Reducing codebook loss with reconfigurable receive antennas
In this study, a reconfigurable antenna codebook feedback (FB) scheme is investigated to reduce precoding codebook loss without increasing the number of FB bits. Analysis and simulations show that increasing the number of receive antenna states (S) has the same effect as codebook size expansion when the codeword and state selection is based on minimising the distance between channel and codeword. In addition, the authors propose an optimum selection approach. The signal to noise ratio (SNR) and rates achieved with perfect FB in a traditional nonreconfigurable antenna system, can be exceeded with only S = 2, using the proposed optimum selection. In fact doubling S gives an approximate SNR gain of 40% compared with S = 1. The authors also consider the effects of channel estimation errors and correlated antenna states. The authors show that the performance losses due to correlation can be quantified with a simple closed form result.