Experiments on Adaptive Antenna Array Transmit Diversity with Carrier Frequency Calibration in Transmit Power-Controlled Forward Link for W-CDMA Mobile Radio

摘要

This paper investigates the interference suppression effect of adaptive antenna array transmit diversity (AAA-TD) using a carrier frequency calibration method when fast transmit power control (TPC) was applied in the W-CDMA forward link. In the proposed scheme, the adaptively generated receiver antenna weights of the reverse link in the coherent adaptive antenna array diversity (CAAAD) receiver were 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 results of laboratory experiments elucidated that in a 4-user environment (3-interfering users), although an error floor above the BER of 10~(-1) was observed with a 1-antenna transmitter due to the severe multipath interference, the average BER of below 10~(-6) was achieved using AAA-TD with 4 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 TPC was ΔE_b/I_0 = - 12 dB. We also showed that by using AAA-TD with fast TPC using outer loop control, the target E_b/I_0 of fast TPC and the required transmit signal energy per bit-to-background noise power spectrum density ratio (E_b/N_0) with AAA-TD for ΔE_b/I_0= -5 dB were almost identical to those of the one-user case irrespective of the direction of arrival of the desired user owing to the multipath suppression effect from interfering users.