Interference And Reliability Analysis Of LTE-R With Linear Coverage

With the rapid development of high-speed railways,the demand for railway communication service has further increased.At the same time,the extremely high speed of train operation also puts more stringent requirements on China's railway mobile communication system.Since the traditional Global System for Mobile Communication-Railway(GSM-R)is a narrowband communication system,its characteristics of low spectrum efficiency and high transmission delay are unable to meet the growing business needs of high-speed railways.The new generation of railway broadband mobile communication system Long Term Evolution for Railway(LTE-R)network has been proposed to carry railway communication services due to its advantages of high efficiency,speed,reliability and low delay.The reliability and validity of data communication are particularly important in railway communication system.As for reliability,LTE-R does not need to plan the spectrum because it has a relatively flexible networking mode and belongs to the same frequency networking.Therefore,the methods of ensuring reliability such as dual-network coverage and spectrum planning in GSM-R are not applicable in the LTE-R system.Therefore,this paper considers to realize redundant coverage on the wireless side of LTE-R system by increasing the overlapping coverage depth between adjacent cells,so as to ensure the reliability of data communication between vehicles and the ground and improve the anti-destructive performance of the entire network.However,the inter-cell interference problem that is introduced along with it needs to be solved urgently.Therefore,area spectral efficiency and outage probability are used as evaluation indexes to measure the effectiveness and reliability of communication systems in this paper,respectively.This paper also studies the influence of the overlapping depth of adjacent cells on the interference and reliability performance of the whole system in LTE-R linear networking scenarios.The main research contents of this paper are as follows:In the study of interference performance,it is the first time to quantitatively evaluate the influence of overlapping depth of neighboring cells on the performance of the whole system.Firstly,the fractional frequency reuse scheme and soft frequency reuse scheme which are suitable for LTE-R linear network are designed in this paper.By using the method of Moment Generating Function(MGF),the closed expressions of area spectral efficiency using the above two frequency reuse schemes are derived.On this basis,the user model is divided into static grouping model and flow level model.The uplink and downlink performance of fractional frequency reuse and soft frequency reuse under these two user models are compared,respectively.Finally,in order to verify the correctness of theoretical derivation of interference model,simulation work has been done in this paper.As for the study of coverage reliability,the useful signal and interference signal in the mixed channel model of path loss,shadow fading and Nakagami-m fast fading can be approximated as obeying the lognormal distribution.Based on the above characteristics,the probability density function expressions of useful signals and interference signals under the two frequency reuse schemes of uplink and downlink are respectively solved in this paper.Thereby,the outage probability of user at any position in the cell of the two frequency reuse schemes related to the overlapping coverage depth is obtained.Finally,the coverage reliability model related to the overlapping depth of adjacent cells in LTE-R system is established and the outage probability expression is derived.The correctness of theoretical derivation is verified by simulation.The obtained performance evaluation results provide a certain reference value and guidance for the coverage of communication along rail transit.The research in this paper also lays the foundation for the future deployment of LTE-R.