Researches On Performance Of Mobile Communication System Of High-Speed Railway

In the recent decade, the high-speed railway systems have been built in many countries of the world. The high-speed railway has many advantages in the aspects of movement velocity, punctuality, comfortableness, etc., so the high-speed train became the preferred transportation vehicle for business travel and journey. Meanwhile, wireless communication technologies have been also developed rapidly. The spectrum efficiency of mobile communication system has been improved with better mobility support. At the moment, the high-speed railway mobile communication system (HSRMCS) appeared, which can provide the mobile information service for passenger. The HSRMCS also pro-vides the wireless services for the train control system (TCS). Currently, for passenger in-formation service (PIS) provisioning, there is no an agreed HSRMCS standard, the qual-ity of experience (QoE) of passenger cannot be guaranteed. On the other hand, although the HSRMCS for TCS has its general standard, such as GSM-R, which cannot provide satisfied service for passengers. Therefore, the design of HSRMCS aims at providing reliable train control service and PIS with QoE in the condition of high-speed movement. To achieve this goal and improve the performance of HSRMCS, it is necessary to develop theoretical and applied research on performance of HSRMCS with performance analysis method of communication system through combining the requirement of TCS, recognize the system from the whole and macro viewpoint.To study the performance of HSRMCS, it is important to study the impact of high-speed railway characteristics on the performance of HSRMCS. This work focuses on three key elements including high mobility, railway communication and system perfor-mance to solve the two key issues:physical layer performance of HSRMCS with interfer-ence, link layer performance of HSRMCS with bearer services. Based on the analysis of characteristic of HSRMCS, the scenario and typical services of this work are described. The stochastic theory, finite state Markov chain (FSMC), queueing theory and cross-layer design are used to study the physical layer and link layer performance of HSRMCS with different scenarios, and also the packet-level channel modeling methodology and differ-ential services multiplexing transmission methodology of HSRMCS are proposed. This work can provide theoretical foundation for the performance optimization of HSRMCS. The main contributions of the dissertation are summarized as follows. 1) Transmission interference (TI) is the key performance indicator of train control information transmission service. Firstly, the impact of the movement velocity, fading channel, handover behavior, transmission requirements of TCS on TI performance are analyzed. Secondly, the quantitatively analysis model of TI is proposed, and we found that the major reason impacting the TI performance is the frequent handover. Finally, a design methodology of TI requirement based on handover time is proposed.2) To solve the problem that frequent handover decreases the TI performance, the distributed antennas system (DAS) scheme with linear cellular coverage is proposed. Based on the proposed coverage scheme, the coverage area, interference performance, signal to interference ratio (SIR), SIR based outage performance and bit error rate are an-alyzed. The approximated SIR probability density function is derived. This work proves that the DAS with linear coverage can improve the performance of HSRMCS in many aspects efficiently.3) To analyze the link layer performance of HSRMCS with fading channel and opti-mize it, a reasonably accurate and mathematically tractable modeling methodology is pro-posed for HSR wireless communication channels. A novel multi-FSMC channel model for HSR communication system is built. The statistical parameters of proposed channel model are derived. The accuracy of the proposed FSMC channel model is validated by extensive simulation results. Finally, the proposed model is used to analyze the perfor-mance of HSR communication system with adaptive modulation transmission.4) The problem that the differential services multiplexing transmission methodology when the HSRMCS for TCS and passenger have an uniform system structure is solved. Applying the scalable modulation (S-Mod) technology can provide bit-level differentiated services for control and monitoring service (CMS) and PIS simultaneously. Different S-Mod transmission schemes have been designed for uplink and downlink transmissions respectively, according to the different QoS requirements. Based on the proposed multi-FSMC channel model, the advantages of the multiplexing traffic transmission methodol-ogy are analyze. Simulation and numerical results show that the proposed S-Mod based solution can substantially improve the spectrum and energy efficiency.