Enhancing 802.11 Wireless Networks with Directional Antenna and Multiple Receivers

When directional antennas are used in 802.11 based wireless LANs, higher network capacity is often accompanied with more collisions. This is due to the enhanced hidden node problem and the deafness problem that arise in the directional transmission/reception scenario. These problems are caused by an inconsistent view of the medium status by neighboring nodes. We have developed a new variation to the 802.11 protocol called sectorized MAC (S-MAC), which employs a novel architecture consisting of multiple directional antennas and multiple receivers. With a new self-interference cancellation scheme, an S-MAC node can continuously monitor the channel status in all directions in order to avoid the aforementioned problems. It is fully compatible with the standard 802.11 protocol and can inter-operate with omni-antenna-based 802.11 nodes. It is applicable to both infrastructure mode and ad hoc mode. Simulation studies show that it achieves significant capacity gains, even if only used in part of the network.