SIST EN 301 391 V1.1.1:2003

• Abstract:

  This EN covers both the basic radio parameters and the protocols to be used with low power devices sending short packets of data, e.g. consumer electronic equipment.

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.060.99 - Other equipment for radiocommunications
• ICS: 33.100.01 - Electromagnetic compatibility in general
• Technical Committee: SS EIT - Technical Board for the electrotechnical, information technology and telecommunications fields
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Dec-2003
• Due Date: 01-Dec-2003
• Completion Date: 01-Dec-2003
• Ref Project: ETSI EN 301 391 V1.1.1 (2000-01) - ElectroMagnetic Compatibility and Radio Spectrum Matters (ERM); Data communications using short range devices; Access protocol, occupation rules and corresponding technical characteristics for the transmission of data

SIST EN 301 391 V1.1.1:2003 is the SIST adoption of the ETSI European standard for electromagnetic compatibility and radio spectrum matters in short range data communications. It specifies the access protocol, occupation rules, and related technical characteristics for low power devices that send short packets of data. The document is aimed at equipment designers, test labs, and compliance teams that need shared RF channel access to work in a predictable way.

What does SIST EN 301 391 V1.1.1:2003 specify?

SIST EN 301 391 V1.1.1:2003 covers radio channel access for Short Range Devices that share a single-frequency channel and transmit small, short-duration data packets. It gives the access rules and the essential parameters needed to use the protocol in practice.

The standard does not set the bit rate, data format, or modulation scheme. It is also not intended for continuous, unbroken data transmission, so it fits bursty control and limited data transfer rather than streaming links.

Annex	What it covers
Annex A	Radiated measurement arrangements and guidance for test sites, antennas, site preparation, and coupling methods

The document is organized into clauses for references, definitions, general requirements, equipment characteristics, protocol description, measurement methods and limits, timing examples, and measurement uncertainty, followed by the normative radiated-measurement annex.

What are the key requirements of SIST EN 301 391 V1.1.1:2003?

Channel access behavior

SIST EN 301 391 V1.1.1:2003 requires devices to sense the RF channel before transmitting and to use the protocol every time they access the channel. The channel may be occupied only if the sensing rules are satisfied, and replies are counted as part of that occupation time.

In practice, this means a product must not grab the channel immediately on demand. It must first verify that the channel has been free for the required observation time, which helps reduce collisions between competing devices.

The protocol is based on Carrier Sense Multiple Access (CSMA) with a pseudorandom delay. The observation time is built from a fixed part, a priority part, and a pseudorandom part, so shorter messages can be given faster access.

Timing and priority limits

SIST EN 301 391 V1.1.1:2003 limits the total channel access duration, including any reply, and also limits the reply carrier delay, the carrier sense delay, the channel accessing carrier attack time, and the antiblocking waiting time. It also requires carrier sensing to be checked at intervals no greater than 250 µs during the observation time.

This matters because implementers must control firmware timing, not just radio power. The message length categories in Clause 6.6 affect the priority delay, so the packet size chosen by the application changes access behavior.

The standard also links duty-cycle handling to the category 3 duty-cycle rules in CEPT/ERC Recommendation 70-03. It further notes an optional antiblocking mechanism so a device can recover when interference makes the channel appear permanently busy.

Conformity and testing

SIST EN 301 391 V1.1.1:2003 ties conformity to both declarations and measurements. The manufacturer must provide a signed declaration, and accredited testing covers channel access duration, reply carrier delay, antiblocking, carrier sense threshold, carrier sense delay, observation time, and channel accessing carrier attack time.

For labs and buyers, this means compliance is not just a paper check. The test setup, test points, fixtures, and operating modes must be suitable for measurement, and the reported uncertainty must fit the standard’s timing uncertainty limit.

What terms does SIST EN 301 391 V1.1.1:2003 define?

• Acknowledgement (ACK) - A reply that confirms reception.
• Negative Acknowledgement (NACK) - A reply that rejects reception or requests another attempt.
• Equipment Under Test (EUT) - The device being measured in the test setup.
• Carrier Sense Multiple Access (CSMA) - A channel-access method where transmission starts only after the channel appears free.
• Observation time - The time window used to decide whether the channel has been continuously free before access.
• Reply carrier delay - The gap between the end of one transmission and the start of an ACK, NACK, or other reply.
• Channel access duration - The full time the channel is occupied by one access attempt, including any replies.

Who uses SIST EN 301 391 V1.1.1:2003?

SIST EN 301 391 V1.1.1:2003 is used by manufacturers of short range radio equipment, especially devices for domestic and industrial data links. Test laboratories use it to measure access timing and carrier-sense behavior, while compliance and quality teams use it to check that products follow the required protocol. It is relevant wherever low power devices share a common RF channel and send short data bursts.

Which standards are used with SIST EN 301 391 V1.1.1:2003?

• EN 300 220-1 - Provides technical characteristics and test methods for short range devices in the 25 MHz to 1000 MHz range.
• EN 300 330 - Covers short range devices and inductive loop systems in the lower-frequency bands listed in the document.
• I-ETS 300 440 - Gives technical characteristics and test methods for short range devices in the 1 GHz to 25 GHz range.
• ETS 300 113 - Supports the carrier attack time measurement method used for this standard.
• ETR 273-2, ETR 273-3, ETR 273-4 - Support verification of anechoic chambers, anechoic chambers with a ground plane, and open area test sites.
• CEPT/ERC Recommendation 70-03 - Supplies the SRD usage framework and the duty-cycle category referenced by the protocol.
• IEC Publication 60489-3 - Supports the acoustic-coupler calibration used in Annex A.

What does the SIST EN 301 391 V1.1.1:2003 document contain?

The document contains the protocol description, the message-priority rules, and the measurement methods and limits that laboratories use for compliance testing. It also includes timing figures that illustrate half-duplex access, analogue control traffic, and maximum throughput behavior.

Annex A gives radiated measurement guidance for anechoic chambers, chambers with a conductive ground plane, and open area test sites. It also covers test antenna use, substitution antenna use, measuring antenna use, site preparation, and acoustic coupling for speech and analogue signal tests.

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.ElectroMagnetic Compatibility and Radio Spectrum Matters (ERM); Data communications using short range devices; Access protocol, occupation rules and corresponding technical characteristics for the transmission of data33.100.01Elektromagnetna združljivost na splošnoElectromagnetic compatibility in general33.060.99Druga oprema za radijske komunikacijeOther equipment for radiocommunicationsICS:Ta slovenski standard je istoveten z:EN 301 391 Version 1.1.1SIST EN 301 391 V1.1.1:2003en01-december-2003SIST EN 301 391 V1.1.1:2003SLOVENSKI
STANDARD
ETSIEN301391V1.1.1(2000-01)EuropeanStandard(Telecommunicationsseries)ElectromagneticcompatibilityandRadiospectrumMatters(ERM);Datacommunicationsusingshortrangedevices;Accessprotocol,occupationrulesandcorrespondingtechnicalcharacteristicsforthetransmissionofdataSIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)2ReferenceDEN/ERM-RP02-034Keywordsaccess,data,mobile,protocol,radioETSIPostaladdressF-06921SophiaAntipolisCedex-FRANCEOfficeaddress650RoutedesLucioles-SophiaAntipolisValbonne-FRANCETel.:[phone]Fax:[phone]SiretN°34862356200017-NAF742CAssociationàbutnonlucratifenregistréeàlaSous-PréfecturedeGrasse(06)N°7803/[e-mail]ETSIdeliverablecanbedownloadedfromhttp://www.etsi.orgIfyoufinderrorsinthepresentdocument,sendyourcommentto:[e-mail]Ideliverablemaybemadeavailableinmorethanoneelectronicversionorinprint.Inanycaseofexistingorperceiveddifferenceincontentsbetweensuchversions,thereferenceversionisthePortableDocumentFormat(PDF).Incaseofdispute,thereferenceshallbetheprintingonETSIprintersofthePDFversionkeptonaspecificnetworkdrivewithinETSISecretariat.CopyrightNotificationNopartmaybereproducedexceptasauthorizedbywrittenpermission.Thecopyrightandtheforegoingrestrictionextendtoreproductioninallmedia.©EuropeanTelecommunicationsStandardsInstitute2000.Allrightsreserved.SIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)3ContentsIntellectualPropertyRights.5Foreword.5Introduction.51Scope.62References.63Definitions,symbolsandabbreviations.73.1Definitions.73.2Symbols.73.3Abbreviations.84General.84.1Applicationsusingthisprotocol.84.2Conformitytothepresentdocument.84.2.1Declarationofconformity.84.2.2Measurementstobeperformed.94.2.3Interpretationofthemeasurementresults.95Technicalcharacteristicsoftheequipment.96Descriptionoftheaccessprotocol.96.1Channelaccessduration.96.2Principles.106.3Procedure.106.4Carriersensing.106.5Observationtime.116.6Messageprioritydelay.116.7DutyCycle.116.8Antiblocking.117Methodsofmeasurementandlimits.127.1Channelaccessduration.127.1.1Definition.127.1.2Methodofmeasurement.127.1.2.1Asingletransmitteraccessingthechannel.127.1.2.2Morethanonetransmitteraccessingthechannel.137.1.3Limit.137.2Replycarrierdelay.137.2.1Definition.137.2.2Methodofmeasurement.137.2.3Limit.137.3Antiblocking.137.3.1Definition.137.3.2Methodofmeasurement.147.3.3Limit.147.4Carriersensethreshold.147.4.1Definition.147.4.2Methodofmeasurement.147.4.3Limit.157.5Carriersensedelay.157.5.1Definition.157.5.2Methodofmeasurement.167.5.3Limit.167.6Observationtime.167.6.1Definition.16SIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)47.6.2Methodofmeasurement.167.6.3Limit.177.7Channelaccessingcarrierattacktime.177.7.1Definition.177.7.2Methodofmeasurement.187.7.3Limit.188Examplesofchannelaccesstiming.199Measurementuncertainty.20AnnexA(normative):Radiatedmeasurement.21A.1Testsitesandgeneralarrangementsformeasurementsinvolvingtheuseofradiatedfields.21A.1.1Anechoicchamber.21A.1.2Anechoicchamberwithaconductivegroundplane.22A.1.3OATS.23A.1.4Testantenna.24A.1.5Substitutionantenna.25A.1.6Measuringantenna.25A.2Guidanceontheuseofradiationtestsites.25A.2.1Verificationofthetestsite.25A.2.2PreparationoftheEUT.25A.2.3PowersuppliestotheEUT.25A.2.4Volumecontrolsettingforanaloguespeechtests.26A.2.5Rangelength.26A.2.6Sitepreparation.26A.3Couplingofsignals.27A.3.1General.27A.3.2DataSignals.27A.3.3Speechandanaloguesignals.27A.3.3.1Acousticcouplerdescription.28A.3.3.2Calibration.28Bibliography.29History.30SIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)5IntellectualPropertyRightsIPRsessentialorpotentiallyessentialtothepresentdocumentmayhavebeendeclaredtoETSI.TheinformationpertainingtotheseessentialIPRs,ifany,ispubliclyavailableforETSImembersandnon-members,andcanbefoundinSR000314:"IntellectualPropertyRights(IPRs);Essential,orpotentiallyEssential,IPRsnotifiedtoETSIinrespectofETSIstandards",whichisavailablefromtheETSISecretariat.LatestupdatesareavailableontheETSIWebserver(http://www.etsi.org/ipr).PursuanttotheETSIIPRPolicy,noinvestigation,includingIPRsearches,hasbeencarriedoutbyETSI.NoguaranteecanbegivenastotheexistenceofotherIPRsnotreferencedinSR000314(ortheupdatesontheETSIWebserver)whichare,ormaybe,ormaybecome,essentialtothepresentdocument.ForewordThisEuropeanStandard(Telecommunicationsseries)hasbeenproducedbyETSITechnicalCommitteeElectromagneticcompatibilityandRadiospectrumMatters(ERM).AnnexAisnormativeandprovidesadditionalinformationconcerningmeasurements.NationaltranspositiondatesDateofadoptionofthisEN:31December1999DateoflatestannouncementofthisEN(doa):31March2000DateoflatestpublicationofnewNationalStandardorendorsementofthisEN(dop/e):30September2000DateofwithdrawalofanyconflictingNationalStandard(dow):30September2000IntroductionThepresentdocumentspecifiesanaccessprotocolintendedtobeusedinequipmentemployingshortrange(radio)devicesforthecordlesstransferofsmalldatapackets.Itisintendedthattheimplementationofthisprotocolissufficientlysimpletosuitthelowcostsnecessaryforsomeproducts.Thepresentdocumentreliesonallequipmentonasharedchannelusingthisprotocol.Theprotocolallowsefficientchannelsharinginhighdatatrafficsituations,andhasbeendevisedtoprovideanequitablesharebetweenallusersofthechannel.Thepresentdocumentonlyappliestoapplicationsthatrequireinfrequentburstsofsmalldatapacketsforthepurposeofcontrolandlimiteddatatransferi.e.notcontinuousunbrokendatatransmission.Thisprotocolreliesontherebeingalimitedradiatedpowerandthereforealimitedrange,thusrestrictingtheoverlapoflocalusers(cellsize)toalevelwheretheprotocolcancopebytimesharingbetweenthem.Datacollisionisminimizedinthisprotocolbyusingcarriersensemultipleaccess(CSMA)whichrequiresthattheradiochannelissilentbeforestartinganytransmission.Arbitrationbetweencompetingusersisachievedbyusingapseudorandomlengthdelayperiodbeforetransmitting.Amechanismforprioritizingmessages,basedonmessagelength,isalsoprovidedaspartofthearbitrationprocess.SIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)61ScopeThepresentdocumentcoversaradiochannelaccessprotocolandprovidesalltheparametersthatareessentialforitsuse.ThepresentdocumenthasbeendesignedtobeusedwithShortRangeDevicessharingacommon,singlefrequency,radiochannelandtransmittingsmall(shortduration)datapackets.StandardsEN300220-1[1],EN300330[2]andI-ETS300440[3]providetechnicalcharacteristicsforshortrangedeviceequipment.Theseproductswillbeco-existingonthesameradiospectrum.Thepresentdocumentspecifiestheaccessprotocolandtheoccupationrulesfordatacommunicationsonaradiochannelsharedbydifferentusers.Thepresentdocumentdoesnotspecifyorimposeanyrestrictiononthebitrate,dataformatormodulationscheme.Thisaccessprotocolisnotintendedforapplicationsrequiringcontinuous(unbroken)datatransmission.2ReferencesThefollowingdocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthepresentdocument.•Referencesareeitherspecific(identifiedbydateofpublication,editionnumber,versionnumber,etc.)ornon-specific.•Foraspecificreference,subsequentrevisionsdonotapply.•Foranon-specificreference,thelatestversionapplies.•Anon-specificreferencetoanETSshallalsobetakentorefertolaterversionspublishedasanENwiththesamenumber.[1]EN300220-1(V1.2):"ElectromagneticcompatibilityandRadiospectrumMatters(ERM);Shortrangedevices;Technicalcharacteristicsandtestmethodsforradioequipmenttobeusedinthe25MHzto1000MHzfrequencyrangewithpowerlevelsrangingupto500mW;Part1:Parametersintendedforregulatorypurposes".[2]EN300330:"ElectromagneticcompatibilityandRadiospectrumMatters(ERM);ShortRangeDevices(SRD);Technicalcharacteristicsandtestmethodsforradioequipmentinthefrequencyrange9kHzto25MHzandinductiveloopsystemsinthefrequencyrange9kHzto30MHz".[3]I-ETS300440:"RadioEquipmentandSystems(RES);ShortRangeDevices(SRDs);Technicalcharacteristicsandtestmethodsforradioequipmenttobeusedinthe1GHzto25GHzfrequencyrange".[4]ETS300113:"RadioEquipmentandSystems(RES);Landmobileservice;Technicalcharacteristicsandtestconditionsforradioequipmentintendedforthetransmissionofdata(andspeech)andhavinganantennaconnector".[5]ETR273-2:"ElectromagneticcompatibilityandRadiospectrumMatters(ERM);Improvementofradiatedmethodsofmeasurement(usingtestsites)andevaluationofthecorrespondingmeasurementuncertainties;Part2:Anechoicchamber".[6]ETR273-3:"ElectromagneticcompatibilityandRadiospectrumMatters(ERM);Improvementofradiatedmethodsofmeasurement(usingtestsites)andevaluationofthecorrespondingmeasurementuncertainties;Part3:Anechoicchamberwithagroundplane".[7]ETR273-4:"ElectromagneticcompatibilityandRadiospectrumMatters(ERM);Improvementofradiatedmethodsofmeasurement(usingtestsites)andevaluationofthecorrespondingmeasurementuncertainties;Part4:Openareatestsite".SIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)7[8]CEPT/ERCRecommendation70-03:"RelatingtotheuseofShortRangeDevices(SRD)".IncludingAppendicesandAnnexes.[9]IECPublication60489-3:"Methodsofmeasurementforradioequipmentusedinthemobileservices.Part3:ReceiversforA3EorF3Eemissions".3Definitions,symbolsandabbreviations3.1DefinitionsForthepurposesofthepresentdocument,thefollowingtermsanddefinitionsapply:attacktime:timetakenbetweenestablishingthatthechannelcanbeaccessedtotheactualinstantofaccess.Thedetaileddefinitionisgiveninsubclause7.7observationtime:definitionisgiveninsubclause6.5bit:binarydigitdatapacket:smallestquantityofdatasentovertheradiochannelinoneaccessperiod.Anumberofusefulbitsarealwayssenttogetherwithcorrespondingredundancybitsinanygivenpacket.Anacknowledgereply,ifused,isalsoincludedinthepacketmessage:userdatatobetransferredinoneormorepacketsinasessionmessagelength:timetakentotransmitamessage;thesumofthecarrierontimeofallthedatapacketsusedandthecarrieroff(silence)timesofallthedatapacketsusedreply:transmissionbyadeviceinanswertothe"initiatingtransmitter".Thisreplycanbeanacknowledge("ACK")oranegativeacknowledge("NACK")and/oralongerpacketofuseful/requestedinformationreplycarrierdelay:timeperiodbetweenendofatransmissionandstartofanacknowledge/replysilence:conditionofnodetectedcarrierenergyintheradiochannelinquestiontransmission(physical):onepackettransmittedbetweencarrieronandfinalcarrieroffofaparticulartransmitter3.2SymbolsForthepurposesofthepresentdocument,thefollowingsymbolsapply:dBdecibeldBmdBrelativeto1mWdBµVdBrelativeto1µVTxtransmitter(radio)SIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)83.3AbbreviationsForthepurposesofthepresentdocument,thefollowingabbreviationsapply:ACKACKnowledgeASKAmplitudeShiftKeyingCSMACarrierSenseMultipleAccessEUTEquipmentUnderTestfccarrierfrequency(bandcentre)FSKFrequencyShiftKeyingNACKNegativeACKnowledgeOATSOpenAreaTestSitePcSteadystatetransmitpowerPmeanMeanleveloftransmitpowerPoffcarrieroffpowerlevelPraccminimumreceiversensitivityneededtocheckthatachannelisfreePrcheckreceivedcarrierpowerlevel,generatedbyacheckingtransmitterPSKPhaseShiftKeyingQAMQuadratureAmplitudeModulationRFRadioFrequencytcreplycarrierdelaytimetffixedpartofobservationtimetoobservationtimetpprioritypartofobservationtimetrpseudorandompartofobservationtime4General4.1ApplicationsusingthisprotocolThisaccessprotocolappliestoawidevarietyofapplicationsoperatingatvariousdataratesinbothdomesticandindustrialfields.Toaccommodatethissituation,fourprioritylevelsareincludedwhichcorrespondtodifferentdatapacketlengths.This,forexample,improvesthechanceofaccessforasimplecontrolfunction(requiringafastresponsetime)infavourofafunctiontransferringalargeamountofdata(lesscriticalofresponsetime).Theprotocolmaybeusedwiththefollowingtypesofcommunication:-point-to-point(sourcetodestination);-point-to-multi-point(sourcetogroup);-multi-point-to-point(polling).4.2ConformitytothepresentdocumentConformitytotherequirementsofthepresentdocumentisbaseduponbothdeclarationsandmeasurements.4.2.1DeclarationofconformityThoseparameterscoveredbymanufacturersdeclarationaregiveninclause6ofthepresentdocument.Asigneddeclarationshallbeprovidedasconfirmationthattheequipmentmeetstherequirementsofthisaccessprotocol.Thisdeclarationmaybesubmittedbythemanufacturer,orhisrepresentative,togetherwiththeapplicationformfortests.Inthecasewherethecontrollingsoftwarefortheequipment(ormodulesthereof)hasnotbeendesignedbythemanufactureroftheradioequipment,theresponsiblepartyforengineeringsuchsoftwareshallalsoprovideasigneddeclarationofconformity.SIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)94.2.2MeasurementstobeperformedThesemeasurementsshallbeperformedforallpartsoftheequipmentincludedinthesystem,designedtousethisprotocol.Clause7ofthepresentdocumentgivesthemethodsofmeasurementsandlimitsfortheseparameters.Themanufacturershallprovideanynecessarytestpointsand/ortestfixtures,dedicatedtestequipment(ifneeded)and/ortestmodesforthepurposeoftestingandmakingmeasurements.Thefollowingmeasurementsandtestsshallbeperformed,inanaccreditedtestlaboratory:-channelaccessduration;-replycarrierdelay;-antiblocking;-carriersensethreshold;-carriersensedelay;-observationtime;-channelaccessingcarrierattacktime.4.2.3InterpretationofthemeasurementresultsTheinterpretationofthemeasurementresultsrecordedinatestreportforthemeasurementsdescribedinthepresentdocumentshallbeasfollows:a)themeasuredvaluerelatedtothecorrespondinglimitshallbeusedtodecidewhethertheequipmentundertestmeetstherequirementsofthepresentdocumentornot;b)theactualmeasurementuncertaintyofthetestlaboratorycarryingoutthemeasurement,foreachparticularmeasurement,shallbeincludedinthetestreport;c)thevaluesoftheactualmeasurementuncertaintyshallbe,foreachmeasurement,equaltoorlowerthanthefiguresgiveninclause9,absolutemeasurementuncertainties.5TechnicalcharacteristicsoftheequipmentThisprotocolisintendedtobeusedbyshortrangedevicesfulfillingtherequirementsofEN300220-1[1],EN300330[2]andI-ETS300440[3]asapplicable.Theuseofshortrangedevices(SRD)isalsocoveredinCEPT/ERCRecommendation70-03[8].Itisrecommendedthatthespreadoftheminimumreceptionsensitivitybetweenallmanufactureddevicesinasystembekeptassmallaspossible.Thisisintheinterestsofminimizingdataclashesbetweencompetingsystems.6DescriptionoftheaccessprotocolAlldevicesfulfillingthepresentstandardshallusethisprotocoleachtimetheyaccesstheRFchannelandtheRFchannelistobeusedonlybysuchdevices.6.1ChannelaccessdurationThetotaltimeduringwhichthechannelmaybeoccupiedforeachaccess(channelaccessduration)shallnotexceedthedurationgiveninsubclause7.1.3.Thisincludesthedurationofanyacknowledgementorreplyfromarespondingdevice.SIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)10Providedthatboththemaximumdurationofchanneloccupation(channelaccessduration)andthereplycarrierdelaylimitsarefulfilled,thechannelmaybeoccupiedbyasequenceofanynumberoftransmissions(involving,possibly,repliesfromoneormoretransmitters).If,therefore,areplyingdevice,ordevicesarerequiredtoreturndata(e.g.forhandshakepurposes),thenthetimetakentodothisshallbeincludedinthechannelaccessduration.Transferoflargequantitiesofdatashallbeachievedbydividingitupintosuitablysmallpacketstosatisfythisprotocol.6.2PrinciplesForthepurposeofchannelaccess,theequipmentdetermineswhetherornotthechannelisfreeandhasbeenfreefortheobservationtimetobymeansofcarriersensinginthechannel.Theobservationtime(seesubclause6.5)consistsofafixedpart,aprioritypartandapseudo-randomadditionalpart.Whenthechannelappearstohavebeencontinuouslyfreebytheendoftheobservationtime,thetransmittermaybeinitiatedandshallbepoweredupwithinthespecifiedtime(theaccessingcarrierattacktimedelay,seesubclause7.7).Thepriorityparthasbeenincludedintheobservationtimeforthepurposeofgivingprioritytoshortermessagesinordertoimprovetheirresponsetimechances.ThetotaldurationoftheRFcarrieremission(accesstime)islimited(seesubclauses6.1and7.1).Theoveralldutycyclelimitationisgiveninsubclause6.7.Thenumberoftransmissionretries(intendedtoovercometransmissioncollisionsandcorruption)shouldbelimitedtoamaximumof5.6.3ProcedureInordertogainaccesstotheradiochanneltheequipmentshalldeterminewhetherornotthechannelis,andhasbeen,freeduringtheobservationtimet0,bymeansofcarriersensing(seesubclause6.4).Ifthechannelappearstobefreethroughouttheobservationtimeandthereisinformationtobesent,thetransmissionshallthenbeinitiatedandRFcarrierradiationcommencedwithinthespecifiedtime(carrierattacktime;seesubclause7.7.1fordefinition).Oncethechannelhasbeenseizeditmaybeoccupiedforuptothemaximumtimeallowedforasinglechanneloccupancy(seesubclauses6.1and7.1).Attheendofatransmission,anotherobservationtimemaystartimmediately,unlessthedutycyclelimithasbeenreached(subclause6.7).Ifare-transmissionisrequired(due,forexample,toa"collision"),thissameprocessshallberepeatedand,onceagain,thechannelshallbedetectedasbeingfreeduringtheobservationtimepriortorepeatingtheattempttotransmit.Toensurethatnootherusercanaccessthechannelduringahalfduplexaccess,amaximumReplycarrierdelaytchasbeendefined(seesubclause7.2).6.4CarriersensingCarriersensing,ormoreappropriatelychannelenergysensing,isthedetectionofwhethertheRFlevelinthereceivechannelexceedsagiventhresholdornot.ThecarriersenseshallbeabletodetectRFsignalswithdifferenttypesofmodulation(e.g.FSK,ASK,PSK,QAMetc.).Thechannelshallberegardedasinuseduringtheobservationtime(seesubclause6.5)iftheleveloftheRFsignalonthechannelexceedsthethresholdgiveninsubclause7.4.3.Carriersensingshalltakeplacethroughouttheobservationtimeeithercontinuouslyoratregularintervalsnotexceeding250µµµµsandthecarriersensedelayshallnotexceedthelimitgiveninsubclause7.5.3.SIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)116.5ObservationtimeTheobservationtimet0isthesumofthefixedparttf,thepriorityparttpandthepseudorandomparttr.t0=tf+tp+tr.Thefixedpart,tfoftheObservationtimeshallbenotlessthan5ms.Theprioritypart,tpoftheobservationtimeshallbenotlessthanthatgiveninthetableinsubclause6.6(0msto8ms).ThepseudorandomparttrshallconsistofarangeofNdifferentvaluesti.ThenumberNofthesedifferentvalues(ti)shallnotbelessthan11.Thedifferentvalues(ti)shallnotbelessthan1msofeachother.ThemeanofalltheseNvaluesshallnotbelessthan5ms.Thesmallestofthesedifferentvalues(ti)maybe0ms.AlloftheseNdifferentvalues(ti)shallbeusedinNsuccessivetransmissiontransactions.6.6MessageprioritydelayAprioritydelaytpshallbeincludedineachobservationtime.Thevalueusedfortpwillbeaccordingtothemessagelengthandisgivenintable1.Table1:MessageprioritydelaycategoriesCategoryDataPacketlengthPrioritydelaytpVeryshortnotgreaterthan12ms≥0msShortnotgreaterthan25ms≥2msNormalnotgreaterthan50ms≥5msLongnotgreaterthan100ms≥8ms6.7DutyCycleThedutycycleofdevicestransmittingmessagesshallbelimitedasgivenforcategory3indutycyclecategories,CEPT/ERCRecommendation70-03[8].DutycyclelimitationsareonlyprovidedinordertoavoidthatadeviceunabletoreceivecorrectlymayblockthechannelwithanunacceptableDutycycle.6.8AntiblockingInthecaseofinterference,thechannelmayappeartobeinconstantuse.Inaccordancewiththeprotocoldefinedsofar,allthedevicesshouldremainintheobservationstatusandthechannelwouldthenbe"blocked".Inordertoavoidtherealblockingofallthedevices,amechanismisprovidedtoallowalsoforchannelaccessinsuchconditions(seesubclause7.3).Thismechanismisoptional,however,thismechanismrequiresaminimumwaittimebeforechannelaccessisallowed.Underallcircumstances,thedutycyclelimitationgiveninsubclause6.7applies.SIST EN 301 391 V1.1.1:2003

ETSIETSIEN301391V1.1.1(2000-01)127MethodsofmeasurementandlimitsAspecialtestmodemaybeusedprovidedthatthenormaloperatingcharacteristicsarenotaffected.7.1Channelaccessduration7.1.1DefinitionThechannelaccessdurationisthetimeelapsedbetweentheinitialaccesscarrierreachingalevelofPmean–20dBandthepointatwhichthepowerfallstothesamelevelattheendofthetransmissionortheendofthereplyinthecaseofamultitransmittercommunication.Figure1:ChannelaccessdurationDeviceswhichareabletoinitiateatransmissionandaretransmittingwithoutresponsetoanypreviousinitialtransmissionfromotherdevicesshallalsobeconsideredforthismeasurement(seesubclause7.1.2.1).Amultitransmitterchannelaccessisoneinwhichseveraltransmittingdevicesaccessthechannelaspartofthesamemessagetransfer.Itconsistsofaninitiatingtransmissionfollowedbyoneorseveralsequentialreplyingtransmissions(seesubclause7.1.2.2).7.1.2MethodofmeasurementTwodifferentmeasurementsarerequiredtobeperformed.Themaximumchannelaccessdurationofadevicethatisabletoinitiateadatapackettransmission(singletransmitter,seesubclause7.1.2.1)shallbemeasured.Themaximumchannelaccessdurationforaninitiatingtransmissionfollowedbyalldevicescapableofreplyingwiththeirtransmissions(seesubclause7.1.2.2)shallalsobemeasured.7.1.2.1AsingletransmitteraccessingthechannelAmeasurementshallbemadeofthetimeelapsedbetweentheinstantwhenthecarrierreachesalevelofPmean-20dBandtheinstantwhenthecarrierfallstothesamelevelattheendofthetransmission.Seefigure1.ThedutycycleisrequiredtobemeasuredinconformancewithEN300220-1[1];EN300330[2]andI-ETS300440[3]asapplicable.PmeanPmean-20dB
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