An improved QoS based routing in available bandwidth measurement using logarithmic backoff algorithm in MANets

In mobile ad hoc networks, channel bandwidth is a very limited resource. When the network is heavily loaded, the rate of collisions and hence the number of retransmissions increase. This leads to a notable decrease in network throughput and hence reduces quality of service because more and more bandwidth is wasted. MAC layer enables sharing the channel among all the nodes in the network effectively. It also enables perfect channel utilization. IEEE802.11 DCF uses exponential backoff algorithm to reduce collision. In this, average backoff value is increased after every collision due the large size of contention window. The time consumed by backoff process is more. Hence, proportion of bandwidth is lost due to collision as well as the overhead is introduced by backoff algorithm. This paper proposes an improved logarithmic based backoff mechanism to reduce collision and to improve the performance of the network. This algorithm uses logarithm of current backoff time to calculate next backoff. The difference between two backoff timers is small. So the chance of losing the channel access is less. Experimental results show that the proposed algorithm achieves better throughput, less delay and significant improvement in packet delivery ratio.