Optical wireless communications with heterodyne detection over turbulence channels with pointing errors

We study the error performance of an heterodyne differential phase-shift keying (DPSK) optical wireless (OW) communication system operating under various intensity fluctuations conditions. Specifically, it is assumed that the propagating signal suffers from the combined effects of atmospheric turbulence-induced fading, misalignment fading (i.e., pointing errors) and path-loss. Novel closed-form expressions for the statistics of the random attenuation of the propagation channel are derived and the bit-error rate (BER) performance is investigated for all the above fading effects. Numerical results are provided to evaluate the error performance of OW systems with the presence of atmospheric turbulence and/or misalignment. Moreover, nonlinear optimization is also considered to find the optimum beamwidth that achieves the minimum BER for a given signal-to-noise ratio value.