Research On Qos Routing And Protocol Optimization Of Vehicle Ad Hoc Network Based On Ant Colony Algorithm

Vehicle Ad Hoc Network(VANET)in special urban application scenarios requires high reliability and stability of routing.Especially when it comes to safety applications such as traffic accident warning,high quality routing guarantee is needed.In this context,finding solutions for Quality of Service(QoS)routing optimization problems in VANETs has been a hot research topic and challenge in this field.In recent years,Ant Colony Algorithm(ACO),as a swarm intelligence heuristic algorithm,has shown good performance in solving NP problems,and can also be successfully applied to routing protocol improvement,providing a solution to the network QoS optimization problems,but there are still some shortcomings that need further optimization.Based on the research of existing VANET routing protocols and ant colony algorithms,the protocol is improved for the problems of link instability,too many route discoveries caused by frequent route restarts,and QoS optimization.And a bidirectional link ant colony routing protocol TARP based on area hierarchy and node metrics is proposed.In the simulation experiments of NS-2,the improved protocol has better comprehensive performance than the two compared protocols.The main work of this paper is as follows.(1)The QoS routing optimization problem is studied and modeled based on the improved ant colony algorithm.The existing VANET network routing protocols are investigated,and the advantages and disadvantages of VANET network routing protocols are sorted out.Based on the ant colony algorithm,the routing algorithm is optimized for the network QoS routing optimization problem,and the global pheromone update rule of the routing algorithm is improved by integrating the effects of QoS constraints such as delay,jitter and packet loss rate,and the penalty factor is added to accelerate the convergence of the algorithm.Through the improved QRAR routing algorithm,the optimal solution to the network QoS routing problem can be found.(2)Regional classification strategy and node communication value measurement strategy of communication nodes are proposed.The regional classification strategy is an algorithm to determine region level of neighboring nodes based on the Friesian signal transmission model and signal transmission range model,which influences the forward ants to search for paths by providing different weights of state transfer rules for neighboring nodes in different regions.The node communication value measurement strategy is to calculate the nodes locally and use the calculated mobility and congestion information as the node communication value.After measuring the node communication value,the information is exchanged between nodes to inspire the forward ants to search for paths according to the guidance of state transfer rules.The two strategies jointly solve the problem of how to select a more stable next-hop node for the ant colony routing protocol from different perspectives.(3)A two-way reply mechanism is proposed.Traditional ant colony routing protocols send back reverse ants after the forward ants arrive at the destination node,and usually establish the route through reverse ants releases the pheromone.The improved routing protocol proposed in this paper makes the destination node send forward ants to the source node again while the source node waits for reverse ants,and a two-way reply link is formed to reply to the source node’s route request in both directions.The strategy judges the path reliability based on the bi-directional path result,and also reduces the ants forward search time under the same population size,but the disadvantage is that it increases the network overhead to some extent.(4)The improved ant colony routing protocol TARP proposed in this paper is simulated and analyzed.Based on the NS-2 simulation platform,a VANET network scenario is established.TARP is simulated and compared with AODV and PAODV protocols.Six evaluation criteria are designed for the application scenarios of this protocol,and the performance of the protocol is verified under three scenarios with changes in node density,node mobility and node congestion.The simulation results show that the improved routing protocol proposed in this paper has a significant decrease in the number of route discoveries compared to the other two protocols,and the other five evaluation criteria tend to be stable.Therefore,it can be shown that the routing protocol in this paper not only meets the QoS requirements,but also improves the link reliability and network stability.