Transmission system, switching control device, switching control method, and program

Abstract

Provided is a switching control device that, on the basis of the allocation of radio resources to terminals wirelessly transmitting signals to transmission devices in the lowermost layer among multiple transmission devices that constitute a communication network layered into multiple layers and transfer received signals to the immediately above layer, calculates the amount of traffic in a predetermined period for each of first transmission devices in a given layer. This switching control device calculates processing power expected to be required for each of second transmission devices in a layer immediately above the layer of the first transmission devices on the basis of the amounts of traffic of the first transmission devices. The switching control device instructs a transfer device, which transfers signals transmitted from the first transmission devices to the second transmission devices, to change a connection destination of a first transmission device under a second transmission device that is determined to be congested on the basis of the processing power.

Description

Technical Field

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

Background Art

[0002] In a mobile network (NW), a terminal is connected to an upper NW such as the Internet via an antenna station and a base station. When the base station becomes overloaded during the communication of the terminal, the mobile NW distributes the load by switching the connection destination of the terminal to another base station with less load. When performing such load distribution, the terminal presents a base station that can be switched from among the base station with which it is connected and other base stations that share available resources.

[0003] FIG. 37 is a diagram showing load distribution in a conventional mobile NW system. In the example shown in FIG. 37, the base station is separated into a distributed station and an aggregation station. Terminals 991a and 991b are connected to an aggregation station 994-1 via an antenna station 992-1 and a distributed station 993-1. Terminal 991c is connected to an aggregation station 994-2 via an antenna station 992-2 and a distributed station 993-2. When bandwidth shortage or overload occurs in the aggregation station 994-1, the terminal 991b presents the aggregation station 994-2 that shares the used resources with the aggregation station 994-1 as a connectable base station. By changing the connection destination of the terminal 991b to the aggregation station 994-2, it is possible to distribute the load to the less-loaded and connectable aggregation station 994-2.

[0004] In recent years, it has also been proposed to virtualize the aggregation stations through base station virtualization and change the connected virtualized aggregation stations according to the load. FIG. 38 is a diagram showing the load distribution of a mobile NW system using virtualization technology. The mobile NW system shown in FIG. 38 is provided with virtualized aggregation stations 995-1 and 995-2 instead of the aggregation stations 994-1 and 994-2 shown in FIG. 37. The virtualized aggregation station 995-1 has a base station controller 996-1 and aggregation stations 997-1-1 and 997-1-2. The virtualized aggregation station 995-2 has a base station controller 996-2 and an aggregation station 997-2. The terminal 991a and the terminal 991b are connected to the aggregation station 997-1-1 via the antenna station 992-1 and the distributed station 993-1. Due to bandwidth congestion or overload of the base station, the terminal 991b may change the connection destination to the aggregation station 997-1-2 or the aggregation station 997-2.

[0005] FIG. 39 is a sequence diagram of the aggregation station switching process in a conventional mobile NW system. The mobile NW system switches the aggregation station by the processes of steps S901 to S914.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the midst of the increasing prevalence of broadband communications with narrow coverage areas such as millimeter waves, it is anticipated that in the future, it will become difficult for terminals to find a base station to which they can connect. For example, in Fig. 37, terminal 991b performs a handover (HO) to concentrator 994-2 due to the load on the destination concentrator 994-1. In this case, terminal 991b switches the connection so as to connect to concentrator 994-2 via antenna station 992-2 and distributed station 993-2. However, the radio wave intensity of terminal 991b may be low under the jurisdiction of antenna station 992-2. Then, problems such as a decrease in the amount of traffic that can be transmitted and packet loss occur, making it difficult to achieve low-latency communication. In addition, when performing a base station switch including up to the antenna station, since it is necessary to instruct terminal 991b to perform a handover to the switching destination, a lot of time is required for the switching sequence.

[0008] Also, in the mobile NW system shown in Fig. 38, due to bandwidth congestion or overload of the base station, terminal 991b may perform a handover (HO). If it is a concentrator change within the same hardware (HW) such as the change from concentrator 997-1-1 to concentrator 997-1-2, the lower levels than distributed station 993-1 may remain connected in the same way as before the handover. This is because base station controller 996-1 processes both the control signal of concentrator 997-1-1 and the control signal of concentrator 997-1-2.

[0009] On the other hand, in the case of load distribution between different aggregation stations by the base station controller, the transmission destination of the control signal is different before and after the switch. Therefore, not only the aggregation station but also the antenna station through which the terminal performs wireless communication must be switched. For example, the terminal 991b switches the connection to the aggregation station 997-1-1 via the antenna station 992-1 and the distribution station 993-1 to the connection to the aggregation station 997-2 via the antenna station 992-2 and the distribution station 993-2. However, similar to the above, the radio wave intensity of the terminal 991b may be low under the antenna station 992-2. In such a case, the amount of traffic that can be transmitted decreases. Furthermore, since retransmission is performed due to the occurrence of packet loss, it takes time until the transmission of the traffic is completed. From these facts, it may be difficult to achieve low-latency communication (such as 5 ms in the wired section).

[0010] Also, as shown in FIG. 39, in the case of conventional aggregation station switching, in order to exchange the data transfer information of the bearer, between the base station controller (gNB-CU-CP) and the source aggregation station (Source gNB-CU-UP), after performing the bearer change procedure by steps S905 and S906, between the base station controller (gNB-CU-CP) and the target aggregation station (Target gNB-CU-UP), the bearer change is performed by steps S907 and S908. Also, the mobile NW system performs the switching procedure lower than the aggregation station and then performs the switching of the aggregation station and the upper optical path by step S910. Therefore, it takes a long time from the start of the switch to the completion of the switch.

[0011] In view of the above circumstances, an object of the present invention is to provide a transmission system, a switching control device, a switching control method, and a program that can reduce the delay caused by load distribution of signal processing.

Means for Solving the Problems

[0012] The transmission system according to one aspect of the present invention comprises: a plurality of transmission devices that form a communication network hierarchically structured in multiple layers and transfer the received signals to the layer above; a transfer device that transfers a signal transmitted from a first transmission device, which is a transmission device of a predetermined layer among the plurality of layers, to a second transmission device among a plurality of second transmission devices that are transmission devices of a layer one above the predetermined layer and to which the first transmission device is connected; and a switching control device that switches the second transmission device to which the first transmission device is connected. The switching control device includes: a traffic volume calculation unit that calculates, based on the allocation of radio resources to a terminal that wirelessly transmits signals to the bottommost transmission device, the traffic volume of signals received by each of the first transmission devices via a transmission device in a layer lower than the predetermined layer within a predetermined period; a required bandwidth calculation unit that calculates, for each of the second transmission devices, the processing capacity predicted to be required in the second transmission device based on the traffic volume in the first transmission device having the second transmission device as the connection destination; a determination unit that determines whether congestion occurs in the second transmission device based on the predicted processing capacity; a switching determination unit that determines to switch the connection destination of at least a part of the first transmission devices having the second transmission device determined to have congestion as the connection destination to a second transmission device determined not to have congestion; and a switching instruction unit that instructs the transfer device to transfer a signal transmitted from a switching target transmission device, which is the first transmission device determined to switch the connection destination based on the determination of the switching determination unit, to the second transmission device that is the connection destination after the switching of the switching target transmission device.

[0013] The switching control device according to one aspect of the present invention constitutes a communication network hierarchically divided into a plurality of layers, and wirelessly transmits a signal to a terminal that transmits a signal wirelessly to the bottommost transmission device among a plurality of transmission devices that constitute the communication network and transfer the received signal to the upper layer. Based on the allocation of radio resources to the terminal, a traffic volume calculation unit calculates the traffic volume of signals received by each of the first transmission devices, which are transmission devices of a predetermined layer among the plurality of layers, via transmission devices lower than the predetermined layer during a predetermined period. For each second transmission device, which is a transmission device of the layer above the first transmission device, a required bandwidth calculation unit calculates the processing capacity predicted to be required in the second transmission device based on the traffic volume in the first transmission device having the second transmission device as the connection destination. A determination unit determines whether congestion occurs in the second transmission device based on the predicted processing capacity. A switching determination unit determines to switch the connection destination of at least some of the first transmission devices having the second transmission device determined to have congestion as the connection destination to a second transmission device determined not to have congestion. A switching instruction unit instructs a transfer device that transfers a signal transmitted from the first transmission device to the second transmission device that is the connection destination of the first transmission device among the plurality of second transmission devices to transfer the signal transmitted from the switching target transmission device, which is the first transmission device determined to switch the connection destination, to the second transmission device that is the connection destination after switching of the switching target transmission device, based on the determination of the switching determination unit.

[0014] The switching control method according to one aspect of the present invention constitutes a communication network hierarchically divided into a plurality of layers, and transmits a signal wirelessly to a terminal that transmits a signal wirelessly to the lowermost transmission device among a plurality of transmission devices that configure the communication network hierarchically divided into a plurality of layers and transfer the received signal to the upper layer. Based on the allocation of radio resources to the terminal, each first transmission device, which is a transmission device of a predetermined layer among the plurality of layers, calculates the traffic volume of the signal received via a transmission device lower than the predetermined layer during a predetermined period. A traffic volume calculation step; for each second transmission device, which is a transmission device of the layer above the first transmission device, based on the traffic volume in the first transmission device having the second transmission device as a connection destination, calculates the processing capacity required in the second transmission device. A required bandwidth calculation step; a determination step of determining whether or not congestion occurs in the second transmission device based on the predicted processing capacity; among the first transmission devices having the second transmission device determined to have congestion as a connection destination, at least a part of the first transmission devices A switching determination step of determining to switch the connection destination to a second transmission device determined not to have congestion; a transfer device that transfers a signal transmitted from the first transmission device to the second transmission device that is the connection destination of the first transmission device among the plurality of second transmission devices, based on the determination in the switching determination step, the signal transmitted from the switching target transmission device, which is the first transmission device determined to switch the connection destination, is transferred to the second transmission device that is the connection destination after switching of the switching target transmission device. And a switching instruction step of instructing to transfer.

[0015] A program according to one aspect of the present invention causes a computer to function as any of the above-described switching control devices.

Advantages of the Invention

[0016] According to the present invention, it is possible to reduce the delay caused by load distribution of signal processing.

Brief Description of the Drawings

[0017]

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Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that those having the same function are denoted by the same reference numerals, and repeated description thereof will be omitted.

[0019] FIG. 1 is a diagram showing the configuration of a mobile NW system 10 according to an embodiment. The mobile NW system 10 is an example of a transmission system. The mobile NW system 10 is, for example, a fifth-generation mobile communication system (hereinafter referred to as "5G"). The mobile NW system 10 includes a terminal 11, an antenna station 12, a distributed station 13, an aggregation station 14, a transfer device 15, and a switching control device 16. The antenna station 12, the distributed station 13, and the aggregation station 14 are examples of hierarchical transmission devices. The mobile NW system 10 is connected to a higher-level NW 20. Each of the M (M is an integer of 1 or more) distributed stations 13 is described as distributed stations 13-1 to 13-M. Under the distributed station 13-m (m is an integer of 1 or more and M or less), K m units (K m is an integer of 1 or more) of antenna stations 12 are described as antenna stations 12-m. Also, each of the N (N is an integer of 2 or more) aggregation stations 14 is described as aggregation stations 14-1 to 14-N. The direction from the terminal 11 to the higher-level NW 20 is described as upstream, and the direction from the higher-level NW 20 to the terminal 11 is described as downstream.

[0020] The terminal 11 is, for example, a 5G UE (User Equipment). The terminal 11 transmits and receives radio signals with the antenna station 12 using the radio resources allocated from the distributed station 13. The allocated radio resources include the start timing and end timing of the time intervals during which transmission and reception of radio signals are respectively permitted. The start timing and end timing are represented by, for example, slots which are the scheduling units for data transmission and reception in a radio frame. The allocated radio resources may further include a coding rate and a modulation method.

[0021] The antenna station 12 is, for example, a 5G RU (Radio Unit). The antenna station 12 receives uplink data by radio signals from the terminal 11. The antenna station 12-m sets the received uplink data as an uplink signal and transmits the uplink signal to the distributed station 13-m via a wired interface. Also, the antenna station 12-m receives a downlink signal from the distributed station 13-m via a wired interface. The antenna station 12 transmits the downlink data addressed to the terminal 11 set in the received downlink signal to the terminal 11 by radio signals.

[0022] The distributed station 13 is, for example, a 5G DU (Distributed unit). The distributed station 13-m receives uplink signals from each of the K m antenna stations 12-m. The uplink signals received by the distributed station 13-m include the uplink data received from the terminal 11 under the jurisdiction of the antenna station 12-m. The distributed station 13 generates an uplink signal obtained by aggregating the uplink data and transmits the generated uplink signal to the aggregation station 14 which is the connection destination of its own station. Also, the distributed station 13 receives a downlink signal in which the downlink data addressed to the terminal 11 under its jurisdiction is set from the aggregation station 14 which is the connection destination of its own station. The distributed station 13-m converts the received downlink signal into a downlink signal corresponding to the radio signals transmitted from each antenna station 12-m. The distributed station 13-m transmits the converted downlink signal to the antenna station 12-m corresponding to that downlink signal.

[0023] The aggregation station 14 is, for example, the CU (Central Unit) of 5G. The aggregation station 14 aggregates the uplink signals received from the subordinate distributed stations 13 and transfers them to the upper-layer NW 20. Also, the aggregation station 14 receives a downlink signal in which downlink data destined for the terminal 11 is set from the upper-layer NW 20, and transfers the received downlink signal to the distributed station 13 connected to the destination terminal 11.

[0024] The transfer device 15 is connected to the distributed station 13, the aggregation station 14, and the switching control device 16. The transfer device 15 transfers the uplink signal received from the distributed station 13 to the destination aggregation station 14 according to the transfer path. Also, the transfer device 15 transfers the downlink signal received from the aggregation station 14 to the destination distributed station 13 according to the transfer path. The signal transfer path in the transfer device 15 is instructed by the switching control device 16.

[0025] The switching control device 16 is connected to the distributed station 13, the aggregation station 14, and the transfer device 15. The switching control device 16 has the function of a 5G base station controller. Further, the switching control device 16 has a function of controlling the switching of the connection between the distributed station 13 and the aggregation station 14. The switching control device 16 switches the aggregation station 14 to which the distributed station 13 is connected so as to disperse the base station load according to the congestion situation or the load situation in the aggregation station 14. Specifically, the switching control device 16 instructs the aggregation station 14 at the connection destination before switching (hereinafter referred to as "the switching source") to release the connection with the distributed station 13, and instructs the aggregation station 14 at the connection destination after switching (hereinafter referred to as "the switching destination") to establish the connection with the distributed station 13. Further, the switching control device 16 instructs the transfer device 15 to switch the transfer path so that signal transfer is performed according to the path after the connection destination is switched. Hereinafter, changing the aggregation station to which the distributed station is connected is referred to as "path switching".

[0026] As described above, in the mobile NW system 10, a transfer device 15 and a switching control device 16 are provided between the distributed stations 13 and the aggregation station 14. The switching control device 16 obtains information on the signal processing capabilities of each aggregation station 14 connected to the transfer device 15 and information on the amount of traffic that will occur from each distributed station 13 connected to the aggregation station 14. Note that since the mobile NW system 10 of the present embodiment performs path switching based on the upstream traffic, the traffic means the traffic of the upstream signal.

[0027] The switching control device 16 receives in advance information on the maximum processable bandwidth as information on the signal processing capabilities of the aggregation station 14. The maximum processable bandwidth is represented by, for example, the maximum buffer amount of the aggregation station 14. Further, the switching control device 16 receives information that enables it to acquire the amount of traffic in the next transmission period of the upstream signal from each distributed station 13. Hereinafter, the transmission period of the upstream signal will be simply referred to as the "transmission period". Based on the information received, if the switching control device 16 predicts that bandwidth congestion or processing overload will occur at the aggregation station 14 in the next or the next subsequent transmission period, it performs a load balancer (load distribution) by path switching. The switching control device 16 determines the aggregation station 14 to which the distributed station 13 is to be switched so that neither bandwidth congestion nor overload occurs at any of the aggregation stations 14. The switching control device 16 performs path switching before the transmission period in which bandwidth congestion or processing overload is predicted according to this determination.

[0028] When the aggregation station 14 is virtualized, instead of receiving information on the maximum processable bandwidth from the aggregation station 14, the switching control device 16 receives information on the resources allocated to the aggregation station 14 from a resource allocation device (not shown). The resource information indicates, for example, the number of CPU cores. Based on the core number information, the switching control device 16 obtains information on the maximum processable bandwidth of the aggregation station 14. The processable bandwidth can also be represented by, for example, the number of resource blocks. A resource block is a unit for allocating radio resources to the terminal 11.

[0029] When performing path switching, the switching control device 16 changes the connection between the aggregation station 14 and the distributed station 13 and then switches the transfer path of the transfer device 15. This enables it to cope with bandwidth congestion and processing overload in all aggregation stations 14 and allows for low-latency switching that is less likely to cause congestion at all times.

[0030] The mobile NW system 10 switches the connection between the distributed station 13 and the aggregation station 14, but it is not necessary for the terminal 11 to perform a handover to change the connected antenna station 12. Therefore, low-latency communication can be realized while avoiding congestion. Furthermore, when the mobile NW system 10 is utilized for high-capacity, low-latency communication and various services, efficient utilization of aggregation station resources becomes possible.

[0031] The following describes detailed embodiments.

[0032] [First Embodiment] In the first embodiment, the distributed station notifies the switching control device of the traffic volume using 5G downlink control information (DCI: Downlink Control Information). DCI includes scheduling information, data modulation, channel coding rate, etc. that are necessary for the terminal to transmit uplink data. The scheduling information is represented by resource blocks. A resource block is represented by a channel and the transmission start timing and transmission end timing using that channel. The transmission start timing and transmission end timing are represented by, for example, slots which are the scheduling unit for data transmission and reception in 5G. In this case, the transmission end timing may be represented by the number of slots corresponding to the elapsed time from the transmission start timing.

[0033] FIG. 2 is a diagram showing the configuration of the mobile NW system 100 according to the first embodiment. The mobile NW system 100 includes a terminal 11, an antenna station 120, a distributed station 130, an aggregation station 140, a transfer device 150, a switching control device 160, and a resource management device 170. The antenna station 120, the distributed station 130, the aggregation station 140, the transfer device 150, and the switching control device 160 respectively correspond to the antenna station 12, the distributed station 13, the aggregation station 14, the transfer device 15, and the switching control device 16 in FIG. 1. The antenna station 120, the distributed station 130, the aggregation station 140, the transfer device 150, the switching control device 160, and the resource management device 170 constitute a mobile NW. The aggregation station 140 is connected to the core network 201 and the Internet 202 via a transfer device 200. The transfer device 200, the core network 201, and the Internet 202 correspond to the upper NW 20 in FIG. 1.

[0034] Each of the M (M is an integer of 1 or more) distributed stations 130 is described as distributed stations 130-1 to 130-M. K m units (K m is an integer of 1 or more) of the antenna stations 120 under the distributed station 130-m are described as antenna stations 120-m. Also, each of the N (N is an integer of 2 or more) aggregation stations 140 is described as aggregation stations 140-1 to 140-N. FIG. 2 shows an example where M = 4, and K1, K2, K3, K4, and N = 2.

[0035] Some of the aggregation stations 140-1 to 140-N may be connected to a transfer device 150a and a switching control device 160a. The transfer device 150a and the switching control device 1 have the same functions as the transfer device 150 and the switching control device 160. The transfer device 150a and the switching control device 160a are connected to distributed stations 130 and aggregation stations 140 not shown in FIG. 2. The resource management device 170 manages the resources of the aggregation station 140.

[0036] The terminal 11, the antenna station 120, the distributed station 130, and the aggregation station 140 each have the functions of a 5G UE, RU, DU, and CU. The terminal 11 is connected to the Internet 202 via the antenna station 120, the distributed station 130, the transfer device 150, the aggregation station 140, the transfer device 200, and the core network 201. In this embodiment, the bearer signals between the antenna station 120 and the distributed station 130, between the distributed station 130 and the aggregation station 140, and between the aggregation station 140 and the transfer device 200 are optical signals. The bearer signal is a signal in which user data transmitted or received by the terminal 11 is set. The core network 201 is, for example, an optical network.

[0037] The transfer device 150 transfers the uplink signal received from the distributed station 130 to the destination aggregation station 140, and transfers the downlink signal received from the aggregation station 140 to the destination distributed station 130. When the bearer signal between the distributed station 130 and the aggregation station 140 is an optical signal, the transfer device 150 is an optical GW (gateway). The optical GW has a plurality of first ports (not shown) and a plurality of second ports (not shown). The first port is connected to the transmission path with the distributed station 130, and the second port is connected to the transmission path with the aggregation station 140. The optical GW outputs an optical signal of a predetermined wavelength input from any one of the first ports to any one of the second ports according to a preset path, and outputs an optical signal of a predetermined wavelength input from any one of the second ports to any one of the first ports according to a preset path. The wavelength corresponding to each first port and each second port, and the path between the first port and the second port are set according to an instruction from the switching control device 160.

[0038] The switching control device 160 receives DCI information from the distributed station 130. Based on the DCI information, the switching control device 160 predicts the total traffic volume to be transmitted to each aggregation station 140 in the next transmission period. Note that the aggregation station 140 may transmit information on the total traffic volume in the next transmission period to the switching control device 160. Further, the switching control device 160 receives information on the buffer amount currently buffered from the aggregation station 140 and bearer information. The bearer information indicates the distributed station 130 to which the aggregation station 140 is connected. When the resource amount of the aggregation station 140 is fixed, the switching control device 160 stores information on the maximum processable bandwidth of the aggregation station 140 calculated in advance from the number of cores of the CPU of the aggregation station 140. When the resource amount of the aggregation station 140 changes, the resource management device 170 transmits aggregation station resource information indicating the resource amount allocated to the aggregation station 140 to the switching control device 160 periodically or when the resource amount changes. The switching control device 160 calculates the current maximum processable bandwidth using the resource amount of the aggregation station 140.

[0039] The switching control device 160 determines the congestion level of the traffic or the overloaded state of the processing in the aggregation station 140-n (n is an integer from 1 to N) by using the predicted total traffic volume transmitted to the aggregation station 140-n, the current buffer volume of the aggregation station 140-n, and the maximum processable bandwidth. That is, the switching control device 160 calculates the required bandwidth of the aggregation station 140-n by using the predicted total traffic volume transmitted to the aggregation station 140-n. The required bandwidth is the bandwidth required for processing the upstream traffic. In other words, the required bandwidth represents the demand traffic volume. When the sum of the required bandwidth and the current buffer volume is greater than or equal to a predetermined value compared to the maximum processable bandwidth, the switching control device 160 determines that congestion occurs because the bandwidth is congested or the processing is in an overloaded state. Note that the bandwidth congestion is caused by an increase in traffic, and the overloaded state of the processing is caused by a shortage of resources in the aggregation station 140, that is, a shortage of the maximum processable bandwidth. When the switching control device 160 determines that congestion occurs in the aggregation station 140-n, the switching control device 160 load-balances the traffic of at least some of the distributed stations 130 whose connection destination is the aggregation station 140-n to other aggregation stations 140 where congestion is not predicted to occur.

[0040] When the distributed station 130 performs connection setting and deletion for the terminal 11 when switching the connection destination aggregation station 140, it takes time for the terminal connection, making low-latency control difficult. Therefore, the aggregation station 140 continues to hold the connection information with the terminal 11. Similarly, the aggregation station 140 also holds the connection information of the base station.

[0041] The transfer device 200 outputs the upstream signal input from the transmission path between the transfer device 200 and the aggregation station 140 to the core network 201, and outputs the downstream signal input from the core network 201 to the transmission path between the transfer device 200 and the destination aggregation station 140. When the signal between the aggregation station 140 and the transfer device 200 is an optical signal, the transfer device 200 is an optical GW or an optical SW (switch).

[0042] Note that part or all of the bearer signals between the antenna station 120 and the distributed station 130, the bearer signals between the distributed station 130 and the aggregation station 140, and the signals between the aggregation station 140 and the transfer device 200 do not have to be optical signals. For example, when the bearer signal between the distributed station 130 and the aggregation station 140 is an electrical signal, the transfer device 150 is a layer 2 switch or a router. Similarly, when the signal between the aggregation station 140 and the transfer device 200 is an electrical signal, the transfer device 200 is a router.

[0043] FIG. 3 is a functional block diagram showing a configuration example of the distributed station 130. In FIG. 3, only the functional blocks related to the present embodiment are extracted and shown. The distributed station 130 includes a user data transceiver unit 131, a communication unit 132, and a control unit 133. The user data transceiver unit 131 transmits and receives bearer signals in the U-Plane. The user data transceiver unit 131 includes a first separation unit 1311, a first optoelectronic conversion unit 1312, an uplink signal generation unit 1313, a first electro-optical conversion unit 1314, a second separation unit 1315, a second optoelectronic conversion unit 1316, a downlink signal generation unit 1317, and a second electro-optical conversion unit 1318.

[0044] The first separation unit 1311 separates the uplink signal and the downlink signal by wavelength. The first separation unit 1311 outputs the uplink signal input from the transmission path between the antenna station 120 to the first optoelectronic conversion unit 1312, and outputs the downlink signal input from the second electro-optical conversion unit 1318 to the transmission path between the antenna station 120. The first optoelectronic conversion unit 1312 converts the uplink signal from an optical signal to an electrical signal. The uplink signal generation unit 1313 generates an uplink signal addressed to the aggregation station 140 with uplink data set by performing protocol processing, header replacement, etc. on the uplink signal converted into an electrical signal. The first electro-optical conversion unit 1314 converts the uplink signal addressed to the aggregation station 140 from an electrical signal to an optical signal and outputs it.

[0045] The second separation unit 1315 separates the upstream signal and the downstream signal according to the wavelength. The second separation unit 1315 outputs the upstream signal generated by the first electro-optical conversion unit 1314 to the transmission line between the transfer device 150, and outputs the downstream signal input from the transmission line between the transfer device 150 to the second electro-optical conversion unit 1316. The second electro-optical conversion unit 1316 converts the downstream signal input from the second separation unit 1315 from an optical signal into an electrical signal. The downstream signal generation unit 1317 generates a downstream signal addressed to each antenna station 120 in which the downstream data acquired from the received downstream signal is set by performing protocol processing, header replacement, etc. on the downstream signal converted into an electrical signal. The second electro-optical conversion unit 1318 converts the downstream signal addressed to each antenna station 120 generated by the downstream signal generation unit 1317 from an electrical signal into an optical signal, and then outputs it to the first separation unit 1311.

[0046] The communication unit 132 transmits and receives control signals to and from other devices such as the antenna station 120, the aggregation station 140, and the switching control device 160. The control signal includes a control signal of the C-plane. The control unit 133 controls the entire distributed station 130 according to the control signal transmitted and received via the communication unit 132. For example, the control unit 133 switches the connection destination aggregation station 140 according to the received control signal. In addition, the control unit 133 manages the lower layer connection between the terminal 11 and the mobile NW system 100. The control unit 133 controls protocol processing, header replacement processing, etc. in the user data transmission / reception unit 131 according to the terminal 11 connected to the lower antenna station 120 of the distributed station 130 and the aggregation station 140 which is the connection destination of the distributed station 130. The control unit 133 may transmit the control signal by an optical signal. When transmitting the control signal by an upstream optical signal, the upstream signal generation unit 1313 sets the control signal output from the control unit 133 as an upstream signal. When transmitting the control signal by a downstream optical signal, the downstream signal generation unit 1317 sets the control signal output from the control unit 133 as an upstream signal. The control signal may be superimposed on the optical signal transmitting the bearer signal, or may be transmitted by an optical signal different from the bearer signal. For example, the control unit 133 sets the control signal for the terminal 11 as a downstream signal. By this control signal, the control unit 133 transmits a DCI indicating the resources allocated to the terminal 11.

[0047] FIG. 4 is a functional block diagram showing a configuration example of the aggregation station 140. In FIG. 4, only the functional blocks related to the present embodiment are extracted and shown. The aggregation station 140 includes a user data transceiver 141, a communication unit 142, and a control unit 143. The user data transceiver 141 transmits and receives U-Plane bearer signals. The user data transceiver 141 includes a first separation unit 1411, a first optoelectronic conversion unit 1412, a buffer 1413, an upstream signal generation unit 1414, a first electro-optical conversion unit 1415, a second separation unit 1416, a second optoelectronic conversion unit 1417, a downstream signal generation unit 1418, and a second electro-optical conversion unit 1419.

[0048] The first separation unit 1411 separates the upstream signal and the downstream signal according to the wavelength. The first separation unit 1411 outputs the upstream signal input from the transmission line between the transfer device 150 to the first optoelectronic conversion unit 1412, and outputs the downstream signal input from the second electro-optical conversion unit 1419 to the transmission line between the transfer device 150. The first optoelectronic conversion unit 1412 converts the upstream signal from an optical signal to an electrical signal. The buffer 1413 temporarily stores the upstream signal converted into an electrical signal by the first optoelectronic conversion unit 1412. The upstream signal generation unit 1414 reads the upstream signal from the buffer 1413, and generates an upstream signal addressed to the upper NW by performing protocol processing, header replacement, and the like. The first electro-optical conversion unit 1415 converts the upstream signal generated by the upstream signal generation unit 1414 from an electrical signal to an optical signal and outputs it to the second separation unit 1416.

[0049] The second separation unit 1416 separates the upstream signal and the downstream signal according to the wavelength. The second separation unit 1416 transmits the upstream signal input from the first electro-optical conversion unit 1415 to the transmission line between the transfer device 200, and outputs the downstream signal received from the transmission line between the transfer device 200 to the second electro-optical conversion unit 1417. The second electro-optical conversion unit 1417 converts the downstream signal input from the second separation unit 1416 from an optical signal to an electrical signal. The downstream signal generation unit 1418 generates a downstream signal addressed to each distributed station 130 in which the downstream data acquired from the received downstream signal is set by performing protocol processing, header replacement, etc. on the downstream signal converted into an electrical signal. The second electro-optical conversion unit 1419 converts the downstream signal addressed to each distributed station 130 generated by the downstream signal generation unit 1418 from an electrical signal to an optical signal, and then outputs it to the first separation unit 1411.

[0050] The communication unit 142 transmits and receives control signals to and from other devices such as the distributed station 130, other aggregation stations 140, the switching control device 160, and the transfer device 200. The control signal includes a C-plane control signal. The control unit 143 controls the entire aggregation station 140 according to the control signals transmitted and received via the communication unit 142. For example, the control unit 143 switches the connected distributed station 130 according to the received control signal. Also, the control unit 143 controls the destination of the upstream signal and the destination of the downstream signal transmitted by the user data transmission / reception unit 141 according to the control signal. The control unit 143 notifies the switching control device 160 of the maximum processable bandwidth of the buffer 1413 and the current buffer amount by the control signal. When a buffer is provided after the upstream signal generation unit 1414, the control unit 143 may notify the switching control device 160 of the maximum processable bandwidth of the buffer after the upstream signal generation unit 1414 and the current buffer amount. The control unit 143 may transmit the control signal by an optical signal. When transmitting the control signal by an upstream optical signal, the upstream signal generation unit 1414 sets the control signal output by the control unit 143 as the upstream signal. When transmitting the control signal by a downstream optical signal, the downstream signal generation unit 1418 sets the control signal output by the control unit 143 as the upstream signal. The control signal may be superimposed on the optical signal transmitting the bearer signal, or may be transmitted by an optical signal different from the bearer signal.

[0051] FIG. 5 is a block diagram showing the configuration of the switching control device 160. The switching control device 160 includes a traffic volume calculation unit 161, a future traffic volume prediction unit 162, a required bandwidth calculation unit 163, a determination unit 164, a switching decision unit 165, a switching instruction unit 166, and a storage unit 167.

[0052] The traffic volume calculation unit 161 calculates the predicted traffic volume of each distributed station 130 in the next transmission period using the DCI information received from each distributed station 130. The DCI information may be the DCI transmitted to the terminal 11, or may be a part of the data set in the DCI and used for calculating the uplink traffic volume in the next transmission period. The predicted traffic volume in the next transmission period is the traffic volume predicted to be transmitted from the distributed station 130 to the aggregation station 140 in the next transmission period following the current uplink signal transmission period. The traffic volume calculation unit 161 calculates the predicted traffic volume in the next transmission period using the DCI information about the next transmission period transmitted to the terminal 11. The future traffic volume prediction unit 162 predicts the future traffic volume of the distributed station 130. The future traffic volume is the predicted traffic volume in the transmission period following the next transmission period.

[0053] The required bandwidth calculation unit 163 receives bearer information from the aggregation station 140. The bearer information includes information on the distributed stations 130 under the connection of the aggregation station 140. The required bandwidth calculation unit 163 calculates the required bandwidth of each aggregation station 140 using the predicted traffic volume of each distributed station 130 and the bearer information. When it is expected that the path switching in the mobile NW system 100 will be completed by the next transmission period, the predicted traffic volume used for calculating the required bandwidth is the predicted traffic volume in the next transmission period calculated by the traffic volume calculation unit 161. When it is expected that the path switching will not be completed by the next transmission period, the predicted traffic volume used for calculating the required bandwidth is the future traffic volume calculated by the future traffic volume prediction unit 162.

[0054] The determination unit 164 calculates the congestion amount of each aggregation station 140 using the required bandwidth of the aggregation station 140 calculated by the required bandwidth calculation unit 163, and the information on the buffer amount and the maximum processable bandwidth received from the aggregation station 140. Note that the determination unit 164 may calculate the maximum processable bandwidth based on the aggregation station resource information received from the resource management device 170. As the congestion amount, the amount of data expected to be stored in the buffer can be used. Specifically, the congestion amount is calculated by subtracting the maximum processable bandwidth from the sum of the required bandwidth and the current buffer amount. The determination unit 164 determines that congestion is predicted when the congestion amount exceeds the threshold value.

[0055] When the determination unit 164 predicts congestion, the switching determination unit 165 determines the distributed station 130 that switches the connection destination and the aggregation station 140 of the switching destination so that the congestion amount in all the aggregation stations 140 becomes equal to or less than a predetermined value, based on the required bandwidth and the congestion amount of each aggregation station 140, and the predicted traffic amount of each distributed station 130.

[0056] The switching instruction unit 166 instructs each device to switch the path so that the upstream signal from the distributed station 130 that is the target of switching the connection destination is transferred to the aggregation station 140 of the switching destination by the start of the transmission period in which congestion is predicted. The storage unit 167 stores various data used for the processing of each unit.

[0057] FIG. 6 is a sequence diagram showing the path switching procedure of the mobile NW system 100. The control units 143 of the aggregation stations 140-1 and 140-2 respectively notify the switching control device 160 of the bearer information indicating the distributed stations 130 connected to their own stations and the maximum processable bandwidth information indicating the maximum processable bandwidth in their own stations (steps S1001, S1002). Note that the resource management device 170 may transmit the bearer information of the aggregation stations 140-1 and 140-2 to the switching control device 160. Further, when the aggregation station 140 is virtualized, instead of the aggregation station 140 transmitting the maximum processable bandwidth information, the resource management device 170 transmits the aggregation station resource information of each aggregation station 140.

[0058] The control unit 133 of each distributed station 130 transmits the information of the DCI transmitted to the terminal 11 as the scheduling result of the uplink signal to the switching control device 160 (step S1003). Each time the distributed station 130 transmits the DCI to the terminal 11, it notifies the switching control device 160 of the DCI information. The notification frequency of the DCI information corresponds to the TTI (Transmission Time Interval), but in 5G, the TTI can be variable. On the other hand, the control units 143 of the aggregation stations 140-1 and 140-2 respectively notify the switching control device 160 of the buffer information indicating the buffer amount of their own stations (steps S1004, S1005).

[0059] Based on the received DCI information, the switching control device 160 calculates the predicted traffic volume in each distributed station 130. The switching control device 160 calculates the required bandwidth of each aggregation station 140 by summing up the predicted traffic volumes of the distributed stations 130 connected to the aggregation station 140 for each aggregation station 140 (step S1006).

[0060] Based on the maximum processable bandwidth and the current buffer amount of each aggregation station 140 and the required bandwidth of each aggregation station 140 calculated in step S1006, the switching control device 160 calculates the congestion amount of each aggregation station 140. The switching control device 160 estimates the presence or absence of bandwidth shortage in each aggregation station 140 using the congestion amount (step S1007). The switching control device 160 estimates that the bandwidth of the aggregation station 140-1 is insufficient.

[0061] The switching control device 160 selects the aggregation station 140-2 estimated not to have insufficient bandwidth as the offloading destination. The switching control device 160 selects a distributed station 130 among some or all of the distributed stations 130 connected to the aggregation station 140-1, and changes the connection destination to the aggregation station 140-2. The selected distributed station 130 is referred to as the switching target distributed station 130. In order to offload the traffic of the switching target distributed station 130, the switching control device 160 transmits a route addition instruction to the aggregation station 140-2 of the offloading destination (switching destination) (step S1008), and notifies the aggregation station 140-1 of the offloading source (switching source) of the route deletion instruction (step S1009). The route addition instruction instructs to use the available bandwidth of the aggregation station 140-2 of the offloading destination to receive the traffic from the switching target distributed station 130. The route deletion instruction instructs to delete the bandwidth for receiving the traffic from the switching target distributed station 130 from the overloaded bandwidth of the aggregation station 140-1 of the offloading source. For the route addition instruction and the route deletion instruction, the BEARER CONTEXT MODIFICATION REQUEST of the bearer change instruction is used. When performing the route addition instruction and the route deletion instruction, the switching control device 160 always keeps the F1 UE context between the antenna station 120 and the distributed station 130 in an established state.

[0062] When the control unit 143 of the aggregation station 140-2 adds the bandwidth for receiving the traffic from the switching target distributed station 130 to the first separation unit 1411 according to the route addition instruction, it transmits a bearer response to the switching target distributed station 130, the switching control device 160, and the aggregation station 140-1 (step S1010, step S1011, step S1012). On the other hand, when the control unit 143 of the aggregation station 140-1 deletes the bandwidth for receiving the traffic from the switching target distributed station 130 from the first separation unit 1411 according to the route deletion instruction, it transmits a bearer response to the switching control device 160 and the aggregation station 140-2 (step S1013, step S1014). The BEARER CONTEXT MODIFICATION RESPONSE is used for the bearer response.

[0063] Upon receiving the bearer response from the aggregation station 140-1, the aggregation station 140-2 transmits an instruction to switch the signal transfer path to the core network 201 (step S1015). The core network 201 switches the signal transfer path according to the switching instruction received from the aggregation station 140-2. The core network 201 performs a switching of the transfer path that changes the transfer source of the upstream signal in which the upstream data from the terminal 11 under the control of the switching target distribution station 130 is set from the aggregation station 140-1 to the aggregation station 140-2. Also, the core network 201 performs a switching of the transfer path that changes the transfer destination of the downstream signal in which the downstream data to the terminal 11 under the control of the switching target distribution station 130 is set to the aggregation station 140-2. The core network 201 transmits a switching completion notification to the aggregation station 140-2 (step S1016).

[0064] Upon receiving the bearer response information from the aggregation station 140-1, the switching control device 160 transmits an instruction to switch the transfer path to the transfer device 150 (step S1017). This switching instruction is an instruction to change the transfer path so that the optical signal input from the first port to which the transmission path to the switching target distribution station 130 is connected is output to the second port to which the transmission path to the aggregation station 140-2 is connected. The transfer device 150 switches the transfer path according to the received switching instruction (step S1018). After the switching, the transfer device 150 outputs the traffic of the upstream signal output from the switching target distribution station 130 to the aggregation station 140-2 (step S1019).

[0065] As described above, in this embodiment, the switching control device 160 transmits a bearer change instruction as a path addition instruction and a bearer change instruction as a path deletion instruction to the concentration station 140 (step S1008, step S1009). The concentration station 140 that has received the bearer change instruction changes the bearer setting according to the instruction. The switching destination concentration station 140 further transmits an optical path switching instruction to the upper device (step S1015). The switching destination concentration station 140 transmits this switching instruction immediately after receiving a bearer response (step S1014) notifying that the bearer setting change from the switching source concentration station 140 has been completed. Thereby, it is possible to shorten the switching time when viewed from End to End. Furthermore, during the process of path switching between the distributed station 130 and the concentration station 140, switching in the upper device may be completed.

[0066] Also, in the above procedure, while the switching source concentration station 140 performs a bearer change procedure according to a path deletion instruction (step S1009), the switching destination concentration station 140 performs a bearer setting procedure according to a path addition instruction (step S1008). Then, bearer response information (step S1014) is transmitted from the switching source concentration station 140 to the switching destination concentration station 140, and bearer response information is transmitted from the switching destination concentration station 140 to the switching source concentration station 140 (step S1012). Thereby, it is possible to exchange bearer data transfer information and perform a faster switch compared to the conventional switch shown in FIG. 39.

[0067] Also, after receiving the bearer responses of the switching destination concentration station 140 and the switching source concentration station 140 respectively, the switching control device 160 transmits a switching instruction to the transfer device 150 (step S1017). Thereby, a problem such as incomplete reception of data transfer information does not occur.

[0068] Also, by transmitting a bearer response from the aggregation station 140 as the switching destination to the distributed station 130 (step S1010), the settings between the distributed station 130 and the aggregation station 140 can be quickly changed. It is assumed that the distributed station 130 has already acquired in advance the connection information (F1 UE context) with the adjacent aggregation station 140 when connecting to the aggregation station 140 as the switching source.

[0069] Subsequently, the processing of the switching control device 160 will be described with reference to FIGS. 7 to 11.

[0070] FIG. 7 is a flowchart showing the bandwidth calculation process of the switching control device 160. The control unit 133 of the distributed station 130 notifies the terminal 11 of the DCI(i) for the next transmission period at time t(i - 1), and further notifies the switching control device 160 of the DCI information in which the DCI(i) is set (i is an integer). The DCI(i) is a DCI indicating the radio resources allocated to the terminal 11 during the transmission period U(i) from time t(i) to time t(i + 1), and the coding rate and modulation method used by the terminal 11.

[0071] The switching control device 160 receives the DCI information in which the DCI(i) is set from the distributed station 130 at time t(i - 1). The traffic volume calculation unit 161 calculates the predicted traffic volume DU(i) of the distributed station 130 during the transmission period U(i) in each distributed station 130 based on the information included in the DCI(i) (step S1101). Further, the traffic volume calculation unit 161 calculates the allocation time interval T(i) from the difference between time t(i) and time t(i + 1) (step S1102). Alternatively, the traffic volume calculation unit 161 may receive the allocation time interval T(i) from the distributed station 130. The traffic volume calculation unit 161 stores the predicted traffic volume DU(i) and the allocation time interval T(i) of each distributed station 130 in the storage unit 167.

[0072] The necessary bandwidth calculation unit 163 receives bearer information from the aggregation station 140 or the resource management device 170 and stores it in the storage unit 167. The necessary bandwidth calculation unit 163 reads the bearer information from the storage unit 167 (step S1103). The traffic volume calculation unit 161 determines whether it is necessary to predict the future traffic volume (step S1104). The future traffic volume is the predicted traffic volume during the transmission period U(i + 1) from time t(i + 1) to time t(i + 2). In the mobile NW system 100, the switching time Tc (for example, 2 msec) is the time required from when the switching control device 160 instructs a route switch until the switch is completed. When the switching time Tc is less than or equal to the allocated time interval T(i) (Tc ≤ T(i)), the route switch can be completed by time t(i). Therefore, the traffic volume calculation unit 161 determines that it is not necessary to predict the future traffic volume (step S1104: NO).

[0073] The necessary bandwidth calculation unit 163 identifies the distributed stations 130 under each aggregation station 140 based on the bearer information (step S1105). The necessary bandwidth calculation unit 163 sums up the predicted traffic volume DU(i) of each distributed station 130 under its jurisdiction for each aggregation station 140 to calculate the necessary bandwidth CU(i) of the aggregation station during the transmission period U(i) (step S1106). The necessary bandwidth calculation unit 163 stores the necessary bandwidth CU(i) of each aggregation station 140 in the storage unit 167 and activates the determination unit 164 (step S1107).

[0074]

[0075] On the other hand, the future traffic volume prediction unit 162 creates a traffic volume prediction model in parallel with the process of step S1104 (step S1108). The traffic volume prediction model is a model that uses the traffic volume of time-series transmission periods as input data and predicts the traffic volume of the next transmission period of those input data. The details of creating the traffic volume prediction model will be described later with reference to FIG. 8.In step S1104, when the switching time Tc is longer than the assigned time interval T(i) (Tc > T(i)), the traffic volume calculation unit 161 determines that it is necessary to predict the future traffic volume (step S1104: YES). This is because it is predicted that the path switching cannot be completed by time t(i). The traffic volume calculation unit 161 instructs the future traffic volume prediction unit 162 to predict the future traffic volume.

[0076] The future traffic volume prediction unit 162 uses the traffic volume prediction model created in step S1108 to predict the future traffic volume DU(i + 1) of each distributed station 130 during the transmission period U(i + 1) from time t(i + 1) to time t(i + 2) (step S1109). The details of the prediction process will be described later with reference to FIG. 9.

[0077] The required bandwidth calculation unit 163 sums up the future traffic volume DU(i + 1) of the subordinate distributed stations 130 for each aggregation station 140 to calculate the required bandwidth CU(i + 1) of the aggregation station during the transmission period U(i + 1). The required bandwidth calculation unit 163 stores the required bandwidth CU(i + 1) of each aggregation station 140 in the storage unit 167 and activates the determination unit 164 (step S1107).

[0078] FIG. 8 is a flowchart showing the traffic volume prediction model creation process of the future traffic volume prediction unit 162. FIG. 8 shows the detailed process in step S1108 of FIG. 7.

[0079] The memory unit 167 stores in advance K time intervals T_1, T_2, …, T_k-1, T_req for the processing target. The time intervals T_1 to T_k-1 are TTIs that can be used when allocating resource blocks to the terminal 11. For example, T_1 to T_k-1 are 125 us, 250 us, 500 us, 1 ms. The allocation time interval T(i) is the same value as any of the time intervals T_1 to T_k-1. The time interval T_req is a value required by an application or the like. The time interval T_req is a value larger than T_1 to T_k-1. The future traffic volume prediction unit 162 may receive the value of the time interval T_req from another device such as the terminal 11 or a device connected to the upper NW and store it in the memory unit 167. The future traffic volume prediction unit 162 selects one unselected time interval from among the time intervals T_1 to T_req and sets it to T_x (step S1201).

[0080] The future traffic volume prediction unit 162 determines whether the allocation time interval T(i) is greater than or equal to the time interval T_x (step S1202). When the future traffic volume prediction unit 162 determines that the allocation time interval T(i) is greater than or equal to the time interval T_x (step S1202: YES), it converts the predicted traffic volume DU(i) of the distributed station 130 into the predicted traffic volume for each time interval T_x (step S1203). That is, the future traffic volume prediction unit 162 calculates that a predicted traffic volume DU_T_x of DU(i) × (time interval T_x / allocation time interval T(i)) will occur for each time interval T_x between time t(i) and time t(i+1).

[0081] For example, assume that the allocation time interval T(i) is 250 us and the time interval T_x is 125 us. The future traffic volume prediction unit 162 predicts that a traffic volume of DU_125us = DU(i) / 2 will occur between time t(i) and time t(i)+125 us and between time t(i)+125 us and time t(i+1). Also, when the time interval T_x is 250 us, the future traffic volume prediction unit 162 predicts that a traffic volume of DU_250us = DU(i) will occur between time t(i) and time t(i+1).

[0082] For each distributed station 130, the future traffic volume prediction unit 162 adds the predicted traffic volume calculated in step S1203 to the time-series predicted traffic volume calculated in the past for the time interval Tx, and stores it in the storage unit 167 (step S1204). The future traffic volume prediction unit 162 learns a traffic volume prediction model for the time interval Tx using the time-series predicted traffic volume of the distributed station 130 for the time interval Tx stored in the storage unit 167 (step S1205).

[0083] For example, let the time-series predicted traffic volume of the distributed station 130 for the time interval Tx be DU_Tx(P), DU_Tx(P - 1), DU_Tx(P - 2), …, DU_Tx(1) in the order of the latest time (P is an integer of 2 or more). For each distributed station 130, the future traffic volume prediction unit 162 generates learning data with DU_Tx(p) as the correct output data and DU_Tx(p - 1) to DU_Tx(p - q) as the input data, while subtracting 1 from the value of p in order from P one by one (q is an integer of 1 or more). The future traffic volume prediction unit 162 learns a traffic volume prediction model representing the correspondence between the input data and the output data using the generated learning data. Note that the future traffic volume prediction unit 162 may learn one traffic volume prediction model using the learning data of all distributed stations 130, or may learn a traffic volume prediction model for the distributed station 130 - m using the learning data of the distributed station 130 - m.

[0084] On the other hand, in step S1202, when the future traffic volume prediction unit 162 determines that the allocated time interval T(i) is smaller than the time interval T_x (step S1202: NO), it performs the process of step S1206. The future traffic volume prediction unit 162 records the predicted traffic volume DU(i) of the distributed station 130-m in a buffer corresponding to the distributed station 130-m and the time interval T_x within the future traffic volume prediction unit 162 or the storage unit 167 (step S1206). The future traffic volume prediction unit 162 determines whether the predicted traffic volume for the time interval T_x is recorded in the buffer corresponding to each distributed station 130 and the time interval T_x (step S1207).

[0085] For example, assume that the allocated time interval T(i) is 250 us and the time interval T_x is 500 us. The future traffic volume prediction unit 162 determines whether the predicted traffic volume for T_x / T(i) = 2 portions is recorded in the buffer corresponding to 500 us. Also, assume that the time interval T_x is 5 ms of T_req. The future traffic volume prediction unit 162 determines whether the predicted traffic volume for T_req / T(i) = 5000 / 250 = 20 portions is recorded in the buffer corresponding to 5 ms. When the future traffic volume prediction unit 162 determines that the predicted traffic volume for the time interval T_x is not recorded in the buffer corresponding to the time interval T_x (step S1207: NO), it performs the process starting from step S1208.

[0086] When the future traffic volume prediction unit 162 determines that the predicted traffic volume for the time interval T_x is recorded in the buffer corresponding to each distributed station 130 (step S1207: YES), it performs the process of step S1204. That is, for each distributed station 130, the future traffic volume prediction unit 162 reads and sums the predicted traffic volume from DU(i - T_x / T(i) + 1) to DU(i) from the buffer corresponding to the time interval T_x, and sets it as DU_T_x(P).

[0087] For example, assume that the allocated time interval T(i) is 250 us and the time interval T_x is 500 us. The future traffic volume prediction unit 162 sums the predicted traffic volume DU(i - 1) and the predicted traffic volume DU(i) to calculate DU_500us(P). Also, assume that the time interval T_x is 5 ms of T_req. The future traffic volume prediction unit 162 sums from the predicted traffic volume DU(i - 19) to the predicted traffic volume DU(i) to calculate DU_5ms(P).

[0088] In the storage unit 167, the time-series predicted traffic volumes DU_T_x(1) to DU_T_x(P - 1) of each distributed station 130 calculated in the past for the time interval T_x are stored. The future traffic volume prediction unit 162 adds the newly calculated predicted traffic volume DU_T_x(P) to these predicted traffic volumes DU_T_x(1) to DU_T_x(P - 1) for each distributed station 130 and stores them in the storage unit 167 (step S1204). The future traffic volume prediction unit 162 performs the process of step S1205 and learns the traffic volume prediction model using the time-series predicted traffic volumes of the time interval T_x.

[0089] After the process of step S1205 or when it is determined as NO in step S1207, the future traffic volume prediction unit 162 determines whether all of the K time intervals T_1 to T_req to be processed have been selected (step S1208). If there are unselected time intervals (step S1208: NO), the future traffic volume prediction unit 162 returns to step S1201 and sets the newly selected time interval to T_x.

[0090] Then, when it is determined that all of the K time intervals to be processed have been selected (step S1208: YES), the future traffic volume prediction unit 162 stores in the storage unit 167 the traffic volume prediction model corresponding to each of the K time intervals T_1 to T_req and the prediction time, which is the time from when the input data is input to the traffic volume prediction model until the output data is output (step S1209).

[0091] Note that the future traffic volume prediction unit 162 may execute the processes of steps S1202 to S1207 for each of the K time intervals T_1 to T_req in parallel.

[0092] FIG. 9 is a flowchart showing the future traffic volume prediction process of the future traffic volume prediction unit 162. FIG. 9 shows the detailed process in step S1109 of FIG. 7. The future traffic volume prediction unit 162 identifies the distributed stations 130 connected to each aggregation station 140 based on the bearer information (step S1301). The future traffic volume prediction unit 162 determines whether it is possible to predict the future traffic volume by the time t(i + 1) when the next transmission period U(i) ends (step S1302). Specifically, the future traffic volume prediction unit 162 determines whether the sum of the allocated time interval T(i) and the switching time Tc is longer than the prediction time of the traffic volume prediction model for the allocated time interval T(i).

[0093] When the future traffic volume prediction unit 162 determines that the allocated time interval T(i)+ the switching time Tc is longer than the prediction time (T(i)+Tc>prediction time), it determines that it is possible to predict the future traffic volume by the end of the next transmission period U(i) (step S1302: YES). For each distributed station 130, the future traffic volume prediction unit 162 inputs the p time-series predicted traffic volumes DU(P) to DU(P - p + 1) from the most recent one of the traffic volume prediction models created for the allocated time interval T(i) into the traffic volume prediction model created for the allocated time interval T(i). The future traffic volume prediction unit 162 calculates the future traffic volume DU(i + 1) of each distributed station 130 in the transmission period U(i + 1) from time t(i + 1) to time t(i + 2) (step S1303). Note that t(i + 2)=t(i + 1)+T(i). The future traffic volume prediction unit 162 writes the calculated future traffic volume DU(i + 1) of each distributed station 130 into the storage unit 167.

[0094] If the predicted time is equal to or greater than the allocated time T(i) plus the switching time Tc (T(i) + Tc ≤ predicted time), the future traffic volume prediction unit 162 determines that it is impossible to predict the future traffic volume until the end of the next transmission period U(i) (step S1302: NO). The future traffic volume prediction unit 162 makes a prediction up to a time interval T_req (for example, 5 ms) ahead that satisfies the service request delay from the time t(i + 1). For each distributed station 130, the future traffic volume prediction unit 162 sums up the predicted traffic volumes in the time series of the allocated time interval T(i) one by one from the latest ones by T_req / T(i), and calculates the predicted traffic volume in the time series of the time interval T_req. For each distributed station 130, the future traffic volume prediction unit 162 inputs the q time series of predicted traffic volumes from the latest one in the time interval T_req into the traffic volume prediction model created for the time interval T_req. Thereby, the future traffic volume prediction unit 162 calculates the future traffic volume DUreq(i + 1) of each distributed station 130 in the transmission period U(i + 1) from the time t(i + 1) to the time t(i + 2) (step S1304). Note that t(i + 2) = t(i + 1) + T_req. The future traffic volume prediction unit 162 writes the calculated future traffic volume DUreq(i + 1) of each distributed station 130 into the storage unit 167.

[0095] For each aggregation station 140, the required bandwidth calculation unit 163 sums up the future traffic volume DU(i + 1) calculated in step S1303 or the future traffic volume DUreq(i + 1) calculated in step S1304 for each subordinate distributed station 130, and calculates the required bandwidth CU(i + 1) of the aggregation station in the transmission period U(i + 1) (step S1305). In step S1107 of FIG. 7, the required bandwidth calculation unit 163 stores the required bandwidth CU(i + 1) of each aggregation station 140 in the storage unit 167.

[0096] Note that if the traffic volume calculation unit 161 cannot calculate the predicted traffic volume of the distributed station 130, it estimates by any one of the following processes (1) to (3).

[0097] (1) The traffic volume calculation unit 161 acquires the DCI transmitted from the distributed station 130 to the aggregation station 140, and calculates the predicted traffic volume by using the acquired DCI instead of the DCI information received from the distributed station 130.

[0098] (2) When the predicted traffic volume of some of the distributed stations 130 under the aggregation station 140 can be calculated, the average of the predicted traffic volumes of the calculated distributed stations 130 is used as the predicted traffic volume of the distributed stations 130 for which the predicted traffic volume could not be calculated.

[0099] (3) The traffic volume calculation unit 161 inputs the predicted traffic calculated in (1) in the past into the traffic volume prediction model to estimate the predicted traffic volume.

[0100] FIG. 10 is a flowchart showing the convergence determination process of the determination unit 164. The determination unit 164 acquires the processable bandwidth of each aggregation station 140 (step S1401). When the determination unit 164 has received in advance the information on the maximum processable bandwidth of the aggregation station 140, it reads out the maximum processable bandwidth from the storage unit 167 and sets it as the processable bandwidth X_resource. When the determination unit 164 has received the aggregation station resource information from the resource management device 170 and stored it in the storage unit 167, it reads out the information on the allocated resources of the aggregation station 140 from the aggregation station resource information. The allocated resources are the number of cores of the aggregation station 140, the occupancy rate of the cores, or the resource blocks in the frequency direction. The greater the number of cores of the CPU, the higher the occupancy rate of the CPU, or the greater the number of resource blocks in the frequency direction, the greater the processable bandwidth. The determination unit 164 calculates the processable bandwidth X_resource of the aggregation station 140 from the read allocated resource amount based on the relationship between the allocated resource amount and the processable bandwidth stored in advance.

[0101] The determination unit 164 reads out the information on the buffer amount X_buffer acquired from the aggregation station 140 and stored in the storage unit 167. Further, the determination unit 164 reads out the required bandwidth CU(i) or CU(i + 1) of the aggregation station 140 stored in the storage unit 167 by the required bandwidth calculation unit 163 in step S1107 of FIG. 7 as the required bandwidth X_traffic. The determination unit 164 calculates the congestion amount X_buf for each aggregation station 140 by the following formula (1) (step S1402).

[0102] X_buf = X_traffic + X_buffer - X_resource …(1)

[0103] The determination unit 164 may calculate the congestion amount X_buf of each aggregation station 140 in parallel or sequentially. The determination unit 164 determines whether the congestion amount X_buf of any one of the aggregation stations 140 exceeds the threshold value TH1 (step S1403).

[0104] For example, when determining that there is no congestion in a state where no data is stored in the buffer, TH1 = 0. Alternatively, the congestion amount that satisfies the allowable delay may be set as TH1. The congestion amount X_tol_buf that satisfies the allowable delay is calculated as in the following formula (2).

[0105] X_tol_buf = X_resource / T1 × T2 …(2)

[0106] T1 is the time from when the switching control device 160 receives the DCI information until the distributed station 130 transmits the actual upstream traffic. The switching time Tc may be used as T1. T2 is the allowable congestion delay obtained by subtracting the transmission delay, processing delay, and switching delay from the allowable delay.

[0107] When the convergence amount X_buf of all the switching control devices 160 is less than or equal to the threshold value TH1, the determination unit 164 determines that no convergence occurs and ends the process (step S1403: NO). That is, the switching control device 160 does not execute path switching. On the other hand, when the convergence amount X_buf of any one of the switching control devices 160 exceeds the threshold value TH1, the determination unit 164 determines that convergence occurs (step S1403: YES). The determination unit 164 instructs the switching decision unit 165 to start the path switching process (step S1404).

[0108] FIG. 11 is a flowchart showing the path switching control process of the switching control device 160. When the switching decision unit 165 is controlled by the determination unit 164 to execute path switching in step S1404 of FIG. 10, the process of FIG. 11 is started.

[0109] The switching decision unit 165 initializes the offloading information stored in the storage unit 167 (step S1501). The switching decision unit 165 generates load information associating the aggregation station 140, the convergence amount of the aggregation station 140, the subordinate distributed stations 130, and the predicted traffic amounts of the subordinate distributed stations 130. The switching decision unit 165 arranges the load information in the order of the convergence amount and writes it into the storage unit 167 (step S1502). The predicted traffic amount is the predicted traffic amount DU(i) used when calculating the aggregation station required bandwidth CU(i) in step S1106, the predicted traffic amount DU(i + 1) calculated in step S1303, or the predicted traffic amount DUreq(i) calculated in step S1304.

[0110] The switching decision unit 165 determines whether there is load information in which a convergence amount exceeding the threshold value TH2 is set (step S1503). The threshold value TH2 may be 0 or a positive value less than or equal to the convergence amount X_tol_buf used as the threshold value TH1 in step S1403 of FIG. 10.

[0111] When the switching determination unit 165 determines that there is a convergence amount exceeding the threshold TH2 (step S1503: YES), it executes the process of step S1504. That is, the switching determination unit 165 refers to the load information and identifies the aggregation station 140-n1 with the largest convergence amount (n1 is any integer from 1 to N) and the aggregation station 140-n2 with the smallest convergence amount (n2 is any integer from 1 to N, n1≠n2). The switching determination unit 165 selects the distribution station 130 with the most predicted traffic among the distribution stations 130 under the aggregation station 140-n1 as the switching target distribution station 130. The switching determination unit 165 changes the switching target distribution station 130 from under the aggregation station 140-n1 to under the aggregation station 140-n2 (step S1504).

[0112] The switching determination unit 165 associates the switching source aggregation station information indicating the aggregation station 140-n1, the switching destination aggregation station information indicating the aggregation station 140-n2, and the switching target distribution station information indicating the switching target distribution station 130 and sets them in the offloading information (step S1505). The switching determination unit 165 repeats the process from step S1502. In step S1502, the switching determination unit 165 deletes the switching target distribution station 130 and the predicted traffic volume of the switching target distribution station 130 from the load information of the aggregation station 140-n1. The switching determination unit 165 updates the convergence degree set in the load information of the aggregation station 140-n1 to a value obtained by subtracting the predicted traffic volume of the switching target distribution station 130. Further, the switching determination unit 165 adds the switching target distribution station 130 and the predicted traffic volume of the switching target distribution station 130 to the load information of the aggregation station 140-n2. The switching determination unit 165 updates the convergence degree set in the load information of the aggregation station 140-n2 to a value obtained by adding the predicted traffic volume of the switching target distribution station 130. The switching determination unit 165 sorts the load information of each aggregation station 140 according to the convergence degree.

[0113] When the switching determination unit 165 determines that there is no convergence amount exceeding the threshold TH2 in any of the load information (step S1503: NO), it ends the generation of the offloading information and instructs the switching instruction unit 166 to start switching (step S1506).

[0114] The switching instruction unit 166 reads out the source aggregation station information, the destination aggregation station information, and the distributed station information to be switched from the offload information. The switching instruction unit 166 sends a route addition instruction for adding the traffic of the distributed station 130 indicated by the distributed station information to be switched to the aggregation station 140 indicated by the destination aggregation station information (step S1507, step S1008 in FIG. 6). Further, the switching instruction unit 166 sends a route deletion instruction for deleting the traffic of the distributed station 130 indicated by the distributed station information to be switched to the aggregation station 140 indicated by the source aggregation station information (step S1508, step S1009 in FIG. 6). The switching instruction unit 166 receives a bearer response to the route addition instruction and a bearer response to the route deletion instruction (step S1509, steps S1011 to S1012 in FIG. 6). The switching instruction unit 166 sends a switching instruction for the transfer path to the transfer device 150 (step S1510, step S1017 in FIG. 6).

[0115] In addition, in the above, the determination unit 164 uses the bandwidth to determine the presence or absence of congestion, but the bit rate of the upstream signal output by the user data transceiver unit 141 of the aggregation station 140 may also be used. The bit rate is calculated by traffic volume / required bandwidth. The required bandwidth calculation unit 163 determines that congestion occurs when the bit rate exceeds 1, and determines that no congestion occurs when the bit rate is 1 or less.

[0116] Also, the switching control device 160 does not have to determine whether the path switching can be completed by the next transmission period. In this case, the switching control device 160 does not have to have the future traffic volume prediction unit 162. The switching control device 160 does not execute the processes of steps S1104, S1108, and S1109 in FIG. 7 and the processes of FIGS. 8 and 9.

[0117] [Second Embodiment] In the second embodiment, the switching control device acquires the required bandwidth from the aggregation station. The second embodiment will be mainly described with differences from the first embodiment.

[0118] The configuration of the mobile NW system according to the second embodiment is the same as that of the mobile NW system 100 according to the first embodiment shown in FIG. 2. However, instead of the switching control device 160 shown in FIG. 5, the mobile NW system 100 includes a switching control device 160a shown in FIG. 12.

[0119] FIG. 12 is a block diagram showing the configuration of the switching control device 160a. The difference between the switching control device 160a shown in FIG. 12 and the switching control device 160 according to the first embodiment shown in FIG. 5 is that it does not have a required bandwidth calculation unit 163. The determination unit 164 receives required bandwidth information indicating the required bandwidth from each aggregation station 140.

[0120] FIG. 13 is a sequence diagram showing the path switching procedure of the mobile NW system 100 according to the present embodiment. The difference between the path switching procedure shown in FIG. 13 and the path switching procedure according to the first embodiment shown in FIG. 6 is that the mobile NW system 100 performs the processes of step S2001 and step S2002 instead of the processes of steps S1004 to S1006. That is, each of the aggregation stations 140-1 and 140-2 transmits required bandwidth information indicating the required bandwidth of its own station to the switching control device 160a in addition to the buffer information (steps S2001, S2002).

[0121] Subsequently, the processing of the switching control device 160a will be described. FIG. 14 is a flowchart showing the bandwidth calculation processing of the switching control device 160a. The switching control device 160a performs the processing shown in FIG. 14 instead of the processing shown in FIG. 7. In FIG. 14, the same parts as the bandwidth calculation processing according to the first embodiment shown in FIG. 7 are denoted by the same reference numerals, and the detailed description thereof is omitted.

[0122] The traffic volume calculation unit 161 of the switching control device 160a performs the same processing as steps S1101 to S1102 in FIG. 7 to obtain the predicted traffic volume DU(i) and the assigned time interval T(i) of each distributed station 130. The traffic volume calculation unit 161 stores the predicted traffic volume DU(i) and the assigned time interval T(i) in the storage unit 167. When the traffic volume calculation unit 161 determines that the prediction of the future traffic volume is unnecessary (step S1104: NO), it activates the congestion determination process of the determination unit 164 (step S2101).

[0123] On the other hand, the future traffic volume prediction unit 162 creates a traffic volume prediction model in parallel with the process of step S1104 (step S1108). When the traffic volume calculation unit 161 determines that the prediction of the future traffic volume is necessary (step S1104: YES), the future traffic volume prediction unit 162 performs the future traffic volume prediction process (step S2102). In step S2102, the future traffic volume prediction unit 162 performs the processes of steps S1301 to S1304 shown in FIG. 9.

[0124] After the process of step S2102, the future traffic volume prediction unit 162 activates the congestion determination process of the determination unit 164 (step S2101). In this case, the predicted traffic volume of each distributed station 130 passed to the determination unit 164 is the future traffic volume DU(i + 1) of each distributed station 130 calculated by the future traffic volume prediction unit 162 in step S1303 of FIG. 9 or the future traffic volume DUreq(i + 1) of each distributed station 130 calculated in step S1304.

[0125] The determination unit 164 of the switching control device 160a performs the same processing as the convergence determination processing of the first embodiment shown in FIG. 10. However, in step S1402, the determination unit 164 reads out the convergence station required bandwidth indicated by the required bandwidth information received from each convergence station 140 and stored in the storage unit 167 as the required bandwidth X_traffic. Since it is determined in step S1104 of FIG. 14 that the prediction of the future traffic volume is unnecessary, when the future traffic volume prediction unit 162 does not perform the processing shown in FIG. 9, the determination unit 164 reads out the convergence station required bandwidth CU(i) in the transmission period U(i). On the other hand, when the future traffic volume prediction unit 162 performs the processing of step S1303 in FIG. 9, the determination unit 164 reads out the convergence station required bandwidth CU(i + 1) in the transmission period U(i + 1) until the allocation time interval T(i) elapses from the time t(i + 1). When the future traffic volume prediction unit 162 performs the processing of step S1304 in FIG. 9, the determination unit 164 reads out the convergence station required bandwidth CU(i + 1) in the transmission period U(i + 1) until the time interval T_req elapses from the time t(i + 1).

[0126] The switching decision unit 165 and the switching instruction unit 166 of the switching control device 160a perform the same processing as the path switching instruction processing of the first embodiment shown in FIG. 11. Note that the predicted traffic volume of the distributed station 130 written by the switching decision unit 165 in the load information in step S1502 is the predicted traffic volume DU(i) when it is determined in step S1104 of FIG. 14 that the prediction of the future traffic volume is unnecessary, and is the future traffic volume DU(i + 1) or the future traffic volume DUreq(i + 1) when it is determined to be necessary.

[0127] Note that the switching control device 160a may include the required bandwidth calculation unit 163 of the first embodiment. When some convergence stations 140 cannot transmit the required bandwidth information, the switching control device 160a calculates the required bandwidth of the convergence station 140 in the same manner as in the first embodiment.

[0128] When the switching control device 160a does not need to determine whether the path switching can be completed by the next transmission period if the process from the estimation of bandwidth shortage to the transfer path switching (steps S1008 to S1018 in FIG. 13) based on the necessary bandwidth information received in steps S2001 and S2002 in FIG. 13 and the predicted traffic volume of the distributed station 130 calculated by the traffic volume calculation unit 161 using the DCI information received in step S1003 in FIG. 13 is completed by the time of traffic transmission. In this case, the switching control device 160a may not have the future traffic volume prediction unit 162. The switching control device 160a does not execute the processes of steps S1104, S1108, and S2102 in FIG. 14.

[0129] When the switching control device cannot calculate a part of the predicted traffic volume of the distributed station 130 connected to the aggregation station 140, in the first embodiment, the required bandwidth of the aggregation station 140 cannot be grasped. Therefore, in this embodiment, the aggregation station 140 notifies the switching control device 160a of the required bandwidth. When performing the process of step S1504 in FIG. 11, the switching determination unit 165 of the switching control device 160a selects a switching target from the distributed stations 130 for which the predicted traffic volume or the future traffic volume has been calculated.

[0130] [Third Embodiment] In this embodiment, the switching control device receives bandwidth information indicating the current uplink signal bandwidth from the distributed station 130 from the aggregation station. The switching control device predicts the required bandwidth of the aggregation station using the time-series bandwidth information. The third embodiment will be mainly described with differences from the first embodiment.

[0131] The configuration of the mobile NW system of the third embodiment is the same as that of the mobile NW system 100 of the first embodiment shown in FIG. 2. However, instead of the switching control device 160 shown in FIG. 5, the mobile NW system 100 includes a switching control device 160b shown in FIG. 15.

[0132] FIG. 15 is a block diagram showing the configuration of the switching control device 160b. The difference between the switching control device 160b shown in FIG. 15 and the switching control device 160 of the first embodiment shown in FIG. 5 is that it has a required bandwidth prediction unit 168 instead of the required bandwidth calculation unit 163. The required bandwidth prediction unit 168 receives bandwidth information from each aggregation station 140. The bandwidth information indicates the current allocation time interval and the bandwidth of the upstream traffic in the current allocation time interval. The allocation time interval is represented by, for example, a slot, but may also be represented by a start time and an end time. The required bandwidth prediction unit 168 predicts the required bandwidth of each aggregation station 140 using the bandwidth information.

[0133] FIG. 16 is a sequence diagram showing the route switching procedure of the mobile NW system 100 of the present embodiment. The difference between the route switching procedure shown in FIG. 16 and the route switching procedure of the first embodiment shown in FIG. 6 is that the mobile NW system 100 performs the processes of steps S3001 to S3003 instead of the processes of steps S1004 to S1006. That is, the control units 143 of the aggregation stations 140-1 and 140-2 transmit the bandwidth information of their own stations to the switching control device 160b in addition to the buffer information for each allocation time interval of the resources to the terminal 11 (steps S3001 and S3002). The bandwidth information indicates the current allocation time interval and the bandwidth of the upstream traffic of its own station in that allocation time interval. The switching control device 160b predicts the required bandwidth of the aggregation station 140-1 based on the bandwidth information received from the aggregation station 140-1, and predicts the required bandwidth of the aggregation station 140-2 based on the bandwidth information received from the aggregation station 140-2 (step S3003).

[0134] Subsequently, the processing of the switching control device 160b will be described. FIG. 17 is a flowchart showing the bandwidth calculation processing of the switching control device 160b. The switching control device 160b performs the processing shown in FIG. 17 instead of the processing shown in FIG. 7. In FIG. 17, the same parts as the bandwidth calculation processing according to the first embodiment shown in FIG. 7 are denoted by the same reference numerals, and their detailed description is omitted.

[0135] The traffic volume calculation unit 161 of the switching control device 160b performs the same processing as steps S1101 to S1102 in FIG. 7 to obtain the predicted traffic volume DU(i) and the allocated time interval T(i) of each distributed station 130. The traffic volume calculation unit 161 stores the predicted traffic volume DU(i) and the allocated time interval T(i) in the storage unit 167.

[0136] When the traffic volume calculation unit 161 determines that the prediction of future traffic volume is unnecessary (step S1104: NO), it instructs the required bandwidth prediction unit 168 to predict the required bandwidth. The required bandwidth prediction unit 168 performs the processing of FIG. 18 described later to predict the required bandwidth at the allocated time interval T(i) of each aggregation station 140 (step S3101). The required bandwidth prediction unit 168 stores the predicted required bandwidth of each aggregation station 140 in the storage unit 167 and activates the determination unit 164 (step S3102).

[0137] On the other hand, the future traffic volume prediction unit 162 creates a traffic volume prediction model in parallel with the processing of step S1104 (step S1108). When the traffic volume calculation unit 161 determines that the prediction of future traffic volume is necessary (step S1104: YES), the future traffic volume prediction unit 162 performs future traffic volume prediction processing (step S2101). In step S2101, the future traffic volume prediction unit 162 performs the processing of steps S1301 to S1304 shown in FIG. 9.

[0138] The required bandwidth prediction unit 168 receives an instruction from the future traffic volume prediction unit 162 and predicts the required bandwidth of each aggregation station 140 during the transmission period U(i + 1) from t(i + 1) until the allocated time interval T(i) elapses, or during the transmission period U(i + 1) from t(i + 1) until the time interval T_req elapses (step S3101). The required bandwidth prediction unit 168 stores the predicted required bandwidth of each aggregation station 140 in the storage unit 167 and activates the determination unit 164 (step S3102).

[0139] FIG. 18 is a flowchart showing the necessary bandwidth prediction process of the necessary bandwidth prediction unit 168. FIG. 18 shows the detailed process of step S3101 in FIG. 17. The necessary bandwidth prediction unit 168 creates time series data indicating the bandwidth of the upstream traffic of each aggregation station 140 over time (step S3201). Details of the creation of the time series data will be described later with reference to FIG. 19. The necessary bandwidth prediction unit 168 creates a necessary bandwidth prediction model using the time series data (step S3202). The creation of the necessary bandwidth prediction model will be described later with reference to FIG. 20. The necessary bandwidth prediction unit 168 predicts the necessary bandwidth of each aggregation station 140 using the necessary bandwidth prediction model generated in step S3202 (step S3203). The necessary bandwidth prediction unit 168 stores the predicted necessary bandwidth of each aggregation station 140 in the storage unit 167 and activates the determination unit 164 (step S3204).

[0140] FIG. 19 is a flowchart showing the time series data creation process of the necessary bandwidth prediction unit 168. FIG. 19 shows the detailed process of step S3201 in FIG. 18. The necessary bandwidth prediction unit 168 performs the process shown in FIG. 19 for each aggregation station 140. The necessary bandwidth prediction unit 168 receives bandwidth information from the aggregation station 140 and writes it into the storage unit 167.

[0141] The necessary bandwidth prediction unit 168 selects one unselected time interval from among the K time intervals T_1, T_2, …, T_k-1, T_req stored in the storage unit 167 and sets it to T_x (step S3301). The necessary bandwidth prediction unit 168 reads the newly received bandwidth information from the storage unit 167. The necessary bandwidth prediction unit 168 reads the allocated time interval T(i-1) and the bandwidth B(i-1) from the read bandwidth information. The bandwidth B(i-1) is the bandwidth of the upstream traffic from time t(i-1) to time t(i). The allocated time interval T(i-1) = time t(i) - time t(i-1). The necessary bandwidth prediction unit 168 determines whether the allocated time interval T(i-1) is less than or equal to the time interval T_x (step S3302).

[0142] When the necessary bandwidth prediction unit 168 determines that the allocated time interval T(i - 1) is less than or equal to the time interval T_x, it converts the bandwidth B(i - 1) into the bandwidth for each time interval T_x (step S3303). That is, the necessary bandwidth prediction unit 168 calculates the bandwidth for each time interval T_x as B(i - 1)×(time interval T_x / allocated time interval T(i - 1)).

[0143] For example, assume that the allocated time interval T(i - 1) is 250 us and the time interval T_x is 125 us. The necessary bandwidth prediction unit 168 calculates that the bandwidth for each of the time periods from time t(i - 1) to time t(i - 1)+125 us and from time t(i - 1)+125 us to time t(i) is B(i - 1) / 2. Also, when the time interval T_x is 250 us, the necessary bandwidth prediction unit 168 sets the bandwidth for the time period from time t(i - 1) to time t(i) as B(i - 1).

[0144] The necessary bandwidth prediction unit 168 adds the bandwidth calculated in step S3303 to the time-series bandwidths acquired in the past for the time interval T_x and stores them in the storage unit 167 (step S3304).

[0145] On the other hand, in step S3302, when the necessary bandwidth prediction unit 168 determines that the allocated time interval T(i - 1) is less than the time interval T_x, it records the bandwidth B(i - 1) in a buffer within the necessary bandwidth prediction unit 168 or the storage unit 167 (step S3305). The necessary bandwidth prediction unit 168 determines whether the bandwidth for the time interval T_x has been recorded in the buffer corresponding to the time interval T_x (step S3306).

[0146] For example, assume that the measurement time T(i - 1) is 250 us and the time interval T_x is 500 us. The necessary bandwidth prediction unit 168 determines whether the measurement bandwidth corresponding to T_x / T(i - 1) = 2 is recorded in the buffer corresponding to 250 us. Also, assume that the time interval T_x is 5 ms of T_req. The necessary bandwidth prediction unit 168 determines whether the measurement bandwidth corresponding to T_req / T(i - 1) = 5000 / 250 = 20 is recorded in the buffer corresponding to 5 ms. If the necessary bandwidth prediction unit 168 determines that the bandwidth for the time interval T_x is not recorded in the buffer corresponding to the time interval T_x (step S3306: NO), it performs the process of step S3307.

[0147] If the necessary bandwidth prediction unit 168 determines that the predicted traffic volume for the time interval T_x is recorded in the buffer corresponding to T_x (step S3306: YES), it performs the process of step S3304. That is, the necessary bandwidth prediction unit 168 reads and sums (T_x / T(i - 1)) bands from the buffer corresponding to T_x. The necessary bandwidth prediction unit 168 adds the calculated total bandwidth to the time-series bandwidth acquired in the past for the time interval T_x and stores it in the storage unit 167.

[0148] After the process of step S3304 or when it determines NO in step S3306, the necessary bandwidth prediction unit 168 determines whether all K time intervals to be processed have been selected (step S3307). If there are unselected time intervals (step S3307: NO), it returns to step S3301 and sets the newly selected time interval as T_x. And when the necessary bandwidth prediction unit 168 determines that all K time intervals to be processed have been selected (step S3307: YES), it ends the process of FIG. 19.

[0149] Note that the necessary bandwidth prediction unit 168 may execute the processes of steps S3302 to S3306 for each of the K time intervals T_1 to T_req in parallel.

[0150] FIG. 20 is a flowchart showing the necessary bandwidth prediction model creation process of the necessary bandwidth prediction unit 168. FIG. 20 shows the detailed process of step S3202 in FIG. 18.

[0151] The necessary bandwidth prediction unit 168 selects one unselected time interval from among the K time intervals T_1, T_2, …, T_k-1, T_req stored in the storage unit 167 and sets it to T_x (step S3401). The necessary bandwidth prediction unit 168 preferentially selects a time interval that matches the assigned time interval T(i) and T_req.

[0152] The necessary bandwidth prediction unit 168 learns a necessary bandwidth prediction model using the time-series bandwidth of T_x stored in the storage unit 167 (step S3402). For example, let the time-series bandwidth of the time interval T_x be B_T_x(P), B_T_x(P-1), B_T_x(P-2), …, B_T_x(1) in the order of the latest time (P is an integer of 2 or more). The necessary bandwidth prediction unit 168 generates learning data with B_T_x(p) as the correct output data and B_T_x(p-1) to B_T_x(p-q) as the input data while sequentially subtracting 1 from the value of p from P (q is an integer of 1 or more). The necessary bandwidth prediction unit 168 learns a necessary bandwidth prediction model representing the correspondence between the input data and the output data using these learning data. Note that the necessary bandwidth prediction unit 168 may learn one necessary bandwidth prediction model using the learning data of all the aggregation stations 140, or may learn the necessary bandwidth prediction model of the aggregation station 140-n using the learning data of the aggregation station 140-n.

[0153] The necessary bandwidth prediction unit 168 determines whether all of the K time intervals to be processed have been selected (step S3403). If there is an unselected time interval (step S3403: NO), the necessary bandwidth prediction unit 168 returns to step S3401 and sets the newly selected time interval to T_x. When the necessary bandwidth prediction unit 168 determines that all of the K time intervals to be processed have been selected (step S3403: YES), it stores in the storage unit 167 the necessary bandwidth prediction model corresponding to each of the K time intervals and the prediction time, which is the time from when the input data is input to the necessary bandwidth prediction model until the output data is output (step S3404).

[0154] FIG. 21 is a flowchart showing the necessary bandwidth prediction process of the necessary bandwidth prediction unit 168. FIG. 20 shows the detailed process of step S3203 in FIG. 18. The necessary bandwidth prediction unit 168 predicts the necessary bandwidth of each distributed station 130 in the transmission period U(i) from time t(i) to time t(i + 1) using the necessary bandwidth prediction model created in the necessary bandwidth prediction model creation process of FIG. 20 (step S3501). Specifically, for each aggregation station 140, the necessary bandwidth prediction unit 168 inputs p time series of bands B_T_x(P) to B_T_x(P - p + 1) from the latest one of the allocated time intervals T(i) into the necessary bandwidth prediction model created for the allocated time interval T(i). B_T_x(P) is the bandwidth of the aggregation station 140 in the transmission period U(i - 1) from time t(i) - T(i) to time t(i). Thereby, the necessary bandwidth prediction unit 168 calculates the necessary bandwidth B_T_x(P + 1) of the aggregation station 140 in the next transmission period U(i) from time t(i) to time t(i + 1).

[0155] The necessary bandwidth prediction unit 168 determines whether it is necessary to predict the future necessary bandwidth (step S3502). The future necessary bandwidth is the necessary bandwidth after time t(i + 1). If the switching time Tc (for example, 2 msec) is less than or equal to the allocated time interval T(i) (Tc < T(i)), the necessary bandwidth prediction unit 168 determines that it is not necessary to predict the future necessary bandwidth and ends the process of FIG. 21 (step S3502: NO).

[0156] When the switching time Tc is longer than the allocated time interval T(i) (Tc > T(i)), the required bandwidth prediction unit 168 determines that prediction of the future required bandwidth is necessary (step S3502: YES). The required bandwidth prediction unit 168 determines whether it is possible to predict the future required bandwidth by the time t(i + 1) when the next transmission period U(i) ends (step S3503). Specifically, the required bandwidth prediction unit 168 determines whether the sum of the allocated time interval T(i) and the switching time Tc is longer than the prediction time of the required bandwidth prediction model for the allocated time interval T(i).

[0157] When the allocated time interval T(i) + the switching time Tc is longer than the prediction time (T(i) + Tc > prediction time), the required bandwidth prediction unit 168 determines that it is possible to predict the required bandwidth by the end of the next transmission period U(i) (step S3503: YES). For each aggregation station 140, the required bandwidth prediction unit 168 inputs p time series of bandwidths B_T_x(P + 1) to B_T_x(P - p + 2) into the required bandwidth prediction model created for the allocated time interval T(i). Thereby, the required bandwidth prediction unit 168 calculates the future required bandwidth of the aggregation station 140 in the transmission period U(i + 1) from the time t(i + 1) to the time t(i + 2) (step S3504). Note that B_T_x(P + 1) is the bandwidth of the aggregation station 140 calculated in step S3501. The required bandwidth prediction unit 168 stores the future required bandwidth calculated in step S3504 in the storage unit 167 as the predicted required bandwidth of the aggregation station 140 in step S3102 of FIG. 17.

[0158] When the prediction time is equal to or longer than the allocated time T(i) + the switching time Tc (T(i) + Tc ≤ prediction time), the necessary bandwidth prediction unit 168 determines that it is impossible to predict the necessary bandwidth until the end of the next transmission period U(i) (step S3503: NO). The necessary bandwidth prediction unit 168 performs prediction from the time t(i + 1) to a time interval T_req (for example, 5 ms) ahead that satisfies the service request delay. The necessary bandwidth prediction unit 168 sums up, for each aggregation station 140, the time-series bandwidths B_T_x(P + 1), B_T_x(P), B_T_x(P - 1),... of the allocated time interval T(i) in order from the newest, T_req / T(i) at a time, to calculate the time-series bandwidth of the time interval T_req. The necessary bandwidth prediction unit 168 inputs q time-series bandwidths from the newest one of the time interval T_req to the necessary bandwidth prediction model created for the time interval T_req. Thereby, the necessary bandwidth prediction unit 168 calculates the future necessary bandwidth of each aggregation station 140 in the transmission period U(i + 1) from the time t(i + 1) to the time t(i + 2) (step S3505). Note that t(i + 2) = t(i + 1) + T_req. The necessary bandwidth prediction unit 168 stores the future necessary bandwidth calculated in step S3505 in the storage unit 167 as the predicted necessary bandwidth of the aggregation station 140 in step S3102 of FIG. 17.

[0159] [Fourth Embodiment] The mobile NW system 100 of the fourth embodiment transmits the information transmitted from the distributed station 130 to the switching control device 160 and the information transmitted from the aggregation station 140 to the switching control device 160 in the above-described embodiments to the switching control device 160 via the transfer device 150. The fourth embodiment will be described centering on the differences from the above-described first to third embodiments. The configuration of the mobile NW system of the fourth embodiment is the same as that of the mobile NW system 100 of the first embodiment shown in FIG. 2.

[0160] FIG. 22 is a sequence diagram showing the route switching procedure of the mobile NW system 100 according to the fourth embodiment. The difference between the route switching procedure shown in FIG. 21 and the route switching procedure of the first embodiment shown in FIG. 6 is that the mobile NW system 100 performs the processes of steps S4001 to S4010 instead of the processes of steps S1001 to S1005.

[0161] That is, the control unit 143 of the aggregation station 140-1 transmits an optical signal with bearer information and maximum processable bandwidth information set thereto to the transfer device 150 (step S4001). The transfer device 150 receives the optical signal with bearer information and maximum processable bandwidth information set thereto from the aggregation station 140-1, and outputs the received optical signal to the switching control device 160 (step S4002). Similarly, the control unit 143 of the aggregation station 140-2 transmits an optical signal with bearer information and maximum processable bandwidth information set thereto to the transfer device 150 (step S4003). The transfer device 150 receives the optical signal with bearer information and maximum processable bandwidth information set thereto from the aggregation station 140-2, and transmits the received optical signal to the switching control device 160 (step S4004).

[0162] Each distributed station 130 transmits an optical signal with DCI information set thereto to the transfer device 150 (step S4005). The transfer device 150 receives the optical signal with DCI information set thereto from the distributed station 130, and transmits the received optical signal to the switching control device 160 (step S4006). The control unit 143 of the aggregation station 140-1 transmits an optical signal with buffer information set thereto to the transfer device 150 (step S4007). The transfer device 150 receives the optical signal with buffer information set thereto from the aggregation station 140-1, and transmits the received optical signal to the switching control device 160 (step S4008). Similarly, the control unit 143 of the aggregation station 140-2 transmits an optical signal with buffer information set thereto to the transfer device 150 (step S4009). The transfer device 150 receives the optical signal with buffer information set thereto from the aggregation station 140-2, and transmits the received optical signal to the switching control device 160 (step S4010).

[0163] 23 is a sequence diagram showing a path switching procedure when the mobile NW system 100 includes a switching control device 160a of the required bandwidth embodiment. The mobile NW system 100 performs the following process instead of the processes of steps S4007 to S1006 shown in FIG. 22. That is, the aggregation station 140-1 transmits an optical signal in which buffer information and required bandwidth information are set to the transfer device 150 (step S4011). The transfer device 150 receives an optical signal in which buffer information and required bandwidth information are set from the aggregation station 140-1 and transmits the received optical signal to the switching control device 160a (step S4012). Similarly, the aggregation station 140-2 transmits an optical signal in which buffer information and required bandwidth information are set to the transfer device 150 (step S4013). The transfer device 150 receives an optical signal in which buffer information and required bandwidth information are set from the aggregation station 140-2 and transmits the received optical signal to the switching control device 160a (step S4014).

[0164] FIG. 24 is a sequence diagram showing a path switching procedure when the mobile NW system 100 includes the switching control device 160b of the third embodiment. The mobile NW system 100 performs the following process instead of the processes of steps S4007 to S1006 shown in FIG. 22. That is, the aggregation station 140-1 transmits an optical signal in which buffer information and bandwidth information are set to the transfer device 150 (step S4021). The transfer device 150 receives an optical signal in which buffer information and bandwidth information are set from the aggregation station 140-1 and transmits the received optical signal to the switching control device 160b (step S4022). Similarly, the aggregation station 140-2 transmits an optical signal in which buffer information and bandwidth information are set to the transfer device 150 (step S4023). The transfer device 150 receives an optical signal in which buffer information and bandwidth information are set from the aggregation station 140-2 and transmits the received optical signal to the switching control device 160b (step S4024). The switching control device 160b performs the process of step S3003 in FIG.

[0165] [Fifth embodiment] In the fifth embodiment, the radio control information acquisition device acquires the information transmitted from each of the distributed station and the aggregation station to the switching control device in the above-described embodiments. This embodiment will be described centering on the differences from the above-described embodiments.

[0166] FIG. 25 is a diagram showing a configuration example of the mobile NW system 101 of this embodiment. The mobile NW system 101 shown in FIG. 25 is different from the mobile NW system 100 of the first embodiment shown in FIG. 2 in that it includes a radio control information acquisition device 181 and a switching control device 182 instead of the switching control device 160.

[0167] The mobile NW system 101 operates in the same manner as the mobile NW system 100 of the first embodiment shown in FIG. 6, except that it performs the following processing instead of the processing of steps S1001 to S1005. That is, each distributed station 130 transmits DCI information to the radio control information acquisition device 181. Also, each aggregation station 140 transmits bearer information, maximum processable bandwidth information, and buffer information to the radio control information acquisition device 181. Further, the resource management device 170 transmits aggregation station resource information to the radio control information acquisition device 181. The radio control information acquisition device 181 aggregates the DCI information received from each distributed station 130, the bearer information, maximum processable bandwidth information, and buffer information received from each aggregation station 140, and the aggregation station resource information received from the resource management device 170, and notifies the switching control device 182. The switching control device 182 performs the same processing as the switching control device 160 of the first embodiment using the information received from the radio control information acquisition device 181.

[0168] Alternatively, the mobile NW system 101 operates in the same manner as the mobile NW system 100 of the second embodiment shown in FIG. 13, except that it performs the following processing instead of the processing from step S1001 to step S2002. That is, each distributed station 130 transmits DCI information to the radio control information acquisition device 181. Also, each aggregation station 140 transmits bearer information, maximum processable bandwidth information, buffer information, and required bandwidth information to the radio control information acquisition device 181. Further, the resource management device 170 transmits aggregation station resource information to the radio control information acquisition device 181. The radio control information acquisition device 181 aggregates the DCI information received from each distributed station 130, the bearer information, maximum processable bandwidth information, buffer information, and required bandwidth information received from each aggregation station 140, and the aggregation station resource information received from the resource management device 170, and notifies the switching control device 182. The switching control device 182 performs the same processing as the switching control device 160a of the second embodiment using the information received from the radio control information acquisition device 181.

[0169] Alternatively, the mobile NW system 101 operates in the same manner as the mobile NW system 100 of the third embodiment shown in FIG. 16, except that it performs the following processing instead of the processing from step S1001 to step S2002. That is, each distributed station 130 transmits DCI information to the radio control information acquisition device 181. Also, each aggregation station 140 transmits bearer information, maximum processable bandwidth information, buffer information, and bandwidth information to the radio control information acquisition device 181. Further, the resource management device 170 transmits aggregation station resource information to the radio control information acquisition device 181. The radio control information acquisition device 181 aggregates the DCI information received from each distributed station 130, the bearer information, maximum processable bandwidth information, buffer information, and bandwidth information received from each aggregation station 140, and the aggregation station resource information received from the resource management device 170, and notifies the switching control device 182. The switching control device 182 performs the same processing as the switching control device 160b of the third embodiment using the information received from the radio control information acquisition device 181.

[0170] [Sixth Embodiment] In the sixth embodiment, the integrated control device controls a plurality of switching control devices. This embodiment will be described centering on the differences from the above-described embodiments.

[0171] FIG. 26 is a diagram showing a configuration example of the mobile NW system 102 of this embodiment. The difference between the mobile NW system 102 shown in FIG. 26 and the mobile NW system 100 of the first embodiment shown in FIG. 2 is that instead of the switching control device 160, an integrated control device 191 and a switching control device 192 are provided. The integrated control device 191 is connected to one or more switching control devices 192. The integrated control device 191 has the same functions as the above-described switching control devices 160, 160a, or 160b, except for the function of the switching instruction unit 166.

[0172] The distributed station 130, the aggregation station 140, and the resource management device 170 notify the integrated control device 191 of various information that was notified to the switching control devices 160, 160a, or 160b in the above-described embodiments. The integrated control device 191 performs the same processing as the above-described switching control devices 160, 160a, or 160b for each switching control device 192, except for the processing executed by the switching instruction unit 166. The integrated control device 191 notifies the switching control device 192 of the offloading information generated in the same manner as the switching determination unit 165. The switching control device 192 performs the same processing as the switching instruction unit 166 using the offloading information received from the integrated control device 191.

[0173] [Seventh Embodiment] In the above-described embodiments, a transfer device and a switching control device are provided in the midhole (MH) of the mobile NW system. In the seventh embodiment, a transfer device and a switching control device are provided in the front hole (FH) of the mobile NW system.

[0174] FIG. 27 is a diagram showing the configuration of a mobile NW system 300 according to the seventh embodiment. The mobile NW system 300 includes a terminal 11, an antenna station 310, a base station 320, a transfer device 330, a switching control device 340, and a resource management device 350. The antenna station 310, the base station 320, the transfer device 330, and the switching control device 340 constitute a mobile NW. The base station 320 includes a distributed station 323 and an aggregation station 325 shown in FIG. 30 described later. The base station 320 is connected to a core network 201 and the Internet 202 via a transfer device 200. Hereinafter, J antenna stations 310 are respectively described as antenna stations 310-1 to 310-J, and M base stations 320 (M is an integer of 2 or more) are respectively described as base stations 320-1 to 320-M. FIG. 27 shows an example where J = 4 and M = 2. In the present embodiment, the bearer signal between the antenna station 310 and the base station 320, and the signal between the base station 320 and the transfer device 200 are optical signals. The transfer device 330 is an optical GW. The first port (not shown) of the transfer device 330 is connected to a transmission path with the antenna station 310, and the second port (not shown) is connected to a transmission path with the distributed station 323.

[0175] When the mobile NW system 300 switches between the antenna station 310 and the distributed station 323 in response to bandwidth congestion or processing overload of the distributed station 323, scheduling is performed above the switching control device 340. Therefore, it is conceivable that the antenna station 310 transmits data to both the target distributed station 323 after switching and the source distributed station 323 before switching. At this time, the antenna station 310 transmits a PUSCH (Physical Uplink Shared Channel) with uplink data set to the source distributed station 323 before switching, and transmits a line quality signal used to determine the next scheduling and information on the required amount of the terminal (MAC layer C-Plane) to the target distributed station 323 after switching.

[0176] FIG. 28 is a diagram showing a part of a slot of a radio signal between the antenna station 310 and the terminal 11. In 5G, there is a procedure in which the terminal transmits a scheduling request (SR), and the distributed station returns DCI to allocate uplink radio resources to the terminal. In another 5G procedure, a physical channel for transmitting uplink data in advance, PUSCH, is allocated to the terminal. When uplink data is generated, the terminal transmits the uplink data by PUSCH without transmitting a scheduling request. In the downlink control channel (PDCCH) transmitted before PUSCH, the allocation of the frequency resource and time resource of PUSCH is set.

[0177] In this embodiment, instead of the DCI of the above-described embodiment, a BSR (Buffer Status Report) and a CQI (Channel Quality Indicator) are used, instead of the bearer information of the above-described embodiment, F1 UE context information is used, instead of the bandwidth of the aggregation station 140, DCI is used, instead of the distributed station 130, the antenna station 310 is used, and instead of the aggregation station 14, the distributed station 323 is used, and it operates in the same manner as the above-described embodiment except for this. The BSR indicates the amount of uplink data buffer in the terminal 11. The CQI indicates the reception quality measured by the terminal 11.

[0178] The configuration of the distributed station 323 is the same as the configuration of the distributed station 130 shown in FIG. 3. However, the first separation unit 1411 is connected to the transmission path between the transfer device 330, and the second separation unit 1416 is connected to the transmission path between the aggregation station 325.

[0179] FIG. 29 is a block diagram showing the configuration of the switching control device 340. The switching control device 340 includes a traffic volume calculation unit 341, a future traffic volume prediction unit 342, a required bandwidth calculation unit 343, a determination unit 344, a switching determination unit 345, a switching instruction unit 346, and a storage unit 347.

[0180] The traffic volume calculation unit 341 calculates the predicted traffic volume for the next transmission period of each terminal 11 using the BSR and CQI acquired from each antenna station 310. The traffic volume calculation unit 341 calculates the predicted traffic volume for the next transmission period by summing up the predicted traffic volumes of the subordinate terminals 11 for each antenna station 310. The future traffic volume prediction unit 342 predicts the future traffic volume of the antenna station 310.

[0181] The required bandwidth calculation unit 343 receives F1 UE context information from the distributed station 323. The F1 UE context information includes information on the subordinate antenna stations 310 connected to the distributed station 323. The required bandwidth calculation unit 343 calculates the required bandwidth for each distributed station 323 using the predicted traffic volume of each antenna station 310 and connection information such as F1 UE context information. When it is expected that the path switching in the mobile NW system 300 will be completed by the next transmission period, the predicted traffic volume used for the calculation of the required bandwidth is the predicted traffic volume for the next transmission period calculated by the traffic volume calculation unit 341. When it is expected that the path switching will not be completed by the next transmission period, the predicted traffic volume used for the calculation of the required bandwidth is the future traffic volume calculated by the future traffic volume prediction unit 342.

[0182] The determination unit 344 sums up the predicted traffic volumes of the antenna stations 310 subordinate to the distributed station 323 to calculate the required bandwidth for each distributed station 323. The determination unit 344 may calculate the required bandwidth for the distributed station 323 based on the DCI received from the distributed station 323. Further, the determination unit 344 acquires information on the processable bandwidth of the distributed station 323 based on the allocated resources of each distributed station 323 indicated by the distributed station resource information received from the resource management device 350. The determination unit 344 calculates the congestion amount for each distributed station 323 using the required bandwidth and the processable bandwidth of the distributed station 323 calculated by the required bandwidth calculation unit 343. The congestion amount is calculated by subtracting the processable bandwidth from the required bandwidth of the distributed station 323. The determination unit 344 determines that congestion is predicted when the congestion amount exceeds a predetermined condition.

[0183] When the judgment unit 344 predicts congestion, the switching decision unit 345 determines the antenna station 310 to switch the connection destination to and the remote station 323 to switch to, based on the required bandwidth and congestion level of each remote station 323 and the predicted traffic level of each antenna station 310, so that the congestion levels in all remote stations 323 are below a predetermined level. The switching instruction unit 346 instructs each device to switch the transfer path so that the uplink signal from the antenna station 310 to be switched is transferred to the remote station 323 to switch to. The storage unit 347 stores data used for processing by each unit.

[0184] 30 is a sequence diagram showing a route switching procedure of the mobile NW system 300. In the diagram, the two remote stations 323 are described as remote stations 323-1 and 323-2. The optical signal from the antenna station 310 to the remote station 323-1 uses a wavelength λ1.

[0185] The resource management device 350 transmits remote station resource information to the switching control device 340 (step S5001). The remote station resource information indicates resources allocated to the remote station 323-1 and the remote station 323-2. Whenever the resources allocated to the remote station 323 change, the resource management device 350 transmits the remote station resource information to the switching control device 340. The switching control device 340 calculates the maximum processable bandwidth for each remote station 323 from the resources allocated to the remote station 323-2.

[0186] Each antenna station 310 transmits the BSR and CQI received from the terminal 11 to the switching control device 340 (step S5002). The remote stations 323-1 and 323-2 each notify the switching control device 340 of F1 UE context information indicating the antenna station 310 to which they are connected and the DCI transmitted to the terminal 11 under their control (steps S5003 and S5004). The transmission frequency of the BSR and CQI and the transmission frequency of the DCI correspond to the TTI.

[0187] The switching control device 340 calculates the predicted traffic volume at each antenna station 310 based on the received BSR and CQI. The switching control device 340 calculates the required bandwidth for each distributed station 323 by summing up the predicted traffic volumes of the antenna stations 310 connected to the distributed station 323 for each distributed station 323 (step S5005). Alternatively, the switching control device 340 calculates the required bandwidth for each distributed station 323 based on the DCI.

[0188] The switching control device 340 calculates the available bandwidth for each distributed station 323 based on the distributed station resource information. The switching control device 340 calculates the congestion level of each distributed station 323 based on the available bandwidth of each distributed station 323 and the required bandwidth of each distributed station 323 calculated in step S5005. The switching control device 340 estimates the bandwidth shortage of the distributed station 323-1 using the calculated congestion level (step S5006).

[0189] The switching control device 340 selects the distributed station 323-2, which is estimated not to have a bandwidth shortage, as the offloading destination. The switching control device 340 selects the antenna station 310 whose connection destination is to be changed to the distributed station 323-2 from among some or all of the antenna stations 310 connected to the distributed station 323-1. The selected antenna station 310 is referred to as the antenna station 310 to be switched. The switching control device 340 transmits a link-up request to the offloading destination distributed station 323-2 (step S5007). The link-up request requests the establishment of a link for the offloading destination distributed station 323-2 to receive traffic using the optical signal of wavelength λ2 from the antenna station 310 to be switched. An RRCreconfig addition indication is used for this link-up request.

[0190] When the offload destination distributed station 323-2 receives a link-up request and establishes a link to receive traffic using the optical signal of wavelength λ2 from the antenna station 310 to be switched, it transmits a link-up permission of wavelength λ2 to the antenna station 310 to be switched, the switching control device 340, and the distributed station 323-1 (step S5008, step S5009, step S5010). The link-up permission is an RRCreconfig addition completion notification.

[0191] On the other hand, when the distributed station 323-2 receives the link-up request in step S5007, it transmits a route addition instruction to the aggregation station 325 which is the connection destination of the distributed station 323-2 (step S5011). The aggregation station 325 establishes a link with the distributed station 323-2 according to the route addition instruction, and further adds a route to the core network 201. The aggregation station 325 returns the completion of the route addition to the distributed station 323-2 (step S5012).

[0192] Based on the RRCreconfig information set in the link-up permission received from the distributed station 323-2, the switching control device 340 transmits a route addition instruction to the transfer device 330 (step S5013). This route addition instruction is an instruction to add a route for outputting the optical signal of wavelength λ2 input from the first port to which the transmission path between the antenna station 310 to be switched is connected, to the second port to which the transmission path between the distributed station 323-2 is connected. The transfer device 330 adds a transfer route according to the received route addition instruction (step S5014).

[0193] The antenna station 310 to be switched transmits data traffic using the optical signal of wavelength λ1 and a control signal using the optical signal of wavelength λ2 (step S5015, step S5016). The data traffic is a U-Plane signal, and the control signal is a C-Plane signal. The transfer device 330 transfers the data traffic to the distributed station 323-1 and transfers the control signal to the distributed station 323-2.

[0194] The switching control device 340 transmits a route deletion request to the distributed station 323-1 (step S5017). This route deletion request requests the deletion of the route between the distributed station 323-1 and the antenna station 310 to be switched. The distributed station 323-1 deletes the route to the antenna station 310 to be switched according to the received route deletion request. The distributed station 323-1 transmits the completion of route deletion to the antenna station 310 and the switching control device 340 (step S5018, step S5019).

[0195] Furthermore, upon receiving the route deletion request transmitted by the switching control device 340 in step S5017, the distributed station 323-1 transmits a route deletion instruction from the antenna station 310 to be switched to the aggregation station 325 (step S5020). The aggregation station 325 to which the distributed station 323-1 is connected deletes the route to the distributed station 323-1 according to the route deletion instruction. The aggregation station 325 returns the completion of route deletion to the distributed station 323-1 (step S5021).

[0196] On the other hand, upon receiving the completion of route deletion from the distributed station 323-1, the switching control device 340 transmits a route deletion instruction to the transfer device 330 (step S5022). This route deletion instruction is an instruction to delete the route that outputs the optical signal input from the first port to which the transmission path to the antenna station 310 to be switched is connected to the second port to which the transmission path to the distributed station 323-1 is connected. The transfer device 330 deletes the route to the distributed station 323-1 according to the received route deletion instruction (step S5023).

[0197] The antenna station 310 to be switched transmits data traffic and control signals using the optical signal of wavelength λ2 (step S5024, step S5025). The transfer device 330 transfers the data traffic and control signals to the distributed station 323-2. In the above, the case where the data traffic and control signals use optical signals of the same wavelength has been described, but different wavelengths may be used.

[0198] Subsequently, the processing of the switching control device 340 will be described with reference to FIGS. 31 to 35.

[0199] 31 is a flow diagram showing the bandwidth calculation process of the switching control device 340. Each antenna station 310 transmits the BSR and CQI received from the terminal 11 to the switching control device 340. The traffic volume calculation unit 341 calculates the predicted traffic volume RU(i) of each antenna station 310 for the next transmission period U(i) from time t(i) to t(i+1) based on the received BSR and CQI (step S5101). Furthermore, the traffic volume calculation unit 341 calculates the allocation time interval T(i) from the difference between time t(i) and time t(i+1) (step S5102). The traffic volume calculation unit 341 stores the predicted traffic volume RU(i) and the allocation time interval T(i) of each antenna station 310 in the storage unit 347.

[0200] The required bandwidth calculation unit 343 receives F1 UE context information from the remote station 323 and stores it in the storage unit 347. The required bandwidth calculation unit 343 reads the F1 UE context information from the storage unit 347 (step S5103). The traffic volume calculation unit 341 determines whether or not it is necessary to predict future traffic volume (step S5104). The time required from when the switching control device 340 instructs route switching in the mobile NW system 300 to when the switching is completed is defined as the switching time Td. The switching time Td is the process from step S5007 to step S5023 in FIG. 30. If the switching time Td is equal to or less than the allocated time interval T(i) (Td≦T(i)), the traffic volume calculation unit 341 determines that it is unnecessary to predict future traffic volume (step S5104: NO).

[0201] The required bandwidth calculation unit 343 identifies the antenna stations 310 connected to each remote station 323 from the F1 UE context information (step S5105). The required bandwidth calculation unit 343 adds up the predicted traffic volumes RU(i) of the antenna stations 310 subordinate to each remote station 323 to calculate the remote station required bandwidth DUr(i) for the transmission period U(i) (step S5106). The required bandwidth calculation unit 343 stores the remote station required bandwidth DUr(i) of each remote station 323 in the storage unit 347 and activates the determination unit 344 (step S5107).

[0202] On the other hand, the future traffic volume prediction unit 342 creates a traffic volume prediction model in parallel with the process of step S5104 (step S5108). Details of the creation of the traffic volume prediction model will be described later with reference to FIG. 32.

[0203] In step S5104, when the switching time Td is longer than the assigned time interval T(i) (Td > T(i)), the traffic volume calculation unit 341 determines that prediction of the future traffic volume is necessary (step S5104: YES). The traffic volume calculation unit 341 instructs the future traffic volume prediction unit 342 to predict the future traffic volume.

[0204] The future traffic volume prediction unit 342 predicts the future traffic volume RU(i + 1) of each antenna station 310 in the transmission period U(i + 1) from time t(i + 1) to time t(i + 2) using the traffic volume prediction model created in step S5108 (step S5109). Details of the prediction process will be described later with reference to FIG. 33.

[0205] The required bandwidth calculation unit 343 sums up the future traffic volumes RU(i + 1) of the subordinate antenna stations 310 for each distributed station 323 to calculate the required bandwidth DUr(i + 1) of the distributed station in the transmission period U(i + 1). The required bandwidth calculation unit 343 stores the required bandwidth DUr(i + 1) of each distributed station 323 in the storage unit 347 and activates the determination unit 344 (step S5107).

[0206] Note that the required bandwidth calculation unit 343 may calculate the required bandwidth DUr(i) of the distributed station using the DCI received from the distributed station 323 instead of the processes of steps S5105 to S5106. In this case, the switching control device 340 does not execute the processes of steps S5104, S5018, and S5108 in FIG. 31 and the processes of FIGS. 32 and 33 described later.

[0207] Fig. 32 is a flow diagram showing the traffic volume prediction model creation process of the future traffic volume prediction unit 342. Fig. 32 shows detailed processing in step S5108 of Fig. 31. In Fig. 32, the same processes as those in the traffic volume prediction model creation process of the first embodiment shown in Fig. 8 are assigned the same reference numerals, and detailed explanations thereof will be omitted.

[0208] The storage unit 347 stores in advance K time intervals to be processed: T_1, T_2, ..., T_k-1, T_req. The future traffic volume prediction unit 342 selects one unselected time interval from the time intervals T_1 to T_req and sets it as T_x (step S1201). The future traffic volume prediction unit 342 determines whether the assigned time interval T(i) is equal to or greater than the time interval T_x (step S1202).

[0209] If the future traffic volume prediction unit 342 determines that the allocated time interval T(i) is equal to or longer than the time interval T_x (step S1202: YES), it converts the predicted traffic volume RU(i) of the antenna station 310 into a predicted traffic volume for each time interval T_x (step S5203) by the same process as in step S1203 in Fig. 8. In other words, the future traffic volume prediction unit 342 calculates that a predicted traffic volume RU_T_x of predicted traffic volume RU(i) × (time interval T_x / allocated time interval T(i)) will occur for each time interval T_x between time t(i) and time t(i+1).

[0210] The future traffic volume prediction unit 342 adds the predicted traffic volume calculated in step S5203 to the time-series predicted traffic volume calculated in the past for the time interval T_x for each antenna station 310, and stores the result in the storage unit 347 (step S5204). The future traffic volume prediction unit 342 learns a traffic volume prediction model for the time interval T_x by using the time-series predicted traffic volume of the antenna station 310 for the time interval T_x stored in the storage unit 347, through processing similar to that of step S1205 in Fig. 8 (step S5205).

[0211] For example, the time-series predicted traffic volumes of the antenna station 310 for the time interval T_x are represented in order from most recent to least recent as RU_T_x(P), RU_T_x(P-1), RU_T_x(P-2), ..., RU_T_x(1) (P is an integer equal to or greater than 2). The future traffic volume prediction unit 342 generates learning data with RU_T_x(p) as the correct output data and RU_T_x(p-1) to RU_T_x(pq) as input data by sequentially subtracting 1 from the value of p (q is an integer equal to or greater than 1). The future traffic volume prediction unit 342 uses this generated learning data to learn a traffic volume prediction model that represents the correspondence between input data and output data.

[0212] On the other hand, if the future traffic volume prediction unit 342 determines in step S1202 that the allocation time interval T(i) is shorter than the time interval T_x (step S1202: NO), it performs the process of step S5206. The future traffic volume prediction unit 342 records the predicted traffic volume RU(i) of the antenna station 310-j (j is an integer between 1 and J) in the buffer of the future traffic volume prediction unit 342 or the storage unit 347 corresponding to the antenna station 310-j and the time interval T_x (step S5206). The future traffic volume prediction unit 342 determines whether the predicted traffic volume for the time interval T_x has been recorded in the buffer corresponding to the time interval T_x (step S5207). The future traffic volume prediction unit 342 determines whether the predicted traffic volume for the time interval T_x has been recorded in the buffer corresponding to each antenna station 310 (step S5207).

[0213] When the future traffic volume prediction unit 162 determines that the predicted traffic volume for the time interval T_x minutes is not recorded in the buffer corresponding to the time interval T_x (step S5207: NO), it performs the processing from step S1208. When the future traffic volume prediction unit 342 determines that, for each antenna station 310, the predicted traffic volume for the time interval T_x minutes is recorded in the buffer corresponding to the time interval T_x (step S5207: YES), it performs the processing of step S5204. That is, the future traffic volume prediction unit 342 reads and sums the predicted traffic volume from RU(i - T_x / T(i)+1) to RU(i) from the buffer corresponding to the time interval T_x, and sets it as RU_T_x(P).

[0214] The storage unit 347 stores the time-series predicted traffic volumes RU_T_x(1) to RU_T_x(P - 1) calculated in the past for the time interval T_x. The future traffic volume prediction unit 342 adds the newly calculated predicted traffic volume RU_T_x(P) to these predicted traffic volumes RU_T_x(1) to RU_T_x(P - 1) for each antenna station 310 and stores them in the storage unit 347 (step S5204). The future traffic volume prediction unit 342 performs the processing of step S5205 and learns the traffic volume prediction model using the time-series predicted traffic volumes for the time interval T_x.

[0215] After the processing of step S5205, or when it determines NO in step S5207, the future traffic volume prediction unit 342 determines whether all of the K time intervals to be processed have been selected (step S1208). When there are unselected time intervals (step S5208: NO), the future traffic volume prediction unit 342 repeats the processing from step S1201. Then, when the future traffic volume prediction unit 342 determines that all of the K time intervals have been selected (step S1208: YES), it stores the traffic volume prediction model corresponding to each of the K time intervals and the prediction time of the traffic volume prediction model in the storage unit 347 (step S5209).

[0216] Note that the future traffic volume prediction unit 342 may execute the processes of steps S1202 to S5207 for each of the K time intervals in parallel.

[0217] FIG. 33 is a flowchart showing the future traffic volume prediction process of the future traffic volume prediction unit 342. FIG. 33 shows the detailed process in step S5109 of FIG. 31. The future traffic volume prediction unit 342 identifies the antenna station 310 connected to each distributed station 323 based on the F1 UE context information (step S5301). The future traffic volume prediction unit 342 determines whether it is possible to predict the future traffic volume by the time t(i + 1) when the next transmission period U(i) ends, by the same process as step S1302 in FIG. 9 (step S5302).

[0218] When the future traffic volume prediction unit 342 determines that it is possible to predict the future traffic volume by the end of the next transmission period U(i) (step S5302: YES), it performs the process of step S5303. The future traffic volume prediction unit 342 inputs, for each antenna station 310, the p time-series predicted traffic volumes RU(P) to RU(P - p + 1) from the latest one of the allocated time intervals T(i) into the traffic volume prediction model created for the allocated time interval T(i). The future traffic volume prediction unit 342 calculates the future traffic volume RU(i + 1) of each antenna station 310 in the transmission period U(i + 1) from time t(i + 1) to time t(i + 2) (step S5303). Note that t(i + 2) = t(i + 1)+T(i). The future traffic volume prediction unit 342 writes the calculated future traffic volume RU(i + 1) of each antenna station 310 into the storage unit 367.

[0219] When the future traffic volume prediction unit 342 determines that it is impossible to predict the future traffic volume by the end of the next transmission period U(i) (step S5302: NO), it performs the process of step S5304. For each antenna station 310, the future traffic volume prediction unit 342 sums up the predicted traffic volumes in the time series of the allocation time interval T(i) one by one from the newest ones, T_req / T(i) at a time, to calculate the predicted traffic volume in the time series of the time interval T_req (for example, 5 ms). For each antenna station 310, the future traffic volume prediction unit 342 inputs the predicted traffic volumes in q time series from the newest one of the time interval T_req into the traffic volume prediction model created for the time interval T_req. Thereby, the future traffic volume prediction unit 162 calculates the future traffic volume RUreq(i + 1) of each antenna station 310 in the transmission period U(i + 1) from time t(i + 1) to time t(i + 2) (step S5304). Note that t(i + 2) = t(i + 1) + T_req. The future traffic volume prediction unit 342 writes the calculated future traffic volume DUr(i + 1) of each antenna station 310 into the storage unit 347.

[0220] For each distributed station 323, the required bandwidth calculation unit 343 sums up the future traffic volume RU(i + 1) calculated in step S5303 or the future traffic volume RUreq(i + 1) calculated in step S5304 for each subordinate antenna station 310 to calculate the required bandwidth DUr(i + 1) of the distributed station in the transmission period U(i + 1) (step S5305). In step S5107 of FIG. 31, the future traffic volume prediction unit 342 stores the required bandwidth DUr(i + 1) of each distributed station 323 in the storage unit 347.

[0221] FIG. 34 is a flowchart showing the convergence determination process of the determination unit 344. The determination unit 344 acquires the processable bandwidth of each distributed station 323 (step S5401). Specifically, the determination unit 344 acquires information on the allocated resources of the distributed station 323 from the distributed station resource information received from the resource management device 350. The allocated resources are the number of cores of the distributed station 323, the occupancy rate of the cores, or the resource blocks in the frequency direction. The determination unit 344 calculates the processable bandwidth Y_resource from the amount of allocated resources indicated by the distributed station resource information based on the relationship between the amount of allocated resources stored in advance and the processable bandwidth.

[0222] The determination unit 344 reads out the distributed station required bandwidth DUr(i) or DUr(i + 1) of the distributed station 323 stored in the storage unit 367 by the future traffic volume prediction unit 342 in step S5107 of FIG. 31, and sets it as the required bandwidth Y_traffic. The determination unit 344 calculates the convergence amount Y_buf for each distributed station 323 by the following formula (3) (step S5402).

[0223] Y_buf = Y_traffic - Y_resource …(3)

[0224] The determination unit 344 may calculate the convergence amount Y_buf of each distributed station 323 in parallel or sequentially. The determination unit 344 determines whether the convergence amount Y_buf of any of the distributed stations 323 exceeds a threshold TH3 (TH3 ≧ 0) (step S5403). When the convergence amount Y_buf is less than or equal to the threshold TH3, the determination unit 344 determines that no convergence occurs and ends the process (step S5403: NO). That is, the switching control device 340 does not execute path switching. On the other hand, when the convergence amount Y_buf exceeds the threshold TH3, the determination unit 344 determines that convergence occurs (step S5403: YES) and instructs the switching decision unit 345 to execute path switching (step S5404).

[0225] FIG. 35 is a flowchart showing the path switching control process of the switching control device 340. When the switching determination unit 345 determines from the determination unit 344 in step S5404 of FIG. 34 that the execution of path switching is controlled by the switching control device, the process of FIG. 35 is started.

[0226] The switching determination unit 345 initializes the offload information stored in the storage unit 347 (step S5501). The switching determination unit 345 generates load information associating the distributed station 323 with the congestion amount of the distributed station 323, the subordinate antenna stations 310, and the predicted traffic amount of the subordinate antenna stations 310. The switching determination unit 345 arranges the load information in the order of the congestion amount and writes it into the storage unit 347 (step S5502). The predicted traffic amount is the predicted traffic amount RU(i) used when calculating the distributed station required bandwidth DUr(i) in step S5106, the predicted traffic amount RU(i + 1) calculated in step S5303, or the predicted traffic amount RUreq(i + 1) calculated in step S5304.

[0227] The switching determination unit 345 determines whether there is load information with a congestion amount set exceeding the threshold TH4 (TH4 ≥ 0) (step S5503). The threshold TH4 may be the same as the threshold TH3 used in step S5403 of FIG. 34. When the switching determination unit 345 determines that there is a congestion amount exceeding the threshold TH4 (step S5503: YES), it executes the process of step S5504. That is, the switching determination unit 345 refers to the load information to identify the distributed station 323-n1 with the largest congestion amount (m1 is any integer from 1 to M) and the distributed station 323-n2 with the smallest congestion amount (m2 is any integer from 1 to M, m1 ≠ m2). The switching determination unit 345 selects the antenna station 310 with the largest predicted traffic among the antenna stations 310 subordinate to the distributed station 323-n1 as the switching target antenna station 310. The switching determination unit 345 changes the switching target antenna station 310 from being subordinate to the distributed station 323-n1 to being subordinate to the distributed station 323-n2 (step S5504).

[0228] The switching determination unit 345 associates the source distributed station information indicating the distributed station 323-n1, the destination distributed station information indicating the distributed station 323-n2, and the antenna station information to be switched indicating the antenna station 310 to be switched, and sets them in the offloading information (step S5505). The switching determination unit 345 repeats the process from step S5502. In step S5502, the switching determination unit 345 deletes the predicted traffic volume of the antenna station 310 to be switched and the antenna station 310 to be switched from the load information of the distributed station 323-n1. The switching determination unit 345 updates the congestion degree set in the load information of the distributed station 323-n1 to a value obtained by subtracting the predicted traffic volume of the antenna station 310 to be switched. Further, the switching determination unit 345 adds the predicted traffic volume of the antenna station 310 to be switched and the antenna station 310 to be switched to the load information of the distributed station 323-n2. The switching determination unit 345 updates the congestion degree set in the load information of the distributed station 323-n2 to a value when the predicted traffic volume of the antenna station 310 to be switched is added. The switching determination unit 345 rearranges the load information of the distributed station 323-n1 and the updated load information of the distributed station 323-n2 according to the congestion degree.

[0229] Then, when the switching determination unit 345 determines that there is no congestion amount exceeding the threshold TH4 (step S5504: NO), it ends the generation of the offloading information and instructs the switching instruction unit 346 to start switching (step S5506).

[0230] The switching instruction unit 346 reads out the source distributed station information, the destination distributed station information, and the antenna station information to be switched from the offloading information. The switching instruction unit 346 transmits a link-up request for requesting the establishment of a link for receiving the traffic from the antenna station 310 to be switched to the distributed station 323 indicated by the destination distributed station information (step S5507, step S5007 in FIG. 30). The switching instruction unit 346 receives a link-up permission as a response corresponding to the link-up request from the destination distributed station 323 (step S5508, step S5009 in FIG. 30). The switching instruction unit 346 transmits a path addition instruction from the antenna station 310 to be switched to the destination distributed station 323 to the transfer device 330 (step S5509, step S5013 in FIG. 30).

[0231] The switching instruction unit 346 transmits a route deletion request to the switching source remote station 323 to delete the route to the switching target antenna station 310 (step S5510, step S5017 in FIG. 30). The switching instruction unit 346 receives a route deletion completion notification from the switching source remote station 323 as a response to the route deletion request (step S5511, step S5018 in FIG. 30). The switching control device 340 transmits a route deletion instruction to the transfer device 330 to delete the transfer route between the switching target antenna station 310 and the switching source remote station 323 (step S5512, step S5022 in FIG. 30).

[0232] Next, an example of the hardware configuration of the switching control devices 160, 160a, 160b, 160c, and 340 will be described. Fig. 36 is a device configuration diagram showing an example of the hardware configuration of the switching control devices 160, 160a, 160b, 160c, and 340. The switching control devices 160, 160a, 160b, 160c, and 340 each include a processor 71, a storage unit 72, a communication interface 73, and a user interface 74.

[0233] The processor 71 is a central processing unit that performs calculations and control. The processor 71 is, for example, a CPU. The processor 71 reads and executes programs from the storage unit 72. Some of the functions of the switching control devices 160, 160a, 160b, 160c, and 340 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The storage unit 72 also has a work area and the like for the processor 71 to execute various programs. The communication interface 73 is connected to other devices so as to be able to communicate with them. The user interface 74 is an input device such as a keyboard, a pointing device (mouse, tablet, etc.), a button, or a touch panel, or a display device such as a display. Human operations are input through the user interface 74. For example, information on the uppermost hierarchical level and information on the lowermost hierarchical level are input through the user interface 74.

[0234] Each of the switching control devices 160, 160a, 160b, 160c, and 340 may be realized by a plurality of computer devices connected to a network. In this case, it is possible to arbitrarily determine which of the plurality of computer devices each functional unit of the switching control devices 160, 160a, 160b, 160c, and 340 is realized by. Furthermore, the same functional unit may be realized by a plurality of computer devices.

[0235] According to the above-described embodiment, the transmission system includes a plurality of transmission devices, a forwarding device, and a switching control device. The transmission system is, for example, the mobile network systems 10, 100, 101, 102, and 300 of the embodiment. The plurality of transmission devices constitute a communication network hierarchized into multiple layers. Each transmission device forwards a received signal to a layer one layer higher. The transmission devices are, for example, antenna stations 12, 120, and 310, remote stations 13, 130, and 323, and central stations 14, 140, and 325. The communication network is, for example, a mobile network. The forwarding device forwards a signal transmitted from a first transmission device, which is a transmission device at a predetermined layer among the multiple layers, to a second transmission device, which is a connection destination of the first transmission device, among a plurality of second transmission devices, which is a transmission device at a layer one layer higher than the predetermined layer. The forwarding device is, for example, the forwarding device 15, 150, and 330 of the embodiment. The switching control device switches the second transmission device to which the first transmission device is connected. The switching control device is, for example, the switching control device 16, 160, 160a, 160b, 160c, or 340 of the embodiment.

[0236] The switching control device includes a traffic volume calculation unit, a required bandwidth calculation unit, a determination unit, a switching determination unit, and a switching instruction unit. The traffic volume calculation unit calculates the traffic volume of signals received by each first transmission device via a transmission device in a layer lower than a predetermined layer during a predetermined period based on the allocation of radio resources to a terminal that wirelessly transmits signals to the lowest-layer transmission device. The required bandwidth calculation unit calculates, for each second transmission device, the processing capacity predicted to be required in the second transmission device based on the traffic volume in the first transmission device having the second transmission device as a connection destination. The determination unit determines whether congestion occurs in the second transmission device based on the predicted processing capacity. The switching determination unit determines to switch the connection destination of at least some of the first transmission devices having the second transmission device determined to have congestion as a connection destination to a second transmission device determined not to have congestion. At this time, the switching determination unit switches the connection destination of the first transmission device so that no congestion occurs in any of the second transmission devices based on the traffic volume of the first transmission device. The switching instruction unit instructs the transfer device to transfer the signal transmitted from the switching target transmission device, which is the first transmission device determined to switch the connection destination, to the second transmission device that is the connection destination after the switching of the switching target transmission device based on the determination of the switching determination unit.

[0237] The switching instruction unit performs a process of transmitting a reception instruction of a signal from the transmission device to be switched to the second transmission device as the switching destination, which is the connection destination of the transmission device to be switched after switching, and a process of transmitting a reception stop instruction of a signal from the transmission device to be switched to the second transmission device as the switching source, which is the connection destination of the transmission device to be switched before switching. For example, the reception instruction is a path addition instruction transmitted in step S1008 of the embodiment, and when reception is stopped, it is a path deletion instruction transmitted in step S1009 of the embodiment. When the second transmission device as the switching destination enables reception of a signal from the transmission device to be switched based on the reception instruction, it transmits a reception instruction response to the transmission device to be switched, the switching control device, and the second transmission device as the switching source. For example, the reception instruction response is a bearer response transmitted in steps S1010 to S1012 of the embodiment. When the second transmission device as the switching source stops reception of a signal from the transmission device to be switched based on the reception stop instruction, it transmits a reception stop response to the switching control device and the second transmission device as the switching destination. For example, the reception stop response is a bearer response transmitted in steps S1013 and S1014 of the embodiment. When the second transmission device as the switching destination receives a reception stop response from the second transmission device as the switching source in addition to the reception instruction of the signal from the transmission device to be switched transmitted by the switching instruction unit, it instructs to switch the connection to the upper network of the transmission system. When the switching instruction unit of the switching control device receives the reception stop response, it instructs the transfer device to transfer the signal transmitted from the transmission device to be switched to the second transmission device as the switching destination.

[0238] The plurality of transmission devices may include an antenna station that converts a radio signal received from a terminal into a wired signal and transmits the converted signal, one or more distribution stations that receive signals from one or more antenna stations subordinate thereto, aggregate the received signals, and transfer them, and an aggregation station that receives signals from one or more distribution stations subordinate thereto and transfers the received signals to an upper network. The first transmission device is a distribution station, and the second transmission device is an aggregation station. Alternatively, the first transmission device is an antenna station, and the second transmission device is a distribution station.

[0239] The first transmission device may transmit a signal to the second transmission device by an optical signal. Also, each time a radio resource is allocated to the terminal, the allocation of the radio resource may be notified to the switching control device.

[0240] The determination unit may determine whether congestion occurs in the second transmission device by using the processing capacity of the second transmission device, the processing amount in the second transmission device, and the predicted processing capacity of the second transmission device. The processing amount in the second transmission device is, for example, the bandwidth of the signal buffered in the second transmission device.

[0241] The determination unit may calculate the processing capacity of the second transmission device based on the amount of resources allocated to the second transmission device.

[0242] The switching control device may further include a future traffic amount calculation unit. The future traffic amount calculation unit calculates a future traffic amount, which is the traffic amount of the first transmission device in the next period, based on the traffic amount in a predetermined period. The required bandwidth calculation unit calculates, for each second transmission device, the processing capacity predicted to be required in the second transmission device based on the future traffic amount in the first transmission device having the second transmission device as a connection destination.

[0243] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and designs and the like within the scope not departing from the gist of the present invention are also included.

Explanation of Reference Numerals

[0244] 10 Mobile NW System 11 Terminal 12-1, 12-2 Antenna Station 13-1, 13-2 Distributed Station 14-1, 14-2 Aggregation Station 15 Transfer Device 16 Switching Control Device 20 Upper NW 71 Processor 72 Storage Unit 73 Communication Interface 74 User Interface 100, 101, 102, 300 Mobile Network System 120, 120-1~120-4, 310, 310-1~310-4 Antenna Station 130, 130-1~130-4, 323-1, 323-2 Distributed station 131 User data transmission / reception unit 132 Communications Department 133 Control Unit 140, 140-1, 140-2, 325 Aggregation Station 141 User data transmission / reception unit 142 Communications Department 143 Control Unit 150, 150a, 330 Transfer device 160, 160a, 160b, 160c, 340 switching control device 161, 341 Traffic volume calculation section 162, 342 Future Traffic Volume Prediction Section 163, 343 Required Bandwidth Calculation Unit 164, 344 Judgment Department 165, 345 Switching decision unit 166, 346 Switching instruction section 167, 347 storage section 168 Required Bandwidth Prediction Unit 170, 350 Resource management device 181 Wireless control information acquisition device 182 Switching control device 191 Integrated Control Device 192 Switching control device 200 Teleporter 201 Core Network 202 Internet 320-1, 320-2 base station 1311, 1411 First separation section 1312, 1412 First optical-electrical conversion unit 1313, 1414 Signal generation unit 1314, 1415 First electrical-optical conversion unit 1315, 1416 Second separation section 1316 and 1417, second photoelectric conversion unit 1317 and 1418, signal generation unit 1318 and 1419, second electro - optical conversion unit 1413, buffer

Claims

1. A plurality of transmission devices that form a communication network hierarchically divided into a plurality of layers and transfer received signals to the upper layer via a transfer device, A transfer device that transfers a signal transmitted from a first transmission device, which is a transmission device of a predetermined layer among the plurality of layers, to a second transmission device among a plurality of second transmission devices, which are transmission devices of a layer one level above the predetermined layer, and which is the connection destination of the first transmission device, A switching control device that switches the second transmission device that is the connection destination of the first transmission device, and includes: The switching control device includes: A traffic volume calculation unit that calculates the traffic volume of signals received by each of the first transmission devices via a transmission device lower than the predetermined layer during a predetermined period based on the allocation of radio resources to a terminal that wirelessly transmits signals to the lowest layer transmission device; A required bandwidth calculation unit that calculates the processing capacity predicted to be required in the second transmission device based on the traffic volume in the first transmission device having the second transmission device as the connection destination for each second transmission device; A determination unit that determines whether or not congestion occurs in the second transmission device based on the predicted processing capacity; A switching determination unit that determines to switch the connection destination of at least a part of the first transmission devices having the second transmission device determined to have congestion as the connection destination to a second transmission device determined not to have congestion; A switching instruction unit that instructs the transfer device to transfer a signal transmitted from a switching target transmission device, which is the first transmission device determined to switch the connection destination based on the determination of the switching determination unit, to the second transmission device that is the connection destination after switching of the switching target transmission device, and includes: A transmission system.

2. The switching instruction unit performs a process of transmitting a reception instruction for a signal from the switching target transmission device to a switching destination second transmission device, which is the second transmission device that is the connection destination after switching of the switching target transmission device, and a process of transmitting a reception stop instruction for a signal from the switching target transmission device to a switching source second transmission device, which is the second transmission device that is the connection destination before switching of the switching target transmission device, When the switching destination second transmission device enables reception of a signal from the switching target transmission device based on the reception instruction, the switching destination second transmission device transmits a reception instruction response to the switching target transmission device, the switching control device, and the switching source second transmission device. When the switching source second transmission device stops receiving the signal from the switching target transmission device based on the reception stop instruction, it transmits a reception stop response to the switching control device and the switching destination second transmission device. When the switching destination second transmission device receives the reception stop response from the switching source second transmission device in addition to the reception instruction, it instructs to switch the connection to the upper network of the transmission system. When the switching instruction unit receives the reception stop response, it instructs the transfer device to transfer the signal transmitted from the switching target transmission device to the switching destination second transmission device. The transmission system according to claim 1.

3. Based on the allocation of radio resources to a terminal that wirelessly transmits a signal to the lowest-layer transmission device among a plurality of transmission devices that constitute a communication network hierarchically divided into a plurality of layers and transfer the received signal to the upper layer via a transfer device, a traffic volume calculation unit that calculates the traffic volume of the signals received by each first transmission device, which is a transmission device of a predetermined layer among the plurality of layers, via the transmission devices lower than the predetermined layer during a predetermined period; For each second transmission device, which is a transmission device of the layer above the first transmission device, a required bandwidth calculation unit that calculates the processing capacity predicted to be required in the second transmission device based on the traffic volume in the first transmission device that has the second transmission device as the connection destination; A determination unit that determines whether congestion occurs in the second transmission device based on the predicted processing capacity; A switching determination unit that determines to switch the connection destination of at least a part of the first transmission devices that have the second transmission device determined to have congestion as the connection destination to a second transmission device determined not to have congestion; Based on the determination of the switching determination unit, the transfer device that transfers the signal transmitted from the first transmission device to the second transmission device that is the connection destination of the first transmission device among the plurality of second transmission devices is instructed to transfer the signal transmitted from the switching target transmission device, which is the first transmission device whose connection destination is determined to be switched, to the second transmission device that is the connection destination after the switching of the switching target transmission device. A switching control device comprising the above.

4. The plurality of transmission devices include An antenna station that converts the wireless signal received from the terminal into a wired signal and transmits the converted signal. A distribution station that receives the signal from one or more of the subordinate antenna stations and aggregates and transfers the received signal; An aggregation station that receives the signal from one or more of the subordinate distribution stations and transfers the received signal to a higher-level network, The first transmission device is the distribution station; The second transmission device is the aggregation station. The switching control device according to claim 3.

5. The plurality of transmission devices include: A plurality of antenna stations that convert a wireless signal received from the terminal into a wired signal and transmit the converted signal; A plurality of distribution stations that receive the signal from one or more of the subordinate antenna stations and aggregate and transfer the received signal; An aggregation station that receives the signal from one or more of the subordinate distribution stations and transfers the received signal to a higher-level network, The first transmission device is the antenna station; The second transmission device is the distribution station. The switching control device according to claim 3.

6. The first transmission device transmits the signal by an optical signal. The switching control device according to any one of claims 3 to 5.

7. The allocation of wireless resources to the terminal is notified to the switching control device each time the wireless resources are allocated to the terminal. The switching control device according to any one of claims 3 to 5.

8. The determination unit determines whether congestion occurs in the second transmission device by using the processing capacity of the second transmission device, the processing amount in the second transmission device, and the predicted processing capacity of the second transmission device. The switching control device according to claim 4.

9. The determination unit calculates the processing capacity of the second transmission device based on the amount of resources allocated to the second transmission device. The switching control device according to claim 8.

10. Further comprising a future traffic volume calculation unit that calculates a future traffic volume, which is the traffic volume of the first transmission device in the next period of the predetermined period, based on the traffic volume of the predetermined period; The required bandwidth calculation unit calculates, for each second transmission device, the processing capacity predicted to be required in the second transmission device based on the future traffic volume in the first transmission device having the second transmission device as a connection destination. The switching control device according to any one of claims 3 to 5.

11. Based on the allocation of radio resources to a terminal that wirelessly transmits a signal to the lowest-layer transmission device among a plurality of transmission devices that constitute a communication network hierarchically divided into a plurality of layers and transfers the received signal to the upper layer via a transfer device, a traffic volume calculation step of calculating, for each first transmission device that is a transmission device of a predetermined layer among the plurality of layers, the traffic volume of signals received during a predetermined period via transmission devices lower than the predetermined layer; For each second transmission device that is a transmission device of the layer above the first transmission device, a required bandwidth calculation step of calculating the processing capacity predicted to be required in the second transmission device based on the traffic volume in the first transmission device having the second transmission device as the connection destination; A determination step of determining whether congestion occurs in the second transmission device based on the predicted processing capacity; A switching determination step of determining to switch the connection destination of at least some of the first transmission devices having the second transmission device determined to have congestion as the connection destination to a second transmission device determined not to have congestion; A switching instruction step of instructing the transfer device that transfers the signal transmitted from the first transmission device to the second transmission device that is the connection destination of the first transmission device among the plurality of second transmission devices to transfer the signal transmitted from the switching target transmission device, which is the first transmission device determined to switch the connection destination in the switching determination step, to the second transmission device that is the connection destination after switching of the switching target transmission device based on the determination in the switching determination step; A switching control method having the above.

12. A program for causing a computer to function as the switching control device according to any one of Claims 3 to 5.

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