Reliability And Security Analysis Of Information Transmission For Wireless Relay Communication Systems On High-speed Railways

By the end of 2016,the high-speed railway operating mileage of China has reached 22,000 km,which ranks the longest operating mileage in the world.The high-speed railway has become one new powerful economic drive for China.The wireless commu-nication system in high-speed railway scenario is significant to guarantee the operation safety and the information transmission.The next generation wireless communication system for high-speed railway aims to provide visible monitoring and control services for high-speed trains,and provide multimedia entertainment services for passengers.Global system of mobile for railway(GSM-R),the current narrowband wireless communication system for railway cannot fullfill the demands of secure and high-data rate transmission.Therefore,how to design a wireless communication system that can guarantee effective and reliable information transmission has become a key issue for the next generation wireless communication on high-speed railways.This paper investigates the reliability and security performance of information trans-mission for wireless relay communication systems in high-speed railway scenario,espe-cially considering the characteristics of fast time-varying channel estimation error and high carriage penetration loss.We design wireless relay transmssion scheme and analyze the reliability and security performance of information transmission in half-duplex relay system,cooperative relay system,full-duplex relay system,and cloud radio access net-work in high-speed railway scenario,respectively.The contributions of this paper mainly include:(1)For the relationship between the information transmission reliability and secu-rity in the presence of channel estimation error of the cooperative relay communication system,we study the outage probability,which represents the information reliability per-formance,and the intercept probability,which indicates the information security per-formance.A relay selection algorithm is proposed to improve the information security performance as well as to guarantee the information reliability performance.We derive the closed-form mathematical expressions of the reliability and security tradeoff.Both theoretical analysis and numerical results show that the relay selection algorithm can ef-fectively reduce the outage probability and the intercept probability with the increasing number of relays.(2)For the relay wireless communication system in high-speed railway scenario,we compare the system capacities of direct transmission scheme and mobile relay scheme.Considering the effect of carriage penetration loss,the closed-form expressions of ergodic capacities of two transmission schemes are deduced in a two-hop relay model.It is found that the mobile relay transmission scheme has better transmission capacity in the case of large carriage penetration loss(above 15 dB).(3)For the distributed mobile relays wireless communication system in high-speed railway scenario,we study a two-phase relay selection transmission scheme and analyze its outage performance.The closed-form expressions of outage probabilities for both direct transmission scheme and mobile relay selection scheme are derived.Our studies show that the mobile relay selection scheme can reduce the outage probability of wire-less communication systems in high-speed railway scenarios with increasing number of mobile relays.(4)For the full-duplex(FD)and half-duplex(HD)mobile relay wireless communi-cation sytem in high-speed railway scenario,the ergodic capacities and the outage proba-bilities are investigated.Both the decode-and-forward and the amplify-and-forward relay modes are considered.Moreover,we study the effect of the carriage penetration loss and the self-interference cancellation ratio on the outage probability.The closed-form expressions of the outage probability,ergodic capacity and outage capacity of both HD and FD relay transmission schemes are derived.The simulation results show that the FD scheme has better reliability and capacity than the HD scheme,especially when the carriage penetration loss is larger than 15 dB.(5)For the reliability and security analysis of the wireless relay communication system in high-speed railway scenario,a three-phase transmission scheme based on the cloud radio access network is proposed.The effect of the channel estimation error and the number of training symbols on system capacity and information security are studied.The outage probability and intercept probability are derived in closed-form expressions to evaluate the security and reliability performance.The mathematical relationship between the outage probability and the intercept probability is derived.It is found that the three-phase relay selection scheme reduces the intercept probability effectively and maintains the outage probability in a low level with the increasing number of mobile relays.