Control device and switching method

Abstract

A control device in a communication system comprising a base station, a plurality of higher-level devices connected to the base station, and a control device connected to the base station and the plurality of higher-level devices, the control device comprising: a rate calculation unit that calculates a transmittable rate that can be transmitted by a terminal device that performs wireless communication with the base station; a transmission time calculation unit that calculates the delay amount of a wireless section between the base station and a terminal device on the basis of the transmittable rate calculated by the rate calculation unit and a transfer amount pertaining to data transfer of the terminal device; and a switching indication unit that, when the sum total of the delay amount of the wireless section and the amount of a delay related to a wired section that occurs between the base station and each higher-level device does not satisfy the value indicated by a delay requirement, switches the connection destination of the base station so as to satisfy the value indicated by the delay requirement and to go through a path in which the delay amount of the wired section is smaller than the path of the switching source.　

Description

Control device and switching method

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

[0002] 5G (Generation) QoS (Quality of Service) aims to guarantee end-to-end communication quality by using 5QI (5G QoS Identifier) ​​and other methods to guarantee bandwidth. However, even if bandwidth is guaranteed at a higher level than the base station (gNodeB) (gNB), if the radio wave conditions in the wireless section between the terminal device (User Equipment) UE and the gNB are poor, a situation may arise in which the transmission volume in the wireless section cannot be increased to the guaranteed bandwidth (communication speed).

[0003] When the reception strength of the desired radio wave in the wireless section between the UE and the gNB is low, or when the strength of the interfering radio wave is greater than the desired radio wave strength, complex coding with a high degree of multi-value cannot be correctly decoded. Therefore, it is necessary to select coding with a low coding rate that has a high probability of being decoded even if an error occurs. Therefore, in an environment with poor radio wave conditions, a small MCS (Modulation and Coding Scheme) is selected, which results in a lower coding rate and a lower effective throughput in the wireless section.

[0004] If there are many other UEs connected to the same gNB and issuing transmission requests, the number of transmission permissions allocated will decrease relatively even if the radio wave strength is strong, and the effective throughput of the wireless section will decrease.

[0005] “5G Quality of Service”, DEVOPEDIA, [Retrieved April 14, 2023], Internet,<URL:https: / / devopedia.org / 5g-quality-of-service > 3GPP 38.214 table 5.1.3.1-1 MCS index table 1 for PDSCH "Intent-based application-network cooperative control technology for video streaming services," NTT Technical Journal, [Retrieved April 14, 2023], Internet,<URL: https: / / journal.ntt.co.jp / article / 18766>

[0006] Conventionally, there are methods for reducing latency in video transmission applications by reducing image quality according to the available bandwidth, which represents the available transmission bandwidth. However, these methods are not suitable for applications that require both high image quality and low latency, such as remote control or high-quality live streaming. Therefore, when the radio wave conditions in the wireless section temporarily deteriorate and the effective rate drops, delays occur in the wireless section, making it impossible to meet the latency requirements of the application. In particular, when the amount of data transmitted from an application at one time is large, such as in a video transmission application, the discrepancy between the rate generated by the application and the reduced effective rate can cause significant latency.

[0007] In view of the above circumstances, the present invention aims to provide a technology that can reduce the overall delay, including the wireless section and the wired section, required for data transfer, even when the radio wave conditions in the wireless section deteriorate.

[0008] One aspect of the present invention is a control device in a communication system comprising a base station, a plurality of upper level devices connected to the base station, and a control device connected to the base station and the plurality of upper level devices, the control device comprising: a rate calculation unit that calculates a transmission rate at which a terminal device that performs wireless communication with the base station can transmit; a transfer time calculation unit that calculates a delay amount in the wireless section between the base station and the terminal device based on the transmission rate calculated by the rate calculation unit and a transfer volume related to data transfer by the terminal device; and a switching instruction unit that, when the sum of the delay amount in the wireless section and the delay amount related to the wired section occurring between the base station and each upper level device does not satisfy a value indicated by a delay requirement, switches the connection destination of the base station so that it goes via a route that satisfies the value indicated by the delay requirement and has a smaller delay amount in the wired section than the route from which it was switched.

[0009] One aspect of the present invention is a switching method performed by a communication system including a base station, a plurality of upper devices connected to the base station, and a control device connected to the base station and the plurality of upper devices, the switching method calculating a transmission rate at which a terminal device that performs wireless communication with the base station can transmit, calculating a delay amount in the wireless section between the base station and the terminal device based on the calculated transmission rate and the data transfer volume related to the data transfer of the terminal device, and if the sum of the delay amount in the wireless section and the delay amount related to the wired section occurring between the base station and each upper device does not satisfy a value indicated by a delay requirement, switching the connection destination of the base station so that it passes through a route that satisfies the value indicated by the delay requirement and has a smaller delay amount in the wired section than the route from which it was switched.

[0010] According to the present invention, even if the radio wave conditions deteriorate in the wireless section, it is possible to reduce the overall delay required for data transfer, including the wireless section and the wired section.

[0011] It is a diagram showing an example of the configuration of a communication system in an embodiment. It is a flowchart showing a process flow (part 1) of a controller in the embodiment. It is a flowchart showing a process flow (part 2) of a controller in the embodiment.

[0012] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of a communication system 100 according to the embodiment. The communication system 100 includes a base station 10, a switching device 20, a plurality of host devices 30, a plurality of servers 40, and a controller 50. In FIG. 1, two host devices 30-1 and 30-2 are shown as the plurality of host devices 30, and two servers 40-1 and 40-2 are shown as the plurality of servers 40. Note that the number of base stations 10, switching devices 20, host devices 30, and servers 40 is not particularly limited.

[0013] In the following description, when there is no need to distinguish between the host devices 30-1 and 30-2, they will be referred to as the host device 30, and when there is no need to distinguish between the servers 40-1 and 40-2, they will be referred to as the server 40. The base station 10 and the switching device 20, the switching device 20 and the host device 30, and the host device 30 and the server 40 are connected by wire. Furthermore, the controller 50 is connected by wire to the base station 10, the switching device 20, and the host device 30. One or more terminal devices 60 are connected wirelessly to the base station 10. In the following description, it is assumed that the base station 10 is connected to the host device 30-1 via the switching device 20.

[0014] The terminal device 60 transmits a flow that is the target of QoS guarantee. For example, the terminal device 60 transmits video data.

[0015] The base station 10 performs wireless communication with one or more terminal devices 60. The base station 10 is, for example, a gNB in ​​5G. The base station 10 acquires transmission parameters before traffic from the terminal devices 60 arrives. The base station 10 transmits information about the acquired transmission parameters to the controller 50. Here, the transmission parameters include, for example, information such as MCS (Modulation Coding Scheme), TDD configuration, and the number of allocated resource blocks. For example, the base station 10 acquires the transmission parameters from a scheduler. The base station 10 acquires a flow transmitted from the terminal device 60. The base station 10 transmits data (for example, video data) included in the acquired flow to the switching device 20.

[0016] The switching device 20 switches the transfer path of the video data transmitted from the base station 10 in response to an instruction from the controller 50. The switching device 20 may be, for example, an L2 switch or an optical switch.

[0017] The host device 30 transmits the video data transmitted from the base station 10 to the server 40. The host device 30 is, for example, a UPF (User Plane Function). Furthermore, the host device 30 calculates the available bandwidth of the wired section between the base station 10 and the host device 30-1 and the delay of the wired section. For example, the host device 30-1 calculates the available bandwidth of the wired section between the base station 10 and the host device 30-1 and the delay of the wired section. The host device 30-2 calculates the available bandwidth of the wired section between the base station 10 and the host device 30-2 and the delay of the wired section. The available bandwidth of the wired section is calculated using an existing method. For example, the available bandwidth of the wired section may be calculated based on the link rate, may be measured in advance, or may be notified from a host controller. When the available bandwidth of the wired section is measured in advance, for example, goodput may be used. The delay of the wired section is calculated using an existing method. For example, the delay of the wired section may be measured in advance or may be notified from a host controller. When measuring the delay in the wired section in advance, for example, Ping may be used. The delay in the wired section represents the delay in the wired path and does not include delays related to image transfer, etc. The higher-level device 30 transmits information on the calculated available bandwidth in the wired section and information on the delay in the wired section to the controller 50.

[0018] The server 40 processes the video data transmitted from the higher-level device 30. For example, the server 40 is an edge server.

[0019] The controller 50 controls each device included in the communication system 100. The controller 50 includes a communication unit 51 and a control unit 52. The controller 50 is one aspect of a control device.

[0020] The communication unit 51 communicates with other devices. The communication unit 51 receives transmission-related parameters from, for example, the base station 10. The communication unit 51 transmits a switching instruction to, for example, the switching device 20. The switching instruction is an instruction to switch the connection destination of the base station 10. Here, the information that can uniquely identify the higher-level device 30 is, for example, the MAC address of the higher-level device 30. Note that the information that can uniquely identify the higher-level device 30 is not limited to the MAC address of the higher-level device 30, and may be other information that can uniquely identify the higher-level device 30. The communication unit 51 receives, for example, information on the available bandwidth of the wired section and information on the delay in the wired section transmitted from each higher-level device 30. The communication unit 51 outputs the received information to the control unit 52.

[0021] The control unit 52 is configured using one or more processors such as a CPU (Central Processing Unit) and a memory. The control unit 52 executes a program to realize the functions of a rate calculation unit 521, a transfer time calculation unit 522, a delay requirement comparison unit 523, and a switching instruction unit 524.

[0022] Some or all of the rate calculation unit 521, transfer time calculation unit 522, delay requirement comparison unit 523, and switching instruction unit 524 may be realized by hardware (including circuitry) such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array), or may be realized by a combination of software and hardware. The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, and non-transitory storage media such as storage devices built into a computer system, such as hard disks. The program may be transmitted via a telecommunications line.

[0023] Some of the functions of the rate calculation unit 521, the transfer time calculation unit 522, the delay requirement comparison unit 523, and the switching instruction unit 524 do not need to be pre-installed in the controller 50, and may be realized by installing additional application programs in the controller 50.

[0024] The rate calculation unit 521 calculates the rate at which the terminal device 60 can transmit based on the information on the transmission parameters received by the communication unit 51. Specifically, the rate calculation unit 521 calculates the rate N at which the terminal device 60 can transmit based on the following equation (1): ｉｎｆｏ Calculate.

[0025]

[0026] In formula (1), N ＲＥ represents the number of allocated resource blocks, R represents the coding rate, and Q ｍ represents the modulation index and v represents the number of layers. Since equation (1) is the transmittable amount per slot, the rate calculation unit 521 calculates the transmittable rate N obtained based on equation (1). ｉｎｆｏ The effective rate per unit time is calculated by multiplying this by the uplink ratio specified by the TDD configuration information.

[0027] The rate calculation unit 521 may directly acquire the transport block size (TBS) and multiply it by the uplink ratio specified by the TDD configuration information to calculate the effective rate per unit time. The rate calculation unit 521 may acquire actual reception rate information from the switching device 20, the host device 30, or the wireless controller, rather than transmission parameter information obtained from the scheduler of the base station 10. The actual reception rate information is, for example, the amount of data received per unit time (number of received bytes) at a port of the host device 30 connected to the base station 10. Because data (main signal) is directly transferred to the switching device 20 and the host device 30, the switching device 20 and the host device 30 can directly grasp the amount of data (main signal) received. The switching device 20 or the host device 30 transfers information on the grasped amount of data (main signal) received to the controller 50. The wireless controller is a device wirelessly connected to the controller 50 and the base station 10. The wireless controller acquires and stores the reception rate for each predetermined time (for example, one minute) from the base station 10. The wireless controller transfers the acquired statistical value of the reception rate for each predetermined time to the controller 50 as information on the amount of data (main signal) received. Using the method described above, the rate calculation unit 521 acquires information on the actual reception rate from either the switching device 20, the higher-level device 30, or the wireless controller.

[0028] The transfer time calculation unit 522 acquires information about the average bit rate and frame rate of video transmitted in a flow transmitted by the terminal device 60. For example, if the switching device 20 is an L2 switch, the transfer time calculation unit 522 acquires information about the average bit rate and frame rate of video based on the Session Description Protocol (SDP). As an example, the base station 10 or the higher-level device 30 may transfer SDP packets to the controller 50, thereby allowing the transfer time calculation unit 522 to acquire information about the average bit rate and frame rate of video. The base station 10 or the higher-level device 30 may transfer information about the average bit rate and frame rate of video included in the SDP packets to the controller 50, thereby allowing the transfer time calculation unit 522 to acquire information about the average bit rate and frame rate of video.

[0029] Similarly, when the switching device 20 is an optical switch, the transfer time calculation unit 522 acquires information on the average video bit rate and information on the frame rate based on the SDP. As an example, the base station 10 or the higher-level device 30 may transfer SDP packets to the controller 50, thereby allowing the transfer time calculation unit 522 to acquire information on the average video bit rate and information on the frame rate. The base station 10 or the higher-level device 30 may transfer information on the average video bit rate and information on the frame rate included in the SDP packets to the controller 50, thereby allowing the transfer time calculation unit 522 to acquire information on the average video bit rate and information on the frame rate.

[0030] The transfer time calculation unit 522 calculates the transfer amount to be transmitted (the amount of data per image) based on the information on the average bit rate and frame rate of the acquired video. Furthermore, the transfer time calculation unit 522 calculates the amount of delay in the wireless section based on the transfer amount to be transmitted and the effective rate per unit time of the wireless section calculated by the rate calculation unit 521. For example, the transfer time calculation unit 522 calculates the amount of delay in the wireless section by dividing the transfer amount to be transmitted by the effective rate per unit time of the wireless section.

[0031] Furthermore, the transfer time calculation unit 522 calculates the amount of delay required for image transfer in the wired section based on the information on the available bandwidth of the wired section received by the communication unit 51 and the amount of data to be transferred. For example, the transfer time calculation unit 522 calculates the amount of delay required for image transfer in the wired section by dividing the amount of data to be transferred by the available bandwidth of the wired section. In this case, the transfer time calculation unit 522 uses the available bandwidth of the wired section obtained from the host device 30 to which the base station 10 is connected as the available bandwidth of the wired section. Therefore, when the base station 10 is connected to the host device 30-1 via the switching device 20, the transfer time calculation unit 522 uses the available bandwidth of the wired section obtained from the host device 30-1 as the available bandwidth of the wired section.

[0032] The delay requirement comparison unit 523 calculates the sum of the delay amount in the wireless section and the delay amount required for image transfer in the wired section calculated by the transfer time calculation unit 522, and the delay amount indicated in the delay information for the wired section received by the communication unit 51. At this time, the delay requirement comparison unit 523 uses the delay amount indicated in the delay information for the wired section obtained from the host device 30 to which the base station 10 is connected, as the delay amount indicated in the delay information for the wired section received by the communication unit 51. Therefore, when the base station 10 is connected to the host device 30-1 via the switching device 20, the delay requirement comparison unit 523 uses the delay amount indicated in the delay information for the wired section obtained from the host device 30-1 as the delay amount indicated in the delay information for the wired section received by the communication unit 51.

[0033] The delay requirement comparison unit 523 compares the calculated total delay amount with the value indicated by the delay requirement. Here, the delay requirement indicates the conditions under which delay is acceptable. The delay requirement indicates the delay amount including the delay in the wireless section, the delay in the wired section, and even the image transfer delay. The delay requirement comparison unit 523 determines, as a result of the comparison, whether the calculated total delay amount satisfies the delay requirement. For example, the delay requirement comparison unit 523 determines that the delay requirement is satisfied if the calculated total delay amount is less than the value indicated by the delay requirement. In this case, the delay requirement comparison unit 523 determines that switching the route of the wired section is not necessary. Because switching the route of the wired section is not necessary, the delay requirement comparison unit 523 does not particularly notify the switching instruction unit 524. The delay requirement is acquired from a higher-level controller.

[0034] On the other hand, if the total value of the calculated delay amounts is equal to or greater than the value indicated by the delay requirement, the delay requirement comparison unit 523 determines that the delay requirement is not satisfied. In this case, the delay requirement comparison unit 523 determines that switching of the route of the wired section is necessary. If the delay requirement comparison unit 523 determines that the delay requirement is not satisfied, it performs processing to identify a higher-level device 30 that satisfies the delay requirement. The delay requirement comparison unit 523 determines the identified higher-level device 30 as the higher-level device 30 to be switched to. The delay requirement comparison unit 523 notifies the switching instruction unit 524 of information indicating the determined higher-level device 30.

[0035] In addition, when there are multiple host devices 30 that satisfy the delay requirements, the delay requirement comparison unit 523 determines one host device 30 according to predetermined conditions as the switching destination host device 30. Here, as the predetermined conditions, the delay requirement comparison unit 523 may determine the host device 30 with the smallest delay in the wired section as the switching destination host device 30, or may determine the host device 30 with the smallest overall delay (the sum of the delay in the wired section, the delay in the wireless section, and the delay required for image transfer in the wired section) as the switching destination host device 30.

[0036] If the delay requirement comparison unit 523 determines that the delay requirement is not satisfied, the delay requirement comparison unit 523 instructs the transfer time calculation unit 522 to calculate the amount of delay required for image transfer in the wired section based on information obtained from another host device 30 (e.g., host device 30-2). The other host device 30 refers to a host device 30 that is not connected to the base station 10 as a data transfer path. Note that if there are two or more other host devices 30, the delay requirement comparison unit 523 may instruct the transfer time calculation unit 522 to calculate the amount of delay required for image transfer in the wired section for each of the other host devices 30.

[0037] The transfer time calculation unit 522 calculates the amount of delay required for image transfer in the wired section based on information about the available bandwidth for the wired section obtained from another host device 30 (e.g., host device 30-2) in response to an instruction from the delay requirement comparison unit 523. When the transfer time calculation unit 522 is instructed by the delay requirement comparison unit 523 to calculate the amount of delay required for image transfer in the wired section for each other host device 30, it calculates the amount of delay required for image transfer in the wired section for each other host device 30.

[0038] Then, the delay requirement comparison unit 523 calculates the sum of the delay amount in the wireless section calculated by the transfer time calculation unit 522 and the delay amount required for image transfer in the wired section, and the delay amount indicated by the delay information in the wired section received by the communication unit 51, for each other higher-level device 30.

[0039] The delay requirement comparison unit 523 uses the total value for each of the other host devices 30 obtained by the above process (for example, the total delay value for the host device 30-2) to identify a host device 30 that satisfies the delay requirement.

[0040] The switching instruction unit 524 transmits a switching instruction to the switching device 20 so that the flow transmitted from the terminal device 60 is transmitted to the higher-level device 30 that is the switching destination notified by the instruction from the delay requirement comparison unit 523. For example, the switching instruction unit 524 generates a switching instruction including information that can uniquely identify the higher-level device 30 that is the switching destination. The switching instruction unit 524 transmits the generated switching instruction to the switching device 20.

[0041] Next, we will explain how the transfer time calculation unit 522 calculates the transfer volume. When transmitting video, the video format can be notified by SDP before the video transmission. Among these, information on the average video bit rate and frame rate can be notified. In the present invention, by using this method, the transfer time calculation unit 522 obtains information on the average video bit rate and frame rate. For the purpose of explanation, we will assume that the delay in the wired section between the base station 10 and the host device 30-1 is 20 ms and the available bandwidth of the wired section is 10 Gbps (Giga bit per second), and that the delay in the wired section between the base station 10 and the host device 30-2 is 2 ms and the available bandwidth of the wired section is 400 Mbps (Mega bit per second). As an example, if the average video bit rate is 400 Mbps and the frame rate is 20 fps (frames per second), we can calculate that the transfer volume per image is 20 Mbit (2.5 MB).

[0042] [When the wireless section is in good condition] If the effective rate of the wireless section is 1 Gbps, the time required for image transfer in the wireless section on a route passing through the higher-level device 30-1 is 20 Mbit / 1 Gbps (bottleneck = wireless section) = 20 ms. The time required for image transfer in the wireless section (20 ms) plus the delay in the wired section (20 ms) totals 40 ms.

[0043] [When the wireless section deteriorates] When the effective rate of the wireless section drops to 400 Mbps, the time required for image transfer in the wireless section on the route passing through the host device 30-1 increases to 20 Mbit / 400 Mbps = 50 ms. The time required for image transfer in the wireless section (50 ms) plus the delay in the wired section (20 ms) totals 70 ms. On the other hand, when the wireless section deteriorates on the route passing through the host device 30-2, the same transfer delay (50 ms) occurs in the wireless section, but the delay in the wired section is reduced. The time required for image transfer in the wireless section (50 ms) plus the delay in the wired section (2 ms) totals 52 ms.

[0044] [When the wireless section is improved] Even when the wireless section is improved, if the image passes through the host device 30-2, the available bandwidth of the wired section of the host device 30-2 is 400 Mbps, which causes the available bandwidth of the wired section to become a bottleneck. As a result, it takes 50 ms for the image to be transferred on the wired section side. This is because, when the wireless section is in good condition, no additional delay is added even when the image passes through the host device 30-2. However, when the wireless section is transmitted at 1 Gbps, the available bandwidth of the path passing through the host device 30-2 becomes 400 Mbps. As a result, a delay similar to shaping is added on the wired section (transfer volume / bottleneck bandwidth = available bandwidth of the wired section), and it takes 50 ms for the image to be transferred on the wired section side. As a result, a decision is made to switch to the host device 30-1 because the delay is smaller when switching to the host device 30-1.

[0045] 2 is a flowchart showing a first processing flow of the controller 50 in the embodiment. At the start of the processing in FIG. 2, it is assumed that the base station 10 is connected to the upper device 30-1 via the switching device 20.

[0046] The rate calculation unit 521 calculates the rate at which the terminal device 60 can transmit based on the information on the transmission parameters received by the communication unit 51. Thereafter, the rate calculation unit 521 calculates the calculated transmittable rate N ｉｎｆｏ The rate calculation unit 521 calculates the effective rate per unit time by multiplying the effective rate per unit time by the uplink ratio specified by the TDD configuration information (step S101). The rate calculation unit 521 outputs information on the calculated effective rate per unit time to the transfer time calculation unit 522.

[0047] The transfer time calculation unit 522 acquires information on the average bit rate and frame rate of the video transmitted in the flow transmitted by the terminal device 60. Based on the acquired information on the average bit rate and frame rate of the video, the transfer time calculation unit 522 calculates the transfer amount to be transmitted (the amount of data per image) (step S102). The transfer time calculation unit 522 calculates the amount of delay in the wireless section based on the effective rate per unit time of the wireless section output from the rate calculation unit 521 and the calculated transfer amount to be transmitted.

[0048] Furthermore, the transfer time calculation unit 522 calculates the amount of delay required for image transfer in the wired section between the base station 10 and the upper device 30-1 (hereinafter referred to as the "amount of delay required for image transfer in the wired section in the upper device 30-1") based on information on the available bandwidth of the wired section between the base station 10 and the upper device 30-1 received by the communication unit 51 (hereinafter referred to as the "available bandwidth of the wired section in the upper device 30-1") and the calculated transfer amount to be transmitted (step S103).

[0049] The transfer time calculation unit 522 outputs information on the calculated delay amount in the wireless section and information on the delay amount required for image transfer in the wired section in the host device 30-1 to the delay requirement comparison unit 523. The delay requirement comparison unit 523 receives as input the information on the delay amount in the wireless section and the information on the delay amount required for image transfer in the wired section in the host device 30-1 output from the transfer time calculation unit 522, and information on the delay in the wired section between the base station 10 and the host device 30-1 received by the communication unit 51. The delay requirement comparison unit 523 calculates the sum of the delay amount indicated by the input information on the delay amount in the wireless section, the delay amount indicated by the information on the delay amount required for image transfer in the wired section in the host device 30-1, and the delay amount indicated by the information on the delay in the wired section between the base station 10 and the host device 30-1.

[0050] The delay requirement comparison unit 523 compares the calculated total value with the value indicated by the delay requirement previously obtained from the upper controller. Based on the comparison result, the delay requirement comparison unit 523 determines whether or not switching of the wired section route is necessary (step S104). If the calculated total value does not satisfy the delay requirement (total value > value indicated by the delay requirement), the delay requirement comparison unit 523 determines that switching of the wired section route is necessary. On the other hand, if the calculated total value satisfies the delay requirement (total value ≦ value indicated by the delay requirement), the delay requirement comparison unit 523 determines that switching of the wired section route is not necessary.

[0051] If the delay requirement comparison unit 523 determines that switching of the wired section route is not necessary (step S104—NO), the controller 50 terminates the processing of FIG. 2. On the other hand, if the delay requirement comparison unit 523 determines that switching of the wired section route is necessary (step S104—YES), the delay requirement comparison unit 523 identifies a host device 30 that satisfies the delay requirement to be used as the switching destination (step S105). Specifically, the delay requirement comparison unit 523 calculates the sum of the delay amount indicated by the information on the delay amount of the wireless section, the delay amount indicated by the information on the delay amount required for image transfer in the wired section between the base station 10 and another host device 30 (e.g., host device 30-2), and the delay amount indicated by the information on the delay in the wired section between the base station 10 and another host device 30 (e.g., host device 30-2), and compares the calculated sum with the value indicated by the delay requirement to identify a host device 30 that satisfies the delay requirement.

[0052] If there are two other host devices 30, namely, 30-2 and 30-3, the delay requirement comparison unit 523 compares the sum of the delay amounts for each of the host devices 30-2 and 30-3 with the value indicated by the delay requirement. For example, the delay requirement comparison unit 523 calculates the sum of the delay amount indicated by the information on the delay amount of the wireless section, the delay amount indicated by the information on the delay amount required for image transfer in the wired section between the base station 10 and the host device 30-2, and the delay amount indicated by the information on the delay in the wired section between the base station 10 and the host device 30-2, and compares the calculated sum with the value indicated by the delay requirement. Furthermore, the delay requirement comparison unit 523 calculates the sum of the delay amount indicated by the information on the delay amount of the wireless section, the delay amount indicated by the information on the delay amount required for image transfer in the wired section between the base station 10 and the host device 30-3, and the delay amount indicated by the information on the delay in the wired section between the base station 10 and the host device 30-3, and compares the calculated sum with the value indicated by the delay requirement.

[0053] In this way, if the delay requirement cannot be satisfied by a route passing through the host device 30-1 to which the current base station 10 is connected, the delay requirement comparison unit 523 determines whether the delay requirement can be satisfied by a route passing through another host device 30. Then, when the delay requirement comparison unit 523 identifies a host device 30 that satisfies the delay requirement, it determines the identified host device 30 that satisfies the delay requirement as the host device 30 to be switched to. If there are multiple host devices 30 that satisfy the delay requirement, the delay requirement comparison unit 523 determines one host device 30 as the host device 30 to be switched to in accordance with predetermined conditions. Here, it is assumed that the host device 30-2 is determined as the host device 30 to be switched to. The delay requirement comparison unit 523 notifies the switching instruction unit 524 of information indicating the determined host device 30-2.

[0054] The switching instruction unit 524 instructs the switching device 20 to switch the path so that the host device 30-2 notified by the delay requirement comparison unit 523 is connected to the base station 10 (step S105). Specifically, the switching instruction unit 524 generates a switching instruction including information that can uniquely identify the host device 30-2 that is the switching destination. The switching instruction unit 524 transmits the generated switching instruction to the switching device 20. As a result, the switching device 20 that has received the switching instruction switches the path to which the base station 10 is connected from the host device 30-1 to the host device 30-2.

[0055] When switching paths as described above, it is assumed that the wireless environment will improve after the switch. If the wireless environment improves and the effective rate significantly returns, delays in image transfer will increase if the available bandwidth for the host device 30 after the switch is smaller than the improved effective rate. Therefore, if the wireless environment improves after the switch, the controller 50 can maintain low-latency communication according to the wireless environment by switching to a path that passes through the host device 30 with a smaller overall delay (when in good condition). This will be described in detail below using FIG. 3.

[0056] 3 is a flowchart showing the process flow (part 2) of the controller 50 in the embodiment. The process at the time of switchback is explained in FIG. 3. It is assumed that, at the start of the process in FIG. 3, the base station 10 is connected to the upper device 30-2 via the switching device 20.

[0057] The rate calculation unit 521 calculates the rate at which the terminal device 60 can transmit based on the information on the transmission parameters received by the communication unit 51. Thereafter, the rate calculation unit 521 calculates the calculated transmittable rate N ｉｎｆｏ The effective rate per unit time is calculated by multiplying the effective rate per unit time by the uplink ratio specified by the TDD configuration information (step S201). The rate calculation unit 521 determines whether a switchback condition is satisfied based on the calculated effective rate per unit time (step S202). The switchback condition is a condition indicating that the communication environment in the wireless section has improved, such as when the effective rate per unit time is equal to or greater than a threshold.

[0058] The rate calculation unit 521 compares the effective rate per unit time with a threshold value, and determines that the reversion condition is satisfied if the effective rate per unit time is equal to or greater than the threshold value. On the other hand, the rate calculation unit 521 compares the effective rate per unit time with the threshold value, and determines that the reversion condition is not satisfied if the effective rate per unit time is less than the threshold value. The threshold value is set in advance. If the rate calculation unit 521 determines that the reversion condition is not satisfied (step S202-NO), the controller 50 ends the processing of FIG. 3.

[0059] If the rate calculation unit 521 determines that the switchback condition is satisfied (step S202—YES), the rate calculation unit 521 outputs information on the calculated effective rate per unit time to the transfer time calculation unit 522. The transfer time calculation unit 522 acquires information on the average bit rate and frame rate of the video transmitted in the flow transmitted by the terminal device 60. The transfer time calculation unit 522 calculates the transfer amount to be transmitted (amount of data per image) based on the acquired information on the average bit rate and frame rate of the video (step S203).

[0060] The transfer time calculation unit 522 calculates the amount of delay in the wireless section based on the effective rate per unit time of the wireless section output from the rate calculation unit 521 and the calculated amount of transfer to be transmitted. Furthermore, the transfer time calculation unit 522 calculates the amount of delay required for image transfer in the wired section between the base station 10 and the other host device 30 (hereinafter referred to as the "amount of delay required for image transfer in the wired section of the other host device 30") based on information on the available bandwidth in the wired section between the base station 10 and the other host device 30 received by the communication unit 51 (hereinafter referred to as the "available bandwidth in the wired section of the other host device") and the calculated amount of transfer to be transmitted (step S204).

[0061] The transfer time calculation unit 522 outputs information on the calculated delay amount in the wireless section and information on the delay amount required for image transfer in the wired section in the other host device 30 to the delay requirement comparison unit 523. The delay requirement comparison unit 523 receives as input the information on the delay amount in the wireless section and the information on the delay amount required for image transfer in the wired section in the other host device 30 output from the transfer time calculation unit 522, and information on the delay in the wired section between the base station 10 and the other host device 30 received by the communication unit 51. The delay requirement comparison unit 523 calculates, for each other host device 30, the sum of the delay amount indicated by the input information on the delay amount in the wireless section, the delay amount indicated by the information on the delay amount required for image transfer in the wired section in the other host device 30, and the delay amount indicated by the information on the delay in the wired section between the base station 10 and the other host device 30.

[0062] The delay requirement comparison unit 523 compares the calculated total value for each of the other host devices 30 with the value indicated by the delay requirement previously obtained from the host controller. As a result of the comparison, the delay requirement comparison unit 523 determines, as the switching destination host device 30, the other host device 30 whose calculated total value satisfies the delay requirement (total value≦value indicated by the delay requirement) and has the smallest overall delay (step S205). Here, it is assumed that the host device 30-1 has been determined as the switching destination host device 30. The delay requirement comparison unit 523 notifies the switching instruction unit 524 of information indicating the determined host device 30-1.

[0063] The switching instruction unit 524 instructs the switching device 20 to switch the path so that the host device 30-1 notified by the delay requirement comparison unit 523 is connected to the base station 10 (step S206). Specifically, the switching instruction unit 524 generates a switching instruction including information that can uniquely identify the host device 30-1 that is the switching destination. The switching instruction unit 524 transmits the generated switching instruction to the switching device 20. As a result, the switching device 20 that has received the switching instruction switches the path to which the base station 10 is connected from the host device 30-2 to the host device 30-1.

[0064] According to the communication system 100 configured as described above, the controller 50 includes a rate calculation unit 521 that calculates a transmission rate at which the terminal device 60 performing wireless communication with the base station 10 can transmit, a transfer time calculation unit 522 that calculates a delay amount in the wireless section based on the transmission rate calculated by the rate calculation unit 521 and the transfer amount related to data transfer by the terminal device 60, and a switching instruction unit 524 that, when the sum of the delay amount in the wireless section and the delay amount related to the wired section does not satisfy a value indicated by a delay requirement, switches the connection destination of the base station 10 to a route that satisfies the value indicated by the delay requirement and has a smaller delay amount in the wired section than the route from which the connection was made. In this way, even if the transfer delay increases due to a deterioration in the network environment, such as a decrease in the effective rate of the wireless section, it is possible to reduce the overall delay required for image transfer, including the wireless section and the wired section, while maintaining image quality, by using a route with less delay in the wired section.

[0065] Furthermore, by using MCS and allocation information, it is possible to detect an increase in delay earlier than when starting switching after measuring the actual reception rate and delay, and it is possible to suppress (shorten) the impact of the increased delay.

[0066] In the communication system 100, when the wireless environment improves and equipment located at a short distance and with a short wired path latency, such as an edge server, is temporarily used, the system can appropriately switch back depending on the communication conditions, even if the communication bandwidth connecting to the edge server is narrow, thereby continuously maintaining a short latency time for video transfer. In other words, the performance requirements for the edge server and the devices connected to the edge server can be lowered. For example, by switching back, even if the edge server is expensive, an economical path can be used as long as the latency is within the allowable latency.

[0067] (Variation 1) The switching device 20 may be integrated with the base station 10 or the controller 50. When the switching device 20 is integrated with the base station 10, the base station 10 is directly connected to the higher-level devices 30-1 and 30-2. The controller 50 then transmits a switching instruction to the base station 10. When the switching device 20 is integrated with the controller 50, the switching device 20 is implemented as an L2 switch.

[0068] In the above-described embodiment, the configuration has been described in which each host device 30 measures information about delays in the wired section in advance using Ping. Alternatively, another controller may measure information about delays in the wired section between each host device 30 and the base station 10 and notify the controller 50 of the measured information.

[0069] Some of the functions of the controller 50 in the above-described embodiment may be implemented by a computer. In this case, a program for implementing these functions 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, the term "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, the term "computer-readable recording medium" may also include media 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 media that store programs for a fixed period of time, such as volatile memory within a computer system that serves as a server or client. The program may be designed to implement some of the above-described functions, or may be capable of implementing the above-described functions in combination with a program already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA.

[0070] 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.

[0071] The present invention can be applied to a communication system in which wireless and wired sections are mixed.

[0072] DESCRIPTION OF SYMBOLS 10... base station, 20... switching device, 30, 30-1, 30-2... upper level device, 40, 40-1, 40-2... server, 50... controller, 60... terminal device, 51... communication unit, 52... control unit, 521... rate calculation unit, 522... transfer time calculation unit, 523... delay requirement comparison unit, 524... switching instruction unit

Claims

1. A control device in a communication system including a base station, a plurality of host devices connected to the base station, and a control device connected to the base station and the plurality of host devices, a rate calculation unit that calculates a transmission rate at which a terminal device that performs wireless communication with the base station can transmit; a transfer time calculation unit that calculates a delay amount in a wireless section between the base station and the terminal device based on the possible transmission rate calculated by the rate calculation unit and a transfer amount related to data transfer of the terminal device; a switching instruction unit that, when the sum of the delay amount in the wireless section and the delay amount related to the wired section occurring between the base station and each higher-level device does not satisfy a value indicated by a delay requirement, switches the connection destination of the base station so as to take a route that satisfies the value indicated by the delay requirement and has a smaller delay amount in the wired section than the route from which the connection was made; A control device comprising:

2. the delay amount relating to the wired section is a delay amount required for image transfer in the wired section and a delay amount of a path between the base station and each higher-level device, the transfer time calculation unit further calculates a delay amount required for image transfer in the wired section based on information on an available bandwidth in the wired section and a transfer amount required for data transfer in the terminal device; The control device according to claim 1 .

3. the transfer time calculation unit calculates a transfer amount related to data transfer of the terminal device based on information on an average bit rate and information on a frame rate of video transmitted by the terminal device; The control device according to claim 1 or 2.

4. a delay requirement comparison unit that compares the sum with a value indicated by the delay requirement to determine whether the sum satisfies the value indicated by the delay requirement; the delay requirement comparison unit determines a host device to be switched to when the sum does not satisfy a value indicated by a delay requirement; The switching instruction unit switches the path so that the base station is connected to the host device that is the switching destination determined by the delay requirement comparison unit. The control device according to claim 1 or 2.

5. when a condition indicating that the communication environment in the wireless section has improved is satisfied after the path switching, the switching instruction unit switches the path so that the base station is connected to a host device that is a switching destination and that satisfies the delay requirement and minimizes the overall delay; The control device according to claim 1 or 2.

6. the rate calculation unit obtains an effective rate in a wireless section as the transmission possible rate before the traffic from the terminal device arrives at a base station; The control device according to claim 1 .

7. the rate calculation unit obtains an effective rate in a wireless section as the possible transmission rate based on a reception rate; The control device according to claim 1 .

8. A switching method performed by a communication system including a base station, a plurality of host devices connected to the base station, and a control device connected to the base station and the plurality of host devices, calculating a transmission rate that can be transmitted by a terminal device that wirelessly communicates with the base station; calculating a delay amount in a wireless section between the base station and the terminal device based on the calculated possible transmission rate and a transfer amount related to data transfer of the terminal device; When the sum of the delay amount in the wireless section and the delay amount related to the wired section occurring between the base station and each higher-level device does not satisfy a value indicated by a delay requirement, the connection destination of the base station is switched so as to take a route that satisfies the value indicated by the delay requirement and has a smaller delay amount in the wired section than the route from which the connection was made. Switching method.

9. A control device in a communication system including a base station, a plurality of host devices connected to the base station, and a control device connected to the base station and the plurality of host devices, a rate calculation unit that calculates a transmission rate at which a terminal device that performs wireless communication with the base station can transmit; a transfer time calculation unit that calculates a delay amount in a wireless section between the base station and the terminal device based on the possible transmission rate calculated by the rate calculation unit and a transfer amount related to data transfer of the terminal device; a switching instruction unit that switches the connection destination of the base station so as to satisfy the value indicated by the delay requirement when the sum of the delay amount in the wireless section and the delay amount related to the wired section occurring between the base station and each upper device does not satisfy the value indicated by the delay requirement; A control device comprising: