Free eBook: Bring the Complexity of the GNSS World Back to your Lab
‘Live-sky’ testing of GNSS receivers has serious limitations, as the same environmental conditions can never be replicated for repeated tests. At the same time, it is a great way of testing new equipment in real-world conditions that include signal interference, multipath and other effects.
Now there’s a way you can capture the richness of the live-sky environment in a way that can be used again and again for controlled testing in the lab.
Download a free eBook to discover how Spirent’s easy-to-use GSS6400 RF Record and Playback system lets you record real-world GNSS conditions for playback in the test lab: You’ll learn:
- How to capture the full richness of real-world GNSS conditions for use in the lab
- Why Record & Playback works best as a complement to RF simulation testing
- How Record & Playback can save substantial amounts of time and money on field trials
Simply enter a few details opposite to receive your free eBook—and happy reading!
About Spirent
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.
Bring the complexity of the
GNSS world back to your lab
An introduction to GNSS RF Record Playback Systems
Global Navigation Satellite Systems
(GNSS) are versatile, cost-effective and
efficient navigation technologies.
GNSS is relied upon in a myriad of applications from the provision
of pedestrian navigation and information, vehicle navigation,
the timing of the world’s nullancial system to spacecraft launch and
enullranullerrestrial manoeuvres, but it is also vulnerable to a wide
variety of factors such as RF interference, multipath, unavailability of
signals and atmospheric disturbancenullnullith so much key infrastructure,
commerce and safety depending on GNSS, proper design and testing
of navigation systems which use GNSS receivers is essentialnull
Page 2SPIRENnullenullonull
nulle benchmark for testing GNSS navigation technology and systems
must be based on a method which allows accurate repeatability
of test signalsnull nulle phrase nullnullime and tide wait for no mannull
is particularly relevant to the GNSS systems in use todaynullNeither the
GNSS constellation of satellites and its signals, or the environmental
conditions in which they are propagated remain the same, nor can
they be precisely repeatednullnullime travel, despite the best efforts of
the movie industry in trying to convince us, is not a realitynull
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nulle fundamental methods for testing and optimisation are RF
simulation and RF record and playbacknullRF simulation has been well
documented and proven over the last null years as an essential piece
in the GNSS test nullgsawnullRecord and Playback, while a relatively
new method, is another essential partnullnullth are indispensible in a
complete endnullonullnd test plannull
nullis nullbook discusses the concept of RF Record and Playback and
introduces the Snullrent GSSnullnull Record PlaybacnullSystem (RPS)
nulla key addition to the GNSS test solutions offered by Spirentnull
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nullat is a GNSS Rnull
Record Playbacnull
System (RPS)null
A GNSS RF RPS does enullctly as the name
suggestsnullnulln simple terms, the whole RF
spectrum in a specinulld bandwidth is
recorded, downnullonverted, digitised and
stored as samples on suitable storage
medianullFor playback, the samples are
converted back to an analogue signal,
upnullonverted and output at the
original RF frenullencynull
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All RF energy in the specinulld bandwidth is recordednullnulln addition
to the wanted GNSS signals, noise in the form of unwanted
interference is presentnullnullis noise is from many sources such as other
RF communications, broadband interference from electrical systems
nullehicle ignition etcnull, and even radiation from solar activitynull
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nulln terms of the recorded GNSS signals, these will be as they arrive
incident upon the recorder’s antenna so they will include the effects of
the propagation environment and the satellite and observer’s motion,
this includes multipath in its full richness, fades, signal loss and
carrier phasenullignal group delay due to atmospheric innullencesnull
nullen played back into a GNSS receiver the GNSS signals will be
enullracted from the noise nullst as they would be if the receiver’s
antenna were pointing skyward receiving real GNSS signalsnull
nulle receiver will then denullodulate them and derive its position,
navigation and time solutionnullnulle behaviour and performance
of the receiver will be determined by the environment
in which the RF energy was recordednull
Page nullSPIRENnullenullonull
nulle nully benefits
of record nullaybacnullsystems
nulleal world richnenull captured
nulle full richness of the nullealnullorld’ operating environment is captured
with an RPS, so in terms of realism, it can’t get much betternull
nullmplete repeatability
nullf the test renullirements are not concerned
with nullantifying the signals then RPS is an
ideal method to use as it allows the signal to
be precisely repeated back in the laboratory,
over and over againnull
Page nullSPIRENnullenullonull
nullnull of unull
An RPS system provides an easynullonullse method for GNSS testingnullAll
you need for record and playback is contained in one bonullwith a built
in hard drive, front panel nullnulldisplay, internal battery and a simple
onenullouch recordnull
nullmplimentary to GNSS nullmulatornull
nulle nullst stage in the design of GNSS products and devices usually
involves the testing of the device using simulated signals, as output
from a Spirent simulatornull
Page nullSPIRENnullenullonull
nullith simulation different scenarios can be produced that may vary
the speed or dynamics corresponding to the application of the
products, add interference, atmospheric effects, obscuration effects,
multipath, satellite ephemeris errors, clock errors etcnullAn important
stage in any complete test plan is then to try the system in the real
worldnullnullowever, repeated nullld trials are enullensive nullthis is obvious
for applications such as aviation and space, but surprisingly so for
automotive and pedestrian applicationsnullnullis is where the RPS comes
innullnullnstead of having to test the product in the nullld, return to the lab
and optimise the system, go back into the nullld again and perform
several iterations it is much simpler to bring the realnullorld into the
labnullRecord the realnullorld signals once on the RPS, and replay them
as often as you like in the comfort of the labnullFurthermore the RF
output of a Spirent simulator can easily be recorded, enullending the
nullnullbility of your testingnull
Page nullSPIRENnullenullonull
So nullat can the GSSnullnull
Record PlaybacnullSystem
(RPS) be nulled fornull
Chipset and GNSS product design
nulleduce nullld trialnull
nulluning of software and algorithms to provide optimum
performance in real world situations occupies a lot
of development timenullnulln particular environments, the
traditional approach has been to position development
resources on site and conduct real time trials whilst
developing improvements and solutions to problemsnull
Page nullSPIRENnullenullonull
nullis has the added difnullulty of not recreating the enullct conditions on
subsenullent tests, and renullires engineers to be away from mainstream
development for enullended periods of timenullnullith the RPS system
the signal environment can be recorded once, maybe at different
times of day or constellation, and then used back at nullasenullfor
subsenullent development and testingnullnullf local personnel are available
for recording, then travel for development engineers is eliminated
entirely because the unit can be controlled remotely andnullr nulles can
be uploaded to a ftp site for download somewhere elsenull
Page nullSPIRENnullenullonull
Pronulle new algorithmnull enullecially
for new high nullnnulltinullty receinullernull
GNSS receivers begin their testing and performance proving with
simulator signals and long test campaignsnullnulloving to the nullreal worldnull
as enullerienced by end customers often renullires the algorithms to be
nullld tested, using repeated runs in known environments such as city
areas and locations with high interference or obscurationnull
nully holding a library of prenullecorded signals from such areas,
much of this work can be achieved without leaving the bench,
thus cutting both costs and development timenull
nullanges to algorithms are easily proven using
the same signals over and over, without the
need for more nullld testingnull
Page nullSPIRENnullenullonull
Customer conformance testing
nullProve you can meet customer’s renullired performancenull
null nullnullmples of this testing include
applications for automotive and
mobile communicationsnull
Page nullSPIRENnullenullonull
Production testing
nullepeatable nullgnalnull
Production testing usually involves the replay of the same signal
scenario for each test run, or using off air signals for testingnull
nulle GSSnullnull provides a cost effective method of repeatable testing
providing GNSS signals under the control of a test Pnull or from its
front panelnullnullnce the test signal has been recorded nulldeally from
a Spirent simulatornullthen consistent replay is obtained, freeing
up the simulator for other work or preventing off air anomalies
interfering with testingnull
Page nullSPIRENnullenullonull
nullalynullng difnullult ennullronmentnull
nullake the problematic signals back to the lab for further analysisnull
GNSS designers recognise that there are many places on earth where
the GNSS signals are disturbed by phenomena such as multipath,
shielding, attenuation, interference or combinations of everythingnull
nullen considering how to tackle such anomalies in the receiver’s
signal processing, the lab environment is much more convenient
than taking all of the tools and development enullipment to the
real sitenullRecording of signals therefore provides a mechanism
for separating the signal environment from the development
one, and providing much better efnulliency at analysing the
problem and providing solutionsnull
Page nullSPIRENnullenullonull
Research
nullnullmproving algorithms
null nullmparing signals from
different parts of the world
null nullonospheric and
sunspot activity
Page nullSPIRENnullenullonull
The GSS6400 Record Playback
System (RPSnullfrom Spirent
nulle GSSnullnull Record Playback System from
Spirent is a simple and efnullient way to capture real
world GNSS signals and replay them in the laboratorynull
Spirent’s GSSnullnull represents the best value and easiest
to use solution on the marketnull nullith the Spirent GSSnullnull
Record Playback System, it’s simple and nullick to record
real GPS signalsnullnullnce captured, the RPS can be used in
the laboratory to replay the captured environment time
and time again to the device under testnullnullou save pronullct
cost while improving product performance and nullalitynull
Page nullSPIRENnullenullonull
nulligh nullidelity nullecord and Playback
nulle GSSnullnull is designed to capture complenullenvironments with the
nullelity to ensure that playback results in the laboratory are truly
representative of captured real world conditionsnullnullualnullit sampling is
renullired in order to adenullately capture the detail of the real signals
over a large enough dynamic rangenullSampling at nullbit provides
inadenullate resolution to fully capture real world signal fades and
dynamics, especially in highnullnterference environmentsnullA nullbit system
loses appronullmately nulltimes as much signal as a dualnullit solutionnull
For most test applications, sampling at bit rates higher than two often
nullst results in huge nulle sinulles and complenull enullensive enullipment
without necessarily improving the useful signal informationnull
nullf you want to test the sensitivity of the GNSS product the whole
signal that the RPS outputs can be attenuated by up to nulldnull
in steps of nulldnull
Page nullSPIRENnullenullonull
nullne box nulla complete and eanull to unull nulllution
nulle GSSnullnull is a selfnullontained unit with everything you need to
start testingnullnullt is the easiest to use solution on the marketnullnullany
other systems renullire peripherals such as personal computers, hard
drives, enullernal power and cablingnullnullith the GSSnullnull it’s simply a
case of connecting the supplied antenna and pressing the one touch
record buttonnull
Page 2nullSPIRENnullenullonull
nullen done, select the renullired nulle from
the two line display and press the play button
and the captured data is replayed at RFnull
nullith a nullnullGnullinternal hard drive up to null hrs of
signal can be recordednullnulln the laboratory, data can
be downloaded using a high speed SAnullA connection,
or nullnulland the unit can be controlled remotely
over the networknull
nulle GSSnullnull is designed for manullmum portability
and is provided with a versatile carrynullandle which also
provides for nullnullble orientation of the unit in the lab
or in the nullldnull
Page 2nullSPIRENnullenullonull
nulle GSSnullnull is designed for manullmnull
nullrtability and is nullovided nullth a versatile
carry-handle nullich also nullovides for nullnullble
orientation of the nullit in the lab or in the field.
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24 hour tenulling
nulle GSSnullnull has other features which allow
you perform tests null hours a day, so you
can optimise the use of the system, or meet
those customer deadlinesnull
nullemote nullntrol
nulle GSSnullnull can be hooked into the nullnternet
as it is identinulld by an null addressnullnullt can then be
controlled remotely through the nullebserver providednull
nullt also has nullnullaccess for remote access direct
to the embedded nullnunullPnull
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nullenull nullutomation
nullt is also possible to write scripts for the embedded
nullnunullPnullthat would automatically control the
output of the RPSnullFor enullmple you
could fully automate a complete
test system that runs different
stored scenarios one after another,
while you record the output
of the system under testnull
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nully not find onull more
abonull the GSSnullnull
Record PlaybacnullSystem
(RPS) from Snullrent, the nullrld
leader in GNSS test solnullions
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