TABLE OF CONTENTS Phillip W. Ward
NAVWARD GPS Consulting
John W. Betz and Christopher J. Hegarty
The MITRE Corporation
This chapter discusses three general classes of RF channel impairments that can degrade GNSS performance. The first class of impairments discussed is interference, which is the focus of Section 6.2. RF signals from any undesired source that are received by a GNSS receiver are considered interference. The interference is often unintentional (e.g., out-of-band emissions from other licensed RF systems). The interference may also be intentional, in which case it is commonly referred to as jamming.
Section 6.3 discusses the second class of RF channel impairments, which is multipath. Invariably there are reflective surfaces between each GNSS spacecraft and the user receiver that result in RF echoes arriving at the receiver after the desired (LOS) signal. These echoes are referred to as multipath, a term that originated from the fact that each transmitted signal is transiting over multiple paths to the receiver the single direct path and a number of indirect (reflected) paths.
The third and final class of channel impairments considered in this chapter, in Section 6.4, is ionospheric scintillation. Ionospheric scintillation is a signal-fading phenomenon that is caused by irregularities in the ionospheric layer of the Earth s atmosphere.
Because GNSS receivers rely on external RF signals, they are vulnerable to RF interference (unintentional interference or jamming). RF interference can result in degraded navigation accuracy or complete loss of receiver tracking. This section first describes...
