MAC-CPI-A Protocol That Prevents Collisions at MAC Layer in Adhoc Networks

Collisions due to interference at MAC layer limit the throughput of Ad Hoc networks using IEEE 802.11 protocol at medium and high load conditions. The proposed MAC layer MAC-CPI-A (Collision Prevention due to Interference) protocol prevents collisions due to interference completely. In the proposed protocol every node refrains from beginning its transmission if any node within its `maximum interference range' is currently engaged in a data transfer. The `maximum interference range' for all nodes is pre-computed as a function of average distance between a transmitter and its receiver, the minimum acceptable Signal to Interference and Noise Ratio (SINR), path loss exponent, the carrier sensing range of a receiver and the maximum noise around a receiver. If the sudden change in signal received by a node is more than a `significant' value defined by the `maximum interference range', then the node infers that another node within its `maximum interference range' has begun its transmission. A scheme for generation of a new signal indicating a sudden increase or decrease in received signal of greater than `significant' value has been detailed.