GNSS Signal Quality Monitoring

This chapter begins with an explanation of the importance of signal quality monitoring (SQM) of global navigation satellite system, (GNSS) followed by a description of SQM requirements, and an overview of current monitoring systems. Next, SQM algorithms and methods are summarized for six parameters: signal power, cross‐correlation, cycle slip, excessive acceleration, code‐carrier divergence, and signal deformation. SQM is a subset of signal monitoring that specifically deals with the assessment of carrier waveform and code performance to ensure that they are within designated limits. The Civil Monitoring Performance Specification provides a section with clarifications and algorithms that provides insight into incomplete SQM requirements including verification of absolute power delivered by each satellite and response time, received carrier‐to‐noise ratio, code‐carrier divergence, signal distortion, carrier phase discontinuities, and bit inversions. Challenges remain for many aspects of GNSS SQM, including algorithm design and implementation for monitoring and assessment.