Directional Hub Slotted Aloha Medium Access Control Protocol for Wireless Sensor Networks with Directional Antennas

The primary contribution of this paper lies in evaluating the throughput performance of a wireless sensor network (WSN) with realistic directional antennas. A simple medium access control (MAC) protocol is proposed, based on the Slotted Aloha protocol but designed to support multiple directional antennas at the hub. A brief review of the throughput analysis for the traditional Aloha protocols is given, followed by an analytical model for the throughput performance for directional hub Aloha protocols. Detailed descriptions of the throughput analysis for a practical WSN with a limited number of users is given. The analytical model is verified using the Riverbed Modeler. The simulation results for throughput show a discrepancy between models for a finite node system and the current analytical model. As the spatial reuse of the network is limited by the antenna pattern, a discussion on the selection of the number of hub antennas is then given, based on achieving the highest possible throughput performance with realistic directional antennas. The analysis and simulation results show a 186% increase in throughput.