JP2017050815A - Relay device, communication system and relay method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a relay device which reduces a delay time of data transmission and reduces jitter, a communication system and a relay method.SOLUTION: A relay device 3 comprises: a request part 340 which makes an allocation request of an uplink band of a second communication terminal to a base station before estimated transmission start timing indicating an estimated time in which predetermined data may be generated, based on the estimated transmission start timing and a data amount of the predetermined data; and an uplink standby part 345 for calculating a waiting time in such a manner that a transmission time required for transmission of the predetermined data from the second communication terminal to a first communication terminalis is fixed within a first allowable delay time, based on an internal processing time required for allocation of a band, a transmission time required for transmission of the predetermined data from the second communication terminal to the relay device 3 and a transmission time required for transmission of the predetermined data from the relay device 3 to the first communication terminal, before the request part 340 makes the allocation request, and causing the request part 340 to await the allocation request based on the waiting time.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a relay device, a communication system, and a relay method.

  Conventionally, the quality of service has been improved by reducing delay fluctuation (jitter) of data transmitted in a communication service. For example, Patent Document 1 discloses that a guard band is provided so that packet transmission that occurs in an aperiodic communication section is completed by the next periodic communication section.

JP 2009-89352 A

  Although the technique described in Patent Document 1 can reduce jitter, there is a problem that communication may be delayed beyond an allowable delay time required by an application that performs communication in some situations. That is, in the technique described in Patent Document 1, by providing the guard band, there is a possibility that the allowable delay time may be exceeded before the application can start communication.

  Therefore, the present invention has been made in view of these points, and an object thereof is to provide a relay device, a communication system, and a relay method capable of reducing delay time of data transmission and reducing jitter.

  The relay device according to the first aspect of the present invention includes a first communication terminal that performs wireless communication via a base station, and a second communication terminal that periodically transmits predetermined data to the first communication terminal. A relay device that relays communication, based on a transmission expected start timing indicating a time at which the predetermined data is expected to occur, and a data amount of the predetermined data, the base before the transmission expected start timing A request unit for requesting an allocation of an uplink band of the second communication terminal to a station, and an internal part related to the allocation of the band before the requesting unit requests the allocation of an uplink band to the base station. Based on a processing time, a transmission time required for transmission of the predetermined data from the second communication terminal to the relay device, and a transmission time required for transmission of the predetermined data from the relay device to the first communication terminal. The waiting time is calculated so that the transmission time required for transmitting the predetermined data from the second communication terminal to the first communication terminal is constant within a predetermined first allowable delay time, and the waiting time is calculated. An uplink standby unit that causes the request unit to wait for the allocation request based on time.

  The first communication terminal transmits control data to the second communication terminal in a non-periodic manner, and the relay device communicates with the first communication terminal via the first communication network and performs second communication. A band occupying unit that communicates with the second communication terminal via a network and occupies a band in the second communication network as a downlink band of the second communication terminal over a predetermined period; and Based on the transmission time required for transmission of the control data from the first communication terminal to the relay device and the transmission time required for transmission of the control data from the relay device to the second communication terminal. The waiting time is such that the transmission time required for transmitting the control data from the first communication terminal to the second communication terminal is constant within a predetermined second allowable delay time. Calculated, and a downstream standby unit to wait the occupation of the band to the band occupancy based on the waiting time.

  The bandwidth occupying unit is connected to another communication terminal that performs communication via the second communication network at an interval shorter than a waiting time for the other communication terminal to wait for signal transmission. A signal indicating that data communication is being performed with a different terminal may be transmitted.

The band occupying unit may occupy a band in the second communication network as a downlink band of the second communication terminal based on a cycle in which the predetermined data is transmitted.
The relay device receives the control data from the first communication terminal, and then sends the control data to the second communication terminal without waiting for a random time that is performed in communication in the second communication network. You may provide the downlink transmission part which transmits.

  The request unit may include an estimation unit configured to estimate, as the internal processing time, a time required for the base station to allocate the uplink band when the predetermined data is generated at the expected transmission start timing.

  The request unit transmits a sounding reference signal for estimating the channel quality of the uplink band, which is referred to when the uplink band is allocated in the base station, to the base station by deteriorating the signal quality. You may have an adjustment part.

  A communication system according to a second aspect of the present invention relays communication between a first communication terminal that performs wireless communication via a base station, a second communication terminal, and the first communication terminal and the second communication terminal. The second communication terminal periodically transmits predetermined data to be transmitted to the first communication terminal to the relay device, and the relay device generates the predetermined data. Then, based on the estimated transmission start timing indicating the expected time and the data amount of the predetermined data, the uplink bandwidth allocation of the second communication terminal to the base station prior to the estimated transmission start timing A requesting unit for making a request, and an internal processing time for the bandwidth allocation before the requesting unit makes the uplink bandwidth allocation request to the base station, the second communication terminal to the relay device The predetermined data from the second communication terminal to the first communication terminal based on a transmission time required for transmission of constant data and a transmission time required for transmission of the predetermined data from the relay device to the first communication terminal An upstream standby unit that calculates a waiting time so that a transmission time required for transmission of the packet is constant within a predetermined first allowable delay time, and causes the requesting unit to wait for the allocation request based on the waiting time; A transmission unit that transmits the predetermined data to the first communication terminal in response to the notification of the allocation of the uplink band from the base station, wherein the first communication terminal transmits the data from the relay device. The predetermined data received is received.

  A relay method according to a third aspect of the present invention includes a first communication terminal that performs wireless communication via a base station, and a second communication in which predetermined data is periodically transmitted to the first communication terminal. A relay method for relaying communication with a terminal, wherein the computer is based on a transmission expected start timing indicating a time at which the predetermined data is expected to be generated and a data amount of the predetermined data. Before the step of making an uplink bandwidth allocation request for the second communication terminal to the base station, and before the computer makes the uplink bandwidth allocation request to the base station, An internal processing time for bandwidth allocation, a transmission time required for transmitting the predetermined data from the second communication terminal to the computer, and the first from the computer A transmission time required for transmitting the predetermined data from the second communication terminal to the first communication terminal based on a transmission time required for transmitting the predetermined data to the communication terminal is a predetermined first allowable delay time. And waiting for the allocation request based on the waiting time.

  According to the present invention, it is possible to reduce the delay time of data transmission and to reduce jitter.

It is a figure which shows the structure of the communication system which concerns on this embodiment. It is a figure which shows the structure of the relay apparatus which concerns on this embodiment. It is a sequence which shows the flow of the process which concerns on the allocation request | requirement of the upstream band which concerns on this embodiment. It is a figure which shows the correspondence of the radio | wireless environment of a relay apparatus, the measured value of scheduling time, and the estimated value of the scheduling time calculated using each of several prediction formulas. It is a figure explaining the calculation method of waiting time.

[Configuration of Communication System S]
FIG. 1 is a diagram illustrating a configuration of a communication system S according to the present embodiment.
The communication system S includes a first communication terminal 1, a base station 2, a relay device 3, and a second communication terminal 4.

  The communication system S includes, for example, a first wireless communication system S1 that performs wireless communication according to LTE (Long Term Evolution) and a second wireless communication system S2 that performs wireless communication according to a wireless LAN.

  In the first radio communication system S1, the first communication terminal 1 performs radio communication with the relay device 3 via the base station 2 which is an LTE radio base station (eNB). In the first wireless communication system S1, other communication terminals different from the first communication terminal 1 also perform wireless communication via the base station 2. In the following description, a communication network corresponding to the first wireless communication system S1 is referred to as a first communication network.

  In the second wireless communication system S2, the relay device 3 functions as an access point and performs wireless communication with the second communication terminal 4. In the second wireless communication system S2, other communication terminals different from the second communication terminal 4 also perform wireless communication with the relay device 3. In the following description, a communication network corresponding to the second wireless communication system S2 is referred to as a second communication network.

  The communication system S is a robot that is difficult to communicate with the first wireless communication system S1 and that can communicate with the second wireless communication system S2 (for example, under the eaves of a house, volcanic area, disaster site, etc.). Is a system for an operator who is located in an environment capable of communication by the first wireless communication system S1 to perform an operation.

The first communication terminal 1 is mounted on a controller that operates a robot, and the second communication terminal 4 is mounted on a robot or the like.
The second communication terminal 4 captures image data (predetermined data) indicating the surroundings of the robot captured by the camera mounted on the robot at a predetermined frame rate via the relay device 3 and the base station 2. 1 to send.

  The first communication terminal 1 provides the controller with the image data received from the second communication terminal 4 via the relay device 3 and the base station 2. The controller has a display unit and displays an image corresponding to the acquired image data. The operator operates the controller while confirming the image captured by the robot displayed on the display unit of the controller. The first communication terminal 1 transmits an operation command (control data) for operating the robot to the second communication terminal 4 via the base station 2 and the relay device 3 in response to the operator operating the controller. To do.

  Here, for example, when the communication in the first wireless communication system S1 or the communication in the second wireless communication system S2 is in a congested state, the communication between the first communication terminal 1 and the second communication terminal 4 is delayed or jitter is generated. Occur. When the robot is operated remotely, communication delays and the occurrence of jitter significantly deteriorate operability.

  For this reason, when the relay apparatus 3 performs communication from the second communication terminal 4 to the first communication terminal 1, the relay station 3 receives the base station 2 before the transmission start timing indicating the time when the image data is expected to be generated. On the other hand, by assigning an uplink communication band (uplink band) that is communication performed from the second communication terminal 4 to the first communication terminal 1, a communication delay is suppressed. Further, the relay device 3 calculates the waiting time so that the transmission time of the image data from the second communication terminal 4 to the first communication terminal 1 is constant within a predetermined allowable time when the upstream band is requested. Then, by waiting for an upstream bandwidth request based on the waiting time, jitter at the time of image data transmission is reduced.

Further, when performing communication (downlink communication) from the first communication terminal 1 to the second communication terminal 4, the relay device 3 occupies the band in the second communication network as the downlink band of the second communication terminal 4 for a predetermined period. This suppresses communication delay. Furthermore, the relay device 3 waits for the operation command transmission time from the first communication terminal 1 to the second communication terminal 4 to be constant within a predetermined allowable time before occupying the downstream band. , And waiting based on the waiting time reduces the jitter at the time of transmission of the operation command. The downlink band is a band corresponding to communication (downlink communication) from the first communication terminal 1 to the second communication terminal 4.
Next, the configuration of the relay device 3 will be described.

[Configuration of Relay Device 3]
FIG. 2 is a diagram illustrating a configuration of the relay device 3 according to the present embodiment. The relay device 3 includes a first communication unit 31, a second communication unit 32, a storage unit 33, and a control unit 34.

  The first communication unit 31 transmits various information to the base station 2. The first communication unit 31 modulates the signal output from the control unit 34 to generate an RF (Radio Frequency) signal, and wirelessly transmits the RF signal to the base station 2 via an antenna (not shown). The first communication unit 31 transmits a sounding reference signal to the base station 2 under the control of the control unit 34. The sounding reference signal is a signal for estimating the channel quality of the upstream band that is referred to when the base station 2 assigns the upstream band of the second communication terminal 4.

In addition, the first communication unit 31 demodulates the RF signal received from the base station 2 via the antenna, and outputs a signal obtained by the demodulation to the control unit 34.
In the following description, the control unit 34 performs wireless communication with the base station 2 via the first communication unit 31.

The second communication unit 32 transmits various information to the second communication terminal 4. The second communication unit 32 modulates the signal output from the control unit 34 to generate an RF signal, and wirelessly transmits the RF signal to the second communication terminal 4 via an antenna (not shown).
The second communication unit 32 demodulates the RF signal received from the second communication terminal 4 via the antenna, and outputs the signal obtained by the demodulation to the control unit 34.
In the following description, the control unit 34 performs wireless communication with the second communication terminal 4 via the second communication unit 32.

  The storage unit 33 is, for example, a ROM, a RAM, a hard disk, or the like. The storage unit 33 stores various programs for causing the relay device 3 to function. The storage unit 33 stores a communication program that causes the control unit 34 of the relay device 3 to function as the request unit 340, the upstream standby unit 345, the upstream transmission unit 346, the bandwidth occupying unit 347, the downstream standby unit 348, and the downstream transmission unit 349. To do. The storage unit 33 may read and store a program stored in a storage medium such as an external memory, or may store a program downloaded from an external device via the base station 2.

  The control unit 34 is, for example, a CPU. The control unit 34 controls functions related to the relay device 3 by executing various programs stored in the storage unit 33. The control unit 34 includes a request unit 340, an upstream standby unit 345, an upstream transmission unit 346, a bandwidth occupying unit 347, a downstream standby unit 348, and a downstream transmission unit 349.

[Uplink allocation request]
The request unit 340 includes an analysis unit 341, an estimation unit 342, an allocation request unit 343, and a quality adjustment unit 344. The request unit 340 causes the analysis unit 341, the estimation unit 342, and the allocation request unit 343 to function, and the transmission expectation indicating the time when image data to be transmitted to the first communication terminal 1 via the base station 2 is expected to be generated Based on the estimated transmission start time as the start timing and the estimated transmission data amount indicating the data amount of the image data, the upstream band of the second communication terminal 4 with respect to the base station 2 before the estimated transmission start time. Request for allocation. Here, the expected transmission start timing is the time when the relay device 3 is expected to complete the reception of the image data transmitted from the second communication terminal 4.

  Before the request unit 340 makes an uplink bandwidth allocation request to the base station 2, the upstream standby unit 345 receives a scheduling time as an internal processing time for the upstream bandwidth allocation from the second communication terminal 4. From the second communication terminal 4 to the first communication terminal 1 based on the transmission time required to transmit the image data to the relay device 3 and the transmission time required to transmit the image data from the relay device 3 to the first communication terminal 1. The waiting time is calculated so that the transmission time required for transmitting the image data is constant within a predetermined first allowable delay time, and the request unit 340 waits for an allocation request based on the waiting time.

  In the following, processing related to the uplink bandwidth allocation request of the second communication terminal 4 will be described using a sequence diagram. FIG. 3 is a sequence showing a flow of processing related to an uplink bandwidth allocation request according to the present embodiment.

  The analysis unit 341 calculates the estimated transmission start time and the estimated transmission data amount (S10). Specifically, the analysis unit 341 analyzes the period of the image data received in the past from the second communication terminal 4 by the relay device 3 and determines the time when the image data to be transmitted to the first communication terminal 1 is expected to be generated. The estimated transmission start time shown is calculated. Further, the analysis unit 341 calculates the estimated transmission data amount indicating the data amount of the image data to be transmitted to the first communication terminal 1 based on the data amount of the image data received by the relay device 3 from the second communication terminal 4 in the past. calculate.

  Further, the analysis unit 341 transmits the image data from the second communication terminal 4 to the relay device 3 based on the time required to receive the image data when the relay device 3 has received image data from the second communication terminal 4 in the past. The transmission time required for transmitting the image data is calculated. In the following description, the transmission time required for transmitting image data from the second communication terminal 4 to the relay device 3 is referred to as a first transmission time.

  Further, the analysis unit 341 transmits the image data from the relay device 3 to the first communication terminal 1 based on the time required to transmit the image data when the relay device 3 has transmitted image data to the first communication terminal 1 in the past. The transmission time required for transmitting the image data is calculated. In the following description, the transmission time required for transmitting image data from the relay device 3 to the first communication terminal 1 is referred to as a second transmission time.

  When the analysis unit 341 calculates the estimated transmission start time and the estimated transmission data amount, the estimation unit 342 determines that the base station 2 is the second communication terminal when image data of the estimated transmission data amount is generated at the estimated transmission start time. The scheduling time indicating the time required for allocation of the uplink bandwidth of 4 is estimated (S20).

  Specifically, the estimation unit 342 estimates the scheduling time using a prediction formula that calculates the scheduling time based on the time series data of the past scheduling time. Here, the storage unit 33 uses, for example, an AR model (Auto-Regressive model), an MA model (Moving Average model), an ARMA model (Auto-Regressive Moving Average model), an exponential smoothing method, and a Brownian method as a plurality of prediction formulas. A prediction formula based on the above is stored.

As a specific example of the prediction formula, a prediction formula corresponding to the AR model will be described. Formula (1) shown below shows a prediction formula corresponding to the AR model.

In Equation (1), the value on the left side indicates the predicted value of the scheduling time at time t + 1 corresponding to the estimated transmission start time. X _t represents an actual scheduling time value at time t. a ₀ , a ₁ ... _ap represent coefficients of the regression equation. b indicates a prediction error. p indicates the order, and the value of p is determined in advance as a parameter. a ₀ , a ₁ ... a _p can be calculated using the past scheduling time. For example, a ₀ , a ₁ ... A _p can be calculated by using the least square method.

  The estimation unit 342 selects a prediction formula suitable for the wireless environment of the relay device 3 from a plurality of prediction formulas stored in the storage unit 33, and calculates a scheduling time based on the prediction formula. For example, the estimation unit 342 identifies the power (reception power) of the signal received by the relay device 3 from the base station 2. Note that the estimation unit 342 specifies what kind of environment the wireless environment of the relay device 3 is based on the transmission power of the relay device 3 and the MCS (Modulation and Coding Scheme) in addition to the received power. May be.

  FIG. 4 is a diagram illustrating a correspondence relationship between the wireless environment of the relay device 3, the actual scheduling time value, and the scheduling time prediction value calculated using each of a plurality of prediction formulas. As shown in FIG. 4, the storage unit 33 stores the scheduling power calculated by using the reception power of the relay device 3 specified by the estimation unit 342 in the past, the measured value of the scheduling time, and each of a plurality of prediction formulas. A predicted value and a difference between the actually measured value and each predicted value are stored in association with each other.

  For example, the estimation unit 342 refers to the information illustrated in FIG. 4 and selects a prediction formula having the smallest difference between the actual measurement value and the predicted value for the received power close to the specified received power. Then, the estimation unit 342 estimates the scheduling time based on the selected prediction formula. Note that the estimation unit 342 may select a prediction formula having the smallest difference value between the actual measurement value and the prediction value when there are a plurality of pieces of data having the same received power as the specified power.

The upstream standby unit 345 calculates a waiting time from the current time until a request for upstream bandwidth allocation is made (S30). Here, the current time is the time when the calculation of the waiting time is started.
Specifically, the upstream standby unit 345 calculates the scheduling time estimated by the estimation unit 342, the estimated transmission start time calculated by the analysis unit 341, the first transmission time calculated by the analysis unit 341, and the analysis unit 341. Based on the second transmission time, the request unit 340 calculates a waiting time that is a time for waiting for an uplink bandwidth allocation request.

FIG. 5 is a diagram for explaining a waiting time calculation method. FIG. 5A is a diagram illustrating an example in which the waiting time W is set in accordance with the time at which the relay device 3 receives image data.
When the current time is tn, the estimated transmission start time is ts, and the scheduling time is ST, the waiting time W is expressed by the following equation (2).
W = (ts−tn) −ST (2)

  When the waiting time W is set as shown in Expression (2), image data is transferred from the second communication terminal 4 to the first communication terminal 1 due to variations in the first transmission time WU, the second transmission time DU, and the scheduling time ST. The time at which the signal is transmitted also fluctuates and jitter occurs.

  Therefore, the upstream standby unit 345 of the present embodiment is configured such that the relay device 3 receives the image data from the second communication terminal 4 (transmission expected start time ts), and the relay device 3 sends the image data to the first communication terminal 1. The jitter is made constant by providing the buffer time WA between the transmission time and the transmission time. Specifically, the upstream standby unit 345 waits so that the time required to transmit the image data from the second communication terminal 4 to the first communication terminal 1 becomes a certain transmission time TU within the first allowable delay time. Time W1 is set. Here, the transmission time TU is, for example, a time shorter by a predetermined percentage than the first allowable delay time.

FIG. 5B is a diagram illustrating an example of setting the waiting time W1. The buffer time WA is expressed by the following equation (3).
WA = TU− (WU + DU) (3)

The waiting time W1 is obtained by adding the buffer time WA to the waiting time W calculated by the equation (2) as shown in the following equation (4).
W1 = W + WA = (ts−tn) + TU− (ST + WU + DU) (4)

The upstream standby unit 345 waits for an upstream bandwidth allocation request from the request unit 340 until the calculated waiting time W1 elapses from the current time (S40).
The allocation request unit 343 includes information indicating the estimated transmission start time and the estimated transmission data amount for the base station 2 in accordance with the elapse of the waiting time W1 calculated by the uplink standby unit 345 from the current time. An uplink bandwidth allocation request is made. The allocation request unit 343 may make an uplink bandwidth allocation request that further includes information indicating the generation cycle of the image data analyzed by the analysis unit 341.

  When the base station 2 receives the bandwidth allocation request from the relay device 3, the base station 2 allocates an upstream band to the relay device 3 based on the estimated transmission start time and the estimated transmission data amount included in the bandwidth allocation request ( S50). The base station 2 notifies the allocation of the uplink band through a physical downlink control channel (PDCCH).

When the scheduling time required for the base station 2 to allocate the uplink bandwidth and the scheduling time estimated by the estimation unit 342 are substantially the same, the base station 2 is substantially the same as the time when the buffer time WA has elapsed from the estimated transmission start time ts. The uplink bandwidth allocation is completed at the time. Thereby, the relay apparatus 3 can transmit image data so that the time when image data is transmitted from the second communication terminal 4 to the first communication terminal 1 becomes the transmission time TU.
The uplink transmission unit 346 transmits the image data to the first communication terminal 1 in response to the notification of the uplink band assignment from the base station 2. That is, the upstream transmission unit 346 transmits the image data to the first communication terminal 1 at a time when the buffer time WA has elapsed from the estimated transmission start time ts.

[Quality adjustment of sounding reference signal]
The control unit 34 uses the quality adjustment unit 344 to adjust the signal quality of the sounding reference signal. The quality adjustment of the sounding reference signal will be described below.

  When the base station 2 receives the sounding reference signal transmitted by the relay device 3, the base station 2 uses the packet quality to make the retransmission rate of each packet transmitted from the relay device 3 constant based on the channel quality notified by the sounding reference signal. MCS (Modulation and Coding Scheme) is adjusted every time. The base station 2 adjusts the MCS so that the retransmission rate of each packet transmitted from the relay device 3 is a predetermined ratio (for example, 10%).

  On the other hand, when retransmission occurs when the first communication unit 31 transmits data to the base station 2, the time required to transmit the image data received from the second communication terminal 4 is requested in the remote operation of the robot. There is a possibility that the first allowable delay time is exceeded.

  Therefore, the quality adjustment unit 344 deteriorates the signal quality of the sounding reference signal for estimating the channel quality of the upstream band, which is referred to when the base station 2 assigns the upstream band of the second communication terminal 4. For example, the quality adjustment unit 344 reduces the signal power of the sounding reference signal by reducing the transmission power when the first communication unit 31 transmits the sounding reference signal compared to the transmission power when transmitting the image data. make worse.

  As described above, when the signal quality of the sounding reference signal is deteriorated as compared with the data transmission, the base station 2 adjusts the retransmission rate of each packet to a predetermined ratio based on the deteriorated signal quality. Do. Since the actual signal quality of the relay device 3 is better than the signal quality notified to the base station 2, the data retransmission rate of the relay device 3 is lower than the retransmission rate set in the base station 2. Thereby, the relay apparatus 3 can reduce the possibility that the first allowable delay time will be exceeded due to retransmission.

[Occupancy of downstream bandwidth]
Since the second communication network performs communication by wireless LAN, each communication device that performs communication in the second communication network performs carrier sense to check whether or not another communication device is performing communication. Then, after confirming that other communication devices are not communicating, each communication device waits for a random time and performs data transmission.

  However, when congestion occurs in communication in the second communication network, it is difficult for each communication device to detect the timing at which other communication devices are not communicating, and data transmission is completed. It takes time.

  Therefore, the band occupying unit 347 occupies the band in the second communication network as the downlink band of the second communication terminal 4 for a predetermined period, thereby allowing the operation command transmitted from the first communication terminal 1 to be transmitted to the second communication without delay. Transmit to terminal 4.

  Specifically, the band occupying unit 347 specifies a time (predetermined period) during which the image data is not transmitted based on the cycle in which the image data is transmitted. Then, the bandwidth occupying unit 347 communicates with other communication terminals that communicate with each other via the second communication network at intervals shorter than the waiting time for the other communication terminals to wait for signal transmission. Transmits a short signal indicating that data communication is being performed with a different terminal over a predetermined period.

  Here, the band occupying unit 347 starts transmission of a short signal in response to, for example, the controller being turned on and the robot can be operated by the controller. The short signal is a signal whose data amount is a predetermined amount or less, for example, an ack signal.

Other communication terminals receive the short signal at intervals shorter than the standby time for which they wait, thereby waiting for data transmission while continuing to receive the short signal. Thereby, the band occupying unit 347 can occupy the band in the second communication network as the downlink band of the second communication terminal 4.
In addition, since the band occupying unit 347 transmits a short signal based on the cycle in which the image data is transmitted, the operation command is transmitted to the second communication so that the transmission of the image data to the first communication terminal 1 is not affected. It can be transmitted to the terminal 4.

  The downstream standby unit 348 transmits a transmission time required for transmission of an operation command (control data) from the first communication terminal 1 to the relay device 3 before the bandwidth occupying unit 347 occupies the bandwidth, and the second communication from the relay device 3 to the second communication. Based on the transmission time required for transmission of the operation command to the terminal 4, the transmission time required for transmission of the operation command from the first communication terminal 1 to the second communication terminal 4 is within a predetermined second allowable delay time. The waiting time is calculated to be constant, and the band occupying unit 347 is made to wait for the band occupation based on the waiting time.

  Specifically, first, the analysis unit 341 starts from the first communication terminal 1 based on the time required to receive the operation command when the relay device 3 has received the operation command from the first communication terminal 1 in the past. The transmission time required for transmitting the operation command to the relay device 3 is calculated. In the following description, the transmission time required to transmit an operation command from the first communication terminal 1 to the relay device 3 is referred to as a third transmission time.

  Further, the analysis unit 341 transmits the operation command from the relay device 3 to the second communication terminal 4 based on the time required to transmit the operation command when the relay device 3 has transmitted the operation command to the second communication terminal 4 in the past. Calculate the transmission time required to transmit the operation command In the following description, the transmission time required to transmit the operation command from the relay device 3 to the second communication terminal 4 is referred to as a fourth transmission time.

The downlink standby unit 348 receives the operation command so that the time during which the operation command is transmitted from the first communication terminal 1 to the second communication terminal 4 becomes a certain transmission time TD within the second allowable delay time. To wait time WB until an operation command is transmitted. Here, the transmission time TD is, for example, a time shorter by a predetermined rate than the second allowable delay time. When the third transmission time calculated by the analysis unit 341 is WD and the fourth transmission time calculated by the analysis unit 341 is DD, the waiting time WB is expressed by the following equation (5).
WB = TD− (WD + DD) (5)

  The downlink transmission unit 349 transmits the operation command to the second communication terminal 4 after the waiting time WS has elapsed from the current time. Here, after the relay device 3 receives the operation command from the first communication terminal 1, the downlink transmission unit 349 transmits the operation command to the second communication terminal without waiting for a random time specified in the wireless LAN. 4 to send.

The band occupying unit 347 transmits the short signal based on the cycle in which the image data is transmitted, but the present invention is not limited to this. The downlink standby unit 348 receives the operation command so that the band of the second communication network is occupied as the downlink band of the second communication terminal 4 when the relay device 3 transmits the operation command. You may calculate waiting time WS until it transmits. Here, assuming that the data transfer time of the maximum frame length in another communication device that performs communication in the second communication network is MT, the transmission start time of the short signal is the time at which the relay device 3 starts transmitting the operation command, The data transfer time MT must be before the time when the waiting time WB has elapsed since the relay device 3 received the operation command. Therefore, the waiting time WS is expressed by the following equation (6). Here, it is assumed that WB> MT.
WS = WB-MT (6)

  The band occupying unit 347 transmits a short signal to another communication device that performs communication in the second communication network in response to the waiting time WS from the time when the relay device 3 receives the operation command. The band in the two communication network is occupied as the downlink band of the second communication terminal 4. Thereby, the transmission time of the operation command from the first communication terminal 1 to the second communication terminal 4 becomes a transmission time TD that is within the second allowable delay time.

[Effect in this embodiment]
As described above, the relay device 3 according to the present embodiment makes a bandwidth allocation request after image data to be transmitted is generated by making an upstream bandwidth allocation request before the expected transmission start time. Compared to the case, the delay time of data transmission can be reduced.
Further, the relay device 3 calculates the waiting time so that the transmission time related to the transmission of the image data from the second communication terminal 4 to the first communication terminal 1 is constant within a predetermined first allowable delay time. Since the bandwidth allocation request is waited based on the waiting time, jitter can be reduced.

  In addition, since the relay device 3 occupies the band in the second communication network as the downlink band of the second communication terminal 4 for a predetermined period, even if congestion occurs in the second communication network, The delay time when transmitting the operation command to the communication terminal 4 can be reduced.

  Further, the relay apparatus 3 has a predetermined second allowable delay before transmitting the operation command from the first communication terminal 1 to the second communication terminal 4 before occupying the band in the second communication network. Since the waiting time is calculated so as to be constant within the time and the occupation of the bandwidth is waited based on the waiting time, jitter can be reduced.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. In particular, the specific embodiments of the distribution / integration of the devices are not limited to those illustrated above, and all or a part thereof may be added in arbitrary units according to various additions or according to functional loads. It can be configured functionally or physically distributed and integrated.

DESCRIPTION OF SYMBOLS 1 ... 1st communication terminal, 2 ... Base station, 3 ... Relay apparatus, 31 ... 1st communication part, 32 ... 2nd communication part, 33 ... Memory | storage part, 34. ..Control unit, 340 ... Request unit, 341 ... Analysis unit, 342 ... Estimation unit, 343 ... Allocation request unit, 344 ... Quality adjustment unit, 345 ... Upstream standby unit, 346 ... Uplink transmission unit, 347 ... Band occupying unit, 348 ... Downlink standby unit, 349 ... Downlink transmission unit, 4 ... Second communication terminal, S ... Communication system

Claims (9)

A relay device that relays communication between a first communication terminal that performs wireless communication via a base station and a second communication terminal that periodically transmits predetermined data to the first communication terminal,
Based on the estimated transmission start timing indicating the time when the predetermined data is expected to be generated and the data amount of the predetermined data, the second communication terminal is connected to the base station before the estimated transmission start timing. A request unit for performing an uplink bandwidth allocation request,
Before the request unit makes an uplink bandwidth allocation request to the base station, internal processing time for the bandwidth allocation, transmission required for transmission of the predetermined data from the second communication terminal to the relay device A transmission time required for transmitting the predetermined data from the second communication terminal to the first communication terminal based on a time and a transmission time required for transmitting the predetermined data from the relay device to the first communication terminal. An upstream standby unit that calculates a waiting time so as to be constant within a predetermined first allowable delay time, and causes the requesting unit to wait for the allocation request based on the waiting time;
A relay device comprising: The first communication terminal transmits control data to the second communication terminal in an aperiodic manner,
The relay device communicates with the first communication terminal via a first communication network and communicates with the second communication terminal via a second communication network,
A band occupying unit that occupies a band in the second communication network as a downlink band of the second communication terminal over a predetermined period;
Before the bandwidth occupying unit occupies the bandwidth, the transmission time required for transmission of the control data from the first communication terminal to the relay device, and the control data from the relay device to the second communication terminal The transmission time required for transmitting the control data from the first communication terminal to the second communication terminal is constant within a predetermined second allowable delay time based on the transmission time required for transmission A waiting time is calculated, and a standby unit for waiting for the band to occupy the band based on the waiting time.
The relay device according to claim 1. The bandwidth occupying unit is connected to another communication terminal that performs communication via the second communication network at an interval shorter than a waiting time for the other communication terminal to wait for signal transmission. Sending a signal indicating that data communication with a different terminal is in progress,
The relay device according to claim 2. The band occupying unit occupies a band in the second communication network as a downlink band of the second communication terminal based on a cycle in which the predetermined data is transmitted.
The relay device according to claim 2 or 3. After receiving the control data from the first communication terminal, a downlink transmission unit that transmits the control data to the second communication terminal without waiting for a random time performed in communication in the second communication network Comprising
The relay device according to any one of claims 2 to 4. The request unit includes an estimation unit that estimates, as the internal processing time, a time required for the base station to allocate the uplink band when the predetermined data is generated at the transmission expected start timing.
The relay device according to any one of claims 1 to 5. The request unit transmits a sounding reference signal for estimating the channel quality of the uplink band, which is referred to when the uplink band is allocated in the base station, to the base station by deteriorating the signal quality. Having an adjustment section,
The relay device according to any one of claims 1 to 6. A communication system comprising a first communication terminal that performs wireless communication via a base station, a second communication terminal, and a relay device that relays communication between the first communication terminal and the second communication terminal,
The second communication terminal periodically transmits predetermined data to be transmitted to the first communication terminal to the relay device,
The relay device is
Based on the estimated transmission start timing indicating the time when the predetermined data is expected to be generated and the data amount of the predetermined data, the second communication terminal is connected to the base station before the estimated transmission start timing. A request unit for performing an uplink bandwidth allocation request,
Before the request unit makes an uplink bandwidth allocation request to the base station, internal processing time for the bandwidth allocation, transmission required for transmission of the predetermined data from the second communication terminal to the relay device A transmission time required for transmitting the predetermined data from the second communication terminal to the first communication terminal based on a time and a transmission time required for transmitting the predetermined data from the relay device to the first communication terminal. An upstream standby unit that calculates a waiting time so as to be constant within a predetermined first allowable delay time, and causes the requesting unit to wait for the allocation request based on the waiting time;
A transmission unit that transmits the predetermined data to the first communication terminal in response to the notification of the allocation of the uplink band from the base station;
The first communication terminal receives the predetermined data transmitted from the relay device;
Communications system. A computer relay method for relaying communication between a first communication terminal that performs wireless communication via a base station and a second communication terminal that periodically transmits predetermined data to the first communication terminal,
Based on the estimated transmission start timing indicating the time at which the predetermined data is expected to be generated and the amount of data of the predetermined data, the computer, with respect to the base station before the estimated transmission start timing, Performing an uplink bandwidth allocation request of the second communication terminal;
Before the computer makes an uplink bandwidth allocation request to the base station, internal processing time for bandwidth allocation, transmission time required for transmission of the predetermined data from the second communication terminal to the computer And a transmission time required for transmitting the predetermined data from the second communication terminal to the first communication terminal based on a transmission time required for transmitting the predetermined data from the computer to the first communication terminal. Calculating a waiting time so as to be constant within a defined first allowable delay time, and waiting for the allocation request based on the waiting time;
A relay method comprising:

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