Research On QoS Routing Protocols Of Mobile Ad Hoc Networks

With the increase of service demand of multimedia traffic, it is an important problem to provide different QoS guarantee for mobile Ad Hoc networks, among which QoS routing is one of the key and focus issues. However, considering the characteristics of mobile Ad Hoc networks, such as its multihop, the mobility of nodes, the limited bandwidth of network, the dynamic network topological structure , the lower computation ability and the storage capacity of mobile nodes, the restricted energy and so on, it is a challenging task to design the QoS routing protocol, and it has become a research and development hot issues of mobile Ad Hoc networks.This paper proposes a routing protocol named RQRP_PE (A Reliable QoS Routing Protocol Based on Path-lifetime Estimation) based on the path stability and reliability considering the characteristics of mobile Ad Hoc networks. This protocol can provide QoS guarantee and it chooses the QoS routing based on the bandwidth restraint, the path-lifetime and the number of route hops.Firstly, RQRP_PE protocol chooses route based on the bandwidth restraint which requires every node in the processes of route discovery and route maintenance must satisfy a certain bandwidth request. It strengthens the handling ability of the network to the sudden traffic and the real-time traffic, and provides a more reliable route for the network. Sencondly, RQRP_PE protocol predicts the link-lifetime of the route link between nodes according to the mobility of nodes and the energy of receiving packets, then predicts the path-lifetime and chooses the route which has the longest lifetime and the shortest route hops among the routes that satisfy the bandwidth restraint. So it greatly enhances the reliability of the chosen route, reduces the number of broken route links that is caused by the nodes movement, improves the adaptability of the route protocol to the topology changes of the network, reduces the overhead to rediscover the route. RQRP_PE protocol chooses the Qos route based on the bandwidth, the path-lifetime and the route hops number, so that it can provide better Qos guarantee. Simultaneously, RQRP_PE protocol uses the destination node to reserve resource and the real-time maintenance in the process of the resource reservation. This idea can further enhance the data successful transmission rate and decrease the delay of route decovery. Furthermore the destination node caches all usable routes acquiring from the process of route discovery. When the route we are using become unusable, we can use the alternate route in the cache and don't need to reconstruct the route. Therefore, it also largely reduces the protocol overhead.This paper has realized the RQRP_PE protocol in the NS2 network simulation platform, compares the protocol with the classical DSR protocol and analyzes their performance. The simulation results indicated that RQRP_PE protocol is more suitable for the environment where network state changes frequently and the real-time multimedia application. It can effectively increase packets delivery rate, reduce the probability of routing broken and reconstruction, decrease the average delay and the route control overhead and improve Qos, especially in highly dynamic mobile Ad Hoc networks.