Space-Frequency Coded Index Modulation With Linear-Complexity Maximum Likelihood Receiver in the MIMO-OFDM System

In this letter, a new multiple-input multiple-output orthogonal frequency division multiplexing with index modulation (MIMO-OFDM-IM) scheme achieving diversity is proposed. It combines space-frequency code and MIMO-OFDM-IM to take advantage of both, and we call it as the space-frequency coded index modulation (SFC-IM) scheme. The proposed SFC-IM scheme can achieve the transmit diversity order of 2 by optimizing an angle parameter. A linear-complexity maximum likelihood receiver is given for the new scheme, which profits from the orthogonality between the real and imaginary parts of the symbols contained in the SFC-IM codewords. The simulation results show the performance advantage of the SFC-IM scheme over the MIMO-OFDM-IM scheme.

I. Introduction

Recently, a novel multicarrier transmission scheme called orthogonal frequency division multiplexing (OFDM) with index modulation (OFDM-IM) [1] has been put forward. As the frequency-domain extension of spatial modulation [2], OFDM-IM conveys information bits not only by -ary constellation symbols, but also by the indices of the active subcarriers. Owing to exploiting subcarrier indices as an extra source of information, OFDM-IM has been proven to achieve significantly better bit error rate (BER) performance than classical OFDM.