Communication control device and communication control method

Abstract

This communication control device comprises: an acquisition unit that acquires wireless control information to be used for controlling path switching between a plurality of lower-level devices, which are communication devices wirelessly connected to a terminal, and at least one higher-level device, which is a communication device connected to any of the lower-level devices, from each of the plurality of lower-level devices; a traffic prediction unit that predicts a future traffic volume in each of the plurality of lower-level devices on the basis of the wireless control information, and predicts a future traffic volume in the upper-level device on the basis of a prediction result; and a switching determination unit that predicts the presence or absence of the occurrence of future congestion on the basis of the predicted future traffic volume in the upper-level device, and determines whether to execute the path switching.

Description

Communication control device and communication control method

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

[0002] When multiple upper-level devices and multiple lower-level devices communicate with each other, or when communication is performed simultaneously by multiple communication devices, congestion may occur and communication delays may occur. Congestion can sometimes be resolved by switching the communication path (hereinafter referred to as "path switching") by a switching device installed in the communication path and changing the connection relationship between the upper-level device and the lower-level device. If the communication traffic (hereinafter simply referred to as "traffic") concentrated on a specific communication device (for example, an upper-level device) can be dispersed to multiple communication devices by path switching, congestion can be resolved and communication delays can be reduced.

[0003] Conventionally, in a communication system having a switching device capable of changing the connection relationship between an upper-level device and a lower-level device, information indicating the amount of traffic (hereinafter simply referred to as "traffic volume") measured by the upper-level device or the lower-level device is collected, and based on the collected traffic volume, a technique exists for determining the presence or absence of congestion and performing path switching. A conventional communication system, for example, calculates a congestion value indicating the degree of congestion based on the traffic volume of each communication path, and performs path switching when the congestion value of any communication path exceeds a threshold.

[0004] However, generally, path switching takes a certain amount of time. Therefore, in a conventional communication system, it is possible to be in a state where congestion occurs from the occurrence of congestion until the path switching is completed. Thus, the time required for path switching is also one of the factors causing communication delays. Since it takes time to collect the actual traffic volume and then perform path switching, it is difficult to determine the presence or absence of congestion in real time (for example, within a few milliseconds) and execute path switching within a predetermined period (for example, within several tens of milliseconds).

[0005] In contrast, there is a technology that avoids congestion by predicting future traffic volume and switching routes in advance based on the predicted value, rather than switching routes based on actual traffic volume (see, for example, Patent Document 1). Such technology can predict and prevent congestion from occurring, thereby further reducing communication delays.

[0006] Generally, traffic often exhibits periodicity due to burst traffic, such as video traffic and traffic in time-division duplex (TDD) communications (see, for example, Non-Patent Document 1). Therefore, especially in situations where terminals do not move much, it is possible to predict future traffic volume with greater accuracy by identifying the periodicity of traffic from past changes in traffic volume and making predictions based on the identified periodicity.

[0007] International Publication No. 2023 / 181139

[0008] "4G / LTE-TDD", ShareTechnote, [Retrieved October 18, 2024], Internet (URL: https: / / www.sharetechnote.com / html / LTE_TDD_Overview.html)

[0009] On the other hand, in situations where terminals are frequently in motion, the number of terminals within the coverage area of ​​the communication station connecting to that terminal fluctuates randomly, making it difficult to identify traffic periodicity from past traffic volumes. Consequently, in the past, there was a challenge in accurately predicting future traffic volumes and achieving low-latency communication in situations where terminals were frequently in motion.

[0010] To address these challenges, one possible approach is to predict changes in the number of terminals by forecasting terminal movement, and then predict future traffic volume based on the predicted changes in the number of terminals. However, this method requires predicting the movement of each individual terminal. Therefore, especially in situations where there are many terminals within a communication station's coverage area, the computational load required for predicting the movement of each terminal becomes enormous.

[0011] In view of the above circumstances, the present invention aims to provide a technology that can predict traffic volume with greater accuracy while suppressing an increase in computational load, even in situations where terminals are frequently moved.

[0012] One aspect of the present invention is a communication control device comprising: an acquisition unit that acquires wireless control information used for controlling route switching between a plurality of lower-level devices, which are communication devices wirelessly connected to a terminal, and at least one upper-level device, which is a communication device connected to any of the lower-level devices; a prediction unit that predicts the future traffic volume of each of the plurality of lower-level devices based on the wireless control information and predicts the future traffic volume of the upper-level device based on the prediction results; and a switching determination unit that predicts whether or not future congestion will occur based on the predicted future traffic volume of the upper-level device and makes a decision on whether to execute the route switching.

[0013] Furthermore, one aspect of the present invention is a communication control method executed by a computer, comprising: an acquisition step of acquiring wireless control information used for controlling route switching between a plurality of lower-level devices, which are communication devices wirelessly connected to a terminal, and at least one upper-level device, which is a communication device connected to any of the lower-level devices; a prediction step of predicting the future traffic volume at the plurality of lower-level devices based on the wireless control information and predicting the future traffic volume at the upper-level device based on the prediction results; and a switching determination step of predicting whether or not future congestion will occur based on the predicted future traffic volume at the upper-level device and making a decision on whether to execute the route switching.

[0014] This invention makes it possible to predict traffic volume with greater accuracy while suppressing the increase in computational load, even in situations where terminals are frequently in motion.

[0015] This is a diagram showing the overall configuration of the communication system 1 in an embodiment of the present invention. This is a diagram showing the overall configuration of the mobile communication system 10 in a first embodiment of the present invention. This is a block diagram showing the functional configuration of the switching instruction device 17 in a first embodiment of the present invention. This is a diagram for explaining the future traffic volume prediction processing by the switching instruction device 17 in a first embodiment of the present invention. This is a flowchart showing the operation of the switching instruction device 17 in a first embodiment of the present invention. This is a block diagram showing the functional configuration of the switching instruction device 17a in a second embodiment of the present invention. This is a diagram for explaining the future traffic volume prediction processing by the switching instruction device 17a in a second embodiment of the present invention. This is a diagram showing an example of the coverage area of ​​the distributed station 13 in a second embodiment of the present invention. This is a flowchart showing the operation of the switching instruction device 17a in a second embodiment of the present invention. This is a block diagram showing the functional configuration of the switching instruction device 17b in a third embodiment of the present invention. This is a flowchart showing the operation of the switching instruction device 17b in a third embodiment of the present invention. This is a block diagram showing the functional configuration of the switching instruction device 17c in a fourth embodiment of the present invention. This is a flowchart showing the operation of the switching instruction device 17c in a fourth embodiment of the present invention. This is a block diagram showing the functional configuration of the switching instruction device 17d in a fifth embodiment of the present invention. This is a flowchart showing the operation of the switching instruction device 17d in a fifth embodiment of the present invention. This is a block diagram showing the functional configuration of the switching instruction device 17e in a sixth embodiment of the present invention. This is a flowchart showing the operation of the switching instruction device 17e in the sixth embodiment of the present invention. This is a diagram showing the hardware configuration of the switching instruction device in the first to sixth embodiments of the present invention.

[0016] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0017] [Overview] First, before describing the individual embodiments of the present invention in detail, we will explain the basic system configuration that is common to each embodiment described below.

[0018] Figure 1 shows the overall configuration of a communication system 1 in an embodiment of the present invention. The communication system 1 includes a plurality of lower-level devices 3, a plurality of upper-level devices 4, and a switching instruction device 7. The lower-level devices 3 and the upper-level devices 4 are connected via a network 5. The network 5 is composed of one or more transfer devices (not shown; devices corresponding to the transfer device 15 shown in Figure 2, which will be described later). The transfer device also functions as a switching device that can change the connection relationship between the lower-level devices 3 and the upper-level devices 4.

[0019] In Figure 1, the four lower-level devices 3 are labeled "lower-level device 3-1" to "lower-level device 3-4," and the two upper-level devices 4 are labeled "upper-level device 4-1" and "upper-level device 4-2." However, the number of lower-level devices 3 and upper-level devices 4 is not limited to these numbers and can be any number. Hereafter, the direction from lower-level device 3 to upper-level device 4 will be referred to as "up," and the direction from upper-level device 4 to lower-level device 3 will be referred to as "down."

[0020] The lower-level device 3 transmits an uplink signal to the connected upper-level device 4. Network 5 forwards the uplink signal to the upper-level device 4 according to the communication path between the lower-level device 3 and the upper-level device 4. The upper-level device 4 also transmits a downlink signal to the connected lower-level device 3. Network 5 forwards the downlink signal to the lower-level device 3 according to the communication path between the lower-level device 3 and the upper-level device 4.

[0021] The switching instruction device 7 instructs each device in the communication system 1 to switch routes. The switching instruction device 7 uses information such as traffic volume and the number of terminals obtained from the lower-level device 3 to predict in advance the traffic volume of some or all communication links (hereinafter referred to as "links") in the communication path between the lower-level device 3 and the upper-level device 4. For each link, the switching instruction device 7 uses the predicted traffic volume information and the switching threshold to determine whether congestion will occur.

[0022] A switching threshold is a threshold used to determine whether or not congestion requiring route switching will occur. The switching threshold is predetermined for each link, for example, based on the link's transmission capacity. An indicator used to represent the link's transmission capacity is, for example, the link rate. The link rate is the maximum communication speed of the link.

[0023] The switching instruction device 7 determines that route switching for load balancing should be performed if congestion is predicted to occur on any of the links. The switching instruction device 7 instructs each device (transmitter, downstream device 3, and upstream device 4, etc.) to switch routes so that at least a portion of the traffic transmitted on the link where congestion is predicted to occur is transmitted on the link where congestion is not predicted to occur. This prevents congestion delays on the links and makes it possible to improve the efficiency of bandwidth utilization.

[0024] As shown in Figure 1, the switching instruction device 7 has a prediction unit 72 and a switching decision unit 75. The prediction unit 72 acquires wireless control information from each device (subordinate device 3, etc.) that is used to predict the traffic volume of each link. Wireless control information includes, for example, the traffic volume observed by the device, the traffic allocation to the device, the number of connected terminals to the device, the location information of the device, the location information and radio wave environment of the terminals, and the required communication quality (hereinafter referred to as "required quality"). Note that the wireless control information may be one or more of these pieces of information. The prediction unit 72 uses the wireless control information to predict the future traffic volume for each link (hereinafter referred to as "future traffic volume").

[0025] The switching determination unit 75 determines in advance whether congestion will occur for each link, using the predicted future traffic volume and the switching threshold. If congestion is predicted, the switching determination unit 75 decides to perform a route switch for load balancing. For example, the switching determination unit 75 decides to perform a route switch from the link where congestion is predicted to a link with lower link utilization. The switching determination unit 75 instructs each device (transfer device, lower-level device 3, and upper-level device 4, etc.) to execute the process for route switching.

[0026] Several embodiments of applying the above-described communication system 1 to a mobile communication system will be described in detail below.

[0027] <First Embodiment> The first embodiment of the present invention will be described below.

[0028] [Overall Configuration of the Communication System] Figure 2 shows the overall configuration of the mobile communication system 10 in the first embodiment of the present invention. The mobile communication system 10 is an example of the communication system 1 described above.

[0029] The mobile communication system 10 is, for example, a fifth-generation mobile communication system (5G). The mobile communication system 10 includes a terminal station 11 (terminal), an antenna station 12, a distributed station 13, an aggregation station 14, a transfer device 15, a switching instruction device 17, and a resource allocation device 16.

[0030] The terminal station 11, antenna station 12, distributed station 13, and aggregation station 14 are the UE (User Equipment), RU (Radio Unit), DU (Distributed Unit), and CU (Central Unit) of the fifth-generation mobile communication system, respectively. The distributed station 13 is an example of a lower-level device 3, and the aggregation station 14 is an example of a higher-level device 4. However, the combination of the device corresponding to the lower-level device 3 and the device corresponding to the higher-level device 4 is not limited to the distributed station 13 and the aggregation station 14, but is arbitrary. The forwarding device 15 is an example of a forwarding device that constitutes the network 5.

[0031] The transfer device 15 also functions as a switching device that can change the connection relationship between the distributed station 13 and the aggregation station 14. The transfer function and switching function of the transfer device 15 may be implemented by separate devices. Furthermore, the switching instruction device 17, the transfer device 15, and the resource allocation device 16 do not necessarily have to be separate devices; they may be configured as an integrated device.

[0032] The aggregation station 14 of the mobile communication system 10 is connected to the upper-level network 20.

[0033] Hereafter, the distributed stations 13 of M units (where M is an integer greater than or equal to 1) will be referred to as "distributed station 13-1" to "distributed station 13-M," respectively. Also, below, the K under distributed station 13-m (where m is an integer greater than or equal to 1 and less than or equal to M) ｍ Stand (K ｍ An antenna station 12 with (where N is an integer of 1 or more) will be referred to as "antenna station 12-m". Similarly, N aggregation stations 14 (where N is an integer of 2 or more) will be referred to as "aggregation station 14-1" through "aggregation station 14-N", respectively. Therefore, the mobile communication system 10 shown in Figure 2 has M=4, K １ = 2, K ２ = 2, K ３ = 2, K ４ This is an example of a mobile communication system where N = 2 and N = 2.

[0034] Terminal station 11 uses radio resources allocated from distributed station 13 to send and receive radio signals with antenna station 12. The radio resources allocated from distributed station 13 include, for example, information indicating the start and end timings of time intervals in which the transmission and reception of radio signals are permitted. The start and end timings are represented, for example, by slots. A slot is a scheduling unit for data transmission and reception in a radio frame. The allocated radio resources may also include information indicating the coding rate and modulation scheme, etc.

[0035] Antenna station 12 receives uplink data from terminal station 11 via a wireless signal. Antenna station 12-m sets the received uplink data as an uplink signal. Then, antenna station 12-m transmits the uplink signal to distributed station 13-m via a wired interface.

[0036] Furthermore, antenna station 12-m receives downlink signals from distributed station 13-m via a wired interface. Antenna station 12 transmits the downlink data destined for terminal station 11, which is set in the received downlink signal, to terminal station 11 via a wireless signal.

[0037] Distributed station 13-m is K ｍEach of the 12-m antenna stations of the station receives an upstream signal. The upstream signal received by the 13-m distribution station includes the upstream data received from the terminal station 11 under the jurisdiction of the 12-m antenna station. The distribution station 13 generates an upstream signal that aggregates the upstream data from each terminal station 11 and transmits the generated upstream signal to the aggregation station 14 at the connection destination of its own station.

[0038] Further, the distribution station 13 receives a downstream signal in which downstream data addressed to the terminal station 11 under its jurisdiction is set from the aggregation station 14 at the connection destination of its own station. The 13-m distribution station converts the received downstream signal into a downstream signal corresponding to the radio signal transmitted from each 12-m antenna station. Then, the 13-m distribution station transmits the converted downstream signal to the 12-m antenna station corresponding to the downstream signal.

[0039] The aggregation station 14 aggregates the upstream signals received from the distribution stations 13 under its jurisdiction and transfers them to the upper network 20. Further, the aggregation station 14 receives a downstream signal in which downstream data addressed to the terminal station 11 is set from the upper network 20 and transfers the received downstream signal to the distribution station 13 connected to the destination terminal station 11.

[0040] The transfer device 15 is connected to the distribution station 13, the aggregation station 14, and the switching instruction device 17. The transfer device 15 also functions as a device that executes path switching. The transfer device 15 transfers signals according to the communication path between the distribution station 13 and the aggregation station 14. That is, the transfer device 15 transfers the upstream signal received from the distribution station 13 to the destination aggregation station 14 according to the communication path.

[0041] Further, the transfer device 15 transfers the downstream signal received from the aggregation station 14 to the destination distribution station 13 according to the communication path. The transfer of signals performed according to the communication path is executed under the instruction from the switching instruction device 17. The resource allocation device 16 manages the resources of the aggregation station 14.

[0042] The switching instruction device 17 is connected to the distribution station 13, the aggregation station 14, and the transfer device 15. Further, the switching instruction device 17 may be connected to the resource allocation device 16. The switching instruction device 17 instructs the transfer device 15 to perform path switching between the distribution station 13 and the aggregation station 14.

[0043] In the mobile communication system 10 according to the present embodiment, the communication path between the distributed stations 13 and the aggregation station 14 is determined by the connection relationship between the distributed stations 13 and the aggregation station 14. Therefore, in the mobile communication system 10, the transfer device 15 is controlled to change the aggregation station 14 to which the distributed station 13 is connected, thereby switching the path between the distributed station 13 and the aggregation station 14.

[0044] Note that the switching instruction device 17 of the present embodiment is configured to determine the presence or absence of future congestion based on the predicted result of the uplink traffic volume. Therefore, hereinafter, "traffic" shall mean the uplink signal traffic unless otherwise specified.

[0045] [Functional Configuration of Switching Instruction Device] Hereinafter, the functional configuration of the switching instruction device 17 will be described. The switching instruction device 17 is a device that predicts the future traffic volume in each aggregation station 14 to predict the presence or absence of congestion, and performs control to execute path switching as necessary. The switching instruction device 17 in the first embodiment predicts the future traffic volume in each distributed station 13 based on the recent transition (variation amount) of the traffic volume per terminal station 11 in each distributed station 13. Then, the switching instruction device 17 predicts the future traffic volume in each aggregation station 14 based on the future traffic volume in each distributed station 13.

[0046] FIG. 3 is a block diagram showing the functional configuration of the switching instruction device 17 in the first embodiment of the present invention. As shown in FIG. 3, the switching instruction device 17 includes a prediction unit 172 and a switching determination unit 175. Further, the prediction unit 172 includes a traffic prediction unit 174.

[0047] The prediction unit 172 receives radio control information from each distributed station 13, which is used to predict the future traffic volume at each distributed station 13. The radio control information in the first embodiment includes data that associates the traffic volume at each distributed station 13 with the number of terminal stations 11 that are located within the coverage area of ​​each distributed station 13 and communicate with it (hereinafter referred to as "number of connected terminals") with time. The traffic prediction unit 174 of the prediction unit 172 uses the radio control information to predict the future traffic volume at each distributed station 13.

[0048] Furthermore, the prediction unit 172 calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14, and the future traffic volume at each distributed station 13. The uplink traffic volume at the aggregate station 14 corresponds to the sum of the uplink traffic volumes received by the aggregate station 14 from each of the distributed stations 13 under its control. The prediction unit 172 outputs information indicating the future traffic volume at each aggregate station 14 to the switching determination unit 175.

[0049] The switching decision unit 175 predicts whether or not future congestion will occur based on the relationship between the future traffic volume for each aggregation station 14 obtained from the prediction unit 172 and a predetermined switching threshold. For example, the switching decision unit 175 calculates a predicted link utilization rate based on the relationship between the future traffic volume for each aggregation station 14 obtained from the prediction unit 172 and a predetermined switching threshold. The switching decision unit 175 then predicts whether or not future congestion will occur based on the predicted link utilization rate.

[0050] The predetermined switching threshold is a value set in advance based on, for example, the link rate and bandwidth of the upstream link. The switching determination unit 175 determines, for example, if there is an aggregation station 14 where it is determined that congestion will occur because the amount of traffic will exceed the bandwidth of the upstream link in the future, it will perform a route switch to distribute the load to a link with available bandwidth. When the switching determination unit 175 determines that a route switch should be performed, it issues instructions to each device (distributed station 13, aggregation station 14 and forwarding device 15) to change the aggregation station 14 to which the distributed station 13 is connected for route switching.

[0051] Specifically, the switching determination unit 175 instructs the aggregation station 14 of the destination before the switch (hereinafter referred to as the "source") to release the connection with the distributed station 13, and instructs the aggregation station 14 of the destination after the switch (hereinafter referred to as the "destination") to connect with the said distributed station 13. Furthermore, the switching determination unit 175 instructs the transfer device 15 to switch the route so that signal transfer is carried out via the communication path after the destination switch.

[0052] [Predicting Future Traffic Volume] The prediction process for future traffic volume at each distributed station 13, performed by the prediction unit 172, will be explained in more detail below.

[0053] The prediction unit 172 acquires wireless control information from each distributed station 13, including the traffic volume and the number of connected terminals at that distributed station 13, for example, on a unit period basis. The traffic prediction unit 174 of the prediction unit 172 calculates the traffic volume per terminal station 11 for several past periods (for example, the most recent five unit periods) based on the traffic volume and the number of connected terminals for each unit period. Then, the traffic prediction unit 174 predicts the future traffic volume per terminal station 11 at each distributed station 13 (for example, the traffic volume for the next unit period) based on the trend of the traffic volume per terminal station 11 over several past periods.

[0054] At this time, the traffic prediction unit 174 predicts the future traffic volume per terminal station 11 in each distributed station 13 by weighting the prediction values ​​so that more recent fluctuations in traffic volume are given greater weight. The following will explain in more detail the future traffic volume prediction process with such weighting using numerical examples.

[0055] Figure 4 is a diagram illustrating the future traffic volume prediction process by the switching instruction device 17 in the first embodiment of the present invention. Figure 4 shows data generated based on radio control information acquired from a single distributed station 13. As shown in Figure 4, the data is in tabular format, with the time, traffic volume, number of connected terminals, traffic volume per terminal station, and traffic volume fluctuation amount associated with each other.

[0056] The prediction unit 172 acquires wireless control information, including time, traffic volume, and number of connected terminals, from each distributed station 13, as shown in Figure 4. As shown in Figure 4, the prediction unit 172 sequentially acquires wireless control information, including traffic volume and number of connected terminals, at times t(-4), t(-3), t(-2), t(-1), and t(0), for example.

[0057] Note that times t(-4), t(-3), t(-2), t(-1), and t(0) are times within a unit period, with time t(0) being the most recent time. For example, as shown in Figure 4, the traffic volume at time t(-4) in a certain distributed station 13 is 2.0 [Gbps], and the number of connected terminals is 10 [units]. Also, for example, as shown in Figure 4, the traffic volume at time t(-3) in the same distributed station 13 is 2.0 [Gbps], and the number of connected terminals is 12 [units].

[0058] Here, as an example, we will explain a case where future traffic volume is predicted based on data from the five most recent time periods. Therefore, Figure 4 shows the data for the five most recent time periods. However, the number of time periods used for the data used in the prediction is not limited to five, but can be any number.

[0059] The traffic prediction unit 174 of the prediction unit 172 calculates the traffic volume per terminal station 11 at each time by dividing the traffic volume value by the number of connected terminals at the same time.

[0060] Therefore, the calculated traffic volume per terminal station 11 at each time point is as shown in Figure 4: 0.2 [Gbps] at time t(-4), 0.17 [Gbps] at time t(-3), 0.175 [Gbps] at time t(-2), 0.136 [Gbps] at time t(-1), and 0.24 [Gbps] at time t(0).

[0061] Next, the traffic prediction unit 174 of the prediction unit 172 calculates the amount of change in the amount of traffic per terminal station 11 for each unit period based on the calculated amount of traffic per terminal station 11 at each time point. The amount of change in the amount of traffic here refers to the difference (one unit period) between the preceding and succeeding time points.

[0062] For example, the traffic volume per terminal station 11 is 0.2 [Gbps] at time t(-4) and 0.17 [Gbps] at time t(-3). Therefore, as shown in Figure 4, the change in traffic volume per terminal station 11 between time t(-4) and t(-3) is -0.03 [Gbps].

[0063] In this way, the traffic prediction unit 174 determines that the change in the amount of traffic per terminal station 11 between time t(-4) and t(-3) is -0.03 [Gbps], the change in the amount of traffic per terminal station 11 between time t(-3) and t(-2) is +0.005 [Gbps], the change in the amount of traffic per terminal station 11 between time t(-2) and t(-1) is -0.039 [Gbps], and the change in the amount of traffic per terminal station 11 between time t(-1) and t(0) is +0.104 [Gbps].

[0064] The traffic prediction unit 174 predicts the future traffic volume per terminal station 11 at each distributed station 13 based on the trend of the fluctuation amount of traffic volume per terminal station 11 calculated in this way. At this time, as described above, the traffic prediction unit 174 predicts the future traffic volume per terminal station 11 by weighting the prediction so that the more recent fluctuation amount of traffic volume is given more weight in the predicted value.

[0065] For example, the traffic prediction unit 174 assigns progressively smaller weights to the following fluctuations in traffic volume per terminal station 11: the fluctuation in traffic volume per terminal station 11 between the most recent time interval t(-1) to t(0), the fluctuation in traffic volume per terminal station 11 between the time interval t(-2) to t(-1), the fluctuation in traffic volume per terminal station 11 between the time interval t(-3) to t(-2), and the fluctuation in traffic volume per terminal station 11 between the time interval t(-4) to t(-3). For example, the traffic prediction unit 174 assigns weights to each of the five fluctuations in the ratio of 8:4:2:1, starting from the most recent unit period. Note that the weight values ​​are not limited to these and can be arbitrary.

[0066] As a result, the formula used by the traffic prediction unit 174 to predict the future traffic volume per terminal station 11 in a given distributed station 13 is, for example, as shown in equation (1) below.

[0067] Future traffic volume per terminal station 11 = 0.24 + 0.104 × (8 / 15) - 0.039 × (4 / 15) + 0.005 × (2 / 15) - 0.03 × (1 / 15) ... (1)

[0068] Based on the wireless control information shown in Figure 4, the value of the future traffic volume per terminal station 11 in a given distributed station 13 is 0.284 [Gbps] by calculating the above equation (1). The traffic prediction unit 174 can predict the future traffic volume in the distributed station 13 by multiplying this future traffic volume per terminal station 11 by the future number of connected terminals in the distributed station 13.

[0069] Furthermore, the future number of connected terminals may be a value predicted based on, for example, the fluctuation in the number of connected terminals over the past few periods, or it may be the value of the most recent number of connected terminals (for example, in the case of Figure 4, 10 [units] at the most recent time, time t(0)). Therefore, for example, if the future number of connected terminals is 10 [units], the future traffic volume at distributed station 13 is predicted to be 2.84 [Gbps] (= (future traffic volume per terminal station 11) 0.284 [Gbps] × (future number of connected terminals) 10 [units]).

[0070] [Operation of the Switching Instruction Device] An example of the operation of the switching instruction device 17 will be described below. Figure 5 is a flowchart showing the operation of the switching instruction device 17 in the first embodiment of the present invention. The operation of the switching instruction device 17 shown in the flowchart of Figure 5 is repeatedly started at predetermined intervals, for example. That is, the prediction of future traffic volume and the decision to execute route switching based on the prediction result are performed at predetermined intervals.

[0071] First, the prediction unit 172 obtains wireless control information from each distributed station 13, which associates the time, traffic volume, and number of connected terminals (step S001). Next, the traffic prediction unit 174 of the prediction unit 172 calculates the traffic volume per terminal station 11 at each time for each distributed station 13 by dividing the traffic volume value by the number of connected terminals (step S002).

[0072] Next, the traffic forecasting unit 174 calculates the amount of change in the amount of traffic per terminal station 11 for each unit period based on the calculated amount of traffic per terminal station 11 at each time (step S003). Next, the traffic forecasting unit 174 predicts the future amount of traffic per terminal station 11 based on the calculated change in the amount of traffic per terminal station 11 for each unit period (step S004).

[0073] At this time, the traffic prediction unit 174 predicts the future traffic volume per terminal station 11 by weighting the prediction values ​​so that more recent fluctuations in traffic volume are given greater consideration, as described above.

[0074] Next, the traffic prediction unit 174 calculates the future traffic volume at each distributed station 13 by multiplying the future traffic volume per terminal station 11 by the future number of connected terminals at that distributed station 13 (step S005). Next, the traffic prediction unit 174 calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14 and the future traffic volume at each distributed station 13 (step S006).

[0075] Next, the switching determination unit 175 predicts whether or not future congestion will occur based on the relationship between the future traffic volume at each aggregation station 14 calculated by the prediction unit 172 and a predetermined switching threshold (step S007). Next, if there is an aggregation station 14 where the future traffic volume exceeds the predetermined switching threshold and congestion is determined to occur (step S008, YES), the switching determination unit 175 decides to perform a route switch to distribute the load to links with available bandwidth and determines the communication path after the switch (step S009).

[0076] Next, the switching determination unit 175 issues instructions to each device for route switching to change the aggregation station 14 to which the distributed station 13 is connected (step S010). Specifically, the switching determination unit 175 instructs the aggregation station 14 from which the switching is initiated to release the connection with the distributed station 13, and instructs the aggregation station 14 to which the switching is initiated to establish a connection with the said distributed station 13. Furthermore, the switching instruction device 17 instructs the transfer device 15 to switch routes so that signal transfer is performed via the communication path after the connection destination has been switched.

[0077] This completes the operation of the switching instruction device 17 as shown in the flowchart of Figure 5.

[0078] As described above, the switching instruction device 17 in the first embodiment of the present invention predicts the future traffic volume at each distributed station 13 based on the recent trend (fluctuation) of the traffic volume per terminal station 11 at each distributed station 13. Then, the switching instruction device 17 predicts the future traffic volume at each aggregation station 14 based on the future traffic volume at each distributed station 13. If there is an aggregation station 14 where the future traffic volume exceeds a predetermined switching threshold and congestion is determined to occur, the switching instruction device 17 performs route switching to distribute the load to links with available bandwidth.

[0079] With this configuration, the switching instruction device 17 in the first embodiment of the present invention can predict future traffic volume without having to perform movement predictions for each terminal station 11, even in situations where the number of connected terminals in the coverage area of ​​the distributed station 13 fluctuates randomly due to frequent movement of terminal stations 11. As a result, the switching instruction device 17 can predict in advance whether or not congestion will occur while suppressing an increase in computational load, even in situations where the number of connected terminals in the distributed station 13 fluctuates randomly, thereby realizing low-latency communication.

[0080] <Second Embodiment> A second embodiment of the present invention will be described below.

[0081] [Overall Configuration of the Communication System] The overall configuration of the mobile communication system in the second embodiment (hereinafter referred to as "mobile communication system 10a") is the same as the overall configuration of the mobile communication system 10 in the first embodiment shown in Figure 2 above, so the explanation will be omitted. The mobile communication system 10a is an example of the communication system 1 described above. The mobile communication system 10a in the second embodiment and the mobile communication system 10 in the first embodiment differ in the configuration of the switching instruction device. Hereinafter, the switching instruction device in the second embodiment will be referred to as "switching instruction device 17a".

[0082] [Functional Configuration of the Switching Instruction Device] The functional configuration of the switching instruction device 17a will be described below. Similar to the switching instruction device 17 in the first embodiment described above, the switching instruction device 17a is a device that predicts the future traffic volume at each aggregation station 14, predicts whether or not congestion will occur, and performs control to execute route switching as necessary. However, the switching instruction device 17a in this embodiment and the switching instruction device 17 in the first embodiment described above differ in the processing that predicts the future traffic volume at each distributed station 13, which is a preliminary process to predicting the future traffic volume at each aggregation station 14.

[0083] In the second embodiment, the switching instruction device 17a predicts the future traffic volume at each distributed station 13 based on the traffic volume and number of connected terminals of the distributed station 13 that is the target of future traffic volume prediction (hereinafter referred to as "the distributed station 13 to be predicted") and the traffic volume and number of connected terminals of other distributed stations 13 adjacent to the distributed station 13 in coverage area (hereinafter referred to as "the adjacent distributed station 13").

[0084] More specifically, in the second embodiment, the switching instruction device 17a predicts the future traffic volume at each distributed station 13, taking into account the inflow of terminal stations 11 from adjacent distributed stations 13 to the distributed station 13 to be predicted. Then, the switching instruction device 17 predicts the future traffic volume at each aggregate station 14 based on the future traffic volume at each distributed station 13.

[0085] Figure 6 is a block diagram showing the functional configuration of the switching instruction device 17a in a second embodiment of the present invention. As shown in Figure 6, the switching instruction device 17a is configured to include a prediction unit 172a and a switching determination unit 175. The prediction unit 172a is configured to include a traffic prediction unit 174a.

[0086] The prediction unit 172a receives radio control information from each distributed station 13, which is used to predict the future traffic volume at each distributed station 13. In the second embodiment, the radio control information includes data that associates the most recent traffic volume value at each distributed station 13 with the most recent number of connected terminals at each distributed station 13. The traffic prediction unit 174a of the prediction unit 172a predicts the future traffic volume at each distributed station 13 using the radio control information. At this time, the traffic prediction unit 174a predicts the future traffic volume at each distributed station 13, taking into account the influx of terminal stations 11 into the target distributed station 13 due to the movement of terminal stations 11 from the coverage area of ​​an adjacent distributed station 13 to the coverage area of ​​the target distributed station 13.

[0087] Furthermore, the prediction unit 172a calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14, and the future traffic volume at each distributed station 13. The uplink traffic volume at the aggregate station 14 corresponds to the sum of the uplink traffic volumes received by the aggregate station 14 from each of the distributed stations 13 under its control. The prediction unit 172a outputs information indicating the future traffic volume at each aggregate station 14 to the switching determination unit 175.

[0088] The switching determination unit 175 predicts whether future congestion will occur based on the relationship between the future traffic volume for each aggregation station 14 obtained from the prediction unit 172a and a predetermined switching threshold. The predetermined switching threshold is a value predetermined based on, for example, the bandwidth of the upper link. If the switching determination unit 175 determines that congestion will occur at any aggregation station 14 because the future traffic volume will exceed the bandwidth of the upper link, it decides to perform a route switch to distribute the load to links with available bandwidth. If the switching determination unit 175 decides to perform a route switch, it issues a route switch instruction to each device to change the aggregation station 14 to which the distributed station 13 is connected.

[0089] Specifically, the switching determination unit 175 instructs the source aggregation station 14 to release the connection with the distributed station 13, and instructs the destination aggregation station 14 to establish a connection with the said distributed station 13. Furthermore, the switching determination unit 175 instructs the transfer device 15 to switch routes so that signal transfer takes place via the communication path after the connection destination has been switched.

[0090] [Predicting Future Traffic Volume] The prediction process for future traffic volume at each distributed station 13, performed by the prediction unit 172a, will be explained in more detail below.

[0091] The prediction unit 172a acquires radio control information from each distributed station 13, including the traffic volume and the number of connected terminals at that distributed station 13. The traffic prediction unit 174a of the prediction unit 172a predicts the future traffic volume at the distributed station 13, taking into account the inflow of terminal stations 11 from adjacent distributed stations 13 to the distributed station 13, based on the traffic volume and number of connected terminals of the distributed station 13 to be predicted and the traffic volume and number of connected terminals of the adjacent distributed station 13.

[0092] At this time, the traffic prediction unit 174a predicts the future traffic volume per terminal station 11 in the target distribution station 13 by weighting the ease with which terminal stations 11 can flow in from each adjacent distribution station 13 to the target distribution station 13. The ease with which terminal stations 11 can flow in from each adjacent distribution station 13 to the target distribution station 13 may be determined in advance based on, for example, past movement records of terminal stations 11, or it may be determined based on the distance (positional relationship) between the coverage area of ​​the target distribution station 13 and the terminal station 11. A more specific explanation will be given below with numerical examples.

[0093] Figure 7 is a diagram illustrating the future traffic volume prediction processing by the switching instruction device 17a in the second embodiment of the present invention. Figure 7 shows tabular data where the distributed station ID, traffic volume, number of connected terminals, and traffic volume per terminal station are associated at a certain point in time. The distributed station ID is identification information that identifies the distributed station 13. In other words, Figure 7 shows data for each distributed station 13.

[0094] Furthermore, as an example, we will assume that the target distributed station 13 is the distributed station 13 with distributed station ID "3", and that the coverage area of ​​each distributed station 13 is arranged as shown in Figure 8.

[0095] Figure 8 shows an example of the coverage area of ​​a distributed station 13 in a second embodiment of the present invention. As shown in Figure 8, the coverage area of ​​distributed station 13 with distributed station ID "3" is adjacent to the coverage areas of distributed stations 13 with distributed station IDs "1", "2", and "4", respectively. Therefore, if the distributed station 13 to be predicted is distributed station 13 with distributed station ID "3", then the distributed stations 13 adjacent to it are distributed stations 13 with distributed station IDs "1", "2", and "4".

[0096] The prediction unit 172a acquires wireless control information from each distributed station 13, including the distributed station ID, traffic volume, and number of connected terminals, from the data shown in Figure 7. For example, as shown in Figure 7, the traffic volume at distributed station 13 with distributed station ID "1" is 2.0 [Gbps] and the number of connected terminals is 10 [units]. Also, as shown in Figure 7, the traffic volume at the predicted distributed station 13 with distributed station ID "3" is 2.1 [Gbps] and the number of connected terminals is 12 [units].

[0097] The traffic prediction unit 174a of the prediction unit 172a calculates the traffic volume per terminal station 11 for each distributed station 13 by dividing the traffic volume value by the number of connected terminals.

[0098] Therefore, as shown in Figure 7, the calculated traffic volume per terminal station 11 is 0.2 [Gbps] for distributed station 13 with distributed station ID "1", 0.075 [Gbps] for distributed station 13 with distributed station ID "2", 0.175 [Gbps] for distributed station 13 with distributed station ID "3", 0.12 [Gbps] for distributed station 13 with distributed station ID "4", and 0.14 [Gbps] for distributed station 13 with distributed station ID "5".

[0099] The traffic prediction unit 174 predicts the future traffic volume per terminal station 11 in the target distribution station 13 based on the traffic volume per terminal station 11 in each distribution station 13 calculated in this manner. At this time, the traffic prediction unit 174 predicts the future traffic volume per terminal station 11 in the target distribution station 13 by considering the inflow ratio of terminal stations 11 from adjacent distribution stations 13 to the target distribution station 13.

[0100] Here, as an example, the ratio of terminal stations 11 flowing from an adjacent distributed station 13 to the distributed station 13 being predicted is assumed to be as follows. Note that, as shown below, the number of terminal stations 11 remaining within the coverage area of ​​the distributed station 13 being predicted is not the number of terminals flowing in, but the number of terminal stations 11 remaining within the coverage area of ​​that distributed station 13.

[0101] The ratio of terminals flowing from the adjacent distributed station ID "1" to the predicted distributed station 13 is 2:1:8:1. Note that the ratio of terminal stations 11 flowing from the adjacent distributed station ID "2" to the predicted distributed station 13 is not limited to this and is arbitrary.

[0102] Note that the distributed station 13 with distributed station ID "5" does not fall under the category of adjacent distributed station 13 because its coverage area is not adjacent to that of the distributed station 13 with distribution station ID "3" that is the target of prediction. In this embodiment, the calculation is performed assuming that there is no inflow of terminal stations 11 from distributed stations 13 other than adjacent distributed stations 13 to the distributed station 13 that is the target of prediction.

[0103] The traffic prediction unit 174a predicts the future traffic volume per terminal station 11 in the target distributed station 13 by weighting the numbers of terminals entering the network (and the number of terminals remaining at the target distributed station 13) according to the ratio. As a result, the calculation formula used by the traffic prediction unit 174a to predict the future traffic volume per terminal station 11 in the target distributed station 13 is, for example, equation (2) below.

[0104] Future traffic volume per terminal station 11 = 0.2 × 2 + 0.075 × 1 + 0.175 × 8 + 0.12 × 1 ... (2)

[0105] Based on the wireless control information shown in Figure 7, the value of the future traffic volume per terminal station 11 at the distributed station 13 targeted for prediction of distributed station ID "3" is 0.166 [Gbps] by calculating the above equation (2). The traffic prediction unit 174a can predict the future traffic volume at the distributed station 13 by multiplying this future traffic volume per terminal station 11 by the future number of connected terminals at the distributed station 13.

[0106] Furthermore, the future number of connected terminals may be a value predicted by considering, for example, the inflow ratio of terminal stations 11 to the predicted distributed station 13, or the value of the most recent number of connected terminals at the predicted distributed station 13 (for example, 12 [units] in the case of Figure 7) may be used. Therefore, for example, if the future number of connected terminals is 12 [units], the future traffic volume at the distributed station 13 is predicted to be 1.99 [Gbps] (= 0.166 [Gbps] × 12 [units]).

[0107] In the above, a specific calculation example was described when the distributed station 13 with distributed station ID "3" is the distributed station 13 to be predicted. However, the traffic prediction unit 174a similarly predicts the future traffic volume for distributed stations 13 with distributed station IDs "1", "2", "4", and "5". Then, based on the predicted future traffic volume at each distributed station 13, the traffic prediction unit 174a predicts the future traffic volume at the aggregation station 14.

[0108] In this embodiment, the prediction unit 172a predicts future traffic volume using the traffic volume and number of connected terminals at the distributed station 13 at the most recent time. However, it may also be configured in combination with the configuration described in the first embodiment above. That is, the prediction unit 172a may calculate the amount of change (trend) in traffic volume per terminal station 11 using the traffic volume and number of connected terminals at the distributed station 13 over the past few periods, and further predict future traffic volume considering the inflow ratio of terminal stations 11 to the distributed station 13 to be predicted.

[0109] [Operation of the Switching Instruction Device] An example of the operation of the switching instruction device 17a will be described below. Figure 9 is a flowchart showing the operation of the switching instruction device 17a in the second embodiment of the present invention. The operation of the switching instruction device 17a shown in the flowchart of Figure 9 is repeatedly started at predetermined intervals, for example. That is, the prediction of future traffic volume and the decision to execute route switching based on the prediction result are performed at predetermined intervals.

[0110] First, the prediction unit 172a obtains wireless control information from each distributed station 13, which associates the distributed station ID, traffic volume, and number of connected terminals (step S101). Next, the traffic prediction unit 174a of the prediction unit 172a calculates the traffic volume per terminal station 11 for each distributed station 13 by dividing the traffic volume value by the number of connected terminals (step S102).

[0111] Next, the traffic prediction unit 174a predicts the future traffic volume per terminal station 11 in the target distribution station 13, taking into account the inflow ratio of terminal stations 11 from each adjacent distribution station 13 to the target distribution station 13 (step S103).

[0112] Next, the traffic prediction unit 174a calculates the future traffic volume at each distributed station 13 by multiplying the future traffic volume per terminal station 11 by the future number of connected terminals at that distributed station 13 (step S104). Next, the traffic prediction unit 174a calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14 and the future traffic volume at each distributed station 13 (step S105).

[0113] Next, the switching determination unit 175 predicts whether or not future congestion will occur based on the relationship between the future traffic volume at each aggregation station 14 calculated by the prediction unit 172a and a predetermined switching threshold (step S106). Next, if there is an aggregation station 14 where the future traffic volume exceeds the predetermined switching threshold and congestion is determined to occur (step S107, YES), the switching determination unit 175 decides to perform a route switch to distribute the load to links with available bandwidth and determines the communication path after the switch (step S108).

[0114] Next, the switching determination unit 175 issues instructions to each device for route switching to change the aggregate station 14 to which the distributed station 13 is connected (step S109). Specifically, the switching determination unit 175 instructs the source aggregate station 14 to release the connection with the distributed station 13 and instructs the destination aggregate station 14 to connect with the said distributed station 13. Furthermore, the switching instruction device 17 instructs the transfer device 15 to switch routes so that signal transfer is carried out via the communication path after the connection destination switch.

[0115] This completes the operation of the switching instruction device 17a as shown in the flowchart of Figure 9.

[0116] As described above, the switching instruction device 17a in the second embodiment of the present invention predicts the traffic volume per terminal station 11 at the distribution station 13 to be predicted, taking into account the inflow ratio of terminal stations 11 from each adjacent distribution station 13, and predicts the future traffic volume at each distribution station 13. Then, the switching instruction device 17a predicts the future traffic volume at each aggregation station 14 based on the future traffic volume at each distribution station 13. If there is an aggregation station 14 where the future traffic volume exceeds a predetermined switching threshold and congestion is determined to occur, the switching instruction device 17a performs route switching to distribute the load to links with available bandwidth.

[0117] With this configuration, the switching instruction device 17a in the second embodiment of the present invention can predict future traffic volume without performing movement predictions for each terminal station 11, even in situations where the number of connected terminals in the coverage area of ​​the distributed station 13 fluctuates randomly due to frequent movement of terminal stations 11. As a result, the switching instruction device 17a can predict in advance whether or not congestion will occur while suppressing an increase in computational load, even in situations where the number of connected terminals in the distributed station 13 fluctuates randomly, thereby realizing low-latency communication.

[0118] <Third Embodiment> A third embodiment of the present invention will be described below.

[0119] [Overall Configuration of the Communication System] The overall configuration of the mobile communication system in the third embodiment (hereinafter referred to as "mobile communication system 10b") is the same as the overall configuration of the mobile communication system 10 in the first embodiment shown in Figure 2 above, so the explanation will be omitted. The mobile communication system 10b is an example of the communication system 1 described above. The mobile communication system 10b in the third embodiment and the mobile communication system 10 in the first embodiment differ in the configuration of the switching instruction device. Hereinafter, the switching instruction device in the third embodiment will be referred to as "switching instruction device 17b".

[0120] [Functional Configuration of the Switching Instruction Device] The functional configuration of the switching instruction device 17b will be described below. Similar to the switching instruction device 17 in the first embodiment described above, the switching instruction device 17b is a device that predicts the future traffic volume at each aggregation station 14, predicts whether or not congestion will occur, and performs control to execute route switching as necessary. However, the switching instruction device 17b and the switching instruction device 17 in the first embodiment described above differ in the processing that predicts the future traffic volume at each distributed station 13, which is a preliminary process to predicting the future traffic volume at each aggregation station 14.

[0121] In the third embodiment, the switching instruction device 17b predicts the movement of terminal stations 11 based on the amount of change in the position of each terminal station 11 located within the coverage area of ​​the distribution station 13 to be predicted, and each terminal station 11 located around the said coverage area. Based on the movement prediction, the switching instruction device 17b predicts the future number of connected terminals within the coverage area of ​​the distribution station 13 to be predicted, and predicts the future traffic volume at each distribution station 13 based on the traffic volume at each distribution station 13 and the predicted number of connected terminals. Based on the future traffic volume at each distribution station 13, the switching instruction device 17b predicts the future traffic volume at each aggregation station 14.

[0122] Figure 10 is a block diagram showing the functional configuration of the switching instruction device 17b in a third embodiment of the present invention. As shown in Figure 10, the switching instruction device 17b is configured to include a prediction unit 172b and a switching determination unit 175. The prediction unit 172b is configured to include a future position estimation unit 173b and a traffic prediction unit 174b.

[0123] The prediction unit 172b receives radio control information from each distributed station 13, which is used to predict future traffic volume at each distributed station 13. In the third embodiment, the radio control information includes the most recent traffic volume value at each distributed station 13 and the location information of each terminal station 11 within the coverage area of ​​the distributed station 13.

[0124] The future position estimation unit 173b of the prediction unit 172b uses the position information for each terminal station 11 included in the radio control information to predict the movement of each terminal station 11 and estimate the number of connected terminals for each distributed station 13 in the future. Specifically, the future position estimation unit 173b identifies the position of each terminal station 11 located within the coverage area of ​​the distributed station 13 and in the surrounding area, based on the position information for each terminal station 11 included in the radio control information.

[0125] The location of each terminal station 11 located within the coverage area of ​​a distributed station 13 is determined based on radio control information obtained from that distributed station 13. Furthermore, the location of each terminal station 11 located in the area surrounding the coverage area of ​​a distributed station 13 is determined based on radio control information obtained from an adjacent distributed station 13.

[0126] The surrounding area referred to here is the range in which the terminal station 11 can enter the coverage area of ​​the distributed station 13 from the outside during the period to be predicted. For example, if the coverage area is a circular area centered on the location of the distributed station 13, then the area within the coverage area and its surroundings referred to here would be, for example, the area within a predetermined distance from the location of the distributed station 13 (for example, within a radius of several kilometers), or a circular area centered on the location of the distributed station 13 with a radius 1.2 times the radius of the coverage area.

[0127] The future location estimation unit 173b performs the above process to identify the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area, for each distributed station 13. The future location estimation unit 173b also performs the above process to identify the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area at predetermined unit intervals.

[0128] The future position estimation unit 173b then calculates the amount of change in the position of each terminal station 11 (for example, the amount of change in the distance traveled and the direction of travel for each terminal station 11). Based on the calculated change amounts, the future position estimation unit 173b estimates the future position of each terminal station 11. The future position estimation unit 173b outputs position information indicating the estimated future position of each terminal station 11 to the traffic prediction unit 174b.

[0129] The future position of each terminal station 11 may be estimated, for example, by using the fluctuation amount in the most recent unit period as the predicted value of the future fluctuation amount, or by using the average value of the fluctuation amounts over multiple past unit periods as the predicted value of the future fluctuation amount.

[0130] The traffic prediction unit 174b of the prediction unit 172b obtains location information indicating the future location of each terminal station 11 from the future location estimation unit 173b. Based on the future location of each terminal station 11 estimated by the future location estimation unit 173b, the traffic prediction unit 174b calculates the future number of connected terminals for each distributed station 13.

[0131] The traffic prediction unit 174b predicts the future traffic volume at each distributed station 13 based on the calculated future number of connected terminals at each distributed station 13. For example, the traffic prediction unit 174b predicts the future traffic volume by multiplying the value of the most recent traffic volume at each distributed station 13 by the ratio of the number of future connected terminals to the number of recent connected terminals.

[0132] Furthermore, the prediction unit 172b calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14, and the future traffic volume at each distributed station 13. The uplink traffic volume at the aggregate station 14 corresponds to the sum of the uplink traffic volumes received by the aggregate station 14 from each of the distributed stations 13 under its control. The prediction unit 172b outputs information indicating the future traffic volume at each aggregate station 14 to the switching determination unit 175.

[0133] The switching determination unit 175 predicts whether future congestion will occur based on the relationship between the future traffic volume for each aggregation station 14 obtained from the prediction unit 172b and a predetermined switching threshold. The predetermined switching threshold is a value predetermined based on, for example, the bandwidth of the upper link. If the switching determination unit 175 determines that congestion will occur at any aggregation station 14 because the future traffic volume will exceed the bandwidth of the upper link, it decides to perform a route switch to distribute the load to links with available bandwidth. If the switching determination unit 175 decides to perform a route switch, it issues a route switch instruction to each device to change the aggregation station 14 to which the distributed station 13 is connected.

[0134] Specifically, the switching determination unit 175 instructs the source aggregation station 14 to release the connection with the distributed station 13, and instructs the destination aggregation station 14 to establish a connection with the said distributed station 13. Furthermore, the switching determination unit 175 instructs the transfer device 15 to switch routes so that signal transfer takes place via the communication path after the connection destination has been switched.

[0135] [Operation of the Switching Instruction Device] An example of the operation of the switching instruction device 17b will be described below. Figure 11 is a flowchart showing the operation of the switching instruction device 17b in the third embodiment of the present invention. The operation of the switching instruction device 17b shown in the flowchart of Figure 11 is repeatedly started at predetermined intervals, for example. That is, the prediction of future traffic volume and the decision to execute route switching based on the prediction result are performed at predetermined intervals.

[0136] First, the prediction unit 172b obtains radio control information from each distributed station 13, which includes the most recent traffic volume value at the distributed station 13 and the location information of each terminal station 11 within the coverage area of ​​the distributed station 13 (step S201). Next, the future location estimation unit 173b of the prediction unit 172b identifies the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding areas, based on the location information of each terminal station 11 included in the radio control information (step S202).

[0137] Next, the future position estimation unit 173b calculates the amount of change in the position of each terminal station 11 (for example, the amount of change in the distance traveled and the direction of travel for each terminal station 11) (step S203). Next, the future position estimation unit 173b estimates the future position of each terminal station 11 based on the calculated amount of change (step S204).

[0138] Next, the traffic prediction unit 174b of the prediction unit 172b calculates the future number of connected terminals for each distributed station 13 based on the future location of each terminal station 11 estimated by the future location estimation unit 173b (step S205).

[0139] Next, the traffic prediction unit 174b predicts the future traffic volume at each distributed station 13 based on the calculated future number of connected terminals at each distributed station 13 (step S206). For example, the traffic prediction unit 174b predicts the future traffic volume by multiplying the value of the most recent traffic volume at each distributed station 13 by the ratio of the number of future connected terminals to the number of recent connected terminals.

[0140] Next, the traffic prediction unit 174b calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14, and the future traffic volume at each distributed station 13 (step S207).

[0141] Next, the switching determination unit 175 predicts whether or not future congestion will occur based on the relationship between the future traffic volume at each aggregation station 14 calculated by the prediction unit 172b and a predetermined switching threshold (step S208). Next, if there is an aggregation station 14 where the future traffic volume exceeds the predetermined switching threshold and congestion is determined to occur (step S209, YES), the switching determination unit 175 decides to perform a route switch to distribute the load to links with available bandwidth and determines the communication path after the switch (step S210).

[0142] Next, the switching determination unit 175 issues instructions to each device for route switching to change the aggregation station 14 to which the distributed station 13 is connected (step S211). Specifically, the switching determination unit 175 instructs the aggregation station 14 from which the switching is initiated to release the connection with the distributed station 13, and instructs the aggregation station 14 to which the switching is initiated to establish a connection with the said distributed station 13. Furthermore, the switching instruction device 17 instructs the transfer device 15 to switch routes so that signal transfer is performed through the communication path after the connection destination has been switched.

[0143] This completes the operation of the switching instruction device 17b as shown in the flowchart of Figure 11.

[0144] As described above, in the third embodiment of the present invention, the switching instruction device 17b estimates the future location of each terminal station 11 based on the location information of each terminal station 11 located within the coverage area of ​​each distributed station 13 and in the surrounding area. Based on the estimated future location of each terminal station 11, the switching instruction device 17b estimates the future number of connected terminals at each distributed station 13. Based on the recent traffic volume at each distributed station 13, the recent number of connected terminals, and the estimated future number of connected terminals, the switching instruction device 17b predicts the future traffic volume at each distributed station 13.

[0145] The switching instruction device 17b then predicts the future traffic volume at each aggregation station 14 based on the future traffic volume at each distributed station 13. If the switching instruction device 17b determines that there is an aggregation station 14 where the future traffic volume exceeds a predetermined switching threshold and congestion will occur, it will perform a route switch to distribute the load to a link with available bandwidth.

[0146] Furthermore, in this third embodiment, the switching instruction device 17b performs movement prediction only for terminal stations 11 located within the coverage area of ​​each distributed station 13 and its surrounding areas. Therefore, compared to the case where movement prediction is performed for all terminal stations 11, including terminal stations 11 located in other areas, the increase in computational load can be suppressed.

[0147] With this configuration, the switching instruction device 17b in the third embodiment of the present invention can predict future traffic volume without needing to predict the movement of all terminal stations 11, even in situations where the number of connected terminals in the coverage area of ​​the distributed station 13 fluctuates randomly due to, for example, frequent movement of terminal stations 11. As a result, the switching instruction device 17b can predict in advance whether or not congestion will occur while suppressing an increase in computational load, even in situations where the number of connected terminals in the distributed station 13 fluctuates randomly, thereby realizing low-latency communication.

[0148] <Fourth Embodiment> A fourth embodiment of the present invention will be described below.

[0149] The switching instruction device 17b in the third embodiment described above performed movement prediction only for terminal stations 11 located within the coverage area of ​​each distributed station 13 and its surrounding areas, thereby limiting movement prediction to only a portion of terminal stations 11. In contrast, the switching instruction device in the fourth embodiment described below (hereinafter referred to as "switching instruction device 17c") has a configuration that further limits the number of terminal stations 11 for which movement prediction is performed, thereby reducing the computational load. Specifically, the switching instruction device 17c in the fourth embodiment further narrows the target to only terminal stations 11 with high required quality (high priority) among the terminal stations 11 located within the coverage area of ​​each distributed station 13 and its surrounding areas, and performs movement prediction.

[0150] [Overall Configuration of the Communication System] The overall configuration of the mobile communication system in the fourth embodiment (hereinafter referred to as "mobile communication system 10c") is the same as the overall configuration of the mobile communication system 10 in the first embodiment shown in Figure 2 above, so the explanation will be omitted. The mobile communication system 10c is an example of the communication system 1 described above. The mobile communication system 10c in the fourth embodiment and the mobile communication system 10 in the first embodiment differ in the configuration of the switching instruction device.

[0151] [Functional Configuration of the Switching Instruction Device] The functional configuration of the switching instruction device 17c will be described below. Similar to the switching instruction device 17 in the first embodiment described above, the switching instruction device 17c is a device that predicts the future traffic volume at each aggregation station 14, predicts whether or not congestion will occur, and performs control to execute route switching as necessary. However, the switching instruction device 17c and the switching instruction device 17 in the first embodiment described above differ in the processing that predicts the future traffic volume at each distributed station 13, which is a preliminary process to predicting the future traffic volume at each aggregation station 14.

[0152] In the fourth embodiment, the switching instruction device 17c identifies the required quality (priority) for each terminal station 11 located within the coverage area of ​​the distributed station 13 to be predicted, and in the vicinity of said coverage area.

[0153] The required quality specified here includes, for example, the delay requirement level and the priority level of QoS (Quality of Service). The priority level of QoS, as used here, refers to, for example, the 5QI (5G network Quality of service class Identifier) ​​value. However, the required quality (priority) used is not limited to this information; any information can be used as long as a priority level can be set.

[0154] The switching instruction device 17c targets terminal stations 11 whose specified required quality (priority) is higher than a predetermined required quality for movement prediction. On the other hand, the switching instruction device 17c does not perform movement prediction for terminal stations 11 whose specified required quality is lower than or equal to a predetermined required quality, and considers their current position to be their future position (i.e., terminal stations 11 with low required quality are considered not to move).

[0155] The switching instruction device 17c predicts the movement of each terminal station 11 that is the target of the movement prediction, based on the amount of change in their respective positions. Based on the movement prediction, the switching instruction device 17c predicts the future number of connected terminals within the coverage area of ​​the target distributed station 13, and predicts the future traffic volume at each distributed station 13 based on the traffic volume at each distributed station 13 and the predicted number of connected terminals. Then, based on the future traffic volume at each distributed station 13, the switching instruction device 17c predicts the future traffic volume at each aggregation station 14.

[0156] Figure 12 is a block diagram showing the functional configuration of the switching instruction device 17c in a fourth embodiment of the present invention. As shown in Figure 12, the switching instruction device 17c is configured to include a prediction unit 172c and a switching determination unit 175. The prediction unit 172c is configured to include a future position estimation unit 173c and a traffic prediction unit 174c.

[0157] The prediction unit 172c receives radio control information from each distributed station 13, which is used to predict the future traffic volume at each distributed station 13. The radio control information in the fourth embodiment includes the most recent traffic volume value at each distributed station 13, location information of each terminal station 11 within the coverage area of ​​the distributed station 13, and information indicating the required quality (priority) for each terminal station 11 (hereinafter referred to as "required quality information").

[0158] The future position estimation unit 173c of the prediction unit 172c uses the position information for each terminal station 11 included in the radio control information to predict the movement of each terminal station 11 and estimate the number of connected terminals for each distributed station 13 in the future. Specifically, the future position estimation unit 173c identifies the position of each terminal station 11 located within the coverage area of ​​the distributed station 13 and in the surrounding area, based on the position information for each terminal station 11 included in the radio control information.

[0159] The future location estimation unit 173c performs the above process to identify the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area, for each distributed station 13. The future location estimation unit 173c also performs the above process to identify the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area at predetermined unit intervals.

[0160] Furthermore, the future position estimation unit 173c identifies the required quality (priority) for each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding areas, based on the required quality information included in the wireless control information. The future position estimation unit 173c targets terminal stations 11 whose identified required quality is higher than a predetermined required quality for movement prediction. On the other hand, the switching instruction device 17c does not perform movement prediction for terminal stations 11 whose identified required quality is below a predetermined required quality, and considers their current position to be their future position.

[0161] The future location estimation unit 173c then calculates the amount of change in the location of each terminal station 11 (for example, the amount of change in the distance traveled and the direction of travel for each terminal station 11) for only the terminal stations 11 that have been narrowed down according to the required quality (priority). Based on the calculated change amounts, the future location estimation unit 173c estimates the future location of each terminal station 11. For terminal stations 11 with high required quality, the future location estimation unit 173c outputs location information indicating the estimated future location of each terminal station 11, and for terminal stations 11 with low required quality, it outputs location information indicating the current location (as location information indicating the future location) to the traffic prediction unit 174c.

[0162] The future position of each terminal station 11 may be estimated, for example, by using the fluctuation amount in the most recent unit period as the predicted value of the future fluctuation amount, or by using the average value of the fluctuation amounts over multiple past unit periods as the predicted value of the future fluctuation amount.

[0163] The traffic prediction unit 174c of the prediction unit 172c obtains location information indicating the future location of each terminal station 11 from the future location estimation unit 173c. Based on the obtained future locations of each terminal station 11, the traffic prediction unit 174c calculates the future number of connected terminals for each distributed station 13.

[0164] The traffic prediction unit 174c predicts the future traffic volume at each distributed station 13 based on the calculated future number of connected terminals at each distributed station 13. For example, the traffic prediction unit 174c predicts the future traffic volume by multiplying the value of the most recent traffic volume at each distributed station 13 by the ratio of the number of future connected terminals to the number of recent connected terminals.

[0165] Furthermore, the prediction unit 172c calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14, and the future traffic volume at each distributed station 13. The uplink traffic volume at the aggregate station 14 corresponds to the sum of the uplink traffic volumes received by the aggregate station 14 from each of the distributed stations 13 under its control. The prediction unit 172c outputs information indicating the future traffic volume at each aggregate station 14 to the switching determination unit 175.

[0166] The switching determination unit 175 predicts whether future congestion will occur based on the relationship between the future traffic volume for each aggregation station 14 obtained from the prediction unit 172c and a predetermined switching threshold. The predetermined switching threshold is a value predetermined based on, for example, the bandwidth of the upper link. If the switching determination unit 175 determines that congestion will occur at any aggregation station 14 because the future traffic volume will exceed the bandwidth of the upper link, it decides to perform a route switch to distribute the load to links with available bandwidth. If the switching determination unit 175 decides to perform a route switch, it issues a route switch instruction to each device to change the aggregation station 14 to which the distributed station 13 is connected.

[0167] Specifically, the switching determination unit 175 instructs the source aggregation station 14 to release the connection with the distributed station 13, and instructs the destination aggregation station 14 to establish a connection with the said distributed station 13. Furthermore, the switching determination unit 175 instructs the transfer device 15 to switch routes so that signal transfer takes place via the communication path after the connection destination has been switched.

[0168] [Operation of the Switching Instruction Device] An example of the operation of the switching instruction device 17c will be described below. Figure 13 is a flowchart showing the operation of the switching instruction device 17c in the fourth embodiment of the present invention. The operation of the switching instruction device 17c shown in the flowchart of Figure 13 is repeatedly started at predetermined intervals, for example. That is, the prediction of future traffic volume and the decision to execute route switching based on the prediction result are performed at predetermined intervals.

[0169] First, the prediction unit 172c obtains radio control information from each distributed station 13, which includes the most recent traffic volume value at the distributed station 13, the location information of each terminal station 11 within the coverage area of ​​the distributed station 13, and the required quality information for each terminal station 11 (step S301). Next, the future location estimation unit 173c of the prediction unit 172c identifies the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding areas, based on the location information for each terminal station 11 included in the radio control information (step S302).

[0170] Next, the future position estimation unit 173c identifies the required quality (priority) for each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding areas, based on the required quality information included in the radio control information (step S303).

[0171] Next, the future position estimation unit 173c determines whether it is necessary to estimate the future position of each terminal station 11 based on the specified required quality (step S304). Specifically, the future position estimation unit 173c determines that terminal stations 11 whose specified required quality is higher than a predetermined required quality are targets for movement prediction. On the other hand, the switching instruction device 17c does not perform movement prediction for terminal stations 11 whose specified required quality is below a predetermined required quality, and considers the current position to be the future position.

[0172] Next, the future location estimation unit 173c calculates the amount of change in the location of each terminal station 11 (for example, the amount of change in the distance traveled and the direction of travel for each terminal station 11) for only the terminal stations 11 that have been narrowed down according to the required quality (priority) (step S305). Next, the future location estimation unit 173c estimates the future location of each terminal station 11 based on the calculated amount of change (step S306). For terminal stations 11 with high required quality, the future location estimation unit 173c outputs location information indicating the estimated future location of each terminal station 11, and for terminal stations 11 with low required quality, it outputs location information indicating the current location (as location information indicating the future location) to the traffic prediction unit 174c.

[0173] Next, the traffic prediction unit 174c of the prediction unit 172c calculates the future number of connected terminals at each distributed station 13 based on the future location of each terminal station 11 obtained (step S307).

[0174] Next, the traffic prediction unit 174c predicts the future traffic volume at each distributed station 13 based on the calculated future number of connected terminals at each distributed station 13 (step S308). For example, the traffic prediction unit 174c predicts the future traffic volume by multiplying the value of the most recent traffic volume at each distributed station 13 by the ratio of the future number of connected terminals to the most recent number of connected terminals.

[0175] Next, the traffic prediction unit 174c calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14, and the future traffic volume at each distributed station 13 (step S309).

[0176] Next, the switching determination unit 175 predicts whether or not future congestion will occur based on the relationship between the future traffic volume at each aggregation station 14 calculated by the prediction unit 172c and a predetermined switching threshold (step S310). Next, if there is an aggregation station 14 where the future traffic volume exceeds the predetermined switching threshold and congestion is determined to occur (step S311, YES), the switching determination unit 175 decides to perform a route switch to distribute the load to links with available bandwidth and determines the communication path after the switch (step S312).

[0177] Next, the switching determination unit 175 issues instructions to each device for route switching to change the aggregation station 14 to which the distributed station 13 is connected (step S313). Specifically, the switching determination unit 175 instructs the aggregation station 14 from which the switching is initiated to release the connection with the distributed station 13, and instructs the aggregation station 14 to which the switching is initiated to establish a connection with the said distributed station 13. Furthermore, the switching instruction device 17 instructs the transfer device 15 to switch routes so that signal transfer is performed via the communication path after the connection destination has been switched.

[0178] This completes the operation of the switching instruction device 17c as shown in the flowchart of Figure 13.

[0179] As described above, in the fourth embodiment of the present invention, the switching instruction device 17c estimates the future location of each terminal station 11 based on the location information of each terminal station 11 located within the coverage area of ​​each distributed station 13 and in the surrounding area. At this time, the switching instruction device 17c estimates the future location only for terminal stations 11 with high required quality (priority), and omits the future location estimation process for terminal stations 11 with low required quality, considering their current location as their future location. Based on the estimated future location of each terminal station 11, the switching instruction device 17c estimates the future number of connected terminals at each distributed station 13. Based on the recent traffic volume at each distributed station 13, the recent number of connected terminals, and the estimated future number of connected terminals, the switching instruction device 17c predicts the future traffic volume at each distributed station 13.

[0180] The switching instruction device 17c then predicts the future traffic volume at each aggregation station 14 based on the future traffic volume at each distributed station 13. If the switching instruction device 17c determines that there is an aggregation station 14 where the future traffic volume exceeds a predetermined switching threshold and congestion will occur, it will perform a route switch to distribute the load to a link with available bandwidth.

[0181] Furthermore, in this fourth embodiment, the switching instruction device 17c focuses on predicting movement only for terminal stations 11 with high required quality (priority), thus reducing the increase in computational load compared to the case where movement prediction is performed for all terminal stations 11.

[0182] With this configuration, the switching instruction device 17c in the fourth embodiment of the present invention can predict future traffic volume without needing to predict the movement of all terminal stations 11, even in situations where the number of connected terminals in the coverage area of ​​the distributed station 13 fluctuates randomly due to, for example, frequent movement of terminal stations 11. As a result, the switching instruction device 17c can predict in advance whether or not congestion will occur while suppressing an increase in computational load, even in situations where the number of connected terminals in the distributed station 13 fluctuates randomly, thereby realizing low-latency communication.

[0183] <Fifth Embodiment> A fifth embodiment of the present invention will be described below.

[0184] The switching instruction device 17b in the third embodiment described above performed movement prediction only for terminal stations 11 located within the coverage area of ​​each distributed station 13 and its surrounding areas, thereby limiting movement prediction to only a portion of terminal stations 11. In contrast, the switching instruction device in the fifth embodiment described below (hereinafter referred to as "switching instruction device 17d") has a configuration that further limits the number of terminal stations 11 for which movement prediction is performed, thereby reducing the computational load. Specifically, the switching instruction device 17d in the fifth embodiment further narrows the target to only terminal stations 11 with a large recent change in position (amount of movement) among the terminal stations 11 located within the coverage area of ​​each distributed station 13 and its surrounding areas, and performs movement prediction.

[0185] [Overall Configuration of the Communication System] The overall configuration of the mobile communication system in the fifth embodiment (hereinafter referred to as "mobile communication system 10d") is the same as the overall configuration of the mobile communication system 10 in the first embodiment shown in Figure 2 above, so the explanation will be omitted. The mobile communication system 10d is an example of the communication system 1 described above. The mobile communication system 10d in the fifth embodiment and the mobile communication system 10 in the first embodiment differ in the configuration of the switching instruction device.

[0186] [Functional Configuration of the Switching Instruction Device] The functional configuration of the switching instruction device 17d will be described below. Similar to the switching instruction device 17 in the first embodiment described above, the switching instruction device 17d is a device that predicts the future traffic volume at each aggregation station 14, predicts whether or not congestion will occur, and controls the execution of route switching as necessary. However, the switching instruction device 17d and the switching instruction device 17 in the first embodiment described above differ in the processing that predicts the future traffic volume at each distributed station 13, which is a preliminary process to predicting the future traffic volume at each aggregation station 14.

[0187] In the fifth embodiment, the switching instruction device 17d calculates the amount of positional variation in a direct return for each terminal station 11 located within the coverage area of ​​the distributed station 13 to be predicted, and in the vicinity of said coverage area. The switching instruction device 17d targets terminal stations 11 for which the calculated variation amount is higher than a predetermined variation amount for movement prediction. On the other hand, the switching instruction device 17d does not perform movement prediction for terminal stations 11 for which the identified variation amount is less than or equal to the predetermined variation amount, and considers their current position to be their future position (i.e., terminal stations 11 with little movement are considered not to move).

[0188] The switching instruction device 17d predicts the movement of each terminal station 11 that is the target of the movement prediction, based on the amount of change in their respective positions. Based on the movement prediction, the switching instruction device 17d predicts the future number of connected terminals within the coverage area of ​​the distribution station 13 that is the target of the prediction, and predicts the future traffic volume at each distribution station 13 based on the traffic volume at each distribution station 13 and the predicted number of connected terminals. Then, based on the future traffic volume at each distribution station 13, the switching instruction device 17d predicts the future traffic volume at each aggregation station 14.

[0189] Figure 14 is a block diagram showing the functional configuration of the switching instruction device 17d in a fifth embodiment of the present invention. As shown in Figure 14, the switching instruction device 17d is configured to include a prediction unit 172d and a switching determination unit 175. The prediction unit 172d is configured to include a future position estimation unit 173d and a traffic prediction unit 174d.

[0190] The prediction unit 172d receives radio control information from each distributed station 13, which is used to predict future traffic volume at each distributed station 13. In the fifth embodiment, the radio control information includes the most recent traffic volume value at each distributed station 13 and the location information of each terminal station 11 within the coverage area of ​​the distributed station 13.

[0191] The future position estimation unit 173d of the prediction unit 172d uses the position information for each terminal station 11 included in the radio control information to predict the movement of each terminal station 11 and estimate the number of connected terminals for each distributed station 13 in the future. Specifically, the future position estimation unit 173d identifies the position of each terminal station 11 located within the coverage area of ​​the distributed station 13 and in the surrounding area, based on the position information for each terminal station 11 included in the radio control information.

[0192] The future location estimation unit 173d performs the above process to identify the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area, for each distributed station 13. The future location estimation unit 173d also performs the above process to identify the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area at predetermined unit intervals.

[0193] The future position estimation unit 173d calculates the amount of change in the position of each terminal station 11 (for example, the amount of change in the distance traveled and the direction of travel for each terminal station 11) based on the position information of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding areas. The future position estimation unit 173d then determines that terminal stations 11 whose calculated change amount is greater than a predetermined change amount are subject to movement prediction. On the other hand, the future position estimation unit 173d does not perform movement prediction for terminal stations 11 whose calculated change amount is less than or equal to the predetermined change amount, and considers their current position to be their future position.

[0194] The future position estimation unit 173d estimates the future position of each terminal station 11 that has been targeted for movement prediction, based on the recent change in the position of the terminal station 11 calculated above. For terminal stations 11 for which movement prediction has been performed, the future position estimation unit 173d outputs position information indicating the estimated future position of each terminal station 11, and for terminal stations 11 for which movement prediction has not been performed, it outputs position information indicating the current position (as position information indicating the future position) to the traffic prediction unit 174d.

[0195] The future position of each terminal station 11 may be estimated, for example, by using the fluctuation amount in the most recent unit period as the predicted value of the future fluctuation amount, or by using the average value of the fluctuation amounts over multiple past unit periods as the predicted value of the future fluctuation amount.

[0196] The traffic prediction unit 174d of the prediction unit 172d obtains location information indicating the future location of each terminal station 11 from the future location estimation unit 173d. Based on the obtained future locations of each terminal station 11, the traffic prediction unit 174d calculates the future number of connected terminals for each distributed station 13.

[0197] The traffic prediction unit 174d predicts the future traffic volume at each distributed station 13 based on the calculated future number of connected terminals at each distributed station 13. For example, the traffic prediction unit 174d predicts the future traffic volume by multiplying the value of the most recent traffic volume at each distributed station 13 by the ratio of the number of future connected terminals to the number of recent connected terminals.

[0198] Furthermore, the prediction unit 172d calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14, and the future traffic volume at each distributed station 13. The uplink traffic volume at the aggregate station 14 corresponds to the sum of the uplink traffic volumes received by the aggregate station 14 from each of the distributed stations 13 under its control. The prediction unit 172d outputs information indicating the future traffic volume at each aggregate station 14 to the switching determination unit 175.

[0199] The switching determination unit 175 predicts whether future congestion will occur based on the relationship between the future traffic volume for each aggregation station 14 obtained from the prediction unit 172d and a predetermined switching threshold. The predetermined switching threshold is a value predetermined based on, for example, the bandwidth of the upper link. If the switching determination unit 175 determines that congestion will occur at any aggregation station 14 because the future traffic volume will exceed the bandwidth of the upper link, it decides to perform a route switch to distribute the load to links with available bandwidth. If the switching determination unit 175 decides to perform a route switch, it issues a route switch instruction to each device to change the aggregation station 14 to which the distributed station 13 is connected.

[0200] Specifically, the switching determination unit 175 instructs the source aggregation station 14 to release the connection with the distributed station 13, and instructs the destination aggregation station 14 to establish a connection with the said distributed station 13. Furthermore, the switching determination unit 175 instructs the transfer device 15 to switch routes so that signal transfer takes place via the communication path after the connection destination has been switched.

[0201] [Operation of the Switching Instruction Device] An example of the operation of the switching instruction device 17d will be described below. Figure 15 is a flowchart showing the operation of the switching instruction device 17d in the fifth embodiment of the present invention. The operation of the switching instruction device 17d shown in the flowchart of Figure 15 is repeatedly started at predetermined intervals, for example. That is, the prediction of future traffic volume and the decision to execute route switching based on the prediction result are performed at predetermined intervals.

[0202] First, the prediction unit 172d obtains radio control information from each distributed station 13, which includes the most recent traffic volume value at the distributed station 13 and the location information of each terminal station 11 within the coverage area of ​​the distributed station 13 (step S401). Next, the future location estimation unit 173d of the prediction unit 172d identifies the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding areas, based on the location information of each terminal station 11 included in the radio control information (step S402).

[0203] Next, the future position estimation unit 173d calculates the amount of change in the position of each terminal station 11 (for example, the amount of change in the distance traveled and the direction of travel for each terminal station 11) based on the position information of each terminal station 11 located within the coverage area of ​​the distributed station 13 and the surrounding area. (Step S403).

[0204] Next, the future position estimation unit 173d determines whether it is necessary to estimate the future position of each terminal station 11 based on the calculated amount of change in the position of the terminal station 11 (step S404). Specifically, the future position estimation unit 173d determines that terminal stations 11 whose calculated change is greater than a predetermined change amount are subject to movement prediction. On the other hand, the future position estimation unit 173d does not perform movement prediction for terminal stations 11 whose calculated change is less than or equal to a predetermined change amount, and considers their current position to be their future position.

[0205] Next, the future location estimation unit 173d estimates the future location of each terminal station 11 based on the calculated fluctuation amount, focusing only on the terminal stations 11 that have been narrowed down according to the fluctuation amount of their most recent location (step S405). The future location estimation unit 173d outputs location information indicating the estimated future location of each terminal station 11 for terminal stations 11 with a large fluctuation amount of their most recent location, and location information indicating the current location for terminal stations 11 with a small fluctuation amount of their most recent location (as location information indicating the future location) to the traffic prediction unit 174d.

[0206] Next, the traffic prediction unit 174d of the prediction unit 172d calculates the future number of connected terminals at each distributed station 13 based on the future location of each terminal station 11 obtained (step S406).

[0207] Next, the traffic prediction unit 174d predicts the future traffic volume at each distributed station 13 based on the calculated future number of connected terminals at each distributed station 13 (step S407). For example, the traffic prediction unit 174d predicts the future traffic volume by multiplying the value of the most recent traffic volume at each distributed station 13 by the ratio of the number of future connected terminals to the number of recent connected terminals.

[0208] Next, the traffic prediction unit 174d calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14, and the future traffic volume at each distributed station 13 (step S408).

[0209] Next, the switching determination unit 175 predicts whether or not future congestion will occur based on the relationship between the future traffic volume at each aggregation station 14 calculated by the prediction unit 172d and a predetermined switching threshold (step S409). Next, if there is an aggregation station 14 where the future traffic volume exceeds the predetermined switching threshold and congestion is determined to occur (step S410, YES), the switching determination unit 175 decides to perform a route switch to distribute the load to links with available bandwidth and determines the communication path after the switch (step S411).

[0210] Next, the switching determination unit 175 issues instructions to each device for route switching to change the aggregate station 14 to which the distributed station 13 is connected (step S412). Specifically, the switching determination unit 175 instructs the source aggregate station 14 to release the connection with the distributed station 13, and instructs the destination aggregate station 14 to connect with the said distributed station 13. Furthermore, the switching instruction device 17 instructs the transfer device 15 to switch routes so that signal transfer is carried out via the communication path after the connection destination switch.

[0211] This completes the operation of the switching instruction device 17d as shown in the flowchart of Figure 15.

[0212] As described above, in the fifth embodiment of the present invention, the switching instruction device 17d estimates the future location of each terminal station 11 based on the location information of each terminal station 11 located within the coverage area of ​​each distributed station 13 and in the surrounding area. At this time, the switching instruction device 17d estimates the future location only for terminal stations 11 with a large recent change in location (recent movement), and omits the future location estimation process for terminal stations 11 with a small recent change in location (recent movement), considering their current location as their future location. Based on the estimated future location of each terminal station 11, the switching instruction device 17d estimates the future number of connected terminals at each distributed station 13. Based on the recent traffic volume at each distributed station 13, the recent number of connected terminals, and the estimated future number of connected terminals, the switching instruction device 17d predicts the future traffic volume at each distributed station 13.

[0213] The switching instruction device 17d then predicts the future traffic volume at each aggregation station 14 based on the future traffic volume at each distributed station 13. If the switching instruction device 17d determines that there is an aggregation station 14 where the future traffic volume exceeds a predetermined switching threshold and congestion will occur, it will perform route switching to distribute the load to links with available bandwidth.

[0214] Furthermore, in this fifth embodiment, the switching instruction device 17d focuses on predicting movement only for terminal stations 11 with a large amount of recent positional change (recent movement), thus reducing the increase in computational load compared to the case where movement prediction is performed for all terminal stations 11.

[0215] With this configuration, the switching instruction device 17d in the fifth embodiment of the present invention can predict future traffic volume without needing to predict the movement of all terminal stations 11, even in situations where the number of connected terminals in the coverage area of ​​the distributed station 13 fluctuates randomly due to, for example, frequent movement of terminal stations 11. As a result, the switching instruction device 17d can predict in advance whether or not congestion will occur while suppressing an increase in computational load, even in situations where the number of connected terminals in the distributed station 13 fluctuates randomly, thereby realizing low-latency communication.

[0216] Furthermore, a configuration combining the configuration of the fifth embodiment described above and the configuration of the fourth embodiment described above may also be used. That is, in the fifth embodiment, the configuration narrows down the terminal stations 11 that are the target of movement prediction to only those terminal stations 11 with a large amount of recent movement, and in the fourth embodiment described above, the configuration narrows down the terminal stations 11 that are the target of movement prediction to only those terminal stations 11 with a high required quality (priority), but a configuration that performs both of these narrowings may also be used.

[0217] <Sixth Embodiment> A sixth embodiment of the present invention will be described below.

[0218] In the third embodiment described above, the switching instruction device 17b was configured to perform movement predictions only for terminal stations 11 located within the coverage area of ​​each distributed station 13 and its surrounding areas. In contrast, the switching instruction device in the sixth embodiment described below (hereinafter referred to as "switching instruction device 17e") has a configuration that further limits the number of terminal stations 11 for which movement predictions are performed to reduce the computational load. Specifically, the switching instruction device 17e in the sixth embodiment narrows down the predictions to only distributed stations 13 with a large number of recently connected terminals within the coverage area, or distributed stations 13 with a large amount of recently accessed traffic, to perform predictions for the number of connected terminals in the future.

[0219] [Overall Configuration of the Communication System] The overall configuration of the mobile communication system in the sixth embodiment (hereinafter referred to as "mobile communication system 10e") is the same as the overall configuration of the mobile communication system 10 in the first embodiment shown in Figure 2 above, so the explanation will be omitted. The mobile communication system 10e is an example of the communication system 1 described above. The mobile communication system 10e in the sixth embodiment and the mobile communication system 10 in the first embodiment differ in the configuration of the switching instruction device.

[0220] [Functional Configuration of the Switching Instruction Device] The functional configuration of the switching instruction device 17e will be described below. Similar to the switching instruction device 17 in the first embodiment described above, the switching instruction device 17e is a device that predicts the future traffic volume at each aggregation station 14, predicts whether or not congestion will occur, and performs control to execute route switching as necessary. However, the switching instruction device 17e and the switching instruction device 17 in the first embodiment described above differ in the processing that predicts the future traffic volume at each distributed station 13, which is a preliminary process to predicting the future traffic volume at each aggregation station 14.

[0221] In the sixth embodiment, the switching instruction device 17e determines for each distributed station 13 whether or not to perform movement prediction for each terminal station 11 based on the number of connected terminals at each distributed station 13. Specifically, the switching instruction device 17e determines to perform movement prediction for each terminal station 11 if the number of most recent connected terminals at each distributed station 13 exceeds a predetermined number of connected terminals. The predetermined number of connected terminals here is, for example, 80% of the number of connected terminals where congestion may occur.

[0222] On the other hand, if the number of connected terminals at each distributed station 13 is less than or equal to a predetermined number of connected terminals, the switching instruction device 17e determines for each distributed station 13 whether or not to perform a movement prediction for each terminal station 11 based on the amount of traffic at each distributed station 13. Specifically, if the amount of traffic at each distributed station 13 exceeds a predetermined amount, the switching instruction device 17e decides to perform a movement prediction for each terminal station 11. The predetermined amount of traffic here is, for example, the amount of traffic that may cause congestion.

[0223] Specifically, the switching instruction device 17e determines that it will not perform movement prediction for each terminal station 11 if the number of most recent connected terminals at each distributed station 13 is less than or equal to a predetermined number of connected terminals, and the amount of most recent traffic at each distributed station 13 is less than or equal to a predetermined amount of traffic. In other words, if the number of most recent connected terminals and the amount of traffic are less than or equal to predetermined values, the switching instruction device 17e predicts that even if there is an influx of traffic from a terminal station 11, it will not be enough to cause congestion, and therefore omits the process of predicting the movement of the terminal station 11.

[0224] When the switching instruction device 17e determines that it is necessary to predict the movement of each terminal station 11, it makes a movement prediction based on the amount of change in the position of each terminal station 11 located within and around the coverage area of ​​the distribution station 13 to be predicted. Then, the switching instruction device 17b predicts the future number of connected terminals within the coverage area of ​​the distribution station 13 to be predicted based on the movement prediction, and predicts the future traffic volume at each distribution station 13 based on the traffic volume of the distribution station 13 and the predicted number of connected terminals.

[0225] On the other hand, if the switching instruction device 17e determines that it does not need to perform movement predictions for each terminal station 11, it considers the number of most recent connected terminals at the distributed station 13 as the number of future connected terminals. Then, the switching instruction device 17e predicts the future traffic volume at each distributed station 13 based on the traffic volume and the number of most recent connected terminals at each distributed station 13. Then, the switching instruction device 17e predicts the future traffic volume at each aggregation station 14 based on the future traffic volume at each distributed station 13.

[0226] Figure 16 is a block diagram showing the functional configuration of the switching instruction device 17e in the sixth embodiment of the present invention. As shown in Figure 16, the switching instruction device 17e is configured to include a prediction execution decision unit 171, a prediction unit 172e, and a switching decision unit 175. The prediction unit 172e is configured to include a future position estimation unit 173e and a traffic prediction unit 174e.

[0227] The prediction unit 172e receives radio control information from each distributed station 13, which is used to predict the future traffic volume at each distributed station 13. The radio control information in the sixth embodiment includes the value of the most recent traffic volume at the distributed station 13, the value of the most recent number of connected terminals at the distributed station 13, and the location information of each terminal station 11 within the coverage area of ​​the distributed station 13.

[0228] The prediction execution decision unit 171 of the prediction unit 172b determines for each distributed station 13 whether or not to perform movement prediction for each terminal station 11, based on the number of most recent connected terminals at each distributed station 13. The prediction execution decision unit 171 determines to perform movement prediction for each terminal station 11 for distributed stations 13 where the number of most recent connected terminals exceeds a predetermined number of connected terminals.

[0229] On the other hand, for distributed stations 13 where the number of connected terminals is less than or equal to a predetermined number of connected terminals, the prediction execution decision unit 171 decides for each distributed station 13 whether or not to perform movement prediction for each terminal station 11 based on the most recent traffic volume at the distributed station 13. For distributed stations 13 where the most recent traffic volume exceeds a predetermined traffic volume, the prediction execution decision unit 171 decides to perform movement prediction for each terminal station 11.

[0230] The prediction execution decision unit 171 determines that it does not perform movement prediction for each terminal station 11 for distributed stations 13 where the number of connected terminals is less than or equal to a predetermined number of connected terminals and the most recent traffic volume is less than or equal to a predetermined traffic volume. The prediction execution decision unit 171 then outputs information to the prediction unit 172e indicating whether or not movement prediction for each terminal station 11 is necessary for each distributed station 13.

[0231] The future position estimation unit 173e of the prediction unit 172e determines that it is necessary to predict the movement of each terminal station 11 in the distributed station 13, and uses the location information of each terminal station 11 included in the radio control information to predict the movement of each terminal station 11 and estimate the future number of connected terminals for each distributed station 13. Specifically, the future position estimation unit 173e identifies the location of each terminal station 11 that exists within the coverage area of ​​the distributed station 13 and in the surrounding area, based on the location information of each terminal station 11 included in the radio control information.

[0232] The future position estimation unit 173e performs the above process to identify the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area, for each distributed station 13 that it has determined to perform movement prediction for each terminal station 11. The future position estimation unit 173b also performs the above process to identify the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area at predetermined unit intervals.

[0233] The future position estimation unit 173e then calculates the amount of change in the position of each terminal station 11 (for example, the amount of change in the distance traveled and the direction of travel for each terminal station 11). Based on the calculated change amounts, the future position estimation unit 173e estimates the future position of each terminal station 11. The future position estimation unit 173e outputs position information indicating the estimated future position of each terminal station 11 to the traffic prediction unit 174e.

[0234] The future position of each terminal station 11 may be estimated, for example, by using the fluctuation amount in the most recent unit period as the predicted value of the future fluctuation amount, or by using the average value of the fluctuation amounts over multiple past unit periods as the predicted value of the future fluctuation amount.

[0235] The traffic prediction unit 174e of the prediction unit 172e obtains location information indicating the future location of each terminal station 11 from the future location estimation unit 173e. Based on the future location of each terminal station 11 estimated by the future location estimation unit 173e, the traffic prediction unit 174e calculates the future number of connected terminals for each distributed station 13 that it has decided to predict the movement of each terminal station 11.

[0236] On the other hand, for each distributed station 13 where the traffic prediction unit 174e has determined that it does not perform movement prediction for each terminal station 11, it considers the most recent number of connected terminals as the future number of connected terminals.

[0237] The traffic prediction unit 174e predicts the future traffic volume at each distributed station 13 based on the future number of connected terminals at each distributed station 13. For example, the traffic prediction unit 174e predicts the future traffic volume by multiplying the value of the most recent traffic volume at each distributed station 13 by the ratio of the number of future connected terminals to the number of recent connected terminals.

[0238] Furthermore, the prediction unit 172e calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14, and the future traffic volume at each distributed station 13. The uplink traffic volume at the aggregate station 14 corresponds to the sum of the uplink traffic volumes received by the aggregate station 14 from each of the distributed stations 13 under its control. The prediction unit 172e outputs information indicating the future traffic volume at each aggregate station 14 to the switching determination unit 175.

[0239] The switching determination unit 175 predicts whether future congestion will occur based on the relationship between the future traffic volume for each aggregation station 14 obtained from the prediction unit 172e and a predetermined switching threshold. The predetermined switching threshold is a value predetermined based on, for example, the bandwidth of the upper link. If the switching determination unit 175 determines that congestion will occur at any aggregation station 14 because the future traffic volume will exceed the bandwidth of the upper link, it decides to perform a route switch to distribute the load to links with available bandwidth. If the switching determination unit 175 decides to perform a route switch, it issues a route switch instruction to each device to change the aggregation station 14 to which the distributed station 13 is connected.

[0240] Specifically, the switching determination unit 175 instructs the source aggregation station 14 to release the connection with the distributed station 13, and instructs the destination aggregation station 14 to establish a connection with the said distributed station 13. Furthermore, the switching determination unit 175 instructs the transfer device 15 to switch routes so that signal transfer takes place via the communication path after the connection destination has been switched.

[0241] [Operation of the Switching Instruction Device] An example of the operation of the switching instruction device 17e will be described below. Figure 17 is a flowchart showing the operation of the switching instruction device 17e in the sixth embodiment of the present invention. The operation of the switching instruction device 17e shown in the flowchart of Figure 17 is repeatedly started at predetermined intervals, for example. That is, the prediction of future traffic volume and the decision to execute route switching based on the prediction result are performed at predetermined intervals.

[0242] First, the prediction unit 172e obtains radio control information from each distributed station 13, including the most recent traffic volume value at the distributed station 13, the most recent number of connected terminals at the distributed station 13, and the location information of each terminal station 11 within the coverage area of ​​the distributed station 13 (step S501). Next, the prediction execution decision unit 171 of the prediction unit 172e determines for each distributed station 13 whether or not to perform movement prediction for each terminal station 11, based on the most recent number of connected terminals at each distributed station 13 and a predetermined threshold (step S502).

[0243] Next, the prediction execution decision unit 171 determines whether to perform movement prediction for each terminal station 11 if the number of recently connected terminals exceeds a predetermined threshold (step S502, YES) (proceed to step S504). On the other hand, if the number of recently connected terminals is below a predetermined threshold (step S502, NO), the prediction execution decision unit 171 determines for each distributed station 13 whether to perform movement prediction for each terminal station 11 based on the recent traffic volume at the distributed station 13 and the predetermined threshold (step S503).

[0244] Next, the prediction execution decision unit 171 determines that for distributed stations 13 whose recent traffic volume exceeds a predetermined threshold (step S503, YES), it will perform movement prediction for each terminal station 11 (proceed to step S504). On the other hand, the prediction execution decision unit 171 determines that for distributed stations 13 whose recent traffic volume is below a predetermined threshold (step S503, NO), it will not perform movement prediction for each terminal station 11 (proceed to step S508). The prediction execution decision unit 171 outputs information to the prediction unit 172e indicating whether or not movement prediction for each terminal station 11 is necessary for each distributed station 13.

[0245] Next, the future position estimation unit 173e of the prediction unit 172e determines that it is necessary to predict the movement of each terminal station 11, and identifies the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area based on the location information of each terminal station 11 included in the radio control information (step S504).

[0246] The future position estimation unit 173e performs the above process to identify the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area, for each distributed station 13 that it has determined to perform movement prediction for each terminal station 11. The future position estimation unit 173b also performs the above process to identify the location of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area at predetermined unit intervals.

[0247] Next, the future position estimation unit 173e calculates the amount of change in the position of each terminal station 11 (for example, the amount of change in the distance traveled and the direction of travel for each terminal station 11) based on the identified position (step S505). Next, the future position estimation unit 173e estimates the future position of each terminal station 11 based on the calculated change (step S506). The future position estimation unit 173e outputs position information indicating the estimated future position of each terminal station 11 to the traffic prediction unit 174e.

[0248] Next, based on the future location of each terminal station 11 estimated by the future location estimation unit 173e, the number of future connected terminals for each distributed station 13 that has decided to perform movement prediction for each terminal station 11 is calculated (step S507). On the other hand, for each distributed station 13 that has decided not to perform movement prediction for each terminal station 11, the traffic prediction unit 174e considers the number of most recent connected terminals based on radio control information as the number of future connected terminals.

[0249] Next, the traffic prediction unit 174e calculates the future traffic volume at each distributed station 13 based on the future number of connected terminals at each distributed station 13 (step S508). For example, the traffic prediction unit 174e predicts the future traffic volume by multiplying the value of the most recent traffic volume at each distributed station 13 by the ratio of the number of future connected terminals to the number of recent connected terminals.

[0250] Next, the traffic prediction unit 174e calculates the future traffic volume at each aggregate station 14 based on the connection relationship between the distributed stations 13 and the aggregate station 14, and the future traffic volume at each distributed station 13 (step S509).

[0251] Next, the switching determination unit 175 predicts whether or not future congestion will occur based on the relationship between the future traffic volume at each aggregation station 14 calculated by the prediction unit 172e and a predetermined switching threshold (step S510). Next, if there is an aggregation station 14 where the future traffic volume exceeds the predetermined switching threshold and congestion is determined to occur (step S511, YES), the switching determination unit 175 decides to perform a route switch to distribute the load to links with available bandwidth and determines the communication path after the switch (step S512).

[0252] Next, the switching determination unit 175 issues instructions to each device for route switching to change the aggregation station 14 to which the distributed station 13 is connected (step S513). Specifically, the switching determination unit 175 instructs the aggregation station 14 from which the switching is initiated to release the connection with the distributed station 13, and instructs the aggregation station 14 to which the switching is initiated to establish a connection with the said distributed station 13. Furthermore, the switching instruction device 17 instructs the transfer device 15 to switch routes so that signal transfer is performed via the communication path after the connection destination has been switched.

[0253] This completes the operation of the switching instruction device 17e as shown in the flowchart of Figure 17.

[0254] As described above, in the sixth embodiment of the present invention, the switching instruction device 17e estimates the future location of each terminal station 11 based on the location information of each terminal station 11 located within the coverage area of ​​the distributed station 13 and its surrounding area, for distributed stations 13 that satisfy at least one of the following conditions: the number of most recent connected terminals exceeds a predetermined number of connected terminals, and the amount of recent traffic exceeds a predetermined amount of traffic. Based on the estimated future location of each terminal station 11, the switching instruction device 17e estimates the future number of connected terminals for each distributed station 13. On the other hand, for distributed stations 13 where the number of most recent connected terminals is less than or equal to a predetermined number of connected terminals, and the amount of recent traffic is less than or equal to a predetermined amount of traffic, the switching instruction device 17e decides not to perform the above-mentioned movement prediction for each terminal station 11 (predicting that congestion will not occur even if there is an influx of terminal stations 11), and considers the number of most recent connected terminals in the distributed station 13 to be the number of future connected terminals.

[0255] The switching instruction device 17e then predicts the future traffic volume for each distributed station 13 based on the most recent traffic volume, the most recent number of connected terminals, and the future number of connected terminals at each distributed station 13. Based on the future traffic volume at each distributed station 13, the switching instruction device 17e then predicts the future traffic volume at each aggregation station 14. If the switching instruction device 17e determines that there is an aggregation station 14 where the future traffic volume exceeds a predetermined switching threshold and congestion will occur, it performs route switching to distribute the load to links with available bandwidth.

[0256] In this sixth embodiment, the switching instruction device 17e performs movement prediction only for terminal stations 11 located within the coverage area of ​​each distributed station 13 and its surrounding areas, provided that at least one of the following conditions is met: the number of most recent connected terminals exceeds a predetermined number of connected terminals, and the amount of most recent traffic exceeds a predetermined amount of traffic.

[0257] In other words, the switching instruction device 17e in the sixth embodiment estimates the future number of connected terminals at a distributed station 13 by performing movement predictions for each terminal station 11 for distributed stations 13 where congestion is expected to occur, but omits such movement predictions for each terminal station 11 for distributed stations 13 where congestion is expected to occur less likely. Therefore, the switching instruction device 17e in the sixth embodiment can suppress the increase in computational load compared to the case where movement predictions are performed for all terminal stations 11.

[0258] With this configuration, the switching instruction device 17e in the sixth embodiment of the present invention can predict future traffic volume without needing to predict the movement of all terminal stations 11, even in situations where the number of connected terminals in the coverage area of ​​the distributed station 13 fluctuates randomly due to, for example, frequent movement of terminal stations 11. As a result, the switching instruction device 17e can predict in advance whether or not congestion will occur while suppressing an increase in computational load, even in situations where the number of connected terminals in the distributed station 13 fluctuates randomly, thereby realizing low-latency communication.

[0259] Furthermore, the configuration of the sixth embodiment described above may be combined with some of the configurations of the first to fifth embodiments mentioned above. For example, the configuration of the sixth embodiment may be combined with at least one of the configurations of the fourth and fifth embodiments mentioned above.

[0260] In other words, in the sixth embodiment, the configuration narrowed down the target terminal stations 11 for movement prediction to only those terminal stations 11 that communicate with distributed stations 13 that satisfy predetermined conditions (i.e., terminal stations 11 that communicate with distributed stations 13 that satisfy at least one of the following conditions: the number of recently connected terminals exceeds a predetermined number of connected terminals, and the amount of recent traffic exceeds a predetermined amount of traffic). In the fourth embodiment described above, the configuration narrowed down the target terminal stations 11 for movement prediction to only those terminal stations 11 with high required quality (priority). In the fifth embodiment described above, the configuration narrowed down the target terminal stations 11 for movement prediction to only those terminal stations 11 with a large amount of recent movement. For example, all of these configurations may be combined to perform three types of narrowing, or any of these configurations may be combined to perform two types of narrowing.

[0261] [Other] In the embodiments described above, the switching control of communication paths between CU and DU in MMH (Mobile Mid Haul) has been explained, but the present invention is not limited to this and can be applied to various networks with convergence points. For example, the present invention can also be applied to the switching control of communication paths between an access point and a server in a Wi-Fi network, and between RU and DU in MFH (Mobile Front Haul).

[0262] In each of the embodiments described above, the switching instruction device is configured to use the same predetermined switching threshold. However, the configuration is not limited to this, and the switching threshold may be a value that fluctuates according to predetermined conditions. For example, the switching threshold may fluctuate according to a specific period or time period.

[0263] Furthermore, the switching instruction device may calculate the accuracy of the traffic volume prediction and determine the switching threshold according to the calculated prediction accuracy. For example, the switching instruction device may determine the switching threshold for each link such that the lower the prediction accuracy, the lower the ratio to the link's transmission capacity. Alternatively, for example, the switching instruction device may not calculate the prediction accuracy and may use the same switching threshold during periods when the change in traffic volume is within a predetermined range.

[0264] Furthermore, in each of the embodiments described above, the switching instruction device predicts future traffic volume using the most recent traffic volume value. However, the configuration is not limited to this, and for example, the switching instruction device may predict future traffic volume using wireless control information such as TBS (Transport Block Size).

[0265] Furthermore, in each of the embodiments described above, the switching instruction device may use machine learning to predict future traffic volume.

[0266] Furthermore, in the embodiment described above, the switching instruction device uses the value of the uplink traffic volume to predict future traffic volume, but it may also use the value of the downlink traffic volume, or it may use the values ​​of both uplink and downlink traffic volumes. Also, in the embodiment described above, the switching threshold is the traffic volume, but the link rate or the like may be used as the threshold.

[0267] Furthermore, there may be multiple forwarding devices 15 that make up network 5. That is, the forwarding devices 15 are connected by communication links to two or more of the distributed stations 13, the aggregation station 14, and other forwarding devices 15. In this case, the traffic volume for each link of each forwarding device 15 is calculated based on the communication path between the distributed station 13 and the aggregation station 14, and the future uplink traffic volume from the distributed station 13.

[0268] The switching instruction device 17 performs the same processing on some or all of these communication links as on the higher-level links described above. The switching instruction device 17 can also reduce the traffic volume of communication links where congestion is expected by changing the communication path of the forwarding device 15 without changing the aggregation station 14 to which the distributed station 13 is connected. In addition, the switching instruction device 17 may instruct other processing to prevent congestion from occurring on communication links where congestion is expected. For example, it may instruct the resource allocation device 16 to increase the resource amount of the forwarding device 15.

[0269] [Hardware Configuration] The following describes examples of the hardware configurations of the switching instruction devices 17, 17a, 17b, 17c, 17d, and 17e. Figure 18 is a device configuration diagram showing examples of the hardware configurations of the switching instruction devices 17, 17a, 17b, 17c, 17d, and 17e in each of the embodiments described above. The switching instruction devices 17, 17a, 17b, 17c, 17d, and 17e each include a processor 91, a storage unit 92, a communication interface 93, and a user interface 94.

[0270] The processor 91 is a central processing unit that performs calculations and control. The processor 91 is, for example, a CPU (Central Processing Unit). The processor 91 reads and executes programs from the memory unit 92. Some of the functions of the switching instruction devices 17, 17a, 17b, 17c, 17d, and 17e may be implemented using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0271] The memory unit 92 further includes a work area for the processor 91 to execute various programs. The communication interface 93 connects to other devices for communication. The user interface 94 is an input device such as a keyboard, pointing device (mouse, tablet, etc.), buttons, touch panel, etc., and a display device such as a display. Human operations are input through the user interface 94. For example, information at the upper and lower levels of the hierarchy is input through the user interface 94.

[0272] Furthermore, each of the switching instruction devices 17, 17a, 17b, 17c, 17d, and 17e may be implemented by multiple computer devices connected to a network. In this case, it is arbitrary which of these multiple computer devices implements each functional part of the switching instruction devices 17, 17a, 17b, 17c, 17d, and 17e. Also, the same functional part may be implemented by multiple computer devices.

[0273] According to the embodiment described above, the communication control device comprises an acquisition unit, a traffic prediction unit, and a switching determination unit. For example, the communication control device is the switching instruction device 7, 17, 17a to 17e in the embodiment, the acquisition unit is the prediction unit 172, 172a to 172e in the embodiment, the traffic prediction unit is the traffic prediction unit 174, 174a to 174e in the embodiment, and the switching determination unit is the switching determination unit 175 in the embodiment.

[0274] The acquisition unit acquires wireless control information from each of the multiple lower-level devices, which are communication devices wirelessly connected to a terminal, and at least one higher-level device, which is a communication device connected to any of the lower-level devices, for use in controlling route switching. For example, the terminal is the terminal station 11 in the embodiment, the lower-level devices are the lower-level devices 3 or distributed stations 13 in the embodiment, and the higher-level device is the higher-level device 4 or aggregation station 14 in the embodiment. The traffic prediction unit predicts the future traffic volume at each of the multiple lower-level devices based on the wireless control information, and predicts the future traffic volume at the higher-level device based on the prediction results. The switching decision unit predicts whether or not future congestion will occur based on the predicted future traffic volume at the higher-level device, and makes a decision on whether to execute route switching.

[0275] In the above-described communication control device, the wireless control information includes information indicating the traffic volume and the number of connected terminals in the lower-level device. The traffic prediction unit may calculate the traffic volume per terminal in multiple lower-level devices based on the wireless control information, and predict the future traffic volume in multiple lower-level devices based on the calculated traffic volume per terminal.

[0276] Furthermore, in the above-described communication control device, the traffic prediction unit may perform weighting calculations based on the time-series fluctuations of the traffic volume per terminal in the lower-level device, or weighting calculations based on the traffic volume per terminal in other adjacent lower-level devices, to predict the future traffic volume in multiple lower-level devices.

[0277] Furthermore, in the above-described communication control device, the wireless control information may further include terminal location information. The above-described communication control device may further include a future location estimation unit. For example, the future location estimation unit is the future location estimation unit 173b in the embodiment. The future location estimation unit may estimate the movement of terminals present in the coverage area and surrounding areas of the lower-level device based on the time-series changes in location information, and estimate the future number of connected terminals in the lower-level device based on the results of the movement estimation. The traffic prediction unit may predict the future traffic volume in multiple lower-level devices based on the estimated number of connected terminals.

[0278] Furthermore, in the above-described communication control device, the wireless control information may also include information indicating the priority of each communication between the terminal and the lower-level device. The future position estimation unit may perform movement estimation only for terminals performing communication of a predetermined priority. For example, the future position estimation unit is the future position estimation unit 173c in the embodiment, and the priority is a priority level based on the delay request level or the required quality (priority) such as QoS in the embodiment. The priority level such as QoS referred to here is, for example, the 5QI value.

[0279] In the above-described communication control device, the future position estimation unit may perform movement estimation only for terminals where the amount of movement estimated by movement estimation is greater than a predetermined value. For example, the future position estimation unit is the future position estimation unit 173d in the embodiment.

[0280] The above-described communication control device may further include a predictive execution decision unit. For example, the predictive execution decision unit is the predictive execution decision unit 171 in the embodiment. The predictive execution decision unit may identify a subordinate device in which the traffic volume value included in the wireless control information exceeds a predetermined value, or in which the number of connected terminals included in the wireless control information exceeds a predetermined value. The future position estimation unit may perform movement estimation only for terminals located in and around the coverage area of ​​the subordinate device identified by the predictive execution decision unit. For example, the future position estimation unit is the future position estimation unit 173e in the embodiment.

[0281] Some or all of the configurations of the switching instruction devices 17, 17a, 17b, 17c, 17d, and 17e in the above-described embodiment may be implemented using a computer. In that case, the function may be implemented by recording a program for implementing this function on a computer-readable recording medium, loading the program recorded on this recording medium into a computer system, and executing it. Here, "computer system" includes hardware such as an OS and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and storage devices such as hard disks built into a computer system. In addition, "computer-readable recording medium" may also include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period of time, such as volatile memory inside a computer system that acts as a server or client in such a case. Furthermore, the above program may be for the purpose of realizing some of the functions described above, or it may be for the purpose of realizing the above functions in combination with a program already recorded in the computer system, or it may be for the purpose of realizing using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0282] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention.

[0283] 1 Communication System 3, 3-1 to 3-4 Lower-level devices 4, 4-1 to 4-2 Higher-level devices 5 Network 7 Switching instruction devices 10, 10a to 10e Mobile communication system 11 Terminal station 12 Antenna station 13 Distributed station 14 Aggregation station 15 Transfer device 16 Resource allocation device 17, 17a to 17e Switching instruction device 20 Higher-level network 72, 172, 172a to 172e Prediction unit 75, 175 Switching decision unit 91 Processor 92 Memory unit 93 Communication interface 94 User interface 171 Prediction execution decision unit 173b to 173e Future location estimation unit 174, 174a to 174e Traffic prediction unit

Claims

An acquisition unit that acquires wireless control information used for controlling route switching between multiple lower-level devices, which are communication devices that wirelessly connect to a terminal, and at least one higher-level device, which is a communication device that connects to any of the lower-level devices, from each of the multiple lower-level devices. A traffic prediction unit predicts the future traffic volume of each of the multiple lower-level devices based on the wireless control information, and predicts the future traffic volume of the higher-level device based on the prediction results. A switching determination unit predicts whether or not future congestion will occur based on the predicted future traffic volume in the above-level device, and makes a decision on whether or not to perform the route switching, A communication control device equipped with the following features. 　 The wireless control information includes information indicating the traffic volume and the number of connected terminals in the lower-level device. The traffic prediction unit calculates the traffic volume per terminal in each of the multiple lower-level devices based on the wireless control information, and predicts the future traffic volume in each of the multiple lower-level devices based on the calculated traffic volume per terminal. 　 The communication control device according to claim 1. 　 The traffic prediction unit predicts future traffic volumes for multiple subordinate devices by performing weighting calculations based on the time-series fluctuations of traffic volume per terminal in the subordinate device, or by performing weighting calculations based on the traffic volume per terminal in other adjacent subordinate devices. The communication control device according to claim 2. 　 The wireless control information further includes the location information of the terminal, A future location estimation unit estimates the movement of the terminals located in and around the coverage area of ​​the lower-level device based on the time-series changes in the aforementioned location information, and estimates the future number of connected terminals in the lower-level device based on the results of the movement estimation. Furthermore, The traffic prediction unit predicts the future traffic volume of the multiple lower-level devices based on the estimated number of connected terminals. 　 A communication control device according to claim 1 or 2. 　 The wireless control information further includes information indicating the priority of each communication between the terminal and the subordinate device, The future position estimation unit performs the movement estimation only for the terminals that perform the communication with a predetermined priority. The communication control device according to claim 4. 　 The future position estimation unit performs the movement estimation only for terminals where the amount of movement estimated by the movement estimation is greater than a predetermined value. The communication control device according to claim 4. 　 Predictive execution determination unit identifies a subordinate device in which the traffic volume value included in the wireless control information exceeds a predetermined value, or the number of connected terminals included in the wireless control information exceeds a predetermined value. Furthermore, The future position estimation unit performs the movement estimation only for the terminals located in and around the coverage area of ​​the subordinate device identified by the prediction execution decision unit. The communication control device according to claim 4. 　 A communication control method performed by a computer, An acquisition step of acquiring wireless control information used for controlling route switching between multiple lower-level devices, which are communication devices that wirelessly connect to a terminal, and at least one higher-level device, which is a communication device that connects to any of the lower-level devices, from each of the multiple lower-level devices, A traffic prediction step involves predicting the future traffic volume of each of the multiple lower-level devices based on the wireless control information, and predicting the future traffic volume of the higher-level device based on the prediction results. A switching decision step that predicts whether or not future congestion will occur based on the predicted future traffic volume in the above-level device, and makes a decision on whether to perform the route switching, A communication control method having

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