Assessment of Transient EMI Impact on LTE Communications Using EVM & PAPR

The brief contact losses between the pantograph and the catenary in high-speed trains create transient interferences, which extend to the frequency bands used by telecommunication systems. This article presents a study of the impact of these transient wideband interferences on LTE communications between the train and a base station. In this study, we set up an experimental test bench, which establishes LTE communication between a communication tester and a USB/LTE dongle in the presence of transient interferences. We analysed the impact of these interferences on the error vector magnitude (EVM) of the received LTE signals and we observed that the EVM evolution does not explain certain communication interruptions. Indeed, interruptions can occur for EVM values significantly inferior to the standard limits. To understand the relationship between the interference characteristics and the communication interruption, we studied the peak to average power ratio (PAPR). Indeed, the PAPR is well suited to analyse transient interferences because it evolves with the amplitude but also with the repetition of the transient. Then, the PAPR measurement can provide a diagnostic assistance to analyse whether along certain railway lines, pantograph-catenary interferences are the cause of the LTE interruptions.