Performance Analysis For Relay-Aided FSO Communication System Over Exponentiated Weibull Fading Channels With Pointing Error Impairments

Wireless optical communication is a new wireless broadband communication technology, which has received extensive research with its cost-effective and high bandwidth. However, FSO links are always vulnerable to some effects from free space. Atmosphere turbulence is the main effect, which leads to random fluctuation and fadings. Another main effect is the pointing error which occurs due to the misalignment between the transmitter and the receiver telescope, and it will increase the bit error rate and affect the quality of communication.So it is very significant to study the mechanism of the above mentioned effects and relay-aided transmission scheme has been proposed as a fading-mitigation technique for FSO communication. In this work, with considering the combined effects of atmosphere turbulence and pointing error, we investigate the performance of the relay-aided FSO communication. The main contents are as follows:1. With the fading induced by pointing error into consideration, the performances of the decode-and-forward multi-hop free-space optical communication system with exponentiated Weibull distribution have been studied. The probability density function of the aggregated channel model and the closed-form expression for the average bit error rate of binary pulse position modulation are derived, and Monte Carlo simulation is provided to confirm the validity of the proposed average bit error rate expression. The performance of average bit error rate is then investigated with different hop number H, turbulence strength, receiver aperture size,beamwidth and jitter variance.2. With the combined effect of turbulence and nonzero boresight pointing error taken into consideration, the closed-form expressions of outage probability of both serial and parallel BPPM relay-aided FSO communication system have been derived, and Monte Carlo simulation confirms the validity of the proposed outage probability expressions. The outage probability decreases with the increase of the transmitted power. In the paralle l relay transmission, for a fixed transmit power, the outage probability will be lower if more parallel relays are employed. If the numbers of the parallel relays are fixed, the outage probability will increase with the increase of the turbulence strength, which can be restrained by aperture averaging effect.This work is applicable for the system design of relay-aide FSO system.