An enhanced virtual carrier mechanism for MANET with multi rate traffic subdomains

Tremendous research effort has been made to reduce the idle time on the wireless medium of mobile adhoc network. Tradeoff among idle channel, collision and throughput was always a challenge. Hidden terminal problem creates collisions. On the other hand exposed terminal problem makes channel unnecessarily idle. Standard virtual carrier mechanism and many other alternative proposals for solving these problems make the unnecessary overhead on the nodes and delay in the network. Many of these schemes depend on the packet size to decide on a prior RTS/CTS exchange before sending data packets. In this paper we propose an enhanced virtual carrier scheme taking in to account the traffic around the nodes instead of packet size. The modified scheme splits the network virtually in to different traffic subdomains. Direct data packet transmission is allowed in low traffic scenarios. Prior RTS/CTS is exchanged only in high traffic subdomains irrespective of the data packet size. In traffic subdomains between low and high either direct transmission or prior RTS/CTS exchange is made depends on the previous subdomain of the node. We evaluated standard RTS/CTS scheme and other recent proposals and compared with our proposal. We measured the performance of our scheme against different performance metrics. Simulation result shows that our scheme outperforms the standard one in various scenarios. The outperformance of the proposed scheme is the outcome of a realistic assumption of low probability for hidden terminals in a low traffic subdomains compared to high traffic subdomains, instead of the unrealistic and pessimistic assumption of ubiquitous hidden terminals throughout the network.