N-Ary Alamouti Space-Time Block Coding With and Without Golden Codewords

Information is conveyed by either time, antenna, and/or frequency in the conventional modulation. In this paper, we propose a novel technique to convey information in Alamouti space-time block coding systems. In the proposed technique, the information can be conveyed by one channel’s phase component with order $N$ . The proposed technique is referred to as $2\times {N_{r}}\,\,N$ -ary Alamouti-STBC ( $N$ -STBC), where $N_{r}$ is the number of receive antennas. The $N$ -STBC with Golden codewords (GCs) is further proposed to improve error performance at high signal-to-noise ratios (SNRs). Moreover, the proposed $N$ -STBC with and without GCs still preserves the orthogonal transmission matrix of the Alamouti-STBC which retains the simple linear maximum-likelihood (L-ML) detection for quasi-static frequency-flat Rayleigh fading channels. The transmitted symbols can be directly estimated by use of the L-ML detection in the $N$ -STBC with and without GCs. However, only the GCs are estimated by use of the L-ML detection in $N$ -STBC with GCs. The signal detection subset based ML detection is further employed to detect the transmitted $M$ -ary quadrature amplitue modulation (MQAM) symbols in $N$ -STBC with GCs. The lower error probability bounds of the $N$ -STBC with and without GCs are derived and validated by simulation results. As an example, the proposed $2\times 4\,\,16$ QAM 16-STBC with GCs almost maintain the error performance of the conventional Alamouti-STBC with GCs at SNRs.