CN102781064B

CN102781064B - Method for improving AODV (Ad hoc on-demand distance vector routing) protocol against wireless Ad hoc network

Info

Publication number: CN102781064B
Application number: CN201210160270.XA
Authority: CN
Inventors: 王慧强; 林俊宇; 田苏梅; 冯光升; 郑晨
Original assignee: Harbin Engineering University
Current assignee: Harbin Engineering University
Priority date: 2012-05-22
Filing date: 2012-05-22
Publication date: 2014-08-06
Anticipated expiration: 2032-05-22
Also published as: CN102781064A

Abstract

The invention aims at providing a method for improving an AODV (Ad hoc on-demand distance vector routing) protocol against a wireless Ad hoc network. The method comprises the following steps: selecting cross-layer routing judgment parameters, namely average values of packet retransmission rates of passing an MAC (media access control) layer of a node of groups of the nearest grouping retransmission rates RTRA (Radio and Television Retailers' Association) and RREQ (route request) of a network node; and adding an inlet pointer mymac to get an interface object of the MAC layer after a network layer gets the inlet pointer, realizing the transfer of the cross-layer parameter RTRA by calling a function of the object, declaring that one pointer points to an own routing agent object, then hanging an interface object of the MAC layer of the node on a routing pointer, and transferring the parameter RTRA from the MAC layer to the network layer by crossing two layers, namely an interface queue layer and a logic link layer. According to the method provided by the invention, the average end-to-end time delay and the average routing overhead of a user can be reduced.

Description

Improving one's methods of a kind of AODV Routing Protocol for Wireless Ad hoc network

Technical field

What the present invention relates to is a kind of network, specifically the Routing Protocol of network.

Background technology

Wireless Ad hoc network, is called again MANET network.Generally the network based on Wireless Ad hoc Network technology is translated into Wireless Ad hoc network, or mobile Ad hoc network, mobile Ad hoc network or wireless multi-hop network etc.Wireless Ad hoc network is a kind of independently network autonomous system being formed by distributed algorithm self-organizing by numerous wireless mobile nodes, has the ability of self-foundation, self and self-management.In network, the status of all nodes is equality, does not need to arrange any fixing infrastructure, has very strong survivability.Each node has the function of terminal and router concurrently and can freely change, these nodes can be spontaneously, promptly establish a communications link, and cooperation, finishes the work jointly mutually, and can in mobile, unsettled situation, effectively utilize Internet resources, effective communication service is provided.Wireless Ad hoc network design is convenient, sets up flexibly, thereby has tempting application prospect in fields such as economy and business.What the AODV Routing Protocol that is widely used in wireless Ad Hoc network was used is exactly minimum hop count criterion, because Ad hoc network topology structure and channel constantly change, makes minimum hop count route metric often can not find out desirable path.And traditional hierarchical design can not be made dynamic adjustment neatly, so the thought that improves network performance by cross-layer design just seems especially important, and the performance of Routing Protocol is an important indicator of network performance.

Summary of the invention

The object of the present invention is to provide and reduce improving one's methods of user's average time delay end to end and a kind of AODV Routing Protocol for Wireless Ad hoc network of average routing cost.

The object of the present invention is achieved like this:

Improving one's methods of a kind of AODV Routing Protocol for Wireless Ad hoc network of the present invention, is characterized in that:

Choose cross-layer routing criterion parameter:

If a node has sent a RTS grouping or a packet, but do not receive corresponding CTS or ACK acknowledgment packet, this node is after back off time so, resend RTS or packet, until receive the maximum that corresponding CTS or ACK acknowledgment packet or number of retransmissions reach setting;

At two variablees of MAC layer statement, record respectively the number of retransmissions of RTS and the number of retransmissions of packet, be NRTS_ and NACK_, and be initialized as 0, for RTS, when node, receive corresponding CTS node in season and send the number of retransmissions NRTS_ counting that this RTS needs, once, this numerical value adds 1 in every re-transmission; If it is maximum retransmission that number of retransmissions has surpassed ShortRetryLimit, the number of retransmissions NRTS_ that just node being sent to this RTS needs is designated as ShortRetryLimit, then just abandon this RTS grouping, equally for packet, when node, receiving the number of retransmissions NACK_ that corresponding ACK node in season sends these packet needs normally counts, once, this numerical value adds 1 in every re-transmission; If it is maximum retransmission that number of retransmissions has surpassed LongRetryLimit, the number of retransmissions NACK_ that node is sent to this packets need is designated as LongRetryLimit, then just abandons this packet;

The nearest packet retransmissions present rate of define grid node is RTRA, shown in being calculated as follows of RTRA:

RTRA=(NRTS_+NACK_)/(NRTS_+NACK_+2），

When network node need to upgrade reverse route, just the RTRA value of the RREQ grouping receiving is updated to the RTRA that network node MAC layer calculates;

Before routing table update, by RREQ packet header, carry this cross-layer information, in packet header in RREQ grouping, add two field RTRA and rq_avRTRA, and be initialized as 0, rq_avRTRA is the mean value of the MAC layer packet retransmissions present rate of the RREQ node that is grouped in process in transmitting procedure, also adds field rt_avRTRA in routing table, represents the average retransmission rate of node in this path, be initialized as 0

Rq_avRTRA is calculated as follows:

rq_avRTRA2=(rq_avRTRA1×(rq_hop_count-1)+RTRA)/rq_hop_count，

Wherein rq_avRTRA1 is the average retransmission rate before upgrading, and initial value is 0; Rq_avRTRA2 is the average retransmission rate after upgrading; Rq_hop_count is the jumping figure from source node to processing RREQ packet node indicating in RREQ grouping;

Realizing cross-layer routing upgrades:

In network layer, obtain after entry reference, add entry reference mymac and obtain MAC layer interface object, and by calling the function of this object, realize the transmission of cross-layer parameters R TRA, state route agent's object of a pointed node oneself, then the MAC layer interface object of this node is hung in route pointer, the queue of parameters R TRA crossover ports and logic link layer are two-layer, from MAC layer, are delivered to network layer.

The present invention can also comprise:

1, the method for described routing update is:

If the source node sequence number of RREQ grouping is greater than the sequence number of the reverse route of the node maintenance of receiving RREQ grouping, or the two equates but in RREQ grouping, the product of rq_avRTRA and jumping figure is less than in reverse route rt_avRTRA and the reverse product of the jumping figure of route, by reverse route destination node sequence number update, is the source node sequence number of RREQ grouping; Oppositely the jumping figure of route is updated to the jumping figure of RREQ grouping; Next hop address is updated to the IP address of the node that sends RREQ copy; Oppositely the average retransmission rate of route is updated to the average retransmission rate of all nodes of RREQ grouping process, and " the out-of-date timer " of list item be set.

Advantage of the present invention is:

(1) this method is applicable to the AODV Routing Protocol of the removable node in Wireless Ad hoc network.

(2) this method utilizes C Plus Plus exploitation to realize based on Linux platform, and due to the characteristic that C Plus Plus self has, so the method access speed of realizing is fast, amount of calculation is little, and EMS memory occupation is low.

(3) this method is improved the AODV Routing Protocol of Ad Hoc network based on cross-layer technology, makes to consider the congestion situation of channel in Route Selection, thereby improves network performance.

Accompanying drawing explanation

Fig. 1 is flow chart of the present invention;

Fig. 2 is MAC layer packet retransmissions present situation in this method;

Fig. 3 a is AODV Routing Protocol (RAODV) comparison diagram 1 after traditional AODV Routing Protocol and improvement, and Fig. 3 b is AODV Routing Protocol (RAODV) comparison diagram 2 after traditional AODV Routing Protocol and improvement.

Specific embodiment party

Below in conjunction with accompanying drawing, for example the present invention is described in more detail:

In conjunction with Fig. 1～3, this method is mainly to improve for the routing update operation in route finding process, and all the other processes of Routing Protocol are constant.

Enforcement of the present invention towards be the AODV Routing Protocol of Wireless Ad hoc network, its function is the Routing Protocol improving based on traditional batch design, makes to consider the congestion situation of channel in Route Selection, improves the performance of wireless network.AODV Routing Protocol after improvement can be applied in the mobile node of any Wireless Ad hoc network.

First, choose cross-layer routing criterion parameter.

What Ad Hoc network was used at MAC layer is the IEEE 802.11 MAC agreements with distributed coordination function.The basis of this agreement is carrier sense multiple access and collision elimination (CSMA/CA) agreement.This agreement is combined with RTS/CTS Handshake Protocol in CSMA, and it is mutual that the RTS/CTS that sending node and receiving node first carried out before transmission packet divides into groups.If a node has sent a RTS grouping or a packet, but do not receive corresponding CTS or ACK acknowledgment packet, this node, after one section of back off time, can resend RTS or packet so.Its re-transmission situation as shown in Figure 2.Node 1 sends RTS to node 2, as long as node 1 does not receive that corresponding CTS replys, the RTS sending before just thinking does not transmit successfully, then retransmits RTS, until node 1 is received the number of retransmissions of corresponding CTS or this RTS grouping, has reached maximum (maximum retransmission).Similar, as long as node 1 do not receive corresponding ACK, will retransmitted data packet, until receiving the number of retransmissions of corresponding ACK or this packet, node 1 reached maximum retransmission.Therefore node number of retransmissions (number of retransmissions that comprises RTS grouping, packet) within the time has recently reflected the fierce degree of channel competition and the congestion condition of localized network.

At two variablees of MAC layer statement, record respectively the number of retransmissions of RTS and the number of retransmissions of packet, i.e. NRTS_ and NACK_, and be initialized as 0.For RTS, the RTS transmission success when node is received corresponding CTS before explanation, the number of retransmissions NRTS_ that at this moment just allowing node send this RTS needs normally counts, and once, this numerical value adds 1 in every re-transmission; If number of retransmissions has surpassed ShortRetryLimit(maximum retransmission), the number of retransmissions NRTS_ that just node being sent to this RTS needs is designated as ShortRetryLimit, then just abandons this RTS grouping.Equally, for packet, when node is received corresponding ACK, the data packet transfer success before illustrating, the number of retransmissions NACK_ that at this moment allowing node send this packet needs normally counts, and once, this numerical value adds 1 in every re-transmission; If number of retransmissions has surpassed LongRetryLimit(maximum retransmission), just make the number of retransmissions NACK_ that just node is sent to this packets need be designated as LongRetryLimit, then just abandon this packet.

The number of times having retransmitted when NRTS_ and NACK_ have just recorded respectively network node the last transmission RTS and packet like this.The nearest packet retransmissions present rate of define grid node is RTRA(Retransmit rate), before each re-transmission, RTS or packet were all transmitted once, so, shown in being calculated as follows of RTRA:

RTRA=(NRTS_+NACK_)/(NRTS_+NACK_+2）

When network node need to upgrade reverse route, just the RTRA value of the RREQ grouping receiving is updated to the RTRA that network node MAC layer calculates.

Before routing table update, by RREQ packet header, carry this cross-layer information.In packet header in RREQ grouping, add two field RTRA and rq_avRTRA, and be initialized as 0.Wherein, RTRA is the packet retransmissions present rate that receives the inherent MAC layer of nearest a period of time of node of RREQ grouping, is also the parameter of obtaining from MAC, and the mean value of the MAC layer packet retransmissions present rate of the node of rq_avRTRA to be RREQ be grouped in process in transmitting procedure.In routing table, also add field rt_avRTRA, represent the average retransmission rate of node in this path, be initialized as 0.

Rq_avRTRA is calculated as follows:

rq_avRTRA2=(rq_avRTRA1×(rq_hop_count-1)+RTRA)/rq_hop_count

Wherein rq_avRTRA1 is the average retransmission rate before upgrading, and initial value is 0;

Rq_avRTRA2 is the average retransmission rate after upgrading;

Rq_hop_count is the jumping figure from source node to processing RREQ packet node indicating in RREQ grouping.

Finally, in Routing Protocol AODV, adopt new route criterion: the product of jumping figure and average retransmission rate, select route.

Then, realizing cross-layer routing upgrades.

The realization correspondence of each layer of TCP/IP be all some classes, as long as obtain the entry reference of protocol layer class, just can make the intercommunication of relevant layers.So as long as obtain entry reference in network layer, just can call in network layer the function of MAC layer, transmit the parameters R TRA of MAC layer.

In network layer, obtain after entry reference, need to add an entry reference mymac and obtain MAC layer interface object, and by calling the function of this object, realize the transmission of cross-layer parameters R TRA.State route agent's object of a pointed node oneself, then the MAC layer interface object of this node is hung in route pointer.Like this, when creating radio node, routing module has just been associated with MAC module.Through modification, parameters R TRA will crossover ports queue and logic link layer two-layer, from MAC layer, be delivered to network layer.

Concrete routing update: if the source node sequence number of RREQ grouping is greater than the sequence number of the reverse route of the node maintenance of receiving RREQ grouping, or the two equates but in RREQ grouping, the product of rq_avRTRA and jumping figure is less than in reverse route rt_avRTRA and the reverse product of the jumping figure of route, by reverse route destination node sequence number update, is just the source node sequence number that RREQ divides into groups; Oppositely the jumping figure of route is updated to the jumping figure of RREQ grouping; Next hop address is updated to the IP address of the node that sends RREQ copy; Oppositely the average retransmission rate of route is updated to the average retransmission rate of all nodes of RREQ grouping process, and " the out-of-date timer " of list item be set.

Similarly, node also can be done the renewal of corresponding forward route after receiving RREP grouping.Modification to the modification of RREP packet header and forward routing update operation is identical with the modification of receiving RREQ grouping, and therefore not to repeat here.

Finally, the AODV Routing Protocol after application enhancements.

AODV Routing Protocol (RAODV) contrast experiment after the traditional AODV Routing Protocol building and improvement is provided with two groups, and each group experiment arranges a parameter and changes, and then observes respectively and analyze the variation of improvement front and back network performance.In each group experiment, the same terms carries out 10 times, a different scene is set at random at every turn, while analyzing the network performance under this condition, asks the mean value of these 10 emulation.

First group: experiment arranges 50 mobile nodes, and experimental period is 300s.Node is randomly dispersed in the plane square region of 1000m*1000m, and maximum number of connections is set to 30.The rate of giving out a contract for a project in CBR source is 0.25 packet each second, and node moves at random to any direction, and the time of staying that moves at random another position from a position is got 10s, and its maximum translational speed is got respectively 1m/s, 4m/s, 8m/s, 12m/s, 16m/s, 18m/s, 20m/s.

Second group: experiment arranges 50 mobile nodes, and experimental period is 300s.Node is randomly dispersed in the plane square region of 1000m*1000m.The rate of giving out a contract for a project in CBR source is 0.25 packet each second.Node moves at random to any direction, and its maximum translational speed is got 10m/s, and the time of staying that moves at random another position from a position is got respectively 10s.Maximum number of connections gets respectively 5,10,15,20,25,28,30.

As shown in Figure 3 a, what abscissa represented is the maximum translational speed of node, and what ordinate represented is average end-to-end time delay.The end-to-end time delay of two kinds of routing algorithms is all increase tendency.Obviously before improving, time delay is little end to end for average end-to-end time delay after improvement, and variation tendency is relatively stable, not the acute variation along with the increase of maximum priming speed.Easily draw, RAODV has better performance.

As shown in Figure 3 b, what abscissa represented is internodal maximum number of connections, and what ordinate represented is average end-to-end time delay.As can be seen from the figure,, along with the increase of internodal maximum number of connections, average end-to-end time delay is not rule variation totally.The average end-to-end time delay of the AODV Routing Protocol before and after contrast improves, although RAODV does not have AODV stable, average end-to-end time delay is totally less than AODV.

Through many experiments, result shows: agreement is after improving, and average end-to-end time delay obviously reduces, and average routing cost also slightly reduces.Therefore, the average routing cost of RAODV agreement and average end-to-end time delay are all improved, and easily draw, the algorithm after improvement is more excellent.

Claims

1. improving one's methods of the AODV Routing Protocol for Wireless Ad hoc network, is characterized in that:

Choose cross-layer routing criterion parameter:

RTRA＝(NRTS_+NACK_)/(NRTS_+NACK_+2)，

Before routing table update, by RREQ packet header, carry this cross-layer information, in packet header in RREQ grouping, add two field RTRA and rq_avRTRA, and be initialized as 0, rq_avRTRA is the mean value of the MAC layer packet retransmissions present rate of the RREQ node that is grouped in process in transmitting procedure, also adds field rt_avRTRA in routing table, represents the average retransmission rate of node in path, be initialized as 0

Rq_avRTRA is calculated as follows:

rq_avRTRA2＝(rq_avRTRA1×(rq_hop_count-1)+RTRA)/rq_hop_count，

Realizing cross-layer routing upgrades:

2. improving one's methods of a kind of AODV Routing Protocol for Wireless Ad hoc network according to claim 1, is characterized in that: the method for described routing update is: