Smart Antenna System Analysis Integration and Performance for Mobile Ad-Hoc Networks

the interaction and integration of several critical components of a Mobile Ad-Hoc Network (MANET) using smart antenna systems. A MANET is a wireless network where the communicating nodes are mobile and the network topology is continuously changing. One of the central motivations for this work comes from the observed dependence of the overall network throughput on the design of the adaptive antenna system and its underlying signal processing algorithms. In fact, a major objective of this work is to study and document the overall efficiency of the network in terms of the antenna pattern and the length of the training sequence used by the beamforming algorithms. This study also considers in sufficient detail problems dealing with the choice of direction of arrival algorithm and the performance of the adaptive beamformer in the presence of antenna coupling effects. Furthermore, the paper presents strategies and algorithms to combat the effects of fading channels on the overall system.

The demand for increased capacity in wireless networks motivated recent research toward wireless systems that exploit space selectivity. As a result, there are many efforts on the design of “smart” antenna arrays. For example, research on antenna design has focused in the selection of attractive radiating elements and antenna architecture that can accommodate the physical and electrical requirements of the system . Signal processing aspects of smart antenna systems has concentrated on the development of efficient algorithms for DOA estimation and adaptive beamforming. To facilitate the reader, a list of acronyms is provided in Table I. Recent work on DOA estimation is reported in . On the other hand, algorithms for adaptive beamforming have departed from the classical LMS type beamformers to more sophisticated CMAs and “eigen-projection algorithms” . Other issues that have been examined are the effects of mutual coupling on adaptive algorithms and combating the effects of fading channels on the overall system . Unlike previous published work that covered each area individually (antenna-array design, signal processing, and communications algorithms and network throughput) for smart antennas, this paper presents a comprehensive effort on smart antennas that examines and integrates antenna-array design, the development of signal processing algorithms (for angle of arrival estimation and adaptive beamforming), strategies for combating fading, and the impact on the network throughput. In particular, this study considers problems dealing with the impact of the antenna design on the network throughput and the impact of mutual coupling on the performance of the adaptive algorithm. In addition, fading channels and tradeoffs between diversity combining and adaptive beamforming have been examined as well as channel coding to improve the system performance. The main goal of this project is to design smart antennas for Mobile Ad-Hoc Network (MANET) devices operating at a frequency of 20 GHz. This objective was instrumental in selecting elements that can conform to the geometry of the device and an array architecture that could control the radiation pattern both in azimuth and elevation directions. Consequently, this resulted in the selection of microstrip patches arranged in a planar configuration. In addition, the number of radiating elements were chosen to meet beamwidth requirements while maintaining reasonable costs and complexity for hardware implementation. Mutual coupling effects between antenna elements are also being considered as they affect the performance of the beamforming and DOA algorithms. Mutual coupling results in radiation patterns that have shallower and shifted nulls and less accurate angles of arrival, thus deteriorating the overall performance of the smart antenna system.

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