A Complete IF Software GPS Receiver: A Tutorial about the Details

ABSTRACT
Research and development continues to extend the capabilities
and to increase the robustness of Global Navigation
Satellite Systems (GNSSs) receivers. Software
receivers are quite valuable in evaluating potential
improvements because of their flexibility. In addition,
software receivers afford batch data processing options
that are not available in hardware implementations. In
developing such a receiver, we have found that many
existing texts and papers on software receivers omit
important implementation details. Here we discuss our
complete Intermediate Frequency (IF) software GPS
receiver and reveal details of the lessons learned during its
construction. Specific topics addressed in this paper
include:
linear and non-linear adaptive analog-to-digital conversion;
acquisition using coherent and non-coherent integration;
search techniques (e.g. , Vernier, M of N, and Tong)
performed in both the time domain and the frequency
domain;
limitations of the DFT approach including leakage;
zero padding and additional DFT enhancements;
tracking utilizing FLLs, PLLs and DLLs;
bit synchronization and navigation data recovery;
frame synchronization and parity decoding;
calculation of the navigation solution; and,
Summary of our MatLAB and C toolkits
This paper will present examples and results we have generated
using sampled GPS signals collected with a high
speed data recorder