mi mo through put drive test web in ar

7/30/2019 Mi Mo Through Put Drive Test Web in Ar

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Maximizing LTE MIMOThroughput Using

Drive Test

Measurements

PCTEL RF Solutions


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James Zik, Senior Product

Marketing Manager, PCTEL, Inc.

Bruce Hoefler, Vice PresidentProduct Management, PCTEL, Inc.


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Mobile Bandwidth Need

18X growth from 2011 to 2016


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Spectrum Crunch

-300

-200

-100

0

100

200

300

2011 2012 2013 2014

SpectrumS

urplus(MHz)

FCC Licensed Spectrum Needs*

Need to get maximum throughput on available spectrum

*FCC, Mobile Broadband: The Benefits of Additional Spectrum (October 2010).


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Air Interface Bottleneck Solutions

How do we Get There?

More Spectrum Limited licensed spectrum available

Expensive

Migration to LTE

LTE MIMO

Carrier grade WiFi and backhaul required 22% of mobile traffic by 2016 (Cisco VNI Mobile 2012)WiFi Offload

Small Cells and DAS (expensive)

Backhaul required to each cell/DAS

Increased Cell

Density

Migration to LTE and LTE Advanced

LTE MIMO

Spectrum

Efficiency

Must employ all of these solutions to solve the spectrum crunch


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Why MIMO?

Low to medium cost method to improve transmission performance(already built-in on many LTE base stations)

Increases physical layer capacity (w/ spatial multiplexing MIMO)

Throughput gain dependent on number of Tx and Rx antennas

i.e. 2x2, 4x4, etc.

LTE Peak Spectral Efficiency per 3GPP

LTE Peak Throughput of 4x

LTE Peak Throughput of 2x

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5

10

15

20

25

30

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-10 -5 0 5 10 15 20 25 30

Peak Physical LayerSpectral Efficiency (b/s/Hz)

SNR (dB)

2x1

2x2

4x4

8x8


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What is MIMO?

MIMO is a smart antenna

technoIogy that employs

multiple antennas at the

Tx and Rx ends

MIMO is NxM (i.e. 2x2,4x2, 4x4, 8x8, etc.) where

N>1 and M>1

2x2 (deployed), 4x4 and

4x2 (emerging),

8x8 (LTE Advanced) Radiated signals traveling

on different paths provide

the possibility of

performance

improvements


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How Does MIMO Work?

Spatial Multiplexing:

Transmits multiple data

streams simultaneously in

the same frequency and

time, taking advantage ofdifferent paths

Requires separate paths

Requires high SNR toimprove throughput

Transmission shown one way (eNB to UE) for simplicity


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Transmission Modes

Single User MIMO Modes

Currently deployed

transmission modes


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Why Test MIMO?

What are we trying to accomplish by testing MIMO?

Determine the air interface Maximum Throughput capacity

for different MIMO Modes (MIMO Gain)

Provide throughput gain of the physical layer for each

transmission mode (using standards number) Optimize the RAN physical layer for Maximum Throughput

Characterize Link efficiency

Troubleshoot the RAN physical layer

Isolate path issues Test for channel independence


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What Parameters are

Necessary for MIMO Testing

Premise: Operators need to understand MIMO transmission

characteristics of the physical layer in RAN

Path measurements

Channel Quality Indicator (CQI as defined by 3GPP)

Throughput (maximum air interface throughput capability)

Channel Condition Number (CN)


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RF Path Measurements Determines if there is a problem with base station port or

a particular antenna with regard to MIMO paths

Antenna, cabling or TX port issues

Measurements are provided for each Tx/Rx antenna pair

4 paths for 2x2 MIMO

RSRP, RSRQ, RS CINR for each path


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CQI

Consistent indicator of theoreticaltransmission physical layerefficiency

CQI measurement is an essentialtool for MIMO

With SISO, CINR translatesdirectly to CQI

With MIMO, CINR does NOTtranslate to CQI i.e. throughput

CQI Index ModulationCode Rate x

1024Efficiency(b/s/Hz)

0 out of range

1 QPSK 78 0.1523

2 QPSK 120 0.2344

3 QPSK 193 0.3770

4 QPSK 308 0.6016

5 QPSK 449 0.8770

6 QPSK 602 1.1758

7 16QAM 378 1.4766

8 16QAM 490 1.9141

9 16QAM 616 2.4063

10 64QAM 466 2.7305

11 64QAM 567 3.3223

12 64QAM 666 3.9023

13 64QAM 772 4.5234

14 64QAM 873 5.1152

15 64QAM 948 5.5547

Source: 3GPP TS 36.213 Ver. 10.7.0 (Sept. 2012)

Table 7.2.3-1: 4-bit CQI


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Throughput

How and where is throughput measured?

Physical Layer Throughput(for RAN optimization)

Throughput measurement includes RAN, Backhaul,

Network Loading, Server, etc.

CQIIndex

Throughput (Mbps)

5 MHz 10 MHz 20 MHz

1 0.55 1.10 2.19

2 0.84 1.69 3.38

3 1.36 2.71 5.43

4 2.17 4.33 8.66

5 3.16 6.31 12.63

6 4.23 8.47 16.93

7 5.32 10.63 21.26

8 6.89 13.78 27.56

9 8.66 17.33 34.65

10 9.83 19.66 39.32

11 11.96 23.92 47.84

12 14.05 28.10 56.19

13 16.28 32.57 65.14

14 18.41 36.83 73.66

15 20.00 39.99 79.99

User layer throughputreduced up to 10X dueto control overhead- Handshaking- Synchronization

- Retransmission

Maximum ThroughputCapacity of the Air Interface

(Physical Layer)


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Condition Number (CN) CN is a measure of the independence (or correlation) of the

channels (paths)

Measured from 0 to 50 dB; lower values are better indicating lowcorrelation

CN helps analyze potential causes for throughput issues but is not usedto calculate throughput

Studies show MIMO can still be effective with high CN if CINR is high

CN (dB) Indication

0 Two totally independent channels, an ideal condition that

can enable maximum throughput

~19* High correlation where MIMO generally would not induce a

condition that would increase throughput

*The CNs indicating the level of correlation are based on industry published approximations and can vary by several dB depending on conditions

Industry Norm


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Interpreting MIMO

Measurements

Separate CN, ECQI and transmission mode

measurements allow operators to diagnose the

causes of low throughput

Low CN and low CQI means there is an interference

or a power issue

High CN and low CQI means high channel correlation

and probable low SINR


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MIMO Testing Benefits

Characterize RF propagation for MIMO

Consistent, repeatable RF data independent of the backhaul, network layer overhead &server loading

Higher dynamic range to determine noise floor and potential interference effects

High data density to locate fading issues and reduced MIMO throughput

Determine channel independence Analyze network problems related to multipath conditions with condition number

Understand how antenna tilt or relocation can affect throughput

Provides result for various transmission modes Understand how different transmission modes affect RAN performance

Troubleshoot antenna/cabling issues and base station Tx port issues Path measurements


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FDD-LTE 2x2 MIMO outdoor DAS

When: April 2012 Outdoor DAS deployed due to cell tower restrictions

Area characterized by high foliage and low antenna height

MIMO oDAS Case Study

Antenna Locations


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How we Tested

Simultaneous oDAS Testing with Scanner and UE Data Card

PCTEL SeeGull EX Scanner

Test data card on another system

Orientation Test

Walk Test vs Drive Test

MIMO Transmission Modes (on the scanner)

RSRP, CN, CINR and Throughput


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Why Use a Scanner

3GPP TR 37.976:

3GPP already defined conducted tests for MIMO and

multiple antenna receivers. but it is clear that the ability to

duplicate these gains in the field is highly dependent on the

performance of the receive-antenna system..

The MIMO OTA throughput is measured at the top of

physical layer of HSPA and LTE system

Scanner use omni-directional antennas

Scanners measure throughput at the physical layer Scanners provide throughput for multiple MIMO transmission

modes

UEs only provide throughput for the MIMO mode the UE is

locked onto

O i t ti A l i


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0

2

4

6

8

10

12

1416

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Frequency

Position: 0

010203040506070

80

Frequency

Position: 90

Position A Average: 2.820 Mbps

Position C Average: 1.232 Mbps

Orientation AnalysisUE Data Card

2.3X difference depending on

orientation due to directionality

of UE antennas

(stationary test)

kb/s

kb/s

MIMO antennas in UEs

are typically very

directional


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0

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#ofDataPoints

Speed AnalysisUE Drive Test (~20 mph)UE Walk Test

UE Throughput drops by 2X w/ drive test, scanner is not affected by speed

Throughput (kb/s)

((

4

2

)

4

)

(42)

0

10

20

30

40

50

60

70

80

1 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

#ofDataP

oints

(24)

Throughput (kb/s)

D i T t D t


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UE Data

Scanner Data

Drive Test Data(Throughput)

0

200

400

600

100 1000 2500 5000 10000 More

#ofDataPoints

UE

0

1000

2000

3000

4000

5000

#ofDataPoints

Scanner

UE Data

Tput (kb/s)

Lost Connection

Significant differences

between scanner & UE

Note: Throughput is very low.

Scanner show higher throughput

since its measuring at the physical

layer

Tput (kb/s)


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Scanner Transmission

Modes (MIMO Gain)

0

200

400

600

800

1000

1200

100 1000 2500 5000 10000 20000 30000 More

#ofDataPoints

Open Loop Transmit Diversity(mode 2)

0

200

400

600

800

1000

100 1000 2500 5000 10000 20000 30000 More

Frequency

Closed Loop SpatialMultiplexing (mode 4)

No throughput gain from multiple data streams

Tput (kb/s) Tput (kb/s)


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RSRP

Test results show marginal RSRP

RSRP

dBm

#ofDataPoints


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CINR for MIMO

CINR

Test results show very LOW CINR

dB

#ofDa

taPoints


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CN for MIMO

MIMO requires high CINR and prefers low CN to maximize throughput

Condition Number (CN)

Test results show low CN

dB

#ofD

ataPoints

DAS C St d


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oDAS Case Study

Conclusions

MIMO is ineffective in this network Network has a severe interference and/or noise problem

Marginal RSRP and very poor CINR

Conditions favorable for MIMO to improve throughput

Low CN

UE Measurements for MIMO must be carefully examined since theyare affected by:

UE Orientation

Speed of movement during the test

Drive test vs walk test for outdoor systems. MIMO Transmission mode the UE is operating in

Another UE may operate in a different transmission mode

A scanner is very effective in characterizing a MIMO network

MIMO Macro Cell


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MIMO Macro Cell

Case Study (Oct 2011)PCI-Best Server by RSRP (Baltimore: Urban Environment)

Focus on BestServer Region

for PCI (best

server)

(PCI, # of data pts)


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LTE RSRP (Best Server)

Excellent RSRP


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MIMO Drive TestTransmit Diversity and MIMO Throughput

Best Server Region

for PCI of interestTransmit Diversity MIMO (mode 4)

Mbps

MIMO Drive Test


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MIMO Drive TestDelta (MIMO-Transmit Diversity)

Throughput

Mbps

Why is (MIMO Transmit Diversity)negative at the cell edge (pink)?

For extremely low CINR, transmit diversity

is more efficient. The UE will switch to

transmit diversity in this region.

Large MIMO gain for much

of the center region of the cell


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MIMO Drive TestCondition Number and CINR

High CN with highMIMO Gain

Condition Number CINR

dB

dB

Very High CINR

Significant MIMO gain exists for LOS condition

if CINR is high even with high CN


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Summary MIMO was very effective for maximizing throughput in the Baltimore

Macro cell case study

MIMO may not be effective in sub-optimal designs, deployments orterrains as shown in the oDAS case study

Testing Benefits with a Scanner Characterize RF propagation for MIMO

Consistent, repeatable RF data independent of the backhaul, network layeroverhead & server loading

Higher dynamic range to determine noise floor and potential interference effects

High data density to locate fading issues and reduced MIMO throughput

Determine channel independence

Analyze network problems related to multipath conditions with condition number Understand how antenna tilt or relocation can affect throughput

Provides result for various transmission modes Understand how different transmission modes affect RAN performance

Troubleshoot antenna/cabling issues and base station Tx port issues Path measurements


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Questions?

Thank you

http://rfsolutions.pctel.com/content.cgi?id_num=36For a free LTE MIMO poster, please visit PCTEL RF Solutions website:
http://rfsolutions.pctel.com/content.cgi?id_num=36http://rfsolutions.pctel.com/content.cgi?id_num=36

mi mo through put drive test web in ar

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