In this work, bit error rate (BER) and channel capacity of a multiple-input multiple-output (MIMO) system employing optical space shift keying (OSSK) scheme (termed as MIMO-OSSK) are investigated under combined effect of atmospheric turbulence (AT) and pointing errors (PEs). The analysis reveals that diversity order of MIMO-OSSK remains intact over all AT regimes and under PE severity. This behaviour is contrary to traditional pulse-based modulation schemes, where diversity order depends upon AT conditions and PE severity. In addition, the analysis also demonstrates that the MIMO-OSSK utilizes receiver diversity efficiently as compared to existing pulse based modulations. In order to examine the effect of all ranges of AT along with PE severity on MIMO-OSSK, three different channel models are considered, i.e., log-normal, gamma-gamma, and negative-exponential. The probability density functions of the sum of squares of difference between two channel coefficients under these channel models are evaluated, to develop analytical expressions of average BER and ergodic channel capacity for the considered set-up. On comparing MIMO-OSSK with same rate MIMO-pulse amplitude modulation (MIMO-PAM) scheme employing repetition coding, it is observed that MIMO-OSSK scheme outperforms MIMO-PAM for a spectral efficiency of more than 2 b/s/Hz, provided that the number of receivers is sufficiently large.
Dr. Mohamed Abaza received the B.Sc. and M.Sc. degrees in electronics and communications engineering from the Arab Academy for Science, Technology and Maritime Transport (AASTMT), Cairo, Egypt, in 2009 and 2012, respectively, and the Ph.D. degree in digital communications from the “Université de Bretagne Occidentale”, Brest, France, in 2015. From 2009 to 2012, he was a Teaching Assistant in AASTMT. He is currently an Assistant Professor with AASTMT, Giza, Egypt. He authored one book, eight international journals, and six international conferences. His current research interests include multiple-input multiple-output systems, relay-assisted cooperative communications, and optical wireless communications. He was Selected as an Outstanding Reviewer for the Optics Communications (Elsevier) in 2016. He serves as a Reviewer for the IEEE, SPIE, OSA, Elsevier, and Hindawi Communication Society's journals.