Performance Analysis For Mixed ?-? Shadowed And Exponentiated Weibull Mixed Dual-hop RF/FSO System With Co-channel Interference

Cloud-radio access network(C-RAN)is the most promising architecture in the fifth generation wireless Mobile Communication(5G).It splits the traditional base station in the mobile communication network into a remote radio unit(RRU)responsible for signal reception and a baseband unit(BBU)responsible for signal processing.In C-RAN,the user forwards a large amount of information to the BBU for processing through the RRU.Therefore,the fronthaul link from the RRU to the BBU requires large transmission capacity and extremely low transmission delay.Traditional radio frequency(RF)communication can't meet the need.Thus,free space optical(FSO)communication has become one of the best solutions currently.FSO communication is a wireless line-of-sight(LOS)communication technology.Compared with traditional RF communication,it has large fronthaul capacity,abundant and free spectrum resources and excellent security.These advantages enable the mixed dual-hop RF/FSO system to be well applied in the C-RAN fronthaul link.Under the C-RAN architecture,the dual-hop RF/FSO system is embodied in that the first hop link from the user to the RRU uses RF communication,and the second hop link from the RRU to the BBU uses FSO communication.The deployment of 5G ultra-dense networks has led to a rapid increase in the number of users,and the co-channel interference(CCI)on the user side cannot be ignored.In this context,studying the performance and improvement scheme of a mixed dualhop RF/FSO system with co-channel interference is a prerequisite for determining whether this architecture can be applied to a C-RAN network.In this article,we first study the performance of a dual-hop RF/FSO system in the presence of co-channel interference.First,we give the system architecture.The entire system consists of a single user,a Decode-and-Forward(DF)relay and a destination node.Among them,the relay is affected by L co-channel interference(CCI).In order to fit the actual communication situation better,we use ?-? shadow fading to describe the RF link to accurately describe the channel characteristics of the direct view and shadow components of 5G microcells.The Exponentiated Weibull(EW)fading model is selected to describe the FSO channel to include the turbulence suppression effect such as aperture averaging technology,and on this basis,channel fading caused by pointing errors is introduced.Furthermore,we deduced the closed expression of the end-to-end outage probability(OP)along with the average bit error rate(ABER)under the BPSK(BPSK)modulation format and we consider the influence of the number of CCIs,the power of interference,pointing error and other factors on the system.It is easy to obtain that the increase in the number or power of CCI will affect the performance of the system;Pointing errors and severe turbulence also deteriorate the system performance.In order to improve the performance of the system,we apply multi-user diversity technology in the first hop.The relay node affected by co-channel interference does not provide equal access opportunities for all users any more.It compares the channel conditions of all users and gives the user with the best channel condition the priority access opportunity.We also analyze the impact of the number of users on the performance of the dual-hop system.Increasing the number of users improves the performance of the system significantly.In addition,we also discussed the effect of aperture averaging technology on the performance of the entire system.