CN108768588A - Based on the distributed network coding method and system for merging request - Google Patents
Based on the distributed network coding method and system for merging request Download PDFInfo
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Abstract
The invention discloses a kind of based on the distributed network coding method for merging request and system, present invention determine that node role is source node, receiving node, intermediate node three classes, source node splits subband, and receiving node actively initiates request of data, and intermediate node is passively made a response：Possess partial data and then selects qualified transmission from existing subband；There is no the certain probability of partial data that can obtain qualified transmission from existing subband, and existing subband cannot be satisfied require when, trial, which merges request operation and carries, to be had subband and is overlapped transmission；Merge unsuccessful use and recompiles the new subband of generation；Otherwise directly forwarding request.The present invention takes full advantage of the sub-band resources of node existing subband and surroundings nodes, introduce the mode for merging request, existing subband is carried as far as possible is overlapped transmission, reduce the number that node recompiles, computing capability is greatly saved, and accordingly reduce the delay of information transmission, improve efficiency of transmission.
Description
Technical field
The present invention relates to the fields such as network information transfer, wireless sensor network, dynamic network, and in particular to one kind is based on
Merge distributed network coding method and the system of request.
Background technology
Network code is a kind of widely used method in network data distribution application, this method by split subband,
Transmission, subband intersect the modes such as coding, full rank decoding respectively, are making full use of channel resource, improve efficiency, the section of information transmission
Bandwidth-saving, increase data redundancy, raising reliability etc. have superior performance, while being also applied to data dispersion storage etc.
Related field.For given network topology structure, feasible network coding scheme how is constructed, a very long time,
The always research hotspot in network information transfer field.For static network, usually can by modes such as linear programmings,
It is solved by the calculating of global information, obtains a feasible network coding scheme.Its optimal solution solves difficulty as network is advised
Mould acutely increases, and more excellent feasible solution can obtain in polynomial time.The node topology relationship of the network overall situation, band herein
The information such as width, computing capability are necessary, and possess the condition for carrying out centralized calculation.
For changing larger dynamic network for topological relation, first, being difficult to grasp Global Topological, bandwidth, calculating in time
The information such as ability, and be not easy to select authoritative node to carry out centralized calculation, therefore distributed coding method is generally used, by each
A node independently determines itself behavior, and the method taken has the modes such as random coded, random forwarding, dispersion solution, whole to obtain
The feasible solution of volume grid in a certain range.Distributed random coding mode is wherein generally acknowledged preferable one kind, for Dynamic Networks
Network has higher information transmission success rate, preferable reliability and faster desin speed, but since purpose is not strong, deposits
It is too many in coding nodes quantity, the serious problem of consumption calculations resource.It is not high for bandwidth, and node computing capability is stronger answers
For, this method applicability is very strong.But for the application network of the types such as Miniature Sensor, node is mended by the energy
It gives, the limitations such as hardware condition, is also that can save then to save in terms of computing resource, it is difficult to carry out high intensity to extend run time
Frequent encoding and decoding.Therefore, for all limited dynamic network of the resources such as computing capability, bandwidth, the collection in static network
The methods of middle planning is difficult to be applicable in, and the modes such as dispersion solution, random coded consume also very greatly computing resource, are ensureing data
Under the premise of efficiency of transmission, it is necessary to further make optimization, save computing capability, improve overall efficiency.
Invention content
The technical problem to be solved in the present invention：For the above problem of the prior art, provide a kind of based on merging request
Distributed network coding method and system, the present invention take full advantage of the sub-band resources of node existing subband and surroundings nodes, draw
Enter to merge the mode of request, carries existing subband as far as possible and be overlapped transmission, by fully excavating node existing resource and week
The cooperation of mid-side node reduces the number that node recompiles, and computing capability is greatly saved, and accordingly reduces information transmission
Delay, improve efficiency of transmission, particularly with the limited dynamic network of node computing capability, there is very strong applicability.
In order to solve the above-mentioned technical problem, the technical solution adopted by the present invention is：
A kind of distributed network coding method based on merging request, implementation steps include：
1) initial data is divided into n subband in advance and introduces corresponding mark vector respectively to n subband by source node
Unique mark is carried out, the identity matrix Y (u) that n initial mark vector is constituted is unit matrix, waits for request of data；
2) receiving node sends out request of data as unit of subband to adjacent intermediate node, is attached in the request of data
There is the identity matrix Y (u) that the mark vector of the subband of the existing u linear independence of receiving node is constituted；
3) after arbitrary intermediate node receives request of data, judge whether this node possesses partial data, if possessed complete
Data then select a mark vector and the subband of identity matrix Y (u) to return to receiving node or upper level intermediate node；Such as
Fruit possesses deficiency of data, then trial obtains qualified subband and returns to receiving node or upper level from existing subband
Intermediate node；Continuing to attempt to merge if the qualified subband failure of trial acquirement asks the existing subband of carrying to be overlapped
The subband that transmission value adjacent node please look for novelty returns to receiving node or upper level intermediate node；If it is unsuccessful to merge request
New subband is then generated by the way of recompiling returns to receiving node or upper level intermediate node；Aforementioned operation all without
Then directly to adjacent intermediate node or source node forwarding request of data until request of data when method generates the subband met the requirements
Reach source node；
4) judge the order of the identity matrix of local existing subband be equal to initial data decile sub-band sum n whether at
It is vertical, it is redirected if setting up and executes next step；Otherwise, it redirects and executes step 3)；
5) receiving node is decoded existing subband, the initial data asked.
Preferably, arbitrary intermediate node receives the detailed execution step after request of data and includes in step 3)：
3.1) judge that present node has the number of sub-bands m that mark SYSTEM OF LINEAR VECTOR is unrelated in subband and includes equal to request of data
Total number of sub-bands n it is whether true, if set up if judge that this node possesses partial data, have in subband from present node and select
The subband for selecting a mark vector and identity matrix Y (u) returns to receiving node or upper level intermediate node；Otherwise, it redirects
Execute step 3.2)；
3.2) judge whether directly to obtain to meet from the existing subband of present node to make identity matrix Y's (u)
The increased subband of order, if it is possible to directly obtain qualified subband, then will directly obtain qualified subband and return
Back to receiving node or upper level intermediate node and exit；Otherwise, it redirects and executes step 3.3)；
3.3) from the existing subband of present node optional one be subband V (i) that other nodes provide, the subband
Corresponding identity matrix is Z) i, t)=[Vi(1), Vi(2) ..., Vi(t)], by the identity matrix Z of the subband V (i) of selection (i,
T) and the identity matrix Y (u) of request of data the two merges the identity matrix Y (u+t) after being merged；
3.4) identity matrix Y (u+t) is sent out as new request matrix to surroundings nodes, if searching out new subband
V (j) meets the order increase so that identity matrix Y (u+t), then to receive and forward new subband V (j) to replace original subband V (i),
And the identity matrix Z (i, t) of V (i) is replaced with into Z (j, u+t)=Y (u+t), and by subband V (j) return to receiving node or
Upper level intermediate node simultaneously exits；Otherwise, it redirects and executes step 3.5)；
3.5) judge whether the subband of the existing linear independence of present node meets the condition of recompiling, if met again
Encoding condition then uses random network code method according to the subband of the existing linear independence of present node, with the side of recompiling
Formula generates the new subband met the requirements, and new subband is returned to receiving node or upper level intermediate node and is exited；Otherwise,
It redirects and executes step 3.6)；
3.6) to adjacent intermediate node or source node forwarding request of data until request of data reaches source node.
Preferably, so that shown in the increased function expression of the order such as formula (1) of identity matrix Y (u) in step 3.2)；
Rank (Y (u+1))=Rank (Y (u))+1 (1)
In formula (1), after Y (u+1) merges for the subsidiary identity matrix of the mark vector of qualified subband, request of data
Obtained new identity matrix, Rank (Y (u+1)) are the order of new identity matrix Y (u+1), and Y (u) is that request of data is subsidiary
Identity matrix, Rank (Y (u)) are the order of identity matrix Y (u), and u is the sub-band number that request of data initiator has linear independence
Amount.
Preferably, so that shown in the increased function expression of the order such as formula (2) of identity matrix Y (u+t) in step 3.4)；
+ 1 (2) Rank (Y (u+t+1))=Rank (Y (u+t))
In formula (2), it is new that Y (u+t+1) is that the mark vector of new subband V (j), identity matrix Y (u+t) are obtained after merging
Identity matrix, Rank (Y (u+t+1)) are the order of new identity matrix Y (u+t+1), and Rank (Y (u+t)) is identity matrix Y (u+
T) order.
Preferably, shown in the function expression such as formula (3) that condition is recompiled in step 3.5)；
Rank (Y (u+m)) > Rand (Y (u)) (3)
In formula (3), Y (u+m) is the identity matrix for having m linear independence subband on the node, identity matrix Y (u) conjunctions
The new identity matrix obtained after and, Rank (Y (u+m)) are the order of new identity matrix Y (u+m), and Y (u) is request of data
Identity matrix, Rand (Y (u)) are the order of identity matrix Y (u).
The present invention also provides a kind of based on the distributed network coded system for merging request, including is saved by source node, reception
The Distributed Computer System of point, intermediate node composition, it is aforementioned based on conjunction that the computer system is programmed to perform the present invention
And the step of distributed network coding method of request.
Compared to the prior art, the present invention has following advantageous effects：
1, the present invention takes full advantage of the sub-band resources of node existing subband and surroundings nodes, and introduces the side for merging request
Formula reduces the number that node recompiles, and saves computing capability, and accordingly reduces the delay of information transmission, improves transmission effect
Rate.
2, the present invention is based on calculate to derive, it is determined that full rank node does not have to recompile, and non-full rank node maximum probability does not have to
The principle recompiled, reduce it is unnecessary recompile number, give from existing subband selection and meet the requirements subband
Basic discriminant approach.
3, the present invention is by the way of merging request, when node itself cannot be satisfied request, considers to rely on existing transmission
Channel, in the case where not increasing bandwidth and not recompiling, overlapped information transmission further reduces and recompiles number.
Description of the drawings
Fig. 1 is the basic procedure schematic diagram of present invention method.
Fig. 2 is the flow diagram of intermediate node in present invention method.
Fig. 3 is under heterogeneous networks scale, in 20 groups of heterogeneous networks topology examples, average coding nodes quantitative comparison.
Fig. 4 is under heterogeneous networks scale, and in 20 groups of heterogeneous networks topology examples, the network weighed from receiving node end is average
Effective throughput, unit K b/s.
Under Fig. 5 heterogeneous networks scales, in 20 groups of heterogeneous networks topology examples, from source node to receiving node network average
According to transmission delay, unit millisecond.
Specific implementation mode
Below by taking the network code data transmission under one group of exemplary dynamic network topology as an example, to the present invention is based on merging to ask
The distributed network coding method asked and system are described in detail.As implementing, the present invention is based on the distributions for merging request
The basic network of network coding method and system uses topology generator BRITE in the present embodiment, produces a series of abide by respectively
The general networking topology being distributed from power-law is as the basic network for case verification, initial network number of nodes difference
It it is 100,200,300,400,500, each scale respectively includes 20 groups of different network topologies.In order to which more preferable expression method is imitated
Fruit sets the network and is used for transmission stream data incessantly, and complete transmitting data stream is 512Kb/s, and source node has most
Big bandwidth 2Mb/s, receiving node maximum bandwidth are 600Kb/s, while allowing to upload and download, other intermediate node available bandwidths
It floats between 64-256Kb/s, relative ability is weaker.Each node does not have Global Topological information, only preserves section nearby
One neighbor list of point is only capable of directly generating information exchange with the node in neighbor list.As time goes by, it is held in network
It is continuous to there is node to be added and release, generally a network total scale is maintained to change little dynamic topological structure.When node exits,
Interdependent node deletes its syntople.When node is added, several line nodes are provided at random as neighbours, and all over time
Phase property optimizes, and chosen distance is relatively close, resource has node more than needed as new neighbor, and neighbor list quantity is had by network size difference
Ceiling restriction.
As shown in Figure 1, implementation steps of the present embodiment based on the distributed network coding method for merging request include：
1) initial data is divided into n subband in advance and introduces corresponding mark vector respectively to n subband by source node
Unique mark is carried out, the identity matrix Y (u) that n initial mark vector is constituted is unit matrix, waits for request of data；
2) receiving node sends out request of data as unit of subband to adjacent intermediate node, is attached in the request of data
There is the identity matrix Y (u) that the mark vector of the subband of the existing u linear independence of receiving node is constituted；
3) after arbitrary intermediate node receives request of data, judge whether this node possesses partial data, if possessed complete
Data then select a mark vector and the subband of identity matrix Y (u) to return to receiving node or upper level intermediate node；Such as
Fruit possesses deficiency of data, then trial obtains qualified subband and returns to receiving node or upper level from existing subband
Intermediate node；Continuing to attempt to merge if the qualified subband failure of trial acquirement asks the existing subband of carrying to be overlapped
The subband that transmission value adjacent node please look for novelty returns to receiving node or upper level intermediate node；If it is unsuccessful to merge request
New subband is then generated by the way of recompiling returns to receiving node or upper level intermediate node；Aforementioned operation all without
Then directly to adjacent intermediate node or source node forwarding request of data until request of data when method generates the subband met the requirements
Reach source node；
4) judge the order of the identity matrix of local existing subband be equal to initial data decile sub-band sum n whether at
It is vertical, it is redirected if setting up and executes next step；Otherwise, it redirects and executes step 3)；
5) receiving node is decoded existing subband, the initial data asked.
Source node possesses complete data, generally also has stronger coding/decoding capability and bandwidth, is capable of providing various want
The code stream of the coding subband and large bandwidth asked.In the present embodiment, initial data is divided into n subband by source node, is denoted as：
Introduce a coefficient vectorNew subband can be encoded out as needed
It, can be with corresponding coefficient as uncoded original sub-band with the new subband for recompiling appearance is substantially
Vectorial V (i) carries out unique mark, and the matrix that initial n uncoded subband vectors are constituted is unit according to battle array
By recompiling, source node can encode altogether sends out infinite a variety of different subbands.
Theorem 1：The node for possessing n linear independence subband, does not recompile, and total energy provides one for arbitrary data request
Available subband.The proof procedure of theorem 1 is as follows：It enables node p possess n linear independence subband, is denoted asSection
Point q possesses m (m < n) a linear independence subband, is denoted asAssuming that the theorem is false, i.e. node p can not be section
Point q provides a useful subband, then any subband on node p may be expressed as on node q the linear of m subband
With that is,Due to having complete data on node p, then also necessarily have on node q complete
Data, this is not inconsistent with (m < n).Thus, it is supposed that invalid, theorem must be demonstrate,proved.According to theorem 1, possess the node of partial data
On, it does not recompile, an existing subband can necessarily be selected to meet request of data.
Therefore, source node waits for the request of intermediate node and receiving node after splitting subband, and coding is sent out not as required
Same subband repeats to reduce, and source node all sends out different subbands to the request of every data.Receiving node receives n system
The subband of number vector linear independence, so that it may to decode complete data, if not yet met, to surroundings nodes acquisition request
More subbands.It needs to take existing subband vectorial when request, be provided on demand convenient for surroundings nodes.
As shown in Fig. 2, arbitrary intermediate node receives the detailed execution step after request of data and includes in step 3)：
3.1) judge that present node has the number of sub-bands m that mark SYSTEM OF LINEAR VECTOR is unrelated in subband and includes equal to request of data
Total number of sub-bands n it is whether true, if set up if judge that this node possesses partial data, have in subband from present node and select
The subband for selecting a mark vector and identity matrix Y (u) returns to receiving node or upper level intermediate node；Otherwise, it redirects
Execute step 3.2)；
3.2) judge whether directly to obtain to meet from the existing subband of present node to make identity matrix Y's (u)
The increased subband of order, if it is possible to directly obtain qualified subband, then will directly obtain qualified subband and return
Back to receiving node or upper level intermediate node and exit；Otherwise, it redirects and executes step 3.3)；
3.3) from the existing subband of present node optional one be subband V (i) that other nodes provide, the subband
Corresponding identity matrix is Z (i, t)=[Vi(1), Vi(2) ..., Vi(t)], by the identity matrix Z of the subband V (i) of selection (i,
T) and the identity matrix Y (u) of request of data the two merges the identity matrix Y (u+t) after being merged；
3.4) identity matrix Y (u+t) is sent out as new request matrix to surroundings nodes, if searching out new son
Meet with V (j) so that the order of identity matrix Y (u+t) increases, then to receive and forward new subband V (j) to replace original subband V
(i), Z (j, u+t)=Y (u+t) and by the identity matrix Z (i, t) of V (i) is replaced with, and subband V (j) is returned into receiving node
Or it upper level intermediate node and exits；Otherwise, it redirects and executes step 3.5)；
3.5) judge whether the subband of the existing linear independence of present node meets the condition of recompiling, if met again
Encoding condition then uses random network code method according to the subband of the existing linear independence of present node, with the side of recompiling
Formula generates the new subband met the requirements, and new subband is returned to receiving node or upper level intermediate node and is exited；Otherwise,
It redirects and executes step 3.6)；
3.6) to adjacent intermediate node or source node forwarding request of data until request of data reaches source node.
In the present embodiment, in step 3.2) so that shown in the increased function expression of the order such as formula (1) of identity matrix Y (u)；
Rank (Y (u+1))=Rank (Y (u))+1 (1)
In formula (1), after Y (u+1) merges for the subsidiary identity matrix of the mark vector of qualified subband, request of data
Obtained new identity matrix, Rank (Y (u+1)) are the order of new identity matrix Y (u+1), and Y (u) is that request of data is subsidiary
Identity matrix, Rank (Y (u)) are the order of identity matrix Y (u), and u is the sub-band number that request of data initiator has linear independence
Amount.Step 3.2) judges whether directly obtain one of condition shown in meeting formula (1) from the existing subband of present node
When subband, possess m (m < n) a linear independence subband on the node of request of data if receiving, for arbitrary request of data Y
(u), in the case where completely random is distributed, approximation is with statistical probabilityIt can be from current m
Useful data are obtained in subband.Under normal conditions, p (m) values are larger.Therefore, greater probability directly obtains symbol from existing subband
The subband of conjunction condition, basis for estimation are that disclosure satisfy that Rank (Y (u+1))=Rank (Y (u))+1.
Step 3.3) is by both identity matrix Z (i, t) of the subband V (i) of selection and identity matrix Y (u) of request of data
Merge the identity matrix Y (u+t) after being merged=[V (1), V (2) ..., V (u), Vi(1), Vi(2) ..., Vi
(t)].Otherwise the order of matrix Y (u+t) is runed counter to certainly less than n with theorem 1.Have Rank (Y (u+t))=min (Rank (Y (u)),
Rank (Z (i, t))), i.e.,：The order of new identity matrix Y (u+t) is both the order of identity matrix Y (u), identity matrix Z (i, t)
In smaller.Y (u+t) is sent out as new request matrix to surroundings nodes, if searching out new subband, if there is
New subband V (j), meets Rank (Y (u+t+1))=Rank (Y (u+t))+1, then former to receive and forward new subband V (j) to replace
There is subband V (i), while meeting the request of data of many aspects, and identity matrix is asked to replace with Z (j, u+t)=Y (u+
t)。
In the present embodiment, so that the increased function expression of order such as formula (2) institute of identity matrix Y (u+t) in step 3.4)
Show；
+ 1 (2) Rank (Y (u+t+1))=Rank (Y (u+t))
In formula (2), it is new that Y (u+t+1) is that the mark vector of new subband V (j), identity matrix Y (u+t) are obtained after merging
Identity matrix, Rank (Y (u+t+1)) are the order of new identity matrix Y (u+t+1), and Rank (Y (u+t)) is identity matrix Y (u+
T) order.
Shown in the function expression such as formula (3) for recompiling condition in the present embodiment, in step 3.5)；
Rank (Y (u+m)) > Rand (Y (u)) (3)
In formula (3), Y (u+m) is the identity matrix for having m linear independence subband on the node, identity matrix Y (u) conjunctions
The new identity matrix obtained after and, Rank (Y (u+m)) are the order of new identity matrix Y (u+m), and Y (u) is request of data
Identity matrix, Rand (Y (u)) are the order of identity matrix Y (u).Wherein, Rank (Y (u+m))=Rank [V (1), V (2) ..., V
(u), Vi(1), Vi(2) ..., Vi(m)].After merging request failure, node is attempted to generate available son using recompiling mode
Band.If having m (m < n) a linear independence subband on the node, it is denoted asReceive request identity matrix Y (u).
If meeting conditional (3), can be generated by general random network coding method, the mode of recompiling meet the requirements it is new
SubbandIt is supplied to the node of request data to use.
In the present embodiment, intermediate node is the node for assisting to carry out data forwarding, need not decode partial data, usually
Also limited resource, which can only be taken out, assists forwarding, computing capability and Bandwidth-Constrained, most of node only to possess a few subband,
In the range of own bandwidth and coding/decoding capability data are provided for surroundings nodes.The behavior of intermediate node is the most complicated, is this
The core of method application, the workload of reduction intermediate node encoding and decoding that can be larger by this method, significantly saves its meter
Calculation ability.Receiving node can also respond the request of other nodes in computing resource and abundant bandwidth, be provided for other nodes
Data.New request of data is actively initiated by receiving node, after other nodes receive new request of data, is thened follow the steps
3).Receiving node receives the subband of n coefficient vector linear independence, so that it may to decode complete data, if not yet full
Foot, then to the more subbands of surroundings nodes acquisition request.It needs to take existing subband vectorial when request, is convenient for surrounding section
Point provides on demand.For having the receiving node of u linear independence subband, request mark Y (u)=[V (1), V (2) ..., V
(u)] be that n × u ties up matrix, if surroundings nodes are capable of providing a new subband V (i), request rank of matrix made to increase, i.e., it is full
Sufficient Rank (Y (u+1))=Rank [V (1), V (2) ..., V (u), V (i)]=Rank (Y (u))+1, then subband V (i) is for this
Node is useful, the order of wherein Rank (Y (u)) representing matrix Y (u).It such as successfully forwarded data, then it is subband V (i) is corresponding
Request identity matrix is denoted as Z (i, u)=[Vi(1), Vi(2) ..., Vi(u)]=Y (u).
For request of data Y (u), pass through step 3.1)~3.5) it can not all generate the subband met the requirements, then directly will
The request of data is transmitted to other nodes around, and meet demand is attempted by other nodes.
When request of data, have the receiving node of u subband, request identity matrix Y (u) is included in request of data and is sent out
It send, is found from surroundings nodes and meet the subband of Rank (Y (u+1))=Rank (Y (u))+1 to provide data.Once request is rung
It should succeed, then form data forwarding link, and continue to exist, the bandwidth of two end nodes be occupied, until respective nodes exit network.
Since network is dynamic change, data forwarding relationship continues dynamic change.In the present embodiment, due to being to change more
Violent dynamic network, tradition, which is commonly used in network coding method, only has random coded mode to be more applicable in, therefore uses Stochastic Networks
Network coding method (lower abbreviation RNC) and the distributed network coding method (lower abbreviation MNC) asked the present invention is based on merging carry out
Compare：
One, computing resource consumes comparative analysis.
Under each scale, topological analog case is generated to 20 groups of different randoms and has carried out statistical average, as shown in Figure 3.?
Most of node will participate in recompiling in traditional RNC methods, and only a small amount of ability is weaker, only forwards the centre of 1 subband
Node need not recompile.In the MNC methods of the embodiment of the present invention, very small amount of node participation is only used and has compiled again
Code, account for about network node sum 10% less than, in terms of encoding and decoding computing capability consumption drastically reduce.
Two, computing resource consumes comparative analysis.
Since in the MNC methods of the embodiment of the present invention, additional data payload is increased in terms of data merge request, and
Additional request of data forwarding has been carried out, has consumed a small amount of bandwidth resources to a certain extent.Network average throughput is compared, such as
Shown in Fig. 4, receiving node average effective handling capacity is given.Although can be seen that the MNC methods of the embodiment of the present invention are less than RNC
The handling capacity of method, but the two is very close, and the additional consumption of handling capacity is not notable.
Three, message delay comparative analysis.
Node respond request, recompile, forward request of data etc. due to, between source node to receiving node not
It can avoid that there is certain data delay, and weigh the important indicator of Transmitting Data Stream quality.Source node is compared to reception
Average data access delay between node, as shown in Figure 5.As seen in Figure 5, as network size increases, data pass
Average retardation all over whole network is increasing, but the delay of the MNC methods of the embodiment of the present invention is generally substantially better than the side RNC
Method, immanent cause be recompile number based on merging request and reduce data, and merge the when of asking be more conducive to select it is excellent
The path of change reduces the hop count of data forwarding.
The present embodiment also provides a kind of distributed network coded system based on merging request, including by source node, reception
The Distributed Computer System of node, intermediate node composition, the computer system are programmed to perform that the present embodiment is aforementioned to be based on
The step of merging the distributed network coding method of request.It should be noted that source node, receiving node, intermediate node are only
It is the division in logical construction, physics realization can carry out realizing using part same physical computer as needed.
The above is only a preferred embodiment of the present invention, protection scope of the present invention is not limited merely to above-mentioned implementation
Example, all technical solutions belonged under thinking of the present invention all belong to the scope of protection of the present invention.It should be pointed out that for the art
Those of ordinary skill for, several improvements and modifications without departing from the principles of the present invention, these improvements and modifications
It should be regarded as protection scope of the present invention.
Claims (6)
1. a kind of based on the distributed network coding method for merging request, it is characterised in that implementation steps include：
1) initial data is divided into n subband and introduces corresponding mark vector respectively to n subband and carried out by source node in advance
Unique mark, the identity matrix Y (u) that n initial mark vector is constituted are unit matrix, wait for request of data；
2) receiving node sends out request of data as unit of subband to adjacent intermediate node, is accompanied with and connects in the request of data
Receive the identity matrix Y (u) that the mark vector of the subband of the existing u linear independence of node is constituted；
3) after arbitrary intermediate node receives request of data, judge whether this node possesses partial data, if possessing partial data
A mark vector and the subband of identity matrix Y (u) is then selected to return to receiving node or upper level intermediate node；If gathered around
There is deficiency of data, then obtaining qualified subband from trial in existing subband returns among receiving node or upper level
Node；Continuing to attempt to merge if the qualified subband failure of trial acquirement asks the existing subband of carrying to be overlapped transmission
The subband that value adjacent node please look for novelty returns to receiving node or upper level intermediate node；It is adopted if merging request is unsuccessful
New subband, which is generated, with the mode recompiled returns to receiving node or upper level intermediate node；It can not all be produced in aforementioned operation
Then directly to adjacent intermediate node or source node forwarding request of data until request of data reaches when the raw subband met the requirements
Source node；
4) judge whether the order of the identity matrix of local existing subband is true equal to the decile sub-band sum n of initial data, such as
Fruit, which sets up then to redirect, executes next step；Otherwise, it redirects and executes step 3)；
5) receiving node is decoded existing subband, the initial data asked.
2. according to claim 1 based on the distributed network coding method for merging request, which is characterized in that in step 3)
Arbitrary intermediate node receives the detailed execution step after request of data：
3.1) it is total equal to what request of data included to judge that present node has the number of sub-bands m that mark SYSTEM OF LINEAR VECTOR is unrelated in subband
Whether number of sub-bands n is true, judges that this node possesses partial data if setting up, has from present node and select one in subband
The subband of a mark vector and identity matrix Y (u) returns to receiving node or upper level intermediate node；Otherwise, execution is redirected
Step 3.2)；
3.2) judge whether directly obtain from the existing subband of present node and meet so that the order of identity matrix Y (u) increases
The subband added, if it is possible to directly obtain qualified subband, then will directly obtain qualified subband and return to
Receiving node or upper level intermediate node simultaneously exit；Otherwise, it redirects and executes step 3.3)；
3.3) from the existing subband of present node optional one be subband V (i) that other nodes provide, which corresponds to
Identity matrix be Z (i, t)=[Vi(1), Vi(2) ..., Vi(t)], by the identity matrix Z (i, t) of the subband V (i) of selection and
Both identity matrix Y (u) of request of data merge the identity matrix Y (u+t) after being merged；
3.4) identity matrix Y (u+t) is sent out as new request matrix to surroundings nodes, if searching out new subband V (j)
Meet so that the order of identity matrix Y (u+t) increases, then to receive and forward new subband V (j) to replace original subband V (i), and by V
(i) identity matrix Z (i, t) replaces with Z (j, u+t)=Y (u+t), and subband V (j) is returned to receiving node or upper one
Grade intermediate node simultaneously exits；Otherwise, it redirects and executes step 3.5)；
3.5) judge whether the subband of the existing linear independence of present node meets the condition of recompiling, recompiled if met
Condition then uses random network code method according to the subband of the existing linear independence of present node, is produced in a manner of recompiling
The raw new subband met the requirements, and new subband is returned into receiving node or upper level intermediate node and is exited；Otherwise, it redirects
Execute step 3.6)；
3.6) to adjacent intermediate node or source node forwarding request of data until request of data reaches source node.
3. according to claim 2 based on the distributed network coding method for merging request, which is characterized in that step 3.2)
In so that identity matrix Y (u) the increased function expression of order such as formula (1) shown in；
Rank (Y (u+1))=Rank (Y (u))+1 (1)
In formula (1), Y (u+1) is obtained after merging for the subsidiary identity matrix of the mark vector of qualified subband, request of data
New identity matrix, Rank (Y (u+1)) is the order of new identity matrix Y (u+1), and Y (u) is the subsidiary mark of request of data
Matrix, Rank (Y (u)) are the order of identity matrix Y (u), and u is the number of sub-bands that request of data initiator has linear independence.
4. according to claim 2 based on the distributed network coding method for merging request, which is characterized in that step 3.4)
In so that identity matrix Y (u+t) the increased function expression of order such as formula (2) shown in；
+ 1 (2) Rank (Y (u+t+1))=Rank (Y (u+t))
In formula (2), Y (u+t+1) is the new mark that the mark vector of new subband V (j), identity matrix Y (u+t) are obtained after merging
Matrix, Rank (Y (u+t+1)) are the order of new identity matrix Y (u+t+1), and Rank (Y (u+t)) is identity matrix Y's (u+t)
Order.
5. according to claim 2 based on the distributed network coding method for merging request, which is characterized in that step 3.5)
In recompile shown in the function expression such as formula (3) of condition；
Rank (Y (u+m)) > Rand (Y (u)) (3)
In formula (3), Y (u+m) is the identity matrix of existing m linear independence subband on the node, after identity matrix Y (u) merging
Obtained new identity matrix, Rank (Y (u+m)) are the order of new identity matrix Y (u+m), and Y (u) is the mark of request of data
Matrix, Rand (Y (u)) are the order of identity matrix Y (u).
6. a kind of formed based on the distributed network coded system for merging request, including by source node, receiving node, intermediate node
Distributed Computer System, which is characterized in that the computer system is programmed to perform any one in Claims 1 to 5
The step of described in based on the distributed network coding method for merging request.
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