JP4730427B2 - COMMUNICATION PROCESSING DEVICE, DATA COMMUNICATION SYSTEM, COMMUNICATION PROCESSING METHOD, AND COMPUTER PROGRAM - Google Patents

Description

  The present invention relates to a communication processing device, a data communication system, a communication processing method, and a computer program. In particular, the present invention relates to a communication processing apparatus, a data communication system, a communication processing method, and a computer program that perform accurate bit rate control in transmission / reception of streaming data.

  In recent years, data communication via the Internet has been actively performed, and home networks that allow communication between devices by connecting home appliances, computers, and other peripheral devices to the network are also spreading in the home. The home network, for example, enables content transmission / reception between network-connected devices and provides convenience and comfort to users, and is expected to become increasingly popular in the future.

  Data distribution processing in which image data held by a server is transmitted to a client via a network and reproduction is performed while receiving data on the client side is called so-called streaming data distribution or data streaming. A server that performs such streaming data distribution is called a streaming server, and a client that receives data from the streaming server is called a streaming client. The streaming server executes data processing such as encoding, generates transmission data, and outputs it to the network. On the other hand, the streaming client temporarily stores received data in a buffer, and then sequentially performs decoding processing and reproduction.

  In many cases, a communication protocol used in data streaming is RTP (Real Time Transport Protocol). RTP does not perform retransmission control in principle. That is, it is a UDP (User Datagram Protocol) type protocol that does not take measures against packet loss or guarantee transmission time. Since retransmission processing is not performed even when packet loss occurs, the protocol is suitable for real-time reproduction without causing a delay due to retransmission processing.

  In communication using RTP, rate control using, for example, RTCP (RTP Control Protocol) is performed. For example, in Patent Document 1, a device on the data receiving side notifies a device on the data transmitting side of a packet loss rate or the like described in an RTCP RR (Receiver Report) packet, and the data transmission state is notified on the transmitting side. A method of estimating and controlling the transmission rate is disclosed.

  In streaming distribution, it is important to perform data distribution at an optimal transmission rate. For example, in Patent Document 2, both data transmission / reception devices measure the uplink or downlink transmission rate, and the device that performs rate control stabilizes by controlling to the smaller one of the measured rates. The structure which performs data transmission specifically is disclosed.

  The streaming distribution by RTP described above has an advantage that no reproduction delay occurs because retransmission is not performed even if packet loss occurs. However, in order to improve data quality, complete data reception is performed on the client side. Are preferred. In addition, when the distribution content is encrypted data or the like, if there is an erasure data part at the time of content decryption on the client side, decryption becomes impossible and reproduction may not be possible. In the case of such contents, a protocol that does not perform retransmission control such as RTP is inappropriate.

  In this way, when transfer data integrity is desired, a protocol for dealing with packet loss, for example, a transport protocol such as TCP (Transmission Control Protocol) is applied. A distribution configuration of image data by TCP is described in Patent Document 3, for example.

  Communication using a transport protocol such as TCP is performed at best effort. When streaming multimedia data, fluctuations in communication bandwidth due to best-effort communication become a serious problem. This problem becomes prominent in TCP, for example. In TCP, since the data arrival time is delayed instead of no data loss, the data arrival time is delayed when the communication bandwidth is narrowed. Due to this delay in data arrival time, video and audio are likely to be interrupted during congestion in TCP streaming. In order to solve this problem, it is common to increase or decrease the bit rate of transmission data in data distribution from a streaming server so as to adapt to fluctuations in communication bandwidth. The bit rate increase / decrease method of multimedia data including video data greatly affects the quality of data streaming.

  In the conventional method, the determination material for the streaming server to increase or decrease the bit rate of the distribution data is mainly information from the client. For example, information on the amount of data stored in the application buffer of the client is used. However, only by calculating the amount of data stored in the application buffer of the client, there is a possibility that data is transmitted at a bit rate that exceeds the allowable bandwidth of the network. Sending data at a bit rate that exceeds the network bandwidth allowance results in congestion, multimedia data does not reach the client as desired, and the amount of data stored in the client's application buffer is depleted, The possibility of interruptions in video and audio increases.

Further, the conventional method using information from the client has a problem that it cannot quickly cope with fluctuations in communication bandwidth. For example, it is assumed that the communication bandwidth between the streaming server and the streaming client is rapidly narrowed due to the appearance of other traffic. If the streaming server responds by reducing the bit rate of the transmission data when the communication bandwidth becomes narrow, the reproduction of the transmission data will not be interrupted. However, in the configuration using the information from the client as in the processing configuration described above, after the communication bandwidth becomes narrower, a decrease in the amount of data stored in the buffer of the client occurs after a certain time, and the buffer data is reduced. It takes time to recognize it on the server side. Therefore, the server cannot respond immediately when the communication bandwidth becomes narrower. As a result, before the processing such as bit rate reduction on the server side is performed, the client's buffer is exhausted, and a situation in which video and audio are interrupted occurs.
Japanese Patent Publication No. 2002-204278 Japanese Patent Publication No. 2004-297565 Japanese Patent Publication No. 2005-005823

  The present invention has been made in view of the above-described problems, and in a streaming data transmission / reception process, a communication processing apparatus, a data communication system, a communication processing method, and a computer that realize data transmission based on an optimal transmission mode. The purpose is to provide a program.

  Furthermore, more specifically, the present invention predicts the optimum value of the bit rate of transmission data on the server side in consideration of the influence of congestion on the communication path and disturbance of the radio link, and based on the predicted value. An object of the present invention is to provide a communication processing device, a data communication system, a communication processing method, and a computer program that realize data streaming according to an optimal data transmission mode by dynamically changing the bit rate.

The first aspect of the present invention is:
A communication processing device as a server that executes data transmission processing for a client,
A data transmission / reception unit for executing communication processing with the client;
A rate control unit that determines a bit rate of transmission data to the client;
A data processing unit for executing transmission data setting processing corresponding to the bit rate determined in the rate control unit,
The rate control unit
The throughput calculated based on the reception interval information of data packets continuously transmitted within the communication connection setting period between server clients is set as the maximum throughput, and the transmission bit rate is set with the bit rate corresponding to the maximum throughput as the maximum allowable bit rate. The communication processing apparatus is characterized by having a bit rate determining unit for determining.

  Furthermore, in an embodiment of the communication processing apparatus of the present invention, the rate control unit receives from the client reception interval information of data packets continuously transmitted within a communication connection setting period between server clients, and the reception interval information And a throughput calculation unit that calculates a maximum throughput based on the transmission data amount, and the bit rate determination unit transmits a bit rate corresponding to the maximum throughput calculated by the throughput calculation unit as a maximum allowable bit rate. It is the structure which determines this.

  Furthermore, in an embodiment of the communication processing apparatus of the present invention, the data transmitting / receiving unit is configured to continuously transmit a packet in which an emergency flag of a packet header is set to a specific value as identification information of a reception interval measurement target packet in a client. It is characterized by being.

  Furthermore, in an embodiment of the communication processing apparatus of the present invention, the bit rate determination unit is configured to determine a bit rate based on a transition of an estimated buffer amount of the client side buffer, and the estimated buffer amount is a predetermined threshold value. In the above case, the bit rate increasing process is performed with the maximum allowable bit rate corresponding to the maximum throughput calculated by the throughput calculating unit as an upper limit.

Furthermore, in an embodiment of the communication processing apparatus of the present invention, the bit rate determination unit includes:
(A) Buffer amount notified from the client at the start of communication: [B_cli (byte)]
(B) Elapsed time since the client started playback: [T (sec)]
(C) The amount of data transmitted from the server during the elapsed time [T (sec)] after the client starts playback: [D_serv (byte)]
(D) Content playback rate that can be acquired from the transmitted content [R (byte / sec)]
The information of (a) to (d) is used to execute the estimation process of the client buffer amount, and the estimated buffer amount of the client side buffer is calculated as follows: Estimated buffer amount of client buffer = B_cli + D_serv−R * T It is the structure which calculates.

  Furthermore, in an embodiment of the communication processing apparatus of the present invention, the data transmitting / receiving unit receives communication band information between the base station and the client from a base station that mediates communication with the client, and the bit rate determining unit Is configured to perform a transmission bit rate determination process based on the communication band information.

  Furthermore, in an embodiment of the communication processing apparatus of the present invention, the communication band information is generated based on data of at least one of RTT, RSSI (radio wave intensity), and transmission rate in communication between the base station and the client. It is characterized by being information.

Furthermore, the second aspect of the present invention provides
It is a communication processing device as a client that executes data reception processing from a server,
A data transmission / reception unit for executing communication processing with the server;
A packet interval measuring unit for measuring a reception interval of data packets received from the server;
The packet interval measurement unit
The reception interval of packets continuously received according to identification information included in a received packet from a server is measured, and the reception interval information or throughput information calculated based on the reception interval is sent via the data transmitting / receiving unit. A communication processing apparatus is characterized in that it is configured to execute processing to be transmitted to a server.

  Furthermore, in an embodiment of the communication processing device of the present invention, the packet interval measuring unit is configured to measure the reception interval of consecutively received packets according to the setting of an emergency flag in a packet header included in a received packet from a server. It is characterized by.

Further, the third aspect of the present invention is as follows.
A data communication system having a server client for executing data transmission / reception processing,
The client
A configuration for measuring a reception interval of continuously received packets according to identification information included in a received packet from a server, and executing processing for transmitting the reception interval information or throughput information calculated based on the reception interval to the server Have
The server
A transmission bit rate is determined using a bit rate corresponding to the maximum throughput calculated based on throughput information received from the client or reception interval information as a maximum allowable bit rate, and data transmission processing to the client is performed according to the determined bit rate The data communication system is characterized in that the configuration is executed.

Furthermore, the fourth aspect of the present invention provides
A communication processing method in a server that executes data transmission processing,
A rate control step for determining a bit rate of transmission data to the client;
A data processing step for executing transmission data setting processing corresponding to the bit rate determined in the rate control step,
The rate control step includes:
The transmission bit rate is set with the throughput calculated based on the reception interval information of the data packets continuously transmitted within the communication connection setting period between the server and client as the maximum throughput and the bit rate corresponding to the maximum throughput as the maximum allowable bit rate. The communication processing method includes a bit rate determining step for determining.

Furthermore, the fifth aspect of the present invention provides
It is a communication processing method in a client that executes data reception processing,
A packet reception interval measuring step for measuring a reception interval of packets continuously received according to the identification information included in the received packet from the server;
An information transmission step of transmitting packet reception interval information measured in the packet reception interval measurement step or throughput information calculated based on the reception interval to a server;
The communication processing method is characterized by comprising:

Furthermore, the sixth aspect of the present invention provides
A computer program for executing rate control of transmission data on a computer;
In the rate control unit, a rate control step for determining a bit rate of transmission data for the client;
In the data processing unit, a data processing step for executing transmission data setting processing corresponding to the bit rate determined in the rate control step,
The rate control step includes:
The transmission bit rate is set with the throughput calculated based on the reception interval information of the data packets continuously transmitted within the communication connection setting period between the server and client as the maximum throughput and the bit rate corresponding to the maximum throughput as the maximum allowable bit rate. A bit rate determination step for determining is executed in a computer program.

  The computer program of the present invention is, for example, a storage medium or communication medium provided in a computer-readable format to a computer system capable of executing various program codes, such as a CD, FD, or MO. It is a computer program that can be provided by a recording medium or a communication medium such as a network. By providing such a program in a computer-readable format, processing corresponding to the program is realized on the computer system.

  Other objects, features, and advantages of the present invention will become apparent from a more detailed description based on embodiments of the present invention described later and the accompanying drawings. In this specification, the system is a logical set configuration of a plurality of devices, and is not limited to one in which the devices of each configuration are in the same casing.

  According to the configuration of the present invention, the maximum throughput is calculated by applying the measurement value of “continuous data transmission and reception confirmation response (ack) reception period”, that is, the [data transmission / reception execution period], and based on this maximum throughput. Thus, the transmission bit rate is controlled. That is, the maximum throughput based on the data transmission / reception period without the data transmission / reception period [data transmission / non-execution period] is calculated, and the bit rate control with the maximum allowable bit rate corresponding to the calculated maximum throughput as the upper limit is performed. Do. This configuration makes it possible to control the bit rate in consideration of the actual transmission rate, and realizes data transmission up to the maximum allowable bit rate that can reliably execute data transmission without excessively increasing or suppressing the bit rate. Is done.

  Furthermore, according to the configuration of the present invention, the maximum throughput is calculated based on the reception interval of the continuous transmission packets measured by the client, and the bit rate control with the calculated maximum throughput as the upper limit can be performed. That is, the maximum throughput determined based on the measurement of actually transmitted packets is calculated, and bit rate control is performed with the maximum allowable bit rate corresponding to the calculated maximum throughput as the upper limit. This configuration makes it possible to control the bit rate in consideration of the actual transmission rate, and realizes data transmission up to the maximum allowable bit rate that can reliably execute data transmission without excessively increasing or suppressing the bit rate. Is done.

  Furthermore, according to the configuration of the present invention, in addition to the bit rate control based on the maximum throughput calculated based on the actual transmission / reception data measurement, the RTT in the wireless communication between the base station and the client measured by the base station (AP), Since the bit rate is controlled on the basis of communication band information such as RSSI and transmission rate, bit rate control can be realized in response to fluctuations in the communication state in wireless communication.

  Hereinafter, the communication processing device, the data communication system, the communication processing method, and the computer program of the present invention will be described in detail with reference to the drawings.

[System Overview]
First, a network configuration example to which the present invention can be applied will be described with reference to FIG. FIG. 1 shows that a server 101 as a content distribution device that executes processing in response to processing requests from various client devices, and clients 121 to 124 as content receiving devices that make processing requests to the server 101 are connected to the network 110. 2 shows a configuration connected via the network, for example, a home network configuration. Examples of client devices include personal computers (PCs) 121 and 122, a portable terminal 123, and a playback device 124. However, various other electronic devices and household electrical appliances can be connected as the client device.

  A client (portable terminal) 123 and a client (playback device) 124 are clients that perform wireless communication via a base station (AP: Access Point) 131, and the clients (PCs) 121 and 122 perform communication via a wired LAN on the server 101. And do. For example, the client 121 (PC) executes communication with the server 101 using the 100 base-TX, and the client (PC) 122 executes communication based on the 10 base-T standard. A client (portable terminal) 123 and a client (playback device) 124 communicate with the server 101 via a base station (AP) 131, and between the base station (AP) 131 and the client (portable terminal) 123, IEEE 802. Wireless LAN communication according to the .11b standard is executed, and wireless LAN communication according to the IEEE 802.11g standard is executed between the base station (AP) 131 and the client (reproducing device) 124.

  As described above, each of the clients 121 to 124 performs communication with the server 101, for example, when receiving video data distribution from the server 101, performs data communication in accordance with a communication standard corresponding to each device, and is different from each other. Data reception is performed at the bit rate. The processing executed by the server 101 in response to a request from the client is, for example, provision of content stored in a storage unit such as a hard disk or DVD attached to the server 101, or live content received via the tuner of the server 101. That is, a content distribution service or the like.

  The network 110 transmits and receives communication packets such as Ethernet (registered trademark) frames via the network 100. That is, the client stores the processing request information in the data portion of the Ethernet (registered trademark) frame and transmits it to the server 101 to execute a data processing request to the server 101. In response to receiving the processing request frame, the server 101 executes data processing, stores it in a communication packet, and transmits it to each client.

  The server 101 establishes a TCP (Transmission Control Protocol) connection separately from the clients 121 to 124 and executes transmission of multimedia data including video data by streaming data distribution, for example. In the configuration of the present invention, data distribution from the server 101 to the clients 121 to 124 in the TCP connection is executed as a process involving dynamic bit rate control.

The dynamic control of this bit rate is
Maximum throughput measurement processing for data communication between the server and each client,
Bit rate control processing with the bit rate corresponding to the measured maximum throughput as the maximum allowable bit rate,
It is executed as a process including these processes. Hereinafter, details of a plurality of embodiments of the bit rate dynamic control processing will be sequentially described.

[Example 1]
FIG. 2 is a block diagram illustrating the functions of the server 200 that executes streaming data distribution and the client 300 that receives and reproduces streaming data. A TCP connection is set between the server 200 and the client 300 to execute communication.

  The server 200 has a content providing unit 201 as a transmission content storage unit. The content providing unit 201 is configured to include a storage function such as a hard disk or a DVD, or a tuner function for receiving content from the outside. Content to be transmitted to the client 300 is input from the content providing unit 201 to the data processing unit 202.

  The data processing unit 202 performs transmission data generation processing such as encoding processing. In this transmission data generation process, encoded data corresponding to the bit rate set in the dynamic rate control unit 210 is generated. In addition, it is good also as a structure which prepares the data corresponding to several bit rates previously, and performs the process which selects transmission data from these several bit rate data.

  The dynamic rate control unit 210 includes a throughput calculation unit 211 and a bit rate determination unit 212. The throughput calculation unit 211 performs monitoring of a communication state executed between the data transmission / reception unit 204 of the server and the data transmission / reception unit 301 of the client, and calculates the throughput based on the monitoring result. The bit rate determination unit 212 determines a data transmission bit rate for the client 300 based on the throughput calculated by the throughput calculation unit 211 and notifies the data processing unit 202 of the data transmission bit rate. Details of the processing of the dynamic rate control unit 210 will be described later.

  The data processing unit 202 executes transmission data encoding according to the bit rate determined by the bit rate determination unit 212 or encoding data selection processing according to the bit rate determined by the bit rate determination unit 212, and transmits the transmission buffer 203. To enter. The data transmission / reception unit 204 transmits data (packets) corresponding to the transmission bit rate stored in the transmission buffer 203 to the client 300 via a TCP connection set with the client 300.

  The client 300 receives the streaming data (packet) from the server 200 via the data transmission / reception unit 301 and stores it in the reception buffer 302. Data stored in the reception buffer 302 is sequentially taken out by the reproduction processing unit 303 and decoded, for example, data decompression processing, or decryption processing is executed if it is encrypted data, and an output unit 304 including a display, a speaker, and the like. Is output.

  FIG. 3 is a diagram illustrating a communication processing sequence between server clients. First, in step S11, a TCP connection establishment process is executed between the server and the client. Thereafter, in step S12, a buffer amount notification process from the client to the server is executed. The buffer amount notification process may be executed as a process included in the connection establishment process.

  In this embodiment, the server notifies the server of the maximum amount of the application buffer of the client that receives the streaming data, that is, the maximum amount of the buffer prepared for receiving the streaming data. A reception buffer 302 in FIG. 2 indicates an application buffer of a client that receives streaming data, and the maximum amount of the reception buffer 302 is notified to the server. For example, when the streaming is streaming data according to the HTTP method, the client notifies the server of the application buffer amount included in the HTTP header. The server uses the buffer amount notified from the client as an index of the bit rate increase / decrease process determined by the dynamic rate control unit 210. This process will be described later. The buffer amount notification from the client to the server is only once at the start of streaming.

  Thereafter, in step S13, distribution of streaming data from the server to the client is executed. In this streaming data transmission processing, dynamic transmission bit rate control is performed in the dynamic rate control unit 210 of the server 200 shown in FIG. 2, and streaming data transmission is performed at an optimum bit rate. Specific processing will be described later. When the transmission of all the streaming data is completed, in step S14, the connection between the server and the client is disconnected and the process is terminated.

  Next, the details of the transmission data bit rate control processing executed by the dynamic rate control unit 210 of the server 200 shown in FIG. 2 will be described with reference to FIGS. First, the throughput calculation process executed by the throughput calculator 211 of the dynamic rate controller 210 will be described with reference to FIG.

  FIG. 4 is a sequence diagram showing the data transfer process of step S13 in FIG. 3 in more detail. The server stores the streaming distribution data in a TCP packet (TCP segment) and sequentially transmits it to the client. Data 1 to data 8 shown in FIG. 4 indicate individual transmission packets. In TCP communication, the client transmits ack as a reception confirmation response of the received packet to the server. In the figure, ack1 to ack4 indicate reception confirmation responses (ack) transmitted from the client to the server. The reception confirmation response (ack) transmitted from the client to the server is not necessarily transmitted from the client corresponding to all transmission data. On the client side, the reception confirmation response (ack) may be omitted when there is no time margin. 4 is a reception confirmation response (ack) for data 1 and data 2, and ack 2 is a reception confirmation response (ack) for data 3 and data 4.

  Data transmission from the server to the client is executed as a continuous transmission process based on the window size presented from the client to the server. For example, transmission of data 1 to data 4 shown in FIG. 4 is a process executed as a continuous transmission process. That is, after the transmission of each packet, if the server performs a process of receiving the receipt confirmation from the client and transmitting the next packet, the throughput is lowered and the efficiency of the data transmission process is reduced.

  In order to prevent this, a window size is determined as a certain amount of data that can be transmitted at once, and packets are continuously transmitted based on this window size. The window size is notified from the client to the server when a session is established, for example. That is, the server notifies the server of the window size as the amount of data that can be collectively received on the client side. On the server side, continuous transmission of packets having a data amount corresponding to the window size is executed based on the window size. In addition, the server notifies the server of the updated window size in the reception acknowledgment (ack) packet transmitted from the client to the server, and the server side sequentially changes the amount of continuous transmission data based on the updated window size. It is good also as composition to do.

  When data transmission based on the window size is executed, data transmission from the server to the client is executed as intermittent data transmission processing as shown in FIG. For example, a period A shown in FIG. 4 is a period until continuous data transmission and reception of the final reception confirmation response (ack) for the transmitted continuous data.

  The period B shown in FIG. 4 is from the end point of the period A, that is, from the reception time of the final reception confirmation response (ack) of the [TCP data group] in the period A to the start of transmission of the next [TCP data group]. It is a waiting time. The period C is a period for receiving the next [TCP data group] after the period B and receiving the reception acknowledgment (ack).

In the conventional throughput calculation method, the amount of transmission data is simply divided by the transmission time. For example, in the case of the data transmission processing sequence of FIG. 3, when obtaining the throughput in the time zone A to C,
Throughput = (transmission data amount of data 1-8) / (time A + B + C)
Throughput was calculated. According to this throughput calculation process, a value greater than the amount of data transmitted from the server is not measured as the TCP throughput.

  However, in data transmission in TCP, when transmitting at a higher bit rate by controlling the data transmission bit rate, it is necessary to determine how far the bit rate can be increased, that is, the maximum allowable bit rate. Become.

  In the configuration of the present invention, the maximum throughput is predicted by dividing the transfer data amount by the time excluding the period B shown in FIG. 4, and the bit rate corresponding to the maximum throughput is set as the maximum allowable bit rate. A period B in FIG. 4 is a period in which the server is not transmitting data to the client. If the portion of period B is included in the time measurement value for throughput calculation, a period in which data transmission / reception is not actually performed is applied to throughput measurement, and there is no contribution to actual throughput. Will be applied to throughput calculation. That is, if the calculation of the maximum throughput is performed after the period B in which no data transmission / reception is performed, the value of the maximum throughput is lowered. That is, the measured value of the TCP throughput in this case does not become a value higher than the bit rate of the content.

In the configuration of the present invention, a period excluding a portion of [data transmission / reception non-execution period] such as period B, that is, a period until continuous data transmission based on the window size and reception of its reception confirmation response (ack), That is, the period A and the period C shown in FIG. 4 are applied as the throughput calculation period. In particular,
Throughput calculation sample 1 = (transmission data amount of data 1 to 4) / (time A + B−B)
Throughput calculation sample 2 = (transmission data amount of data 5 to 8) / (time C + DD)
:
Throughput calculation sample n
As described above, a plurality of throughput calculation samples are calculated, and the maximum throughput is calculated based on the plurality of throughput calculation samples. In the above equation, D is a data non-transmission period that occurs after period C shown in FIG.

  As described above, the maximum throughput calculation process of the present invention uses only the “continuous data transmission and reception confirmation response (ack) reception period” of A and C shown in FIG. The period to be applied, and the [data transmission / reception non-execution period] like the period B shown in FIG. With this process, only the effective period during which actual data transmission and response (ack) reception is performed in the TCP session is the application period of the throughput calculation process, and the maximum true TCP throughput can be measured.

  As described above, in the transmission of data packets in the TCP session, continuous transmission of data based on the window size is executed. In other words, data packets are continuously transmitted without waiting for a reception confirmation response (ack) when a window is open on the client side. Therefore, as shown in FIGS. 4A and 4C, “continuous data transmission and reception acknowledgment (ack) reception period”, that is, [data transmission / reception execution period] and B [data transmission / reception non-execution period] ] Alternately occur.

4A and 4C, the TCP packet data transmitted in the “continuous data transmission and reception confirmation response (ack) reception period”, that is, the [data transmission / reception execution period] is referred to as a “TCP data group”. Call it. [Data transmission / reception execution period] corresponding to each TCP data group is greatly affected by the window and instantaneous congestion. Therefore, the value fluctuates greatly, and the measurement result of the maximum throughput is not stable. In the present invention, in order to avoid this problem, as described above, a plurality of throughput calculation samples, that is,
Throughput calculation sample 1 = (transmission data amount of data 1 to 4) / (time A + B−B)
Throughput calculation sample 2 = (transmission data amount of data 5 to 8) / (time C + DD)
:
Throughput calculation sample n
And the throughput is calculated based on the plurality of throughput calculation samples. It should be noted that, in the throughput calculation sample data, a process of excluding a measurement result that is significantly different from other sample data as an exceptional value is executed.

  In this embodiment, the procedure of the maximum throughput calculation process executed by the throughput calculator 211 of the dynamic rate controller 210 of the server 200 shown in FIG. 2 will be described with reference to the flowchart shown in FIG. The throughput calculation unit 211 sets a period from the start of continuous data transmission based on the window size to reception of a reception confirmation response (ack) for the transmitted continuous data as a data transmission / reception execution period. The maximum throughput is calculated based on the transmission data amount. FIG. 5 is a flowchart illustrating a processing flow from when the server 200 establishes a TCP connection with a client, executes communication, and disconnects the TCP connection.

  First, in step S101, the server establishes a TCP connection with a client as a distribution target of streaming data. At the time of establishing the connection, the server receives a buffer amount (corresponding to the window size) notification from the client.

  If it is determined in step S102 that there is a data transmission request from an upper layer application, transmission of a TCP segment (packet) is started in step S103, and the transmission start time [Ts] is stored in the memory. This packet transmission is executed as a continuous transmission process of packets having a data amount corresponding to the window size previously notified from the client. For example, a plurality of data transmission processes in the period A shown in FIG.

  In step S104, the server determines whether or not a reception confirmation response (TCP ACK) from the client has been received. If the reception confirmation response (TCP ACK) has not been received, the process proceeds to step S105, where it is determined whether the TCP transmission window is MAX, that is, whether a packet having a data amount corresponding to the window size has been transmitted. If the packet having the data amount corresponding to the window size has not been transmitted, the TCP segment (packet) is continuously transmitted in step S106.

  When the TCP transmission window is MAX, that is, when a packet having a data amount corresponding to the window size has been transmitted, a reception confirmation response is awaited. In step S104, if a reception confirmation response is received, the process proceeds to step S107, where it is determined whether or not a reception confirmation response (TCP ACK) corresponding to the last segment of the transmitted TCP segment has been received. Wait until you receive. The reception confirmation response (TCP ACK) corresponding to this final segment is, for example, ack2 in period A in FIG.

  If it is determined in step S107 that the reception confirmation response (TCP ACK) corresponding to the final segment has been received, the reception time [Te] of the reception confirmation response (TCP ACK) corresponding to the final segment is stored in the memory in step S108. .

  Next, in step S109, a throughput calculation sample response time Tn = Te−Ts is calculated. This processing is executed in the throughput calculation unit 211 in the dynamic rate control unit 210 of the server 200 shown in FIG. This Tn = Te−Ts is a measured value of the “continuous data transmission and reception acknowledgment (ack) reception period” of the periods A and C shown in FIG.

  Next, in step S110, it is determined whether or not the number n of measurement samples is equal to or greater than a predetermined threshold [Thn]. If the measurement sample number n is not equal to or greater than the predetermined threshold [Thn], it is determined in step S111 whether or not the communication is continuing. If the communication is continuing, the process proceeds to step S102, and further the measurement sample number n Is repeated until the threshold value [Thn] is equal to or greater than a predetermined threshold [Thn], and the sample corresponding time Tn = Te−Ts for throughput calculation is collected. This process is performed by, for example, a “continuous data transmission and reception confirmation response (ack) reception period” in the periods A and C in FIG. Thn] is a process of collecting until it becomes equal to or greater than.

  If it is determined in step S110 that the number n of measurement samples is equal to or greater than a predetermined threshold [Thn], the process proceeds to step S112, and the value greatly deviates during the measurement sample, that is, the throughput calculation sample correspondence times T1 to Tn. In step S113, only the throughput calculation sample correspondence times T1 to Tn from which the exceptional value is removed are applied to calculate the maximum throughput.

The throughput calculation in step S113 calculates the maximum throughput as follows:
Maximum throughput = (Σ (transmission data amount in each data transmission / reception execution period)) / (Σ (each data transmission / reception execution period))
Calculate as However, in the above equation, Σ (transmission data amount in each data transmission / reception execution period) and Σ (each data transmission / reception execution period) do not include the period corresponding to the exceptional value and the transmission data amount.

  In this way, the throughput calculation unit 211 in the dynamic rate control unit 210 of the server 200 illustrated in FIG. 2 calculates the maximum throughput based on the measurement time and the amount of transmission data of a plurality of [data transmission / reception execution periods]. The throughput calculated in this process does not include the data transmission / reception non-execution period (B) shown in FIG. The throughput calculation unit 211 inputs this calculated throughput as the maximum throughput to the bit rate determination unit 212 of the dynamic rate control unit 210 of the server 200 shown in FIG.

  The processing of the bit rate determination unit 212 will be described with reference to FIGS. As shown in FIG. 6, the bit rate determination unit 212 inputs the maximum throughput calculated by the throughput calculation unit 211 by the above processing, estimates the buffer amount of the client, determines the bit rate, and performs the encoding process or the encoded data. The bit rate determination information of the transmission data is input to the data processing unit 202 that executes the selection process.

In the bit rate determination unit 212, the client buffer amount estimation processing is performed by the following processing. That is,
Buffer amount notified from the client at the start of communication: [B_cli (byte)]
Elapsed time since the client started playback: [T (sec)]
The amount of data transmitted from the server during the elapsed time [T (sec)] since the client started playback: [D_serv (byte)]
Content playback rate that can be acquired from the transmitted content [R (byte / sec)]
Using these pieces of information, the client buffer amount is estimated.

  The server can determine that the reproduction of the transmission content has been started in the client because the data amount actually transmitted by the server exceeds the buffer amount [B_cli] notified from the client. In other words, the client accumulates data in the buffer by the amount of the client buffer [B_cli] before starting the content reproduction, and when the server transmits that amount of data, the server fills the client buffer. It is determined that playback has started.

  When content playback is started on the client side, the buffer amount of the client is [B_cli], and after time T has elapsed after the start of playback, the server transmits data of [D_serv (byte)] to the client, Transmission data is accumulated in the client buffer. The client reproduces the data amount of [R * T (byte)], and this data amount is erased from the client buffer.

Based on these data transitions, the server
B_cli + D_serv-R * T
Is estimated to be the current client buffer size. The buffer amount estimated in this way is estimated in the range of 0 to MAX as shown in the buffer amount information 250 in FIG. MAX corresponds to the client buffer amount [B_cli]. The bit rate determining unit 212 is configured to determine the bit rate based on the transition of the estimated buffer amount of the client side buffer as described above. When the estimated buffer amount is equal to or greater than a predetermined threshold, the bit rate determining unit 212 calculates the bit rate. Bit rate increase processing is performed with the maximum allowable bit rate corresponding to the maximum throughput as the upper limit.

  The processing sequence of the bit rate determination unit 212 will be described with reference to the flowchart shown in FIG. In step S201, the bit rate determination unit 212 determines whether or not the buffer amount is smaller than a predetermined threshold Th1. The buffer amount is a buffer amount estimated by the above-described estimation process. When it is determined that the buffer amount is smaller than the predetermined threshold Th1, the process proceeds to step S202, and a transmission bit rate reduction process is executed. This process is a process in the case where the buffer amount in the buffer amount information 250 shown in FIG.

  If it is determined in step S201 that the buffer amount is not smaller than the predetermined threshold Th1, the process proceeds to step S203, and it is determined whether or not the buffer amount is larger than the predetermined threshold Th2. If the buffer amount is not greater than the predetermined threshold Th2, the process returns to step S201. This processing is processing when the buffer amount in the buffer amount information 250 shown in FIG. 6 is in the Bb area.

  When the buffer amount is larger than the predetermined threshold Th2, the process proceeds to step S204, and the bit rate of the current transmission data is compared with the maximum throughput calculated by the throughput calculation unit 211 by the above-described processing. If the bit rate of the current transmission data is smaller than the bit rate corresponding to the maximum throughput calculated by the throughput calculation unit 211, the process proceeds to step S205, and processing for increasing the bit rate of the transmission data is executed. However, the bit rate corresponding to the maximum throughput calculated by the throughput calculation unit 211, that is, the maximum allowable bit rate is set as the upper limit value. If the bit rate of the current transmission data is equal to the maximum allowable bit rate corresponding to the maximum throughput calculated by the throughput calculation unit 211, the process returns to step S201 without controlling the bit rate. This process is a process in the case where the buffer amount in the buffer amount information 250 shown in FIG.

  Note that the throughput calculation process in the flowchart shown in FIG. 5 described above is repeatedly executed every predetermined period while data communication continues, and the throughput calculation unit 211 sequentially updates the maximum throughput to the bit rate determination unit 212. input. The bit rate determining unit 212 also repeatedly executes the processing shown in the flowchart of FIG. 7 and sequentially determines the bit rate based on the maximum allowable bit rate corresponding to the latest maximum throughput calculated by the throughput calculating unit 211. Therefore, bit rate control based on the maximum throughput according to the network status is performed.

  In the present embodiment, as described with reference to FIG. 4, the “continuous data transmission and reception confirmation response (ack) reception period” of the periods A and C shown in FIG. The maximum throughput is calculated by applying the measurement value, and the transmission bit rate is controlled with the maximum allowable bit rate corresponding to the maximum throughput as the upper limit. That is, the maximum allowable bit corresponding to the calculated maximum throughput is calculated by calculating the maximum throughput based on the data transmission / reception period without the period [data transmission / reception non-execution period] such as period B shown in FIG. Bit rate control is performed with the rate as the upper limit. With this configuration, it is possible to control the bit rate in consideration of the actual transmission rate, and it is possible to achieve data transmission up to the maximum bit rate that can reliably execute data transmission without excessively increasing or suppressing the bit rate. The

[Example 2]
Next, as a second embodiment, a configuration example in which the client side calculates throughput based on received data or calculates a value to be applied to throughput calculation, and the server executes bit rate control based on the calculated value will be described. .

  FIG. 8 is a block diagram illustrating functions of the server 200 that executes streaming data distribution and the client 300 that receives and reproduces streaming data according to the second embodiment. A TCP connection is set between the server 200 and the client 300 to execute communication.

  A difference from the configuration of the first embodiment described above with reference to FIG. 2 is that the client 300 includes a packet interval measuring unit 305. Other configurations are the same as those in FIG. However, processing in each component is different. Hereinafter, the configuration of the second embodiment will be described with a focus on differences from the first embodiment.

  In the configuration of the second embodiment, the data transmission / reception unit 204 of the server 200 continuously transmits data transmission packets whose emergency flag (URG flag) is ON [1] at predetermined intervals. The urgent flag is normally transmitted as ON [1] when urgent data is included in the TCP packet. In this embodiment, packets with the emergency flag (URG flag) set to ON [1] are continuously transmitted to indicate that the packet is a packet for measuring the TCP packet reception interval regardless of the presence or absence of emergency data. To do.

  A data communication sequence between server clients will be described with reference to FIG. Also in the second embodiment, as in the first embodiment, after the connection is established between the server and the client, the streaming data is distributed from the server to the client. The data communication sequence illustrated in FIG. 9 is a diagram illustrating details of the data transfer process in step S13 illustrated in FIG. 3 described in the first embodiment.

  In the second embodiment, as illustrated in FIG. 9, the server transmits data to the client sequentially from data 1 as a TCP packet. The server continuously transmits the urgent flag to ON [1] for a packet that is requested to measure the packet reception interval at the client. This is a packet in which the emergency flag set in the header of the TCP packet of packet n and packet n + 1 shown in FIG. 9 is set to ON [1]. Two consecutive packets with the urgent flag set to ON [1] are set as throughput measurement pair packets.

  When the client continuously receives two packets whose urgent flag is set to ON [1], the client measures the reception interval [t]. Based on this measured value, the throughput is calculated and notified to the server. Alternatively, the reception interval data [t] may be notified to the server, and the server may calculate the throughput based on the reception interval data [t].

  The server executes bit rate control with the throughput calculated based on the continuous packet reception interval data [t] as the maximum throughput and the bit rate corresponding to the maximum throughput as the maximum allowable bit rate. With reference to FIGS. 10 and 11, server processing and client processing sequence in the second embodiment will be described.

  First, the processing of the server will be described with reference to FIG. FIG. 10 is a flowchart illustrating a processing flow from when the server 200 establishes a TCP connection with the client, executes communication, and disconnects the TCP connection.

  First, in step S301, the server establishes a TCP connection with a client as a streaming data distribution target. If it is determined in step S302 that there is a data transmission request from the client application, transmission of a TCP segment (packet) is started in step S303.

  In step S304, the server determines whether the transmission packet for the client is a throughput measurement pair packet. If the transmission packet is a pair packet for throughput measurement, the process proceeds to step S305, where a packet with the emergency flag set to ON [1] is generated and continuously transmitted. If the transmission packet is not a throughput measurement pair packet, the process advances to step S306 to generate and transmit a packet with the emergency flag set to OFF [0].

  If it is determined in step S307 that communication is continuing, the processes in and after step S302 are repeatedly executed. If the communication is completed, the process proceeds to step S308, where the TCP connection is disconnected and the process is terminated.

  Next, the processing on the client side will be described with reference to the flowchart of FIG. FIG. 11 is a flowchart for explaining the flow of processing from when the client 300 establishes a TCP connection with the server 200, executes communication, and disconnects the TCP connection.

  First, in step S351, the client establishes a TCP connection with a server as a streaming data distribution source. In step S352, the client receives a TCP packet from the server, and stores the reception time of the TCP packet in the memory in step S353.

  In step S354, it is determined whether or not the emergency flag of the received packet is ON [1]. If No, the process returns to step S352. If Yes, it is confirmed whether the urgent flag of the previous received packet is also ON [1]. If No, the process returns to step S352. If Yes, the process proceeds to step S356, and the reception interval [t] between two consecutive packets whose urgent flag is ON [1] is calculated. This process is executed in the packet interval measuring unit 305 of the client 300 shown in FIG.

In step S357, the maximum throughput is calculated based on the reception interval [t] between two consecutive packets.
Maximum throughput = (data amount of packet after pair packet) / t
Is calculated by This calculation process is also executed by the packet interval measurement unit 305.

  In step S358, it is determined whether or not the calculation information is fed back to the server. If not, the communication is determined to be continued in step S360. If it is continued, the process returns to step S352 and the process is repeated. If it is determined in step S358 that the calculated information is fed back to the server, the process proceeds to step S359, and the calculated throughput information or the reception interval information is transmitted to the server.

  After the process of step S359, it is determined in step S360 that the communication is continued. If the communication is continued, the process returns to step S352 and the process is repeated. If it is determined in step S360 that communication has ended, the TCP connection is disconnected in step S361.

  As described above, when the client continuously receives two packets with the urgent flag set to ON [1], the client measures the reception interval [t] and determines the throughput based on the measured value. The calculation may be performed and notified to the server, but the reception interval data [t] may be notified to the server, and the server may calculate the throughput based on the reception interval data [t]. In this case, it is not necessary for the client to execute the process in step S357.

On the server side, when the information received from the client is the reception interval data [t], the throughput calculation unit 211 of the server 200 uses the same throughput calculation formula as above based on the reception interval data [t], that is,
Throughput = (total data amount of pair packet / 2) / t
To calculate the maximum throughput.

  The server-side bit rate determination unit 212 uses the throughput received from the client or the throughput calculated by the server throughput calculation unit 211 based on the reception interval data [t] received from the client as the maximum throughput. Input to 212.

  The processing in the bit rate input unit 212 is the same as that in the first embodiment, and the bit rate control processing described above with reference to FIG. 7 is executed. Even in this processing, the maximum throughput is measured based on the reception interval of actual continuous transmission packets. That is, a maximum throughput that does not consider a period [data transmission / reception non-execution period] that does not contribute to data transmission / reception such as period B described above with reference to FIG. 4 is calculated, and the maximum allowable bit corresponding to the calculated maximum throughput Bit rate control with the rate as the upper limit can be performed. As described above, the second embodiment also performs the bit rate control according to the maximum allowable bit rate corresponding to the maximum throughput determined based on the measurement of actually continuously transmitted packets. With this configuration, it is possible to control the bit rate in consideration of the actual transmission rate, and it is possible to achieve data transmission up to the maximum bit rate that can reliably execute data transmission without excessively increasing or suppressing the bit rate. The

[Example 3]
Next, a configuration for performing bit rate control by applying information acquired in a base station (AP: Access Point) will be described as a third embodiment.

  In the network configuration of FIG. 1, a client (portable terminal) 123 and a client (playing device) 124 execute communication with the server 101 via a base station (AP) 131.

  When a server delivers streaming data to a client via a base station (AP), the server needs to first perform a process of finding an optimal base station (AP) between server clients. First, the AP discovery process will be described with reference to FIG.

  First, before starting streaming, the server 200 that performs streaming distribution transmits an “AP discovery message” in which two MAC addresses of the server 200 itself and the streaming data distribution destination client 123 are stored in the subnet in step S401. Broadcast.

  The broadcast “AP discovery message” is received by all base stations (APs) connected to the LAN. The figure shows two base stations a (APa) 400a and base station b (APb) 400b. In step S402, each AP 400a, 400b that has received the “AP discovery message” from the server 200 determines whether a node having the client MAC address included in the “AP discovery message” exists in the wireless link. Check the association list.

  If there is a corresponding MAC address in the association list, the AP knows that it is on the streaming communication path. Note that the received “AP discovery message” is discarded without being transferred to the wireless link, regardless of whether the corresponding MAC address is present in the association list.

  If it is found that the AP exists on the streaming communication path, in step S403, the AP, in the example of FIG. 12, the base station a (APa) 400a adds to the MAC addresses of the server 200 and the client 123, An “AP discovery response message” storing the MAC address of the base station a (APa) 400 a itself is transmitted to the server 200 by unicast. The streaming delivery execution server 200 knows that a wireless link (bottleneck) exists on the path of streaming to be performed. When it is found that the AP does not exist on the streaming communication path, the AP does not transmit an “AP discovery response message”.

  Through the above exchange, the server that executes streaming data distribution and the base station (AP) on the communication path can grasp each other's MAC address, so communication between them (radio link information is notified from the AP to the server) ) Is possible. Note that when the corresponding MAC address is deleted from the association list of the base station (AP) itself due to movement of the client that receives the streaming data, power off, etc., the base station (AP) cancels the notification to the server.

  Further, by periodically transmitting the “AP discovery message” by the server, not only during the start of streaming, but also during the streaming, it becomes possible to cope with the case where the streaming client performs handover between APs. That is, at the moment when the AP connected at the destination receives the “AP discovery message”, the destination AP returns an “AP discovery response message” to the server and starts to notify the status of the wireless link. Note that the AP connected before moving, in which the MAC address of the corresponding streaming client has been deleted from its association list, cancels the notification of the wireless link information to the server.

  In addition, when the notification from the base station (AP) to the server is performed not by an L2 (data link layer) level message but by an upper level (IP) message, the “AP discovery message” and “AP discovery response message” In addition to the MAC address, an IP address is also stored. Further, the base station (AP) may immediately notify the server of the radio link information instead of the “AP discovery response message”.

  By such AP discovery processing, the relationship between the server that executes streaming delivery, the base station (AP), and the client is set. In the third embodiment, a server that performs streaming distribution performs bit rate control by applying information acquired in a base station (AP) on a streaming distribution path.

  With reference to FIG. 13, functions of the server 200 that executes streaming data distribution, the client 300 that receives and reproduces streaming data, and the base station (AP) 400 on the streaming distribution path according to the third embodiment will be described. . A TCP connection via the base station (AP) 400 is set between the server 200 and the client 300 to execute communication.

  The configurations of the server 200 and the client 300 are the same as the configurations of the first embodiment described above with reference to FIG. However, the processing in the server 200 is different. As illustrated in FIG. 13, the base station (AP) 400 includes a data transmission / reception unit 401, a communication band monitoring unit 402, and a communication band information generation unit 403.

  The communication band monitoring unit 402 of the base station (AP) 400 monitors values such as RTT (Round Trip Time), RSSI (radio wave intensity), and transmission rate in the L2 (data link layer) layer of the wireless communication section. RTT is the time from when a packet is transmitted from the base station (AP) 400 until a response is returned from the client. The monitoring operation in the communication band monitoring unit 402 of the base station (AP) 400 is periodically performed.

  Data processing for notifying the server of the communication section information acquired by the communication band monitoring unit 402 is performed in the communication band information generation unit 403 as necessary. Examples of data processing include derivation of weighted average values and standard deviation values. A weighted average value and a standard deviation value are derived for each value such as RTT, RSSI, and transmission rate, and a report value to the server is generated. The data generated by the communication band information generation unit 403 is notified to the server 200 via the data transmission / reception unit 401 and the communication network.

  Communication band information transmitted from the base station (AP) 400 to the server 200 is received by the data transmitting / receiving unit 204 of the server 200 and input to the bit rate determining unit 212 of the dynamic rate control unit 210. The bit rate determination unit 212 analyzes the communication band information acquired from the base station (AP) 400 by using a determination algorithm, and when it is determined that the bit rate of streaming data should be reduced, the bit rate is immediately reduced. Let

  The determination algorithm is executed, for example, as a comparison process between the communication band information acquired from the base station (AP) 400 and the threshold held by the bit rate determination unit 212. Specifically, for example, parameters such as weighted average values and standard deviation values based on RTT, RSSI, transmission rate, etc. included in the communication band information acquired from the base station (AP) 400 are held by the bit rate determination unit 212. When the threshold value is exceeded N times consecutively, processing such as decreasing the bit rate is executed. The reason for performing the threshold comparison a plurality of times is to prevent the bit rate from being reduced unnecessarily, for example, when the parameter suddenly exceeds the threshold value only once.

  The processing of the bit rate determining unit 212 in the third embodiment will be described with reference to FIGS. In the third embodiment, the bit rate control is performed by using the throughput calculation process in the first or second embodiment together. As shown in FIG. 14, the bit rate determining unit 212 receives the maximum throughput calculated by the throughput calculating unit 211 by the processing of the first embodiment or the second embodiment, and the communication acquired from the base station (AP) 400 described above. Parameters such as a weighted average value and a standard deviation value based on bandwidth information, specifically, RTT, RSSI, transmission rate, etc. in wireless communication between the base station and the client are input. Further, the client buffer amount estimation process described above is executed to determine the bit rate, and the bit rate of the transmission data is determined for the data processing unit 202 that executes the encoding process or the encoding data selection process. Enter information. As shown in the buffer amount information 250 in FIG. 14, the estimated buffer amount in the range of 0 to MAX is acquired by the bit rate determining unit 212 as the estimated buffer amount of the client.

  The processing sequence of the bit rate determination unit 212 will be described with reference to the flowchart shown in FIG. In step S501, the bit rate determination unit 212 determines whether communication band information has been input from the base station (AP) 400. Specifically, it is a parameter such as a weighted average value or standard deviation value based on RTT, RSSI, transmission rate, and the like. If it is determined in step S501 that communication band information has been input from the base station (AP) 400, the process proceeds to step S502, and analysis processing of the communication band information input from the base station (AP) 400 is executed.

  The analysis processing in step S502 is, for example, a comparison processing between the communication band information acquired from the base station (AP) 400 and the threshold held by the bit rate determination unit 212 as described above. For example, parameters such as weighted average values and standard deviation values based on RTT, RSSI, transmission rate, and the like in wireless communication between the base station and the client acquired from the base station (AP) 400, and threshold values held by the bit rate determination unit 212 This is executed as a comparison process.

  In step S503, it is determined as a result of the analysis in step S502 whether or not it is determined that the transmission bit rate needs to be reduced. If it is determined that the transmission bit rate needs to be reduced, the process proceeds to step S504. The reduction process is executed. In step S505, it is determined whether the transmission bit rate can be increased as an analysis result in step S502. If it is determined that the transmission bit rate can be increased, the process proceeds to step S506. Executes bit rate increase processing. However, the bit rate corresponding to the maximum throughput calculated by the throughput calculation unit 211 is set as the maximum allowable bit rate, that is, the upper limit value. This upper limit is the maximum allowable bit rate corresponding to the maximum throughput calculated by the throughput calculation unit 211 or the client described in the first and second embodiments.

  In step S503 and step S505, based on the analysis of the communication band information acquired from the base station (AP) 400, it is determined that the transmission bit rate needs to be reduced or increased, as described above. As a result of the comparison processing between the parameters such as the weighted average value and the standard deviation value based on RTT, RSSI, transmission rate, etc. in the wireless communication between the base station and the client acquired from 400, and the threshold held by the bit rate determination unit 212, When the same result occurs continuously several times, it is determined that the bit rate change control is necessary.

  For example, if the state where the RTT in the wireless communication between the base station and the client is longer than the threshold value a continues, the transmission bit rate is lowered. When the state shorter than the threshold value b continues, the transmission bit rate is increased. When the RSSI (radio wave intensity) in the wireless communication between the base station and the client continues to be higher than the threshold value c, the transmission bit rate is increased. When the state lower than the threshold value d continues, the transmission bit rate is reduced. When the state in which the bit rate in the wireless communication between the base station and the client is lower than the threshold value e continues, the transmission bit rate is lowered. When the state higher than the threshold value f continues, processing such as increasing the transmission bit rate is performed.

  The processes in steps S507 to S509 are the same as those in the first embodiment, and are processes for controlling the bit rate based on the estimated buffer amount. That is, in step S507, the bit rate determination unit 212 determines whether or not the buffer amount is smaller than a predetermined threshold value Th1. If it is determined that the buffer amount is smaller than the predetermined threshold Th1, the process proceeds to step S504, and a transmission bit rate reduction process is executed. This processing is processing when the buffer amount in the buffer amount information 250 shown in FIG. 14 is in the area of Ba.

  If it is determined in step S507 that the buffer amount is not smaller than the predetermined threshold Th1, the process proceeds to step S508, and it is determined whether or not the buffer amount is larger than the predetermined threshold Th2. If the buffer amount is not greater than the predetermined threshold Th2, the process returns to step S501. This processing is processing when the buffer amount in the buffer amount information 250 shown in FIG. 6 is in the Bb area.

  If the buffer amount is larger than the predetermined threshold value Th2, the process proceeds to step S506, where the current transmission data bit rate and the maximum throughput calculated by the throughput calculation unit 211 according to the process of the first embodiment or the process of the second embodiment. Thus, the maximum allowable bit rate corresponding to the maximum throughput calculated by the client or the throughput calculation unit 211 is compared. If the bit rate of the current transmission data is smaller than the maximum allowable bit rate corresponding to the maximum throughput, the process proceeds to step S506, and processing for increasing the bit rate of the transmission data is executed. However, the maximum allowable bit rate is the upper limit value. If the bit rate of the current transmission data is equal to the maximum allowable bit rate corresponding to the maximum throughput, the process returns to step S501 without controlling the bit rate. This processing is processing when the buffer amount in the buffer amount information 250 shown in FIG. 14 is in the Bc area.

  In the process of the third embodiment, in addition to the bit rate control based on the maximum throughput calculated according to the throughput calculation process of the first or second embodiment, the RTT in the wireless communication between the base station and the client measured by the base station (AP). Since the bit rate control is performed based on communication band information such as RSSI and transmission rate, bit rate control that responds quickly to changes in the communication state in wireless communication is realized. Further, as in the first and second embodiments, the throughput calculation value based on the effective data transmission / reception period is set as the maximum throughput, so that the bit rate can be controlled in consideration of the actual transmission rate, and the bit rate can be increased. Data transmission is realized with an upper limit of the maximum bit rate at which data transmission can be performed reliably without being excessively suppressed or suppressed.

  If it is determined that it is difficult to continue streaming data distribution between server clients based on communication band information in wireless communication between the base station and the client measured by the base station (AP), the server or base station ( (AP) may notify the client that it is difficult to continue streaming data distribution. The client displays a notification on the display and executes processing for notifying the user that data distribution is difficult. By this processing, the user can take appropriate measures such as bringing the client terminal close to the base station (AP) or taking measures such as stopping the device causing the failure, for example, the microwave oven.

[Hardware example of server, base station (AP), client]
Next, a hardware configuration example of a server, a base station (AP), and a client will be described with reference to FIG. As described with reference to FIG. 1, the server and the client can be configured by various devices. FIG. 16 shows an example of a hardware configuration applicable as a server, a base station (AP), and a client.

  The hardware configuration of FIG. 16 will be described. A CPU (Central Processing Unit) 501 executes various processes in accordance with programs stored in a recording medium 514 such as a ROM (Read Only Memory) 502 or an HDD (Hard Disk Drive), etc. It functions as a communication control processing means. A RAM (Random Access Memory) 503 appropriately stores programs executed by the CPU 501 and data. The CPU 501, ROM 502, and RAM 503 are connected to each other via a bus 521.

  An input / output interface 522 is connected to the bus 521. The input / output interface 522 includes, for example, an input unit 511 including a keyboard, a switch, a button, a pointing device, or a mouse operated by a user. An output unit 512 including an LCD, a CRT, a speaker, and the like that presents various types of information to the user is connected. Further, a communication unit 504 functioning as a data transmission / reception unit, and a recording medium 514 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory are mounted, and a drive 513 that executes data reading or writing processing from the recording medium 514. Is connected. However, in the base station (AP), the input unit 511, the output unit 512, the drive 513, the recording medium 514, and the like are not necessarily required. A setting unit for performing various settings may be provided.

  The configuration illustrated in FIG. 16 is an example of a device that can be used as a server, a base station (AP), or a client as the network connection device illustrated in FIG. 1, but the network connection device is not limited to the configuration illustrated in FIG. It can be configured by an electronic device or an information processing apparatus. Therefore, it is possible to have a hardware configuration unique to each device.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiments without departing from the gist of the present invention. In other words, the present invention has been disclosed in the form of exemplification, and should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

  The series of processes described in the specification can be executed by hardware, software, or a combined configuration of both. When executing processing by software, the program recording the processing sequence is installed in a memory in a computer incorporated in dedicated hardware and executed, or the program is executed on a general-purpose computer capable of executing various processing. It can be installed and run.

  For example, the program can be recorded in advance on a hard disk or ROM (Read Only Memory) as a recording medium. Alternatively, the program is temporarily or permanently stored on a removable recording medium such as a flexible disk, a CD-ROM (Compact Disc Read Only Memory), an MO (Magneto optical) disk, a DVD (Digital Versatile Disc), a magnetic disk, or a semiconductor memory. It can be stored (recorded). Such a removable recording medium can be provided as so-called package software.

  The program is installed on the computer from the removable recording medium as described above, or is wirelessly transferred from the download site to the computer, or is wired to the computer via a network such as a LAN (Local Area Network) or the Internet. The computer can receive the program transferred in this manner and install it on a recording medium such as a built-in hard disk.

  Note that the various processes described in the specification are not only executed in time series according to the description, but may be executed in parallel or individually according to the processing capability of the apparatus that executes the processes or as necessary. Further, in this specification, the system is a logical set configuration of a plurality of devices, and the devices of each configuration are not limited to being in the same casing.

  As described above, according to the configuration of the present invention, the maximum throughput is calculated by applying the “continuous data transmission and reception acknowledgment (ack) reception period”, that is, the measured value of [data transmission / reception execution period]. The transmission bit rate is controlled based on the maximum throughput. That is, the maximum throughput based on the data transmission / reception period without the data transmission / reception period [data transmission / non-execution period] is calculated, and the bit rate control with the maximum allowable bit rate corresponding to the calculated maximum throughput as the upper limit is performed. Do. This configuration makes it possible to control the bit rate in consideration of the actual transmission rate, and realizes data transmission up to the maximum allowable bit rate that can reliably execute data transmission without excessively increasing or suppressing the bit rate. Is done.

  Furthermore, according to the configuration of the present invention, the maximum throughput is calculated based on the reception interval of the continuous transmission packets measured by the client, and the bit rate control with the calculated maximum throughput as the upper limit can be performed. The maximum throughput determined based on the measurement of actually transmitted packets is calculated, and bit rate control is performed with the maximum allowable bit rate corresponding to the calculated maximum throughput as the upper limit. This configuration makes it possible to control the bit rate in consideration of the actual transmission rate, and realizes data transmission up to the maximum allowable bit rate that can reliably execute data transmission without excessively increasing or suppressing the bit rate. Is done.

  Furthermore, according to the configuration of the present invention, in addition to the bit rate control based on the maximum throughput calculated based on the actual transmission / reception data measurement, the RTT in the wireless communication between the base station and the client measured by the base station (AP), Since the bit rate is controlled on the basis of communication band information such as RSSI and transmission rate, bit rate control can be realized in response to fluctuations in the communication state in wireless communication.

It is a figure which shows the network structural example which can apply this invention. It is a block diagram explaining the structure of the server and client as a transmission / reception apparatus of streaming data. It is a figure explaining the data delivery processing sequence based on establishment of the TCP connection performed between server clients. It is a figure explaining the continuous delivery processing sequence of the data based on window size. It is a figure which shows the flowchart explaining the process sequence of the server in Example 1 of this invention. It is a figure explaining the process of the bit rate determination part in Example 1 of this invention. It is a figure which shows the flowchart explaining the process sequence of the bit rate determination part in Example 1 of this invention. It is a block diagram explaining the structure of the server and client as a streaming data transmission / reception apparatus corresponding to Example 2 of this invention. It is a figure explaining the emergency flag setting data transmitted in the data transmission / reception process between the server clients of Example 2 of this invention. It is a figure which shows the flowchart explaining the process sequence of the server in Example 2 of this invention. It is a figure which shows the flowchart explaining the process sequence of the client in Example 2 of this invention. It is a figure explaining the AP discovery process sequence of a server. It is a block diagram explaining the structure of the server as a streaming data transmission / reception apparatus corresponding to Example 3 of this invention, a client, and a base station (AP). It is a figure explaining the processing sequence of the bit rate determination part in Example 3 of this invention. It is a figure which shows the flowchart explaining the process sequence of the bit rate determination part in Example 3 of this invention. It is a figure explaining the hardware which comprises a server, a client, and a base station.

Explanation of symbols

101 Server 110 Network 121, 122 Client (PC)
123 client (mobile terminal)
124 client (playback device)
131 Base station (AP)
200 server 201 content providing unit 202 data processing unit 203 transmission buffer 204 data transmission / reception unit 210 dynamic rate control unit 211 throughput calculation unit 212 bit rate determination unit 300 client 301 data transmission / reception unit 302 reception buffer 303 reproduction processing unit 304 output unit 305 packet Interval measurement unit 400 Base station (AP)
401 Data Transmission / Reception Unit 402 Communication Bandwidth Monitoring Unit 403 Communication Bandwidth Information Generation Unit 501 CPU
502 ROM
503 RAM
504 Communication unit 511 Input unit 512 Output unit 513 Drive 514 Recording medium 521 Bus 522 I / O interface

Claims (8)

A communication processing device as a server that executes data transmission processing for a client,
A data transmission / reception unit for executing communication processing with the client;
A rate control unit that determines a bit rate of transmission data to the client;
A data processing unit for executing transmission data setting processing corresponding to the bit rate determined in the rate control unit,
The rate control unit
The throughput calculated based on the reception interval information of data packets continuously transmitted within the communication connection setting period between server clients is set as the maximum throughput, and the transmission bit rate is set with the bit rate corresponding to the maximum throughput as the maximum allowable bit rate. configuration der having a bit rate determination unit for determining is,
The bit rate determining unit
The bit rate is determined based on the transition of the estimated buffer amount of the client-side buffer. When the estimated buffer amount is equal to or greater than a predetermined threshold, the bit rate increases up to the maximum allowable bit rate corresponding to the maximum throughput. It is a configuration that performs processing,
The bit rate determining unit
(A) Buffer amount notified from the client at the start of communication: [B_cli (byte)]
(B) Elapsed time since the client started playback: [T (sec)]
(C) The amount of data transmitted from the server during the elapsed time [T (sec)] after the client starts playback: [D_serv (byte)]
(D) Content playback rate that can be acquired from the transmitted content [R (byte / sec)]
Using the information of (a) to (d), it is configured to execute a client buffer amount estimation process,
Estimated buffer size of client buffer = B_cli + D_serv−R * T
As
A communication processing apparatus characterized by calculating an estimated buffer amount of a client-side buffer . The rate control unit
Receiving a reception interval information of data packets continuously transmitted within a communication connection setting period between server clients from a client, and having a throughput calculation unit for calculating a maximum throughput based on the reception interval information and a transmission data amount;
The bit rate determining unit
The communication processing apparatus according to claim 1, wherein a transmission bit rate is determined with a bit rate corresponding to the maximum throughput calculated by the throughput calculation unit as a maximum allowable bit rate. The data transmitter / receiver
2. The communication processing apparatus according to claim 1, wherein a packet in which an emergency flag in a packet header is set to a specific value is continuously transmitted as identification information of a reception interval measurement target packet in a client. The data transmitter / receiver
From the base station that mediates communication with the client, receiving communication band information between the base station and the client,
The bit rate determining unit
The communication processing apparatus according to claim 1, wherein the communication processing apparatus is configured to perform transmission bit rate determination processing based on the communication band information. The communication band information is
5. The communication processing apparatus according to claim 4 , wherein the communication processing apparatus is information generated based on at least one of RTT, RSSI (radio wave intensity), and transmission rate in communication between the base station and the client. A data communication system having a server client for executing data transmission / reception processing,
The client
A configuration for measuring a reception interval of continuously received packets according to identification information included in a received packet from a server, and executing processing for transmitting the reception interval information or throughput information calculated based on the reception interval to the server Have
The server
A transmission bit rate is determined using a bit rate corresponding to the maximum throughput calculated based on throughput information received from the client or reception interval information as a maximum allowable bit rate, and data transmission processing to the client is performed according to the determined bit rate configuration der that the execution is,
The server further includes:
The bit rate is determined based on the transition of the estimated buffer amount of the client-side buffer. When the estimated buffer amount is equal to or greater than a predetermined threshold, the bit rate increases up to the maximum allowable bit rate corresponding to the maximum throughput. It is a configuration that performs processing,
(A) Buffer amount notified from the client at the start of communication: [B_cli (byte)]
(B) Elapsed time since the client started playback: [T (sec)]
(C) The amount of data transmitted from the server during the elapsed time [T (sec)] after the client starts playback: [D_serv (byte)]
(D) Content playback rate that can be acquired from the transmitted content [R (byte / sec)]
Using the information of (a) to (d), it is configured to execute a client buffer amount estimation process,
Estimated buffer size of client buffer = B_cli + D_serv−R * T
As
A data communication system characterized by calculating an estimated buffer amount of a client side buffer . A communication processing method in a server that executes data transmission processing,
A rate control step for determining a bit rate of transmission data to the client;
A data processing step for executing transmission data setting processing corresponding to the bit rate determined in the rate control step,
The rate control step includes:
The transmission bit rate is set with the throughput calculated based on the reception interval information of the data packets continuously transmitted within the communication connection setting period between the server and client as the maximum throughput and the bit rate corresponding to the maximum throughput as the maximum allowable bit rate. A bit rate determination step to determine ;
When the estimated buffer amount of the client side buffer is equal to or larger than a predetermined threshold, a bit rate increasing step for performing a bit rate increasing process with the maximum allowable bit rate corresponding to the maximum throughput as an upper limit is executed,
In the bit rate increasing step,
(A) Buffer amount notified from the client at the start of communication: [B_cli (byte)]
(B) Elapsed time since the client started playback: [T (sec)]
(C) The amount of data transmitted from the server during the elapsed time [T (sec)] after the client starts playback: [D_serv (byte)]
(D) Content playback rate that can be acquired from the transmitted content [R (byte / sec)]
Using these pieces of information (a) to (d), the client buffer amount estimation processing is executed,
Estimated buffer size of client buffer = B_cli + D_serv−R * T
As
A communication processing method characterized by calculating an estimated buffer amount of a client side buffer . A computer program for executing rate control of transmission data on a computer;
In the rate control unit, a rate control step for determining a bit rate of transmission data for the client;
In the data processing unit, a data processing step for executing transmission data setting processing corresponding to the bit rate determined in the rate control step,
In the rate control step,
The transmission bit rate is set with the throughput calculated based on the reception interval information of the data packets continuously transmitted within the communication connection setting period between the server and client as the maximum throughput and the bit rate corresponding to the maximum throughput as the maximum allowable bit rate. A bit rate determination step to determine ;
When the estimated buffer amount of the client side buffer is equal to or larger than a predetermined threshold, a bit rate increasing step for performing a bit rate increasing process with the maximum allowable bit rate corresponding to the maximum throughput as an upper limit is executed,
In the bit rate increasing step,
(A) Buffer amount notified from the client at the start of communication: [B_cli (byte)]
(B) Elapsed time since the client started playback: [T (sec)]
(C) The amount of data transmitted from the server during the elapsed time [T (sec)] after the client starts playback: [D_serv (byte)]
(D) Content playback rate that can be acquired from the transmitted content [R (byte / sec)]
Using these pieces of information (a) to (d), the client buffer amount estimation processing is executed,
Estimated buffer size of client buffer = B_cli + D_serv−R * T
As
Computer program characterized Rukoto to execute the calculation processing of the estimated buffer amount of a client buffer.