CN103957085B - Media access control method for wireless mesh network based on network coding - Google Patents
Media access control method for wireless mesh network based on network coding Download PDFInfo
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Abstract
The invention discloses a media access control method for a wireless mesh network based on network coding. The media access control method comprises the steps of a data package receiving stage, a data package transmitting stage and an ACK monitoring stage. According to the protocol, a network coding mechanism is introduced into a media access control layer, and throughput is increased compared with the traditional media access control method based on conflict avoidance. The media access control method is high in decoding success rate, less in control expenditure, low in calculation consumption of hardware, strong in portability, good in compatibility and capable of relieving network congestion partially.
Description
Technical field
The present invention relates to radio network technique field is and in particular to a kind of wireless network medium based on network code accesses
Control method it is adaptable to provide high-throughput for service purpose wireless mesh network.
Background technology
How to improve the emphasis research topic that data throughout is wireless mesh network.Feelings in channel medium resource-constrained
Under condition, the data transport service of high-quality of handling up for access device offer high bandwidth height, to the physical layer of wireless mesh network, medium
MAC layer proposes high requirement.Meanwhile, the networking equipment price general charged of wireless mesh network is cheap, data buffer storage ability,
Calculation processing power is limited, it is ensured that media access control method efficient stable runs equally under so harsh hardware condition
It is a critical problem.Because network code has remarkable effect to throughput hoisting, in addition, network code need extra hard
Part resource, so, it is one based on the wireless mesh network media access control method that network code has stability autgmentability concurrently
Breach.
Wireless mesh network has extensive application in recent years.The predominantly densely populated place such as enterprise, school, market, station
Place provides wireless network access solution.It is primarily characterized in that deployment convenient, with low cost, automatic network-building, autgmentability
High.Dispose in cable network difficult, in the case that autgmentability cannot ensure, substitute underlying basis using wireless mesh network and set
Apply, be the most simple and effective method.Using wireless mesh network provide Internet access service it is critical that how for numerous
Wireless terminal provides height to handle up, stable data transmission mechanism.In prior art, the data in order to improve wireless mesh network gulps down
The amount of telling, mainly has following several research：
The first kind：Physical layer more high bandwidth；The shortcoming of the method is by hardware technology, improves single-frequency bandwidth or multifrequency is multiple
With technical difficulty is big, increased radio reception device price, terminal device is had high demands, belong to a kind of solution cured the symptoms, not the disease
Certainly method.High-frequency communication, multi-band communication simultaneously, the cost exchanging handling capacity for is the electromagnetic pollution in wireless signal space.
Equations of The Second Kind：Internet chance route；The shortcoming of the method is that additional communication expense is big, controls complicated, realizes difficulty
Greatly.Routing Protocol is generally operational in Internet, chance route normal work using control information need additional transmissions to complete,
This leads to data link layer to pay overhead.And chance route implementing is got up, technical difficulty is big, and hardware resource is disappeared
Consumption is not also studied in detail.
3rd class：Tightened up media access control method；The shortcoming of such method is requirement wireless netted network node
Reach and node between what a certain degree of tacit agreement will do that is to say, that being aware of each other, between node, clock is synchronous
Require high.And, once certain equipment goes wrong in network, the other equipment of collaboration also will face same problem.
Network universality, robustness, autgmentability are problematic in that.
4th class：Internet adds network code mechanism；The shortcoming of such method is network code independent of medium access
Key-course and TCP layer, need to provide reliable broadcast service using extra radio broadcasting agreement.Meanwhile, this kind of method meeting
Manufacture the bigger virtual bottleneck node of scope in a network, lead to network congestion on a large scale.And, the congestion control reason of Internet
By can lead to this kind of method cannot normal work.In addition, this kind of method also seldom considers the consumption to hardware resource, realize
Carry out technical difficulty big, apparatus adaptability is poor.
Independent of the network code mechanism of media access control layer and TCP layer, each node chance will monitor neighbours' section
The packet of point broadcast, is placed in the caching of oneself, in case using during decoding.The defect that do so is brought mainly has：1) no save
The monitoring neighbor data bag of system is catastrophic to local cache consumption.Its caching consumes in addition to link load, is also subject to neighbours
Number affects.And whether these packets of listening to can be utilized is also unknown number.The chance that throughput hoisting is paid becomes
Ben Taigao, application is uncertain high, poor controllability.2) whether node prediction neighbours have cached certain packet, Main Basiss chain
Road transmission success rate ETX index carries out probability Estimation.According to ROC Calibration Theory, what it used estimates that model has fixing mistake
Rate by mistake.High in number of nodes, terminal device is many, and Communication Jamming is big, in the case that radio link quality is poor, this fixed error rate
Quite a few coding bag can be led to can not to be correctly decoded, thus wasting more hardware resources and channel resource.3) this
Mechanism is generally pursued every time coding and is all organized in once packet as much as possible, to reduce the number of broadcast times of individual node.But
This way is in practice and improper.One may not all of destination node can be correctly decoded, and two reliably to broadcast association
View, when destination node is many, often limits node communication in larger scope, causes entire area channel utilization low
Under.
Content of the invention
Wireless mesh network media access control method based on network code is shown with common media access control method
Write different, draw for deficiency in throughput hoisting ability for the existing wireless mesh network media access control method and Internet
Enter many defects of encoding mechanism, a kind of present invention height of proposition is handled up, low consumption, has the medium access control of universality robustness concurrently
Method processed.
In order to realize above-mentioned task, the technical solution used in the present invention is：
A kind of wireless mesh network media access control method based on network code, in this wireless mesh network, when
After one node receives the packet that neighbor node is sent, judge that this packet is general data bag or coded data
Bag：
If coded data packet, then this coded data packet is decoded, successfully decoded obtains the general data of needs
Bag, decoding is unsuccessful, abandons this coded data packet；
If general data bag, then judge whether this general data bag reaches the formation condition of coded data packet, such as reach
To then encoding to it, and the coded data packet obtaining after coding is broadcasted to neighbor node；
The formation condition of coded data packet and cataloged procedure are as follows：
In this wireless mesh network, at least two neighbor nodes of node A, if the forwarding queue of initial time node A
For sky, then from the beginning of initial time：After node A receives the general data bag p2 that neighbor node is sent, in forwarding queue
Find a general data bag p1, meet formula 1 and formula 2 if there is p1 simultaneously, then p1 and p2 coding is become coded number
According to bag p；
(formula 1)
In equation 1, s1, s2 be respectively packet p1, p2 source node MAC Address, d1, d2 be respectively p1, p2 next
The MAC Address of hop node, t1, t2 are respectively the time that p1, p2 reach node A, and θ value is 0.3 second；
(formula 2)
In formula 2, r and c is respectively node A from the beginning of initial time, receives the general data bag of neighbor node transmission
Accumulative number and node A forwarding queue in, meet the accumulative number of the general data bag of formula 1, wherein r every time add up 1,
C adds up 2, ξ value every time for 0.08.
Further, general data bag p1 and p2 be through also or operation coding becomes coded data packet p, specially：
The MAC Address of general data bag p2 destination node and p1 destination host MAC Address are done also or computing, acquired results
Insert the destination host MAC field of p1；General data bag p2 source host MAC Address and p1 source host MAC Address are also done or transports
Calculate, acquired results insert the MAC field of the source node of p1；The data division of the data division of p2 and p1 is done also or computing, institute
Obtain the data division field that result inserts p1；If the data portion length of p1 and p2 is inconsistent, by a side shorter for length
Afterbody fills out 0 cover, and the new packet of generation is coded data packet p.
Further, in this wireless mesh network, in each node, it is provided with resource queue, when node is general by one
After logical packet is successfully sent to another node, this general data bag is moved into resource queue from forwarding queue, and is
This general data bag starts a count-down device, and count-down device initial value is θ, after count-down device zero, by this general data bag
Remove from resource queue.
Further, after node receives a coded data packet, it is decoded operate：Node is from the resource of oneself
General data bag corresponding with the coded data packet receiving is found, by the general data finding bag and the coded number receiving in queue
Carry out also or computing, obtaining the general data bag of needs according to bag.
Further, after node A generates coded data packet p, the step that p is broadcasted is as follows：
Step S1, creates broadcast RTS frame, the MAC Address of the next-hop node of general data bag p1, p2 is write RTS frame
In, and determine channel occupancy duration Tb, Tb is added to the call duration time field of broadcast RTS frame, Tb computational methods are as follows：
Tb=5 × SIFS+ (82+L) × t0(formula 3)
In formula 3, SIFS is the shortest stand-by period constant of 802.11 agreement regulations, and L is the length of coded data packet p,
t0Time required for one byte of transmission, determined by link bandwidth；
Step S2, node A broadcasts RTS frame request channel；
Step S3, after neighbor node receives RTS frame, determines that oneself replys the stand-by period Tcts of RTS frame, and when waiting
Between after reply CTS frame to node A；Tcts computational methods are as follows：
(formula 4)
In formula 4, iMAC is the MAC Address of this neighbor node, and d1, d2 are the next-hop node of packet p1, p2 respectively
MAC Address；
Step S4, node A has sent broadcast RTS frame, waits 2 × SIFS+28 × t0After time, check the CTS frame receiving
Situation, if the CTS frame that the next-hop node receiving p1, p2 respectively is replied, node A starts after waiting the SIFS time to send to compile
Code packet p, wait is kept out of the way in otherwise node A entrance.
Advantages of the present invention mainly have following some：
1. increased network throughput；
Due to introducing network code mechanism to data link layer, the present invention inherently improves network throughput.Hard
The network data handling capacity of 7%-40% in the case of part condition is constant, can be improved using the present invention.
2. transplantability is strong, and compatibility is good；
Good backward compatible due to having done to CSMA/CA, therefore support that the equipment of the present invention same can not support this
Bright equipment proper communication, networking.Meanwhile, the present invention increases and enhances MAC sublayer, to other aspects of network
Do not constitute impact, interface is transparent.
3. it is decoded into power high, additional communication is few；
Different from other network code mechanism, the present invention uses ACK frame data packet header to transmit necessary coding information, section
Point does not use ETX route chi to be predicted, and therefore, do not have that predicated error brings cannot decode phenomenon.And, the present invention is not
The control information relying on other agreements (as chance route) is it is not necessary to transmit independent control information between node.
4. hardware consumption is few；
Compared with other network code mechanism, this method more focuses on the occupancy to cache resources and computing resource.Node is not
Again chance monitor neighbours between communication, thus storage decoding resource caching consumption be down to minimum.
5. part solves network congestion problem；
In the network not having congestion control, when offered load is big, unavoidable around trunk roads bottleneck node and bottleneck node
Congestion phenomenon occurs.This method exactly utilize the big advantage of bottleneck node transmission information amount it would be possible to data packet coding one
Rise.Thus allowing these packets quickly through bottleneck node, reducing congestion, slowing down the generation of congestion.
Brief description
Fig. 1 is encoding mechanism principle and network design schematic diagram；
Fig. 2 is data is activation phase process figure；
Fig. 3 is data reception phase procedure chart；
Fig. 4 is that ACK frame monitors phase process figure；
Fig. 5 (a) and Fig. 5 (b) is the structural representation of frame in the present invention；
Fig. 6 is coded data packet broadcasting process schematic diagram；
Fig. 7 is this programme overall flow figure；
Fig. 8 is the impact to code machine meeting for the research offered load and ξ determines schematic diagram；
Fig. 9 is the experimental result picture on code machine meeting quantity impact for the research θ；
Figure 10 (a), Figure 10 (b), Figure 10 (c), Figure 10 (d) are under identical ω, different θ, decode resource queue's service condition
Figure；
Figure 11 (a), Figure 11 (b), Figure 11 (c), Figure 11 (d) are under different ω, the impact to three kinds of node proportions for the θ
Schematic diagram；
Figure 12 (a), Figure 12 (b) are the research experimental result pictures to each method performance impact for the offered load；
Figure 13 (a), Figure 13 (b) are the research experimental result pictures to each method performance impact for the link transmission success rate；
Figure 14 (a), Figure 14 (b), Figure 14 (c), Figure 14 (d) are that research offered load uses the reality of impact to each method caching
Test result figure；
Specific embodiment
Applicant disposes large-scale wireless mesh network between floors, is to provide to equipment such as mobile phone, notebook computers
Internet access service, needs the media access control method that handling capacity is high, compatibility is good, consumption resource is few, is respectively connect with ensureing
Enter the data service quality of equipment.For node hardware condition is limited, the complexity feelings such as demand of handling up height, quality of wireless channel difference
Condition is it is proposed that wireless mesh network media access control method based on network code.
This method uses network code mechanism to improve handling capacity, therefore when wireless mesh network is disposed, except network edge
Outside node, other nodes at least will have 2 neighbor nodes, and in all neighbor nodes, at least has 1 to can not be mutually straight
Connect the neighbor node of letter, as shown in Figure 1.Node B, C, D are in the communication range of A, but node D is in the communication range of B,
Only in this way, node A could encode to the round data on this link of B-A-D, else if D is in the communication range of B
Interior, B will be directly passed to D data, and A will not obtain code machine meeting.
The all node locations of this method are fixed or only small movement.The communication radius of all nodes are constant.Each section
It is respectively provided with and safeguards three queues in point：Forwarding queue, for depositing the packet that will be sent to other nodes, can be general
Logical packet or coded data packet；Resource queue, for depositing the general data bag using during decoding；Reduction queue,
For depositing the general data bag that after coded data packet sends unsuccessfully, restoring operation uses.
The network code mechanism that this method is used, its core concept is, as shown in figure 1, node D sends commonly first
Packet p1 will forward through transit node A to B, centre；After A receives p1, at once p1 is not transmitted to B, but p1 is delayed
Deposit a period of time；Node B sends another general data bag p2 to node D, needs also exist for A transfer；After A receives p2, p2 and
P1 is encoded to together, and coded data packet p1 p2 is broadcasted, and after node B and D receives coding bag p1 p2, is all decoded
Operation, the general data bag each being needed.Whole process consumes three communication cycles, than original " receive and forward "
Process reduces by a communication cycle, thus reaching the purpose of lifting handling capacity.
This method based on 802.11 agreements, the general data bag used in scheme, in as 802.11 agreements, two
It is used for the packet of transfer data information between node.In this programme, on the basis of 802.11 agreements are original, increased broadcast
RTS frame, coded data packet, coding three kinds of frame formats of ACK frame, essentially identical in the form and 802.11 of all kinds of frame data bags,
Difference is to increased, in general data bag frame entity head, the packet id field that length is 4B, in coded data packet frame
Entity head increased packet id field data packet length field.Fig. 5 (a), Fig. 5 (b) give all numbers using
According to frame (bag) form, therefore it is divided into Fig. 5 (a) and two figures of Fig. 5 (b) because picture is larger, but its expression is a set of；Table 1 with
As a example the example of Fig. 1, give in the middle of the structure of packet (frame) that this programme is used, with 802.11 in identical packet
The explanation of the different field of (frame) implication, except these fields, remaining field is identical with the implication of field in 802.11 agreements.Its
In " frame " be data link layer concept, be the unit of packet.In this programme, " frame " is identical with the implication of " bag ", refer both to containing
Control information data information is in interior bit sequence.It is emphatically the discussion to frame or bag internal structure, therefore in this programme
The place of all appearance " frame " all can use " bag " to replace, and such as " coded frame data " refers to " coded data packet ".
Table 1
First, the inventive method detailed step
In the wireless mesh network structure of the present invention, in addition to fringe node, remaining node all enters according to this method
The forwarding of row packet and processing procedure, the thing that these nodes are done is identical, therefore for the ease of clearly introducing this
Scheme, as a example the model shown in below by Fig. 1, scheme is simplified to an information exchange unit, that is, between tri- nodes of A, B, D
Information interactive process illustrating；A node in this model can be in mesh network arbitrary one in addition to fringe node
Individual node, and B, D node is the neighbor node of A, and D needs to send general data bag p1 to B, and the transmission of B needs is common simultaneously
Packet p2 is to node D.
In this programme, produce packet in different intra-nodes and receive stage, packet sending node and the monitoring of ACK frame
In the stage, separately below each stage is described in detail.
1. packet receives the stage
In this programme, it is sent to the packet of destination node from source node, when source node obtains this packet, referred to as
General data bag, the packet structure in this packet and 802.11 is identical, is uniquely a difference in that the frame in this packet is real
Body head increased the packet id field that length is 4B, and this id field is generated by source node.General data bag is each in a network
In the transmittance process of individual node, if it meets encoding condition at certain node, just two general data packet encoders are become
Coded data packet is simultaneously broadcasted；As it does not meet encoding condition, then this general data bag is according to the common number in the middle of 802.11 agreements
Equally forwarded according to bag, thus completing the transmittance process at this node, therefore one node receives the number that neighbor node is sent
Just there are two types according to bag：General data bag and coded data packet.
After a node A receives the packet that neighbor node is sent, judge that this packet is general data bag or volume
Code packet, as shown in Figure 3；
Step S10, determines the type of packet
After node physical layer receives completely errorless packet, judge that this is one according to packet MAC header length
General data bag or coded data packet.Frame is divided into three parts：Frame head (Mac header), frame entity (body), FCS domain.
If MAC header length is 30B, show to receive a general data bag, if MAC header length is 36B, show to receive
To a coded data packet.
For coded data packet, this coded data packet is decoded, successfully decoded obtains the general data bag of needs；Solution
Code is unsuccessful, abandons this coded data packet；After obtaining general data bag, this packet is regarded the new packet receiving by node
Equally processed；
For general data bag, the packet ID that node extracts this data packet frame entity head first is denoted as idx, then
The resource queue of oneself searches.If have found the decoding resource bag comprising idx, the general data bag receiving was described once
It is a part for certain coded data packet, but that coded data packet is not successfully received, upper hop node is coded number
After bag decoding, carry out retransmission operation, therefore node will remove the decoding resource bag searching out.If can not find comprising idx
Decoding resource bag, illustrate that the general data bag receiving can carry out coded treatment.
The formation condition of coded data packet and cataloged procedure are as follows：
The forwarding queue of setting initial time node A is sky, does not have packet in forwarding queue.Each node is slow
Deposit middle maintenance two shaping variable r and c, four list lattice b.The initial time value of r and c is zero, from the beginning of initial time,
The value of two variables constantly adds up always；B deposits the auxiliary information of general data bag in forwarding queue.
Here the moment that initial time illustrates that the solution of the present invention and defines, in this moment, node A's
There is no packet in forwarding queue.This initial time can be understood as the time point that node A is arranged in sensor network, that is,
In moment when sensor node is started working, the value of variable r and c safeguarding from this moment, node A is just from the beginning of 0
Add up always.
After node A receives the general data bag p2 that neighbor node B sends, seek from the front to the back in the form b of forwarding queue
Look for a general data bag p1, meet formula 1 and formula 2 if there is p1 simultaneously, then p1 and p2 coding is become coded data
Bag p；
(formula 1)
In equation 1, s1, s2 be respectively packet p1, p2 source node MAC Address, d1, d2 be respectively p1, p2 next
The MAC Address of hop node, node A can be obtained by routing algorithm；T1, t2 are respectively the time that p1, p2 reach node A, θ value
For 0.3 second, its determination process was shown in experiment two.
Condition given by formula 1 is that, after node A receives general data bag p2, there is packet in its forwarding queue
P1 does not also forward, and p1 and p2 meets：The next-hop node (destination node) of p1 is the source node of p2, the source section of p1
Point is the next-hop node (destination node) of p2, and the time difference that p2 and p1 reaches node A, (i.e. the source node of p1 was also in money less than θ
The copy of an in store p1 in the queue of source), after meeting these conditions, be given in Fig. 1 example, D needs to send and commonly counts
According to bag p1 to B, B needs to send general data bag p2 to this situation of node D simultaneously；
(formula 2)
In formula 2, r receives accumulative of the general data bag that neighbor node sends for node A from the beginning of initial time
The value of r, as long as that is, A receives a general data bag, is just added 1 by number；In the forwarding queue of c finger joint point A, meet the general of formula 1
The accumulative number of logical packet, you can the number of the packet being encoded, if the bar of a general data bag coincidence formula 1
Part, can be encoded, then the value of c cumulative 2；ξ is a fixed constant, and its value is 0.08；K is code switch, works as k<During ξ,
Illustrate that present node works in case of a low load, or neighbouring network is providing service for the application such as FTP, Streaming Media, then should
General data bag does not need to encode, and the general data bag according to 802.11 is forwarded；And k>During ξ, illustrate to flow through present node
Data flow direction complicated enough, the coding of general data bag should be carried out using this method, the determination process of ξ value is shown in experiment one.
Step S11, the coding of general data bag
To meeting general data bag p1 and p2 of encoding condition through also or operation coding becomes coded data in this programme
Bag p, i.e. p=p1 p2, specially：
General data bag p2 is put into reduction queue by node A, in case reduction process makes when coded data packet p sends unsuccessfully
With.After node A destination node MAC field in the MAC header of p1, increase a destination node 2MAC field, wherein write
The destination node MAC Address of p2；Do also or computing with the destination host MAC Address of destination host MAC and p2 of p1, acquired results
Insert the destination host MAC field of p1；Do also or computing with the source host MAC Address of source host MAC and p2 of p1, acquired results
Insert the source host MAC field of p1；After the frame solid data bag id field of p1, add packet ID, p1 frame entity number of p2
According to partial-length, p2 frame solid data partial-length；Also make of the frame solid data part of p1 and the frame solid data part of p2
Or computing, acquired results insert the frame solid data part field of p1, if the data portion length of p1 and p2 is inconsistent, will
0 cover is filled out in the shorter square tail portion of length；The new packet then generating after both codings is coded data packet p.
Step S12, coding information is transmitted
Node A by general data bag p2 be encoded to p1 together with after, make one coding ACK frame, the suffix ID1 word of this frame
Section inserts the packet ID of packet p1 frame header, and suffix ID2 field inserts the packet ID of packet p2 frame header.Wait
After the SIFS time, node A is sent to node B by encoding ACK frame.
Step S13, coded data packet decodes
After A makes coded data packet p, to neighbor node broadcast.After packet p1 is sent to node A by node D, section
P1 is moved into resource queue by point D from forwarding queue, and starts a count-down device, count-down device for this general data bag p1
Initial value is θ, after count-down device zero, this general data bag is removed from resource queue.It is moved into common in resource queue
Packet p1 uses when D receives and is decoded by the coded data packet that p1 generates.
Its neighbor node D receives the p of A broadcast, and the head from the frame entity of this p first extracts packet 1ID, data
Bag 2ID, packet 1 length, packet 2 length, are denoted as id1, id2, l1, l2 respectively.Node D seeks in the resource queue of oneself
Look for general data bag corresponding with coded data packet p receiving, that is, frame entity head comprises the general data bag of id1 or id2.Look for
To after this general data bag is denoted as p3, if can not find p3, illustrating that p can not be successfully decoded, p abandoned.
Node D extracts packet ID data packet length from p3, is denoted as id3 and l3 respectively.If id3 is equal to id2,
Destination node MAC field by the destination node 2MAC address reproduction of coded data packet p to p3；Destination host MAC ground with p3
The coding destination host MAC Address of location and p does also or computing, and acquired results put into the destination host MAC field of p3；Source with p3
The coding source host MAC Address of host MAC address and p does also or computing, and acquired results put into the source host MAC field of p3；With
Encoded data portion in data division in p3 frame entity and p coded frame entity does also or computing, if acquired results length
More than l2, then intercepted, l2 byte before only retaining, and the result after intercepting is write the frame solid data part of p3.id3
It is similar to equal to way during id1；The packet p2 that the p3 of new production obtains after decoding.
Node D, when decoding p, determines and replys ACK frame stand-by period Tack, then reply common ACK frame to node A, table
Bright oneself have received coded data packet, and packet is successfully decoded.After node D is successfully decoded p, by the p3 processing
Packet submits to Internet.
Note：The coded data packet decoding process of step S13 introduction, is explained with node D for present node,
And if node A receives the coded data packet that other nodes are sent, it is the same with the decoding process of this part.It is current with D
Node explains the explanation being to carry out with the example that Fig. 1 provides, actually in application process, the process that node A is completed
It is all generations in each node in addition to fringe node, B-A-D is that abstracting is used for explaining this programme
Naive model, B, D are the same with the process that A completes in fact.
2. packet transmission phase
Step S20, determines channel occupancy type
Node A judges the length of first packet MAC header in the forwarding queue of oneself, if 30B, explanation
This is a general data bag, according to 802.11 RTS-CTS flow operations.
If MAC header length is 36B, explanation will broadcast a coded data packet, such as coded data packet p, such as 2
Shown.
Step S21, creates RTS frame
Create a broadcast RTS frame, the MAC Address of oneself is added to the source node MAC field of this frame, by the MAC of p
Destination node 1MAC in header and destination node 2MAC field copy to the corresponding field of this coding RTS frame, with shown in Fig. 1
As a example model, the MAC Address of next-hop node of general data bag p1, p2 will copy to the MAC field of this broadcast RTS frame；
It is then determined that channel occupancy duration Tb, Tb is added to RTS frame traffic time field, Tb computational methods are as follows：
Tb=5 × SIFS+ (82+L) × t0(formula 3)
In formula 3, SIFS is the shortest stand-by period constant of 802.11 agreement regulations, and L is the length of coded data packet p,
t0Time required for one byte of transmission, determined by link bandwidth；Fig. 6 is that coded data packet sends overall process schematic diagram,
Tb is that from node A starts to send broadcast RTS frame and arrives node B and terminate transmission time of being experienced of ACK frame, includes altogether 5 SIFS
Time, 1 broadcast RTS frame transmission time, 2 CTS frame transmission times, 1 coded frame data transmission time and 2 common ACK
Frame transmission time.Broadcast RTS frame length 26B, CTS frame and common ACK frame length are all 14B.
Step S22, node A broadcasts RTS frame request channel；
Step S23, after neighbor node receives RTS frame, determines that oneself replys the stand-by period Tcts of RTS frame, and is waiting
CTS frame be replied to node A after time；Tcts computational methods are as follows：
(formula 4)
In formula 4, iMAC is this neighbor node, and such as neighbor node D receives this RTS frame, the as MAC Address of D, d1, d2
The MAC Address of the next-hop node of packet p1, p2 respectively, i.e. the MAC Address of B and D；After node D waits the Tcts time, such as
Fruit does not have node using channel around finding, then reply CTS frame to node A, show that oneself can be communicated with node A.Connecing
Tb-Tcts-40 × the t getting off0In time, even if the RTS frame receiving the transmission of other nodes does not do any reply more yet.If section
Point D finds that surrounding channel is currently being used, then directly lose the RTS frame that node A sends.The thing that node B is done is identical with D.
Step S24, judges channel request result
Node A has sent broadcast RTS frame, waits 2 × SIFS+28 × t0After time, check the CTS frame condition receiving, such as
Fruit receives the CTS frame that the next-hop node of p1, p2 is replied respectively, channel request success is described, then after node A waits the SIFS time
Start to send coded data packet p, if only receiving a CTS frame or not receiving CTS frame, the failure of specification request channel, section
Point A enters and keeps out of the way wait.
After node D receives the coded frame data of A broadcast, it is decoded operating (detailed process is shown in step S13), and determines back
The stand-by period Tack of multiple ACK frame, Tack computational methods are as follows：
Wherein iMAC is the MAC Address of node D, and MACheader.DtMAC1 is the mesh of the coded data packet that node D receives
Node 1MAC address, i.e. the MAC Address of B；MACheader.DtMAC2 is destination node 2MAC address, i.e. the MAC Address of D.
Node D waits the Tack time, if encode wrapping decoding correctly, replys common ACK frame to node A, otherwise direct discarding receives
Coded data packet.The thing that node B is done is identical with D.
Step S25, judges retransmission state
After p=p1 p2 is sent by node A, wait 2 × SIFS+28 × t0Time, check the ACK frame feelings receiving
Condition.If node A receives two ACK frames from node B and node D respectively, illustrate that B and D has been received by coded data packet p1
P2 is simultaneously successfully decoded, and at this moment p is removed by node A from forwarding queue, and finds p2 from the reduction queue of oneself, and p2 is removed.
If an ACK frame is all confiscated, enter and keep out of the way wait.
If only receiving the ACK frame of node D reply, without receiving the ACK frame of B reply, illustrate that B could not be properly received volume
Code packet p or can not be correctly decoded.Now, node A needs to find general data bag p2 from the reduction queue of oneself, directly
Replace the p1 p2 in forwarding queue with p2, then keep out of the way wait.
If only receiving the ACK frame of node B reply, without receiving the ACK frame of D reply, illustrate that B could not be properly received volume
Code packet p1 p2 or can not be correctly decoded.Node A finds general data bag p2 from the reduction queue of oneself.Node A needs
Destination node 2MAC field (address) in the MAC header of coded data packet p1 p2 is removed；With encoding destination host
The destination host MAC Address of MAC Address and p2 does also or computing, replaces the coding destination host MAC Address of p with acquired results；
Make also or computing of the source host MAC Address of coding source host MAC Address and p2, replace the coding source host of p with acquired results
MAC Address；Remove packet 2ID data bag 2 length of coded data packet frame entity head；With coded number in the frame entity of p
Do the encoded data portion also or computing replacing p with acquired results according to part and data division in the frame entity of p2；According to coding
The remaining packet of frame entity head 1 length blocks coded frame entity, abandons redundance；Refresh the FCS field of p；Last from
P2 is removed in reduction queue.So, just coded data packet p is reduced into packet p1, then keeps out of the way wait.
3.ACK frame monitors the stage
The embodiment of the present invention ACK frame monitoring stage includes updating resource queue, safeguards resource timer etc..Major function is
Management decoding resource queue.In this stage, node not only will be intercepted and will be sent to the ACK frame of oneself, also will keep out of the way
During treating, the ACK frame of transmission between other nodes of idle listening.
Fig. 4 monitors phase process figure for ACK frame, illustrates that the present embodiment ACK frame monitors stage mistake in conjunction with Fig. 1, Fig. 5 and Fig. 6
Journey figure comprises the following steps that：
Step S30, determines ACK frame state.After node listens to ACK frame, check that the destination node MAC field of ACK frame is
The no MAC Address with oneself is identical.If identical, illustrate that this ACK frame is the confirmation of the packet that oneself was sent just now, need
Update resource queue establishing resource timer；If it is not the same, illustrating that this ACK frame is that idle listening obtains, check this ACK
Whether frame is coding ACK frame, wherein whether comprises suffix id field, if not containing suffix id field, directly by this ACK
Frame abandons, and otherwise, needs to safeguard resource timer.
Step S31, updates resource queue.After node B transmission general data bag p2 is to node A, wait SIFS, if confiscated
To ACK frame, illustrate that p2 sends unsuccessfully, enter and keep out of the way wait.If receiving ACK frame, no matter whether this ACK frame encodes ACK frame,
All illustrate that A has had successfully received p2.General data bag p2 is moved into resource queue from forwarding queue by node B, and is resource bag p2
Start a count-down device, count-down device initial value is θ, after count-down device zero, resource bag p2 is removed from resource queue.Cause
It is according to formula 1, count-down device is zeroed, node A will not encode to p2 again.
Step S32, checks coding information.If the ACK frame that node B receives belongs to coding ACK frame, node A is described not only
Be properly received general data bag p2, and by p2 with other data packet codings to together.Node B is from the suffix of ACK frame
Extract packet ID in ID1 and be denoted as id1, i.e. the packet ID of general data bag p1 frame entity head.Node B stops step S31
In for resource bag p2 open count-down device, prevent p2 from surprisingly being removed, lead to coded data packet p1 p2 not decode.Node B
The packet ID of general data bag p2 frame entity head is changed to id1, so that the operation of step S13.Hereafter, general data bag p2 from
It is removed only two kinds situations in resource queue to occur：One is that coded data packet p reaches and is successfully decoded, and two is frame entity head
Packet for id1 reaches (step S13).
Step S33, updates count-down device.After node D transmission general data bag p1 is to node A, receives node A and reply really
Recognize ACK frame, that is a common ACK frame, and according to step S31, p1 is moved to the resource queue of node D, and one is fallen to count
When device be resource bag p1 timing.Although this posterior nodal point D does not send data using channel, communication range to be intercepted always
Communication between other nodes interior.Node A receives after node B is sent to its general data bag p2 and reaches encoding condition, will
P2 encodes, and replys a coding ACK frame to node B.This of now node D meeting idle listening encodes ACK frame.Node D carries
Suffix ID1 taking coding ACK frame is denoted as id1, extracts suffix ID2 and is denoted as id2.Node D searches frame entity head in resource queue
Portion is id1 resource bag, if it is found, the coding ACK frame that explanation idle listening arrives is relevant with oneself, the resource finding bag frame is real
Body head is changed to id2, and stops the count-down device of this resource bag；If can not find, this coding ACK frame is described with oneself no
Close, directly abandoned.
2nd, in the inventive method each relevant parameter determination：
Experiment one：The impact to code machine meeting for the research offered load, and the determination of ξ；
Step one, emulation experiment scene initialization：
It is 1400m that applicant simulates a length, and width is the wireless mesh network of 600m, wherein 86 sections of arrangement
Point.In this experiment, the communication radius of each node are 175m, and the link transmission success rate between node is surveyed by physical environment
?.A length of 5s during experiment simulation every time, each node is per second to produce ω packet, and destination address is selected at random, each data
The length of bag is 1000B, and link bandwidth is 54Mbps, and Internet uses minimum hop number to route, and is loaded by ω controlling network.
Step 2, takes ω=50, and 100,150 ... 300, for the value of each ω, take θ=0.25s, 0.50s, 0.75s,
1.00s, therefore, has done 6 × 4 groups of assessments altogether.In order to ensure the authenticity of experimental result, every group of assessment has carried out 1000 realities
Test, the desired value taking result is as every group of final result.
Step 3, analysis and process experimental data：
Fig. 8 shows under different ω values, in step S23The situation of change of (data flow complexity).In figure is not
Collinear represent different θ values.From experimental result it can be seen that：(1) for different θ, data flow complexity has same tendency.
(2) work as ω<When 50, data flow complexity increases very fast；Increase with ω, data flow complexity is gradually lowered, and then tends to steady
Fixed.(3) the data flow complexity curve distance of different θ is close.These three observe result explanation, when offered load hour, node
It is easy to get channel resource, the packet in forwarding queue seldom, almost can not find the packet being encoded to together；
Increase with offered load, forwarding queue starts to pile up packet, occur in that many two packets can be encoded to together
Situation is that is to say, that code machine can increase；But it is possible to the total amount being encoded to packet together accounts for the ratio receiving packet
It is not to increase always, when offered load reaches a very high value, data flow complexity levels off to a constant, and this is normal
Amount is relevant with deployment with the network bandwidth.That is, when offered load is very high, the factor of impact data flow complexity is mainly
The complexity of data flow in network.Therefore, we pass through to observe, when<When 0.08, it has been only possible to two kinds of situations and has occurred：One is
In the case of node and its neighbours are operated in low-load, forwarding queue is essentially sky；Two is node and its neighbours for FTP, stream
Some special applications such as media provide service, and in network, the complexity ratio of data flow is relatively low, substantially unidirectional.In order to reduce
Algorithm complexity, ξ is defined as 0.08 by us.
Experiment two：The impact to code machine meeting quantity for the research θ；
Step one, emulation experiment scene initialization：
It is 1400m that applicant simulates a length, and width is the wireless mesh network of 600m, wherein 86 sections of arrangement
Point.In this experiment, the communication radius of each node are 175m, and the link transmission success rate between node is surveyed by physical environment
?.A length of 5s during experiment simulation every time, each node is per second to produce ω packet, and destination address is selected at random, each data
The length of bag is 1000B, and link bandwidth is 54Mbps, and Internet uses minimum hop number to route, and is loaded by ω controlling network.
Step 2, takes θ=0.25s, 0.50s, 0.75s, 1.00s, takes ω=10, and 20,30,40,50,100,150,200,
250,300, altogether carry out 4 × 10 groups of assessments.In order to ensure the authenticity of experimental result, every group of assessment has carried out 1000 realities
Test, the desired value taking result is as every group of final result.
Step 3, analysis and process experimental data：
Fig. 9 shows under different θ, and code machine can situation of change.In figure is not collinear to represent different ω values.From experimental result
It can be seen that：(1) work as ω<When 50, code machine can increase little with θ and change；(2) work as ω>When 50, code machine can be with
θ increases and increases.Observe result explanation for this two, when offered load hour, even if θ is big again, be also not in more coding
Chance, main node is easy to apply for that the data is activation that will forward to channel is gone out；When offered load is big, increase with θ,
Code machine can be gradually increasing, and the growth trend under different loads is basically identical, and this increases acceleration is to have data flow
Complexity determines.In addition, the vertical range ratio of 6 lines is larger below in Fig. 9, much larger than the vertical range of above 4 lines, say
The complicated impact to code machine meeting of bright network is some larger.This experiment finally give it was concluded that θ to code machine can impact
Be far from ω greatly, because can not set very big in order to obtain more code machine meetings by θ.
Experiment three：The impact that research θ takies to nodal cache, and the determination of θ；
Step one, emulation experiment scene initialization：
It is 1400m that applicant simulates a length, and width is the wireless mesh network of 600m, wherein 86 sections of arrangement
Point.In this experiment, the communication radius of each node are 175m, and the link transmission success rate between node is surveyed by physical environment
?.A length of 5s during experiment simulation every time, each node is per second to produce ω packet, and destination address is selected at random, each data
The length of bag is 1000B, and link bandwidth is 54Mbps, and Internet uses minimum hop number to route, and is loaded by ω controlling network.
The caching of each node is allocated as follows：Forwarding queue length does not limit, decoding resource queue length 400, if decoding resource team
Row, using finishing, separately have the emergent queue that length is 500 to use for depositing decoding resource, recover queue and take and decoding resource team
There is correlation in row service condition, do not discuss.
Step 2, takes θ from 0.1s to 1.0s, and leapfrog is 0.1s, takes ω from 50 to 300, and leapfrog is 50, has altogether carried out 10
× 6 groups of assessments.In order to ensure the authenticity of experimental result, every group of assessment has carried out 1000 experiments, has taken the desired value of result to make
For every group of final result.
Step 3, analysis and process experimental data：
Figure 10 (a-d) shows under identical ω, different θ, resource queue's service condition.In figure different shape point represents difference
The node of consumption level：Square nodes resource consumption is serious, not only consumes Gan Liao resource queue, also employs emergent queue；Circular
Node resource is using normal；Rhombus node resource use on the low side, utilization rate is low.From experimental result it can be seen that：(1) when θ is less,
The resource queue of most nodes is not fully used；(2) although the resource queue of most node obtains fully when θ is larger
Using, but the node that resource queue is exhausted also has a lot.
Figure 11 (a-d) shows under different ω, the impact to three kinds of node proportions for the θ.Permissible from experimental result
Find out：(1) when offered load is less, increase with θ, the distribution proportion of three kinds of nodes is held essentially constant；(2) bear in network
When load is in middle reaches, compare the light situation of load, the low node of Buffer Utilization is greatly reduced, and is all converted into normal node,
But meanwhile, under this intermediate part load, increase with θ, understand the ill node that some normal node is converted into redness, work as θ>
During 0.3s, this change is particularly evident；(3) when offered load is higher, the low node of Buffer Utilization is less, but this node
Quantity also begin to receive the impact of θ, and, the quantity of ill node is instead few than under intermediate part load, and this is due to bearing high
In the case of load, data volume can be dispersed in wide range, rather than quickly to a part of node sinks.
These observe result explanation, and in the case that offered load is relatively low, the service condition to caching of θ does not almost have shadow
Ring, this is the deployment of the network of principal element and the link-quality of impact Buffer Utilization, when offered load is higher, the choosing of θ
Select and can bring two main impacts, one is the quantity of impact poor efficiency node, two is the quantity of the ill node of impact.From this
Experiment, finally giving as a result, wanting to increase Buffer Utilization, control ill node in the range of standing, θ takes simultaneously
0.3s.
3rd, the contrast experiment of the inventive method and additive method
Getting off, we test to verify the advantage that the inventive method is with respect to other agreements by one group.Experiment mainly to
The performance of lower three kinds of algorithms is compared：
(1)FSNC：I.e. method proposed by the present invention.
(2)CSMA/CA：This agreement is 802.11 to use most media access control methods, is entered using RTS-CTS mechanism
Row conflict avoidance, does not have reliable broadcast module, does not have encoding mechanism.
(3)XORs：The method is first classical case combining network code with practical application, is also to be ground
Study carefully and most methods are discussed.Different from method proposed by the present invention, network code mechanism is placed on media access control layer by XORs
And TCP layer between, modification is not all made to two levels.
In these experiments, we used this concept of information throughput and do measurement index, it is meant that：Unit interval
Interior, the information content sum of the packet that all nodes of the whole network send, wherein information content, refer to also participate in during coding or transport
The number of the packet calculated, not having encoded packet information content permanent is 1.Experiment mainly to prove from following several respects
The advantage of the present invention：
1. the impact to protocol capabilities for the offered load, the 2. impact to protocol capabilities for the link transmission success rate, 3. network is negative
Carry the impact that caching is utilized.
(1) impact to protocol capabilities for the offered load：
Artificial network initializes：
It is 1400m that applicant simulates a length, and width is the wireless mesh network of 600m, wherein 86 sections of arrangement
Point.In this experiment, the communication radius of each node are 175m, and the link transmission success rate between node is surveyed by physical environment
?.A length of 5s during experiment simulation every time, each node is per second to produce ω packet, and destination address is selected at random, each data
The length of bag is 1000B, and link bandwidth is 54Mbps, and Internet uses minimum hop number to route, and is loaded by ω controlling network.
According to result of the test before, our setup parameter θ are 0.3s, and ξ is 0.08.
Emulation experiment process：
In this experiment, ω=10 are taken, 20,30,40,50,100,150,200,250,300, altogether carry out 10 groups and commented
Estimate.In order to ensure experimental result authenticity, for each method, every group of assessment has carried out 1000 tests, has taken the expectation of result
Value is as every group of final result.
Experimental result：
Figure 12 (a, b) shows the relation in the middle of each agreement the whole network multi-to-multi handling capacity and offered load ω.From in figure
As can be seen that increasing with offered load, not having the handling capacity of the CSMA/CA of encoding mechanism to be gradually increased and then tending to be steady,
This be due to offered load higher when, channel width is depleted, and the whole network is handled up will not infinitely be increased down；FSNC compares CSMA/
CA has obvious throughput hoisting, maintains essentially in more than 7%, can reach 40% when；Offered load be in 50 to 100 it
Between when, the handling capacity of XORs is higher than FSNC, this is because XORs with FSNC compares, main difference is that employing chance detects
Listen, chi is route according to ETX and carries out neighbor state prediction, by multiple packet encoders to together.But in the case of load is relatively low and higher,
The handling capacity of XORs be not so good as FSNC, this is because, load relatively low when, XORs find less than by multiple packet encoders to machine together
Meeting, thus abandoning encoding, when loading higher, has part of nodes once by multiple data packet codings together, it is more right to be broadcast to
As, but it is because that XORs is also specifically used reliable Radio Broadcasting Agreements, when this results in broadcast code bag, request channel is very tired
Difficulty, often due to some node channel hurries and cancels whole broadcasting process；In addition, the packet in large information capacity is being broadcasted
When, the neighbours of all receiving nodes can not use channel, and it is low to which results in channel resource utilization rate in larger scope,
Thus have impact on the whole network handling capacity.This description of test, FSNC has higher handling up than CSMA/CA, has more preferably than XORs simultaneously
Adaptability, can adapt to multiple network load.
(2) impact to protocol capabilities for the link transmission success rate：
Artificial network initializes：
It is 1400m that applicant simulates a length, and width is the wireless mesh network of 600m, wherein 86 sections of arrangement
Point.In this experiment, the communication radius of each node are 175m, a length of 5s during each experiment simulation, the generation per second of each node
ω packet, destination address is selected at random, and the length of each packet is 1000B, and link bandwidth is 54Mbps, and Internet makes
With minimum hop number route, loaded by ω controlling network.According to result of the test before, our setup parameter θ are 0.3s, and ξ is
0.08.
Emulation experiment process：
In this experiment, ω=100 are taken, 300, generated using random, meet the link transmission success rate generation of Gaussian Profile
For actually measured link transmission success rate, Gaussian Profile desired value takes 1 to 0.8, and leapfrog is 0.02.Altogether carry out 2 groups to comment
Estimate, in order to ensure experimental result authenticity, for each agreement, every group of assessment has carried out 1000 tests, taken the expectation of result
Value is as every group of final result.
Experimental result：
Figure 13 (a, b) shows under intermediate part load and high load condition, each agreement the whole network multi-to-multi handling capacity and chain
Relation between the transmission success rate of road.It can be seen that in the case of intermediate part load, being deteriorated with channel circumstance, CSMA/
CA and FSNC is required for paying extra information throughput to overcome the wrong bag packet loss phenomenon that channel circumstance brings, and XORs is in letter
In the case that road environment is good, there is higher handling capacity, because at this being, the very high ratio of result that neighbours' forecast model of XORs draws
Example is all correct, but is deteriorated with channel circumstance, and the forecast model accuracy of XORs starts to reduce, and a lot of coding bags can not be by
It is successfully decoded, handling capacity starts close to FSNC.In high load situations, XORs and CSMA/CA handle up closely, this is
During due to XORs broadcast high information quantity coding bag, the neighbours of all receiving nodes as silent status, are led to regional letter
Road utilization rate is low, thus have impact on the whole network handling up；And, both agreements handle up little with link-quality change and
Change, when this is due to loading high, channel has not been provided that extra bandwidth for data packet retransmission.Now, FSNC is still
Remain 7% lifting of handling up.This description of test, the performance of FSNC is affected less, robustness by link transmission success rate
Higher.
(3) impact that offered load utilizes to caching：
Artificial network initializes：
It is 1400m that applicant simulates a length, and width is the wireless mesh network of 600m, wherein 86 sections of arrangement
Point.In this experiment, the communication radius of each node are 175m, and the link transmission success rate between node is surveyed by physical environment
?.A length of 5s during experiment simulation every time, each node is per second to produce ω packet, and destination address is selected at random, each data
The length of bag is 1000B, and link bandwidth is 54Mbps, and Internet uses minimum hop number to route, and is loaded by ω controlling network.
According to result of the test before, our setup parameter θ are 0.3s, and ξ is 0.08.
Emulation experiment process：
In this experiment, ω=60 are taken, 100,200,300, altogether carry out 4 groups of assessments, true in order to ensure experimental result
Reality, for each agreement, every group of assessment has carried out 1000 tests, and the desired value taking result is as every group of final result.
Experimental result：
Figure 14 (a-d) shows that two methods of XORs and FSNC decode the use of caching resource queue and the pass of offered load
System.It can be seen that under various offered loads, the caching usage amount of XORs node is all high than FSNC, and some situations are very
To exceeding several times, this is because XORs node not only caches itself forwarded over data, neighbours' section that also caching chance listens to
The data of point, and neither one good cache management mechanism.In addition, XORs point is more more extensive than the distribution of FSNC point, and
FSNC point is more concentrated it is meant that the caching of XORs uses and differs greatly, method less stable, and the distribution to caching is more difficult to control
System, by contrast, FSNC is more stable, is also easier to control.
Claims (4)
1. a kind of wireless mesh network media access control method based on network code is it is characterised in that in this wireless mesh
In network, after a node receives the packet that neighbor node is sent, judge this packet be general data bag or
Coded data packet：
If coded data packet, then this coded data packet is decoded, successfully decoded obtains the general data bag of needs, solution
Code is unsuccessful, abandons this coded data packet；
If general data bag, then judge whether this general data bag reaches the formation condition of coded data packet, such as reach then
It is encoded, and the coded data packet obtaining after coding is broadcasted to neighbor node；As formation condition can not be reached, then
This general data bag is forwarded according to 802.11 agreements；
The formation condition of coded data packet and cataloged procedure are as follows：
In this wireless mesh network, at least two neighbor nodes of node A, if the forwarding queue of initial time node A is sky,
Then from the beginning of initial time：After node A receives the general data bag p2 that neighbor node is sent, forwarding queue is found one
Individual general data bag p1, meets formula 1 and formula 2 if there is p1 simultaneously, then p1 and p2 coding is become coded data packet p；
In equation 1, s1, s2 are respectively the source node MAC Address of packet p1, p2, and d1, d2 are respectively p1, p2 next-hop section
The MAC Address of point, t1, t2 are respectively the time that p1, p2 reach node A, and θ value is 0.3 second；
In formula 2, r and c is respectively node A from the beginning of initial time, receives the tired of the general data bag that neighbor node sends
In the forwarding queue of meter number and node A, meet the accumulative number of the general data bag of formula 1, cumulative 1, c is every every time for wherein r
Secondary cumulative 2, ξ value is 0.08；
Described general data bag p1 and p2 through also or operation coding becomes coded data packet p, specially：
General data bag p2 destination host MAC Address and p1 destination host MAC Address are done also or computing, acquired results insert p1
Destination host MAC field；General data bag p2 source host MAC Address and p1 source host MAC Address are done also or computing, gained
Result inserts the source host MAC field of p1；The data division of the data division of p2 and p1 is done also or computing, acquired results are inserted
The data division field of p1；If the data portion length of p1 and p2 is inconsistent, 0 benefit is filled out in a square tail portion shorter for length
Position, the new packet of generation is coded data packet p.
2. the wireless mesh network media access control method based on network code as claimed in claim 1 it is characterised in that
In this wireless mesh network, in each node, it is provided with resource queue, when a general data bag is successfully transmitted by node
After another node, this general data bag is moved into resource queue from forwarding queue, and starts for this general data bag
One count-down device, count-down device initial value is θ, after count-down device zero, this general data bag is removed from resource queue.
3. the wireless mesh network media access control method based on network code as claimed in claim 2 it is characterised in that
After node receives a coded data packet, it is decoded operate：Node is found from the resource queue of oneself and is received
Coded data packet corresponding general data bag, the general data finding bag and the coded data packet that receives are carried out also or fortune
Calculate, obtain the general data bag of needs.
4. the wireless mesh network media access control method based on network code as claimed in claim 1 it is characterised in that
After described node A generates coded data packet p, the step that p is broadcasted is as follows：
Step S1, creates broadcast RTS frame, the MAC Address of the next-hop node of general data bag p1, p2 is write in RTS frame, and
Determine channel occupancy duration Tb, Tb is added to the call duration time field of broadcast RTS frame, Tb computational methods are as follows：
Tb=5 × SIFS+ (82+L) × t0(formula 3)
In formula 3, SIFS is the shortest stand-by period constant of 802.11 agreement regulations, and L is the length of coded data packet p, t0For passing
Time required for a defeated byte, determined by link bandwidth；
Step S2, node A broadcasts RTS frame request channel；
Step S3, after neighbor node receives RTS frame, determines that oneself replys the stand-by period Tcts of RTS frame, and after the stand-by period
Reply CTS frame to node A；Tcts computational methods are as follows：
In formula 4, iMAC is the MAC Address of this neighbor node, and d1, d2 are the MAC of the next-hop node of packet p1, p2 respectively
Address；
Step S4, node A has sent broadcast RTS frame, waits 2 × SIFS+28 × t0After time, check the CTS frame condition receiving,
If the CTS frame that the next-hop node receiving p1, p2 respectively is replied, node A starts after waiting the SIFS time to send coded number
According to bag p, wait is kept out of the way in otherwise node A entrance.
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| "基于网络编码的MAC协议研究";王龙翔;《中国优秀硕士论文全文数据库》;20140115;I136-357 * |
| "无线多跳网络中基于网络编码的MAC机制研究";黄勐;《中国优秀硕士学位论文全文数据库》;20111215;I136-529 * |
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