| Summary: | 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 <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>. The proposed technique is referred to as <inline-formula> <tex-math notation="LaTeX">$2\times {N_{r}}\,\,N$ </tex-math></inline-formula>-ary Alamouti-STBC (<inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>-STBC), where <inline-formula> <tex-math notation="LaTeX">$N_{r}$ </tex-math></inline-formula> is the number of receive antennas. The <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>-STBC with Golden codewords (GCs) is further proposed to improve error performance at high signal-to-noise ratios (SNRs). Moreover, the proposed <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>-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 <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>-STBC with and without GCs. However, only the GCs are estimated by use of the L-ML detection in <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>-STBC with GCs. The signal detection subset based ML detection is further employed to detect the transmitted <inline-formula> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula>-ary quadrature amplitue modulation (MQAM) symbols in <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>-STBC with GCs. The lower error probability bounds of the <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>-STBC with and without GCs are derived and validated by simulation results. As an example, the proposed <inline-formula> <tex-math notation="LaTeX">$2\times 4\,\,16$ </tex-math></inline-formula>QAM 16-STBC with GCs almost maintain the error performance of the conventional Alamouti-STBC with GCs at SNRs.
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