Modifications in IEEE 802.11 to Prevent Collisions due to Interference in MANETS

due to interference signal are frequent in multi-hop wireless networks. Interference signal can be reduced below a threshold level if all parallel transmitter-receiver pairs maintain a minimum of "safe-distance" between them. A node observes a "significant" sudden increase or decrease in its received signal whenever another node within its "safe- distance" begins or ends its transmission. Thus, if any node observes a sudden increase in its received signal by more than the "significant" value, it infers that another node within its "safe-distance" has begun its transmission. Similarly, when any node observes a sudden decrease in its received signal by more than the "significant" value, it infers that another node within its "safe-distance" has completed its transmission. In this paper we propose a protocol where a node begins its transmission only if it has a minimum of "safe-distance" from the nearest parallel transmitter-receiver pair, and compute the values of "safe-distance" and the "significant" change in received signal. We then propose modifications in IEEE 802.11 protocol such that every node ensures a minimum of "safe-distance" from the nearest transmitter-receiver pair before it begins its transmission. Analysis shows that when all receivers in the network have a Signal to Interference & Noise Ratio SINR ≥ β, collisions due to interference can be completely prevented. It also brings out the situations where interference might exceed 1/β-N; however, the probability of interference exceeding 1/β-N lies between 0 and 0.1577*10 -5 .