Introduction - Understanding GPS: Principles and Applications - page 15

Chapter 2 provides the fundamentals of user PVT determination. Beginning
with the concept of TOA ranging, the chapter develops the principles for obtaining
three-dimensional user position and velocity as well as UTC (USNO) from GPS.
Included in this chapter are primers on GPS reference coordinate systems, Earth
models, satellite orbits, and constellation design.
In Chapter 3, the GPS system architecture is presented. This includes descrip-
tions of the space, control (i.e., worldwide ground control/monitoring network),
and user (equipment) segments. Particulars of the constellation are described. The
U.S. government nominal constellation is provided for those readers who need to
conduct analyses using a validated reference constellation. Satellite types and corre-
sponding attributes are provided, including the Block IIR, Block IIR-M, and Block
IIF. One will note the increase in the number of transmitted civil and military navi-
gation signals as the various satellite blocks progress. Of considerable interest are
interactions between the control segment (CS) and the satellites. This section pro-
vides a thorough understanding of the measurement processing and building of the
navigation data message. The navigation data message provides the user receiver
with satellite ephemerides, satellite clock corrections, and other information that
enable the receiver to compute PVT. An overview of user receiving equipment is
presented, as well as related selection criteria relevant to both civil and military
users.
Chapter 4 describes the GPS satellite signals and their generation. This chapter
examines the properties of the GPS satellite signals, including frequency assign-
ment, modulation format, navigation data, and the generation of PRN codes. This
discussion is accompanied by a description of received signal power levels, as well as
their associated autocorrelation characteristics. Cross-correlation characteristics
are also described. The chapter is organized as follows. First, background informa-
tion on modulations that are useful for satellite radionavigation, multiplexing tech-
niques, and general signal characteristics, including autocorrelation functions and
power spectra, is provided. Section 4.3 describes the legacy GPS signals, defined
here as those signals broadcast by the GPS satellites up through the Block IIR space
vehicles (SVs). Next, an overview of the GPS navigation data modulated upon the
legacy GPS signals is presented. The new civil and military signals that will be
broadcast by the Block IIR-M and later satellites are discussed in Section 4.5.
Finally, Section 4.6 summarizes the chapter.
Receiver signal acquisition and tracking techniques are presented in Chapter 5.
Extensive details of the numerous criteria that must be addressed when designing or
analyzing these processes are offered. Signal acquisition and tracking strategies for
various applications are examined, including those required for high-dynamic stress
and indoor environments. The processes of obtaining pseudorange, delta range, and
integrated Doppler measurements are described. These observables are used in the
formulation of the navigation solution.
Chapter 6 discusses the effects of various channel impairments on GPS perfor-
mance. The chapter begins with a discussion of intentional (i.e., jamming) and
nonintentional interference. Degradations to the various receiver functions are
quantified, and mitigation strategies are presented. A tutorial on link budget com-
putations, needed for interference analyses and useful for other GPS systems engi-
neering purposes, is included as an appendix to the chapter. Section 6.2 addresses