About Gnss; Gnss Systems Overview - R&S SMW-K44 User Manual

Satellite Navigation

4 About GNSS

Global navigation satellite system (GNSS) employs the radio signals of several naviga-
tion standards, like GPS, Galileo, GLONASS, and BeiDou. For several years, GPS
used to be the only standard available for civilian navigation through its C/A civilian
code. Nowadays, the GNSS signals and systems are undergoing fast development,
some systems are getting modernized and some are new. In the foreseeable future,
several more GNSS satellites utilizing more signals and new frequencies are available.
The GNSS implementation in the R&S SMW enables you to generate the signal of up
to 24 or 48 GNSS satellites, depending on the installed options. Signal generation is
performed in real time and thus not limited to a certain time period.

4.1 GNSS Systems Overview

Brief introduction to the global navigation satellite systems
●
GPS
The Global Positioning System (GPS) consists of several satellites circling the
earth in low orbits. The satellites transmit permanently information that can be used
by the receivers to calculate their current position (ephemeris) and about the orbits
of all satellites (almanac). The 3D position of a receiver on the earth can be deter-
mined by carrying out delay measurements of at least four signals emitted by differ-
ent satellites.
Being transmitted on a single carrier frequency, the signals of the individual satel-
lites can be distinguished by correlation (gold) codes. These ranging codes are
used as spreading code for the navigation message which is transmitted at a rate
of 50 bauds.
●
Galileo
Galileo is the European global navigation satellite system that provides global posi-
tioning service under civilian control. It is planed to be inter-operable with GPS and
GLONASS and other global satellite navigation systems.
The fully deployed Galileo system consists of 30 satellites (27 operational and 3
spares). Three independent CDMA signals, named E5, E6 and E1, are perma-
nently transmitted by all Galileo satellites. The E5 signal is further subdivided into
two signals denoted E5a and E5b (see
●
GLONASS
Glonass is the Russian global navigation satellite system that uses 24 modernized
Glonass satellites touring the globe. Together with GPS, up to 54 GNSS satellites
are provided, which improves the availability and therefore the navigation perform-
ance in high urban areas.
User Manual 1178.6379.02 ─ 01
GNSS Systems Overview
Figure 4-1).
About GNSS
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