Collision Avoidance And Energy Saving Multipath Routing Algorithms For Ad Hoc Networks

As Ad Hoc networks have the specialities of limited transmission bandwidth, dynamic topology and constraint energy, the routing strategys in traditional wired networks and wireless cellular networks can not be directly used. Therefore we have to design new routing protocols for Ad Hoc networks. Moreover, since all the nodes have routing function in Ad Hoc networks, there exist multiple paths from the source to the destination. In addition, using multipath routing can efficiently enhance network bandwidth, fairly utilize network resources and prolong network lifetime. So it is more suitable to adopt multipath routing protocol. This paper pays more attention to multipath routing, and mainly discusses two aspects, namely collision avoidence and energy saving.In Ad Hoc networks, due to the factors such as signal degradation, noise, channel interference and so on, the actual bandwidth which mobile terminals can got was far less than the theoretical maximum. Furthermore, owing to the wireless multicast advantage, when a node sent message, the message can be received by all nodes in its coverage, so collision among multiple paths is serious, even leading into data transmission failure. Therefore, this paper presents a maximally collision-avoided node-disjoint multipath routing algorithm to alleviate the collision problem. This algorithm defines correlation factor to weigh the collision probability among multipaths when transmitting data simultaneously, then chooses the node-disjoint multipath whose collision probability is minimum. Simulation results show that NDCF algorithm can obviously improve packet delivery ratio and reduce end to end delay.Since energy of Ad Hoc network nodes is supplied by battery, and generally used in dangerous emergency environment, once exhausted can not charge up and stop working, which will affects the entire network topology connectivity and reduces communications quality. However, the current level of technology is difficult to significantly improve the battery capacity. Therefore, energy management is an important aspect for Ad Hoc researches. This paper presents two energy saving algorithms: (1) EPCM algorithm, it can reduce the times of route discovery broadcast through using cashed path informations in the routing table, and according to the principles of minimum total transmission powerand node-disjoint to select paths. The simulation results show that EPCM can reduce control overhead, decrease the number of control packets and efficiently saving energy. (2) ECCA algorithm, it is a tradeoff between collision avoidance and energy saving. Firstly, calculate an upper limit according to service requirement, and then find a minimum energy node-disjoint multi-path routing satisfying the limit. The simulation results show that the algorithm compared to pure minimum energy algorithm STPS can obviously reduce the packet loss rate, but not add energy consumption or prolong the time of finding routing.