Smart Antennas for Mobile Wireless Communications

The paper introduces two newly developed smart antennas, ESPAR antenna and ESMB antenna, for mobile wireless computing terminals and mobile stations. The configurations of these smart mobile terminal antennas at the operating frequency approximately over 2.4GHz are illustrated and the applications of using these smart antennas at mobile computing terminals and mobile stations are proposed. The performance comparison of these smart antennas and the beam control circuits, and the beam- forming and selection algorithm is discussed. I. INTRODUCTION he smart antenna technology has been introduced to mobile wireless communication systems to overcome three major impairments; multipath fading, delay spread and co-channel interference and to increase system performance and capacity. However, the development of smart antenna technology, such as the structures of antenna arrays and adaptive antenna algorithms, only concerns the applications in base stations. Recently several Ad Hoc mobile computing networks were developed based on smart antennas at mobile computing terminals, such as, ATR WACNet using ESPAR antenna, Directional CSMA/CA using sectored antennas and MAC Protocols using directional antennas in Ad Hoc Network (1-3). Like traditional smart antennas at base stations, smart mobile terminal antennas can be also classified as adaptive beam-forming antennas and switched multiple-beam antenna arrays depending on the antenna structures and control algorithms. It is possible to use smart antennas at mobile stations alone without installing smart antennas at the base stations and achieve about the same improvement in coverage and capacity as with smart antennas at the base stations. Smart antennas can also be installed at both ends to allow several parallel SDMA channels to be established for one between the mobile station and base station (4).