IEEE Transactions on Communications

A. Bhowal and R. S. Kshetrimayum, "Advanced Optical Spatial Modulation Techniques for FSO Communication," IEEE Transactions on Communications, vol. 69, no. 2, Feb. 2021, pp. 1163-1174.

Abstract: In this paper, spectral efficiency of free-space optical (FSO) communication is enhanced by the utilization of advanced schemes of optical spatial modulation (OSM). Optical generalized spatial modulation (OGSM), optical enhanced spatial modulation (OESM), and optical improved quadrature spatial modulation (OIQSM) are proposed for performance improvement of FSO systems over Gamma-Gamma (G-G) channel incorporating pointing errors and path loss effect. These methods are investigated in terms of bit error rate (BER) and the analytical BER upper bound results are corroborated by Monte Carlo simulations. Both spatial domain and symbol domain errors are considered while calculating BER upper bounds. The specifications required to implement the schemes are also presented. The proposed methods offer benefits of reduced cost and power consumption, and BER performance improvement over OSM for higher spectral efficiencies. The upper bounds of BER are tight for all values of transmit power for various configurations of the proposed schemes.

A. Bhowal and R. S. Kshetrimayum, "Relay based Hybrid FSO/RF communication employing Hybrid Spatial Modulation and Transmit Source Selection," IEEE Transactions on Communications, vol. 68, no. 8, Aug. 2020, pp. 5018-5027.

Abstract: In this paper, performance analysis of a relay based hybrid free space optical and radio frequency (FSO/RF) communication system is achieved by calculating outage probability. Some advanced concepts like hybrid spatial modulation (HSM), transmit source selection (TSS) and HSM along with TSS for such hybrid systems are proposed for the first time. These cooperative systems employ decode and forward (DF) scheme at the relay. The performance of these schemes are compared with the existing ones analytically and validated by means of Monte Carlo simulations. The FSO channel model incorporates pointing errors for outdoor scenarios. The system performance is influenced by various parameters which is explored extensively in this paper.