Fully Improved Quadrature Spatial Modulation

In this paper, novel space modulation techniques (SMT), which we called fully improved quadrature spatial modulation (FIQSM) and fully improved quadrature space shift keying (FIQSSK), are presented for multiple-input-multiple-output (MIMO) communication systems. In these techniques, the improved structure that allows the use of an arbitrary number of T x antennas is implemented. Unlike other SMT schemes, the spectral efficiency (SE) of proposed techniques increases linearly with the increase in the number of T x antennas and a twofold increase in the number of spatially modulated bits is achieved with the aid of quadrature spatial structure. The bit error rate (BER) performance of the proposed techniques is investigated over Rayleigh fading channels for several MIMO designs. The average BER performances are also obtained analytically with the help of pairwise error probability and union-bound techniques in order to validate the simulation results. In addition, SE values achieved for varying SNR at a BER of 10(-3) are obtained for both correlated and uncorrelated Rayleigh channels. In these figures, spatial multiplexing is considered as a benchmark as well as SMTs. As a result, the proposed modulation schemes outperform the benchmarks (e.g., spatial modulation, generalized spatial modulation, quadrature spatial modulation) in terms of BER at different spectral efficiencies. Additionally, the receiver complexity of the FIQSM scheme is equal to the benchmarks at the same spectral efficiency and the receiver complexity of the FIQSSK is lower than the others.