Closed-Loop Transmit Diversity with Imperfect Feedback

In the closed-loop transmit diversity systems, feedback delay and feedback error, as well as the sub-optimum reconstruction of the quantized feedback data, are the usual sources of deficiency. We address the efficient reconstruction of the beamforming weights in the presence of the feedback imperfections, by exploiting the residual redundancies in the feedback stream. We propose two approaches to improve the performance. One is based on using a channel predictor at the receiver to compensate for the delay. Another approach deals with the feedback imperfections in a unified reconstruction algorithm using JSCC techniques. Furthermore, we introduce the concept of Blind Antenna Verification (BAV). The closed-loop Mode 1 of the 3GPP standard is used as a benchmark, and the performance is examined within a Wideband-CDMA simulation framework. It is demonstrated that the proposed algorithms outperform the standard at all mobile speeds, and are suitable for the implementation in practice.