Wireless communication device, wireless communication system, and wireless communication method

Abstract

A radio communication device (100) includes a control unit (120) that, when performing communication with another radio communication device (200), can control the performance of data communication that simultaneously uses multiple cell groups including a cell, which is selected when communication with the other radio communication device (200) in a non-communication mode is established and is capable of controlling a control plane, and other cells.

Description

[Technical Field]

[0001] The present invention relates to a wireless communication device, a wireless communication system, and a wireless communication method. [Background technology]

[0002] Generally, in a wireless communication system, processing of the RRC (Radio Resource Control) layer is performed. In the RRC layer processing, for example, connection setup, modification, release, etc. are performed between a base station device and a terminal device. For example, in LTE (Long Term Evolution) or LTE-A (LTE-Advanced), which are standard technologies for 4G, RRC connected mode (RRC_CONNECTED) and RRC idle mode (RRC_IDLE) are defined as RRC layer states. The RRC connected mode is, for example, a mode in which data communication can be performed between a base station device and a terminal device. The RRC idle mode is, for example, a mode in which data communication is not performed between a base station device and a terminal device, and in which the terminal device is in a power saving state.

[0003] In fifth-generation mobile communications (5G or NR (New Radio)), in addition to RRC connected mode and RRC idle mode, an RRC inactive mode (RRC_INACTIVE) has been introduced. RRC inactive mode has the same low power consumption as RRC idle mode and is a mode that allows for quick transition to RRC connected mode when transmitting data. In RRC inactive mode, the context of the terminal device (hereinafter referred to as "UE context") is held in the base station device. The UE context is identification information that identifies information about the terminal device, such as the terminal device's location, communication capabilities, and various parameters. Because the UE context is held in the base station device in this way, the core network considers the terminal device to be connected to the base station device even in the RRC inactive mode. As a result, when the terminal device returns from RRC inactive mode to RRC connected mode, signal transmission and reception between the base station device and the core network is omitted, and quick transition to the RRC connected mode is achieved.

[0004] When in a non-communication mode such as RRC idle mode or RRC inactive mode, the terminal device measures the signal strength (RSRP: Reference Signal Received Power) from surrounding base station devices, selects the cell of the base station device with the highest signal strength, and camps on it. When the terminal device returns to a communication mode such as RRC connected mode and starts communication, it performs wireless communication using the cell on which it is camped. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 065814 [Non-patent literature]

[0006] [Non-Patent Document 1] 3GPP TS36.133 V17.1.0(2021-03) [Non-licensed document 2] 3GPP TS36.211 V16.5.0(2021-03) [Non-licensed document 3] 3GPP TS36.212 V16.5.0(2021-03)

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[0007] Incidentally, some wireless communications performed by terminal devices use multiple carriers, such as dual connectivity (DC) and carrier aggregation (CA). When a terminal device returning to a communication mode performs wireless communications using multiple carriers, the terminal device measures signal strength from surrounding base station devices after returning to the communication mode and reports the measurement results to the cell on which it camped during the non-communication mode. The base station device that receives the report determines the cell (or carrier) to be used for DC or CA from the measurement results and performs settings on the terminal device to perform DC or CA.

[0008] However, the above-described communication using multiple carriers has a problem in that a delay occurs before the communication is started. That is, the terminal device transitions from a non-communication mode to a communication mode in a first stage, and then performs radio-related measurements in a second stage to add a cell (or carrier) to start communication by DC or CA. For this reason, it is difficult to start DC or CA immediately after transitioning to the communication mode, which causes a communication delay. Such a delay at the start of communication adversely affects, for example, the throughput of TCP / IP (Transmission Control Protocol / Internet Protocol).

[0009] The disclosed technology has been developed in consideration of the above points, and aims to provide a wireless communication device, a wireless communication system, and a wireless communication method that can suppress delays in communications using multiple carriers. [Means for solving the problem]

[0010] In one aspect, the wireless communication device disclosed in the present application has a control unit that, when communicating with another wireless communication device, can control the implementation of data communication simultaneously using multiple cell groups including a cell that can control the control plane and other cells, which were selected when communication with the other wireless communication device was established in a non-communication mode. [Effects of the Invention]

[0011] According to one aspect of the wireless communication device, the wireless communication system, and the wireless communication method disclosed in the present application, it is possible to suppress delays in communication using multiple carriers. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a wireless communication system according to the first embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of the base station device. [Figure 3] FIG. 3 is a block diagram showing the configuration of the terminal device. [Figure 4] FIG. 4 is a sequence diagram showing a cell selection method according to the second embodiment. [Figure 5] FIG. 5 is a sequence diagram showing an operation when a communication mode is changed. [Figure 6] FIG. 6 is a sequence diagram showing a cell selection method according to the third embodiment. [Figure 7] FIG. 7 is a sequence diagram showing a cell selection method according to another embodiment. [Figure 8] FIG. 8 is a sequence diagram showing an operation at the time of communication mode transition according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of a wireless communication device, a wireless communication system, and a wireless communication method disclosed in the present application will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments.

[0014] (Embodiment 1) 1 is a diagram showing an example of the configuration of a wireless communication system according to embodiment 1. The wireless communication system shown in FIG.

[0015] Base station devices 100-1 to 100-3 are wireless communication devices that are connected to core network 10 and are capable of wireless communication with terminal devices 200 located within their cells. Although not shown in the figure, base station devices 100-1 to 100-3 are connected to each other via, for example, an X2 interface or an Xn interface. In Fig. 1, the cells formed by each of base station devices 100-1 to 100-3 are indicated by dashed lines.

[0016] When communicating with the terminal device 200, the base station devices 100-1 to 100-3 have a control unit that can control the implementation of data communication simultaneously using a group of multiple cells consisting of a cell that can control a control plane (C-plane) and other cells, which was selected when communication was established with the terminal device 200 in a non-communication mode. That is, the base station devices 100-1 to 100-3 serve as primary base stations, one of which forms a primary cell that is a cell that can control the C-plane, and at least one other of which serves as a secondary base station, one of which forms a secondary cell that is a cell that transmits and receives data on the user plane (U-plane).

[0017] When the terminal device 200 in non-communication mode establishes communication, these base station devices 100-1 to 100-3 are selected as primary base stations for primary access or secondary base stations for secondary access. In other words, while the terminal device 200 is in non-communication mode, the primary base station and secondary base station are selected from the base station devices 100-1 to 100-3. Therefore, when the terminal device 200 transitions from the non-communication mode to the communication mode, the base station devices 100-1 to 100-3 can immediately start communication, for example, by DC, as the primary base station and secondary base station.

[0018] When the terminal device 200 is located within a cell, the terminal device 200 is a wireless communication device capable of wireless communication with the base station devices 100-1 to 100-3 that form the cell. The terminal device 200 can operate by switching between a communication mode such as an RRC connected mode and a non-communication mode such as an RRC inactive mode.

[0019] When terminal device 200 transitions to the communication mode and communicates with base station devices 100-1 to 100-3, terminal device 200 has a control unit that receives control from base station devices 100-1 to 100-3 of the communication partners and controls the implementation of data communication simultaneously using a plurality of cell groups consisting of a cell that can control the C-Plane and other cells, which were selected when communication with base station devices 100-1 to 100-3 was established in the non-communication mode. That is, terminal device 200 performs data communication with a primary base station and a secondary base station among base station devices 100-1 to 100-3.

[0020] The terminal device 200 performs settings related to the primary base station and secondary base station selected from the base station devices 100-1 to 100-3 while in the non-communication mode. Therefore, when the terminal device 200 transitions from the non-communication mode to the communication mode, it can immediately start communication with the primary base station and secondary base station by, for example, DC.

[0021] As described above, according to the present embodiment, when a terminal device transitions to a communication mode and communicates with a base station device, the terminal device starts communication with the primary base station and the secondary base station selected in the non-communication mode, thereby suppressing delays in communication using multiple carriers.

[0022] (Embodiment 2) In the second embodiment, a case will be described in which a terminal device performs call setup between a primary base station and a secondary base station while in a non-communication mode. The configuration of the wireless communication system according to the second embodiment is the same as that of the first embodiment (FIG. 1), and therefore the description thereof will be omitted.

[0023] 2 is a block diagram showing a configuration of base station device 100 according to embodiment 2. Base station device 100 has a configuration equivalent to that of base station devices 100-1 to 100-3. Base station device 100 shown in FIG. 2 includes network interface (hereinafter abbreviated as "network IF") 110, processor 120, memory 130, and radio communication unit 140.

[0024] The network IF 110 is wired connected to the core network 10, and transmits and receives signals to and from devices such as an AMF (Access and Mobility management Function) that configure the core network 10. The network IF 110 also includes an interface, such as an X2 interface, that connects to other base station devices, and transmits and receives signals to and from other base station devices.

[0025] The processor 120 is a control unit that includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), and performs overall control of the base station device 100. Furthermore, when establishing communication with the terminal device 200 in a non-communication mode such as an RRC inactive mode, the processor 120 controls the implementation of data communication simultaneously using a cell group selected in the non-communication mode of the terminal device 200, the cell group including a primary cell that can control the C-plane and other secondary cells. That is, when the base station device 100 is selected as the primary base station, the processor 120 acquires identification information of the secondary base station from the terminal device 200 and performs control to execute DC by the base station device 100 and the secondary base station. Furthermore, when the base station device 100 is selected as the secondary base station, the processor 120 performs control to execute DC by the primary base station and the base station device 100 in accordance with the control by the primary base station.

[0026] The memory 130 includes, for example, a random access memory (RAM) or a read only memory (ROM), and stores information used in processing by the processor 120.

[0027] The wireless communication unit 140 performs wireless communication with the opposing terminal device 200. The wireless communication unit 140 transmits, for example, a UE context generated by the processor 120 to the terminal device 200. The wireless communication unit 140 also receives data transmitted from the terminal device 200. Note that the wireless communication unit 140 can perform predetermined communication with the terminal device 200 even when the opposing terminal device 200 is in a non-communication mode.

[0028] 3 is a block diagram showing a configuration of a terminal device 200 according to Embodiment 2. The terminal device 200 shown in FIG.

[0029] The wireless communication unit 210 performs wireless communication with the opposing base station device 100. The wireless communication unit 210 transmits and receives various signals to and from the base station device 100 for switching the communication mode and non-communication mode of the terminal device 200. For example, when the terminal device 200 establishes communication with the base station device 100, the wireless communication unit 210 receives information related to the UE context from the base station device 100. Note that the wireless communication unit 210 can perform predetermined communication with the base station device 100 even when the terminal device 200 is in the non-communication mode.

[0030] The processor 220 is a control unit that includes, for example, a CPU, FPGA, or DSP, and performs overall control of the terminal device 200. The processor 220 also switches the mode of the terminal device 200 between, for example, a communication mode such as an RRC connected mode and a non-communication mode such as an RRC inactive mode. The processor 220 controls the implementation of data communication simultaneously using a cell group selected during a non-communication mode such as an RRC inactive mode, and including a primary cell that can control the C-Plane and other secondary cells. That is, under control from the primary base station, the processor 220 performs control to execute DC between the primary base station and the secondary base station selected during the non-communication mode.

[0031] The memory 230 includes, for example, a RAM or a ROM, and stores information used in processing by the processor 220.

[0032] Next, a wireless communication method in the wireless communication system configured as above will be described with reference to Fig. 4. In the following description, it is assumed that the wireless communication system includes base station devices 100-1 and 100-2 having the same configuration as base station device 100.

[0033] During the non-communication mode, the terminal device 200 measures the signal strength from surrounding base station devices including the base station devices 100-1 and 100-2, and selects a primary base station and a secondary base station. Here, it is assumed that the terminal device 200 selects, for example, the base station device 100-1 with the highest signal strength as the primary base station, and the base station device 100-2 with a signal strength equal to or greater than a predetermined threshold as the secondary base station.

[0034] Then, in the non-communication mode, the terminal device 200 transmits an access stratum (AS) message (hereinafter referred to as "AS message") requesting a connection in order to establish communication with the base station device 100-1, which is the primary base station (step S101). Examples of this AS message include an RRC connection request and a connection resume request.

[0035] In response to this AS message, the base station device 100-1 transmits an AS message for predetermined settings to the terminal device 200 (step S102), and the terminal device 200 transmits an AS message notifying the base station device 100-1 of the completion of the connection (step S103). The AS message notifying the completion of the connection can include information indicating that the base station device 100-1 is the primary base station. That is, the terminal device 200 can notify the base station device 100-1 that it has selected the base station device 100-1 as the primary base station. Upon receiving this notification, the base station device 100-1 can understand that it is the primary base station and that a secondary base station will be added. Note that the information indicating that the base station device 100-1 is the primary base station may be included in the AS message requesting the connection in step S101.

[0036] When a connection between the terminal device 200 and the base station device 100-1 is established, a Non-Access Stratum (NAS) message (hereinafter referred to as a "NAS message") for registration (e.g., location registration) is transmitted from the terminal device 200 to the core network 10 via the base station device 100-1 (step S104). When the terminal device 200 is registered in the core network 10, a NAS message indicating that the registration has been accepted is transmitted from the core network 10 to the terminal device 200 via the base station device 100-1 (step S105).

[0037] Furthermore, in the base station device 100-1, a UE context related to the terminal device 200 is generated. Then, temporary identification information including identification information of the terminal device 200 and identification information of the base station device 100-1 is generated as identification information of the UE context. As this temporary identification information, for example, an I-RNTI (Inactive-Radio Network Temporary Identifier) can be used. The I-RNTI is 40-bit identification information that can simultaneously identify a terminal device and a base station device. Because the I-RNTI is 40-bit identification information, if the number of bits allocated to the identification information of the base station device is increased, the number of identifiable base station devices increases, but the number of identifiable terminal devices decreases. Furthermore, if the number of bits allocated to the identification information of the base station device is reduced, the number of identifiable base station devices decreases, but the number of identifiable terminal devices increases. As identification information of the UE context, any information other than the I-RNTI that can identify the UE context can be used.

[0038] The generated UE context is held by the base station device 100-1, and information about the UE context is notified to the terminal device 200, for example, by an AS message for releasing the connection (step S106). Upon receiving this notification, the terminal device 200 holds the information about the UE context and releases the connection with the base station device 100-1. At this time, the terminal device 200 may transition to, for example, the RRC inactive mode.

[0039] Then, the terminal device 200 transmits an AS message requesting connection to establish communication with the base station device 100-2, which is the secondary base station (step S107). In response to this AS message, the base station device 100-2 transmits an AS message for predetermined settings to the terminal device 200 (step S108), and the terminal device 200 transmits an AS message notifying the base station device 100-2 of completion of connection (step S109). The AS message notifying the completion of connection can include information indicating that the base station device 100-2 is a secondary base station. That is, the terminal device 200 can notify the base station device 100-2 that it has selected the base station device 100-2 as a secondary base station. Upon receiving this notification, the base station device 100-2 can recognize that it is a secondary base station. Note that the information indicating that the base station device 100-2 is a secondary base station may be included in the AS message requesting connection in step S107.

[0040] Furthermore, the AS message requesting connection in step S107 or the AS message notifying completion of connection in step S109 can include identification information for identifying base station device 100-1, which is the primary base station. As this identification information, for example, information related to the UE context notified from base station device 100-1 to terminal device 200 can be used. By being notified of the identification information for identifying the primary base station, base station device 100-2 can identify the primary base station when communicating with terminal device 200 via DC.

[0041] Here, the terminal device 200 has already completed registration with the core network 10 via the base station device 100-1, which is the primary base station. Therefore, when the terminal device 200 establishes a connection with the base station device 100-2, the terminal device 200 can omit registration with the core network 10. Therefore, no NAS message is transmitted or received between the terminal device 200 and the core network 10, and a UE context for the terminal device 200 is generated in the base station device 100-2. Then, temporary identification information including identification information for the terminal device 200 and identification information for the base station device 100-2 is generated as identification information for the UE context. As with the identification information generated by the base station device 100-1, for example, the I-RNTI can be used as this temporary identification information. Because the I-RNTI is 40-bit identification information, if the number of bits assigned to the identification information for the base station device is increased, the number of identifiable base station devices increases, but the number of identifiable terminal devices decreases. Furthermore, if the number of bits assigned to the identification information for the base station device is reduced, the number of identifiable base station devices decreases, but the number of identifiable terminal devices increases. As the information for identifying the UE context, any information other than the I-RNTI that can identify the UE context can be used.

[0042] The generated UE context is held by the base station device 100-2, and information about the UE context is notified to the terminal device 200, for example, by an AS message for releasing the connection (step S110). Upon receiving this notification, the terminal device 200 holds the information about the UE context and releases the connection with the base station device 100-2. At this time, the terminal device 200 may transition to, for example, the RRC inactive mode.

[0043] In this way, during the non-communication mode, the terminal device 200 selects the primary base station and the secondary base station according to the signal strength, requests connection to each of the primary base station and the secondary base station, and receives notification of the UE context from each of the primary base station and the secondary base station. Therefore, when the terminal device 200 returns to the communication mode, it can immediately perform communication by DC with the primary base station and the secondary base station.

[0044] FIG. 5 is a sequence diagram showing the operation of the wireless communication system when the terminal device 200 transitions from the non-communication mode to the communication mode.

[0045] For example, when downlink data addressed to the terminal device 200 occurs, paging is executed to call the terminal device 200 from the core network 10 via the base station device 100-1, which is the primary base station (step S201). The terminal device 200 that has received the paging transmits an AS message requesting a connection to the base station device 100-1 in order to return to communication mode (step S202). This AS message is, for example, an RRC connection resume request.

[0046] In response to this AS message, base station device 100-1 transmits an AS message for predetermined settings to terminal device 200 (step S203), and terminal device 200 transmits an AS message notifying base station device 100-1 of completion of connection (step S204). The AS message notifying of completion of connection can include identification information that identifies base station device 100-2, which is the secondary base station. As this identification information, for example, information related to the UE context notified from base station device 100-2 to terminal device 200 can be used.

[0047] When base station device 100-1 is notified of the identification information that identifies base station device 100-2, which is the secondary base station, it can notify base station device 100-2 that it will execute DC communication with terminal device 200 (step S205). Base station device 100-2 already knows that it is a secondary base station and has identified base station device 100-1, which is the base station that will be the primary access, so it replies to base station device 100-1 with a message confirming that it will execute DC communication (step S206). Then, base station device 100-1 notifies terminal device 200 of connection settings for executing DC communication (step S207).

[0048] Upon receiving this notification, the terminal device 200 sends a NAS message requesting a service to the core network 10 (step S208), and the core network 10 returns a response to the request, and the base station device 100-1 notifies the terminal device 200 of the connection settings (step S209).

[0049] This completes the connection for DC between the terminal device 200 and the base station devices 100-1 and 100-2, and wireless communication is performed between the terminal device 200 and the base station device 100-1, which is the primary base station (step S210), and wireless communication is performed between the terminal device 200 and the base station device 100-1 via the base station device 100-2, which is the secondary base station (step S211). That is, communication by DC is performed between the terminal device 200 and the base station devices 100-1 and 100-2.

[0050] As described above, according to the present embodiment, the terminal device selects a primary base station and a secondary base station during non-communication mode and receives notification of UE context from the primary base station and the secondary base station. Then, when the terminal device transitions to communication mode and performs communication with the base station device, it starts communication with the primary base station and the secondary base station selected during non-communication mode. Therefore, when the terminal device transitions to communication mode, it is not necessary to measure signal strength and select the primary base station and the secondary base station, and delays in communication using multiple carriers can be suppressed.

[0051] (Embodiment 3) In the third embodiment, a case will be described in which a primary base station acquires a result of measurement of signal strength by a terminal device in RRC idle mode (IDLE Mode Measurement) and selects a secondary base station. The configuration of a wireless communication system according to the third embodiment is the same as that of the first embodiment (FIG. 1), and therefore a description thereof will be omitted. In addition, the configurations of base station device 100 and terminal device 200 according to the third embodiment are the same as those of the second embodiment (FIGS. 2 and 3), and therefore a description thereof will be omitted.

[0052] Fig. 6 is a sequence diagram showing a wireless communication method in a wireless communication system according to embodiment 3. In Fig. 6, the same components as in Fig. 4 are assigned the same reference numerals. In the following description, it is assumed that the wireless communication system includes base station devices 100-1 and 100-2 having the same configuration as base station device 100.

[0053] During the non-communication mode, the terminal device 200 measures the signal strength from surrounding base station devices including the base station devices 100-1 and 100-2, and selects a primary base station. Here, it is assumed that the terminal device 200 selects, for example, the base station device 100-1 with the highest signal strength as the primary base station.

[0054] Then, in the non-communication mode, the terminal device 200 transmits an AS message requesting a connection to establish communication with the base station device 100-1, which is the primary base station (step S101). Examples of this AS message include an RRC connection request and a connection resume request.

[0055] In response to this AS message, the base station device 100-1 transmits an AS message for predetermined settings to the terminal device 200 (step S102), and the terminal device 200 transmits an AS message notifying the base station device 100-1 of the completion of connection (step S103). The AS message notifying the completion of connection can include information indicating that the base station device 100-1 is the primary base station, as well as flag information indicating that the terminal device 200 is measuring signal strength in RRC idle mode. That is, the terminal device 200 can notify the base station device 100-1 that it has selected the base station device 100-1 as the primary base station, and can also notify the base station device 100-1 that it is a terminal device that supports IDLE Mode Measurement. Upon receiving this notification, the base station device 100-1 can determine that it is the primary base station and that a secondary base station will be added. Note that the information indicating that the base station device 100-1 is the primary base station and the flag information may be included in the AS message requesting the connection in step S101.

[0056] When a connection between the terminal device 200 and the base station device 100-1 is established, a NAS message for registration is transmitted from the terminal device 200 to the core network 10 via the base station device 100-1 (step S104). When the terminal device 200 is registered in the core network 10, a NAS message indicating that the registration has been accepted is transmitted from the core network 10 to the terminal device 200 via the base station device 100-1 (step S105).

[0057] Then, the base station device 100-1, which has determined that it is the primary base station, requests the terminal device 200 to report the signal strength measurement results obtained by IDLE Mode Measurement (step S301). In response to this request, the terminal device 200 reports the signal strength measurement results measured in RRC idle mode to the base station device 100-1 (step S302). The signal strength measurement results include the signal strength measurement results from base station devices surrounding the terminal device 200, including the base station device 100-2.

[0058] The base station device 100-1 selects a secondary base station according to the signal strength measurement result. Specifically, the base station device 100-1 selects as the secondary base station a base station device whose signal strength at the terminal device 200 is equal to or greater than a predetermined threshold. Here, it is assumed that the base station device 100-2 is selected as the secondary base station. After selecting the secondary base station, the base station device 100-1 requests the base station device 100-2, which is the secondary base station, to generate a UE context to be assigned to the terminal device 200 (step S303). In response to this request, the base station device 100-2 generates a UE context for the terminal device 200 and notifies the base station device 100-1 of identification information for the generated UE context (step S304).

[0059] Meanwhile, the base station device 100-1 also generates a UE context related to the terminal device 200. Then, temporary identification information including identification information of the terminal device 200 and identification information of the base station device 100-1 is generated as identification information of the UE context. As this temporary identification information, for example, an I-RNTI (Inactive-Radio Network Temporary Identifier) can be used. The I-RNTI is 40-bit identification information that can simultaneously identify a terminal device and a base station device. Because the I-RNTI is 40-bit identification information, if the number of bits allocated to the identification information of the base station device is increased, the number of identifiable base station devices increases, but the number of identifiable terminal devices decreases. Furthermore, if the number of bits allocated to the identification information of the base station device is reduced, the number of identifiable base station devices decreases, but the number of identifiable terminal devices increases. As identification information of the UE context, any information other than the I-RNTI that can identify the UE context can be used.

[0060] The generated UE context is held by the base station device 100-1, and information about the UE context is notified to the terminal device 200, for example, by an AS message for releasing the connection (step S305). At this time, the information about the UE context generated by the base station device 100-1 is notified to the terminal device 200 together with the information about the UE context notified from the base station device 100-2. That is, information about the UE context generated for the terminal device 200 by each of the base station devices 100-1 and 100-2 is notified together to the terminal device 200. Upon receiving this notification, the terminal device 200 holds the information about the UE context and releases the connection with the base station device 100-1. At this time, the terminal device 200 may transition to, for example, the RRC inactive mode.

[0061] In this way, during non-communication mode, the terminal device 200 selects a primary base station according to signal strength and requests connection, and the primary base station acquires measurement results of the signal strength from the terminal device 200 and selects a secondary base station. Then, the primary base station acquires information about the UE context from the secondary base station and notifies the terminal device 200 of information about the UE context generated by the primary base station and the secondary base station. Therefore, when the terminal device 200 returns to the communication mode, it can immediately perform communication by DC with the primary base station and the secondary base station. That is, as in embodiment 2 (FIG. 5), when the terminal device 200 transitions from the non-communication mode to the communication mode, there is no need to measure signal strength and select the primary base station and the secondary base station, and delays in communication using multiple carriers can be suppressed.

[0062] As described above, according to the present embodiment, when a terminal device selects a primary base station in non-communication mode, the primary base station selects a secondary base station and notifies the terminal device of information related to the UE context generated by the primary base station and the secondary base station. Then, when the terminal device transitions to communication mode and performs communication with the base station device, it starts communication with the primary base station and secondary base station selected in non-communication mode. Therefore, when the terminal device transitions to communication mode, there is no need to measure signal strength to select the primary base station and secondary base station, and delays in communication using multiple carriers can be suppressed.

[0063] In the above embodiments, an example has been described in which the only secondary base station is base station device 100-2, but multiple base station devices may be selected as secondary base stations. That is, for example, in embodiment 2, terminal device 200 may select multiple secondary base stations in the non-communication mode, transmit AS messages requesting connection to each of the secondary base stations, and receive notification of UE context from each of the secondary base stations.

[0064] Also, for example, in embodiment 3, base station devices 100-2 and 100-3 may be selected as secondary base stations as shown in Fig. 7. As shown in Fig. 7, when base station device 100-1, which is the primary base station, selects base station devices 100-1 and 100-2 as secondary base stations in accordance with the signal strength at terminal device 200, it requests these secondary base stations to generate UE contexts to be assigned to terminal device 200 (step S303). In response to this request, base station devices 100-2 and 100-3 each generate a UE context and notify base station device 100-1 of information related to the generated UE contexts (step S304).

[0065] In this way, by using multiple base station devices as secondary base stations, terminal device 200 can perform communication using cells of the primary base station and multiple secondary base stations when transitioning to a communication mode. Figure 8 is a sequence diagram showing the operation of the wireless communication system when terminal device 200 transitions from a non-communication mode to a communication mode. In Figure 8, the same parts as in Figure 5 are assigned the same reference numerals. Here, it is assumed that base station device 100-1 is selected as the primary base station, and base station devices 100-2 and 100-3 are selected as secondary base stations.

[0066] For example, when downlink data addressed to the terminal device 200 occurs, paging is executed to call the terminal device 200 from the core network 10 via the base station device 100-1, which is the primary base station (step S201). The terminal device 200 that has received the paging transmits an AS message requesting a connection to the base station device 100-1 in order to return to communication mode (step S202). This AS message is, for example, an RRC connection resume request.

[0067] In response to this AS message, base station device 100-1 transmits an AS message for predetermined settings to terminal device 200 (step S203), and terminal device 200 transmits an AS message notifying base station device 100-1 of completion of connection (step S204). The AS message notifying of completion of connection includes identification information that identifies base station devices 100-2 and 100-3, which are secondary base stations. As this identification information, for example, information on UE context generated for terminal device 200 by base station devices 100-2 and 100-3, respectively, can be used.

[0068] When base station device 100-1 is notified of the identification information identifying base station devices 100-2 and 100-3 as secondary base stations, it notifies base station devices 100-2 and 100-3 that it will communicate with terminal device 200 via multiple access (step S205). Base station devices 100-2 and 100-3 each recognize that they are secondary base stations and have identified base station device 100-1 as the primary base station, and therefore return a message to base station device 100-1 confirming that they will communicate via multiple access (step S206). Then, base station device 100-1 notifies terminal device 200 of connection settings for communicating via multiple access (step S207).

[0069] Upon receiving this notification, the terminal device 200 sends a NAS message requesting a service to the core network 10 (step S208), and the core network 10 returns a response to the request, and the base station device 100-1 notifies the terminal device 200 of the connection settings (step S209).

[0070] This completes the setup for multiple access between the terminal device 200 and the base station devices 100-1 to 100-3, and wireless communication is performed between the terminal device 200 and the base station device 100-1, which is the primary base station (step S210), and wireless communication is performed between the terminal device 200 and the base station device 100-1 via the base station devices 100-2 and 100-3, which are secondary base stations (steps S211, S401). That is, communication by multiple access is performed between the terminal device 200 and the base station devices 100-1 to 100-3.

[0071] In this way, even when multiple base station devices are selected as secondary base stations, when the terminal device 200 transitions to a communication mode, there is no need to measure the signal strength to select the base station that will be the primary access and the secondary base station, and delays in communication using multiple carriers can be reduced.

[0072] In the above embodiments, the case where terminal device 200 is connected to base station devices 100-1 and 100-2 by dual connectivity (DC) has been mainly described as an example, but the communication methods in the above embodiments can also be applied to carrier aggregation (CA) that uses multiple carriers. That is, in the above embodiments, the base station devices 100-1 and 100-2 have been described as separate entities that each form a cell, but even in the case where one base station device forms a primary cell and a secondary cell, a communication method similar to that in the above embodiments can be applied. [Explanation of symbols]

[0073] 110 Network Interface 120, 220 processors 130, 230 memory 140, 210 Radio Communication Department

Claims

1. A receiving unit capable of receiving information capable of identifying a cell that can control a control plane selected by another wireless communication device in a non-communication mode; a control unit that can control, when communicating with the other wireless communication device, the implementation of data communication simultaneously using a plurality of cell groups including a cell that can control the control plane and other cells, which were selected when communication with the other wireless communication device in the non-communication mode was established; A wireless communication device comprising:

2. The control unit When the identification information regarding the secondary base station corresponding to the other cell is acquired from the other wireless communication device, the secondary base station is notified that the data communication will be performed.

2. The wireless communication device according to claim 1.

3. The control unit When establishing communication with the other wireless communication device in the non-communication mode, the other wireless communication device is notified of identification information that can simultaneously identify the device itself and the other wireless communication device.

2. The wireless communication device according to claim 1.

4. The control unit When establishing communication with the other wireless communication device in the non-communication mode, a measurement result of a received signal strength in the other wireless communication device is acquired, a secondary base station corresponding to the other cell is determined according to the measurement result, and identification information to be assigned to the other wireless communication device is requested from the secondary base station.

2. The wireless communication device according to claim 1.

5. A transmitter capable of transmitting information capable of identifying a cell that can control a selected control plane during a non-communication mode; a control unit that, when communicating with another wireless communication device, receives control from the other wireless communication device and controls the implementation of data communication simultaneously using a plurality of cell groups including a cell that can control the control plane and other cells, which were selected when communication with the other wireless communication device was established during the non-communication mode; A wireless communication device comprising:

6. The control unit notifying a primary base station corresponding to a cell capable of controlling the control plane of identification information relating to a secondary base station corresponding to the other cell; 6. The wireless communication device according to claim 5.

7. The control unit When establishing communication with the other wireless communication device during the non-communication mode, identification information that can simultaneously identify the device itself and the other wireless communication device is notified by the other wireless communication device.

6. The wireless communication device according to claim 5.

8. The control unit When establishing communication with the other wireless communication device during the non-communication mode, notify the other wireless communication device of information indicating that the other wireless communication device is a primary base station corresponding to a cell that can control the control plane, or information indicating that the other wireless communication device is a secondary base station corresponding to the other cell.

6. The wireless communication device according to claim 5.

9. A wireless communication system having a first wireless communication device and a second wireless communication device, the first wireless communication device, a receiving unit capable of receiving information capable of identifying a cell capable of controlling a control plane selected by the second wireless communication device in a non-communication mode; a first control unit that can control, when communicating with the second wireless communication device, the implementation of data communication simultaneously using a plurality of cell groups including a cell that can control the control plane and other cells, which are selected when communication with the second wireless communication device in the non-communication mode is established; the second wireless communication device, a transmitter capable of transmitting information capable of identifying a cell capable of controlling a selected control plane during a non-communication mode; and a second control unit that, when communicating with the first wireless communication device, receives control from the first wireless communication device and controls the implementation of data communication simultaneously using the plurality of cell groups selected when communication with the first wireless communication device is established during the non-communication mode. A wireless communication system comprising:

10. 1. A wireless communication method performed by a wireless communication device, comprising: receiving information identifying a cell that can control a selected control plane of another wireless communication device in a non-communication mode; When communication with the other wireless communication device is performed, the control unit 100 controls the execution of data communication simultaneously using a group of multiple cells including a cell that can control the control plane and other cells, which was selected when communication with the other wireless communication device in the non-communication mode was established.

1. A wireless communication method comprising the steps of:

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