COMMUNICATION DEVICE, CONTROL METHOD AND PROGRAM FOR COMMUNICATION DEVICE

Abstract

To avoid delay in providing services on a network while reducing power consumption in a communication device that simultaneously connects to a plurality of base stations.SOLUTION: A communication device performs control to transition from an RRC_CONNECTED state conforming to the 3GPP (3rd Generation Partnership Project) (R) standard to an RRC_INACTIVE state after a wireless communication path is established between a first base station and a second base station, and after the transition to the RRC_INACTIVE state, to receive notification signals from the first base station and the second base station, respectively.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a communication device that can be connected to a plurality of networks, and a control method and program for the communication device. [Background technology]

[0002] 2. Description of the Related Art In recent years, there have been imaging devices that are capable of recording moving images captured within the device itself, and, as necessary, streaming moving images and distributing still images via public wireless communication lines. In this way, an imaging device that delivers images intermittently does not need to be constantly connected to a public wireless communication line to reserve a bandwidth. For this reason, a communication device (User Equipment: UE) connected to a fourth-generation (hereinafter, referred to as "4G") public wireless communication line transitions between a number of states. Specifically, the communication device transitions between two states: RRC_CONNECTED, in which a communication bandwidth has been reserved and unicast data communication is in progress, and RRC_IDLE, in which a communication bandwidth has not been reserved and unicast data communication is not in progress. In the latter RRC_IDLE state, the communication device can only receive broadcast data.

[0003] In addition, in communication devices connected to public wireless lines of 5th generation (hereinafter referred to as "5G") New Radio (NR), RRC_INACTIVE is added to the above two states. In this RRC_INACTIVE state, the communication band is secured and there is no unicast data communication, that is, only broadcast data can be received. By using these multiple RRC (Radio Resource Control) state transitions, it is possible to save power and use wireless communication resources effectively. For example, in the above-mentioned imaging device, power saving and effective use of wireless communication resources can be achieved by setting the imaging device to the RRC_CONNECTED state while imaging a scene that requires distribution, and transitioning to the RRC_INACTIVE state while imaging a scene that does not require distribution.

[0004] Patent Document 1 discloses a mobile station that can specify whether multiple carrier bands in carrier aggregation are continuous or intermittent, and can switch between using a common or separate timer for intermittent reception installed for a primary cell and a secondary cell. By executing intermittent reception control in carrier aggregation in accordance with the transmission cycle of a control signal from a base station, high power consumption of the mobile station can be reduced. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-161076 A Summary of the Invention [Problem to be solved by the invention]

[0006] In 5G (NR), communication devices can connect to multiple base stations (BS) via public wireless communication lines and use Dual Connectivity (DC) to simultaneously provide communication services. By bundling multiple carriers between multiple base stations, broadband data communication becomes possible.

[0007] However, the details of a control method for transitioning from RRC_CONNECTED to RRC_INACTIVE in a communication device using two base stations in DC have not yet been specified in the 3GPP (registered trademark) standard. Specifically, in the 3GPP standard, during RRC_INACTIVE, the communication device must monitor the paging channel (hereinafter referred to as "PCH"), which is a control channel that receives control signals transmitted from the base station being used to all communication devices within the cell. However, it is not specified whether a communication device executing DC must monitor the PCH of the base station of the master cell group or the PCH of the base station of the secondary cell group during RRC_INACTIVE.

[0008] Here, if the communication device continues to monitor the PCHs of both the base station of the master cell group and the base station of the secondary cell group during RRC_INACTIVE, standby power consumption increases. On the other hand, if the communication device is made to monitor only the PCH of the base station of the master cell group during RRC_INACTIVE, for example, the change in the wireless line quality of the base station of the secondary cell group cannot be detected. Therefore, whether or not the DC using two base stations can return to RRC_CONNECTED cannot be determined until the DC returns to RRC_CONNECTED, and the response when resuming a service on standby in the communication device is reduced.

[0009] The present invention has been made in consideration of at least one of the above problems. One aspect of the present invention aims to prevent a delay in the provision of services on a network while reducing power consumption in a communication device that simultaneously connects to multiple base stations. [Means for solving the problem]

[0010] In order to solve the above problems, a communication device according to the present invention comprises: of Base station and second of A transition means for transitioning from an RRC_CONNECTED state conforming to a 3GPP (3rd Generation Partnership Project standard) (registered trademark) standard to an RRC_INACTIVE state after a wireless communication path with a base station is established, and a transition means for transmitting a notification from each of the first base station and the second base station after transitioning to the RRC_INACTIVE state. Paging signal conforming to the 3GPP standard A control means for controlling the receiving device to receive a signal; In the control step, a reception control is performed to try to receive paging signals from the first base station and the second base station by listening to a first paging channel on which the first base station broadcasts paging signals and a second paging channel on which the second base station broadcasts paging signals. R Characterized by . Effect of the Invention

[0011] According to one aspect of the present invention, in a communication device that is simultaneously connected to a plurality of base stations, it is possible to reduce power consumption and avoid delays in the provision of services on a network. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a block diagram showing an example of the hardware and functional configuration of the communication device according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing state transitions of a communication device (UE) defined in 3GPP. [Diagram 3] 1A and 1B are diagrams showing the monitoring states of the paging channel in RRC_CONNECTED and RRC_INACTIVE during DC execution, respectively. [Figure 4] FIG. 2 is a diagram showing an example of a network configuration of a system for uploading images captured by a capture device (UE) moving between cells according to the first embodiment. [Diagram 5] 6 is a flowchart showing an example of a processing procedure of a monitoring control process executed when the communication device according to the first embodiment monitors a moving speed. [Figure 6] 10 is a flowchart showing an example of a processing procedure of a process in which a communication device according to the first embodiment checks a PCH signal received from a PCH during RRC_INACTIVE. [Figure 7] 10 is a flowchart showing an example of a processing procedure of a process for checking a PCH signal received from a PCH when the communication device according to the first embodiment transitions to an RRC_CONNECTED state. [Figure 8] 4 is a diagram showing an example of a processing sequence between a communication device and a plurality of cell groups when the communication device according to the first embodiment moves among a plurality of wireless cells. [Figure 9] 4 is a diagram showing an example of a processing sequence between a communication device and a plurality of cell groups when the communication device according to the first embodiment moves among a plurality of wireless cells. [Figure 10] 4 is a diagram showing an example of a processing sequence between a communication device and a plurality of cell groups when the communication device according to the first embodiment moves among a plurality of wireless cells. [Figure 11] 4 is a diagram showing an example of a processing sequence between a communication device and a plurality of cell groups when the communication device according to the first embodiment moves among a plurality of wireless cells. [Figure 12]4A to 4C are diagrams for explaining examples of types of uploaded images in a system for uploading captured images by a capture device (UE) according to the first embodiment. [Figure 13] FIG. 11 is a block diagram showing an example of the hardware and functional configuration of a communication device according to a second embodiment. [Figure 14] 10 is a flowchart showing an example of a processing procedure of a monitoring control process executed when a communication device according to a second embodiment monitors a standby service. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment for carrying out the present invention will be described in detail with reference to the attached drawings. Note that the embodiment described below is one example of a means for realizing the present invention, and should be appropriately modified or changed depending on the configuration of the device to which the present invention is applied and various conditions, and the present invention is not limited to the following embodiment. Also, not all of the combinations of features described in the present embodiment are necessarily essential to the solution of the present invention.

[0014] Hereinafter, an example will be described in which the communication device is a communication device capable of public wireless communication using Dual Connectivity (hereinafter, referred to as "DC") conforming to the 3GPP standard, but the present embodiment is not limited to this. For example, the communication device may use another method capable of connecting to multiple base stations (BS) and simultaneously providing communication services. In the following, an example will be described in which the communication device is an imaging device that can record moving images being captured in itself and can stream moving images or still images via a public wireless communication line as necessary, but the present embodiment is not limited to this. The communication device may be any communication device that has a function of performing public wireless communication in DC, including, but not limited to, a digital video camera, a mobile phone, a smartphone, a PC (Personal Computer), a notebook PC, a server, etc. In addition, the communication device may be a mobile or stationary body, or may be mounted on a mobile body.

[0015] (Embodiment 1) <Hardware and functional configuration of communication device> FIG. 1 is a diagram showing an example of the hardware and functional configuration of a communication device according to the present embodiment. The communication device (User Equipment (hereinafter, referred to as "UE") 1 in FIG. 1 includes a CPU 101, a RAM 102, a ROM 103, a 5G communication unit 104, a 4G communication unit 105, a GPS receiving unit 106, a display unit 107, an operation unit 108, and an imaging unit 109. The UE 1 further includes a non-volatile memory unit 110 , a movement detection unit 111 , a channel selection unit 112 , a power supply source determination unit 113 , and a power supply unit 114 . The components of the UE 1 in Fig. 1 are communicatively connected to each other via a system bus. The UE 1 does not need to include all of the modules described above, and may include additional modules in addition to the configuration in Fig. 1.

[0016] A CPU (Central Processing Unit) 101 centrally controls the operation of the UE 1, and controls each component (102 to 114) via a system bus. That is, when executing various processes, the CPU 101 loads necessary programs and the like from storage media such as a ROM 103 and a non-volatile storage unit 110 into a RAM 102, and executes the programs and the like to realize various functional operations. A RAM (Random Access Memory) 102 functions as a main memory, a work area, etc. for the CPU 101, and temporarily stores programs and data. The ROM (Read Only Memory) 103 is a non-volatile memory that stores control programs and parameters that do not require modification and are necessary for the CPU 101 to execute various processes. These control programs and the like may be stored in the non-volatile storage unit 110, an external memory, or a removable storage medium (not shown).

[0017] The 5G communication unit 104 is a communication module for connecting the UE1 to a fifth generation (5G) public wireless communication network. The 4G communication unit 105 is a communication module for connecting the UE1 to a fourth generation (4G) public wireless communication network. A GPS (Global Positioning System) receiving unit 106 receives a signal from a GPS. The display unit 107 displays, for example, an image captured by the imaging unit 109 and stored in a non-volatile storage unit 110 or the like, and displays the results of various processes, such as the results of operations performed by the operation unit 108 . An operation unit 108 has an image capture button, a network setting button, etc., and provides a user interface to the CPU 101 and each unit. The imaging unit 109 is composed of an optical lens, a CCD, etc., and captures images such as still images and moving images. The non-volatile storage unit 110 is configured with a non-volatile memory, and stores moving images and still images captured by the imaging unit 109. The non-volatile storage unit 110 may also store various programs and parameters.

[0018] The movement detection unit 111 detects the movement of the UE1. Based on the result of movement detection by the movement detection unit 111, the channel selection unit 112 selects which of the multiple base stations (BSs) connected to the UE1 should monitor for a paging signal from a corresponding paging channel. Note that a paging channel (hereinafter referred to as "PCH") is a control channel that can be transmitted from a base station to all UEs in a cell. Also, a paging signal (hereinafter referred to as "PCH signal") is a control notification signal transmitted from a base station to all UEs via the PCH. The power supply source determination unit 113 determines the type of power source that is supplying power to the UE 1 or the device in which the UE 1 is installed. The power supply unit 114 supplies power to each unit of the UE 1 or the device in which the UE 1 is installed.

[0019] <State transition of communication device> FIG. 2 is a diagram showing state transitions of UE1 conforming to the 5G public wireless communication standard defined in the 3GPP standard. UE1 transitions between three states: RRC_CONNECTED is a state (mode) in which a unicast wireless communication path with a base station (BS) is connected, wireless communication resources for data communication have been allocated, and unicast data communication is possible. Upon receiving a release signal 21 of RRC (Radio Resource Control) from the base station (BS), the UE 1 transitions to RRC_CONNECTED. RRC_IDLE is a state (mode) in which the unicast wireless communication path with the base station (BS) is not connected, wireless communication resources for data communication are also released, and unicast data communication is not possible. In RRC_IDLE, only control signals broadcast from the base station (BS) can be received. Upon receiving an RRC connection signal 22 from the base station (BS), UE 1 returns to the RRC_CONNECTED state.

[0020] On the other hand, when UE1 receives an RRC inactivation signal 23 from the base station (BS) in the RRC_CONNECTED state, UE1 transitions to RRC_INACTIVE. RRC_INACTIVE is a mode in which the unicast communication path with the base station (BS) is not connected, but wireless communication resources for data communication remain allocated. In RRC_INACTIVE, unicast data communication is not possible, but only control signals broadcast from the base station (BS) can be received. Upon receiving an RRC connection signal 24 from the base station (BS), UE1 returns to RRC_CONNECTED.

[0021] Fig. 3 is a schematic diagram showing the usage state of a wireless communication path via a public wireless communication line with multiple base stations (BS) when UE1 is executing DC (Dual Connectivity). Fig. 3(a) shows the usage state of the wireless communication path in RRC_CONNECTED, and Fig. 3(b) and Fig. 3(c) show the usage state of the wireless communication path in RRC_INACTIVE. In RRC_CONNECTED in Fig. 3(a), when UE1 receives an inactivation signal 23 from a base station (MCG_BS) 31 that controls a master cell group, UE1 transitions to RRC_INACTIVE. Note that a master cell (primary cell) is a cell that ensures a connection between UE1 and a wireless network. The base station (MCG_BS) that controls a master cell group is hereinafter referred to as a master cell base station.

[0022] On the other hand, when UE1 receives a connection signal 24 from the master cell base station (MCG_BS) in RRC_INACTIVE in FIG. 3(b) and FIG. 3(c), UE1 returns to RRC_CONNECTED. Referring to FIG. 3(a), in RRC_CONNECTED, UE1 monitors PCH 31a through which a master cell base station (MCG_BS) 31 transmits a PCH signal. At the same time, UE1 monitors PCH 32a through which a base station (SCG_BS) 32 that manages a group of secondary cells transmits a PCH signal. Note that a secondary cell is a cell that provides wireless communication resources in addition to the master cell. The base station (SCG_BS) that manages a group of secondary cells is hereinafter referred to as a secondary cell base station. The UE 1 also has a user channel (UCH) 31 b for transmitting and receiving data to and from the master cell base station (MCG_BS) 31 , and a UCH 32 b for transmitting and receiving data to and from the secondary cell base station (SCG_BS) 32 .

[0023] In the 5G public wireless communication standard, in RRC_INACTIVE, the PCH continues to be monitored and the UCH wireless connection is released, but by retaining wireless communication resources to the base station, the procedure for reconnecting to the same base station is simplified. However, the 5G public wireless communication standard does not specify the behavior of which PCH should be monitored when UE1 executing DC transitions from RRC_CONNECTED to RRC_INACTIVE. For this reason, two approaches shown in FIG. 3(b) and FIG. 3(c) can be considered. FIG. 3(b) shows a case where monitoring of PCH signals from both the PCH 31a of the master cell base station (MCG_BS) 31 and the PCH 32a of the secondary cell base station (SCG_BS) 31 is continued. FIG. 3(c) shows a case where monitoring of the PCH signal from the PCH 31a of the master cell base station (MCG_BS) 31 continues, while monitoring of the PCH signal from the PCH 32a of the secondary cell base station (SCG_BS) 32 is suspended.

[0024] In the method of Fig. 3(b), even during RRC_INACTIVE, monitoring of the PCHs of both the master cell base station (MCG_BS) 31 and the secondary cell base station (SCG_BS) 32 continues. Therefore, when returning to RRC_CONNECTED, it is possible to determine in advance whether or not a unicast wireless communication path for DC can be set up, and the response of the service resumption in standby in UE1 is improved, but the power consumption of UE1 is not minimized. On the other hand, in the method of Fig. 3(c), the UE1's power consumption can be minimized to the same level as in the RRC_IDLE state because the UE1 only monitors the PCH of the master cell base station (MCG_BS) 31. However, until the UE1 returns to the RRC_CONNECTED state, it cannot determine whether or not a unicast wireless communication path for DC can be set up, and the response to service resumption during standby is reduced.

[0025] In this way, whether to prioritize power consumption or improved response time for restarting the service depends on the characteristics of the service that uses DC and the state of UE 1. For this reason, it is difficult to uniquely determine whether to use the method shown in Figure 3(b) or Figure 3(c) in RRC_INACTIVE. Therefore, in this embodiment, a PCH from which PCH signal should be monitored is selected according to the state and service characteristics of the UE 1. Details of this channel selection process in this embodiment will be described later with reference to Figs.

[0026] FIG. 4 is an example of a use case of the UE1 according to this embodiment, and shows an example of a network system in which the UE1 serves as a capture device, which is an in-vehicle camera, captures images while the vehicle is moving or stopped, and uploads the images to a server. A vehicle 2 in Fig. 4 is equipped with UE1, which is an on-board camera, and travels from within a master cell area 1 indicated by a dashed line in Fig. 4 to within a master cell area 2 indicated by a dashed line. In the master cell area 1, a master cell base station (MCG_BS_1) 311 controls the master cell, and in the master cell area 2, a master cell base station (MCG_BS_2) 312 controls the master cell. Secondary cell base stations (SCG_BS_1 to SCG_BS_3) 321 to 323 control their respective secondary cells.

[0027] The UE1 secures unicast wireless communication paths to each of the master cell base stations (MCG_BS_1-2) 311 or 312 and the secondary cell base stations (SCG_BS_1-3) 321-323 by using a DC capable of securing broadband communication. The UE1 uploads captured images to a database 5 of a server via a core network 3 accommodating these master cell base stations and secondary cell base stations. The uploaded captured images may be configured in the database 5 as a dynamic map in which various additional information required to support the autonomous driving of a vehicle is added to three-dimensional geospatial information, for example. The configuration of this dynamic map will be described in detail later with reference to FIG. 12. The UE 1 mounted on the vehicle 2 is in the RRC_CONNECTED state during the period when it is necessary to upload captured images, and transitions to the RRC_INACTIVE state during the period when it is not necessary to upload captured images.

[0028] As the vehicle 2 moves, the UE 1 executes handover control between the master cell base stations (MCG_BS_1-2) 311 and 312 and between the secondary cell base stations (SCG_BS_1-3) 321-323. Next, taking the case where a cell handover occurs while the UE1, which is a capture device, is waiting for the start of an upload service for a captured image as an example, the selection control of the monitored PCH of the UE1 according to this embodiment will be described.

[0029] <Automatic Selection Processing of PCH Based on Monitoring of UE1's Movement Speed> FIG. 5 is a flowchart showing an example of the processing procedure of the monitoring control process executed when the UE1 according to Embodiment 1 monitors the movement speed. The UE1 monitors its own movement state as an internal control state of its own device at regular intervals, and starts the process of FIG. 5 every time the monitoring timing of the movement speed arrives. In S51, the 5G communication unit 104 of the UE1 determines whether its own device is in DC connection and is in RRC_INACTIVE. If its own device is not in DC connection or is not in RRC_INACTIVE (S51: N), since the monitoring procedure of the PCH signal via the PCH addressed to its own device is uniquely determined by the 5G public radio communication standard, the process ends.

[0030] On the other hand, if its own device is in DC connection and is in RRC_INACTIVE (S51: Y), in S52, the movement detection unit 111 of the UE1 detects the movement situation of its own device and supplies the result of the movement detection to the CPU101, and proceeds to S53. In S53, the CPU101 of the UE1 determines whether the UE1 is moving based on the result of the movement detection from the movement detection unit 111. If it is not moving (S53: N), it proceeds to S55. In S55, the channel selection unit 112 of the UE1 stops monitoring the PCH signal transmitted by the secondary cell base station (SCG_BS_1) 321 for the secondary cell group (SCG) of the UE1 via the PCH32a addressed to the UE1, and ends the process.

[0031] On the other hand, in S53, if the UE1 is moving (S53: Y), it proceeds to S54. In S54, the channel selection unit 112 of UE1 starts monitoring the PCH signal transmitted by the secondary cell base station (SCG_BS_1) 321 to UE1 via PCH32a and proceeds to S56. In S56, the CPU 101 of UE1 determines whether or not a status in which DC cannot be executed (hereinafter referred to as "DC execution impossible status") is defined and continues for a certain period. Note that the DC execution impossible status referred to in S56 is set by executing the processes described later with reference to FIG. 6.

[0032] If it is determined that it is within a certain period defined after the DC execution impossible status is set (S56: N), the process proceeds to S58. In S58, the CPU 101 of UE1 continues the RRC_INACTIVE state and ends the processing of one processing unit executed when the movement monitoring timing arrives. On the other hand, if it is determined that the DC execution impossible status continues beyond a certain period (S56: Y), the process proceeds to S57, and the 5G communication unit 104 of UE1 makes a transition to RRC_CONNECTED and ends the processing. Note that after the return to RRC_CONNECTED is completed, UE1 reconfigures the radio communication path for DC according to the control defined in the 5G public radio communication standard.

[0033] <DC Execution Impossible Status Monitoring Process of UE1> FIG. 6 is a flowchart showing an example of the processing procedure of a process for determining whether or not the execution of DC can be maintained and setting the status information of the DC execution impossible status, which is executed every time the above-described PCH monitoring timing arrives at UE1. UE1 determines whether or not the execution of DC can be maintained by monitoring the PCH at a certain period, and activates the process of FIG. 6 every time the PCH monitoring timing arrives. When executing the process of FIG. 6, UE1 is in the RRC_INACTIVE state.

[0034] In S61, the 5G communication unit 104 of UE1 determines whether or not its own device is executing DC. If the own device is not executing DC (S61: N), the monitoring procedure for the PCH signal via the PCH addressed to the own device is uniquely determined by the 5G public wireless communication standard, and therefore the processing is terminated.

[0035] On the other hand, if the own device is executing DC (S61: Y), in S62, the 5G communication unit 104 of UE1 determines whether monitoring of the PCH signal transmitted by the secondary cell base station (SCG_BS_1) 321 to UE1 via PCH 32a is paused. If monitoring of the PCH 32a for the secondary cell base station (SCG_BS_1) 321 is not suspended (S62:N), the process branches to S63. In S63, the 5G communication unit 104 of UE1 determines whether or not the 5G communication unit 104 has successfully received the PCH signal most recently transmitted by the secondary cell base station (SCG_BS_1) 321 to UE1 via the PCH 32a. If the most recent PCH signal transmitted by the secondary cell base station (SCG_BS_1) 321 to UE1 via the PCH 32a is successfully received (S63: Y), proceed to S67, and if the PCH signal is not successfully received, proceed to S64. In S67, the CPU 101 of the UE1 clears the DC execution disabled status stored in the storage unit, and ends the process.

[0036] On the other hand, returning to S62, if monitoring of the PCH 32a for the secondary cell base station (SCG_BS_1) 321 is suspended, in S64, the UE 1 checks the contents of the PCH signal transmitted by the master cell base station (MCG_BS_1) 311 via the PCH 31a. Specifically, the CPU 101 of the UE 1 checks the contents of a RAN-based Notification area, which is notification information broadcast by using a PCH signal transmitted from the master cell base station (MCG_BS_1) 311. In S65, the CPU 101 of the UE1 determines whether or not the content of the RAN-based Notification area confirmed in S64 includes information of a cell other than the master cell.

[0037] If the RAN-based Notification area does not contain information about cells other than the master cell, such as a secondary cell (S65: N), the process proceeds to S66, and the CPU 101 of the UE1 sets the DC execution disabled status to on and ends the process. On the other hand, if the RAN-based Notification area contains information about cells other than the master cell, such as a secondary cell (S65: Y), the process proceeds to S67, and the CPU 101 of the UE1 clears the DC execution disabled status and ends the process. In this way, in this embodiment, while in the RRC_INACTIVE state, the UE1 updates the DC execution disabled status prior to reconnection, and upon expiration of a certain period of this DC execution disabled status, makes a transition to RRC_CONNECTED.

[0038] <DC connection determination process executed when UE1 transitions to RRC_CONNECTED> FIG. 7 is a flowchart showing an example of the processing procedure of the DC connection determination process executed when the UE1 transitions to RRC_CONNECTED. The UE1 activates the process shown in FIG. 7 every time it transitions to RRC_CONNECTED. In S71, the 5G communication unit 104 of the UE1 determines whether the UE1 is in the middle of DC execution. If the UE1 is not in the middle of DC execution (S71: N), the process proceeds to S77, and it immediately transitions to RRC_CONNECTED and ends the process. On the other hand, if the UE1 is in the middle of DC execution (S71: Y), the process proceeds to S72, and the 5G communication unit 104 of the UE1 determines whether monitoring of the PCH signal transmitted by the secondary cell base station (SCG_BS_1) 321 to the UE1 via the PCH 32a is paused.

[0039] If monitoring of the PCH signal from the PCH 32a for the secondary cell base station (SCG_BS_1) 321 is not paused (S72: N), the process proceeds to S77 and immediately transitions to RRC_CONNECTED. On the other hand, if monitoring of the PCH signal from the PCH 32a is paused (S72: Y), the process proceeds to S73. In S73, the 5G communication unit 104 of UE1 resumes monitoring the PCH signal transmitted by the secondary cell base station (SCG_BS_1) 321 to UE1 via PCH32a. In S74, the 5G communication unit 104 of UE1 determines whether it has successfully received the PCH signal from the secondary cell base station (SCG_BS_1) 321 via PCH32a. If the UE1 successfully receives the PCH signal from the secondary cell base station (SCG_BS_1) 321 via PCH32a (S74: Y), it proceeds to S77 and immediately transitions to RRC_CONNECTED. On the other hand, if it fails to receive the PCH signal from PCH32a (S74: N), it proceeds to S75.

[0040] In S75, the 5G communication unit 104 of UE1 requests to secure a radio communication path via a new secondary cell base station for the secondary cell via the master cell base station (MCG_BS_1) 311 for the master cell. In S76, if the 5G communication unit 104 of UE1 fails to secure the radio communication path via the new secondary cell base station requested in S75 (S76: N), it interrupts DC execution, proceeds to S77, and transitions to the RRC_CONNECTED state only with the master cell base station. On the other hand, if it successfully secures the radio communication path via the new secondary cell base station (S76: Y), it returns to S74 and waits to receive the PCH signal from the new secondary cell base station secured in S76.

[0041] <State Transition Sequence of Monitoring Control Processing Associated with the Movement of UE1> Hereinafter, with reference to FIGS. 8 to 11, the state transition sequence of the monitoring control processing executed by UE1 according to the present embodiment will be described in order in time series. UE1, which is a capture device, is mounted on the vehicle 2 as shown in FIG. 4, and determines the movement status of its own device using information from sensors installed inside UE1 or in the vicinity of UE1 such as inside the vehicle 2. Then, when UE1 is in RRC_INACTIVE, it automatically selects the PCH to be monitored by UE1 based on the determined movement status of its own device.

[0042] 4, a vehicle 2 equipped with a UE1 that is a capture device is assumed to be located within a master cell area 1 controlled by a master cell base station 311. Here, it is assumed that initially, the UE1 is enjoying a wireless communication service by executing DC between the master cell base station (MCG_BS_1) 311 and a secondary cell base station (SCG_BS_1) 321. It is assumed that the UE1 is uploading a captured image to a database 5 of a dynamic map server, for example. 8, for example, it is assumed that uploading of a captured image from UE1 to the database 5 of the server is interrupted. In this case, in S81, the core network 4 and the master cell base station (MCB_BS_1) 311 and secondary cell base station (SCB_BS_1) 321 of the radio area network (RAN) detect the interruption of payload data communication from UE1. By detecting the interruption of payload data communication, the core network 4 and the base stations (master cell base station 311 and secondary cell base station 321) recognize the condition for prompting UE1 to transition from RRC_CONNECTED to RRC_INACTIVE.

[0043] In S82, upon recognizing the condition for transition to RRC_INACTIVE, the master cell base station (MCG_BS_1) 311 transmits a message to the UE1 to instruct the UE1 to release the RRC connection. In S83, the master cell base station (MCG_BS_1) 311 transmits a message to the secondary cell base station (SCG_BS_1) 321 to instruct the secondary cell base station (SCG_BS_1) 321 to suspend communication so as to maintain the communication path secured for UE1. Thereafter, in S84, the master cell base station (MCG_BS_1) 311 transitions to RRC_INACTIVE. The UE1 and the secondary cell base station (SCG_BS_1) 321 also transition to RRC_INACTIVE upon receiving the messages in S82 and S83, respectively.

[0044] After transitioning to RRC_INACTIVE, UE1 periodically executes the PCH (Paging Channel) confirmation process described above with reference to FIG. Specifically, UE1 executes a PCH confirmation process at the timing when the master cell base station (MCG_BS_1) 311 transmits a PCH signal to UE1 via each PCH in S85, and at the timing when the secondary cell base station (SCG_BS_1) 321 transmits a PCH signal to UE1 via each PCH in S86.

[0045] Here, it is assumed that the vehicle 2 carrying the UE1 has moved. At this stage, it is assumed that the UE1 has received the PCH signal from the master cell base station (MCG_BS_1) 311 in S87, but has failed to receive the PCH signal from the secondary cell base station (SCG_BS_1) 321 in S88. In this case, in response to the failure to receive the PCH signal transmitted to the UE1, the UE1 detects the loss of the PCH signal notified via the PCH 32a from the secondary cell base station (SCG_BS_1) 321 in S89.

[0046] 6. Upon detecting loss of the PCH signal from the secondary cell base station via the PCH, the UE1 checks the information of the RAN_Based Notification Area notified by the master cell base station (MCG_BS_1) 311 in the PCH signal in S64 of FIG. Here, an example will be described in which there is no information on a valid secondary cell in the RAN_Based Notification Area. In S65 of S6, it is determined that there is no valid secondary cell other than the master cell (S65:N), and in S66, UE1 sets a DC execution impossible status at the time of wireless reconnection.

[0047] When the vehicle carrying UE1 moves, a DC infeasible state is set due to continuous movement in a specific direction. Therefore, even if UE1 continues to wait for a PCH signal broadcast from the secondary cell base station (SCG_BS_1) 321, reception of the PCH signal broadcast from the secondary cell base station (SCG_BS_1) 321 does not resume. As described with reference to Fig. 5, when the DC unexecutable status continues for a certain period of time or more, UE1 transitions to RRC_CONNECTED with the master cell base station (MCG_BS_1) 311. When UE1 transitions to RRC_CONNECTED with the master cell base station (MCG_BS_1) 311, in S75, UE1 requests the core network 4 via the master cell base station (MCG_BS_1) 311 to allocate a new secondary cell base station.

[0048] With reference to FIG. 9, an example of a control sequence in UE1 accompanying a request for allocation of a new secondary cell base station will be described. In S91, UE1 detects that the signal loss continues for a certain period of time after the PCH signal broadcast from the secondary cell base station (SCG_BS_1) 321 via the PCH is lost. With the loss of the PCH signal broadcast from the secondary cell base station (SCG_BS_1) 321 as a trigger, UE1 transitions to RRC_CONNECTED with the master cell base station (MCG_BS_1) 311 as shown in FIG. Returning to FIG. 9, in S92, the UE1 transmits to the master cell base station (MCG_BS_1) 311 a reconnection request (Redume Request) for resuming the RRC connection. In S93, the master cell base station (MCG_BS_1) 311 that has received the RRC connection reconnection request returns an RRC connection reconnection message (Resume) to the UE1, and instructs the UE1 to reconnect to the master cell base station (MCG_BS_1) 311. In S94, UE1, which has received the RRC connection reconnection message (Redume), restores the wireless connection with the master cell base station (MCG_BS_1) 311. After that, UE1 returns an RRC connection reconnection completion message (Resume Complete) to the master cell base station (MCG_BS_1) 311 to notify the master cell base station (MCG_BS_1) 311 of the completion of the reconnection.

[0049] In S95, upon receiving the RRC connection reconnection completion message from the UE1, the master cell base station (MCG_BS_1) 311 transmits a reconnection message (Resume) to the secondary cell base station (SCG_BS_1) 321. In S96, the secondary cell base station (SCG_BS_1) 321 fails in wireless connection with the UE 1 due to a deterioration in wireless line quality accompanying the movement of the vehicle 2. Therefore, in S97, the secondary cell base station (SCG_BS_1) 321 notifies the master cell base station (MCG_BS_1) 311 of the failure of the wireless connection by sending a reconnection response message (Resume Response).

[0050] In S98, when the DC unexecutable status continues for a certain period of time, UE1 establishes a unicast wireless communication path with the master cell base station (MCG_BS_1) 311, executes the process of FIG. 7, and transitions to RRC_CONNECTED. In S99, the master cell base station (MCG_BS_1) 311 secures a communication path to the new secondary cell base station and changes the communication path for the secondary cell base station. Specifically, the master cell base station (MCG_BS_1) 311 changes the communication path for the secondary cell base station to a communication path to the new secondary cell base station (SCG_BS_2) 322. This is a process executed when the secondary cell base station closest to the UE1 is changed from the secondary cell base station (SCG_BS_1) 321 to the secondary cell base station (SCG_BS_2) 322 due to the movement of the vehicle 2.

[0051] In S100, the master cell base station (MCG_BS_1) 311 transmits to the former secondary cell base station (SCG_BS_1) 321 a UE Context Release message instructing the release of the communication context reserved for UE1. In S101, the master cell base station (MCG_BS_1) 311 transmits an RRC connection release message (Release) to the UE 1. By executing S100 and S101, the UE 1 recognizes that the allocation of the communication context has been changed from the old secondary cell base station (SCG_BS_1) 321 to the new secondary cell base station (SCG_BS_2) 322 (S76, S74 in FIG. 7). 7, if the reception of a PCH signal via a PCH from the new secondary cell base station (SCG_BS_2) 322 is successful (S74: Y), the process proceeds to S77. In S77, the UE1 temporarily transitions to RRC_CONNECTED using DC between the master cell base station (MCG_BS_1) 311 and the new secondary cell base station (SCG_BS_2) 322.

[0052] Here, it is assumed that the resumption of payload data communication is not detected at this point after the upload of the captured image from the UE1 to the server database 5 is interrupted. In this case, in S102, the master cell base station (MCG_BS_1) 311, the secondary cell base station (SCG_BS_2) 322, and the core network 4 recognize this as a condition for prompting the UE1 to transition from RRC_CONNECTED to RRC_INACTIVE. Referring to FIG. 10, UE1, which has transitioned to RRC_INACTIVE in S102, periodically executes the PCH confirmation process described above with reference to FIG. Specifically, the UE1 executes the PCH confirmation process at the timing when the master cell base station (MCG_BS_1) 311 transmits a PCH signal to the UE1 in S103, and at the timing when the secondary cell base station (SCG_BS_2) 322 transmits a PCH signal to the UE1 in S104.

[0053] Here, it is assumed that the vehicle 2 carrying the UE1 has further moved. At this stage, it is assumed that reception of the PCH signal from the master cell base station (MCG_BS_1) 321 via the PCH 31a has failed in S105. Note that, at this stage, the PCH signal from the secondary cell base station (SCG_BS_2) 322 via the PCH 32a is still received by the UE1 in S106. In this case, the failure to receive the PCH signal transmitted to the UE1 triggers the UE1 to detect, in S107, deterioration in the quality of the PCH signal from the master cell base station (MCG_BS_1) 311 via the PCH 31a due to further movement of the vehicle 2.

[0054] When the vehicle carrying UE1 moves, the quality of the PCH signal from the master cell base station (MSG_BS_1) 311 deteriorates due to continuous movement in a specific direction. Therefore, even if UE1 continues to wait for the PCH signal from the master cell base station (MCG_BS_1) 311 via the PCH 31a, reception of the PCH signal from the master cell base station (MCG_BS_1) 311 does not resume. In S108 to S113, the UE1 transitions to RRC_CONNECTED with the master cell base station in response to quality deterioration of the PCH signal via the PCH 31a transmitted from the master cell base station (MCG_BS_1) 311. After that, the UE1 waits for allocation of a new master cell base station, which is executed on the core network 4 side.

[0055] 11, in S114, the core network 4 determines that handover processing from the old master cell base station (MCG_BS_1) 311 to the new master cell base station (MCG_BS_2) 312 is necessary, and executes the handover processing. Here, it is assumed that the resumption of payload data communication is not detected at this point after the upload of the captured image from the UE1 to the server database 5 is interrupted. Therefore, the master cell base station (MCG_BS_2) 312 of the handover destination and the core network 4 recognize this as a condition for prompting the UE1 to transition from RRC_CONNECTED to RRC_INACTIVE.

[0056] In S115, upon recognizing the condition for transition to RRC_INACTIVE, the master cell base station (MCG_BS_2) 312 transmits a message to the UE 1 to instruct the UE 1 to release the RRC connection. In S116, the master cell base station (MCG_BS_2) 312 transmits to the secondary cell base station (SCG_BS_2) 322 a message instructing the suspension of communication for UE1. Thereafter, in S117, the master cell base station (MCG_BS_2) 312 transitions to RRC_INACTIVE. The UE1 and the secondary cell base station (SCG_BS_2) 322 also transition to RRC_INACTIVE upon receiving the messages in S115 and S116, respectively.

[0057] After transitioning to RRC_INACTIVE, UE1 periodically executes the PCH confirmation process described above with reference to FIG. After the vehicle 2 carrying UE1 stops moving, there is no change in the quality of the PCH signal transmitted to UE1 via the PCH by the master cell base station (MCG_BS_2) 312 at S118 and by the secondary cell base station (SCG_BS_2) 322 at S119. Referring to FIG. 5, upon recognizing that the vehicle 2 has stopped, the UE 1 stops monitoring the PCH signal broadcast from the secondary cell base station (SCG_BS_2) 322 via the PCH until the vehicle 2 starts moving (S53: N, S55).

[0058] Fig. 12 shows, as an example, the types of information that UE1, which is a capture device mounted on a vehicle 2, uploads to database 5 of a map server, which is a dynamic map creation server, and the types of communication services that correspond to these types of information. The multiple communication services shown in Fig. 12 are communication services that are in a standby state while UE1, which is a capture device, is in RRC_INACTIVE and are scheduled to be executed after UE1 returns to RRC_CONNECTED. The dynamic map 122 shown in FIG. 12 is partitioned into information with different update frequencies. Specifically, the dynamic map 112 includes dynamic information that is updated approximately every second, semi-dynamic information that is updated approximately every minute, semi-static information that is updated approximately every hour, and static information that is updated approximately every month.

[0059] Among the multiple types of communication services 121, for example, a video captured during low-speed driving on a general road, which can capture pedestrians on the road or changes in traffic signals, is uploaded to dynamic information approximately every second. For example, when an image of a traffic jam or accident is detected, a video or still image captured during driving, which can capture the occurrence of the detected traffic jam or accident, is uploaded to quasi-dynamic information approximately every minute. For example, when construction or traffic regulations are detected, still images taken while driving that can capture the occurrence of the detected construction or traffic regulations are uploaded to the quasi-static information about once every hour. For example, when construction or traffic regulations are detected, still images taken while driving that can capture the increase in the number of buildings or traffic lanes that are not included in the map information being used are uploaded to the static information about once every month. In the above use case of the dynamic map creation server, in this embodiment, UE1 transitions to RRC_CONNECTED during the period when it is necessary to upload captured images, and transitions to RRC_INACTIVE during the period when it is not necessary to upload captured images. Then, while the vehicle 2 equipped with UE1, which is a capture device, is running, UE1 monitors the PCH to both the master cell base station and the secondary cell base station in the RRC_INACTIVE state, and receives PCH signals from both.

[0060] In this embodiment, to detect the movement of UE1, which is a capture device mounted on the vehicle 2, the movement detection unit 111 of UE1 may detect the movement by using, for example, an acceleration sensor. Alternatively, the GPS receiving unit 106 of UE1 may detect the movement by updating the GPS signal transmitted from the GPS. Alternatively, the power supply source determination unit 113 of the UE 1 may detect movement by monitoring the state of the power supply line of the vehicle 2 in which the UE 1 is mounted and detecting a change in the power supply line to the vehicle 2. For example, the power supply source determination unit 113 may detect that the vehicle 2 is moving while there is power supply from the ignition (IG) power source, and may detect that the vehicle 2 is stopped while there is power supply from the accessory (ACC) power source. Furthermore, power supply source determining section 113 of UE 1 may detect movement according to a change in the value of a received signal strength indicator (RSSI) of a PCH signal intermittently broadcast from a base station.

[0061] As described above, according to the present embodiment, the communication device 1 transitions between RRC_CONNECTED and RRC_INACTIVE states while securing unicast communication paths via the master cell base station and the secondary cell base station using DC. For example, the communication device 1 transitions to RRC_CONNECTED during a period when it is necessary to upload captured images, and transitions to RRC_INACTIVE during a period when it is not necessary to upload captured images. The communication device 1 detects its own moving state, and while detecting the movement, monitors the PCH signals transmitted by both the master cell base station and the secondary cell base station via their respective PCHs. On the other hand, while not detecting the movement, the communication device 1 switches the monitoring target channel so as to monitor only the PCH signal transmitted by the master cell base station via the PCH. As a result, in a communication device that uses a DC that enables broadband communication, it becomes possible to reduce power consumption while avoiding a decrease in service response caused by the movement of the device.

[0062] (Embodiment 2) Hereinafter, with reference to FIGS. 13 and 14, only the differences from the above-described Embodiment 1 will be described in detail. In Embodiment 1, according to the moving state of the communication device 1, a PCH (paging channel) to be monitored during RRC_INACTIVE was selected. In contrast, in Embodiment 2, as an internal control state, according to the response characteristics required by the service to be executed when returning to RRC_CONNECTED, a PCH to be monitored during RRC_INACTIVE is selected.

[0063] FIG. 13 shows an example of the hardware configuration and functional configuration of the UE1 according to Embodiment 2. As shown in FIG. 13, the UE1 according to the present embodiment has the same configuration as that of Embodiment 1 shown in FIG. 1, and further a service information storage unit 115 is added. In the UE1 shown in FIG. 13, the movement detection unit 111 may be omitted. The service information storage unit 115 stores, as service information, responses required by the UE1 after returning to RRC_CONNECTED for each service mounted on the UE1, for example, high response, low response, etc. The service information may be defined according to the real-time property required by the service to be resumed, the data capacity to be transmitted, the moving state of the UE1, and the like. For example, in a use case where the UE1, which is a capture device, is mounted on the vehicle 2, a service for streaming a video of a pedestrian around an intersection captured during a steering operation of the vehicle 2 while the vehicle 2 is running requires a high response. On the other hand, a service for distributing an imaging image for security purposes triggered by the detection of an abnormality by a sensor mounted on the vehicle 2 while the vehicle 2 is not running usually does not require a high response. Thus, in the present embodiment, the service information storage unit 115 stores the respective response characteristics for the services waiting to be executed on the UE1.

[0064] <Automatic Selection Process of PCH by Monitoring Scheduled Services of UE1> FIG. 14 is a flowchart showing an example of the processing procedure of the monitoring control process executed when the UE1 according to Embodiment 2 monitors the services scheduled to operate after returning to RRC_CONNECTED. UE1 periodically monitors the status of the service scheduled to be executed by the own device, and starts the process of FIG. 14 every time the monitoring timing arrives. The process of S51 is the same as that of the first embodiment shown in S51 of FIG. If UE1 is RRC_INACTIVE in S51 (S51: Y), proceed to S141. In S141, the service information storage unit 115 of UE1 refers to the stored service information and determines a response required for a waiting service that is scheduled to be executed after returning to RRC_CONNECTED.

[0065] In S142, if it is determined that the service to be executed after returning to RRC_CONNECTED does not need to be resumed with high response (S142: N), the process proceeds to S55. In S55, the UE1 stops receiving the PCH signal transmitted from the secondary cell base station to the UE1 via the PCH 32a. On the other hand, if it is determined that the service to be executed after returning to RRC_CONNECTED needs to be resumed with high response (S142: Y), the process proceeds to S54. In S54, UE1 starts a reception process of a PCH signal transmitted from the base station for the secondary cell to UE1 via the PCH for the secondary cell. The process from S56 to S58 is the same as the process from S56 to S58 shown in FIG. After completing the return to RRC_CONNECTED, UE1 reconfigures the wireless communication path for DC in accordance with the control specified in the 5G public wireless standard.

[0066] 12, for example, the channel selection unit 112 of UE1 may monitor the PCH signals transmitted by both the master cell base station and the secondary cell base station while detecting the standby for uploading "video shot while driving at low speed on a general road" which requires a high response. On the other hand, UE1 may switch the monitored channel to monitor only the PCH signal transmitted by the master cell base station while detecting the standby for uploading "video or still image shot while driving" for capturing construction or regulation on a motorway which does not require a high response. For example, when resuming a service that requires a response time of within one second, the channel selection unit 112 of the UE1 may monitor the PCH signals from both the master cell base station and the secondary cell base station.

[0067] As described above, according to this embodiment, the communication device 1 uses DC to secure unicast communication paths via the master cell base station and via the secondary cell base station, and transitions between RRC_CONNECTED and RRC_INACTIVE states. The communication device 1 detects the status of the service on standby in the own device, and while detecting that the service requiring a high response is on standby, monitors the PCH signals transmitted by both the master cell base station and the secondary cell base station via their respective PCHs. On the other hand, while not detecting that the service requiring a high response is on standby, the communication device 1 switches the monitoring channel so as to monitor only the PCH signal transmitted by the master cell base station via the PCH. As a result, in a communication device that uses a DC that enables broadband communication, it becomes possible to reduce power consumption while avoiding a decrease in service response caused by the movement of the device.

[0068] The present invention can also be realized by a program that realizes part or one or more functions of the above-mentioned embodiments. That is, the program can be supplied to a system or device via a network or a storage medium, and one or more processors in a computer (or a CPU, MPU, etc.) of the system or device read and execute the program. The program may also be provided by recording it on a computer-readable recording medium. In addition, the functions of the embodiments are not limited to those that are realized by a computer executing a program read out by the computer. For example, an operating system (OS) running on a computer may perform a part or all of the actual processing based on instructions from the program, and the functions of the above-mentioned embodiments may be realized by the processing. [Explanation of symbols]

[0069] 1...Communication device (UE), 2...Vehicle, 4...Core network, 5...Database, 31, 311, 312...Master cell base station, 32, 321, 322...Secondary cell base station, 101...CPU, 102...RAM, 103...ROM, 104...5G communication unit, 105...4G communication unit, 106...GPS receiving unit, 107...Display unit, 108...Operation unit, 109...Imaging unit, 110...Non-volatile memory unit, 111...Movement detection unit, 112...Channel selection unit, 113...Power supply source determination unit, 114...Power supply unit, 115...Service information storage unit

Claims

1. 1. A communication device, comprising: A transition means for transitioning from an RRC_CONNECTED state to an RRC_INACTIVE state in accordance with 3GPP (3rd Generation Partnership Project standard) (registered trademark) standard after a wireless communication path between the first base station and the second base station is established; a control means for controlling to receive a paging signal conforming to the 3GPP standard from each of the first base station and the second base station after transitioning to the RRC_INACTIVE state; having The control means receives paging signals from each of the first base station and the second base station by listening to a first paging channel on which the first base station broadcasts paging signals and a second paging channel on which the second base station broadcasts paging signals.

2. 2. The communication device according to claim 1, wherein the first base station is a master base station and the second base station is a secondary base station.

3. 3. The communication device according to claim 1, wherein the communication device establishes a wireless communication path with the first base station and the second base station using a DC (Dual Connectivity) function conforming to the 3GPP standard.

4. the control means, when the communication device has transitioned to the RRC_INACTIVE state and the state of the communication device is a first state, controls to receive a paging signal from each of the first base station and the second base station, and when the communication device has transitioned to the RRC_INACTIVE state and the state of the communication device is a second state, executes a second control instead of the above control, in which a paging signal is received from one of the first base station and the second base station and a paging signal is not received from the other of the first base station and the second base station; The communication device according to any one of claims 1 to 3, characterized in that the first state is a state in which the communication service that the communication device should resume after the communication device returns to the RRC_CONNECTED state is a communication service that requires responsiveness, and the second state is a state in which the communication service that the communication device should resume after the communication device returns to the RRC_CONNECTED state is not a communication service that requires responsiveness.

5. A communication device as described in any one of claims 1 to 4, characterized in that it has a receiving means for receiving a GPS signal.

6. The communication device according to claim 1 , further comprising an imaging unit.

7. A method for controlling a communication device, comprising: a transition step of transitioning from an RRC_CONNECTED state to an RRC_INACTIVE state in accordance with the 3GPP (3rd Generation Partnership Project standard) (registered trademark) standard after a wireless communication path between the first base station and the second base station is established; a control step of controlling to receive a paging signal conforming to the 3GPP standard from each of the first base station and the second base station after transitioning to the RRC_INACTIVE state; having A control method characterized in that, in the control step, reception control is performed to attempt to receive paging signals from each of the first base station and the second base station by listening to a first paging channel on which the first base station broadcasts paging signals and a second paging channel on which the second base station broadcasts paging signals.

8. A computer of the communication device a transition step of transitioning from an RRC_CONNECTED state to an RRC_INACTIVE state in accordance with the 3GPP (3rd Generation Partnership Project standard) (registered trademark) standard after a wireless communication path between the first base station and the second base station is established; a control step of controlling to receive a paging signal conforming to the 3GPP standard from each of the first base station and the second base station after transitioning to the RRC_INACTIVE state; A program for executing The program, characterized in that in the control step, reception control is performed to attempt to receive paging signals from each of the first base station and the second base station by listening to a first paging channel on which the first base station broadcasts paging signals and a second paging channel on which the second base station broadcasts paging signals.

Images