A New Doppler Removal and Correlation Method for Software GNSS Receivers


Description of Technology

Researchers at the University of Calgary have developed a new method for Doppler removal and correlation in software Global Navigation Satellite System (GNSS) receivers. These processes are typically very computationally expensive making methods of reducing the computational burden very attractive. By performing the Doppler removal on all tracked satellites simultaneously, as opposed to traditional approaches that remove the Doppler on a satellite-by-satellite basis, this process increased the speed and efficiency of the signal acquisition process, as well as reducing the number of computations needed for Doppler removal.

GNSS signals consist of a carrier wave modulated by a ranging code which contains information used to identify the satellite and to determine its approximate distance. As part of signal tracking in GNSS recievers, the incoming carrier frequency, and opitionally phase, must be generated within the receiver to match the incoming signal. The two signals (local and incoming) are then effectively multiplied together in a process known as Doppler removal. If the local and incoming signals match, the result of the Doppler removal process contains no carrier frequency component and consists entirely of the ranging code. This signal is then multiplied by time-shifted versions of the receiver generated ranging code in a process known a correlation.

Areas of Application
  • Software-based GNSS are flexible, adaptable and cost effective
  • Software-defined GNSS receivers will serve a wide range of uses from researchers developing novel GNSS applications to mobile and software radio users
  • By improving on traditional hardware receivers, software receivers will enable real-time power density analysis, raw IF data collection, storage and replay, as well as multi sensor integration
IP Status
Competitive Advantages
  • Increased speed, sensitivity and efficiency of the GPS signal acquisition process - the number of frequency bins that can be searched in a given amount of time increases without increasing the computational resources used
  • Reduces the number of computational calculations used for Doppler removal by approximately 24-28 per cent, therefore reducing the processing power required by the receiver
  • Performance benefits are independent of platform and operating system used
Stage Of Development
  • A series of simulations have been run to analyze the power, phase tracking and code tracking performance of the new method.
  • Real data has been collected and analyzed to verify the algorithm implementation