Distributed Power Control for Ad Hoc Networks with Smart Antennas

An IEEE 802.11-based media access control (MAC) protocol was recently proposed for ad hoc network stations using smart antennas. The protocol uses omni-directional RTS/CTS interactions to estimate the channel between sending and receiving stations. The two stations then communicate using beamformed transmission on both ends of the link, at a reduced transmit power. Although large increases in capacity are possible using this approach, the improvements are a strong function of the transmit power reduction, and the optimal value is highly situation dependent. In this paper, we introduce a distributed power control mechanism that enables such networks to dynamically achieve capacity results close to the optimal limits. Our approach is to collect interference data at the receivers during DATA/ ACK periods, and to communicate this information between the stations associated with the links in question. The proposed protocol is successful in adapting to different physical situations and our results indicate that capacities can be achieved that are very close to the best static local power control schemes.