A Configurable GPS Accumulated I and Q Signal Component Simulator in Matlab®

Phillip M. Corbell and Mikel M. Miller

Abstract:	In order to simulate, analyze, and compare receiver tracking methods and their performance prior to developing and testing real hardware, the accumulated In-phase (I) and Quadrature-phase (Q) signal components inside a GPS receiver's tracking loops must be simulated. These I and Q signal components are also required for simulating ultra-tightly integrated GPS/INS systems. Since valid results from software simulations require averaging multiple Monte Carlo runs, this I and Q simulator benefits greatly from a low computational requirement. To meet these requirements in the field of GPS software simulation, a flexible GPS I and Q generator module was developed in Matlab. Proven mathematical models were used to simulate up to twelve GPS Signals, generating early, prompt, and late accumulated I and Q signal components for each signal. The I and Q generator models and tracks the tracking loop errors, and easily allows for varying integration times, even during a simulation. The mathematical model was verified against the output of a simulated receiver, implemented in Simulink. The verification process showed that the mathematical model generates a very good approximation of the accumulated I and Q components, with reduced quality when using longer integration times and very high dynamics. Overall, the model works well and is easily manipulated through a single function-call interface. The developed model is useful in simulating a wide variety of signal tracking algorithms, including ultra-tightly integrated GPS/INS systems, for which it has already been used. The model fills a critical void in generating low-level processed GPS signal components for testing tracking algorithms without simulating a receiver's tracking loops directly. Only the receiver trajectory, satellite ephemeris, signal strengths, and a few other truth environment parameters are needed to create validated I and Q signal components, pseudoranges, and carrier-phase measurements. It enables further research into the performance and comparison of signal tracking methods and ultra-tightly integrated GPS/INS designs.
Published in:	Proceedings of the 2001 National Technical Meeting of The Institute of Navigation January 22 - 24, 2001 Westin Long Beach Hotel Long Beach, CA
Pages:	205 - 215
Cite this article:	Corbell, Phillip M., Miller, Mikel M., "A Configurable GPS Accumulated I and Q Signal Component Simulator in Matlab®," Proceedings of the 2001 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 2001, pp. 205-215.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In