Impace of Interference on the New COSSAP GPS Receiver and Mitigation Techniques Evaluation

Rene Jr. Landry, Vincent Calmettes, Alain Ducasse

Abstract:	Over the past few years, many projects using CDMA techniques have being studied and now already exist or are under construction. Civil GPS navigation represents only one potential application of CDMA in Signal Communication. These Systems are known to have many advantages over FDMA and TDMA, one being its robustness against interferences. Nevertheless, it appears in many papers and reports that GPS Receivers may be perturbed by several kinds of interferences. These interferences are already known at this time, since the near future civil projects of aircraft navigation using the GPS System and their impact is becoming to be well understood. However the Mitigation Techniques to reject these interferences and to improve the pre-correlation signal-to-noise ratio are still to be developed to enhance the GPS Receiver robustness. This paper starts with a short review of the GPS Receiver phase of perturbations and a synthesis amalgam of potential Pre-Correlation mitigation solutions for the GPS Receiver. Our study is an investigation of one potential mitigation technique for electromagnetic interference rejection on the GPS C/A-code of a receiver operating in an aeronautical environment. Section II shows the basic principle of one way of implementing the Adaptive Transversal Filter Solution. In order to evaluate an anti-jamming filter for civil use, a GPS Receiver Simulator was found to be useful. Because the software-based receiver is more flexible, less expensive and more accurate compared with the hardware receivers in receiver designs and GPS Application System Analysis, a Generic GPS Receiver has been implemented in a software, named COSSAP, to validate the technique developed in this paper. Section III of this paper describes the COSSAP Generic GPS Receiver design for this application. Using Monte Carlo Simulations, the Pre-Correlation DSP solution is tested to show the performances and the improvement. It appears that using a notch filter in DSP just after the ADC (Analogue-to-Digital Converter) and before the numerical loops (DPLL and DDLL) permits large improvements over the normal configuration. Attenuation of CWI’s (Continuous Wave Interference) from 30 to 55dB have been measured. This paper is not restricted to the GPS community but intends to give an overview of the Notch Filtering well suited for Code Division Multiple Access as a potential Mitigation Technique. The paper applied the technique to a GPS Receiver to show the feasibility of the work and the last section shows the testbed of a hardware filter connected to a GEC Plessey GPS Receiver (Builder Kit II) and the results obtained in this configuration.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	333 - 343
Cite this article:	Landry, Rene Jr., Calmettes, Vincent, Ducasse, Alain, "Impace of Interference on the New COSSAP GPS Receiver and Mitigation Techniques Evaluation," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 333-343.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In