An Ad Hoc Routing Protocol For Rapid Detecting Asymmetric Link

Mobile Ad Hoc Network is one kind of self-organization and distributed network which has no fixed network topology, no network management center and has been formed by mobile terminal which connected of wireless links. The existence of the asymmetric link problems has been brought by wireless network environment. It is not feasible that most on-demand Mobile Ad Hoc Network (MANET) routing schemes typically assume operation over symmetrical and bidirectional routing paths because the properties of wireless devices are inherent heterogeneous. It is because of higher nodes’ mobility, the interference of environment and the differences of transmission power that radio links between a set of wireless devices may be asymmetrical and unidirectional. So it is significant to design an Ad Hoc routing protocol which is fit for the asymmetric link.Due to the deficiencies of the traditional Ad Hoc networks routing protocols, an efficient routing scheme named AODV-PL which is based on the path loss estimation technique to detect and deal with asymmetrical is proposed in this paper. The ultimate goal of our scheme is how to rapidly detect the asymmetric link in a relatively short time and a lower price, and look for the higher stability transmission path. The connectivity and stability have been improved under the optimal balance between the routing performance and cost. In the proposed scheme, the improvement of AODV has been made that unidirectional links are rapidly predicted during route discovery. In addition, the more stable routing path has been chosen according to the link metric factor which is defined by the received signal strength index (RSSI), the average maintain time of the link and the ratio of signal and noise. Because of the broken link which almost around the node has been caused by nodes’mobility, it is possible to improve the success rate of routing repair and diminish the repair time that combines source routing repair with local routing repair.At last, the performance of the proposed scheme has been obtained by analyzing and comparing AODV with AODV-Black protocol in the simulation. Firstly, the proposed scheme is compared to AODV-Black in the metric which includes packet delivery ratio, end to end delay and normalized routing load to analyze the performance that deals with asymmetric links. Secondly, the performance in the traditional AODV, AODV-Black and AODV-PL has been achieved by raising the number of nodes in the network. The simulation result shows that the proposed scheme is more suitable for a sparsely connected network that has a high presence of unidirectional links. The rate of packet transmitted has been improved in AODV-PL, which is better applied to the Ad hoc networks with asymmetric links.