Spectrally efficient adaptive generalized spatial modulation MIMO systems

Abstract

We propose a spectrally efficient and low complexity spatial modulation (SM) transmission scheme for a multiple-input multiple-output (MIMO) system. As compared to conventional generalized spatial modulation (GSM), which can achieve fixed data rates, the proposed adaptive generalized spatial modulation (AGSM) uses adaptive modulation in combination with the GSM. The AGSM MIMO scheme improves the spectral efficiency (SE) of GSM by increasing the modulation order of transmission in better channel conditions. GSM maps information into a spatial symbol and a constellation symbol of constant modulation order but in proposed AGSM, the constellation size increases as the channel conditions improves keeping the bit-error-rate (BER) below a certain threshold value. The proposed technique is compared with the adaptive spatial modulation (ASM). It is shown that for the same SE, the proposed AGSM requires less number of antennas than ASM. The performance of AGSM MIMO is validated through Monte-Carlo simulations. The results show that AGSM reduces the number of transmit antennas compared to ASM without any BER degradation.