Combined effect of coherent adaptive antenna array diversity and SINR-based fast transmit power control in W-CDMA reverse link

This paper evaluates through laboratory and field experiments the combined effect of the coherent adaptive antenna array diversity (CAAAD) receiver an d signal-to-interference plus background noise ratio (SINR)-based fast tran smit power control (TPC) in order to improve performance beyond that of spa ce diversity (SD) with maximal ratio combining (MRC) in all low-to-high sig nal-to-interference power ratio (SIR) channels in the W-CDMA reverse link. Although the previously proposed CAAAD receiver comprising an adaptive ante nna array based on the minimum mean square error (MMSE) criterion and a coh erent Rake combiner was very effective in suppressing interference in low S IR (interference is severe) channels, SD employing MRC in noise limited cha nnels (high SIR) outperformed the CAAAD because of its uncorrelated recepti on of fading Variation due to its large antenna separation. The laboratory experimental results showed that the required average transmit signal energ y per bit-to-background noise spectrum density (E-b/N-0) with the CAAAD rec eiver using fast TPC is lower than that with an SD receiver over a wide ran ge of maximum Doppler frequency values from f(D) = 5Hz to 500Hz in a low-to -high SIR channel. The results of the field experiments also showed that co mbining CAAAD and fast TPC is a powerful means to reduce severe multiple ac cess interference (MAI) from high rate users in a low-to-high SIR environme nt and is more effective than using the SD receiver with the same number of antennas, i.e., the measured BER was improved by approximately one order o f magnitude, when the relative transmit power of the desired user was 8 dB with two antennas at the average received SIR at the antenna input of -12dB .