ISSN: (Online) 2321 -4155
ISSN: (Print) 2320 -7000

JOURNAL OF INDIAN RESEARCH
VOLUME : 2, ISSUE : 4, October-December, 2014 (ISSN No. : 2321-4155)
 
STUDIES OF REAL-TIME DOA-BASED SMART ANTENNA SYSTEMS IN WIRELESS COMMUNICATION APPLICATION
Giriraj Prajapati & Dr. K.C. Mahajan
 
ABSTRACT
We designed, built, and tested a real-time processor for a direction-of-arrival-based smart antenna GSM 1800 base station with eight half-wavelength spaced antenna elements. The processing steps include direction-of-arrival (DOA) estimation, user identification, tracking, beam forming and signal reconstruction. We demonstrate that the accuracy of DOA estimation is not of primary concern, but the robustness is. This can be assessed by a new parameter, the estimation range. Tracking of reliable user DOAs only, increases the robustness against interference. Our tracking concept is compatible with frequency hopping. We quantify the benefits of smart antennas by the statistics of the gain in carrier-to interference ratio (C/I) and in signal-to-noise ratio (SNR), both measured at the 90 or 99% levels with actual transmitted data. In an urban environment with large angular spread and overlap of user and interferer signals, the C/I gain is as high as 18 dB. Interferer nulling increases the C/I gain only slightly, but enhances robustness against angular spread, particularly if broad nulls are applied. Separating SNR gain in its contributions due to beam forming and diversity gives valuable insight into the way of operation. In uplink, the processor can exploit angular diversity. The entire suite of processing steps is done within less than 1 ms, demonstration in that sophisticated DOA-based smart antenna processing is feasible in real time. Our solution does not require any change in the GSM standard.
 
KEYWORD
Angular diversity, carrier-to-interference ratio(C/I) improvement, component angular spread, directionof- arrival estimation, signal-to-noise ratio (SNR), smart antenna.
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