Control device, communication system, and communication control method

Abstract

A communication system according to the present invention includes first and second access points, an upper node device for managing the connection of a wireless terminal, and an optical network for connecting the first and second access points to the network to which the upper node device is connected. The control device includes an upper node cooperation unit, a route calculation unit, and a route control unit. The upper node cooperation unit receives, from the upper node device, a notification that a wireless terminal communicating with a communication destination device connected to the network via the first access point starts handover to the second access point. The route calculation unit calculates the route of an optical path between the second access point and the network in the optical network. The route control unit controls the optical network so as to connect the optical path between the second access point and the network by the calculated path, and notifies the upper node device after the setting is completed.

Description

Control device, communication system, and communication control method

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

[0002] A wireless terminal is connected to a server that provides an application via an access point (AP). In conventional technology, even when the AP to which the wireless terminal is connected is changed, communication with the server to which the wireless terminal was connected before the handover is continued (see, for example, Patent Document 1). In such a communication system, a mobile terminal selects an AP to connect to by detecting a deterioration in communication quality, and establishes a connection between the selected AP and the server, thereby continuing communication with the same server.

[0003] Japanese Patent Application Laid-Open No. 2018-148439

[0004] In the conventional technology, an IP (Internet Protocol) network is used for communication between the AP and the server, which is the upper device of the communication system, and it is assumed that IP reachability exists. However, when assuming the application of an optical network between the AP and the server, there is a problem in that no consideration is given to route control in the optical transmission line section or wavelength control used in the transmission line.

[0005] In view of the above circumstances, the present invention aims to provide a control device, a communication system, and a communication control method that can control the optical network between an AP and a wireless terminal's communication destination so that communication of the wireless terminal can continue even during handover.

[0006] A control device according to one embodiment of the present invention is a control device that controls an optical network in a communication system having a first access point, a second access point, an upper node device that manages connections of wireless terminals, and an optical network that connects the first access point and the second access point to the network to which the upper node device is connected, and includes: an upper node cooperation unit that receives a notification from the upper node device that the wireless terminal, which is communicating with a communication destination device connected to the network via the first access point, will initiate a handover to the second access point; a route calculation unit that calculates the route of an optical path between the second access point and the network in the optical network; and a route control unit that controls the optical network to set up an optical path between the second access point and the network using the route calculated by the route calculation unit, and notifies the upper node device when the setting of the optical path is complete.

[0007] A communication system according to one aspect of the present invention includes a first access point, a second access point, an upper node device that manages connections of wireless terminals, an optical network that connects the first access point and the second access point to a network to which the upper node device and a communication destination device of the wireless terminal are connected, and a control device that controls the optical network, wherein the optical network transmits, via a first optical path between the first access point and the network, one or both of an optical signal including a signal from the wireless terminal to the communication destination device and an optical signal including a signal from the communication destination device to the wireless terminal, and the control device communicates with the communication destination device connected to the network via the first access point. a higher-level node cooperation unit that receives a notification from the higher-level node device that the wireless terminal associated with the higher-level node device will initiate handover to the second access point; a route calculation unit that calculates the route of a second optical path between the second access point and the network in the optical network; and a route control unit that controls the optical network to set the second optical path between the second access point and the network using the route calculated by the route calculation unit, and notifies the higher-level node device when setting of the second optical path is complete, and the optical network transmits, via the second optical path, one or both of an optical signal including a signal from the wireless terminal to the destination device and an optical signal including a signal from the destination device to the wireless terminal.

[0008] A communication control method according to one aspect of the present invention is a communication control method for controlling an optical network in a communication system having a first access point, a second access point, an upper node device that manages connections of wireless terminals, and an optical network that connects the first access point and the second access point to the network to which the upper node device is connected, and includes a receiving step of receiving a notification from the upper node device that the wireless terminal, which is communicating with a communication destination device connected to the network via the first access point, will initiate a handover to the second access point; a route calculation step of calculating the route of an optical path between the second access point and the network in the optical network; and a route control step of controlling the optical network to set up an optical path between the second access point and the network using the route calculated in the route calculation step, and notifying the upper node device when the setting of the optical path is completed.

[0009] A communication control method according to one aspect of the present invention includes a first transmission step in which an optical network connecting a first access point and a second access point to an upper node device that manages connections of wireless terminals and a network to which a communication destination device of the wireless terminal is connected transmits, via a first optical path between the first access point and the network, one or both of an optical signal including a signal from the wireless terminal to the communication destination device and an optical signal including a signal from the communication destination device to the wireless terminal; and a control device notifying the upper node device that the wireless terminal, which is communicating with the communication destination device connected to the network via the first access point, will start handover to the second access point. a route calculation step of calculating a route of a second optical path between the second access point and the network in the optical network; a route control step of controlling the optical network to set the second optical path between the second access point and the network according to the route calculated in the route calculation step, and notifying the upper node device when the setting of the second optical path is completed; and a second transmission step of the optical network transmitting, by the second optical path, one or both of an optical signal including a signal from the wireless terminal to the destination device and an optical signal including a signal from the destination device to the wireless terminal.

[0010] According to the present invention, it is possible to control the optical network included between the AP and the communication destination of the wireless terminal so that communication of the wireless terminal can be continued even during handover.

[0011] FIG. 1 is a diagram illustrating an overview of a communication system according to a first embodiment. FIG. 2 is a diagram illustrating a configuration of a communication system according to the first embodiment. FIG. 3 is a sequence diagram illustrating processing of the communication system according to the first embodiment. FIG. 4 is a diagram illustrating an overview of a communication system according to a second embodiment. FIG. 5 is a diagram illustrating a configuration of a communication system according to the second embodiment. FIG. 6 is a sequence diagram illustrating processing of the communication system according to the second embodiment. FIG. 7 is a diagram illustrating an example of the hardware configuration of a controller according to the first and second embodiments.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] First Embodiment FIG. 1 is a diagram illustrating an overview of a communication system 1 according to a first embodiment of the present invention. The communication system 1 includes multiple access points (APs) 2, an upper node 3, an upper node 4, and a controller 5. The access points 2, the upper node 3, and the upper node 4 are each connected to a trunk NW via an aggregation network (NW). The aggregation network is, for example, an optical access network. The trunk NW transfers signals between the devices. Although only two access points 2 are shown in FIG. 1 , the communication system 1 may include three or more access points 2. Hereinafter, the two access points 2 will be referred to as access points 2-1 and 2-2. A wireless terminal 6 communicates with the access point 2 wirelessly. Although only one wireless terminal 6 is shown in FIG. 1 , multiple wireless terminals 6 may communicate with the access point 2. The upper node 3 controls the connection of the wireless terminal 6. The upper node 4 receives a main signal from the wireless terminal 6 and / or transmits a main signal to the wireless terminal 6. Hereinafter, the direction from the wireless terminal 6 to the upper node 3 or 4 will be referred to as "upstream," and the direction from the upper node 3 or 4 to the wireless terminal 6 will be referred to as "downstream."

[0014] In this embodiment, an optical path can be established for a handover method in cooperation with an upper node 3 when information about a wireless terminal 6 connected to an access point 2 cannot be exchanged between the access points 2. For example, before handover, the wireless terminal 6 is connected to an access point 2-1. The access point 2-1 performs upstream and downstream communications with the upper node 4 via route R1. The communication system 1 establishes route R2 between the upper node 4 and the access point 2-2 in response to a handover that changes the access point 2 to which the moving wireless terminal 6 is connected. Specifically, the upper node 3 sends a handover trigger to the controller 5, and the controller 5 establishes an optical path in the aggregated network included in route R2 in response to the handover. This allows a consistent optical transmission path to be used for each wireless terminal 6. This embodiment makes it possible to provide services to a specific wireless terminal 6 while maintaining the same wavelength, even during a handover in which connectivity is not established between access points 2.

[0015] 2 is a diagram showing an example of the configuration of the communication system 1. The access point 2 is connected to a network 8 via an optical network 7. The upper node 3 and the upper node 4 are connected to the network 8. The optical network 7 is an access network for connecting the access point 2 to the network 8. The network 8 is a communication network for transferring signals between devices. The network 8 is, for example, an IP (Internet Protocol) network, but may also be configured to include the trunk network shown in FIG. 1 and an aggregation network to which the upper node 3 and the upper node 4 are connected.

[0016] The optical network 7 includes a plurality of optical communication devices connected by optical fibers. In Fig. 2, these optical communication devices include an optical transceiver 71, an optical transmission device 72, and an optical transceiver 73. The optical communication devices may also include L2 / L3 switches and routers.

[0017] The optical transceiver 71 converts an upstream signal transmitted by the access point 2 from an electrical signal to an optical signal and outputs it to the optical fiber. The optical transceiver 71 also converts a downstream optical signal transmitted through the optical fiber into an electrical signal and outputs it to the access point 2. The optical transceiver 71 may be provided within the access point 2. The wavelength of the optical signal to be transmitted and received can be set arbitrarily in the optical transceiver 71.

[0018] The optical transmission device 72 has ports connected to a plurality of optical fibers, and an optical signal input from one of the ports is output from another port. The port from which the optical signal is input and output depends on the optical path set in the optical transmission device 72.

[0019] The optical transceiver 73 converts the upstream signal transmitted through the optical fiber from an optical signal to an electrical signal and outputs it to the network 8. The network 8 routes the upstream signal to the destination upper node 3 or upper node 4. The optical transceiver 73 also receives a downstream signal transmitted by the upper node 3 or upper node 4 from the network 8, converts the received downstream signal from an electrical signal to an optical signal, and outputs it to the optical fiber. The wavelength of the optical signal to be transmitted and received can be set arbitrarily in the optical transceiver 73.

[0020] When the wireless terminal 6 is under the control of the access point 2-1, an upstream optical signal set with an upstream signal from the wireless terminal 6 and a downstream optical signal set with a downstream signal addressed to the wireless terminal 6 are transmitted via an optical path P1 set in the optical network 7. The optical path P1 corresponds, for example, to a part of the route R1 shown in FIG. 1 . When the wireless terminal 6 moves to the control of the access point 2-2, the controller 5 receives a notification from the upper node 3 and sets an optical path P2 in the network 8. The optical path P2 corresponds, for example, to a part of the route R2 shown in FIG. 1 . Signals from the wireless terminal 6 that is now under the control of the access point 2-2 are transmitted and received via the optical path P2. That is, the upstream optical signal set with an upstream signal transmitted by the wireless terminal 6 and the downstream optical signal set with a downstream signal addressed to the wireless terminal 6 are transmitted via the optical path P2. Note that route changes within the network 8 are controlled by the upper node 3 or a route control device (not shown) that receives an instruction from the upper node 3.

[0021] As described above, the communication system 1 notifies the controller 5 of information from the upper node 3, thereby controlling the optical transmission path based on control information related to wireless communication of the wireless terminal 6. The controller 5 cooperates with the upper node 3, thereby realizing optical path control in cooperation with the upper node 3, unlike conventional methods. For example, it is possible to continue occupying a wavelength on a wireless terminal 6 basis.

[0022] The controller 5 includes an upper node linking unit 51, a route control unit 52, and a route calculation unit 53. The upper node linking unit 51 transmits and receives information to and from the upper node 3. The route control unit 52 controls the routes of optical communication devices such as the optical transceiver 71, optical transmission device 72, optical transceiver 73, and L2-L3 switch / router devices in the optical network 7. The route control unit 52 also sets wavelengths for the optical transceivers 71 and 73. The route calculation unit 53 calculates routes when constructing optical paths in the optical network 7.

[0023] 3 is a sequence diagram showing the operation of the communication system 1. The access point 2-1 is the source AP to which the wireless terminal 6 is connected before handover. The access point 2-2 is the target AP to which the wireless terminal 6 is connected after handover. The optical transceiver 71 connected to the access point 2-1 is connected to the network 8 via the optical path P1 shown in FIG. 2. The optical signal that sets the signal to be transmitted and received by the wireless terminal 6 is assigned a wavelength λ1.

[0024] When the access point 2-1 determines that handover of the wireless terminal 6 is necessary due to a deterioration in the quality of wireless communication between the access point 2-1 and the wireless terminal 6, the access point 2-1 transmits a handover request (Handover requested) in which a terminal ID is set to the upper node 3 (step S111). The terminal ID is identification information of the wireless terminal 6.

[0025] Upon receiving the handover request, the upper node 3 acquires information about the access point 2-2, which will be the handover destination of the wireless terminal 6, by any method. For example, the upper node 3 may receive a notification from the access point 2-2 that it is the handover destination of the wireless terminal 6, or may receive information about the communication quality between the access point 2-2 and the wireless terminal 6 from each access point 2 and select the access point 2-2 as the handover destination based on the communication quality. The upper node 3 transmits a HO (Handover) start notification to the controller 5, which includes Source AP information indicating the access point 2-1, Target AP information indicating the access point 2-2, and wavelength information indicating the wavelength λ1 (step S112). The upper node 3 then transmits a handover request to the access point 2-2 (step S113). The access point 2-2 transmits a handover request acknowledgement (Handover request ACK) to the upper node 3 (step S114).

[0026] When the upper node cooperation unit 51 of the controller 5 receives the notification of the start of handover, it transmits a route and wavelength switching request in which source AP information, target AP information, and wavelength information are set to the route control unit 52 (step S115). When the route control unit 52 receives the route and wavelength switching request, it transmits a route calculation request in which target AP information is set to the route calculation unit 53 (step S116).

[0027] The route calculation unit 53 calculates the route of the optical path P2 from the optical transceiver 71 connected to the access point 2-2 identified by the Target AP information to the optical transceiver 73 connected to the network 8 (step S117). Any conventional technique can be used for the route calculation. The route calculation unit 53 transmits a switching route notification including information about the calculated route of the optical path P2 to the route control unit 52 (step S118).

[0028] The route control unit 52 transmits a route setting instruction to each optical transmission device 72 related to the generation of the optical path P2, the route setting instruction including the wavelength λ1 and route information for the optical transmission device 72 to generate the route of the optical path P2 (step S119). The optical transmission device 72 sets the route of the optical path P2 to be used for the optical signal of wavelength λ1 in accordance with the route setting instruction received from the controller 5 (step S120). When the route setting is completed, the optical transmission device 72 returns a completion notification to the controller 5 (step S121).

[0029] In step S119, the route control unit 52 may transmit a route setting instruction to delete the optical path P1 used by the wavelength λ1 to each optical transmission device 72 related to the optical path P1. The optical transmission device 72 changes the setting to delete the route of the optical path P1 used by the wavelength λ1 in accordance with the route setting instruction received from the controller 5. When the route setting change is completed, the optical transmission device 72 returns a completion notification to the controller 5.

[0030] The route control unit 52 transmits wavelength information indicating the wavelength λ1 and a wavelength setting including the terminal ID to the optical transceivers 71 and 73 that terminate the optical path P2 (step S122). The optical transceivers 71 and 73 update their settings to convert the signal with the terminal ID notified by the wavelength setting into an optical signal with the wavelength λ1 (step S123). After updating their settings, the optical transceivers 71 and 73 return a completion notification (step S124).

[0031] In step S122, the route control unit 52 may transmit a stop instruction for the wavelength λ1 to the optical transceivers 71 and 73 that terminate the optical path P1. Upon receiving the stop instruction, the optical transceivers 71 and 73 stop using the wavelength λ1 and return a completion notification.

[0032] The route control unit 52 of the controller 5 transmits the completion notification received from the optical transceiver 71 and the optical transceiver 73 to the upper node cooperation unit 51 (step S125). The upper node cooperation unit 51 may or may not transmit the completion notification to the upper node 3 (step S126).

[0033] The upper node 3 transmits a handover request command to the access point 2-1 (step S127). On the other hand, when the access point 2-2 starts wireless communication with the wireless terminal 6, it transmits a handover notify to the upper node 3 (step S128). The upper node 3 transmits a UE context release command to the access point 2-1 (step S129). When the access point 2-1 releases wireless communication with the wireless terminal 6, it returns a UE context release command complete to the upper node 3 (step S130). This completes switching of the communication destination of the wireless terminal 6 from the access point 2-1 to the access point 2-2 (step S131).

[0034] Through the above procedure, the communication system 1 establishes an optical path for connecting the target AP to the upper node 4 when a handover is performed. The controller 5 performs optical path calculation and control upon receiving a handover request from the source AP to the upper node 3.

[0035] Second Embodiment The second embodiment is a case where the first embodiment is applied to a 5G communication system.

[0036] FIG. 4 is a diagram illustrating an overview of a communication system 11 according to the second embodiment. The communication system 11 includes multiple gNBs (gNodeBs) 12, an AMF (Access and Mobility Management Function) 13, a UPF (User Plane Function) 14, and a controller 50. The gNBs 12, the AMFs 13, and the UPFs 14 are each connected to a trunk network via an aggregation network. The communication system 11 is configured in such a way that the access point 2 of the communication system 1 shown in FIG. 1 is replaced with a gNB 12, the upper node 3 with an AMF 13, the upper node 4 with a UPF 14, and the wireless terminal 6 with a UE (User Equipment) 16. Of the two gNBs 12 shown in FIG. 4, the gNB 12 to which the UE 16 is connected before handover is referred to as Source gNB 12-1, and the gNB to which the UE 16 is connected after handover is referred to as Target gNB 12-2.

[0037] In this embodiment, an optical path is established using information from a 5th Generation Core network (5GC). For example, before handover, UE 16 is connected to source gNB 12-1. Source gNB 12-1 transmits and receives uplink and downlink main signals to and from UPF 14 using the NG interface via route R11. When source gNB 12-1 notifies AMF 13 of an N2 handover (HO) via the N2 interface, controller 50 establishes a new optical path in the aggregation network included in route R12 from target gNB 12-2 to UPF 14. This allows UE 16 that has moved to target gNB 12-2 to accommodate services using the same wavelength before and after HO, as shown in the figure.

[0038] Furthermore, once N2HO (NGAP Handover), in which the AMF 13 manages handovers between two gNBs 12, is performed for a pair of gNBs 12, the controller 50 establishes an optical path Xn between those gNBs 12. This enables handovers between those gNBs 12 to be managed using XnHO, without N2HO. This reduces the communication interruption time during handover. However, the controller 50 deletes the learned optical path Xn if a certain period of time has passed since the route of the learned optical path Xn ceased to be used. This embodiment enables services to be provided to a specific UE while maintaining the same wavelength even during N2HO. Furthermore, if gNBs 12 have an interface connecting them, establishing a direct optical path between gNBs 12 on which N2HO has been performed once enables XnHO from the second switching onwards, thereby reducing the communication interruption time during N2HO.

[0039] First, a communication system 11 without XnHO will be described. Fig. 5 is a diagram showing an example configuration of the communication system 11. The communication system 11 has a RAN (Radio Access Network) having a gNB 12, a CN (Core Network) including an AMF 13 and a UPF 14, and a controller 50. The RAN controls traffic from the UE 16. The CN controls the RAN. The controller 50 controls the optical transmission devices and NW devices that constitute the APN.

[0040] The gNB 12 is connected to the network 8 via an optical network 7. As in the first embodiment, the optical network 7 includes a plurality of optical communication devices connected by optical fibers. In FIG. 5 , these optical communication devices include an optical transceiver 71, an optical transmission device 72, and an optical transceiver 73, but may also include an L2 / L3 switch or router device. The AMF 13 and the UPF 14 are connected to the network 8.

[0041] The optical transceiver 71 converts the upstream signal transmitted by the gNB 12 from an electrical signal to an optical signal and outputs it to the optical fiber. The optical transceiver 71 also converts the downstream optical signal transmitted through the optical fiber to an electrical signal and outputs it to the gNB 12. The optical transceiver 73 converts the upstream signal transmitted through the optical fiber from an optical signal to an electrical signal and outputs it to the network 8. The optical transceiver 73 also receives the downstream signal transmitted by the AMF 13 or UPF 14 from the network 8, converts the received downstream signal from an electrical signal to an optical signal and outputs it to the optical fiber.

[0042] When UE16 is under the control of source gNB12-1, an upstream optical signal set with an upstream signal transmitted by UE16 and a downstream optical signal set with a downstream signal addressed to UE16 are transmitted via optical path P11. Optical path P11 corresponds, for example, to a portion of route R11 shown in FIG. 4. When UE16 moves to the control of target gNB12-2, the controller 50 receives a notification from AMF13 and sets optical path P12 in the optical network 7. Optical path P12 corresponds, for example, to a portion of route R12 shown in FIG. 4. An upstream optical signal set with an upstream signal from UE16 and a downstream optical signal set with a downstream signal addressed to UE16 are transmitted via optical path P12. Note that route changes within the network 8 are controlled by AMF13 or a route control device (not shown) that receives instructions from AMF13.

[0043] As described above, the communication system 11 controls the optical transmission path based on the 5GC control information by notifying the controller 50 of information from the AMF 13. Unlike the conventional technology, the controller 50 cooperates with the AMF 13 to realize optical path control in cooperation with the AMF 13. In other words, it is possible to continue to occupy the wavelength on a per-UE 16 basis.

[0044] The controller 50 includes a 5GC linking unit 55, a route control unit 56, and a route calculation unit 57. The 5GC linking unit 55 transmits and receives information to and from the AMF 13. The route control unit 56 controls the routes of optical communication devices such as the optical transceiver 71, optical transmission device 72, optical transceiver 73, and L2-L3 switch / router devices in the optical network 7. The route control unit 56 also sets wavelengths for the optical transceivers 71 and 73. The route calculation unit 57 performs route calculations when constructing optical paths in the optical network 7.

[0045] 6 is a sequence diagram showing the operation of the communication system 11. The optical transceiver 71 connected to the source gNB 12-1 is connected to the network 8 via the optical path P11 shown in FIG. 5. The optical signal that sets the signal to be transmitted and received by the UE 16 is assigned a wavelength λ1.

[0046] When the source gNB 12-1 determines that handover of the subordinate UE 16 is necessary, the source gNB 12-1 transmits a handover request (Handover requested) in which a terminal ID is set to the AMF 13 (Step S211). The terminal ID is identification information of the UE 16.

[0047] When the AMF 13 receives the handover request, it acquires information about the target gNB 12-2, which is the handover destination of the UE 16, by any method. The AMF 13 transmits a notification of the start of HO (Handover) to the controller 50, which notification includes Source AP information indicating the source gNB 12-1, Target AP information indicating the target gNB 12-2, and wavelength information indicating the wavelength λ1 (step S212). Furthermore, the AMF 13 transmits a handover request to the target gNB 12-2 (step S213). The target gNB 12-2 transmits a handover request response (Handover request ACK) to the AMF 13 (step S214).

[0048] When the 5GC cooperation unit 55 of the controller 50 receives the notification of the start of HO, it transmits a route and wavelength switching request in which source AP information, target AP information, and wavelength information are set to the route control unit 56 (step S215). When the route control unit 56 receives the route and wavelength switching request, it transmits a route calculation request in which target AP information is set to the route calculation unit 57 (step S216).

[0049] The route calculation unit 57 calculates the route of the optical path P12 from the optical transceiver 71 to which the target gNB12-2 identified by the target AP information is connected to the optical transceiver 73 connected to the network 8 (step S217). The route calculation unit 57 transmits a switching route notification to the route control unit 56, which includes information on the calculated route of the optical path P12 (step S218).

[0050] The route control unit 56 transmits a route setting instruction to each optical transmission device 72 related to the generation of the optical path P12, the route setting instruction including the wavelength λ1 and route information for the optical transmission device 72 to generate the route of the optical path P12 (step S219). The optical transmission device 72 sets the route of the optical path P12 to be used for the optical signal of wavelength λ1 in accordance with the route setting instruction received from the controller 50 (step S220). When the route setting is completed, the optical transmission device 72 returns a completion notification to the controller 50 (step S221).

[0051] In step S219, the route control unit 56 may transmit a route setting instruction to delete the optical path P11 used by the wavelength λ1 to each optical transmission device 72 related to the optical path P11. The optical transmission device 72 changes the setting to delete the route of the optical path P11 used by the wavelength λ1 in accordance with the route setting instruction received from the controller 50. When the change in the route setting is completed, the optical transmission device 72 returns a completion notification to the controller 50.

[0052] The route control unit 56 transmits wavelength information indicating the wavelength λ1 and a wavelength setting including the terminal ID to the optical transceivers 71 and 73 that terminate the optical path P12 (step S222). The optical transceivers 71 and 73 update their settings to convert the signal with the terminal ID notified by the wavelength setting into an optical signal with the wavelength λ1 (step S223). After updating their settings, the optical transceivers 71 and 73 return a completion notification (step S224).

[0053] In step S222, the route control unit 56 may transmit a stop instruction for the wavelength λ1 to the optical transceivers 71 and 73 that terminate the optical path P11. Upon receiving the stop instruction, the optical transceivers 71 and 73 stop using the wavelength λ1 and return a completion notification.

[0054] The route control unit 56 of the controller 50 transmits the completion notification received from the optical transceiver 71 and the optical transceiver 73 to the 5GC linkage unit 55 (step S225). The 5GC linkage unit 55 may or may not transmit the completion notification to the AMF 13 (step S226).

[0055] The AMF 13 transmits a handover request command (Handover request COMMAND) to the source gNB 12-1 (step S227). On the other hand, when the target gNB 12-2 starts wireless communication with the UE 16, it transmits a handover notification (Handover NOTIFY) to the AMF 13 (step S228). The AMF 13 transmits a UE context release command (UE context release command) to the source gNB 12-1 (step S229). When the source gNB 12-1 releases wireless communication with the UE 16, it returns a UE context release command complete (UE context release command complete) to the AMF 13 (step S230). This completes the switching of the communication destination of the UE 16 from the source gNB 12-1 to the target gNB 12-2 (step S231).

[0056] As described above, when source gNB12-1 sends a Handover requested to AMF13, the controller 50 performs optical path calculation and control.

[0057] Next, a communication system 11 that performs XnHO will be described. Figure 7 is a diagram showing an example configuration of a communication system 11 that performs XnHO. The controller 50 shown in Figure 7 differs from the controller 50 shown in Figure 5 in that it further includes a monitoring unit 58. The monitoring unit 58 monitors the status of the optical path established by the controller 50 and confirms IP reachability between the gNBs 12.

[0058] N2HO involves a large amount of communication with 5GC, which places a burden on switching and lengthens communication interruption times. Conventionally, direct IP reachability could not be ensured by assigning IP addresses between areas. The communication system 11 of this embodiment enables gNBs 12 to communicate directly with each other by changing the route of the optical transmission device 72. By enabling gNBs 12 to communicate with each other, XnHO can be applied when any UE 16 performs a handover between those gNBs 12. However, the controller 50 deletes Xn routes that are rarely used for XnHO and have not been used for a certain period of time in order to conserve wavelengths.

[0059] 8 and 9 are sequence diagrams showing the operation of the communication system 11. In FIG. 8, the same processes as those shown in FIG. 6 are assigned the same reference numerals, and their description will be omitted. When the AMD 13 receives a handover request (Handover requested) transmitted from the UE 16 in step S211, it transmits a notification of the start of N2HO to the controller 5 (step S212a). Furthermore, when the route calculation unit 57 receives a route calculation request transmitted from the route control unit 56 in step S216, it reads out the Target AP information set in the route calculation request. The route calculation unit 57 calculates the route of the optical path P12 for N2HO from the optical transceiver 71 to which the target gNB 12-2 identified by the Target AP information is connected to the optical transceiver 73 connected to the network 8 (step S217a). Furthermore, the communication system 11 receives the completion notification from the optical transceivers 71 and 73 in step S224, and after determining that the route of the optical path P12 for N2HP has been set, sets and monitors the route for Xn (step S300).

[0060] 9 shows the operation of the communication system 11 in step S300. The route control unit 56 sends an Xn route calculation request, in which Source AP information and Target AP information are set, to the route calculation unit 57 (step S301). The route calculation unit 57 calculates the Xn route in the optical network 7 between the source gNB 12-1 indicated by the Source AP information and the target gNB 12-2 indicated by the Target AP information (step S302). Any conventional technology can be used to calculate the Xn route. The route calculation unit 57 sends an Xn route notification, in which information about the calculated Xn route is set, to the route control unit 56 (step S303).

[0061] The route control unit 56 transmits to each optical transmission device 72 related to the generation of the Xn route a route setting instruction that sets route information for the optical transmission device 72 to generate the Xn route and the wavelength λ2 to be used for communication between the source gNB 12-1 and the target gNB 12-2 (step S304). The optical transmission device 72 sets the Xn route to be used for the optical signal of wavelength λ2 in accordance with the route setting instruction received from the controller 50 (step S305). When the optical transmission device 72 completes the setting of the Xn route, it returns a completion notification to the controller 50 (step S306).

[0062] The route control unit 56 transmits a wavelength setting to the optical transceiver 71 terminating the Xn route, indicating that the route is an Xn route between the source gNB 12-1 and the target gNB 12-2 and including wavelength information indicating the wavelength λ2 (step S307). The optical transceiver 71 updates the setting so that signals between the source gNB 12-1 and the target gNB 12-2 notified by the wavelength setting are transmitted and received using optical signals with wavelength λ2 (step S308). After updating the setting, the optical transceiver 71 returns a completion notification (step S309).

[0063] The route control unit 56 transmits a route alive / dead monitoring instruction, in which information specifying the route for Xn to be monitored is set, to the monitoring unit 58 (step S310). The monitoring unit 58 monitors the alive / dead status of the route for Xn to be monitored specified by the route alive / dead monitoring instruction (step S311). When the monitoring unit 58 detects that the route for Xn has not been used for a predetermined period of time, it notifies the route control unit 56 of a route deletion instruction, in which information specifying the route for Xn is set (step S312).

[0064] The route control unit 56 transmits a route setting including route information in which the route for Xn has been deleted to each optical transmission device 72 on the route for Xn (step S313). The optical transmission device 72 performs setting to delete the route for Xn based on the route information included in the route setting received from the controller 50 (step S314). When the optical transmission device 72 completes setting the route information in which the route for Xn has been deleted, it returns a completion notification to the controller 50 (step S315).

[0065] In conventional procedures, optical transmission paths were fixed, so dynamic changes were not possible unless IP reachability was available during construction. In this embodiment, optical transmission paths can be dynamically configured in accordance with the occurrence of N2HO. Furthermore, although N2HO takes time to complete switching between gNBs, XnHO can be implemented by constructing an optical path using an optical transmission path between base station pairs where N2HO has been implemented. With APN, the path can be constructed with low latency even if the route is extended.

[0066] According to the above-described embodiment, the controller receives a signal from an upper node that controls multiple access points to switch (handover) the access point to which the wireless terminal is connected, and the controller controls the optical transmission path to construct an optical path tailored to the wireless terminal.

[0067] For example, if the communication system is 5G, by introducing a controller (5GC interoperability function unit) that can operate in conjunction with a 5GC (5th Generation Core network) in addition to a normal cellular system (RAN, CN), it is possible to set up an optical transmission path that is in line with the handover control of the cellular system.

[0068] Furthermore, when N2HO occurs in accordance with the movement of a UE, optical path control can be realized on a UE-by-UE basis according to the above-described embodiment.

[0069] Furthermore, once N2HO has occurred between base stations, IP reachability can be guaranteed and designed by the controller, enabling switching by XnHO from the second time onwards. This reduces the load on the cellular system and shortens the duration of communication interruptions caused by the cellular system.

[0070] The controller also monitors the status of the optical paths between the base stations established as described above, and deletes the optical paths if no communication is performed within a set time. This allows for efficient management of the number of optical paths.

[0071] The controllers 5 and 50 may be realized by a plurality of computer devices connected to a network. In this case, it is possible to arbitrarily select which of the plurality of computer devices each function unit of the controllers 5 and 50 is realized by.

[0072] 10 is a device configuration diagram showing an example of the hardware configuration of the controllers 5 and 50. The controllers 5 and 50 include a processor 91, a storage unit 92, a communication interface 93, and a user interface 94.

[0073] The processor 91 is a central processing unit that performs calculations and control. The processor 91 is, for example, a CPU (central processing unit) or a GPU (graphics processing unit). The processor 91 reads and executes programs from the storage unit 92. The storage unit 92 further has a work area and the like for the processor 91 to execute various programs. The communication interface 93 is connected to other devices so as to be able to communicate with them. The user interface 94 is an input device such as a keyboard, a pointing device (mouse, tablet, etc.), a button, a touch panel, etc., and a display device such as a display. Human operations are input via the user interface 94.

[0074] At least some of the functions of the controllers 5 and 50 described above are realized by the processor 91 reading and executing a program from the storage unit 92. The program of the controllers 5 and 50 may be recorded on a computer-readable recording medium. Examples of the computer-readable recording medium include portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. The program of the controllers 5 and 50 may be transmitted via a telecommunications line. Note that at least some of the functions of the controllers 5 and 50 may be realized using hardware such as an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a field-programmable gate array (FPGA).

[0075] According to the above-described embodiment, the communication system includes a first access point, a second access point, an upper node device that manages connections of wireless terminals, and an optical network that connects the first access point and the second access point to a network to which the upper node device is connected. The upper node device is, for example, the upper node 3 in the embodiment. A destination device of the wireless terminal is also connected to the network. The destination device is, for example, the upper node 4 in the embodiment. The optical network transmits, via a first optical path between the first access point and the network, one or both of an optical signal including a signal from the wireless terminal to the destination device and an optical signal including a signal from the destination device to the wireless terminal. The control device controls the optical network in the communication system. The control device corresponds, for example, to the controllers 5 and 50 in the embodiment.

[0076] The control device has an upper node cooperation unit, a route calculation unit, and a route control unit. The upper node cooperation unit receives a notification from the upper node device that a wireless terminal communicating with a communication destination device connected to the network via a first access point will initiate a handover to a second access point. The route calculation unit calculates the route of an optical path between the second access point and the network in the optical network. The route control unit controls the optical network to set an optical path between the second access point and the network according to the route calculated by the route calculation unit, and notifies the upper node device when the optical path setting is complete.

[0077] The route control unit may calculate an inter-access point route, which is a route of an inter-access point optical path between the first access point and the second access point. The route control unit controls the optical network to set the inter-access point optical path according to the inter-access point route.

[0078] The control device may further include a monitoring unit that monitors the optical paths between the access points. When the monitoring unit detects that the optical paths between the access points have not been used for a predetermined period of time, the route control unit controls the optical network to delete the optical paths between the access points.

[0079] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments, and include designs within the scope of the present invention that do not deviate from the gist of the present invention.

[0080] 1 Communication system 2-1, 2-2 Access point 3 Upper node 4 Upper node 5 Controller 6 Wireless terminal 7 Optical network 8 Network 11 Communication system 12-1 Source gNB 12-2 Target gNB 13 AMF 14 UPF 16 UE 50 Controller 51 Upper node cooperation unit 52 Route control unit 53 Route calculation unit 55 5GC cooperation unit 56 Route control unit 57 Route calculation unit 58 Monitoring unit 71 Optical transceiver 72 Optical transmission device 73 Optical transceiver 91 Processor 92 Memory unit 93 Communication interface 94 User interface

Claims

1. A control device for controlling an optical network in a communication system having a first access point, a second access point, an upper node device that manages connections of wireless terminals, and an optical network that connects the first access point and the second access point to the network to which the upper node device is connected, comprising: an upper node cooperation unit that receives a notification from the upper node device that the wireless terminal, which is communicating with a communication destination device connected to the network via the first access point, will initiate a handover to the second access point; a route calculation unit that calculates the route of an optical path between the second access point and the network in the optical network; and a route control unit that controls the optical network to set up an optical path between the second access point and the network according to the route calculated by the route calculation unit, and notifies the upper node device when the setting of the optical path has been completed.

2. The control device according to claim 1, wherein the route control unit calculates an inter-access point route, which is a route of an inter-access point optical path between the first access point and the second access point, and the route control unit controls the optical network to set the inter-access point optical path using the inter-access point route.

3. The control device according to claim 2, further comprising a monitoring unit that monitors the optical path between the access points, wherein the route control unit controls the optical network to delete the optical path between the access points when the monitoring unit detects that the optical path between the access points has not been used for a predetermined period of time.

4. A system comprising: a first access point; a second access point; an upper node device that manages connections of wireless terminals; an optical network that connects the first access point and the second access point to a network to which the upper node device and a communication destination device of the wireless terminal are connected; and a control device that controls the optical network, wherein the optical network transmits, via a first optical path between the first access point and the network, one or both of an optical signal including a signal from the wireless terminal to the communication destination device and an optical signal including a signal from the communication destination device to the wireless terminal, and an optical signal including a signal from the communication destination device to the wireless terminal, and wherein the control device comprises: an upper node coordinating unit that receives a notification from the upper node device that the wireless terminal, which is communicating with a communication destination device connected to the network via the first access point, will initiate a handover to the second access point; a route calculation unit that calculates a route of a second optical path between the second access point and the network in the optical network; and a route control unit that controls the optical network to set the second optical path between the second access point and the network according to the route calculated by the route calculation unit, and notifies the upper node device when setting of the second optical path is completed. the optical network transmits, via the second optical path, one or both of an optical signal including a signal from the wireless terminal to the destination device and an optical signal including a signal from the destination device to the wireless terminal.

5. A communication control method for controlling an optical network in a communication system having a first access point, a second access point, an upper node device that manages connections of wireless terminals, and an optical network that connects the first access point and the second access point to a network to which the upper node device is connected, comprising: a receiving step of receiving a notification from the upper node device that the wireless terminal, communicating with a communication destination device connected to the network via the first access point, will initiate a handover to the second access point; a route calculation step of calculating a route for an optical path between the second access point and the network in the optical network; and a route control step of controlling the optical network to set up an optical path between the second access point and the network according to the route calculated in the route calculation step, and notifying the upper node device when the setting of the optical path has been completed.

6. A first transmission step in which an optical network connecting a first access point and a second access point to a network to which an upper node device managing the connection of wireless terminals and a communication destination device of the wireless terminal are connected transmits one or both of an optical signal including a signal from the wireless terminal to the communication destination device and an optical signal including a signal from the communication destination device to the wireless terminal via a first optical path between the first access point and the network; a reception step in which a control device receives from the upper node device a notification that the wireless terminal communicating with a communication destination device connected to the network via the first access point will initiate a handover to the second access point; a route calculation step in which a route of a second optical path between the second access point and the network in the optical network is calculated; and a route control step in which the optical network is controlled to set the second optical path between the second access point and the network according to the route calculated in the route calculation step, and notifies the upper node device when the setting of the second optical path is completed. a second transmission step in which the optical network transmits, via the second optical path, one or both of an optical signal including a signal from the wireless terminal to the destination device and an optical signal including a signal from the destination device to the wireless terminal.

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