JP2004153617A - Communication system, radio communication terminal, data distributing device and communicating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system capable of optimally using communication resources by quickly obtaining an optimum transmitting speed when a line of a radio section is stopped. <P>SOLUTION: In this communication system in which a server 20 transmits contents data to a radio communication terminal 10 through a radio communication line, the server 20 is provided with a receiving means for receiving status information and/or quality information transmitted from the radio communication terminal and an encoding rate determining means for determining an encoding rate at which the server transmits the contents data. The encoding rate determining means determines an encoding rate on the basis of the receiving status information while communicating with the radio terminal device and determines an encoding rate on the basis of the quality information when communication is restarted after the communication with the radio communication terminal is stopped. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless communication system for performing data communication, and more particularly to a wireless communication system capable of changing a transmission rate in a wireless section.
[0002]
[Prior art]
In recent years, the transmission capacity of a communication line has increased in a mobile communication network, and not only conventional text data such as mail and WWW data but also large data such as a still image has been transmitted. In the future, it is considered that data having a larger data amount and real-time properties (for example, moving image data such as video) will be distributed.
[0003]
There is a method using streaming technology as a distribution method of moving image data. In order to ensure real-time performance of data reproduction during streaming, RTP (Realtime Transport Protocol) defined by RFC1889 as a data transfer protocol and its control protocol. RTCP (RTP Control Protocol) is used. In the streaming server, the use of the RTCP information makes it possible to predict the reception rate on the client side. Using this, streaming is performed by a variable rate control method that controls the transmission rate of the server. In transmitting information, there is known a technique of controlling a transmission rate so as to gradually increase the transmission rate based on RTCP data from a receiving terminal.
[0004]
A high-speed packet communication network using a 1xEV-DO (1x Evolution Data Only) system has been proposed as a technique for improving the transmission efficiency of a downlink from a base station to a wireless communication terminal. In the 1xEV-DO system, a wireless communication terminal estimates communication quality based on a CIR (desired wave to interference wave ratio) based on a pilot signal transmitted by a base station and obtains a communicable transmission rate. Then, based on the transmission rate, a communication mode which is a combination of modulation schemes is selected and transmitted to the base station. The base station performs scheduling based on the communication mode received from each wireless communication terminal, and sets a transmission rate for each wireless communication terminal. The base station preferentially allocates communication resources to radio communication terminals having a high communicable transmission rate in consideration of an improvement in transmission efficiency of the entire system.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. H11-341064
[Problems to be solved by the invention]
However, in the case of controlling the transmission rate from a server in the transmission of streaming data using a wireless communication line, feedback information (reception from the client terminal) including information based on data transmission and reception between the client terminal and the server is included. Report), if the radio wave condition deteriorates or radio waves from the base station are unexpectedly cut off (for example, the If data is not transmitted / received to / from the server, the reception rate becomes 0, and thus there is a problem in that it is not possible to predict fluctuations in the bandwidth of the communication line between the server and the client terminal based on the feedback information. .
[0007]
When the transmission rate of the server is controlled using DRC (Data Rate Control), which is information used to determine the transmission rate of the wireless section, the optimum rate is determined immediately upon the start of communication. However, when a plurality of client terminals are connected to the radio base station, the transmission rate of the radio section fluctuates due to the scheduling process in which the radio base station allocates a band to the plurality of client terminals. In many cases, communication can be performed only at a rate lower than the rate specified by the DRC requested from the station, and the client terminal has a problem that the rate based on the DRC is not always the optimum rate.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a communication system capable of quickly obtaining an optimum transmission speed and using communication resources optimally when a line in a wireless section is interrupted.
[0009]
[Means for Solving the Problems]
A first invention is a communication system for transmitting content from a data distribution device to a wireless communication terminal via a wireless communication line, wherein the wireless communication terminal includes reception status information of data transmitted from the data distribution device. Status information transmitting means for transmitting to the data distribution apparatus, detection means for detecting the quality of the wireless communication line, and line quality information transmission for transmitting information on the line quality detected by the detecting means to the data distribution apparatus Means, wherein the data distribution device receives the reception status information and / or the quality information transmitted from the wireless communication terminal, and encodes the content data from the data distribution device. Coding rate determination means for determining a rate, wherein the coding rate determination means determines the reception status during communication with the wireless communication terminal. Determines the coding rate based on distribution, the the communication resuming after communication with the wireless communication terminal is disrupted and determines the coding rate based on the quality information.
[0010]
In a second aspect based on the first aspect, the wireless communication terminal transmits the quality information to the data distribution device when the wireless communication line is disconnected.
[0011]
In a third aspect based on the first or second aspect, the wireless communication terminal transmits the reception status information and the quality information to the data distribution device as response information relating to data transmitted from the data distribution device. It is characterized by doing.
[0012]
In a fourth aspect based on the first to third aspects, when the communication using the wireless communication line is resumed, the wireless communication terminal transmits the quality information to the data distribution device by the line quality information transmitting means. And then transmitting the reception status information to the data distribution device by the reception status information transmitting means.
[0013]
In a fifth aspect based on the first to fourth aspects, the data distribution device determines the coding rate based on the quality information received by the reception unit, and then the reception unit receives the reception status information. In some cases, the coding rate determination means determines the coding rate based on the received reception status information.
[0014]
A sixth invention is a wireless communication terminal for receiving, via a wireless communication line, content data transmitted from a data distribution device, transmitting reception status information of the data transmitted from the data distribution device to the data distribution device Receiving state information transmitting means, detecting means for detecting the quality of the wireless communication line, line quality information transmitting means for transmitting information on the line quality detected by the detecting means to the data distribution apparatus, and receiving state information A receiving unit that receives the content data transmitted at the coding rate determined based on the line quality information.
[0015]
A seventh invention is characterized in that, in the sixth invention, when the wireless communication line set up with the wireless base station is interrupted, the quality information is transmitted to the data distribution device.
[0016]
In an eighth aspect based on the sixth or seventh aspect, the reception status information and the quality information are transmitted to the data distribution device as response information on data transmitted from the data distribution device. .
[0017]
In a ninth aspect based on the sixth to eighth aspects, when communication using the wireless communication line is resumed, the line quality information transmitting means transmits the quality information to the data distribution device, and thereafter, And transmitting the reception status information from the reception status information transmitting means to the data distribution device.
[0018]
A tenth invention is a data distribution apparatus for transmitting content data to a wireless communication terminal via a wireless communication line, wherein the content data reception status information and / or the quality information of the wireless communication line are received from the wireless communication terminal. Receiving means, and an encoding rate determining means for determining an encoding rate of the content data, wherein the encoding rate determining means is configured to determine an encoding rate based on the reception status information during communication with the wireless communication terminal. And determining a coding rate based on the quality information when communication is resumed after the communication with the wireless communication terminal is interrupted.
[0019]
In an eleventh aspect based on the tenth aspect, after the coding rate is determined based on the quality information received by the receiving means, when the receiving means receives the reception status information, the coding rate determination is performed. The means determines an encoding rate based on the reception status information.
[0020]
A twelfth invention is a communication method for transmitting content data from a data distribution device to the wireless communication terminal via a wireless communication line, wherein the wireless communication terminal transmits reception status information of the data transmitted from the data distribution device. Transmit to the data distribution device, the data distribution device determines the encoding rate of the content data based on the reception status information during communication with the wireless communication terminal, between the wireless communication terminal When the communication is resumed after the communication is interrupted, the quality information is transmitted to the data distribution device, and the data distribution device determines an encoding rate of the content data based on the quality information.
[0021]
In a thirteenth aspect based on the twelfth aspect, the wireless communication terminal transmits the quality information to the data distribution device when the wireless communication line is disconnected.
[0022]
In a fourteenth aspect based on the twelfth or thirteenth aspect, the wireless communication terminal transmits the reception status information and the quality information to the data transmitted from the data distribution device even during communication with the data distribution device. And transmitting the response information to the data distribution device.
[0023]
In a fifteenth aspect based on the twelfth to fourteenth aspects, the wireless communication terminal transmits the quality information to the data distribution device when communication using the wireless communication line is resumed, and thereafter, The reception status information is transmitted to the data distribution device.
[0024]
In a sixteenth aspect based on the twelfth to fifteenth aspects, when the data distribution device receives reception status information after determining a coding rate based on the quality information received by the receiving means, the data distribution device receives the information. The encoding rate is determined based on the reception status information.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0026]
FIG. 1 is a block diagram illustrating a configuration of a wireless communication system according to an embodiment of the present invention.
[0027]
The client terminal 10 is a data distribution device (streaming) that transmits real-time content data (moving images, still images, music, audio, subtitles, and the like) via the wireless base station 30 and a network (such as an IP network) 40. Server 20).
[0028]
The client terminal 10 is a wireless communication terminal such as a mobile phone that supports data communication, a PDA (Personal Digital Assistants), or a computer device to which a data communication card with a built-in wireless device is added. The client terminal 10 has an antenna 11 that receives a radio wave (downlink signal) from the radio base station 30 and transmits a radio wave (uplink signal) to the radio base station 30. It is connected to the. The radio unit 12 includes a transmission unit and a reception unit. The transmission unit generates a high-frequency signal to be transmitted from the antenna 11, and the reception unit amplifies and converts the frequency of the high-frequency signal received by the antenna 11 to generate a baseband signal Is output to the transmission / reception unit 13.
[0029]
The transmission / reception unit 13 includes a modulation / demodulation circuit and a CODEC unit, and demodulates a baseband signal by the demodulation circuit. The demodulated signal is sent to the CODEC unit, where it is decoded into a data signal. The CODEC unit encodes the data signal, and the encoded signal is sent to the transmission / reception unit 13 and modulated. The modulated signal is converted into a high-frequency signal by the transmission unit and transmitted from the antenna 11.
[0030]
The transmission / reception unit 13 is connected to a reception buffer 14 for temporarily storing streaming data received by the client terminal 10 so that even if there is a short-term reduction in transmission rate, disconnection of a line, etc. Is played without interruption. The data read from the reception buffer 14 is sent to the decoding unit 15 and decodes data encoded as a moving image file such as MPEG into a video signal. Then, the decoded video data is displayed on the display unit 16, and the content data (for example, moving image data) is reproduced.
[0031]
The control unit 17 controls each unit of the client terminal 10 such as the wireless unit 12, the transmission / reception unit 13, the reception buffer 14, and the decoding unit 15. Specifically, the transmission / reception frequency and transmission / reception timing are controlled by designating a channel to the radio unit 12. In addition, according to a predetermined communication protocol, it generates various control signals for setting up, releasing, and registering a wireless communication line between the client terminal 10 and the wireless base station 30, and controls transmission and reception of these signals.
[0032]
Furthermore, in the embodiment of the present invention, since the wireless communication network is a 1xEV-DO network, the client terminal 10 receives and obtains a signal (for example, a pilot signal, a control packet, and the like) transmitted from the wireless base station 30. Based on the CIR, DRC information, which is a signal indicating a communication mode selected as capable of performing data communication efficiently, is transmitted to the wireless base station 30 as wireless communication line quality information. Therefore, the control unit 17 obtains the CIR obtained from the received signal, and determines the transmission rate by referring to the conversion table stored in advance. Then, it generates DRC information based on the determined transmission rate and sends it to the radio unit 12. As described above, the detecting unit for detecting the line quality is configured by the wireless unit 12. The control unit 17 and the wireless unit 12 constitute a line quality information transmitting unit.
[0033]
Further, the control unit 17 monitors the packets of the data transmitted from the streaming server 20, and receives a reception report including a packet loss rate, the number of lost packets, the maximum value of the sequence number of the received packet, the arrival interval jitter, and the like. RR) is transmitted to the streaming server 20 as data reception status information. In this way, the control unit 17 and the wireless unit 12 constitute a reception status information transmission unit.
[0034]
Further, the control unit 17 instructs the decoding unit 15 on information for decoding.
[0035]
The wireless base station 30 has an antenna 31 connected to a wireless unit, receives a radio wave (uplink signal) from the client terminal 10, and transmits a radio wave (downlink signal) to the client terminal 10. The radio unit includes a transmission unit and a reception unit. The transmission unit generates a high-frequency signal to be transmitted from the antenna 31, and the reception unit performs amplification, frequency conversion, and the like on the high-frequency signal received by the antenna 31, and generates a baseband signal. Output to the transmitting / receiving unit.
[0036]
The transmission / reception unit includes a modulation / demodulation circuit and a CODEC unit, and demodulates a baseband signal by the modulation / demodulation circuit. The demodulated signal is sent to the CODEC unit, where it is decoded into a data signal. The CODEC unit encodes the data signal, and the encoded signal is sent to the transmitting / receiving unit and modulated. The modulated signal is converted into a high-frequency signal by the transmission unit and transmitted from the antenna 31.
[0037]
An interface unit is connected to the transmission / reception unit, and the wireless base station 30 is connected to a network 40 such as the Internet via the interface unit.
[0038]
The wireless base station 30 includes a control unit that controls each unit (a wireless unit, a transmitting / receiving unit, an interface unit, and the like) of the wireless base station 30. Specifically, the control unit controls a transmission / reception frequency and transmission / reception timing by designating a channel to the radio unit. In addition, in response to a connection request from a client terminal, the connection permission / rejection and the number of connections of the client terminal are controlled.
[0039]
Furthermore, in the embodiment of the present invention, since the wireless communication network is a 1 × EV-DO network, data to be assigned to each client based on the quality information of the wireless communication line transmitted from the client terminal 10 and the number of connected client terminals. The communication bandwidth is determined, and the transmission rate of the wireless communication line to each client terminal 10 is determined.
[0040]
In other words, the control unit and the radio unit of the radio base station 30 constitute line quality information receiving means for receiving the radio communication line quality information (DRC information) transmitted from the client terminal 10, and the control unit controls the radio communication line. Transmission rate determining means for determining a data transmission rate is configured.
[0041]
The data distribution device is a device that transmits (distributes) content data such as moving image data to a wireless communication terminal, and stores moving image data and the like. The data distribution device is a device on the service providing side, for example, a computer device such as a server, and is described as a server in the present embodiment. The storage device that stores the content such as moving image data may be provided inside the server or outside the server.
[0042]
The streaming server 20 is a computer device that transmits data to the client terminal 10. The streaming server 20 stores the video source 21 in a storage device (storage device, hard disk, or the like). This video source is read from the storage device and sent to the encoding unit 22. The encoding unit 22 encodes the video source based on a moving image encoding standard such as MPEG and sends the encoded video source to the transmission unit 23. The transmitting unit 23 packetizes the data encoded based on the communication protocol and transmits the packetized data to the network 40.
[0043]
The rate prediction unit 24 predicts the rate of data transmitted from the streaming server 20 and determines the data encoding rate. That is, in the present invention, the client terminal 10 receives the packet including the packet loss rate, the number of lost packets, the maximum value of the sequence number of the received packet, the arrival interval jitter, and the like as the reception status information of the data transmitted from the streaming server 20. The report is transmitted to the streaming server 20. Further, the client terminal 10 transmits DRC information to the streaming server 20 as quality information of a wireless communication line between the client terminal 10 and the wireless base station 30. Then, the streaming server 20 determines a data encoding rate from the streaming server 20 based on the received reception report (reception status information) and the DRC information (line quality information).
[0044]
The control unit 25 controls each unit of the streaming server 20 such as the encoding unit 22 and the transmission unit 23. Specifically, the data encoding rate is received from the rate prediction unit 24, and an encoding method and information for encoding (for example, DCT coefficients, quantization coefficients, and the like) that match the encoding rate are transmitted to the encoding unit 22. Instruct. Also, the number of packets transmitted from the transmission unit 23 is controlled. Note that the method of determining the coding rate may be a method of selecting one of the contents already coded at different rates.
[0045]
FIG. 2 is a sequence diagram of the communication system according to the first embodiment of this invention.
[0046]
When setting up a session between the client terminal 10 and the streaming server 20, a session request signal for requesting a session is transmitted from the client terminal 10, and a session permission signal for permitting the session is transmitted from the streaming server 20. After that, the client terminal 10 selects a communication mode from the desired wave to interference wave ratio when the session permission signal is received, and transmits the DRC information.
[0047]
The streaming server 20 determines an optimum rate for the client terminal 10 to receive from the received DRC information, and sets the rate determined from the DRC information as an initial value of an encoding rate of data from the streaming server 20.
[0048]
Upon receiving the data transmission start request signal (PLAY) transmitted from the client terminal 10, the streaming server 20 transmits video data and audio data encoded according to a standard such as MPEG. At this time, the encoding rate of the data from the streaming server 20 is the rate determined from the received DRC information.
[0049]
Then, the streaming server 20 transmits the transmission report to the client terminal 10 at a predetermined timing. In response to the transmission report, the client terminal 10 transmits the reception report to the streaming server 20 and reports the reception status of the data transmitted from the streaming server 20.
[0050]
Upon receiving the reception report, the streaming server 20 determines, as the reception report, the encoding rate of the data to be transmitted next (the encoding bit rate for video data and audio data, the bit rate for text data, and the like). . Note that the data encoding rate is determined by selecting one of the already encoded contents or encoding the content at the determined rate.
[0051]
Here, the wireless communication line is interrupted (this interruption occurs when the client terminal 10 enters a tunnel or behind a building and cannot receive radio waves from the wireless base station 30). If the data transmitted from the streaming server 20 does not reach the client terminal 10, the client terminal 10 does not receive the data. Therefore, the reception status information of the data transmitted to the streaming server 20 as the reception report is the lowest value. Become. Further, since the transmission report does not reach the client terminal 10, the client terminal 10 does not return the reception report.
[0052]
The client terminal 10 monitors the arrival status of data from the streaming server 20 using a timer, and when data from the streaming server 20 does not arrive for a predetermined time, communication between the client terminal 10 and the streaming server 20 is interrupted. (Wireless disconnection).
[0053]
When the wireless communication line is restored, the client terminal 10 receives the pilot signal transmitted from the wireless base station 30, calculates the CIR, selects a communication mode from the CIR, and transmits the DRC information.
[0054]
The streaming server 20 calculates an optimum rate for the client terminal 10 to receive from the received DRC information, and sets the rate determined from the DRC information as an encoding rate of data from the streaming server 20. Then, the streaming server 20 restarts data transmission to the client terminal 10.
[0055]
Then, after the data transmission is resumed, the data encoding rate is determined again using the reception report.
[0056]
FIG. 3 is a sequence diagram of the communication system according to the second embodiment of this invention.
[0057]
When setting up a session between the client terminal 10 and the streaming server 20, a session request signal for requesting a session is transmitted from the client terminal 10, and a session permission signal for permitting the session is transmitted from the streaming server 20. After that, the client terminal 10 selects a communication mode from the desired wave to interference wave ratio when the session permission signal is received, and transmits the DRC information.
[0058]
The streaming server 20 calculates an optimum rate for the client terminal 10 to receive from the received DRC information, and sets the rate determined from the DRC information as an initial value of the encoding rate of data from the streaming server 20.
[0059]
Upon receiving the data transmission start request signal (PLAY) transmitted from the client terminal 10, the streaming server 20 transmits video data and audio data encoded according to a standard such as MPEG. At this time, the encoding rate of the data from the streaming server 20 is the rate determined from the received DRC information.
[0060]
Then, the streaming server 20 transmits the transmission report to the client terminal 10 at a predetermined timing. In response to the transmission report, the client terminal 10 transmits the reception report to the streaming server 20 and reports the reception status of the data transmitted from the streaming server 20. In the second embodiment, DRC information indicating wireless communication channel quality is included in a reception report in addition to data reception status information (see FIG. 4).
[0061]
Upon receiving the reception report, the streaming server 20 extracts the reception status information and determines the encoding rate of the data to be transmitted next.
[0062]
Here, the wireless communication line is interrupted (this interruption occurs when the client terminal 10 enters a tunnel or behind a building and cannot receive radio waves from the wireless base station 30). If the data transmitted from the streaming server 20 does not reach the client terminal 10, the client terminal 10 does not receive the data. Therefore, the reception status information of the data transmitted to the streaming server 20 as the reception report is the lowest value. Become.
[0063]
The client terminal 10 monitors the arrival status of data from the streaming server 20 using a timer, and when the data from the streaming server 20 does not arrive for a predetermined time, communication between the client terminal 10 and the streaming server 20 is interrupted. It is determined that it has been done.
[0064]
Then, when the wireless communication line is restored, the client terminal 10 transmits a reception report to the streaming server 20. The reception status information included in the reception report transmitted at this time has the lowest value, but the DRC information indicating the radio communication line quality is the signal transmitted from the radio base station 30 (for example, pilot signal, control signal, etc.). Packet) based on the CIR calculated from the CIR.
[0065]
The streaming server 20 extracts DRC information from the received reception report, calculates an optimal rate for the client terminal 10 to receive, and sets the rate determined from the DRC information as an encoding rate of data from the streaming server 20. I do. Then, the streaming server 20 restarts data transmission to the client terminal 10.
[0066]
After the data transmission is restarted, the data encoding rate is determined again using the reception status information included in the reception report.
[0067]
FIG. 4 is a format diagram of a reception report according to the second embodiment of this invention.
[0068]
The reception report according to the second embodiment of the present invention includes reception status information 102 and DRC information 103 following the header information 101.
[0069]
The reception status information 102 includes the packet loss rate, the number of lost packets, the maximum value of the sequence number of the received packet, the arrival interval jitter, and the like as the reception status information of the data transmitted from the streaming server 20 in the same manner as the reception report described above. , The information normally contained in the received report. Further, the DRC information 103 includes a communication mode selected based on the CIR of a signal transmitted from the wireless base station 30.
[0070]
FIG. 5 is a chart showing changes in the data rate between the client terminal 10 and the streaming server 20 when the wireless communication line is cut off and restored.
[0071]
When the wireless communication line is cut off, the data transmission rate drops sharply.
[0072]
According to the related art, when the wireless communication line is restored, the reception status information of the data of the reception report transmitted from the client terminal 10 has the lowest value, so the lowest data rate is set to the initial value (point B). The streaming server 20 starts transmitting data. Then, the transmission rate is gradually increased using a reception report according to the RTCP procedure defined in RFC1890 (shown by a broken line).
[0073]
On the other hand, according to the present invention, when the wireless communication line recovers, the streaming server sets the data rate according to the wireless communication line quality defined by the DRC information transmitted from the client terminal 10 as an initial value (point A). 20 starts data transmission. Then, the transmission rate is gradually increased using the reception report (shown by a solid line).
[0074]
【The invention's effect】
In the first invention, the coding rate is determined based on the reception status information during the communication, and the coding rate is determined based on the channel quality information detected by the wireless communication terminal when the communication is resumed after the communication is interrupted due to a wireless disconnection or the like. Is determined, the coding rate of data during communication and the coding rate of data at the time of starting communication can be improved, so that an appropriate coding rate can always be set according to network conditions. .
[0075]
In the second invention, the wireless communication terminal transmits the quality information to the data distribution device when a wireless communication line set between the wireless base station and the wireless base station is interrupted. The prediction accuracy of the data encoding rate can be improved.
[0076]
In the third invention, since the reception report includes the radio communication line quality information and transmits the message, it is possible to suppress an increase in traffic without increasing the number of messages (control signals) transmitted and received during data transmission.
[0077]
In the fourth invention, after receiving the reception status from the wireless communication terminal after resuming the communication, the data encoding rate is determined based on the reception status, so that the transmission is switched to the transmission according to the effective rate during the communication. Can be.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a wireless communication system according to an embodiment of the present invention.
FIG. 2 is a sequence diagram of a communication system according to a first embodiment of the present invention; FIG. 3 is a sequence diagram of a communication system according to a second embodiment of the present invention; FIG. FIG. 14 is a format diagram of a reception report according to the second embodiment.
FIG. 5 is a chart showing a change in data rate when the wireless communication line is cut off and restored.
[Explanation of symbols]
Reference Signs List 10 client terminal 11 antenna 12 radio unit 13 transmission / reception unit 14 reception buffer 15 decoding unit 16 display unit 17 control unit 20 streaming server 21 video source 22 encoding unit 23 transmission unit 24 rate prediction unit 25 control unit 30 radio base station 31 antenna 40 network

Claims (16)

In a communication system for transmitting content data from a data distribution device to a wireless communication terminal via a wireless communication line,
The wireless communication terminal,
A reception status information transmission unit that transmits reception status information of the data transmitted from the data distribution device to the data distribution device,
Detecting means for detecting the quality of the wireless communication line,
Line quality information transmitting means for transmitting information on the line quality detected by the detecting means to the data distribution device,
The data distribution device,
Receiving means for receiving the reception status information and / or the quality information transmitted from the wireless communication terminal;
Encoding rate determining means for determining an encoding rate for encoding the content data from a data distribution device,
The coding rate determination means determines a coding rate based on the reception status information during communication with the wireless communication terminal, and includes the quality information when communication is resumed after communication with the wireless communication terminal is interrupted. A communication system for determining a coding rate based on the communication rate. The communication system according to claim 1, wherein the wireless communication terminal transmits the quality information to the data distribution device when the wireless communication line is disconnected. The communication according to claim 1, wherein the wireless communication terminal transmits the reception status information and the quality information to the data distribution device as response information regarding data transmitted from the data distribution device. system. When the communication using the wireless communication line is resumed, the wireless communication terminal transmits the quality information to the data distribution device by the line quality information transmitting unit, and thereafter, the reception status information transmitting unit The communication system according to any one of claims 1 to 3, wherein reception status information is transmitted to the data distribution device. The data distribution device, after determining the coding rate based on the quality information received by the receiving means, when the receiving means receives the reception status information, the coding rate determination means, the received reception status The communication system according to any one of claims 1 to 4, wherein a coding rate is determined based on the information. In a wireless communication terminal that receives the content data transmitted from the data distribution device via a wireless communication line,
A reception status information transmission unit that transmits reception status information of the data transmitted from the data distribution device to the data distribution device,
Detecting means for detecting the quality of the wireless communication line,
Line quality information transmitting means for transmitting information on the line quality detected by the detecting means to the data distribution device,
A wireless communication terminal comprising: receiving means for receiving content data transmitted at an encoding rate determined based on the reception status information or the line quality information. The wireless communication terminal according to claim 6, wherein when the wireless communication line set with the wireless base station is interrupted, the quality information is transmitted to the data distribution device. The wireless communication terminal according to claim 6, wherein the reception status information and the quality information are transmitted to the data distribution device as response information regarding data transmitted from the data distribution device. When communication using the wireless communication line is resumed, the line quality information transmitting unit transmits the quality information to the data distribution device, and thereafter, the reception status information transmitting unit transmits the reception status information to the data. The wireless communication terminal according to any one of claims 6 to 8, wherein the transmission is performed to a distribution device. In a data distribution device that transmits content data to a wireless communication terminal via a wireless communication line,
Receiving means for receiving reception status information of the content data and / or quality information of the wireless communication line from the wireless communication terminal;
Encoding rate determining means for determining a rate for encoding the content data,
The coding rate determination means determines a coding rate based on the reception status information during communication with the wireless communication terminal, and includes the quality information when communication is resumed after communication with the wireless communication terminal is interrupted. A data distribution device that determines an encoding rate based on the data rate. After determining the coding rate based on the quality information received by the receiving means, when the receiving means receives the reception status information, the coding rate determination means performs coding based on the reception status information. The data distribution device according to claim 10, wherein a rate is determined. In a communication method for transmitting content data from a data distribution device to the wireless communication terminal via a wireless communication line,
The wireless communication terminal transmits reception status information of data transmitted from the data distribution device to the data distribution device,
The data distribution device, during communication with the wireless communication terminal, determines an encoding rate of the content data based on the reception status information,
Upon resuming communication after the communication with the wireless communication terminal is interrupted, the quality information is transmitted to the data distribution device, and the data distribution device determines an encoding rate of the content data based on the quality information. A communication method, comprising: The communication method according to claim 12, wherein the wireless communication terminal transmits the quality information to the data distribution device when the wireless communication line is disconnected. The wireless communication terminal transmits the reception status information and the quality information to the data distribution device as response information regarding data transmitted from the data distribution device even during communication with the data distribution device. The communication method according to claim 12 or 13, wherein the communication method is performed. The wireless communication terminal, when communication using the wireless communication line is resumed, transmits the quality information to the data distribution device, and thereafter transmits the reception status information to the data distribution device. The communication method according to any one of claims 12 to 14, wherein The data distribution device, when determining the coding rate based on the quality information received by the receiving unit and receiving the reception status information, determines the coding rate based on the received reception status information. The communication method according to any one of claims 12 to 15, wherein

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