Performance of a tree-based collision resolution algorithm for random access with smart antennas

A smart antenna´s ability to simultaneously resolve more than one user on the same channel is exploited to help expedite the process of random access, especially for reverse channel signalling. However, the use of a smart antenna requires frequent array adaptation, a difficult task in a random access environment. In our paper of 2003, we proposed and studied the SINR performance of a media access protocol intended for use with smart antennas. In this paper, we study the random access performance of the proposed protocol when a tree-based fast collision resolution algorithm is used. The maximum achievable throughput and an upper bound on the expected delay are found. The impact of the number of antennas on the performance with both flat fading and frequency selective fading is studied. Typical results show significant improvement in throughput for systems with smart antennas. We also show that dynamically adjusting the retransmission probability in the collision resolution process is not worthwhile since this extra complexity produces a gain of only about 6.2% in the best case.