Adaptive generalized space shift keying and downlink multi-user transmission in MIMO fading channels

To achieve spatial diversity and improve the average bit error probability (ABEP) of Generalized Space Shift Keying (GSSK) in Multiple-Input and Multiple-Output (MIMO) channels with low feedback overhead and computational complexity, we propose a three-step adaptive precoding strategy for single-user GSSK (SU-GSSK) transmission by exploiting the channel state information at the transmitter (CSIT). First, a norm based reference receive antenna selection is conducted to maximize the selection gain. Second, active transmit antennas are coherently superposed to boost the signal to noise ratio (SNR) on the reference receive antenna. Third, phase-rotation processing is introduced to maximize the Euclid distance of the spatial constellation diagram. By applying the above steps, better ABEP performance can be obtained compared to the baseline schemes, with remarkably reduced feedback and complexity. Moreover, combining with the proposed adaptive precoding strategy, we design a resource-saving method for multi-user (MU) data conveying by preprocessing and stacking all users´ spatial constellations on increased number of active antennas and then implement a downlink MU-GSSK transmission scheme to provide several times the sum rate compared to SU-GSSK with acceptable ABEP performance. Complexity analysis and simulations show the effectiveness and scalability of our proposed schemes.