Research On Wireless Fronthaul Based On Aggregated Wireless Optical And Millimeter Wave

In the traditional cloud radio access network(C-RAN),optical fiber direct drive is the preferred solution for the fronthaul network.Compared with fiber fronthaul's high cost and hard maintenance,wireless fronthaul has the advantages of low cost and flexible deployment,which can solve the hard deployment problem of optical fiber in special environment.Therefore,it is a powerful supplement for wireless fronthaul.However,wireless fronthaul is faced with the problems such as lack of spectrum resources,low transmission capacity,and power limitation.In view of the above problems,this study proposes the wireless fronthaul scheme based on free space optical(FSO)and millimeter-wave(MMW)aggregated communication systems,which takes advantage of the multiple input multiple output(MIMO)FSO-MMW aggregated communication system's huge spectrum resources and high transmission capacity to achieve high speed and low delay fronthaul link.Diversity gain and multiplexing gain are the key indicators to measure the transmission rate and reliability of FSO-MMW aggregated system,and there is a tradeoff relationship between the two,that is,the diversity-multiplexing tradeoff(DMT).DMT reflects the resource allocation of FSOMMW aggregated communication system,which is the upper bound for FSO-MMW aggregated communication system under different coding schemes.However,the DMT theory of aggregated MIMO system has not been studied yet.In view of the problems such as hard to achieve high speed and low delay wireless fronthaul,lack of DMT theory for FSO-MMW aggregated communication system,this study carries out the following work:(1)Establish the optimal DMT theory system for FSO-MMW aggregated system.On the basis of the signal-to-noise ratio(SNR)approaching infinity,the outage probability of the aggregated communication system is derived,the relationship between the outage probability and the SNR is analyzed,and the diversity gain of the aggregated communication system can be obtained by combining the aggregated channel model.Then,the multiplexing gain of the aggregated communication system is deduced according to the relationship between the transmission rate and the SNR of the aggregated communication system,and the DMT relationship of the aggregated communication system is established.Finally,the upper and lower bounds of the optimal DMT curve can be obtained from the upper and lower bounds of the error probability of the aggregated system,analyzed the influence of the FSO link on the optimal DMT of the aggregation system under three atmospheric turbulence intensities,namely strong,medium,and weak,and the optimal DMT curve of the aggregated communication system should be analyzed under different aggregated channel models.(2)Propose a C-RAN wireless fronthaul scheme based on FSO-MMW aggregated communication system.The problems of the wireless fronthaul's low transmission capacity and lack of spectrum resources can be resolved by FSO-MMW aggregated communication system,and the capacity performance of the fronthaul network can be improved by the technologies such as beamforming.Meanwhile,a joint optimization algorithm has been put forward to solve the power limitation problem of wireless fronthaul,which can firstly improve the user's rate equal to its rate threshold and minimize the transmit power of the remote radio unit.Then,utilizing the constraint relationship between the rate of fronthaul link and user's receiving rate to allocate power between the FSO link and the MMW link on the aggregated transmitter to reduce the transmit power of the aggregated transmitter,so as to optimize the total power of CRAN.And considering the situation of multiple user receivers,using non-orthogonal multiple access to overcome signal interference between multiple users,while using beamforming technology to improve transmission capacity and reliability.At last,the numerical simulation results have proved that the joint optimization algorithm proposed in this study can reduce the power consumption of the C-RAN system effectively,and the influence of the parameters such as the number of users and bandwidth on the total power of C-RAN has also been analyzed.This study has 27 figures,1 table,and 94 references.