CN102932866A - Opportunistic routing mechanism applicable to multi-radio-frequency multi-channel Ad hoc network - Google Patents

Abstract

The invention provides a method for realizing an opportunistic routing mechanism applicable to a multi-radio-frequency multi-channel Ad hoc network. The method comprises the following steps of: establishing candidate forwarding node sets with priorities on control channels through routing requests and routing reply information, wherein if a node is closer to a host node, the priority of the node is higher; sharing channel state information by periodically broadcasting HELLO packets; constructing neighbor lists stored with channel interference values; through calculating an average channel interference value of potential forwarding node sets, choosing forwarding channels according to interference situation of receiving ends so as to reduce channel interference; and preventing repeated forwarding of data packets through priority comparison and cross-layer acknowledge character (ACK) coordination so as to increase packet delivery ratio. By the multi-radio-frequency multi-channel opportunistic routing, a plurality of orthogonal channels can be fully used; network throughput is increased exponentially; and through an opportunity forwarding mechanism, forwarding nodes which are closer to the host node can be fully used for forwarding in a scenery with poor channel quality, so that the delivery ratio is high, and end-to-end time delay is small.

Description

A kind of chance routing mechanism that is applicable to many radio frequencies multichannel Ad hoc network

Technical field

The present invention relates to a kind of routing mechanism of wireless multihop self-organizing network, particularly a kind of implementation method based on the multi channel chance routing mechanism of many radio frequencies.

Background technology

The chance route is a kind of emerging routing mode, and its broadcast nature and multi-user diversity that takes full advantage of wireless medium improves network performance.To select unique optimal path to carry out the data retransmission mode of clean culture different from traditional routing mechanism, the chance route is general sets up the candidate's forward node collection with priority according to certain rule first, and packet transmits in the range of nodes that candidate's forward node collection limits in the mode of broadcasting.After candidate's forward node centralized node is received packet, carry out distributed collaborative by certain algorithm, packet is propagated to the direction of destination node.Because the chance route is not fixed unique forward node, but takes full advantage of those very links of " lucky ", can greatly improve the delivery ratio of data, is specially adapted to the mobile ad-hoc network of topological dynamic change.

Along with the development of the communication technology, existing business constantly increases the demand of the network bandwidth.Injection frequently single channel routing mechanism can not take full advantage of existing frequency spectrum resource, and for example: 12/3 orthogonal channel resource that the 802.11a/b standard has been distributed only has an energy to be utilized simultaneously usually.The reduction of wireless network card cost is so that the gradually rise in mobile ad-hoc network of many radio frequencies multichannel technology, multichannel patulous research based on various typical single channel routes receives much concern, and especially the chance route is combined with many radio frequencies multichannel technology to have especially great development potentiality.Reduce cochannel by many radio frequencies multichannel technology and disturb, and overcome the unstable of wireless channel by the redundant transmission of chance route, thereby improve the throughput of whole network.

Summary of the invention

The present invention is directed to the cochannel that traditional Ad hoc network single channel route exists and disturb, and the defective such as transmission of wireless signals is unstable, aim to provide a kind of based on the multi channel chance method for routing of many radio frequencies.Multichannel aspect, node are according to the real-time change of channel disturbance situation, and the channel forwarding data that Dynamic Selection is suitable can take full advantage of a plurality of orthogonal channels that standardization distributes, and increases exponentially network throughput.Simultaneously, chance is transmitted thought can take full advantage of all available node resources in the network, and especially those nodes nearer apart from destination node come forwarding data, to reach higher delivery ratio and lower time delay.The present invention takes following steps to realize:

Step 1: carry out structure and the renewal of candidate's forward node collection by control channel

Channel initialization is control channel and data channel, and the control channel steady job mainly is responsible for Candidate Set structure and control information mutual on the control radio frequency interface.Data channel is responsible for the transmission of data, can switch at the enterprising Mobile state of different radio frequency interface according to the channel disturbance value.

When packet had just arrived source node route layer, owing to there not being candidate's forward node collection, source node was with data cached bag and open the pathfinding process.Inundation route requests on control channel.After intermediate node is received route requests, the address of oneself and the jumping figure of distance sources node are write in the route request information, continue this message of broadcasting.For fear of broadcast storm and message winding, intermediate node arranges thresholding to the route requests hop count of chummage, and has write for local node and to receive still in the route requests that the route requests of oneself transmitting no longer transmits.Destination node is whenever received a route request information just according to reverse route of intermediate node information acquisition of record wherein, and a route replies message is replied in clean culture, comprises all intermediate node addresses and to the jumping figure of destination node.Source node is received after the route replies message just the candidate's forward node collection that has priority according to wherein intermediate node information architecture, and is higher from the node priority of destination node close to more.Considered mulitpath answer route replies message, source node dynamically updates candidate's forward node collection according to the route replies message of receiving.

Step 2: neighbor node is surveyed and data channel interference value computational methods

Each node wraps the shared channel state information by periodically broadcasting HELLO at control channel, carries each node channel usage and channel disturbance value in the HELLO bag, and node makes up the neighbor node collection according to the HELLO bag of receiving.In certain cycle, suppose that node x receives grouping M altogether on channel k, then node calculates channel disturbance value on this channel by following formula:

${\mathrm{CIS}}_x^k=\underset{i=1}{\overset{M}{\mathrm{\Σ}}}({\mathrm{Pr}}_i^k+\frac{{\mathrm{Pr}}_i^k}{{\mathrm{SINR}}_i^k})$

Wherein

The channel disturbance value of representation node x on channel k.

The received power that represents i grouping, The received signal to noise ratio that represents i grouping.Because

So

Calculate the Noise and Interference in the channel when whenever receiving a packet i

Calculate the performance number of upper all noises of channel k and other groupings, reacted the disturbed condition that the soon grouping of transmission may be subject to.

Step 3: data retransmission and forwarding channel selection algorithm

After candidate's forward node collection structure of source node was finished, log-on data bag forwarding mechanism was carried to candidate's forward node collection in the packet, broadcasts away at certain data channel.The selection algorithm of transmitting channel is:

1. source node occurs simultaneously candidate's forward node collection and neighbor node collection and obtains potential forward node collection (potential forwarding nodes, PFNs)

2. calculate the average interference value that potential forward node is concentrated each channel according to neighbor list.

For example: the average interference value on the channel k is avgCIS ^kBe calculated as follows:

$\mathrm{avg}{\mathrm{CIS}}^k=\frac{\underset{x\∈\mathrm{PFNs}}{\mathrm{\Σ}}{\mathrm{CIS}}_x^k}{\left|x\right|}$

Wherein

Be the concentrated interference value sum of node on channel k of potential forward node, | x| is the node number.AvgCIS ^kConsider the existing interference of receive data bag on channel k of all neighbor nodes, as whether selective channel k carries out the judgment condition that packet is broadcasted, adopted this mechanism towards receiving terminal, can keep network connection, avoided simultaneously blind tin of problem.

Step 4: utilize priority and ACK to carry out packet and confirm

In order to improve the bag arrival rate, packet will start retransmission mechanism when can not receive from the repetitive data packet affirmation of priority node or ACK affirmation in the certain hour after broadcasting, retransmit maximum times and be made as empirical value according to service conditions.Tradition MAC layer can not start the ACK affirmation mechanism for broadcast packe, in case the consequence of bringing like this is the link-quality extreme difference, packet meeting packet loss is serious.The present invention has designed repetitive data packet and ACK double acknowledge at route layer and MAC layer for this type of broadcast packet respectively.

Packet is by global sequence's unique identification, in case receive the packet from priority node, just thinks that packet successfully is sent to from the node of destination node close to more.Consider that transmitting channel may switch, the packet that causes high priority to transmit can't feed back to some low priority node, the present invention requires priority node to receive for the first time packet, immediately at this channel broadcasting ACK, guarantee that with dual the upper hop node learns that packet successfully sends after the random back.

Description of drawings

Accompanying drawing described herein consists of the application's a part in order to a further understanding of the present invention to be provided, and illustrative examples of the present invention and explanation thereof are used for explaining the present invention, do not consist of to improper restriction of the present invention, in the accompanying drawings:

Fig. 1 is structure and the renewal of candidate subset.

Fig. 2 (a) (b) is respectively packet structure, ACK frame format.

Fig. 3 (a) (b) (c) (d) (e) be respectively MAC layer packet transaction mechanism, route layer bag treatment mechanism, routing request packet handling process, routing reply bag handling process and packet receives and forwarding process.

Embodiment

The invention will be further described below in conjunction with embodiment, but this embodiment should not be construed as limitation of the present invention.

1. the structure of candidate's forward node collection and renewal

Suppose that network comprises 14 nodes, each node configures 3 wave points, and having 4 orthogonal channels can use.When network had just been set up, each node default interface 0 used channel CH=0 as control channel, and other interfaces are random selects 3 remaining orthogonal channels as data channel, has provided a certain moment channel usage in the upper left corner of part of nodes such as Fig. 1.

Source node is initiated pathfinding in control channel broadcasting RREQ grouping, comprises source IP address, purpose IP address, RREQ ID, hop count, forward routing table in the RREQ grouping; After intermediate node is received RREQ, IP address, the distance sources node jumping figure of local node write the forward routing table, hop count increases progressively and continues broadcasting.Intermediate node judges being limited to 3 on the same route requests hop count according to RREQ ID, and no longer transmits for the RREQ that the local node address has write the forward routing table.

Destination node receives that whenever an immediately clean culture of RREQ returns back to RREP message of source node, RREP message mainly comprises source IP address, purpose IP address, oppositely routing table (got by the forward routing table, comprise via node IP address and apart from the destination node jumping figure).

The RREQ message of the identical RREQ ID that arrives for different time, destination node can be replied a plurality of RREP message, and source node is set up candidate's forward node collection according to the reverse routing table among a plurality of RREP.Wherein higher from the fewer node priority value of destination node jumping figure.Such as Fig. 1, source node S is initiated RREQ three times altogether to destination node D, receives three RREP.Receive that at every turn RREP carries out the renewal of a candidate subset.Forward and reverse routing table sees the following form 1, and candidate subset is upgraded and be the results are shown in following table 2.

The forward and reverse routing table of table 1

RREQID	The forward route	Reverse route
			1	S-1-5-8-D	D-8-5-1-S
2	S-2-6-7-D	D-7-6-2-S
			3	S-3-4-6-7-D	D-7-6-4-3-S

Table 2 candidate subset is upgraded the result

2. neighbor node is surveyed and data channel interference value computational methods

Each node is periodically broadcasted HELLO bag, the cycle during according to channel the change situation arrange, tentatively be 1s.Channel variation more the fast period less.Node basis corresponding received power, Signal to Interference plus Noise Ratio value when each channel is received grouping calculates the channel disturbance value, and utilizes the HELLO bag to carry this message and broadcast; Neighbours' HELLO bag is received in simultaneously each node utilization, sets up neighbor list.The neighbor list example that source node is set up among Fig. 1 is as follows:

Table 3 source node neighbor list

Attention: the interference value of certain channel is that 0 identification nodes is not operated on this channel in the table, otherwise namely is operated on this channel.

3. data retransmission and transmit the channel selection algorithm

After setting up candidate's forward node collection for the first time, source node sends data cached bag immediately, and candidate's forward node collection is carried into data packet head.Each packet that sends all carries candidate's forward node collection of recent renewal later on.

For fear of broadcast storm, increased overall unique packet number at data packet head, scope is 0～232-1, recycles.Node is preserved the chained list with (source, purpose, overall unique packet number) index in this locality, receive (source, purpose, overall unique packet number) information preservation that a bag just will wrap afterwards.The structure of packet is shown in accompanying drawing 2 (a).

Bump for fear of a plurality of via nodes while broadcast data packet, according to priority height random back certain hour, the higher time of keeping out of the way of priority is shorter before each node for data forwarding bag.When each node sends packet, calculate each data channel average interference value, source node is calculated as follows table as example in Fig. 1:

Average interference value on each channel of table 4 source node

The average interference value of data channel 2 is minimum, and source node carries out the broadcasting of packet with selective channel 2.

4. utilizing priority and ACK to carry out packet confirms

When node is received Frame at certain data channel, behind the random back certain hour, reply an ACK at this channel, the destination address of ACK is broadcast address, carries this packet unique packet number of the overall situation and local node precedence information.After other nodes are received ACK in the network, by judging whether the affirmation from high priority, determine whether delete corresponding data cached bag.Prove through lot of experiments, extremely short ACK frame can not take the large volumes of channels resource and owing to being to reply at same channel, can not have blind tin of problem, has greatly improved the bag arrival rate.Detailed mac layer frame, route layer data bag handling process are seen Fig. 3.

The content that is not described in detail in this specification belongs to the known prior art of this area professional and technical personnel.

The above only is better enforcement of the present invention, and is in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (5)

1. the many radio frequencies multichannel chance routing mechanism in the mobile ad-hoc network, its step is as follows:

A) on control channel, obtain as required the candidate's forward node collection that has priority in the network between the source to destination node, prioritization is carried out according to distance destination node distance;

B) periodic broadcast contains the HELLO bag of channel condition information, makes up the neighbor node collection that contains the channel disturbance value;

C) source node appends to candidate's forward node collection on the head of packet, by calculating the average channel interference value of potential forward node collection, selects the interference value minimum channel to carry out data and sends;

D) via node carries out according to its priority of concentrating at candidate's forward node the transfer sequence of packet, the packet head adds sequence-number field restriction node can only successfully transmit once identical bag, avoid repeating transmitting, the ACK of cross-layer confirms further to reduce data packet retransmission.

2. method according to claim 1 is characterized in that, steps A further comprises: just can start as required candidate's forward node collection and set up process when node has data to send; Candidate's forward node collection is to make up according to the middle forward node that comprises in the routing reply message, and wherein each node priority is determined by distance destination node jumping figure, and jumping figure is less, and priority is higher; Equal priority can have a plurality of nodes; After source node was received first candidate's forward node collection of routing reply message construction, after this data cached bag of forwarding immediately whenever received routing reply, will continue to upgrade candidate's forward node collection.

3. method according to claim 1 is characterized in that, step B further comprises: behind the network construction, each node wraps the shared channel state information by periodically broadcasting HELLO; Node is set up the neighbor node collection that contains the channel disturbance value by the channel conditions message of carrying; In one-period, node calculates channel disturbance value on this channel by following algorithm:

The ratio sum of the signal to noise ratio the when received power of the interference value of node on certain channel received power all packets in sum+cycle of all packets in sum=cycle and this packet of reception.

4. method according to claim 1 is characterized in that, step C further comprises: source node adds sequence-number field on the head of packet with at packet of network layer unique identification, can avoid repeating transmitting; Candidate's forward node collection is carried to the packet head and packet is transmitted together, transmits the channel selector and is made as:

1) obtains potential forward node collection according to the common factor of neighbor node collection and candidate's forward node collection;

2) the node number of the interference value sum of the average interference value of certain channel=all potential forwarding collection nodes on this channel/potential forwarding collection.

5. method according to claim 1, it is characterized in that, step D further comprises: be positioned at the concentrated node of candidate's forward node and all have an opportunity the packet of receiving is transmitted, wherein the node of high priority is only transmitted the packet of oneself not transmitting that the low priority node is sent, and the node of low priority is no longer transmitted the packet that the node of high priority is sent; Double acknowledge by ACK and packet can improve the transmitted in packets accuracy, and avoids reducing simultaneously data packet retransmission because channel switches the blind tin of problem of bringing.

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