Time-space backoff for fair node throughput in wireless networks using power control

Spatial backoff has recently been applied for contention resolution in wireless networks as an alternative to algorithms that backoff in time, such as the binary exponential backoff algorithm used in IEEE 802.11. Despite its success in saving energy and increasing spatial reuse, the use of transmission power control in spatial backoff has negative consequences to node throughput fairness. In this paper we study a variant of the hidden terminal problem that arises from link asymmetries, and its impact on the expected node throughput. We give an analytical model that relates throughput to the transmission power level and backoff window size. Using the model we propose a time-space (TS) backoff algorithm with the objective of fair node throughput and incorporate it into a carrier sense multiple access (CSMA) protocol as CSMA/TS. Through simulation we show that CSMA/TS achieves a high fairness index value while attaining good total throughput in most scenarios.