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Jan Šafář, Paul Williams and František Vejražka

Abstract

According to a recent Business Case produced by the General Lighthouse Authorities of the United Kingdom and Ireland (GLAs), e-Loran is the only system that, when combined with GNSS, can achieve cost effective resilient Positioning, Navigation and Timing (PNT) by 2018 for maritime e-Navigation. The GLAs currently operate a trial e-Loran service from Harwich, UK and are working towards establishing e-Loran Initial Operational Capability (IOC) in the seven busiest UK ports and port approaches by mid-2013. A future extension of e-Loran coverage to the entire GLA service area will require the installation of additional transmitting stations. When planning the installation of e-Loran transmitters service providers will need a good understanding of the effects of the new signals on the system’s performance. Since all e-Loran stations share the same frequency band and the e-Loran signals propagate over vast distances, special attention needs to be paid to the issue of intra-system interference. This is also referred to as Cross-Rate Interference (CRI) and is inherent to the way e-Loran operates.

In this paper we examine the impact of CRI on the position accuracy performance of e-Loran receivers. First, a signal processing model for a typical e-Loran receiver is developed. This could provide the e-Loran community with a unified framework for receiver performance evaluation. Numerical and, where possible, analytical results obtained from the model are then presented, describing the achievable accuracy performance under different interference conditions. The theoretical results are also compared to those obtained from measurements made on a commercially available receiver driven by a signal simulator.

Our analysis shows that modern e-Loran signal processing algorithms can achieve a substantial reduction of the negative effects of CRI. However, there is still an appreciable residual effect, which should be taken into account when designing future e-Loran networks and determining their coverage and performance