MIMO Webinar

Slide 1 June 2011

Verifying MIMO Operation and Downlink Coverage for LTE & TD-LTE

Andy Standen, Product Manager Eric Hakanson, Senior Product Manager

22 June 2011

Slide 2 Mar 2011 Company Confidential

Agenda

�  LTE MIMO Overview

�  The MIMO Measurement Challenge

� Anritsu’s LTE MIMO Measurement Solution

� Anritsu’s LTE RRH Measurement Solution

� Example measurements, troubleshooting problems

� Downlink Coverage Troubleshooting

� New LTE Measurements

� Conclusion

� Q&A


LTE MIMO Overview (2X2 examples)

�  Multiple Input, Multiple Output

  Input = Transmitter

  Output = Receiver

  2x2 common today

}  2 Tx in eNodeB, 1 Tx in UE

�  Transmit Diversity

  Data stream repeated from all Tx

  Increase coverage

  Increase throughput at cell edge

}  Less error correction

�  Spatial Multiplexing

  Different data streams

  Higher data rate

  Relies on Multipath

  Requires good SNR

MIMO Transmit Diversity

MIMO Spatial Multiplexing


The MIMO Measurement Challenge

� Severe co-channel interference

 Due to MIMO } With 1 receiver

 Multi-channel measurement receivers expensive

 Direct-connect measurements? } “Precoding” precludes

Precoding causes bad EVM measurements on live traffic, even when connected directly to the transmitter


The LTE MIMO Measurement Challenge

�  LTE uses frequency reuse (“N”) of 1

 Additional co-channel interference

� Connection between transmitters and antenna

 Sector Alpha antenna pair

 1 Tx from Alpha, 1 Tx from Beta

� Some eNodeBs have sync only on 1st transmitter

 Others have on all transmitters

 Different troubleshooting method

� Remote Radio Heads (RRHs) or …Units (RRUs)

 Complicate connecting to transmitter


eNodeB: Remote Radio Unit

�  Single Sector

  2x2 MIMO } 2 radios per sector } Tx1 has Sync Signal } Tx2 may have Sync Signal

�  Test Needs

  Transmitter

 Antenna & jumper cables

  LTE signal quality } OTA if no access to RRU

  Interference

 Coverage

 Backhaul

  Fiber

Tx1 / Rx1

Tx2 / Rx2

Dire

ctio

nal C

oup

ler /

Te

st P

ort

Channel Cards

Power Supply

Remote Radio Heads Ideally located close

to antenna

Radio Server

RF Cable Jumper if close to antenna

Backhaul GigE ….

GPS Antenna

Fiber Optic Baseband Cable with DC Power

Antennas

Air Interface

Interference


Anritsu’s LTE MIMO Measurement Solution

�  Over-the-air measurements of Physical Broadcast Channel (PBCH)   Good indicator of

eNodeB health

  Measures all transmitters

�  Reference Signal power of each transmitter   OTA Tx Test measurement

�  Throughput test to verify backhaul

�  When problem detected   Verify with direct-connect

measurement

  Test Model signal

  Each transmitter


MIMO Indicator

� Shows which transmitter detected

 For EVM measurements } OTA or direct-connect } Both show green for OTA-measuring both transmitters


Anritsu’s LTE RRH Measurement Solution

�  “Tx Test” measurement

�  Optimal OTA transmitter test   Verifies low co-channel interference

  Verifies MIMO

  OTA EVM

  Frequency Error

�  Also useful for non-RRH

  Verifies complete system

�  Guideline – OTA

  One cell ID }  Or at least 20 dB dominance

  RS Delta power < 3 dB

  EVM < 10% }  Measure at installation, track

changes

  Frequency Error < 10 Hz (GPS)

  Only quality indicator


Qualifications for OTA EVM Measurements

� Must be in a “sweet spot”

 Good power level } Ideally >> -80 dBm RS power

 Low co-channel interference } >20 dB dominance } Ideally only 1 signal

 About 500 yards/meters from antenna, center of sector

 No large reflectors nearby

� Directional antennas

 If necessary

� May need to move slightly to get optimal RS Delta Power

 See Tx Test measurement later in webinar


Sweet Spot Examples

�  Poor Dominance = bad OTA EVM

� >20 dB Dominance = medium OTA EVM

� 1 signal = good OTA EVM


Troubleshooting Misconnected Transmitters

�  Tx Test

  Incorrect Cell ID } Scanner

  Only 1 Transmitter } Delta RS Power

  Wrong connection to antenna } Depends on eNodeB

manufacturer »  Sync on 1 Tx »  Sync on All Tx »  See next slides


Wrong Connection to Antenna—Sync on 1 Tx

�  Lots of power, no Cell ID

� =>Both Tx swapped  To Tx without Sync

 One without Sync, one disconnected

 Disconnect other Tx to identify

�  Lots of power, no sweet spot  Bad antenna

 Large reflector

 Non-Sync Tx swapped with Sync Tx from other sector


Wrong Connection to Antenna—Sync on 1 Tx

�  Plenty of power

� High Dominance

� Very high EVM

� =>Tx without Sync swapped with another Tx without Sync

 Disconnect other transmitters to identify


Wrong Connection to Antenna—Sync on All Tx

�  Lots of power, no Cell ID

  Unlikely

  Serious transmitter problem

�  Lots of power, no sweet spot

  Bad antenna

  Large reflector

  One Tx swapped with Tx from other sector } Sector obvious } RS Power Delta

graph for which Tx


Wrong Connection to Antenna—Sync on All Tx

�  Plenty of Power

� High Dominance

� Very high EVM

� =>Failed Tx or strong interference

 Directional antenna helps eliminate interference


Downlink Coverage Troubleshooting

� Complement to Drive Tester

� Allows technician to troubleshoot coverage problems

� Supplement data gathered by Drive Tester


On-Screen Mapping – Save as KML, CSV, JPG New!

�  Similar to SPA Coverage Mapping

  Download maps with Map Master

  Off-screen data points

still valid

  Thresholds adjustable

  Export to .kml or

tab-delimited

  Helps operator see where measurements made

�  Included with LTE OTA options


Import Into Google Maps Either Autosave from Scanner or Internal Mapping


New LTE Measurements

�  Power vs. Resource Block

� Control Channel Power Table


Power vs. Resource Block New!

�  Power vs. RB   Shows eNodeB activity

  Utilization helpful to see traffic loading, and impact on RF spectrum

�  Guideline

  Non—varies with traffic

�  Consequences

  RF performance can vary with traffic

�  Common faults

  Poor RF performance or coverage can increase loading

} Simpler modulation

} More FEC

} More re-transmissions


Control Channels – Table View New!

�  Same measurements as “Bar Graph” view   Power/RE: what UEs usually show   Total Power: what some eNodeB

configuration tools show


Conclusion

�  Tx Test measurement checks MIMO & RRH transmitters

� Coverage Mapping helps troubleshoot coverage problems

� Additional measurements for troubleshooting eNodeB problems

Slide 24 June 2011

Q&A

Please submit questions using your GoToWebinar control panel

Slide 25 June 2011

Thank You For Attending

For further information on this webinar, please send e-mail to:

[email protected] [email protected]

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