comments on the rdof uplink service objective...comments on the rdof uplink service objective ex...
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LYAandc-AheadareregisteredtrademarksofLemay-YatesAssociatesInc.©LYA,2019
December19,2019
Comments on the RDOF Uplink Service Objective Ex parte presentation – FCC Docket 19-126
¢ The 20 Mbps uplink objec9ve likely adds substan9al cost without correspondingconsumerbenefit.� Traffic is typically 90% download/10% upload – thus unlike 100/20, the 10/1, 25/3, 50/5
Mbpsservice9ersarebeHermatcheswithactualtrafficusage.
¢ Inconsideringfixedwirelessdeploymentscenarios,a20Mbpsuplink9er likelyaddstwo to three9mes the cost compared to a10Mbpsuplinkdeployment, due to theneedtobuildaddi9onalsites.� Theseincreasedcoststranslateto:
¢ Reducedcompe99onatthe100Mbps9er;¢ ReducedbroadbanddeployedintheRDOF.
¢ While100/20MbpswasusedintheCAF-IIAuc9on,inmanyconsumerapplica9ons,10vs. 20 Mbps upload is unlikely to drive differences in the actual usage or serviceofferings–e.g.HDstreaming,videocalls,onlinegaming.
Background: 100/10 Mbps vs. 100/20 Mbps
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¢ TheRDOFUplinkobjec9veisbiasedtowardsoperatorswhodonothavetorelysolelyonCBRSand/orwhichhaveconsiderableotherspectrumresourcestheycanuse(withorwithoutcarrieraggrega9onwithCBRS).� Intra-bandCarrierAggrega9on(PAL–Band48)–channelbandwidthsare10MHzor20MHz;
cancombineuptofive20MHzchannelstogetupto100MHz… � Butanyoneoperatorcanonlyacquire4PALsundertheFCC’sdrabrules,sohavetorelyon
combiningPALswithGAA.
¢ For operators with limited spectrum resources, and that may be consideringdeployment using CBRS only – Band 48, the upstream target will be difficult if notimpossible tomeet inmanycaseswith20MHzofspectrum,andevenpoten9ally incaseswhereacarriercouldacquirethefull40MHzallowed.
¢ AndspecifictoCBRS,thereislimitedequipmentavailable–anumberofthecer9fied
OnGo CPE devices only support Band 48. And there are limited carrier aggrega9onopportuni9esavailable.
RDOF Uplink Service Objective and CBRS
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¢ The tablebelowsummarizesbands supportedbya selec9onofCBRSOnGoCer9fiedCPEdevices:
¢ In total thereare54approvedOnGoenduserdevices.Over50%(28devices)aremobilephones or hotspots, 24% (13 devices) are “modules”. Only four OnGo devices arespecificallytargetedforfixedwirelessdeploymentaswouldberelevanttoRDOF.
¢ ThefourconsumerCPEdevicesforFixedServiceapplica9onsonlysupportBand48.� Thus,theyworkwithlimitedspectrumresources–max40MHzPALs,combinedwithGAA,� By only suppor9ng one band, there are no inter-band carrier aggrega9on op9ons available that
couldbeusedtoincreaseoverallthroughput.¢ Ontheotherhand,thesampleofthreedevicesdesignedformobilesupportabroadsetof
bands,whichprovideformoreop9onstomeetdifferentserviceobjec9ves.¢ Fixedserviceoperatorsdonotnecessarilyhaveaccesstomul9plebands,andinanycasedo
nothavethemobileinfrastructuretosupportthesedevices.
Current CBRS CPE and Spectrum
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¢ Also an important considera9on is that TD-LTE for Band 48 operates with fixedconfigura9onssharingbandwidthbetweenUL&DL:� FrameConfig1has~55%devotedtoDLand40%devotedtoUL� FrameConfig2has~75%devotedtoDLand20%devotedtoUL
¢ Configura9on1providesgreatercapacityforuplink,butmayhaveinsufficientcapacitytomeetthe100MHzdownlinkobjec9ve.
¢ Giventheimportanceofdownlinkspeed,however,Configura9on2istypicallyusedbyvendors as it most closely matches Internet traffic profiles. In this case there is lessspectrumavailableforuplink.� AndoperatorsusingTDDincommonbandinthesameareaneedtocoordinateconfigura9on
tominimizeinterference(andmaximizespectrumalloca9on).¢ The design of the customer premises equipment (CPE) is what dictates uplink
performance. The following analysis provides a basic performance comparisonof twoCBRS CPE devices – NOTE: the analysis is “best case” under ideal condi9ons, notaccoun9ngforspecificsofterrainorgeography.
CBRS Configurations
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¢ ConsideringtwoexamplesofCPE…¢ CPE Device #1 – Zyxel – It is designed for fixed service and supports 573 Mbps
downlink but only15Mbps uplink. This does notmeet CAF-RDOF 20Mbps uplinkrequirement(forAboveBaselineservice).ThedeviceusesBand48only.� Downlink256QAMwith4x4MIMO;Uplinkis64QAMandnoMIMO� ThedeviceusesTDDConfigura9on2–UL:DLra9o2:6–soDLis75%ofthe20MHzchannel.
¢ CPE Device #2 – Inseego – It is designed for mobile service and supports 2 Gbpsdownlink and uplink speeds up to 316Mbps. The device supports Bands 2 (PCS), 4(AWS), 5 (Cellular), 13 (Lower 700), 48 (CBRS), 66 (AWS), with up to 5 x carrieraggrega9on(i.e.5x20MHz).ItalsosupportsmmWavebandsn260andn261–39GHzand28GHz.� Ondownlink ituses4x4MIMO,256QAMand5xcarrieraggrega9on(LTEUECategory20),
Foruplinkituses256QAMandprovidesfor3xcarrieraggrega9on(LTEUECategory13).
CPE and Uplink Performance
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¢ With CPE Device #1 performance, the RDOF Above Baseline service objec9ve obencannotbemet–downlinkanduplink(sinceuplinkislimitedto15Mbpsmaximum).
¢ Even with the more advanced CPE Device #2 performance, with only 20 MHz ofspectrum, theobjec9vesareobennotmet.With40MHzof spectrum, theDevice#2scenariomeetsobjec9vesmoreobenusing50%downlink,50%uplink.
¢ Oneway of improving performance is to increase the number of sites,which in turnincreasesdeploymentcosts.Asshownabove,withmoresitesandthuslowersubscribercountspersite,theperformanceobjec9vesaremetinmorecases,butnotalways.
¢ Toachievethis,however,thenumberofsiteswouldhavetobedoubledortripled–i.e.byincreasingdeploymenttoreducesubscribersfrom20-30persitedownto10persite.
Performance Comparison
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¢ Foranoperator todeployCBRS, there is limitedequipmentavailable– anumberofthecer9fiedOnGodevicesonlysupportBand48.� Therearealsolimitedcarrieraggrega9onopportuni9esavailableforBand48
¢ The FCC objec9ves for 100/20 do not respect the rela9ve downlink vs. uplinkperformanceinpar9cularofCBRSequipment.Ontheotherhand,using75%ofMHztosupportdownlink(CBRSTDDConfigura9on2)wouldbeHermeet100Mbpsobjec9ve,andwouldmorereadilyprovideatleast10Mbpsuplinkinsteadof20Mbps.
¢ Onewayof improvingperformance is to increasethenumberofsites,which inturnincreasesdeploymentcosts.Toachievethis,however,thenumberofsiteswouldhavetobedoubledortripled–makingdeploymentmuchlesseconomic.
¢ TheRDOFUplinkobjec9veisbiasedtowardsoperatorswhodonothavetorelysolelyon CBRS and/or which have other spectrum resources they can apply (mee9ngobjec9veswithcarrieraggrega9on).
¢ IftheUplinkobjec1vewerechangedto10Mbps,thiswouldallowoperatorstomeettheAboveBaselineserviceobjec1veonamuchbroaderbasis.Thiswould increase compe11on for the Above Baseline service objec1ve andincreasedeploymentincurrentlyunderservedandunservedareas.
Conclusions
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