WO2010032370A1 - 伝送レート制御装置及び伝送レート制御方法 - Google Patents
伝送レート制御装置及び伝送レート制御方法 Download PDFInfo
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- WO2010032370A1 WO2010032370A1 PCT/JP2009/003863 JP2009003863W WO2010032370A1 WO 2010032370 A1 WO2010032370 A1 WO 2010032370A1 JP 2009003863 W JP2009003863 W JP 2009003863W WO 2010032370 A1 WO2010032370 A1 WO 2010032370A1
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- transmission rate
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L47/00—Traffic control in data switching networks
- H04L47/10—Flow control; Congestion control
Definitions
- the present invention relates to a transmission rate control apparatus and a transmission rate control method for controlling a transmission rate according to a band estimated to be usable in communication via a best effort type network.
- TFRC TCP Friendly Rate Control
- a terminal using TFRC calculates a transmission rate X using the following equation (1) based on RTT (Round Trip Time) indicating a round trip delay time of data between terminals and a packet loss state.
- X [bps] is a transmission rate corresponding to a band estimated to be usable in communication via the network.
- s is the packet size [bytes]
- R is RTT [seconds]
- b is a constant.
- T_RTO is a value indicating a timeout according to the TCP protocol, and 4R is used.
- P is a loss event rate representing a packet loss situation.
- the loss event rate P is a loss rate that is specified for the TFRC to control the transmission rate smoothly. A packet loss that occurs within one round-trip time is counted as one loss event, and the history of this loss event is recorded. Is used to calculate.
- FIG. 8 is a graph illustrating a method of calculating a loss event rate using a loss event history disclosed in Non-Patent Document 2.
- the vertical axis 21 shown in FIG. 8 indicates the sequential number in the packet, and the horizontal axis 22 indicates the passage of time.
- the arrival packet ( ⁇ , Packet Arrival) plot 23 shows the time when the packet arrived at the receiving terminal and the sequential number at that time.
- a plot 24 of a lost packet (x, Packet Lost) shows a time when a loss event occurs and a sequential number at that time.
- the arrival packet number 25 from the latest loss represents the number of packets that have arrived at the receiving terminal since the most recent event loss occurred.
- Loss event interval 26 1 to 26 8 represent the number of packets arriving at the receiving terminal during the loss event and loss events.
- Weight 27 1 -27 8 shows a weight to be multiplied by the corresponding loss event interval 26.
- Weighted event loss 28 1 to 28 8 are obtained by multiplying the loss event interval 26 and the weight 27.
- TFRC a reciprocal of a weighted loss event interval obtained by calculating a weighted average for the loss event intervals 26 for the past eight generations is calculated as a loss event rate (P).
- the loss event interval is obtained by (loss event interval 26 1 ⁇ weight 27 1 +... + Loss event interval 26 8 ⁇ weight 27 8 ) / (weight 27 1 +... + Weight 27 8 ).
- the TFRC uses the weighted loss event rate calculated using the loss event history as one of the parameters to control the transmission rate to change smoothly.
- the TFRC cannot immediately change the transmission rate to an appropriate value in response to a sudden change in the bandwidth available for communication with the destination terminal.
- FIG. 9 is a diagram illustrating an example of a configuration of a video conference system using a best effort type network.
- the video conference system shown in FIG. 9 is provided with terminals 11, 12, and 13 for transmitting and receiving video and audio streaming data. Each terminal sets a transmission rate using the TFRC described above.
- the terminal 11 and the terminal 12 are communicably connected via the domestic network ND.
- the terminal 13, the terminal 11, and the terminal 12 are connected to be communicable via the domestic network ND, the overseas line L, and the overseas network NA.
- broadband transmission such as 10 Mbps can be realized for both the domestic network ND and the overseas network NA.
- transmission via the overseas line L is a bottleneck due to the overseas line L, and the bandwidth of about 2 Mbps is the limit.
- the transmission rate is set to the narrowest band among the bands used for communication between terminals.
- each terminal sets a transmission rate according to the performance of communication through the domestic network ND, the overseas line L, and the overseas network NA.
- the domestic network ND and the overseas network NA can each realize transmission of about 10 Mbps, while the overseas line L can only implement transmission of about 2 Mbps. Therefore, each terminal sets the transmission rate to 2 Mbps.
- the terminal 13 interrupts the communication and switches to the two-party communication between the terminals 11 and 12 that use only the domestic network ND.
- the terminals 11 and 12 set the transmission rate according to the performance of communication through only the domestic network ND.
- the domestic network ND can realize transmission of about 10 Mbps.
- the terminals 11 and 12 change the transmission rate from 2 Mbps to 10 Mbps.
- the transmission rate is smoothly changed. Therefore, in the video conference system shown in FIG. 9, even if the bandwidth that can be used for communication between the terminals 11 and 12 suddenly increases as a result of the terminal 13 interrupting communication, the transmission rate at the terminals 11 and 12 immediately increases. Do not shift to a higher bit rate. Until the transition to the high bit rate, the available bandwidth and the transmission rate are not matched, and the network bandwidth is not fully utilized. For this reason, it is desirable that the time until the transmission rate shifts to a high bit rate is short.
- An object of the present invention is to provide a transmission rate control device and a transmission rate control method capable of changing a transmission rate to a target bit rate in a short time when a band estimated to be usable during communication via a network changes rapidly. Is to provide.
- the present invention is a transmission rate control device used in a transmission rate control system that controls a transmission rate according to a band estimated to be usable in communication between two communication terminals via a best effort network,
- a communication history storage unit that stores a communication history performed via the network for each communication terminal, and a round-trip delay time calculation unit that calculates a round-trip delay time caused by communication with a predetermined communication terminal via the network;
- the target loss event rate calculated by the predetermined communication terminal and the round-trip delay time caused by communication with the predetermined communication terminal calculated by the round-trip delay time calculation unit A target transmission rate calculation unit that calculates a target transmission rate based on the transmission rate, and a transmission that controls the transmission rate so as to change from the currently set transmission rate to the target transmission rate calculated by the target transmission rate calculation unit And a rate control unit.
- the present invention is a transmission rate control apparatus for controlling a transmission rate according to a band estimated to be usable in communication through a best effort network, and a communication history performed through the network is stored for each communication terminal.
- a communication history storage unit stored in the communication history, a round-trip delay time calculation unit that calculates a round-trip delay time caused by communication with the communication terminal via the network, and communication with a predetermined communication terminal recorded in the communication history Target transmission set by communication with the predetermined communication terminal based on the past transmission rate realized in step 1 and the round-trip delay time generated by the communication with the predetermined communication terminal calculated by the round-trip delay time calculation unit
- a transmission rate comprising: a target transmission rate calculation unit that calculates a rate; and a transmission rate control unit that changes the transmission rate currently set to the target transmission rate To provide a control device.
- the present invention is a transmission rate control method performed in a transmission rate control system that controls a transmission rate according to a band estimated to be usable in communication between two communication terminals via a best effort network,
- a first communication terminal that communicates with a second communication terminal via the network calculates a round-trip delay time caused by communication with the second communication terminal via the network, and the second communication
- the target loss event rate based on the past transmission rate realized by the terminal communicating with the second communication terminal performed by the first communication terminal and the round-trip delay time calculated by the first communication terminal.
- the first communication terminal calculates a target transmission rate based on the target loss event rate calculated by the second communication terminal and the round-trip delay time, and the first communication terminal , To provide a transmission rate control method for controlling transmission rate to change to the target transmission rate from the transmission rate set in the present time.
- the transmission rate control device and the transmission rate control method according to the present invention when the band estimated to be usable during communication via the network changes rapidly, the transmission rate is changed to the target bit rate in a short time. can do.
- the figure which shows the communication system with which transmission terminal X1, X2 and receiving terminal Y1, Y2 were connected to the network N The block diagram which shows the internal structure of the transmission terminal X1 of 1st Embodiment.
- a timing chart showing processing performed when a bandwidth that can be used for communication between transmitting and receiving terminals is rapidly changed.
- the timing chart which shows the process performed when the zone
- the graph which shows the method of calculating a loss event rate using the history of the past loss event disclosed by nonpatent literature 2
- the figure which shows an example of a structure of the video conference system using a best effort type
- FIG. 1 a communication system in which transmission terminals X1 and X2 that transmit streaming data and reception terminals Y1 and Y2 that receive streaming data are connected to a best effort network N. explain.
- the transmission terminals X1 and X2 and the reception terminals Y1 and Y2 are communication terminals that use the technology of TFRC (TCP Friendly Rate Control).
- FIG. 2 is a block diagram illustrating an internal configuration of the transmission terminal X1 according to the first embodiment.
- the transmission terminal X1 of the first embodiment includes an encoder 101, a redundant code processing unit (FEC processing unit) 103, a packet processing unit 105, a buffer 107, a packet transmission unit 109, Control packet reception unit 111, RTT calculation unit 113, communication history storage unit 115, transmission rate calculation unit 117, control unit 119, call monitoring unit 121, change method determination unit 123, and temporary transmission rate notification unit 125, an ARQ unit 127, and a clock 129.
- FEC processing unit redundant code processing unit
- Encoder 101 encodes content data such as video and audio according to a predetermined encoding rate.
- the redundant code processing unit 103 generates a redundant code for the receiving terminal Y1 to perform error detection or error correction such as FEC (Forward Error Correction) from the content data encoded by the encoder 101. Further, the redundant code processing unit 103 adds the generated redundant code to the content data encoded by the encoder 101 and outputs the content data.
- FEC Forward Error Correction
- the redundant code described above is a code by an XOR operation, a Reed-Solomon code, or the like. Further, the redundant code generation by the redundant code processing unit 103 may be performed on a packet obtained by the packet processing unit 105 described later. Further, the generated redundant code may be combined into one packet together with the encoded content data, or may be provided in a packet different from the encoded content data packet.
- the packet processing unit 105 packetizes the data in which the redundant code is added to the content data encoded by the encoder 101, and stores the created packet in the buffer 107.
- the buffer 107 temporarily stores packets before being sent to the network N. When packets are stored in the buffer 107, they may be stored in the order in which encoded content or redundant codes are generated, or may be stored interleaved.
- the packet transmission unit 109 transmits the packet stored in the buffer 107 to the network N at the transmission rate instructed by the control unit 119.
- the transmission terminal X1 uses the round trip delay time (hereinafter referred to as “RTT”) generated by communication between the transmission and reception terminals via the network N.
- RTP Round trip delay time
- Information indicating the packet transmission time Tx is given.
- a packet to which information indicating the transmission time Tx is added is an RTP (Real-time Transport Protocol) packet including content data.
- the packet to which the information indicating the transmission time Tx is added is an RTCP (Real-time Transport Control Protocol) packet for controlling the transmission of the RTP packet, or another control packet.
- the transmission time Tx is obtained from the clock 129 provided in the transmission terminal X.
- the control packet receiver 111 receives the receiver report and feedback packet transmitted from the receiving terminal Y1.
- the receiver report is an RTCP packet including information on the loss event rate P calculated by the receiving terminal Y1. Further, the transmission time Tx transmitted from the transmission terminal X is given to the feedback packet.
- the receiver report may include the transmission time Tx transmitted from the transmission terminal X.
- the communication history storage unit 115 stores a communication history including the maximum value, the minimum value, and the average value of the transmission rate, loss rate, loss event rate, and round-trip delay time (RTT) of communication with each communication terminal performed in the past. Store for each communication terminal.
- the communication history storage unit 115 may record a loss rate, a loss event rate, and a dispersion rate related to the RTT.
- the statistical value recorded in the communication history storage unit 115 does not need to be a statistical value of the entire communication time of each communication terminal, and even if it is a statistical value during a predetermined time before communication disconnection, the communication time zone It may be a statistical value for each.
- the transmission rate calculation unit 117 uses the equation (1) described in the background art based on the RTT calculated by the RTT calculation unit 113, the loss event rate P included in the receiver report received by the control packet reception unit 111, and the like. Calculate the transmission rate.
- the control unit 119 instructs the packet transmission unit 109 to transmit packets at the transmission rate calculated by the transmission rate calculation unit 117.
- the call monitoring unit 121 monitors the connection status with the communication terminal with which the transmission terminal X1 communicates via the network N.
- the call monitoring unit 121 determines whether or not there is a possibility that the bandwidth that can be used in communication with the receiving terminal Y1 may change suddenly.
- the change method determination unit 123 is controlled to operate. Specifically, it is determined that the available bandwidth changes drastically triggered by the addition or deletion of a call connection destination terminal or a rapid change in RTT. For example, as described in the explanation of the background art, when communication with a terminal of an overseas network is completed, started, or when the RTT is suddenly shortened or increased due to line switching or the like, use Judge that the possible bandwidth changes rapidly.
- the change method determination unit 123 includes a transmission rate maximum value (hereinafter referred to as “past transmission rate”) Xp included in the communication history with the receiving terminal Y1 recorded in the communication history storage unit 115, and the current transmission rate. Based on the above, the change policy CP is determined.
- the past transmission rate is not limited to the maximum value of the transmission rate, and may be an average value.
- the past transmission rate may be the maximum value or the average value of the loss event rate included in the communication history with the receiving terminal Y1 recorded in the communication history storage unit 115.
- the past transmission rate may be obtained by substituting the round trip time (RTT) calculated by the RTT calculation unit 113 into the equation (1).
- the change policy CP indicates how the current transmission rate is changed to the past transmission rate Xp.
- the linear bit rate change is represented as a change policy CP_PROP.
- the linear bit rate change is, for example, a change in which the transmission rate is increased or decreased step by step for each RTT.
- the steady bit rate change is expressed as a change policy CP_CBR.
- the bit rate change form differs between when the transmission rate is increased and when it is decreased, it is expressed as a change policy CP_AIMD.
- the change in the bit rate having a different form is, for example, a change in which the change policy CP_CBR is applied when the transmission rate is increased and the change policy CP_PROP is applied when the transmission rate is decreased.
- the change method determining unit 123 determines one of these three change policies CP according to the difference between the current transmission rate and the past transmission rate Xp. For example, the change method determination unit 123 selects the change policy CP_PROP when the difference is greater than a predetermined value, and selects the change policy CP_CBR when the difference is less than or equal to the predetermined value. Note that the change method determining unit 123 may determine a change policy set in advance.
- the change method determining unit 123 determines the time Tr required to change from the current transmission rate to the past transmission rate Xp according to the sign of the value obtained by subtracting the current transmission rate from the past transmission rate Xp.
- the sign of the value is positive, that is, when the transmission rate is increased
- the change method determining unit 123 is n times the round-trip delay time R calculated by the RTT calculating unit 113 (n is a positive integer and constant). Is set to the required time Tr.
- the sign of the value is negative, that is, when the transmission rate is lowered, the change method determination unit 123 sets log (n) times the round-trip delay time R as the required time Tr.
- the temporary transmission rate notifying unit 125 transmits the past transmission rate Xp read from the communication history storage unit 115, the change policy CP determined by the change method determining unit 123, and the required time Tr to the receiving terminal Y1. Further, the temporary transmission rate notifying unit 125 transmits information related to the round trip delay time R calculated by the RTT calculating unit 113 to the receiving terminal Y1.
- the ARQ unit 127 accepts an RTP packet retransmission request (NAK) sent from the receiving terminal Y1. If the packet indicated by the accepted NAK is stored in the buffer 107, the ARQ unit 127 instructs the packet transmission unit 109 to retransmit the packet to the receiving terminal Y1.
- NAK RTP packet retransmission request
- the packet receiving unit 201 receives a packet transmitted from the transmission terminal X via the network N.
- the buffer 203 temporarily stores packets received by the packet receiving unit 201.
- the packet processing unit 205 reads the packet from the buffer 203 and extracts the encoded content data and redundant code.
- the redundant code processing unit 207 periodically performs error detection or error correction of the encoded content data using the read redundant code.
- the decoder 209 decodes the encoded content data after error detection or error correction.
- the situation monitoring unit 211 uses the function of detecting the occurrence of a loss event defined in RFC 3448 shown in Non-Patent Document 1, and based on the packets stored in the buffer 203, the situation monitoring unit 211 Monitor arrival status.
- the situation monitoring unit 211 records in the communication history storage unit 213 the loss event interval c (k) obtained from the time at which the loss event occurred and the sequential number at that time.
- the time when the loss event occurs is obtained from the clock 229 provided in the receiving terminal Y1.
- FIG. 8 described in the background art is also a graph showing an example of the history of loss events at the receiving terminal Y1.
- the communication history storage unit 213 stores the loss event interval c (k) output from the situation monitoring unit 211 as a communication history for each communication terminal. Further, the communication history storage unit 213 stores information on the eight generation weights W (1) to W (8) used in the temporary loss event interval calculation unit 217 and the loss event rate calculation unit 221. Incidentally, the weight is the same as the weight 27 1 -27 8 shown in FIG.
- the target loss event rate calculation unit 215 calculates the target loss event rate TP using the following equation (2) from the past transmission rate Xp and the round trip time (RTT) R sent from the transmission terminal X1.
- RTT round trip time
- a transmission rate between the current transmission rate and the past transmission rate Xp is used as the parameter Xp substituted in the following equation (2).
- the temporary loss event interval calculation unit 217 uses the calculated target loss event rate TP and the eight generation weights W (1) to W (8) to generate temporary loss event intervals tc (1) to tc (1) to eight generations. tc (8) is calculated by equation (3). The temporary loss event interval calculation unit 217 reads the eight generation weights W (1) to W (8) from the communication history storage unit 213.
- Tc (k) in the above equation (3) is a temporary loss event interval of the kth generation.
- W (k) is a weight assigned to the kth generation.
- AW is the sum of weights W (1) to W (8) assigned to the first to eighth generations. Note that the symbol [] in equation (3) is a Gaussian symbol. [x] represents the maximum integer less than or equal to the real number x.
- the call monitoring unit 219 monitors the connection status with the communication terminal with which the receiving terminal Y1 communicates via the network N.
- the call monitoring unit 219 determines whether or not there is a possibility that the bandwidth that can be used for communication with the transmission terminal X1 may change suddenly.
- the loss event interval used by the event rate calculation unit 221 is switched.
- the loss event rate calculation unit 221 calculates, as the loss event rate P, the reciprocal of the weighted loss event interval obtained by taking a weighted average with respect to the loss event intervals for eight generations.
- Loss event intervals for eight generations used as one of the parameters by the loss event rate calculation unit 221 are loss event intervals c (1) to c (8) for eight generations recorded in the communication history storage unit 213. .
- the loss event intervals for 8 generations are temporary loss event intervals tc (1) to tc (8) for 8 generations calculated by the temporary loss event interval calculation unit 217.
- the eight generation weights W (1) to W (8) are read from the communication history storage unit 213.
- the loss event rate calculation unit 221 normally calculates the loss event rate P using the loss event intervals c (1) to c (8) for eight generations recorded in the communication history storage unit 213. However, if the call monitoring unit 219 determines that the bandwidth available for communication with the transmission terminal X1 has changed abruptly, the temporary loss event interval tc for eight generations calculated by the temporary loss event interval calculation unit 217. (1) to tc (8) are used. Therefore, the loss event rate calculation formula at the normal time is the following formula (4), and the loss event rate calculation formula when the band is rapidly changed is the following formula (5).
- the receiver report generation unit 223 generates a receiver report including the loss event rate P calculated by the loss event rate calculation unit 221.
- the control packet transmission unit 225 transmits the receiver report generated by the receiver report generation unit 223 to the transmission terminal X1 in the form of an RTCP packet every time a loss event occurs or periodically (for example, every RTT). Further, the control packet transmission unit 225 transmits a feedback packet to which information indicating the transmission time Tx is added to the transmission terminal X1 according to the packet including the transmission time Tx transmitted from the transmission terminal X1.
- the ARQ unit 227 detects the loss of the RTP packet transmitted from the transmission terminal X1 from the difference between the sequential numbers of the packets stored in the buffer 203.
- the ARQ unit 227 transmits a retransmission request (NAK) of the detected lost packet to the transmission terminal X1, and registers the retransmission request process to count the time.
- NAK retransmission request
- the ARQ unit 227 retransmits the retransmission request, registers the retransmission request process, and counts the time again.
- the ARQ unit 227 stops counting the time and cancels the registered retransmission request process.
- the loss event rate calculation unit 221 uses the temporary loss event intervals tc (1) to tc (8) for eight generations calculated in step S107 and the weights W (1) to W (8) for eight generations, A target loss event rate P is calculated (step S109).
- the target loss event rate P calculated in step S109 is transmitted to the transmission terminal X1 (step S111).
- the transmission rate calculation unit 117 calculates the target transmission rate using the target loss event rate P, the round trip delay time (RTT) R, and the like (step S113).
- the control unit 119 changes the transmission rate so as to send the packet at the target transmission rate calculated in step S113 (step S115).
- the loss event interval c (k) is included in the receiver report received by the control packet reception unit 301 of the present embodiment.
- the loss event interval c (k) is recorded in the communication history storage unit 115.
- the loss event rate P is not included in the receiver report, and the loss event rate P is calculated by the loss event rate calculation unit 311 included in the transmission terminal X2.
- the value that the transmission rate calculation unit 303 of this embodiment substitutes for the loss event rate P which is one of the parameters of Expression (1), is the value calculated by the loss event rate calculation unit 311.
- the call monitoring unit 305 provided in the transmission terminal X2 monitors the connection status with the communication terminal with which the transmission terminal X2 communicates via the network N.
- the call monitoring unit 305 determines whether or not the bandwidth available for communication with the receiving terminal Y2 has changed abruptly. Further, the call monitoring unit 305 switches the loss event interval used by the loss event rate calculation unit 311 by controlling the change method determination unit 123 to operate when the band changes rapidly.
- FIG. 6 is a block diagram showing an internal configuration of the receiving terminal Y2 of the second embodiment.
- the receiving terminal Y2 in FIG. 6 includes a packet receiving unit 201, a buffer 203, a packet processing unit 205, a redundant code processing unit (FEC processing unit) 207, a decoder 209, a situation monitoring unit 401, a receiver report generation unit 403, and a control packet transmission.
- FIG. 6 the same reference numerals are given to components common to FIG. 3 that shows the receiving terminal Y ⁇ b> 1 of the first embodiment.
- the status monitoring unit 401 included in the receiving terminal Y2 monitors the arrival status of the packet transmitted from the transmitting terminal X2 based on the packet stored in the buffer 203, as in the first embodiment. However, the status monitoring unit 401 according to the present embodiment sends the loss event interval c (k) obtained from the time when the loss event occurs and the sequential number at that time to the receiver report generation unit 403.
- the recipient report generation unit 403 included in the reception terminal Y2 generates a recipient report including the loss event interval c (k) obtained from the situation monitoring unit 401.
- FIG. 7 is a timing chart illustrating processing performed when it is determined in the communication system according to the second embodiment that a bandwidth that can be used for communication between transmission and reception terminals changes rapidly.
- the change method determination unit 123 of the transmission terminal X2 determines the change policy CP and the required time Tr (step S201).
- the target loss event rate calculation unit 307 calculates the target loss event rate TP (step S203).
- the temporary loss event interval calculation unit 309 calculates 8 generations of temporary loss event intervals tc (1) to tc (8) (step S205).
- the loss event rate calculation unit 311 uses the temporary loss event intervals tc (1) to tc (8) for eight generations calculated in step S205 and the weights W (1) to W (8) for the eight generations, A target loss event rate P is calculated (step S207).
- the transmission rate realized in the past is used. After generating a history of loss event intervals, transmission rate control using TFRC is performed. Therefore, the transmission rate can be changed to the target bit rate in a short time.
- the transmission terminals X1 and X2 of the above embodiment include the redundant code processing unit 103 and the ARQ unit 127, and the reception terminals Y1 and Y2 include the redundant code processing unit 207 and the ARQ unit 227.
- the redundant code processing unit 103 included in the transmission terminals X1 and X2 generates a redundant code from the encoded content data, assigns it to the encoded content data, and outputs it.
- the redundant code processing unit 207 of the receiving terminals Y1 and Y2 periodically performs error detection or error correction of the encoded content data using the read redundant code.
- the ARQ unit 127 included in the transmission terminals X1 and X2 accepts the retransmission request (NAK) of the RTP packet sent from the reception terminals Y1 and Y2. If the packet indicated by the received NAK is stored in the buffer 107, the ARQ unit 127 instructs the packet transmission unit 109 to retransmit the packet to the receiving terminals Y1 and Y2. In addition, the ARQ unit 227 included in the receiving terminals Y1 and Y2 detects the loss of the RTP packet transmitted from the transmitting terminals X1 and X2 from the difference in the sequential numbers of the packets stored in the buffer 203.
- NAK retransmission request
- the ARQ unit 227 transmits the detected retransmission request (NAK) of the lost packet to the transmission terminals X1 and X2, registers the retransmission request process, and counts the time.
- the ARQ unit 227 retransmits the retransmission request when the count of this time becomes larger than the round trip time between the transmission terminal X1 and the reception terminal Y1, or when the count becomes larger than the round trip time between the transmission terminal X2 and the reception terminal Y2. Furthermore, the ARQ unit 227 registers the retransmission request process and counts the time again.
- the ARQ unit 227 stops counting the time and cancels the registered retransmission request process.
- the redundant code processing unit 103 when the redundant code processing unit 103 of the transmission terminals X1 and X2 generates the redundant code, the redundant code processing unit 103 generates a redundant code corresponding to the content data amount in response to an instruction from the control unit 119. Change the length.
- the length of the redundant code with respect to the content data amount will be described as “redundant code strength”. For example, when the strength of the redundant code is 25%, the redundant code processing unit 103 generates a redundant code having a length that is 1 ⁇ 4 of the content data amount. Further, increasing the strength of the redundant code means changing the strength of the redundant code from 25% to 50%, for example.
- the call monitoring units 121 and 305 of the transmission terminals X1 and X2 determine that the bandwidth that can be used for communication with the reception terminals Y1 and Y2 changes rapidly.
- the control unit 119 instructs the redundant code processing unit 103 to generate a redundant code with a redundant code strength different from that of the normal time.
- the strength of the redundant code at this time may be increased or decreased according to the change policy CP and the transmission rate control. Note that the control unit 119 instructs the redundant code processing unit 103 to restore the strength of the redundant code after the required time Tr determined by the change method determining unit 123 has elapsed.
- the target loss event rate calculation unit 215 of the receiving terminal Y1 receives the change policy CP.
- the target loss event rate calculation unit 215 changes the time for which packets are temporarily stored in the buffer 203 of the receiving terminal Y1 (reception allowable delay time) during the required time Tr.
- the target loss event rate calculation unit 215 receives the change policy CP that rapidly increases the transmission rate, the probability of occurrence of packet loss increases, so that the reception terminal Y1 has an increased opportunity to make a retransmission request to the transmission terminal X1.
- the allowable reception delay time is extended. As a result, retransmission is performed a plurality of times, and support for occurrence of packet loss can be increased.
- the transmission rate control device is useful as a communication terminal or the like that changes a transmission rate to a target bit rate in a short time when a band that is estimated to be usable during communication via a network suddenly changes. is there.
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Abstract
Description
図2は、第1の実施形態の送信端末X1の内部構成を示すブロック図である。図2に示すように、第1の実施形態の送信端末X1は、エンコーダ101と、冗長符号処理部(FEC処理部)103と、パケット処理部105と、バッファ107と、パケット送信部109と、制御パケット受信部111と、RTT算出部113と、通信履歴記憶部115と、伝送レート算出部117と、制御部119と、呼監視部121と、変更方法決定部123と、一時伝送レート通知部125と、ARQ部127と、クロック129とを備える。
また、送受信端末間の通信で利用可能な帯域が急激に変化する要因として、低ビットレートでしか通信できない無線端末との通信が終了した場合が考えられる。しかし、このようなユースケースでも本実施形態の通信システムは、伝送レートを短時間で目標のビットレートに変更することができる。
図5は、第2の実施形態の送信端末X2の内部構成を示すブロック図である。図5における送信端末X2は、エンコーダ101、冗長符号処理部(FEC処理部)103、パケット処理部105、バッファ107、パケット送信部109、制御パケット受信部301、RTT算出部113、通信履歴記憶部115、伝送レート算出部303、制御部119、呼監視部305、変更方法決定部123、目標損失イベント率算出部307、一時損失イベント間隔算出部309、損失イベント率算出部311、ARQ部127、及びクロック129とを備える。図5において、第1の実施形態の送信端末X1を示す図2と共通する構成要素には同じ参照符号が付されている。
上記実施形態の送信端末X1,X2は冗長符号処理部103及びARQ部127を備え、受信端末Y1,Y2は冗長符号処理部207及びARQ部227を備える。上述したように、送信端末X1,X2が備える冗長符号処理部103は、符号化されたコンテンツデータから冗長符号を生成し、符号化されたコンテンツデータに付与して出力する。また、受信端末Y1,Y2の冗長符号処理部207は、読み出した冗長符号を用いて、符号化されたコンテンツデータの誤り検出又は誤り訂正を定期的に行う。
Y1,Y2 受信端末
N ベストエフォート型のネットワーク
101 エンコーダ
103 冗長符号処理部(FEC処理部)
105 パケット処理部
107 バッファ
109 パケット送信部
111,301 制御パケット受信部
113 RTT算出部
115 通信履歴記憶部
117,303 伝送レート算出部
119 制御部
121,305 呼監視部
123 変更方法決定部
125 一時伝送レート通知部
127 ARQ部
129 クロック
201 パケット受信部
203 バッファ
205 パケット処理部
207 冗長符号処理部(FEC処理部)
209 デコーダ
211,401 状況監視部
213 通信履歴記憶部
215,307 目標損失イベント率算出部
217,309 一時損失イベント間隔算出部
219 呼監視部
221,311 損失イベント率算出部
223,403 受信者レポート生成部
225 制御パケット送信部
227 ARQ部
229 クロック
Claims (20)
- ベストエフォート型のネットワークを介した2つの通信端末間の通信で利用可能と推定される帯域に応じて伝送レートを制御する伝送レート制御システムで用いられる伝送レート制御装置であって、
前記ネットワークを介して行った通信履歴を通信端末毎に記憶する通信履歴記憶部と、
前記ネットワークを介した所定の通信端末との通信で生じた往復遅延時間を算出する往復遅延時間算出部と、
前記通信履歴に記録されている前記所定の通信端末との通信で実現された過去伝送レート、及び前記往復遅延時間算出部が算出した前記所定の通信端末との通信で生じた往復遅延時間に基づいて前記所定の通信端末が算出した目標損失イベント率と、前記往復遅延時間算出部が算出した前記所定の通信端末との通信で生じた往復遅延時間と、に基づいて目標伝送レートを算出する目標伝送レート算出部と、
前記現時点で設定されている伝送レートから前記目標伝送レート算出部が算出した目標伝送レートに変更するよう伝送レートを制御する伝送レート制御部と、
を備えた伝送レート制御装置。 - 前記所定の通信端末が算出する目標損失イベント率は、前記通信履歴に記録されている前記所定の通信端末との通信で実現された過去伝送レート、及び前記往復遅延時間算出部が算出した前記所定の通信端末との通信で生じた往復遅延時間に基づいて所定数の目標損失イベント間隔を算出し、当該所定数の目標損失イベント間隔の各々に割り当てられた重みを用いた前記所定数の目標損失イベント間隔の加重平均値の逆数を、前記目標損失イベント率として算出することを特徴とする請求項1記載の伝送レート制御装置。
- 請求項1又は2に記載の伝送レート制御装置であって、
前記過去伝送レートは、前記通信履歴に記録されている前記所定の通信端末との通信で実現された伝送レートの最大値であることを特徴とする伝送レート制御装置。 - 請求項1~3のいずれか一項に記載の伝送レート制御装置であって、
前記過去伝送レートと前記現時点で設定されている伝送レートの差分の符号に応じて、前記伝送レート制御部が前記現時点で設定されている伝送レートから前記目標伝送レートに変更するまでの所要時間を決定する変更方法決定部を備えたことを特徴とする伝送レート制御装置。 - 請求項4に記載の伝送レート制御装置であって、
前記変更方法決定部は、前記現時点で設定されている伝送レートに対して前記過去伝送レートが大きいとき、前記往復遅延時間のn倍(nは正の整数)を前記所要時間として決定することを特徴とする伝送レート制御装置。 - 請求項4に記載の伝送レート制御装置であって、
前記変更方法決定部は、前記現時点で設定されている伝送レートに対して前記目標伝送レートが小さいとき、前記往復遅延時間のlog(n)倍(nは正の整数)を前記所要時間として決定することを特徴とする伝送レート制御装置。 - 請求項4~6のいずれか一項に記載の伝送レート制御装置であって、
前記伝送レート制御部は、前記所要時間の経過に比例して、前記現時点で設定されている伝送レートから前記目標伝送レートに変更するよう伝送レートを制御することを特徴とする伝送レート制御装置。 - 請求項1~7のいずれか一項に記載の伝送レート制御装置であって、
前記所定の通信端末に送信するデータから、所定の冗長符号の強度に応じて冗長符号を生成する冗長符号処理部を備え、
前記冗長符号処理部は、前記伝送レート制御部が前記現時点で設定されている伝送レートから前記目標伝送レートに変更中は、当該変更前の冗長符号の強度とは異なる冗長符号の強度に応じて冗長符号を生成することを特徴とする伝送レート制御装置。 - 請求項1~8のいずれか一項に記載の伝送レート制御装置であって、
前記所定の通信端末は、前記ネットワークを介して受信したパケットを一時蓄積するバッファを備え、
前記伝送レート制御部が前記現時点で設定されている伝送レートから前記目標伝送レートに変更中、前記所定の通信端末は、前記バッファにパケットを一時蓄積する時間を当該変更前とは異なる時間に設定することを特徴とする伝送レート制御装置。 - ベストエフォート型のネットワークを介した通信で利用可能と推定される帯域に応じて伝送レートを制御する伝送レート制御装置であって、
前記ネットワークを介して行った通信履歴を通信端末毎に記憶する通信履歴記憶部と、
前記ネットワークを介した通信端末との通信で生じた往復遅延時間を算出する往復遅延時間算出部と、
前記通信履歴に記録されている所定の通信端末との通信で実現された過去伝送レートと、前記往復遅延時間算出部が算出した前記所定の通信端末との通信で生じた往復遅延時間とに基づいて、前記所定の通信端末との通信で設定する目標伝送レートを算出する目標伝送レート算出部と、
現時点で設定されている伝送レートから前記目標伝送レートに変更する伝送レート制御部と、
を備えたことを特徴とする伝送レート制御装置。 - 請求項10に記載の伝送レート制御装置であって、
前記目標伝送レート算出部は、前記通信履歴に記録されている前記所定の通信端末との通信で実現された過去伝送レートと、前記往復遅延時間算出部が算出した前記所定の通信端末との通信で生じた往復遅延時間とに基づいて目標損失イベント率を算出し、当該算出した目標損失イベント率及び前記往復遅延時間に基づいて前記目標伝送レートを算出することを特徴とする伝送レート制御装置。 - 請求項11に記載の伝送レート制御装置であって、
前記目標伝送レート算出部は、前記通信履歴に記録されている前記所定の通信端末との通信で実現された過去伝送レートと、前記往復遅延時間算出部が算出した前記所定の通信端末との通信で生じた往復遅延時間とに基づいて所定数の目標損失イベント間隔を算出し、当該所定数の目標損失イベント間隔の各々に割り当てられた重みを用いた前記所定数の目標損失イベント間隔の加重平均値の逆数を、前記目標損失イベント率として算出することを特徴とする伝送レート制御装置。 - 請求項10~12のいずれか一項に記載の伝送レート制御装置であって、
前記過去伝送レートは、前記通信履歴に記録されている前記所定の通信端末との通信で実現された伝送レートの最大値であることを特徴とする伝送レート制御装置。 - 請求項10~13のいずれか一項に記載の伝送レート制御装置であって、
前記過去伝送レートと前記現時点で設定されている伝送レートの差分の符号に応じて、前記伝送レート制御部が前記現時点で設定されている伝送レートから前記目標伝送レートに変更するまでの所要時間を決定する変更方法決定部を備えたことを特徴とする伝送レート制御装置。 - 請求項14に記載の伝送レート制御装置であって、
前記変更方法決定部は、前記現時点で設定されている伝送レートに対して前記過去伝送レートが大きいとき、前記往復遅延時間のn倍(nは正の整数)を前記所要時間として決定することを特徴とする伝送レート制御装置。 - 請求項14に記載の伝送レート制御装置であって、
前記変更方法決定部は、前記現時点で設定されている伝送レートに対して前記目標伝送レートが小さいとき、前記往復遅延時間のlog(n)倍(nは正の整数)を前記所要時間として決定することを特徴とする伝送レート制御装置。 - 請求項14~16のいずれか一項に記載の伝送レート制御装置であって、
前記伝送レート制御部は、前記所要時間の経過に比例して、前記現時点で設定されている伝送レートから前記目標伝送レートに変更することを特徴とする伝送レート制御装置。 - 請求項10~17のいずれか一項に記載の伝送レート制御装置であって、
前記所定の通信端末に送信するデータから、所定の冗長符号の強度に応じて冗長符号を生成する冗長符号処理部を備え、
前記冗長符号処理部は、前記伝送レート制御部が前記現時点で設定されている伝送レートから前記目標伝送レートに変更中は、当該変更前の冗長符号の強度とは異なる冗長符号の強度に応じて冗長符号を生成することを特徴とする伝送レート制御装置。 - ベストエフォート型のネットワークを介した2つの通信端末間の通信で利用可能と推定される帯域に応じて伝送レートを制御する伝送レート制御システムで行われる伝送レート制御方法であって、
前記ネットワークを介して第2の通信端末と通信を行う第1の通信端末が、前記ネットワークを介した前記第2の通信端末との通信で生じた往復遅延時間を算出し、
前記第2の通信端末が、前記第1の通信端末が行った当該第2の通信端末との通信で実現された過去伝送レート、及び前記第1の通信端末で算出された往復遅延時間に基づいて目標損失イベント率を算出し、
前記第1の通信端末が、前記第2の通信端末で算出された目標損失イベント率と、前記往復遅延時間とに基づいて目標伝送レートを算出し、
前記第1の通信端末が、前記現時点で設定されている伝送レートから前記目標伝送レートに変更するよう伝送レートを制御することを特徴とする伝送レート制御方法。 - ベストエフォート型のネットワークを介した通信で利用可能と推定される帯域に応じて伝送レートを制御する伝送レート制御方法であって、
前記ネットワークを介した通信端末との通信で生じた往復遅延時間を算出し、
所定の通信端末との通信で実現された過去伝送レートと、前記所定の通信端末との通信で生じた往復遅延時間とに基づいて、前記所定の通信端末との通信で設定する目標伝送レートを算出し、
現時点で設定されている伝送レートから前記目標伝送レートに変更することを特徴とする伝送レート制御方法。
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