The field of satellite navigation has witnessed the
advent of a number of new systems and technologies: after
the landmark design and development of the Global Positioning
System (GPS), a number of new independent Global Navigation
Satellite Systems (GNSSs) were or are being
developed all over the world: Russia's GLONASS, Europe's
GALILEO, and China's BEIDOU-2, to mention a few. In this ever-changing context, the availability of reliable and flexible receivers is becoming a priority for a host of
applications, including research, commercial, civil, and military.
Flexible means here both easily upgradeable for future needs
and/or on-the-fly reprogrammable to adapt to different signal
formats. An effective approach to meet these design goals is the
software-defined radio (SDR) paradigm. In the last few years, the
availability of new processors with high computational power
enabled the development of (fully) software receivers whose
performance is comparable to or better than that of conventional
hardware devices, while providing all the advantages of a flexible
and fully configurable architecture. The aim of this tutorial paper
is surveying the issue of the general architecture and design
rules of a GNSS software receiver, through a comprehensive
discussion of some techniques and algorithms, typically applied
in simple PC-based receiver implementations
