WO2012001866A1 - 通信端末、通信方法、プログラム、及び集積回路 - Google Patents
通信端末、通信方法、プログラム、及び集積回路 Download PDFInfo
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- WO2012001866A1 WO2012001866A1 PCT/JP2011/002727 JP2011002727W WO2012001866A1 WO 2012001866 A1 WO2012001866 A1 WO 2012001866A1 JP 2011002727 W JP2011002727 W JP 2011002727W WO 2012001866 A1 WO2012001866 A1 WO 2012001866A1
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- delay time
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/02—Details
- H04L12/16—Arrangements for providing special services to substations
- H04L12/18—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast
- H04L12/1854—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast with non-centralised forwarding system, e.g. chaincast
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/02—Details
- H04L12/16—Arrangements for providing special services to substations
- H04L12/18—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast
- H04L12/1863—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast comprising mechanisms for improved reliability, e.g. status reports
- H04L12/1868—Measures taken after transmission, e.g. acknowledgments
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client
- H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
- H04N21/64—Addressing
- H04N21/6405—Multicasting
Definitions
- the present invention relates to a communication terminal and a communication method for controlling a reproduction delay time when performing stream distribution using an ALM (Application Layer Multicast) distribution tree.
- ALM Application Layer Multicast
- video data loss packet loss
- the video data is lost, the video or audio reproduced by the terminal 12 on the receiving side is disturbed. In order to prevent this disturbance, it is necessary to have the lost packet transmitted again to the terminal 11 on the transmission side.
- the receiving terminal 12 requests the transmitting terminal 11 to retransmit the lost video packet (p2). Then, as shown in FIG. 14, the transmitting terminal generally retransmits the corresponding video packet (p2) in response to a request from the receiving terminal 12.
- the reproduction start time of the video packet (p2) at the receiving terminal 12 is set in consideration of the time required for retransmission. There is a need to. Specifically, as shown in FIG. 15, it is necessary to start reproduction with a delay of 1 RTT from the first scheduled arrival time of the video packet (p2).
- RTT Real Trip Time
- RTT is the time required for a packet to reciprocate between the terminal 12 on the receiving side and the terminal 11 on the transmitting side.
- the time from the first scheduled arrival time to the reproduction start time is usually called a reproduction delay time.
- a reproduction delay time In the one-to-one communication as shown in FIGS. 11 to 15, it is based on the RTT between the transmitting and receiving terminals. Generally set.
- the reproduction delay time is set so that, for example, the reproduction delay time is a multiple of RTT or more than RTT.
- stream distribution using an ALM distribution tree is known as a technique for simultaneously distributing video data to a plurality of terminals.
- An outline of the ALM distribution tree will be described with reference to FIGS. 16 and 17.
- the plurality of terminals 11, 12, 13, 14, 15, 16, and 17 are connected to a star communication network 10 such as the Internet or a LAN (Local Area Network) as shown in FIG. 16.
- a star communication network 10 such as the Internet or a LAN (Local Area Network) as shown in FIG. 16.
- the amount of data is the bandwidth of the line connected to the terminal 11.
- the upper limit of the width may be exceeded and a delay may occur.
- a logical hierarchical structure is constructed with the terminal 11 that is the distribution source of the stream data as the apex (root terminal). That is, the terminal 11 distributes the stream data only to the terminals 12 and 13. Then, the terminals 12 and 13 reproduce the stream data received from the terminal 11, and distribute it to the subordinate terminals 14, 15, 16, and 17, respectively. According to the above configuration, traffic can be distributed, so that stream delivery without delay can be realized.
- the first retransmission method is a method of retransmitting lost data from the root terminal (distribution source) of the ALM distribution tree. Specifically, as illustrated in FIG. 18, the terminal 23 requests the terminal 20 that is the root terminal to retransmit the lost data (indicated by a one-dot chain line). The terminal 20 that has received a retransmission request from the terminal 23 transmits retransmission data (indicated by a broken line) to the terminal 23.
- the second retransmission method is a method of retransmitting lost data from the parent terminal of the own terminal (the parent terminal of the own terminal on the distribution tree). Specifically, as illustrated in FIG. 19, the terminal 23 requests the terminal 21 that is the parent terminal to retransmit the lost data (dashed line). Then, the terminal 21 that has received a retransmission request from the terminal 23 transmits retransmission data (broken line) to the terminal 23.
- the third retransmission method is a method of retransmitting lost data from a third terminal (other than the root terminal and the parent terminal) other than the above. Specifically, as illustrated in FIG. 20, the terminal 23 requests the terminal 22 having no connection relationship on the ALM distribution tree to retransmit the lost data (dashed line). Then, the terminal 22 that has received a retransmission request from the terminal 23 transmits retransmission data (broken line) to the terminal 23.
- the RTT that is the reference for setting the reproduction delay time is the RTT between the terminal 23 and the terminal 20 that is the root terminal.
- the RTT that is the reference for setting the reproduction delay time is the RTT between the terminal 23 and the terminal 21 that is the parent terminal.
- the RTT that is the reference for setting the reproduction delay time is the RTT between the terminal 23 and the terminal 22 that is the third terminal.
- Non-Patent Document 1 sets a fixed reproduction delay time for each terminal without being aware of the RTT between the retransmission data receiving terminal and the retransmission data transmission source terminal.
- this causes a reduction in communication quality. This is because the system is not aware of the delay between the actual terminals, so that the playback delay time to be set is too short, so that the lost video data is played back without being recovered or the playback delay to be set is set. This is because if the time is too long, the reproduction start time is delayed more than necessary.
- FIGS. 21 and 22 show how data flows along the route of terminal 20 ⁇ terminal 21 ⁇ terminal 23 ⁇ terminal 27 in the ALM distribution tree shown in FIG.
- FIG. 22 shows an environment in which network delays between terminals are equal (hereinafter referred to as an equal delay environment), and FIG. 22 illustrates an environment in which network delays between terminals are not equal (hereinafter referred to as an unequal delay environment).
- the network delay refers to, for example, the time required to transmit one packet from the parent terminal to the child terminal on the ALM distribution tree, and typically corresponds to a half of RTT.
- RTT network delay ⁇ 2”.
- the description will be made assuming that the packet p is lost between the terminals 20-21.
- the network delay between the terminals in the equal delay environment is 100 ms.
- the network delay between the terminals 20-21 is 200 ms, and the network delay between the other terminals is 100 ms.
- the reproduction delay time of each of the terminals 21 to 34 is set to be equal to the RTT with the parent terminal (transmission data transmission source terminal) (that is, twice the network delay). To do.
- the loss data is retransmitted by the second retransmission method described above.
- each of these terminals (terminals 21, 23, 27) transmits a retransmission request of the packet p to the parent terminal when the scheduled arrival time of the packet p has passed, and the parent terminal transmits the packet p. Will be resent.
- the temporal flow of this operation will be described in the order of an equal delay environment (FIG. 21) and an unequal delay environment (FIG. 22).
- the network delay between the terminals 20-21 is 200 ms.
- the retransmission packet from the terminal 20 arrives at the terminal 21 400 ms after the first scheduled arrival time of the packet p. That is, the terminal 21 can retransmit the packet p to the terminal 23 after 400 ms (the retransmission request from the terminal 23 waits for 200 ms on the terminal 21). Therefore, the retransmitted packet p arrives at the terminal 23 400 ms after the first scheduled arrival time.
- the playback delay time of the terminal 23 is 200 ms, when the retransmitted packet p arrives at the terminal 23, the playback start time has already passed (the terminal 27 is also the same). The same).
- the first retransmission method when the first retransmission method is applied, since retransmission data is directly received from the root terminal, this problem does not exist without being affected by a difference in delay between other terminals. However, since the number of retransmission requests transmitted to the root terminal increases in proportion to the number of receiving nodes, the first retransmission method has a drawback of reducing the processing capacity and bandwidth of the root terminal. Absent.
- the present invention has been made in view of the above problems, and an object thereof is to provide a communication terminal and a communication method capable of reproducing stream data with high quality even when stream data loss occurs on a transmission path. To do.
- a communication terminal is one of a plurality of communication terminals that receive and reproduce stream data distributed from a root terminal.
- Each of the plurality of communication terminals is assigned an ALM (Application Layer Multicast) that sequentially transmits retransmission data of the stream data from the parent terminal to the child terminal by assigning one parent terminal and zero or more child terminals to each of the plurality of communication terminals.
- ALM Application Layer Multicast
- Consists of a distribution tree The one communication terminal is a round-trip delay time necessary for transmitting and receiving data in a section between two adjacent terminals on the ALM distribution tree, from the root terminal to the one communication terminal.
- a reproduction delay time determination unit that determines a reproduction delay time using the maximum value of round trip delay times of each section of the stream, and the stream data received from the root terminal is determined by the reproduction delay time determination unit And a playback control unit that plays back with a delay of the playback delay time.
- retransmission data is transmitted using the ALM distribution tree.
- the transmission method of stream data is not particularly limited. For example, it may be transmitted using the same ALM distribution tree as the retransmission data, may be transmitted using an ALM distribution tree different from the retransmission data, or may be transmitted from the root terminal without using the ALM distribution tree. You may transmit directly with respect to each communication terminal.
- the “parent terminal” in this specification refers to a transmission source terminal that directly transmits data to the own terminal in the ALM distribution tree.
- the “child terminal” refers to a transmission destination terminal to which the own terminal directly transmits data in the ALM distribution tree.
- the playback delay time determination unit may determine an integer multiple of the maximum value of the round trip delay time as the playback delay time.
- the round-trip delay time between the one communication terminal and its parent terminal is rtt (self)
- the reproduction delay time of the one communication terminal is x (self)
- the parent terminal When the reproduction delay time is defined as x (parent) and the positive integer is defined as ⁇ self , the reproduction delay time determination unit uses the following formula 1 when rtt (self) ⁇ x (parent) is satisfied.
- the reproduction delay time x (self) is determined.
- the reproduction delay time x (self) is determined using the following equation 2.
- the one communication terminal requests a retransmission request unit that requests the parent terminal to transmit retransmission data corresponding to the loss. May be provided.
- the retransmission request unit may repeatedly request transmission of retransmission data at an interval that is greater than or equal to the round trip delay time between the one communication terminal and its parent terminal and less than or equal to the maximum value of the round trip delay time. Good. This further improves the possibility that retransmission data can be acquired by the reproduction time.
- the one communication terminal includes a round-trip delay time measuring unit that measures the round-trip delay time between the one communication terminal and the parent terminal, and the root terminal to the parent terminal on the ALM distribution tree.
- a round trip delay time management unit that receives a round trip delay time notification including one or more round trip delay times from the parent terminal and transmits the round trip delay time measured by the round trip delay time measurement unit to the child terminal And may be provided. Thereby, it is possible to distribute necessary information (round trip delay time) to each communication terminal while minimizing the traffic of the communication network.
- the round-trip delay time management unit may receive the round-trip delay time notification at predetermined time intervals.
- the round trip delay time measurement unit may measure the round trip delay time between the one communication terminal and its parent terminal every time the round trip delay time notification is received.
- the reproduction delay time determination unit receives one or more round-trip delay times included in the round-trip delay time notification and the round-trip delay time measured by the round-trip delay time measurement unit every time the round-trip delay time notification is received.
- the reproduction delay time may be determined using the delay time.
- a communication terminal is one of a plurality of communication terminals that receives and reproduces stream data distributed from a root terminal.
- Each of the plurality of communication terminals is assigned an ALM (Application Layer Multicast) that sequentially transmits retransmission data of the stream data from the parent terminal to the child terminal by assigning one parent terminal and zero or more child terminals to each of the plurality of communication terminals.
- ALM Application Layer Multicast
- Consists of a distribution tree The one communication terminal is a round-trip delay time necessary for transmitting and receiving data in a section between two adjacent terminals on the ALM distribution tree, from the root terminal to the one communication terminal.
- a reproduction delay time determining unit that determines a reproduction delay time using the round trip delay time of the section in which the loss rate of the stream data is the largest among the sections, and the reproduction delay time after receiving the stream data
- a reproduction control unit that reproduces the reproduction with a delay by the reproduction delay time determined by the determination unit.
- the stream data can be reproduced with higher quality by determining the reproduction delay time using the round trip delay time of the section with the largest loss rate in consideration of the loss rate of the stream data in each section.
- the one communication terminal includes a loss rate measuring unit that measures the loss rate between the one communication terminal and its parent terminal, and 1 from the root terminal to the parent terminal on the ALM distribution tree.
- a loss rate management unit that receives the loss rate notification including the loss rate from the parent terminal and transmits the loss rate notification including the loss rate measured by the loss rate determining unit to the child terminal may be provided.
- the loss rate management unit may receive the loss rate notification at predetermined time intervals.
- the loss rate measuring unit may measure the loss rate between the one communication terminal and its parent terminal every time the loss rate notification is received.
- the reproduction delay time determination unit uses one or more of the loss rates included in the loss rate notification and the loss rate measured by the loss rate measurement unit each time the loss rate notification is received. Thus, the reproduction delay time may be determined.
- the communication method is executed by one communication terminal among a plurality of communication terminals that receive and reproduce stream data distributed from a root terminal.
- Each of the plurality of communication terminals is assigned an ALM (Application Layer Multicast) that sequentially transmits retransmission data of the stream data from the parent terminal to the child terminal by assigning one parent terminal and zero or more child terminals to each of the plurality of communication terminals.
- ALM Application Layer Multicast
- the communication method is a round-trip delay time required for transmitting and receiving data in a section between two adjacent terminals on the ALM distribution tree, and each communication method from the root terminal to the one communication terminal
- a reproduction delay time determining step for determining a reproduction delay time using the maximum value of the round trip delay times of the section; and the reproduction delay determined by the reproduction delay time determining step for the stream data received from the root terminal.
- a program according to an aspect of the present invention is executed by one communication terminal among a plurality of communication terminals that receive and reproduce stream data distributed from a root terminal.
- Each of the plurality of communication terminals is assigned an ALM (Application Layer Multicast) that sequentially transmits retransmission data of the stream data from the parent terminal to the child terminal by assigning one parent terminal and zero or more child terminals to each of the plurality of communication terminals.
- ALM Application Layer Multicast
- the program is a round-trip delay time required for transmitting and receiving data in a section between two adjacent terminals on the ALM distribution tree, and each section from the root terminal to the one communication terminal
- a reproduction delay time determining step for determining a reproduction delay time using a maximum value of the round-trip delay times of the first and second reproduction delay times determined by the reproduction delay time determining step for the stream data received from the root terminal.
- the one communication terminal is caused to execute a reproduction control step of reproducing with a delay of only one.
- An integrated circuit is mounted on one communication terminal among a plurality of communication terminals that receive and reproduce stream data distributed from a root terminal.
- Each of the plurality of communication terminals is assigned an ALM (Application Layer Multicast) that sequentially transmits retransmission data of the stream data from the parent terminal to the child terminal by assigning one parent terminal and zero or more child terminals to each of the plurality of communication terminals.
- ALM Application Layer Multicast
- the integrated circuit has a round-trip delay time required for transmitting and receiving data in a section between two adjacent terminals on the ALM distribution tree, and each of the communication terminals from the root terminal to the one communication terminal A reproduction delay time determining unit that determines a reproduction delay time using the maximum value of the round trip delay times of the section, and only the reproduction delay time determined by the reproduction delay time determining unit after receiving the stream data A playback control unit that plays back with delay.
- the quality of stream data such as video and audio reproduced at each receiving terminal can be improved.
- FIG. 1 is a functional block diagram of a communication terminal according to Embodiment 1.
- FIG. 2 is a flowchart showing the operation of the communication terminal according to Embodiment 1.
- FIG. 3 is a detailed functional block diagram of the communication terminal according to Embodiment 1.
- FIG. 4 is a diagram illustrating an example of a retransmission request transmission destination (left side) and retransmission data transmission destination in the ALM distribution tree.
- FIG. 5 is a diagram showing an example of the reproduction delay time determined by each of the methods 1 to 3.
- FIG. 6 is a diagram illustrating an example of a data flow in the case of the technique 1.
- FIG. 7 is a diagram illustrating an example of a data flow in the case of the method 2.
- FIG. 1 is a functional block diagram of a communication terminal according to Embodiment 1.
- FIG. 2 is a flowchart showing the operation of the communication terminal according to Embodiment 1.
- FIG. 3 is a detailed functional block diagram of the communication terminal according to Em
- FIG. 8 is a diagram illustrating an example of a data flow in the case of Method 3.
- FIG. 9 is a diagram showing a procedure for transmitting an RTT notification message.
- FIG. 10 is a diagram illustrating an example of the RTT included in the RTT notification message.
- FIG. 11A is a diagram illustrating an example of a physical format of a magnetic disk which is a recording medium body.
- FIG. 11B is a front view, a cross-sectional view, and a diagram showing the magnetic disk of the case that holds the magnetic disk.
- FIG. 11C is a diagram showing a configuration for recording and reproducing the program on a flexible disk.
- FIG. 12 is a conventional diagram showing an example in which data loss occurs on a communication network.
- FIG. 12 is a conventional diagram showing an example in which data loss occurs on a communication network.
- FIG. 13 is a conventional diagram illustrating an example of requesting retransmission of lost data.
- FIG. 14 is a conventional diagram illustrating an example of transmitting retransmission data.
- FIG. 15 is a conventional diagram illustrating an example of a method for determining a retransmission delay time.
- FIG. 16 is a conventional diagram showing a conventional network configuration.
- FIG. 17 is a conventional diagram showing an example in which an ALM distribution tree is configured by the terminal of FIG.
- FIG. 18 is a conventional diagram for explaining the first data retransmission method.
- FIG. 19 is a conventional diagram for explaining the second data retransmission method.
- FIG. 20 is a conventional diagram for explaining the third data retransmission method.
- FIG. 21 is a conventional diagram showing an example of a retransmission processing flow in an equal delay environment.
- FIG. 22 is a conventional diagram illustrating an example of a retransmission processing flow in an unequal delay environment.
- FIG. 23 is a conventional diagram showing an example of the relationship between network delay and playback delay time.
- FIG. 1 is a functional block diagram of the communication terminal 100.
- FIG. 2 is a flowchart showing the operation of the communication terminal 100.
- the communication terminal 100 includes a reproduction delay time determination unit 1010 and a reproduction control unit 1020, as shown in FIG.
- the communication terminal 100 is one of a plurality of communication terminals (not shown in FIG. 1) that receive and reproduce stream data distributed from the root terminal.
- a plurality of communication terminals are each assigned one parent terminal and zero or more child terminals, whereby ALM (Application Layer Multicast) distribution in which retransmission data of stream data is sequentially transmitted from the parent terminal to the child terminals. Make up a tree.
- ALM Application Layer Multicast
- the playback delay time determination unit 1010 determines the playback delay time using the maximum value of the round trip delay times of each section from the root terminal to the communication terminal 100 (S11).
- the round-trip delay time is a round-trip delay time necessary for transmitting and receiving data in a section between two adjacent terminals on the ALM distribution tree, and typically corresponds to RTT or the like.
- the playback control unit 1020 plays back the stream data received from the root terminal with a delay of the playback delay time determined by the playback delay time determination unit 1010 (S12). Specifically, the playback control unit 1020 temporarily stores the stream data received from the root terminal in a buffer (not shown), and reads out and plays back from the buffer at the timing when the playback delay time has elapsed after reception.
- FIG. 3 is a detailed functional block diagram of the communication terminal 100.
- 3 includes a retransmission request transmission unit 101, a retransmission data transmission unit 201, an ALM control unit 301, a reproduction delay time determination unit 401, an RTT management unit 402, and an RTT measurement unit 501.
- Prepare. 1 corresponds to the reproduction delay time determination unit 401 in FIG. 3
- the reproduction control unit 1020 in FIG. 1 corresponds to the ALM control unit 301 in FIG.
- the ALM control unit (reproduction control unit) 301 receives stream data from the parent terminal on the ALM distribution tree, stores the received stream data in a buffer (not shown), and transmits it to the child terminal. Further, the ALM control unit 301 reproduces the stream data held in the buffer after the reproduction delay time has elapsed.
- the RTT measuring unit (round trip time measuring unit) 501 measures the RTT between the own terminal and the parent terminal.
- a method for measuring RTT is not particularly limited, and for example, an existing RTT measurement method used in RTCP (Real-time Transport Control Protocol) can be used.
- the RTT management unit (round trip delay time management unit) 402 receives an RTT notification message (round trip delay time notification) from the parent terminal, and the RTT (round trip delay time) between the own terminal and the parent terminal measured by the RTT measurement unit 501 Is sent to the child terminal.
- the RTT notification message received from the parent terminal includes the RTT of each section from the root terminal to the parent terminal on the ALM distribution tree.
- the playback delay time determination unit 401 determines the playback delay time using the RTT included in the RTT notification message received from the parent terminal by the RTT management unit 402 and the RTT measured by the RTT measurement unit 501, and performs ALM control. Notification to the unit 301. A specific method for determining the reproduction delay time will be described later.
- the retransmission request transmission unit (retransmission request unit) 101 requests the parent terminal to transmit retransmission data corresponding to the loss when a loss occurs in a part of the stream data received from the root terminal.
- the retransmission request transmission unit 101 repeatedly transmits a retransmission request until retransmission data is acquired.
- the retransmission interval at this time is an interval that is not less than the round trip delay time between the communication terminal 100 and its parent terminal and not more than the maximum value of the round trip delay times of each section from the root terminal to the own terminal. desirable.
- retransmission data transmission unit 201 In response to receiving a retransmission request from a child terminal, retransmission data transmission unit 201 acquires the data indicated in the retransmission request from the buffer of ALM control unit 301 and transmits the data to the child terminal that is the transmission source of the retransmission request. . If the data to be retransmitted does not exist in the buffer of the ALM control unit 301, the process waits until the data is received and transmits it promptly after reception.
- method 1 is a method in which the maximum value of RTT between terminals through which retransmission data to the terminal passes is used as a reproduction delay time.
- Method 2 is a method in which the maximum value in Method 1 is further multiplied by an integer to obtain a reproduction delay time.
- Method 3 is to set a value derived based on the following formulas 1 and 2 as the reproduction delay time of the terminal itself. Note that “terminal through which retransmission data to the own terminal passes” refers to all terminals upstream of the own terminal (route from the own terminal to the root terminal).
- FIG. 4 exemplifies retransmission by the parent terminal (second retransmission method), and assumes a case where data loss occurs between the terminals 20-21. In this case, the terminal 21 and the downstream terminals 23, 24, and 27 to 30 are affected. Therefore, the terminal 21 transmits a retransmission request to the terminal 20, the terminals 23 and 24 to the terminal 21, the terminals 27 and 28 to the terminal 23, and the terminals 29 and 30 to the terminal 24 (left side in FIG. 4).
- the terminals 20, 21, 23, and 24 that receive these retransmission requests are transmitting retransmission data to the terminals that transmitted the retransmission requests (right side in FIG. 4).
- the retransmission data to each terminal passes through each upstream terminal. That is, when a loss occurs in an arbitrary section of the distribution tree (pointing to “communication path between two adjacent terminals”), the retransmission data passes through all terminals downstream of the loss occurrence section. In addition, there is a possibility that the loss occurrence section is the highest section including the root terminal. In this case, the terminals through which the retransmission data passes are all terminals constituting the ALM distribution tree.
- the maximum value of RTT in each section upstream from each terminal is set as the playback delay time of each terminal.
- the reproduction delay time of the terminal 21 is 200 ms.
- the reproduction delay time of the terminal 23 is 200 ms (the RTT between the terminals 20-21).
- the reproduction delay time of the terminal 27 is 200 ms (the RTT between the terminals 20-21).
- the reproduction delay time can be set in the same manner.
- FIG. 6 shows a temporal transition of the retransmission processing performed between the terminals 20, 21, 23, and 27 when the packet p is lost between the terminals 20-21.
- packet p transmitted from terminal 20 is sent to terminal 21 at time t 1 after 100 ms, further to terminal 23 at time t 2 after 50 ms, and further to time t 3 after 50 ms.
- the terminal 27 is scheduled to be reached. However, since a loss of the packet p occurs in the section between the terminal 20 and the terminal 21, the terminals 21, 23, and 27 cannot receive the packet p even when the scheduled time comes.
- the terminal 21 transmits a retransmission request to the terminal 20 at time t 1 .
- This retransmission request reaches the terminal 20 at time t 3 after 100 ms from the transmission of the terminal 21.
- the terminal 23 transmits a retransmission request to the terminal 23 at time t 2
- the terminal 27 transmits a retransmission request to the terminal 23 at time t 3 .
- the retransmission request transmitted from the terminal 23 reaches the terminal 21 at time t 3 after 50 ms
- the retransmission request transmitted from the terminal 27 reaches the terminal 23 at time t 4 after 50 ms.
- the terminal 20 that has received the retransmission request from the terminal 21 at time t 3 immediately transmits the retransmission packet p ′ to the terminal 21.
- the retransmission packet p ′ reaches the terminal 21 at time t 5 after 100 ms from the transmission of the terminal 20.
- the terminal 21 that has received the retransmission request from the terminal 23 at time t 3 does not hold the packet p, it waits as it is. Then, the terminal 21 transmits the retransmission packet p ′ to the terminal 23 as a response to the previous retransmission request at the timing when the retransmission packet p ′ is received from the terminal 20 at time t 5 .
- the retransmission packet p ′ reaches the terminal 23 at time t 6 after 50 ms from the transmission of the terminal 21.
- the terminal 23 that has received the retransmission request from the terminal 27 at time t 4 does not hold the packet p, it waits as it is. Then, the terminal 23 transmits the retransmission packet p ′ to the terminal 27 as a response to the previous retransmission request at the timing when the retransmission packet p ′ is received from the terminal 21 at time t 6 .
- the retransmission packet p ′ reaches the terminal 27 at time t 7 after 50 ms from the transmission of the terminal 23.
- each terminal 21, 23 FIG. 6 shows that the retransmitted data arriving at 27 is in time for reproduction. Note that this is a case where data loss occurs between the terminals 20-21, which is the maximum RTT interval, but when data loss occurs in another interval (for example, the interval between terminals 21-23), retransmission is performed. Since the time required for data arrival is much shorter, the retransmission data always arrives in time for reproduction of the terminals 23 and 27 in this case.
- each terminal can receive retransmission data more reliably. More specifically, when the retransmission data itself is lost in the middle, each terminal is provided with a time margin that can be retransmitted again. For example, if retransmission data does not arrive after waiting for the reproduction delay time calculated in Method 1 after transmitting a retransmission request, it can be considered that the retransmission data has been lost in the middle, and the retransmission request can be transmitted again.
- the reproduction delay time of each terminal is set so that the retransmission packet received as a response to the second retransmission request is in time for reproduction.
- Method 2 sets the playback delay time of its own terminal to an integer multiple of the maximum value of the upstream RTT. For example, as shown in FIG. 5, the reproduction delay time of each of the terminals 21 to 34 is set to twice the maximum value of the upstream RTT (that is, the reproduction delay time in Method 1). In this case, if each of the terminals 21 to 34 continues to transmit a retransmission request at intervals of the maximum RTT of method 1, it can withstand a single loss of retransmission data.
- FIG. 7 shows a temporal transition of processing when the retransmission packet p ′ is lost. Note that detailed description of processing common to the method 1 shown in FIG.
- the retransmission packet p ′ is lost between the terminals 21-23 between the time t 5 and the time t 6 .
- the terminals 23 and 27 continue to transmit retransmission requests at intervals of 200 ms that is the maximum upstream RTT. That is, the terminal 23 transmits a second retransmission request to the terminal 21 at a time t 6 that is 200 ms after the time t 2 that is the first scheduled arrival time of the packet p. Similarly, the terminal 27 transmits a second retransmission request to the terminal 23 at time t 7 that is 200 ms after time t 3 that is the first scheduled arrival time of the packet p.
- the terminal 21 receives the second retransmission request from the terminal 23 at time t 7 and transmits the retransmission packet p ′ to the terminal 23 again. Then, the retransmission packet p ′ transmitted from the terminal 21 reaches the terminal 23 300 ms after the first scheduled arrival time t 2 . Similarly, the terminal 23 receives the second retransmission request from the terminal 27 at time t 8 and transmits the retransmission packet p ′ to the terminal 27 again. Then, the retransmission packet p ′ transmitted from the terminal 23 reaches the terminal 27 300 ms after the first scheduled arrival time t 3 .
- the retransmission packet p ′ arrives at the terminals 23 and 27 within 400 ms which is the reproduction delay time of the terminals 23 and 27. That is, the retransmission packet p ′ is in time for reproduction by the terminals 23 and 27.
- the loss of the retransmission packet p ′ occurs in a link other than the maximum RTT link (maximum RTT section), and thus the retransmission packet p ′ is earlier than the reproduction delay time.
- the retransmission packet p ′ arrives after 400 ms. Since this is just equal to the playback delay time, it is in time for playback.
- the value of x to be multiplied by the maximum RTT may be determined in consideration of the real time property of the stream data, the stability of the communication network, and the like.
- the interval at which the retransmission request is continuously transmitted is not limited to the maximum RTT, but may be any upstream RTT. For example, even if the retransmission request is continued to be transmitted at an interval of RTT with the parent terminal (RTT between terminals 21-23 in the case of terminal 23, RTT between terminals 23-27 in the case of terminal 27). Good.
- Method 2 described above uses an integral multiple of the maximum RTT as the reproduction delay time, so that even when a loss of retransmission data occurs in the maximum RTT link, it can be dealt with.
- Method 3 is to allow the number of times ⁇ n to be retransmitted to each terminal n to be set individually.
- the reproduction delay time x (n) of each terminal n may be determined using the following formula 1 or formula 2.
- the reproduction delay time of terminal n is x (n)
- the reproduction delay time of the parent terminal of terminal n is x (parent)
- the RTT between terminal n and its parent terminal is rtt (n )
- a positive integer set for each terminal n is defined as ⁇ n .
- Equation 1 and Equation 2 of Method 3 indicate that it is desired to try retransmission ⁇ n times between the terminal n and its parent terminal, and this value is individually set for each terminal n. Can be set. As a result, the number of retransmission attempts differs for each terminal.
- FIG. 8 shows the temporal transition of processing of the terminals 20, 22, 25, and 31 in the case of the method 3. Note that the terminals 22, 25, and 31 shown in FIG. 8 continue to transmit retransmission requests at intervals of the maximum RTT on the retransmission data path, that is, the terminals 22 are at 100ms intervals, and the terminals 25 and 31 are at 300ms intervals. Shall.
- the terminal 22 transmits a retransmission request to the terminal 20 at a scheduled arrival time t 11 of the packet p and a time t 13 after 100 ms. Then, as a response to the second retransmission request, the terminal 22 receives the retransmission packet p ′ from the terminal 20 at time t 15 after 200 ms after the initial scheduled arrival time t 11 .
- the terminal 25 transmits a retransmission request to the scheduled arrival time t 14 of the packet p to the terminal 22. Then, as a response to the first retransmission request, the terminal 25 receives the retransmission packet p ′ from the terminal 22 at time t 20 after 300 ms after the initial scheduled arrival time t 14 .
- the terminal 31 transmits a retransmission request to the terminal 25 at a scheduled arrival time t 15 of the packet p and a time t 21 after 300 ms. Then, the terminal 31 as a response to the second time retransmission request, at time t 23 after 400ms the original estimated time of arrival t 15, and receives a retransmission packet p 'from the terminal 25.
- each terminal It can be seen that the retransmitted packet p ′ has arrived in time for the reproduction time.
- the interval at which the retransmission request is continuously transmitted is not limited to the maximum RTT, but may be any upstream RTT.
- RTT with a parent terminal in the case of terminal 22, RTT between terminals 20-22, in the case of terminal 25, RTT between terminals 22-25, in the case of terminal 31, between terminals 25-31
- the retransmission request may continue to be transmitted at an interval of (RTT).
- each terminal acquires each RTT on the path of retransmission data and autonomously calculates the reproduction delay time of its own terminal.
- a specific terminal such as a root terminal is concentrated. And may be distributed to each terminal.
- each terminal becomes an RTT that requires only an RTT between terminals upstream from its own terminal on the ALM distribution tree.
- the terminal 20 which is the root terminal transmits an RTT notification message m1 to the terminal 21 and an RTT notification message m2 to the terminal 22, as shown in the left diagram of FIG. At this time, since the terminal 20 does not have a parent terminal, the RTT notification messages m1 and m2 that do not actually include the RTT information are transmitted.
- the terminal 21 that has received the RTT notification message m1 receives a new RTT notification message m3 including the RTT between its own terminal and the parent terminal (terminal 20), as shown in the middle diagram of FIG. 9 and FIG. , M4 are transmitted to the terminals 23 and 24.
- the RTT between the own terminal and the parent terminal is measured by the RTT measuring unit 501 in FIG.
- the terminal 22 that has received the RTT notification message m2 transmits new RTT notification messages m5 and m6 including the RTT between the own terminal and the parent terminal (terminal 20) to the terminals 25 and 26.
- Each terminal can calculate the reproduction delay time using the content of the RTT notification message received from the parent terminal and the RTT between the parent terminal measured by each terminal.
- an existing RTT measurement method such as a method used in RTCP (Real Time Transport Protocol) can be used.
- an RTT notification message that further includes the reproduction delay time determined by each terminal may be transmitted to the child terminal.
- the necessary RTT is obtained by a top-down method (method in which processing flows from upstream to downstream) as shown in FIG. 8, but each terminal connected to its own terminal
- RTT with a terminal hereinafter referred to as an adjacent terminal
- RTT with a terminal hereinafter referred to as an adjacent terminal
- each terminal measures the RTT with the parent terminal or the RTT with the adjacent terminal, and notifies the root terminal individually or with a bottom-up method (method in which processing flows from the downstream to the upstream), and the route
- the terminal may notify the RTT necessary for each terminal individually or by multicast on the distribution tree.
- other collection methods may be used.
- the playback delay time determination process described above may be executed only once when distribution of stream data is started, and the playback delay time may be fixed during the distribution of the stream data.
- the reproduction delay time determination process may be repeatedly executed at predetermined time intervals to update the reproduction delay time during stream data distribution.
- the RTT management unit 402 receives an RTT notification message at predetermined time intervals.
- the RTT measurement unit 501 measures the RTT between the own terminal and the parent terminal.
- the reproduction delay time determination unit 401 uses the RTT included in the RTT notification message and the RTT newly measured by the RTT measurement unit 501 to perform a reproduction delay time determination process. May be executed.
- the playback delay time is shortened during distribution of stream data, it is necessary to fast-forward or skip stream data already held in the buffer. Further, if the reproduction delay time becomes long during the distribution of the stream data, it is necessary to temporarily interrupt the reproduction of the stream data already held in the buffer or to perform the slow reproduction.
- the update interval of the playback delay time may be changed according to the communication network environment. For example, the update interval may be shortened when the communication environment is unstable, and the update interval may be lengthened when the communication environment is stable.
- a restriction may be placed on the update of the playback delay time according to the characteristics of the stream data. For example, in the case of stream data (for example, video conferencing) that requires a high level of real-time performance, updating is permitted only when the playback delay time is short, and stream data (for example, music) that is not allowed to be interrupted is updated. In such a case, the update may be permitted only when the reproduction delay time becomes long.
- stream data for example, video conferencing
- stream data for example, music
- Embodiment 2 Next, the configuration and operation of the communication terminal according to Embodiment 2 will be described. In addition, description of a common point with Embodiment 1 is abbreviate
- the communication terminal according to Embodiment 2 includes a loss rate management unit and a loss rate measurement unit in addition to communication terminal 100 shown in FIG. Further, a specific method for determining the reproduction delay time by the reproduction delay time determination unit 401 is different.
- the loss rate measurement unit measures the loss rate of stream data between the terminal itself and its parent terminal. Specifically, the PER (Packet Error Rate) of the received stream data may be calculated with reference to the sequence number of the TCP header.
- PER Packet Error Rate
- the loss rate management unit receives a loss rate notification including the loss rate of each section from the root terminal to the parent terminal on the ALM distribution tree from the parent terminal, and the loss rate measured by the loss rate determining unit is included in the loss rate notification. To the child terminal.
- the loss rate notification may be transmitted and received as a message different from the RTT notification message in the same manner as the RTT notification message.
- a specific processing method is common to the RTT notification message of the RTT management unit 402.
- the loss rate information may be included in the RTT notification message.
- the reproduction delay time determination unit uses the loss rate included in the loss rate notification received by the loss rate management unit and the loss rate measured by the loss rate measurement unit. To determine the playback delay time. Specifically, the playback delay time is determined using the RTT of the section where the loss rate of the stream data is the largest among the sections from the root terminal to the own terminal.
- the quality of the stream data reproduced by the ALM control unit 301 is further improved. improves.
- the present invention can be realized not only as a communication terminal and a communication method as in the first and second embodiments, but also as a program for causing the communication method computer of the first and second embodiments to execute.
- FIG. 11A to FIG. 11C are explanatory diagrams when the computer system is used by using the flexible disk FD storing the communication method of the first and second embodiments.
- FIG. 11A shows an example of a physical format of the magnetic disk MD which is a recording medium body.
- FIG. 11B shows a front view, a sectional view, and the magnetic disk MD of the case F that holds the magnetic disk MD.
- FIG. 11C shows a configuration for recording and reproducing the program on the flexible disk FD.
- the flexible disk FD includes a magnetic disk MD that is a recording medium body and a case F that holds the magnetic disk MD.
- a plurality of tracks Tr are formed concentrically from the outer periphery toward the inner periphery, and each track Tr is divided into 16 sectors Se in the angular direction. Therefore, in the flexible disk FD storing the program, a communication method as the program is recorded in an area allocated on the magnetic disk MD.
- the program when the program is recorded on the flexible disk FD, the communication method as the program is written from the computer system Cs via the flexible disk drive FDD.
- the program is read from the flexible disk FD by the flexible disk drive FDD and transferred to the computer system Cs.
- the flexible disk FD is used as the recording medium, but the same can be done using an optical disk.
- the recording medium is not limited to this, and any recording medium such as an IC card or a ROM cassette capable of recording a program can be similarly implemented.
- the constituent elements constituting the communication device may be constituted by one system LSI (Large Scale Integration).
- the system LSI is an ultra-multifunctional LSI manufactured by integrating a plurality of components on a single chip.
- the present invention can be used for video distribution using an ALM distribution tree or a remote lecture system.
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Abstract
Description
図1及び図2を参照して、本発明の実施の形態1に係る通信端末100の構成及び動作を説明する。なお、図1は、通信端末100の機能ブロック図である。図2は、通信端末100の動作を示すフローチャートである。
次に、実施の形態2に係る通信端末の構成及び動作を説明する。なお、実施の形態1との共通点の説明は省略し、相違点を中心に説明する。実施の形態2に係る通信端末は、図3に示される通信端末100に加えて、損失率管理部と、損失率測定部とを備える。また、再生遅延時間決定部401による再生遅延時間の具体的な決定方法が異なる。
また、本発明は、実施の形態1、2のように、通信端末及び通信方法として実現できるだけではなく、実施の形態1、2の通信方法コンピュータに実行させるためのプログラムとして実現してもよい。
11,12,13,14,15,16,17,20,21,22,23,24,25,26,27,28,29,30,31,32 端末
100 通信端末
101 再送要求送信部
201 再送データ送信部
301 ALM制御部
401,1010 再生遅延時間決定部
402 RTT管理部
501 RTT測定部
1020 再生制御部
Claims (12)
- ルート端末から配信されるストリームデータを受信して再生する複数の通信端末のうちの一の通信端末であって、
前記複数の通信端末は、それぞれに1つの親端末と、0以上の子端末とが割り当てられることによって、前記ストリームデータの再送データを前記親端末から前記子端末に順次送信するALM(Application Layer Multicast)配信木を構成し、
該一の通信端末は、
前記ALM配信木上の隣接する2つの端末の間の区間でデータを送受信するのに必要な往復遅延時間であって、前記ルート端末から該一の通信端末までの各区間の往復遅延時間のうちの最大値を用いて再生遅延時間を決定する再生遅延時間決定部と、
前記ルート端末から受信した前記ストリームデータを、前記再生遅延時間決定部で決定された前記再生遅延時間だけ遅延させて再生する再生制御部とを備える
通信端末。 - 前記再生遅延時間決定部は、前記往復遅延時間の最大値の整数倍を、前記再生遅延時間と決定する
請求項1に記載の通信端末。 - 該一の通信端末は、さらに、前記ルート端末から受信したストリームデータの一部に損失が生じた場合に、前記親端末に対して、当該損失に対応する再送データの送信を要求する再送要求部を備え、
前記再送要求部は、該一の通信端末とその親端末との間の往復遅延時間以上で、且つ前記往復遅延時間の最大値以下の間隔で、再送データの送信を繰り返し要求する
請求項1~3のいずれか1項に記載の通信端末。 - 該一の通信端末は、さらに、
該一の通信端末とその親端末との間の前記往復遅延時間を測定する往復遅延時間測定部と、
前記ALM配信木上の前記ルート端末から前記親端末までの1以上の前記往復遅延時間を含む往復遅延時間通知を前記親端末から受信し、前記往復遅延時間測定部で測定された前記往復遅延時間を含めて前記子端末に送信する往復遅延時間管理部とを備える
請求項1~4のいずれか1項に記載の通信端末。 - 前記往復遅延時間管理部は、所定の時間間隔毎に前記往復遅延時間通知を受信し、
前記往復遅延時間測定部は、前記往復遅延時間通知を受信する度に、該一の通信端末とその親端末との間の前記往復遅延時間を測定し、
前記再生遅延時間決定部は、前記往復遅延時間通知を受信する度に、前記往復遅延時間通知に含まれる1以上の前記往復遅延時間と、前記往復遅延時間測定部で測定された前記往復遅延時間とを用いて、前記再生遅延時間を決定する
請求項5に記載の通信端末。 - ルート端末から配信されるストリームデータを受信して再生する複数の通信端末のうちの一の通信端末であって、
前記複数の通信端末は、それぞれに1つの親端末と、0以上の子端末とが割り当てられることによって、前記ストリームデータの再送データを前記親端末から前記子端末に順次送信するALM(Application Layer Multicast)配信木を構成し、
該一の通信端末は、
前記ALM配信木上の隣接する2つの端末の間の区間でデータを送受信するのに必要な往復遅延時間であって、前記ルート端末から該一の通信端末までの各区間のうちの前記ストリームデータの損失率が最も大きい区間の前記往復遅延時間を用いて再生遅延時間を決定する再生遅延時間決定部と、
前記ストリームデータを受信してから、前記再生遅延時間決定部で決定された前記再生遅延時間だけ遅延させて再生する再生制御部とを備える
通信端末。 - 該一の通信端末は、さらに、
該一の通信端末とその親端末との間の前記損失率を測定する損失率測定部と、
前記ALM配信木上の前記ルート端末から前記親端末までの1以上の前記損失率を含む損失率通知を前記親端末から受信し、前記損失率定部で測定された前記損失率を含めて前記子端末に送信する損失率管理部とを備える
請求項7に記載の通信端末。 - 前記損失率管理部は、所定の時間間隔毎に前記損失率通知を受信し、
前記損失率測定部は、前記損失率通知を受信する度に、該一の通信端末とその親端末との間の前記損失率を測定し、
前記再生遅延時間決定部は、前記損失率通知を受信する度に、前記損失率通知に含まれる1以上の前記損失率と、前記損失率測定部で測定された前記損失率とを用いて、前記再生遅延時間を決定する
請求項8に記載の通信端末。 - ルート端末から配信されるストリームデータを受信して再生する複数の通信端末のうちの一の通信端末により実行される通信方法であって、
前記複数の通信端末は、それぞれに1つの親端末と、0以上の子端末とが割り当てられることによって、前記ストリームデータの再送データを前記親端末から前記子端末に順次送信するALM(Application Layer Multicast)配信木を構成し、
該通信方法は、
前記ALM配信木上の隣接する2つの端末の間の区間でデータを送受信するのに必要な往復遅延時間であって、前記ルート端末から該一の通信端末までの各区間の往復遅延時間のうちの最大値を用いて再生遅延時間を決定する再生遅延時間決定ステップと、
前記ルート端末から受信した前記ストリームデータを、前記再生遅延時間決定ステップで決定された前記再生遅延時間だけ遅延させて再生する再生制御ステップとを含む
通信方法。 - ルート端末から配信されるストリームデータを受信して再生する複数の通信端末のうちの一の通信端末により実行されるプログラムであって、
前記複数の通信端末は、それぞれに1つの親端末と、0以上の子端末とが割り当てられることによって、前記ストリームデータの再送データを前記親端末から前記子端末に順次送信するALM(Application Layer Multicast)配信木を構成し、
該プログラムは、
前記ALM配信木上の隣接する2つの端末の間の区間でデータを送受信するのに必要な往復遅延時間であって、前記ルート端末から該一の通信端末までの各区間の往復遅延時間のうちの最大値を用いて再生遅延時間を決定する再生遅延時間決定ステップと、
前記ルート端末から受信した前記ストリームデータを、前記再生遅延時間決定ステップで決定された前記再生遅延時間だけ遅延させて再生する再生制御ステップとを、該一の通信端末に実行させる
プログラム。 - ルート端末から配信されるストリームデータを受信して再生する複数の通信端末のうちの一の通信端末に搭載される集積回路であって、
前記複数の通信端末は、それぞれに1つの親端末と、0以上の子端末とが割り当てられることによって、前記ストリームデータの再送データを前記親端末から前記子端末に順次送信するALM(Application Layer Multicast)配信木を構成し、
該集積回路は、
前記ALM配信木上の隣接する2つの端末の間の区間でデータを送受信するのに必要な往復遅延時間であって、前記ルート端末から該一の通信端末までの各区間の往復遅延時間のうちの最大値を用いて再生遅延時間を決定する再生遅延時間決定部と、
前記ストリームデータを受信してから、前記再生遅延時間決定部で決定された前記再生遅延時間だけ遅延させて再生する再生制御部とを備える
集積回路。
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CN102714626B (zh) | 2016-04-06 |
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