Research On Mixed RF/FSO Relay System

Free space Optical Communication(FSO)is also known as wireless optical communication,which refers to the wireless communication technology that uses the wave band to transmit information in the atmospheric transmission medium.FSO communication has many advantages.Such as high data rate,low power consumption,rapid deployment,strong anti-interference ability,no frequency license,etc,FSO communication is widely used in the optical fiber network backup,cellular backhaul networks and military secure communications,ground and satellite communications,etc.With the advent of the era of a new generation of wireless communication,users of high data rate,high bandwidth demand increasing capacity of network,can effectively solve the "last mile access problem" communication network of wireless optical communication system is gradually become a hot research content.At the same time,FSO communication is also an important solution to the problem of hyperdense network in the next generation communication system.FSO signal transmit in the atmospheric channel.However,under the influence of atmospheric turbulence the amplitude and phase of FSO signal will flicker or distort.Thus,how to reduce the influence of atmospheric turbulence is one of the most important research on FSO communication.To solve the transmission problems of the FSO signal in atmospheric channel,mixed Radio Frequency/free space optical communication(RF/FSO)technology will FSO technology with traditional RF(radio frequency,the RF)communication technology,the combination of play to their respective advantages,not only improved the whole communication system performance but also expand the communication distance.In a mixed RF/FSO relay system,information source to the relay using RF channel transmission,electrical signals in the relay by subcarrier modulation(subcarrier intensity modulation,SIM)way into FSO signals,relay and obtaining-information using FSO channel transmission.The main research contents of this paper are as follows:(1)The hybrid RF/FSO relay system model is proposed.The FSO channel is the atmospheric turbulence fading channel which obeys the m-distributed turbulence model,the RF channel is Rayleigh fading channel and the dual RF transmissionantenna is adopted.The relay is the amplification and forwarding relay with fixed gain.The statistical characteristics of signal-to noise ratio(SNR)are derived in this model.(2)The outage performance of the hybrid RF/FSO relay system based on the dual RF transmission antenna is analyzed.According to the characteristics of end-to-end SNR communication system,the hybrid Meijer-G function is deduced from the RF/FSO relay system end-to-end outage probability and ber closed analytical expression.The accuracy of the derived results are verified with simulation.This paper also compares the system performance of the hybrid RF/FSO relay system using single antenna and double antenna transmission.The outage probability under different threshold conditions are compared.The results show that the hybrid RF/FSO relay system has better performance than the single antenna system.(3)The symbol error probability of hybrid RF/FSO relay system based on dual RF transmission antennas is studied.The Meijer-G function is used to derive the end to end symbol error probability expression of hybrid RF/FSO relay system.And the accuracy of the derived result is verified by simulation.It is verified that the symbol error probability of hybrid RF/FSO relay system based on dual RF transmission antenna is lower than that of single antenna RF/FSO relay system.