Research On The Resource Management Algorithm For High-Speed Railway Broadband Communication Based On TD-LTE

In recent years, high-speed railway has been developed quickly around the world. In order to satisfy the passenger’s demand for wireless communication, dedicated networks should be designed. High-speed railway communication system based on TD-LTE has great advantages. It can make up the shortages of traditional solutions, such as single service, high price, low data rate, and so on. Radio resource management is of great importance to improve the system performance. Therefore, it is significant to conduct research on radio resource management in the high-speed railway communication system.There are a series of challenges for radio resource management in the high-speed railway communication system. Existing radio resource management algorithms for conventional cellular mobile communication networks cannot be directly applied to the high-speed railway communication system. For the high-speed railway broadband communication networks based on TD-LTE, new challenges will be faced in the research on radio resource management. Radio admission control needs to consider the impact of frequent handover and changing channel state in order to guarantee the quality of service (QoS) requirement. Moreover, Doppler shift and changing channel state have a great effect on resource allocation efficiency.In this dissertation, for the challenges to radio admission control and resource allocation in high-speed railway communication system, corresponding approaches are proposed by combining existing research results and the characteristic of high-mobility. In addition, relevant performance metrics are evaluated by simulation. The main contributions of the dissertation are summarized as follows:1. The problem of radio admission control in high-speed railway communication system is investigated. First of all, an admission control scheme considering bit error rate (BER) is proposed in order to satisfy the data rate requirement of different services in high-mobility scenario. Compared with an admission control strategy that does not take BER into account, the number of admitted services in the above admission control scheme will decrease to some extent. Secondly, for the purpose of admitting services as more as possible, service priority strategy is also adopted to solve admission control problem. Furthermore, for handover services, bandwidth borrowing method based on spring model is developed to guarantee their access requests. Simulation results show that both admission control scheme considering BER and service priority and admission control scheme considering BER and bandwidth borrowing approach have lower blocking probability and dropping probability than an existing admission control scheme.2. A multi-dimensional resource allocation strategy for high-speed railway orthogonal frequency-division multiplexing (OFDM) system with multiple-input multiple-output (MIMO) antennas is presented. Firstly, sub-carriers, antennas, time slots, and power are jointly considered. The problem of multi-dimensional resource allocation is modeled as a nonlinear integer programming problem. The effect of Doppler shift on inter-carrier interference is analyzed to calculate the transmission power. The objective is to minimize the total transmission power while satisfying QoS requirement of each user. Moreover, optimal and approximate solutions are obtained by linearization and quadratic fitting, respectively. Finally, total transmission power and average CPU time under the optimal and approximate solutions are compared by simulation. Simulation results have proved that approximate solution has lower total transmission power than optimal solution while the computational complexity is higher.3. The research on resource allocation problem in high-speed railway orthogonal frequency-division multiple access (OFDMA) system is conducted. First, the effect of the moving speed on Doppler shift is analyzed to calculate the inter-carrier interference power. The problem of sub-carriers, antennas, time slots, and power allocation is formulated as as a mixed-integer nonlinear programming problem. The optimization objective is to maximize system throughput under the constraint of total transmission power. Besides, in order to reduce computational complexity, suboptimal solution to the optimization problem is achieved by using quantum-behaved particle swarm optimization (QPSO) algorithm. Finally, system throughput is compared between QPSO algorithm and a traditional particle swarm optimization (PSO) algorithm by simulation. Simulation results demonstrate that QPSO algorithm has a better performance than PSO algorithm.