Signal space diversity with and without Alamouti transmit diversity using generalised selection combining.
The first contribution is based on M-ary quadrature amplitude modulation (M-QAM) constellations with signal space diversity (SSD) using a single transmit and receive antenna system in the presence of Rayleigh fading. Two commonly used techniques to derive an angle of rotation is investigated across different ordered M-QAM signal constellations to determine the optimum angle of rotation for this system. Thereafter a closed form expression using the nearest neighbour (NN) approach to quantify the symbol error rate (SER) in the presence of fading channels is presented. The diversity order and the signal-to- noise ratio (SNR) gap is investigated for different generalised selection combining (GSC) cases for an M-QAM with SSD system. The second contribution is based on an Alamouti coded M-QAM scheme with SSD and GSC using a two transmit and receive antenna system in the presence of Rayleigh fading. A closed form expression using the NN approach is used to accurately derive the SER performance of an Alamouti coded M-QAM with single rotated SSD and GSC system. An additional level of diversity is added by rotating a constellation once again. Simulation results of M-QAM with double rotated SSD and GSC are used to compare the actual performance differences between single and double rotated SSD for this system. All deductions presented are validated with the aid of simulations.