Dual-Hop Optical Wireless Relaying Over Turbulence Channels With Pointing Error Impairments

In this paper, we present analytical expressions for the performance of dual-hop urban optical wireless communication system under the combined influence of atmospheric turbulence induced-fading and misalignment-fading (pointing errors). The system employs an amplify and forward relay with the assumption that channel state information is available at transmitting as well as receiving terminals. The atmospheric turbulence channels are modeled by independent but not necessarily identically distributed (i.n.i.d) Gamma-Gamma fading statistics with pointing error impairments. Using a tight upper bound for the end-to-end signal to noise ratio of the system, we derive the novel closed form expressions for the moment generating function and probability density function all in terms of Meijer´s G-function. Based on the aforementioned statistical results, accurate closed-form expressions for average symbol error rate for M-ary phase shift keying modulation schemes, outage probability and the ergodic capacity under four adaptive transmission policies namely optimal rate adaptation, optimal power and rate adaptation, channel inversion with fixed rate and truncated channel inversion with fixed rate are derived in terms of Meijer´s G -function function. Finally, the proposed mathematical analysis is accompanied with various numerical examples to demonstrate the effect of different system parameters on the system performance.