Performance Analysis For Mixed RF/FSO System With Multiuser Diversity

The next generation mobile communication system has considerable demand for capacity,data rate and radio frequency(RF)resources due to the deepening of social informatization degree.However,traditional RF technology is facing the challenge of spectrum resources shortage.Free space optical(FSO)communication is a kind of wireless line-of-sight(LOS)communication technology,which uses the atmosphere as the transmission medium and the near-infrared spectrum as the carrier for information.Compared to its RF counterpart,FSO technology not only has abundant and free spectrum resources,but also owns large capacity,high data transmission rate,high security advantages enough to rival the optical fiber.And it is flexible to employ on the harsh environments where fiber links may not be available or expensive to install.Nevertheless,FSO is sensitive to atmosphere conditions,which limits the transmission distance.By contrast,RF links can be adapted for a wide range of weather conditions.Mixed RF/FSO system combines the advantages of traditional RF and FSO,is recognized as a promising solution to the problem of “The last mile access” in cellular networks.In this thesis,we investigate the performance of mixed RF/FSO system with multiuser diversity over fading channels for finding the way to improve the performance.Specifically,the considered system consists of K users,a decode-and-forward(DF)relay and a destination.The K RF links can be multiplexed into a single FSO link at the DF relay.To make the best use of multi-user situation,the relay needs to receive the data of the user with best channel condition and forward it to the destination.Furthermore,we suppose that the RF link experiences?-? shadowed fading which combines multipath fading with LOS shadowing,whereas the FSO link is subject to Exponentiated Weibull(EW)distributed turbulence.Based on the above analysis,we first derive the analytical expressions of the end-to-end outage probability(OP)and the average bit error rate(ABER)with binary phase shift keying(BPSK)modulation scheme of the overall system,which is given in chapter 3.Then,we present the asymptotic expressions at high signal-to-noise(SNR)regimes.More specifically,we investigate the outage and error performance with various channel parameters,turbulence strength and the number of users.In addition,considering FSO link quality is affected by atmospheric turbulence,atmospheric attenuation,dynamic pointing error caused by the random jitter of transceivers and inherent static aiming error.Similarly,in chapter 4,we derive the extended channel model of FSO link under the combined effects of atmospheric turbulence,atmospheric loss and pointing errors.Based on this,we give the formulas of OP and ABER under various pointing error scenarios.Finally,we further analyze the influence of aperture averaging technology on the whole system.The results provide a potential performance improvement scheme for the design of dual-hop mixed RF/FSO system in engineering.