Ch 9. GNSS Interoperability

Overview:

The International Committee on Global Navigation Satellite Systems (ICG) is headquartered at the United Nations Vienna International Center (VIC) in Austria. Part of its Mission Statement is to “encourage coordination among providers of global navigation satellite systems (GNSSs), regional systems, and augmentations in order to ensure greater compatibility, interoperability, and transparency.”

Every GNSS signal is characterized by many parameters, including center frequency, waveform, signal spectrum, number of chips in the spreading code, time duration of the spreading code, number and relative power of the signal components, overlay modulation, data modulation symbol rate, data bit rate, type of message error correction, structure of messages, received signal power, satellite antenna gain pattern, time base, geodesy, and geographic reference frame.

Differences in signal parameters that can be accommodated by software are easier and less expensive to implement than differences that require hardware modifications. If signals from different systems are received with one antenna, employ the same radio frequency and/or intermediate frequency (RF/IF) amplifiers and filters, and are converted to digital form by a common analog‐to‐digital (A/D) converter, all other differences usually can be accommodated by firmware in digital processing chips or by software in subsequent signal processing steps.