Efficient Handover Scheme And Algorithm Of High-Speed Railway Communications

High-speed railway plays a vital role for worldwide public transportation. With the full construction of passenger high-speed railway lines and the rapid development of the Internet, not only the high-speed train control equipment, but also a variety of mobile terminals carried by high-speed train passengers moving at more than300km/h have higher wireless communication reliability and bandwidth requirements. In order to provide better quality of services for high-speed mobile users, Long Term Evolution for Railway as a next generation mobile communication system for the railway is getting more and more attentions in recent years. Related research is gradually going deeper. It is well known that in the wireless cellular network system, the handover is a key factor to guarantee the quality of service to mobile users. With the increase in mobile terminal speed, handover problem in mobile communication systems becomes more prominent. How to ensure the user’s broadband wireless communications in the high-speed railway scenario is a major research topic. In order to satisfy the high-speed train user demand for broadband wireless communications, this thesis mainly researches aspects such as handover and access control schemes and algorithms in the high-speed railway scenario.Firstly, this thesis analyzes the difficulties and characteristics of high-speed railway wireless communication scenarios, including the multi-path effect, the Doppler frequency shift, the penetration loss and the fast handover issue. Unlike public mobile communication systems, railway mobile communication systems suffer from more complicated multipath effect, larger Doppler frequency shift, higher handover failure rate and train body loss.Next, this thesis provides a comprehensive review of various types of domestic and international handover schemes and handover algorithm in the high-speed railway communication scenarios, classifies them properly, and gives a research outlook. Besides, Data Envelopment Analysis is applied for the first time to evaluate various existing and novel handover models in high-speed railway communications from the efficiency, reliability and economy point of view. Evaluation results serve as research references.After that, this thesis proposes efficient handover schemes for high-speed railway communications. Through the establishment of a two-hop model, the employment of multi-input multi-output technology, joint analysis of the physical layer and MAC layer, and considerations of application priorities and overheads, the schemes overcome problems in high-speed railway wireless communication scenario to some extent. Simulation results show that the proposed schemes can provide higher data rates, higher reliability, smaller delay for high-speed train communications.Finally, this thesis proposes efficient access control schemes and algorithms for high-speed railway communications. Through the establishment of the system model and the traffic model, and using defined metrics, including access ratio and resource utilization ratio, optimization problem models are established and algorithms are therefore proposed to solve them for the first time. With the help of high-speed railway scenario characteristics, a position-based access factor is proposed to balance the call access ratios in the system. In addition, through jointly consideration of the defined performance metrics, a preliminary separating resource reservation scheme is proposed. Besides, a method to determine the resource reservation proportions and a joint access control scheme are proposed for the first time as further improvements for the separating resource reservation scheme. This thesis also put the proposed schemes and algorithms under simulation and comparative analysis. Numerical results show that the applications of the position-based access factor, the separating resource reservation scheme, and the joint access control scheme can improve the user’s quality of service and the system efficiency.The thesis has42figures,9tables and103references.