Performance Analysis Of Atmospheric Wireless Optical Communication System Over M-distributed Channel Model

Wireless optical communication(WOC)technology,which is also called free space optical communication(FSO)technology,has received wide attention in the field of communication because of its great advantages such as abundant spectrum resources,high speed,large capacity,effective cost,high security,and license-free spectrum.FSO technology has now get application in the military communication and satellite communication,etc.However,the laser beam in FSO system is transmitted in the atmosphere.The random turbulence of the atmosphere will lead to random fluctuation of the optical power at the receiver.The discrete particles in the atmosphere will cause the scattering of the laser signal,which will weaken the intensity of the laser signal.In addition,there exist pointing errors between the receiver and the transmitter.Atmospheric turbulence,atmospheric attenuation and pointing errors all affect the FSO system performance.Therefore,for the development of FSO system,it is of great significance to learn how to overcome the adverse effects of the above three factors and improve the FSO system performance.In this paper,based on the M distributed model,the system performance of multihop relay-assisted FSO system and low-density parity-check(LDPC)-coded orthogonal frequency-division multiplexing(OFDM)-FSO system under the combined effects of atmospheric turbulence,atmospheric attenuation and pointing errors are studied.The main contents are as follows: 1.Based on M distributed model,the average bit error rate,outage probability and channel capacity performance of the BPSK modulated multihop relay-assisted FSO system are studied in detail under the combined effects of atmospheric turbulence,atmospheric attenuation and pointing errors.On the basis of the channel models with independent and non-identically statistical behaviour,the CDF and PDF expressions at each relay node are given respectively.Then,with the help of the generalized Gauss–Laguerre quadrature rule,the ABER,outage probability and average channel capacity expressions of the BPSK modulated multihop relay-assisted FSO system under non-identically and independently distributed channel model are derived.Based on the numerical analysis and Monte Carlo simulation results,the performances of multihop relay-assisted FSO system are analyzed when turbulence strength,weather condition,pointing error and the number of relay nodes change.2.Considering the M distribution,under the combined influence of atmospheric turbulence,atmospheric attenuation and pointing errors,when applying OFDM modulation technology and LDPC coding technology,the average bit error rate and outage probability performance of FSO system are studied in detail.The PDF and CDF regarding the aggregated channel model are derived,the analytical ABER and outage probability expressions for both QAM and PSK OFDM systems are then obtained.Monte Carlo simulation is offered to confirm the correctness of the propose models.Moreover,LDPC codes are added into the simulation to enhance system performance.The ABER and outage probability performance are analyzed with different turbulence strengths,weather conditions,normalized beam width,normalized jitter,and specifically,different values of M distribution parameter ?.This work can provide reference for the design of FSO system.