Achieving scalable performance in large-scale IEEE 802.11 wireless networks

In large-scale wireless networks, interference among nodes limits channel spatial re-use and is a main hurdle for scalable performance. There are two types of interference: (1) physical interference due to the receiver´s inability to decode a signal when the power received from other signals is large; (2) protocol interference imposed by the specific multi-access protocol being used. The paper models both interference types in terms of a set of inequality constraints for the IEEE 802.11 CSMA/CA protocol. Based on the inequalities, we investigate the impact of some parameters (basic-rate, data-rate, and physical-preamble-rate) on channel spatial re-use. Regardless of the parameter settings, the total capacity in an 802.11 network reaches a ceiling as the number of nodes, n, increases. We identify the fundamental causes for the non-scalable performance, and show that 802.11 can be made to be scalable with a simple modification, achieving O(n) throughput without adaptive power control. We believe that this is the first paper to demonstrate this.