Performance analysis of space diversity S-ALOHA with steerable beam smart antenna 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 different beamwidths, number of beams, beam steering patterns, and beam service times on the achieved performance of S-ALOHA an 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 an better. We propose and analyze an energy efficient version of S-ALOUA which uses a beam sensed backoff algorithm at the user terminal. We show that the beam sensed backoff algorithm results in significant energy saving that could potentially increase battery life in wireless user terminals