CN100433614C - A data packet recovery method - Google Patents

Abstract

The present invention discloses a data packet recovery method aiming at the phenomena of errors and losses in the transmission process of data packets, which can effectively decrease errors in the transmission process of the data packets. At a sending node, a set of multiple data packets which are continuous in time is called a data packet group; one or multiple redundant data packets used for correcting errors are added to the end of each data packet group, wherein the error correcting packets are obtained through calculation according to a certain coding method by all the data packets of a current data packet group and all or part of the data packets of at least one previous data packet group, and any one error correcting packet is associated with more than one data packet groups; correspondingly, at a receiving node, the errors of the data packet groups can be corrected in combination with the error correcting packets in the multiple data packet groups. Consequently, compared with the traditional error correcting method of data packets, the method of the present invention offers stronger error correcting capability.

Description

A kind of data packet recovery method

Technical field

The present invention relates to a kind of data packet recovery method, relate in particular to the restoration methods that packet is made mistakes or lost in the real time communication.

Background technology

During transmission of digital signals, because channel transfer characteristic is paid no attention to and thought of The noise, signal waveform can degenerate on actual channel, and the packet that receiving node is received just might be damaged.Simultaneously, because queuing in the network, influence such as congested, packet also might be lost in transmission course.For the packet that recovers to make mistakes in the transmission course or lose, must use effective error control method.

June nineteen ninety, the 9th IEEE computer and federation of corresponding society (INFOCOM ' 90) the 1st volume 124-131 page or leaf disclose one piece of article, the author is N.Shacham, P.McKenney etc., article name is " data packet recovery method that uses coding and cache management in the express network " (Packet recovery in high-speed networks using coding andbuffer management), provided multiple forward error correction data bag restoration methods, wherein the restoration methods of individual data bag is described below.

Fig. 1 is the schematic diagram of existing redundant correcting bag generation method.At sending node, the redundant correcting bag is to be generated according to certain coding method by the packet of the k in this group in each data packet group, and as can be seen, every group redundant correcting bag only is associated with packet in this group.This error correction packets generation method may further comprise the steps:

1), k packet continuous in time be as one group, the packet of transmission has sequence-number field and Cyclical Redundancy Check (Cyclic Redundancy check, CRC) check field;

2), at sending node, with k packet step-by-step xor operation in a group (Exclusive-Or XOR) generates error correction packets:

$C_{C,i}=\underset{j=0}{\overset{k-1}{\mathrm{\Σ}}}{C}_{j,i},$ i＝0，1，2，…m-1

Wherein, C _{J, i}Be the i position of j packet, C _{C, i}Be the i position of error correction packets, m represents that each data is surrounded by m bit.F among the figure ₀() represents a kind of coding method, used parity check coding method here.

The code efficiency of said method is k/k+1, and k is all packet numbers in a group, and k+1 is all packet numbers and a redundancy packet number sum in a group.As seen, redundancy packet is few more, and code efficiency is high more.

The method of the packet that recovers in the packet receiving course to make mistakes or lose may further comprise the steps:

1), each packet that receives is carried out CRC check, and judged whether data-bag lost according to sequence number;

2) if in this group packet that receiving node is received, there is not packet to make mistakes or lose, ignore the redundant correcting bag of following;

3) if in this group packet that receiving node is received, there are and only have data to contract out mistake or lose, can know according to sequence number the position of this packet to be assumed to be t packet in the data packet group, utilize the XOR relation between the packet, then

$C_{i,j}=(\underset{j=0}{\overset{k-1}{\mathrm{\Σ}}}{C}_{j,i}+C_{C,i}),$ I=0,1,2 ..., m-1, and j ≠ t

The packet of makeing mistakes or losing can recover fully.

As shown in the above, existing forward error correction (Forward Error Collection, FEC) data packet recovery method has the place of its deficiency: redundant corrected data packets only with own place group in packet relevant, the place one's entire reliance upon error correcting capability of error correction packets in this group of error correcting capability; In data package can the data recovered bag number, be subjected to the restriction of the error correcting capability of the corrected data packets in this group; In order to improve error correcting capability, must increase the length of error correction packets, will increase the burden of bandwidth consumption so; Because the error correcting capability of error correction packets is limited in data package, this method also is not suitable for makeing mistakes or losing of continuous packet.

Summary of the invention

The present invention proposes a kind of generation method of redundant correcting bag; error correction packets in one of them data packet group not only is associated with the packet of this group; and be associated with packet in a plurality of data packet group; that is to say that any one data packet group protected by the corrected data packets that is distributed in a plurality of data packet group, thereby bigger error correcting capability is provided.

Be the step that sending node redundant correcting bag generates below.In the present invention, each packet that send all has the error checking and correction ability, is used for the error code of check data bag itself.Each packet also has sequence-number field, is used for the position that designation data wraps in sequence.

At first, with continuous data packet stream segmentation, the set of several packets continuous in time is as one group of packet.Then, in each data packet group, add a redundant data packets that is used for error correction, be called error correction packets.

The generation method of redundant correcting bag may further comprise the steps: calculate the redundant correcting bag by the entire packet of current data package and the entire packet or the partial data bag of at least one data packet group of front according to certain coding method; Add this redundant correcting bag to described current data package.Current data package and at least one data packet group of front of participating in calculating are considered to interrelated.

The present invention also provides a kind of data packet recovery method, after receiving node receives a data package, is to realize like this to the step of its error detection occurs and recovery.

If the packet number of makeing mistakes in the current data package or losing is less than or equal to the error correcting capability of current group of redundant correcting bag, then recover the packet make mistakes or lose by the redundant correcting bag in the current data package; If, then uniting the error correction packets of the error correction packets of current data package and at least one follow-up data package greater than the error correcting capability of current group of redundant correcting bag, the packet number of makeing mistakes or losing in the current data package recovers the packet of makeing mistakes or losing.

The inventive method can be recovered the packet of makeing mistakes or losing fast and effectively, thereby reduces the error rate in the transmission course.And the present invention especially can recover continuous packet and make mistakes or lose.

Description of drawings

Fig. 1 is the schematic diagram of existing redundant correcting bag generation method;

Fig. 2 is the schematic diagram of redundant correcting bag generation method according to an embodiment of the invention;

Fig. 3 is that j organizes the contribution B of packet to current group of error correction packets according to an embodiment of the invention _{J, M}The calculating schematic diagram;

Fig. 4 (a) is l the schematic diagram that the data package carries out error correction to u1 data package by being associated;

Fig. 4 (b) carries out the schematic diagram of error correction by l the data package that is associated to makeing mistakes in two data packages.

Embodiment

Below in conjunction with the drawings and specific embodiments the present invention is elaborated.

Fig. 2 is the schematic diagram of redundant correcting bag generation method according to an embodiment of the invention.In the present embodiment, total l data package is associated, and promptly each a data packet group and front l-1 data package is associated, and generates the error correction packets of this group with parity check coding method.

The following describes the process that generates the redundant correcting bag at sending node.

Each packet that will send among the present invention all has the CRC check field, is used for the error code of check data bag itself.Each packet also has sequence-number field, is used for the position that designation data wraps in sequence.When data-bag lost, can number know which data-bag lost by checking sequence.For the sake of simplicity, stipulate in the present embodiment that each length of data package is fixed as mbits.Certainly this not necessarily, length of data package can change.

At first, with continuous data packet stream segmentation, a k continuous in time packet is as a data package.Here stipulate that the packet number in each data packet group fixes, but this neither be necessary.U supposes k＜m as group sequence number (u 〉=0).

Then, in each data packet group, add a redundant data packets that is used for error correction, be called error correction packets.This error correction packets is that the information by current data package and front l-1 data package calculates with parity check coding method, that is to say that l continuous in time in the present embodiment data package is interrelated.Because the coding method that present embodiment adopts, each error correction packets has only the recovery capability of a packet.

Suppose that u data package is the current data package, a current data package and front l-1 data package is associated, according to the error correction packets B in the parity check coding method generation current data package _uFormula as follows:

$B_u=\underset{j=u-l+1}{\overset{u}{\mathrm{\Σ}}}{B}_{j,u}..................................................\left(1\right)$

Wherein, B _{J, u}(u-l+1≤j≤u) is defined as in l the data package that is associated packet in j the data package for B _uContribution.As seen B _uAll relevant with the information of each data packet group of l data package.

B so _{J, u}How to obtain? B _{J, u}By all packet A to the j group _{J, u}(0≤n≤k-1) be offset xor operation (XOR) to obtain,

$B_{j,u}=\begin{array}{}\end{array}\left[\begin{array}{c}{I}_m\\ 0_{s(k-1)\×m}\end{array}\right]A_{j,0}+\left[\begin{array}{c}{0}_{s\×m}\\ I_m\\ 0_{s(k-2)\×m}\end{array}\right]A_{j,1}+\left[\begin{array}{c}{0}_{2s\×m}\\ I_m\\ 0_{s(k-3)\×m}\end{array}\right]A_{j,2}+...+\left[\begin{array}{c}{0}_{\mathrm{ns}\×m}\\ I_m\\ 0_{s(k-n-1)\×m}\end{array}\right]A_{j,n}+...+\left[\begin{array}{c}{0}_{s(k-1)\×m}\\ I_m\end{array}\right]A_{j,k-1}.---\left(2\right)$

Wherein, s represents the bit of packet skew, and the computational methods of s will be discussed in more detail below.

A _{J, n}(n packet in j data package of the expression of 0≤n≤k-1), it is a capable single-row vector of m in formula (2) $\left[\begin{array}{c}{A}_{j,n,0}\\ A_{j,n,1}\\ .\\ .\\ .\\ A_{j,n,m}\end{array}\right],$ A _{J, n, 0}The 0th bit of representing j n packet in the data package ..., the rest may be inferred, A _{J, n, m}The m bit of representing j n packet in the data package.

I _mRepresentation unit diagonal matrix, m are line number and columns; 0 _{S (k-1) * m}0 matrix of expression s (k-1) row m row ..., 0 _{S (k-n-1) * m}0 matrix of expression s (k-n-l) row m row; 0 _{S * m}0 matrix of the capable m row of expression s ..., 0 _{Ns * m}0 matrix of the capable m row of expression ns.

In the present embodiment, for simply, length of data package is fixed as the m bit, the packet number of each data packet group also all is k, but this just the present invention for convenience of explanation, those skilled in the art should be able to understand data packet length among the present invention by the present invention and the packet number of data packet group all can change.

Fig. 3 is that j organizes the contribution B of packet to current group of error correction packets according to an embodiment of the invention _{J, u}The calculating schematic diagram.The result of calculation of this schematic diagram is identical with the result that formula (1) and (2) obtain, and Fig. 3 is the schematic form with concrete packet, and formula (1) and (2) are the forms with math equation.B _{I, u}Calculating be for A _{I, n}(the skew xor operation (XOR) of 0≤n≤k-1).The 1st packet (n=0) in j data package is placed on the 1st row; The 2nd packet (n=1) is placed on the 2nd row, and is offset the s bit to the right, s=jmod (l) wherein, and just j is divided by the remainder of l, and l is the data packet group number that is associated here, and j is the sequence number of the data packet group that receives of receiving node; Corresponding, it is capable that n packet is placed on n, and be offset the ns bit to the right.Fill with 0 in the room that is produced, and obtains a matrix.This matrix is just obtained B with xor operation _{J, u}

Used parity check coding method computing error correction bag in the present embodiment, also can use other coding method, as reed solomon coding method or other coding method.

In the present embodiment, can obtain the redundancy rate R of this coding method _e, redundancy rate is defined as the ratio of total redundancy packet length and total long data packet, according to formula (1),

$R_e=\frac{\mathrm{ml}+\underset{i=0}{\overset{l-1}{\mathrm{\Σ}}}(k-1)\·i}{k\·m\·l}=\frac{2\mathrm{ml}+(l^2-l)(k-1)}{2k\·m\·l}$

Traditional packet FEC method with a packet recovery capability, redundancy rate R _tJustice is

$R_t=\frac{1}{k}$

For most application, data packet length m is far longer than k and l, R like this _eVery near R _tCompare with the redundancy rate of traditional data packet recovery method, it is big that the redundancy rate of the inventive method does not become basically.Particularly work as l and equal 1, that is to say that redundant data packets only depends on the notebook data group and produces, we obtain R _e=R _t

After error correction packets generated, after all packets sent in one group, the error correction packets of this group was followed by transmission.

The following describes corresponding data packet recovery method.After receiving node receives a data package, just carry out error detection occurs and recovery.

At first, each packet that receives is carried out CRC check, and whether judged whether data-bag lost continuously according to sequence number.Here suppose not go wrong in the relevant data packet group in current data package front, perhaps have mistake still successfully to recover the packet of makeing mistakes or losing.

If in the current group of packet that receiving node is received, there is not packet to make mistakes or lose, ignore the redundant correcting bag of following.

If there is and only has 1 data to contract out mistake in the current data package, according to top supposition, error correction is surrounded by the ability of recovering a packet, then can recover the packet of makeing mistakes or losing by this error correction packets, establishes this and makes mistakes or the packet sequence number of losing is kl.

According to hypothesis, the packet that does not have data-bag lost, makes mistakes or lose, makes mistakes in the l-1 that is associated previously data package recovers, and u data package is the current data package, B _uBe the error correction packets of current data package, then according to the generation method of error correction packets as can be known, front l-1 data package is for B _uContribution B _{J, u}(u-l+1≤j≤u-1) is known, with they substitution formula (1), obtains the contribution B of current group of packet to current group of error correction packets _{U, u},

$B_{u,u}=B_u-\underset{j=u-l+1}{\overset{u-l}{\mathrm{\Σ}}}{B}_{j,u},---\left(3\right)$

Then with B _{U, u}Substitution formula (2) obtains

$B_{u,u}=\begin{array}{}\end{array}\left[\begin{array}{c}{I}_m\\ 0_{s(k-1)\×m}\end{array}\right]A_{u,0}+\left[\begin{array}{c}{0}_{s\×m}\\ I_m\\ 0_{s(k-2)\×m}\end{array}\right]A_{u\·1}+\left[\begin{array}{c}{0}_{2s\×m}\\ I_m\\ 0_{s(k-3)\×m}\end{array}\right]A_{u,2}+...+\left[\begin{array}{c}{0}_{\mathrm{ns}\×m}\\ I_m\\ 0_{s(k-n-1)\×m}\end{array}\right]A_{u,n}+...+\left[\begin{array}{c}{0}_{s(k-1)\×m}\\ I_m\end{array}\right]A_{u,k-1}....\left(4\right)$

Any packet A then _{J, n}Lose or make mistakes and from formula (4), to be restored.

If n is arranged in the current data package, and (2≤n≤l) individual data contract out mistake, and the error correcting capability of current data package is a packet, the error correction packets that then must wait for follow-up data packet group arrives, and uniting a plurality of error correction packets provides the recovery capability of the individual packet of l (l 〉=2) at the most:

Suppose that u data package is the current data package, the packet of losing in the current data package is

(0≤n ₀＜n ₁＜...＜n _(l-1)≤ k-1), and back l-1 data package do not have data-bag lost;

Error correction packets B with the current data package _uAnd all packets can obtain packet in the current data package to the contribution B of current group error correction packets to the contribution substitution formula (1) of u data package in front l-1 the data package being associated of current data package _{U, u}, see formula (3),

After follow-up l-1 data package arrives, with the error correction packets B of u+1 data package _U+1And all packets except that current group of u can obtain the contribution B of current data package to the error correction packets of u+1 data package to the contribution substitution formula (1) of u+1 data package in front l-1 the data package being associated of u+1 data package _{U, u+1},

$B_{u,u+1}=B_{u+1}-\underset{j=u-l+2}{\overset{u+1}{\mathrm{\Σ}}}{B}_{j,u+1},j\≠u,---\left(5\right)$

Equally, can obtain the contribution B of current data package to the error correction packets of u+2 data package _{U, u+2}..., the current data package is to the contribution B of the error correction packets of u+l-1 data package _{U, u+l-1},

Above-mentioned these values, known related data packets value and error correction packets value are updated to formula (2), obtain following formula after dissolving,

In this formula, B _E0, B _E1, B _E2..B _{E (u+l-1)}Be known value, finding the solution this equation group can obtain

(0≤n ₀＜n ₁＜...＜n _(l-1)≤ k-1).

Situation about above relating to is such: if in the current data package n is arranged ₁(2≤n ₁≤ l) individual data contract out mistake, and the error correcting capability of current data package is a packet, then must wait for follow-up n ₁The error correction packets of individual data package arrives, and uniting a plurality of error correction packets provides n ₁The recovery capability of individual packet.Be depicted as l the schematic diagram that the data package carries out error correction to u1 data package as Fig. 4 (a) by being associated.If so follow-up n ₁Does individual data package also have packet to make mistakes or lose? if this occurs, then must recover earlier wherein last error data package, and the like, up to makeing mistakes or lose all and recover in all data packet group.This is above doing detailed description,,

Fig. 4 (b) expression is carried out the schematic diagram of error correction by l the data package that is associated to makeing mistakes in two data packages.Shown in the figure, suppose follow-up n at u1 ₁Data-bag lost is also arranged, as at u in-1 data packet group ₂(u in the individual data package ₁＜u ₂≤ u ₁+ n ₁-1) n is arranged ₂Individual data packet loss.Because u ₁The recovery of data packet group must be used u ₂So the information of data packet group is u ₁The recovery of data packet group must be waited until u ₂Data packet group is carried out after recovering successfully.u ₁Data packet group has the packet mistake, and according to the generating algorithm of error correction packets, u _iData packet group (u ₂≤ u _i≤ u ₁+ error correction packets in l-1) generates all and u ₁Data packet group is relevant, like this u _iData packet group (u ₂≤ u _i≤ u ₁+ error correction packets in l-1) all can not be used for other error correction data packet.Sequence number (u only ₁+ l-1) afterwards data packet group can be used for u ₂The error correction of data packet group.If satisfy

u ₁+ l+n ₂-1≤u ₂+ l-1, perhaps u ₁+ n ₂≤ u ₂... ... ... ... .. (7)

Then from sequence number (u ₁+ l) to (u ₁+ l-1+n ₂) n ₂Individual data package can be united and is used for u ₂The error correction of data packet group, the promptly selected associated data package that is used for error correction can not have makes mistakes, otherwise losing of packet can not be resumed.The recovery that also can use the same method that makes mistakes in other the follow-up data package.

Than traditional data packet recovery method, under the situation of close code efficiency and redundancy, the inventive method has tangible advantage.Traditional data packet recovery method in a data package can data recovered the number of bag, be subjected to the restriction of the error correcting capability of the corrected data packets in this group, if just cannot recover when makeing mistakes error correcting capability above error correction packets.And in the method for the present invention, when the error data bag in the data package surpasses the error correcting capability of error correction packets in this group,, provide bigger error correcting capability by uniting follow-up error correction packets, than original method, bigger error correcting capability is arranged.And the present invention can effectively recover the packet of makeing mistakes or losing, thereby reduces the error rate in the transmission course.

Though the present invention is described, yet according to the description of front, many to substitute, revise with changing be conspicuous for a person skilled in the art in conjunction with specific embodiment.Therefore, the present invention will comprise that this within design that all drop on accompanying Claim and the scope substitutes, revises and change.

Claims (9)

1. the generation method of a redundant correcting bag is characterized in that, said method comprising the steps of:

Calculate the redundant correcting bag by the entire packet of current data package and the entire packet or the partial data bag of at least one data packet group of front according to certain coding method;

Add described redundant correcting bag to described current data package.

2. the method for claim 1 is characterized in that, described coding method comprises following method; Parity check coding method, and reed solomon coding method.

3. method as claimed in claim 2 is characterized in that,

The set of supposing a k continuous in time packet is as a data package, and u is group sequence number, u 〉=0, A _{U, n}Represent n packet in the u data packet group, wherein, 0≤n≤k-1, a current data package and front l-1 data package is associated, then according to the error correction packets B in the parity check coding method generation current data package _uFormula as follows:

$B_u=\underset{j=u-l+1}{\overset{u}{\mathrm{\Σ}}}{B}_{j,u}---\left(1\right)$

Wherein, B _{J, u}Be defined as j the packet in the data package for B _uContribution, wherein, u-l+1≤j≤u;

B _{J, u}By all packet A to the j group _{J, n}Be offset xor operation and obtain, wherein, 0≤n≤k-1,

$B_{j,u}=\left[\begin{array}{c}{I}_m\\ 0_{s(k-1)\×m}\end{array}\right]A_{j,0}+\left[\begin{array}{c}{0}_{s\×m}\\ I_m\\ 0_{s(k-2)\×m}\end{array}\right]A_{j,1}+\left[\begin{array}{c}{0}_{2s\×m}\\ I_m\\ 0_{s(k-3)\×m}\end{array}\right]A_{j,2}+\·\·\·+\left[\begin{array}{c}{0}_{\mathrm{ns}\×m}\\ I_m\\ 0_{s(k-n-1)\×m}\end{array}\right]A_{j,u}+\·\·\·+\left[\begin{array}{c}{0}_{s(k-1)\×m}\\ I_m\end{array}\right]A_{j,k-1}---\left(2\right)$

Wherein, m represents length of data package, and s represents the bit that is offset, A _{J, n}It in formula (2) a single-row vector $\left[\begin{array}{c}{A}_{i,n,0}\\ A_{j,n,1}\\ .\\ .\\ .\\ A_{l,n,m-1}\end{array}\right],$ A _{J, n, r}The r position of representing j n packet in the data package, wherein, 0≤r≤m-1;

I _mThe representation unit diagonal matrix; 0 _{S (k-1) * m}0 matrix of expression s (k-1) row m row ..., 0 _{S (k-n-1) * m}0 matrix of expression s (k-n-1) row m row; 0 _{S * m}0 matrix of the capable m row of expression s ..., 0 _{Ns * m}0 matrix of the capable m row of expression ns.

4. method as claimed in claim 3 is characterized in that, s=j mod (l), and promptly j is divided by the remainder of l, and j is meant j the data package that receiving node receives.

5. method as claimed in claim 3 is characterized in that described length of data package can change, and the packet number in each data packet group also can change.

6. a data packet recovery method is characterized in that, comprises step:

If the packet number of makeing mistakes in the current data package or losing is less than or equal to the error correcting capability of current group of redundant correcting bag, then recover the packet make mistakes or lose by the redundant correcting bag in the current data package;

If, then uniting the error correction packets of the error correction packets of current data package and at least one follow-up data package greater than the error correcting capability of current group of redundant correcting bag, the packet number of makeing mistakes or losing in the current data package recovers the packet of makeing mistakes or losing.

7. method as claimed in claim 6 is characterized in that,

Under the situation that the packet of do not have data-bag lost in the data packet group that is associated in front, make mistakes or lose, makeing mistakes has recovered,

If there are and only have data to contract out mistake in the current data package, then the error correction packets by the current data package is recovered the packet of makeing mistakes or losing; Suppose that u data package is the current data package, B _uBe the error correction packets of current data package, then according to corresponding error correction packets generation method, a current data package front l-1 data package is for B _uContribution B _{J, u}Be known, wherein, u-l+1≤j≤u-1 obtains the contribution B of current group of packet to current group of error correction packets _{U, n},

$B_{u,u}=B_u-\underset{j=u-l+1}{\overset{u-1}{\mathrm{\Σ}}}{B}_{j,u}---\left(3\right)$

Obtain B then _{U, n}

$B_{u,u}=\left[\begin{array}{c}{I}_m\\ 0_{s(k-1)\×m}\end{array}\right]A_{u,0}+\left[\begin{array}{c}{0}_{s\×m}\\ I_m\\ 0_{s(k-2)\×m}\end{array}\right]A_{u,1}+\left[\begin{array}{c}{0}_{2s\×m}\\ I_m\\ 0_{s(k-3)\×m}\end{array}\right]A_{u,2}+\·\·\·+\left[\begin{array}{c}{0}_{\mathrm{ns}\×m}\\ I_m\\ 0_{s(k-n-1)\×m}\end{array}\right]A_{u,u}+\·\·\·+\left[\begin{array}{c}{0}_{s(k-1)\×m}\\ I_m\end{array}\right]A_{u,k-1}---\left(4\right)$

Wherein, m represents length of data package, and k represents the packet number of a data package, and u represents the group sequence number of data packet group, wherein, u 〉=0, s represents the bit that is offset, A _{U, n}Represent n packet in u the data package, wherein, 0≤n≤k-1;

Any packet A then _{U, n}Lose or make mistakes and can both from formula (4), be restored, wherein, 0≤n≤k-1.

8. method as claimed in claim 6, it is characterized in that, if n data of current data package contract out mistake, wherein, 2≤n≤l, and the error correcting capability of current data package is a packet, must wait for that then the error correction packets of follow-up data packet group arrives, and uniting a plurality of error correction packets provides the recovery capability of l packet at the most:

Suppose that u data package is the current data package, the packet of losing in the current data package is

And back l-1 data package do not have data-bag lost; Wherein, 0≤n ₀＜n ₁＜...＜n _(l-1)≤ k-1;

Error correction packets B according to the current data package _uFront l-1 the data package that is associated with the current data package is to B _uContribution B _{J, u}, wherein, u-l+1≤j≤u-1 can obtain packet in the current data package to the contribution B of current group error correction packets _{U, n}, see formula (3),

After u+1 follow-up data package arrives, according to B _N+1, and B _{J, u+1}, wherein, u-l+2≤j≤u+2, j ≠ u can obtain B _{U, u+1},

$B_{u,u+1}=B_{u+1}-\underset{j=u-l+2}{\overset{u+1}{\mathrm{\Σ}}}{B}_{j,u+1},j\≠u,---\left(5\right)$

Equally, can obtain B _{U, u+2}. ..., B _{U, n+l-1},

According to above-mentioned these values, known related data packets value and error correction packets value, can obtain following formula,

(6)

B _E0, B _E1, B _E2... B _{E (n+l-1)}Be known value, therefore finding the solution this equation group can obtain

Wherein, 0≤n ₀＜n ₁＜...＜n _(l-1)≤ k-1.

9. method as claimed in claim 8 is characterized in that, also comprises step:

If in the current data package n is arranged ₁Individual data contract out mistake, wherein, and 2≤n _1≤L, and the error correcting capability of current data package is a packet, then must wait for follow-up n ₁The error correction packets of individual data package arrives, and uniting a plurality of error correction packets provides n ₁The recovery capability of individual packet; If follow-up n ₁Individual data package has packet to make mistakes or lose, and then recovers wherein last error data package earlier, and the like.

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