Relay Assisted Bi-directional Communication in Generalized Turbulence Fading

The bi-directional relaying has recently emerged as the spectrally efficient communication technique. In bi-directional relaying, two users exchange their information, with the help of a relay, in two time slots and, hence, achieve full-rate transmission. This paper considers a relay assisted bi-directional free-space optical communication system under the influence of generalized atmospheric turbulence fading and misalignment errors. The turbulence induced fading channels, which are independent but not necessarily identical, are modeled with M-distribution. In the presence of the misalignment fading characterized by the pointing errors, the new closed-form expressions for the outage probability and error rate are derived. The error performance of the considered system is analyzed for subcarrier intensity modulation-based M-ary phase-shift keying and M-ary quadrature-amplitude modulation constellations. The analytical results are validated through Monte Carlo simulations.