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Application Note: Reduce ‘Real-World’ Drive Testing Times Using Receiver NMEA Data

Using Receiver NMEA Data in a Simulator Test Scenario

Testing a GNSS receiver’s response to dynamic motion and real GNSS signals can be a slow and expensive exercise. Moreover, the usefulness of such a ‘real-world’ test is limited by the impossibility of repeating it under identical conditions.

Download the Application Note and discover the how Spirent RF simulators can use NMEA data to dramatically reduce the time and cost associated with ‘real-world’ drive testing. Topics include:

  • Capturing NMEA data with a GNSS receiver
  • Converting NMEA data to simulated motion
  • The benefits of representative testing vs. exact ‘real -world’ replication

Simply enter a few details opposite to receive the Application Note—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.

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    Using Receiver NMEA Data In a Simulator Test Scenario APPLICATION NOTE Spirent Communications PLC Paignton, Devon, TQ4 7QR, England Webnull nulltpnullnullnullnullpirentnullomnullositioning Telnull null4 nullnull nullnullnull nullanull null4 nullnull nullnullnull Copnullignull nullnullnull Spirentnull nulll Rignulls Reservednull nulll onulltnull compannullnames andnullr brand names andnullr product names renullrred to in tnulls document, in particular, tnull name nullpirentnulland its logo device, are eitnullr registered trademarnull or trademarnull onull Spirent plc and its subsidiaries, pending registration in accordance nulltnullrelevant national lanullnullnulll otnullr registered trademarnull or trademarnull are tnull propertnull onulltnullir respective onullersnull Tnull innullrmation contained in tnulls document is subnullct to cnullnge nulltnullut notice and does not represent a commitment on tnull part onullSpirentnull Tnull innullrmation in tnulls document is believed to be accurate and reliablenull null ever, Spirent assumes no responsibilitnull or liabilitnullnullr annullerrors or inaccuracies tnullt manullappear in tnull documentnull Page 2SPIRENT Application Note Contents nulludience 4 Introduction null RnullSimulation null Tnullical nullS Simulators null nullEnull Data 7 Conclusions null Page 3SPIRENT Application Note Audience Tnulls nullpplication nullote is nullr users onullSpirent simulators nullo are designing, developing, integrating and testing nullSS receivers or snulltems, and need to ensure tnullir products nullll pernullrm in tnull intended applicationnull Spirent recommends nullou nullve a basic understanding onullsatellite navigation principles and Rnullsimulation as a test metnulld and tnull use onullSpirentnulls Simnullnull and SimPLEnullnullsimulator control sonullnullrenull See renullrence nulland null Page 4SPIRENT Application Note Introduction Tnullre is a steadnullgronullnullin tnull use onullnullSS in nenulland enullsting marnulltsnull Consenullentlnull, tnullre is an increasing reliance on nullSS tecnullolognullnull Witnulltnulls in mind, it is important nullr designers, manunullcturers and consumers onulltnullse products to understand nullat to enullect nullom sucnull snulltemsnullTnulls includes nullrmulating an understanding onulltnull limitations and problems onullnullSS tecnullologiesnull Tnulls application note enulllains nullnulltnull use onulla nullSS simulator can drasticallnullreduce test times associated nulltnullpernullrming nullealnullorldnull drive testingnullTanullng a receiver into tnull open, subnullcting it to dnullamic motion nullile navigating nullom real nullSS signals, recording tnull nullEnull data and analnulling tnull results tanulls time, but continual repeating onulltnulls process tanulls signinullantlnulllonger, and in almost all cases places a large burden on tnull associated pronullct time and budgetnull In addition to tnulls, test conditions on subsenullent renulluns can never be nullitnullullnull repeated and onullen provides data onull little use to tnull design optimisation and iteration processnull null test metnulldolognullis described tnullt tanulls a nulle onullrecorded receiver nullEnull data and converts it into a motion tranullctornullnulle allonullng a renullun onulltnull original navigation senullence to be made, nullicnullcan tnulln be repeated enullctlnull, time and againnull It also snullnull nullnullsatellite visibilitnull nullom tnull nullEnullnulls nullnullmessage can be used to control ponuller onulltnull simulated satellites, so replicating tnull signal obscuration enullerienced bnulltnull receiver nullen it logged tnull datanull Page 5SPIRENT Application Note nulligure null RnullSimulation nulllonull RF nullinullnulltion null RnullConstellation Simulator reproduces tnull environment onulla nullSS receiver on a dnullamic platnullrm bnullmodelling tnull venullcle and satellite motion, signal cnullracteristics, atmospnullric and otnullr enullnullcts, so tnullt tnull receiver nullll actuallnull navigate, in tnull lab, according to tnull parameters onulltnull test scenarionull nullnullits vernullnature, simulation is a representation onulltnull real nullrldnull Simulation cannot reproduce tnull nullll ricnulless onullreal nullrld conditionsnull null common misconception is tnull need to enullctlnullreplicate real nullrld conditions nullr a nullSS test to be validnullnullonullever, application onullrepresentative enullnullcts via simulation is proven nullver some null nullears onulltestingnullto enullercise receivers and adenullatelnullidentinull tnullir limitations allonullng nullr design centring and optimisationnullnullore importantlnull, it gives complete repeatabilitnull, control and enullct nullonulledge nulldonull to bit level nullonulltnull signal stimulating tnull receivernull Tnulls is not possible nullen using real nullSS signals nullr test purposesnullWe snulluld loonull upon simulator testing as representing tnull real nullrld, ratnullr tnulln replicating itnull Continued, successnulll deplonullent onullreceiver designs in mannullapplications proves tnullt tnull simulators being used nullr tnullir development and verinullation are accurate in tnullir implementation onulltnull nullSS environmentnull nulligure nullsnullnull tnull concept onullsimulation nullsing a nullSnullnull simulatornull Tnullicanullnullnullnullinullnulltors nulll tnull test metnulldologies discussed in tnulls nullpplication nullote can be pernullrmed using annullonulltnull multinullnullnnel simulators in Spirentnulls range tnullt are controlled bnull Spirentnulls Simnullnull or SimPLEnullnullsonullnullrenull nullor nullrtnullr innullrmation on Spirentnulls range onullSimulators, contact nullour local Spirent representative, or visit nullnullnullpirentnullomnull positioningnull Page nullSPIRENT Application Note NMEA Data Tnull nullational nullarine Electronics nullsociation is a nonnullronull null organisation tnullt nulls developed a specinullation called nullEnullnullnull tnullt denulles tnull internullce betnulleen various pieces onullmarine electronic enullipmentnull Tnull standard permits marine electronics to send innullrmation to computers and to otnullr marine enullipmentnullnullS receiver communication is also denulled in tnulls specinullation and over time nulls been adopted as tnull standard communication protocol nullr all commercial nullS receivers, not nullst ones used in tnull marine sectornull nullnder tnull nullEnullnullnull standard, all cnullracters used are printable nullCII tenull nulllus carriage return and line nullednull nullEnullnullnull data is sent at 4nullnullbaudnull Tnull data is transmitted in tnull nullrm onull nullsentencesnull Eacnullsentence starts nulltnull a nullnull a tnull letter nulltalnullr IDnull a tnulleenulletter nullsentence IDnull nullllonulled bnulla number onull data nulllds separated bnullcommas, and terminated bnullan optional cnullcnullum, and a carriage returnnulline nullednullRenullrence nullgives tnull nullll specinullation onullnullEnull message nullrmats nullr nullSnull Canulluring and using NMEA in a sinullnulltor scenarionull Simnullnull gives nullou tnull abilitnullto construct a motion tranullctornullnullr nullour simulated venullcle using a suite onullcommands tnullt are entered into a nulle in a senullential mannernull Tnullse commands are tnulln enullecuted nullen tnull scenario is run, and tnull simulator dnullamicallnullcnullnges tnull Rnullsignal to represent tnulls motion nulln addition to tnull modelled satellite motionnull Tnulls provides a ponullernulll metnulld onullstimulating tnull receiver under test in a dnullamic nullnullnull Tnull receiver nullll navigate in tnull same nullnull as inullit nullere pnullsicallnullmovingnullTnull dnullamic pernullrmance onulltnull simulator is sucnulltnullt motion can be generated nullr annullsituation nullom a subnullillimetre movement to vernull nullgnulldnullamicsnull Tnullre manullnullnullever be situations nullere nullou mignull nullnt to subnullct nullour receiver to motion tnullt represents a realnullinull tranullctornullnull Tnulls could be a nullurnenullalong a real road, railnullnullline, nullgnull patnull snullpping lane or nullrest nulllnullng trailnullSucnullnullealnull tranullctories are necessarnullin situations nullr enullmple, nullere tnull receiver being tested is reporting its position on an electronic map, and so its navigated tranullctornullmust nullmatcnullnull tnull map databasenullWitnullrecorded nullEnull data, and a simulator nullou can test a receiver under tnullse conditionsnull Page nullSPIRENT Application Note Canulluring NMEA data nullost commercial nullSS receivers nullve tnull abilitnullto record to a nulle, or output nullEnull data describing tnullir navigation statenullnullsing tnullse nullatures nullou can log tnull motion tnullt tnull receiver undernullent and use tnulls innullrmation to create a motion nulle tnullt can be replanulled in a simulator scenarionull Wnulln recording tnull data, it is important to ensure tnullt tnull receiver antenna is located in a position nullere it nulls as good a vienull onulltnull snull as possiblenullTnulls nullll ensure tnull receivernulls navigation is as accurate as is possible, given its local operating environmentnullnullor enullmple, inullnullou are using an innullar receiver nulltnullan enullernal antenna option, it is alnullnull better to use an enullernal antenna mounted on tnull roonull onulltnull venullclenullInulltnull option enullsts, nullou snulluld also set tnull nullEnull message rate o tnull nullstest availablenullnullormallnullnull second, but some receivers nullve a nullgnullr ratenull Section 4nullnull discusses some otnullr considerations regarding tnull nullalitnullonulltnull captured nullEnull datanull nullinullENnulls NMEA data to nulltion conversion utinulltnull Tnulls utilitnullis designed to enable nullou to tanull logged nullEnull data and use tnull Pnull and satellite visibilitnullinnullrmation contained nulltnulln it to renullreate motion and signal ponuller variations in a simulator scenarionullTnull utilitnullenullsts as part onulltnull standard Simnullnull sonullnullre pacnullgenull It can be accessed under tnull nullTools null nulleneral nulltilitiesnull menunull nullternativelnull, it enullsts as a tool nulltnulln SimPRnullESS, nullicnull is a compiled nullTLnull standalone data processing application, also supplied as standard nulltnullSimnullnullnullSimPRnullESS is accessed via tnull nullToolsnull menu in Simnullnullnull nulligure nullsnullnull tnull nullEnull to nullotion conversion utilitnullnullndonullnull Tnull utilitnullconverts nullour receivernulls logged nulle onullnullEnull nullnull messages into a motion nulle nullnullmtnullnullr replanullin SimnullnullnullTnull motion nulle contains motion commands at nullnullms intervalsnull nullso, tnull utilitnullcan generate a command nulle tnullt Simnullnull nullll use to control satellite visibilitnulland receiver ponuller levelnull It uses satellite innullrmation nullom nullEnull nullnull messages to replicate tnull satellite visibilitnullnull nulligure null nullEnull to nullotion Conversion nulltilitnull Page null SPIRENT Application Note Tnull utilitnullis easnullto use bnullpernullrming tnull nullllonullng stepsnull null Enter tnull patnullonulltnull current scenario in tnull nullirectornullnull entrnullbonull null Select tnull location onullnullour recorded nullEnull data nullenull null Specinull tnull desired location nullr tnull converted output nulle nullt is normallnulltnull scenario nulllder, but does not nullve to benull null Inullsatellite visibilitnullcontrol is renullired, ticnulltnull nullnablednull bonulland specinull tnull location nullr tnull generated nullcommandnull nullenull null Clicnulltnull nullunnull button, tnull utilitnull processes tnull data, giving progress innullrmation displanulled to tnull rignull onull tnull nullunnull buttonnull null Wnulln done, nullou can close tnull utilitnullnull In Simnullnull, nullou can nonullselect and enable tnull nulles nullou nullve nullst converted and tnullnullnullll tnulln be used in tnull scenarionull Tnull steps are snullnull belonullnullRenullrence null gives detail on nullnullto use Simnullnullnull Motion Finull nullnulln tnull main nullI page onullSimnullnull, in tnull scenario tree, under nullenullcle nullnullotion, rignullnulllicnullon tnull nullser nullotion nullilenull and clicnullnullselectnull Tnulls brings up tnull nullelect nulle dialognull nullndonullnullInullnullou opted to save tnull converted nulle in tnull current scenario directornull, tnulln it nullll appear at tnull top onulltnull list under nulliles available nullom tnull current scenarionull nullClicnullon tnull nulle, and clicnullnullelectnull nullTnull name onulltnull nulle nullou selected nullnullnull nullmotionnullmtnull nonullappears in tnull scenario tree and nullll be used nullen tnull scenario runsnullSee nulligure null Tnull scenario is nonullsetnullp to run nulltnull motion data nullom tnull converted nullEnull nulle and nulltnulla user actions nulle tnullt nullll cnullnge satellite ponuller levels according to tnull satellite visibilitnulltnullt nulls enullerienced bnull tnull receiver nullicnulllogged tnull nullEnull datanull Tnull nullal action nullou need to tanull is to ensure tnullt tnull satellite constellation being used bnulltnull simulator matcnulls tnull one visible to tnull receiver nullen it recorded tnull nullEnull Inulltnulls is not done, tnulln tnull user action nulle commanding ponuller cnullnges to satellites nullll be meaningless, as it nullll be calling nullr cnullnges to satellites tnullt manullnot be presentnullnullnullonlnullmotion is used, not satellite visibilitnull, tnulls step is not renullirednull Simnullnull allonull nullou to load a nullnull or SEnullnullrmatted almanac nullicnullreplaces tnull internal onenullnullS nullnull and SEnullalmanacs nullr past dates are available via tnull nullnited States Coast nulluard nullavigation Centre atnull nullnullnullavcennullscgnullovnullpsnulllmanacsnulltm nulligure null Simnullnull Scenario nullile Tree Page nullSPIRENT Application Note To load an almanac tnullt corresponds to tnull date on nullicnullnullou recorded nullour nullEnull datanull null Doublenulllicnulltnull nullignal Sources nullenull under nullPS Constellationnull in tnull scenario nulle treenullTnulls brings up tnull Signal Sources nulle nullndonullnull null nullnder nullotionnull in tnull list on tnull lenull, clicnullon nullrbitsnull tnulls brings up tnull orbital data nullr Snullnull null nullt tnull bottom onulltnull nullndonullis a nulload nullnullnull and nulload SEnull buttonnullClicnullon tnull desired button, and enter tnull patnull nullr tnull almanac nulle nullou nullve donullloaded nullom tnull nullebsitenull nullClicnullnullnull null Clicnullnull in tnull Signal Sources nulle nullndonulland enter a name nullnullnullnullnulleenull nullnullnulland clicnullnull nulligure 4 snullnull tnull nullrbits page in tnull Signal Sources nullilenull nullou nonullneed to set tnull start date and time onulltnull scenario to matcnulltnull date and time tnullt tnull nullEnull data nulls recordednull To do tnullsnull null Doublenulllicnullnulltart Timenull at tnull top onull tnull scenario nulle treenullTnull nulltart time and durationnull nullndonullpops up, as snullnull in nulligure null null Enter tnull date and time in tnull appropriate nullldsnullClicnullnullnull Wnulln tnull scenario is started, tnull simulator nullll be simulating signals nullom a constellation tnullt matcnulls tnull one seen bnull tnull receiver nullen it undernullent tnull motion recorded as in tnull nullEnull datanull Including annullobscuration onullponuller level cnullnges enullerienced bnulltnull receiver due to enullernal obstructionsnull nulligure 4 Signal Sources nullrbits Page nulligure null Start Date, Time nullDuration Windonull Page nullSPIRENT Application Note Points to note nulltnullrecorded NMEA Accuracnull Tnull accuracnullonulltnull nullal motion data used in tnull Simnullnull scenario ultimatelnull depends on tnull accuracnullonulltnull Pnull solution calculated bnulltnull receiver nullen it recorded tnull original nullEnull datanullTnull nullEnull to motion conversion utilitnullnullitnullullnull converts tnull data it is given nullincluding annullinnullrent errorsnullTnulls is important nullen testing devices nulltnullnullsnapnullonulloadnull algoritnullsnull Data nulltnulllarge position errors manull, nullen run in a test scenario cause problems nullr a receiver tnullt is supposed to be navigating along a specinull route, but is receiving a signal tnullt manulls it navigate along a dinullnullrent, erroneous tranullctornullnull Sometimes tnulls is benenullial, as tnull error can be deliberatelnullused to test tnull abilitnull onulltnull receivernulls map sonullnullre to remain snapped to tnull route nullile enulleriencing poor navigation accuracnullnullIn annullcase, tnull accuracnullonulltnull nullEnull must be understood, and inullnecessarnull, annullerroneous lines onull data deleted or correctednull Renullication onullreanullnullnull situations Renullreating tnull actual tranullctornulland satellite visibilitnullmanullnulllp to renullreate a realnullinull scenario nullor enullmple, one in nullicnulla receiver enullerienced some problems navigatingnull but it is important to note tnullt being able to renullroduce tnull tranullctornulland satellite obscuration is onlnulla partial representationnullTnull signal environment nullultipatnull atmospnullre and so onnullis not recorded in tnull nullEnull datanullTnullrenullre, it is not sanull to assume tnull problem can be replicated using tnulls metnulld alonenullTnulls is anotnullr enullmple onullnullnullattempting enullct replication onullreal conditions must be done nulltnullcautionnull Representation is vernullonullen better tnulln replication nullr test purposes, as it allonull control and repeatabilitnullonullenullnullcts to meet test obnullctivesnull Page nullSPIRENT Application Note Concnullsions We nullve seen tnullt it manull, in some instances, be desirable to replicate in a simulator scenario, a real motion tranullctornullas travelled bnulla receivernull Tnulls application note nulls snullnull nullnull to tanull tnull Pnull and satellite visibilitnull innullrmation nullom receivernullogged nullEnull data and convert it into a motion nulle and user actions commandnullle respectivelnull, using tnull supplied utilitnullnulltnulln Simnullnull and use it in a simulator scenarionull It nulls also enulllained some onulltnull limitations onulltnulls approacnullnullere replication onullerroneous events is desired, and nullnullcontrolled and representative testing is usuallnull a nullr more benenullial metnulld tnulln enullct replication onulltnull real nullrldnull Renullrenced Docunullnts null Tnull nullEnull nullnull Internullce Standard nullersion nullnull nullational nullarine Electronics nullsociationnull null Dnullnullnullnullnull latest Issue Simnullnull Sonullnullre nullser nullanual nullpirent Documentnull null Dnullnullnullnullnull latest issue SimPLEnullnull Sonullnullre nullser nullanual nullpirent Documentnull Page nullSPIRENT Application Note nullnullssarnullonullTernull nullSS nulllobal nullavigation Satellite Snulltem nullI nullrapnullcal nullser internullce nullEnull nullational nullarine Electronics nullsociation Pnull Position nullelocitnulland Time solution nullom a nullS receiver Scenario In tnulls contenull, a nullSS simulation running on eitnullr Simnullnull or SimPLEnullsimulator control sonullnullrenull SEnull Snulltems Enullnullctiveness nullodel nullS satellite almanac Snull nullS Satellite nullenullcle nullnull nullS nullmanac nullamed anuller tnull tonull onullnulluma, nullinullona nullere earlnull receiver tests nullere carried out in null77null Page nullSPIRENT Application Note CONTACT Unull nullot a snullrtnullonenull If you have a smartphone download a QR Code reader and then point your phone camera at the QR Code to read the graphic. nullnullrent Conullunications null4 nullnull nullnullnull globalsalesnullpirentnullom nullnullnullpirentnullomnullositioning nullnullrent Federanullnullnulltenull null 7null nullnullnullnull innullnullpirentnullderalnullom nullnullnullpirentnullderalnullom nullaceboonull LinnulldIn Tnulltter Tecnullorati nulloogle nullunull Digg Delicious Reddit Stumbleupon nullnullnot snullre tnulls docunullntnull Dnullnull7 ISSnull nullnull RevnullnullnullSept nullnull nulle are adding nenullcontent to our nullenullite on a regunullr nullsisnull nullonullarnulltnulls nullnnull nullnullnullpirentnullomnullositioning nullisit tnull nullnullrent nullnull nullognulltnullre are currentnull over null nullsts nulltnull2 to 3 nenullnullsts added eacnullnulleenull Catcnullunullon nullatnulls nenullnull nullnullnullpirentnullomnulllognullositioningnullspnull Need nullre innullrnulltionnull gnssnullolutionsnullpirentnullom