Communication control device, communication system, and communication control method

Abstract

This communication control device comprises: a traffic prediction unit that predicts a future traffic volume on the basis of traffic-related information transmitted from a plurality of upper level devices and / or a plurality of lower level devices; an estimation unit that estimates, on the basis of the traffic-related information, a signal-free interval which is a period during which no signal flows; a timing control unit that determines a timing for path switching on the basis of the result of the signal-free interval estimation by the estimation unit; and a switching instruction unit that, when it has been detected, on the basis of the future traffic volume predicted by the traffic prediction unit, that congestion will occur, transmits switching instructions to a device that transfers signals between the plurality of upper level devices and the plurality of lower level devices, said switching instructions including information that indicates a switching destination candidate and information indicating the timing for path switching which was determined by the timing control unit.　

Description

COMMUNICATION CONTROL DEVICE, COMMUNICATION SYSTEM, AND COMMUNICATION CONTROL METHOD

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

[0002] When multiple communication devices communicate simultaneously, such as when multiple upper devices and multiple lower devices communicate with each other, congestion may occur, resulting in communication delays. Congestion may be resolved by switching the communication path (hereinafter referred to as "path switching") using a switching device installed on the communication path, thereby changing the connection relationship between the upper device and the lower device. If communication traffic (hereinafter referred to as "traffic") concentrated on a specific communication device (e.g., an upper device) can be distributed 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 that can change the connection relationship between a higher-level device and a lower-level device, there is a technology that collects information indicating the amount of traffic measured by the higher-level device and the lower-level device (hereinafter referred to as "traffic volume"), determines whether congestion has occurred at the offload destination based on the collected traffic volume, and performs route switching.

[0004] International Publication No. 2023 / 181139

[0005] Conventional communication systems predict traffic volume in advance and switch routes before congestion occurs based on the predicted results. However, since traffic is generally not transmitted (buffered) while route switching is in progress, if switching is performed while traffic caused by congestion is being transmitted, the congestion delay will be added to the switching delay. This causes a communication delay.

[0006] In view of the above circumstances, an object of the present invention is to provide a communication control device, a communication system, and a communication control method that can reduce communication delays.

[0007] One aspect of the present invention is a communication control device comprising: a traffic prediction unit that predicts future traffic volume based on information regarding traffic transmitted from at least one of a plurality of upper devices or a plurality of lower devices; an estimation unit that estimates no-signal sections, which are periods when no signals are flowing, based on the traffic information; a timing control unit that determines the timing of path switching based on the estimation result of the no-signal sections by the estimation unit; and a switching instruction unit that, when congestion is detected to occur based on the future traffic volume predicted by the traffic prediction unit, transmits a switching instruction to a device that transfers signals between the plurality of upper devices and the plurality of lower devices, the switching instruction including information indicating a candidate switching destination and information indicating the timing of the path switching determined by the timing control unit.

[0008] One aspect of the present invention is a communication system comprising a transfer device that transfers signals between multiple upper devices and multiple lower devices, and a communication control device that controls the transfer path of signals by the transfer device, wherein the communication control device comprises: a traffic prediction unit that predicts future traffic volume based on information related to traffic transmitted from at least one of the multiple upper devices or the multiple lower devices; an estimation unit that estimates no-signal sections, which are periods when signals do not flow, based on the traffic information; a timing control unit that determines the timing of path switching based on the estimation result of the no-signal sections by the estimation unit; and a switching instruction unit that, when congestion is detected based on the future traffic volume predicted by the traffic prediction unit, sends a switching instruction to the transfer device that includes information indicating a switching destination candidate and information indicating the timing of the path switching determined by the timing control unit, and the transfer device comprises: a switching destination setting unit that sets a switching destination identified by the information indicating the switching destination candidate in accordance with the information indicating the timing of the path switching included in the switching instruction transmitted from the communication control device; and a switching unit that changes the connection relationship between the multiple lower devices and the multiple upper devices so that signals are transferred to the switching destination set by the switching destination setting unit.

[0009] One aspect of the present invention is a communication control method executed by a computer, which predicts future traffic volume based on information regarding traffic transmitted from at least one of multiple upper devices or multiple lower devices, estimates signal-free sections, which are periods when no signals are flowing, based on the traffic information, determines the timing of route switching based on the estimated signal-free sections, and, when congestion is detected based on the predicted future traffic volume, sends a switching instruction including information indicating a switching destination candidate and information indicating the determined timing of route switching to a device that transfers signals between the multiple upper devices and the multiple lower devices.

[0010] The present invention makes it possible to reduce communication delays.

[0011] 1 is a diagram showing the configuration of a communication system which is an example of a conventional communication system. FIG. 2 is a diagram showing the configuration of a mobile communication system which is an example of a conventional communication system. FIG. 3 is a block diagram showing the configuration of a switching instruction device of a mobile communication system which is an example of a conventional communication system. FIG. 4 is a diagram showing the flow of processing in a switching instruction device of a mobile communication system which is an example of a conventional communication system. FIG. 5 is a flowchart showing the process of predicting traffic volume of a remote station in a prediction unit. FIG. 6 is a flowchart showing the process of creating a traffic volume prediction model in the prediction unit. FIG. 7 is a flowchart showing the process of predicting future traffic volume in the prediction unit. FIG. 8 is a flowchart showing the process of predicting traffic volume of an upper link in the prediction unit. FIG. 9 is a flowchart showing the process of calculating a switching threshold in a switching threshold determination unit. FIG. 10 is a diagram showing an example of a lookup table. FIG. 11 is a flowchart showing the switching judgment process in a switching judgment unit. FIG. 12 is a flowchart showing the switching judgment process in the switching judgment unit. FIG. 13 is a diagram showing the execution timing of processing in route switching by a conventional communication system. FIG. 14 is a diagram for explaining problems in route switching by a conventional communication system. FIG. 15 is a diagram showing the execution timing of processing in route switching by a communication system of each embodiment of the present invention. FIG. 16 is a block diagram showing the configuration of a communication system in a first embodiment of the present invention. FIG. 17 is a block diagram showing the functional configuration of a switching instruction device in a first embodiment of the present invention. FIG. 18 is a block diagram showing the functional configuration of a switching device in a first embodiment of the present invention. Fig. 1 is a diagram for explaining the processing of a no-signal interval estimation unit and a timing control unit in the first embodiment of the present invention. Fig. 2 is a diagram for explaining the processing of a no-signal interval estimation unit and a timing control unit in the first embodiment of the present invention. Fig. 3 is a flowchart showing the flow of processing performed by a switching instruction device in the first embodiment of the present invention. Fig. 4 is a flowchart showing the flow of processing performed by a switching device in the first embodiment of the present invention. Fig. 5 is a diagram for explaining the processing of a no-signal interval estimation unit and a timing control unit in the second embodiment of the present invention. Fig. 6 is a block diagram showing the functional configuration of a switching instruction device in a third embodiment of the present invention.FIG. 10 is a flowchart showing the flow of processing performed by a no-signal interval estimation unit in a third embodiment of the present invention. FIG. 11 is a block diagram showing the functional configuration of a switching instruction device in a fourth embodiment of the present invention. FIG. 12 is a flowchart showing the flow of processing performed by a traffic prediction unit in a fourth embodiment of the present invention. FIG. 13 is a block diagram showing the functional configuration of a switching instruction device in a fifth embodiment of the present invention. FIG. 14 is a flowchart showing the flow of processing performed by a switching instruction unit in a fifth embodiment of the present invention. FIG. 15 is a block diagram showing the functional configuration of a switching instruction device in a sixth embodiment of the present invention. FIG. 16 is a flowchart showing the flow of processing performed by a traffic prediction unit in a sixth embodiment of the present invention. FIG. 17 is a flowchart showing the flow of processing performed by a no-signal interval estimation unit in a seventh embodiment of the present invention. FIG. 18 is a flowchart showing the flow of processing performed by a no-signal interval estimation unit in an eighth embodiment of the present invention. FIG. 19 is a flowchart showing the flow of processing performed by a switching instruction unit in a ninth embodiment of the present invention.

[0012] Hereinafter, a communication control device, a communication system, and a communication control method according to embodiments of the present invention will be described in detail with reference to the drawings. Components having the same functions in each embodiment will be assigned the same reference numerals, and repeated explanations of those functions may be omitted.

[0013] In order to make the description of the configuration of the communication system according to the embodiment of the present invention easier to understand, an example of the configuration of a conventional communication system will be described first for comparison.

[0014] FIG. 1 is a diagram showing the configuration of a communication system 1, which is an example of a conventional communication system. The communication system 1 has 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 device 4 are connected via a network 5. The network 5 includes one or more transfer devices (not shown; devices corresponding to the transfer device 15 shown in FIG. 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 device 4.

[0015] 1, the four lower devices 3 are respectively referred to as lower devices 3-1 to 3-4, and the two upper devices 4 are respectively referred to as upper devices 4-1 and 4-2. Hereinafter, the direction from the lower device 3 to the upper device 4 will be referred to as "upstream," and the direction from the upper device 4 to the lower device 3 will be referred to as "downstream."

[0016] The lower device 3 transmits an upstream signal to the connected upper device 4. The network 5 transfers the upstream signal to the upper device 4 according to the communication path between the lower device 3 and the upper device 4. The upper device 4 also transmits a downstream signal to the connected lower device 3. The network 5 transfers the downstream signal to the lower device 3 according to the communication path between the lower device 3 and the upper device 4. The switching instruction device 7 instructs each device, such as a transfer device, to switch the communication path.

[0017] The switching instruction device 7 uses information such as traffic volume or traffic allocation volume (hereinafter collectively referred to as "traffic volume") acquired from the lower-level device 3 and the upper-level device 4 to predict in advance the traffic volume of some or all communication links (hereinafter simply referred to as "links" or "flows") in the communication path between the lower-level device 3 and the upper-level device 4. The switching instruction device 7 determines a switching threshold for each link based on the traffic volume prediction accuracy and the transmission capacity of the link.

[0018] For example, the link rate can be used as an index representing the transmission capacity of a link. The link rate is the maximum communication speed of the link. The switching threshold is a threshold used to determine whether congestion requiring a switch of the communication path (route switching) is predicted to occur. For example, even for the same link rate, the switching instruction device 7 determines a lower switching threshold as the prediction accuracy of the traffic volume becomes lower.

[0019] The switching instruction device 7 determines whether congestion will occur for each link using the predicted traffic volume and a switching threshold. If congestion is predicted to occur in any link, the switching instruction device 7 determines to perform path switching for load balancing. The switching instruction device 7 instructs switching of communication paths (path switching) so that at least a portion of the traffic transmitted through a link predicted to be congested is transmitted through a link predicted not to be congested. This enables optimal communication path switching according to prediction accuracy. Furthermore, link congestion delays are reduced, enabling higher bandwidth utilization efficiency.

[0020] As shown in FIG. 1 , the switching instruction device 7 includes a prediction unit 71, a switching threshold determination unit 72, and a switching determination unit 75. The prediction unit 71 acquires prediction information from each device to be used for predicting the traffic volume of each link. The prediction information includes, for example, the traffic volume observed by the device, the traffic allocation volume to the device, the number of terminals connected to the device, and communication quality. The prediction unit 71 predicts the future traffic volume for each link using the prediction information. Any existing technology can be used to predict the future traffic volume.

[0021] The switching threshold determination unit 72 includes a prediction accuracy calculation unit 73 and a threshold calculation unit 74. The prediction accuracy calculation unit 73 calculates prediction accuracy for each link based on past prediction results of future traffic volume and actual traffic volume. The threshold calculation unit 74 determines a switching threshold for each link such that the ratio to the link's transmission capacity (e.g., link rate) becomes lower as the prediction accuracy becomes lower.

[0022] The switching determination unit 75 determines in advance whether congestion will occur for each link using the predicted future traffic volume value and a switching threshold. If congestion is predicted, the switching determination unit 75 determines to perform route switching for load balancing. For example, the switching determination unit 75 determines to perform route switching from a link where congestion is predicted to occur to a link with a lower link utilization rate. The switching determination unit 75 instructs each device to perform processing for route switching.

[0023] An example in which the communication system 1 is applied to a mobile communication system will be described below.

[0024] 2 is a diagram showing the configuration of a mobile communication system 10, which is an example of a conventional communication system. The mobile communication system 10 is an example of the communication system 1. The mobile communication system 10 is, for example, a fifth-generation mobile communication system (5G). The mobile communication system 10 includes a plurality of terminal stations 11, a plurality of antenna stations 12, a plurality of remote stations 13, a plurality of central stations 14, a transfer device 15, a switching instruction device 17, and a resource allocation device 16.

[0025] The terminal station 11, the antenna station 12, the distributed station 13, and the central station 14 are UE (User Equipment), RU (Radio Unit), DU (Distributed unit), and CU (Central unit), respectively, of a fifth-generation mobile communication system. The distributed station 13 is an example of a lower-level device 3, and the central station 14 is an example of a higher-level device 4. However, the combination of a device corresponding to the lower-level device 3 and a device corresponding to the higher-level device 4 is not limited to the combination of the distributed station 13 and the central station 14, and is arbitrary. The transfer device 15 is an example of a transfer device that constitutes the network 5.

[0026] The transfer device 15 also functions as a switching device that can change the connection relationship between the remote stations 13 and the central station 14. The transfer function and the switching function of the transfer device 15 may be realized by separate devices. The switching instruction device 17, the transfer device 15, the resource allocation device 16, and other devices do not necessarily need to be separate devices, and may be configured as an integrated device.

[0027] The mobile communication system 10 is connected to an upper network 20. Here, the M (M is an integer equal to or greater than 1) remote stations 13 are referred to as remote stations 13-1 to 13-M, respectively. Furthermore, the Km (Km is an integer equal to or greater than 1) antenna stations 12 subordinate to the remote station 13-m (m is an integer equal to or greater than 1 and equal to or less than M) are referred to as antenna stations 12-m, respectively. Furthermore, the N (N is an integer equal to or greater than 2) central stations 14 are referred to as central stations 14-1 to 14-N, respectively. Therefore, the mobile communication system 10 shown in FIG. 2 is an example of a mobile communication system in which M=4, K1=2, K2=2, K3=2, K4=2, and N=2.

[0028] The terminal station 11 transmits and receives radio signals to and from the antenna station 12 using radio resources allocated by the remote station 13. The allocated radio resources include information indicating the start and end timings of time periods during which radio signal transmission and reception are permitted. The start and end timings are represented by, for example, slots. A slot is a unit of scheduling for data transmission and reception in a radio frame. The allocated radio resources may further include information indicating a coding rate and a modulation method.

[0029] The antenna station 12 receives uplink data from the terminal station 11 via a wireless signal. The antenna station 12-m sets the received uplink data as an uplink signal and transmits the uplink signal to the remote station 13-m via a wired interface. The antenna station 12-m also receives a downlink signal from the remote station 13-m via a wired interface. The antenna station 12 transmits the downlink data addressed to the terminal station 11, which is set in the received downlink signal, to the terminal station 11 via a wireless signal.

[0030] The remote station 13-m receives uplink signals from each of the Km antenna stations 12-m. The uplink signals received by the remote station 13-m include uplink data received by the antenna station 12-m from the terminal stations 11 under its control. The remote station 13 generates an uplink signal that aggregates the uplink data and transmits the generated uplink signal to the central station 14 to which the remote station 13 is connected. The remote station 13 also receives a downlink signal from the central station 14 to which the remote station 13 is connected, in which downlink data addressed to the terminal stations 11 under its control is set. The remote station 13-m converts the received downlink signal into a downlink signal corresponding to the radio signal to be transmitted from each antenna station 12-m. The remote station 13-m transmits the converted downlink signal to the antenna station 12-m corresponding to the downlink signal.

[0031] The central station 14 aggregates the uplink signals received from the subordinate remote stations 13 and transfers them to the upper network 20. The central station 14 also receives downlink signals from the upper network 20, in which downlink data addressed to the terminal stations 11 is set, and transfers the received downlink signals to the remote stations 13 connected to the destination terminal stations 11.

[0032] The transfer device 15 is connected to the remote stations 13, the central station 14, and the switching instruction device 17. The transfer device 15 is an example of a switching device that switches (switches) communication paths. The transfer device 15 transfers signals along the communication path between the remote stations 13 and the central station 14. That is, the transfer device 15 transfers upstream signals received from the remote stations 13 to the destination central station 14 along the communication path. The transfer device 15 also transfers downstream signals received from the central station 14 to the destination remote station 13 along the communication path. The transfer of signals along the communication path is performed under instructions from the switching instruction device 17. The resource allocation device 16 manages the resources of the central station 14.

[0033] The switching instruction device 17 is connected to the remote station 13, the central station 14, and the transfer device 15. The switching instruction device 17 may further be connected to the resource allocation device 16. The switching instruction device 17 instructs the transfer device 15 (switching device) to switch the communication path between the remote station 13 and the central station 14. In the mobile communication system 10, the communication path between the remote station 13 and the central station 14 is determined based on the connection relationship between the remote station 13 and the central station 14. Therefore, in the mobile communication system 10, the path between the remote station 13 and the central station 14 is switched by controlling the transfer device 15 (switching device) to change the central station 14 to which the remote station 13 is connected.

[0034] Also, as an example, it is assumed here that the switching instruction device 17 of the mobile communication system 10 determines, based on the upstream traffic, whether or not congestion has occurred on the central station 14 side, which corresponds to the higher-level device 4. Therefore, unless otherwise specified, traffic in the following description refers to the traffic of upstream signals.

[0035] 3 is a block diagram showing the configuration of a switching instruction device 17 of a mobile communication system 10, which is an example of a conventional communication system. The switching instruction device 17 includes a prediction unit 171, a switching threshold value determination unit 172, and a switching determination unit 175.

[0036] The prediction unit 171 receives radio information from the remote stations 13 as prediction information. The radio information includes information indicating radio resources to be allocated to terminal stations 11 under the control of the remote stations 13. The radio information is, for example, link control information (DCI: Downlink Control Information). The prediction unit 171 uses the radio information from the remote stations 13 to calculate the future traffic volume of each remote station 13.

[0037] Furthermore, the prediction unit 171 calculates the future traffic volume of each upper link based on the connection relationship between the remote stations 13 and the aggregation station 14 and the future traffic volume of each remote station 13. The upper link is the link between the aggregation station 14 and the transfer device 15. The upstream traffic volume of the upper link between the aggregation station 14-n (n is an integer between 1 and N) and the transfer device 15 corresponds to the total value of the traffic volume of the upstream signals that the aggregation station 14-n receives from each of the remote stations 13 under its control. The prediction unit 171 outputs the future traffic volume of the upper link to the switching threshold determination unit 172 and the switching determination unit 175, respectively.

[0038] The switching threshold determination unit 172 includes a prediction accuracy calculation unit 173 and a threshold calculation unit 174. The prediction accuracy calculation unit 173 receives information indicating actual traffic volume from the remote station 13. The prediction accuracy calculation unit 173 calculates the actual traffic volume flowing through each upper link based on the actual traffic volume and the connection relationship between the remote station 13 and the central station 14. The prediction accuracy calculation unit 173 calculates prediction accuracy for each upper link based on the future traffic volume predicted in the past by the prediction unit 171 and the actual traffic volume. The threshold calculation unit 174 calculates a switching threshold for each upper link based on the link rate and prediction accuracy. The threshold calculation unit 174 outputs the calculated switching threshold for each upper link to the switching determination unit 175.

[0039] The switching determination unit 175 calculates a predicted link utilization rate for each upper link based on the future traffic volume value acquired from the prediction unit 171 and the switching threshold acquired from the threshold calculation unit 174. If there is an upper link for which it is determined that congestion will occur due to a high predicted link utilization rate, the switching determination unit 175 determines to perform path switching by changing the aggregation station 14 to which the remote station 13 is connected. If the switching determination unit 175 determines to perform path switching, it instructs each device (the remote station 13, the aggregation station 14, and the transfer device 15) to perform path switching.

[0040] Specifically, the switching determination unit 175 instructs the central station 14 that is the connection destination before the path switching (hereinafter referred to as the "switching source") to release the connection with the remote station 13, and instructs the central station 14 that is the connection destination after the path switching (hereinafter referred to as the "switching destination") to connect with the remote station 13. Furthermore, the switching instruction device 17 instructs the transfer device 15 (switching device) to switch the path so that signals are transferred via the communication path after the path switching.

[0041] 4 is a diagram showing a processing flow in the switching instruction device 17 of the mobile communication system 10, which is an example of a conventional communication system. The prediction unit 171 predicts future traffic volume of an upper link, for example, for a period D(a) (step S1). The prediction accuracy calculation unit 173 obtains information indicating the future traffic volume predicted in step S1 from the prediction unit 171 and stores the information until it obtains information indicating the actual traffic volume for the period D(a) (step S2).

[0042] The prediction accuracy calculation unit 173 receives information indicating the actual traffic volume of the upper link for period D(a) (step S3). The prediction accuracy calculation unit 173 calculates the prediction accuracy based on the stored future traffic volume for period D(a) and the received actual traffic volume for period D(a). The threshold calculation unit 174 determines a switching threshold based on the link rate and prediction accuracy of the upper link (step S4). The threshold calculation unit 174 outputs the determined switching threshold to the switching determination unit 175.

[0043] Meanwhile, the prediction unit 171 calculates the future traffic volume of the upper link for period D(b), which is a period after period D(a) (step S5). The switching determination unit 175 acquires the switching threshold output from the threshold calculation unit 174 in step S4 (step S6). Furthermore, the switching determination unit 175 acquires information indicating the future traffic volume for period D(b), calculated in step S5, from the prediction unit 171 (step S7). The switching determination unit 175 determines whether or not route switching is necessary based on the acquired switching threshold and the value of the future traffic volume for period D(b) (step S8).

[0044] As described above, the future traffic volume acquired by the switching threshold value determination unit 172 is the traffic volume at an earlier time than the future traffic volume acquired by the switching determination unit 175 .

[0045] Next, a detailed description will be given of the processing of the switching instruction device 17. First, a description will be given of the processing of predicting future traffic volume of each upper link in the prediction unit 171. The prediction unit 171 performs the processing of steps S1 and S5 in Fig. 4 by the processing of Figs. 5 to 8 below.

[0046] 5 is a flowchart showing the process of predicting the traffic volume of a remote station in the prediction unit 171. At time t(i-1), the remote station 13 notifies the terminal station 11 of DCI(i) for the next transmission period, and further notifies the switching instruction device 17 of DCI information in which DCI(i) is set (i is an integer). DCI(i) is DCI that indicates the radio resources to be allocated to the terminal station 11 in slot SL(i) from time t(i) to time t(i+1), and the coding rate and modulation scheme to be used by the terminal station 11.

[0047] Specifically, the DCI includes scheduling information, an MCS (Modulation and Coding Scheme), and the like, which are necessary for the terminal station 11 to transmit uplink data. The scheduling information is represented by a resource block. The resource block is represented by a channel and the transmission start timing and transmission end timing using that channel. The MCS represents the data modulation and channel coding rate. The TBS (Transport Block Size) is determined based on the resource block size and the MCS. The TBS makes it possible to predict the traffic volume.

[0048] At time t(i-1), the switching instruction device 17 receives DCI information in which DCI(i) is set from each remote station 13. Based on the information included in DCI(i), the prediction unit 171 calculates the predicted traffic volume DU(i) of the remote station 13 for the period D(i) corresponding to the slot SL(i) (step S111). Furthermore, the prediction unit 171 calculates the allocated time interval T(i) from the difference between time t(i) and time t(i+1) (step S112). The allocated time interval T(i) corresponds to the duration of the slot SL(i), i.e., the duration of the period D(i) from time t(i) to time t(i+1). The prediction unit 171 may receive the allocated time interval T(i) from the remote station 13. The prediction unit 171 stores the predicted traffic volume DU(i) of each remote station 13, the allocated time interval T(i), and the period D(i) in association with each other.

[0049] The prediction unit 171 creates a traffic volume prediction model (step S113). The traffic volume prediction model is a model that uses traffic volumes of q (e.g., q=100) slots in a time series as input data and predicts the traffic volume of the slot next to the input data. Details of creating the traffic volume prediction model will be described later with reference to FIG. 6.

[0050] The prediction unit 171 predicts the future traffic volume DU(i+1) of each remote station 13 during the period D(i+1) from time t(i+1) to time t(i+2) using the traffic volume prediction model created in step S113 (step S114). Details of the prediction process will be described later with reference to Fig. 7. After the process of step S114, the prediction unit 171 performs the process of Fig. 8, which will be described later, to calculate the traffic volume for each upper link.

[0051] 6 is a flowchart showing the process of creating a traffic volume prediction model by the prediction unit 171. FIG. 6 shows the detailed process of step S113 in FIG.

[0052] The prediction unit 171 stores in advance K time intervals to be processed: T_1, T_2, ..., T_k-1, and T_req. The time intervals T_1 to T_k-1 are the time lengths of slots available for allocation of resource blocks to the terminal station 11. For example, T_1 to T_k-1 are 125 [us], 250 [us], 500 [us], and 1 [ms]. The allocation time interval T(i) is the same value as one of the time intervals T_1 to T_k-1. The time interval T_req is a value required by an application or the like. The time interval T_req is a value greater than T_1 to T_k-1. The prediction unit 171 selects one of the time intervals T_1 to T_req that has not yet been selected, and sets it as T_x (step S121).

[0053] The prediction unit 171 determines whether the allocated time interval T(i) is equal to or greater than the time interval T_x (step S122). If the prediction unit 171 determines that the allocated time interval T(i) is equal to or greater than the time interval T_x (step S122: YES), the prediction unit 171 converts the predicted traffic volume DU(i) of the remote station 13 into a predicted traffic volume for each time interval T_x (step S123).

[0054] That is, the prediction unit 171 calculates that a predicted traffic volume DU_T_x of predicted traffic volume DU(i) × (time interval T_x / allocated time interval T(i)) will occur for each time interval T_x between time t(i) and time t(i+1). For example, assume that the allocated time interval T(i) is 250 us and the time interval T_x is 125 us. The prediction unit 171 predicts that a traffic volume of DU_125 us = DU(i) / 2 will occur between time t(i) and time t(i)+125 us and between time t(i)+125 us and time t(i+1), respectively.

[0055] The prediction unit 171 adds the predicted traffic volume calculated in step S123 to the time-series predicted traffic volume previously calculated for the time interval T_x for each remote station 13 and stores the result (step S124). The prediction unit 171 learns a traffic volume prediction model for the time interval T_x using the stored time-series predicted traffic volumes of the remote stations 13 for the time interval T_x (step S125).

[0056] For example, the time-series predicted traffic volumes of the remote station 13 for the time interval T_x are assumed to be DU_T_x(P), DU_T_x(P-1), DU_T_x(P-2), ..., DU_T_x(1) in order of most recent time (P is an integer equal to or greater than 2). The prediction unit 171 generates learning data for each remote station 13, using DU_T_x(p) as the correct output data and subtracting 1 from the value of p in order from P, with DU_T_x(p-1) to DU_T_x(p-q) as input data (q is an integer equal to or greater than 1, for example, q=100). The prediction unit 171 uses this generated learning data to train a traffic volume prediction model that represents the correspondence between input data and output data.

[0057] On the other hand, if the prediction unit 171 determines in step S122 that the allocated time interval T(i) is smaller than the time interval T_x (step S122: NO), it performs the process of step S126. The prediction unit 171 records the predicted traffic volume DU(i) of the remote station 13-m in a buffer within the prediction unit 171 that corresponds to the remote station 13-m and the time interval T_x (step S126). The prediction unit 171 determines whether the predicted traffic volume for the time interval T_x has been recorded in the buffer that corresponds to each remote station 13 and the time interval T_x (step S127).

[0058] For example, assume that the allocated time interval T(i) is 250 [us] and the time interval T_x is 500 [us]. The prediction unit 171 determines whether the predicted traffic volume for T_x / T(i) = 2 has been recorded in the buffer corresponding to 500 [us]. If the prediction unit 171 determines that the predicted traffic volume for the time interval T_x has not been recorded in the buffer corresponding to the time interval T_x (step S127: NO), the prediction unit 171 performs the processing from step S128.

[0059] The prediction unit 171 performs the process of step S124 when it determines that the predicted traffic volume for the time interval T_x has been recorded in the buffer corresponding to the time interval T_x for each remote station 13 (step S127: YES). That is, the prediction unit 171 reads out the predicted traffic volume DU(i-T_x / T(i)+1) to the predicted traffic volume DU(i) for each remote station 13 from the buffer corresponding to the time interval T_x, and sums them up to obtain DU_T_x(P).

[0060] For example, suppose the allocated time interval T(i) is 250 [us] and the time section T_x is 500 [us]. The prediction unit 171 sums the predicted traffic volume DU(i-1) and the predicted traffic volume DU(i) to calculate DU_500 [us] (P).

[0061] The prediction unit 171 stores the time-series predicted traffic volumes DU_T_x(1) to DU_T_x(P-1) of each remote station 13 that were previously calculated for the time interval T_x. The prediction unit 171 adds the newly calculated predicted traffic volume DU_T_x(P) to these predicted traffic volumes DU_T_x(1) to DU_T_x(P-1) for each remote station 13 and stores them (step S124). The prediction unit 171 performs the process of step S125 and learns a traffic volume prediction model using the time-series predicted traffic volume for the time interval T_x.

[0062] After the process of step S125, or if the determination in step S127 is NO, the prediction unit 171 determines whether all of the K time intervals to be processed, T_1 to T_req, have been selected (step S128). If there is an unselected time interval (step S128: NO), the prediction unit 171 returns to step S121 and sets the newly selected time interval to T_x.

[0063] Then, if the prediction unit 171 determines that all K time intervals to be processed have been selected (step S128: YES), it stores a traffic volume prediction model corresponding to each of the K time intervals T_1 to T_req and a predicted time, which is the time from when input data is input to the traffic volume prediction model to when output data is output (step S129).

[0064] Fig. 7 is a flowchart showing the process of predicting future traffic volume by the prediction unit 171. Fig. 7 shows detailed processing in step S114 of Fig. 5. The prediction unit 171 determines whether it is possible to predict future traffic volume by time t(i+1), when the next period D(i) ends (step S131). Specifically, the prediction unit 171 determines whether the sum of the allocated time interval T(i) and the switching time Tc is longer than the prediction time of the prediction model for the traffic volume of the allocated time interval T(i).

[0065] If the allocation time interval T(i) + switching time Tc is longer than the predicted time (T(i) + Tc > predicted time), the prediction unit 171 determines that it is possible to predict future traffic volume by the end of the next period D(i) (step S131: YES). The prediction unit 171 inputs the p most recent time-series predicted traffic volumes DU(P) to DU(P-p+1) for the allocation time interval T(i) into the traffic volume prediction model created for each remote station 13. The prediction unit 171 calculates the future traffic volume DU(i+1) for each remote station 13 during the period D(i+1) from time t(i+1) to time t(i+2) (step S132). Note that t(i+2) = t(i+1) + T(i). The prediction unit 171 stores the calculated future traffic volume DU(i+1) for each remote station 13.

[0066] If the predicted time is equal to or greater than the allocation time T(i) + switching time Tc (T(i) + Tc ≦ predicted time), the prediction unit 171 determines that it is impossible to predict future traffic volume by the end of the next period D(i) (step S131: NO). The prediction unit 171 performs prediction from time t(i+1) to the time interval T_req (e.g., 5 ms) ahead, which satisfies the service request delay. For each remote station 13, the prediction unit 171 adds up the predicted traffic volumes of the time series for the allocation time interval T(i) in units of T_req / T(i) in descending order of time to calculate the predicted traffic volume of the time series for the time interval T_req. For each remote station 13, the prediction unit 171 inputs the predicted traffic volumes of the most recent q time series for the time interval T_req into the traffic volume prediction model created for the time interval T_req.

[0067] As a result, the prediction unit 171 calculates the future traffic volume DUreq(i+1) of each remote station 13 during the period D(i+1) from time t(i+1) to time t(i+2) (step S133). Note that t(i+2) = t(i+1) + T_req. The prediction unit 171 sets the future traffic volume DUreq(i+1) to the future traffic volume DU(i+1) calculated in step S114 of FIG. 5 .

[0068] FIG. 8 is a flowchart showing the process of predicting the traffic volume of the upper link in the prediction unit 171. After the process shown in the flowchart of FIG. 5, the prediction unit 171 executes the process of predicting the traffic volume of the upper link shown in the flowchart of FIG. 8. The traffic volume of the upper link between the central station 14-n and the transfer device 15 is the same as the traffic volume of the central station 14-n. Therefore, the prediction unit 171 first acquires bearer information that the switching instruction device 17 has received in advance from the central station 14 (step S141). The bearer information is used as connection information that indicates the connection between the upper device and the lower device. By acquiring the bearer information, the prediction unit 171 recognizes the connection relationship between the remote station 13 and the central station 14.

[0069] The prediction unit 171 sums up, for each central station 14, the future traffic volume DU(i+1) of the subordinate remote stations 13 calculated in step S114 of Fig. 5. As a result, the prediction unit 171 calculates the future traffic volume L(i+1), which is the traffic volume of the upper link connected to the central station 14 during the period D(i+1) (step S142). Specifically, the prediction unit 171 calculates the future traffic volume L(i+1) as follows:

[0070] Future traffic volume L(i+1)=Σfuture traffic volume DU(i+1)×if(aggregate station-distributed station connection)

[0071] The above if (aggregate station-remote station connection) is a flag that takes the value of 1 if the aggregate station 14 is designated as the connection destination of the remote station 13, and takes the value of 0 if not. The prediction unit 171 outputs the period D(i+1) and the future traffic volume L(i+1) of each upper link to the switching threshold determination unit 172 and the switching determination unit 175 (step S143).

[0072] 9 is a flowchart showing the calculation process of the switching threshold value in the switching threshold value determination unit 172. The process shown in the flowchart in FIG. 9 corresponds to the process in step S4 in FIG. 4. The prediction accuracy calculation unit 173 receives information on the period D(a) and the future traffic volume L(a) of each upper link from the prediction unit 171 (step S151). This corresponds to the period D(i+1) and the future traffic volume L(i+1) of each upper link output by the prediction unit 171 in step S143 in FIG. 8.

[0073] Next, the prediction accuracy calculation unit 173 acquires the actual traffic volume of each remote station 13 during the period D(a) (step S152). For each central station 14, the prediction accuracy calculation unit 173 sums up the actual traffic volumes for the period D(a) acquired in step S152 for the remote stations 13 under its control, to calculate the actual traffic volume L'(a), which is the actual traffic volume of the upper link connected to the central station 14. Note that the prediction accuracy calculation unit 173 may receive the actual traffic volume L'(a) during the period D(a) from the central station 14.

[0074] The prediction accuracy calculation unit 173 acquires the link rate of each upper link. The prediction accuracy calculation unit 173 calculates the prediction accuracy for each upper link in the period D(a) (step S153). For example, the prediction accuracy calculation unit 173 calculates the following error rate as the prediction accuracy:

[0075] Error rate = | future traffic volume L(a) - actual traffic volume L'(a) | ÷ (actual traffic volume L'(a)) × 100

[0076] Alternatively, the prediction accuracy calculation unit 173 may calculate the following RMSE (Root Mean Squared Error) or MAE (Mean Absolute Error) used to evaluate prediction accuracy. Note that in the following equations (1) and (2), fi represents the future traffic volume L(a), and yi represents the actual traffic volume L'(a).

[0077]

[0078]

[0079] Next, the threshold calculation unit 174 calculates a switching threshold to be used after the period D(a) using the prediction accuracy calculated in step S153 (step S154). For example, when the threshold calculation unit 174 calculates the error rate in step S153, it calculates the switching threshold TH of the upper link by the following formula (3).

[0080] Switching threshold TH = link rate × (100 - error rate) ÷ 100 (3)

[0081] Alternatively, when the threshold calculation unit 174 calculates the RMSE or MAE by the above formula (1) or formula (2) in step S153, it converts the pre-stored lookup table into an error rate.

[0082] 10 is a diagram showing an example of a lookup table. The lookup table is data that associates prediction accuracy with an error rate and a calculation formula for a switching threshold. The threshold calculation unit 174 reads out an error rate corresponding to the prediction accuracy from the lookup table. The threshold calculation unit 174 uses the read error rate to calculate the switching threshold TH for each upper link according to the above formula (3).

[0083] In FIG. 9, the threshold calculation unit 174 outputs the switching threshold TH of each upper link calculated in step S154 to the switching determination unit 175 (step S155).

[0084] For example, accuracy is used to calculate the prediction accuracy. However, it is uncertain whether the prediction accuracy can actually be guaranteed. In this embodiment, the traffic volume is predicted in advance, and then the actual traffic flows. Therefore, as described above, the prediction accuracy is calculated using the difference between the actual traffic volume and the predicted traffic volume.

[0085] Fig. 11 is a flowchart showing the switching determination process in the switching determination unit 175. The process in Fig. 11 corresponds to the process in step S8 in Fig. 4. The switching determination unit 175 performs the process shown in Fig. 11 for each upper link. The switching determination unit 175 receives information on the period D(b) and the future traffic volume L(b) of each aggregation station 14 from the prediction unit 171 (step S161). These correspond to the period D(i+1) and the future traffic volume L(i+1) of each aggregation station 14 output by the prediction unit 171 in step S143 in Fig. 8.

[0086] The switching determination unit 175 receives the switching threshold TH for each upper link output by the threshold calculation unit 174 in step S155 of Fig. 9 (step S162). Using the switching threshold TH, the switching determination unit 175 calculates a predicted link usage rate for each upper link by the following equation (4) (step S163).

[0087] Predicted link utilization rate=future traffic volume L(b) / switching threshold TH (4)

[0088] Before substituting the future traffic volume L(b) into equation (4), the switching determination unit 175 converts it into the same traffic volume per unit time as the link rate by, for example, dividing it by the length of the period D(b). The switching determination unit 175 determines whether the calculated predicted link utilization rate exceeds 1 (step S164). If the switching determination unit 175 determines that the link utilization rate is 1 or less (i.e., if the switching determination unit 175 determines that the future traffic volume is equal to or less than the switching threshold), congestion is predicted not to occur, and therefore the processing shown in the flowchart of FIG. 11 is terminated. On the other hand, if the switching determination unit 175 determines that the predicted link utilization rate exceeds 1 (i.e., if the switching determination unit 175 determines that the future traffic volume will exceed the switching threshold), congestion is predicted to occur, and therefore route switching is to be performed (step S165).

[0089] Fig. 12 is a flowchart showing the switching determination process in the switching determination unit 175. When it is determined in step S165 of Fig. 11 that route switching is to be performed, the switching determination unit 175 starts executing the process shown in the flowchart of Fig. 12.

[0090] The switching determination unit 175 acquires from the prediction unit 171 the future traffic volume for each upper link for period D(b), information on the distributed stations 13 subordinate to the aggregate station 14 connected to that upper link, and the future traffic volume DU(b) for that distributed station 13 for period D(b). The switching determination unit 175 determines to switch the connection destination of one or more distributed stations 13 subordinate to the aggregate station 14 using an upper link whose predicted link utilization rate exceeds 1 to another aggregate station 14. At this time, the switching determination unit 175 uses the future traffic volume DU(b) of each distributed station 13 to determine the switching destination aggregate station 14 for the distributed station 13 to be switched to, so that the future traffic volume for each upper link is equal to or less than the switching threshold TH for that upper link (step S171).

[0091] The switching determination unit 175 transmits a path addition instruction to the source central station 14 to add traffic from the remote station 13 to be switched (step S172). Furthermore, the switching determination unit 175 transmits a path deletion instruction to the source central station 14 to delete traffic from the remote station 13 to be switched (step S173). Furthermore, the switching determination unit 175 transmits a path switching instruction to the transfer device 15 to instruct it to switch the communication path between the remote station 13 to be switched and the source central station 14 to the communication path between the remote station 13 to be switched and the destination central station 14 (step S174).

[0092] As described above, the communication system 1 and the mobile communication system 10, which are examples of conventional communication systems, predict future traffic volume of the upper link during period D(a) and calculate the prediction accuracy based on the future traffic volume and the actual traffic volume. The communication system 1 and the mobile communication system 10 determine the switching threshold based on the link rate and prediction accuracy of the upper link. Then, the communication system 1 and the mobile communication system 10 predict future traffic volume of the upper link during period D(b), which is a period after period D(a), and determine whether or not route switching is necessary based on the switching threshold and the future traffic volume.

[0093] For example, in the conventional communication system 1 as described above, the prediction unit 71 of the switching instruction device 17 predicts future traffic volume for each upper-level device 4. Then, based on the prediction result, the switching determination unit 75 predicts the occurrence of congestion and determines whether path switching is necessary. At this time, the switching determination unit 75 starts processing to predict the occurrence of congestion and determine whether path switching is necessary when the prediction results of future traffic volume for all upper-level devices 4 have been collected.

[0094] However, in such a conventional communication system 1, it is not possible to predict the occurrence of congestion and determine whether or not a route change is necessary until the results of predictions of future traffic volumes are collected for all of the higher-level devices 4. As a result, the implementation of the route change may be delayed.

[0095] 13 and 14 are diagrams showing the execution timing of processing in path switching in a conventional communication system. FIGS. 13 and 14 illustrate a case in which a communication system 1 has one central station (e.g., central station #1) as a higher-level device 4 and two distributed stations (e.g., distributed stations #1 and #2) as lower-level devices 3. Furthermore, FIGS. 13 and 14 show the signal transmission patterns of distributed stations #1 and #2 and the signal transmission pattern of central station #1. In FIGS. 13 and 14, "U" represents an uplink slot, "D" represents a downlink slot, and "F" represents a flexible slot. An uplink slot is a slot used for transmitting upstream traffic. A downlink slot is a slot used for transmitting downstream traffic. A flexible slot is a slot used for either upstream or downstream transmission.

[0096] As shown in Fig. 13, when remote station #1 and remote station #2 transmit upstream traffic at the same time, the total traffic generated at central station #1 is the sum of the traffic of remote station #1 and the traffic of remote station #2. Collection of traffic information (hereinafter referred to as "traffic information") for central station #1 is started, and a prediction of the future traffic volume of central station #1 is performed. As shown in Fig. 13, if the prediction of future traffic volume detects that congestion will occur at central station #1 at a certain timing, in a conventional communication system, as shown in Fig. 14, switching is performed so that the switching is completed at the timing when congestion occurs.

[0097] 14 shows, as an example, a case where switching is performed so that uplink traffic (UL #5 in FIG. 14) transmitted from remote station #2 is transferred to central station #2 instead of central station #1, thereby making it possible to avoid congestion occurring in central station #1.

[0098] FIG. 15 is a diagram illustrating a problem with path switching in a conventional communication system. In FIG. 13, no signal is transmitted before congestion occurs in central station #1. Therefore, even if path switching is performed immediately before congestion occurs, there is no impact. In contrast, as shown in FIG. 15, if a signal (UL #5 traffic in FIG. 15) is transmitted immediately before the timing when congestion is predicted to occur in central station #1, the conventional communication system will perform path switching at the timing when the signal is transmitted. In this way, if path switching is performed when traffic is being transmitted, traffic will not be transmitted while the path switching is being performed. In other words, since traffic is buffered while the path switching is being performed, if the path switching is performed when traffic caused by congestion is being transmitted, the congestion delay will be added to the path switching delay. This may result in a communication delay.

[0099] In contrast, in the communication system in each embodiment of the present invention described below, when congestion is detected, for example, as shown in Fig. 16, the timing of switching is determined to be a period before the congestion occurs during which no traffic flows between the lower-level device 3 (distributed stations #1 and #2 in Fig. 16) and the upper-level device 4 (central station #1 in Fig. 16) (hereinafter referred to as a "no-signal section"). Fig. 16 is a diagram showing the execution timing of processing in route switching by the communication system in each embodiment of the present invention.

[0100] As shown in FIG. 16 , by determining a no-signal section as the switching timing, path switching can be performed when no signal is flowing. In the example shown in FIG. 16 , path switching is performed when no signal is flowing, so that part of the traffic of UL #5 and UL #6 in central station #1 is transferred to another central station (e.g., central station #2, not shown), thereby avoiding congestion. To make the traffic state before switching easier to understand, FIG. 16 shows that UL #6 exceeds the processable bandwidth of central station #1 (the dotted line in central station #1 shown in FIG. 16 ). However, as described above, part of the traffic of UL #5 and UL #6 in central station #1 is transferred to another central station. Therefore, UL #6 does not exceed the processable bandwidth of central station #1. As described above, in the communication systems in each embodiment of the present invention described below, congestion delay as a switching delay can be suppressed. As a result, communication delay can be reduced.

[0101] In the communication system of each embodiment, when congestion is detected not only in a no-signal section but also in upstream traffic, the timing of downstream transmission where congestion does not occur may be determined as the switching timing. This makes it possible to suppress congestion delay as a switching delay. As a result, communication delay can be reduced. Below, specific configurations for achieving the above effects will be described using each embodiment as an example.

[0102] 17 is a block diagram showing the configuration of a communication system 1a according to a first embodiment of the present invention. The communication system 1a includes a plurality of lower-level devices 3, a plurality of upper-level devices 4, a switching instruction device 7a, and a switching device 8a. The lower-level devices 3 and the upper-level devices 4 are communicatively connected via the switching device 8a.

[0103] The lower device 3 transmits an upstream signal to the connected upper device 4. The upstream signal transmitted from the lower device 3 is transferred to the destination upper device 4 via the switching device 8a. The lower device 3 transmits wireless traffic information to the switching instruction device 7a. The wireless traffic information in the first embodiment includes at least information indicating the TBS.

[0104] The upper device 4 transmits a downstream signal to the connected lower device 3. The downstream signal transmitted from the upper device 4 is transferred to the destination lower device 3 via the switching device 8a. The upper device 4 transmits traffic information and processable bandwidth (link rate) to the switching instruction device 7a. The traffic information in the first embodiment includes at least information indicating the TBS.

[0105] The switching instruction device 7a instructs the switching device 8a to switch the communication path. The switching instruction device 7a predicts future traffic volume based on collected wireless traffic information or traffic information and estimates no-signal sections. If the switching instruction device 7a determines that congestion will occur, it instructs the switching device 8a to perform path switching in the no-signal section.

[0106] In response to an instruction from the switching instruction device 7a, the switching device 8a switches the transfer path of signals transmitted and received between the lower device 3 and the upper device 4. In other words, the switching device 8a changes the connection relationship between the lower device 3 and the upper device 4.

[0107] 18 is a block diagram showing the functional configuration of a switching instruction device 7a according to the first embodiment of the present invention. The switching instruction device 7a includes an information collection unit 711, a no-signal-interval estimation unit 712, a timing control unit 713, a traffic prediction unit 714, a switching determination unit 715, and a switching instruction unit 716.

[0108] The information collection unit 711 collects wireless traffic information transmitted from each lower-level device 3, and traffic information and processable bandwidth (link rate) information transmitted from each upper-level device 4. Using the collected wireless traffic information, the information collection unit 711 converts the TBS included in the wireless traffic information into upstream time-series traffic data. Here, the upstream time-series traffic data is data indicating the timing at which upstream traffic is transmitted in time series.

[0109] Furthermore, the information collection unit 711 uses the collected traffic information to convert the TBS included in the traffic information into downlink time-series traffic data. Here, the downlink time-series traffic data is data that indicates the timing of downlink traffic transmission in time series. Hereinafter, unless there is any particular distinction between the uplink time-series traffic data and the downlink time-series traffic data, they will simply be referred to as time-series traffic data. The information collection unit 711 outputs the time-series traffic data to the no-signal section estimation unit 712 and the traffic prediction unit 714, and outputs information on the processable bandwidth (link rate) to the traffic prediction unit 714.

[0110] The no-signal interval estimation unit 712 estimates no-signal intervals based on the time-series traffic data output from the information collection unit 711. For example, the no-signal interval estimation unit 712 estimates an interval in which no traffic is flowing, as indicated by the time-series traffic data, as a no-signal interval. Furthermore, the no-signal interval estimation unit 712 estimates an interval in which traffic is flowing, as indicated by the time-series traffic data, as a signal transmission interval. The no-signal interval estimation unit 712 outputs interval information including information indicating the estimated signal transmission interval and no-signal interval to the timing control unit 713. Note that the no-signal interval estimation unit 712 may output interval information including only information indicating the no-signal interval to the timing control unit 713.

[0111] The timing control unit 713 determines the timing of switching the communication path based on the section information output from the no-signal section estimation unit 712. Specifically, the timing control unit 713 determines the no-signal section included in the section information as the switching timing. The timing control unit 713 outputs information indicating the determined switching timing to the switching instruction unit 716.

[0112] The traffic prediction unit 714 predicts the future traffic volume of each lower-level device 3 at each time by using the upstream time-series traffic data among the time-series traffic data output from the information collection unit 711. The traffic prediction unit 714 outputs the prediction results indicating the future traffic volume of each lower-level device 3 at each time and information on the processable bandwidth (link rate) to the switching determination unit 715.

[0113] The switching determination unit 715 determines whether or not path switching is necessary based on the prediction result output from the traffic prediction unit 714 and information on the processable bandwidth (link rate). For example, the switching determination unit 715 determines that path switching is necessary if it detects that congestion will occur, and determines that path switching is not necessary if it does not detect that congestion will occur. Specifically, the switching determination unit 715 predicts the future traffic volume of each host device 4 at each time using the future traffic volume of each lower device 3 at each time. Here, if there is a host device 4 whose future traffic volume exceeds the processable bandwidth (link rate), the switching determination unit 715 determines that congestion will occur. If there is no host device 4 whose future traffic volume exceeds the processable bandwidth (link rate), the switching determination unit 715 determines that congestion will not occur.

[0114] The switching determination unit 715 determines a switching destination candidate when congestion occurs. For example, the switching determination unit 715 determines, as a switching destination candidate, a host device 4 that can accommodate part of the upstream traffic at the time when congestion is estimated to occur. Here, a host device 4 that can accommodate part of the upstream traffic at the time is a host device 4 that does not exceed its processable bandwidth (link rate) even if it accommodates part of the upstream traffic. The switching determination unit 715 outputs information indicating the determined switching destination candidate to the switching instruction unit 716.

[0115] The switching instruction unit 716 generates a switching instruction including information indicating the switching destination candidate output from the switching determination unit 715 and information indicating the switching timing output from the timing control unit 713. The switching instruction unit 716 transmits the generated switching instruction to the switching device 8a.

[0116] 19 is a block diagram showing the functional configuration of the switching device 8a according to the first embodiment of the present invention. The switching device 8a includes an acquisition unit 81, a switching destination setting unit 82, and a switching unit 83.

[0117] The acquisition unit 81 acquires a switching instruction transmitted from the switching instruction device 7 a and outputs the acquired switching instruction to the switching destination setting unit 82 .

[0118] The switching destination setting unit 82 sets the switching destination specified by the information indicating the switching destination candidate in the switching unit 83 in accordance with the switching timing included in the switching instruction output from the acquisition unit 81 .

[0119] The switching unit 83 switches the signal transfer path in accordance with an instruction from the switching destination setting unit 82. Specifically, the switching unit 83 changes the connection relationship between the lower device 3 and the higher device 4 so that the signal is transferred to the switching destination set by the switching destination setting unit 82.

[0120] Fig. 20 is a diagram for explaining the processing of the no-signal interval estimation unit 712 and the timing control unit 713 in the first embodiment of the present invention. Note that Fig. 20 explains the case where there is only upstream traffic. Fig. 20 (A) is a diagram showing an example of upstream time-series traffic data. As shown in Fig. 20 (A), it is shown that upstream signals are transmitted from the lower device 3 in the interval from time t2 to time t3 and the interval from time t11 to time t12. In Fig. 20 (A), the transmission of upstream signals is indicated as UL#1, UL#2, UL#3, and UL#4.

[0121] Here, when upstream traffic is transmitted as shown in Fig. 20(B), the no-signal interval estimation unit 712 estimates the interval from time t4 to time t10 as the no-signal interval, as shown in Fig. 20(C). Note that the signal transmission interval shown in Fig. 20(C) represents the interval in which a signal flows between the lower-level device 3 and the upper-level device 4. In Fig. 20(C), the signal transmission interval represents the interval in which a signal flows from the lower-level device 3 to the upper-level device 4.

[0122] The signal transmission interval shown in (C) of Fig. 20 can be identified based on the uplink time-series traffic data. In the example shown in (B) of Fig. 20, it can be seen that traffic #1 flows at time t2, traffic #2 at time t3, traffic #3 at time t11, and traffic #4 at time t12 based on the uplink time-series traffic data. Therefore, the no-signal interval estimation unit 712 can identify the period during which traffic flows as the signal transmission interval based on the uplink time-series traffic data.

[0123] The signal-free period shown in Fig. 20C represents the period from the start of signal transmission to the start of the next signal transmission, with a signal-free section in between. The signal-free period shown in Fig. 20C can be identified based on upstream time-series traffic data.

[0124] 20C , when the no-signal interval estimation unit 712 estimates a no-signal interval, the timing control unit 713 notifies the switching instruction unit 716 of the no-signal interval from time t4 to time t10 estimated by the no-signal interval estimation unit 712 as the switching timing. This allows the switching instruction unit 716 to instruct the switching device 8a to perform path switching during the no-signal interval from time t4 to time t10. As a result, switching can be performed during the no-signal interval.

[0125] 21 is a diagram for explaining the processing of the no-signal interval estimation unit 712 and the timing control unit 713 in the first embodiment of the present invention. Note that FIG. 21 illustrates a case where not only upstream traffic but also downstream traffic is present. (A) of FIG. 21 is a diagram illustrating an example of upstream time-series traffic data and downstream time-series traffic data. As shown in (A) of FIG. 21, it is indicated that an upstream signal is transmitted from the lower-level device 3 in the interval from time t2 to time t3 and the interval from time t11 to time t12, and that a downstream signal is transmitted from the upper-level device 4 in the interval from time t4 to time t9 and the interval from time t13 onward (at least the interval from time t13 to time t15).

[0126] In (A) of Fig. 21, transmissions of uplink signals are indicated as UL#1, UL#2, UL#3, and UL#4, and transmissions of downlink signals are indicated as DL#1 and DL#2. Here, when the uplink traffic and the downlink traffic are transmitted as shown in (B) of Fig. 21, the no-signal interval estimation unit 712 estimates the intervals at time t1 and time t10 as no-signal intervals, as shown in (C) of Fig. 21.

[0127] The signal transmission section (upstream) shown in Fig. 21C represents a section in which a signal flows from the lower-level device 3 to the upper-level device 4. The signal transmission section (downstream) shown in Fig. 21C represents a section in which a signal flows from the upper-level device 4 to the lower-level device 3. The signal transmission section (upstream) can be identified based on the time-series traffic data for the upstream, and the signal transmission section (downstream) can be identified based on the time-series traffic data for the downstream.

[0128] 21B, it can be seen that traffic #1 flows from time t2 to time t2 and traffic #3 flows from time t11 to time t12 based on the uplink time-series traffic data, and traffic #2 flows from time t4 to time t9 based on the downlink time-series traffic data. Therefore, the no-signal interval estimation unit 712 can identify the period during which traffic flows as a signal transmission interval based on the uplink time-series traffic data and the downlink time-series traffic data.

[0129] The no-signal period shown in Fig. 21C represents the period from the start of signal transmission to the start of the next signal transmission, with a no-signal section in between. The no-signal period shown in Fig. 21C can be identified based on the uplink time-series traffic data and the downlink time-series traffic data.

[0130] 21C , when the no-signal interval estimation unit 712 estimates a no-signal interval, the timing control unit 713 notifies the switching instruction unit 716 of the no-signal intervals at time t1 and time t10 estimated by the no-signal interval estimation unit 712 as switching timings. This allows the switching instruction unit 716 to instruct the switching device 8a to perform path switching at either the no-signal interval, time t1, or time t10. As a result, switching can be performed in the no-signal interval.

[0131] 22 is a flowchart showing the flow of processing performed by the switching instruction device 7a in the first embodiment of the present invention. The information collection unit 711 collects each piece of information from each lower device 3 and each upper device 4 (step S201). The information collection unit 711, for example, collects wireless traffic information from each lower device 3 and collects traffic information and processable bandwidth information from each upper device 4. The information collection unit 711 converts the wireless traffic information into upstream time-series traffic data based on the TBS indicated in the collected wireless traffic information. Furthermore, the information collection unit 711 converts the traffic information into downstream time-series traffic data based on the TBS indicated in the collected traffic information.

[0132] The information collection unit 711 outputs the converted uplink time-series traffic data and downlink time-series traffic data to the no-signal interval estimation unit 712. Furthermore, the information collection unit 711 outputs the converted uplink time-series traffic data and information on the processable bandwidth to the traffic prediction unit 714. The no-signal interval estimation unit 712 estimates no-signal intervals based on the uplink time-series traffic data and downlink time-series traffic data output from the information collection unit 711 (step S202). The no-signal interval estimation unit 712 outputs information indicating the estimated no-signal intervals to the timing control unit 713.

[0133] The timing control unit 713 calculates the switching timing based on the information indicating the no-signal interval output from the no-signal interval estimation unit 712 (step S203). The timing control unit 713 outputs the information indicating the calculated switching timing to the switching instruction unit 716. The traffic prediction unit 714 calculates the future traffic volume of each lower-level device 3 based on the upstream time-series traffic data output from the information collection unit 711 (step S204). The traffic prediction unit 714 outputs the information indicating the calculated future traffic volume of each lower-level device 3 and information on the processable bandwidth to the switching determination unit 715.

[0134] The switching determination unit 715 determines whether congestion will occur based on the information indicating the future traffic volume of each lower-level device 3 and the information on the processable bandwidth output from the traffic prediction unit 714 (step S205). If the switching determination unit 715 determines that congestion will not occur (step S205—NO), the switching instruction device 7a terminates the processing of FIG. 22. On the other hand, if the switching determination unit 715 determines that congestion will occur (step S205—YES), the switching determination unit 715 determines a switching destination candidate (step S206). The switching determination unit 715 outputs information indicating the determined switching destination candidate to the switching instruction unit 716. The switching instruction unit 716 generates a switching instruction including information indicating the switching timing output from the timing control unit 713 and information indicating the switching destination candidate output from the switching determination unit 715. The switching instruction unit 716 transmits the generated switching instruction to the switching device 8a (step S207).

[0135] 23 is a flowchart showing the flow of processing performed by the switching device 8a in the first embodiment of the present invention. The acquisition unit 81 acquires a switching instruction transmitted from the switching instruction device 7a (step S251). The acquisition unit 81 outputs the acquired switching instruction to the switching destination setting unit 82. The switching destination setting unit 82 sets a switching destination and switching timing in the switching unit 83 based on information indicating switching destination candidates and information indicating switching timing included in the switching instruction output from the acquisition unit 81 (step S252).

[0136] The switching unit 83 determines whether it is the switching timing set by the switching destination setting unit 82 (step S253). If the switching unit 83 determines that it is not the switching timing (step S253—NO), the switching unit 83 waits until the switching timing arrives. If the switching unit 83 determines that it is the switching timing (step S253—YES), the switching unit 83 switches the connection destination between the lower-level device 3 and the higher-level device 4 so that a signal is transferred to the switching destination set by the switching destination setting unit 82 (step S254).

[0137] As described above, the switching instruction device 7a provided in the communication system 1a in the first embodiment of the present invention comprises: a traffic prediction unit 714 that predicts future traffic volume based on traffic information transmitted from a plurality of higher-level devices 4 and wireless traffic information transmitted from a plurality of lower-level devices 3; a no-signal section estimation unit 712 that estimates a no-signal section based on the traffic information or the wireless traffic information; a timing control unit 713 that determines the no-signal section estimated by the no-signal section estimation unit 712 as the timing for path switching; and a switching instruction unit 716 that, when congestion is detected to occur based on the future traffic volume predicted by the traffic prediction unit 714, transmits a switching instruction to the switching device 8a, the switching instruction including information indicating a candidate switching destination and information indicating the switching timing determined by the timing control unit 713.

[0138] As described above, in the communication system 1a according to the first embodiment, no-signal intervals are estimated and future traffic is predicted at the timing when traffic information (e.g., TBS) or wireless traffic information (e.g., TBS) is collected, and switching is performed in the no-signal intervals after congestion of future traffic is detected. This allows switching control of the switching device 8a to be performed in accordance with the no-signal intervals. Therefore, switching is already completed at the timing when traffic is transmitted, making it possible to avoid the influence of buffering delays due to switching delays.

[0139] Second Embodiment A second embodiment of the present invention will now be described. The overall configuration diagram of a communication system in the second embodiment is similar to the overall configuration diagram of the communication system 1a in the first embodiment shown in FIG.

[0140] The communication system 1a in the second embodiment described below differs from the communication system 1a in the first embodiment in that the no-signal interval is estimated using information about TDD (Time Division Duplex) in addition to information about TBS. Here, the information about TDD is, for example, TDD config. TDD config is information indicating the allocation ratio between uplink communication slots and downlink communication slots in TDD. In other words, TDD config is information indicating a signal transmission pattern. The differences from the first embodiment will be described in detail below.

[0141] The lower device 3 transmits an uplink signal to the connected upper device 4. The uplink signal transmitted from the lower device 3 is transferred to the destination upper device 4 via the switching device 8a. The lower device 3 transmits wireless traffic information to the switching instruction device 7a. The wireless traffic information in the second embodiment includes at least information indicating the TBS and information related to TDD.

[0142] The information collection unit 711 collects wireless traffic information transmitted from each lower device 3, and traffic information and processable bandwidth (link rate) information transmitted from each higher device 4. The information collection unit 711 outputs time-series traffic data to the no-signal interval estimation unit 712 and traffic prediction unit 714, outputs information related to TDD to the no-signal interval estimation unit 712, and outputs processable bandwidth (link rate) information to the traffic prediction unit 714.

[0143] The no-signal interval estimation unit 712 estimates no-signal intervals based on the time-series traffic data and information related to TDD output from the information collection unit 711. Specifically, the no-signal interval estimation unit 712 calculates the average traffic volume using the time-series traffic data, and estimates no-signal intervals based on the information related to TDD and the average traffic volume.

[0144] Furthermore, the no-signal interval estimation unit 712 estimates intervals where traffic indicated by the time-series traffic data flows as signal transmission intervals. The no-signal interval estimation unit 712 outputs interval information including information indicating the estimated signal transmission intervals and no-signal intervals to the timing control unit 713. Note that the no-signal interval estimation unit 712 may also output interval information including only information indicating the no-signal intervals to the timing control unit 713.

[0145] 24 is a diagram for explaining the processing of the no-signal interval estimation unit 712 and the timing control unit 713 in the second embodiment of the present invention. Note that FIG. 24 illustrates a case where not only upstream traffic but also downstream traffic is present. (A) of FIG. 24 is a diagram illustrating an example of upstream time-series traffic data and downstream time-series traffic data. As shown in (A) of FIG. 24, an upstream signal is transmitted from the lower-level device 3 in the interval from time t2 to time t3 and the interval from time t11 to time t12, and a downstream signal is transmitted from the upper-level device 4 in the interval from time t4 to time t9 and the interval from time t13 onward (at least the interval from time t13 to time t15).

[0146] In (A) of Fig. 24, the transmission of uplink signals is indicated as UL#1, UL#2, UL#3, and UL#4, and the transmission of downlink signals is indicated as DL#1 and DL#2. Here, consider a case where uplink traffic is transmitted as shown in (B) of Fig. 24, and downlink traffic is transmitted as shown in (C) of Fig. 24. The no-signal period estimation unit 712 calculates the no-signal period based on the following equation (5) using the TDD Config information shown in (D) of Fig. 24. Note that x in equation (5) ｓｌｏｔ represents the traffic transmission amount per slot. Note that the following formula (5) is based on the state shown in FIG.

[0147] Signal transmission time = traffic #2 × (t9 - t4 + 1) / x ｓｌｏｔ Signal transmission period = t2 to t3 + signal transmission time No-signal period = t3 + signal transmission period + 1 to t10 ... Equation (5)

[0148] Here, we will provide some additional information about equation (5). Based on (A) in FIG. 24, an uplink signal is transmitted from time t2 to t3, and the downlink transmission interval (the interval to which the downlink signal is assigned) is from time t4 to t9. Under these circumstances, depending on the amount of downlink traffic, traffic may not be transmitted during the period from time t4 to t9, and transmission may be completed in an earlier period, such as from time t4 to t6, and the time during which the downlink signal is transmitted is calculated as the signal transmission time. In other words, the signal transmission time shown in equation (5) can be expressed as follows:

[0149] Signal transmission time = total traffic volume to be transmitted / traffic volume that can be transmitted in one slot

[0150] In equation (5), the total traffic volume scheduled for transmission is calculated as traffic #2 × (t9 - t4 + 1). The no-signal interval shown in equation (5) occurs after the signal transmission interval (t4 to t4 + signal transmission time) from time t3 onwards. In the above example, since downlink signals are transmitted during the period from time t4 to t9, the signal transmission time = t2 to t3 + t4 to t9 = t2 to t9. Therefore, the no-signal interval occurs after time t9, that is, from time t10 onwards. Note that uplink signal transmission begins at time t11, so the no-signal interval estimation unit 712 estimates the no-signal interval to be from t10 to t10. Furthermore, since uplink signal transmission begins at time t2, the no-signal interval estimation unit 712 also estimates the previous time t1 as a no-signal interval.

[0151] Through the above processing, the no-signal section estimation unit 712 estimates the section from time t1 to time t10 as a no-signal section, as shown in FIG. 24(E).

[0152] 24(E), when the no-signal interval estimation unit 712 estimates a no-signal interval, the timing control unit 713 notifies the switching instruction unit 716 of the no-signal intervals at time t1 and time t10 estimated by the no-signal interval estimation unit 712 as switching timings. This allows the switching instruction unit 716 to instruct the switching device 8a to perform path switching at either the no-signal interval, time t1, or time t10. As a result, switching can be performed in the no-signal interval.

[0153] As described above, in the communication system 1a according to the second embodiment of the present invention, in addition to the TBS, TDD Config information indicating a signal transmission pattern is transmitted from each lower-level device 3 as wireless traffic information. The no-signal-period estimation unit 712 included in the switching instruction device 7a estimates no-signal periods based on the TBS and TDD Config information transmitted from each lower-level device 3. Specifically, the no-signal-period estimation unit 712 calculates an average traffic volume based on the TBS and performs a predetermined calculation based on the calculated average traffic volume and the TDD Config information to estimate no-signal periods. This allows for more accurate estimation of no-signal periods. As a result, switching control of the switching device 8a can be performed in accordance with the no-signal periods. Therefore, switching has already been completed by the time traffic is transmitted, making it possible to avoid the effects of buffering delays due to switching delays.

[0154] Third Embodiment A third embodiment of the present invention will now be described. The overall configuration diagram of a communication system according to the third embodiment is similar to the overall configuration diagram of the communication system 1a according to the first embodiment shown in FIG. 17.

[0155] The communication system 1a in the third embodiment described below differs from the communication system 1a in the second embodiment in that, in addition to TBS information and TDD information, information indicating communication quality such as 5QI (5G Quality of Service Identifier) ​​is used, and when a no-signal interval is not found by the no-signal interval estimation unit, a signal transmission interval that satisfies predetermined conditions is estimated and the estimated signal transmission interval is determined as the switching timing. The differences from the second embodiment will be described in detail below, but the present invention is also applicable to the case where a no-signal interval is not found in the first embodiment.

[0156] 25 is a block diagram showing the functional configuration of a switching instruction device 7aa according to the third embodiment of the present invention. The switching instruction device 7aa includes an information collection unit 711, a no-signal-interval estimation unit 712, a timing control unit 713, a traffic prediction unit 714, a switching determination unit 715, a switching instruction unit 716, and a switching slot determination unit 717.

[0157] The lower device 3 transmits an uplink signal to the connected upper device 4. The uplink signal transmitted from the lower device 3 is forwarded to the destination upper device 4 via the switching device 8a. The lower device 3 transmits wireless traffic information to the switching instruction device 7aa. The wireless traffic information in the third embodiment includes at least information indicating TBS, information related to TDD, and information indicating communication quality.

[0158] The information collection unit 711 collects wireless traffic information transmitted from each lower device 3, and traffic information and processable bandwidth (link rate) information transmitted from each higher device 4. The information collection unit 711 outputs time-series traffic data to the no-signal interval estimation unit 712 and traffic prediction unit 714, outputs information related to TDD and information indicating communication quality to the no-signal interval estimation unit 712, and outputs processable bandwidth (link rate) information to the traffic prediction unit 714.

[0159] Similar to the method described in the second embodiment, the no-signal interval estimation unit 712 estimates a no-signal interval based on the time-series traffic data and information related to TDD output from the information collection unit 711. Note that, similar to the method described in the first embodiment, the no-signal interval estimation unit 712 may estimate a no-signal interval based on the time-series traffic data. The no-signal interval estimation unit 712 outputs interval information indicating the no-signal interval estimation result, information indicating communication quality, the time-series traffic data, and information related to TDD to the switching slot determination unit 717. Note that, if the no-signal interval estimation result indicates that there is no no-signal interval, the no-signal interval estimation unit 712 outputs interval information including information indicating that there is no no-signal interval to the switching slot determination unit 717, and if there is a no-signal interval, the no-signal interval estimation unit 712 outputs interval information including information indicating the no-signal interval to the switching slot determination unit 717.

[0160] The switching slot determination unit 717 estimates the switching slot based on the interval information output from the no-signal interval estimation unit 712. Specifically, the switching slot determination unit 717 estimates the switching slot when the interval information indicates that there is no no-signal interval, i.e., when there is no no-signal interval. On the other hand, when the interval information includes information indicating a no-signal interval, i.e., when there is a no-signal interval, the switching slot determination unit 717 does not perform any particular processing and outputs the interval information to the timing control unit 713.

[0161] If the section information indicates that there is no no-signal section, the switching slot determination section 717 calculates the allowable delay for uplink communication and downlink communication using information indicating communication quality (e.g., 5QI) output from the no-signal section estimation section 712. Next, the switching slot determination section 717 calculates the average downlink traffic volume using the downlink time-series traffic data, and calculates the delay time required for switching when switching in the downlink section (hereinafter referred to as "switching delay") based on the information related to TDD and the average downlink traffic volume.

[0162] The switching slot determination unit 717 compares the calculated allowable delay with the switching delay, and if the switching delay does not exceed the allowable delay, outputs section information including information indicating the downlink transmission section to the timing control unit 713. On the other hand, if the switching delay exceeds the allowable delay, the switching slot determination unit 717 considers switching at the next timing.

[0163] Here, the processing of the switching slot determination unit 717 will be specifically described. For example, when congestion occurs in the uplink, if the downlink time series traffic is y=[y1, y2, y3, ..., yn] and the TDD slots are [t1, t2, t3, ..., tn], and it is considered whether to perform switching at time t1, if the switching time is one slot, the switching delay T ｌａｔｅｎｃｙ is calculated based on the following formula (6), and when the switching time is 2 slots, the switching delay T ｌａｔｅｎｃｙ is calculated based on the following formula (7).

[0164] T ｌａｔｅｎｃｙ =(y1+y2) / link ｒａｔｅ ...Formula (6)

[0165] T ｌａｔｅｎｃｙ =(y1+y2+y3) / link ｒａｔｅ ...Formula (7)

[0166] The switching instruction device 7aa is configured to ｌａｔｅｎｃｙ If the delay time T exceeds the threshold, the switching is not performed and the switching at the next time t2 is considered. ｌａｔｅｎｃｙ If the delay does not exceed the allowable delay, the switching instruction device 7aa sets the switching timing to time t1.

[0167] The timing control unit 713 determines the timing of switching the communication path based on the section information output from the switching slot determination unit 717. Specifically, the timing control unit 713 determines, as the switching timing, a downlink transmission section identified by information indicating a downlink transmission section included in the section information. Note that, when information indicating a no-signal section is included in the section information output from the switching slot determination unit 717, the timing control unit 713 determines the no-signal section as the switching timing, as in the first or second embodiment. The timing control unit 713 outputs information indicating the determined switching timing to the switching instruction unit 716.

[0168] 26 is a flowchart showing the flow of processing performed by the switching slot determination unit 717 in the third embodiment of the present invention. The processing in FIG. 26 is executed when the interval information output from the no-signal interval estimation unit 712 includes information indicating that there is no no-signal interval.

[0169] The switching slot determination unit 717 calculates the allowable delay for uplink and downlink communications using information indicating communication quality (e.g., 5QI) output from the no-signal-interval estimation unit 712 (step S301). Here, for example, it is assumed that the switching slot determination unit 717 calculates that the allowable delay for uplink is 5 ms and the allowable delay for downlink is 20 ms. It is assumed that the signal transmission pattern (TDD slot) indicated by the information related to TDD is expressed as [t1, t2, t3, ..., tn], where n is an integer equal to or greater than 1.

[0170] The switching slot determination unit 717 sets n in the signal transmission pattern tn to 1 (step S302). Next, the switching slot determination unit 717 calculates the average downlink traffic volume using the downlink time-series traffic data, and calculates the switching delay based on the TDD information and the average downlink traffic volume (step S303). The switching slot determination unit 717 determines whether the switching delay is less than the allowable delay (step S304). If the switching slot determination unit 717 determines that the switching delay is less than the allowable delay (step S304—YES), the switching slot determination unit 717 outputs interval information including information indicating the downlink transmission interval to the timing control unit 713 (step S305).

[0171] On the other hand, if the switching slot determination unit 717 determines that the switching delay is equal to or greater than the allowable delay (step S304-NO), the switching slot determination unit 717 adds 1 to n (step S306). Thereafter, the switching slot determination unit 717 executes the process of step S303 again.

[0172] As described above, in the communication system 1a according to the third embodiment of the present invention, in addition to TDD Config information indicating the TBS and signal transmission pattern, information indicating communication quality such as 5QI is transmitted from each lower-level device 3 as wireless traffic information. When the no-signal-interval estimation unit 712 is unable to estimate a no-signal interval (there is no no-signal interval), the switching slot determination unit 717 included in the switching instruction device 7aa estimates the uplink allowable delay and the downlink allowable delay based on the information indicating the communication quality transmitted from each lower-level device 3. Furthermore, the switching slot determination unit 717 calculates the average downlink traffic volume based on the TBS transmitted from each lower-level device 3, and calculates the switching delay when switching in the downlink interval by performing a predetermined calculation based on the calculated average downlink traffic volume and the TDD Config information. The switching slot determination unit 717 then compares the calculated allowable delay with the switching delay, and if the switching delay does not exceed the allowable delay, outputs interval information including information indicating the downlink transmission interval to the timing control unit 713. As described above, in the communication system 1a according to the third embodiment of the present invention, when there is no signal-free interval and the switching delay does not exceed the allowable delay, switching is performed during the signal transmission interval. As a result, in the signal transmission interval that satisfies the above-described predetermined conditions, switching control of the switching device 8a can be executed in accordance with the signal transmission interval. Therefore, switching is already completed when traffic is transmitted, and it is possible to avoid the influence of buffering delay due to switching delay.

[0173] Fourth Embodiment A fourth embodiment of the present invention will now be described. The overall configuration diagram of a communication system in the fourth embodiment is similar to the overall configuration diagram of the communication system 1a in the first embodiment shown in FIG.

[0174] The communication system 1a in the fourth embodiment described below differs from the communication system 1a in the third embodiment in that the number of milliseconds ahead to predict is determined based on the switching timing due to a no-signal section and the predicted time / switching time. The differences from the third embodiment will be described in detail below.

[0175] 27 is a block diagram showing the functional configuration of a switching instruction device 7b according to the fourth embodiment of the present invention. The switching instruction device 7b includes an information collection unit 711, a no-signal-interval estimation unit 712, a timing control unit 713b, a traffic prediction unit 714b, a switching determination unit 715, and a switching instruction unit 716.

[0176] The timing control unit 713b calculates the switching timing based on the information indicating the no-signal interval included in the interval information output from the no-signal interval estimation unit 712. The timing control unit 713b outputs the information indicating the switching timing to the switching instruction unit 716, and outputs the information indicating the switching timing and the information indicating the no-signal period to the traffic prediction unit 714b.

[0177] The traffic prediction unit 714b determines how many milliseconds ahead to predict based on the information indicating the switching timing and the information indicating the signal-free period output from the timing control unit 713b, the predicted time acquired in past traffic predictions, and the switching timing. The traffic prediction unit 714b predicts the traffic at the determined prediction destination time.

[0178] 28 is a flowchart showing the flow of processing performed by the traffic prediction unit 714b in the fourth embodiment of the present invention. The traffic prediction unit 714b receives inputs of a switching time, information indicating the switching timing, time-series traffic data, and information indicating a past predicted time (step S401). Here, the switching time represents, for example, the time required for switching in the switching device 8a. The traffic prediction unit 714b calculates a total time by adding the input past predicted time and the switching time (step S402). The traffic prediction unit 714b determines whether the subtracted time, which is the switching timing indicated by the information indicating the switching timing minus the latest traffic reception time, exceeds the total time calculated in the processing of step S402 (step S403).

[0179] If the traffic prediction unit 714b determines that the subtracted time obtained by subtracting the latest traffic reception time from the switching timing indicated in the information indicating the switching timing exceeds the total time (step S403-YES), the traffic prediction unit 714b predicts the traffic volume for the total time obtained by adding the past predicted time and the switching time (step S404).

[0180] On the other hand, if the traffic prediction unit 714b determines that the subtracted time obtained by subtracting the latest traffic reception time from the switching timing indicated in the information indicating the switching timing does not exceed the total time (step S403-NO), the traffic prediction unit 714b predicts the traffic volume for the total time obtained by adding the past predicted time, the switching time, and the time of the signal-free period (step S405).

[0181] The traffic prediction unit 714b feeds back the prediction result (step S406). Specifically, the traffic prediction unit 714b stores the prediction result predicted in the process of step S405 so that it can be used the next time the process shown in FIG. 28 is executed. The traffic prediction unit 714b outputs information indicating the predicted future traffic volume to the switching determination unit 715.

[0182] As described above, the communication system 1a according to the fourth embodiment of the present invention determines how far into the future the future traffic volume should be predicted in accordance with the timing of switching. This allows the communication system 1a according to the fourth embodiment to predict the future traffic volume within a range that requires such prediction. As a result, efficient switching becomes possible.

[0183] Fifth Embodiment A fifth embodiment of the present invention will now be described. The overall configuration diagram of a communication system in the fifth embodiment is similar to the overall configuration diagram of the communication system 1a in the first embodiment shown in FIG.

[0184] The communication system 1a in the fifth embodiment described below differs from the communication system 1a in the fourth embodiment in that, if switching is not completed within a no-signal section, the delay time required for buffering is compared with the congestion delay when switching is performed in a no-signal section after congestion has occurred, and switching is performed at a timing when the delay is small. The differences from the fourth embodiment will be described in detail below.

[0185] 29 is a block diagram showing the functional configuration of a switching instruction device 7c according to the fifth embodiment of the present invention. The switching instruction device 7c includes an information collection unit 711, a no-signal-interval estimation unit 712, a timing control unit 713b, a traffic prediction unit 714b, a switching determination unit 715, and a switching instruction unit 716c.

[0186] The switching instruction unit 716c determines whether switching is possible within the expected switching timing based on the switching candidate reception timing, the switching timing, and the switching time. If switching is possible within the expected switching timing, the switching instruction unit 716c performs switching at the switching timing. In other words, if switching is possible within the expected switching timing, the switching instruction unit 716c transmits a switching instruction to the switching device 8a, the switching instruction including information indicating the switching timing and information indicating the switching destination candidate.

[0187] On the other hand, if switching is not possible within the expected switching timing, the switching instruction unit 716c calculates a buffering delay based on the switching time and traffic volume. The switching instruction unit 716c compares the congestion delay calculated for the switching destination candidate with the calculated buffering delay, and if the congestion delay is greater than the buffering delay, performs switching at the switching timing. If the congestion delay is equal to or less than the buffering delay, performs switching at the next switching timing. The next switching timing is, for example, the switching timing plus the radio signal period.

[0188] Here, the buffering delay is calculated based on the switching time, the traffic transmission rate, and the upper link rate as follows:

[0189] Buffering delay = Switching time x Traffic sending rate / Upper rate

[0190] 30 is a flowchart showing the flow of processing performed by the switching instruction unit 716c in the fifth embodiment of the present invention. The switching instruction unit 716c receives information indicating a switching destination candidate, information indicating a congestion delay, and information indicating a switching timing (step S501). Based on the received information, the switching instruction unit 716c determines whether the switching candidate reception time exceeds the time obtained by adding the switching time to the switching timing (step S502).

[0191] If the switching instruction unit 716c determines that the switching candidate reception time exceeds the time obtained by adding the switching time to the switching timing (step S502—YES), the switching instruction unit 716c determines whether the congestion delay exceeds the buffering delay (step S503).If the switching instruction unit 716c determines that the congestion delay exceeds the buffering delay (step S503—YES), or if the switching instruction unit 716c determines that the switching candidate reception time does not exceed the time obtained by adding the switching time to the switching timing (step S502—NO), the switching instruction unit 716c performs switching at the switching timing (step S504).

[0192] On the other hand, if the switching instruction unit 716c determines that the congestion delay does not exceed the buffering delay (step S503-NO), the switching instruction unit 716c performs switching at a timing that adds a no-signal period to the switching timing (step S505).

[0193] As described above, in the communication system 1a according to the fifth embodiment of the present invention, if switching is not completed within a no-signal section, the delay time required for buffering delay is compared with the congestion delay when switching is performed in a no-signal section after congestion has occurred, and the switching is performed at a timing when the congestion delay is small. This allows the switching to be performed at a timing when the impact of delay is small. Therefore, it is possible to avoid the impact of buffering delay due to switching delay.

[0194] Sixth Embodiment A sixth embodiment of the present invention will now be described. The overall configuration diagram of a communication system in the sixth embodiment is similar to the overall configuration diagram of the communication system 1a in the first embodiment shown in FIG. 17 described above.

[0195] The communication system 1a according to the sixth embodiment described below differs from the communication system 1a according to the first embodiment in that time series prediction is not performed for signal-free periods, but only for signal transmission periods. The differences from the first embodiment will be described in detail below.

[0196] 31 is a block diagram showing the functional configuration of a switching instruction device 7d according to the sixth embodiment of the present invention. The switching instruction device 7d includes an information collection unit 711, a no-signal-interval estimation unit 712d, a timing control unit 713, a traffic prediction unit 714d, a switching determination unit 715, and a switching instruction unit 716.

[0197] The no-signal interval estimation unit 712d estimates no-signal intervals based on the time-series traffic data and information related to TDD output from the information collection unit 711. Furthermore, the no-signal interval estimation unit 712d estimates, as a signal transmission interval, an interval through which traffic indicated by the time-series traffic data flows. The no-signal interval estimation unit 712d outputs interval information including information indicating the estimated signal transmission intervals and no-signal intervals to the timing control unit 713 and the traffic prediction unit 714d.

[0198] The traffic prediction unit 714d predicts future traffic volume only for the signal transmission section based on the signal transmission section included in the section information output from the no-signal section estimation unit 712d and the time-series traffic data output from the information collection unit 711.

[0199] 32 is a flowchart showing the flow of processing performed by the traffic prediction unit 714d in the sixth embodiment of the present invention. Information on signal transmission intervals, no-signal intervals, and time-series traffic is input to the traffic prediction unit 714d (step S601). Based on the input information indicating the signal transmission intervals and the no-signal intervals, the traffic prediction unit 714d determines whether a future traffic time falls within a signal transmission interval (step S602).

[0200] If the traffic prediction unit 714d determines that the future traffic time is within the signal transmission interval (step S602—YES), the traffic prediction unit 714d predicts the future traffic volume based on the information indicating the signal transmission interval and the information indicating the time-series traffic (step S603). On the other hand, if the traffic prediction unit 714d determines that the future traffic time is not within the signal transmission interval (step S602—NO), the processing in FIG. 32 ends.

[0201] As described above, the communication system 1a according to the sixth embodiment of the present invention does not perform time series prediction for signal-free periods, but only predicts signal transmission periods, thereby making it possible to reduce the amount of calculation required for prediction.

[0202] (Modifications) In the above-described embodiment, the difference from the first embodiment has been described as an example, but the configuration of the sixth embodiment can be applied to any of the second to fifth embodiments.

[0203] Seventh Embodiment A seventh embodiment of the present invention will now be described. The overall configuration diagram of a communication system in the seventh embodiment is similar to the overall configuration diagram of the communication system 1a in the first embodiment shown in FIG.

[0204] The communication system 1a in the seventh embodiment described below differs from the communication system 1a in the second embodiment in that when computational resources are tight, TDD estimation is not performed even in the case of dynamic TDD only when a predetermined condition is satisfied, and switching is always performed in the slot through which uplink traffic or downlink traffic is transmitted. The differences from the second embodiment will be described in detail below.

[0205] The no-signal interval estimation unit 712 determines whether the TDD information included in the wireless traffic information transmitted from each lower-level device 3 is fixed TDD or dynamic TDD. Specifically, the no-signal interval estimation unit 712 determines whether the TDD information is fixed TDD or dynamic TDD based on changes in the TDD config measured in advance. The no-signal interval estimation unit 712 does not estimate TDD if the TDD information is fixed TDD. On the other hand, if the TDD information is dynamic TDD and the traffic fluctuations are compared and found to be identical to past traffic based on the time-series traffic fluctuations, the no-signal interval estimation unit 712 uses past TDD without performing TDD estimation. Note that the no-signal interval estimation unit 712 performs TDD estimation if the TDD information is dynamic TDD and the traffic fluctuations are not compared and found to be identical to past traffic based on the time-series traffic fluctuations. This reduces the amount of calculation required for TDD estimation.

[0206] Fig. 33 is a flowchart showing the flow of processing performed by the no-signal interval estimation unit 712 in the seventh embodiment of the present invention. The processing shown in Fig. 33 is executed when computational resources are tight. Information related to TDD and time-series traffic information are input to the no-signal interval estimation unit 712 (step S701). The no-signal interval estimation unit 712 determines whether or not the no-signal interval estimation unit 712 is in fixed TDD mode based on the input information related to TDD (step S702). If the no-signal interval estimation unit 712 determines that the no-signal interval estimation unit 712 is in fixed TDD mode (step S702—YES), the no-signal interval estimation unit 712 ends the processing shown in Fig. 33.

[0207] On the other hand, if the no-signal interval estimation unit 712 determines that the mode is not fixed TDD (step S702—NO), the no-signal interval estimation unit 712 determines whether the past signal transmission interval and the transmission interval of the time-series traffic are the same (step S703).If the no-signal interval estimation unit 712 determines that the past signal transmission interval and the transmission interval of the time-series traffic are the same (step S703—YES), the no-signal interval estimation unit 712 ends the processing of FIG.

[0208] On the other hand, if the no-signal interval estimation unit 712 determines that the past signal transmission interval and the transmission interval of the time-series traffic are not the same (step S703-NO), the no-signal interval estimation unit 712 calculates the no-signal interval and the signal transmission interval (step S704). The no-signal interval estimation unit 712 feeds back the calculated no-signal interval and the signal transmission interval. In other words, the no-signal interval estimation unit 712 uses the calculated no-signal interval and the signal transmission interval in the next processing of step S703.

[0209] As described above, in the communication system 1a according to the seventh embodiment of the present invention, when calculation resources are tight, in the case of dynamic TDD, TDD estimation is not performed only when a predetermined condition is satisfied, and switching is always performed in the slot through which uplink traffic or downlink traffic is transmitted. This makes it possible to reduce the amount of calculation required for TDD estimation.

[0210] Eighth Embodiment An eighth embodiment of the present invention will now be described. The overall configuration diagram of a communication system in the eighth embodiment is similar to the overall configuration diagram of the communication system 1a in the first embodiment shown in FIG.

[0211] The communication system 1a in the eighth embodiment described below differs from the communication system 1a in the fifth embodiment in that when computational resources are tight, TDD estimation is not performed even in the case of dynamic TDD only when a predetermined condition is satisfied, and switching is always performed in the slot through which uplink traffic or downlink traffic is transmitted. The differences from the fifth embodiment will be described in detail below.

[0212] The no-signal interval estimation unit 712 does not estimate TDD in the case of fixed TDD, but in the case of dynamic TDD, if the traffic fluctuations are compared with past traffic and are the same based on the time-series traffic fluctuations, it uses past TDD without estimating TDD. This reduces the amount of calculation required for TDD estimation. More specifically, if dynamic TDD is used and the traffic fluctuations are different from past traffic, the no-signal interval estimation unit 712 determines whether the processor load (CPU (Central Processing Unit) load) of the switching instruction device 7c exceeds the processable amount.

[0213] If the no-signal interval estimation unit 712 determines that the processor load exceeds the processable amount, it sets the no-signal transmission timing to the 10 ms slot start timing, sets the signal transmission start timing to the guard time, and does not update the TDD until the processor load decreases (for example, the processor load becomes less than the processable amount). Updating the TDD means changing the transmission timing of uplink or downlink traffic, for example, by changing the TDD config.

[0214] Fig. 34 is a flowchart showing the flow of processing performed by the no-signal interval estimation unit 712 in the eighth embodiment of the present invention. In Fig. 33, the same processes as in Fig. 33 are denoted by the same reference numerals as in Fig. 33, and descriptions thereof will be omitted. In the processing of step S703, if the no-signal interval estimation unit 712 determines that the past signal transmission interval and the transmission interval of the time-series traffic are not the same (step S703-NO), the no-signal interval estimation unit 712 determines whether the CPU load exceeds the processable amount (step S751).

[0215] If the no-signal interval estimation unit 712 determines that the CPU load exceeds the processable amount (step S751—YES), the no-signal interval estimation unit 712 sets the no-signal transmission timing to a 10 ms slot start timing and the signal transmission start timing to a guard time, and terminates the processing of FIG. 34 . On the other hand, if the no-signal interval estimation unit 712 determines that the CPU load does not exceed the processable amount (step S751—NO), the no-signal interval estimation unit 712 calculates the no-signal interval and the signal transmission interval (step S753). The no-signal interval estimation unit 712 feeds back the calculated no-signal interval and the signal transmission interval. That is, the no-signal interval estimation unit 712 uses the calculated no-signal interval and the signal transmission interval in the next processing of step S703.

[0216] As described above, in the communication system 1a according to the eighth embodiment of the present invention, when calculation resources are tight, in the case of dynamic TDD, TDD estimation is not performed only when a predetermined condition is satisfied, and switching is always performed in the slot through which uplink traffic or downlink traffic is transmitted. This makes it possible to reduce the amount of calculation required for TDD estimation.

[0217] Ninth Embodiment A ninth embodiment of the present invention will now be described. The overall configuration diagram of a communication system in the ninth embodiment is similar to the overall configuration diagram of the communication system 1a in the first embodiment shown in FIG.

[0218] The communication system 1a in the ninth embodiment described below differs from the communication system 1a in the fifth embodiment in that the delay requirements are calculated for each traffic, and after confirming that the delay due to switching satisfies the delay requirements, switching is performed in order starting with the traffic that has the greatest impact on congestion. If the delay requirements are not satisfied, switching of the traffic with the next highest priority (with looser delay requirements) is considered. The differences from the fifth embodiment will be described in detail below.

[0219] The switching decision unit 715 calculates the congestion delay of the optical path, multiple candidate switching destinations for congestion avoidance, and the congestion delay at that time based on the future traffic volume of each lower-level device 3 and the processable bandwidth (link rate) of the upper-level device 4.

[0220] The switching instruction unit 716c calculates a switching operation that satisfies the allowable delay based on the allowable delay, the congestion delay of the optical path calculated by the switching determination unit 715, the switching destination candidates, and the switching timing determined by the timing control unit 713. The allowable delay is calculated based on information indicating communication quality (e.g., 5QI). The method of calculating the allowable delay is the same as in the third embodiment.

[0221] 35 is a flowchart showing the flow of processing performed by the switching instruction unit 716c in the ninth embodiment of the present invention. In FIG. 35, the same processes as those in FIG. 30 are denoted by the same reference numerals as in FIG. 30, and their explanations are omitted. In the processing of step S503, if the switching instruction unit 716c determines that the congestion delay does not exceed the buffering delay (step S503-NO), the switching instruction unit 716c determines whether the buffering delay exceeds the allowable delay (step S551).

[0222] If the switching instruction unit 716c determines that the buffering delay exceeds the allowable delay (step S551—YES), the switching instruction unit 716c then performs processing on the switching destination candidate (step S552). Then, the processing of step S551 is executed. If the switching instruction unit 716c determines that the buffering delay does not exceed the allowable delay (step S551—NO), the switching instruction unit 716c performs switching at a timing that adds a signal-free period to the switching timing (step S553).

[0223] As described above, the communication system 1a according to the ninth embodiment of the present invention calculates the delay requirement for each traffic, and after confirming that the delay due to switching satisfies the delay requirement, switches traffic in order, starting with the traffic that has the greatest impact on congestion. If the delay requirement is not satisfied, the system considers switching traffic with the next highest priority (with a looser delay requirement). This makes it possible to suppress the impact of delay.

[0224] According to the above-described embodiment, the communication control device includes a traffic prediction unit, an estimation unit, a timing control unit, and a switching instruction unit. For example, the communication control device corresponds to the switching instruction devices 7a to 7d in the embodiment, the traffic prediction unit corresponds to the traffic prediction units 714, 714b, and 714d in the embodiment, the estimation unit corresponds to the no-signal-interval estimation units 712 and 712d in the embodiment, the timing control unit corresponds to the timing control units 713 and 713b in the embodiment, and the switching instruction unit corresponds to the switching instruction units 716 and 716c in the embodiment.

[0225] The traffic prediction unit predicts future traffic volume based on information about traffic transmitted from at least one of the multiple higher-level devices or the multiple lower-level devices. The estimation unit estimates no-signal sections, which are periods when no signals flow, based on the traffic information. The timing control unit determines the timing of path switching based on the estimation result of the wireless signal section by the estimation unit. When congestion is detected based on the future traffic volume predicted by the traffic prediction unit, the switching instruction unit transmits a switching instruction to a device that transfers signals between the multiple higher-level devices and the multiple lower-level devices, the switching instruction including information indicating a switching destination candidate and information indicating the timing of path switching determined by the timing control unit.

[0226] The traffic information is wireless traffic information or traffic information in the embodiment, such as information about TBS or TDD, or information indicating communication quality (e.g., 5QI). The device that transfers signals between the multiple higher-level devices and the multiple lower-level devices is a switching device 8a in the embodiment. The higher-level device is the higher-level device 4 in the embodiment, and the lower-level device is the lower-level device 3 in the embodiment.

[0227] The estimation unit may estimate an average traffic volume based on information relating to traffic, and estimate a no-signal section based on information indicating a signal transmission pattern and the estimated average traffic volume.

[0228] In addition, the above-mentioned specified condition is that the allowable delay for upstream or downstream communication does not exceed the delay time required for route switching by the device that forwards the signal, and the device may further include a determination unit that, when the estimation result of the no-signal section by the estimation unit includes information indicating that the no-signal section could not be estimated, estimates the allowable delay based on information regarding traffic and determines a signal transmission section that satisfies the specified condition based on the estimated allowable delay.

[0229] The above determination unit is the switching slot determination unit 717 in the embodiment.

[0230] In addition, the traffic prediction unit may determine which timing to predict based on the predicted time obtained in past traffic predictions, the switching time required for route switching by the device that forwards the signal, information indicating the timing of route switching determined by the timing control unit, information regarding traffic, and information indicating the signal transmission pattern.

[0231] In addition, if the switching is not completed at the timing of the route switching determined by the timing control unit, the above-mentioned switching instruction unit may compare the delay time required for buffering delay with the congestion delay time when the switching is performed at a timing after congestion occurs, and if the delay time is less than the congestion delay time, send a switching instruction to the device that forwards the signal, or if the delay time is greater than the congestion delay time, wait for a predetermined period before sending the switching instruction.

[0232] In addition, the above-mentioned estimation unit may determine whether to estimate a no-signal section only when the condition of limited computational resources is met, when the information indicating the signal transmission pattern changes dynamically, and based on traffic fluctuations indicated in the information regarding traffic.

[0233] Furthermore, according to the above-described embodiment, the communication system includes a transfer device and a communication control device. For example, the transfer device is a switching device 8a in the embodiment, and the communication control device is a switching instruction device 7a to 7d in the embodiment. The transfer device transfers signals between a plurality of higher-level devices and a plurality of lower-level devices. The communication control device controls the transfer path of the signals by the transfer device.

[0234] The communication control device includes a traffic prediction unit, an estimation unit, a timing control unit, and a switching instruction unit. For example, the communication control device corresponds to the switching instruction devices 7a to 7d in the embodiment, the traffic prediction unit corresponds to the traffic prediction units 714, 714b, and 714d in the embodiment, the estimation unit corresponds to the no-signal-interval estimation units 712 and 712d in the embodiment, the timing control unit corresponds to the timing control units 713 and 713b in the embodiment, and the switching instruction unit corresponds to the switching instruction units 716 and 716c in the embodiment. The operations of the traffic prediction unit, the estimation unit, the timing control unit, and the switching instruction unit have been described above, and therefore will not be described here.

[0235] The transfer device includes a switching destination setting unit and a switching unit. For example, the switching destination setting unit is the switching destination setting unit 82 in the embodiment, and the switching unit is the switching unit 83 in the embodiment. The switching destination setting unit sets a switching destination specified by information indicating a switching destination candidate in accordance with information indicating the timing of path switching included in a switching instruction transmitted from the communication control device. The switching unit changes the connection relationships between the multiple lower devices and the multiple upper devices so that a signal is transferred to the switching destination set by the switching destination setting unit.

[0236] Part or all of the configuration of the switching instruction device in the above-described embodiment may be implemented by a computer. In this case, a program for implementing this function may be recorded on a computer-readable recording medium, and the program may be loaded and executed by a computer system. Note that the term "computer system" as used herein includes hardware such as an operating system (OS) and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, read-only memories (ROMs), and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording medium" may also include devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or devices that store programs for a fixed period of time, such as volatile memory within the computer system that serves as the server or client. The program may be designed to implement part of the above-described functions, or may be capable of implementing the above-described functions in combination with programs already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0237] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0238] 1, 1a...communication system, 3, 3-1 to 3-4...lower-level devices, 4, 4-1 to 4-2...higher-level devices, 7, 7a to 7d...switching instruction device, 8a...switching device, 10...mobile communication system, 11...terminal station, 12, 12-m...antenna station, 13, 13-1 to 13-M...remote station, 14, 14-1 to 14-N...aggregate station, 15...transfer device, 16...resource allocation device, 17...switching instruction device, 20...higher-level network, 71...prediction unit, 72...switching threshold determination unit, 73...prediction accuracy calculation unit, 7 4...Threshold calculation unit, 75...Switching determination unit, 171...Prediction unit, 172...Switching threshold determination unit, 173...Prediction accuracy calculation unit, 174...Threshold calculation unit, 175...Switching determination unit, 711...Information collection unit, 712, 712d...No signal interval estimation unit, 713, 713b, 713d...Timing control unit, 714, 714b, 714d...Traffic prediction unit, 715...Switching determination unit, 716, 716c...Switching instruction unit, 717...Switching slot determination unit, 81...Acquisition unit, 82...Switching destination setting unit, 83...Switching unit

Claims

1. A traffic prediction unit that predicts a future traffic volume based on information regarding traffic transmitted from at least one of a plurality of upper devices or a plurality of lower devices; an estimation unit that estimates a signal-free section, which is a period during which no signal flows, based on the information regarding the traffic; a timing control unit that determines a path switching timing based on an estimation result of the signal-free section by the estimation unit; and a switching instruction unit that transmits a switching instruction including information indicating a switching destination candidate and information indicating the path switching timing determined by the timing control unit to a device that transfers signals between the plurality of upper devices and the plurality of lower devices when it is detected that congestion occurs based on the future traffic volume predicted by the traffic prediction unit. A communication control device comprising:

2. The estimation unit estimates an average traffic volume based on the information regarding the traffic, and estimates the signal-free section based on the information indicating the signal transmission pattern and the estimated average traffic volume. The communication control device according to claim 1.

3. When information indicating that the signal-free section could not be estimated is included as an estimation result of the signal-free section by the estimation unit, a determination unit that estimates an allowable delay based on the information regarding the traffic and determines a signal transmission section that satisfies a predetermined condition based on the estimated allowable delay is further provided. The predetermined condition is that the allowable delay for upstream communication or downstream communication does not exceed the delay time required for path switching by the device that transfers the signal. The communication control device according to claim 1.

4. The traffic prediction unit determines at which timing to perform the prediction based on the prediction time obtained from past traffic predictions, the switching time required for path switching by the device that transfers the signal, the information indicating the path switching timing determined by the timing control unit, the information regarding the traffic, and the information indicating the signal transmission pattern. The communication control device according to any one of claims 1 to 3.

5. The switching instruction unit, when the switching is not completed at the timing of path switching determined by the timing control unit, compares the delay time required by buffering delay with the convergence delay time when switching is performed at the timing after the occurrence of convergence. If the delay time is less than or equal to the convergence delay time, the switching instruction is transmitted to the device that transfers the signal. If the delay time is greater than the convergence delay time, the transmission of the switching instruction is waited for a predetermined period. The communication control device according to any one of claims 1 to 3.

6. The estimation unit determines whether to estimate the silent period based on the variation of the traffic indicated by the information regarding the traffic, only when the condition that the calculation resources are in shortage is satisfied and the information indicated by the signal transmission pattern varies dynamically. The communication control device according to any one of claims 1 to 3.

7. A communication system including a transfer device that transfers signals between a plurality of upper devices and a plurality of lower devices, and a communication control device that controls the signal transfer path of the transfer device. The communication control device includes: a traffic prediction unit that predicts a future traffic volume based on information regarding traffic transmitted from at least any one of the plurality of upper devices or the plurality of lower devices; an estimation unit that estimates a silent period, which is a period during which no signal flows, based on the information regarding the traffic; a timing control unit that determines the timing of path switching based on the estimation result of the silent period by the estimation unit; and a switching instruction unit that transmits a switching instruction including information indicating a switching destination candidate and information indicating the timing of path switching determined by the timing control unit to the transfer device when it is detected that convergence occurs based on the future traffic volume predicted by the traffic prediction unit. The transfer device includes: a switching destination setting unit that sets a switching destination specified by the information indicating the switching destination candidate according to the information indicating the timing of path switching included in the switching instruction transmitted from the communication control device; and a switching unit that changes the connection relationship between the plurality of lower devices and the plurality of upper devices so that a signal is transferred to the switching destination set by the switching destination setting unit. A communication system.

8. A communication control method executed by a computer, predicting a future traffic volume based on information regarding traffic transmitted from at least one of a plurality of upper devices or a plurality of lower devices, estimating a no-signal section, which is a period during which no signal flows, based on the information regarding the traffic, determining a timing for route switching based on an estimation result of the no-signal section, and when it is detected that congestion occurs based on the predicted future traffic volume, transmitting a switching instruction including information indicating a switching destination candidate and information indicating the determined timing for route switching to a device that transfers signals between the plurality of upper devices and the plurality of lower devices.

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