Research On Interference Suppression Of Vehicle-to-Ground Wireless Communication In Urban Rail Transit CBTC System Based On TD-LTE

The Communication Based Train Control(CBTC)system is the preferred signal system for urban rail transit.The wireless communication technology of the vehicle ground usually adopts Wireless Local Area Network(WLAN)technology that operates in the common frequency band of 2.4 GHz.Wireless network coverage is vulnerable to external interference.In order to solve the problems of multiple interference sources,small coverage of wireless access cells,frequent handovers,etc.,time division-long term evolution(TD-LTE)technology is introduced in the vehicle-to-ground wireless communication system.However,due to the limited available frequency band resources for urban rail transit,TD-LTE based CBTC system adopts the same frequency networking scheme for wireless communication in the vehicle.When the users in adjacent cells use the same frequency band resources,the frequency interference between cells is more serious.As a result,the communication quality of the edge users is affected and the system performance is degraded.Therefore,the interference and interference suppression schemes of TD-LTE co-frequency networking in CBTC system wireless communication are analyzed.A solution that can effectively suppress the interference is proposed to improve the performance of the system and realize the safe operation of the train.First of all,through the accurate estimation of the isolation of the same frequency between the adjacent cells in different links,the inter-cell interference problem is solved.When the isolation degree is calculated by using the propagation path loss formula corrected by the weighted least squares algorithm,the path loss has large deviation and the accuracy of the algorithm is relatively low.Therefore,a propagation model correction scheme based on the dynamic particle swarm optimization algorithm is proposed.The idea of correcting the propagation model based on the dynamic particle swarm optimization algorithm is to randomly initialize a set of particles in the solution space.The position of each particle represents a potential solution to the problem.During the search process,the position of the extremum particles is found,then,using the fitness function evaluates the position of the extremum particles and determine if the position is the optimal solution.Secondly,for the problem of co-channel interference between neighboring cells on the same link,a dynamic frequency spectrum multiplexing algorithm based on soft frequency reuse and a power control solution are proposed.Since soft frequency reuse can bring about system capacity enhancement on the spatial scale,and dynamic spectrum access technology can improve spectrum utilization in the time dimension,it can improve spectrum utilization by combining soft frequency reuse and dynamic spectrum access technology.The goal of based on soft frequency reuse,the dynamic spectrum reuse algorithm first performs spectrum sensing,introduces a policy that the authorized user must avoid when the non-authorized user accesses the idle frequency band,and then adjusts the signal power in the frequency band to achieve synchronous access.Finally,the simulation of propagation model correction scheme based on dynamic particle swarm optimization algorithm is simulated by MATLAB.The simulation of dynamic frequency reuse algorithms and power control schemes based on soft frequency reuse is also performed.Simulation results show that the two schemes proposed in this paper are reasonable and feasible.The problem of co-channel interference among vehicle-to-ground wireless communication cells in CBTC system based on TD-LTE is solved in both vertical and horizontal aspects,and the purpose of interference suppression is achieved.