Research On Application Of Software Defined Radio In Railway Wireless Communication

With the development of modernization railway and high railway intelligent transportation system, railway wireless communication is faced with increasingly high demand on safety, reliability, real-timeness, and integration. Now China wireless train dispatching system acted as information exchanging equipment between trains and stations popularized in the whole railway. But because of its analog modulation mode and most voice information transmission, it cannot serve as information channel of railway intelligent transportation system. So a new-type railway wireless communication system which is high-speed, reliable, economic and can transmit great amount of data should be developed urgently. In this thesis, the discussion is carried out aiming at how to set up a high-speed railway wireless accessing channel based on advanced software defined radio technology and digital signal processing technology. In the proprietary frequency band (450 MHz) of railway, security information can be transmitted real-timely between trains and stations. So it can provide secure, reliable and high-powered dispatching system for railway operation and control. Finally, the traditional wireless communication system of VHF/UHF can be improved from analog to digital, from only voice information to voice, data and image information. The main contents of this thesis include:(1) The research background of software defined radio in the domestic and international communication fields and the current situation and existing problems of Sino-foreign railway wireless communication system are analyzed. And aiming at the actual conditions of railway wireless communication such as the communication style being various, the mode being not unified and the functions being single, the viewpoint of developing railway wireless communication system through adopting the software defined radio is put forward.(2) The theories and methods about the realization of the software defined radio are discussed. The band-pass sampling technology and multirate digital signal processing technology and their applications are analyzed emphatically. Through undersampling technology, high/intermediate frequency signal can be sampled not-distortedly by thelow frequency signal; And through multirate digital signal processing technology, the sample speed of the digital signal can be converted such as DDC, DUC. Thus the processing of the high speed and wideband data can be finished.(3) The typical structure of software defined radio and some corresponding key technologies of software defined radio's realization is discussed; And the scheme of the high-speed mobile accessing system product machine based on wideband intermediate frequency software defined radio is given. Finally the hardware structure of the system and the realization of each module are analyzed in detail.(4) In this thesis, aiming at the key section of the Software Defined Radio—intermediate and low frequency digital signal processing, a kind of new practical hardware platform of software defined radio based on DSP is presented. And the hardware /software design and realization of the platform are described in detail. In addition, the performance of the platform is analyzed.Finally, the contents of the thesis are concluded, and the deficiencies which need to be improved and the work which need to be studied further are given.