An Adaptive Mechanism for High Efficiency and Fairness in IEEE 802.11 Wireless Lans
Wireless local area networks own their popularity mainly to the robust characteristics of distributed medium access schemes. However, as new user applications diverge from the traditional data-centric model, the introduction of distributed medium access methods that achieve high efficiency in terms of both throughput and fairness becomes of utmost importance. IEEE 802.11 is the most widely used access scheme for wireless networks. In this paper, we address a shortcoming of IEEE 802.11 as indicated by previous studies, namely the inability of the protocol to adapt to different working conditions. We study and evaluate a low complexity mechanism that allows a network employing the IEEE 802.11 protocol to adapt its operating parameters according to the offered load. Simulation studies further document and confirm the high throughput and fairness performance of the proposed scheme.
Wind farms in a competitive electricity market may suffer from economic losses due to the intermittent nature of wind power. This paper proposes a solution by establishing direct trade between a wind farm and a flexible load. Unlike traditional cooperation scheme, the benefits of wind farm and flexible load are considered individually. Each participant of the trade considers the other's reaction to its decision and adjust its strategy until both sides are satisfied. Uncertainties of wind power generation, energy market prices, and the rest loads are considered. To solve the model, L-shaped method and Lagrangian Relaxation are adopted to decompose the problem. Study cases show that the revenue of the wind farm and the cost of the flexible load can be improved compared with the case when there is no direct trade.