CN102752184A - Data communication system for real-time multicast service and method thereof - Google Patents

Abstract

The invention provides a data communication system for real-time multicast service, which comprises a data transmitting end, a parameter setting unit and a data receiving end, wherein the data transmitting end comprises a data grouping unit, a forward error correcting and coding unit, a transmitting unit and a retransmission processing unit; and the data receiving end comprises a receiving unit, a forward error correcting and decoding unit, a data analysis unit and a retransmission request unit. The invention also provides a data communication method for the real-time multicast service, which comprises the following steps of: self-adaptively setting a general error correction structure optimal parameter; transmitting a data package for the first time and processing a retransmission request message by the transmitting end; and in a processing step, receiving the data package by the receiving end. According to the data communication system and method for the real-time multicast service, the general error correction structure optimal parameter is set in a self-adaptive way, limited bandwidth resource in the communication network can be effectively utilized, and an end-to-end target reliability requirement of the real-time service under the strict time delay limiting condition can be satisfied.

Description

The data communication system and the method thereof that are used for real-time multicast service

Technical field:

The present invention relates to the real-time multi-casting communication field in communication network, propose a kind ofly to be used for the data communication system of real-time multicast service and to guarantee the reliability method end to end of real-time multicast service.

Background technology:

Multicast is one of 3 kinds of basic destination address types of IPv6 packet, and multicast is some communication to multiple spot, and IPv6 does not adopt the multicast term among the IPv4, but regards broadcasting a specific example of multicast as.

Ip multicast (also claiming multi-address broadcast or multicast) technology is that one or more main frame of a kind of permission (multicast source) sends the TCP/IP network technology of single packet to multiple host (once, the while).Multicast is one of effective ways of saving the network bandwidth as some communication to multiple spot.In the application of network audio/video broadcasting, in the time need the signal of a node being sent to a plurality of node, no matter be to adopt repetition point-to-point communication mode, still adopt broadcast mode, all can the serious waste network bandwidth, have only multicast to be only best choice.Multicast can make one or more multicast sources only send to specific multi-broadcast group to packet, and has only the main frame that adds this multi-broadcast group just can receive packet.At present, the ip multicast technology is widely used in aspects such as network audio/video broadcasting, AOD/VOD, the network teleconference, multimedia remote education, " push " technology (like stock market etc.) and reality-virtualizing game.

Some application has such requirement: some processes that are distributed in everywhere need be with the mode collaborative work of group, and the process in the group will be sent message to other all members usually.Promptly there is so a kind of method to send message,, compares but very little with whole network size though the number of members of these groups is a lot to some groups that clearly define.Send message for such group and be called the broadcasting of multiple spot point, be called for short multicast.

Along with the high speed development of communication network, real time business has attracted increasing attention.IP-based multicast system adopts traditional real-time transport protocol (rtp) to provide about information such as the receiving terminal and the qualities of reception usually.Yet traditional RTP does not provide any mechanism to guarantee the operation quality requirement (QoS) of real-time multicast service.Yet because the special QoS demand of real time business and the diversity and the complexity of existing communication net environment, traditional procotol has satisfied not the QoS demand of real time business.For example: Traditional TCP protocol is excessive owing to postponing, and can't satisfy the strict delay requirement of real time business; And udp protocol is not owing to provide any mechanism for correcting errors, and can't satisfy the reliability requirement of real time business.

At moving communicating field, some relevant international organizations have proposed special preliminary solution to the real-time multimedia multicast service.For example, " broadcast multi-broadcasting " draft agreement of " multimedia broadcast multicast " draft agreement of 3GPP tissue proposition and the proposition of 3GPP2 tissue.These two schemes all are based on the method for pure forward error correction coding (FEC).In field of Internet communication, the consensus standard that proposes at present is based on the pure FEC or the method for request retransmission (ARQ) automatically mostly, for example the method that all is based on ARQ adopted of the consensus standards such as RTP/AVPF that define of the NORM of RFC3940 definition and RFC4585.

For real-time multicast service, owing to have strict time delay restriction, the bigger occasion of link time-delay then can't be used based on the mechanism that retransmits in the multicast scene, and the error correction scheme of this moment can only be selected the method for FEC; In the less occasion of link time-delay, then can use based on the mechanism that retransmits, in this case, then there is numerous error correction methods available, like ARQ, methods such as I class HARQ and II class HARQ.Existing research shows: in multi-broadcast group under the less situation of number of users, because of not needing coding-decoding operation, thereby have the simple advantage of realization based on the method for ARQ, and efficient is close with the HARQ method, thereby can be used as preferred option; When number of users more for a long time, then the method based on HARQ strengthens in the advantage aspect the throughput performance gradually, can be used as method for optimizing and substitutes the method based on ARQ; But when number of users arrived to a certain degree more, then the method based on FEC became optimum method.

Can know based on above introduction, in order to reach the qos requirement of the most effectively utilizing telecommunication network resource to satisfy real-time multicast service, must adopt a kind of method that possesses adaptation function: this method can be selected the most effectively error correction method automatically according to the variation of multicast scene.Present real-time multicast field in communication network; Still there is not to select automatically according to current multicast scene situation automatically the solution of optimum error correction method; In order to the reliability requirement under the strict time delay that satisfies real-time multicast service, the throughput performance of while maximization network.

Summary of the invention:

The technical problem that the present invention will solve is the changing condition according to real-time multicast system scene in the communication network; A kind of data communication system and method thereof that is used for real-time multicast service is provided; The most effectively to utilize the mode of finite bandwidth resource in the communication network, satisfy the reliability requirement under the strict time delay restriction of real time business.

For solving the problems of the technologies described above, the present invention proposes a kind of data communication system that is used for real-time multicast service: comprise data sending terminal, parameter set unit, data receiver; Wherein, said data sending terminal comprises packet unit, forward error correction coding unit, transmitting element, retransmission process unit; Said data receiver comprises receiving element, decoding FEC unit, data parsing unit, repeat requests unit;

Said parameter set unit is used for the present situation according to real-time multicast system, general error correction structural parameters is set, and is sent to packet unit, transmitting element, retransmission process unit, receiving element, repeat requests unit respectively;

In data sending terminal,

Said packet unit is used for the general error correction structural parameters that are provided with according to parameter set unit, and the real time business data flow is divided into groups and is packaged into packet;

Said forward error correction coding unit is used for packet grouping of cells packet is carried out encoding operation, produces the redundant data packets that general error correction structural parameters are ascertained the number;

Said transmitting element is used for according to general error correction structural parameters said packet data package being sent to data receiver;

Said retransmission process unit is used to handle the request retransmission information of obtaining from receiving terminal, judges whether to produce new redundant data packets according to general error correction structural parameters and lays equal stress on and newly send to data receiver;

In data receiver,

Said receiving element is used for receiving the packet data package that data sending terminal transmits according to general error correction structural parameters, and sends to the decoding FEC unit;

Said decoding FEC unit is used to accomplish the decode operation of packet data package, when decoding successfully, then decoded information packet is sent to the data parsing unit; When the decoding failure, then send failure information to the repeat requests unit;

Said data parsing unit is used to resolve decoded information packet, and recovers original real time business data flow;

Said repeat requests unit is used for when receiving the failure information of decoding FEC unit, judges whether to send re-transmission request message according to general error correction structural parameters and gives data sending terminal.

Further, the data communication system that is used for real-time multicast service of the present invention, general error correction structural parameters comprise the number of the redundant data packets that length, the quantity of redundant data packets, maximum retransmit wheel number, the re-transmission of information packet is stylish.

The present invention also provides a kind of data communications method that is used for real-time multicast service, comprises the steps:

Steps A according to the present situation of real-time multicast system, is provided with general error correction structural parameters, and sends general error correction structural parameters to data sending terminal, data receiver;

Step B, data sending terminal in chronological sequence divides into groups to pack to operate to the real time business data flow in proper order, then every group of packet is carried out encoding operation, forms several redundant data packets;

Step C, the present situation of data sending terminal monitoring multicast system when situation changes, then returns steps A and resets general error correction structural parameters; When situation does not change, then get into next step;

Step D, the general error correction structural parameters transfer data packets that data sending terminal notification data receiving terminal adopts steps A to be provided with after the feedback acknowledgment message that receives data receiver, is sent redundant data packets to data receiver;

The general error correction structural parameters that step e, data receiver adopt steps A to be provided with receive redundant data packets, and have judged whether that packet drop takes place:

E-1, when there not being packet drop to take place, data receiver carries out decode operation to the redundant data packets that receives, and resolves to recover original real time business data flow;

E-2, when packet drop took place, data receiver judged whether to allow to send repeat requests to data sending terminal according to general error correction structural parameters;

When the result when not allowing, data receiver is decoded to the packet that has received and decoded information packet is passed to the upper strata;

When the result was permission, data receiver was given data sending terminal with the request repeat message feedback;

Step F, data sending terminal receive the request repeat message of data receiver, and call general error correction structural parameters and judge whether to allow to the data receiver data retransmission;

When the result when not allowing, end operation then;

When the result was permission, data sending terminal formed new redundant data packets through encoding operation, and adopted the mode of multicast to send new redundant data packets to data receiver, returned step e.

Further, the data communications method that is used for real-time multicast service of the present invention, general error correction structural parameters comprise length, the redundant data packets of information packet quantity, maximum retransmit wheel number, retransmit the number of stylish redundant data packets.

Further; The data communications method that is used for real-time multicast service of the present invention, described in the steps A in real time the present situation of multicast system comprise that packet loss, link round trip delay time, the packet data package of the number of users in the multicast system, every link on average send blanking time.

The present invention adopts technique scheme to have following beneficial effect:

The all functions module of general error correction structure is distributed in terminal equipment (that is: transmitting terminal and receiving terminal) and accomplishes, and need not do any transformation to the intermediate link of communication system;

The performance of general error correction structure is confirmed by the parameter of its setting.Through adaptive method, can change the parameter of this general error correction structure arbitrarily, finally reach ability self adaptation change of external conditions and the purpose of optimization of system performance;

The actual process of transmitting terminal and receiving terminal all is to move around the parameter that general error correction structure is set.Parameter changes, and then corresponding variation can take place processing procedure, reaches the actual motion effect purpose consistent with the target expected performance with this.

The present invention provides the professional system and method for transmission real-time multimedia in a kind of suitable communication system.Change the parameters optimization that a kind of general error correction structure is set through adaptive environment; Not only can satisfy the target reliabilities requirement of real-time multimedia business under strict time delay restrictive condition; And can reach the purpose of efficiency optimizationization, thereby the bandwidth resources in the effectively saving system.

Description of drawings:

Fig. 1 is a system construction drawing of the present invention;

Fig. 2 is the general error correction structure chart under the strict time delay restriction;

Fig. 3 is the general error correction structural parameters of adaptive optimization flow charts;

Fig. 4 is the first information packet process chart of transmitting terminal;

Fig. 5 is that transmitting terminal is handled the request repeat message flow chart;

Fig. 6 is that receiving terminal receives the processing data packets flow chart.

Embodiment:

As shown in Figure 1, data communication system of the present invention comprises data sending terminal, parameter set unit, data receiver; Wherein, data sending terminal comprises packet unit, forward error correction coding unit, transmitting element, retransmission process unit; Data receiver comprises receiving element, decoding FEC unit, data parsing unit, repeat requests unit.

Wherein parameter set unit is used for the present situation according to real-time multicast system, general error correction structural parameters is set, and is sent to packet unit, transmitting element, retransmission process unit, receiving element, repeat requests unit respectively.

Wherein, transmitting terminal will be accomplished following function:

1: the function that the real time business data flow is divided into groups to pack;

2: the function of packet data package being accomplished forward error correction coding;

3: the function of handling request repeat message.

Receiving terminal will be accomplished following function:

1: when receiving the enough packet of grouping mesopodium, packet data package is carried out the function of decoding FEC;

2: according to circumstances construct suitable request repeat message, send the function of transmitting terminal to

3: the resolving information packet, extract the real time business data message, recover the function of original real time business data flow.

Parameter set unit is accomplished following function: according to the present situation of real-time multicast system in the communication network, the optimized parameter of general error correction structure is set, makes it to use optimum error correction method to operate in optimum state.Through optimized parameter is set, transmitting terminal with receive using optimized parameter to accomplish the function of above-mentioned definition, reach the most effectively to utilize Internet resources to satisfy the purpose of the reliability under the strict time delay restrictive condition of real-time multicast service with this.

First process data packet of transmitting terminal is accomplished the grouping packing function to the real time business data flow; And produce the redundant data packets of the some of general error correction structural parameters definition, in first process, send to all receiving terminals of multi-broadcast group in the lump through the mode of multicast.

Transmitting terminal is handled the process of request repeat message and will be handled the request repeat message of all receiving terminals, and this process will judge whether according to the parameter of universal architecture setting to send redundant data packets, and send what redundant data packets.

The processing procedure of receiving terminal reception packet will be accomplished the decoding FEC function of packet data package, be responsible for from information packet, parsing the real time business data message, recover original business data flow.If decoding failure, receiving terminal also need to judge whether to construct request repeat message according to the delay requirement of real time business, the request transmitting terminal is retransmitted the redundant data packets of some, in order to the information packet of recovering to lose.

As shown in Figure 1, in data sending terminal, the packet unit is used for the general error correction structural parameters that are provided with according to parameter set unit, and the real time business data flow is divided into groups and is packaged into packet; The forward error correction coding unit is used for packet grouping of cells packet is carried out encoding operation, produces the redundant data packets that general error correction structural parameters are ascertained the number; Transmitting element is used for according to general error correction structural parameters said packet data package being sent to data receiver; The retransmission process unit is used to handle the request retransmission information of obtaining from receiving terminal, judges whether to produce new redundant data packets according to general error correction structural parameters and lays equal stress on and newly send to data receiver.

In data receiver, receiving element is used for receiving the packet data package that data sending terminal transmits according to general error correction structural parameters, and sends to the decoding FEC unit; The decoding FEC unit is used to accomplish the decode operation of packet data package, when decoding successfully, then decoded information packet is sent to the data parsing unit; When the decoding failure, then send failure information to the repeat requests unit; The data parsing unit is used to resolve decoded information packet, and recovers original real time business data flow; The repeat requests unit is used for when receiving the failure information of decoding FEC unit, judges whether to send re-transmission request message according to general error correction structural parameters and gives data sending terminal.

System configuration handling process of the present invention is as shown in Figure 2, and wherein, transmitting terminal is responsible for the real time business data flow is packaged into packet, and concrete encapsulation requires to confirm according to the parameter of general error correction structure; Be responsible for packet data package is carried out encoding operation through forward error correction coding, produce the redundant data packets that structural parameters ascertained the number; Then be responsible for handling the request retransmission message that gets access to from receiving terminal through retransmission process; Judge whether that according to structural parameters needs produce new redundant data packets and retransmit to each receiving terminal then; If desired; Then be the new redundant data packets that the grouping of request retransmission produces some, the mode through multicast retransmits to all receiving terminals.

Receiving terminal is accomplished the decode operation of packet data package through decoding FEC; According to the forward error correction scheme that structure adopted; Receive the packet data package of some when receiving terminal after, this module can recover all information packet in this grouping through decode operation; If the packet data package number that receives is not enough, then decoding failure.When operating in the decoding failure, repeat requests has an effect; If decoding failure; To judge whether also to allow retransmission processes to take place according to the delay requirement of real time business and the round trip delay time situation of link, and, then construct suitable re-transmission request message and send to transmitting terminal if allow; The redundant data packets of request repeat some is in order to the information packet of recovering to lose in certain grouping.The resolving information packet is accomplished the parsing work to all information packet that in time receive, and through the content of resolving information data, through operations such as reorganization, recovers original real time business data flow.

Concrete function of the present invention realizes depending on the setting of its parameter, for the ease of describing other handling processes of the present invention, and the symbol of four groups of parameters using in the general error correction structural parameters of definition below:

Table 1: the parameter-definition of general error correction structure

Secondly, in order to realize the adaptive optimization setting of parameter, this method must be estimated throughput performance, reliability performance and the delay performance when in current multicast scene, using this method.For this reason, will use the parameter sets of the current multicast scene of symbol " S " expression below, wherein comprise relevant informations such as current Link State, multi-broadcast group size and real time business data rate.In conjunction with above four types of parameters of definition, can estimate in current multicast scene throughput performance, reliability performance and delay performance when using designated parameter through proper functions.Provide the definition of these three functions below, as shown in table 2:

Table 2: the function definition that the present invention uses

Rely on the parameter of general error correction structure, the overall operation of multicast system will be made up of following four processes in real time: the general error correction structural parameters of adaptive optimization process; The transmitting terminal information data packet procedures of running initially; Transmitting terminal handles request repeat message and receiving terminal receives processing data packets.These four processes are the relations that intercouple, and through cooperatively interacting, and reach the whole actual motion effect purpose consistent with Expected Results.In conjunction with the definition of above-mentioned parameter and function, be described in detail respectively in the face of four processing procedures of the present invention down.

As shown in Figure 3, be multicast system adaptive optimization parameter setting up procedure, details are as follows for its concrete steps:

A1: the employed parameter of this method of initialization, i.e. K, N _p, N _MaxWith

All transmitting terminals in the multicast scene and receiving terminal will use these parameter operations.In the method, the critical process of system's operation is made up of following processes A2, A3 and A4;

A2: the information of all relevant current operations in the transmitting terminal gathering system, so that search is applicable to the parameters optimization of current scene.The packet loss, link round trip delay time, the packet package packet that mainly comprise the number of users in the multicast scene, every link on average send information such as blanking time;

A3: according to current system information, transmitting terminal is with the run search program, and search is applicable to the best parameter of current scene.Its optimization aim is set to satisfy at the same time under the situation of target delay requirement and reliability requirement, makes the throughput-maximized of system.Utilize three functions of above-mentioned definition, this optimization problem can be represented as follows:

Maximization

Satisfy condition:

satisfies the target reliabilities requirement

satisfies strict target delay requirement

Through solving above-mentioned optimization problem, can obtain best parameter K, N immediately _p, N _MaxWith

A4: after transmitting terminal obtains parameters optimization, use control messages that the most optimized parameter is delivered to all receiving terminals, notice prepares to adopt the parameters optimization transfer data packets; Have only after transmitting terminal receives the feedback acknowledgment message of all receiving terminals, just begin to adopt the parameters optimization transfer data packets, receiving terminal also will adopt parameters optimization to receive packet;

A5: transmitting terminal can be through being provided with the mode of timer or regular sensed system parameter, and whether situation such as monitoring link circuit condition or multicast scene variation has taken place.If do not change, system then still uses parameter current to continue operation; If variation has taken place, repeating step A2-A4 then.

As shown in Figure 4, be the first information data packet procedures of transmitting terminal, details are as follows for its concrete steps:

B1: real time business data flow in chronological sequence order gets into transmitting terminal, sends data flow is deposited in the fifo queue.

B2: transmitting terminal by the time order and function that the gets into packing operation of dividing into groups in proper order, that is, is packaged into equal-sized information packet with data flow to data flow, and to these packets line number that divides into groups to go forward side by side, wherein every group contains K information packet then.

B3: transmitting terminal in chronological sequence order carries out encoding operation to every group of information packet successively, produces N _pIndividual redundancy information, the encryption algorithm of employing are the system-kill sign indicating number, and Reed-Solomon sign indicating number or Raptor sign indicating number etc. are typically arranged; Notice that this method can adopt any deletion error correcting code to realize.

B4: transmitting terminal is successively with every group of K information packet and corresponding N _pIndividual redundancy information sends to all receiving terminals in the multi-broadcast group.

As shown in Figure 5, handle the request repeat message process for transmitting terminal, details are as follows for its concrete steps:

D1: transmitting terminal receives the request repeat message of certain receiving terminal, through resolving message content, can know this receiving terminal request repeat r redundancy information at least, is used to recover the information packet that its designated packet is lost;

D2: transmitting terminal inquiry is to the re-transmission record of this grouping, can know the wheel number that has retransmitted till the current time, representes with symbol w here;

D3: transmitting terminal has judged whether to surpass the maximum retransmit wheel number restriction of regulation, if do not surpass restriction, then expression allows transmitting terminal to retransmit redundant data packets, promptly carries out D4; If surpassed restriction, process ends then;

D4: to the grouping of this request repeat message appointment, transmitting terminal query history record, obtain the redundant data packets number that retransmitted in the epicycle retransmission processes, be designated as m here;

D5: transmitting terminal judges that whether m is less than R (w+1) r, if then carry out D6; Otherwise, process ends;

D6: transmitting terminal is through encoding operation, for this divides into groups to produce R (w+1) r-m new redundant data packets;

D7: through adopting the mode of multicast, transmitting terminal all users in multi-broadcast group send the whole redundant data packets that generate in the D6 process.

D2-D3 and D4-D5 process can wholely be exchanged in said process.

As shown in Figure 6, for receiving terminal receives the processing data packets process, details are as follows for its concrete steps:

C1: after receiving terminal receives packet, according to its sequence number of being with judge that which belongs to divides into groups, and is cached to it in corresponding packet buffering area then;

C2: receiving terminal judges whether the number of data packets in this packet buffer enough can carry out decode operation; If of course, then carry out C3; If could would carry out C4;

C3: receiving terminal is carried out decode operation to the packet data package in the buffering area, solves K original information data bag in this grouping;

C4: receiving terminal judges whether that the situation of packet loss takes place, and determination methods can adopt methods such as bag sequence number detection method or timer expiry detection method, if there is packet drop to take place, then carries out C5; Otherwise the reception handling process to this packet finishes; The execution sequence of noting C4 and C2 can exchange;

C5: according to the packet situation that receives in the packet data package buffering area, receiving terminal judges whether and need send request repeat information to transmitting terminal that the request transmitting terminal is retransmitted a certain amount of redundancy information, is used for recovering the packet that this grouping is lost;

C6: according to the strict delay requirement of real-time multimedia service application, receiving terminal judges whether also to allow to retransmit and takes place, if do not allow, then carries out C7; If allow, then carry out C9.The execution sequence of noting C6 and C5 can exchange;

C7: receiving terminal is delivered to the upper strata with all information packet that receive in the packet buffer or decoding obtains;

C8: receiving terminal go out clearly the retransmission timer that is provided with of promising this packet buffer; The execution sequence of noting C8 and C7 can exchange;

C9: receiving terminal is according to the packet situation that receives in this packet buffer, and structure includes the minimal amount of request repeat redundant data packets to the request repeat message of this grouping, and the mode through multicast or clean culture feeds back to transmitting terminal then;

C10: receiving terminal is provided with retransmission timer, waits for that transmitting terminal retransmits required redundancy information.If this timer expiry, transmitting terminal then repeat C2-C10.

Do further detailed description in the face of the majorized function that relates among the present invention down, certain that notes that this group function is based on pair set " S " specifically defines, and the perhaps modification of suitable simplification based on these functions can reach approximate performance.

Appendix 1: relevant mathematical definition

In order to simplify description, this appendix provides and function and describes the relevant mathematical formulae and the definition of symbol.At first, the employed parameter in the definition set " S ", the parameter sets of the current multicast scene of " S " expression wherein comprises relevant informations such as current Link State, multi-broadcast group size and real time business data rate.As shown in the table.

Table 3: all parameter-definitions that comprised in the set " S "

Secondly, calculate the packet loss and the maximum round-trip delay of the worst link, that is:

P _e(j _max)＝max(P _e(1)，P _e(2)，...，P _e(N _recv))

RTT _max＝max(RTT(1)，RTT(2)，...，RTT(N _recv))

Then, (m, n p) calculate like lower probability: to any receiving terminal, be under the situation of P at its link packet drop rate, transmitting terminal sends m packet to defined function C, and this receiving terminal receives the probability of n packet, that is:

$C(m,n,p)=\left(\begin{array}{c}m\\ n\end{array}\right){(1-p)}^n{\left(p\right)}^{m-n}$

Wherein is together following.

Then, the average packet loss ratio

of definition multicast system is:

$\stackrel{\‾}{P_e}=\frac{\underset{i=1}{\overset{N_{\mathrm{recv}}}{\mathrm{\Σ}}}{P}_e\left(j\right)}{N_{\mathrm{recv}}}$

At last, the function of two parameter sizes of comparison of definition is following:

$f_{\mathrm{cmr}}(x1,x2)=\left\{\begin{array}{c}0,x1=x2\\ 1,x1>x2\end{array}\right.$

Appendix 2: estimation maximum delay function:

According to the RTT that obtains _Max, maximum end-to-end delay will be estimated by following formula:

$F_D(K,N_p,N_{\max },\stackrel{\mathrm{\ρ}}{R},s)=(\frac{1}{2}+N_{\max })\·{\mathrm{RTT}}_{\max }+(K+N_p)\·T_s$

Appendix 3: the function of estimation reliability performance:

At first, the parameter K and the N of given embodiment _p, it is following to define two groups of functions:

$P^{=m}=C(K+N_p,K-m,\stackrel{\‾}{P_e})$

$P^{<m}=\underset{i=0}{\overset{N_p+m-1}{\mathrm{\&Sigma;}}}C(K+N_p,K+N_p-i,\stackrel{\&OverBar;}{P_e})$

Secondly, on the basis of definition, definition is to three meta-function P of j receiving terminal in front _Req(m, c, j) as follows:

$P_{\mathrm{req}}(m,c,j)=C(K+N_p,K-c,P_e\left(j\right))\underset{h=f_{\mathrm{cmr}}(m,c)}{\overset{N_{\mathrm{recv}}-1}{\mathrm{\&Sigma;}}}\left(\begin{array}{c}{N}_{\mathrm{recv}}-1\\ h\end{array}\right){\left(P^{=m}\right)}^h{\left(P^{<m}\right)}^{N_{\mathrm{recv}}-h-1}$

At last, use the function of front definition, adopt the final packet loss performance of j receiving terminal of computes:

$F_R^j(K,N_p,N_{\max },\stackrel{\mathrm{\&rho;}}{R},S)=\frac{1}{K}\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}\underset{b=\max (N_p+1,i)}{\overset{N_p+i}{\mathrm{\&Sigma;}}}\underset{m=b-N_p}{\overset{K}{\mathrm{\&Sigma;}}}i\&CenterDot;\frac{\left(\begin{array}{c}K\\ i\end{array}\right)\left(\begin{array}{c}{N}_p\\ b-i\end{array}\right)}{\left(\begin{array}{c}K+N_p\\ b\end{array}\right)}{P}_{\mathrm{req}}(m,b-N_p,j)P_f(b,m,j,N_{\max })$

Wherein: 1≤j≤N _Recv

In this formula, function P _f(b, m, j, N _Max) value adopt following two step alternative manners to calculate:

The first step is by following formula initialization P _fThe value of (b, m, j, 1);

$P_f(b,m,j,1)=\underset{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HDA0000056267210000041.png"\; state="\{\{state\}\}">r</figure-callout>}}^1=0}{\overset{r_{\max }^1}{\mathrm{\&Sigma;}}}\left(C(R\left(1\right)\&CenterDot;m,{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HDA0000056267210000041.png"\; state="\{\{state\}\}">r</figure-callout>}}^1,P_e\left(j\right))\right)$

Wherein, ${\mathrm{<figure-callout\; id="1"\; label="r\; Max"\; filenames="HDA0000056267210000041.png"\; state="\{\{state\}\}">r</figure-callout>}}_{\mathrm{Max}}^{}=b-N_p-1;$

In second step, calculate P by following iterative formula _f(b, m, j, N _Max) value:

$P_f(b,m,j,w)=P_f(b,m,j,w-1)\left(\underset{r^w=0}{\overset{r_{\max }^w}{\mathrm{\&Sigma;}}}C(R\left(w\right)\&CenterDot;\max (0,b-N_p-\underset{q=1}{\overset{w-1}{\mathrm{\&Sigma;}}}{r}^q,r^w,P_e\left(j\right))\right)$

Wherein,

And 1＜w≤N _Max

Appendix 4: the function of estimated throughput performance:

At first, use the multicast system average packet loss ratio of definition, it is following to define two groups of functions:

$P_{\mathrm{lost}}^{=i}\left(m\right)=C(m,m-i,\stackrel{\&OverBar;}{P_e})$

$P_{\mathrm{lost}}^{<i}\left(m\right)=\underset{n=0}{\overset{i-1}{\mathrm{\&Sigma;}}}C(m,m-n,\stackrel{\&OverBar;}{P_e})$

According to the packet loss performance of all receiving terminals that estimate in the appendix 3, then the throughput performance of system can be by computes:

$F_T(K,N_p,N_{\max },\stackrel{\mathrm{\&rho;}}{R},S)=\frac{1-\frac{1}{N_{\mathrm{recv}}}\underset{j=1}{\overset{N_{\mathrm{recv}}}{\mathrm{\&Sigma;}}}{F}_R^j(K,N_p,N_{\max },\stackrel{\mathrm{\&rho;}}{R},S)}{1+\frac{N_p}{K}+\frac{1}{K}\underset{w=1}{\overset{N_{\max }}{\mathrm{\&Sigma;}}}\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}i\&CenterDot;R\left(w\right)\&CenterDot;P_{\max }^{=i}\left(w\right)}$

Wherein the computational methods of

are divided into following two kinds of situation:

● situation 1:w=1

$P_{\max }^{=i}\left(1\right)=\underset{h=1}{\overset{N_{\mathrm{recv}}}{\mathrm{\&Sigma;}}}\left(\begin{array}{c}{N}_{\mathrm{recv}}\\ h\end{array}\right){\left(P^{=i}\right)}^h{\left(P^{<i}\right)}^{N_{\mathrm{recv}}-h},1\&le;m\&le;k$

● situation 2:1＜w≤N _Max

$P_{\max }^{=i}\left(w\right)=\underset{m=i}{\overset{k}{\mathrm{\&Sigma;}}}\underset{g=1}{\overset{N_{\mathrm{recv}}}{\mathrm{\&Sigma;}}}{P}_{\mathrm{req},\max }(m,g,w-1).$

$\left(\underset{h=1}{\overset{g}{\mathrm{\&Sigma;}}}\left(\begin{array}{c}g\\ h\end{array}\right){\left(P_{\mathrm{lost}}^{=(R(w-1)-1)\&CenterDot;m+i}(R(w-1)\&CenterDot;m)\right)}^h{\left(P_{\mathrm{lost}}^{<(R(w-1)-1)\&CenterDot;m+i}(R(w-1)\&CenterDot;m)\right)}^{g-h}\right)$

In situation 2, function P _{Req, max}(two step iterative process below value w) adopts are calculated for m, g:

The first step: by following formula initialization P _{Req, max}(m, g, w) value under the w=1 situation

$P_{\mathrm{req},\max }(i,h,1)=\left(\begin{array}{c}{N}_{\mathrm{recv}}\\ h\end{array}\right){\left(P^{=m}\right)}^h{\left(P^{<m}\right)}^{N_{\mathrm{recv}}-h}$

Wherein: 1≤i≤k; 1≤h≤N _Recv

Second step: calculate by following iterative formula, can obtain P _{Req, max}(m, g is w) at 1＜w≤N _MaxValue under the situation:

$P_{\mathrm{req},\max }(i,h,w)=\underset{m=i}{\overset{k}{\mathrm{\&Sigma;}}}\underset{g=h}{\overset{N_{\mathrm{recv}}}{\mathrm{\&Sigma;}}}{P}_{\mathrm{req},\max }(m,g,w-1).$

$\left(\begin{array}{c}g\\ h\end{array}\right){\left(P_{\mathrm{lost}}^{=(R(w-1)-1)\&CenterDot;m+i}(R(w-1)\&CenterDot;m)\right)}^h{\left(P_{\mathrm{lost}}^{<(R(w-1)-1)\&CenterDot;m+i}(R(w-1)\&CenterDot;m)\right)}^{g-h}$

In sum, for effectively to utilize the mode of bandwidth resources limited in the communication network, satisfy the reliability of real-time multicast service, the present invention proposes in a kind of assurance communication network in real time multicast service method for ensuring reliability end to end.Can know by above-mentioned embodiment; This method only needs that transmitting terminal and receiving terminal are carried out suitable transformation and just can realize; And implementation is simple flexibly, as the mode that adopts software or hardware upgrade all can, need not existing communication network or system are done any transformation.Thereby the present invention has and realizes the advantage simple and convenient, that cost is cheap, is highly susceptible to applying.

Claims (5)

1. a data communication system that is used for real-time multicast service is characterized in that: comprise data sending terminal, parameter set unit, data receiver; Wherein, said data sending terminal comprises packet unit, forward error correction coding unit, transmitting element, retransmission process unit; Said data receiver comprises receiving element, decoding FEC unit, data parsing unit, repeat requests unit;

Said parameter set unit is used for the present situation according to real-time multicast system, general error correction structural parameters is set, and is sent to packet unit, transmitting element, retransmission process unit, receiving element, repeat requests unit respectively;

In data sending terminal,

Said packet unit is used for the general error correction structural parameters that are provided with according to parameter set unit, and the real time business data flow is divided into groups and is packaged into packet;

Said forward error correction coding unit is used for packet grouping of cells packet is carried out encoding operation, produces the redundant data packets that general error correction structural parameters are ascertained the number;

Said transmitting element is used for according to general error correction structural parameters said packet data package being sent to data receiver;

Said retransmission process unit is used to handle the request retransmission information of obtaining from receiving terminal, judges whether to produce new redundant data packets according to general error correction structural parameters and lays equal stress on and newly send to data receiver;

In data receiver,

Said receiving element is used for receiving the packet data package that data sending terminal transmits according to general error correction structural parameters, and sends to the decoding FEC unit;

Said decoding FEC unit is used to accomplish the decode operation of packet data package, when decoding successfully, then decoded information packet is sent to the data parsing unit; When the decoding failure, then send failure information to the repeat requests unit;

Said data parsing unit is used to resolve decoded information packet, and recovers original real time business data flow;

Said repeat requests unit is used for when receiving the failure information of decoding FEC unit, judges whether to send re-transmission request message according to general error correction structural parameters and gives data sending terminal.

2. the data communication system that is used for real-time multicast service according to claim 1 is characterized in that: said general error correction structural parameters comprise the number of the redundant data packets that length, the quantity of redundant data packets, maximum retransmit wheel number, the re-transmission of information packet is stylish.

3. a data communications method that is used for real-time multicast service is characterized in that, comprises the steps:

Steps A according to the present situation of real-time multicast system, is provided with general error correction structural parameters, and sends general error correction structural parameters to data sending terminal, data receiver;

Step B, data sending terminal in chronological sequence divides into groups to pack to operate to the real time business data flow in proper order, then every group of packet is carried out encoding operation, forms several redundant data packets;

Step C, the present situation of data sending terminal monitoring multicast system when situation changes, then returns steps A and resets general error correction structural parameters; When situation does not change, then get into next step;

Step D, the general error correction structural parameters transfer data packets that data sending terminal notification data receiving terminal adopts steps A to be provided with after the feedback acknowledgment message that receives data receiver, is sent redundant data packets to data receiver;

The general error correction structural parameters that step e, data receiver adopt steps A to be provided with receive redundant data packets, and have judged whether that packet drop takes place:

E-1, when there not being packet drop to take place, data receiver carries out decode operation to the redundant data packets that receives, and resolves to recover original real time business data flow;

E-2, when packet drop took place, data receiver judged whether to allow to send repeat requests to data sending terminal according to general error correction structural parameters;

When the result when not allowing, data receiver is decoded to the packet that has received and decoded information packet is passed to the upper strata;

When the result was permission, data receiver was given data sending terminal with the request repeat message feedback;

Step F, data sending terminal receive the request repeat message of data receiver, and call general error correction structural parameters and judge whether to allow to the data receiver data retransmission;

When the result when not allowing, end operation then;

When the result was permission, data sending terminal formed new redundant data packets through encoding operation, and adopted the mode of multicast to send new redundant data packets to data receiver, returned step e.

4. the data communications method that is used for real-time multicast service according to claim 3 is characterized in that: said general error correction structural parameters comprise the number of the redundant data packets that length, the quantity of redundant data packets, maximum retransmit wheel number, the re-transmission of information packet is stylish.

5. the data communications method that is used for real-time multicast service according to claim 3 is characterized in that: described in the steps A in real time the present situation of multicast system comprise that packet loss, link round trip delay time, the packet data package of the number of users in the multicast system, every link on average send blanking time.

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