Adaptively Sampled Near-Field Smart Array Antenna for Indoor Wireless Communications

Giuseppe ABREU  Ryuji KOHNO  

IEICE TRANSACTIONS on Communications   Vol.E84-B   No.7   pp.1743-1759
Publication Date: 2001/07/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Adaptive Array Antenna Techniques for Advanced Wireless Communications)
Category: Adaptive Algorithms and Experiments
adaptive array antenna,  smart antennas,  indoor near-field beamforming,  wireless LAN,  

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The worldwide availability of the Industrial Scientific and Medical (ISM) bands has prompted the proposal of several communication systems for indoor application at the 2.4 and 5 GHz bands. Although adaptive array antennas have been thoroughly investigated for various outdoor scenarios, their application to indoor communications has been overlooked. Experimental results indicating that conventional array antenna techniques exhibit poor performance when implemented indoors have recently been published. An important peculiarity of the indoor channel is the coexistence of both near-field and far-field propagating waves. Therefore, algorithms that can indifferently cope with both near-field and far-field wavefronts for source location and beamforming are desirable. In this paper, the following are presented. First, a mathematical analysis of the performance of array antennas in the indoor environment is taken up. Second, a new, simple, cost-effective and statistically coherent scheme, the Adaptive Sampling algorithm, is proposed for location estimation of sources anywhere from near field to far field. It is shown that the proposed algorithm achieves ubiquitous source location, allowing for symmetric uplink/downlink beamforming with seamless performance. Finally, the performance of the proposed Adaptively Sampled Array Antenna is performance analyzed via computer simulations under the specifications of the IEEE802.11b DS Wireless Local Area Network (W-LAN).