Dynamic Resource Management For High-Speed Railway Wireless Communication Systems

High-speed railway(HSR)is favored by countries all over the world for its efficien-cy,convenience,safety,comfort and environmental protection,and has been flourishing on a global scale.In recent years,the scale of China's high-speed railway construction has been increasing,and the operating mileage of HSR is close to 30,000 kilometers.Nowadays,China has become the fastest growing country for high-speed railways in the world.High-speed railway is an important part of national transportation industry,and has an important strategic significance for the economic development and modernization.With the vigorous development of high-speed railway,the relatively high speed be-tween the train and the ground and the tremendous services transmission requirements pose a huge challenge to the design of HSR mobile communication systems.On one hand,the mobile communication system for HSR needs to provide the safe and reliable control and monitoring services for the train control system.On the other hand,it also needs to offer multimedia services for the passengers with high quality of experience.In order to ensure efficient,reliable,real-time multi-service transmissions,resource man-agement methods which are suitable for HSR mobile communication systems should be specifically studied.Radio resource management is a key technology for high-speed rail-way mobile communication systems,and it is also an essential mean to optimize the performance index of the system.In view of this,the research on wireless resource man-agement is of great significance for system performance improvement.Taking full considerations of the inherent characteristics and typical scenarios in HSR wireless environments,this dissertation tries to jointly utilize theoretical analysis,mathematical modeling and system simulation to investigate the dynamic resource man-agement problem in HSR wireless communication systems.The main innovations and contributions of this dissertation are summarized as follows:1)In terms of the time-varying wireless channels and stochastic packet arrivals,we inves-tigate the utility-based dynamic resource management problem in high-speed railway mobile communications.Under the restriction of the network stability and the limited resources,the problem of jointly optimizing the power control and resource allocation is finally modeled as a stochastic network optimization problem,in which the influ-ence of Doppler effect among the carriers is considered.By utilizing the Lyapunov optimization technique,the original problem is firstly transformed into a queue sta-bility problem,and then a dynamic resource management algorithm based on power control and resource allocation is proposed.Moreover,the algorithm can be extended to high-speed railway station area to further improve the effectiveness and reliability of the transmission for the system.Both theoretical analysis and simulation result-s demonstrate that the proposed algorithm can effectively suppress the influence of inter-carrier interference in high-speed mobile scenario,and it can achieve a tradeoff between the average throughput utility and the queue backlogs.2)Taking both the integrity and the continuity of service transmission into account,we investigate the downlink resource scheduling problem of delay-sensitive services in the HSR interval scenario.In this problem,the impact of continuously covered base s-tations and non-continuously covered infostations on packet transmission is analyzed.Considering the Doppler effect and the train trajectory,the dynamic scheduling prob-lem is formulated as a two-stage optimization programming.Through the constraint relaxation and problem transformation,the problem is simplified by fully exploit-ing the inherent structure and the norm approximation method,and then two offline scheduling algorithms are proposed.Inspired by the proposed offline strategies,we next develop the window-based online algorithm and greedy online algorithm.Final-ly,the simulation results based on the HSR scenarios show that the performance of proposed online scheduling algorithms are close to the offline algorithms,and both the proposed offline algorithms and the online algorithms achieve better performance than the conventional schemes.These proposed algorithms effectively guarantee the transmission requirements of the delay-sensitive services and improve the real-time and the effectiveness of service transmission.3)In terms of the stochastic packet arrivals and the strict delay requirements,we in-vestigate a dynamic resource management problem for the delay-sensitive services in high-speed railway station area.We consider the problem of jointly optimizing the user association and the power control in different timescales,which is modeled as a non-convex and mixed-integer non-linear programming problem.Through the prob-lem reformulations and transformations,two different centralized user association and power control schemes are presented,which are based on the successive convex ap-proximation and the reweighted l1-minimization techniques respectively.In order to reduce the complexity of the resource management,a distributed joint optimization algorithm based on alternating direction method of multipliers(ADMM)algorithm is further proposed.Finally,based on the optimal structure for the single user case,an online scheduling algorithm suitable for the real-time data packet transmission is proposed.The simulation results verify the convergence of the proposed algorithms,and show that these algorithms can effectively reduce the total power consumption and achieve better performance.