CN102638820A - Prediction method for link stability of Ad Hoc network - Google Patents

Abstract

The invention discloses a prediction method for link stability of an Ad Hoc network, which includes steps: firstly, assessing direct stability of the link; secondly, assessing indirect stability of the link; thirdly, assessing comprehensive stability of the link; fourthly, taking stability as a foundation for a multicast routing protocol so as to solve the problem that the multicast routing protocol based on the existing link stability serving as a routing standard is unable to adapt to an unstable environment with high mobility, strong interference and the like. The prediction method for link stability of the Ad Hoc network is simple in calculation, low in working capacity during a process of accessing the link stability, stable in holistic performance and strong in adaptability for the network and low in energy consumption and has low requirements for hardware.

Description

Link stability prediction method in the Ad Hoc network

Technical field

The invention belongs to Ad Hoc network (MANET) field, be specifically related to link stability prediction method in the AdHoc network of link stability.

Background technology

Ad Hoc network is a kind of wireless network of dynamic reconfigurable, and each node serves as main frame and router simultaneously.As main frame, node need move the application of himself; As router, node is responsible for according to ad hoc routing protocol data being transmitted.The AdHoc network is widely used in occasions such as disaster assistance (like earthquake, fire) and distributed collaboration computing.

In actual applications, because a node often need send identical data to a plurality of nodes, so multicast routing protocol is arisen at the historic moment.Yet because mobile ad hoc network has such as characteristics such as the moving at random of node, Limited resources, insecure channels, traditional multicast protocol can not be adapted to the MANET network environment well.

The mobile at random dynamic change that causes network topology structure of node has increased the frequency of route again, and then has influenced network performance.Therefore, need a kind of appraisal procedure to link stability, and as evaluation index, in route selection, avoid unsettled link, this can greatly improve the overall performance of network undoubtedly.

Research to link stability is also few in the adhoc field at present; Most of research hypothetical network environment is a constant; Only the mobility of node is studied, as quantizing, utilize statistical method to the node motion behavior modeling and predict next mobile behavior constantly of node etc. to the position and the velocity vector of node by GPS.Yet, in practical application, be not that each node all has the GPS module, and the GPS module has very big error in indoor environment, and statistical method carries out modeling based on probability theory to node, has certain limitation and accuracy to remain to be discussed.In addition; In existing research, without exception, all are the angles that stand in detection node; Link between detection node and the tested node is assessed; The angle that does not stand in tested node is carried out stability assessment to its residing chain environment, and therefore existing link stability Forecasting Methodology has significant limitation, and effect is unsatisfactory.Accordingly; Can not adapt to unstable environment such as high mobility, high interference with link stability well as the multicast routing protocol of route standard; Therefore, need a kind of more reasonably link stability appraisal procedure and corresponding multicast routing protocol to solve above problem.

Summary of the invention

The purpose of this invention is to provide link stability prediction method in a kind of AdHoc network; The link that causes because of node motion in the adhoc network frequently opens circuit to solve, the route problem of unstable, and the performance (like the delivery rate that increases bag, reduce end-to-end time-delay etc.) that improves network is to adapt to the high mobility environment.

For this reason, the technical scheme of the present invention's employing is:

Link stability prediction method in a kind of AdHoc network, it is through the signal strength signal intensity sampling to continuous reception, to approach the true environment of network realistically; To detection node and tested node; Assess the stable situation of each bar link of its environment of living in respectively, take all factors into consideration detection node and tested node is right, calculate comprehensive stability property value; And with this routing standard as stable multicast routing protocol, concrete steps are:

The first step is to the direct stability assessment of link

Node is kept neighborhood through timed sending hello message, and when detection node was received the hello message that its neighbor node sends, detection node was that tested node is kept one to receive signal strength signal intensity be that received power is tabulated for each neighbor node;

Second step, the indirect stability assessment of link

Tested node adopts with the same method of the first step stability of its neighbor node is assessed; Because this stability is intended to tested node environment of living in is assessed, therefore reject after the extra high node of mobility, other node stabilitys are got average, average is low more, and the residing environment of then tested node is stable more, on the contrary environment is more unstable;

The 3rd step, the assessment of link comprehensive stability property, what be about to link directly adopts the method synthesis of weighted sum to calculate with indirect stability assessment value;

The 4th step, based on the multicast routing protocol of stability, based on the multicast routing protocol of stability with stability as the routing standard.

The direct stability assessment value of link in the said first step:

According to Friis free space propagation model, received power P _RXRatio P with transmitted power _TXWith square being inversely proportional to of transmission range R, promptly $\frac{P_{\mathrm{RX}}}{P_{\mathrm{TX}}}\∝\frac{1}{R^2}$ Or $R\∝\sqrt{\frac{P_{\mathrm{TX}}}{P_{\mathrm{RX}}}};$

Suppose the following P of being limited to of received power _Min, promptly when received power is lower than this value, can produce higher bit error rate, cause the re-transmission of packet, correspondingly, the transmission range of this moment is R _MaxThe P of all nodes _MinBe initialized as a fixed value,, think that the received power that goes up when being carved into for the moment the merit reception is approximately equal to P at this moment when certain neighbor node shifts out its communication range _Min, therefore use the P that power upgrades this node that accepts in a moment _Min

Suppose that detection node i is P to the n sub-sampling value of tested node j received power _n ^Ij, then, have according to Friis free space propagation model

Again because

P wherein _TXBe the transmitted power of node, R _n ^IjDistance when being the n time power sampling between sending node and receiving node, P _Min ⁱBe the minimum received power of detection node i, R _MaxFor received power is P _Min ⁱThe time corresponding maximum transmission distance, therefore, have

If node keeps relative distance to change slowly, think that then the link stability between the two is good, thus following formula is got the direct stability assessment value of variance as link between detection node i and the tested node j, that is:

$d\_S_{\mathrm{ij}}=\sqrt{P_{\min }^i}\mathrm{var}\{\frac{1}{\sqrt{P_1^{\mathrm{ij}}}},\frac{1}{\sqrt{P_2^{\mathrm{ij}}}},\mathrm{\Λ},\frac{1}{\sqrt{P_n^{\mathrm{ij}}}}\}$

Obtained the computing formula of the direct stability assessment value of link thus, assessed value is more little, and link stability is good more.

The indirect stability assessment value of link in said second step:

Suppose that tested nodes X has n neighbours (Y ₁, Y ₂Y _n), nodes X is to its neighbor node Y _KThe stability assessment value is calculated identical with the first step, that is:

$S_X\left(Y_K\right)=\sqrt{P_{\min }^X}\mathrm{var}\{\frac{1}{\sqrt{P_1^{{\mathrm{XY}}_K}}},\frac{1}{\sqrt{P_2^{{\mathrm{XY}}_K}}},\mathrm{\Λ},\frac{1}{\sqrt{P_n^{{\mathrm{XY}}_K}}}\}$

Because tested nodes X has n neighbours, and indirect link stability is the assessment to tested nodes X environment of living in, and therefore, the X node need calculate its n neighbour's stability assessment value, i.e. S _X(Y ₁), S _X(Y ₂) ... S _X(Y _n); In order to eliminate the least influence of stable node, to this n stability ordering and get its minimum 0.5n value, be assumed to be S _X(Y _T1), S _X(Y _T2) ... S _X(Y _T0.5n), then this 0.5n value is got the assessed value of average as tested nodes X environment of living in, i.e. the indirect stability assessment value of link:

in_S _X＝avg(S _X(Y _T1)，S _X(Y _T2)，ΛS _X(Y _T0.5n))

Obtained the computing formula of the indirect stability assessment value of link thus, assessed value is more little, and the residing network environment of tested node is stable more.

The comprehensive stability property of link between assessment detection node i and tested node j in said the 3rd step:

S _ij＝w ₁*d_S _ij+w ₂*in_S _j(w ₁+w ₂＝1)

Tested node j not only serves as the sender but also serve as the recipient.

In said the 4th step based on the multicast routing protocol of stability with stability as the routing standard, when node produced route request information, an additional specific territory was with the stability assessment value in the path that characterizes process in route request information; The stability assessment value of one paths equal the stability assessment maximum of all links of process, promptly the stability of a paths depends on one section least stable link; When node is received routing reply message, from all paths, select the minimum path of a stability assessment value to activate.

Detailed process is:

A. the group membership adds

Node adds multicast group need pass through three phases: route request stage, routing reply stage and route activate the stage

When a node will add multicast group or have message to send to multicast group, but it is not group membership and when not leading to the route of multicast tree, it sends a RREQ message; The destination address domain dest_addr of message is the address of multi-broadcast group, and source address source_addr is the address of this node oneself; RREQ message increase an extra Path_Stable territory with the record node the stability assessment value in path of process;

After a node was received RREQ message, at first whether inspection had handled identical RREQ, if then abandon, otherwise calculated the comprehensive stability value of last a jumping link according to link stability appraisal procedure set forth above; With Path_Stable territory among stationary value of calculating and the RREQ relatively, be the higher value in the two then, continue to transmit this RREQ message then the Path_Stable area update;

If a node is multicast member or the route of leading to multicast tree is arranged; After receiving RREQ; With this RREQ buffer memory a period of time; Arrive this node owing to have same RREQ message in the meantime from different paths, so this node selects the minimum RREQ message in Path_Stable territory to send routing reply message RREP;

When an intermediate node is received RREP message; Creating a multicast routing table entry based on this RREP is that un-activation is not set of Activated_Flag with this entry state of tense marker; Upgrade its Path_Stable territory simultaneously, continue then to transmit RREP message along the reverse path of RREQ message establishing;

A node possibly received a plurality of RREP message, but it is that the big perhaps more stable less RREP message in Path_Stable territory of RREP sequence number is handled to what upgrade only, and other RREP message abandons simply;

When RREP message arrival source node promptly asks to add the node of multicast group; Source node buffer memory a period of time; From a plurality of RREP message of receiving, select minimum the carrying out in a Path_Stable territory route activates is MACT message; That is: will be Activated_Flag set for activating at the route entry status indication that the routing reply stage creates, other unactivated route entrys be because overtime and deleted by respective nodes;

B. the group membership leaves

When a group membership hopes to leave multicast tree, if it is the routing node of other nodes then does not take any measure.If it is a leaf node; Then on it, one jump a beta pruning message of clean culture Prune; By the corresponding route entry of this descendant node of hop node deletion on it; If cause a hop node also to become leaf node after the deletion, then continue jumping transmission beta pruning message execution cut operator on it;

C. link opens circuit

When opening circuit on the multicast tree, it is invalid that the branch that opens circuit can become; At this moment, upstream node is deleted invalid node from its route entry, and downstream node is responsible for link repair then; The reparation of opening circuit of send downstream node RREQ and additional multi-broadcast group reconstruction message; In the multi-broadcast group reconstruction message, comprise multi-broadcast group jumping figure territory Group_Hop_Cnt with the open circuit jumping figure of nodal distance tree root node of record, the node that has only hop count to be not more than this counting could respond RREQ message, has avoided the generation of route loop like this; After receiving RREP message, it is said identical that route activation and group membership add part;

D. safeguard multicast tree

Each node timed sending hello message is with the received power tabulation of maintenance of neighbor relation and renewal neighbor node; In addition, the tree root node timed sending GroupHello message of each multicast tree, simultaneously the tree root sequence node number increases 1; When the multicast tree member receives GroupHello message, send MACT message and carry out the route activation, guarantee that thus each node can obtain the up-to-date routing iinformation of multicast tree;

E. multicast tree merges

Under mobile environment, because the mobility of node, ad hoc network may be divided into several mutual disconnected zones, and its oneself multicast tree is safeguarded in each zone; Because the mobility of node; Two or more disconnected zones may be communicated with once more; In order to clear away confusion, the tree root node that has maximum sequence number becomes the tree root node of new multicast tree, and other tree root node stop are sent GroupHello message and wait for the reconstruction of multicast tree.

The method that the present invention adopts compared with prior art has following advantage:

(1) signal strength signal intensity that the present invention is based on continuous reception message is calculated; Add fashionable as new node; Have only when new node and the neighborhood of detection node maintenance a period of time; This node just can be included in the computer capacity of link stability, has reduced because of new node adds the unstable situation of the calculating that causes, and has higher adaptability and stability.

(2) compare with the method for merely node motion speed being assessed, the present invention is not by other third party's modules (like GPS), and accuracy is higher.

(3) with only detection node to be carried out the method for stability assessment different, the present invention carries out the link stability assessment from detection node and two angles of tested node, and assessment result is comprehensive, credible and adaptability is good.

(4) the present invention calculates simply, and assessment link stability process operand is low, and not high to hardware requirement, energy consumption is little.

(5) the link stability appraisal procedure is applied in the multicast routing protocol based on stability, makes the present invention can be widely used in the actual demand, improve stability of network, and then increase work efficiency.

Description of drawings

Fig. 1 is a link Calculation on stability sketch map in the embodiment of the invention.

Fig. 2 is based on group membership's adition process flow chart in the stable multicast routing protocol.

Embodiment

Provide one embodiment of the present of invention below and combine accompanying drawing that the present invention is done explanation further.

Among Fig. 1, Fig. 2

(1) the direct stability assessment of link

According to Friis free space propagation model, received power (P _RX) with the ratio (P of transmitted power _TX) with square being inversely proportional to of transmission range (R), promptly $\frac{P_{\mathrm{RX}}}{P_{\mathrm{TX}}}\∝\frac{1}{R^2}$ Or $R\∝\sqrt{\frac{P_{\mathrm{TX}}}{P_{\mathrm{RX}}}}.$

In the present invention, suppose the following P of being limited to of received power _Min, promptly when received power is lower than this value, can produce higher bit error rate, cause the re-transmission of packet, correspondingly, the transmission range of this moment is R _MaxBecause the residing environment of different nodes is different, so P _MinValue different, in the present invention, the P of all nodes _MinBe initialized as a fixed value,, can think that the received power that goes up when being carved into for the moment the merit reception is approximately equal to P at this moment when certain neighbor node shifts out its communication range _Min, therefore use the P that power upgrades this node that accepts in a moment _Min

Shown in accompanying drawing 1 (a), suppose that detection node i is P to the n sub-sampling value of tested node j received power _n ^Ij, then, have according to Friis free space propagation model

Again because P wherein _TXBe the transmitted power of node, R _n ^IjDistance when being the n time power sampling between sending node and receiving node, P _Min ⁱBe the minimum received power of detection node i, R _MaxFor received power is P _Min ⁱThe time corresponding maximum transmission distance, therefore, have

If node keeps relative distance to change slowly, can think that then the link stability between the two is good, so can get the direct stability assessment value of variance to following formula as link between detection node i and the tested node j.That is:

$d\_S_{\mathrm{ij}}=\sqrt{P_{\min }^i}\mathrm{var}\{\frac{1}{\sqrt{P_1^{\mathrm{ij}}}},\frac{1}{\sqrt{P_2^{\mathrm{ij}}}},\mathrm{\Λ},\frac{1}{\sqrt{P_n^{\mathrm{ij}}}}\}$

Obtained the computing formula of the direct stability assessment value of link thus.Assessed value is more little, and link stability is good more.

(2) the indirect stability assessment of link

Shown in accompanying drawing 1 (b), tested nodes X has n neighbours (Y ₁, Y ₂Y _n).Nodes X is to its neighbor node Y _KThe stability assessment value is calculated identical with (1), that is:

$S_X\left(Y_K\right)=\sqrt{P_{\min }^X}\mathrm{var}\{\frac{1}{\sqrt{P_1^{{\mathrm{XY}}_K}}},\frac{1}{\sqrt{P_2^{{\mathrm{XY}}_K}}},\mathrm{\Λ},\frac{1}{\sqrt{P_n^{{\mathrm{XY}}_K}}}\}$

Because tested nodes X has n neighbours, and indirect link stability is the assessment to tested nodes X environment of living in, and therefore, the X node need calculate its n neighbour's stability assessment value, i.e. S _X(Y ₁), S _X(Y ₂) ... S _X(Y _n).In order to eliminate the least influence of stable node (link), the present invention is to this n stability ordering and get its minimum 0.5n value, is assumed to be S _X(Y _T1), S _X(Y _T2) ... S _X(Y _T0.5n), then this 0.5n value is got the assessed value of average as tested nodes X environment of living in, i.e. the indirect stability assessment value of link:

in_S _X＝avg(S _X(Y _T1)，S _X(Y _T2)，ΛS _X(Y _T0.5n))

Obtained the computing formula of the indirect stability assessment value of link thus.Assessed value is more little, and the residing network environment of tested node is stable more.

(3) link comprehensive stability property assessment

Direct, the indirect stability value of comprehensive link, the present invention adopts the comprehensive stability property of link between following method assessment detection node i and tested node j:

S _ij＝w ₁*d_S _ij+w ₂*in_S _j(w ₁+w ₂＝1)

Can find out that the present invention is in the computational stability assessed value, tested node j not only serves as the sender but also serve as the recipient.

(4) based on the multicast routing protocol of stability

A. the group membership adds

Can find out that by accompanying drawing 2 node adds multicast group need pass through three phases: route request stage, routing reply stage and route activate the stage.

When a node will add multicast group or have message to send to multicast group, but it is not group membership and when not leading to the route of multicast tree, it sends a RREQ message.The destination address domain dest_addr of message is the address of multi-broadcast group, and source address source_addr is the address of this node oneself.In the present invention, RREQ message increased an extra Path_Stable territory with the record node the stability assessment value in path of process.

After a node was received RREQ message, at first whether inspection had handled identical RREQ, if then abandon, otherwise calculated the comprehensive stability value of last a jumping link according to link stability appraisal procedure set forth above.With Path_Stable territory among stationary value of calculating and the RREQ relatively, be the higher value in the two then, continue to transmit this RREQ message then the Path_Stable area update.

If a node is multicast member or the route of leading to multicast tree is arranged; After receiving RREQ; With this RREQ buffer memory a period of time; Arrive this node owing to have same RREQ message in the meantime from different paths, so this node selects the minimum RREQ message in Path_Stable territory to send routing reply message RREP.

When an intermediate node is received RREP message; Creating a multicast routing table entry based on this RREP is un-activation (Activated_Flag is set not) with this entry state of tense marker; Upgrade its Path_Stable territory simultaneously, continue then to transmit RREP message along the reverse path of RREQ message establishing.

A node possibly received a plurality of RREP message, but it only (the RREP sequence number is bigger) or more stable (the Path_Stable territory is less) RREP message of upgrading are handled, other RREP message abandons simply.

When RREP message arrives source node when (request adds the node of multicast group); Source node buffer memory a period of time; From a plurality of RREP message of receiving, select the minimum route of carrying out in a Path_Stable territory to activate (MACT message); That is: the route entry status indication that will create in the routing reply stage is for activating (Activated_Flag set), and other unactivated route entrys are because overtime and deleted by respective nodes.

B. the group membership leaves

When a group membership hopes to leave multicast tree, if it is the routing node of other nodes then does not take any measure.If it is a leaf node; Then on it, one jump a beta pruning message of clean culture Prune; By the corresponding route entry of this descendant node of hop node deletion on it; If cause a hop node also to become leaf node after the deletion, then continue jumping transmission beta pruning message execution cut operator on it.

C. link opens circuit

When opening circuit on the multicast tree, it is invalid that the branch that opens circuit can become.At this moment, upstream node is deleted invalid node from its route entry, and downstream node is responsible for link repair then.The reparation of opening circuit of send downstream node RREQ and additional multi-broadcast group reconstruction message.In the multi-broadcast group reconstruction message, comprise multi-broadcast group jumping figure territory (Group_Hop_Cnt) with the open circuit jumping figure of nodal distance tree root node of record, the node that has only hop count to be not more than this counting could respond RREQ message, has avoided the generation of route loop like this.After receiving RREP message, it is said identical that route activation and group membership add part.

D. safeguard multicast tree

In this agreement, each node timed sending hello message is with the received power tabulation of maintenance of neighbor relation and renewal neighbor node.In addition, the tree root node timed sending GroupHello message of each multicast tree, simultaneously the tree root sequence node number increases 1.When the multicast tree member receives GroupHello message, send MACT message and carry out the route activation, guarantee that thus each node can obtain the up-to-date routing iinformation of multicast tree.

E. multicast tree merges

Under mobile environment, because the mobility of node, ad hoc network may be divided into several mutual disconnected zones, and its oneself multicast tree is safeguarded in each zone.Because the mobility of node; Two or more disconnected zones may be communicated with once more; In order to clear away confusion, the tree root node that has maximum sequence number becomes the tree root node of new multicast tree, and other tree root node stop are sent GroupHello message and wait for the reconstruction of multicast tree.

Thus; Network node has been accomplished the foundation and the maintenance of multicast routing tree according to link stability appraisal procedure of the present invention; The embodiments of the invention simulation result shows, adopts method of the present invention, compares with existing other technologies; Network has the highest bag delivery rate, low end-to-end time-delay and higher network throughput under mobile environment, the overall performance of network is stable, adaptability is strong.

Claims (6)

1. link stability prediction method in the Ad Hoc network, it is through the signal strength signal intensity sampling to continuous reception, to approach the true environment of network realistically; To detection node and tested node, assess the stable situation of each bar link of its environment of living in respectively, take all factors into consideration detection node and tested node is right; Calculate comprehensive stability property value; And, it is characterized in that concrete steps are with this routing standard as stable multicast routing protocol:

The first step is to the direct stability assessment of link

Node is kept neighborhood through timed sending hello message, and when detection node was received the hello message that its neighbor node sends, detection node was that tested node is kept one to receive signal strength signal intensity be that received power is tabulated for each neighbor node;

Second step, the indirect stability assessment of link

Tested node adopts with the same method of the first step stability of its neighbor node is assessed; Because this stability is intended to tested node environment of living in is assessed, therefore reject after the extra high node of mobility, other node stabilitys are got average, average is low more, and the residing environment of then tested node is stable more, on the contrary environment is more unstable;

The 3rd step, the assessment of link comprehensive stability property, what be about to link directly adopts the method synthesis of weighted sum to calculate with indirect stability assessment value;

The 4th step, based on the multicast routing protocol of stability, based on the multicast routing protocol of stability with stability as the routing standard.

2. link stability prediction method in the Ad Hoc network as claimed in claim 1 is characterized in that, the direct stability assessment value of link in the said first step:

According to Friis free space propagation model, received power P _RXRatio P with transmitted power _TXWith square being inversely proportional to of transmission range R, promptly $\frac{P_{\mathrm{RX}}}{P_{\mathrm{TX}}}\∝\frac{1}{R^2}$ Or $R\∝\sqrt{\frac{P_{\mathrm{TX}}}{P_{\mathrm{RX}}}};$

Suppose the following P of being limited to of received power _Min, promptly when received power is lower than this value, can produce higher bit error rate, cause the re-transmission of packet, correspondingly, the transmission range of this moment is R _MaxThe P of all nodes _MinBe initialized as a fixed value,, think that the received power that goes up when being carved into for the moment the merit reception is approximately equal to P at this moment when certain neighbor node shifts out its communication range _Min, therefore use the P that power upgrades this node that accepts in a moment _Min

Suppose that detection node i is P to the n sub-sampling value of tested node j received power _n ^Ij, then, have according to Friis free space propagation model

Again because

P wherein _TXBe the transmitted power of node, R _n ^IjDistance when being the n time power sampling between sending node and receiving node, P _Min ⁱBe the minimum received power of detection node i, R _MaxFor received power is P _Min ⁱThe time corresponding maximum transmission distance, therefore, have

If node keeps relative distance to change slowly, think that then the link stability between the two is good, thus following formula is got the direct stability assessment value of variance as link between detection node i and the tested node j, that is:

$d\_S_{\mathrm{ij}}=\sqrt{P_{\min }^i}\mathrm{var}\{\frac{1}{\sqrt{P_1^{\mathrm{ij}}}},\frac{1}{\sqrt{P_2^{\mathrm{ij}}}},\mathrm{\Λ},\frac{1}{\sqrt{P_n^{\mathrm{ij}}}}\}$

Obtained the computing formula of the direct stability assessment value of link thus, assessed value is more little, and link stability is good more.

3. link stability prediction method in the Ad Hoc network as claimed in claim 1 is characterized in that, the indirect stability assessment value of link in said second step:

Suppose that tested nodes X has n neighbours (Y ₁, Y ₂Y _n), nodes X is to its neighbor node Y _KThe stability assessment value is calculated identical with the first step, that is:

$S_X\left(Y_K\right)=\sqrt{P_{\min }^X}\mathrm{var}\{\frac{1}{\sqrt{P_1^{{\mathrm{XY}}_K}}},\frac{1}{\sqrt{P_2^{{\mathrm{XY}}_K}}},\mathrm{\Λ},\frac{1}{\sqrt{P_n^{{\mathrm{XY}}_K}}}\}$

Because tested nodes X has n neighbours, and indirect link stability is the assessment to tested nodes X environment of living in, and therefore, the X node need calculate its n neighbour's stability assessment value, i.e. S _X(Y ₁), S _X(Y ₂) ... S _X(Y _n); In order to eliminate the least influence of stable node, to this n stability ordering and get its minimum 0.5n value, be assumed to be S _X(Y _T1), S _X(Y _T2) ... S _X(Y _T0.5n), then this 0.5n value is got the assessed value of average as tested nodes X environment of living in, i.e. the indirect stability assessment value of link:

in_S _X＝avg(S _X(Y _T1)，S _X(Y _T2)，ΛS _X(Y _T0.5n))

Obtained the computing formula of the indirect stability assessment value of link thus, assessed value is more little, and the residing network environment of tested node is stable more.

4. link stability prediction method in the Ad Hoc network as claimed in claim 1 is characterized in that, the comprehensive stability property of link between assessment detection node i and tested node j in said the 3rd step:

S _ij＝w ₁*d_S _ij+w ₂*in_S _j (w ₁+w ₂＝1)

Tested node j not only serves as the sender but also serve as the recipient.

5. link stability prediction method in the Ad Hoc network as claimed in claim 1; It is characterized in that; In said the 4th step based on the multicast routing protocol of stability with stability as the routing standard; When node produced route request information, an additional specific territory was with the stability assessment value in the path of sign process in route request information; The stability assessment value of one paths equal the stability assessment maximum of all links of process, promptly the stability of a paths depends on one section least stable link; When node is received routing reply message, from all paths, select the minimum path of a stability assessment value to activate.

6. link stability prediction method in the Ad Hoc network as claimed in claim 5 is characterized in that detailed process is:

A. the group membership adds

Node adds multicast group need pass through three phases: route request stage, routing reply stage and route activate the stage

When a node will add multicast group or have message to send to multicast group, but it is not group membership and when not leading to the route of multicast tree, it sends a RREQ message; The destination address domain dest_addr of message is the address of multi-broadcast group, and source address source_addr is the address of this node oneself; RREQ message increase an extra Path_Stable territory with the record node the stability assessment value in path of process;

After a node was received RREQ message, at first whether inspection had handled identical RREQ, if then abandon, otherwise calculated the comprehensive stability value of last a jumping link according to link stability appraisal procedure set forth above; With Path_Stable territory among stationary value of calculating and the RREQ relatively, be the higher value in the two then, continue to transmit this RREQ message then the Path_Stable area update;

If a node is multicast member or the route of leading to multicast tree is arranged; After receiving RREQ; With this RREQ buffer memory a period of time; Arrive this node owing to have same RREQ message in the meantime from different paths, so this node selects the minimum RREQ message in Path_Stable territory to send routing reply message RREP;

When an intermediate node is received RREQ message; Creating a multicast routing table entry based on this RREP is that un-activation is not set of Activated_Flag with this entry state of tense marker; Upgrade its Path_Stable territory simultaneously, continue then to transmit RREP message along the reverse path of RREQ message establishing;

A node possibly received a plurality of RREP message, but it is that the big perhaps more stable less RREP message in Path_Stable territory of RREP sequence number is handled to what upgrade only, and other RREP message abandons simply;

When RREP message arrival source node promptly asks to add the node of multicast group; Source node buffer memory a period of time; From a plurality of RREP message of receiving, select minimum the carrying out in a Path_Stable territory route activates is MACT message; That is: will be Activated_Flag set for activating at the route entry status indication that the routing reply stage creates, other unactivated route entrys be because overtime and deleted by respective nodes;

B. the group membership leaves

When a group membership hopes to leave multicast tree, if it is the routing node of other nodes then does not take any measure.If it is a leaf node; Then on it, one jump a beta pruning message of clean culture Prune; By the corresponding route entry of this descendant node of hop node deletion on it; If cause a hop node also to become leaf node after the deletion, then continue jumping transmission beta pruning message execution cut operator on it;

C. link opens circuit

When opening circuit on the multicast tree, it is invalid that the branch that opens circuit can become; At this moment, upstream node is deleted invalid node from its route entry, and downstream node is responsible for link repair then; The reparation of opening circuit of send downstream node RREQ and additional multi-broadcast group reconstruction message; In the multi-broadcast group reconstruction message, comprise multi-broadcast group jumping figure territory Group_Hop_Cnt with the open circuit jumping figure of nodal distance tree root node of record, the node that has only hop count to be not more than this counting could respond RREQ message, has avoided the generation of route loop like this; After receiving RREP message, it is said identical that route activation and group membership add part;

D. safeguard multicast tree

Each node timed sending hello message is with the received power tabulation of maintenance of neighbor relation and renewal neighbor node; In addition, the tree root node timed sending Group Hello message of each multicast tree, simultaneously the tree root sequence node number increases 1; When the multicast tree member receives GroupHello message, send MACT message and carry out the route activation, guarantee that thus each node can obtain the up-to-date routing iinformation of multicast tree;

E. multicast tree merges

Under mobile environment, because the mobility of node, ad hoc network may be divided into several mutual disconnected zones, and its oneself multicast tree is safeguarded in each zone; Because the mobility of node; Two or more disconnected zones may be communicated with once more; In order to clear away confusion, the tree root node that has maximum sequence number becomes the tree root node of new multicast tree, and other tree root node stop are sent GroupHello message and wait for the reconstruction of multicast tree.

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