Modelado y validación de un sistema digital de comunicaciones de gran ancho de banda de aplicación en vehículos de transporte

Abstract

This Thesis proposes a digital communications system that enables the transmission of huge amount of information, between equipment on board of a transport vehicle. This increases the transmission capacity of control and supervision systems currently installed. Moreover, the system is able to work simultaneously with other on-board systems sharing the same physical medium. Therefore it reduces the economic and resources costs of a new system installation in the vehicle significantly. To carry out the development of the digital system proposed, the research work begins by studying the electromagnetic model of a transmission line in a railway vehicle. Such analysis has confirmed the viability of this Thesis. In a second stage, the research work was focused on the development of a communication system based on Orthogonal Frequency Division Multiplexing (OFDM) technique. That technique was chosen due to its bit rate capacity and bandwidth optimization. OFDM is used in other communication system such as WLAN, DSL, PLC or DVB-T. In this research stage we defined all configuration parameters according to transmission line model. In the third research stage, a software simulation tool of the developed system has been created. This simulator analyzes different vehicle configurations and calculates optimum parameters of the system by using the line transmission models obtained at the first stage. Besides, the simulator enables the study of the performance while sharing the same transmission channel for different services. A test platform, based on a FPGA technology, has been developed to validate the communication system and the simulator. This prototype is able to transmit 8 Mbps throughout using a 30 meters long cable in a 3 MHz bandwidth. Finally, a test bench has been developed in the laboratory. It was used to compare the performance of the developed system with another system currently used in railway vehicles, specifically with the IEC 61375-1 standard for Train Communication Network (TCN). Both systems shared the transmission line. This final study validated the research work carried out in the Thesis and demonstrated that the bit rate in a transport vehicle can be increased with reduced costs and minimum installation problems.