07 ITG524 Heidelberg Doetsch

7/30/2019 07 ITG524 Heidelberg Doetsch

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LTE-Advanced Field TrialCoordinated Multipoint Reception

Uwe Dtsch, Bell Labs

July-2010


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2 | UL CoMP Trial Berlin | June. 2010 All Rights Reserved Alcatel-Lucent 2010

Motivation

Coordinated multipoint transmission / reception (CoMP)

Candidate technology for LTE-Advanced (a.k.a. network MIMO)

Enhance cell edge spectral efficiency

More consistent QoS throughout the network

Enhanced user experience

CoMP particularly promising in UL

UE transmit power limitation at cell edge

Coherent combining can be realized w/o changes of LTE air interface and

w/o changing the total number of antennas in the network

Significant UL throughput gains observed in simulations

Objectives:

Prove feasibility of UL CoMP in realistic LTE environment

Quantify macro-diversity gains of UL CoMP in the field


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UL CoMP basic principle

Exchange over X2 interface

CoMP with 3 sites

CoMP with 2 sites

Exchange over X2 interface

UL signal from one user isreceived in multiple cells

Radio resources allocatedmultiple times, i.e. multi-userMIMO over multiple cells

Coherent combining of ULsignals in a central unit

Transfer of I/Q samples orsoft bits to the central unit

Over X2 interface or using adistributed RF architecture

LTE eNB


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Framework

Field trials within EASY-C research project

UL CoMP drive test conducted in Berlin testbed

Partners in Berlin trial: Alcatel-Lucent Bell Labs: LTE eNB central processing

Deutsche Telekom Laboratories (T-Labs): antenna sites, fiber links, van

Fraunhofer Heinrich Hertz Institute (HHI): Berlin testbed

Kathrein: remote radio heads

EASY-C research project:

Key technologies for next generation cellular networks

Funded by German government

Partners from academia and industry

Mobile network operators: T-Mobile and Vodafone

Two testbeds in Berlin and Dresden www.easy-c.com


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LTE UL CoMP setup (4Rx)

Architecture: Central processing unit + two distributed

remote radio heads (RRH) with two crosspolarized antennas each

1st RRH on T-Labs building 2nd RRH on Technical University Berlin

About 570m distance between RRH sites

RRHs connected via CPRI optical fibre links

Length of fibre links ~3km

System parameters: 2.6GHz carrier

5 MHz bandwidth

UL peak data rate = 8.5 Mbps (16QAM SIMO)

LTE eNodeB

CentralProcessingUnit

2.5Gbps CPRI fibre links

~3km length

RemoteRadioHeads

+

antennas


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UL COMP Lab measurements with 2Rx and 4 Rx for fading profile

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

-5 0 5 10 15 20 25 30 35

UL SINR per path [dB]

UL

Throughput[kBit/s]

4Rx

2Rx

LTE eNodeB

2.5GbpsCPRI fibre

links

RRHs

FadingEmulator(Spirent)

Rx1

Rx2

Rx3

Rx4

Measurement Set up

Tx1

Test mobile

Splitter1:4

Main results:

Gains confirmed

increased received energy for 4RX vs. 2RX 3dB

plus diversity gain depending from fadingchannel

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 5 10 15 20 25 30 35

(estimated) UL SINR [dB]

UL

Throughput[kBit/s]

4Rx

2Rx

3dB+ diversity gain

diversity gain


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Field Test Berlin

T-Labs TU Berlin

Heinrich Hertz Institute

T-Labs

HHI

TUB

Optical fiber network

~570m distance

User equipmentcarried in van


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Consistency Check : Static user @ cell edge

static field measurement matches lab data

approximately 4 dB gain in SINR

80 % throughput gain

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 5 10 15 20 25 30 35

(estimated) UL SINR [dB]

UL

Throu

ghput[kBit/s]

4Rx

2Rx

diversity gain

2 Rx TLabs

2 Rx TUB

4 Rx TLabs

4 Rx TLabs

Simulated a cell edge situation:

- Static UE was positioned outside HHI (cell edge position, no velocity)

- Lab measurements for comparison

2 Rx TLabs/TUB


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Determination of serving cell

HHI

1Tx2Rx

T-LabsTUB

2Rx 2Rx UL SIR T-Labs > UL SIR TUB

2Rx UL SIR TUB > UL SIR T-Labs

Mapping of strongest Cell for drive route

T-labs site dominates

Handovers would not be toofrequent

UL

SIR(d

B)


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UL Throughput gain of Macro Diversity compared to 2Rx Handover

1Tx2Rx

T-Labs

HHI

TUB

2Rx

Serving Cell TUB

Significant MacroDiversity gaincompared toHandover Scenariowith 2 Rx for SIRthreshold 0 dB

Throughput[kBit/s]

Position

Serving Cell TUB


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TLabs Site: Macro Diversity compared to 2Rx Handover

Serving Cell: TLabs

Significant throughput improvementwith Macro Diversity compared to

Handover Scenario with 2 Rx for SIRthreshold 0 dB

Serving Cell: TLabs

Significant improvement of UL SINR forthe Macro Diversity Case

SINR gains, but throughput limited by modulation 64 QAM would help here


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Field Test Berlin

T-Labs TU Berlin

Heinrich Hertz Institute

T-Labs

HHI

TUB

Optical fiber network

~570m distance

User equipmentcarried in van


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Throughput improvement


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Throughput improvement

TUB

2Rx

1Tx

2Rx

HHI


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Throughput and SNR improvement

Throughput CDFs show the

improvement in throughput

and SINR


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Summary

Industrys first live field test of CoMP in LTE network

Feasibility of UL CoMP in realistic LTE environment has been proven

Central processing with distributed RRHs (>500m apart) Digital Baseband transmission over optical fibers of ~3km length

UL coherent combining validated for MMSE receiver

No issues with optical transmission delay

Receiver can handle delay spread and alignment of timing advance

Quantitative results of test:

Significant UL throughput enhancements observed for user at cell edge

Potential improvement identified for 64 QAM modulation


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07 ITG524 Heidelberg Doetsch

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