Research And Simulation Of Handover Algorithm In TD-LTE Systems Based On LTE-SIM Platform

Because of poor channel environment, combined with high speed of user equipment, the handover performance is very poor in high speed railway scenario of TD-LTE (Time Division-Long Term Evolution) communication system, not only frequent dropping calls but also pingpang effect happens a lot. This paper proposes two solutions to the problem, the first is improved and optimized handover algorithm of traditional event-triggered hard handover algorithm, the situation is between two cell which have the same frequentcy, the first improved handover algorithm takes into account of the velocity factor of the user equipment, this handover method points out that different scope of speeds can be taken with different handover parameters in order to get better handover performance, the paper also finds out the most appropriate combination of parameters which includes handover margin and time to trigger, the paremeter combination is used for different speed scope by LTE-SIM simulation software in high-speed railway hilly scene scenario. Another improved handover is soft handover algorithm used for TD-LTE systems in high-speed railway environment, soft handover is removed in LTE because it is much more complex than hard handover, but there is enough spectrum of resources to meet the requirements of the system in railway situation, and can develop its own TD-LTE communication system equipment because of private network character in railway, these indicate that the soft handover algorithm in TD-LTE system in high-speed railway environment is feasible, the paper also make simulations of soft handover algorithm in LTE-SIM platform in hilly scene scenario, the result shows that the soft handover can get higher handover success rate than the hard one, wireless link failure probability can be greatly reduced, thus the user experience is better.