Background technique
Broadcast frame is considerable maintenance mechanism within a wireless communication network, and mobile node can be allowed to know depositing for networkEntering the basic parameter of network added by acquisition, the information of oneself is broadcasted to neighbor node.
Under CSMA/CA mechanism, when a node will send broadcast frame, busy monitoring first is carried out to channel, such asFruit listen to channel be it is not busy, then wait for a period of time, if listened to if channel is the free time in this period,It then randomly chooses a timeslice in a prior defined time window to continue to listen to the busy of channel, if at thisBetween in piece, channel is always idle, then just sending broadcast frame；If channel is busy, that is, channel is occupied, then utilizesBack off algorithm, such as: binary exponential backoff algorithm until back off time arrives, then carries out channel monitoring, repeats the above process,Until channel idle, start to send the information to be transmitted.
And in this process, the solution after broadcast frame collides and loses is not provided.The hair of broadcast framePassing through journey does not have the handshake mechanism of RTS/CTS, when transmitting broadcast frame, it may occur that following several situations: first is that hidingThe problem of terminal, a node can receive the broadcast frame sended over from other nodes simultaneously, lead to the conflict of broadcast frame；TwoIt is under multi-channel model, a node gives its neighbor node to send broadcast frame, and its neighbor node on a control channelData frame may be sent on a data channel, since transceiver channel is not on a frequency point, will lead to the loss of broadcast frame.
These above-mentioned situations can occur under CSMA/CA mechanism, but the mechanism does not provide solution to the problem.CauseThis proposes the broadcast channel method for reliable transmission under CSMA/CA mechanism, maintenance cordless communication network that can be fast and reliable.EspeciallyBe in wireless Ad Hoc and Mesh network, due to network capacity becomes larger, within the scope of coverage neighbor node number increase, topologyCaused by structure change when broadcast frame loss, it can also make network fast convergence and the routing that timely updates.
Summary of the invention
Goal of the invention: the object of the present invention is to provide a kind of CSMA/CA machines that can effectively solve the problem that broadcast frame loss problemBroadcast channel method for reliable transmission under system.
Technical solution: the broadcast channel method for reliable transmission under CSMA/CA mechanism of the present invention, node receive neighboursAfter the broadcast frame that node is sent, if not receiving neighbours section yet later by the period thresholding that the neighbor node sends broadcast frameThe new broadcast frame sent is put, then the broadcast frame new to the neighbor node request retransmission.
Further, after node receives the broadcast frame that neighbor node is sent, start timer, if having received the neighbor nodeThen timer resets and starts timing next time to the new broadcast frame sent, if the timing of timer has reached the neighbor nodeThe period thresholding for sending broadcast frame does not receive new broadcast frame but yet, then the broadcast frame new to the neighbor node request retransmission.
Further, the period thresholding that the described neighbor node sends broadcast frame is calculated according to formula (1):
N=T+t+ Δ t (1)
In formula (1), N is period thresholding, and T is broadcast frame sending cycle, and t is the unidirectional air interface transmission of single-hop of the neighbor nodeTime delay, Δ t are shake time delay.
Further, the shake time delay includes processing delay, channel handover delay and antenna transmitting-receiving handover delay.
Further, to the process of the new broadcast frame of the neighbor node request retransmission are as follows: node is sent to the neighbor nodeThen BREQ frame waits the neighbor node to retransmit new broadcast frame, if having received new broadcast in preset latent periodFrame, then ending request retransmission processes；If the waiting time is more than that preset latent period does not receive new broadcast frame yet, determineThe neighbor node and this node change neighbor information table not in the same network, delete the neighbor node, and to other neighboursNode broadcasts information.
Further, if node needs to send data to the neighbor node, BREQ frame is existed together with data informationThe neighbor node is sent on data channel.
Further, the BREQ frame includes subframe type field, source node id field and destination node id field.
The utility model has the advantages that effectively being solved the invention discloses the broadcast channel method for reliable transmission under a kind of CSMA/CA mechanismIt the problem of broadcast frame loss, copes in the case that network capacity becomes larger, neighbor node increases within the scope of coverage,Frame loss is broadcasted to network fast convergence and routing update work bring pressure, especially in multichannel ad hoc network and Mesh netEffect is more prominent in network.
Specific embodiment
With reference to the accompanying drawings and detailed description, technical solution of the present invention is further introduced.
Present embodiment discloses the broadcast channel method for reliable transmission under a kind of CSMA/CA mechanism, and node receivesAfter the broadcast frame that neighbor node is sent, start timer, the timing if the new broadcast frame for having received neighbor node transmissionThink highly of and set and start timing next time, if the timing of timer has reached the neighbor node and sent the period thresholding of broadcast frame butNew broadcast frame is not received yet, then the broadcast frame new to the neighbor node request retransmission.
The period thresholding that the neighbor node sends broadcast frame is calculated according to formula (1):
N=T+t+ Δ t (1)
In formula (1), N is period thresholding, and T is broadcast frame sending cycle, and t is the unidirectional air interface transmission of single-hop of the neighbor nodeTime delay, Δ t are shake time delay.Shake time delay includes processing delay, channel handover delay and antenna transmitting-receiving handover delay.
The process of the broadcast frame new to the neighbor node request retransmission are as follows: node sends BREQ frame to the neighbor node, soIt waits the neighbor node to retransmit new broadcast frame afterwards, if having received new broadcast frame in preset latent period, terminatesRequest retransmission processes；If the waiting time is more than that preset latent period does not receive new broadcast frame yet, determine that the neighbours savePoint not in the same network, changes neighbor information table with this node, deletes the neighbor node, and broadcast to other neighbor nodesInformation.BREQ frame includes subframe type field, source node id field and destination node id field.If that lose is multiple neighboursThe broadcast frame of node, the destination node id field in that BREQ frame are just substituted with multicast address.If node request retransmission whenTime needs to send data to the neighbor node, BREQ frame can also be sent to this together with data information on a data channelNeighbor node.The length of latent period can be the sum of the length of multiple broadcast cycles.
The selection that BREQ frame sends channel can defer to following principle: for the BREQ frame of unicast, select in idle numberIt is believed that being sent on road Fd；If there are the contacts of data service for the neighbor node of node and reception BREQ frame, can be in the twoBREQ frame and data information are sent on the Fd channel of foundation simultaneously；If being lost the broadcast frame of multiple neighbor nodes, controllingMulticast sends BREQ frame on channel Fc processed.
Neighbor node sends broadcast frame and refers to that neighbor node sends the selection broadcast of starting point random algorithm by frame after the power-upFrame sends start time, and sends the process of broadcast frame periodically on control channel Fc with fixed cycle T.Frame sends starting pointRandom algorithm refers in a defined time window one value of random selection, then by this time value and node ID number intoThe start time point of broadcast frame is initiated in row logical operation after being powered on.
Control channel Fc refers to the dedicated channel to send broadcast frame and negotiation information.The channel is established rules really, can beNode power on after select default configuration channel, be also possible to after node powers on through by channel negotiation come out.This control letterRoad Fc can carry out dynamic negotiation according to channel quality, but the whole network shares a control channel, and broadcast frame is being controlledIt is sent on channel processed.
Node in present embodiment is the abbreviation of " apparatus for network node ", in the wireless signal coverage area of nodeOther nodes that can be communicated with each other are known as the adjacent node of this node, and node can be terminal device, trunking or base stationEquipment.Cordless communication network is a non-stop layer, distributed mobile network, its in the node and the same network in networkHe can communicate with each other node, support the increase of arbitrary node and exit.Multichannel CSMA/CA mechanism, refers to interactive letterThe transmission process of breath follows CSMA/CA, that is to say, that first to investigate the busy of channel at first, wait until channel idleWhen, send message；If channel be it is busy, select back off time, listen to channel, until channel idle is got off, there is transmissionThe qualification of message.
Technical solution of the present invention is further introduced with one embodiment below.
Cordless communication network in the present embodiment is as shown in Figure 1, there are multiple nodes in network, and there are two each node toolsChannel, a channel is for receiving signal；Another channel both can be used for sending signal, can be used for receiving signal, butIt is that transmitting-receiving cannot carry out simultaneously.
Below using node B as the sending node of broadcast frame, receiving node of the node A as broadcast frame, node C is as sectionIt is described in detail for the receiving node of point A transmission data.
As shown in Fig. 2, after node A receives the broadcast frame that node B is sent, parsing broadcast frame obtain B node ID number andThe information such as broadcast frame sending cycle T.Then node B is calculated according to formula (1) and sends the period thresholding N of broadcast frame, and startedTimer starts timing.When node B sends next frame broadcast frame to node A, node A sends data frame to node C,Since node A can not receive information when sending information, so the next frame broadcast frame that node B is sent to node A just connectsIt can not receive.When node A reaches period thresholding N for the timer of node B, node A sends BREQ frame to node B, waits sectionPoint B retransmits next frame broadcast frame, if having received next frame broadcast frame in preset latent period, ending request was retransmittedJourney；If the waiting time is more than that preset latent period does not receive next frame broadcast frame yet, predicate node B and this node do not existIn the same network, neighbor information table is changed, deletion of node B, and to other neighbor node broadcast messages.If Node A requestsIt needs to send data to node B when re-transmission, BREQ frame can also be sent jointly to node B together with data information.
Fig. 3 is the process that node B sends broadcast frame, after node B is powered on, starting point random algorithm is sent using frame, for sectionPoint B selects the initiation time point of broadcast frame, as gap periods sends broadcast frame using broadcast cycle T.Wherein, frame sends starting pointRandom algorithm is one value t of random selection in a defined time window W, then by this time value t and node ID number intoThe start time point of broadcast frame is initiated in row logical operation after being powered on.
Below using node B, C, D, E, F, G as the sending node of broadcast frame, node A is as the receiving node of broadcast frameExample is described in detail.
As shown in figure 4, parsing these broadcast after node A receives the broadcast frame that neighbor node B, C, D, E, F, G are sentFrame, obtains the ID number of each neighbor node, and node A is recorded in the information table of respective neighbor node according to the ID number of neighbor nodeUnder at the time of receive broadcast frame, each neighbor node is then calculated according to formula (1) and sends the period thresholding N of broadcast frame, and is openedEach timer is moved, timing is started.If each timer is not up to period thresholding N, node A has just had been received by each neighboursThe broadcast frame of node, then without starting retransmission mechanism.If the timer for node E has reached period thresholding N, and node AThe next frame broadcast frame that node E is sent is not received yet, then node A sends BREQ frame to node E, and node E is waited to retransmit next frameBroadcast frame, if having received next frame broadcast frame in preset latent period, ending request retransmission processes；If waitedBetween be more than that preset latent period does not receive next frame broadcast frame yet, then predicate node E and this node not in the same network,Change neighbor information table, deletion of node E, and to other neighbor node broadcast messages.If being directed to the timer of node B, C and DRespective period thresholding N is had reached, and node A does not receive the next frame broadcast frame that node B, C and D are sent yet, then node A existsTo node B, C and D multicast BREQ frame in control channel, node B, C and D is waited to retransmit next frame broadcast frame, if presetNext frame broadcast frame is had received in latent period, then ending request retransmission processes；If the waiting time is more than preset waiting weekPhase does not receive the next frame broadcast frame of one or more nodes yet, then determines respective nodes and this node not in the same networkIn, neighbor information table is changed, deletes respective nodes, and to other neighbor node broadcast messages.