Phonak Insight. Roger - The new wireless technology standard

Phonak Insight

Roger

The new wireless technology standard

Roger is a new wireless technology standard. Based on Roger, platforms and products will emerge over the coming years. This

brochure describes the details of, and the reasoning behind, the Roger technology. Roger allows for low-delay and reliable

broadband audio broadcast towards miniature low-power receivers, that can be connected to hearing instruments or cochlear

implant sound processors, as well as towards soundeld loudspeakers. Roger is much more than a simple digital radio system.

Sophisticated adaptive algorithms at dierent levels in the Roger architecture give Roger a performance level which was not

previously considered physically possible. At the same time, automatic features and simple pairing concepts make management

and use of Roger systems very easy.

• Isitpossibletolowerthenoisefloorandtoenhancethe

system’sdynamicrangeintheaudiodomain?

• Isitpossibletoaltogetheravoiddeadspotsinaroomwhere

thewirelessmicrophonedoesnotreachareceiver?

• Isitpossibleforthenewstandardtoavoidinterferencefrom

similarnearbysystemsorfromanyotherappliancessuchas

WiFi(2.4GHz)networks,tubelighting(lowfrequencyinductive

interferences),Bluetoothdevices(2.4GHz),differentgenera-

tionsofGSMnetworks(800to900MHz)orfromsunlight(as

oftenisthecasewithinfraredsystems)?

• Isitpossibletocreateastandardthatcanbothsendand

receive?

• Isitpossibletosendcontroldatainparalleltotheaudio

stream?

• Isitpossibletocreateonetechnologystandardfortheentire

world,whichallowsusersthefreedomtotravelandusetheir

systemseverywhere,withouthavingtochangechannels,and

whichcanbeservicedeverywhere?

Thechoiceoftransmissiontechnologyinthedevelopmentofanew

wirelessstandardhasatremendousimpactonseveralimportant

featuresofthefinalplatformsandproducts.Itwasthefollowing

listofquestionsthatsteeredPhonaktodevelopanewwireless

technologystandardfromscratchandnottopicksomethingofthe

shelf.

• Isitpossibletogosignificantlybeyondtheperformanceofthe

besttechnologyavailabletoday,intermsofspeechrecognition

innoise,overdistanceandinreverberation?

• Isitpossibletoreduceset-upcomplexity,managementand

usageofwirelesssystemsforlistenerswithhearingloss?

• Isitpossibletodevelopanewtechnologystandardthatdoes

notforceschoolstowriteoffinvestmentsofthepastbutlets

themtransitiongraduallytothenewstandard?

• Isitpossibletodevelopanewstandardthatoffersfulland

seamlesscompatibilitywithotherbrandsofhearinginstru-

ments,withallbrandsofcochlearimplants,withsolutionsfor

listenerswithnormalhearing,andwithsoundfieldsystems?

• Isitpossibletoenlargetheaudiobandwidthandkeepthe

end-to-endaudiodelayofthenewstandardwithinacceptable

limits?

Reasons for the new standard

2 PhonakInsight|Roger–thenewwirelesstechnologystandard

Forexistingtechnologieswecouldonlygivepositiveanswerstojust

afewofthesequestions,butnoexistingtechnologiescouldprovide

satisfyinganswerstoallofthem,especiallynottothefirstfour

questionsofthislonglist.Themostimportantquestion–Canwe

furtherimprovespeechunderstandinginnoise?–definitelyrequired

Rogerisanadaptivedigitalwirelesstransmissiontechnologyrun-

ningonthe2.4GHzband.Audiosignalsaredigitizedandpackaged

inveryshort(160μs)digitalburstsofcodes(packets)andbroadcast

severaltimes,eachatdifferentchannelsbetween2.4000and

2.4835GHz.Frequencyhoppingbetweenchannels,incombination

withrepeatedbroadcast,avoidsinterferenceissues.End-to-end

audiodelayiswellbelow25ms,andRogersystemsaretap-proof.

ThefrequencyhoppingRogeremploysisadaptive,whichmeans

onlyfreechannelsareused.Rogerreceiversregularlytalkbackto

thetransmittingwirelessmicrophones,informingthesystemabout

whichchannelsaresteadilyoccupied(byanyothernearbysystem

operatingat2.4GHz,likeaWiFinetwork)andwhichchannelsare

free.TheRogerwirelessmicrophonethenautomatically‘hops’

aroundtheseoccupiedchannels.TheRogerwirelessmicrophones

canalsosensethepresenceofaWiFinetwork,andrespondtothis

accordingly.

Simulationcalculationsforaworst-casescenariowithoneRoger

systeminstackedblocksof8x8x2metersrevealedthatnoself-

interferencewilloccur.Inotherwords,thereisnolimittothe

numberofRogersystemsthatcanbeusedinonebuilding.

If,despiteallefforts,aRogeraudiopacketisnotreceivedcorrectly,

intelligentpacketlossconcealmentalgorithmsonthereceiver

side‘fillintheblanks’toensuresuperbsoundqualityandlistening

comfort.

Incomparison,withBluetooththerepetitionofpacketbroadcastis

onlyondemandofthereceiver,orevenwithoutrepetitionwiththe

SCOprotocol(usedinthefirstheadsets).Ifacknowledgementofa

packet’sreceptiondoesnotarriveattheBluetoothtransmitter,the

packetisbroadcastagain.ThismeansthatBluetoothreceiversare

quasi-continuouslytransmittingbacktothetransmitter,which

significantlyincreasespowerconsumptionattheBluetoothreceiver.

WithBluetooththemaximumnumberofreceivers

isalsolimitedtothree,whichmeansthatevenjusttwolisteners

withbinauralear-levelBluetoothreceiverscannotlistentooneand

thesameBluetoothstream,letalonelargergroups.IntheBluetooth

headsetprotocoltheaudiodelayisstillacceptable(10to15ms),

buttheaudiobandwidthisoftenlimited(upto4kHz),unlessone

usesthe‘widebandspeech’featureofthehands-freeprofileversion

1.6,whichcangoupto7kHz.IntheBluetoothAudioStreaming

protocol,A2DP,thebandwidthincreasesto20kHz,buttheaudio

delayofwellover100mspreventsitfrombeingsuitableforlive

face-to-facecommunication.OnlywithspecialBluetoothchipson

bothendscanthisdelaybereduced,toaround40ms.Additionally,

theA2DPBluetoothprotocolallowsforjustonereceiver,andthe

anewapproach.ThisinspiredPhonaktodevelopanewstandard,

withtheambitionofmakingzerocompromises.Ittookmany

yearsandalargegroupofaudiologistsandengineersworkingin

micro-electronics,software,acoustics,radiofrequency,protocols

andmechanicaldesigntodevelopthenewstandard:Roger.

powerconsumptionatthatreceiverisevenhigherthaninthehead-

setprotocol.

Rogersystemsbroadcastaudiopacketsatdifferentchannelswithin

the2.4GHzband(between2.4000and2.4385GHz),whichmeans

differentcarrierwavelengthsareselected.Areceivercanreceive

suchpacketsdirectlyvialineofsight,butalsothroughadifferent

pathwhentheelectromagneticradiowavesarereflectedfromthe

walls,thefloorortheceiling.Thedifferentlengthsofthedifferent

signalpathscanenhanceorreducetheelectromagneticfield’s

strengthatthepositionofthereceivingantenna,dependingonthe

phaseandamplitudedifferencesofthedifferentwaves.Thisinter-

ferencebehaviorisdependentonthewavelength.Randomly

selectingthedifferentchannelsatwhichanaudiopacketisbroad-

castsomewhatreducesthelikelihoodthatallwaveswillcancel

eachotheroutatthereceivingantennabymultipathfadingifmore

thanonereceivingantennaisused.Inotherwords,ifoneofthe

antennasissufferingfrommultipathfading(receivingsignalsthat

canceleachother),thereisahighprobabilitythattheotherantenna

willnotsufferfrommultipathfading.

Insummary,themitigationofinterferenceisachievedbytime

diversity(broadcastingaudiopacketsseveraltimesafterone

another),byfrequencydiversity(broadcastingaudiopacketsat

differentcarrierwavelengths,enhancingthechancethatifone

Digital adaptive wireless at 2.4GHz

Figure 1

Byhoppingfrequenciesandrepeatedbroadcastofaudiopackets,mutual

interferencecanbeminimized.

Time [ms]

Frequency [MHz]

3PhonakInsight|Roger–thenewwirelesstechnologystandard

packetiscanceledatarrival,anotherpacketisnotcanceled),and,in

thecaseofRogerDynamicSoundField,alsobyspacediversity(em-

ploymentoftworeceivingantennasseparatedinspace,optimizing

reception).(SeeFigure2).

Rogeroffersafullaudiofrequencybandwidth,from200Hzto

7300Hz.Thesystem’sinternalsignal-to-noiseratioisaround55dB.

WithRogernolineofsightisrequiredasitiswithmanyinfrared

systems,andinterferencefromsunlightorotherstronglightsources

cannotoccur.

WithRogeritisnotonlypossibletotransmitanaudiosignal,but

alsototransmitandreceivecontroldata,forinstancesuchasis

requiredwhensettingupand/ormaintainingaMultiTalkerNetwork

andtocontinuouslymonitorvariousnetworkcomponentstoensure

properoperation.

Electromagneticwavesat2.4GHzhaveawavelengthofabout

12.5cm.Thisallowsforthedesignofnew,smallwirelessmicro-

phoneswithshort,built-inantennas.At800MHzthewavelength

is37.5cmandat200MHz(inthetraditionalFMfrequencyrange)

thewavelengthis1.5m,whichrequiresforinstancetheexternal

microphonecabletobetheradioantenna.

Forminiaturizedear-levelreceiversPhonakdevelopedaRogerchip

(seeFigure3),asnoexistingintegratedcircuitcouldfulfillthe

demands.TheRogerchipcontains6.8milliontransistors(aPentium

ProProcessorbycomparisonhas5.5million).Analoganddigital

blocksaresituatednexttoRAM,ROM,EEPROMandFlashmemory

blocksonaminisculechip.

Rogerwirelessmicrophonescontinuallyestimatetheambientnoise

levelwiththehighestprecision.Thesemeasurementsinturncontrol

thegainofRogerreceivers.Inparallelwiththebroadbandaudio

signal,controlbitsaresenttoRogerreceiverstoadaptivelyadjust

thegaintosuittheacousticalenvironmentinwhichtheRoger

systemisbeingused.Therangeofadaptationislargerthanin

DynamicFM.Thisadvanceddynamicbehaviorhasledtosignificant

improvementsinspeechrecognitioninnoise,especiallyathigher

noiselevelsofupto80dB(A)(noiselevelsthatarequitecommonin

dailylife,especiallyinpublicplacesandintheworkplace).Related

studyresults–byprofessorLindaThibodeau,PhD,andDr.Jace

Wolfe,PhD–aresummarizedintwoPhonakFieldStudyNews

editions:‘RogerforHearingInstruments’and‘RogerforCochlear

Implants’.Figure4showsthemainfindingsofDr.Thibodeau’sstudy.

The Roger chip

Performance in noise

Figure 3

TheRogermicrochip.

Figure 2

Mitigationofinterferencebytime,frequencyandspacediversity.

Frequency diversity

Spatial

diversity

Time diversity

Figure 4

HINTpercentcorrectscoresfortotalwordscorrectasafunctionofnoiselevelfor

traditionalFM,DynamicFMandRoger.Distancebetweenloudspeakergenerating

speechandlistenerwas5.5m.N=11.Atthe80dB(A)noiselevel9participants

scored<10%fortraditionalFM,6scored<10%forDynamicFM,andonly1scored

<10%forRoger.

Ambient noise level (dB(A)

Percent Words Correct (HINT)

100

0 50Quiet 807570656055

Traditional FM Dynamic FM Roger

Nexttothisinnovativedynamicbehavior,Rogeralsousesanew

advancedalgorithmforthebeamformingofthewirelessmicro-

phone.Thisbeamformeriscapableofsuppressingnoisefromthe

leftandrightsidessimultaneously,withoutintroducingin-acceptable

distortionoroverallfrequencyresponsechanges.Forwireless

microphonesinhigh-noisesurroundings,thisbeamformersignifi-

cantlyimprovesthesignal-to-noiseratioatthesource,enhancing

intelligibilityforthelistener.

PhonakInsight|Roger–thenewwirelesstechnologystandard4

Oneofthebarrierstotheuptakeofwirelesstechnologyhasbeen

itscomplexityorperceivedcomplexity.Themanagementofwireless

solutionsintheschoolenvironment–withspecialfittingsoftware

requiredtoallocateandprogrammicrophoneandreceiverchannels

–hasalsobeenaburden.WithRoger,frequencyplanningandpro-

grammingisnolongerrequired.Networkbuildingisquick,simple

andveryuser-friendly.ThepairingofaRogerinspirowithaRoger

DynamicSoundFieldloudspeakerisequallysimple;justonepressof

abutton,andoncepairedthetwocomponentsstaypaired(including

afterswitchoff).

TheinspiroandDynaMicwirelessschoolmicrophonesarecapable

oftransmittingbothDynamicFMradiowavestoDynamicFM

receivers,andRogerwavestoRogerreceiversandRogerDynamic

SoundField.Thisdualtransmissionmodeallowsschoolstogradu-

allyphaseoutDynamicFMreceiversandphaseinRogerreceivers.

(Note:theinspiroinquestionmustbeinspiroPremium(firmware

version3.0orlater).Thesamefirmwareversionsarerequiredfor

theDynaMic.)Afirmwareupgradeto4.0willgivethesewireless

microphonesdualtransmissionmodecapabilities.Thesameistrue

fortheinspiroAudioHub.

PowerconsumptioniswellwithinreasonablelimitsbothforRoger

wirelessmicrophonesandforRogerreceivers.Afullycharged

schoolRogerwirelessmicrophonebatterywilllast7to8hours

whenoperatingindualtransmissionmode;easilylongenoughto

coverafullschoolday.

Rogerminiaturizedear-levelreceiversinactivemodeconsume

around3mA.Thiscannormallybesuppliedbyahearinginstru-

mentbatterywithoutproblems.

As2.4GHzisafreelyaccessiblebandworldwide(aso-calledISM

band:Industry,ScienceandMedical),nolicenseisnecessary.This

meansusersofRogersystemscanenjoythefreedomtotraveland

usetheirsystemsaroundtheworld.ServicingRogersystemswhile

travelingisalsosimplifiedasthestandardisthesameinevery

country.

Ease of management and use of Roger

Dual transmission mode

Power consumption

Freedom to travel