On the performance of closed-loop transmit diversity with non-ideal feedback

A closed-loop transmit diversity system is evaluated, taking several major feedback non-idealities into account both separately and in combination, contrasting most previous work in the field. The focus of the study is on the trade-off between quantization errors and feedback periodicity (i.e., a trade-off between sparse high-resolution data and frequent low-resolution data). Different number of transmit antennas, transmission rates and receiver velocities are investigated. In addition, we also study the impact of feedback delay. Some main results are as follows: For each receiver velocity and feedback channel rate, there exists an optimal choice of quantization resolution, and hence an optimal choice of feedback period. Furthermore, there is an optimum choice of the number of transmit antennas to employ for a given degree of Doppler and a given feedback rate. Finally, the bit error rate performance for a fixed feedback rate and a given receiver velocity is practically independent of the transmission rate.