Research On Handover Algorithm And Key Technology For High-Speed Railway Communication System

With the4G systems technology getting mature, the TD-LTE fourth generation communication system dominated by the Chinese will be put into commercial use. This paper focuses on the problem of switching technology to implement high-speed rail network dedicated TD-LTE systems. Two of the proposed decision algorithms are presented which are based optimization algorithm A3trigger events and applied in special railway network switching algorithm based on GPS information.This paper describes the impact generated by high-speed railway environment to the communication system, including the speed and the channel environment in two ways. Secondly, it introduces the LTE network architecture dedicated high-speed rail network, the network element functions and signaling interfaces based on different switching processes. The application of simulation software platform LTE-Sim for are described in detail, including the original platform module architecture, simulation scenario configuration, and the addition of functional modules in accordance with the needs, which includes a new network topology, modified mobile management module, high-speed physical layer (350km/h) fading model, the RRC layer adds filtering module, and the new handover algorithm module.In the specific projects part, this paper conducts a simulation study in the reference signal received power (RSRP) which has impacts to the switch decision, designs to achieve a more accurate power measurement methods, and makes simulation study on factors affecting the signal received power. Then I study the the deal reported problem of received signal power, add the RRC layer differential filtering module, and do a lot of simulation research on the choice of a lot of filtering parameters. It comes to a reasonable conclusion and provides the parameters of the algorithm switching basis. This paper analyzes the theory on the classic event-triggered switching algorithm A3. I analyzed performance of the algorithm with the LTE-Sim simulation platform, analyzes the packet loss rate, the radio link failure rate and the probability of ping-pong handover of the algorithm at various speeds of the scene. On the basis of the classical algorithm I proposed two optimized algorithms. The optimized algorithm based on train speed can select different adaptive threshold and hysteresis switching time power threshold by dividing the speed of the train, which improve the success rate of switching. The optimized algorithm based on statistical characteristics reduces the rate of dropped calls effectively by eliminating the time lag threshold to determine and using a statistical threshold value instead of time. Then the two optimized algorithms were verified by a large number of simulations. Compared with the classical A3algorithm, the system performance has been greatly improved.Then this paper roposes and studys the handoff algorithm based on GPS information, and analyzes the applicable scenes of the algorithm. Details of the principles and signaling flow of the algorithm are described. This paper also accomplished the simulation of algorithm on different speeds, and figured out the optimum theoretical switching positions. The algorithm uses the characteristics of the railway network deployments private network to achieve a simplified signaling flow, prevent the occurrence of ping-pong handover and optimize the system performance.