Performance study of serial-parallel combined relay orthogonal frequency division multiplexing free space optical system based on M distribution model

We propose a serial-parallel combined relay orthogonal frequency division multiplexing (OFDM) free space optical (FSO) communication system in which the relay protocol of the system is decode and forward. Considering the joint attenuation effect of the light intensity scintillation caused by atmospheric turbulence, path loss and pointing error between the transmitter and receiver on the atmospheric channel fading model, we derive the Meijer G closed-form expressions of outage probability and symbol error rate (SER) of the system over the Malaga (M) distribution model. Furthermore, the effects of key factors such as weather conditions, mapping orders, serial-parallel combined structure parameters, and number of subcarriers on the outage performance and SER performance of the proposed system are analyzed through simulations. Numerical results show that under certain conditions, compared with serial relay or parallel relay, the serial-parallel combined relay structure can further expand the communication coverage and bring greater advantages to the performance of the OFDM-FSO system. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE).