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Optimum Weight Generation Method for Adaptive Antenna Array Transmit Diversity in W-CDMA Forward Link
Shinya TANAKA Taisuke IHARA Mamoru SAWAHASHI
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 2001/12/01
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Spread Spectrum Techniques and Applications)
DS-CDMA, adaptive antenna array, interference suppression, carrier frequency calibration,
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This paper investigates the optimum transmit-antenna-weight generation method for adaptive antenna array transmit diversity (AAA-TD) in the W-CDMA forward link: AAA-TD with beam and null steering (BNST), AAA-TD with beam steering (BST), or switched beam transmit diversity with fixed weights (SBTD-FW). The achievable BER performance after carrier frequency calibration in the transmit beam pattern is compared among the three methods assuming a different carrier frequency in a 2-GHz band with the carrier separation of 184.5 MHz based on computer simulations. The simulation results show that the achievable BER performance in the forward link using AAA-TD with BNST is almost identical to that using AAA-TD with BST when there are many more interfering users than there are array antennas, except for the special case when a small number of higher rate users exists in the reverse link. This is because by performing carrier frequency calibration, the directions of the beam nulls are shifted from the real directions of arrival (DOAs) of the interfering users. However, we also show that the required transmit Eb/N0 at the average BER of 10-3 using AAA-TD with BST is decreased by approximately 1.0 to 1.2 dB compared to that using SBTD-FW with 12 beams.