Cooperative and Non-Cooperative Control in IEEE 802.11 WLANs

Numerous techniques for optimal performance of an IEEE 802.11 WLAN have been investigated. These techniques make use of either power control or PHY (physical layer) rate control or both to achieve maximum throughput levels for the network at minimum power consumption. However most of these techniques are non-cooperative by definition. Here, we analyse cooperative and non-cooperative rate and power control in an 802.11 WLAN that uses the Distributed Coordination Function (DCF). We formulate a payoff function comprising of the throughput and costs related to power consumption. The payoff function is optimized and closed form expressions for the optimal PHY rate are obtained. In the cooperative approach we seek to obtain the optimal rates under two different scenarios – max-min fair rate and global multirate allocation. In the non-cooperative approach we consider only multirate allocation. We consider optimization problems for both finite number of nodes n and for the limit n→ ∞ and obtain explicit expressions for the optimal PHY rate. Single node throughputs corresponding to the optimal PHY rates are numerically studied and it is observed that network performance in the cooperative scenario is superior to that in the non-cooperative scenario.