Impact of Channel Imperfections on Spatial Modulation OFDM

In this paper, the effect of channel imperfections on the performance of spatial modulation (SM) and V-BLAST (vertical-Bell Labs layered space-time) combined with OFDM (orthogonal frequency division multiplexing) transmission is presented. Channel imperfections include Rician fading, spatial correlation and mutual antenna coupling. Recently, SM-OFDM is proposed as a multi-antenna transmission approach that results in an increase in spectral efficiency by systematically mapping a block of information bits to a single transmit antenna (out of a set of antennas) and an information symbol. This principle is applied to each subchannel, i.e. for an entire OFDM symbol at any given subchannel and time instant only one antenna is transmitting. For each subchannel this might be a different antenna, though, depending on the sequence of incoming bits. Consequently, inter-channel interference (ICI) at the receiver input is entirely avoided while high spectral efficient is maintained. In this paper, the effect of channel imperfections on SM-OFDM and V-BLAST-OFDM for coded and uncoded systems are studied. For the same spectral efficiency and a BER (bit error ratio) of 10~3, SM-OFDM is shown to perform 4 dB better than V-BLAST-OFDM in the presence of Rician fading and by 7 dB in the presence of all channel imperfections.