(A) new MAC protocol for improving the performance in multi-hop wireless ad hoc networks

Abstract

Since IEEE 802.11 is common in the market, it is utilized as MAC protocol for wireless ad hoc network. However, it has been designed to be used be used in 1 hop network that it is not a suitable protocol for multi-hop wireless ad hoc networks. The reason for its unsuitability for multi-hop wireless ad hoc networks could be hidden node and exposed node problem, and choice of larger sensing, BEB (Binary Exponential Back-off) and so on. When an on-demand routing protocol is used with IEEE 802.11 DCF (Distributed Coordination Function), the route for transmitting packet will be formed by nodes which has less competition (fewer neighbors) than others for the medium access because of the above these problems. This effect will make that the routing path will be longer and decrease network performance. To solve this problem, we propose a new MAC protocol that makes a shorter routing path, enabling better performance in multi-hop wireless ad hoc network in this paper. The new protocol modifying IEEE 802.11 DCF uses two schemes-modifying beacon transmission algorithm for effective exchange of the number of neighbors and the amount of transmission, and adaptation of CW (Contention Window) as comparing its own information with those of neighbor nodes. The protocol gives priority to the node with more neighbors and less transmission. It will shorten the routing path by making the node with many neighbors to pass. The result of this is that the performance will be increased. Through simulation, we compare the performance with proposed protocol and pure 802.11 DCF. Simulation results show that the proposed algorithm improves performance in terms of successful transmission rate, transmission delay, average hops to transmit and total consumption energy. And also, except for a little of processing overhead, proposed algorithm did not require any additional overhead.