MAC-Layer Capture: A Problem in Wireless Mesh Networks using Beamforming Antennas

Beamforming antennas have been shown to improve spatial reuse in wireless networks. Protocols that aim to exploit beamforming antennas have leveraged benefits from directional transmission as well as directional reception. We argue that exploiting antenna characteristics for transmission and reception alone, is not sufficient Controlling the antenna during the idle state of a node is necessary to attain further improvements. A node that does not control its antenna during the idle state will waste time in receiving packets not intended for it. These packets will eventually be dropped at the MAC layer, reducing channel utilization. With suitable beamforming, a node might be able to utilize this time for concurrent communication. We call this the problem of MAC-layer Capture in view of a node getting engaged in receiving unproductive packets. We present MAC and routing protocols to address MAC-layer capture. Simulation results show that improvements from avoiding MAC-layer capture can be substantial in static mesh networks.