CellCell SpectralSpectral Efficiency Efficiency ofof a a CellCell SpectralSpectral Efficiency Efficiency ofof a a 3GPP LTE3GPP LTE--AdvancedAdvanced SystemSystem

Daniel Bültmann, Torsten Andre

17. Freundeskreistreffen Workshop 201012 03 201012.03.2010

D. Bültmann, ComNets, RWTH Aachen Faculty 6

Schedule Schedule ofof IMTIMT--A A ProcessProcess

Today

2004

WINNER I/II WINNER +

2D.Bültmann, ComNets, RWTH Aachen Faculty 6

Technologies Technologies forfor IMTIMT--AdvancedAdvanced

B f i

CoordinatedMultipoint IMT-

Focus on Relays

MIMO

Beamforming

RelaysSpectrumAggregation

pTx/Rx

Dat

aR a

te

AdvancedCompare Deployments

Compare Reuse Schemes

Compare ResourceIMT-2000 Compare Resource

Partitioning

Antenna Patterns

Evaluate IMT-A Scenarios

Apply Method to LTE-A

3D.Bültmann, ComNets, RWTH Aachen Faculty 6

Problem DefinitionProblem Definition

Evaluation of IMT-Advanced criteria

• Peak Spectral Efficiency• Peak Spectral Efficiency– Foundation for cell spectral efficiency

• Cell Spectral Efficiency– Determined by system level

simulation– Path loss model with

randomized LoS/NLoS link randomized LoS/NLoS link conditions

– Frequency Reuse Schemes

An analytical model for the downlink is d l d

4D.Bültmann, ComNets, RWTH Aachen Faculty 6

developed

Problem DefinitionProblem Definition

Investigated Frequency Reuse Schemes

Evaluation of IMT Advanced criteria• Peak Spectral Efficiency

ga d qu y u

Evaluation of IMT-Advanced criteria• Peak Spectral Efficiency– Foundation for cell spectral efficiency

An analytical model for the downlink is d l d

5D.Bültmann, ComNets, RWTH Aachen Faculty 6

developed

Introduction to Long Term Evolution (LTE)Introduction to Long Term Evolution (LTE)

• OFDMA/SC-FDMA

• FDD/TDD

• MIMO– 4x4 (DL)– 2x2 (UL)

6D.Bültmann, ComNets, RWTH Aachen Faculty 6

Peak Spectral EfficiencyPeak Spectral Efficiency

• Minimum overheads, 64QAM-1/1, 4x4 MIMO (DL), 2x2 (UL) perfect channel2x2 (UL), perfect channel

DL UL

Required 15.0 6.75

FDD 16 3 8 5FDD 16.3 8.5

TDD 15.8 8.1

7D.Bültmann, ComNets, RWTH Aachen Faculty 6

Cell Spectral EfficiencyCell Spectral Efficiency

• Definition– Scenario net capacity per bandwidth and

cell [bps/Hz/Cell]

• Pathloss– Either LoS or NLoS link depending on

probability conditional on distance d– Random SINR depending on distances to all

bbase stations

8D.Bültmann, ComNets, RWTH Aachen Faculty 6

Cell Spectral EfficiencyCell Spectral Efficiency

• Definition– Scenario net capacity per bandwidth and

cell [bps/Hz/Cell]

η++++=

)(...)()()(

)(5721

4,4 dPdPdP

dPdSINR

LoSRxLoSRxNLosRx

LoSRx

hl

η)()()( 57,2,1, LoSRxLoSRxNLosRx

• Pathloss– Either LoS or NLoS link depending on

b b l d l d dprobability conditional on distance d– Random SINR depending on distances to all

b t ti

9D.Bültmann, ComNets, RWTH Aachen Faculty 6

base stations

Analytical ModelAnalytical Model

• Idea: compute all permutations and p pdetermine exact mean SINR

• Necessity to weight the permutation by its occurance probability its occurance probability

• Mean SINR

10D.Bültmann, ComNets, RWTH Aachen Faculty 6

Cell Spectral EfficiencyCell Spectral Efficiency

• CSE depends on achievable SINR; fromSINR derive possible throughputBSsSINR derive possible throughput

BSs

BSs

BSsTable lookup and interpolation

BSs BSs

SINR MCS FER ARQ THR

BSs

BSsBSs

MACL THRFERTHR ⋅−= )1(3BSs

11D.Bültmann, ComNets, RWTH Aachen Faculty 6

CellCell SpectralSpectral EfficiencyEfficiency

• Capacity according toThroughput Distribution

proportional fair

Gross

• Spectral Efficiency

CCbit

Peak Spectral Efficiency

BCCCSE net

bitcell ⋅= Net

12D.Bültmann, ComNets, RWTH Aachen Faculty 6

Cell Spectral Efficiency ResultsCell Spectral Efficiency Results

• Reuse Schemes • SISO, 100MHz b d id hbandwidth

• Requirement: 2.2 bps/Hz/cell

13D.Bültmann, ComNets, RWTH Aachen Faculty 6

Relay Enhanced CellsRelay Enhanced Cells

• LTE-Advanced supports Relaying for capacity enhancement and coverage extension

• Include one and three relays per cell to increase spectral efficiency (capacity enhancement)– Position at 3/4th of the cell radius

256QAM wireless backhaul error free conditions– 256QAM wireless backhaul, error free conditions– Cell capacity according to

21

111

hophopcomposite CCC+=

• Power mask concept extended to relays– Base stations and relays use distinct resources– Frequency reuse schemes within set

of relays

14D.Bültmann, ComNets, RWTH Aachen Faculty 6

Throughput in Relay Enhanced CellThroughput in Relay Enhanced Cell

• Uniform frequency reuse, one relay per cell

BSs

RN

BSsBSs

BS

RNBSBS

RN BSsBSs

BSs

15D.Bültmann, ComNets, RWTH Aachen Faculty 6

Cell Spectral Capacity for Relay Enhanced CellsCell Spectral Capacity for Relay Enhanced Cells

• SISO, 100MHz ,bandwidth

• Capacity according • Capacity according to

CCCC bitbit ⋅+⋅B

CCCCCSE netBSBSnetRNRN ., ⋅+⋅

=

• Required: 2.2bps/Hz/cell

16D.Bültmann, ComNets, RWTH Aachen Faculty 6

Conclusion & OutlookConclusion & Outlook

ConclusionsIntroduction of method to derive cell spectral efficiency– Introduction of method to derive cell spectral efficiencyanalytically

• Can be applied to InH, UMa, RMa scenarios• Can be applied to FDD/TDD• Can be applied to FDD/TDD• Allows for investigation of combinations of power masks and RN

deployment

– LTE-Advanced fulfills Peak Spectral Efficiency p yrequirement

– Resource Partitioning between Relays needed if morethan 1 Relay per sector is deployedthan 1 Relay per sector is deployed

Outlook– Include realistic model of the wireless backhaul– Investigate Cell Edge User performance gains– Optimize deployments (ISD, downtilt vs. relay

di t t )

17D.Bültmann, ComNets, RWTH Aachen Faculty 6

distance, etc.)

Thank you for your attention!Thank you for your attention!

Daniel Bültmanndbn@comnets rwth-aachen dedbn@comnets.rwth-aachen.de

Torsten Andretae@comnets.rwth-aachen.de

18D.Bültmann, ComNets, RWTH Aachen Faculty 6