Assigning channels by link directionality in a medium access control protocol for IEEE 802.11 ad hoc networks

This study attempts to exploit the potential of link directionality to increase the achievable capacities of ad hoc networks. When an IEEE 802.11 ad hoc network achieves capacity C by using a single channel, the targeted capacity by using two channels should be 2C. However, most of the dual-channel 802.11 protocols proposed in the literature appear only to be able to achieve less than 60% of the 2C targeted capacity. The authors thus propose a link-directionality-based dual-channel medium access control protocol in an attempt to double the capacities of networks using the single-channel IEEE 802.11 protocol. The main idea is to assign channels according to link directionality to allow a link to transmit simultaneously within the carrier-sensing region of another link provided that these transmissions do not interfere with each other. Simulations show that our proposed scheme can achieve more than 85% of our targeted capacities, 0.85 X 2C = 1.7C, in large-scale random topologies. In lattice and irregular topologies, the throughput is boosted up to 2.83C and 2.13C, respectively. An approach for capacity analysis is also introduced to determine the throughput improvements that can be achieved by our proposed protocol. We believe using link directionality for channel allocations is a key step that yields significant potential for multiplying the capacity of ad hoc networks.