Free eBook: Choosing a GNSS Simulator
There are multiple satellite signal testing options available for developers of GNSS-enabled devices, but not all of them deliver the breadth and accuracy of results that you need. So how do you decide on the right one for you?
Download a free eBook to discover:
- The different GNSS testing options available
- The advantages and limitations of each one
- How to choose the best GNSS testing method for your device
Simply enter a few details opposite to receive your free eBook—and happy reading!
Spirent has been the global leader in GNSS testing for near 30 years. Spirent delivers navigation and positioning test equipment and services to governmental agencies, major manufacturers, integrators, test facilities and space agencies worldwide.
Getting it right. Why all simulators are not the same
Getting it Right
Product designers, manufacturers and system integrators involved
in GPS development have used GPS simulators for R&D, integration,
verification and production testing for years. But with the
proliferation of GPS applications coupled with the commercialisation
of GnullnullnullS, the development of future Glonulll nullavigation Satellite
Systems nullnullSnulland the integration of these systems, GPS and GnullS
testing has nullcome more mainstream.
nullf this is new to you, donnull worry, we
can help you as all GnullS simulators
and test approaches are not the
same. nullou need to understand what
these devices can do and how they
can nullnefit your particular needs.
Page 2SPIRENT eBook
The case for RF simulation
nulle case for using a GNSS simulator when designing any form of
location aware enullipment is a compelling one. nulle anulllity to control
test conditions, to simulate new satellite systems long nullfore they
go nullivenulland the ability to precisely repeat tests time and time again
is a nully application of simulation that cannot null achieved through
using live satellites for testing.
nullere is however, a case where
capturing the richness of live snull
signals to playnullcnulllater in the lanull
complements simulation as a source
of GnullS signals for test. But more
of that later.
What is a simulator?
null Rnullnullnstellation Simulator reproduces the environment of a
GnullS receiver on a dynamic platform nully modelling vehicle and
satellite motion, signal characteristics, atmospheric and other
effects, causing the receiver to actually navigate according to
the parameters of the test scenario.
Gnull nullnullnullproduction test simulator
Page 4SPIRENT eBook
nullowever, during the past decade, a numnullr of alternative devices
have emerged that claim to offer a complementary or alternative to
GnullS simulation in a numnullr of different ways.
nulle minullnow includes nulln no particular ordernull
null nullve snull
null Rnullrecord and playnullcnullsystems nullPSnull
null Singlenullhannel Rnullsimulators
null nullultichannel Rnullconstellation simulators
So where would we use these devices and how do nulldecide whatnulls
right for menullWell that all depends on your test renullirements as all
approaches nulling with them a minullof pros and cons.
Page 5SPIRENT eBook
The tests required
nullnullratory testing of any GnullS receiver design nullll renullire a range onull
standard tests in order to enullercise the nullll nullnctionality of the receiver
under nullth nullnormalnulland nullspecialnulloperating conditions. nullese tests,
which might null carried out individually or comnullned, will comprisenull
null nullime to first finull
null nullcnullisition sensitivity
null nullracnullng sensitivity
null Reacnullisition time
null Static navigation accuracy
null Dynamic navigation accuracy
null Radio frenullency interference
So how does each solution stacnullup against renullirementsnull
nullnullore information on GnullS Receiver testing can null found nully downloading the eBoonullnullimulator versus real world testingnull
nulle first onulltacle that will null encountered in integrating GNSS
receiver testing into a production test setup is pretty onullvious.
null such tests are performed at the end of the production
line, they are inevitanully performed indoors. nulld regardless
of whether the enullipment is designed to wornullindoors or
outdoors, the roof and walls of the nullilding will introduce
varianulles into the test that will negate its effectiveness.
Sonullalled nullivenullnullnulltesting is therefore impossinulle without
relaying the GnullS signals from outdoors to the production
Page 7SPIRENT eBook
nullt is a relatively simple enullercise to capture live GnullS signals
and renulladiate them within the production test environment.
nullowever, this comes with its own set of shortcomings.
nullirst, radiating any signal in such an environment might have
unforeseen consenullences on other tests that are performed on
the productnulland conversely, other Rnullsignals and noise within
the production test area may well impact on the integrity of the
Page 8SPIRENT eBook
nullore importantly, though, the inherently dynamic nature of GnullS
signals means that while each unit may well null tested in the
same physical location null.e. in the production tester finullurenull
the relative positions of the GnullS satellites will null different
for every unit tested. nulld, not surprisingly, this manulls direct
comparison nulltween results unrelianulle at nullst.
Page 9SPIRENT eBook
Realnullorld, livenullnull testing does have some advantages e.g.
younullre testing real signals and at the very nullsic level,
itnulls inenullensive nullt it has some significant drawnullcnull which,
in practice, preclude controlled testing.
null nullesting using real signals
null nulln null inenullensive
null null end user or test site cannot have any control
over the GnullS signal nulling transmitted
null nulle signals seen incident to the GPS receiver antenna
are constantly changing as the GPS system
constantly changes nullrecessesnull
Page 10SPIRENT eBook
null nullere are occasional signal errors, often unnullown
to the receiver at the time
null nullmospheric conditions change significantly and
have a significant impact on single frenullency
null nullesting at multiple geographic locations proves
to null enullensive
Page 11SPIRENT eBook
null pseudolite nullr pseudo satellitenullis simply a device used to
emulate the role onulla satellite, and as such can null thought of
as a simulator. nullis class of devices includes transmitters used
to augment indoor coverage as well as those used to simulate
future satellite constellations nullfore launch.
Page 12SPIRENT eBook
null Pseudolites are not for testing
null nulley can null used to augment GnullS, nullt manullr issues arenull
null Modinulld receiver needed to cope nullth high ponullr signals
and stationary transmitters
null nullostly used for professional applications
nullnullgnullmining or use in container ports
Page 13SPIRENT eBook
RF record and nullaynullck system nullPSnull
nullGNSS null nullS does enullctly as the name suggests. nulln simple terms,
the whole Rnullspectrum in a specified nullndwidth is downconverted,
digitised and stored as samples on suitanulle storage media.
nullor playnullcnull the samples are converted nullcnullto an analogue signal,
upnullonverted and output at the original Rnullfrenullency.
nulll Rnullenergy in the specified nullndwidth is recorded. nulln addition to
the GnullS signals interference is also recorded. nullis may null from
many sources such as other Rnullcommunications, nulloadnullnd
interference from electrical systems nullehicle ignition etc.null and even
radiation from solar activity. nulloise is also inevitanully added nully the
recording and playbacnullprocess, nullt with appropriate lownulloise gain
at the start of the process this can null minimised.
Page 14SPIRENT eBook
nulln terms of the recorded GnullS signals, these will null as they arrive
incident upon the recordernulls antenna so they will include the effects of
the propagation environment and the satellite and onullervernulls motion,
this includes multipath in its full richness, fades, signal loss and carrier
phasenullignal group delay due to atmospheric innullences.
null null RPS gives you the power and nullnullnulllity of performing one field
test and repeating it many times in the lanull.
null Records all signals in nullnd
null Record real world environments and effects
null nulln null a cost effective solution
SPIRENT eBook Page 15
null RPS is complementary to GnullS simulation and is important
for the verification part of a complete GnullS test plan, where
precise nullowledge of the test signal is not important, nullt precise
repeatanulllity of the signal nullichnessnull of the real world is
null nullou cannull test future signals e.g. Galileo
null Results can null difficult to interpret
null RPS has limited control
null nulldeal for testing in complenull
environments, where recreation of
signal and fading effects in a
simulator is a manullr challenge
Sinnulle channel RF simulators
nulln the face of it, a simple single channel Rnullsimulator would appear
to null suitanulle for GnullS receiver testing. nullowever, many of the
range of tests renullired nullee page null are not possinulle. Single channel
units are widely used for production testing where nullstimulationnullof
one receiver channel as a GonulloGo or sensitivity test is enough to
determine the circuitry wornull. nullor R&D testing a single channel can
help with simulating the receiver Rnulland enanulling single channel
tracnullng and sensitivity measurements. nullowever, there is more to
testing a GnullS receiver than simply producing a signal at the correct
Page 17SPIRENT eBook
null Without the anulllity to simulate a full satellite constellation
a receiver cannot null fully tested for its primary function
null null future receiver tests will include more than nullst GPS null
nullnull code, a single channel Rnullsimulator should have the
capanulllity to test GnullnullnullS null and Galileo null either out of
the nullnullor through a field upgrade
null Rnullpower level accuracy and stanulllity are important to
ensure valid results
Page 18SPIRENT eBook
nullultichannel RF constellation
nullere is, however, one solution that is capanulle of handling all
of the tests necessary for designing, developing and integrating
GnullS receivers in the lanullratory.
nulle multichannel GnullS constellation simulator is capanulle of
running all seven standard tests of GnullS receiver performance,
together with their individual variations. Whatnulls more, todaynulls
simulators can null used to produce signals from satellite
constellations that do not yet enullst in the real world, allowing
developers to create multinullnullS designs that will wornullrelianully
with GPS, GnullnullnullS, Galileo and nullmpass systems.
Page 19SPIRENT eBook
nullis type of enullipment is widely used for R&D, integration,
validation, production and post sales testing.
null null multichannel GnullS constellation simulator should provide
the capanulllity to recreate the GnullS Rnullsignal in such way
that it should null fully representative of the real signal
enullected nully a receiver
null nullt should allow a user to control the simulation environment
and all parameters of the signal should null nullown to the user
null null multichannel GnullS constellation simulator should enanulle the
provision of complete repeatanulllity in the signal creation
null Results are easily interpreted, nullantifianulle and certifianulle
null nullounullre not testing real world signals
Page 20SPIRENT eBook
nullo complement simulation testing at the verification stage, the
enullense of field trials can null dramatically reduced nully nullinging the
realnullorld nullcnullto the nullnullwith a Record & PlaynullcnullSystem nullPSnull
Page 21SPIRENT eBook
While the manullrity of the simulation options offer some of the
attrinulltes renullired for testing GnullS receivers, many of these
instruments also have their shortcomings nullt as mentioned
previously, it depends on your test application.
nulle nully point to note is that the marnullts we operate in are
changing fast. nulle GPS system is nulling moderninulled, GnullnullnullS
is almost at full strength, Galileo and nullmpass signals will null
coming online over the nenull few years. nullgmentation systems
such as nullnullS, WnullS and the soon to null GnullGnull and nullSS
systems add to the minullof signals and technologies availanulle to
those developing GnullS.
Page 22SPIRENT eBook
nully system you are loonullng to purchase must null anulle to support
these signals now or have a defined roadmap of when that support
will null availanulle.
nullt Spirent we advocate a progressive approach to testing,
incorporating simulation, Record & Playnullcnullwith final confirmation
using real world signalsnull
Page 23SPIRENT eBook
Progressive testing anullroanulles
Statistical results analysis
nullown pronullem areas
nullve nullrive nullesting
Page 24SPIRENT eBook
nulle Snullrent GNSS annullnullinulli Solutions
Spirent is the industry leader for GnullS simulator products.
Digital Rnullsignal generation techninulles patented nully Spirent have
led to the development of highnulldelity, worldnulleading GnullS Rnull
Spirent offers several different models of GnullS simulators that
support a variety of different applications and cover the full spectrum
of civilian and military GnullS testing needs.
Spirent products range from nullsic singlenullhannel simulators,
suitanulle for simple production testing, through multinullhannel,
multinullonstellation simulators, suitanulle for the most
demanding research and engineering applications.
Page 25SPIRENT eBook
nullor more comprehensive testing, Spirent also offers products that
simulate additional system elements simultaneously with the GnullS
constellation signals, such as inertial sensors, various automotive
sensors, nullsisted GPS nullnullPSnullnullnullsisted GnullnullnullS nullnullnullnullnullSnull
data, SBnull and GBnull augmentation system signals, interference
signals, GnullS Record & Playnullcnulland Winulli Positioning.
Record & Playnullcnull
Winulli nullccess Point
Page 26SPIRENT eBook
Why not nulld out more
anullut choosinnulla nullSS simulator
for the lanullratory from Snullrentnull
the nullrld leader in nullSS
nullf you found this article of interest, find out more
nullisit the Spirent GnullS nullog
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