CN102905337A - Routing method based on cross-layer design in self-organized network - Google Patents

Abstract

The invention aims to provide a routing method based on cross-layer design in a self-organized network. According to the invention, based on the cross-layer idea, an SR (smooth of retry count) is redefined in a routing protocol through two variables, namely, SSRC (station short retry count) and SLRC (station long retry count) to express retry counts during the frame transmission process, and PSAC (Probability of Successful Access to Channel) is determined on the basis, so as to achieve the aim of selecting the optimal channel. On the basis of multi-channel multi-interface AODV (Ad hoc on demand distance vector routing), by combining the SR and the current length of each buffering queue in each interface, the LTC (Link Transmitting Capacity) is determined to be taken as the routing probability. By comprehensively consideration of the PSAC and the routing probability, the purpose of obtaining high handling capacity and short delay by low route load is achieved in a multi-channel multi-interface AdHoc scene.

Description

The method for routing that designs based on cross-layer in the self-organizing network

Technical field

The present invention is a Routing Protocol that is applicable to multi-signal-channel and multi-interface Ad Hoc network environment, belongs to communication technical field.

Background technology

The AdHoc network is the acentric wireless multi-hop network of a kind of self-organizing, and it can not rely on any intrinsic radio infrastructure and can set up anywhere or anytime provisional network.It is a kind of equity network with special purpose, is playing the part of again the role of router when each node in the network is being played the part of the terminal role, realizes network service by internodal forwarding.Be summed up, compare common fixed network and mobile network, Ad Hoc network has following characteristics:

(1) without division center.Ad Hoc network does not have fixing control centre, and equal between all nodes namely is a peer-to-peer network.Node in the network can add and deviated from network at any time, and the fault of any node can not affect the operation of whole network, has very strong survivability.

(2) self-organizing.Network set up, launch not need to rely on any network facilities of setting up in advance.By layered protocol and distributed algorithm coordination behavior separately, node just can rapidly, automatically form an independently network afterwards in start between the node.

(3) multi-hop route.When node will with its wireless transmitter coverage outside node when communicating, need other intermediate node to carry out multi-hop and transmit.Different from the multi-hop of fixed network, the multi-hop route in the Ad Hoc network is to be finished by common network node, rather than is finished by the routing device (such as router) of special use.

(4) dynamic topology.Ad Hoc network is a dynamic network.Network node can move arbitrarily, startup and shutdown whenever and wherever possible, and these all can make topology of networks change at any time.These characteristics are so that Ad hoc network all has obvious difference with common mobile communications network and fixed network at aspects such as network organization, architecture, Protocol Designs.

Along with the development of radio communication, Ad Hoc network comes into one's own in increasing field.Have benefited from independent networking, self-organizing, dynamic topology, without the good characteristic such as division center, multi-hop route, survivability be strong, Ad Hoc network has all occupied one seat in commercial communication and military communication field, such as emergency disaster relief, ground observation, field rescue etc.

But we should see that as a kind of emerging network technology, it still has the problems to be solved such as many.Most critical be that it has the at random mobile continuous variation that causes network topology of node, time-variant wireless channel environment, limited characteristics such as channel width, these have proposed challenge for Design and implementation Ad Hoc network, so must be carefully go to consider from the every aspect of network architecture.The network layer of high spot reviews in this patent for example needs design can adapt to that topology changes fast, stable routing mechanism, and the overheads such as route maintenance information can be controlled at a zone of reasonableness, to guarantee the efficient utilization of Internet resources.

The research of Ad Hoc network routing protocol is very deep.Different by the drive pattern of finding route, class can be divided three classes: active (Proactive), response type (Reactive) and mixed type (Hybrid).Active Routing Protocol is also referred to as Proactive routing protocols or table drives Routing Protocol, each node of this protocol requirement needs to set up and safeguard the routing table of the recent route information that arrives all nodes, all routing iinformations are consistent, Typical Representative such as DSDV, OLSR etc.; The response type Routing Protocol claims again on-demand routing protocol or source forcing Routing Protocol, and it is a kind of Routing Protocol of passive type, only just can trigger route discovery processes and seek the route that arrives purpose, Typical Representative such as DSR, AODV etc. when business demand is arranged; Hybrid Routing Protocol then is to combine active and the corresponding advantage of response type, selects suitable route type of drive, Typical Representative such as ZRP agreement according to actual conditions.

In the early stage Ad Hoc network, owing to the restriction of hardware technology, equipment price and the needs of avoiding mutual coordination between the node, most of terminal all is single channel list interface type, and the network performance that forms thus is very limited.Along with the raising of system to throughput demand, a plurality of transceivers of equipment have been a trend of in the future Ad Hoc network terminal development in a terminal, and the reduction of the development of hardware technology and equipment cost has aggravated this trend especially.IEEE 802.11 has defined a plurality of nonoverlapping channels in 2.4GHz and 5GHz frequency range, but when a plurality of wireless channel time spent, at the more than one R-T unit of terminal equipment, adjacent different nodes are communicated on different channels simultaneously, can greatly reduce thus the phase mutual interference between the adjacent node, reduce time delay, improve the throughput of system.Can say that multi-signal-channel and multi-interface is a main trend of following Ad Hoc network Development.And how to distribute and make good use of these channels, and corresponding route metric is proposed on this basis, become the study hotspot of current Ad Hoc network routing protocol.

Summary of the invention

Technical problem: the objective of the invention is to provide the method for routing that designs based on cross-layer in the self-organizing network, i.e. multi-signal-channel and multi-interface Ad Hoc method for routing.The method is calculated channel allocation tolerance and route metric by the method for cross-layer design, can realize obtaining higher bag arrival rate, throughput of system with lower routing cost, reduces simultaneously the average delay of system.

Technical scheme: the present invention has provided in the self-organizing network method for routing based on the cross-layer design.The method is carried out channel allocation according to successfully accessing channel probability, determines route metric based on the link transmission ability simultaneously, and the method can obtain higher bag arrival rate and throughput of system with lower routing cost, and reduces simultaneously the average delay of system.

The cross-layer technology is to improve a kind of effective means of mobile Ad Hoc network resource utilization.So-called cross-layer is exactly to break to a certain extent or change original between layers communication restriction, change original protocol layer interface, by using between layers mutual, so that the at all levels of protocol stack can be shared local information, to eliminate the redundant interaction between each layer of wireless network, greatly reduce communication overhead, the overall performance of optimization system.For the Ad Hoc network that becomes when, limited bandwidth large for time delay, channel, the impact that the benefit that the cross-layer design brings is brought much larger than mutual between layers complexity.Therefore, it is necessary that the thought that adopts cross-layer to design in Ad Hoc network designs with combined optimization, and it can improve the overall performance of wireless network.Existing cross-layer design can roughly be divided into following a few class: physical layer and the design of MAC layer cross-layer; Physical layer and the design of network layer cross-layer; Physical layer and the design of transport layer cross-layer; MAC layer and the design of network layer cross-layer; MAC layer and the design of transport layer cross-layer; Network layer and the design of transport layer cross-layer.

The method comprises following content:

A. determine the channel allocation tolerance of broadcast packet: the neighbours that establish node A concentrate N neighbor node, and then the channel of the broadcast packet of channel j success access probability PSAC is among the node A

FC wherein _j(n) be illustrated in the bag quantity that one-period interior nodes A transmits to its neighbor node n by channel j, Be illustrated in i the re-transmission index SR value of wrapping that one-period interior nodes A sends to neighbor node n by channel j, SR _MaxRe-transmission index during for bust this, the best broadcast channel of node A selects tolerance to be:

$\mathrm{BestChannelForBroadcast}\left(A\right)=\left\{j\right|\underset{j\∈[0,K-1]}{\max }\left\{{\mathrm{PSAC}}_j^{\mathrm{Broadcast}}\left(A\right)\right\}\},$ Wherein K represents all available numbers of channel of node A;

B. determine the channel allocation tolerance of non-broadcast packet: non-broadcast packet channel allocation tolerance is only considered to transmit bag to the average re-transmission index SR value of down hop, suppose that node A works as skip before, and Node B is down hop, and then channel j for the successful access probability PSAC of the channel of non-broadcast packet is among the node A:

FC wherein _j(B) be illustrated in the bag quantity that one-period interior nodes A transmits to Node B by channel j, Be illustrated in one-period interior nodes A by the re-transmission index SR value of channel j to i bag of Node B transmission, calculate the PSAC value of all K channel, the channel of PSAC value maximum is as optimum channel;

C. determine the route metric based on link transmission ability LTC: establish set PATHS={P ₁, P ₂... ..P _mComprised all the m paths from source node S to destination node D, gather

The expression path P _tIn point sequence, altogether l jumps, path P _tQ to jump be from node h _Q-1To node h _q, node h then _Q-1To node h _qLink transmission ability LTC is:

$\mathrm{LTC}(h_{q-1},h_q)=\mathrm{\β}\×{\mathrm{PSAC}}_j^{\mathrm{Data}}(h_{q-1},h_q)+(1-\mathrm{\β})(1-\frac{C_j}{C_{\max }}),$ Wherein β is weight factor, β ∈ (0,1), C _jRepresent the current buffer queue length of interface corresponding to channel j, C _MaxRepresent the maximum of egress buffer formation, routing metric is

RM (P _t) reacted path P _tThe bottleneck value of the link that passes through when source node is found mulitpath is arranged, selects the maximum path of RM value as optimal path;

D. within certain cycle, when node is received the HELLO bag of certain neighbor node for the first time, no matter by which channel receive during this bag, all will respectively reply an ACK information by each interface to this neighbor node immediately, the time in cycle is identical with the broadcast cycle that HELLO wraps;

E. the optimal path discovery procedure is as follows:

Step 1: if there is not the route of destination node in the source node routing table, then carry out route discovery by the inundation routing request packet, when intermediate node is received routing request packet, it at first sets up reverse route in routing table, if it to the LTC value of previous dive less than the LTC value of storing in the routing request packet, then with the LTC value in this value renewal routing request packet, the route weight of reverse link is characterized by the LTC value in the routing request packet;

Step 2: whether node inspection oneself is destination node, if not, then directly transmit this routing request packet, if then turn step 3;

Step 3: reply the routing reply bag along reverse link, the LTC value update mechanism in the routing reply bag is the same with routing request packet, and the routing metric RM value of forward link can be determined by the LTC value in the routing reply bag bag;

Step 4: after source node is received the routing reply bag in all paths, select the maximum path of routing metric RM value as optimal path.

Beneficial effect: the routing algorithm that designs based on cross-layer in the Ad Hoc scene that the present invention has provided at multi-signal-channel and multi-interface, the load that this algorithm synthesis the has been considered link transmission capacity of channel carries out the selection of route, can obtain higher bag arrival rate and throughput of system with lower routing cost, and reduce simultaneously the average delay of system.

Description of drawings

Fig. 1 is based on the Routing Protocol model of network layer and the design of MAC layer cross-layer, in the Routing Protocol of layer Network Based and the design of MAC layer cross-layer, the Routing Protocol of network layer determines Route Selection and channel selection by the feedback information that receives from the MAC layer, and will select accordingly to feed back to the MAC layer, determine the employed transceiver of transmission information and channel.

Embodiment

The given cross-layer routing protocol of the present invention namely designs by MAC layer and network layer cross-layer, concrete model as shown in Figure 1, in the Routing Protocol of layer Network Based and the design of MAC layer cross-layer, the Routing Protocol of network layer determines Route Selection and channel selection by the feedback information that receives from the MAC layer, and will select accordingly to feed back to the MAC layer, determine the employed transceiver of transmission information and channel.In the present invention, the number of channel of each terminal and number of ports are assumed to be equal, as being made as K.In the transport process of bag, bag of every transmission transmits this and wraps employed channel and retransmit index and all recorded by meeting.Be that the MAC layer can constantly be delivered to retransmission information in the network layer.The re-transmission index that Routing Protocol in the network layer will be collected draws the transmittability of each channel through the calculating of certain algorithm, and the destination of comprehensive suite determines to transmit bag used channel and path again.

Concrete agreement is achieved as follows: two variablees during the management information bank in the IEEE 802.11 MAC agreements is safeguarded, the short frame number of retransmissions of SSRC() and the long frame number of retransmissions of SLRC().Thought based on cross-layer, by these two variablees in Routing Protocol, define retransmit index SR (smooth of retry count) characterize transmit in the frame process number of retransmissions, and define on this basis channel and select tolerance channel success access probability obability of Successful Access to Channel), reach the target of selecting preferred channels with this.On the basis of multi-signal-channel and multi-interface AODV, in conjunction with the current length of buffer queue in SR and each interface, determine route metric link transmission ability LTC (Link Transmitting Capacity).Measure the Routing Protocol CL-IAOR that realizes in the multi-signal-channel and multi-interface Ad Hoc scene, obtain higher throughput and lower time delay with lower routing overhead for comprehensive above-mentioned two.

Adopt the Ad Hoc network of 802.11 agreements, the MAC layer of each node is being safeguarded two variablees: short frame number of retransmissions SSRC (Station Short Retry Count) and long frame number of retransmissions SLRC (Station Long Retry Count).Both are in difference: in the situation that RTS/CTS mechanism is triggered, if the length of Frame less than the regulation the RTS threshold values, then the number of retransmissions of this Frame is indicated with SSRC, otherwise indicates with SLRC.The retransmission counter initial value is 0, the every re-transmission of frame once, this value adds 1.If counter arrives maximum, then will abandon this transmission and be discarded in medium this frame waiting for transmission of transmit queue, unison counter is reset to 0 again.In general, the maximum of SSRC and SLRC is set as respectively 6 and 3.Here redefine a re-transmission index SR (Smooth of Retry) and transmit the RTS frame of a required re-transmission of frame and the number of times of Frame to represent a node:

Wherein SSRC is short frame number of retransmissions, and span is the integer between 0 to 6, the long frame number of retransmissions of SLRC, span is the integer between 0 to 3, and t is the weight factor of these two number of retransmissions of balance, and span is between 0 to 1, retransmit index SR and when bust this, obtain maximum, SR _Max=6t+4 (1-t).

SR is a parameter of a concentrated expression node access channel capacity and network topology change thereof.T*SSRC in the formula (1) has shown that node and active node on every side seize the ability of channel.If successfully receive the CTS frame, then expression is preengage the channel success and is begun to transmit the DATA frame; The t*SLRC part has then reflected the residing network condition of node when node sends Frame after obtaining channel, because Ad Hoc nodes moves at random, may have some active nodes to move towards this node direction this moment, thereby clash with the transmission of this secondary data, so node will retransmit the DATA frame, thereby the Internet resources and the time that consume when not being wasted in the reservation channel, weight coefficient t can obtain certain balance between these two parts.So far, obtain characterizing the parameter S R of node access channel capacity by the number of retransmissions analysis to the transmission of MAC layer data.

Below by SR value definition channel allocation tolerance and route metric.

1, based on channel success access probability PSAC(Probability of Successful Access to Channel) method for channel allocation.

Be less than in the scene of the number of channel at number of ports, in order to guarantee the connectedness of network, be necessary to guarantee by some rational distribution mechanisms the connectedness of network, for example set a public control channel, be used for sending control bag and other broadcast packet.And the present invention is applicable to the node number of channel multi-signal-channel and multi-interface AdHoc network identical with number of ports.In the number of channel situation identical with number of ports, the connectedness of network does not need to guarantee by setting a public control channel.Be used for carrying out the transmission of broadcast packet if set a channel, can increase on the contrary the collision probability of broadcast packet.Therefore, among the present invention, channel allocation tolerance is divided into channel allocation tolerance and the non-broadcast packet channel allocation tolerance of broadcast packet.It should be noted that in this agreement that following channel allocation tolerance is not adopted in the broadcasting of HELLO bag, but broadcasts in each channel, this is conducive to make up accurately the SR value in network topological diagram and the renewal Routing Protocol.

(1) channel allocation of broadcast packet tolerance

The neighbours that suppose node A concentrate N neighbor node, and then the successful access probability PSAC of the channel of the broadcast packet of channel j value is defined as follows among the node A:

${\mathrm{PSAC}}_j^{\mathrm{Broadcast}}\left(A\right)=1-\frac{\underset{n=1}{\overset{N}{\mathrm{\Σ}}}\underset{i=0}{\overset{{\mathrm{FC}}_j\left(n\right)}{\mathrm{\Σ}}}{\mathrm{SR}}_i^j\left(n\right)}{\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{FC}}_j\left(n\right)\×{\mathrm{SR}}_{\max }}---\left(2\right)$

FC wherein _j(n) be illustrated in the bag quantity that one-period interior nodes A transmits to its neighbours n by channel j,

Be illustrated in i the SR value of wrapping that one-period interior nodes A sends to neighbours n by channel j.Thus, by formula (3), can be easy to obtain Value is between 0 and 1.It reacted a upper T in the cycle node A transmit the average re-transmission situation of bag to all neighbours by channel j.This value is larger, can illustrate that to a certain extent to select this channel more reliable as the broadcast packet channel.Therefore the best broadcast channel of node A selects tolerance to be:

$\mathrm{BestChannelForBroadcast}\left(A\right)=\left\{j\right|\underset{j\∈[0,K-1]}{\max }\left\{{\mathrm{PSAC}}_j^{\mathrm{Broadcast}}\left(A\right)\right\}\}---\left(3\right)$

Wherein K represents all available numbers of channel among the node A.

(2) non-broadcast packet channel allocation tolerance

Different from broadcast packet channel allocation tolerance is that non-broadcast packet channel allocation tolerance is only considered to transmit bag to the average SR value of down hop.Suppose that node A works as skip before, and Node B is down hop, channel j is as follows for the channel success access probability PSAC of non-broadcast packet among the defined node A:

${\mathrm{PSAC}}_j^{\mathrm{Data}}(A,B)=1-\frac{\underset{i=0}{\overset{{\mathrm{FC}}_j\left(B\right)}{\mathrm{\Σ}}}{\mathrm{SR}}_i^j\left(B\right)}{{\mathrm{FC}}_j\left(B\right)\×{\mathrm{SR}}_{\max }}---\left(4\right)$

FC wherein _j(B) be illustrated in the bag quantity that one-period interior nodes A transmits to Node B by channel j,

Be illustrated in i the SR value of wrapping that one-period interior nodes A sends to Node B by channel j.Similarly,

Value also between 0 to 1, its reaction be the quality of node A link condition when using channel j to Node B.Value is more near 1, and expression is disturbed fewer, and link condition is also just better.Therefore, when a non-broadcast packet of transmission, Routing Protocol will be learnt first its down hop, then calculates the corresponding PSAC value of each channel, and selects the maximum channel of PSAC value as optimum channel.

2, based on link transmission ability LTC(Link Transmitting Capacity) route metric

Assumption set PATHS={P ₁, P ₂... ..P _mComprised all the m paths from source node S to destination node D, gather

The expression path P _tIn point sequence, altogether l jumps, path P _tQ to jump be from node h _Q-1To node h _qDefinition link transmission ability LTC(Link Transmitting Capacity) as follows:

$\mathrm{LTC}(h_{q-1},h_q)=\mathrm{\β}\×{\mathrm{PSAC}}_j^{\mathrm{Data}}(h_{q-1},h_q)+(1-\mathrm{\β})(1-\frac{C_j}{C_{\max }})---\left(5\right)$

Wherein β is a weight factor of two parts in balance equation the right, and β ∈ (0,1) can get different value according to different network topology situations.J represents the channel number that is used for transmission package in the q jumping, C _jRepresent the current buffer queue length of interface j, C _MaxRepresent the maximum of egress buffer formation.From formula (6), can find out that LTC is dimeric.The link-quality that first's representative should be jumped, it can effectively weigh the disturbed condition around this link.What second portion characterized is the loading condition of current link, and obviously, queue length is longer, and explanation will use the bag quantity of this link transmission more, and link load is also just higher.Can find out easily also that by formula (6) the LTC value of forward link and the LTC value of reverse link are different.Therefore, be different from other major parts and regard link as symmetrical method, the link that characterizes by LTC is asymmetrical, thereby LTC can reflect the quality of link more accurately.

By LTC defined above, routing metric RM of the present invention (Routing Metric) is defined as follows:

$\mathrm{RM}\left(P_t\right)=\underset{q=\mathrm{1,2}..l}{\min }\left\{\mathrm{LTC}(h_{q-1},h_q)\right\}---\left(6\right)$

RM (P _t) reacted path P _tThe bottleneck value of the link that passes through, obviously, this bottleneck value is larger, and the path is better.Therefore, when source node is found mulitpath is arranged, select the maximum path of RM value as optimal path.

3, the realization of Routing Protocol

Routing Protocol of the present invention is to make improvements realization on the basis of AODV, except keeping routing table entry in the AODV Routing Protocol, has increased to these clauses and subclauses of the employed channel of down hop.For the SR value information that guarantees to preserve in the Routing Protocol effective, in certain cycle T, when node was received the HELLO bag of certain neighbor node for the first time, no matter this bag by which channel received, and all will respectively reply an ACK information by each interface to this neighbor node immediately.By sending this ACK information, node can obtain up-to-date each channel SR value to this neighbor node.Thus, can periodically refresh the SR information of preserving in the route, guarantee the validity of SR value.Otherwise if send packet to this neighbor node by certain channel in a upper T cycle interior nodes, the SR value of this neighbor node of then preserving will be 0 or certain expired invalid value.For simplicity, the time of setting cycle T is consistent with the broadcast cycle of HELLO bag in agreement.And in fact the value of being somebody's turn to do is the same with the HELLO packet broadcast cycle, all should adjust according to the concrete condition of network topology change.

If there is not the route of certain destination node in the source node routing table, then it can be by inundation RREQ(routing request packet) bag carries out route discovery.When intermediate node was received the RREQ bag, it at first set up reverse route in routing table.If it less than the LTC value of storing among the RREQ, then upgrades LTC value in the RREQ bag with this value to the LTC value of previous dive.Obviously, the LTC value among the RREQ is with the route weight of calculating reverse path.After this, node should check looks at oneself whether destination node, if not, then transmit this RREQ bag.Intermediate node is not allow to reply RREP(routing reply bag) bag, even it has the effective routing to destination node, reason is that the value of each bar LTC of path is real-time change.If destination node is then replied the RREP bag along reverse link, the LTC value update mechanism in the RREP bag is similar with RREQ.Thus, the RM value of forward link can be determined by the LTC value in the RREP bag.Different from AODV is that source node should wait for a period of time to obtain more routing information after receiving the RREP bag, selects at last the maximum path of RM value as optimal path.

Claims (1)

1. In the self-organizing network based on the method for routing of cross-layer design, it is characterized in that the method comprises following content:

   A. determine the channel allocation tolerance of broadcast packet: the neighbours that establish node A concentrate N neighbor node, and then the channel of the broadcast packet of channel j success access probability PSAC is among the node A

   

   FC wherein _j(n) be illustrated in the bag quantity that one-period interior nodes A transmits to its neighbor node n by channel j,

   

   Be illustrated in i the re-transmission index SR value of wrapping that one-period interior nodes A sends to neighbor node n by channel j, SR _MaxRe-transmission index during for bust this, the best broadcast channel of node A selects tolerance to be:

   $\mathrm{BestChannelForBroadcast}\left(A\right)=\left\{j\right|\underset{j\∈[0,K-1]}{\max }\left\{{\mathrm{PSAC}}_j^{\mathrm{Broadcast}}\left(A\right)\right\}\},$ Wherein K represents all available numbers of channel of node A;

   B. determine the channel allocation tolerance of non-broadcast packet: non-broadcast packet channel allocation tolerance is only considered to transmit bag to the average re-transmission index SR value of down hop, suppose that node A works as skip before, and Node B is down hop, and then channel j for the successful access probability PSAC of the channel of non-broadcast packet is among the node A:

   

   FC wherein _j(B) be illustrated in the bag quantity that one-period interior nodes A transmits to Node B by channel j,

   

   Be illustrated in one-period interior nodes A by the re-transmission index SR value of channel j to i bag of Node B transmission, calculate the PSAC value of all K channel, the channel of PSAC value maximum is as optimum channel;

   C. determine the route metric based on link transmission ability LTC: establish set PATHS={P ₁, P ₂... ..P _mComprised all the m paths from source node S to destination node D, gather The expression path P _tIn point sequence, altogether l jumps, path P _tQ to jump be from node h _Q-1To node h _q, node h then _Q-1To node h _qLink transmission ability LTC is:

   $\mathrm{LTC}(h_{q-1},h_q)=\mathrm{\β}\×{\mathrm{PSAC}}_j^{\mathrm{Data}}(h_{q-1},h_q)+(1-\mathrm{\β})(1-\frac{C_j}{C_{\max }}),$ Wherein β is weight factor, β ∈ (0,1), and, C _jRepresent the current buffer queue length of interface corresponding to channel j, C _MaxRepresent the maximum of egress buffer formation, routing metric is

   

   RM (P _t) reacted path P _tThe bottleneck value of the link that passes through when source node is found mulitpath is arranged, selects the maximum path of RM value as optimal path;

   D. within certain cycle, when node is received the HELLO bag of certain neighbor node for the first time, no matter by which channel receive during this bag, all will respectively reply an ACK information by each interface to this neighbor node immediately, the time in cycle is identical with the broadcast cycle that HELLO wraps;

   E. the optimal path discovery procedure is as follows:

   Step 1: if there is not the route of destination node in the source node routing table, then carry out route discovery by the inundation routing request packet, when intermediate node is received routing request packet, it at first sets up reverse route in routing table, if it to the LTC value of previous dive less than the LTC value of storing in the routing request packet, then with the LTC value in this value renewal routing request packet, the route weight of reverse link is characterized by the LTC value in the routing request packet;

   Step 2: whether node inspection oneself is destination node, if not, then directly transmit this routing request packet, if then turn step 3;

   Step 3: reply the routing reply bag along reverse link, the LTC value update mechanism in the routing reply bag is the same with routing request packet, and the routing metric RM value of forward link can be determined by the LTC value in the routing reply bag bag;

   Step 4: after source node is received the routing reply bag in all paths, select the maximum path of routing metric RM value as optimal path.

Images