A closed-form solution of BER for a convolutional coded non-Hermitian OFDM FSO system with polarization diversity

Abstract In this article, we investigate the performance of convolutional coding against the fading associated due to atmospheric turbulence as well as the polarization-induced crosstalk in free-space optical (FSO) communication system. The performance of FSO system strongly depends on atmospheric turbulence. Orthogonal frequency division modulation (OFDM) is one kind of solution for frequency selective fading channel. The OFDM modulated output signal is complex, which is not possible to transmit through FSO channel. To overcome this constraint, we consider non-Hermitian approach by adding polarization diversity. However, polarization add crosstalk to the system, which deteriorates the system bit error rate (BER) performance. All the analytical simulation results are presents graphically by using MATLAB software. All the provided results are in terms of system’s BER by varying the number of OFDM subcarrier, local oscillator power, link distance, and mean misalignment angle. Our earlier published article where we used space frequency block code (SFBC) and reported that almost 7.5 dB coding gain possible. In this proposed system model, we considered convolutional code instead of SFBC and found a significant amount almost 10 dB coding gain at a BER of 10 −12 when all the system’s parameter remains unchanged. Finally, we developed the closed-form expression of system’s average BER.