CN100556000C

CN100556000C - Set up the method for route under a kind of unidirectional link environment

Info

Publication number: CN100556000C
Application number: CNB2007101764563A
Authority: CN
Inventors: 陈月云; 段国强
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2007-10-29
Filing date: 2007-10-29
Publication date: 2009-10-28
Anticipated expiration: 2027-10-29
Also published as: CN101150518A

Abstract

Set up the method for route under a kind of unidirectional link environment, this method is applicable to AD Hoc network field, to reduce the influence of one way link in AD Hoc network information transfer.This method is passed through increasing neighbors information in the RREQ message format, make the existence of setting up the node affirmation one way link as early as possible in the process in route, the unnecessary energy loss that produces to reduce one way link to propagate message once more makes the AODV routing procedure can support one way link preferably and be easy to realize.And periodically send the Hello2 message by each node, reduce expense problems of too in the Hello method.Reduce energy loss in the occasion of the needs such as to make military operation, disaster relief and mobile meeting, sensor network of originally improving one's methods use AD Hoc network, can prolong the useful life of the additional node of noenergy.

Description

Set up the method for route under a kind of unidirectional link environment

Technical field:

The present invention relates to that a kind of of AODV routing procedure improves one's methods in the Ad Hoc network, reduce the method for routing cost under particularly a kind of unidirectional link environment, belong to network technology, the communication technology, be applicable to Ad Hoc network application field.

Background technology

Ad Hoc network is that a kind of equity that has no center, self-organizing, rapid deployment and characteristics such as move is a network, is known as multihop network (Multi-hop Network) or self-organizing network (Self-organized Network) again.Compare with traditional cellular network, Ad Hoc network does not have master controller, and net structure and management function are born in the distributed operation of all nodes jointly.It can be set up and remove at any time, has very strong fault-tolerance and robustness, is widely used for military operation, disaster relief and occasions such as mobile meeting, sensor network.

As the grouping multi-hop wireless network that a kind of infrastructureless is supported, Ad Hoc network has obtained people and has more and more paid close attention to, and one of them important field of research is exactly wireless route technology.In order to adapt to various application scenario, the researcher has designed many Routing Protocols.Wherein, AODV (Ad hoc On-Demand Distance Vector) routing procedure is one of wireless self-networking Routing Protocol of recommending of MANET (the Mobile Ad hoc Networks) working group of IETF (Internet Engineering Task Force).It is simple, practicality and superior performance, can realize the used basic function of route, by a kind of agreement of people's primary study.But the AODV routing procedure part that still comes with some shortcomings does not support that one way link is exactly one of them.Therefore, how to improve the AODV routing procedure---make it not only can support one way link, and can rationally control expense, become one of problem demanding prompt solution.

The AODV routing procedure is divided into route querying and two stages of route maintenance.Relate to three kinds of basic message: RREQ (Route Request) message, RREP (Route Reply) message and RERR (Route Error) message altogether, AODV also uses a kind of special RREP message, i.e. hello packet in addition.

(1) route querying

The route querying process is divided into RREQ stage and RREP stage:

1) RREQ process

A source node S broadcasting route request information (RREQ) wherein comprises parameters such as source node address, destination node address, jumping figure, request ID.Each RREQ is unique definite by request ID and source node IP address.

After intermediate node a, c and e etc. receive RREQ,, source node IP at first by inspection＜request ID〉information judges whether to receive this RREQ message, if then abandon, to avoid occurring route loop; Otherwise in self routing table, set up the reverse route (oppositely route) of a hop node in the sensing, be used for the RREP message of loopback correspondence.As shown in Figure 1, just can write down next jumping (next) of going to node S (dest) and be node S after node a, c, e receive the RREQ that source node S sends in routing table separately, other nodes are also adopted to use the same method and are set up separately reverse route.

Intermediate node is then by judging the method for aim sequence number, check in self buffer whether have than new routing information, if the effective route that exists RREQ to search, and ' D ' sign (expression does not allow intermediate node to reply the RREP message) is not set in the RREQ frame, then initiates route response; Otherwise contained jumping figure is increased progressively 1, and this RREQ message flooded broadcast is again gone out, after destination node D receives RREQ, till source node S loopback RREP message.

2) RREP process

As shown in Figure 2, comprise parameters such as source node address, destination node address, destination node sequence number, jumping figure and life span in RREP (Routing Reply) message, node feeds back to source node S to the RREP message by the reverse route of setting up previously.RREP is that the mode with clean culture sends.

The intermediate node f that transmits RREP can upgrade routing table, and contents such as downstream node D, jumping figure, effective time, aim sequence number of route transmitted in record, and according to the reverse route of precedence record the RREP message is transmitted to upstream node e, until source node S.After source node S is received the RREP message, just obtained to arrive the route of destination node D.Next source node S just can carry out transfer of data with this route.

It should be noted that: though RREQ can propagate into destination node D along mulitpath, RREP only passes source node back along the path (S, f, e and D) that arrives at first, i.e. the shortest route of select time tolerance.

(2) route maintenance

After route table items was set up, each node in the route all will be carried out the task that routing table was kept, managed to route.Its method is: each active ways is all periodically broadcasted hello packet to adjacent node by last node.When route no longer was used, node will be deleted corresponding entry from routing table.Simultaneously, when node is found the situation of link disconnection is arranged, can take following two kinds of counter-measures:

A kind of is directly to transmit routing error message (RERR) notification source node, has indicated in the RERR message owing to chain rupture causes the destination node that can't arrive.The intermediate node of RRER process then can be in regular turn with the erasing of information of relevant this route, and RRER can search a route that arrives destination node D after being transmitted back to source node S again.

Another kind of way is called local the reparation, when chain rupture place when destination node is nearer, can in subrange, initiate the route that RREQ finds destination node by the upstream node of chain rupture place, can shorten the time of route querying like this and reduce packet loss; If local the reparation fails, then need to carry out according to first kind of measure.

In order to overcome the influence of one way link to the AODV routing procedure, multiple improving one's methods is suggested in succession.A kind of more representational method---Hello method described in article " Routing Performance in the Presence of Unidirectional Links in Multihop Wireless Network ".The Hello method require each node all periodically broadcasting comprise one of its neighbors information and jump hello packet, this method has been expanded the hello packet content of basic AODV algorithm, has promptly increased information of neighbor nodes on the basis of former hello packet.This method requires each node all to keep a adjacent node tabulation NNL (Neighbor Node List) to write down the hello packet sender (being its neighbor node collection) known to it.Certain node in network when receiving the hello packet of another node C transmission as node D, is then retrieved the entrained adjacent node information of this hello packet to distinguish whether oneself is among them.If, then C is provided with to show the link symmetry between D and the C at the relevant field of its NNL record; Otherwise refusal is set up contrary (instead) and is abandoned to route and with this hello packet.Can understand the existence of one way link and and then avoid setting up route thereon by NNL like this.

The Hello method makes the AODV routing procedure support one way link well by the expansion hello packet, but this method adopts periodically, the hello packet of big byte, has increased routing cost significantly.Article that R.Ogier etc. show " TopologyDissemination Based on Reverse-Path Forwarding (TBRPF) " propose to use the increment hello packet, though can reduce the capacity of Hello bag, its expense is still and can not be ignored.

Summary of the invention

The method that the objective of the invention is to set up under a kind of unidirectional link environment route makes AODV support one way link preferably and is easy to and realizes, to improve the bigger problem of cost that expense causes in the Hello method.

(1) Hello2 message

Different with the Hello method is that it has used original hello packet (only comprise self information, do not comprise neighbors information), but requires each node all to broadcast hello packet.For convenience of explanation, in the literary composition this message called after Hello2 message.

The Hello2 message is the RREP grouping of a life span TTL=1, comprises following RREP message composition territory:

A) destination node IP address and local node IP address;

B) destination node sequence number and local node sequence number;

C) jumping figure is made as 0;

D) life-span.

(2) RREQ2 message

The RREQ2 message is expanded on RREQ message basis and is obtained, and it also includes the information of neighbor node except the information that comprises the RREQ regulation.Message format as shown in Figure 3.

(3) course of work

The RREQ stage in the AODV process:

1) desires to search route and when initiating the route requests process, from its neighbor node table, extract neighbors information earlier when source node, be combined into the RREQ2 message then

2) after intermediate node is received the RREQ2 message that source node sends,, then the neighbors information that comprises among the RREQ2 is changed the neighbors information of doing oneself, and transmit this message if found the information of oneself in the neighbors information therein; And when finding the information of oneself in the RREQ2 message that intermediate node fails receiving, then abandon this RREQ2 message, do not set up reverse route yet, thereby eliminated the influence of one way link.

3) when the RREQ2 message propagates into destination node, it is also with 2) method that adopted judges, and if between upstream node link be two-way.Then set up reverse route and loopback routing reply message RREP.

4) Hello2 method require each node broadcasting Hello2 message in cycle all.Every one-period, whether node inspection oneself has sent a broadcast (RREQ etc.) in last one-period, if do not send, and Hello2 message of this node broadcasts then.A node is determined to connect by the message of accepting its neighbor node transmission, if receive in the past one deletion time cycle an one neighbors the Hello2 message but after a segment length in the time in life-span, do not receive any message of this neighbors again, this node just should think that the route of this neighbors of arrival lost efficacy so.If a node receives the Hello2 message of an one neighbors, then this node should affirm that the route that an activity is arranged oneself arrives this neighbors; If there has been a route, then can be with the corresponding increase of the life-span of this route.

The Hello2 method has not only been inherited the advantage of Hello method preferably, and has obviously improved the excessive problem of its expense:

(1) on the time, the Hello2 method has been used for reference the thought as required of AODV routing procedure, makes the propagation of neighbors information (information of neighbor nodes that node is known) suffer restraints in time.

(2) on the space, both routing cost can be reduced, also processing expenditure can be reduced.

(3) in the Hello2 method reception of RREQ2 and one way link determine it is synchronous, the reception of RREQ and retransmission method have limited redundant neighbors information processing.

(4) in addition, can also utilize the thought of basic AODV routing procedure, reduce the transmission of Hello2 message---when having sent control message such as RREQ2, RREP at the appointed time when node, can send the Hello2 message again, because therefrom can obtain the entrained information of Hello2 message.

Description of drawings

Fig. 1 is an AODV routing procedure RREQ search procedure.

→ expression RREQ

Represent reverse route

The expression source node

The expression destination node

Be intermediate node

Fig. 2 is that AODV routing procedure RREP confirms process.

→ expression RREQ

Represent reverse route

The expression source node

The expression destination node

Be intermediate node

Fig. 3 is the concrete form of RREQ2 message.

J is for adding sign

R is for repairing sign

G does not reply the RREP sign for there being the request road

The single destination node sign of D

U unknown nucleotide sequence number

Fig. 4 is a Hello2 method route requests schematic diagram, and RREQ2 message wherein only is used to show that its content is made up of RREQ and neighbors information.

→ expression one way link

---the expression two-way link

Fig. 5 is the bag delivery rate of Hello method and Hello2 method.

Fig. 6 for when node number, business model, network topology structure identical, under the high power node proportion different situations, the routing cost (1) of Hello method and Hello2 method.

Fig. 7 for when node number, business model, high power node ratio identical, but under the different situation of network topology structure, the routing cost (2) of Hello method and Hello2 method.

Fig. 8 for when the node number, network topology structure is identical, high power node ratio is identical, but under the different situation of business model, the routing cost (3) of Hello method and Hello2 method.

Fig. 9 is identical for working as high power node ratio, and the node number changes, under the situation that network topology structure, business model also change thereupon, and the routing cost (4) of Hello method and Hello2 method.

Embodiment

By improvement to the Hello method, obtain a kind of new Hello2 method, and come The Realization of Simulation Hello method and Hello2 method, and compare the two performance on key performance by the NS2 simulator, estimate the performance of Hello2 method effectively.

The concrete course of work of Hello2 method:

(1) as shown in Figure 4, desire to search route and when initiating the route requests process, from its neighbor node table, extract neighbors information (a) earlier, be combined into the RREQ2 message with RREQ then when source node S.The concrete form of RREQ2 message wherein is referring to shown in Figure 3.

(2) after intermediate node a receives the RREQ2 message that S sends, if found the information of oneself in the neighbors information therein, proof S can reach a, a also can reach S simultaneously, be that link between S, a is two-way, this moment, a was when transmitting route requests, also needed the neighbors information that comprises among the RREQ2 is changed the neighbors information (S, b) of doing oneself, and transmitted this message; Fail in the RREQ2 message of receiving (node S sends), to find the information of oneself and work as c, prove that then S can reach c, but c is unreachable S, the Radio Link that is the two is unidirectional, then c abandons this RREQ2 message, does not also set up reverse route, thereby has eliminated the influence of one way link.

(3) when the RREQ2 message propagates into destination node D, it is also judged with the method that (2) are adopted, and then knows that the link between e, D is two-way.Thereafter the task of D is set up reverse route and loopback routing reply message RREP exactly, and this part work is with basic AODV.

(4) Hello2 method require each node broadcasting Hello2 message in cycle all.Every one-period, whether node inspection oneself has sent a broadcast (RREQ etc.) in last one-period, if do not send, and Hello2 message of this node broadcasts then.A node is determined to connect by the message of accepting its neighbor node transmission, if receive in the past one deletion time cycle an one neighbors the Hello2 message but after a segment length in the time in life-span, do not receive any message of this neighbors again, this node just should think that the route of this neighbors of arrival lost efficacy so.If a node receives the Hello2 message of an one neighbors, then this node should affirm that the route that an activity is arranged oneself arrives this neighbors; If there has been a route, then can be with the corresponding increase of the life-span of this route.

Expense is analyzed:

(1) neighbors information is only just propagated when the needs route, and promptly it is to propagate with the propagation of RREQ2.Neighbors information is then propagated with periodic hello packet in the Hello method, and the two is compared, and this part expense of Hello2 method obviously reduces; And, when route search is failed, still need mutual neighbors information between node when adopting the Hello method, but adopt the Hello2 method then to need not mutual neighbors information.

(2) neighbors information is only propagated in limited scope, and this depends on the tied mechanism of Hello2 method to RREQ2 message spread scope.With Fig. 4 is example, when source node S is initiated the route search process, because the c node does not participate in routing forwarding, so the RREQ2 message can not occur in the network that c, f, h form.Thereby can not be sent out attached to the neighbors information in the RREQ2 message yet.So routing cost further reduces.

(3) in the Hello2 method reception of RREQ2 and one way link determine it is synchronous, the reception of RREQ and retransmission method have limited redundant neighbors information processing; And the reception of RREQ and one way link definite asynchronous in the Hello method, so receiving node must be handled the neighbors information of receiving.With Fig. 4 is example, and when the b node sent the RREQ2 message, a and e node all can receive this message, but a node knows it is duplicate message by judging the RREQ ID in the message, then abandons this message.But the Hello method is quite different, when a receive that b sends comprise the high-capacity H ello message of neighbors information the time, still need to handle.

(4) because the Hello2 message that the Hello2 method is used is consistent on form with the hello packet of AODV substantially, so can utilize the thought of basic AODV routing procedure, reduce the transmission of Hello2 message---when having sent control message such as RREQ2, RREP at the appointed time when node, can send the Hello2 message again, because therefrom can obtain the entrained information of Hello2 message.And the high-capacity H ello message in the Hello method does not obviously possess such advantage, because its message content can't be with the content to replace in control such as the RREQ message.

Write the NS2 program, The Realization of Simulation Hello method and Hello2 method.The network of simulation analysis and business model major parameter are as follows:

(1) this paper is by the radio transmit power of self-defined node, makes that each node has different coverages in the network, and then produces one way link.Introduced two kinds of node transmitting powers in the experiment altogether, the coverage of corresponding node is respectively 250m and 400m.The transmitting power of normal condition lower node is 250m.Produce the one way link of varying number then by the ratio of high transmit power node in the change network.

(2) under 4 kinds of different network rings scapes, carried out Performance Evaluation altogether.

1) the node number is fixed as 30, business model, network topology structure be identical, and high power node proportion difference is respectively 0%, 10%, 20%, 30%, 40%, 50%.Total simulation time is 150s.

2) the node number is fixed as 20, business model is constant, high power node fixed ratio is 40%, but the network topology structure difference.Total simulation time is 150s.

3) the node number is fixed as 20, network topology structure is identical, high power node fixed ratio is 40%, but the business model difference.

4) high power node fixed ratio is 30%, and the node number changes, and network topology structure, business model also change thereupon.

(3) general parameter: business model is fixed bit rate (CBR) business, and CBR bag size is 512B, and the total simulation time of network is 150s.

Simulation result and analysis:

(1) node number, business model, network topology structure are identical, high power node proportion difference.The bag delivery rate of Hello method and Hello2 method and routing cost such as Fig. 5, shown in Figure 6.

As seen the bag delivery rate of the two is basic identical, along with all decline to some extent of increase of high power node ratio in the network.When the high power node reaches 15, proportion is 50% o'clock, and bag delivery rate still maintains about 94%.On the other hand, increase along with high power node in the network, the expense of the two all can increase, the Hello method is to increase because of the increase of neighbor node number, it is more relatively that but the increase of route querying number of times makes that the expense of Hello2 method increases, but compare still saving much with the Hello method.

(2) node number, business model, high power node ratio are identical, but the network topology structure difference.The routing cost of Hello method and Hello2 method as shown in Figure 7.

The variable effect of visible network topology neighbors information, make the expense of Hello method present certain fluctuation variation, the difference of neighbors information (influencing the size of RREQ2 message) and network connectivty (influencing the quantity forwarded of RREQ2 message) also causes the expense of Hello2 method the fluctuation variation to occur simultaneously.

(3) the node number, network topology structure is identical, high power node ratio is identical, but business model difference.The routing cost of Hello method and Hello2 method as shown in Figure 8.

The result shows that when only business model changed, the expense of Hello method was almost constant, and this meets true.But then bigger to the influence of the expense of Hello2 method, this mainly is that increase owing to RREQ2 causes, but the latter still lacks much than the former.

(4) high power node ratio is identical, and the node number changes, and network topology structure, business model also change thereupon.The routing cost of Hello method and Hello2 method as shown in Figure 9.

The result shows that the variation of node number is all bigger to the routing cost influence of Hello method and Hello2 method, because each node in the network all will participate in the transmission of periodicity Hello or Hello2 message; Simultaneously the change of node density, network topology structure causes that neighbors information presents the trend that increases progressively, and this will cause the expense of Hello method and the difference between Hello2 method expense increasing, i.e. the expense of Hello2 method saving will get more and more.

Claims

1, set up the method for route under a kind of unidirectional link environment, it is characterized in that: in the RREQ process and Hello process of AD Hoc network A ODV routing procedure:

1) desires to search route and when initiating the route requests process, from its neighbor node table, extract neighbors information earlier when source node, be combined into the RREQ2 message then; The RREQ2 message is expanded on RREQ message basis and is obtained, and it also includes the information of neighbor node except the information that comprises the RREQ regulation;

2) after intermediate node is received the RREQ2 message that source node sends, in neighbors information therein, found the information of oneself, then the neighbors information that comprises among the RREQ2 has been changed the neighbors information of doing oneself, and transmit this message; And when finding the information of oneself in the RREQ2 message that intermediate node fails receiving, then abandon this RREQ2 message;

3) when the RREQ2 message propagates into destination node, it is also with 2) method that adopted judges, and if between upstream node link be two-way, then set up reverse route and loopback routing reply message RREP;

4) the Hello2 message adopts original hello packet form, only comprise self information, do not comprise neighbors information, each node is the broadcasting Hello2 message in cycle all, every one-period, whether node inspection oneself has sent a broadcast RREQ in last one-period, when not sending, Hello2 message of this node broadcasts then, a node is determined to connect by the message of accepting its neighbor node transmission, in a deletion time cycle in the past, receive the Hello2 message of an one neighbors, but after a segment length in the time in life-span, do not receive any message of this neighbors again, this node just determines that the route that arrives this neighbors lost efficacy so; When a node receives the Hello2 message of an one neighbors, then this node determines oneself to have the route of an activity to arrive this neighbors; There is a route when, then can be with the corresponding increase of the life-span of this route.

2, according to claims 1 described method, it is characterized in that: the form of RREQ2 message is included as 8 bit type sign indicating numbers, 5 bit JRGDU sign indicating numbers, 11 bit reserved words, 8 bit multi-hops forwarding counter, 32 bit route requests identification codes, 32 bit destination node IP addresses, 32 bit destination node sequence numbers, 32 bit route requests RREQ source node IP addresses, the sequence number of 32 bit route requests RREQ source nodes, 32 bit neighbors counters, 1 to 100 32 bit neighbors IP address.