Optical transmission device control device, base station control device, optical transmission device, control method, and optical path switching method

Abstract

Provided is an optical transmission device control device in a signal transfer system comprising: a plurality of base stations that accommodate one or more wireless terminals; a plurality of optical transmission devices that are connected to at least one of the plurality of base stations; an optical transmission device control device that controls the plurality of optical transmission devices; and a base station control device that controls the plurality of base stations. The optical transmission device control device comprises an information analysis unit that, in response to movement of one or more of the wireless terminals, instructs the base station control device to change the connection with the one or more moved wireless terminals, and in conjunction with the timing at which the connection with the one or more moved wireless terminals is changed, instructs each optical transmission device that is an optical path switching target to switch optical paths.　

Description

Optical Transmission Device Control Device, Base Station Control Device, Optical Transmission Device, Control Method, and Optical Path Switching Method

[0001] The present invention relates to an optical transmission device control device, a base station control device, an optical transmission device, a control method, and an optical path switching method.

[0002] In a conventional mobile communication network, as shown in FIG. 10, an optical path is generated between a base station and a core node that is the connection destination of the base station. Then, communication is performed between the base station and the core node via the generated optical path. FIG. 10 is a diagram showing a configuration example of a conventional signal transfer system. As shown in FIG. 10, the signal transfer system includes a core node, an optical transmission device, an optical transmission device controller, a base station controller, and a base station.

[0003] The core node communicates with a wireless terminal via an optical transmission device and a base station. The optical transmission device is a device that transfers signals exchanged between the core node and the wireless terminal. The optical transmission device controller is a device that controls the optical transmission device. The base station controller is a device that controls the base station. The base station is wirelessly connected to the wireless terminal, transmits the signal transferred from the optical transmission device to the wireless terminal, and transfers the signal received from the wireless terminal to the optical transmission device.

[0004] Unlike a conventional packet network, research is underway on an all-photonic network (APN: All-Photonic Network) that provides a large-capacity and low-latency line by allocating dedicated resources of one wavelength to one user or one traffic flow using wavelength multiplexing (see, for example, Non-Patent Document 1). In order to be able to provide the dedicated resources of one wavelength in the all-photonic network to the wireless terminals in the mobile communication network as well, it is necessary for the optical path of the dedicated wavelength allocated for each wireless terminal or traffic flow to be switched along with the handover due to the movement of the wireless terminal (see, for example, 9.2.3 of Non-Patent Document 2). Such standards in the mobile communication network are established by 3GPP (Third Generation Partnership Project) (3GPP is a registered trademark).

[0005] “Open All-Photonic Network Functional Architecture”, IOWN Global Forum, 2023. “3GPP TS38.300 V18.2.0”, 3GPP, 2024. “O-RAN.WG1.Use-Cases-Detailed-Specification-R003-v13.00”, O-RAN Alliance, 2024. “3GPP TS 23.501 V19.0.0”, 3GPP, 2024.

[0006] Unlike packet networks where routing can be changed by changing the destination address, mobile communication networks using all-photonic networks cannot switch the optical path between the base station and core node at the appropriate timing in conjunction with handover. As a result, there was a problem where packet loss occurred, such as packets that should have been sent to the source base station or core node being mistakenly sent to the destination base station or core node.

[0007] In view of the above circumstances, the present invention aims to provide a technology that enables switching of a specific optical path related to a wireless terminal in response to the movement of the wireless terminal, while suppressing packet loss.

[0008] One aspect of the present invention is an optical transmission device control device in a signal transmission system comprising: a plurality of base stations accommodating one or more wireless terminals; a plurality of optical transmission devices connected to at least one of the plurality of base stations; an optical transmission device control device for controlling the plurality of optical transmission devices; and a base station control device for controlling the plurality of base stations, wherein the optical transmission device control device comprises an information analysis unit that, in response to the movement of one or more wireless terminals, instructs the base station control device to change the connection with the one or more wireless terminals that have moved, and instructs each optical transmission device subject to optical path switching to switch the optical path in conjunction with the timing at which the connection change with the one or more wireless terminals that have moved is performed.

[0009] One aspect of the present invention is a base station control device in a signal transfer system comprising: a plurality of base stations accommodating one or more wireless terminals; a plurality of optical transmission devices connected to at least one of the plurality of base stations; an optical transmission device control device for controlling the plurality of optical transmission devices; and a base station control device for controlling the plurality of base stations, wherein the base station control device comprises a control determination unit that transmits a handover instruction to each base station subject to handover when it receives a handover execution instruction from the optical transmission device control device or another device in response to the movement of one or more wireless terminals.

[0010] One aspect of the present invention is an optical transmission device in a signal transfer system comprising a plurality of base stations accommodating one or more wireless terminals, and a plurality of optical transmission devices connected to at least one of the plurality of base stations, wherein the optical transmission device includes an optical control unit that performs optical path switching in conjunction with the timing at which a connection change is performed with the one or more wireless terminals that have moved, at each base station that is subject to handover in response to the movement of the one or more wireless terminals.

[0011] One aspect of the present invention is a control method performed by an optical transmission device control device in a signal transmission system comprising a plurality of base stations accommodating one or more wireless terminals, a plurality of optical transmission devices connected to at least one of the plurality of base stations, an optical transmission device control device for controlling the plurality of optical transmission devices, and a base station control device for controlling the plurality of base stations, wherein, in response to the movement of one or more wireless terminals, the control method instructs the base station control device to change the connection with the one or more wireless terminals that have moved, and instructs each optical transmission device subject to optical path switching to switch the optical path in conjunction with the timing at which the connection change with the one or more wireless terminals that have moved is performed.

[0012] One aspect of the present invention is a control method performed by a base station control device in a signal transfer system comprising a plurality of base stations accommodating one or more wireless terminals, a plurality of optical transmission devices connected to at least one of the plurality of base stations, an optical transmission device control device for controlling the plurality of optical transmission devices, and a base station control device for controlling the plurality of base stations, wherein when the optical transmission device control device or another device receives a handover execution instruction in response to the movement of one or more wireless terminals, the control method transmits a handover instruction to each base station subject to the handover.

[0013] One aspect of the present invention is an optical path switching method performed by an optical transmission device in a signal transfer system comprising a plurality of base stations accommodating one or more wireless terminals and a plurality of optical transmission devices connected to at least one of the plurality of base stations, wherein the optical path switching is performed in conjunction with the timing at which a connection change is performed with the one or more wireless terminals that have moved, at each base station that is subject to handover in response to the movement of the one or more wireless terminals.

[0014] The present invention makes it possible to switch specific optical paths related to a wireless terminal in response to the movement of the wireless terminal, while suppressing packet loss.

[0015] This figure shows an example of the configuration of the signal transfer system in the first embodiment. This is a sequence diagram showing the processing flow of the signal transfer system in the first embodiment. This figure shows an example of the configuration of the signal transfer system in a modified version of the first embodiment. This figure shows an example of the configuration of the signal transfer system in the second embodiment. This figure shows an example of the configuration of the signal transfer system in the third embodiment. This figure shows an example of the configuration of the signal transfer system in the fourth embodiment. This is a sequence diagram showing the processing flow of the signal transfer system in the fourth embodiment. This figure shows an example of the configuration of the signal transfer system in the fifth embodiment. This figure shows an example of the configuration of the signal transfer system in the sixth embodiment. This figure shows an example of the configuration of a conventional signal transfer system.

[0016] One embodiment of the present invention will be described below with reference to the drawings.

[0017] (First Embodiment) Figure 1 shows an example of the configuration of the signal transfer system 100 in the first embodiment. The signal transfer system 100 is a system that transfers signals from one communication device to another. The signal transfer system 100 includes, for example, a core node 10, an optical transmission device 20, an optical transmission device 25, an optical transmission device controller 30, a base station 40, and a base station controller 50. One or more wireless terminals 60 are wirelessly connected to the base station 40. In the following description, the direction from the core node 10 toward the wireless terminal 60 is described as the downlink direction, and the direction from the wireless terminal 60 toward the core node 10 is described as the uplink direction.

[0018] Figure 1 shows a configuration in which the signal transmission system 100 comprises one optical transmission device 20, two optical transmission devices 25-1 to 25-2, and two base stations 40-1 to 40-2. Note that the number of optical transmission devices 25 and base stations 40 is not limited as long as there are two or more, and the number of optical transmission devices 20 is not limited as long as there is one or more.

[0019] The core node 10 and the optical transmission device 20, the optical transmission device 20 and the optical transmission device 25, and the optical transmission device 25 and the base station 40 are connected by, for example, an optical transmission path. The optical transmission path is a path for transmitting optical signals, and is, for example, an optical fiber. The optical transmission path may include an optical amplifier for amplifying the optical signals.

[0020] Furthermore, the optical transmission device controller 30 and the base station controller 50, the optical transmission device controller 30 and the optical transmission device 20, the optical transmission device controller 30 and the optical transmission device 25, and the base station controller 50 and the base station 40 are connected, for example, by control lines that transmit control signals.

[0021] In describing the first embodiment, we assume that the initial state is that the wireless terminal 60 is connected to base station 40-1 and then to core node 10 via optical transmission device 25-1 and optical transmission device 20. Then, we assume that when the wireless terminal 60 moves and a handover becomes necessary, the wireless terminal 60 connects to base station 40-2 and then to core node 10 via optical transmission device 25-2 and optical transmission device 20. Note that base station 40-1 may also be referred to as the source base station and base station 40-2 as the destination base station.

[0022] The core node 10 is a device that communicates with each of the one or more wireless terminals 60 that are wirelessly connected to each base station 40. For example, the core node 10 receives uplink signals transmitted from the wireless terminals 60 and transmits downlink signals to the wireless terminals 60. The core node 10 is one form of a higher-level device.

[0023] Optical transmission devices 20 and 25 are devices that transfer signals exchanged between the core node 10 and one or more wireless terminals 60. Optical transmission device 20, for example, receives an uplink signal transmitted from a wireless terminal 60 from optical transmission device 25 and transfers it to the core node 10. Optical transmission device 20, for example, transfers a downlink signal transmitted from the core node 10 to the optical transmission device 25 to which the destination wireless terminal 60 is connected.

[0024] The optical transmission device 25, for example, receives an uplink signal transmitted from the wireless terminal 60 from the connected base station 40 and forwards it to the optical transmission device 20. The optical transmission device 25, for example, forwards a downlink signal forwarded from the optical transmission device 20 to the connected base station 40.

[0025] Furthermore, the optical transmission devices 20 and 25 perform dedicated optical path switching processing in response to optical path switching control instructions transmitted from the optical transmission device controller 30. The optical path switching control instructions are instructions to cause the optical transmission devices 20 and 25 to switch optical paths. A dedicated optical path is an optical path with a different wavelength from the basic optical path that is normally used, and is, for example, an optical path with a dedicated wavelength assigned to each wireless terminal 60 or traffic flow. In this way, a dedicated optical path is set up to transmit a specific traffic flow of a specific wireless terminal 60. The dedicated optical path switching processing is the process of switching the connection destination of the dedicated optical path in the section from the core node 10 to the base station 40.

[0026] When communication takes place between the wireless terminal 60 and the core node 10, the optical transmission devices 20 and 25 generate an optical path for transferring optical signals in the section from the core node 10 to the base station 40. This optical path is the basic optical path normally used to exchange all signals transmitted and received by each wireless terminal 60 connected to the same base station 40 with the core node 10. In the basic optical path, as described above, multiple traffic flows from each wireless terminal 60 connected to the same base station 40 will be mixed together. In contrast, a dedicated optical path is an optical path set up to transmit a specific traffic flow, so other traffic flows will not be mixed in.

[0027] In response to an optical path switching control instruction transmitted from the optical path switching controller 30, the optical transmission device 20 switches the dedicated optical path that corresponds to the wireless terminal 60 whose connection destination has been switched due to handover, and which is formed between the core node 10 and the optical transmission device 25. The optical transmission device 20 may, for example, delete the dedicated optical path formed with optical transmission device 25-1 and form a new dedicated optical path with optical transmission device 25-2. Alternatively, instead of deleting and forming a dedicated optical path, the optical transmission device 20 may change the input / output port of the signal for the dedicated optical path from a port for optical transmission device 25-1 to a port for optical transmission device 25-2.

[0028] The optical transmission device 25 switches the dedicated optical path that corresponds to the wireless terminal 60 whose connection destination has been switched due to handover, in response to an optical path switching control instruction transmitted from the optical transmission device controller 30. The dedicated optical path is formed between the core node 10 and the optical transmission device 20. The optical transmission device 25-1 deletes, for example, the dedicated optical path formed between the optical transmission device 20 and the base station 40-1. The optical transmission device 25-2 forms a new dedicated optical path between, for example, the optical transmission device 20 and the base station 40-2.

[0029] The optical transmission device controller 30 is a control device that controls the optical transmission devices 20 and 25. Here, the control of the optical transmission devices 20 and 25 means the control of switching optical paths in the optical transmission devices 20 and 25. The optical transmission device controller 30 acquires information regarding wireless communication between the base station 40 and the wireless terminal 60 (hereinafter referred to as "wireless control information") from the base station 40 for each traffic flow.

[0030] The wireless control information includes wireless bandwidth information for each traffic flow, information indicating priority for each traffic flow, and wireless quality information. The wireless bandwidth information for each traffic flow is, for example, the PDCP (Packet Data Convergence Protocol) throughput for each traffic flow (see, for example, Non-Patent Document 3). The wireless bandwidth information for each traffic flow may also be the PDCP SDU Data Volume and PDCP PDU size for each Scheduling Request, Uplink Grant, Buffer Status Report, QFI (QoS Flow Indicator). The information indicating priority for each traffic flow is the QCI (QoS Class Indicator), 5QI (5G QoS Indicator), etc. (see, for example, Non-Patent Document 4). Wireless quality information includes RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), RSSI (Received Signal Strength Indicator), etc., for each wireless terminal 60.

[0031] Based on the acquired wireless control information for each traffic flow, the optical transmission device controller 30 determines that a handover of the wireless terminal 60 is necessary. In this case, it issues a handover instruction to the base station controller 50 and transmits optical path switching control instructions to the optical transmission devices 20 and 25. The optical transmission device controller 30 also takes into account the delay time based on pre-held delay information when transmitting optical path switching control instructions to the optical transmission devices 20 and 25.

[0032] The delay information is information regarding the signal transmission delay that occurs between the core node 10 and the base stations 40, and includes, for example, the distance between the core node 10 and each base station 40, processing delays by the optical transmission devices 20 and 25 (e.g., transmission delay, delay from receiving an instruction to switch optical paths until the optical path switching is performed, etc.), or control delays from the optical transmission device controller 30 to the optical transmission devices 20 and 25 (e.g., the distance from the optical transmission device controller 30 to the optical transmission devices 20 and 25).

[0033] When switching optical paths, if the optical path switching is not performed at the appropriate timing in conjunction with the path switching associated with the handover sequence between the core node 10 and the base station 40, packet loss may occur because packets that should be sent to the source base station are sent to the destination base station instead. To prevent this packet loss, the optical transmission device controller 30 adjusts the timing of the instruction to the optical transmission devices 20 and 25 for optical path switching control. Here, adjusting the instruction timing means delaying the instruction timing for optical path switching control by taking delay information into account, or conversely, advancing the instruction timing for optical path switching control. In this example, for example, the optical transmission device controller 30 takes into account the delay due to the distance between the base station 40 and the core node 10, and the time difference from receiving the optical path switching control instruction until the optical path switching is activated, and adjusts the transmission timing of the optical path switching control so that the optical path switching is activated just before the core node 10 starts sending downlink signals to the destination base station.

[0034] In this way, the optical transmission device controller 30 adjusts the transmission timing of the optical path switching control so that when the wireless terminal 60 moves, it can instruct the base station controller 50 to change the connection with the moved wireless terminal 60, and in conjunction with the timing at which the connection change with the moved wireless terminal 60 is executed, it can instruct each optical transmission device 20, 25 that is subject to optical path switching to switch the optical path.

[0035] The base station 40 is a device that communicates with each of the one or more wireless terminals 60. The base station 40 transmits signals transferred from the optical transmission device 25 to the wireless terminals 60 wirelessly, and converts signals received from the wireless terminals 60 into optical signals and transfers them to the optical transmission device 25. When a handover process becomes necessary due to the movement of a wireless terminal 60, the base station 40 performs the handover process in accordance with instructions from the base station controller 50.

[0036] The base station 40 may be, for example, a Wi-Fi® access point. Therefore, the signal transfer system 100 may be applied to wireless communication systems other than mobile communication systems. This is also true in the embodiments shown below.

[0037] The base station controller 50 is a device that controls the base stations 40. Here, controlling the base station 40 means switching the connection with the wireless terminal 60 in response to a handover execution instruction. In response to a handover instruction from the optical transmission device controller 30, the base station controller 50 transmits a handover instruction to each base station 40 that is subject to the handover.

[0038] The wireless terminal 60 is a user terminal operated by a user. The wireless terminal 60 has one or more traffic flows. The wireless terminal 60 communicates wirelessly with the base station 40. For example, the wireless terminal 60 receives downlink signals transmitted from the core node 10 via the base station 40. For example, the wireless terminal 60 transmits uplink signals destined for the core node 10 to the base station 40.

[0039] [Device Configuration] Next, we will describe the specific configuration of each device.

[0040] The optical transmission device 20 includes an optical control unit 21. The optical control unit 21 switches optical paths according to optical path switching control instructions transmitted from the optical transmission device controller 30. For example, when the optical control unit 21 receives an optical path switching control instruction, it deletes the dedicated optical path formed between the core node 10 and the optical transmission device 25-1 and forms a new dedicated optical path between the core node 10 and the optical transmission device 25-2. Alternatively, instead of deleting and forming a dedicated optical path, the optical control unit 21 may change the input / output port of the optical signal transmitted through the dedicated optical path of the optical transmission device 20 from a port for optical transmission device 25-1 to a port for optical transmission device 25-2.

[0041] In this way, the optical control unit 21, in response to receiving an optical path switching control instruction, switches the optical path so that signals can be sent and received between the moving wireless terminal 60 and the core node 10 by forming a new dedicated optical path between the core node 10 and the optical transmission device 25-2.

[0042] The optical transmission device 25 includes an optical control unit 26. The optical control unit 26 switches optical paths according to an optical path switching control instruction transmitted from the optical transmission device controller 30. The optical control unit 26-1 of the optical transmission device 25-1 deletes the dedicated optical path formed between the optical transmission device 20 and the base station 40-1 when it receives an optical path switching control instruction. The optical control unit 26-2 of the optical transmission device 25-2 forms a new dedicated optical path between the optical transmission device 20 and the base station 40-2 when it receives an optical path switching control instruction.

[0043] In this way, the optical control unit 26, in response to receiving an optical path switching control instruction, switches the optical path so that signals can be sent and received between the mobile wireless terminal 60 and the core node 10 by forming a new dedicated optical path between the optical transmission device 20 and the base station 40-2.

[0044] The base station 40 includes an information acquisition unit 41 and a radio control unit 42. The information acquisition unit 41 acquires radio control information for each traffic flow exchanged between the wireless terminal 60 and the core node 10. Note that the information acquisition unit 41 may acquire external information such as the movement information of an automobile or the trajectory of a drone as radio control information. In the following description, as an example, the case where the information acquisition unit 41 acquires radio control information for each traffic flow from the wireless terminal 60 to the core node 10 will be described. The information acquisition unit 41 notifies the optical transmission device controller 30 of the acquired radio control information.

[0045] The radio control unit 42 performs a handover between the base stations 40-1 and 40-2 in response to an instruction from the base station controller 50.

[0046] The optical transmission device controller 30 includes an information analysis unit 31. The information analysis unit 31 acquires the radio control information acquired by the information acquisition unit 41 of each base station 40. The information analysis unit 31 determines whether a handover of the wireless terminal 60 is necessary based on the acquired radio control information. An existing method is used as the method for determining whether a handover is necessary.

[0047] When the information analysis unit 31 determines that a handover of the wireless terminal 60 is necessary, it issues a handover instruction to the base station controller 50 and transmits an optical path switching control instruction to the optical transmission devices 20 and 25. Note that, as described above, the transmission timing of the optical path switching control instruction is implemented at a timing taking into account the delay information.

[0048] The base station controller 50 includes a control decision unit 51. The control decision unit 51 transmits a handover instruction to each of the base stations 40-1 and 40-2 according to the handover instruction received from the optical transmission device controller 30.

[0049] [Operation] Figure 2 is a sequence diagram showing the processing flow of the signal transfer system 100 in the first embodiment. In Figure 1, the optical transmission devices 20 and 25 are collectively referred to as the optical transmission device (group). At the start of processing in Figure 1, it is assumed that the wireless terminal 60 is connected to the base station 40-1, which is the mobile base station. Therefore, the user signal transmitted from the wireless terminal 60 is transferred to the core node 10 via the base station 40-1.

[0050] The wireless terminal 60 transmits measurement information to each base station 40-1 and 40-2 (steps S101 and S102). Now, suppose the wireless terminal 60 moves closer to base station 40-2 in response to the user of the wireless terminal 60 moving. The information acquisition units 41-1 and 41-2 of each base station 40-1 and 40-2 acquire the measurement information transmitted from the wireless terminal 60. The information acquisition units 41-1 and 41-2 notify the optical transmission device controller 30 of the acquired measurement information as wireless control information (steps S103 and S104).

[0051] The information analysis unit 31 of the optical transmission device controller 30 analyzes the wireless control information notified from each base station 40-1, 40-2 to determine whether a handover is necessary (step S105). Here, it is determined that a handover is necessary. The information analysis unit 31 of the optical transmission device controller 30 sends a handover instruction to the base station controller 50 (step S106). If a handover is determined to be necessary, the information analysis unit 31 needs to send an optical path switching control instruction to each optical transmission device 20, 25 in order to switch the optical path. However, if the optical path switching is performed immediately, packet loss may occur. Therefore, the information analysis unit 31 adjusts the timing of the transmission of the optical path switching control instruction so that the optical path switching is performed just before the core node 10 starts transmitting the downlink signal to the destination base station, taking into account a delay corresponding to the distance between the base station 40 and the core node 10, or the time difference from the timing when the optical transmission devices 20, 25 receive the optical path switching control instruction until they actually perform the optical path switching.

[0052] The control decision unit 51 of the base station controller 50 instructs the target base stations 40-1 and 40-2 to perform a handover in response to a handover instruction from the optical transmission device controller 30 (steps S107, S108). Base stations 40-1 and 40-2 switch their connection with the wireless terminal 60 in response to the handover instruction from the base station controller 50 (step S109). As a result, for example, the base station 40 to which the wireless terminal 60 will connect is switched from base station 40-1 to base station 40-2. Once the connection switch is complete, base station 40-2, which is the destination base station, sends a route change request to the core node 10 (step S110).

[0053] The core node 10 receives a route change request transmitted from the base station 40-2. The core node 10 processes the route change in response to the received route change request (step S111). Specifically, when the core node 10 transmits a signal destined for the wireless terminal 60, it changes the route so that it passes through the optical transmission device 25-2.

[0054] When the optical transmission device controller 30's information analysis unit 31 reaches the timing for transmitting optical path switching control, it transmits an optical path switching control instruction to the optical transmission devices 20 and 25 (step S112). The optical control units 21 and 26 of the optical transmission devices 20 and 25 switch the dedicated optical paths according to the optical path switching control instruction from the optical transmission device controller 30 (step S113). Specifically, the optical control unit 26-1 of optical transmission device 25-1 deletes the dedicated optical path with optical transmission device 20. The optical control unit 26-2 of optical transmission device 25-2 creates a dedicated optical path with optical transmission device 20. The optical control unit 21 of optical transmission device 20 switches to form a dedicated optical path with optical transmission device 25.

[0055] Through the above process, the user signal transmitted from the wireless terminal 60 is transferred to the core node 10 via the base station 40-2 (destination base station). Here, the deletion of the dedicated optical path between the optical transmission device 25-1 and the optical transmission device 20, as described earlier, may be performed when the processing in step S111 is completed and the path between the optical transmission device 25-1 and the optical transmission device 20 is no longer needed.

[0056] When the core node 10 completes the route change process, it sends a route change response to the base station 40-2 indicating that the route change process is complete (step S114). The base station 40-2 receives the route change response sent from the core node 10. In response to the received route change response, the base station 40-2 causes the mobile base station 40-1 to release the connection of the wireless terminal 60 (step S115).

[0057] According to the signal transfer system 100 configured as described above, the optical transmission device controller 30 instructs the base station controller 50 to change the connection with the moved wireless terminal 60 in response to the movement of the wireless terminal 60, and the information analysis unit 31 instructs each optical transmission device 20, 25 that is subject to optical path switching to switch the optical path in conjunction with the timing at which the connection change with the moved wireless terminal 60 is executed.

[0058] With this configuration, when a handover becomes necessary due to the movement of the wireless terminal 60, the optical paths of the optical transmission devices 20 and 25 can be switched in conjunction with the change in connection to the destination base station to which the wireless terminal 60 is connected after the move. As described above, if the switching timing of the optical paths of the optical transmission devices 20 and 25 is too early, packets may be lost because signals that should be forwarded to the source base station are forwarded to the destination base station instead. In contrast, the optical transmission device controller 30 in this embodiment switches the optical paths in conjunction with the change in connection to the destination base station to which the wireless terminal 60 is connected after the move. Therefore, it becomes possible to switch specific optical paths related to the wireless terminal in response to the movement of the wireless terminal 60 while suppressing packet loss.

[0059] Furthermore, the signal transfer system 100 includes a control determination unit 51 that transmits a handover instruction to each base station 40 subject to the handover when the base station controller 50 receives a handover execution instruction from the optical transmission device controller 30 in response to the movement of the wireless terminal 60.

[0060] In this way, the base station controller 50 receives a handover execution instruction from the optical transmission device controller 30, which controls each optical transmission device 20, 25. Therefore, the optical transmission device controller 30 can understand that the base station 40 to which the wireless terminal 60 is connected will switch due to the handover. As a result, the base station controller 50 sends a handover instruction to each base station 40 that is subject to the handover, and in response to the change in the base station 40 to which the wireless terminal 60 is connected, the optical path switching in the optical transmission devices 20, 25 is also executed in conjunction. Therefore, in response to the movement of the wireless terminal 60, it becomes possible to switch specific optical paths related to the wireless terminal while suppressing packet loss.

[0061] (Modified Configuration) In the configuration shown in Figure 1, an orchestrator may be provided as a higher-level control device above the optical transmission device controller 30 and the base station controller 50, and the orchestrator may be configured to relay communication between the optical transmission device controller 30 and the base station controller 50. Figure 3 is a diagram showing an example configuration of a signal transfer system 100a in a modified configuration of the first embodiment. The signal transfer system 100a is a system that transfers signals from one communication device to another. The signal transfer system 100a includes, for example, a core node 10, an optical transmission device 20, an optical transmission device 25, an optical transmission device controller 30, a base station 40, a base station controller 50, and an orchestrator 55a. The signal transfer system 100a differs from the signal transfer system 100 in that it newly includes an orchestrator 55a. The differences from the signal transfer system 100 will be explained below.

[0062] The information analysis unit 31 of the optical transmission device controller 30 generates a handover instruction if it determines that a handover is necessary. The information analysis unit 31 transmits the generated handover instruction to the orchestrator 55a.

[0063] The orchestrator 55a is a higher-level control device positioned above the optical transmission device controller 30 and the base station controller 50. The orchestrator 55a includes an information transfer unit 56. The information transfer unit 56 relays information between the optical transmission device controller 30 and the base station controller 50. For example, the information transfer unit 56 relays a handover instruction transmitted from the optical transmission device controller 30 to the base station controller 50.

[0064] The control decision unit 51 of the base station controller 50 receives the handover instruction relayed by the orchestrator 55a. The control decision unit 51 transmits the received handover instruction to each base station 40-1, 40-2.

[0065] (Second Embodiment) In the second embodiment, a signal transmission system using a distributed central station and distributed stations as base stations will be described. More specifically, in the second embodiment, an optical transmission device is installed in a section called MMH (Mobile Midhaul), and the distributed stations perform a handover based on the result of the optical transmission device controller's determination of whether or not a handover is necessary.

[0066] Figure 4 shows an example of the configuration of the signal transfer system 100b in the second embodiment. The signal transfer system 100b is a system that transfers signals from one communication device to another. The signal transfer system 100b includes, for example, an optical transmission device 20, an optical transmission device 25, an optical transmission device controller 30, a base station 40b, and a base station controller 50. The base station 40b consists of a central station 65 and one or more distributed stations 70. In Figure 4, the case in which the base station 40b consists of a central station 65 and two distributed stations 70 is explained as an example, but there may be three or more distributed stations 70. Thus, the signal transfer system 100b differs in configuration from the signal transfer system 100 in that it does not have a core node 10 and instead of a base station 40, it has a base station 40b consisting of a central station 65 and distributed stations 70. The following explanation will focus on the differences from the signal transfer system 100.

[0067] The central station 65 and the optical transmission device 20, the optical transmission device 20 and the optical transmission device 25, and the optical transmission device 25 and the distributed station 70 are connected, for example, by optical transmission lines. In addition, the optical transmission device controller 30 and the base station controller 50, the optical transmission device controller 30 and the optical transmission device 20, the optical transmission device controller 30 and the optical transmission device 25, and the base station controller 50 and the distributed station 70 are connected, for example, by control lines that transmit control signals.

[0068] In describing the second embodiment, we assume that the initial state is that the wireless terminal 60 is connected to distributed station 70-1 and then to the central station 65 via optical transmission device 25-1 and optical transmission device 20. Then, we assume that when the wireless terminal 60 moves and a handover becomes necessary, the wireless terminal 60 connects to distributed station 70-2 and then to the central station 65 via optical transmission device 25-2 and optical transmission device 20. Note that distributed station 70-1 may also be referred to as the source distributed station and distributed station 70-2 as the destination distributed station.

[0069] For example, in the second embodiment, the central station 65 is one or more CUs (Central Units) in the mobile communication system, and the distributed station 70 is a DU (Distributed Unit) in the mobile communication system. In this case, the section between the CUs and DUs where the optical transmission devices 20 and 25 are installed is called the MMH.

[0070] Furthermore, the central station 65 may be a Wi-Fi controller, and the distributed stations 70 may be Wi-Fi access points. The signal transfer system 100b does not necessarily have to be applied to a mobile communication system, and may be applied to wireless communication systems other than mobile communication systems.

[0071] The central station 65 is a device that communicates with each of the one or more wireless terminals 60 that are wirelessly connected to each distributed station 70. For example, the central station 65 receives uplink signals transmitted from the wireless terminals 60 and transmits downlink signals to the wireless terminals 60. The central station 65 is one form of a higher-level device.

[0072] The distributed station 70 is a device that communicates with the wireless terminal 60. Through communication with the wireless terminal 60, the distributed station 70 transmits signals transferred from the optical transmission device 25 to the wireless terminal 60, or transfers signals received from the wireless terminal 60 to the optical transmission device 25 at the transfer destination.

[0073] [Device Configuration] The distributed station 70 includes an information acquisition unit 41 and a radio control unit 42. The information acquisition unit 41 of the distributed station 70 performs the same processing as the information acquisition unit 41 in Figure 1. The radio control unit 42 of the distributed station 70 performs the same processing as the radio control unit 42 in Figure 1. However, it is necessary to read the base station 40 as the distributed station 70.

[0074] [Operation] The processing performed by the signal transfer system 100b is the same as in Figure 2 if you replace the core node 10 in Figure 2 with the central station 65, the base station 40-1 with the distributed station 70-1, and the base station 40-2 with the distributed station 70-2.

[0075] With the signal transfer system 100b configured as described above, even in a configuration where base stations 40b are distributed and optical transmission devices 20 and 25 are installed in the MMH, the same effects as in the first embodiment can be obtained.

[0076] (Modification) The signal transfer system 100b may, similar to the first embodiment, include an orchestrator as a control device above the optical transmission device controller 30 and the base station controller 50, and the orchestrator may be configured to relay communication between the optical transmission device controller 30 and the base station controller 50.

[0077] (Third Embodiment) In the third embodiment, a signal transmission system using a distributed central station and distributed stations as base stations will be described. More specifically, in the third embodiment, an optical transmission device is installed in a section called MFH (Mobile Fronthaul), and the distributed stations perform a handover based on the result of the optical transmission device controller's determination of whether a handover is necessary.

[0078] Figure 5 shows an example of the configuration of the signal transfer system 100c in the third embodiment. The signal transfer system 100c is a system that transfers signals from one communication device to another. The signal transfer system 100c includes, for example, an optical transmission device 20, an optical transmission device 25, an optical transmission device controller 30, a base station 40c, and a base station controller 50. The base station 40c consists of a central station 65c and one or more distributed stations 70c. In Figure 5, the case in which the base station 40c consists of a central station 65c and two distributed stations 70c is explained as an example, but there may be three or more distributed stations 70c. Thus, the signal transfer system 100c differs in configuration from the signal transfer system 100 in that it does not have a core node 10 and instead of a base station 40, it has a base station 40c composed of a central station 65c and distributed stations 70c. The following explanation will focus on the differences from the signal transfer system 100.

[0079] The central station 65c and the optical transmission device 20, the optical transmission device 20 and the optical transmission device 25, and the optical transmission device 25 and the distributed station 70c are connected, for example, by an optical transmission path. In addition, the optical transmission device controller 30 and the base station controller 50, the optical transmission device controller 30 and the optical transmission device 20, the optical transmission device controller 30 and the optical transmission device 25, and the base station controller 50 and the distributed station 70c are connected, for example, by a control line that transmits control signals.

[0080] In describing the third embodiment, we assume that the initial state is that the wireless terminal 60 is connected to distributed station 70c-1 and then to the central station 65c via optical transmission device 25-1 and optical transmission device 20. Then, we assume that when the wireless terminal 60 moves and a handover becomes necessary, the wireless terminal 60 connects to distributed station 70c-2 and then to the central station 65c via optical transmission device 25-2 and optical transmission device 20. Note that distributed station 70c-1 may also be referred to as the source distributed station and distributed station 70c-2 as the destination distributed station.

[0081] For example, in the third embodiment, the central station 65c is one or more DUs in the mobile communication system, and the distributed station 70c is a RU (Radio Unit) in the mobile communication system. In this case, the section between the DUs and RUs where the optical transmission devices 20 and 25 are installed is called the MFH (Mobile Fronthaul).

[0082] Furthermore, the central station 65c may be a Wi-Fi controller, and the distributed stations 70c may be Wi-Fi access points. The signal transfer system 100c does not necessarily have to be applied to a mobile communication system, and may be applied to wireless communication systems other than mobile communication systems.

[0083] The central station 65c is a device that communicates with each of the one or more wireless terminals 60 that are wirelessly connected to each distributed station 70c. For example, the central station 65c receives uplink signals transmitted from the wireless terminals 60 and transmits downlink signals to the wireless terminals 60. Furthermore, the central station 65c acquires wireless control information and notifies the optical transmission device controller 30 of the acquired wireless control information. The central station 65c is one embodiment of a higher-level device.

[0084] The distributed station 70c is a device that communicates with the wireless terminal 60. Through communication with the wireless terminal 60, the distributed station 70c transmits signals transferred from the optical transmission device 25 to the wireless terminal 60, or transfers signals received from the wireless terminal 60 to the destination optical transmission device 25.

[0085] The optical transmission device controller 30 acquires wireless control information notified from the central station 65c. The processing performed by the optical transmission device controller 30 after acquiring the wireless control information is the same as in the first embodiment.

[0086] [Device Configuration] The central station 65c is equipped with an information acquisition unit 66. The information acquisition unit 66 acquires wireless control information for each traffic flow that the wireless terminal 60 exchanges with the central station 65c. The information acquisition unit 66 notifies the optical transmission device controller 30 of the acquired wireless control information.

[0087] The distributed station 70c is equipped with a radio control unit 42. The radio control unit 42 in the distributed station 70c performs the same processing as the radio control unit 42 in Figure 1.

[0088] [Operation] The processing performed by the signal transfer system 100c is the same as in Figure 2 if you replace the core node 10 in Figure 2 with the central station 65, the base station 40-1 with the distributed station 70c-1, and the base station 40-2 with the distributed station 70c-2.

[0089] With the signal transfer system 100c configured as described above, even in a configuration where base stations 40c are distributed and optical transmission devices 20 and 25 are installed in the MFH, the same effects as in the first embodiment can be obtained.

[0090] (Modification) The signal transfer system 100c may, similar to the first embodiment, include an orchestrator as a control device above the optical transmission device controller 30 and the base station controller 50, and the orchestrator may be configured to relay communication between the optical transmission device controller 30 and the base station controller 50.

[0091] (Fourth Embodiment) In the fourth embodiment, the signal transmission system does not include a base station controller and an optical transmission device controller, and the base station performs the handover based on the result of determining whether or not a handover is necessary for each optical transmission device.

[0092] Figure 6 shows an example configuration of the signal transfer system 100d in the fourth embodiment. The signal transfer system 100d is a system that transfers signals from one communication device to another. The signal transfer system 100d includes, for example, a core node 10, an optical transmission device 20d, an optical transmission device 25d, and a base station 40d. One or more wireless terminals 60 are wirelessly connected to the base station 40d. The signal transfer system 100d differs from the signal transfer system 100 in that it does not include an optical transmission device controller 30 and a base station controller 50, and instead of optical transmission devices 20, 25 and base station 40, it includes optical transmission devices 20d, 25d and base station 40d. The differences from the signal transfer system 100 will be explained below.

[0093] Figure 6 shows a configuration in which the signal transmission system 100d comprises one optical transmission device 20d, two optical transmission devices 25d-1 to 25d-2, and two base stations 40d-1 to 40d-2. Note that the number of optical transmission devices 25d and base stations 40d is not limited as long as there are two or more, and the number of optical transmission devices 20d is not limited as long as there is one or more.

[0094] The core node 10 and the optical transmission device 20d, the optical transmission device 20d and the optical transmission device 25d, and the optical transmission device 25d and the base station 40d are connected, for example, by optical transmission lines. Furthermore, each optical transmission device 20d, 25d and the base station 40d are connected by control lines that transmit control signals.

[0095] In describing the fourth embodiment, we assume that the initial state is that the wireless terminal 60 is connected to base station 40d-1 and then to the core node 10 via optical transmission device 25d-1 and optical transmission device 20d. Then, we assume that when the wireless terminal 60 moves and a handover becomes necessary, the wireless terminal 60 connects to base station 40d-2 and then to the core node 10 via optical transmission device 25d-2 and optical transmission device 20d. Note that base station 40d-1 may also be referred to as the source base station and base station 40d-2 as the destination base station.

[0096] Optical transmission devices 20d and 25d are devices that transfer signals exchanged between the core node 10 and one or more wireless terminals 60. Optical transmission device 20d, for example, receives an uplink signal transmitted from a wireless terminal 60 from optical transmission device 25d and transfers it to the core node 10. Optical transmission device 20d, for example, transfers a downlink signal transmitted from the core node 10 to the optical transmission device 25d to which the destination wireless terminal 60 is connected.

[0097] The optical transmission device 25d, for example, receives an uplink signal transmitted from the wireless terminal 60 from the connected base station 40d and forwards it to the optical transmission device 20d. The optical transmission device 25d, for example, forwards a downlink signal forwarded from the optical transmission device 20d to the connected base station 40d.

[0098] Furthermore, the optical transmission devices 20d and 25d acquire wireless control information from the mobile base station for each traffic flow. Based on the acquired wireless control information for each traffic flow, the optical transmission devices 20d and 25d determine that a handover of the wireless terminal 60 is necessary, and issue a handover instruction to the mobile base station, as well as switch the optical path within their own devices. The handover instruction to the mobile base station may be issued by the optical transmission device 20d-1 connected to the mobile base station, or by another optical transmission device 20d-2 or optical transmission device 25d.

[0099] The optical transmission devices 20d and 25d perform optical path switching within their own devices, taking into account the delay time based on pre-held delay information. That is, the optical transmission devices 20d and 25d may adjust the transmission timing of the optical path switching control, similar to the optical transmission device controller 30 in the first embodiment. When the transmission timing for the optical path switching control is reached, the optical transmission devices 20d and 25d perform the dedicated optical path switching process.

[0100] When it is time to transmit optical path switching control, the optical transmission device 20d switches the dedicated optical path that corresponds to the wireless terminal 60 whose connection destination has been switched due to handover, and which is formed between the core node 10 and the optical transmission device 25d. The optical transmission device 20d deletes the dedicated optical path formed with, for example, the optical transmission device 25d-1 and forms a new dedicated optical path with the optical transmission device 25d-2. Alternatively, instead of deleting and forming a dedicated optical path, the optical transmission device 20d may change the input / output port of the signal for the dedicated optical path from a port for optical transmission device 25d-1 to a port for optical transmission device 25d-2.

[0101] When it is time to transmit optical path switching control, the optical transmission device 25d switches the dedicated optical path that corresponds to the wireless terminal 60 whose connection destination has been switched due to handover, and which is formed between the core node 10 and the optical transmission device 20d. The optical transmission device 25d-1 deletes, for example, the dedicated optical path formed between the optical transmission device 20d and the base station 40d-1. The optical transmission device 25d-2 forms a new dedicated optical path, for example, between the optical transmission device 20d and the base station 40d-2.

[0102] The base station 40d is a device that communicates with each of the one or more wireless terminals 60. The base station 40d transmits signals transferred from the optical transmission device 25d to the wireless terminals 60 wirelessly, and converts signals received from the wireless terminals 60 into optical signals and transfers them to the optical transmission device 25d. When a handover process is required due to the movement of a wireless terminal 60, the base station 40d performs the handover process according to instructions from each optical transmission device 20d, 25d. For example, when a moving base station requires a handover process due to the movement of a wireless terminal 60, it obtains handover instructions from each optical transmission device 20d, 25d. The moving base station notifies the destination base station of the obtained handover instructions. As a result, the handover process is performed between base station 40d-1 and base station 40d-2.

[0103] The base station 40d may be, for example, a Wi-Fi® access point. Therefore, the signal transfer system 100d may be applied to wireless communication systems other than mobile communication systems. This is also true in the embodiments shown below.

[0104] [Device Configuration] Next, we will describe the specific configuration of each device.

[0105] The optical transmission device 20d comprises an optical control unit 21 and an information analysis unit 22. The information analysis unit 22 acquires wireless control information transmitted from the mobile base station. Based on the acquired wireless control information, the information analysis unit 22 determines whether or not a handover of the wireless terminal 60 is necessary. An existing method is used to determine whether or not a handover is necessary.

[0106] If the information analysis unit 22 determines that a handover of the wireless terminal 60 is necessary, it transmits an optical path switching control instruction to the optical control unit 21. The timing of transmitting the optical path switching control instruction is determined by taking delay information into account, as described above. At this point, the information analysis unit 22 may also issue a handover instruction to the mobile base station.

[0107] The optical control unit 21 switches optical paths according to the optical path switching control instruction transmitted from the information analysis unit 22. For example, when the optical control unit 21 receives the optical path switching control instruction, it deletes the dedicated optical path formed between the core node 10 and the optical transmission device 25d-1 and forms a new dedicated optical path between the core node 10 and the optical transmission device 25d-2. Alternatively, instead of deleting and forming a dedicated optical path, the optical control unit 21 may change the input / output port of the optical signal transmitted on the dedicated optical path of the optical transmission device 20d from a port for optical transmission device 25d-1 to a port for optical transmission device 25d-2.

[0108] In this way, the optical control unit 21, in response to receiving an optical path switching control instruction, switches the optical path so that signals can be sent and received between the moving wireless terminal 60 and the core node 10 by forming a new dedicated optical path between the core node 10 and the optical transmission device 25d-2.

[0109] The optical transmission device 25d comprises an optical control unit 26 and an information analysis unit 27. The information analysis unit 27 acquires wireless control information transmitted from the mobile base station. Based on the acquired wireless control information, the information analysis unit 27 determines whether or not a handover of the wireless terminal 60 is necessary.

[0110] If the information analysis unit 27 determines that a handover of the wireless terminal 60 is necessary, it transmits an optical path switching control instruction to the optical control unit 26. The timing of transmitting the optical path switching control instruction is determined by taking delay information into account, as described above. At this point, the information analysis unit 27 may also issue a handover instruction to the mobile base station.

[0111] The optical control unit 26 switches optical paths according to the optical path switching control instruction transmitted from the information analysis unit 27. The optical control unit 26-1 of the optical transmission device 25d-1 deletes the dedicated optical path formed between the optical transmission device 20d and the base station 40d-1 when it receives the optical path switching control instruction. The optical control unit 26-2 of the optical transmission device 25d-2 forms a new dedicated optical path between the optical transmission device 20d and the base station 40d-2 when it receives the optical path switching control instruction.

[0112] In this way, the optical control unit 26, in response to receiving an optical path switching control instruction, switches the optical path so that signals can be sent and received between the mobile wireless terminal 60 and the core node 10 by forming a new dedicated optical path between the optical transmission device 20d and the base station 40d-2.

[0113] The mobile base station (base station 40d-1) includes an information acquisition unit 41-1, a radio control unit 42-1, and a control determination unit 43-1. The information acquisition unit 41-1 acquires radio control information for each traffic flow exchanged between the radio terminal 60 and the core node 10. In the following description, as an example, the case in which the information acquisition unit 41-1 acquires radio control information for each traffic flow from the radio terminal 60 to the core node 10 will be described. The information acquisition unit 41-1 notifies each optical transmission device 20d, 25d of the acquired radio control information.

[0114] The control decision unit 43-1 transmits a handover instruction to the destination base station and the radio control unit 42-1 according to the handover instruction received from one of the optical transmission devices 20d, 25d.

[0115] The wireless control unit 42-1 performs a handover to the destination base station in response to instructions transmitted from the control decision unit 43-1.

[0116] The destination base station (base station 40d-2) is equipped with a radio control unit 42-2. The radio control unit 42-2 performs a handover to the source base station in response to instructions transmitted from the source base station.

[0117] [Operation] Figure 7 is a sequence diagram showing the processing flow of the signal transfer system 100d in the fourth embodiment. In Figure 7, each optical transmission device 20d, 25d is collectively referred to as the optical transmission device (group). At the start of processing in Figure 7, it is assumed that the wireless terminal 60 is connected to the base station 40d-1, which is the mobile base station. Therefore, the user signal transmitted from the wireless terminal 60 is transferred to the core node 10 via the base station 40d-1.

[0118] The wireless terminal 60 transmits measurement information to each base station 40d-1 and 40d-2 (steps S201 and S202). Now, suppose the wireless terminal 60 moves closer to base station 40d-2 in response to the user of the wireless terminal 60 moving. The information acquisition unit 41-1 of each base station 40d-1 acquires the measurement information transmitted from the wireless terminal 60. The information acquisition unit 41-1 notifies each optical transmission device 20d and 25d of the acquired measurement information as wireless control information (step S203).

[0119] The information analysis units 22 and 27 of each optical transmission device 20d and 25d analyze the radio control information notified from the mobile base station to determine whether a handover is necessary (step S204). Here, it is determined that a handover is necessary. The information analysis unit 27-1 of optical transmission device 25d-1 transmits a handover instruction to the mobile base station (step S205). Note that here, an example is shown in which the information analysis unit 27-1 of optical transmission device 25d-1 transmits a handover instruction to the mobile base station, but optical transmission device 20d or optical transmission device 25d-2 may also transmit the handover instruction to the mobile base station.

[0120] If a handover is deemed necessary, the information analysis units 22 and 27 need to send optical path switching control instructions to the optical control units 21 and 26 of each optical transmission device 20d and 25d in order to switch the optical paths. However, if the optical path switching is performed immediately, packet loss may occur. Therefore, the information analysis units 22 and 27 adjust the timing of the transmission of the optical path switching control instructions, taking into account a delay corresponding to the distance between the base station 40 and the core node 10, or the time difference from the moment the optical transmission devices 20d and 25d receive the optical path switching control instructions until they actually perform the optical path switching, so that the optical path switching is performed just before the core node 10 begins to transmit the downlink signal to the destination base station.

[0121] The control decision unit 43-1 of the source base station instructs the radio control unit 42-1 within its own device to perform a handover in response to a handover instruction from the optical transmission device 25d-1. Furthermore, the control decision unit 43-1 of the source base station instructs the destination base station (base station 40d-2) to perform a handover (step S206). Base stations 40d-1 and 40d-2 switch their connection with the radio terminal 60 in response to the handover instruction (step S207). As a result, for example, the base station 40d to which the radio terminal 60 is connected is switched from base station 40d-1 to base station 40d-2. Once the connection switch is complete, base station 40d-2, which is the destination base station, sends a route change request to the core node 10 (step S208).

[0122] The core node 10 receives a route change request transmitted from the base station 40d-2. The core node 10 processes the route change in response to the received route change request (step S209). Specifically, when the core node 10 transmits a signal to the wireless terminal 60, it changes the route so that it passes through the optical transmission device 25d-2.

[0123] The information analysis units 22 and 27 of each optical transmission device 20d and 25d transmit an optical path switching control instruction to the optical control units 21 and 26 when it is time to transmit the optical path switching control. For example, the information analysis unit 22 of optical transmission device 20d transmits an optical path switching control instruction to the optical control unit 21 when it is time to transmit the optical path switching control. For example, the information analysis unit 27 of optical transmission device 25d transmits an optical path switching control instruction to the optical control unit 26 when it is time to transmit the optical path switching control (step S210). The optical control units 21 and 26 of optical transmission devices 20d and 25d switch the dedicated optical path according to the optical path switching control instruction (step S211). Specifically, the optical control unit 26-1 of optical transmission device 25d-1 deletes the dedicated optical path with optical transmission device 20d. The optical control unit 26-2 of optical transmission device 25d-2 creates a dedicated optical path with optical transmission device 20d. The optical control unit 21 of the optical transmission device 20d switches to form a dedicated optical path with the optical transmission device 25d.

[0124] Through the above process, the user signal transmitted from the wireless terminal 60 is transferred to the core node 10 via the base station 40d-2 (destination base station). Here, the deletion of the dedicated optical path between the optical transmission device 25d-1 and the optical transmission device 20d, as described earlier, may be performed when the process in step S209 is completed and the path between the optical transmission device 25d-1 and the optical transmission device 20d is no longer needed.

[0125] When the core node 10 completes the route change process, it sends a route change response to the base station 40d-2 indicating that the route change process is complete (step S212). The base station 40d-2 receives the route change response sent from the core node 10. In response to the received route change response, the base station 40d-2 releases the connection of the wireless terminal 60 to the source base station 40d-1 (step S213).

[0126] With the signal transfer system 100d configured as described above, the same effects as in the first embodiment can be obtained even in a configuration that does not include an optical transmission device controller 30 and a base station controller 50.

[0127] (Fifth Embodiment) In the fifth embodiment, a signal transmission system using a distributed central station and distributed stations as base stations in the fourth embodiment will be described. More specifically, in the fifth embodiment, optical transmission equipment is installed in a section called MMH, and the signal transmission system does not include a base station controller and an optical transmission equipment controller, and the base station performs handover based on the result of determining whether or not a handover is necessary for each optical transmission equipment.

[0128] Figure 8 shows an example configuration of the signal transfer system 100e in the fifth embodiment. The signal transfer system 100e is a system that transfers signals from one communication device to another. The signal transfer system 100e includes, for example, an optical transmission device 20d, an optical transmission device 25d, and a base station 40e. One or more wireless terminals 60 are wirelessly connected to the base station 40d. The base station 40e consists of a central station 65 and one or more distributed stations 70e. In Figure 8, the case in which the base station 40e consists of a central station 65 and two distributed stations 70e is explained as an example, but there may be three or more distributed stations 70e. Thus, the signal transfer system 100e differs in configuration from the signal transfer system 100d in that it does not have a core node 10 and instead of a base station 40d, it has a base station 40e consisting of a central station 65 and distributed stations 70e. The following explanation will focus on the differences from the signal transfer system 100d.

[0129] The central station 65 and the optical transmission device 20d, the optical transmission device 20d and the optical transmission device 25d, and the optical transmission device 25d and the distributed station 70e are connected, for example, by optical transmission lines. Furthermore, each optical transmission device 20d, 25d and the distributed station 70e are connected by control lines that transmit control signals.

[0130] In describing the fifth embodiment, we assume that the initial state is that the wireless terminal 60 is connected to distributed station 70e-1 and then to the central station 65 via optical transmission device 25d-1 and optical transmission device 20d. Then, we assume that when the wireless terminal 60 moves and a handover becomes necessary, the wireless terminal 60 connects to distributed station 70e-2 and then to the central station 65 via optical transmission device 25d-2 and optical transmission device 20d. Note that distributed station 70e-1 may also be referred to as the source distributed station and distributed station 70e-2 as the destination distributed station.

[0131] For example, in the fifth embodiment, the central station 65 is one or more CUs in the mobile communication system, and the distributed station 70e is a DU in the mobile communication system. In this case, the section between the CUs and DUs where the optical transmission devices 20d and 25d are installed is called the MMH.

[0132] Furthermore, the central station 65 may be a Wi-Fi controller, and the distributed stations 70e may be Wi-Fi access points. The signal transfer system 100e does not necessarily have to be applied to a mobile communication system, and may be applied to wireless communication systems other than mobile communication systems.

[0133] The central station 65 is a device that communicates with each of the one or more wireless terminals 60 that are wirelessly connected to each distributed station 70e. For example, the central station 65 receives uplink signals transmitted from the wireless terminals 60 and transmits downlink signals to the wireless terminals 60. The central station 65 is one form of a higher-level device.

[0134] The distributed station 70e is a device that communicates with the wireless terminal 60. Through communication with the wireless terminal 60, the distributed station 70e transmits signals transferred from the optical transmission device 25d to the wireless terminal 60, or transfers signals received from the wireless terminal 60 to the destination optical transmission device 25d. Furthermore, the distributed station 70e acquires wireless control information and notifies each optical transmission device 20d, 25d of the acquired wireless control information.

[0135] When a handover is required due to the movement of the wireless terminal 60, the distributed station 70e performs the handover process according to instructions from each optical transmission device 20d, 25d. For example, when a moving distributed station requires a handover due to the movement of the wireless terminal 60, it obtains handover instructions from each optical transmission device 20d, 25d. The moving distributed station notifies the destination distributed station of the obtained handover instructions. As a result, the handover process is performed between distributed station 70e-1 and distributed station 70e-2.

[0136] [Device Configuration] The mobile source distributed station (distributed station 70e-1) comprises an information acquisition unit 41-1, a radio control unit 42-1, and a control decision unit 43-1. The information acquisition unit 41-1 of the mobile source distributed station performs the same processing as the information acquisition unit 41-1 in Figure 6. The radio control unit 42-1 of the mobile source distributed station performs the same processing as the radio control unit 42-1 in Figure 6. The control decision unit 43-1 of the mobile source distributed station performs the same processing as the control decision unit 43-1 in Figure 6. However, the mobile source base station and destination base station must be read as the mobile source distributed station and destination distributed station.

[0137] The destination distributed station (distributed station 70e-2) is equipped with a radio control unit 42-2. The radio control unit 42-2 in the destination distributed station performs the same processing as the radio control unit 42-2 in Figure 6. However, the source base station and destination base station must be read as the source distributed station and destination distributed station.

[0138] [Operation] The processing performed by the signal transfer system 100e is the same as in Figure 7, provided that the core node 10 in Figure 7 is read as the central station 65, the source base station (base station 40d-1) is read as the source distributed station (distributed station 70e-1), and the destination base station (base station 40d-2) is read as the destination distributed station (distributed station 70e-2).

[0139] With the signal transfer system 100e configured as described above, the same effects as in the fourth embodiment can be obtained even in a configuration where the base stations 40e are distributed and the optical transmission devices 20d and 25d are installed in the MMH.

[0140] (Sixth Embodiment) In the sixth embodiment, a signal transmission system using a distributed central station and distributed stations as base stations will be described. More specifically, in the sixth embodiment, optical transmission equipment is installed in a section called MFH, and the signal transmission system does not include a base station controller and an optical transmission equipment controller, and the base station performs handover based on the result of determining whether or not handover is necessary for each optical transmission equipment.

[0141] Figure 9 shows an example of the configuration of the signal transfer system 100f in the sixth embodiment. The signal transfer system 100f is a system that transfers signals from one communication device to another. The signal transfer system 100f includes, for example, an optical transmission device 20d, an optical transmission device 25d, and a base station 40f. One or more wireless terminals 60 are wirelessly connected to the base station 40f. The base station 40f consists of a central station 65f and one or more distributed stations 70f. In Figure 9, the case in which the base station 40f consists of a central station 65f and two distributed stations 70f is explained as an example, but there may be three or more distributed stations 70f. Thus, the signal transfer system 100f differs in configuration from the signal transfer system 100f in that it does not have a core node 10 and has a base station 40f consisting of a central station 65f and distributed stations 70f instead of the base station 40d. The differences from the signal transfer system 100d will be explained below.

[0142] The central station 65f and the optical transmission device 20d, the optical transmission device 20d and the optical transmission device 25d, and the optical transmission device 25d and the distributed station 70f are connected, for example, by optical transmission lines. Furthermore, each optical transmission device 20d, 25d and the distributed station 70f are connected by control lines that transmit control signals.

[0143] In describing the sixth embodiment, we assume that the initial state is that the wireless terminal 60 is connected to distributed station 70f-1 and then to the central station 65f via optical transmission device 25d-1 and optical transmission device 20d. Then, we assume that when the wireless terminal 60 moves and a handover becomes necessary, the wireless terminal 60 connects to distributed station 70f-2 and then to the central station 65f via optical transmission device 25d-2 and optical transmission device 20d. Note that distributed station 70f-1 may also be referred to as the source distributed station and distributed station 70f-2 as the destination distributed station.

[0144] For example, in the sixth embodiment, the central station 65f is one or more DUs in the mobile communication system, and the distributed station 70f is an RU in the mobile communication system. In this case, the section between the DUs and RUs where the optical transmission devices 20d and 25d are installed is called the MFH (Mobile Fronthaul).

[0145] Furthermore, the central station 65f may be a Wi-Fi controller, and the distributed stations 70f may be Wi-Fi access points. The signal transfer system 100f does not necessarily have to be applied to a mobile communication system, and may be applied to wireless communication systems other than mobile communication systems.

[0146] The central station 65f is a device that communicates with each of the one or more wireless terminals 60 that are wirelessly connected to each distributed station 70f. For example, the central station 65f receives uplink signals transmitted from the wireless terminals 60 and transmits downlink signals to the wireless terminals 60. Furthermore, the central station 65f acquires wireless control information and notifies each optical transmission device 20d, 25d of the acquired wireless control information. The central station 65f is one form of a higher-level device.

[0147] The distributed station 70f is a device that communicates with the wireless terminal 60. Through communication with the wireless terminal 60, the distributed station 70f transmits signals transferred from the optical transmission device 25d to the wireless terminal 60, or transfers signals received from the wireless terminal 60 to the destination optical transmission device 25d.

[0148] Furthermore, if a handover process becomes necessary due to the movement of the wireless terminal 60, the distributed station 70f performs the handover process according to instructions from each optical transmission device 20d, 25d. For example, if a moving distributed station needs to perform a handover process due to the movement of the wireless terminal 60, it obtains handover instructions from each optical transmission device 20d, 25d. The moving distributed station notifies the destination distributed station of the obtained handover instructions. As a result, the handover process is performed between distributed station 70f-1 and distributed station 70f-2.

[0149] Each optical transmission device 20d, 25d acquires wireless control information notified by the central station 65f. The processing performed by each optical transmission device 20d, 25d after acquiring the wireless control information is the same as in the fourth embodiment.

[0150] [Device Configuration] The central station 65f is equipped with an information acquisition unit 66. The information acquisition unit 66 acquires wireless control information for each traffic flow that the wireless terminal 60 exchanges with the central station 65f. The information acquisition unit 66 notifies each optical transmission device 20d, 25d of the acquired wireless control information.

[0151] The mobile source distributed station (distributed station 70f-1) comprises a radio control unit 42-1 and a control decision unit 43-1. The radio control unit 42-1 of the mobile source distributed station performs the same processing as the radio control unit 42-1 in Figure 6. The control decision unit 43-1 of the mobile source distributed station performs the same processing as the control decision unit 43-1 in Figure 6. However, the mobile source base station and destination base station must be read as the mobile source distributed station and destination distributed station.

[0152] The destination distributed station (distributed station 70f-2) is equipped with a radio control unit 42-2. The radio control unit 42-2 in the destination distributed station performs the same processing as the radio control unit 42-2 in Figure 6. However, the source base station and destination base station must be read as the source distributed station and destination distributed station.

[0153] [Operation] The processing performed by the signal transfer system 100f is the same as in Figure 7, provided that the core node 10 in Figure 7 is read as the central station 65f, the source base station (base station 40d-1) is read as the source distributed station (distributed station 70f-1), and the destination base station (base station 40d-2) is read as the destination distributed station (distributed station 70f-2).

[0154] With the signal transfer system 100f configured as described above, even in a configuration where base stations 40f are distributed and optical transmission devices 20d and 25d are installed in the MFH, the same effects as in the fourth embodiment can be obtained.

[0155] The optical transmission devices 20, 20d, optical transmission devices 25, 25d, optical transmission device controller 30, base stations 40, 40b, 40c, 40d, and base station controller 50, which are included in the signal transmission systems 100, 100a, 100b, 100c, 100d, 100e, and 100f, are configured using, for example, a processor such as a CPU (Central Processing Unit), memory, and a communication interface. Each of the optical transmission devices 20, 20d, optical transmission devices 25, 25d, optical transmission device controller 30, base stations 40, 40b, 40c, 40d, and base station controller 50 functions as a communication device equipped with a functional unit that performs specific processing by having the processor execute a program.

[0156] The above program provides functions for enabling the communication device to function as either an optical transmission device 20, 20d, an optical transmission device 25, 25d, an optical transmission device controller 30, a base station 40, 40b, 40c, 40d, or a base station controller 50. Note that all or part of these functions may be implemented using hardware including electronic circuits (or circuits) such as LSIs (Large Scale Integrated Circuits), ASICs (Application Specific Integrated Circuits), PLDs (Programmable Logic Devices), or FPGAs (Field Programmable Gate Arrays).

[0157] The above program may be recorded on a computer-readable non-temporary recording medium. Computer-readable non-temporary recording media include, for example, portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), CD-ROMs (Compact Disc Read Only Memory), and storage devices such as hard disks built into computer systems.

[0158] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention.

[0159] The present invention can be applied to a communication system and a communication control method for accommodating wireless terminals.

[0160] 10...Core node, 20, 20d, 25, 25-1 to 25-2, 25d, 25d-1 to 25d-2...Optical transmission device, 21, 26, 26-1 to 26-2...Optical control unit, 22, 27, 27-1 to 27-2, 31...Information analysis unit, 30...Optical transmission device controller, 40, 40-1 to 40-2, 40b, 40c, 40d, 40d-1 to 40d-2, 40e, 40f...Base station, 41, 41-1 to 41-2, 66...Information acquisition unit, 42, 42-1 to 42-2...Wireless control unit, 50...Base station controller, 51...Control decision unit, 55a...Orchestrator, 56...Information transfer unit, 60...Wireless terminal, 65, 65c...Central station, 70, 70-1 to 70-2, 70c, 70c-1 to 70c-2, 70e, 70e-1 to 70e-2, 70f, 70f-1 to 70f-2... Distributed stations, 100, 100a, 100b, 100c, 100d, 100e, 100f... Signal transfer systems

Claims

1. An optical transmission device control device in a signal transmission system comprising: a plurality of base stations accommodating one or more wireless terminals; a plurality of optical transmission devices connected to at least one of the plurality of base stations; an optical transmission device control device for controlling the plurality of optical transmission devices; and a base station control device for controlling the plurality of base stations, the optical transmission device control device comprising: an information analysis unit that, in response to the movement of one or more wireless terminals, instructs the base station control device to change the connection with the one or more wireless terminals that have moved, and instructs each optical transmission device subject to optical path switching to switch the optical path in conjunction with the timing at which the connection change with the one or more wireless terminals that have moved is performed.

2. The optical transmission device control device according to claim 1, wherein the information analysis unit acquires wireless control information, which is information relating to wireless communication between the base station and the wireless terminal, from each of the plurality of base stations, and when it determines that a handover is necessary based on the acquired wireless control information, it instructs the base station control device to change the connection with the one or more wireless terminals that have moved, and instructs each optical transmission device that is subject to the optical path switching to switch the optical path.

3. A base station control device in a signal transfer system comprising: a plurality of base stations accommodating one or more wireless terminals; a plurality of optical transmission devices connected to at least one of the plurality of base stations; an optical transmission device control device for controlling the plurality of optical transmission devices; and a base station control device for controlling the plurality of base stations, the base station control device comprising: a control determination unit that transmits a handover instruction to each base station subject to handover when it receives a handover execution instruction from the optical transmission device control device or another device in response to the movement of one or more wireless terminals.

4. An optical transmission device in a signal transfer system comprising a plurality of base stations accommodating one or more wireless terminals, and a plurality of optical transmission devices connected to at least one of the plurality of base stations, the optical transmission device comprising: an optical control unit that performs switching of optical paths in conjunction with the timing at which a connection change with the moved one or more wireless terminal is performed at each base station subject to handover in response to the movement of the one or more wireless terminals.

5. The optical transmission apparatus according to claim 4, further comprising: an information analysis unit that acquires radio control information, which is information relating to wireless communication between a base station and a wireless terminal, from each of the plurality of base stations, and when it is determined that a handover is necessary based on the acquired radio control information, instructs the base station to be handovered to change the connection with the one or more wireless terminals that have moved, and instructs the optical control unit to switch the optical path.

6. A control method performed by an optical transmission device control device in a signal transmission system comprising a plurality of base stations accommodating one or more wireless terminals, a plurality of optical transmission devices connected to at least one of the plurality of base stations, an optical transmission device control device for controlling the plurality of optical transmission devices, and a base station control device for controlling the plurality of base stations, the control method comprising: instructing the base station control device to change the connection with the one or more wireless terminals that have moved in response to the movement of the one or more wireless terminals; and instructing each optical transmission device subject to optical path switching to switch the optical path in conjunction with the timing at which the connection change with the one or more wireless terminals that have moved is performed.

7. A control method performed by a base station control device in a signal transfer system comprising a plurality of base stations accommodating one or more wireless terminals, a plurality of optical transmission devices connected to at least one of the plurality of base stations, an optical transmission device control device for controlling the plurality of optical transmission devices, and a base station control device for controlling the plurality of base stations, wherein when the optical transmission device control device or another device receives a handover execution instruction in response to the movement of one or more wireless terminals, the control device transmits a handover instruction to each base station subject to the handover.

8. An optical path switching method performed by an optical transmission device in a signal transfer system comprising a plurality of base stations accommodating one or more wireless terminals and a plurality of optical transmission devices connected to at least one of the plurality of base stations, wherein the optical path switching is performed in conjunction with the timing at which a connection change is performed with the one or more wireless terminals that have moved, in response to the movement of one or more wireless terminals at each base station subject to handover.

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