| Wireless multihop networks are gaining popularity in applications such as mesh networks, wireless backbones, and sensor networks. Typically, communication protocols designed for such networks have explicitly or implicitly assumed an omnidirectional antenna at the radio layer. With recent progress in signal processing and antenna technologies, smart beamforming antennas have become feasible at cheaper prices, making them an attractive replacement to omnidirectional antennas. With beamforming antennas, the ability to guide RF energy in desired directions can lead to higher spatial reuse of the channel. Also, the higher communication range of beamforming antennas can be exploited to achieve stronger network connectivity, and to obtain fewer hop routes. However, existing protocols considered suitable for omnidirectional antennas are incapable of achieving these benefits. We have identified several weaknesses in these protocols, that together degrade overall network performance. We have addressed these weaknesses, and developed a better understanding of the improvements achievable with beamforming antennas. Based on the insights, we have designed medium access control (MAC) and routing protocols to suitably exploit the benefits of beamforming. We have demonstrated part of our solutions on a small prototype testbed, equipped with electronically steerable antennas. |
