Measurement and Processing to Determine Land-mobile Radio (LMR)
Channel OccupancyRandy Hoffman
ISART 2005
Topics of DiscussionTopics of Discussion
Who are we?Who are we? Purpose of measurementsPurpose of measurements ChallengesChallenges Techniques for Techniques for
measurement measurement Post processing methodsPost processing methods
Radio Spectrum Measurement Radio Spectrum Measurement
Program - MissionProgram - Mission
To provide the Executive Branch, critically needed:
Radio spectrum data
Data analysis
Reports and summaries
SecretaryDeputy Secretary
Chief of Staff
Deputy Chief of Staff
Office of Public Affairs
Office of BusinessLiason
Office of Policyand Stragegic Planning
Office ofWhite House Liason
General Counsel
Inspector General
Chief Financial Officer andAssist Sec for Admin
Chief Information Officer
Under Secretaryand Administrator
National Oceanic andAtmospheric Admin
Under Secretary forInternational Trade
International TradeAdministration
Under Secretary forIndustry and Security
Bureau of Industryand Security
Under Secretary forEconomic Affairs
Economic andStatistics Admin
Under Secretary forTechnology
TechnologyAdministration
Under Secretary forIntellectual Property & Dir
U.S. Patent andTrademark Office
Assist Secfor Oceans &Atmosphere& DeputyAdmin
Assist Secfor MarketAccess &Compliance
Assist Secfor ImportAdmin
Assist Sec &Dir GeneralU.S. &Foreign
Comm Serv
Assist Secfor Trade
Development
Assist Secfor ExportAdmin
Assist Secfor ExportEnforcement
ChiefEconomist
DirectorBureau ofEconomicAnalysis
DirectorBureau ofthe Census
Assist Secfor
TechnonlogyPolicy
DirectorNational TechInformationServices
DirectorNational Instof Standards
andTechnology
Assistant Secretaryfor Economic Devel
Economic DevelAdministration
National Director
Minority BusinessDevelopment Agency
Assistant Secretary forCommunications and
InformationNat'l Telecommunications& Information Admin
U.S. Department of Commerce
National Telecommunications and Information Administration
NTIAOffice of the Assistant Secretary
Office of SpectrumManagement
Office of PolicyCoordination andManagement
Office ofInternational Affairs
Office ofCongressionalAffairs
Office of PublicAffairs
Office of Telecomand InformationApplications
Institude forTelecommunicationSciences
Office of PolicyAnalysis andDevelopment
Office of ChiefCounsel
ResponsibilitiesResponsibilities
Under Departmental Organization Order Under Departmental Organization Order 25-7, issued 5 October 1992, and 25-7, issued 5 October 1992, and amended 3 December 1993, the amended 3 December 1993, the NTIA NTIA Office of Spectrum Management (OSM) is Office of Spectrum Management (OSM) is responsible for identifying and making responsible for identifying and making arrangements for measurementsarrangements for measurements necessary to provide NTIA and the various necessary to provide NTIA and the various departments and agencies with departments and agencies with information information to ensure effective and to ensure effective and efficient use of the spectrum.efficient use of the spectrum.
The Radio Spectrum Measurement SystemThe Radio Spectrum Measurement System (RSMS) resides at ITS and is tasked to (RSMS) resides at ITS and is tasked to perform spectrum measurementsperform spectrum measurements as as required to fulfill this mission.required to fulfill this mission.
Why LMR Measurements?Why LMR Measurements?
Update Update usage trendusage trend information information comparing data collected in mid 70’s comparing data collected in mid 70’s – – for future LMR spectrum for future LMR spectrum managementmanagement..
To determine To determine current usage:current usage:– to help with decisions regarding how to to help with decisions regarding how to
makemake federal federal LMR radio operations LMR radio operations more efficientmore efficient..
– Provide information for realistic Provide information for realistic design design of possible shared trunked systemof possible shared trunked system..
ChallengesChallenges
Wide dynamic rangeWide dynamic range– Need for high sensitivity (low noise Need for high sensitivity (low noise
figure)figure)– Strong local signalsStrong local signals– 100 dB Dynamic Range100 dB Dynamic Range
ChallengesChallenges
ChallengesChallenges
Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing
– Need to resolve individual channels Need to resolve individual channels with a minimum of 12.5 kHz spacingwith a minimum of 12.5 kHz spacing
– Requires: Requires: narrow resolution bandwidthnarrow resolution bandwidth sharp roll-offsharp roll-off large stopband attenuation.large stopband attenuation.
ChallengesChallenges
Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing Differentiation from system noiseDifferentiation from system noise
– Need to know what is system noise Need to know what is system noise and what is signaland what is signal
ChallengesChallenges
ChallengesChallenges
Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing Differentiation from system noiseDifferentiation from system noise Impulsive noiseImpulsive noise
– Need to reduce the probability that Need to reduce the probability that impulsive noise is mistaken for a impulsive noise is mistaken for a signalsignal
ChallengesChallenges
Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing Differentiation from system noiseDifferentiation from system noise Impulsive noiseImpulsive noise Strong out-of-band signalsStrong out-of-band signals
– System overloadSystem overload– Complicate in-band thresholdsComplicate in-band thresholds
ChallengesChallenges
Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing Differentiation from system noiseDifferentiation from system noise Impulsive noiseImpulsive noise Strong out-of-band signalsStrong out-of-band signals Strong in-band signalsStrong in-band signals
– System overloadSystem overload
ChallengesChallenges
Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing Differentiation from system noiseDifferentiation from system noise Impulsive noiseImpulsive noise Strong out-of-band signalsStrong out-of-band signals Strong in-band signalsStrong in-band signals
– Intermodulation productsIntermodulation products
IM = +/- mF1 +/-nF2
ChallengesChallenges
Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing Differentiation from system noiseDifferentiation from system noise Impulsive noiseImpulsive noise Strong out-of-band signalsStrong out-of-band signals Strong in-band signalsStrong in-band signals
– Sideband noiseSideband noise
Measurement SystemMeasurement System
Measurement ProcedureMeasurement Procedure Careful site selectionCareful site selection Signals detected by measuring RF energy at the Signals detected by measuring RF energy at the
channel frequency – channel frequency – inferring LMR transmissioninferring LMR transmission if if signal greater than system noise.signal greater than system noise.
Digitized at Digitized at 30 Msamples/s30 Msamples/s in 5.5 MHz bandwidth in 5.5 MHz bandwidth chunkschunks
Do Do fftfft with with flattop windowflattop window, , decimateddecimated to 12.5 kHz or to 12.5 kHz or 15 kHz spacing with samples centered on the 15 kHz spacing with samples centered on the channels, and channels, and downloaded via internetdownloaded via internet connection. connection.
Acquisition every Acquisition every 200 ms200 ms (up to (up to 480 channels480 channels) ) Capability for Capability for message length statisticsmessage length statistics.. Measure for Measure for 4 minutes / 5.5 MHz span4 minutes / 5.5 MHz span and switch to and switch to
next span. Sufficient data to characterize the next span. Sufficient data to characterize the channel every hour. Measure channel every hour. Measure 24 hours/day for a 24 hours/day for a weekweek..
Throw awayThrow away data during data during overloadoverload conditions conditions
Median ProcessingMedian Processing
Resolution BandwidthResolution Bandwidth
Post Processing – Post Processing – IntermodulationIntermodulation
Post Processing – Post Processing – IntermodulationIntermodulation
Post Processing – Post Processing – IntermodulationIntermodulation
Post Processing – Post Processing – IntermodulationIntermodulation
Post Processing – Sideband Post Processing – Sideband NoiseNoise
Post Processing – Min Post Processing – Min ThresholdThreshold
Post Processing – Min Post Processing – Min ThresholdThreshold
Post Processing – Impulsive Post Processing – Impulsive NoiseNoise
SummarySummary Challenges and SolutionsChallenges and Solutions
– Wide Dynamic RangeWide Dynamic Range– Narrow Channel SpacingNarrow Channel Spacing– Differentiation from System NoiseDifferentiation from System Noise– Impulsive NoiseImpulsive Noise– Strong Out-of-band SignalsStrong Out-of-band Signals– Strong In-band SignalsStrong In-band Signals
OverloadOverload Intermodulation ProductsIntermodulation Products Sideband NoiseSideband Noise
Report – to be published this yearReport – to be published this year
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