NULLHOC : a MAC protocol for adaptive antenna array based wireless ad hoc networks in multipath environments

A medium access control (MAC) protocol for ad hoc networks of nodes with antenna arrays is presented. The antenna array is used for transmit and receive beamforming with the purpose of increasing spatial reuse by directing s at active transmitters and receivers in the neighborhood. In contrast to previous work with directional antennas, our approach is applicable to flat fading multipath channels, such as in indoor or in other rich scattering environments. The MAC protocol is designed to support the control information exchange needed to direct s toward other users involved in existing communication sessions. Knowledge of the channel coefficients between a transmitter or receiver and its neighbors is used to design transmit or receive beamformer weights that implement the requisite ing. Simulations are used to demonstrate the improvements in throughput and transmit powers that are obtained in this approach relative to the conventional IEEE 802.11 MAC protocol.