The Research And Improvement Of Broadcasting Algorithm In Ad Hoc Network

Mobile Ad hoc network (MANET) is a self-organizing and multi-hop network structure,in which nodes share common wireless channel and can move freely without the aid of a fixednetworking infrastructure. Each routing terminal acts as a router that forwards data packets toall the other nodes in the network, thereby extending the range and the coverage ofcommunications links among mobile nodes. So it can be applied to modern battle field,disaster rescue, sensor networks and other environments, therefore has drawn wide attentionfrom the military and the academic.Broadcasting is a fundamental communication service in mobile Ad hoc networks. It isalso an important operation in route query phase in many on-demand routing protocols. Inimplementing broadcast service, blind flooding is commonly used in mobile Ad hoc networksin the past for its simplicity and reliable accessibility. Though blind flooding is simple, itconsumes plenty of network resources as it produces a large number of duplicate messages ina dense network. It may also lead to serious redundancy, contention and collision in mobileAd hoc networks, a problem referred to as the broadcast storm problem. To alleviate thebroadcast storm problem, the number of retransmissions has to be reduced.This paper proposes a novel broadcasting algorithm for Ad hoc network, which is namedConditional Broadcasting Algorithm, based on current broadcasting schemes. In the proposedscheme, node calculates its re-broadcasting probability for each of its neighbors based on itsdistances with neighbors, node density, and node mobility speed, which are acquired throughexchanging Hello message periodically with neighbors. After receive a broadcast packet, eachnode decides whether to rebroadcast or not based on pre-decided re-broadcasting probability.In order to evaluate the performance of the CBA algorithm, we apply the proposed ideato AODV protocol, which is named AODV with Conditioned Broadcasting (AODV-CB) inthis paper, and compare it with the original AODV base on OPNET Modeler platform. Weevaluate the two protocols under different node density, traffic load, and node mobility speedscenarios. Simulation results show that the proposed broadcast scheme lessens broadcastingredundancy effectively with a high packet delivery ratio.