Analysis of Potential CW Interference Effects Caused by UWB Devices on GNSS Receivers

摘要

Ultra Wide Band (UWB) signal transmission has been around since late 1950´s. Thanks to rapid advance in recent years and cost effective enabling technologies, UWB is now envisaged for a variety of applications from localization up to high data rate wireless communication, through wall imaging or ground penetrating radars. rnRegulation is a main issue for the success of UWB development in the next years. UWB regulation activities are well advanced in the USA and ongoing in Asia as well as in Europe. rnThe FCC was the first to introduce such a regulation. Mainly motivated by interferences studies between GPS and UWB emitters, the FCC strongly limited the power density authorised for each UWB device transmitting on the 960-1600 MHz, with a specific mention for power density measured in each kHz. rnUWB appears generally as a noise floor increase factor, degrading the positioning accuracy. However, several documents reporting test highlighted the CW-like effect on GPS C/A receivers caused by UWB interferers with specific Pulse Repetition Frequency (PRF). As an example, UWB waveforms with a PRF of 19.94 MHz caused the GPS receiver to lose lock with a minimal addition of UWB power. rnThis paper details the CW interference effects experienced by any GNSS receiver and bring an analytical derivation of the CW impact within the GNSS receiver at each stage of signal processing. Based on an analytical description of correlation process and on simulations of carrier and code tracking loops, the influence of each parameter impacting the loss of lock on the pure navigation signal is analyzed. It leads to a formulation of the probability of occurrence of this event, explaining how it can conduct to non integrity or discontinuity risks. rnSpecificities of SBAS signals are analysed in order to evaluate their robustness to CW in comparison with GPS and finally the vulnerability of envisaged Galileo codes and signals structures are discussed.