Full-Diversity Achieving Precoding for Asymmetric MIMO Using Partial CSIT

Abstract

For a block fading n _t × n _r ,n _t > n _r MIMO channel, we propose a precoding scheme that achieves both n _t n _r th order diversity as well as rate of n _t symbols per channel use, feeding back B(n _t -1) bits as partial channel state information to the transmitter (CSIT), where 2 ^B is the number of quantization states available. We establish the optimality of the uniform quantizer which achieves minimum loss in coding gain due to quantization of feedback values of our precoding scheme in comparison to the non-uniform quantization. We also lay down the guidelines for constellation sets with which our precoding scheme can achieve full diversity. We also derive the order of complexity involved in computing the precoder matrix and show that it is independent of the size of constellation sets. We compare our BER results with that of precoding schemes in the literature utilizing full CSIT as well as that with partial CSIT. We also investigate the loss in error rate performance due to imperfect channel knowledge at the receiver and present simulation results to verify our claims.