BPSK based MIMO with heterodyne detection for enhancing optical wireless communication performance under effect of atmospheric turbulence and pointing errors

In this paper, the performance of Optical Wireless Communication (OWC) under atmospheric turbulence and pointing errors is enhanced by employing MIMO transceivers and heterodyne BPSK and DPSK modulations. We have derived new closed-form expressions for the bit error rate (BER) of MIMO optical wireless communications based on BPSK and DPSK with heterodyne detection for atmospheric turbulence only, pointing error only, and both effects combined. Numerical simulations reveal that the effect of turbulence and pointing errors increases with Rayleigh variance and normalized jitter variance, while it diminishes with normalized pulse width. The BER values for SISO-BPSK and SISO-DPSK, considering a normalized pulse width of 4, normalized jitter of 2, Rayleigh variance of 2, and SNR of 16 dB, are 7.50x10-3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$7.50 \times 10<^>{ - 3}$$\end{document} and 1.48x10-2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.48{ } \times 10<^>{ - 2}$$\end{document}, respectively. It is evident that the BER of SISO OWC experiences significant degradation for both modulation techniques. However, through the employment of a MIMO transceiver with an increased number of receivers and transmitters, the BER experiences a substantial reduction. The BER values for MIMO-BPSK and MIMO-DPSK under the same conditions are remarkably low, standing at 1.24x10-12\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.24{ } \times 10<^>{ - 12}$$\end{document} and 2.38x10-10\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2.38 \times 10<^>{ - 10}$$\end{document}, respectively. These results underscore that, for both SISO and MIMO systems, BPSK outperforms DPSK. The power penalty of SISO-BPSK, for Rayleigh variance and normalized pulse width, is twice that of MIMO-BPSK under the same conditions. The results show that we can use MIMO with heterodyne BPSK to reduce the BER caused by atmospheric turbulence and pointing errors.