio signal from the antenna 211 .

Network communication unit 213 is connected to core network 220A. Network communication unit 213 performs network communication with mobility management device 221A and gateway device 222A under the control of control unit 214 .

The control unit 214 controls the radio communication unit 212 and performs various controls in the base station 210A. Control unit 214 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The memory may include at least one of ROM, EPROM, EEPROM, RAM and flash memory. The processor may include a digital signal processor (DSP), which performs digital processing of digital signals, and a central processing unit (CPU), which executes programs. Note that part of the memory may be provided in the wireless communication unit 212 . Also, the DSP may be provided in the wireless communication unit 212 .

In the base station 210 configured in this way, the control unit 214 receives from the UE 100 a switching notification for transitioning from the RRC connected state in the first network 200A and switching communication to the second network 200B. and the first network 200A for setting up the transition to the RRC inactive state. After executing the presetting procedure, the network communication unit 213 transmits a handover request message requesting preparation of resources for handover of the UE 100 to the adjacent base station. The handover request message contains pre-configured information about the pre-configured procedure. Thereby, the neighboring base station can take over the presetting information regarding the presetting procedure from the base station 210 by the handover request message without executing the presetting procedure after the handover of the UE 100 . As a result, it becomes unnecessary to execute the pre-configuration procedure every time the handover procedure is executed, and an increase in signaling due to the pre-configuration procedure caused by the handover of the UE 100 can be suppressed.

The preconfiguration information may also include suspend configuration information indicating the configuration for the RRC inactive state sent to the UE 100 in the preconfiguration procedure. Thereby, the neighboring base station can know the suspend setting information transmitted to the UE 100 in the pre-setting procedure. The neighboring base station can grasp the operation of the UE 100 in the RRC inactive state even if the UE 100 autonomously transitions to the RRC inactive state based on the suspend setting information. Therefore, there is no need to perform a pre-configuration procedure between the UE 100 and the adjacent base station, and an increase in signaling due to the pre-configuration procedure due to handover of the UE 100 can be suppressed.

The wireless communication unit 212, in the pre-setting procedure, expects transition from the RRC idle state to the RRC inactive state instead of the RRC idle state in the first network 200A when switching communication from the first network 200A to the second network 200B. Information may be received from the UE 100 . The control unit 214 may include suspend setting information in the handover request message based on the expectation information. Thereby, the neighboring base station can know the suspend setting information transmitted to the UE 100 in the pre-setting procedure. The neighboring base station can grasp the operation of the UE 100 in the RRC inactive state even if the UE 100 autonomously transitions to the RRC inactive state based on the suspend setting information. Therefore, there is no need to perform a pre-configuration procedure between the UE 100 and the adjacent base station, and an increase in signaling due to the pre-configuration procedure due to handover of the UE 100 can be suppressed.

In the preset procedure, radio communication section 212 receives, from UE 100, expectation information indicating that transition to at least the RRC inactive state is expected in first network 200A when switching communication from first network 200A to second network 200B. may receive. The control unit 214 may include expectation information in the handover request message. Thereby, the neighboring base station can know the expected information without receiving the expected information from the UE 100 after the handover. For example, the neighboring base station transmits the suspend configuration information to the UE 100 using the RRC reconfiguration message without receiving the preconfiguration request message, thereby suppressing an increase in signaling due to the preconfiguration procedure caused by the handover of the UE 100.

The handover request message may contain the RRC reconfiguration generated by the base station. The RRC reconfiguration in the handover request message may contain preconfiguration information. This can reduce the impact on existing mechanisms.

The network communication unit 213 may receive, from the neighboring base station, a response message to the handover request message including suspend setting information indicating the setting of transition to the RRC inactive state in the neighboring base station. The radio communication unit 212 may transmit to the UE 100 an RRC reconfiguration message used to perform handover from the base station to the neighboring base station. The RRC reconfiguration message may include suspend configuration information. This eliminates the need to perform a pre-configuration procedure between the UE 100 and the adjacent base station after handover, and can suppress an increase in signaling due to the pre-configuration procedure due to the handover of the UE 100.

Note that the operation of the functional unit (specifically, at least one of the antenna 211, the wireless communication unit 212, the network communication unit 213, and the control unit 214) provided in the base station 210A is regarded as the operation of the base station 210A. I have something to explain.

(Operation of mobile communication system)
The operation of the mobile communication system 1 will be explained.

(1) First Operation Example A first operation example of the mobile communication system 1 will be described with reference to FIGS. 5 and 6. FIG. In the operation example shown in FIG. 5, the first network 200A has a base station 210A1 and a base station 210A2. The base station 210A1 and the base station 210A2 are in a relationship of adjacent base stations. Base station 210A1 manages cell C11, and base station 210A2 manages cell C12. UE 100 is located in cell C11 managed by base station 210A1 of first network 200A. UE100 is in an RRC connected state in first network 200A, and an RRC connection is established between base station 210A1 and UE100. Cell C11 is a serving cell for UE100.

In the following, communication between UE100 and base station 210A1 may be communication between UE100 and cell C11 in which UE100 resides. Communication between the UE 100 and the base station 210B (cell C12) is the same.

Step S101:
The UE 100 and the base station 210A1 perform a pre-configuration procedure for setting the transition to the RRC inactive state between the UE 100 and the base station 210A1. Specifically, the communication unit 120 of the UE 100 transmits a Pre-configuration Request message to the base station 210A1. The radio communication unit 212 of the base station 210A1 receives the preset request message from the UE100. The pre-configuration procedure is performed before the UE 100 transmits the switching notification, that is, before the base station 210A1 receives the switching notification from the UE 100. In this operation example, the operations in steps S101 and S102 are executed in the preset procedure.

The pre-configuration request message may be a message for requesting suspend configuration information via an RRC reconfiguration message. Details of the suspend setting information will be described later.

The preset request message is expectation information (RRC_INACTIVE expectation) indicating that transition from the RRC connected state to the RRC inactive state is expected in the first network 200A when switching communication from the first network 200A to the second network 200B. may contain

The UE 100 may transmit a preset request message, for example, when receiving a service that is expected to be continuously exchanged in the first network 200A. Note that the UE 100 may use an existing message (eg, UE Assistance Information message) as the preset request message.

Step S102:
The radio communication unit 212 of the base station 210A1 transmits the RRC reconfiguration message to the UE100. The communication unit 120 of the UE 100 receives the RRC reconfiguration message from the base station 210A1.

The RRC reconfiguration message is a message for modifying the RRC connection between the first network 200A and the UE 100. In response to receiving the pre-configuration request message, wireless communication unit 212 can transmit an RRC reconfiguration message in response to the pre-configuration request message. The RRC reconfiguration message includes suspend configuration information (suspendConfig). Therefore, the radio communication unit 212 transmits the suspend setting information to the UE 100 using the RRC reset message.

The suspend setting information indicates settings for the RRC inactive state. Note that the suspend setting information includes, for example, RNA information (ran-NotificationAreaInfo). The RNA information may include a list of cells set as RAN (radio access network) areas (cellList) and a list of RAN area codes or RA codes as RAN areas (ran-AreaConfigList). The control unit 130 of the UE 100 can determine whether the UE 100 exists within the RAN area based on the RNA information. In addition, when the UE 100 exists outside the RNA area, an RNA update procedure for updating the RAN area is performed.

If the base station 210A1 does not approve the request from the UE 100, the base station 210A1 does not have to transmit the RRC reconfiguration message. The base station 210A1 may not send an RRC reconfiguration message including suspend configuration information, eg, if it does not support the pre-configuration procedure.

The control unit 130 of the UE 100 holds suspend setting information. Even if the UE 100 receives the suspend setting information, the UE 100 does not immediately transition to the RRC inactive state, so it is not necessary to immediately apply the suspend setting information.

After that, the UE 100, for example, measures radio quality (for example, reception strength, reception quality, etc.) for cell C11, which is the serving cell, and adjacent cells. UE100 performs the process of step S103, when the conditions which report a measurement result are satisfy|filled.

Step S103:
The communication unit 120 of the UE 100 transmits a measurement report including measurement results to the base station 210A1. The radio communication unit 212 of the base station 210A1 receives the measurement report from the UE100.

The control unit 214 of the base station 210 determines whether or not to handover the UE 100 from the cell C11 to another cell based on the measurement report. For example, when the measurement result included in the measurement report indicates that the radio quality of cell C11 is worse than the threshold and the radio quality of cell C12 is better than the threshold, the control unit 214 transfers the UE 100 from cell C11 to cell C12. determine to execute handover to

When determining to hand over the UE 100 to a cell managed by another base station 210, the control unit 214 executes the process of step S104. In this operation example, the description will proceed assuming that the control unit 214 determines to hand over the UE 100 to the cell C12 of the base station 210A2.

Step S104:
Network communication unit 213 of base station 210A1 transmits a handover request message to base station 210A2. The network communication unit 213 of the base station 210A2 receives the handover request message from the base station 210A1.

The handover request message is a message requesting preparation of resources for handover of UE 100 . In this operational example, the handover request message is sent after performing the pre-configuration procedure.

The handover request message contains pre-configuration information (Pre-configuration) about the pre-configuration procedure. The controller 214 can include pre-configuration information in the handover request message. The pre-configuration information may include suspend configuration information sent to the UE 100 in the pre-configuration procedure.

The control unit 214 may include suspend setting information in the handover request message based on the expectation information. For example, the control unit 214 may include suspend setting information in the handover request message when the expectation information indicates that the transition to the RRC inactive state is expected. Also, when transmitting the suspend setting information to the UE 100, the control unit 214 may include the suspend setting information in the handover request message.

The handover request message may contain handover preparation information that is used to transfer information used to the target base station to handover to during handover preparation. The handover preparation information may include RRC reconfiguration generated by base station 210A1. Therefore, the handover request message contains the RRC reconfiguration. The RRC reconfiguration in the handover request message may contain preconfiguration information. Also, the handover preparation information may include pre-configuration information within RRC re-configuration or may include pre-configuration information outside of RRC re-configuration. Also, the handover request message may include pre-configuration information within the handover preparation information and may include pre-configuration information outside of the handover preparation information.

The control unit 214 of the base station 210A2 may determine that suspend setting information is set in the UE 100, for example, when the handover request message includes a pre-setting procedure. On the other hand, the control unit 214 may determine that the suspend setting information is not set in the UE 100 when the pre-setting procedure is not included in the handover request message.

If the control unit 214 of the base station 210A2 approves the handover request of the UE 100, it executes the process of step S105. Note that the control unit 214 may transmit a handover rejection message when not approving the handover request.

Step S105:
The network communication unit 213 of the base station 210A2 transmits a handover request acknowledgment message to the base station 210A1. Network communication unit 213 of base station 210A1 receives the handover request acknowledgment message from base station 210A2.

The handover request acknowledgment message is a message to inform the source base station about the resources prepared at the target base station. The handover request acknowledgment message is a response message to the handover request.

Step S106:
The radio communication unit 212 of the base station 210A1 transmits to the UE 100 an RRC reconfiguration message used for performing handover from (the cell C11 of) the base station 210A1 to (the cell C12 of) the base station 210A2. Radio communication section 212 transmits an RRC reconfiguration message to UE 100 in response to the reception of the handover request acknowledgment message. Communication unit 120 of UE 100 receives the RRC reconfiguration message. UE100 performs the process of step S107 according to reception of an RRC reset message.

Note that the RRC reconfiguration message includes at least the identifier of the handover destination cell C12 and all the information necessary to access cell C12.

Step S107:
Controller 130 of UE 100 executes a random access procedure between UE 100 and base station 210A2 in order to execute handover of base station 210A2 to cell C12. Thereby, the control unit 130 of the UE 100 moves the RRC connection to the base station 210A2. An RRC connection is established between UE 100 and base station 210A2 (cell C12). The control unit 130 of the UE 100 executes the process of step S108.

Step S108:
Communication unit 120 of UE 100 transmits an RRC reconfiguration complete message to base station 210A2 (cell C12). The radio communication unit 212 of the base station 210A2 receives the RRC reconfiguration complete message from the UE100.

The control unit 130 of the UE 100 retains the suspend setting information received by the RRC reconfiguration message in step S102 even after executing the handover.

Thereafter, as shown in FIG. 6, the UE 100 is located in cell C12 managed by base station 210A2 of first network 200A, and located in cell C2 managed by base station 210B of second network 200B. there is UE 100 is in an RRC connected state in first network 200A and is communicating in first network 200A. The UE 100 receives services such as voice communication from the first network 200A, for example. Note that "during communication in the first network" means that the UE 100 is at least in an RRC connected state in the first network 200A, and does not necessarily have to continuously exchange data with the first network 200A. good.

As shown in FIG. 6, the UE 100 is in RRC idle state in the second network 200B. Note that the UE 100 may be in the RRC inactive state in the second network 200B. UE 100 monitors paging from second network 200B while maintaining the RRC connected state in first network 200A. The UE 100 can monitor paging, for example, during a communication interruption period with the first network 200A.

In the following, similarly to the above, communication between UE 100 (RRC processing unit 131) and base station 210A2 is, for UE 100, UE 100 (RRC processing unit 131) and cell C12 of base station 210A2, that is, the cell in which UE 100 is located. It may be communication with C12. Communication between UE 100 (RRC processing unit 131) and base station 210B (cell C2) is the same.

Communication between UE 100 and nodes belonging to first network 200A (eg, base station 210A (cell C1), mobility management device 221A, gateway device 222A) may be referred to as communication between UE 100 and first network 200A. . The same applies to the UE 100 and nodes belonging to the second network 200B.

In the following description, the RRC processing unit 131 and the NAS processing unit 132 of the UE 100 communicate with the first network 200A (specifically, transmit/receive/notify messages, etc.) via the communication unit 120. For the sake of simplification, the description of communication via the communication unit 120 will be omitted as appropriate. Similarly, the explanation that the communication between the RRC processing unit 131 and the NAS processing unit 132 of the UE 100 and the second network 200B is communication via the communication unit 120 will be omitted as appropriate. Therefore, the transmission and/or reception of messages by the RRC processing unit 131 and NAS processing unit 132 of the UE 100 may be transmission and/or reception of messages by the communication unit of the UE 100 .

Further, the explanation will proceed assuming that each of the mobility management device 221A, which is the core network device of the first network 200A, and the mobility management device 221B, which is the core network device of the second network 200B, is an AMF.

Step S201:
The AMF 221B transmits a paging request requesting transmission of paging addressed to the UE 100 to the base station 210B. Network communication unit 213 of base station 210B receives the paging request.

The paging request may include paging cause information (Paging Cause) indicating the reason for paging. The paging reason information may indicate, for example, whether the reason for paging is a voice call.

Step S202:
The radio communication unit 212 of the base station 210B transmits a paging message (Paging) addressed to the UE 100 in response to receiving the paging request. The communication unit 120 of the UE 100 receives the paging message from the base station 210B. Communication unit 120 receives a paging message from second network 200B during communication in the RRC connected state in first network 200A.

A paging message is used for notification to one or more UEs 100 . A paging message is an RRC layer message. A paging message contains the identifier (ID) of UE100, for example. More specifically, for example, the paging message includes a list of paging records, and one paging record in the list includes the UE 100 ID. For example, the ID is the UE 100's 5G-S-TMSI or full I-RNTI (Inactive Radio Network Temporary Identifier).

The paging message may include paging reason information. The paging reason information may be associated with the ID of the UE 100, for example.

When the paging message includes the ID of UE 100 and UE 100 is in the RRC inactive state for second network 200B while communicating with first network 200A, RRC processing section 131 performs the process of step S105. can run.

Note that RRC processing section 131 may be in a case where the paging message includes the ID of UE 100 and UE 100 is not communicating with first network 200A. If it is in the active state, it may perform the specified processing upon receiving the paging message without performing the subsequent processing.

Step S203:
The RRC processing unit 131 provides a paging reception notification to the NAS processing unit 132 . The NAS processing unit 132 receives from the paging reception notification. The paging reception notification is for notifying that the UE 100 has received paging. The RRC processing unit 131 may indicate to the NAS processing unit 132 that the paging message has been received when the UE 100 is in the RRC inactive state by the paging reception notification.

The paging acknowledgment may include paging reason information. Note that the paging reception notification may include the identifier of the UE 100, for example, when the UE 100 is in the RRC idle state.

The NAS processing unit 132 determines the priority of communication with the first network 200A and communication with the second network 200B. Specifically, the NAS processing unit 132 determines which of the communication with the first network 200A and the communication with the second network 200B corresponding to paging is prioritized (or which one is preferred). Note that the NAS processing unit 132 may determine which of the connection with the first network 200A and the connection with the second network 200B is more important.

The NAS processing unit 132 determines which of the communication with the first network 200A and the communication with the second network 200B corresponding to paging should be prioritized based on the service provided by the first network 200A. You can For example, when the NAS processing unit 132 receives the paging reason information, based on the paging reason indicated by the paging reason information, the NAS processing unit 132 separates communication with the first network 200A and communication with the second network 200B corresponding to paging. You may decide which one to give priority to. In this operation example, the NAS processing unit 132 determines that communication with the second network 200B that supports paging has priority over communication with the first network 200A.

Step S204:
The NAS processing unit 132 provides a switching notification instruction (long time switch instruction) to the RRC processing unit 131 . The RRC processing unit 131 receives the switching notification instruction from the NAS processing unit 132 .

The switching notification instruction instructs the RRC processing unit 131 to transmit a switching notification (long time switch). The switching notification instruction may instruct transmission of an inactive switching notification described later, or may instruct transmission of an idle switching notification described later. The NAS processing unit 132 may instruct transmission of an inactivity switching notification when expecting a transition to the RRC inactive state. The NAS processing unit 132 may instruct transmission of an idle switching notification when expecting a transition to the RRC idle state.

Based on at least one of the service provided by the first network 200A and the paging reason information (paging reason), the NAS processing unit 132 expects a transition to the RRC inactive state or waits for a transition to the RRC idle state. It may decide whether to expect a transition. In this operation, it is assumed that the NAS processing unit 132 has decided to expect a transition to the RRC inactive state. Therefore, the switching notification instruction instructs transmission of an inactive switching notification.

Step S205:
The RRC processing unit 131 controls transmission of switching notification to the first network 200A. The RRC processing unit 131 transmits a switching notification to the base station 210A2 using an RRC message. The radio communication unit 212 of the base station 210A2 receives the switching notification from the UE100.

The switch notification is a notification to temporarily leave the first network 200A in order to switch communication from the first network 200A to the second network 200B. More specifically, the switching notification is a notification to the effect that the first network 200A will transition from the RRC connected state (that is, leave).

A switch notification may be referred to as an inactive switch notification when it indicates that the first network 200A expects a transition from the RRC connected state to the RRC inactive state. Therefore, the inactive switching notification is, for example, a switching notification including expectation information (RRC_INACTIVE expectation) indicating that the first network 200A expects a transition from the RRC connected state to the RRC inactive state. The RRC processing unit 131 transmits an inactive switching notification as the switching notification.

Note that the switching notification may be referred to as an idle switching notification when it indicates that the first network 200A expects a transition from the RRC connected state to the RRC idle state. Therefore, the idle switching notification may be, for example, a switching notification including expectation information (RRC_IDLE expectation) indicating that the first network 200A expects a transition from the RRC connected state to the RRC idle state.

Step S206:
The RRC processing unit 131 starts a reception timer. The RRC processing unit 131 starts the reception timer in response to the transmission of the inactivity switching notification in step S205.

The RRC processing unit 131 holds a reception timer. The reception timer is a timer that counts a predetermined time after the inactivity switching notification is transmitted to the first network 200A. Therefore, the receive timer expires after the predetermined time has elapsed. The operation of UE 100 when the reception timer expires will be described later.

The RRC processing unit 131 may receive from the first network 200A a timer value indicating a predetermined time to be set in the reception timer. The RRC processing unit 131 may receive, for example, a timer value from the base station 210A2 (cell C12). The RRC processing unit 131 may receive the timer value by, for example, an RRC reconfiguration message. The timer value may have been received by the UE 100 from the base station 210A1 (cell C11) in step S102, or may have been received at another timing.

Step S207:
The radio communication unit 212 of the base station 210A2 transmits to the UE 100 a switch notification response (long time switch response) that is a response to the switch notification. However, in this operation example, the UE 100 cannot receive the switching notification response. Although base station 210A2 transmits an RRC release message to UE 100, UE 100 may not be able to receive the RRC release message.

Step S208:
The reception timer expires when a predetermined period of time elapses from the transmission of the switching notification.

Step S209:
When the RRC processing unit 131 does not receive a response to the inactive switching notification from the first network 200A, the RRC processing unit 131 switches from the RRC connected state to the RRC inactive state in the first network 200A using the suspend setting information held in step S102. Perform transition control. If the control unit 130 of the UE 100 does not receive a response to the inactivity switching notification from the first network 200A by the time the reception timer expires, it uses the retained suspend setting information to exit the RRC connected state in the first network 200A. Control to transition to the RRC inactive state may be performed. For example, the control unit 130 can apply parameter values included in the retained suspend setting information. Therefore, the UE 100 can autonomously transition to the RRC inactive state even if it does not receive the switching notification response.

Step S210:
After transitioning to the RRC inactive state in first network 200A, UE 100 communicates with second network 200B.

(2) Second Operation Example With reference to FIG. 7, a second operation example will be described, mainly focusing on differences from the above-described operation example. In the second operation example, a case will be described in which the UE 100 receives a response to the switching notification before the reception timer expires. Note that the operations before the operations in FIG. 7 are the same as those in the first operation example, so descriptions thereof will be omitted.

Steps S301 to S306:
This is the same as steps S201 to S206.

Step S307:
The radio communication unit 212 of the base station 210A2 transmits a switching notification response to the UE100. The RRC processing unit 131 receives the switching notification response from the base station 210A2. A switch notification response is sent by an RRC message.

Also, the radio communication unit 212 of the base station 210A2 transmits an RRC release message to the UE100. Communication unit 120 (RRC processing unit 131) of UE 100 receives the RRC release message from base station 210A2. The RRC release message may contain suspend configuration information. The suspend setting information may be the same as or different from the suspend setting information included in the RRC reconfiguration message in step S102. The control unit 214 of the base station 210A2 may include, in the suspend setting information, the same parameter value as the suspend setting information transmitted in step S102, for example. Alternatively, the control unit 214 may include, in the suspend setting information, only parameter values updated from the suspend setting information transmitted in step S102, for example. If the parameter value has not been updated from the suspend setting information transmitted in step S102, the control unit 214 does not have to include the parameter value (information element) to be applied to the UE 100 in the suspend setting information. That is, the suspend setting information does not include parameter values to be applied to the UE 100, and the contents of the suspend setting information may be absent.

Although the base station 210A2 separately transmits the switching notification response and the RRC release message, the present invention is not limited to this. Base station 210A2 may, for example, send an RRC release message as a handover notification response.

Step S308:
The RRC processing unit 131 stops the reception timer. The RRC processing unit 131 may stop the reception timer in response to receiving the switching notification response or the RRC release message.

Step S309:
The RRC processing unit 131 (control unit 130), in response to stopping the reception timer or receiving the RRC release message, based on the suspend setting information included in the response, switches from the RRC connected state to the RRC connection in the first network 200A. Control to transition to the active state may be performed.

The RRC processing unit 131 (control unit 130) can apply parameter values included in the suspend setting information included in the RRC release message. For example, if the suspend setting information includes only some parameter values (information elements) or the suspend setting information does not include parameter values (information elements) that should be applied to the UE 100, the RRC processing unit 131 does not include the suspend setting information. may be updated and applied, and other parameter values already held in step 102 may be applied as is. Therefore, the UE 100 operates in the RRC inactive state in the first network 200A based on the suspend setting information received before handover.

Step S310:
This is the same as step S210.

(3) Third Operation Example A third operation example will be described with reference to FIG. 8, mainly focusing on differences from the above-described operation example. In the third operation example, the UE 100 determines whether or not to omit the pre-configuration procedure after handover.

Step S401:
The communication unit 120 of the UE 100 transmits a preset request message to the base station 210A1 as in step S101. The radio communication unit 212 of the base station 210A1 receives the preset request message from the UE100.

The expectation information included in the pre-configuration request message may indicate, for example, that the first network 200A expects to transition to the RRC inactive state instead of the RRC idle state. The expectation information may also indicate, for example, that the first network 200A expects at least a transition to the RRC inactive state. In this case, the expectation information indicates, for example, that a transition to the RRC inactive state is expected in a predetermined case (hereinafter referred to as a first condition), and a case other than the predetermined case (hereinafter referred to as a second condition). appropriately called) to indicate that it expects to transition to the RRC idle state.

The first condition may be, for example, that the UE 100 is provided with a service in which continuous communication such as a voice call is assumed in the first network 200A at the time of transmission of a switching notification, which will be described later. The second condition may be a case where the UE 100 is provided with a service for which continuous exchange is not assumed. Further, the first condition is, for example, that the UE 100 transmits information (a so-called busy indicator) indicating that communication with the first network 200A is prioritized over communication with the second network 200B to the second network 200B. No ongoing interaction between the UE 100 and the second network 200B, such as sending a switchover notification for the second network 200B, or renewing the registration of the second network 200B. The second condition may be, for example, that the UE 100 responds to paging of the second network 200B. Also, the second condition may be that the UE 100 responds to the paging of the second network 200B and receives a service such as a voice call that is assumed to be continuous communication.

Steps S402 and S403:
This is the same as steps S102 and S103.

Step S404:
The network communication unit 213 of the base station 210A1 transmits a handover request message to the base station 210A2 as in step S104.

The controller 214 of the base station 210A1 may include preset information in the handover request message. Specifically, the control unit 214 may include the suspend setting information and the expectation information received from the UE 100 in the handover request message.

The control unit 214 of the base station 210A2 may generate suspend setting information based on preset information included in the handover request message. The control unit 214 generates suspend setting information (hereinafter referred to as second suspend setting information) based on, for example, suspend setting information (hereinafter referred to as first suspend setting information) received from the base station 210A1. may The second suspend setting information is suspend setting information applied to the UE 100 after handover.

The control unit 214 may generate the second suspend setting information, for example, based on the expectation information received from the base station 210A1. The parameter value included in the second suspend setting information may be the same parameter value as the first suspend setting information, or may be a different parameter value. The second suspend setting information may include only parameter values different from the parameter values included in the first suspend setting information. When the control unit 214 determines that the same parameter value as the first suspend setting information should be applied to the UE 100, even if the second suspend setting information that does not include the parameter value (information element) to be applied to the UE 100 is generated. good.

Step S405:
The network communication unit 213 of the base station 210A2 transmits a handover request acknowledgment message to the base station 210A1, as in step S105.

The control unit 214 may include the second suspend configuration information (suspendConfig) as information to be transmitted to the UE 100 in the handover request acknowledge message. When including the second suspend setting information in the handover request approval message, the control unit 214 includes full configuration information (fullConfig) for releasing the setting information set in the UE 100 from the handover source cell C11 in the handover request approval message. Absent. On the other hand, if the control unit 214 does not include the second suspend setting information in the handover request approval message, the control unit 214 may include the full configuration information in the handover request approval message.

Step S406:
Similarly to step S106, the radio communication unit 212 of the base station 210A1 transmits to the UE 100 an RRC reconfiguration message used for executing handover from (the cell C11 of) the base station 210A1 to (the cell C12 of) the base station 210A2. Send. The communication unit 120 of the UE 100 receives the RRC reconfiguration message from the cell C11.

The control unit 214 of the base station 210A1 may include information to be transmitted to the UE 100 included in the handover request acknowledge message (for example, second suspend setting information, full configuration information, etc.) in the RRC reconfiguration message.

Step S407:
Based on the RRC reconfiguration message, the control unit 130 of the UE 100 determines whether or not to omit the preconfiguration procedure between the UE 100 and the cell C12 after handover to the cell C12. The control unit 130 may execute the determination operation shown in FIG. 9 . The determination operation will be described later.

Steps S408 and S409:
This is the same as steps S107 and S108.

Step S410:
The wireless communication unit 212 of the base station 210A2 broadcasts a system information block (SIB). Communication unit 120 of UE 100 receives the SIB from cell C12 (base station 210A2).

The SIB may contain supporting information indicating that cell C12 supports performing pre-configuration procedures. If cell C12 supports execution of the pre-configuration procedure, the controller 214 of base station 210A2 may include support information in the SIB indicating that cell C12 supports execution of the pre-configuration procedure. On the other hand, if the cell C12 does not support the execution of the pre-configuration procedure, the control unit 214 may include support information in the SIB indicating that the cell C12 does not support the execution of the pre-configuration procedure. Alternatively, the control unit 214 may not include the support information in the SIB.

The control unit 130 of the UE 100 may determine, based on the SIB, whether or not to execute the presetting procedure after handover to the cell C12. For example, when the SIB includes support information indicating that the cell C12 supports execution of the pre-configuration procedure, the control unit 130 determines to perform the pre-configuration procedure after the handover to the cell C12. In this case, the control unit 130 may execute the process of step S411. On the other hand, if the SIB does not include support information indicating that the cell C12 supports execution of the pre-configuration procedure, the control unit 130 determines to omit the pre-configuration procedure after the handover to the cell C12. In this case, the control unit 130 may omit the process of step S411.

Step S411:
The communication unit 120 of the UE 100 transmits a preset request message to the base station 210A2 as in step S101. The radio communication unit 212 of the base station 210A2 receives the preset request message from the UE100.

Step S412:
The radio communication unit 212 of the base station 210A2 transmits the RRC reconfiguration message to the UE 100 as in step S102. The communication unit 120 of the UE 100 receives the RRC reconfiguration message from the base station 210A.

Subsequent operations are the same as those in the first operation example or the second operation example.

(Example of judgment operation)
A determination operation example of the UE 100 will be described with reference to FIG. 9 .

Step S501:
Control unit 130 determines whether the RRC reconfiguration message includes full configuration information. That is, the control unit 130 determines whether or not to execute a full configuration procedure for releasing the setting information set in the UE 100 . The control unit 130 determines to execute the full configuration procedure when the RRC reconfiguration message includes the full configuration information. The control unit 130 determines not to perform the full configuration procedure when the RRC reconfiguration message does not include the full configuration information. Therefore, if the RRC reconfiguration message includes full configuration information (Yes), the process of step S507 is executed. On the other hand, if the RRC reconfiguration message does not contain full configuration information (No), the process of step S502 is executed.

Step S502:
The control unit 130 determines whether the RRC reconfiguration message includes suspend setting information (that is, second suspend setting information). If the RRC reset message includes suspend setting information (Yes), the process of step S503 is executed. On the other hand, if the RRC reconfiguration message does not include suspend setting information (No), the process of step S507 is executed.

Step S503:
The control unit 130 determines to omit the pre-configuration procedure after the handover to the cell C12. Note that the control unit 130 may consider that the pre-setting information is handed over from the cell C11 to the cell C12 by including the suspend setting information in the RRC re-setting message.

Step S504:
Control unit 130 determines whether or not there is content in suspend setting information (that is, second suspend setting information). That is, the control unit 130 determines whether or not the suspend setting information includes parameter values (information elements) to be applied to the UE 100 . If there is suspend setting information content, or if the suspend setting information does not include the parameter value to be applied to the UE 100 (Yes), the process of step S505 is executed. On the other hand, if there is suspend setting information content, that is, if the suspend setting information does not include the parameter value to be applied to the UE 100 (No), the process of step S506 is executed.

Step S505:
Based on the parameter values (information elements) included in the suspend setting information (ie, the second suspend setting information), the control unit 130 determines the parameters included in the held suspend setting information (ie, the first suspend setting information). Update value. That is, control unit 130 updates the parameter values included in the first suspend setting information received in the pre-setting procedure, based on the parameter values included in the second suspend setting information.

Step S506:
The control unit 130 maintains the parameter values included in the retained suspend setting information (that is, the first suspend setting information).

Step S507:
The control unit 130 discards (or releases) the retained suspend setting information (that is, the first suspend setting information). The control unit 130 may erase (or clear) the parameter value included in the first suspend setting information.

If the first suspend setting information is discarded, the control unit 130 may determine to execute the pre-setting procedure in the post-handover cell C12. The control unit 130 may determine to perform the pre-configuration procedure in cell C12 after handover if the SIB from cell C12 includes the aforementioned support information. Note that the control unit 130 may consider that the preset information has not been handed over from the cell C11 to the cell C12.

[Other embodiments]
In the above-described embodiments, the switching notification for each operation example may be called a long time switch, or may be called another name. The switching notification may be, for example, a message or information element used in a switching procedure for leaving RRC_CONNECTED state.

In the above-described embodiment, the base station 210A1 transmits the suspend setting information to the UE 100 using the RRC reconfiguration message in response to receiving the preset request message, but the present invention is not limited to this. The base station 210A1 may transmit the suspend configuration information to the UE 100 using the RRC reconfiguration message even if it does not receive the preset request message. Note that the base station 210A may transmit suspend setting information to the UE 100 using an RRC message other than the RRC reconfiguration message and the RRC release message.

In the above-described embodiment, the timer value may be pre-stored in the UE 100. Therefore, the UE 100 does not have to receive the timer value from the first network 200A.

In the above-described embodiment, the reception timer is used to control the transition to the RRC inactive state, but the present invention is not limited to this. The control unit 130 of the UE 100, for example, when the reception strength and/or reception quality of the radio signal from the cell C1 of the base station 210 is below a threshold value, determines to transition to the RRC inactive state, and the process of step S111. may be started.

In the above-described embodiments, the handover between base stations was described as an example, but the present invention is not limited to this. The operations described above may also be performed in an intra-base station handover. Thus, in the case of handover from a cell managed by base station 210A1 to another cell managed by base station 210A1, base station 210A1 may, for example, include the latest Suspend setting information may be included.

The steps in the operation of the above-described embodiments do not necessarily have to be performed in chronological order in the order depicted in the flow diagrams or sequence diagrams. For example, the steps in the operations may be performed out of order or in parallel with the order illustrated in the flow diagrams or sequence diagrams. Also, some steps in the operation may be omitted and additional steps may be added to the process. Furthermore, each operation flow described above is not limited to being implemented independently, but can be implemented by combining two or more 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.

A program that causes a computer to execute each process performed by the UE 100 or the base station 210 may be provided. The program may be recorded on a computer readable medium. A computer readable medium allows the installation of the program on the 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, but may be, for example, a recording medium such as CD-ROM or DVD-ROM. Alternatively, circuits for executing each process performed by the UE 100 or the base station 210 may be integrated, and at least part of the UE 100 or the base station 210 may be configured as a semiconductor integrated circuit (chipset, SoC).

It should be noted that in the above embodiments, "transmit" may mean performing processing of at least one layer in the protocol stack used for transmission, or transmitting signals wirelessly or by wire. It may mean physically transmitting. Alternatively, "transmitting" may mean a combination of performing the at least one layer of processing and physically transmitting the signal wirelessly or by wire. Similarly, "receive" may mean performing processing of at least one layer in the protocol stack used for reception, or physically receiving a signal wirelessly or by wire. may mean that Alternatively, "receiving" may mean a combination of performing the at least one layer of processing and physically receiving the signal wirelessly or by wire.

Although the embodiments have been described in detail with reference to the drawings, the specific configuration is not limited to the above, and various design changes can be made without departing from the spirit of the invention.

1: mobile communication system 100: UE
101: antenna 120: communication unit 121: reception unit 122: transmission unit 130: control unit 131: RRC processing unit 132: NAS processing unit 200: base station 200A: first network 200B: second network 210A, 210A1, 210A2: base Station 210B: Base station 211: Antenna 212: Wireless communication unit 212a: Reception unit 212b: Transmission unit 213: Network communication unit 214: Control unit 220A: Core network 220B: Core network 221A: Mobility management device 221B: Mobility management device 222A: Gateway device 222B: gateway device

Claims (7)

Having a user equipment (100) communicating with a first network (200A) using a first subscriber identity module (111) and communicating with a second network (200B) using a second subscriber identity module (112) A base station (210A1) of the first network (200A) in a mobile communication system (1),
Before receiving a switching notification from the user device (100) for transitioning from the RRC connected state in the first network (200A) and switching communication to the second network (200B), the user device (100) and the first network (200A), a control unit (214) that performs a pre-configuration procedure for configuring a transition to the RRC inactive state;
a network communication unit (213) that transmits a handover request message requesting preparation of resources for handover of the user equipment (100) to a neighboring base station (210A2) after executing the pre-configuration procedure;
The base station, wherein the handover request message includes pre-configuration information regarding the pre-configuration procedure. The base station according to claim 1, wherein said pre-configuration information comprises suspend configuration information indicating a configuration for said RRC inactive state sent to said user equipment (100) in said pre-configuration procedure. In the presetting procedure, when switching communication from the first network (200A) to the second network (200B), transition to the RRC inactive state instead of the RRC idle state in the first network (200A) Further comprising a wireless communication unit (212) that receives expectation information indicating expectations from the user device (100),
The base station according to Claim 2, wherein the control unit (214) includes the suspend setting information in the handover request message based on the expectation information. In the presetting procedure, when switching communication from the first network (200A) to the second network (200B), at least a transition to the RRC inactive state is expected in the first network (200A). further comprising a wireless communication unit (212) for receiving expected information to be indicated from the user device (100);
The base station according to any one of claims 1 to 3, wherein said controller (214) includes said expectation information in said handover request message. the handover request message includes an RRC reconfiguration generated by the base station (210A1);
5. The base station according to any one of claims 1 to 4, wherein said RRC reconfiguration in said handover request message comprises said pre-configuration information. The network communication unit (213) transmits a response message to the handover request message including suspend setting information indicating setting of transition to the RRC inactive state in the neighboring base station (210A2) to the neighboring base station (210A2). receive from
further comprising a radio communication unit (212) that transmits to the user equipment (100) an RRC reconfiguration message used to perform handover from the base station (210A1) to the neighboring base station (210A2);
The base station according to any one of claims 1 to 5, wherein said RRC reconfiguration message includes said suspend configuration information. A user equipment (100) communicating with a first network (200A) (200A) using a first subscriber identity module (111) and communicating with a second network (200B) using a second subscriber identity module (112) A communication control method executed by a base station (210A1) of the first network (200A) in a mobile communication system (1) having
Before receiving a switching notification from the user device (100) for transitioning from the RRC connected state in the first network (200A) and switching communication to the second network (200B), the user device (100) and the first network (200A), performing a pre-configuration procedure for configuring a transition to the RRC inactive state;
sending a handover request message to a neighboring base station (210A2) requesting preparation of resources for handover of the user equipment (100) after performing the pre-configuration procedure;
The communication control method, wherein the handover request message includes pre-configuration information regarding the pre-configuration procedure.

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