Analysis and Enhancements for IEEE 802.11 Networks Using Directional Antenna With Opportunistic Mechanisms

Directional antennas are introduced to improve the performance of IEEE 802.11-based wireless networks by allowing stations equipped with directional antennas to beam the data in a specific direction. Since IEEE 802.11 has been developed with omni antennas in mind, deploying IEEE 802.11 in a directional antenna environment leads stations to be conservative in blocking their own transmissions in favor of the ongoing transmissions. This conservative behavior conflicts with the main directional antennas´ objective of increasing the spatial reuse channel by supporting simultaneous transmissions. In this paper, we analytically show that an IEEE 802.11 station with directional antenna is conservative in terms of assessing channel availability, with as much as 60% of unnecessary blocking assessments. This percentage increases up to 90% in case we allow the station to alter the way it accesses its media access control (MAC) data queue. Motivated with this analysis, we design and evaluate two enhancement schemes for IEEE 802.11 networks when using directional antennas. The first enhancement is to augment the IEEE 802.11 protocol with additional information (location of the stations) that gives a station the flexibility to transmit data while there are ongoing transmissions in its vicinity. The second enhancement, using the augmented protocol, alters the way the IEEE 802.11 accesses its data queue. Simulation shows improvement in network throughput of up to 40% in the case of applying the first enhancement and up to 60% in the case of applying the second enhancement.