Performance study of a serial relay CC-OGSM-SD free space optical system based on an M distribution model

This paper proposes a novel, to the best of our knowledge, convolutional coding (CC)-optical generalized spatial modulation (OGSM)-spatial diversity (SD) serial relay system under M distribution. In this work, two types of SD schemes are considered both at the relay node and receiver, and the decode-and-forward (DF) relay transmission protocol is adopted. Taking into account the combined effects of path loss, pointing error, and atmospheric turbulence, the closed-form expressions for the average bit error rate (ABER) of the serial relay uncoded and CC-OGSM-SD free space optical (FSO) system are derived using Meijer's G-function. On the basis of theoretical derivation, the ABER of the proposed system and other common multiple input multiple output schemes in FSO systems are compared through simulation. In addition, the effects of the number of relay nodes, link distance between relays, and different OGSM configurations, SD schemes, and coding rates on the ABER of the system are also analyzed via simulation. Monte Carlo simulations indicate the correctness of the numerical results. The simulation results show that the serial relay CC-OGSM-SD FSO system has lower ABER and higher spectral efficiency.