ABSTRACT
Designing an efficient and effective Media Access Control (MAC) protocol with collision avoidance capability in a mobile ad hoc network is a very challenging task because the network is self-organizing without centralized network control. Moreover, the medium in a wireless network is, by nature, a shared resource where a sender normally uses omni-directional broadcast mode to transmit a message for its intended destination. As a result, other users who are within the transmission range of the sender will also have to “listen” to its message even though they are not the intended receivers of this message. In this context, it is important to ensure a collision-free message communication environment even when multiple senders want to communicate with multiple receivers using the common shared medium. Imagine a situation (Figure 2.1) with seven nodes (I, E, S, D, H, J, and N) where sender E is trying to send a message to receiver I and sender H is trying to send a message to receiver J
simultaneously. Let us also
assume that I
is within the transmission range of E
only and J
is within the transmission range of H
only. In other words, I can only listen to E and not to H. Similarly, J can only listen to H and not to E. This is a conflict-free communication environment where both communications can progress simultaneously without interfering with each other. However, this scenario is rare in the dynamic environment of an ad hoc network. Let us further assume that while E is talking to I, another node S wants to send a message to N. The node N is in the listening range of both E and S. So, there will be collision at receiver N and N will not be able to receive any message from S.
