A Novel Transmission Scheme with Spatial Modulation for Coded OFDM Systems

In this paper, a novel transmission scheme with spatial modulation is proposed for coded orthogonal frequency division multiplexing (OFDM). The multiple-input multiple-output (MIMO) technique, so-called spatial modulation (SM), divides input data into antenna index and data signals, transmitting data signals through the specific antenna chosen by the antenna index. In order to retrieve data stream at the receiver, SM needs to detect the antenna index which means that data signals are transmitted via a certain antenna. For this reason, it should be guaranteed that channel matrix is orthogonal. For the real environment, a MIMO channel has difficulty in maintaining orthogonality due to spatial correlation. Moreover, the receiver of the conventional SM is operated by hard decision, so that this scheme has a limit to be adopted for practical systems. Therefore, soft-output demappers for the conventional and proposed schemes are derived to detect antenna index and data stream by soft decision, and a novel transmission scheme combined with spatial modulation is proposed to improve the bit error rate (BER) performance of the conventional scheme.