Spatial Modulation - A New Low Complexity Spectral Efficiency Enhancing Technique

The multiplexing gain of multiple antenna transmission strongly depends on transmit and receive antenna spacing, transmit antenna synchronization, and the algorithm used to eliminate interchannel interference (ICI) at the receiver. In this paper, a new transmission approach, called spatial modulation, that entirely avoids ICI and requires no synchronization between the transmitting antennas while maintaining high spectral efficiency is presented. A block of information bits is mapped into a constellation point in the signal and the spatial domain, i.e. into the location of a particular antenna. The receiver estimates the transmitted signal and the transmit antenna number and uses the two information to de-map the block of information bits. For this purpose, a novel transmit antenna number detection algorithm called iterative-maximum ratio combining (i-MRC) is presented. Spatial modulation is used to transmit different number of information bits and i-MRC is used to estimate both the transmitted signal and the transmit antenna number. The results are compared to ideal V-BLAST (vertical-Bell Lab layered space-time) and to MRC. Spatial modulation outperforms MRC. The (bit-error-ratio) BER performance and the achieved spectral efficiency is comparable to V-BLAST. However, spatial modulation results in a vast reduction in receiver complexity.