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Feasibility of Smart Antennas for the Small Wireless Terminals
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Smart antenna is a potential performance enhancement tool in a communications link that can be used at either end (transmitter or receiver) of the link in the form of beamforming or diversity operation. While receive smart antenna techniques and operations have matured over the years, transmit smart antenna is relatively a new concept that has seen its growth over the past few years. Both these smart antenna operations have been traditionally designed for base station applications. But with the advent of high-speed processors, transmit smart antenna can also be feasible at a small wireless terminal (SWT). This dissertation studied the feasibility of using smart antenna at a SWT. Both smart transmit and receive antennas are studied, including multiple input and multiple output (MIMO) systems, however the emphasis is placed on transmit smart antennas. The study includes algorithm developments and performance evaluations in both flat fading and frequency selective channels. Practical issues, i.e., latency and amount of feedback, related to transmit smart antenna operation are discussed. Various channel measurements are presented to assess the performance of a transmit smart antenna in a real propagation environment. These include vector channel measurements for narrowband and wideband signals, channel reciprocity, and effect of antenna element spacing on diversity performance. Real-time demonstrations of transmit smart antenna have been performed and presented, and, the applicability of the proposed techniques in the Third Generation standards and wireless local area networks (WLAN) is discussed. Receive beamforming with a small number of antenna elements (which is usually the case for a SWT) is analyzed in an interference-limited environment.
- Doctoral Dissertations