MAC protocol design and capacity study for space division multiple access systems

Smart antennas have the ability to cancel both cochannel interference (CCI) and inter-symbol interference (ISI), and thus could be used in a cellular system to enhance coverage or increase capacity. A few of the key issues faced in deploying smart antennas in wireless systems are addressed in this dissertation.; A long standing problem is that of providing fast and efficient array adaptation in a random access packet-switching environment. This dissertation considers the media access design problem when smart antennas are used in a wireless data network where multipath fading is present. We propose a random access and reservation based media access scheme in which the antenna weights will be computed from slot to slot to capture the actual interference and multipath fading environment.; Performance of our proposed scheme under the condition of both flat Rayleigh fading and frequency selective fading is evaluated, and the training overhead is found, from which important design parameters with array training may be deduced. We assume throughout that, once adapted at the beginning of a slot, the antenna adapts throughout the packet to maintain the same SINK over the entire slot. Different receiver structures and different system parameters are compared, providing guidelines for system design. Bounds are also produced for the mean delay performance. Typical results show that in an interference limited multi-cell environment, smart antennas can be used to significantly increase frequency reuse. With 100% frequency reuse, our MAC protocol can support multiple users in each cell, and the number of users supported increases linearly with the number of antenna elements.; We then study the random access performance of the proposed protocol when tree splitting fast collision resolution algorithm is used. Found are the maximum achievable throughput and an upper bound on the expected delay. The impact of the number of antennas on the performance in both flat fading and frequency selective fading environments 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 the extra complexity needed offset the gain of only about 6.2% in the best case.; Finally, we address the fundamental question of the ultimate capacity region of space division multiple access system where a number of mobile users constrained in power try to communicate with the base station under multipath fading environment. We express the capacity limit as an outage region over the space of transmission rates from the mobile users. Any particular set of rates contained in this region can be transmitted with an outage probability smaller than a certain value. We find lower and upper bounds on the outage capacity region for two users case and extend them to multiple users cases wherever possible. The bounds provide a yardstick against which the performance of any system can be compared.