Performance Analysis of Space Diversity Steerable Beam Smart Antenna S-ALOHA with Arrays

We analyze the throughput, delay and energy efficiency performance of space diversity slotted ALOHA when multibeam smart antenna arrays, capable of steering the beams selectively on smaller sectors, are used at the base station receiver. Analytical expressions to establish the effect of diITerent beamwidths, number of beams, beam steering patterns, and beam service times on the achieved performance of S-ALOHA are derived. We show that under high load conditions steered beams with long beam service times offer better performance, whereas under light loads static coverage patterns are better. W e propose and analyze an energy efficient version of S-ALOHA which uses a beam sensed backoff algorithm at the user terminal. We show that the beam sensed backoff algorithm results in significant energy savings that could potentially increase battery life in wireless user terminals.