Adaptive antenna array transmit diversity in FDD forwad link for W-CDMA and broadband packet wireless access
Hidekazu Taoka, Shinya Tanaka, T. Ihara, Mamoru Sawahashi · IEEE Wireless Communications · 2002
This article presents a transmitter antenna weight generation method in adaptive antenna array transmit diversity (AAA-TD) that focuses on the calibrations in wideband direct sequence code-division multiple access (W-CSDMA) and broadband packet wireless access in FDD systems. In our scheme, the adaptively generated receiver antenna weights of the reverse link in the coherent adaptive antenna array diversity receiver are used as transmitter antenna weights, however, with calibration of the phase/amplitude variations of the parallel radio frequency receiver/transmitter circuits corresponding to the number of array antennas (RF circuitry calibration) and with calibration of the transmitter beam pattern due to the difference in carrier frequency between the reverse and the forward links (carrier frequency calibration). The interference suppression effect of AAA-TD employing a carrier frequency calibration and RF circuitry calibration in the W-CDMA forward link is also investigated by laboratory experiments. The experimental results elucidate that in a four-user environment (three interfering users), although an error floor above BER of 10 -1 is observed with a one-antenna transmitter due to the severe multipath interference, average BER of below 10 -6 is achieved using AAA-TD with four antennas, when the ratio of the target signal energy per bit-to-interference plus background noise power spectrum density ratio (E b /I 0 ) of the desired user to interfering user for fast transmission power control is ΔE b /I 0 = -12 dB.