Understanding 5G Guide

Understanding 5G

Understanding 5G

Introduction ............................................................................................................................. 1

5G Mobile Broadband Objective .......................................................................................... 2

Capacity ................................................................................................................... 2

Coverage ................................................................................................................. 3

Convenience ........................................................................................................... 3

Looking in the past - Cellular generations ............................................................. 5

5G Project Summary ........................................................................................................... 8

ITUprojecttodefinespectrumusageworldwide................................................9

5G Requirements ................................................................................................................ 12

Technical challenges and targets ....................................................................... 12

Internet of Things (IoT) capacity requirements ............................................ 15

Volume of data .................................................................................................. 15

Types of data ........................................................................................................ 16

New types of services ...................................................................................... 17

Research subjects ................................................................................................. 21

Extremedensification.........................................................................................21

Air interfaces for higher data rates and capacity ........................................................ 23

Cell coverage improvements ............................................................................ 25

Key technologies ................................................................................................. 25

Networkdesign....................................................................................................26

Newfrequenciesforradioaccess.....................................................................31

Air access and modulation schemes ............................................................ 33

In-band fullduplex ............................................................................................ 37

Massive MIMO ..................................................................................................... 41

Trafficmanagement............................................................................................43

Future Testing for 5G .......................................................................................................... 44

Test & measurement challenges ...................................................................... 41

FutureTestInstruments.....................................................................................................49

Networktest.........................................................................................................49

RFcomponentandmoduletest...........................................................................49

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User device/terminal test .................................................................................... 50

Devicecertification&carrieraggregation ....................................................51

Field test ................................................................................................................ 52

Current test technology ....................................................................................... 50

Introduction to 5G Waveforms ......................................................................................... 56

Detailed Analysis of an Example FBMC Waveform ...................................................... 61

FBMC concepts .................................................................................................... 61

FBMC modulator in Matlab ............................................................................... 64

FBMCwaveform inMS2830A ......................................................................... 67

Conclusion...........................................................................................................................75

1 | Understanding 5G

Introduction

Makingupnewdefinitions inthetelecomsmarket isgenerallyfrowneduponand

inmany cases the technical definitions are overtakenbymarketing andpublicity

definitions: ITUdefined4G tobe IMT-Advanced (100Mbpswhenuser ismoving,

1 Gbps when stationary) but the market decided otherwise. LTE, and even LTE-

Advanced, did not fully meet these requirements, but on the other hand, some

operators called HSPA+ a “4G” technology or Long Term HSPA Evolution as a 4G

technology,bothformarketingandcompetitivereasons.

Anewmobilenetwork“generation”usuallyreferstoacompletelynewarchitecture,

whichhastraditionallybeenidentifiedbytheradioaccess:AnalogtoTDMA(GSM)to

CDMA/W-CDMAandfinallytoOFDMA(LTE).Sotheindustryhasstartednowtorefer

tothenextfundamentalstepbeyondfourthgenerationOFDMA(LTE)networksas

being“5G”.Itisclearthat5Gwillrequireanewradioaccesstechnology,andanew

standard to address current subscriber demands that previous technologies cannot

answer. However, 5G research is driven by current traffic trends and requires a

completenetworkoverhaulthatcannotbeachievedonlythroughgradualevolution.

Software-driven architectures, fluid networks that are extremely dense, higher

frequencyandwiderspectrum,billionsofdevicesandGbpsofcapacityareafewof

the requirements that cannot be achieved by LTE and LTE-Advanced.

Thispaperwillreviewthetechnologyandusecasesthataredrivingthefutureof

mobilebroadbandnetworks,andderivefromhereasetoffuturerequirements.We

willthenlookatthekeytechnicalchallengesandsomeoftheresearchsubjectsthat

areaddressingthese.Examplesofthis includeCloud-RAN,massiveMIMO,mmW

access, and new air interface waveforms optimized for HetNet and super-dense

networks.

Thepaperwill then review the impactof these5Gdevelopments to the test and

measurement industry.Wewill look at both how the 5G technology will change

the requirements and parameters we will need to test, and also at how the 5G

technology will be used by Test andMeasurement to align the testmethods to

networkevolutions.

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The final section of the paper will take amore in-depth review of some specific

waveformsbeingevaluated forair interfaceaccess.Wewill study the theoryand

objectivesforthewaveforms,andthenseehowthewaveformscanbesimulatedand

analyzedusingtestequipment.Suchanexerciseisimportantasthesetestsneedto

bemadeearlyinR&Dtoevaluatetheimpactandinter-actionofthewaveformsonto

realdevicetechnology,toevaluatetherealperformance.Thiswillalsoinformclosely

the level of device technology development needed to support the widespread

deploymentofthedifferenttypesofwaveforms.

5G Mobile Broadband Objectives

The definitions of “5G”, like the previous “4G” networks, is asmuch amarketing

activityasitisaplatformfortheintroductionofnewtechnologiesintothenetworks.

Thispaperwillstudythedifferenttechnologiesandconceptsbeingproposedfor5G

networks,andreviewthemtogetherwiththedifferenttestmethodsandtechniques

thatmayberequiredtosupportthem.Thispaperwillnotcoverindetailthebusiness

caseorinvestmentjustificationsfor5G,beyondthesimpleneedtoreducecostsfor

anoperatorandtomatchthecostofaserviceofferedtothevaluethattheuserwill

perceivefromtheservice.Equally,thestrictdefinitions(suchasthosefromITU)of

5Gnetworkswillnotbedebatedindetail,butratherthegeneralindustrytrendsand

activitiesthathavebeenassociatedwith“5G”willbecovered.

Theconceptfor“5G”isbothanevolutionofwirelessnetworkstomeetfuturedemands

fordata,andarevolutioninarchitecturetoenableaflexibleandcostefficientnetwork

thatcanbeefficientlyscaled.Thesearethenetworkoperatoroperationaldemands

onthenetworkandtechnology,buttheyaredrivenbythedemandsforthetypeuser

experiencewhichshouldbeoffered.Theseuserexperiencedemandsthatprovide

theunderlyingrequirementfor“5G”are:

Capacity

Aperceptionofaninfiniteinternet:The5Gnetworkshouldgivetheuseraperception

thatthecapacityofthenetworkisinfinite,thatisthereisalwaysenoughdatacapacity

available for whatever data transfer is required. This means in effect that there

shouldbeenoughbandwidthfortheservicesbeingrun,atthetimeandplacethat


theserviceisbeingused.Soifthenetworkisflexibleinhowthelimitedresources/

capacityaredeployedinbothtimeandspace,thenthenetworkcanreacttolocal

datademandsandgiveenoughcapacity.Thusthenetworkdoesnotneedtohavean

infinitecapacity,butenoughfinitecapacityandflexibilitytomeettherealtimeneeds

of the services being run.

Intermsoftargetsandheadlinefigures,thegeneralconsensusis10Gb/speakdata

rateforstaticusers (i.e. indoorareas)and1Gb/sfor lowmobilityusers.Asa low

endlimit,nolessthan100Mb/sshallbereachedinurbanareas.Massivescalability

formillionsofdevicesbelongingtothewidelyknownIoTorM2Mmarketswillbe

demanded,whichwillconsequentlybeleadingtoacapacityintermsofnumberof

connecteddeviceswhichis1000xtimesbiggerthancurrentnetworks.

Coverage

A consistent user experience at any time/place is needed. This means that in effect

thenetworkcoveragecanprovidealwaysenoughperformance for theusecases

atanylocation.Asthenetworkisexpectedtohaveflexibilityinhowresourcesare

configuredanddeployed,thedynamicselectionofdifferentradioresourceswillbe

used to provide coverage based on service needs.

Convenience

Theparametersdefiningconveniencearesplitintotwokeytypes,dependingonwhat

type of interaction is taking place; either human interaction of machine interaction.

For human interaction the requirement is for a “Tactile internet”, providing real

time inter-activeapplications (1mSresponse/latency,RoundTripTimeRTT)where

the response time of a cloud based service is real time to the user. This is required

todeliveratrue“multiuser”experiencewhereseveralusersinter-actonthesame

servicesimultaneously(.e.multi-usergames,augmentedreality).Averyoptimistic

targetthatrequireshighlevelsofintegrationbetweenthe5Gaccessnetwork,core

networks,andapplicationserversandenvironments.

Formachinetomachineinteraction,oneofthekeyrequirementsisforalongbattery

life for embedded machines (typically required 10 years). This is required to support

the typical operational life of embedded “smart meters” and monitoring applications.

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Toachievethis,newtechniquestominimizethe“on”timeofthepowerconsuming

radiocircuitsisrequired,plussimplifiedandrobustaccessandprotocolprocedures

tominimizeprocessingrequirements.

Inoverall,5Gwillstronglyhighlightitselfasagreenertechnology,aimingtoreduce

upto90%ofthepowerconsumptionindevicesandnetworkcenters.Thisisavery

optimistictargetthatwillrequireastrongeffort fromOEMsandmobilefirmware

developers.Thereisstronguserdemandtoreducepowerconsumptionofdevices,

toextendnormalbatterylifebeyondjustaday.Butincreasinglytherewillbedemand

toreducepowerconsumptionforthenetwork,bothfromanenvironmentalpoint

andalsofromacostofenergypointthatdrivescostofrunningthenetworks.

CapacityLatency

Energyconsumption

Cost

User data rates

Coverage

Physical limits

1000010-100

110

M2M

10

100 Mbit/s

Gbit/s

millisecond

Low-end data rates

Ultra reliability

data rates

Ultra low cost

Years batteryfor M2M

latency

x more devices

x more traffic

Fig 1 - 5G Mobile Broadband Objectives


Looking in the past: Cellular Generations

It is well understood now

in the industry that the

“mobile phone” business

has gone through a

complete transformation

over the last 20 years and

through the evolution of

3G and 4G. Where it had

started as a “telephone”

device centered around

making and receiving

voice calls, with any

supplementary data

services as a side activity,

today the smartphone is

seen as very much a data

centric device giving access

to a full range of data based

services and applications,

aswellasbeingaplatform

for many local applications

and services that may

not even rely on cellular

data services (e.g. camera,

personalnavigation,fitness

monitor). This trend has

given rise to the great

increase in volumes of

data being transported

acrosstelecomnetworks,in

particularvideocontentbeingauserofhighdatabandwidthwhilstalsobeingeasily

consumed and discarded by users.

Fig2-MobileCommunications:from1Gto5G

Peo

ple

Peo

ple &

Things

Device SpecificationsDevice S

Smar

t grids

Smart Car

Co

nnected HouseYear

StandardsTechnologyBandwidthData rates

1991AMPS, TACSAnalog--

YearStandards

1991GSM, GPRS, EDGE,

DigitalNarrow Band<80-100 Kbit/s

YearStandards

2001UMTS/HSPA,

DigitalBroad Bandup to 2 Mbit/s

YearStandards

TechnologyBandwidthData rates

2010LTE, LTE-AdvancedDigitalMobile Broad BandxDSL-like experience

1 hr HD movie in 6 minutes

YearStandards


2020-2030-DigitalUbiquitous connectivityFiber-like experience

1 hr HD movie in 6 seconds

Entertainment

eH

ealth

Data rates / applications

Generation

Traffic Priority

Car-to-car communication

Apps beyondimagination

Domotics



CDMA2000 1X/1xEV-DO Rev. A

CDMA (IS-95)

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1979

1991

2001

2009

1G- Basic Mobility- Basic Services- Incompatibility- Analog

- Advanced Mobility (Roaming)- More Services (data presence)- Toward Global Solution - Digital System

First Commercial deployment

- Seamless Roaming- Service Concept & Models- Global Solution- High Data Rate

- IP Based Mobility- Very high Data Rate- Convergence

2G

3G

4G

5G

Analog Voice

Digital voice +simple data

Data +Position

Video

Fig 3 - Evolution of standards in mobile technology

From1979withthe1Gcommercialdeployments,anewtechnologyhasemerged

every 10 years. The second generation, first digital mobile technology and first

approachtoaglobalsolutionwascommerciallylaunchedontheGSMstandardin

Finlandin1991,introducingrelevantbenefitssuchasasignificantlymoreefficient

spectrumornewdataserviceslikeSMStextmessages.

Nevertheless,thissecondgenerationdidnotfulfilltheemergingdemandforInternet

access inmobilephones. This reason lead to thedevelopmentof3G, released in

2001,whichwasspecifiedfromITU-R(IMT-2000)andwasconsideredasarevolution

inmobiledatarates,seamlessroamingandnewserviceconceptsandmodels.

1

11

10

10

10

100

100

100

1000

1000

1000

Low

Med

high

perfect

1000

User data rate(Mbps)

Mobility (km/h)Coverage/Availability

End to Endlatency

2G focused onvoice availabilityand basic SMSsupport

2G Target

1

11

10

10

10

100

100

100

1000

1000

1000

Low

Med

high

perfect

1000



End to Endlatency

2.5G focused ondata trading offwith efficiency/availability

2.5G Targets

Introductionof data packet(GPRS/EDGE)

Fig 4 - 2G Target Fig 5 - 2.5G Targets

7|Understanding5G

Thelaststepwasheldin2009,with4Gtechnologyprincipallyaimingfortheall-IP

mobilebroadbandnetwork,averyhighdatarateandtheconvergenceofallservices

intoamuchsimplerarchitecture.4Gwasaimingverymuchonhigherdata rates

andlowerlatencycomparedto3G,andalsotothesimplifiedallIParchitecturethat

gavemore deployment flexibility compared to 3G. However, 4G did not address

theneedsfordensernetworksandcapacitydemandsexplodingatanunforeseen

rate,asthe“smartphonerevolution”hadnotstartedwhenthe4Grequirementsand

technologieswerefirstspecifiedandselected.

So “5G” is setting out to provide a technical solution to the problems of todays 4G

networksthatcannotbeeasilyaddressedusingtheexistingtechnology,problems

thathavearisenfromthechangingdemandsonthetelecomnetworkoverthelast8

yearsas4Gwasdefinedanddeveloped.Butalso,5Gisattemptingtolook8yearsinto

thefuture(year2022isatypicalscheduleforwhen5Gnetworksmaybedeployedin

largescale)andtryingtopredictboththerequirementsontelecomnetworksatthis

time,andthetechnologieswhichmayberequiredtomeetthis.

11

10

10

100

100 1000

1000


Mobility (km/h)The requirementsfro high mobility3G from ITU-R (IMT-2000) focusedon mobility and bitrate

3G Targets

1

11

10

10

10

100

100

100

1000

1000

1000


Mobility (km/h)

End to Endlatency

Clear requirementsfrom ITU-RMore requirementsto define 4G

4G Targets

Fig 6 - 3G Targets Fig7-4GTargets

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5G Project Summary

2014 2015 2016 2017 2018 2019 202120202014 2015 2016 2017CORE TECHNOLOGY

STANDARDIZATION

COMMERCIAL R&D

TRIALS COMMERCIAL

DEPLOYMENTJapan OlympicsKorea WinterOlympics

WRC-15WRC-18

5G PPPMETIS5GIC

NGMN (requirements)ITU3GPP (beyond Rel 12/13)IETFIEEE

WRC-15 - more mobile broadband frequencies - Harmonize 700 MHz bands

WRC-18 - more bands needed for 5GIndustry R&D

Technology Standardization New Spectrum Allocations

Fig 8 - Expected timeframe for 5G

5Gdevelopment,asanyothertechnology,canbescheduledinto3mainstages:firstly,

the definition of requirements and key technologies, secondly the development

and standardization processes, and eventually real demonstrations plus further

commercial deployments.

During2015,concepts,visionandrequirementsfor5Ghavebeendefined.Selection

of key technologies, and demonstrations as proof of concepts have emerged as

well. R&D on the core technology will continue evolving from the work pieces

carriedoutduringpreviousyearsandmay lastuntil thefirsthalfof2017.Within

this period, international groups such as 5G Public Private Partnership (5G PPP)

belongingtoHorizon2020Europeanresearchprogram,ARIB2020adhocgroupin

JapanorIMT2020andBeyondpromotiongroupinChinawilldrivethebasisforthe

newtechnology.Othernationalgroups like5GInnovationCenterbasedatSurrey

University in UK or New YorkWireless University consortium are also important

technology hubs contributing in the 5G approach.

9|Understanding5G

Thestandardizationprocess startedduring2015, to layoutaplanofactivities to

review requirementsand technologiesand thenproducea setof standards. This

activity is taking theguidance fromWRC15 in termsof candidatenew frequency

bands tostudy for5G,andre-useofexistingmobilebroadband frequencies.The

3GPPschedule fordevelopment,writingandapprovalofstandardsmay lastuntil

thesecondhalfof2019,soinparallelwewillseeahugeeffortinR&Dagainstthese

emergingstandards.WeexpecttoseefirstdeploymentsbasedonthepartialRelease

15 standards in mid-2018.

Aswith2G,3Gand4G,theremaybeseveraldifferentcompetingstandardsforthe

networks,comingfromdifferentstandardsbodies,aswellassomemoreproprietary

technologieslookingtobedefinedwithinthestandards.Itisthereforepossiblethat

severalstandardsappearinparallelattheearlystage,andnodominantstandardmay

appearforsometime(e.g.GSMvsIS-54vsIS95,UMTSvsCDMA2000,LTEvsWiMAX).

Theinterestingnoteisthatfor4Gtheindustrywasmuchquickertosettleontoa

single standardand therewas less interest inmultiple standards simultaneously.

Thevariousfactorsinfluencingthisincludethecostscalesofvolumeandtheneed

for global roaming. If this remains true for 5G thenwe are likely to see a quick

convergence onto a single set of 5G standards rather than several different sets of

standards.As3GPPisusedforalmostall4Gnetworks,itcouldbeexpectedthatthe

4Gto5Gevolutionof3GPPwouldbethemostnaturalrouteformostoperators.

In2018,theWinterOlympicstakingplaceinSouthKoreapresentsagoodchance

tolaunchtrialsordemonstrationsofstandardsbasednetworksinrealscenarios.A

secondWRCmeetingwillbeheldinthebeginningof2019,whichwillalsoaddressthe

discussionsfornewglobalfrequencybandsallocations.Finally,theJapanSummer

Olympics in 2020 looks set to become a starting point for a live demonstration of 5G

that could be based on a commercial deployment.

ITU project to define spectrum usage worldwide, WRC15 and WRC19.

Oneofthefundamentalneedsof5GistherequirementformoreRFspectrum,tobe

abletocarrytheeverincreasingvolumeofdatabeingtransmittedwirelesslyacross

thenetworks.Thisappliestotheneedforwirelessbackhaul(akeyenablerforsome

ofthedeploymentscenarios),aswellastothewell-publicizedneedformorecapacity

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on the air interface for delivery of data to the terminals/devices. Global spectrum

usage and allocations are agreed under the World Radio Council (WRC) as part of the

InternationalTelecomsUnion(ITU).Inthisforum,globalagreementontheallocation

andpurposeofdifferentfrequencybandsismade.Withinthepurpose,thereisthen

definedlimitationsonthelicensing,typesofwaveforms(butnotspecificselectionof

particularstandards),andusage.Thiscoversalltypesofapplicationssuchaspublic

broadcast,mobilephoneanddataservices,militaryuse(radio,radar,etc.),satellite

services, public emergency services, unlicensed services (e.g. Wi-Fi, garage door

openers,remotecontroltoys,walkie-talkie).Thechangeofmosttypesofbroadcast

from analogue to digital broadcast has freed up much spectrum due to the higher

spectralefficiencyofdigitalformats.However,theamountoffreedspectrumisnot

enough tomeet the growing data capacity needs of telecoms networks. Hence,

there is a need to allocate (or re-allocate) some other spectrum bands to the purpose

ofmobilephonenetworks. Telecomnetwork serviceshave traditionallypreferred

frequencybandsintherange450MHzto2.6GHz,asthisgivesthebestperformance

in terms of range (propagation through atmosphere and buildings) and cost of

technologytoimplementit.However,suchlowfrequencieshavelimitedamountof

MHzofbandwidthavailable.Tofindmorebandwidthrequiresthemovetohigher

frequencies, where more spectrum is available, but with the trade-off of lower

coverage and higher cost technology in the terminals/devices.

So a number of research projects are looking at re-using the lower frequency

spectrum to get more capacity from these preferred frequency bands. Other

projectsarelookingathowtoovercomethepropagationandcostbarrierstousing

thehigherfrequencyspectrum.Inparallel,thehigherfrequencyspectrumisalready

usedforwirelessbackhaul links(wheredirectionalantennaareusedtoovercome

propagationissues),andfurtherresearchisbeingmadetoincreasecapacityofthese

links. A key factor for this research is the modeling and understanding of propagation

andreflectionsatthesefrequencies,toseeiftheyaresuitableforbothindooruse

andnonlineofsight,andtounderstandhowwellMIMOcanbeappliedtoincrease

capacity.


There is also research to implement “non line of sight” data links to overcome one of

theprincipleweaknessescurrentlyinhighfrequencybackhaullinks,thatofrequiring

directlineofsightbetweenthetwoantennasinthedatalink.Thisobviouslylimits

the deployment scenarios that are possible, making indoor or city/urban use

almostimpossible,andrequiringspecificantennamaststobeerectedinalmostall

deployments today.

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5G Requirements

There are several projects and groups working worldwide to define 5G needs,

technologyrequirements,userrequirements,andotherviewsonwhat5Gshouldbe.

ThemobilenetworkoperatorshavebuiltupanecosystemcommunitycalledNext

GenerationMobileNetworks (NGMN)which iscreatinga requirementsdocument

fromtheperspectiveofwirelessnetworkoperators.NGMNhadpreviouslyagreed

requirements for 4G networks, and selected LTE as a preferred technology. The

NGMNisanoperatorledforum,butwithparticipationfromtheequipment/network

vendorsandsupplychain,totryandaligntheindustryneeds.

Technical Challenges and Targets

Thereareseveralkeychallengestobemetwithfuture5Gnetworks,lookingatthe

performance needs of future networks and identifying affordable technologies

whichmaybedevelopedtosupportthese.

1

1

10

100

1000



End to Endlatency

5G Targetsby use case

1

10

1000

1

100

10

1000

1 10 100 500500.5

Low

perfect

Battery life(days)

Cost(Euro)

TrafficVolume density

(Tbps/km2)

Connection density(Users/km2)

Optimised for

Optimised for

Optimised for

Optimised for

1

102

104

106

Med

10

5

100

100

1000

1000

high

Fig9-5GTargetsbyusecase


5Gispromotingtargetsinalldifferentservicelayers,itisanall-optimizednetwork

designedtosupportthehighestuserdataratewithunlimitedcoverageandwithin

challengingmobility scenarios, capable foramassivenumberof connectionsper

km2whilstalsoreducingthelatencytothe“immediate”feelingandthecostand

powerconsumptionofdevicestotheirminimalpossiblefigure.Ensuringall these

parameters would transform 5G into the most complete wireless network ever

seen, tremendouslyattractive forautomotive,M2Mandevenupcoming futuristic

applications.Thisiswhatwecall“Performanceoriented”usecase.

1

1

10

100

1000



End to Endlatency


1

10

1000

1

100

10

1000

1 10 100 500500.5

Low

perfect

Battery life(days)

Cost(Euro)


(Tbps/km2)


1

102

104

106

Med

5

100

100

1000

1000

5050

0010

ct100

10

Me

100

100010

1

100

0

00000 1

10

1000

high

104

1

100

10

Performance oriented

Fig10-5GTargetsbyusecase:PerformanceOriented

Thisusecasecanbeappliedtomultipleupcominganddemandedservices,suchas

3Dvideosin4Kscreens,augmentedreality,workandplayinthecloudor,simplya

highest possible data throughput (Gigabytes in a second) performance.

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1

10

100



End to Endlatency


1

10

1000

1

100

10

1 500500.5

Low

Battery life(days)

Cost(Euro)


(Tbps/km2)


1

102

106

5

100

1000

10

100

100

10

1

100

0001

10

1000

high

Reliability/latencyoriented

Cost and Powerconsumption oriented

perfect

100

1

1000

10

104

Med

1000

5050

1000

100

Fig11-5GTargetsbyusecase:Reliability/LatencyandCostandPoweroriented

5Gwill also lookata “Reliability/latencyoriented”usecase,whichwillfit into the

needs of services like Industry automation, critical information broadcast or self-

driving cars. In this case, 5G technology shouldadapt itself to amuchoptimized

network in terms of coverage, latency and mobility. The connection density for

Industryautomationorcriticalinformationbroadcastisnotimportant,astheywill

notrepresentahighamountofusersconcentratedinaspecificarea.Evenforself-

drivingapplications,shouldnotbearestrictingparameterbecausetheseuserswill

bemoving,thusdrivingimportancetomobilityoptimization.

Eventually,thereisathirdusecaseinwhichthelowcostandlongbatterylifearethe

mostimportantpremises.5Gwillfulfilltherequirementsformillionsofsmartdevices

enteringintothenetworkandbuildingahuge“Sensornetwork”interconnectingthe

citiesaroundtheglobe.Thisusecasewillhavetoconsiderahighconnectiondensity


profileaswell,assomeurbanareascouldbeintensivelyinvadedbythousandsof

devices.

From the different key targets and use cases, some of the targets creating the

technicalchallengesareasfollows:

Internet of Things (IoT) capacity requirements

The IoT is predicted to create a massive increase in the number of devices/

connectionsacrosswirelessnetworks.Itisenvisagedthatmanybillionsofdevices

will be connected to thenetworks, althoughmanyof themwill beonly sending/

receivingdataonanintermittentofverylowdatarate.Thiswillcreatenewdemands

in termsof the capacityof thenetwork to transmitdata,butalso the capacity in

termsofnumberofconnectedusersthatcanbemanagedbythenetwork.Incurrent

3GPPbasednetworkstherearelimitsonnumbersofusersthatcanbeconnected

tospecificnetworknodes,andthis limitmaybe insufficientforfutureneeds.The

capacity requirement is expressed both in terms of number of users connected

(registered) to thenetwork,andalso in termsofnumberofusersactive (making

simultaneousdatatransactions)onaspecificnetworknode.

Volume of data

Datawillbeoneofthekeydriversfor5G.Firstly,continuingthelegacyfromLTE,voice

willbetotallyhandledasanapplicationsimplyusingthedataconnectivityprovided

by the communication system and not as a dedicated service. This is an additional

increaseinadatagrowingpaceofbetween25%and50%annuallyandisexpected

tocontinuetowards2030duetotheincreaseinsizeofcontentandthenumberof

mobileapplicationsrequiringhighdatarates,theriseinscreenresolutionwiththe

recent introduction of 4K (8K already in development and expected beyond 2020)

and the developments in 3D video.

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Traffic growth towards 2030

Rel

ativ

e g

row

th100,000

10,000

1,000

100

10

1

2010 2012 2014 2016 2018 2020 2022 2024 2026 2028 2030

Year

Up to 1000x trafficgrowth may be met through LTE-A evolution

5G will see up to 10000xtraffic growth and requiredisruptive technologycomponents

Traffic volume per subscriber

+ 50% per year+ 25% per year

Traffic subscriber base

+ 10% per year

Mobile broadband penetration

reaching 100% by 2020

Fig12-Predictedtrafficvolumetowards2030*(FigurefromNokia5Gwhitepaper)

Types of data

Ithasbeenwidelydiscussedandseenintheindustryoverthelast5yearsthatthere

isaneedtoincreasethecapacityofthenetworkwithoutincreasingthecost.Users

are consuming increasingly more volume of data (mainly through video services)

but are reluctant to pay 100x more subscription costs to cover the 100x volume of

datatheyuse.Sothereisamajorchallengetoincreasethecapacityofthenetwork

(bothvolumeofuserplanedata,andvolumeof controlplanedataandattached

devices to be managed). One technology already being developed in 3GPP for LTE

networksistoseparatethedistributionofcontrolanduserdataplanestoalignto

data requirements. One typical example is to provide the control plane signaling

toawideareausingamacrocell,andthenuserplanedataviasmallcellswithin

the coverage of the macrocell. This enables a higher capacity of user plane data

withinthearea,duetohigherfrequencyre-useofthesmallcells,withouttheadded

complexity of requiring control plane function and co-ordination across many small

cells(whichthenrequiresahighamountofbackhaulcapacitytocarrythisinter-cell

control information).

17|Understanding5G

Asecondevolutioninthenetworkdesign,complementarytotheuser/controlplane

separation,isthemovetowardscloudservicesandcloudRAN.Inthisconcept,some

ofthefunctionoftheRANnetwork(e.g.eNodeBinLTEnetworks)ismovedfromthe

cell site or eNodeB back into a cloud service. This provides a key technology platform

to support scaling and economy, leading to deployment flexibility, and easier re-

configuration.Thisisbecausenowthecoresignalingandintelligenceisheldwithin

thecloud,andtheonlylocalizedphysicalelementsaretheRFtransceiverstoconnect

tousers.Thisreducesthecost/complexityof the localizedelements,givingbetter

flexibilityandcostefficientscalabilityofdeployment.

New types of services

Highly reliable communications links are an emerging trend for cellular network

systems.Medicalmonitoringsolutionsarealsomovingincreasinglytousewireless

networks,toprovideremotepatientmonitoring/careaswellasgreateraccessfor

remotesupport tomedicalstaff.Emergencyservices, (e.g.police/fire/ambulance)

providecriticalservicesthatrequirehighreliabilityvoicelinks,withoutissuesofcall

drop,busynetworketc.Today’ssolutionsprovidehighreliabilitybyhavingdedicated

networks,butwith limiteddata capacityorperformance,and requiringhighcost

investments to provide even reasonable coverage. Future requirements are for high

datarate,andrealtimeinteraction,sothesecriticalservicescanrespondfasterand

withmoreimmediateremoteconnections.

Real time and Virtual Reality services. As augmented reality becomes deployed into

portable/personaldevices,sothedemandonnetworkperformanceisdramatically

increased. One key aspect is that the latency (delay) must be very small to enable

trueinter-actionbetweentherealandvirtualenvironments.Thehumanbrainisvery

sensitive to timedelayswhenprocessingvisualdata,due to theprocesses in the

braintoconverteyeimagepatternsintoimageswe“see”inourmind.Ifthenetwork

cannot interactwith our eye/brain process in real time then a true virtual reality

servicecannotbedelivered.Thekeytodeliveryofsuchaserviceislatency,andso

eachstepinthelinkbetweendeviceasservermustbeoptimizedforlatency,and

weneedtotest/measurenotonlytheendtoendlatency(RoundTripTime,RTT)but

alsothelatencyineachlink,andhavemethodstoinvestigatethecauseofexcessive

delays/failures.

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ThereismuchdiscussioninthewirelesscommunicationsindustryaboutMachineto

Machine(M2M)communicationbeingabigdriverforfuturegrowth,asanenabling

transport technology for the Internet of Things (IoT). Although there are many case

studiesandpotentialbusinessmodelsbeingdeveloped, there isone segmentof

theindustrywhichisalreadypushingforwardinthisarea,theautomotivebusiness.

There are a number of automotive applications already under development or in

earlytrials/deployment:

•In-Vehicleinfotainmentdrivesmobilewirelesslinkcapacitytothe“vehicleasahub”.

•Useofvehicleasbasestationorrelaynodeduetoenoughbatterypower.

•IntelligentTransportSystems(ITS)creatingdemandforVehicletoVehicle(V2V),vehicletoInfrastructure(V2I),andgenericVehicletootherdevices(V2x).

•Autonomousdriving,convoydriving,safetyalertandtrafficmanagement.

Oneareathathasbeentraditionallyoutsideofcellularnetworkcommunicationsis

DevicetoDevicecommunications,whichisdirectlinkswithoutrelayofinformation

throughthebase-stationornetwork.Suchtraditional“walkietalkie”systemshave

beeninexistenceforalongtime,usinglimitedaccesscontroltopreventinterference

or overlapping of messages. However, the ability to transmit data is severely

limited,andtheneedtohaveaseparatedeviceforthiswalkietalkiemodeversus

aconventionalcellulardevicehasbecomeauserissue.Previouscellularnetworks

havedeveloped“pushtotalk,PTT”technologytodeliverasimilaruserexperience

whereavoicemessageisdeliveredtoallusersonthesamefrequency/network(like

awalkietalkie),andthishasbeenshowntobetechnicallyfeasible.Thelimitationis

stillthatthecellularinfra-structureisrequiredtorelaythemessages,andforcritical

communications (e.g. emergency services) then it can not be relied that there is

workinginfra-structurewithsufficientcoveragewhenitisneeded(e.g.earthquake

disaster zone). Hence the development of Device to Device (D2D) to allow direct

communications.ThistechnologyisalreadybeingdevelopedinLTE-A(e.g.‘SideLink’),

butisexpectedtohaveamuchmorerobustimplementationin5Gwherethenetwork

isalreadydesigned/optimizedtocarrythistypeofcommunications.

19|Understanding5G

5Gwillintroducemorerequirementsofthetransportnetworkandoverallarchitecture

in order to ensure support for any-to-any communication, so not only device to

device but also node to node self-backhauling. Intelligent Transport Systems (ITS)

fortrafficcontrolandpassengersafetypurposescouldalsobenefitfromthiskindof

communication technology.

Fig13-DevicetoDeviceCommunication*(PicturefromEricssonResearchBlog:“D2DCommunications – What Part Will It Play in 5G?”)

5G architecture will support D2D better than LTE can do nowadays. However,

D2D communication still implies new challenges for devices design, security or

interferenceandmobilitymanagement,betweenothers.D2Dwouldalsoinfluence

newbreakthroughsinbackhauldesign,whichwillberequiredtoenableverydense

networkingofradionodes.Nodeswith‘plug-and-play’techniquestoaccessandself-

organizeavailable spectrumblocks forbackhaulingwillbekey forenablinghigh-

frequency spectrum radio access.

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CellularCommunication

Network Control

Direct (D2D)Communication

Fig 14 - Device to Device and Cellular communications share the same radio resources

*(PicturefromEricssonResearchBlog:“D2DCommunications–WhatPartWillItPlay

in5G?”-ThenetworkcontrolsandoptimizestheuseoftheresourcesforbothCellular

communicationandD2D,resultinginenhancedperformanceandqualityofservice.)

All of the above challenges are now starting to drive the areas of research,

highlightingthelimitationsofcurrentnetworksandtheenvisagedrequirementsof

futurenetworks.Currenttechnologydevelopmentsanduserdemandsaremerely

providing a glimpse of the nature of 5G networks. At themoment, cost is not a

majordriverof5Gtechnologydiscussions,allowingamuchwiderlistofcandidate

technologiestobeconsidered.Inordertodiscussthesetechnologiesmeaningfully,

cost analysis is also not a key factor in this article. It is the radical and disruptive

changestotheexistingnetworkthatareoutlined.

Itisclearthatanewairinterfacewillbeneeded.CurrentR&Dworksuggeststhat

a5Gnetworkwillconsistofseveralair interfacescoexisting inthesamenetwork.

Fromatheoreticalperspective,thisisideal(e.g.OFDMdoesnotlenditselftosmall

cellsandHetNetsandthereareother,bettercandidates),butfromanoperational

and economic perspective, this would mean significant development costs and

deployment effort.

Sotheresearchissplitintonewwaveformsbelow6GHzfordeploymentintoexisting

radio bands to increase efficiency and overcome interference issues, and new

waveformsabove24GHzwhichareoptimizedforthehigherfrequencyandwider

bandwidthsavailable.


Research subjects

Theacademiccommunity,andindustryresearchprograms,arecurrentlyinvestigating

a number of subjects to identify and develop key technologies. The research subjects

are based around the generic technical needs for 5G to meet the objectives and

targets previously outlined.

Low powerconsumption

Up to mmWavecommunication

FlexibleSpectrum Use

Always ON,low overhead

Flexible UL/DLduplexing

1 ms RTT

10 GBps

Low cost

Native supportfor Access, Self-

Backhauling, D2D

Internet Cloud

Fig 15 - Research Subjects for 5G

Extreme densification

Networkdensificationisnotnew.Assoonas3Gnetworkswerecongested,mobile

operatorsrealizedtheneedtointroduceeithernewcells intothesystemormore

sectors. This has evolved to includemanyflavors of small cells,which essentially

movetheaccesspointmuchclosertotheenduser.Thereissimplynootherwayto

increasetheoverallsystemcapacityofamobilenetworksignificantly.5Gnetworks

are likely to consist of the several layers of connectivity that HetNet architecture is

currentlysuggesting:amacrolayerforlowerdataspeedconnectivity;averygranular

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layerforveryhighdataspeeds;andmanylayersinbetween.Networkdeployment

and coordination are major challenges to be addressed here, as they increase

exponentiallywithrespecttothenumberofnetworklayers.

As we have indicated already, 5G networks would be principally designed

for data-centric applications rather than voice-centric applications. Network

densificationisverysuitableforincreasingthecapacityanddataratetomeetthe

future demands.With the increasing density of networks, also the backhaul will

become more heterogeneous and possibly also scenario dependent. The high data

ratesof5Gwouldimplythatthebackhaul/fronthaulwouldneedtobefiberopticto

achievethedataratesrequired(i.e.1-10Gb/spersector).Nevertheless,Millimeter

wavebackhaul/fronthaulisanotherattractiveoption,probablycheaperandsurely

easiertodeploythanfiber,buttechnologicalandregulatorychallengesareyettobe

addressed.Inaddition,theconnectivityamongthenetworknodesshouldallowfor

fastdirectexchangeofdatabetweenthem,whichwillbechallenginginUltraDense

Network (UDN)deployments. The radioaccessnetworkswill alsobe impactedby

theheterogeneousbackhaulstructure,e.g.latencydifferencesondifferenttypesof

backhaullinkswillimpactintercellcoordinationandcooperationalgorithms.

Itislikelythatthecostimplicationsofdevelopinganentirelynewbackhaulnetwork

willinsteaddrivetheindustrytodevelopnewtechnologythatisabletouseexisting

IPnetworktechnologyandinfrastructureinabetterway.Alreadyin4Gtherewasa

migrationto“allIP”networksandsupportofIPv6signaling.Thishasalsoevolvedto

providebetteruseofMPLStechnologyforIProutinginthenetwork,andOTNfor

corenetworks.Ascloudservices,NFVandSDNeachevolveincurrentIPnetworks,

it isexpectedthatthesebecomekeytechnologiestoresolvethegapbetweenthe

costandperformanceofcurrentmobilenetworkbackhaulversustheidealnew5G

backhaul.

Thenewnetworkarchitecturemaybefocusedalso intothepublicconcernabout

EMF induced by wireless networks. By reducing the distance between receivers

andtransmitters,smallcellsenabletheminimizationofthepoweremittedbythe

mobilesdevicesandthetotalEMFexposure.5Garchitecturecombiningsmallcells,

heterogeneousnetworksandoffloadingshouldinherentlyenableminimizingboth

thehumanEMFexposureandthepowerconsumptionofthenetwork.


Air interfaces for higher data rates and higher capacity

Incurrent4GLTE(OFDMA)networkswerequireself-interferenceavoidance,which

isstrictlyatimingbasedapproach,andthiscauseshigherpowerconsumptionand

significantwasteofcontrolplanesignalingresources.Interferenceresistantaccess

schemes in 5G that could replace the currently used OFDM are under intensive

evaluation.MoreefficientorthogonalschemessuchasFBMC,UFMCorGFMD,which

introduce a better use of the spectrum are excellent candidates for the upcoming 5G

accesswaveform.Generally,orthogonaltransmissioncanavoidself-interferenceand

thisleadstoahighersystemcapacity.However,forrapidaccessofsmallpayloads,the

procedure to assign orthogonal resources to different users may require extensive

signalingandleadtoadditionallatency.Thussupportfornon-orthogonalaccess,as

acomplementtoorthogonalaccess,isbeingconsideredaswell.Examplesinclude

Non-Orthogonal Multiple Access (NOMA) and Sparse- Code Multiple Access (SCMA).

Orthogonalmulti-carrierwaveformswillstillremainasthepreferredschemebecause

theyfitverywellwithMIMOtechniques,whichwillbemassivelydeployed.UL/DL

fullduplexandsimultaneoustransmission,alongwithwiderbandwidthsfrom100

MHzonwards,willdrivetheairinterfacetosupporthigherdatarates.Itisexpected

thatmulti-carrier schemes will usemultiple carriers of either 20MHz or 100MHz

bandwidth,togivescalableRFbandwidth.

Ontheotherside,millionsoflowdataratedevicesforMachineTypeCommunications

(MTC) may require new interfaces with much lower network capacity demand,

buthighrobustness, inordertoensureconnectivityatanytime.DevicetoDevice

communications, especially thought for public safety and services applications,

wouldalso join thisgroup.Thefirst steps to thisarebeing taken in LTE-A,being

categorizedas“CategoryM”devices,wheretheairinterfaceandnetworksignaling

andsupported features/data rateareminimized inorder toprovide lowerpower

consumptionofdevicesandlowercostofdevices.

A further development for the air interface is the area of Cognitive Radio. This is the

capabilityforadevicetosensetheRFenvironmentandmakeconfigurationdecisions

based on the local RF characteristics. Examples of such functionality are the sensing

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ofunusedRFspectrum(socalled‘whitespaces’)andthenthetemporaryuseofthese

unused“whitespace”frequenciesfordatatransmission.Amoreadvancedexample

is intheareaofSoftwareDefinedRadio (SDR),wheretheradiomodemisableto

re-configureitselftosupporttheprotocolsandRFtransmissionformatsbeingused

locally,basicongenericTx/Rxcircuitsandthensoftwarebasedmodemfunctions

thataredynamicallysettomatchlocalprotocols.Thedevicewillfirstsamplethelocal

RFenvironment,andthenbasedonevaluationoftheRFcharacteristics,asuitable

modemconfigurationandprotocolstackisloadedfrommemory(orfromthecloud)

tosupportthelocalnetwork.

Cell coverage improvements

TheconceptsofMacrocellandSmallcelloverlays,emergingpreviouslyin3Gand

LTE-A,willgrowinimportancefor5G.Complexheterogeneousnetworkswillappear

asahighnumberofsmallcellsthatoperateonasinglefrequencyband,eachserving

small areas.Wewill seemultiple-antenna systems providing SpatialMultiplexing

techniques, i.e. transmitting different data streams through each element and,

consequentlyincreasingthedatarate,andalsobeamformingantennatechniques

for improving the quality of transmission or the signal-to- interference-plus-noise

ratio(SINR),whichhavealreadybecomepopularfromTD-LTEdeployment.“Massive

MIMO”ordenseantennaarrayscomposedby,forexample,64x64elements,willsuit

tommWsystemsduetothesmallphysicalsizeandprecisefocusingtheycanoffer.

Co-operative antenna techniques refers to the capability of handling the information

received from spatial distributed antennas belonging to different nodes in a

wirelessnetwork.ApplicationintoSingleUserMIMO(SU-MIMO)hasbeenthefirst

appearanceofthesetechniquesinLTE-Advance.Inthenextstep,co-operativeMIMO

ordistributedMIMOwillgroupmultipleradiodevices(includingusers’devices)to

formvirtualantennaarrayssothattheycancooperatewitheachotherbyexploiting

the spatial domain and improving coverage and cell edge throughput. Some devices

canalsobetreatedasrelaystohelpthecommunicationbetweenthenetworkand

device.Thisisconsideredasoneofthenewemergingtechnologiesin5G,thusmany

researchchallengesincooperativeantennashavetobeaddressedbeforethewide

deployment.


Key technologies

Basedupon the research subjectareasdiscussed, thereareanumberof specific

technologyneedswhicharecurrentlybeinginvestigatedtoidentifyspecificsolutions

andcandidatetechnologiestobeusedwithin5Gnetworks.

Microwave highpower BS

Sensors

Downlink

Uplink

Microwave lowpower BS

Control

Data

mmWave RS

mmWaveindoor

MobileDevice

D2D

Centralizedbase-band

Fig 16 - Key Technologies for 5G

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Network design

A parallel evolutionary trend to 5G is software virtualization and cloud services,

wherethecorenetworkisimplementedontoadistributedsetofdatacentersthat

provideserviceagility,centralizedcontrol,andsoftwareupgrades.SDN,NFV,cloud,

and open ecosystems are likely to be the foundations of 5G and there is an ongoing

discussionabouthowtotakeadvantageoftheseintonewnetworkarchitectures.

An adaptive network solution framework will become a necessity for interfacing

withboth LTE andnewair interface evolution: Cloud, SDNandNFV technologies

willreshapetheentiremobilenetworkdesignprinciples.Asthethree-tierhierarchy

(access, forwarding, and control) of network architecture is being replaced by

flatter architectures, virtualizedapplication software is replacingdiscretenetwork

elements,andnetworkinfrastructureisbecomingmore‘programmable’.WithSDN

thenetworkwilldynamicallyadaptitselftoprovidetheconnectivityservicesthatbest

servetheapplication,andabetterapproachwilleventuallyproducenetworksthat

aremuchmoreflexible inprovidingnewservicesandmonetizingthenetwork,as

wellasbeingmoreefficientintheiruseofresources.Suchacapabilityisnowbeing

introducedundertheconceptofnetwork“slicing”,whereasliceismadeacrossthe

differentdomainsofthenetworktoconfigureforaspecificservice.

Access Plane Forwarding Plane

Control Plane

WiFiCentralization

Mesh

Ad-Hocnetwork

Edgecaching

CentricDC

Servicesteering

Distributed GW

Network Controller

Infra-structure Pipeline Value-added

services Context

OTT MVNO Enterprise

Radio MM Policy O&M Orches-tration

Serviceexposure

Controllermodular

API

Figure 17 - Three-planes based 5g network architecture

27|Understanding5G

NetworkFunctionVirtualization(NFV)worksbyvirtualizing intosoftwaretheroles

ofthevariousnetworkfunctionelementsintoaseriesofVirtualNetworkFunctions

(VNF). These different VNFs run on standardized hardware (servers), leading to

the virtualization of the physical network infrastructure that provides a seamless

deployment. VNFs are then linked together to provide a specific service for the

customer, using service chaining which is configured, managed, and monitored

through the operators service orchestration function. Service providers can now

integrate this optimized virtual infrastructure with their service orchestration

systems.ThisallowsthemtointegratetheirOSS/BSSimplementationfordynamic

routing,billinganddeliveryofservices.

Current mobile networks have evolved from a traditional Datacom network

architecture,wherethedataflowiscentralizedandtheaccesscontrol is localized

at the access point. This means in effect that all user data travels from one access

point(whereitentersthenetwork)toacentralizedlocation(gateways)andthenback

outtotheaccessplanewhereitisdeliveredtotherecipientaccesspoint.Similarly,

accessiscontrolledlocallyatanaccesspoint(e.g.eNodeB),butneedstobecentrally

co-ordinatedso controlplanemessagesmustpass through thenetwork.Bothof

thesephenomenaareincreasingthevolumeoftrafficthatmustbecarriedacross

thenetwork.Thereisnowresearchintonewarchitecturesthatreversebothofthese

designs. Firstly then, user plane data is now considered to flowdirectly between

accessnodes,andnot througha centralhub, so itonly travelsonce through the

network.Sothemovetoacentralizedcontrolplaneandadistributeddataplanecan

offerareductioninnetworktrafficloadforagivenvolumeofcustomerdatabeing

carried.Toachievethishoweverdoesrequiresignificantlyhigherconnectivityand

lowlatencylinksbetweenallnodes,butcelldensificationandNFV/SDNtechnologies

are already driving in this direction so it may be that 5G can leverage directly from

this.TheconceptofNFViswellsuitedtothis,asthenetworkcontrolfunctionscan

be virtualized and housed centrally in servers tominimize traffic flow across the

network.Similarly,userplanedatacanenter/leavethenetwork,andcanroutetoany

accesspoint,byusingvirtualizedgatewayfunctionsratherthanneedingtoberouted

to/fromacentralizedgatewayphysicalelement.

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A parallel technology/architecture development alongside the User Plane and

Control Plane routing, is also the separation of these two data types at the air

interface.IncurrentLTEnetworks,thereisachallengeinmanagingthecontrolplane

signalingin“smallcells”duetotheinterferenceofcellswithoverlappingcoverage

(the challenge and implementation of eICIC and derivatives). But this overlapping

coverage and deployment of many small cells is required to provide enough capacity

intheUserPlaneforthe largevolumesofdata.SoweseethattheControlPlane

andUser Plane have different requirements and different restrictions, which are

clashingwitheachother.Soonepossiblesolutionistoseparatethemondifferent

airinterfacelinks.ThustheControlPlanecanberoutedtoawidecoverageMacro

cell, providingunifiedand co-ordinated scheduling and control information to all

usersinaparticularregion,whilstthecorrespondinguserplanedataiscarriedon

localizedsmallcellsclosetotheuser.Thisgivesgreateruserplanecapacitywithout

interference problems on the control plane. This concept is a natural extension of

the principles of Carrier Aggregation and Cross-Carrier Scheduling that are already

introduced intoLTE-Advancednetworks.A secondevolutionof this concept is to

separate downlink and uplink transmissions to separate cell sites. This has the

advantageofallowingthedownlinkdatatoberoutedbythenetworktoacellthat

hasenoughcapacityforthedata,butallowstheuserdevicetosenduplinktoacell

thatislocatedcloseby,andhencereducetheamountoftransmitpowerrequiredby

theuseruplinktransmission.Thiswillreduceinterferenceontheuplink,andallow

a longer battery life “talk time” for the user device. Whilst all of these technologies

offergreatbenefits, theydodemandsignificantly largervolumesofcontrolplane

datainthenetwork,toensureallcellsitesrelatedtoasingleuserdatatransmission

areco-ordinatedandlinkedtogether.CurrentLTE-Anetworkswerenotdesignedfor

suchhighcapacityandlowlatencycontrolplanedata,andaskdiscussedpreviously

theNFV/SDNarchitectureconceptmaybebettersuitedtothisnetworkdesignidea.

SowecanseethatSDN,NFV,andcloudarchitectureswillplayavitalrole innext

generationofnetworkarchitecture. It canprovidean implementationmodel that

easilyandcosteffectivelyscaleswiththevolumeofdataandvastincreaseexpectedin

connecteddevices.Secondly,itallowsserviceproviderstomoreeasilyandefficiently

manage a dynamic network, with great flexibility to re-configure the network

29|Understanding5G

functions and capacity. Thirdly, SDN/NFV provides a practical implementation for

moreefficient routingofbothUserPlaneandControlPlanedata, to reduce total

datavolumetravellingacrossthenetwork,andtoreducelatencieswithmoredirect

routingthananarchitecturebasedoncentralizedhardwarefunctions.Thiswillbetter

supporttheseparationofControlPlaneandUserPlanedata,andtheseparationof

downlinkanduplinkdata.

Figure 18 - NGMN 5G architecture (Source NGMN)

CloudRAN isa specific concept that is rapidlybeingdevelopedandprepared for

commercialdeployment.ThisaimstocentralizethefunctionsoftheRANnetwork

(e.g.eNodeBforLTE,NodeB&RNCfor3G)withinthecloudservers,suchthatonly

the physical transceiver and antenna elements of the eNodeB need to be physically

locatedatthecellsite.Thisprovidesforamorecostefficientdeployment,especially

for“smallcells”orlocalcellsitesusedtoboostcapacityorfillgapsincoverage.The

CloudRANconceptistakingadvantageoftechnologiessuchasCPRI,thatallowthe

basebandtoTRXlinkofthebasestationtobecarriedondedicatedhighspeedoptical

fiberlinks.ThistechnologyhasalreadybeendevelopedforRemoteRadioHeaduse

(RRH), where the TRX/ Antenna is separated from the base station baseband by

several meters (top and bottom of cell site mast) up to separation of hundreds of

metersorofkilometers(e.g.forinbuildingorshoppingmalldeployment,wherea

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singlebasebandservesallTRX/antennasites).SoCloudRANisextendingthesame

conceptfurthersuchthatallTRX/Antennasitesinanetworkregioncanbeconnected

byafiberringtoacentralizedbasebandserver.Ofcoursethistechnologycurrently

reliesonhavingdedicatedfiberaccesstoeachcellsite,andthiscanlimitdeployment

in some scenarios.Wewill see later therefore that there is parallel research into

providingasuitablewirelessbackhaulforCloudRAN.Thekeychallengehereisto

havelowenoughlatencyandhighavailabilityacrossawirelessbackhaul,because

thebasebandalgorithms in theNodeB require latenciesof very fewmilliseconds

in order to meet the timing requirements of the scheduler and re-transmission

functions in the basestation.

Severalnetworksarecurrentlyprovidingconnectivityforend-userdevices:cellular,

Wi-Fi,mm-wave,anddevice-to-deviceareafewexamples.5Gsystemsarelikelyto

tightly coordinate the integration of these domains to provide an uninterrupted user

experience.However,bringingthesedifferentdomainstogetherhasproventobe

aconsiderablechallengeandHotspot2.0 isperhapsthefirstexampleofcellular/

Wi-Fiintegration.Whethera5Gdevicewillbeabletoconnecttoseveralconnectivity

domains remains to be seen, and amajor challenge is the ability to successfully

switchfromonetoanother.

Themigrationto5Gnetworksmaybedoneina“stepbystep”approach,withexisting

4G operators looking to boost the capacity/data rates to 5G levels by using a 5G air

interfaceworkingontoanexisting4Gcorenetwork.Withsuchadeployment, the

5Gairinterfaceiseffectivelyanchoredtoexisting4Gnetwork.Soitislikelythatwe

willfirstsee5Gairinterfacedeployedwitha4Gcorenetworkanchor,andthenin

asecondphasethecorenetworkcouldbeupgradedtoa5Garchitectureandthen

boththe4Gand5Gcouldbedeliveredfroma5Gcorenetworkanchor.Oneofthe

mainconcernpointshereistheabilityoftheanchornetworktosupporthand-over

to other access technologies, as this capability is a fundamental requirement for

launchinganetwork.Sotheinter-RATrequirementsofthespecificoperator,andthe

technicalabilitiesofthecorenetworkanchorfunctionwilltogetherdeterminehow

eachnetworkisupgradedto5G.


New frequencies for radio access

As the RF spectrum up to 6 GHz has been fully allocated to different uses and

services, the need for wider bandwidth of radio to support higher capacity data

links is pushing the industry to investigate higher frequencies. Even if additional

frequency bands below 6 GHz weremade available formobile communications,

therearestill fundamental limitsontheamountofbandwidththatcouldpossibly

becomeavailable.Thereare,however,muchwiderbandwidthsofspectruminthe

higherfrequencybands,whichreachashighas100GHz.Thefundamentalphysicsof

RFpropagationmeansthatnetworkdesignforsuchhighfrequenciesismuchmore

complicated than network planners are accustomed to, as the center frequency

increasesthenbuildingpenetrationbecomesmoredifficultuptothepointwherea

buildingbecomesanopaquebarrierformillimeterwavesignals.However,thereis

significantspectrumthatcouldbeavailableinthesebands,andthismaybeusedfor

short-range,point-to-point,line-of-sightconnections,providinghighspeedandhigh

capacitywirelessconnectivity.

Mm-wavecouldbeusedbyindoorsmallcellstoprovideveryhigh-speedconnectivity

inconfinedareas.Thehigh-frequencynatureofmm-wavemeansantennascanbe

verysmallwithonlyasmallimpactondeviceformfactor.Anumberofmarketanalysts

stillbelievemm-waveisaradicaltechnologyandmayrequiremanyyearsofR&Dto

becost-effectiveforthemassmarket.Therearestillkeyissueswiththeperformance

of semiconductors at these frequencies, givingan impacton the cost andpower

consumptionofdevicessuchasamplifiersandmixers,which fundamentally limit

the range/sensitivity of radio transceivers. This technology is now evolving from

specialisthighcostmarketstobecomingaffordableforhighvolumeandlowcost

massed markets as the semiconductor technology is further developed.

It is interesting to note that developments inmm-wave are not new: theWiGig

allianceisfocusingon60GHzspectrum.Overthelastfewyearstherehavealsobeen

a number of acquisitions of specialist mm-Wave technology companies by major

telecomplayers,astheyseektoincreasetechnologycapabilityandIPRinthisarea.

Aprimetargetwerethecompanieswhichhaveemergedoverthelast10yearsto

useadvancesinsemiconductortechnologytorealizecostefficientmm-Wavecircuit

technologyforthe60GHzband

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Itisclearthat5GwillneedGbitsbackhauland,sofar,onlyfiberopticsandwireless

canprovidethisservice.Ononeside,thedrawbacksoffiberarethecostandthe

difficultiesforinstallationinurbanlocations.Ontheotherside,wirelesswouldneed

mm-Wave band to meet the high data rate requirements. The disadvantage here

isthatmm-WaveneedsLineofSight(LOS)operation.Technicallyspeaking,itcould

be overcome by electrically steerable antennas and directional mesh for a true SON

backhaulinaNonLineofSight(NLOS)environment.Insupportofthis,thereisnow

agrowingareaof research forNLOSmm-Wave links,whichuseadvancedMIMO

toenablehighdataratelinksintoadenseurbanenvironmentwherethecomplex

multipathenvironmentmaybeusedtosynthesizemanydifferentspatialpathsto

support a dense backhaul.

Meshnetworkingreferstoanetworktopologyinwhicheachnode(calledamesh

node)relaysdataforthenetwork.Allnodescooperateinthedistributionofdatainthe

network.InaSmallCellmeshbackhaul,mm-Waveisavaluabletechnologybecause

longbackhaul linksarenotrequiredandLOScanbesatisfied. Inthesenetworks,

each node establishes optimal paths to its neighbors using self- configuration

techniques.WhenlinkcongestionordeterioratingRFconditionsoccur,newpaths

aredeterminedbasedonQoSrequirementssuchaslatency,throughputandpacket-

error rate and the mesh self-tunes itself to achieve optimal performance. Such a

densenetworkisconfiguredtohaveredundantlinksandmanypossiblenodes,and

itisthisdifferencetoconventionalbackhaulthatgivestheflexibilityandenablesthe

self-configurationcapability.

Wecaneasilyseethat thecombinationofmm-WaveNLOSandmeshnetworking

givesaveryattractiveconceptforfuturedensecitydeployments.Itallowsforgreat

capacity,dynamicmanagementofcapacity,andavoidstheneedforextensivefiber

deploymentsandsignificant infra-structureprojects. Instead the infra-structure is

flexiblydeployedandconfigured,andnolongerisalimitingissueonthelocationand

deployment of cells sites.


Figure19-mmWmulti-hopdirectionalmeshsmall-cellbackhaul*(Figurefrom“SmallCellMillimeterWaveMeshBackhaul”whitepaper,InterDigital)

Air Access and modulation schemes

Previousgenerationnetworks(2G,3G,4G)havebeendesignedas“signalstrength

limitednetworks”, that isthecoverageofthenetworkwasdefinedbytheareaof

adequatesignalstrength(signaltonoiseratio,SNR).Advancesintheair interface

weredesigned to improve the SNRandhence increase coverageand capacity of

thenetwork,givinghigherdataratesavailableacrossthecellduetoahigherSNR.

Thebaseassumptionforthiswasthelimitingfactoristhepropagationlossofthe

signal,andafteracertainlevelofsignallossthentheSNRnolongersupportsthe

requireddata channel (Shannon’s law). The extremedemands on capacity of the

networkshavedriventhearchitecturetoimplement“hyperdensification”through

smallcells,whichgivesmorecapacity inanetworkgiventhe limitedRFspectrum

resourceavailable.But thishasnowmovedthenetworkcoverage limitationfrom

beingaSNRlimitedtobeinginterferencelimited.Withmanysmallcellsdeployed,

thereisalwaysagoodSNRavailable,butwithmanycellsoverlappingincoverage

(heterogeneousnetworks)thenthelimitationbecomesthelimitofinterferencefrom

othercellsrather thantheSNRduetopropagation loss.Sonowthenetworkhas

becomeinterferencelimited,andthedevelopmentisnowunderwaytolookatnew

airinterfacetechnologiesthataremoreresistanttoRFinterference,asOFDMdoes

not offer good resistance to interference from other neighbor cells. 4G/LTE is using

OFDMA as the air interface access method due to its ability to easily support scalable

www.anritsu.com|34

bandwidth,leadingtoflexibleglobaldeploymentandscalabilitytosupporthigher

bandwidthsforhigherdatarates.Akeyissueforhighbandwidthsystemsislinearity

and distortion across the band. OFDM overcomes this by using many highly linear

andhighlyefficientsmallersub-bands.

A key weakness has come with OFDMA however, that is not aligned with the

capacity and density explosion that has hit the cellular industry. OFDMA does not

readilymanage interference,eitherexternal interferenceorself-interferencefrom

neighbor cells or overlapping coverage from small cells or local capacity hotspots.

LTE(Release8&9)hasabasicfrequencydomainmanagementtechniquecalledICIC

tomanagethisproblemforuserdatainoverlappingcells,butthisdoesnotmanage

the overlapping control plane data and cell broadcast/sync channels of adjacent

cells.Toovercomethis,LTE-Ahasintroducedatimedomainmanagementforthis

control signaling called eICIC and feICIC. Whilst these can succeed to manage the

control/broadcastinterferenceduetooverlappingcells,theydosobylimitingtimes

fortransmissionandhencereducecapacityofthenetwork.

So,thekeyresearchthemefornewmodulation/accessschemesistoallowtheflexible/

scalable bandwidth of OFDMA, but to overcome the interference management

issues in dense networks and Heterogeneous Network (HetNet) architectures

expected for5Gwithoutsacrificingcapacityorspectralefficiency.Thisproblem is

eventually leading tonewair interface technologiesormodulationschemessuch

asFBMC(FilterBankMulti-Carrier),whichimprovesthespectralefficiencyandcan

dramaticallyreduceinterference,UF-OFDM(UniversalFiltered-OFDM),whichshows

upmoreflexibletocombineMTCorTDD/FDDschemeswithwiderbandwidthsto

increasepeakdatarates,andGFDM(GeneralizedFrequencyDivisionMultiplexing)

whichisaflexiblemulti-carriertransmissiontechniquewhichbearsmanysimilarities

to OFDM but the main difference is that the carriers are not orthogonal to each

other for better control of the out-of-band emissions and the reduces the peak to

averagepowerratio,PAPR.Amoredetailedanalysisofsomecandidatewaveforms

ispresentedinthelaterchapterwherecandidatesaresimulatedandthenanalyzed.

Alongwith the newOFDMbasedwaveforms (which by definition are orthogonal

waveforms for each user) there is also research into non-orthogonalwaveforms,


whereusersdonothaveseparatetime/frequencyplotsbutsharetheresource in

another(noorthogonalway).TheprincipleofNon-orthogonalaccesswasusedin3G,

whichusesCDMAaccess,whereeachuserorcellhasauniquespreading/scrambling

codetoseparatethesignals,buttheysharethesametime/frequencyspace.CDMA

wasshowntohavelimitationsinspectralefficiencyandimplementationissuesfor

widerbandwidthhighdata rateapplications.Nowtherearenewaccessmethods

being evaluated that enable such non-orthogonal access to be applied to increase

capacity or flexibility of the network. The leading research includes NOMA with

SuccessiveInterferenceCancellation(SIC)whichalsocalledSemiOrthogonalAccess

(SOMA),SparseCodeMultipleAccess(SCMA),andInterleaveDivisionMultipleAccess

(IDMA).

SOMA expands the radio resource allocation for the frequency and time domains

usedinOFDMAbysuper-imposingmultipleusersignalsusingthepowerdomain,

toincreasethespectrumefficiencyevenfurtherandtoincreasethecapacity.Figure

1showsanexampleoffrequencyre-usage.Multipleusersinthepowerdomainare

superposedatthesymbollevel.Figure2showsanexampleofsuperpositioncoding

where theUser2propagationchannel loss is lower than theUser1propagation

channelloss.WhenusingQPSKasthemodulationmethodforeachuser,thesymbol

constellation after superposition approaches a constellation like that of 16QAM.

www.anritsu.com|36

Figure 20 -

Q

I

Q

I

Q

I+ =

x2

x1 x1

x2

User 2 (QPSK) User 1 (QPSK) Superposition User 1 & 2

Frequency domainFrequency domain

Pow

er d

omai

n

Pow

er d

omai

n

NOMA/SOMAOFDMA

User 1 User 2 User 3

Superposition Encoding Example

The receiver circuits are built using successive interference cancellation (SIC). As

User2hasbetterChannelgainthanUser1(lownoise,andsobothUser1andUser

2signals canbeclearly received), theUser2desiredownsignal isdecodedafter

subtractingtheeffectofUser1(usingSICtofirstsubtractoutUser1signal)from

thereceivedsignal.Ontheotherhand,User1decodes itsownsignalbytreating

theUser2signalasnoise.User2withlowchannellossisassignedthelowerpower

modulationpatternandtheUser1withthehighchannellossisassignedthehigher

powermodulationpattern tooptimize thesignalquality forallusers, resulting in

improvedspectrumefficiency.

SCMA isa relativelynewwirelessmulti-accessmethod. Itavoids theQAMsymbol

mapping used by conventional CDMA coding technologies and implements each

binarydatawordbycodingitdirectlyintomultidimensionalcodewords.Eachuser

or layer assigns the binary data output from the encoder directly to the complex

codeword (physical resources dimensions) according to a predefined spreading

code of an SCMA codebook. Multi-user connections are implemented by assigning a

different unique code book to each user or layer.

37|Understanding5G

A message parsing algorithm is used because the SCMA codebook contains sparse

code words, this achieves near-optimal detection of multiplexed data without

increasing the complexity of processing at the receiver side.

IDMA is a multi-access method which is very new to the industry. In IoT/M2M

communications there are expected to be a large number of connected devices

sendingsmallnumbersofpackets,and insteadofusingpacketschedulingbased

on OMA the NOMA method is being considered because it has good robustness to

interference and does not require scheduling (this helps extend battery life of devices).

IDMAwithinNOMA is shown tohaveexcellentuserdiscriminationcharacteristics

and using a multi-user interference canceled can achieve a higher throughput

comparedtothesametypeoftrafficonOFDMA.Additionally,IDMAiswellsuitedto

low-coding-rateerrorcorrectionandisconsideredappropriatefortransmittingthe

largenumberofmultiplexedsmall-packetsignalsusedbyIoT,M2M,etc.

In Band Full duplex

Allmobilecommunicationnetworkshavereliedonaduplexmodetomanagethe

isolationbetweentheuplinkanddownlink.Therearefrequencyduplex–FDD(such

asLTE,whereuplinkanddownlinkareseparatedinfrequencyandoperateatthe

sametime)–andtimeduplexschemes–TDD(wherethetransmitterandreceiver

transmitatdifferenttimesbutusethesamefrequency,asinTD-LTE).Aduplexmode

isnecessarytocoordinateuplinkanddownlinktopreventthetransmittersaturating

the receiver and blocking any signal reception, but now full duplex technologies

arenowbeingresearched.Inthisfullduplexschemeadevicebothtransmitsand

receivesatthesametime,thusachievingalmostdoublethecapacityofanFDDor

TDD system.

www.anritsu.com|38

TX Data

RX Data

Modulator(BB)

Demodulator(BB)

DAC

ADC

PA

LNA

Duplexer

f1

LO

LO

TX Signal

RX Signal

ANT

Post-LNA digital cancellation

(Subtract a digital TX copy

from the RX input signal at the

demodulator).

Shall account for both linear

and non-linear TX distortions.

Pre-LNA analogue cancellation

(Subtract an analogue TX copy

from the RX input signal at the

LNA).

Shall account for the ADC

resolution to avoid saturation.

Antenna and Duplexer design

to minimize leakage and

antenna reflection.

DigitalCancellation

AnalogueCancellation

Isolation

20-30 dB 20-30 dB 25-40 dB

Both use knowledge of TX signal

Fig 21 - Sources of Interference

There are major technology challenges to achieving what is essentially self-

interference cancellation, and major changes in both networks and devices are

requiredforfullduplexoperation.However,thepotentialincreaseinoverallcapacity

issubstantial,makingfullduplexaveryimportanttechnologyforthefutureofmobile

networks.InacurrentLTEnetwork,thetransmitteratthedeviceendmaybeupto

23dBmoutputpower,andrequiresbelow-113dBmreceiversensitivity,soatotal

of136dBisolationwouldberequiredintheextremecase.Wecanseethatcurrent

researchhasreported110dBisolation,soitisimprovingbutstillsomewayoff.Itis

thereforeunderstudytoseeifausefulfigurecouldbeachievedinthetimeframeof

5G deployment.

Sothekeytoachievinghighercapacity (spectrumefficiency)via“fullduplex” is to

solvethetransmit–receiveisolationproblem,protectingthereceiverfromsaturation

by the transmitter. The traditional approach is to use normal circuit design principles

forbestpossibleisolation(worksforduplexorleakageandantennareflection),but

thisdoesnotgiveenough isolation for therequiredreceiversensitivity,anddoes

not protect againstmultipath reflections beyond the antenna that create strong

interference.Sothenewapproachtosolvethisprobleminvolvesaddedinterference

cancellation, so that any residual interference can be removed and the required

39|Understanding5G

sensitivity achieved. This cancellation is required at both the analogue stage and the

digitalstage,togiveenoughperformanceatanaffordablesize/price.

Duplexer Leakage Antenna Reflection Multipath Reflections

TX Data

RX Data

Modulator(BB)

Demodulator(BB)

DAC

ADC

PA

LNA

Duplexerf1

LO

LO

TX Signal

RX Signal

ANT

Due to practical limitations

in the duplexer design

and additional mismatch at

the duplexer’s output

connection to the transmission

line connecting it to the

antenna.

Due to mismatch between the

transmission line impedance and

the antenna’s input impedance.

Due to reflection in the

surrounding environment.

+ +20-30 dB 20-30 dB 24-40 dB

Figure 22 - Cancellation of Interference

AlongsidetheTx-Rxisolationproblemateachradio,thereisalsotheneedforproper

access co-ordination for themultipledevices in thenetwork.Suchschemes, such

asTDMA,CDMA,OFDMAarealreadyexisting.Butasnewandmoreefficientaccess

schemesaredevelopedfor5G,theymayalsohavetotakeintoaccountthefullduplex

modewhentheaccessco-ordinationmethodsarebeingevaluated.Differentaccess

schemeswillchangetherequirementsforchannelmeasurementsandcancellation

algorithms,andthiswoulddirectlyaffecttherealworldperformanceandefficiency

of any full duplex modes.

One use case that is attracting attention is the use of full duplex to enable “self

backhaul” in a small cell environment. This effectively means that a small cell can

use theair interface toprovidebackhaul toamacrocell,andsimultaneouslyuse

the same air interface to provide service to a local small cell. This enables simple

placementofsmallcellsintothenetworkasrangeextenderstoimprovecoveragein

indoor conditions. The small cell is able to simultaneously communicate to devices

inthecellandtothemacrocell,withbothTxandRxrunningsimultaneously.The

www.anritsu.com|40

scheduling algorithms of the macro cell and small cell need to be carefully aligned

suchthatanyUE’sinthecellarenotsubjecttointerferencebetweenmacroandsmall

cell(asthedevicesdonothavefullduplexcapability),andalsoprovideinterference

cancellation information to devices and the macro cell receivers.

Fig 23 - Reported Performance of Interference Cancellation

Antenna CancellationTX 1 TX 2RX

d d + λ/2

Power SplitterRF Analog

Baseband RF

DAC

Encoder

noise canceller chipInput

OutputRF Analog

RF Baseband

RF Interference Cancellation

RFInterferenceReference

Digital InterferenceCancellation

DecoderDigital

InterferenceReference

ADC

TX Signal Path RX Signal Path

1

2

3T

∑∑

Analog Cancellation Circuit

DAC

C

Tb

Digital Cancellation

TX

RX

PA

ADC

∑

R

Sing

le A

nten

naD

esig

n

Attenuation& Delay

R + iT

xx

R + aTCirculator

d1a1

dNaN

controlalgorithm

Eliminates all linear andnon-linear distortion

fixeddelays

variableattenu-ators

RSSIRF Reference

Balun

Balun Cancellation

Baseband RF

DAC

RF Baseband

∑

ADC

Decoder Encoder

FIR filter

Digital Interference Cancellation

Digital InterferenceReference

ControlFeedback

ChannelEstimate


DAC

DAC

ADC

TxRadio

RxRadio

TxRadio

+

RF

RF

RF

BB

BB

BB

x1

c1

y1

Node 1 Node 2

hz

hab hAB

+

Antenna a Antenna A

Antenna b Antenna B

haBhAb

D

hZ

TxRadio

RxRadio

TxRadio

RF

RF

RF

DAC

DAC

ADC

BB

BB

BB

x2

c2

y2


d d + λ/2


Baseband RF

DAC

Encoder


OutputRF Analog

RF Baseband




DecoderDigital


ADC


1

2

3T

∑∑


DAC

C

Tb


TX

RX

PA

ADC

∑

R

Sing

le A

nten

naD

esig

n

Attenuation& Delay

R + iT

xx

R + aTCirculator

d1a1

dNaN

controlalgorithm


fixeddelays


RSSIRF Reference

Balun

Balun Cancellation

Baseband RF

DAC

RF Baseband

∑

ADC

Decoder Encoder

FIR filter



ControlFeedback

ChannelEstimate


DAC

DAC

ADC

TxRadio

RxRadio

TxRadio

+

RF

RF

RF

BB

BB

BB

x1

c1

y1

Node 1 Node 2

hz

hab hAB

+

Antenna a Antenna A

Antenna b Antenna B

haBhAb

D

hZ

TxRadio

RxRadio

TxRadio

RF

RF

RF

DAC

DAC

ADC

BB

BB

BB

x2

c2

y2


d d + λ/2


Baseband RF

DAC

Encoder


OutputRF Analog

RF Baseband




DecoderDigital


ADC


1

2

3T

∑∑


DAC

C

Tb


TX

RX

PA

ADC

∑

R

Sing

le A

nten

naD

esig

n

Attenuation& Delay

R + iT

xx

R + aTCirculator

d1a1

dNaN

controlalgorithm


fixeddelays


RSSIRF Reference

Balun

Balun Cancellation

Baseband RF

DAC

RF Baseband

∑

ADC

Decoder Encoder

FIR filter



ControlFeedback

ChannelEstimate


DAC

DAC

ADC

TxRadio

RxRadio

TxRadio

+

RF

RF

RF

BB

BB

BB

x1

c1

y1

Node 1 Node 2

hz

hab hAB

+

Antenna a Antenna A

Antenna b Antenna B

haBhAb

D

hZ

TxRadio

RxRadio

TxRadio

RF

RF

RF

DAC

DAC

ADC

BB

BB

BB

x2

c2

y2


d d + λ/2


Baseband RF

DAC

Encoder


OutputRF Analog

RF Baseband




DecoderDigital


ADC


1

2

3T

∑∑


DAC

C

Tb


TX

RX

PA

ADC

∑

R

Sing

le A

nten

naD

esig

n

Attenuation& Delay

R + iT

xx

R + aTCirculator

d1a1

dNaN

controlalgorithm


fixeddelays


RSSIRF Reference

Balun

Balun Cancellation

Baseband RF

DAC

RF Baseband

∑

ADC

Decoder Encoder

FIR filter



ControlFeedback

ChannelEstimate


DAC

DAC

ADC

TxRadio

RxRadio

TxRadio

+

RF

RF

RF

BB

BB

BB

x1

c1

y1

Node 1 Node 2

hz

hab hAB

+

Antenna a Antenna A

Antenna b Antenna B

haBhAb

D

hZ

TxRadio

RxRadio

TxRadio

RF

RF

RF

DAC

DAC

ADC

BB

BB

BB

x2

c2

y2

60 dB 73dB

~80 dB

110 dB!

Cancellation

Stanford

RiceStanford2010

SICapproaches

2013

20112010


Massive MIMO

MIMO has been deployed in LTE and LTE-Advanced

networks, where the base station and user equipment

usemultipleantennastoincreaselinkefficiency.Massive

MIMO refers to the technique where the base station

employs a much higher number of antennas that create

localized beams towards each device. The gains in

capacity are enormous but so are the technical challenges

associatedwith this technology.Abasic formof thishas

beenintroducedinLTE-A,calledbeamforming,butisonly

operationaltoasingledeviceatanyonetime,andhasonly

limited directivity/gains due to the limited number of base-

station antenna supported in LTE-A.

Massive MIMO is building upon previous research and development in phased array

antennasthatwasprincipallydevelopedforelectronicallysteeredradarsystems.The

basicconceptisthatanarrayoflowgainandlowdirectivityantennasarebuilt,and

thenthephaserelationshipbetweenthesignalsoneachantennacarefullymanaged

Fig 24 - 128 port antenna

RF/Antennas

Baseband

IP

LTE Infrastructure

CPRI

Full Dimension MIMO (Rel-13)

FD MIMO eNB

Highly directional streams and special multiplexing

High order MU-MIMO transmissionto more than 10 EUs

Fig 25 - Full Dimension MIMO

www.anritsu.com|42

such that the composite signal from all the sub-antennas gives a high gain and

directional beam that is controlled by electronically adjustable phase shifters. This

conceptisnowcombinedwiththeMIMOconcept,thatusesbasebandprocessingto

exploitmultiplespatialpathsbetweensetsofantennassuchthatmultiplechannels

ofdatacanbetransmittedsimultaneously,anduseMIMOspatialcodingtoseparate

the channels of data to different users according to their spatial position and the

unique channel propagation characteristics of each Tx-Rx combination.

SomassiveMIMOwillsupportmanyseparatedatachannels,basedonthewidespatial

diversityoftheTx-Rxlinks,andthecapacityhereisincreasedbyhavingmanyTxand

Rxantennas.SowherecurrentMIMOuses2or4antennasforTxandRx,massive

MIMOmaybeusingupto128antennas.Thiswillleadtomuchhigherdatacapacity

inamassiveMIMOcell,duetotheabilitytosynthesizemanyseparatesimultaneous

datapathstoindividualusers.Thisiscombinedwiththeenhancedbeamformingthat

ispossiblewithmanymoreantennas,toprovidehighlydirectionalbeams(reducing

interference and enhancing signal to noise ratio) and even 3D beamforming that

enablesthenetworktomanagebothnearandfarawaydevicesatthesametime

withoutsaturatingorblockingsignals.

As5Gisnowbeinginvestigatedforhigherfrequencybands(24-86GHz)thenatthese

higher frequencies the large arrays can be implemented into a smaller form factor

bytakingadvantageofthehigherfrequency(shorterwavelength).Thisenablesthe

scalingoftheantennasizedowntoamuchsmallersizewhilststillmaintainingthe

correctproportionsinrelationtowavelength.(e.g.correctseparationofantennaand

correctantennapatchsize), such thatanarraywith tensorhundredsofantenna

elementscouldberealizedintoapracticalformfactor.

ThebasicphysicsprinciplesformassiveMIMOarenowproven,andexperimental

systemsarebeingdeployed.Twoofthekeychallengestomaturethetechnologynow

aretomanagetheamountofcomputingpowerrequired,andtocreatestandardized

orinter-operablealgorithmssothatmulti-vendorandglobalsolutionscanberealized.

Todate, theprocessingpower requiredmeans themassiveMIMOdeployment is

notsuitableforportabledevicesduetosizeandpowerconsumption,andsofirst

deploymentsarefocusedmoretofixedwirelessaccessschemesandprovisioning


ofwireless backhaul to a dense deployment of small cells inNLOS scenarios. As

processingpoweravailableindevicesisincreased,andimplementationofmassive

MMO algorithms is optimized to reduce receiver processing requirements, then

massive MIMO is expected to be deployed into the access scheme for user devices.

Inaddition,thealgorithmsusedsofarareproprietaryandverycomplex,andassuch

are only deployed into proprietary systems. To be included into a global telecoms

standard then there needs to be open information on implementations such that any

supplier can build either basestation or user device and be sure of interoperability of

equipment coming from different suppliers.

Traffic Management

Asthedeploymentofall-IPbasednetworksisbeingrolledoutalreadyin4Gnetworks

usingIPv6,thentheabilitytoofferdifferentiatedtrafficqualityaccordingtotheneeds

of theservice isbeingdeployed. Aswireless servicesexpand,andamuchwider

rangeofservicesaredeliveredacross thenetwork, thenanendtoendcapability

to support quality of service is required to ensure the required performance level

foreachservice.Asmanymorerealtimeservicesaredeployed,takingaccountof

thepossiblelowlatencycapability,thenensuringthequalityofserviceiscriticalfor

theapplicationsandservicestosucceed.Thetrafficmanagementwillberequired

tomanagetheexpectedveryhighvolumeoftrafficacrossthenetwork,andmust

beintegratedtothephysicallayercontrolproceduresforeachlinkinthenetwork

toensurethetrafficiscorrectlymanaged.Thiswillmeanthatallphysicallinkswill

needsuitablecontrolmechanisms,andthenetworkwillrequiremethodstoinform

the individual physical links of the required quality of service. Although this capability

is includedincurrentpacketdatanetworkssuchasHSPAandLTE,thescheduling

of data ismade locally and not co-ordinated across the network in an optimum

way.SoNFVandC-RANmayoffermoreefficientplatformsonwhichtheendtoend

quality canbemanaged,asallnetworkmanagementandschedulingcontrol can

be centralized and shared across different network functions. So one part of 5G

networkresearchanddefinitionwillbe lookingat theoptimizationof trafficflow,

andend-to-endQualityofService,inordertoensurethatthenetworkisdelivering

the required performance. Such a control system must be fully integrated to each

newnetworkelementinaseamlessandunifiedwaytoprovideanefficientnetwork

control function.

www.anritsu.com|44

Future Testing for 5G

As thenetwork concepts and technologies develop for 5G, so the corresponding

testmethodsandprocesseswillevolvetomatchthis.Future5Gtestmethodswill

needtoprovideahighconfidencetooperatorsthatthetechnologyandservicesare

implementedaccordingtospecification,andthatthequalityofserviceismatchingto

the requirements of the application or service being delivered.

Afullydata-centric5Gnetworkwithaverywideanddiversesetofapplicationstotest

wouldrequireamassiveeffortinstandalonetesting.Testautomation,monitoring

andbuilt in test systemswillbeessential foranalyzingproperly theperformance

ofsuchanetwork.Inaddition,theemergentsolutiontouseUltraDenseNetworks

(UDN)forinterconnectingtheradioaccesselementswiththebackhaularchitecture

usingcloudnetworkswillenablethedevelopmentofcloudbasedtestservicesfor

testingeverythingfromeverywhere.So,although5Gwillintroducemanynewtest

requirementsandchallengesbytheuseofSDN/NFVandcloudservices,thissame

technology can also be used for creating new test solutions that address these

needs.Withthisinmind,cloudsolutionsareseenasboththenewdemandandthe

newsolutionfor5Gnetworktesting.

Test and Measurement challenges

Oneaspect that is expected to characterize 5Gnetworks is that it is not a single

technologyorfeature,butthatitisanintegratedsetoftechnologiesandfeatures

designtoworktogetherinanoptimumwaytosupportawiderangeofapplications

andusecases.Fromatestingpointofview,thismeansthataswellastestingofthe

newtechnologiesbeingimplemented,therewillbemoreofaneedtotestthemany

different combinations of technologies and network elements to ensure correct

interoperability.Thisisfurthercomplicatedby“virtualization”andthefactthatspecific

networkfunctions(thenormalwayinwhichnetworkelementsaretested)mayno

longer be physically realized in a specific piece of hardware, butmay bemoved

aroundthenetworkorsplitacrossdifferentpartsofthenetwork.Thisvirtualization

of thenetworkand its functionswill requireacorrespondingvirtualizationof the

testing methods and tools to be used.


Wehave seen in the earlier chapters the requirements on 5Gnetworks in terms

of target performance. These targets then lead us to a set of network KPI’s and

performance attributes to measure.

Key parameters for testing 5G.

•TrafficdensityTbps/km2.

•ConnectionDensity.Connectedusersandactiveusers.Connections/km2.

•Userdatathroughputatapplicationlevel,bothpeakandaverage.

•Latencyendtoendthroughnetwork,androundtriptime(RTT).

•Reliability(errorrates)

•Availability(coverage,handovers,mobility,capacity).

•Battery Life (mobile devices) andpower consumption/power saving (network elements).

•Waveform/accessspectralefficiency.

•Resourceandsignalingefficiencyandoverheadratio.

Whendesigning the testmethods for 5G, it is necessary topay special attention

formobilitytests.There isaneedtospecifywhichpartsofthenetworkaretobe

usedduringmobility/roamingprocedures,toensurewetestonlytheseandlimitthe

mobility combinations. This is due to the high complexity of different carriers and

datalinkswithintheHetNet,meaningthatnotallpossibledatabearercombinations

should be supported in all mobility test combinations. By reducing the mobility

combinations,thevolumeoftestingcouldbesignificantlyreducedandmaintained

at amanageable level. In addition, we can see thatmany use cases (e.g. smart

meters)willhavelowornomobilityrequirements,butthedynamicchangingofthe

networkmay result in suchdevices still requiringmobilityacrossdifferentaccess

mediumsdependingonthestatusofthenetwork.Somobilitytestingduetonetwork

configurationchangesratherthandevicelocationchangesmayberequired.

Whenwelookattheareaofdevicetesting,wemustnowevaluatehowthenetwork

simulatortechnologymustevolvetosimulatesucha5Gnetwork.

DuetothelackofavailableRFspectrumtomeetcapacityneeds,thereisnowastrong

push to utilize higher frequencies and themore availablemillimeterwavebands

www.anritsu.com|46

(currently looking at 24 - 86 GHz frequencies). Although individual regions have

specific licensing conditions, it is generally accepted that there ismore spectrum

likelytobeavailable,andspecificallymorecontiguousbandwidthavailable,atthese

higherfrequencybands.Utilizationofthesehigherfrequencybandswillputfurther

demands on the test equipment to provide corresponding support.

The test industry already has available basic RF measurement tools (spectrum

analyzersetc)thatsupportthedesignandtestofradiounitsatthesefrequencies,

andtheyarealreadyinuseintheindustry.But,cellularnetworktestingintroduces

needsformorecomplexnetworksimulators,andthesehavenotyetbeendeveloped

formillimeterwavebands.Oneofthekeychallengesinthisareaisthatitisexpected

that a 5G networkwill use awide range of operating frequency bands, and

may dynamically switch between them,butmostuserdevicesareexpected to

beoptimizedforspecificusecasescenarios.Thereforethedeviceswillnothavea

standardizedorcompletesetofradiointerfacetechnologies,insteadeachdevicewill

supportaspecificsubsetoftechnologies.Thisissimilartothe4Gsituationofdevices

having specific radio band support rather than support for all 40+ standardized

frequency bands, but now with an added second dimension of millimeter wave

bandsandtechnologiestosupport.Networksimulatorshavesupportedthisissuein

thebelow6GHzbandbyusingaflexibleopenRFarchitecture,butthismaynotscale

uptomillimeterwavebandsandtodifferentaccesstechnologies.

Alongwiththeneedformorefrequencybandstosupport,thereisalsoatrendtowards

widerbandwidthchannelstosupporthigherdatarates.Whilst itcanbeexpected

thatthecoretechnologyforsuchwidebandwidthswillnaturallybedevelopedforthe

networkelements(e.g.basestationtransceivertechnology),therearespecificissues

fornetworksimulatortechnologyintermsofhavingagenericimplementationthat

scalesfordifferentnetworks,ratherthanaspecificimplementationthatisneeded

forrealnetworkelements.Thisrequirementforadditionalflexibilityinconfiguration

becomes a key challenge in designing the RF performance and connectivity in a

network simulator, being able to support thewide range ofmulti-carrier signals

expectedfroma5Gnetwork.

MassiveMIMOhasbecomeakey termandattractive technology for5G,offering

significantgainsintrafficdensityaswellasdatathroughputpeakrates.Withthis

47|Understanding5G

technology then come some key challenges for testing. A MIMO system comprises

oftwomainelements,thebasebandprocessingalgorithmsandtheRFchannel.The

MIMOsystemworksbyhavingthebasebandalgorithmrespondtotheRFchannel

characteristics.Asthebaseband issplitbetweenthetransmitterandthereceiver,

andforacellularnetworkthesetwoelementscomefromdifferentsuppliers(infra

vendoranddevicevendorareoftendifferent), then the fulldetailedoperationof

the parameters required for the algorithm must be specified in the technology

standards documents. For massive MIMO this is likely to be a very complex and

detailed specification to ensure full interoperability. So in themassiveMIMO test

weneedtoreplicateeachoftheconditionsinthemassiveMIMOspecification,by

usinga fadingsimulator toreplicatetheRFchannel inacontrolledwayandthen

test the performance of the system (i.e. verify the data throughput rate achieved).

Whenweare testing thenetwork thenwemusthaveacontrolledreferenceuser

device,andwhen testing theuserdeviceweneed tohaveacontrolled reference

network.Asusually themost complexalgorithmprocessinganddecisionmaking

isinthenetwork(topreservepowerinmobiledevices,andreducecostimpacton

userdevices),thenthebiggestchallengecomeswhencreatingareferencenetwork

simulatortotestthemobile,asitmusthaveafullyopenandflexibleimplementation

forconfiguringandcontrollingtheprocessingalgorithms.

Asecondchallengerelatedtothisarea is the issueof “connector-lessdevices”,as

large arrays required formassiveMIMO and designs formillimeterwavewill be

constructedintocompactformtobecost/deploymentefficient.Thiscompactform

means that there is unlikely to be space for RF connectors or test ports to attach test

equipment.Sotheexpectedscenarioisfor“connectorless”testing,andhencethe

needformore“overtheair”OTAtesting.OTAisanestablishedtechniquecurrently,

but uses large and expensive RF chambers, and is a relatively slow process. The

industry challenge is to introduce more compact and cost effective OTA test solutions

thatarescalableforbothRF(below6GHz)andmillimeterwaveband(24-86GHz)

use. Massive MIMO also introduces further challenges in terms of compact and

affordable test systems tomeasurebeam forming,beamshape, compositegain,

andotherantennaparametersrelatedtothesynthesizedelectronicbeams.Studies

arecurrentlyunderwaytoevaluatenearfieldmeasurementtechniquestoenable

www.anritsu.com|48

a compact test system, whilst being able to extrapolate to the far field antenna

performance.

Wehaveseenthatnotonlyishigherdatarateandwiderbandwidthakeyfeaturefor

5G,buthyperdensenetworksarealsorequired.Thelimitingfactorforsuchhyper

dense deployments is the signal to noise ratio due to interference from neighboring or

co-located cells. And so the ability to accurately re-create and measure performance

insuchadenseandcomplexRFenvironmentbecomesakeynewtestitemfor5G.

AlongsidethecreationofthecomplexRFenvironment,thehyperdensecellnetwork

testingwillalsorequiredetailedtestingoftheRFmeasurementsandreportsfrom

bothnetworkanddevices,thesearerequiredtoenableasmartaccesssystemand

operation in a complex RF interference environment. This then leads to a massive

increaseintestingoftheRFmeasurementandreportingfunctionsofthenetwork/

devices,asthisisthekeyinformationusedtoinformthenetwork/devicealgorithms

onhowtooptimizenetworkaccess.

One of the most challenging technologies discussed for 5G is the concept of full RF

duplex,wherethetime/frequencyseparationbetweentransmitandreceivepathis

changedtosimultaneoususe.Thisoffersaveryattractivebenefitintermsofavailable

capacity,butintroducessomekeychallengesfortestingandsimulating.Aswehave

seeninearlierchapters,thekeytosuccessforthistechnologyissufficientisolation

betweenTxandRxpaths.ThisisachievedwithacombinationofbothRFisolation

methods and IF/baseband compensation algorithms. So for testing we need to

provide a very high isolation test environment that is capable to measure beyond the

designspecificationsofthe5Gsystem.Thecoretechnologyrequiredtoimplement

thefullRFduplexconceptisexpectedtogiveenoughperformanceforthis.However,

thechallengecomesinthatthetestequipmentmustusuallybeflexibleforusein

differentRFbands,whereasfullRFduplextechnologyisexpectedtobeoptimized

forspecificfrequencybands.Thereforethetestequipmentmustmeetacriticalcost/

performancepointintryingtoimplementacosteffectivetestsolution,balancingthe

bandspecificRFneedsversusthecosteffectivenessofageneralsolution.Without

suchacosteffectivetestsolution,therecanbesignificantcostbarriertohavinga

widedeploymentofthetechnologyintheindustry.

49|Understanding5G

Future Test Instruments

Network test

Inahighlevelperspective,NFVandcloudwillrequiremoreintelligenceandanalysis

inthetestinstrumentsasthenetworkbecomesmoredynamicoralive.Thephysical

elements in thenetworkwill bedivided into specific/dedicatedhardware suchas

antennas and radio transceivers, and general purpose hardware such as server/

computingplatforms.Eachofthesewillhavespecifichardwarerelatedcharacteristics

tobetested,suchasradioemissionsorsensitivity,orprocessordatarateorlatency.

Theprotocolaspectswillbetestedseparately,initiallyinavirtualenvironment(i.e.

inter-actionofprotocolstackshousedonsoftwareplatformsratherthanontarget

hardware).Finally,theintegrationofsoftware/protocolontothehardwareplatform

needstobetested.InSDN/NFV,thisthenbecomesmorechallengingasthehardware

platformwillnotbeaspecificplatformoptimizedfortherequiredprotocol.Thiswill

meanthattheperformanceofthenetworkwillneedtobeconstantlyverifiedaseach

virtualizednetwork function is locatedormoved todifferent hardware elements.

This type of monitoring is expected to be made using independent probes in the

network,whichareindependentofthenetworkhardwareplatformsandcanquickly

detect any performance issues.

Aswithcurrentnetworks,itwillbenecessarytotestandmonitorthedifferentdata

links,toidentifyanybottlenecksorrestrictionsindatacapacity,sotheoverallcapacity

canbeoptimizedandmaintainedattherequired levels.ButwithSDN/NFVthese

statisticsneedtobeprovidedinrealtimesothatanydynamiceffectsduetosoftware

configurationalgorithmscanbedetected.This isbecausenetwork functions (and

henceanyproblems)maynotstaticallylieonaspecifichardwarecomponentoruse

specificnetworklinksbutcouldbesoftwareredefinedbythenetwork,andsoareal-

timemonitoringsystemwillberequiredtoidentifywhenaconfigurationisusedthat

does not meet the performance requirements.

RF component and module test

5Gwillbringdevicesoperatinginmuchhigherfrequencybands,widerbandwidths

andmulti-carrierdesigns.Moreandmoreintegratedtechnologyisexpected,which

will produce amore complex analysis for interference limited devices. Generally

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speaking, the futureRFdevice testing ischallenging,andwillask forveryprecise

instrumentation in order to deal with millimeter wave transceivers and better

intelligence for Massive MIMO or AESA (Active electronically scanned array) radios.

Inaddition,thenearfieldeffectsandloadpullonmassiveMIMOantennasinuser

deviceswillneedtobefullycharacterized.Ingeneral,itisexpectedthat5GRFdevices

willbewiderbandwidth,lowdistortion,andlowpower,tosupportthewidebandand

densespectralefficiencyof5Gwaveforms.TheuseoffullduplexRFwouldrequire

significantworkinthetestandcharacterizationofRFisolationandcouplingbetween

devices.ThesemoredemandingRFrequirementswillneedtobeaddressedwhilst

aimingforhigherlevelsofRFcircuitintegrationtoreducecost,andinmanycases

theseareconflictingrequirements.

User device / terminal test

Testinga5Gfull-capablehandsetwillbecomeaveryextensiveprocessifweextend

current handset test procedures. We can expect many more band combinations

or RF duplex scenarios,massive number of transmitters and increasing types of

receivers, leading tomanyvariations indevices thatwill constantlybe increasing.

Userdevicesprobablywillnolongerbetestedusingcablesbecause‘OverTheAir’

(OTA)performancewillbeessential inthetestingprocess,forexampleinMassive

MIMO testing. More complex shield boxes and chambers will be required, even

tunabletoverydifferentfrequencybands.Alongsidethis,thesimulationofmultipath

using fadingsimulatorswillgrow further in importance,andalso in the technical

demands and capability required in such equipment. As the MIMO and HetNet

algorithms becomemore complex and powerful, then correspondingly powerful

fading simulators are required to test and verify the algorithms. The integration of

thenetwork simulator and the fading simulator thenbecomesa critical issue, to

enable accurate set-up of required scenarios.

Applicationtestingwithinanend-to-endenvironmentwillincreaseincomplexityand

customerexperiencetestingmaybecomeembeddedintothenetworksanddevices,

forexampleusingsmartsoftwareagents.Findingthebottleneckinthethroughput,

incomplexQoSandmulti-linktransmissions,becomesfarmorechallenging.Asthe

uplinkanddownlink,controlanduserplanes,areeachseparated,thenthelimitation


indatathroughputcancomefromanyoftheseareas.Soevenwhenthedownlink

user plane has enough capacity to deliver the required data rates, the downlink

controlplaneneedscorrespondingcapacityandlatencytoscheduleit,andtheuplink

needslowenoughlatencytocarrythefastHARQfeedbackandMIMOreports(or

similar control loop data) to maintain the high throughput.

Oneareaofdevicetestingthathasgrownsignificantlyin4GisUserExperienceTests,

andthisisexpectedtogrowfurtherastherangeofuserexperiencesandusecases

growbasedon5Gtechnology.Oneareaofbigconcernfrom4Gisthebatterylife,

whereasmartphonecannotbeused forasingle fulldayandusersneedregular

accesstochargingpoints.Itisexpectedthat5Gwillneedtoofferbetterbatterylife,

butwithmoredataprocessing.Testsystemshaveevolvedinrecentyearstoprovide

specificandrepeatablerealworldscenarios(e.g.browsing,email,chat)toevaluate

batterylifeversusareferencedailysetofactivities.For5G,theexpectedlowlatency

of“tactileinternet”isexpectedtogiveamoredirectinter-actionbetweenuserand

apps/services,soevaluatinghowtheair interfaceandmodemlinkenablesthisor

impairsthiswillbeanimportantuserexperiencetest.

Device certification and approval, and Carrier Acceptance Testing

Withthelaunchof3Gnetworks,therewasanindustryinitiativetoreducethevolume

ofhandsettesting,andavoidrepeatedorredundanttesting,byintroducingindustry

forumssuchasGCFwith theconceptof “testonce,useanywhere”basedaround

standardizedandagreedtesting.Withthelaunchof4G,ithasbeenseenthatthe

testneedsfordevicesaredivergingascarriershavesignificantlydifferentnetwork

architecturesdue to thewide rangeofoptions.Also,4Gnetworksarenow inter-

workingwithnon3GPPnetworks(e.g.IMS,WiFi)andtheseparatetestingregimes

ofeachnetworktechnologyarenotaligned,soasingletestplancannotcoverthis.

So some major operators have introduced more operator specific test plans to

ensurecompliancetotheirspecificnetworkneeds.Lookingforwardto5G,withthe

muchmorediversesetofnetworkconnectivity fromHetNet’s, thenextrapolating

thecurrenttestmethodswillleadtoalargeincreaseinvolumeoftesting.Thekey

challengeinthis isthatthewiderangeofnetworkflexibility/diversityrequiredfor

managingawide rangeofdiverseuse caseswould lead toa verywide rangeof

industry standard test cases and scenarios. But moving away from an industry

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standardizedregimetoindividualtestplanswillalsoincreasedrasticallythevolume

oftesting.Sothistrade-offofdeploymentflexibilityversusstandardizedtestingwill

beakeyitemtoaddressin5Gnetworkdefinitions.

The divergent range of device types, M2M, Augmented Reality, smart meters

etc. expected on the network will also lead to divergent test needs and critical

functionality. Some smartmeter applicationsmay prioritize battery life and cost,

tradingoffversusdatarate,latencyandconnectionavailability.Equally,augmented

realitywouldprioritizedatarateandlatencyaboveall,andcriticalcommunications

(e.g. first responder, health & monitoring) may prioritize connection availability

ashighestpriority.Tohandlethesedivergentneedsandcharacteristics, it is likely

thatfurtherclassesor“classtypes”ofuserdeviceswillneedtobespecifiedin5G

standards,sothatcorrespondingtestregimesandmethodscanbedefinedtomatch

the different needs or classes of user devices.

Anotherareaofdevelopment that isbecomingmore relevantnow in theareaof

5G is that of Cognitive Radio, and SoftwareDefined Radios.When such a device

usesageneralpurposeRFtransceiver,itisessentialtoensureitmeetstherequired

RF performance for the specific protocols and modulation schemes being used.

Withoutsuchtests,theSDRdevicemayproduceexcess interferencethatdisrupts

thenetwork,orsufferfromexcessdistortion/non-linearitythatmeansdatalossand

communication failures. For the Protocol part of such a modem a key test is to ensure

thetimingrequirementscanbemaintained,asitisimplementedinnon-optimized

circuitsandsomaysufferfromslowprocessing/responsetomessages.

Field Test

Testinginthefieldwillalsogrowincomplexity.Findingthesuitabletestlocationsina

HetNetmaybecomeadifficultordynamicprocess,notonlyforcapturingthetarget

ULorDLstreambutalsofortheseparationbetweenControlandUserplanes.This

isbecausetheHetNetitselfwillbedynamicinitsuseofavailableresources,andthe

available resources may also be a dynamic parameter.

Aswehaveconsideredintheearliertechnicaldiscussions,a5GHetNetmayoperate

in an interference limited scenario (i.e. data rates and Signal to Noise Ratio are limited

byinterferenceratherthanpropagationlosses).Thiswillleadtoaparadigmshiftin


hownetworkcoverageisdefinedandmeasured.Traditionalcoveragemappingat

themodeling,planninganddesignstages,infieldtrials,andduringdrivetesting,is

all based upon signal strength and assumes noise limited effects due to propagation

losses. In 5G, we can predict that installation tests, coverage mapping, and de-

buggingofissueswillbemuchmorefocusedontheinterferenceenvironment.

LoadtestforHetNet,lookingatcapacity,throughputandlatencyasthemainKPI’s

willbecomeanevermorecomplexissue.Wemaystillusetraditionaldrivetest,and

probebasednetworkmonitoring,togatherthesebasicuserKPI’s.Butaswehave

seen,theseparametersarehighlyvariabledependingonconditionsintheHetNet

and results can not be simply interpreted to establish performance and capability

of the network. This is because such capabilities are the result of the complex

algorithms tobeused forschedulingandroutingofdata.So, tomoreaccurately

evaluatethenetworkcapability,wemayneedtomeasureandrecordthevaluesof

theparametersgoingintothesealgorithms,andnotonlytheresultingperformance.

Sokeyparameterslikethroughputandlatencywillneedtobedefinedinrelationto

networkload,capacity,andinterferencelevels.

Current test technology examples in early 5G development

Evenintheearlystageof5Gdevelopment,

there are already test systems capable for

evaluating the upcoming technologies.

Amongst these, wide band Capture and

Replay systems for RF and I/Q signal

generation and analysis are important

in the development of new transmitters

andreceivers.Usingmodelingsoftwareto

createnewwaveformsandthenrealizingandevaluatingperformanceinrealdevices

isthefirststepbeforethestandardizationstage.ThiswillFig23-MS2830ASpectrum/

SignalAnalyzer+VectorSignalGeneratorbelookedatasaworkedexampleinthe

nextchapter.Itisusedfortheinvestigationofnewwaveforms,toseethespectral

properties,andthentoseehowthewaveformsareperformingonrealdevicesand

circuits(e.g.harmonicdistortion,non-linearitydistortionetc).Similarly,newdevice

technologyisevaluatedwithnewwaveformstoseetheRFperformance.

Fig 26 - MS2830A Spectrum/Signal Analyzer+VectorSignalGenerator

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Broadbandmulti-port VNA’s will continue

addressing the characterization of new

mmW devices and MMIC’s. Especially for

massiveMIMO,thereistheneedtoensure

thatrelativelylowcostandcompactdevices

and antennaswill have sufficiently stable

and repeatable RF/phase characteristics.

Also,asnewtechnologiesinsemiconductor

gates and processing enable lower cost

mmWdevices,thesedevicesneeddetailed

evaluation to ensure the RF performance

is not compromised by lower cost manufacturing. In addition, there is industry

activity now to change themethod of device characterization from narrow band

CWmeasurementstowidebandmodulatedmeasurements.Particularlyforactive

devicesitisimportanttoseethedevicebehaviorunderwidebandmodulatedsignal

conditions.Sofartheindustryhasonlymeasureddevices(e.g.Sparameters,load

pull, compressionetc)underCWconditionsandextrapolatedbymodeling to the

widebandmodulatedperformance.Withsophisticatednew5Gwaveformsthenitwill

beimportanttocharacterizetheseparameterswithdevicesdirectlyunderwideband

modulatedconditions.Thisrequirestheuseofnewgenerationwidebandmodulated

VectorNetworkAnalyzers(VNA’s)thatarecapabletosupportnewrequirementssuch

as “modulated S parameters”.

Inthenetworkside,highspeedBERTS(64

GB/channel) are used for testing next

generationopticaldevicesinfiberlinksand

data centers. As the processing power in

datacentersandserverfarmsisincreased,

to support cloud computing, then the

inter-connect between individual server

blades and server stacks needs to be high

speed,lowlatency,andlowdistortion.New

modulation schemes are being introduced

Fig27-ME7838A/E/DVectorStarBroadband VNA

Fig 28 - MP1800A Signal Quality Analyzer


intohighspeedopticalcommunications,suchasPhaseAmplitudeModulation(PAM),

withPAM4andPAM8having4or8differentstatespossibleandhenceincreasethe

datarateversuspuredigital (2state,on/off) transmission.But toenable this, the

linearityofthemodulatorsandde-modulatorsneedstobeverified,andthisisdone

using Eye diagrams and Bit Error Rate Tester (BERT).

100 Gb/s link analysis, traffic flow, and

OTN mappings for cloud networks are also

available solutions these days. It is expected

that the key parameters of delay, jitter, and

bandwidth will remain as in today’s testing,

butwiththecorrespondingnewtargetvalues.

Fig29-MT1100ANetworkMasterFlex - All-in-one transport tester

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Introduction to 5G Waveforms

Thissectionintroducesthereadertothreeofthedifferentwaveformsthatarebeing

consideredtobepartof5G,andhighlightsthedifferencesofFBMC,GFDMandUF-

OFDMversustoday’sOFDMusedin4G.

The5Gradioaccesstechnology(RAT)mustfulfillthedatatrafficdemandinthenext

yearswith rates above 10 Gbps and sub-millisecond latency. These rates can be

achieved,principally,withbandwidthsofatleast200MHz,andusingmultiple-input

multiple- output (MIMO) antenna techniques and interference rejection combining

(IRC)receivers.Ideally,thewaveformtobeusedshouldhavegoodimplementation

properties,suchaslimitedcomputationalcomplexityforthegeneration/detection,

limitedtime/frequencyoverhead,goodlocalizationintime,goodspectralcontainment

andsimpleextensiontoMIMO,amongstothers.Ithasbeenshownin4GthatOFDM

is suitable for both the good MIMO implementation and also the simple processor

implementationintheuserdevices,andso5Gwaveformsarelookingtobuildonthis

and further evolve OFDM to overcome the current limitations.

FBMC, Filter Bank Multi-Carrier: FBMC has gained a high degree of interest as

a potential 5G waveform candidate. This modulation scheme provides many

advantages.FBMChasmanysimilaritiestoCP-OFDM,(OFDMusingacyclicprefix,

whichisthespecificvariantusedasthe4Gwaveform).Insteadoffilteringthewhole

bandas in thecaseofCP-OFDM,FBMCfilterseachsub-carrier individually.FBMC

doesnothaveacyclicprefixandasaresult it isable toprovideaveryhigh level

ofspectralefficiency.Thesub-carrierfiltersareverynarrowandrequirelongfilter

timeconstants,typicallythetimeconstantisfourtimesthatofthebasicmulti-carrier

symbollengthandasaresult,singlesymbolsoverlapintime.Thisalsomeansthat

FBMCisnotsuitedtolowlatencyshortburstdatatraffic,nortoconventionalMIMO.

Toachieveorthogonality,offset-QAMisusedasthemodulationscheme.

UF-OFDM, Universal Filtered OFDM: This waveform can be considered as an

enhancementofCP-OFDM.ItdiffersfromFBMCinthatinsteadoffilteringeachsub-

carrierindividually,UF-OFDMsplitsthesignalintoanumberofsub-bandswhichit

thenfilters.UF-OFDMdoesnothavetouseacyclicprefixsocanachievehighspectral

57|Understanding5G

efficiency, although one can be used to improve the inter-symbol interference

protection,andcanbesuitableforconventionalMIMO.

GFDM,GeneralizedFrequencyDivisionMultiplexing:GFDMisaflexiblemulti-carrier

transmission techniquewhich bearsmany similarities to OFDM and can support

conventional MIMO. The main difference is that the carriers are not orthogonal to

each other. GFDM provides better control of the out-of-band emissions and reduced

peaktoaveragepowerratio,PAPR.Bothoftheseissuesarethemajordrawbacksof

OFDMtechnology.Inaddition,asitcansupportamixofinter-leavedsub-carriers,

soitcansupportlowlatencyandshortbursttrafficdata.Thetrade-offforGFDMis

not so good sidelobes and out of band emissions compared to FBMC and UF-OFDM.

Wecanbuildamathematicalmodelofeachoftheabovewaveforms,andcompare

themtoCyclicPrefixOFDM(CP-OFDM)whichisthewaveformusedcurrentlyin4G.We

canthenexperimenttoseetheperformanceofeachwaveform,andalsoanalyzethe

co-existenceofeachwaveformtoseehowtheycanbedeployedalongsideexisting

4Gwaveformswithoutcausingorsufferingfrominterference.Astheexpecteduse

case for thesewaveforms is below6GHz, for deployment alongside or on topof

existing4Gnetworks,thentheco-existencepropertiesbecomeanimportantfactor.

WecanbuildsuchatestenvironmentusingVectorSignalGenerator,VectorSignal

Analyzer,andmathematicalmodelingandanalysistools.Theset-upisshownbelow:

Fig30-Configurationofwaveformtestenvironment

www.anritsu.com|58

In thefirstexperimentweare investigating thepropertiesofUF-OFDM.Wehave

createdtwowaveformsofthecurrent4GtypeCP-OFDM,andputthemintoaco-

existence scenario to give a baseline of the current problem in 4G. We can see clearly

thatthesignalquality(EVM)isdegraded,andthisisduetotheoutofbandemissions

from each waveform interfering with the neighbor waveform. So reduction of

thisemission isakeyfactortoenableco-existence.Oneofthewaveformsisnext

changedtoUF-OFDMandthenthesamescenariorepeated.Nowwecanseemuch

bettersignalquality,duetothemuchbetteroutofbandemissionscharacteristicsof

UF-OFDM versus CP-OFDM.

Fig31-CombiningtwoCP-OFDMsignals

Fig32-CombiningCP-OFDMwithUF-OFDM

59|Understanding5G

InthesecondexperimentweareinvestigatingthepropertiesofFBMCandtheissue

of inter-symbol interferencedueto lackofcyclicprefix.TheSymbolTimingOffset

(STO)mustbecarefullyselectedtoavoidinter-symbolinterferencewithintheoffset

QAM scheme. We see in the next figure the performance/degradation of signal

qualitywithtwodifferentvaluesofSTO,withthelargerSTOof0.2causingsevere

loss of signal quality.

Fig 33 - The effect of timing offset for FBMC

InthethirdexperimentweareinvestigatingthepropertiesofGFDM,specificallythe

flexibilitytosupportdifferentsub-carrierswithinasingleradioframe(e.g.highdata

rateand lowdata rateusers). In the testwecansee that receiverneeds tohave

special processing to handle the inter-symbol interference and that a conventional

receiver is not able to properly decode the signal. This is due to the non-orthogonal

interleavedsub-carriersthatgivetheextraflexibilitybutcauseinterferencetothefull

sub-carriers. We can see that the received constellation diagram is not matching the

transmittedconstellationdiagram,andthataspecialstageofadditionalsub-carrier

filteringisrequiredtomanagethesenon-orthogonalsub-carriers.

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Fig34-GFDMwaveformanalysis


Detailed analysis of an example FBMC waveform.

This section introduces the reader to a more detailed analysis of the FBMC

waveformsthatareconsideredfor5Gandthedetailedanalysismethod.Ithighlights

theadvantagesof FBMCversusOFDM,providesbasic concepts about FBMCand

demonstrateshowwe can load these signals intoAnritsu’s SignalGenerators for

immediate evaluation on real devices.

Orthogonal Frequency Division Multiplexing (OFDM) derived waveforms such as

Filter Bank Multi-carrier (FBMC) are considered as the most attractive candidates for

a5Gwaveform.ThemaindifferencebetweenOFDMandFBMCisthepulseshaping

appliedateachsub-carrier.Ononehand,OFDMusesthesimplesquarewindowin

thetimedomain,whichleadstoaveryefficientimplementationbasedontheInverse

Fast Fourier Transform (IFFT) spreading of the original block of data symbols and

gettingthesub-carriersorthogonal.Ontheotherhand,inFBMC,thepulseshaping

ateachsub-carrierisdesignedinawaythatsomeoftheOFDMlimitationscanbe

circumvented,likeabetterfrequencycontainmentandimprovedsystemoverhead

(noneedsofcyclicprefix),butitismorecomplexduetotheusageoflongprototype

filters.

InthisanalysisispresentedthemostcommonFBMCprinciple,whichistheOFDM/

OQAMmodel.Itmeansthat,apartfromtheFBMCprototypefilterappliedateach

sub-carrier,themodulationschemeusedisoftheoffset-QAMtype,whichgivesasa

result the elimination of the Inter-Symbol Interference (ISI).

Filter Bank Multi-Carrier (FBMC) Concepts

TheschemeofaFBMCtransmitterappearsinthefollowingfigure.Itcanbeobserved

thatitissimplyformedbyaSynthesisFilterBank,whosefiltersareofFiniteImpulse

Response(FIR)type.Furthermore,onlyasingleprototypefilterisneeded,soeach

sub-channel is filterer by same form and BW. Basically, the input information is

divided in N sub-channels (typically a power of 2) and, after applying a possibly

needed oversampling, are passed through the correspondent prototype filter,

centered in one of the sub-carriers inside the band.

www.anritsu.com|62

K

K

K

s0(n)

s1(n)

sN1(n)

Transmittedsymbols areOffset QAM

H(f)

H(f)

H(f)

e j2�f0n

e j2�f1n

e j2�fxn-1n

Sub-channels Filters: All ofthem have the same BW asthe Prototype Filter H(f)

Output signal

f

Synthesis Filter Bank - Finite Impulse Response (FIR) filter banks - Orthogonal filter banks -> a single Prototype Filter H(f) is needed

: info divided in N sub-channels(typically a power of 2)

Fig 35 - Synthesis Filter Bank for FBMC Transmitters

As we introduced before, the key feature of FBMC modulators is the prototype

filterappliedateachsub-carrier.Thus,thedefinitionofthisfilterisrelevantinthe

designofthesesystems.Inourcase,wehavechosenthePhydyas(PHYsical layer

forDYnamicAccesSandcognitiveradio)prototypefilter[3].Thisfilterisdesignedin

suchamannerthatonly immediatelyadjacentsub-channelfiltersaresignificantly

overlappingwitheachotherinthefrequencydomain.

Thenextfigurerepresentsamorerealisticwayofoursystem. In thiscase, itcan

already be seen the OQAM modulation and the combination of the IFFT (for splitting

the symbol energy into the different sub-carriers) and the impulse response of the

prototypefilterapplied.OQAMmakesthesymbolsbeingtransmittedalternativelyon

therealpartandtheimaginarypart,soIn-phase(I)andQuadrature(Q)components

haveatimeoffsetofhalfsymbolinterval(T/2).Oncewehavethebasebandsignal,we

modulate it to RF band (fc) and transmit the real part to the channel.


The symbols are transmittedalternatively on the real part

and the imaginary part

e j2�fct

In-phase (I) and Quadrature (Q) components have a time offset of half symbol interval (T/2)

Modulationto RF hand

Equivalent to IFFT

To channel

h(t)

h(t - )T2

h(t)

h(t - )T2

h(t)

h(t - )T2

Σ

x(t)

{-}

s N-1(t)I

js 0 (t)Q

s 1 (t)I

js 1 (t)Q

s 0 (t)I

js N-1(t)Q

Sk (t) = Σ∞

n = -∞Sk [n] = (t - nT)δ

Sk [n] = sk [n] + jsk [n]QI

2�Te j(N-1)( t + )

�2

2�Te j ( t + )

�2

Figure 36 - Offset QAM Modulation in FBMC Transmitters

Following[5],thePrototypefiltercoefficientsHkareobtainedandusedforbuilding

theimpulseresponsewiththeform:

whereKissuchasthefilterlengthisL*K.

ItisimportanttohighlightthatthecoefficientsjustdependonK,butdonotdepend

onthefilterlength,thus,thisapproachisscalable.Forexample,forK=4,

ΣR-1

R=1

(-1)k Hk cos ( (n +1)) 2 � kK Nh[n] = H0 + 2 1

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H0=1

H1=0.97160

H2=√2/2

H3=0.235147

and these values give an iterative procedure that can be used for K>4.

NotethatthebiggerK,themorerejectionbetweenadjacentsub-channelsandthe

biggersystemdelay.Consequently,acomprehensivevalueshouldbechosen.Inour

case,wewillworkwithK=4,whichwillproduceadifferenceof40dBbetweenthe

mainandsecondlobesofthefilter’sfrequencyresponse.

FBMC Modulator in Matlab

Once we have chosen Matlab as the

mathematical software for programming

the FMBC signals, the first target is to

implement the Prototype filter based on

thedesignwecouldseeabove.

The Prototype filter can be easily

programmedinMatlab, justselectingthe

number of sub-carriers N and applying the

impulseresponseformulawiththefilter’s

coefficients.Then,thetimeandfrequency

responsesappearrespectivelyinfigures29

and 30.

In figure 29 (Prototype filter’s time

response)wecanappreciatethealmost

40 dB rejection between the main and

second lobes, which principally achieves

thedesiredfrequencycontainmentthatwe

need for future communications.

Samples

Time domain

Am

plit

ude

1.2

1

0.8

0.6

0.4

0.2

0

-0.210 20 30 40 50 60

h [n]

Fig37-Prototypefilter’stimeresponse

Normalized Frequency (x � rad/sample)

Frequency domain

No

rmal

ized

Mag

nitu

de

(dB

)

0.50.1 0.80.60.40.2

0

0.3

-120

-20

-100

-40

-80

-60

-140

-160

-1800 0.7 0.9

Relative Side-lobe Attenuation: -39.9 dBH [f]

Fig38-Prototypefilter’stimeresponse


The next stepwould be building the FBMCmodulator. Our approach provides a

tuning variable that permits the repetition of a certain number of random FBMC

symbolstobetransmitted.Inthisway,wecananalyzeafterwardsthedifferencein

thespectrumbetweenasignalformedwithfewsymbolsandanotheronewithmany

symbols.

Time (ns)

Time domain

Am

plit

ude

150

0.1

250

0.4

0.2

0

0.3

50

-0.1

100 200

-0.2

-0.3350

real (f_signal) for 1 FBMC symbol (rep=1)fs=200 MHz

Figure39-FBMCSymbolinTimeDomain

Firstly,wecanobservethetimeformofasingle-FBMC-symbolsignal.Ifweanalyzeit

in the frequency domain.

Frequency (MHz)

Frequency domain

Mag

nitu

de

(dB

)

5010 80604020

0

30

-120

-20

-100

-40

-80

-60

-140

-1600 70 90

Spectrum (f_signal, rep=1fs=200 MHz

Energy divided incertain sub-carriers

Fig 40 - FBMC Symbol in Frequency Domain

www.anritsu.com|66

Itcanbeobservedthat,withjustoneFBMCsymboltransmitted,notallsub-carriers

havebeenexcited,butonlytheonesappearingingreen.Thedifferentsub-carriers

willberandomlyexcited,dependingontheresultoftheIFFTovertheO-QAMsignal.

Itcanalsoberealizedthatonlyadjacentsub-carriersimpactsontheircorrespondent

neighbors,i.e.onlythesumofthemainlobesofadjacentsub-carriersarerelevantin

thespectrum.Thisisveryimportant,becausewecouldseparatedifferentsignalsby

justonesub-carrierspacingbetweenthemandstillbeingeasilyrecognizable.

Only the sum of the main lobes of the adjacent sub-

carriers are relevant in the spectrum

Fig41-FrequencyrelationshipbetweenFMBCsignallobes

The next scenario consists in creating a 100-FBMC-symbols signal for appreciating

thedifferenceinthespectrumwiththepreviousone.Inthiscase,onecouldexpect

thatwith100symbolswewillhaveallthesub-carriersexcited,thus,wewillhaveto

obtainaflatspectrum.Inthenextfigure

Time (ns)

Time domain

Am

plit

ude

1.5-0.8

2.5

0.4

0.2

0

0.6

0.5

-0.4

1 2

-0.2

-0.6

3

real (f_signal) for 100 FBMC symbols (rep=100)fs=200 MHz

x104

Fig 42 - 100-FBMC-Symbols signal in Time Domain

67|Understanding5G

…itisdemonstratedthatafterusing100FBMCsymbolsthespectrumbecomesflat,

i.e.thesignalenergyhasbeendividedbetweenallthesub-carriers.

Frequency (MHz)

Frequency domainN

orm

aliz

ed M

agni

tud

e (d

B)

5010 80604020

0

30

-120

-20

-100

-40

-80

-60

-140

-160

0 70 90-180

Spectrum (f_signal, rep=100fs=200 MHz

Spectrumbecomes flat.

Energy divided inall sub-carriers

Fig 43 - 100-FBMC-Symbols signal in Frequency Domain

FBMC Waveform in MS2830A

After successfully testing the FBMCmodulator inMatlab, it is time to send these

signalstoourSGinternalmemory,sowecanreproducethemandusethemwith

realdevices.Inthiscase,theall-in-oneSignalGenerator+SignalAnalyzer+Spectrum

AnalyzerMS2830Ahasbeenchosenforourexperiment.

Fig 44 - Anritsu IQProducer

www.anritsu.com|68

TheMS2830ASGcanreadexternalIQwaveformsfileswithextensions.wvdand.wvi,

whichleadstotheneedofusingAnritsuIQProducerforconvertingthedatafrom

Matlabintothesetypeoffiles.ItwillconsistinsavingthewaveformdatafromMatlab

intoaComma-SeparatedValuesfile(.csv)and,then,usingIQProducerforconverting

itintothereadablewaveformfiles.

This isthestageoftheprocesswhentheuserwillselectthesamplingfrequency,

which will determine the signal bandwidth at RF frequencies. The software IQ

ProducerforMS2830Aallowsamaximumsamplingfrequencyof160MHz,sothe

widestsignalwillhaveexactlythatbandwidth.

Fig 45 - Convert tool in Anritsu IQProducer

WecanusetheIQProducerTimeDomainapplicationforviewingthesignalloaded:

Fig 46 - IQProducer Time Domain Application

69|Understanding5G

Once the waveform has been properly converted and before sending it to the

MS2830A,wecanusetheIQProducerTimeDomainapplicationforanalyzingthe

formofthesignaltobeloaded.ThissoftwarealsooffersFFTviewerforanalyzingthe

signal in the frequency domain if needed.

LoadingthewaveformintotheMS2830Aisverystraightforward.It isenoughjust

creating the folder “Convert_IQProducer” in the path C:\Program Files\Anritsu

Corporation\SignalGenerator\System\Waveforms\ofourMS2830A,sharing itand

sendingtherethe.wvdand.wvifiles.TheSetUpneededforthisoperationconsists

uniquelyinanEthernetconnectionfromtheMS2830AtoourLaptop(SetUpfigure)

andMatlabcanbeusedagainforsendingthesefilesautomatically.

Fig47-5GWaveformDemonstrationSetUp

Then,goingthroughSG/LoadPatternandSG/SelectPatternfunctionsthewaveform

is easily prepared for being transmitted.

Fig48-Selecting5GwaveformpatternsinMS2830A

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ConnectingtheoutputtotheinputofourMS2830A,wecanusetheSPAforviewing

the signal transmitted. In this first example, a single-FBMC-symbol signal with a

bandwidthof20MHzcanbeappreciatedinthefigure.Agoodrejectionatbothsides

ofthesignalisachieved,asitwasexpected.

ThenextfigureshowsthesignalfromtheSAfunction,showingmoreclearlythesub-

carriers that have been excited for this FMBC symbol.

Fig49-5GWaveformSpectruminSpectrumAnalyzermode

•ConnecttheOutputtotheInput•SPA•SignalBW=20MHz•Clearlydistinguishedsub-carrier

•ConnecttheOutputtotheInput•SA•SignalBW=20MHz•Clearlydistinguishedsub-carrier

Fig50-5GWaveformSpectruminSignalAnalyzermode

20 MHz

2.5 MHz

20 MHz

14 MHz

71|Understanding5G

Following the same procedure with a 100-FBMC-symbols signal, we can observe

theproperconversionofthesignalusingIQProducer,bothintimeandfrequency

domain.

Signal with 100 FBMC Symbolsfs=20 MHz

Fig 51 - IQProducer Analysis on 100-FBMC-Symbols signal

Then, once loaded into the MS2830A SG and analyzed with the SPA, the highly

contained flat spectrumwithmore than 30 dB of rejection at both sides can be

observedinthisfigure.

Afurtherexampleconsistsinsimulatinga100MHzsignalformedby5FBMCcarriers.

Fig 52 - Spectrum design of 5-carriers FBMC signal

www.anritsu.com|72

Inthiscase,considering17.5MHzbandwidthateachcarrier,whicheachofthemhas

beenbuiltwith16sub-carriersatthesametime,wecouldprovethataRBWaround

1MHzwouldclearlycapturethedifferentsub-carriersbeingexcited.Thisiswhatwe

representinthefollowingfigure.

Fig53-SingleSweepofFBMCsignalinSpectrumAnalyzer

Playingwiththisscenario,theusercanmeasuremorecomplexparameterssuchas

AdjacentLeakagePowerRatio(ACLR)insinglecarriermode,multi-carriercontiguous

or multi-carrier non-contiguous.

Fig54-ACLRMeasurementon5Gwaveforms

73|Understanding5G

Apartfromthesefunctionalities,MS2830Acandigitizetheserealsignals intodata

filesthatcanbesentbacktoMatlab,wheretheycanbeprocessedandcompared

withtheoriginalsignals.

Fig55-Capturingreal5GwaveformswithMS2830A

Asanexample,inthenextfigure,wecaneasilynoticehowthenoisefloorlevelofthe

signalcomingfromtheMS2830Ahasincreasedincomparisonwiththeonecreated

originallyinMatlab,mainlycausedbytheeffectofthesignalgenerator.

Fig56-Comparisonofcapturedwaveformwithsimulatedwaveform

www.anritsu.com|74

In summary, it is possible to create almost anywaveform desiredwithoutmuch

difficultyandgivethedesignersthechancetoevaluatetheperformanceofpossible

5Gcommunicationstechnology.Wehavedemonstratedhowtoeasilyload,reproduce

andanalyzenewkindsofsignalsinourMS2830A.

75|Understanding5G

Conclusions

Wehaveseeninthisguidethatthenextgeneration5Gcellularwirelessnetworksare

aimingataverydiversesetofusecasesandapplicationsforwirelessconnectivity

withinsociety.Aswellasmeetingtheconstantdemandformorebandwidth,higher

datarates,andwidercoverage,thenew5Gnetworkswillaimtoopenupmoreuse

casessuchasSmartMeters,FirstResponder,CriticalHealthCare,andMachineto

Machine(M2M)applicationsbyofferinganetworkandtechnologysuitableforthis

muchwidersetofusecases.Thereareanumberofkeynewperformancetargets

beingsetfor5G,matchingtotheseenvisagedusecases.

Severalkeynewtechnologiesareemergingaskeybuildingblocksfor5G.Wehave

seen that cloud services, Network Function Visualization, and Software Defined

Networks,willbethekeyelementstothenetworkinfra-structure,providingamore

flexible,scalable,anddynamicnetwork infrastructurethatcanadapttousecases

and requirements ina fasterandcosteffectiveway.Thiswill lead to theconcept

ofnetwork“slicing”tomanageanddeliverservices.HeterogeneousNetworks(Het

Net)areexpected tobeakeyelement foraccessnetworkarchitecture.Thisuses

amulti-layerapproachtocoverageandcapacity,combiningmacrocellsandsmall

cells,usingdifferentaccessinterfacessimultaneously,andselectingaccessmethods

basedonvariousparameterssuchastraffictype,congestion,latencyetc.Theresult

of the development of HetNet technology is that 5G is expected to not be a single

access technology, but a combination of different legacy and new technologies

whichcomplementeachother.

Ontheairinterface,thekeychallengeistofindenoughavailablebandwidthtomeet

thedata capacity andperformance requirementswhicharepredictedby theuse

cases.Lookingfornewbandwidththatmaybecomeavailableisdrivingtheindustry

tohigherfrequency,andtomillimeterwavesolutions.Heretherearepropagation

andtechnologycostissuesthatneedtobeovercome.Atthesametime,“Massive

MIMO”isbeingdevelopedasanimprovementtotheairinterfacethatwillgivehigher

capacityduetobetterspectralefficiencyandspectrumre-usewithinacell.Thereare

implementationissuesformassiveMIMOrelatingtosizeandcost,butmaturingof

millimeterwavetechnologyishelpinghere.Fortheairaccessmethod,theindustry

hasseen thatOFDMA,used inLTE,doesnotmeet the interferencehandlingand

www.anritsu.com|76

thespectrumdensitydemandsoffutureHetNet.So,newaccesswaveformsbased

onimprovedspectrumorthogonality,orusingnon-orthogonalwaveforms,arenow

beinginvestigatedforanewairaccessmethod.

For the test andmonitoring industry, 5G is presentingmany new challenges as

wellasopportunities.Testingofthecoreandaccessnetworkelementsischanging

asSDN/NFVaredeployed,asthetestofthephysicalentityandtestofthe logical

functionare separated rather than testedasan integratednetworkelement. 5G.

RF andmillimeterwave component testingwill evolve tomeasure characteristics

using modulated wideband signals, to more accurately determine performance

whenusingnextgenerationwaveformsthatwillhaveverystringentperformance

requirements, leading to the need for broadbandmeasurement equipment and

the need forOTA test fixtures and chamberswhich are compact and affordable.

Devicetestingandcertificationislikelytobesignificantlyimpactedbythechanges

in5G.Withsuchadiverserangeofdevicetypes,ofaccessmethods,andusecases,

then the standardized testingmethods based around “test once, use anywhere”

willneed toevolve togiveacostefficientway tocover thismuchwider rangeof

test requirements. In field testing and monitoring, we can see that HetNet and

interference limitednetworkperformancewillbring inanewsetofrequirements

formeasuringnetworkperformance,coverage,capacityetc, inordertorelatethe

networkconditionstotheuserexperience.Alongsidethesenewtestdemands,we

can also see that 5G technology may also bring to the test and monitoring industry

somenewtechnologiesthatcanalsobeusedtoimplementtestsolutions.Socloud

based systems and visualizationmay also be used to create innovative new test

methods and solutions.

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