Brief Announcement: Exploration and Mitigation of Deafness Problems in Directional Antennas Based Wireless Ad-Hoc Networks

摘要

A switched antenna system can provide transmission or reception in any desired direction by an array of directional antennas. Directional antennas have tremendous potential for improving the performance of wireless ad hoc networks. While offering higher spatial reuse and larger transmission range, they also pose new challenges. Deafness is one of such problems, which arises when a transmitter fails to communicate to its intended receiver either because the receiver is beamforming towards a different direction. As we have identified, generally, there might be three kinds of deafness problems. First, deafness-Ⅰ happens when the intended receiver is a transmitter or receiver engaged in an ongoing transmission. Second, deafness-Ⅱ occurs when the intended receiver lies in the area covered by an ongoing transmission and hence becomes deaf to the transmitter. Third, unlike the former two kinds of deafness which occur because RTSs cannot be heard by the intended receivers, deafness-Ⅲ arises when the receiver has actually received RTS but cannot reply CTS, because it is aware of that this CTS will interfere with an ongoing transmission nearby. If left unaddressed, deafness problems not only severely degrade the performance at MAC layer but also considerably influence the upper-layer protocols, which would probably offset the benefits of directional antennas.