Research On Ad Hoc Routing Algorithm In Intelligent Transportation Systems

The vehicle network has the following characteristics: a band of was the limited area,the network nodes in the direction of motion is only along the strip of regional upstreamand downstream two kinds; nodes moving fast, the entire network topology changes in thecharacteristics of fast and highly efficient , stable routing requirements. in this paper, for theabove characteristics based on the AODV routing protocol improvements, proposed a newlinear-demand routing protocol (L-AODV). L-AODV protocol not only has the advantagesof on-demand routing protocols, but also has the better line-shaped networks link stability,greatly reducing the routing request for the number of broadcast packets, providing a betternetwork performance.L-AODV protocol can be used to link-time selection as a measure of link qualityrouting standards. Link disruption is the most important factor of the quality of networkcommunication, but because of the network node is a random movement, so in some cases,Link disruption is inevitable, in this case no doubt the last interruption link of the routeoffers the most Link stability and good communication quality.L-AODV protocol route discovery process is three-stage. The source node broadcastsRREQ to destination node. The destination node sends RREP to source node after receivingthe RREP. Intermediate nodes select the Predecessor node to forward RREP based onavailable link the time. After receiving the RREP, The source node selects the link whichhas the longest available link the time to build up route to the destination node and thensend RREP to the destination node through this route.L-AODV routing protocol by setting the distal and proximal signal reception powerthreshold R and P to the signal received power control, and as a standard to judge linkquality. In wireless networks, wireless signal strength will increase as the distance betweenthe nodes rapidly decreased, according to the application environment in which theattenuation of the signal transmission range is also another difference. Wireless signalstrength concrete expression in the node that is the signal received power SRP (SignalReceive Power).When the two nodes moving towards each other that ?SRP >0, if the signal received power of two nodes is greater than near-end signal reception power threshold P, it meansthat the description of the two nodes close enough to receive the upstream chain Roadinformation do not need the pre-hop node to forward, at this time L-AODV protocoloptimize the link. The redundant intermediate nodes send a link optimization request to thepredecessor node and successor node to launch link optimization process. After receivingthe link optimization request, Predecessor node updates the routing table, changes therouting point redundant node to successor node and sends route notification to inform theupstream node. After receiving the link optimization request, successor node updates therouting table, changes the routing point redundant node to predecessor node and sends routenotification to inform the downstream node, link optimization process is complete.When two nodes move contrarily that ?SRP <0, if the signal received power of twonodes is less than the remote signal reception power threshold R, is illustrated in the linkbetween two nodes soon interrupted, at this time L-AODV routing protocol quickly fix thelink. The current node sends a 2 Hops link repair packet to the successor node. Afterreceiving the link repair packet, Successor nodes choose the intermediate node whose LinkAvailable Time is longest as an alternative precursor node, updates the routing table andsends a link reply to forward node through the route, at the same time sends routenotification to inform the downstream node. Intermediate nodes update the routing tableafter the receipt of reply and then forwarded to the former node, the node before, afterreceipt of reply, update the routing table, the original point to point routing nodes in themiddle of a successor node, and to inform the upstream node sends the routing.Intermediate nodes by adding the link, link repair process is complete.As the L-AODV protocol uses the three-stage route discovery process, and node needto collect the link information before select routing, so there is lots of control packets andlink delays problems in L-AODV and for these two problems in the presented here proposean optimized linear routing protocol based on AODV (OL-AODV). OL-AODV protocolresolves both issues by improving the link quality metrics and optimization of routingresponse process.OL-AODV protocol link comprehensive consideration the time available, thereceiving time, the number of hops three factors affect, then according to the different focuscoupled with a different weight values, the end result as the link quality metrics. To reducethe link latency link can be used to provide better real-time, the purpose of the target nodeto set the receive packet delay time Threshold. When the destination node receiving the firstrequest of a different routing group start time, when the time exceeds the value received packet delay time the packet directly discarded. The node selects the optimal link to thesource node to establish a reverse route within Threshold times, and through this route tothe source node sends route reply packet. As the middle node has been completed at thistime link the collection of information, so intermediate nodes will choose the best routereply packet to forward RREP. Ultimately source node receives the only route the responsepacket, and thus the establishment of a forward route to the destination node. This put thethree-stage L-AODV protocol for the two-step route discovery process optimization, andeffective to reduce the excessive intermediate nodes in the target node to receive the linkgenerated in the process of delayIn this paper, achieve the L-AODV protocol and OL-AODV protocol and built a labenvironment under the NS, and then according to the experimental results from the routingoverhead, the data points according to packet arrival rate, data throughput of analysis andcomparison AODV protocol, L - AODV protocol and OL-AODV protocol. Experimentsshow that L-AODV protocol and OL-AODV compared to AODV protocol provide a betterrouting overhead, the data points according to packet arrival rate and data throughput whennode movement speed, packet sending rate faster circumstances. OL-AODV protocol hasthe optimal network performance in three kinds of routing protocol.