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AbstractCurrently, 3GPP standardizes an evolved UTRAN

(E-UTRAN) within the Release 8 Long Term Evolution (LTE)

project. Targets include higherspectral efficiency, lower latency,

higher peak datarate when compared to previous 3GPP air inter-

faces. The air interface of E-UTRAN isbased on OFDMA and

MIMO in downlinkand on SCFDMA in uplink. Main challenges

fora terminal implementation include efficientrealization ofthe

innerreceiver, especially forchannel estimation and equalisation,

and the outerreceiver including aturbo decoder which needstohandle datarates of up to 75 Mbps perspatial MIMO stream. We

show thatthe innerreceivercan nicely and straightforwardly be

parallelized due to frequency domain processing. In addition to

the computational complexity of even a simple linear equaliser,

one of the challenges is an efficient implementation considering

necessary flexibility for different MIMO modes, powerconsump-

tion and silicon area. This paper will briefly overview the current

LTE standard, highlighta functional data flow through the single

entities ofan LTE terminal and elaborate more on possible first

implementation details, including sample algorithms and first

complexity estimates.

IndexTerms 3GPP LTE, OFDM, MIMO, receiver design

I. INTRODUCTION

HEmobileradionetwork technologyfamilyofthe3GPP

(3rdGenerationPartnershipProject)aswellas itsprede-

cessorETSI (EuropeanTelecommunicationsStandards Insti-

tute),includingGSM/EDGE(GlobalSystemforMobilecom-

munications/Enhanced Data rate for GSM Evolution) and

UMTS/HSPA (Universal Mobile Telecommunication Sys-

tem/High Speed Packet Access) technologies, now accounts

forover85% ofallmobilesubscribersworldwide.Thefurther

increasingdemandonhighdataratesinnewapplicationssuch

asmobileTV,onlinegaming,multimediastreaming,etc.,has

motivatedthe3GPPtoworkonthelongtermevolution(LTE)

projectsincelate 2004.Overalltargetwastoselectandspecifytechnology thatwouldkeep3GPPs technologies at the fore-

frontofmobilewirelesswellintothenextdecade.

Key objectives of the 3GPP LTE, whose radio access is

calledEvolvedUMTSTerrestrialRadioAccessNetwork(E-

UTRAN), include substantially improved end-user through-

puts,sectorcapacity,reduceduserplanelatency,significantly

improveduserexperiencewithfullmobility,simplifiedlower-

cost network and reducedUserEquipment (UE) complexity.

Currently, first 3GPP LTE specification is being finalized

within 3GPP Rel-8. Specifically, thephysical layer hasbe-

comequitestablerecentlyforafirstimplementation.

The air interface ofE-UTRAN isbased onOFDMA (Or-

thogonal Frequency Division Multiple Access) and MIMO

(Multiple-Input Multiple Output) in downlink (DL) and on

SCFDMA (Single Carrier Frequency Division Multiple Ac-

cess)inuplink(UL)direction.Mainchallengesforaterminal

implementation include efficient realization of the inner re-

ceiver,especiallyforchannelestimationandequalisation,andthe outer receiver including a turbo decoderwhich needs to

handledataratesofupto75MbpsperspatialMIMOstream.

We show that the inner receiver can nicely and straightfor-

wardlybeparallelizedduetofrequencydomainprocessing.In

addition to thepurecomputationalcomplexityofevenasim-

ple linear equaliser,oneof the challenges is anefficient im-

plementation considering necessary flexibility for different

MIMOmodes,lowpowerconsumptionandsmallsiliconarea.

Thispaper is structured as follows: In section II,we first

giveabriefoverviewofthe3GPPLTEsystem,especiallythe

physicallayer.AnexampleLTEUEimplementationincluding

thecorefunctionalalgorithmsofthebasebandprocessingdata

flowisdescribedinsectionIII.InsectionIV wewillevaluate

the computational and memory requirements for an example

implementation, and highlight the challenges. Finally, some

concludingremarksaregiveninsection V.

II. OVERVIEWOFTHE3GPPLTE

The3GPPLTEphysicallayerisresponsibletoconveydata

and control informationbetween anLTEbase station called

eNB (evolvedNode B) and theUE.TheLTE hasbeen de-

signed to meet, among others, the following physical layer

requirements [1]

-Bandwidthscalablefor1.4,3,5, 10, 15, 20 MHz.

-Antennaconfiguration: Upto 4x4 DLMIMO.InULonlyantennaselectionisspecified,i.e.asinglespatiallayer.

-Peak data rate scaling withbandwidth and number of

spatialMIMOlayers.AbsolutepeakratesareDL300 Mb/s

(4 layers)andUL 75Mb/s (1 layer, 64-QAM)within 20

MHzbandwidth.

By using OFDM, LTE is inprinciple aligning with many

IEEE 802 family standards, such as 802.16/WiMAX or

802.11/WiFi. However, within the 3GPP cellular standard

family, OFDMbasedLTE is totallydifferent from itsprede-

cessorssuchas time/frequency-divisionmultiple-accessbased

On3GLTETerminalImplementation Standard,

Algorithms,ComplexitiesandChallenges

Jens Berkmann,CeciliaCarbonelli,FrankDietrich,ChristianDrewes,Wen Xu

InfineonTechnologiesAGAmCampeon 1-12,85579 Neubiberg,Germany

first_name.last_name@infineon.com

(InvitedPaper)

T

978-1-4244-2202-9/08/$25.00 2008 IEEE

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