JP2009021888A - Data communication apparatus and data communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data communication apparatus which uses a general-purpose communication protocol to determine transmission characteristics within a communication network and performs data communication corresponding to a transmission state of data, and a data communication method of the data communication apparatus. <P>SOLUTION: In the present invention, in data communication setting up a connection between a video monitor 40 and a client monitor 41 by means of a TCP/IP that is a general-purpose communication protocol, when the client monitor 41 receives continuous packets of a data amount indicated by a window size from a video server 40, an acknowledgement is transmitted to the video server 40 and with a time at which the acknowledgement is transmitted as a base, a time from the base to reception of the next packet from the video server 40 is measured as a delay time. A histogram of delay times is then created, transmission characteristics of a communication network are determined from the histogram, and a transmission parameter of data to be transmitted/received is adjusted in accordance with a transmission state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a data communication device and a data communication method in a communication network in which one transmission medium is shared by a plurality of communication terminals (data communication devices), and in particular, establishes a connection with any other data communication device and video. The present invention relates to a data communication apparatus that performs continuous data communication such as voice, and a data communication method of the data communication apparatus.

  In a communication system in which a plurality of terminals share one transmission medium and communicate with each other, for example, when a propagation environment deteriorates in wireless communication, a transmission error occurs, and retransmission control of packets transmitted by the transmitting terminal is performed. Transmission delay occurs. Also, when a plurality of terminals start transmission at the same time, the transmission medium is shared, so that a waiting time for transmission data occurs and a transmission delay occurs.

  If transmission delay occurs in streaming transmission of video and audio data, the transmission image quality and sound quality will deteriorate, so the transmission terminal or reception terminal detects the transmission delay and adjusts the transmission data or transmission method. There is a need.

  There are three conventional methods for ensuring transmission delay.

  First, the transmission terminal receives reproduction quality information from the reception terminal, transmits a test signal for determining transmission parameters based on the reproduction quality information, accumulates and analyzes the result, and optimizes the communication state This is a method for learning a simple transmission method (see Patent Document 1).

  Second, when the data distribution device determines the congestion state from the packet loss rate and the delay time, determines the transmission error occurrence state from the transmission error rate, and determines that it is congested and not a transmission error occurrence state. When the packet delivery rate is lowered, it is determined that the packet is in a congested state and a transmission error occurrence state, the delivery method is changed (see Patent Document 2).

Third, the receiving terminal notifies the transmitting terminal of control information indicating the reception state of the packet, and the transmitting terminal stores the transmission data and the transmission time until the confirmation response of the receiving terminal is returned. The transmission abnormal state is determined by the time difference between the packet having the longest time and the transmission time, and during the transmission abnormal state, the retransmission request of the receiving terminal is ignored, and control is performed so that only new data is transmitted with priority. This is a method of transmitting a determination result of a transmission state together with data (see Patent Document 3).
Japanese Patent Laid-Open No. 2003-249977 JP 2001-160824 A Japanese Patent No. 3520793

  However, in the methods of Patent Document 1 and Patent Document 3, it is necessary to exchange data indicating the transmission path state between the transmitting terminal and the receiving terminal, and the data itself that transmits the transmission path state is delayed or transmitted. If this is not possible, there is a problem that further control means is required to synchronize the control states of both the transmitting terminal and the receiving terminal.

  Furthermore, in order to exchange special control information for the transmission state, a mechanism for interpreting or determining special data for both the transmitting terminal and the receiving terminal is required, and TCP / IP (Transmission Control Protocol / Internet Protocol) is required. For communication terminals using such general-purpose communication protocols, there is a problem that the effect does not appear.

  In the method of Patent Document 2, it is impossible to determine whether the cause of the congestion state is a packet loss due to a transmission error or an increase in traffic due to an increase in data transmission from another terminal. There was a problem that control could not be performed.

  The present invention solves the above-mentioned conventional problems, and determines data transmission characteristics in a communication network using a general-purpose communication protocol such as TCP / IP, and performs data communication according to the transmission characteristics. An object is to provide a data communication device and a data communication method of the data communication device.

  A data communication apparatus according to claim 1 of the present invention is a receiver that performs data communication by establishing a connection with a data communication apparatus on a transmission side via a communication network in which one transmission medium is shared by a plurality of data communication apparatuses. The data communication device on the side transmits a packet including a window size indicating the size of data that can be continuously received, and receives data composed of a plurality of continuous packets transmitted from the data communication device on the transmission side A communication unit, a detection unit that detects whether data including a plurality of continuous packets has been received, and a continuous packet having a data size indicated by the window size is received, or after reception of data is started When a preset time has elapsed, the data communication device on the transmitting side that has transmitted the continuous packet is received A packet transmitted from the data communication apparatus on the transmission side from the acknowledge control unit that transmits the acknowledge including the sequence number of the received data and the window size, and the time when the acknowledge is transmitted as a base point A delay time measuring unit that measures the time until the signal is received as a delay time, and a different value range is set, the delay time is compared with the value range, and the delay time is within the value range. A plurality of comparators that output signals, a histogram generation unit that counts the pulse signal for each comparator and generates a histogram of the delay time from the count result, and transmission of data in the communication network based on the histogram A transmission characteristic determination unit for determining characteristics, and transmission / reception according to the transmission characteristics. Characterized in that it comprises a transmission parameter setting section for setting the transmission parameters of the data to be.

  The data communication device according to claim 2 of the present invention is the data communication device according to claim 1, wherein the delay time measurement unit uses a time at which the acknowledgment is transmitted as a base point, and The time until the first packet transmitted from the data communication apparatus is received is measured as the delay time.

  The data communication apparatus according to claim 3 of the present invention is the data communication apparatus according to claim 1, wherein when the acknowledge control unit receives a continuous packet of the data size indicated by the window size, A first acknowledge that sets the window size to 0 is transmitted to the transmitting data communication apparatus, and a second acknowledge that sets the window size to a preset value after a preset time has elapsed. The delay time measurement unit uses the time when the second acknowledgment is transmitted as a base point, and determines the time from the base point until the first packet transmitted from the data communication device on the transmission side is received. The delay time is measured.

  The data communication device according to claim 4 of the present invention is the data communication device according to claim 1, wherein the delay time measurement unit uses a time at which the acknowledgment is transmitted as a base point, and from the base point, the transmission side The time until receiving a packet including arbitrary data transmitted from a data communication apparatus is measured as a delay time.

  A data communication apparatus according to claim 5 of the present invention is the data communication apparatus according to claim 1, wherein the acknowledgment control unit detects that reception of data is not detected, or the amount of received data is the window. If the size has not been reached, the acknowledgment is transmitted when the data reception time exceeds a predetermined time.

  A data communication device according to claim 6 of the present invention is the data communication device according to claim 1, wherein a plurality of threshold values respectively defining a range of each of the comparators are initialized in advance, and the delay time measurement unit It further includes a range controller that inputs a delay time and changes any of the threshold values based on the input delay time.

  The data communication device according to claim 7 of the present invention is the data communication device according to claim 6, wherein the range control unit sets a maximum value or a minimum value among a plurality of threshold values defining a range of each comparator. The threshold value is changed based on the delay time, and a threshold value other than the maximum value and the minimum value is obtained by constant division of a value obtained by subtracting the minimum value from the maximum value.

  The data communication device according to claim 8 of the present invention is the data communication device according to claim 1, wherein the transmission characteristic determination unit includes a frequency of the shortest delay time and a frequency of the second shortest delay time in the histogram. And a difference value α2 between the frequency of the longest delay time and the frequency of the second longest delay time in the histogram, and a mathematical formula from the difference value α1 and an arbitrary constant α (α> 0). (9) is used to calculate a transmission error state characteristic amount β1, and from the difference value α2 and the arbitrary constant α, the communication waiting state characteristic amount β2 in the communication network is calculated according to Equation (10). The transmission characteristic is determined from the characteristic quantity β1 and the characteristic quantity β2.

[Equation 9]
β1 = α1 / α (9)

[Equation 10]
β2 = α2 / α (10)

  The data communication device according to claim 9 of the present invention is the data communication device according to claim 1, wherein the transmission characteristic determination unit obtains a difference value of the frequency of each delay time in the histogram and is set in advance. A maximum delay time in which the difference value becomes larger than a constant is obtained, and a cumulative distribution is obtained by accumulating the frequency of each delay time in the histogram, and corresponds to the maximum accumulated value M and the maximum delay time from the cumulative distribution. The accumulated value m is obtained, the characteristic amount m1 of the transmission error state is calculated by the equation (11), the characteristic amount m2 of the communication waiting state in the communication network is calculated by the equation (12), and the characteristic amount m1 and The transmission characteristic is determined from the characteristic amount m2.

[Equation 11]
m1 = m / M (11)

[Equation 12]
m2 = (M−m) / M (12)

  A data communication system according to claim 10 of the present invention is a data communication system in which data communication is performed by establishing a connection between the data communication apparatuses in a communication network in which one transmission medium is shared by a plurality of data communication apparatuses. A transmission side data communication device that transmits data including a plurality of consecutive packets and includes a transmission window size indicating a data size that can be transmitted continuously, and a data size that can be received continuously. A reception-side data communication device that receives data including a plurality of consecutive packets and transmits a packet including a reception window size that is indicated by the transmission-side data communication device. Receiving the packet including the window size, and receiving the window A data communication device on the receiving side, comprising: a communication unit that transmits a continuous packet of a data size indicated by Izu; and a communication control unit that assigns a sequence number determined for each connection to data in the packet to be transmitted Received data consisting of a plurality of consecutive packets transmitted from the data communication device on the transmitting side, and received a data consisting of a plurality of consecutive packets and a communication unit for transmitting an acknowledgment for the received data. When a continuous packet having a data size indicated by the window size is received or when a preset time has elapsed since the start of data reception, the continuous packet is transmitted. For the data communication device on the transmission side, the sequence number of the data received normally and the window size An acknowledgment control unit that transmits an acknowledgment including the delay time, and a delay time that measures the time until a packet transmitted from the data communication device on the transmission side is received as a delay time, based on the time when the acknowledge is transmitted When different value ranges are set with the measurement unit, the delay time and the value range are compared, and when the delay time is within the value range, a plurality of comparators that output a pulse signal, and the pulse for each comparator A histogram generation unit that counts signals and generates a histogram of the delay time from the count result; a transmission characteristic determination unit that determines transmission characteristics of data in the communication network based on the histogram; and according to the transmission characteristics And a transmission parameter setting unit for setting transmission parameters for data to be transmitted and received. It is characterized by.

  A data communication method according to claim 11 of the present invention establishes a connection with a data communication device on the transmission side via a communication network in which one transmission medium is shared by a plurality of data communication devices, and performs data communication. A data communication method of a data communication device on the reception side to perform, a notification step of notifying the data communication device on the transmission side of a window size indicating the size of data that can be continuously received, and data consisting of a plurality of continuous packets A receiving step for receiving, a detecting step for detecting whether data comprising a plurality of consecutive packets has been received, and when a continuous packet having a data size indicated by the window size is received, or when data reception is started To a data communication device on the transmitting side that transmitted the continuous packet when a preset time has elapsed Then, an acknowledgment step for transmitting an acknowledgment including the sequence number of the normally received data and the window size, and the time at which the acknowledgment is transmitted are used as a base point. A delay time measuring step for measuring the time until a received packet is received as a delay time, a value range setting step for setting a plurality of different value ranges, and comparing the measured delay time with each value range, When the delay time is within the range, a counting step for counting, a histogram creation step for creating a histogram of the delay time from the count result for each range, and based on the histogram, data of the communication network A transmission characteristic determining step for determining transmission characteristics; and the transmission Depending on the sex, and a transmission parameter setting step of setting the transmission parameters of the data transmitted and received, characterized in that.

  A data communication method of a data communication system according to claim 12 of the present invention performs data communication by establishing a connection between the data communication devices in a communication network in which one transmission medium is shared by a plurality of data communication devices. A data communication method of a data communication system, the data communication method of the data communication device on the transmission side is a notification step of notifying the data communication device on the reception side of a transmission window size indicating the size of data that can be continuously transmitted; A transmission step of transmitting data consisting of a plurality of consecutive packets; and a communication control step of assigning a sequence number determined for each connection to the data in the packet to be transmitted. The data communication method transmits a reception window size indicating the size of data that can be received continuously. A notification step of notifying the data communication device, a reception step of receiving data consisting of a plurality of consecutive packets, a detection step of detecting whether the data consisting of a plurality of consecutive packets has been received, and the window size When a continuous packet having the data size indicated is received, or when a preset time has elapsed since the start of data reception, a sequence of data normally received to the data communication apparatus that transmitted the continuous packet An acknowledgment step for transmitting an acknowledgment including a number and the window size, and a time from when the acknowledgment is transmitted to a time when a packet transmitted from the data communication device on the transmission side is received. The delay time measurement step that measures A range setting step for setting a plurality of range ranges, the measured delay time is compared with each range, a count step for counting when the delay time is within the range, and a count for each range A histogram creation step for creating a histogram of the delay time from the result, a transmission characteristic determination step for determining a transmission characteristic of data in the communication network based on the histogram, and transmission of data to be transmitted / received according to the transmission characteristic And a transmission parameter setting step for setting parameters.

  In the data communication method according to claim 13 of the present invention, in the data communication method according to claim 11 or claim 12, the delay time measurement step is based on a time when the acknowledgment is transmitted, and from the base point, The time until receiving the first packet transmitted from the data communication apparatus on the transmission side is measured as a delay time.

  The data communication method according to claim 14 of the present invention is the data communication method according to claim 11 or 12, wherein when the acknowledge step receives a continuous packet having a data size indicated by the window size, A first acknowledgment that sets the window size to 0 is transmitted to the data communication device on the transmission side that has transmitted the continuous packets. After a preset time has elapsed, the window size is set to a preset value. 2, and the delay time measuring step receives the first packet transmitted from the data communication apparatus on the transmission side, based on the time when the second acknowledge is transmitted. The time until is measured as the delay time.

  In the data communication method according to claim 15 of the present invention, in the data communication method according to claim 11 or claim 12, the delay time measuring step is based on a time at which the acknowledgment is transmitted, and from the base point, A time until receiving a packet including arbitrary data transmitted from the data communication apparatus on the transmission side is measured.

  A data communication method according to a sixteenth aspect of the present invention is the data communication method according to the eleventh or twelfth aspect, wherein the acknowledge step is performed when no data reception is detected or when the received data is received. If the amount does not reach the window size, the acknowledgment is transmitted when a data reception time exceeds a predetermined time.

  A data communication method according to claim 17 of the present invention is the data communication method according to claim 11 or 12, wherein the data communication method of the data communication device on the receiving side includes a plurality of ranges each defining the respective range. It further includes a range control step of changing any one of the threshold values based on the delay time measured in the delay time measurement step.

  The data communication method according to claim 18 of the present invention is the data communication method according to claim 17, wherein the range control step sets a maximum value or a minimum value among a plurality of threshold values defining the range as the delay. The threshold value is changed based on time, and a threshold value other than the maximum value and the minimum value is obtained by constant division of a value obtained by subtracting the minimum value from the maximum value.

  The data communication method according to claim 19 of the present invention is the data communication method according to claim 11 or 12, wherein the transmission characteristic determination step includes the frequency of the shortest delay time and the second shortest delay in the histogram. A difference value α1 with respect to the frequency of time and a difference value α2 between the frequency with the longest delay time and the frequency with the second longest delay time in the histogram are obtained, and an equation ( 13) to calculate the characteristic amount β1 of the transmission error state, and to calculate the characteristic amount β2 of the communication waiting state in the communication network from the difference value α2 and the arbitrary constant α by the equation (14). The transmission characteristic is determined from β1 and the characteristic amount β2.

[Equation 13]
β1 = α1 / α (13)

[Formula 14]
β2 = α2 / α (14)

  The data communication method according to claim 20 of the present invention is the data communication method according to claim 11 or 12, wherein the transmission characteristic determination step obtains a difference value of the frequency of each delay time in the histogram, A maximum delay time in which the difference value becomes larger than a set constant is obtained, and a cumulative distribution is obtained by accumulating the frequency of each delay time in the histogram, and the maximum cumulative value M and the maximum delay time are obtained from the cumulative distribution. And a characteristic value m1 of a transmission error state is calculated by Expression (15), a characteristic quantity m2 of a communication waiting state in the communication network is calculated by Expression (16), and the characteristic amount is calculated. The transmission characteristic is determined from m1 and characteristic quantity m2.

[Equation 15]
m1 = m / M (15)

[Equation 16]
m2 = (M−m) / M (16)

  The data communication device of the present invention transmits a packet including a window size indicating the size of data that can be continuously received, and receives data composed of a plurality of continuous packets transmitted from the data communication device on the transmission side. When a continuous packet having a data amount indicated by the window size is received, or when a preset time has elapsed since the start of data reception, the transmitting side that has transmitted the continuous packet Acknowledgment including the sequence number of the received data and the window size to the data communication device, based on the acknowledgment control unit that transmits the acknowledgment and the time when the acknowledgment was transmitted, and from the base point, the data communication on the transmitting side Delay that measures the time until a predetermined packet transmitted from the device is received as a delay time The time measurement unit and each different value range are set, the delay time and the value range are compared, and when the delay time is within the value range, a plurality of comparators that output a pulse signal, and for each comparator A histogram generation unit that counts pulse signals and generates a histogram of the delay time from the count result, a transmission characteristic determination unit that determines transmission characteristics of data in the communication network based on the histogram, and the transmission characteristics And a transmission parameter setting unit that sets data transmission parameters accordingly.

  Thus, in a communication network using a general-purpose communication protocol such as TCP / IP, the transmission characteristics between the data communication device on the transmission side and the data communication device on the reception side are determined only by the data communication device on the reception side. Thus, the data transmission parameters can be adjusted according to the determination result.

  In the data communication apparatus of the present invention, when the acknowledgment control unit receives a continuous packet having the data amount indicated by the window size, the window size is transmitted to the data communication apparatus on the transmitting side that has transmitted the continuous packet. The first acknowledge to be 0 is transmitted, and after a preset time has elapsed, a second acknowledge having the window size set to a preset value is transmitted, and the delay time measurement unit is configured to transmit the second acknowledge. The time until the first packet transmitted from the data communication apparatus on the transmission side is received as the delay time is measured from the time when the acknowledgment of the first is transmitted as a base point.

  Thereby, the processing delay of the data communication device on the transmission side, that is, the delay time for the transmission data communication device to write the transmission data to the transmission buffer can be suppressed.

  In the data communication device of the present invention, a plurality of threshold values that define the range of each comparator are initialized in advance, and a delay time is input from the delay time measurement unit, and the delay time is input based on the input delay time. It further has a range controller for changing any one of the threshold values.

  As a result, the transmission characteristic of data in the communication network can be accurately grasped by changing the range of the histogram of the delay time according to the transmission characteristic.

  Further, the data communication method of the present invention includes a notification step of notifying the transmission side data communication device of a window size indicating the size of data that can be continuously received, and a reception step of receiving data comprising a plurality of consecutive packets. A detection step for detecting whether data consisting of a plurality of consecutive packets has been received, and a preset value when a continuous packet having the data size indicated by the window size is received or after reception of data is started An acknowledgment step for transmitting an acknowledgment including the sequence number of the received data and the window size to the data communication device on the transmission side that has transmitted the continuous packet when time has elapsed; and the time at which the acknowledgment was transmitted From the base point, send from the data communication device on the transmitting side. A delay time measuring step for measuring the time until a received packet is received as a delay time, a value range setting step for setting a plurality of different value ranges, and comparing the measured delay time with each value range, When the delay time is within the range, a counting step for counting, a histogram creation step for creating a histogram of the delay time from the count result for each range, and based on the histogram, data of the communication network The data communication method of the data communication apparatus on the receiving side includes a transmission characteristic determination step for determining a transmission characteristic and a transmission parameter setting step for setting a transmission parameter for data to be transmitted and received according to the transmission characteristic. .

  Thereby, in a communication network using a general-purpose communication protocol such as TCP / IP, the transmission characteristic between the data communication device on the transmission side and the data communication device on the reception side is determined only on the reception side, and the determination result The data transmission parameters can be adjusted accordingly.

  In the data communication method of the present invention, when the acknowledge step receives a continuous packet having a data amount indicated by the window size, the window size is set to 0 on the transmitting side data communication apparatus that has transmitted the continuous packet. The first acknowledge is transmitted, and after a preset time has elapsed, a second acknowledge having the window size set in advance is transmitted, and the delay time measuring step includes the second acknowledge The time from when the acknowledge is transmitted is used as a base point, and the time from the base point until the first packet transmitted from the data communication apparatus on the transmission side is received is measured as the delay time.

  Thereby, the processing delay of the data communication device on the transmission side, that is, the delay time for the transmission data communication device to write the transmission data to the transmission buffer can be suppressed.

  In addition, the data communication method of the present invention further includes a range control step of changing any one of a plurality of threshold values that respectively define the range based on the delay time measured in the delay time measurement step. Features.

  As a result, the transmission characteristic of data in the communication network can be accurately grasped by changing the range of the histogram of the delay time according to the transmission characteristic.

Hereinafter, embodiments of a data communication apparatus and a data communication method of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a diagram illustrating an example of a communication network using the data communication apparatus (transmission terminal and reception terminal) and the data communication method according to the first embodiment.

  In FIG. 1, a communication terminal A (1), a communication terminal B (2), a communication terminal C (3), and a communication terminal D (4) transmit data to each other using wireless communication as a data communication method. In the wireless communication of FIG. 1, a network is formed using a CSMA / CA (Carrier Sense Multiple Access Avoidance) method in which one wireless frequency band is shared and communication is performed by detecting the communication state of each other. .

  In the first embodiment, the communication terminal A (1) becomes a transmission terminal (video server), the communication terminal B (2) becomes a reception terminal (client monitor), and the communication terminal B (2) transmits a communication terminal in response to a transmission request. A (1) continuously transmits video content. At this time, it is assumed that the communication terminal C (3) and the communication terminal D (4) are performing data communication regardless of the communication between the communication terminal A (1) and the communication terminal B (2).

  FIG. 4 is a communication block diagram illustrating a block configuration of layers included in a transmission / reception terminal that performs video transmission and a data flow on a communication network. The video server 40 and the client monitor 41 are both a MAC / PHY layer (Media Access Layer / Physical Layer) 42, TCP / IP (Transmission Control Protocol), which is a transmission method and transmission control method compliant with the IEEE 802.11 wireless communication standard. / Internet Protocol) is used.

  The application layer 44 on the video server 40 side records a plurality of video contents as files on a hard disk (HDD), and transmits continuous video data at a speed for performing real-time video display in response to a request from the client monitor 41. . The transmission data 45 a read from the HDD is temporarily stored in the transmission buffer 46. The transmission buffer 46 is a memory having a FIFO (First In First Out) configuration. Although only one transmission buffer 46 is shown in FIG. 4, each of the application layer, TCP / IP layer, and MAC / PHY layer has a transmission buffer necessary for communication.

  The client monitor 41 detects the packet 45b addressed to its own terminal transmitted by the video server 40, temporarily stores it in the reception buffer 47, notifies the upper application layer 44 of the reception, and the application layer 44 Received data 45c is input to a decoding unit (not shown) and reproduced as a video on a monitor (not shown).

  The communication protocol 43 of the video server 40 and the communication protocol 43 of the client monitor 41 communicate with each other by TCP. In TCP, a connection is established at the start of communication, and the communication flow is controlled by the port number and sequence number determined for each connection.

  In TCP, an acknowledgment (acknowledgment response) is transmitted from the receiving terminal (client monitor 41) to the transmitting terminal (video server 40) to indicate that reception has been established for each transmitted packet. The transmitting terminal can know the packet received by the receiving terminal from the sequence number included in the acknowledgement. When a large amount of data such as video is transmitted, an acknowledgment is not transmitted for each transmission packet, but an acknowledgment is transmitted collectively for a plurality of transmitted packets. Therefore, in TCP, the receiving terminal transmits the number of bytes that can be continuously received as the window size in the packet header.

  Configurations and operations of the video server 40 and the client monitor 41 will be described with reference to FIGS.

  FIG. 2 is a block diagram illustrating a configuration example of the video server (data communication device on the transmission side) 40. The video server 40 includes a hard disk (HDD) 11, a controller 10, a memory 12, and a communication unit 13.

  The controller 10 includes a system control unit 15 that controls the entire system, a communication control unit 16 that performs TCP / IP communication protocol control and access control to the communication unit 13, and reads the video file 14 stored in the HDD 11. The file control unit 17 controls writing.

  The memory 12 is a means for the controller 10 to temporarily store data.

  The communication unit 13 includes a communication controller 20, a PHY 21, and a communication memory 22, and performs wireless communication. The communication controller 20 performs control of data transmission / reception with the communication control unit 16 and control of the PHY 21. The PHY 21 transmits and receives data in wireless communication. The communication memory 22 is a local memory of the communication controller 20 and plays a role of a transmission buffer such as temporarily storing transmission data from the controller 10 and reception data.

  The communication unit 13 receives the packet including the window size from the data communication device on the reception side, and transmits a continuous packet of the data size indicated by the reception window size. It plays a role of assigning a sequence number determined for each connection to the data in the packet to be transmitted.

  FIG. 3 is a block diagram showing a configuration example of the client monitor (data communication device on the receiving side) 41. The client monitor 41 includes a controller 30, a memory 12, a communication unit 13, a decoding unit 32, a display unit 33, a delay time processing unit 35a, and a transmission characteristic determination unit 70.

  The controller 30 includes a system control unit 25 that controls the entire system, a communication control unit 16 that performs TCP / IP communication protocol control and access control to the communication unit 13, and an acknowledge control unit that controls an acknowledgment of transmitted data. 38 and a transmission characteristic determination unit 70 that determines transmission characteristics of data in the communication network.

  The memory 12 is a local memory of the controller 30, and temporarily stores commands and data in the control of the entire system, and temporarily stores transmission and reception data in the communication protocol control.

  The communication unit 13 and the communication control unit 16 have functions similar to those of the video server 40.

  The system control unit 25 temporarily stores the compressed image data received by the communication unit 13 in the memory 12 and appropriately transmits it to the decoding unit 32 at the time of image display.

  The decoding unit 32 stores the compressed image data up to a decodable unit, and decodes the compressed image data into an image that can be displayed on the monitor 39 of the display unit 33 when the data of the decoding unit is ready.

  The display unit 33 displays the image data from the decoding unit 32 on the monitor 39.

  In the client monitor 41, in order to detect the data transmission state in communication, the delay time processing unit 35a measures the delay time of data transmission, and the transmission characteristic determination unit 70 determines based on the measurement result of the delay time. Determine the transmission characteristics of data in the communication network.

  As described above, the communication unit 13 has a function of receiving data composed of a plurality of continuous packets transmitted from the data communication device (video server 40) on the transmission side and transmitting an acknowledgment for the received data. The system control unit (detection unit) 25 plays a role of detecting whether the data composed of a plurality of continuous packets has been received. The acknowledge control unit 38 receives a continuous packet having the data size indicated by the window size. Or an acknowledgment including a sequence number of the data normally received and the window size to the video server 40 that has transmitted the continuous packet when a preset time has elapsed since the start of data reception. The delay time processing unit 35a is responsible for transmitting the acknowledgment when the acknowledgment is transmitted. The transmission characteristic determination unit 70 plays a role of measuring a time until a packet transmitted from the video server 40 is received as a delay time, based on the histogram of the delay time. The system control unit (transmission parameter setting unit) 25 plays a role of setting transmission parameters of data to be transmitted and received in accordance with the transmission characteristics.

  A method for measuring the delay time by the client monitor 41 will be described with reference to FIGS. 13, 5, and 9. FIG.

  FIG. 13 is a flowchart of delay time measurement by the client monitor 41.

  The client monitor 41 shown in FIG. 4 establishes a TCP connection for requesting the video server 40 to transfer the video file (step S1). Next, the system control unit 25 of the client monitor 41 detects reception of data transmitted by the video server 40 (step S2). If reception of data is detected, has the received data amount reached the window size? Is determined (step S3). On the other hand, if reception of data is not detected, or if the amount of received data has not reached the window size, a predetermined maximum continuous packet reception time has been exceeded, that is, the window timer has expired. Is determined (step S4). When either of these events occurs, that is, when the amount of received data reaches the window size or when the window timer expires, the acknowledge control unit 38 performs an acknowledge process based on the control of the system control unit 25. (Step S5). When the acknowledge process is performed, the delay time processing unit 35a performs a delay time measurement process (step S6). Next, based on the result of the delay time measurement in step S6, the delay time processing unit 35a obtains the delay time distribution characteristic (step S7), and the transmission characteristic determination unit 70 determines the transmission characteristic from the delay time distribution characteristic. (Step S8), the system control unit 25 sets a transmission parameter of data to be transmitted and received based on the determination result (Step S9). Next, the system control unit 25 determines whether or not the received image data is the last image data (step S10). If the received image data is the last image data, the communication unit 13 via the communication control unit 16 is determined. To disconnect the connection (step S11).

  If no data reception is detected in step S2, if it is determined in step S3 that the amount of received data does not reach the window size, or if it is determined that the image received in step S10 is not the last image data. If YES, the process returns to the received data detection process in step S2.

  FIG. 5 is a time chart for explaining a delay time measuring method by the client monitor 41 according to the first embodiment.

  In FIG. 5, a transmission terminal signal 50 indicates packets transmitted by the video server 40 (transmission terminal) in time series. The receiving terminal signal 52 indicates packets transmitted from the client monitor 41 (receiving terminal) to the video server 40 in time series. The reception trigger signal 54 is a trigger signal that occurs (turns on) when the client monitor 41 receives a packet addressed to its own terminal. The ACK trigger signal 55 is a trigger signal that occurs (turns on) when the client monitor 41 transmits an acknowledgment to a specific terminal. The delay measurement state 56 shows a state in which the delay time is measured over time.

  The video server 40 transmits the continuous packet 51 up to the data amount indicated by the window size. The client monitor 41 transmits an acknowledge 53 when either the amount of data indicated by the window size is received or when a predetermined continuous packet maximum reception time is exceeded, or one of the events occurs. When the acknowledge 53 is transmitted, the ACK trigger 55a of the ACK trigger signal 55 is turned ON, and the delay measurement state 56 is set to the delay timer start 56a. Then, the delay timer is stopped at the reception trigger 54a indicating that the next packet from the video server 41 has arrived. Thereby, the delay measurement state 56 becomes the state of the delay timer stop 56b. The measurement result of the delay time timer at that time is stored in the memory 12 as the delay time 59.

  FIG. 9 is a time chart for explaining another method for measuring the delay time by the client monitor 41 according to the first embodiment. In the delay time measuring method shown in FIG. 9, the video server 40 transmits the continuous packet 51 up to the data amount indicated by the window size. The client monitor 41 responds with an acknowledge 53 when one of the events occurs, that is, the amount of data indicated by the window size has been received or the maximum reception time of a predetermined continuous packet has been exceeded. When the acknowledge 53 is responded, the ACK trigger 55a of the ACK trigger signal 55 is turned ON, and the delay measurement state 56 is set to the state of the delay timer start 56a. Next, it is detected whether any data is included in the packet transmitted from the video server 40 after the delay timer start 56a. Then, the reception trigger 54b is turned ON at the timing when the packet 51b including arbitrary data is received, and the delay time is stopped. Thereby, the delay time state 56 becomes the state of the delay timer stop 56b. The measurement result of the delay time timer at this time is stored in the memory 12 as the measurement time 59. In FIG. 9, the packet 51b is the second packet received after the delay timer start 56a, but may be any packet in a specific order.

  The delay time processing by the delay time processing unit 35a of the client monitor 41 will be described with reference to FIGS.

  FIG. 14 is a flowchart of the delay time processing by the delay time processing unit 35a, and shows the processing performed in the delay time processing step S6 of FIG.

  First, when the acknowledge process in step S5 shown in FIG. 13 is performed, the delay time processing unit 35a determines whether or not the ACK trigger 55a is in an ON state (step S20), and if it is ON, starts a delay timer. (Step S21). Thereafter, it is determined whether or not the next reception trigger is turned on, and a wait cycle is entered until it is turned on (step S22). Here, when the delay time is measured by the delay time measuring method shown in FIG. 5, it is determined whether the reception trigger 54a shown in FIG. 5 is turned on and the delay time is measured by the delay time measuring method shown in FIG. Determines whether the reception trigger 54b shown in FIG. If the reception trigger is turned on, the delay timer is stopped (step S23). The measured value of the delay time timer at this time is the delay time. Next, the delay time processing unit 35a compares the delay time with each value range by using a plurality of comparators in which different value ranges are set in advance in order to create a delay time histogram (step S24). Then, the output of the comparator is counted up by an appropriate range counter, and a delay time histogram is created (step S25).

  FIG. 6 is a block diagram illustrating a configuration example of the delay time processing unit 35 a of the client monitor 41.

  The delay time processing unit 35 a compares the delay time measuring unit 63 that measures the delay time, the delay time with a predetermined range, a comparator 65 that outputs the comparison result, and a plurality of outputs that count the output of the comparator 65. A histogram creation unit 66 including a range counter 67 and a counter bus 68 for transmitting the count result of the range counter 67 to the transmission characteristic determination unit 70 of the controller 30 are provided.

  A plurality of comparators 65 are provided, each having a different value range, comparing the delay time with the value range, and outputting a pulse signal when the delay time is within the value range, creating a histogram The unit 66 plays a role of counting the pulse signal for each comparator and creating a histogram of the delay time from the count result.

  The delay time measurement unit 63 receives the ACK trigger signal 55 and the reception trigger signal 54 from the controller 30, and the comparator 65 receives the control signal 64 from the controller 30. The ACK trigger signal 55 is a trigger signal that occurs at the timing when the receiving terminal (client monitor 41) transmits an acknowledgement. The reception trigger signal 54 is a trigger that occurs when a packet addressed to the terminal arrives. The delay time measuring unit 63 measures the interval between two triggers of the ACK trigger signal 55 and the reception trigger signal 54 as a delay time under the control of the control signal 64 from the controller 30. The delay time measuring unit 63 outputs the measured delay time to the comparator 65 as delay time data 69a. Further, a delay time measurement completion trigger signal 69b indicating that the measurement of the delay time is completed is output to the comparator 65. The delay time data 69a from the delay time measuring unit 63 is held in the comparator 65 as a delay time at the timing when the delay time measurement completion trigger signal 69b is turned on, that is, at the timing of the delay timer stop 56b shown in FIGS. Is done.

  FIG. 8 is a block diagram illustrating a configuration example of the comparator 65. The delay time 80 is delay time data 69a held by the delay time measurement completion trigger signal 69b. The window comparator 81 inputs the first threshold value from the input MAX and the second threshold value smaller than the first threshold value from the input MIN, compares the delay time 80 with the first threshold value and the second threshold value, and the delay time 80 is When it is within the range defined by the first threshold value and the second threshold value, that is, when second threshold value <delay time 80 ≦ first threshold value, a pulse signal (count) is output. In FIG. 8, the thresholds 1 to n input to the window comparator 81 have a relationship of threshold n <threshold 5 <threshold 4 <threshold 3 <threshold 2 <threshold 1. The window comparator 81a receives the delay time 80, inputs the threshold value 1 from the input MAX, and inputs the threshold value 2 from the input MIN, compares the threshold value 1, the threshold value 2, and the value of the delay time 80, and threshold value 2 <delay time. When the condition of 80 ≦ threshold 1 is satisfied, a pulse signal (count 1) is output. Similarly, the other window comparators 81b to 81n compare the delay time 80 with the first threshold value input from the input MAX and the second threshold value input from the input MIN, and second threshold value <delay time 80 ≦ first. When the threshold condition is satisfied, a pulse signal (count 2 to count n) is output.

  Threshold value 1 to threshold value n are predetermined values. A communication session between the video server 40 (transmission terminal) and the client monitor 41 (reception terminal) occurs, and a connection between them is established. At this time, the window comparators 81a to 81n are set through the control signal 64 from the controller 30.

  As described above, the pulse signal output from the window comparator 81 is input to the range counter 67 of the histogram creation unit 66. Each value range counter 67 has a pulse counter corresponding to any value range of the window comparators 81a to 81n, and counts up the pulse signal of the window comparator 81 to which the value range is suitable. As a result, the client monitor 41 receives continuous data from the video server 40 and transmits an acknowledgment to measure delay time variation.

  The transmission characteristic determination unit 70 of the controller 30 can read the count value of the range counter 67 of the histogram creation unit 66 at any time through the counter bus 68. The transmission characteristic determination unit 70 determines the data transmission characteristic from the value of the range counter 67. Hereinafter, the transmission characteristic determination process will be described with reference to FIG.

  7A to 7C are frequency distribution (histogram) diagrams of delay times. The horizontal axis in the figure indicates the delay time. The vertical axis represents the number of times (frequency) that the delay time has occurred in each range, that is, the count value of the range counter. The count value of each range counter 67 read by the transmission characteristic determination unit 70 of the controller 30 represents the situation at the time of data transmission.

  In a transmission state where only a transmission error occurs due to the influence of noise or the like, error retransmission occurs frequently, so the frequency of short delay times increases. That is, the number of occurrences of a short delay time increases. On the other hand, the longer the delay time, the smaller the number of occurrences. Therefore, the delay time distribution is as shown in FIG.

  In a transmission state in which a waiting state occurs in communication of the own terminal by communication of another terminal, the number of occurrences of a short delay time is the same as the number of occurrences of a long delay time due to the randomness of the communication. Therefore, as shown in FIG. 7B, a frequency distribution of delay times indicating a distribution constant only in the communication waiting state is obtained.

  As shown in FIG. 7C, the actual transmission characteristic is a general frequency distribution of delay time that occurs in a mixed state of two distribution states of transmission error and communication waiting. For this reason, the controller 30 reads the count value of the range counter 67, and obtains the difference value α1 of the number of occurrences at the two value ranges with the shortest delay time and the difference value α2 of the number of occurrences at the two value ranges with the longest delay time. calculate. Then, as an arbitrary constant α (α> 0), a transmission error characteristic amount β1 is obtained by Expression (17), and a communication waiting time characteristic amount β2 is calculated by Expression (18).

[Equation 17]
β = α1 / α (17)

[Equation 18]
β = α2 / α (18)

  When the transmission error characteristic amount β1 is large and the communication waiting time characteristic amount β2 is small, it is determined that the transmission state is relatively short and a transmission error has occurred. However, when the communication waiting time characteristic amount β2 is 0, it can be determined that the transmission state is good. If the transmission error characteristic amount β1 and the communication waiting time characteristic amount β2 are equal, it is determined that the communication amount between the communication terminals is relatively increased, and that transmission waiting is occurring. As described above, the transmission characteristic determination unit 70 determines the transmission characteristic of data, and the system control unit 25 adjusts the window size, the packet length, the response time of the acknowledgment, etc. suitable for the transmission characteristic, and the transmission path Adjust the transmission parameters appropriate for the situation.

  As described above, according to the first embodiment, general-purpose between a video monitor (transmitting terminal) and a client monitor 41 (receiving terminal) in a communication network in which one transmission medium is shared by a plurality of communication terminals. In data communication for establishing a connection using TCP / IP, which is a typical communication protocol, when the client monitor 41 receives a continuous packet of the data amount indicated by the window size from the video server 40, or a predetermined continuous packet An acknowledgment control unit 38 that controls transmission of an acknowledgment to the video server 40 when the maximum reception time of the time is exceeded, and measures a time from when the acknowledgment is transmitted until a predetermined packet is received as a delay time, A delay time processing unit 35a for creating a histogram of delay times; Since the transmission characteristic determination unit 70 for determining the transmission characteristic of data in the network is provided, the transmission characteristic of the data in the communication network is determined only by the client monitor 41, and the data to be transmitted / received according to the transmission characteristic Parameters can be adjusted.

(Embodiment 2)
Next, a data communication apparatus and a data communication method according to Embodiment 2 will be described. The second embodiment is different from the first embodiment in the method of measuring the delay time by the delay time processing unit 35b of the client monitor 41. Since the network form of the communication terminal and the configuration of the video server 40 are the same as those of the first embodiment, the description thereof is omitted.

  FIG. 15 is a flowchart of delay time measurement by the client monitor 41 according to the second embodiment.

  First, the client monitor 41 shown in FIG. 4 establishes a TCP connection for requesting the video server 40 to transfer the video file (step S30). The system control unit 25 detects the reception of data transmitted by the video server 40 (step S31), and if the reception of data is detected, determines whether the amount of received data has reached the window size (step S32). . On the other hand, if reception of data could not be detected, or if the amount of received data did not reach the window size, whether the predetermined maximum continuous packet reception time was exceeded, that is, the window timer timed out Is determined (step S33). When one of these events occurs, that is, when the amount of received data reaches the window size or when the window timer expires, the acknowledge control unit 38 controls the window size based on the control of the system control unit 25. An acknowledge process is performed to set 0 to 0 (step S34). With this acknowledgment, the video server 40 determines that the client monitor 41 cannot perform reception processing, and temporarily stops data transmission. After a predetermined time has elapsed, the acknowledge control unit 38 performs an acknowledge process for setting the window size to N bytes, which is a normal window size (step S35), and the delay time process unit 35b performs a delay time measurement process for data transmission. (Step S36). Next, the delay time processing unit 35b obtains a delay time distribution characteristic based on the delay time measurement result in step S36 (step S37), and the transmission characteristic determination unit 70 determines the data of the communication network from the delay time distribution characteristic. The transmission characteristic is determined (step S38), and the system control unit 25 sets transmission parameters for data to be transmitted and received based on the determination result (step S39). Next, the system control unit 25 determines whether the received image data is the last image data (step S40). If the received image data is the last image data, the system control unit 25 controls the communication unit 13 via the communication control unit 16. Then, the connection is disconnected (step S41).

  If no data reception is detected in step S31, if it is determined in step S33 that the amount of received data does not reach the window size, or if it is determined that the image received in step S40 is not the last image data. If YES, the process returns to the received data detection process in step S31.

  FIG. 10 is a time chart for explaining a delay time measuring method by the client monitor 41 according to the second embodiment. The transmission terminal signal 50 indicates packets transmitted from the video server 40 in time series. The receiving terminal signal 52 indicates packets transmitted by the client monitor 41 in time series. The reception trigger signal 54a is a trigger signal that is generated (turned ON) when the client monitor 41 receives a packet addressed to its own terminal. The ACK trigger signal 55 is a trigger signal that occurs (turns on) at the timing when the client monitor 41 transmits an acknowledgment. The delay measurement state 56 indicates a state of delay time measurement by the client monitor 41.

  The video server 40 (transmission terminal) transmits the continuous packet 51 up to the data amount indicated by the window size. The client monitor 41 (receiving terminal) transmits an acknowledge 53 when an event occurs in which either the data amount indicated by the window size is received or a predetermined continuous packet maximum reception time is exceeded. To do. Here, an acknowledge 53 with a window size of 0 bytes is transmitted to the video server 40. The video server 40 that has received the acknowledge 53 has already set the next transmission data in the transmission buffer. However, since the notified window size is 0 bytes, the transmission operation cannot be performed.

  After a predetermined time has elapsed, the client monitor 41 transmits the acknowledge 53a again. Here, an acknowledge 53a is transmitted with a window size of N bytes, which is a prescribed reception size. The client monitor 41 stops the transmission once with the window size = 0 and sets the data in the transmission buffer of the video monitor 40 in order to grasp the transmission characteristics in the time from the transmission of the acknowledgment to the reception of the first packet. After that, by setting the window size to N, the processing delay of the video monitor 40, that is, the delay of the time for the controller 10 of the video monitor 40 to write data in the transmission buffer is reduced. The video monitor 40 that has received the acknowledge 53a continuously transmits the data set in the transmission buffer.

  When the acknowledge 53a is transmitted, the client monitor 41 turns on the ACK trigger 55a of the ACK trigger signal 55 and sets the delay measurement state 56 to the delay timer start 56a state in order to start measuring the delay time. Then, in order to end the measurement of the delay time with the reception trigger 54a indicating that the next packet from the video server 40 has arrived, the delay measurement state 56 is set to the delay timer stop 56b. The measurement result of the delay time timer at that time is stored in the memory 12 as the delay time 59.

  The delay time processing by the delay time processing unit 35b of the client monitor 41 will be described with reference to FIG. FIG. 11 is a block diagram illustrating a configuration example of the delay time processing unit 35b of the client monitor 41 according to the second embodiment. The delay time processing unit 35b is different from the delay time processing unit 35a according to the first embodiment in that the range time control unit 127 is provided. Since the other components are the same as those of the delay time processing unit 35a, the same reference numerals are given and description thereof is omitted.

  The value range control unit 127 updates the value range set in each window comparator 81, that is, the values of the threshold value 1 to the threshold value n. More specifically, the value range control unit 127 is preset with a plurality of threshold values that respectively define the value ranges of the respective comparators 81, inputs a delay time from the delay time measurement unit, and based on the input delay time To change any of the threshold values. This is to adjust the range of each window comparator 81 according to the transmission environment as time elapses in order to appropriately grasp the transmission characteristics that change according to the transmission environment.

  The delay time data 69a from the delay time measuring unit 63 is transmitted to the comparator 65, and the delay time measurement completion trigger signal 69b is generated, that is, at the timing of the delay timer stop 56b shown in FIG. Retained. Further, the delay time data 69 a and the delay time measurement completion trigger signal 69 b are also output to the range controller 127.

  As shown in FIG. 8, the comparator 65 includes window comparators 81 a to 81 n, and each window comparator 81 compares the delay time 80 with a preset value range. The delay time 80 is delay time data 69a held by the delay time measurement completion trigger signal 69b.

  When the communication session between the video server 40 (transmission terminal) and the client monitor 41 (reception terminal) occurs and the connection is established as the thresholds 1 to n shown in FIG. 8, the controller 30 shown in FIG. A predetermined initial value is set in the comparator 65 through the control signal 64. Similarly, the threshold values 1 to n are set as initial values in the range controller 127.

  The range controller 127 holds the delay time data 69a when the delay time measurement completion trigger signal 69b occurs. Since the delay time data may change every time the delay time is measured, the maximum value (threshold value 1) or the minimum value (threshold value n) is obtained based on the value of the delay time data 69a and necessary. Update if there is. For example, it is updated when it differs from the initial value by a predetermined value or more. When either value is updated, the update data 128 is output to the comparator 65, and the threshold value 1 to the threshold value n in the comparator 65 are changed. In addition, an update notification signal 129 is output to notify the controller 30 that there has been an update.

  The range controller 127 obtains threshold values other than the maximum value and the minimum value by the following equation (19), where n (n> 0) is the number of window comparators.

[Equation 19]
δ range = (maximum value−minimum value) / n
Threshold 2 = Maximum value−δ range Threshold 3 = Maximum value−2 × δ range Threshold 4 = Maximum value−3 × δ range Threshold 5 = Maximum value−4 × δ range (19)

  In the initial operation of the range controller 127, the maximum value becomes unstable. Therefore, the controller 30 can stop the operation of the range controller 127 for a predetermined time through the control signal 64.

  Further, the controller 30 can read the count value of the range counter 67 of the histogram creation unit 66 at any time through the counter bus 68. The transmission characteristic determination unit 70 of the controller 30 determines the data transmission characteristic from the count value of the range counter 67 of the histogram creation unit 66. Hereinafter, a method for determining transmission characteristics will be described with reference to FIG.

  FIGS. 12A to 12C are frequency distribution (histogram) diagrams of delay times. The horizontal axis in FIG. 12 indicates the delay time. FIG. 12A shows data distribution characteristics of the range counter, and shows data read from the range counter 67 by the transmission characteristic determination unit 70 of the controller 30. In FIG. 12A, the effective delay time Dmax indicates the maximum delay time when the count value of the range counter is not zero. The transmission characteristic determination unit 70 obtains the difference value of the frequency between each range of the histogram, that is, the difference value λ1 to λn of the count result of each range counter 67. FIG. 12B is a diagram illustrating the relationship between the difference value and the delay time. As illustrated in FIG. 12B, the transmission characteristic determination unit 70 obtains the difference between each difference value λ and the constant A, and obtains the maximum delay time D that makes the difference value λ larger than the constant A. Here, the constant A is set so that the delay time D is ½ of the effective delay time Dmax. FIG. 12C is a cumulative distribution of delay times. The controller 30 accumulates the frequency of the delay time in each range of the histogram, that is, the count value of the range counter 67, and obtains the cumulative distribution shown in FIG. Then, the transmission error characteristic amount m1 is obtained from Expression (20) from the cumulative value m at the point of the delay time D and the total value M of all the range counters 67, and the communication waiting time characteristic is obtained from Expression (21). The quantity m2 is determined.

[Equation 20]
m1 = m / M (20)

[Equation 21]
m2 = (M−m) / M (21)

  If the transmission error characteristic amount m1 is large and the communication waiting time characteristic amount m2 is small, it is determined that the transmission state is relatively short and a transmission error has occurred. Since the characteristic amount m1 is also a delay amount due to a transmission error, it can be determined that the transmission state is good when the characteristic amount m1 is close to the sum M. When the characteristic amount m2 of the communication waiting time is large, it is determined that the data communication amount of other communication terminals in the communication network is relatively increased and that transmission waiting is occurring. In this way, the transmission characteristic determination unit 70 determines the transmission characteristic of data, adjusts the window size, packet length, acknowledgment response time, etc. suitable for the transmission state, and adjusts the transmission parameters suitable for the transmission state. Do.

  As described above, according to the second embodiment, general-purpose between a video monitor (transmitting terminal) and a client monitor 41 (receiving terminal) in a communication network in which one transmission medium is shared by a plurality of communication terminals. In data communication for establishing a connection using TCP / IP, which is a typical communication protocol, when the client monitor 41 receives a continuous packet of the data amount indicated by the window size from the video server 40, or a predetermined continuous packet When the maximum reception time is exceeded, an acknowledge 53 with a window size of 0 is responded to the video server 40, and after a predetermined time has elapsed, an acknowledge control unit that performs control to transmit an acknowledge 53a with a window size of normal N bytes 38 and receive the first packet after the second acknowledge is sent A delay time processing unit 35b that measures the time until the delay time and creates a histogram of the delay time, a transmission characteristic determination unit 70 that determines a transmission characteristic of data in a communication network from the histogram, and a delay time processing unit And a range control unit 127 that sets the range of the histogram according to the delay time measured by 35b, so that only the client monitor 41 determines the data transmission characteristics in the communication network and sets the transmission state. Accordingly, transmission parameters of data to be transmitted / received can be adjusted. In addition, the processing delay of the video server 40 that is the transmission terminal, that is, the delay time for the video server 40 to write the transmission data in the transmission buffer can be suppressed. Further, the range control unit 127 can change the range of the histogram according to the transmission state, and as a result, the client monitor 41 can accurately grasp the transmission state.

  The present invention relates to data communication in which a connection is established with a general-purpose protocol with another data communication device in a communication network in which one transmission medium is shared by a plurality of communication terminals (data communication devices), and continuous data is transmitted and received. It is useful as an apparatus and a data communication method.

It is a figure which shows the example of a communication network of the data communication apparatus in Embodiment 1, 2 of this invention. It is a block diagram which shows the structural example of the video server which concerns on Embodiment 1, 2 of this invention. It is a block diagram which shows the structural example of the client monitor which concerns on Embodiment 1, 2 of this invention. It is a communication block diagram of the transmission / reception terminal which performs the video transmission in Embodiment 1, 2 of this invention. It is a time chart for demonstrating the measuring method of the delay time by the client monitor which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structural example of the delay time process part of the client monitor which concerns on Embodiment 1 of this invention. It is a frequency distribution figure of the delay time of the data transmission in Embodiment 1 of this invention. It is a figure which shows the structural example of the comparator of the client monitor which concerns on Embodiment 1 of this invention. It is a time chart for demonstrating the measuring method of the delay time by the client monitor which concerns on Embodiment 1 of this invention. It is a time chart for demonstrating the measuring method of the delay time by the client monitor which concerns on Embodiment 2 of this invention. It is a block diagram which shows the structural example of the delay time process part of the client monitor which concerns on Embodiment 2 of this invention. It is a frequency distribution figure of the delay time of the data transmission in Embodiment 2 of this invention. It is a flowchart figure of delay time measurement by the client monitor which concerns on Embodiment 1 of this invention. It is a flowchart figure of the delay time process by the delay time process part of the client monitor which concerns on Embodiment 1 of this invention. It is a flowchart figure of delay time measurement by the client monitor which concerns on Embodiment 2 of this invention.

Explanation of symbols

1 Communication terminal A
2 Communication terminal B
3 Communication terminal C
4 Communication terminal D
10, 30 Controller 11 HDD
12 Memory 13 Communication unit 14 Video files 15 and 25 System control unit 16 Communication control unit 17 File control unit 20 Communication controller 21 PHY
22 Communication memory 32 Decoding unit 33 Display unit 35a, 35b Delay time processing unit 38 Acknowledgment control unit 39 Monitor 40 Video server 41 Client monitor 42 MAC / PHY layer 43 Communication protocol layer 44 Application layer 45a Transmission data 45b Packet 45c Reception data 46 Transmission Buffer 47 Reception buffer 50 Transmission terminal signal 51 Continuous packet 52 Reception terminal signal 53 Acknowledge 53a Acknowledgment 54 Reception trigger signal 54a Reception trigger 55 ACK trigger signal 55a ACK trigger 56 Delay measurement state 56a Delay timer start 56b Delay timer stop 59 Delay time 63 Delay Timer 64 Control signal 65 Comparator 66 Histogram creation unit 67 Range counter 68 Counter bus 69a Delay time data 69b Delay time Measurement completion trigger 70 Transmission characteristic determination unit 80 Delay time 81a to 81n Window comparator 127 Range control unit 128 Update data 129 Update notification signal A Constant D Delay time Dmax Effective delay time M Sum of accumulated values m Cumulative value m1 Transmission error characteristic amount m2 Communication waiting time characteristic amount α Difference value β1 Transmission error characteristic amount β2 Communication waiting time characteristic amount λ Difference value

Claims (20)

In a data communication apparatus on the receiving side that performs data communication by establishing a connection with the data communication apparatus on the transmission side via a communication network in which one transmission medium is shared by a plurality of data communication apparatuses.
A communication unit that transmits a packet including a window size indicating the size of data that can be continuously received, and that receives data including a plurality of continuous packets transmitted from the data communication device on the transmission side;
A detection unit for detecting whether data comprising a plurality of consecutive packets is received;
When a continuous packet having the data size indicated by the window size is received or when a preset time has elapsed since the start of data reception, the data communication device on the transmission side that has transmitted the continuous packet An acknowledgment control unit for transmitting an acknowledgment including the sequence number of the received data and the window size;
A delay time measurement unit that measures the time from when the acknowledgment is transmitted as a base point, to the time when a packet transmitted from the transmission side data communication device is received as a delay time;
A different value range is set, a plurality of comparators that output a pulse signal when the delay time and the value range are compared, and the delay time is within the value range,
A histogram creating unit that counts the pulse signal for each comparator and creates a histogram of the delay time from the count result;
A transmission characteristic determination unit that determines transmission characteristics of data in the communication network based on the histogram;
A transmission parameter setting unit that sets transmission parameters of data to be transmitted and received according to the transmission characteristics;
A data communication device. The data communication apparatus according to claim 1, wherein
The delay time measurement unit uses the time when the acknowledgment is transmitted as a base point, and measures the time from the base point until the first packet transmitted from the data communication device on the transmission side is received as the delay time.
A data communication device. The data communication apparatus according to claim 1, wherein
When the acknowledge control unit receives a continuous packet of the data size indicated by the window size, the acknowledge control unit transmits a first acknowledge with the window size set to 0 to the transmitting data communication apparatus that has transmitted the continuous packet. , After a preset time has elapsed, send a second acknowledgment with the window size set to a preset value,
The delay time measurement unit includes:
The time from when the second acknowledgment is transmitted as a base point, and the time from the base point until the first packet transmitted from the data communication device on the transmission side is received is measured as the delay time.
A data communication device. The data communication apparatus according to claim 1, wherein
The delay time measurement unit uses the time when the acknowledgment is transmitted as a base point, and measures the time from the base point until receiving a packet including any data transmitted from the data communication device on the transmission side as a delay time To
A data communication device. The data communication apparatus according to claim 1, wherein
The acknowledgment control unit, when reception of data is not detected, or when the amount of received data does not reach the window size, when the data reception time exceeds a predetermined time, Sending the acknowledgment;
A data communication device. The data communication apparatus according to claim 1, wherein
A plurality of threshold values that predefine a value range of each of the comparators are initialized in advance, and a delay time is input from the delay time measurement unit, and the value range that changes any of the threshold values based on the input delay time A control unit;
A data communication device. The data communication apparatus according to claim 6, wherein
The range controller changes a maximum value or a minimum value among a plurality of threshold values defining a range of each comparator based on the delay time, and sets a threshold value other than the maximum value and the minimum value to the maximum value. By subtracting the value obtained by subtracting the minimum value from the value by constant division,
A data communication device. The data communication apparatus according to claim 1, wherein
The transmission characteristic determination unit includes a difference value α1 between the frequency of the shortest delay time and the frequency of the second shortest delay time in the histogram, the frequency of the longest delay time and the frequency of the second longest delay time in the histogram. Is calculated from the difference value α1 and an arbitrary constant α (α> 0) by Equation (1), and the difference value α2 and the arbitrary constant are calculated. a characteristic amount β2 of communication waiting state in the communication network is calculated from α and a mathematical expression (2), and the transmission characteristic is determined from the characteristic amount β1 and the characteristic amount β2.
A data communication device.
[Equation 1]
β1 = α1 / α (1)
[Equation 2]
β2 = α2 / α (2) The data communication apparatus according to claim 1, wherein
The transmission characteristic determining unit obtains a difference value of the frequency of each delay time in the delay time histogram, obtains a maximum delay time in which the difference value is larger than a preset constant, and sets each delay in the histogram. Cumulative distribution is obtained by accumulating the frequency of time, the maximum cumulative value M and the cumulative value m corresponding to the maximum delay time are obtained from the cumulative distribution, and the characteristic amount m1 of the transmission error state is calculated by Equation (3). And calculating the characteristic amount m2 of the communication waiting state in the communication network by the equation (4), and determining the transmission characteristic from the characteristic amount m1 and the characteristic amount m2.
A data communication device.
[Equation 3]
m1 = m / M (3)
[Equation 4]
m2 = (M−m) / M (4) In a data communication system in which data communication is performed by establishing a connection between the data communication devices in a communication network in which one transmission medium is shared by a plurality of data communication devices.
Transmitting data consisting of a plurality of consecutive packets, and including a transmission window size indicating a data size that can be transmitted continuously and including the transmission window size in the packet, and a data size that can be received continuously A data communication device on the receiving side for transmitting a packet including a reception window size and receiving data including a plurality of continuous packets;
The data communication device on the transmission side receives the packet including the window size from the data communication device on the reception side, and transmits a continuous packet of the data size indicated by the reception window size; and
A communication control unit for attaching a sequence number determined for each connection to the data in the packet to be transmitted,
The receiving side data communication device is:
A communication unit that receives data consisting of a plurality of continuous packets transmitted from the data communication device on the transmission side, and transmits an acknowledgment for the received data;
A detection unit for detecting whether data comprising a plurality of consecutive packets is received;
When a continuous packet having the data size indicated by the window size is received or when a preset time has elapsed since the start of data reception, the data communication device on the transmission side that has transmitted the continuous packet An acknowledgment control unit for transmitting an acknowledgment including a sequence number of data normally received and the window size;
A delay time measurement unit that measures, as a delay time, a time until a packet transmitted from the data communication device on the transmission side is received, based on a time at which the acknowledgment is transmitted;
A different value range is set, a plurality of comparators that output a pulse signal when the delay time and the value range are compared, and the delay time is within the value range,
A histogram creating unit that counts the pulse signal for each comparator and creates a histogram of the delay time from the count result;
A transmission characteristic determination unit that determines transmission characteristics of data in the communication network based on the histogram;
A transmission parameter setting unit that sets transmission parameters of data to be transmitted and received according to the transmission characteristics;
A data communication system. A data communication method for a data communication device on a receiving side that establishes a connection with a data communication device on a transmission side via a communication network in which one transmission medium is shared by a plurality of data communication devices, and performs data communication,
A notification step of notifying the transmitting side data communication device of a window size indicating the size of data that can be continuously received;
A receiving step for receiving data comprising a plurality of consecutive packets;
A detection step for detecting whether data comprising a plurality of consecutive packets has been received; and a time set in advance after reception of data is started when a continuous packet having a data size indicated by the window size is received. An acknowledgment step of transmitting an acknowledgment including the sequence number of the data normally received and the window size to the data communication device on the transmission side that has transmitted the continuous packet when the time has elapsed;
A delay time measurement step of measuring, as a delay time, a time from when the acknowledge is transmitted as a base point to a time when a packet transmitted from the data communication device on the transmission side is received from the base point;
A range setting step for setting a plurality of different range ranges,
A counting step of comparing the measured delay time with each range and counting when the delay time is within the range;
A histogram creation step for creating a histogram of the delay time from the count result for each range;
A transmission characteristic determination step for determining a transmission characteristic of data in the communication network based on the histogram;
A transmission parameter setting step for setting a transmission parameter of data to be transmitted and received according to the transmission characteristic,
A data communication method characterized by the above. A data communication method for a data communication system that establishes a connection between the data communication devices in a communication network that shares a single transmission medium with a plurality of data communication devices, and performs data communication,
The data communication method of the data communication device on the transmission side is
A notification step of notifying the receiving side data communication device of a transmission window size indicating the size of data that can be transmitted continuously;
A transmission step of transmitting data consisting of a plurality of consecutive packets;
A communication control step of attaching a sequence number determined for each connection to the data in the packet to be transmitted,
The data communication method of the data communication device on the receiving side is
A notification step for notifying the data communication device on the transmission side of the reception window size indicating the size of data that can be continuously received;
A receiving step for receiving data comprising a plurality of consecutive packets;
A detection step of detecting whether data comprising a plurality of consecutive packets is received;
When receiving a continuous packet of the data size indicated by the window size, or when a preset time has elapsed since the start of data reception, for the data communication device on the transmission side that transmitted the continuous packet, An acknowledge step of transmitting an acknowledge including a sequence number of data normally received and the window size;
A delay time measuring step of measuring, as a delay time, a time from when the acknowledgment is transmitted as a base point, until a packet transmitted from the data communication device on the transmission side is received from the base point;
A range setting step for setting a plurality of different range ranges,
A counting step of comparing the measured delay time with each range and counting when the delay time is within the range;
A histogram creation step for creating a histogram of the delay time from the count result for each range;
A transmission characteristic determination step for determining a transmission characteristic of data in the communication network based on the histogram;
A transmission parameter setting step for setting a transmission parameter of data to be transmitted and received according to the transmission characteristic,
A data communication method characterized by the above. The data communication method according to claim 11 or 12,
The delay time measurement step uses the time at which the acknowledgment is transmitted as a base point, and measures the time from the base point until the first packet transmitted from the data communication device on the transmission side is received as a delay time.
A data communication method characterized by the above. The data communication method according to claim 11 or 12,
In the acknowledge step, when a continuous packet having a data size indicated by the window size is received, a first acknowledge with the window size set to 0 is transmitted to the data communication device on the transmission side that has transmitted the continuous packet, After a preset time has elapsed, a second acknowledge signal is transmitted with the window size set to a preset value,
The delay time measuring step uses the time when the second acknowledgment is transmitted as a base point, and the time from the base point until the first packet transmitted from the data communication device on the transmission side is received as the delay time. taking measurement,
A data communication method characterized by the above. The data communication method according to claim 11 or 12,
The delay time measurement step uses the time when the acknowledgment is transmitted as a base point, and measures the time from the base point until reception of a packet including arbitrary data transmitted from the data communication device on the transmission side.
A data communication method characterized by the above. The data communication method according to claim 11 or 12,
The acknowledge step is performed when the reception of data exceeds a predetermined time when reception of data is not detected or when the amount of received data does not reach the window size. Send an acknowledge,
A data communication method characterized by the above. The data communication method according to claim 11 or 12,
The data communication method of the data communication device on the receiving side includes a value range control step of changing any one of a plurality of threshold values that respectively define the value ranges based on the delay time measured in the delay time measurement step. In addition,
A data communication method characterized by the above. The data communication method according to claim 17,
In the range control step, a maximum value or a minimum value among a plurality of threshold values defining the range is changed based on the delay time, and threshold values other than the maximum value and the minimum value are changed from the maximum value to the maximum value. Find by subtracting the value obtained by subtracting the minimum value,
A data communication method characterized by the above. The data communication method according to claim 11 or 12,
The transmission characteristic determining step includes a difference value α1 between the frequency of the shortest delay time and the frequency of the second shortest delay time in the histogram, the frequency of the longest delay time and the frequency of the second longest delay time in the histogram. The transmission error state characteristic amount β1 is calculated from the difference value α1 and an arbitrary constant α by the mathematical formula (5), and the mathematical formula (5) is calculated from the differential value α2 and the arbitrary constant α. 6) calculating a communication waiting characteristic amount β2 in the communication network, and determining the transmission characteristic from the characteristic amount β1 and the characteristic amount β2.
A data communication method characterized by the above.
[Equation 5]
β1 = α1 / α (5)
[Equation 6]
β2 = α2 / α (6) The data communication method according to claim 11 or 12,
The transmission characteristic determination step obtains a difference value of the frequency of each delay time in the histogram, obtains a maximum delay time at which the difference value is larger than a preset constant, and calculates a frequency of each delay time in the histogram. Cumulative distribution is obtained, a maximum cumulative value M and a cumulative value m corresponding to the maximum delay time are obtained from the cumulative distribution, a characteristic quantity m1 of a transmission error state is calculated by Formula (7), 8) calculating a characteristic amount m2 of a communication waiting state in the communication network, and determining the transmission characteristic from the characteristic amount m1 and the characteristic amount m2.
A data communication method characterized by the above.
[Equation 7]
m1 = m / M (7)
[Equation 8]
m2 = (M−m) / M (8)

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