Key Technology Research On Digital Television Transmission In High Speed Railway

ABSTRACT:With the rapid development of Chinese high-speed railway, the total operation miles of high speed rail has become the first place in the world. As the high speed railway brings great convenience to travel of passenger, it is easy to foresee that more and more people will choose high speed railway as their transfer mode in the future. Therefore, digital video transmission in high speed railway becomes a new research hotspot. The realization of digital video transmission in high speed railway is also challengeable. The standards of digital television transmission include standards on digital television terrestrial broadcasting, standards on digital television satellite broadcasting and standards based on mobile communication network. With the continuous development of long-term-evolution(LTE) system, the performance of communication network has been enhanced. So Multimedia Broadcast Multicast Service (MBMS) in the communication network has a very good development prospects.Firstly, the related concepts of MBMS are introduced in this thesis, and Multimedia Broadcast Single Frequency Network(MBSFN) is particularly discussed. The MBSFN inherits SFN nature, where multiple transmitters send the same content over the same channel. SFN allows the overlapping of coverage areas, then greatly improves the performance of communication in the area of cell edge and the quality of coverage. Therefore, based on the related technology of the MBMS in the LTE system, this paper proposes a new overlay network architecture for digital TV transmission in high speed railway. And this overlay network uses the MBSFN transmission mode in the LTE system to transmit digital TV signals.Secondly, this paper introduces a variety of wireless propagation models. For the communication environment in the high speed railway, we choose WINNERII D2a model through the comparison and analysis. For the new overlay network, this thesis analyzes its performance by theoretical derivation and system simulation. The performance analysis includes the average Signal-to-Interference plus Noise Ratio (SINR) analysis at the receiving end and spectral efficiency in the MBSFN area. The average SINR analysis uses the selected propagation model and analyzes the performance in detail by theoretical derivation and simulation. The analysis results show that the new overlay network can use the characteristics of single frequency network to improve the average SINR in the cell edge. Moreover, the analysis of spectral efficiency in MBSFN area further illustrates the advantages of the new overlay network.Finally, the primary explosion on Raptor code for MBMS is made. In this part, we introduce the basic concepts of the fountain codes and the advantages of fountain codes which are used in the broadcast and multicast service. Then we briefly introduce the encoding and decoding methods of the LT codes (Luby Transform Codes) and Raptor codes. Moreover, the Raptor code for MBMS and its encoding and decoding algorithm are introduced. Some simulation are used to analyze the performance of the Raptor code for MBMS in the channels with different erasure probability. The simulation results show that the Raptor code for MBMS has good performance on anti-erasure in the system.