An Interference Avoidance Technique for Ad Hoc Networks Employing Array Antennas

Array antennas have the potential to increase the capacity of wireless networks, but a distributed beamforming algorithm for maximizing the capacity in asynchronous, decentralized mobile ad hoc networks is yet to be found. In this paper we pursue an interference avoidance policy, based upon channel reciprocity in time-division duplexing, and arrive at a practical signaling technique for array antenna enhanced ad hoc networks in multi-path environments with fading. The beamforming scheme may be incorporated in an RTS-CTS-data-ACK based medium access control protocol without necessitating any exchange of channel state information. In computer simulations we find that the interference avoidance effectively bounds the packet transmission disruption probability, and that the resulting single hop transport capacity increases almost linearly with the number of antennas under certain conditions.