MIMO communication systems using hierarchical modulation

This paper considers multiple-input multiple-output (MIMO) communication systems using hierarchical modulation. The disadvantage of the maximum-likelihood (ML) receiver is that the computational complexity increases exponentially with the number of transmit antennas and the number of bits per modulation symbol. Using MIMO communication system with 16-ary hierarchical quadrature amplitude modulation (16-HQAM), we propose a receiver structure which can be an alternative to maximum-likelihood (ML) receiver. 16-HQAM involves a base layer and an enhancement layer. In the proposed receiver, the base layer is detected first with a minimum mean square error (MMSE) detector which is followed by ML detection of the enhancement layer. We examine the bit error rate (BER) performance of our low complexity receiver structure and compare it to the performance of other receiver structures. This work does not consider channel coding, which will be included along with the analysis of the proposed system in future studies.