The Research Of Ad Hoc Networks

Ad hoc Network is a multi-hop wireless network and is composed of multiple wireless mobile nodes without infrastructure. Ad hoc Networks can be used for disaster relief and meet command of the battlefield, it is due to the infrastructure-less and the rapid expansion can be achieved . In recent years, with the rapid development of laptop, PDA, mobile terminal equipment and wireless technologies, Ad hoc networks gradually become research focus.Mobile nodes in Ad hoc Network would inevitably lead to frequent changes the topology of network which results in great increasment of the collision of data transmission. Therefore, how to choose the great backoff algorithm for establishing a good Ad hoc Network is one of the current research focus.In this paper, we studied the backoff algorithms of IEEE 802.11 protocols in Ad hoc network and its related issues, including the four following areas:First of all, we introduced the meaning ,characteristics, applications and architecture of Ad hoc networks.Secondly, the DCF backoff mechanism of IEEE802.11 protocols in Ad hoc networks were reviewed, a brief overview of the performance evaluation criteria were given.Finally, for solving the collision problems in Ad hoc networks and being based on game theory and the addition of a dynamic threshold and the Ridge distribution function, a new improved dynamic threshold Ridge backoff algorithm was given,DR,for short. DR was a backoff algorithm in which each node could calculate the number of other active nodes according to the channel competition and determine how to retreat with the greatly reduction of conflicts in the network . By NS simulation tool, the results of simulation showed that the improved backoff algorithm would improve network performance in heavy-load network, about 20% and could effectively solve the fairness of channel competition between each node and also proved that the new backoff algorithm could effectively reduce the chance of data conflicts. And it would not significantly increase the conflicts with the great increasment of the load, thereby it greatly improved the efficiency of data transmission, and it could do well in the larger, more complex network topologies.