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New Challenges in Modern

Wireless Field Testing

Nils Schapmann, Rohde & SchwarzMobile Network Testing, APAC

Agenda in brief ….

� The Base station and BTS evolution steps

� BTS Installation and Antenna Measurements

� PIM (Passive Intermodulation) Base station Testing

� Over - the - Air Measurements

� IR (Interference Hunting ) Spectrum Clearance

� Questions & Answers

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1992 – 2002

BTS in a Cabinet Solution

Mobile Networks Field Services

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Base station Value Chain Evolution 2002 � 2020

Backbone

Connection

Channel

Coding

Digital Radio Interface

TRX Filter TMA AntennaBasicUnit

Digital

Remote Radio Head

Active Integrated Antenna

Active Antenna Beamforming

Radio

2006

2012

2020

BTS Evolution towards RF Frontend

Supply Chain Dynamics & Rollouts

CA

PE

X S

pend

on

Wire

less

Infr

astr

uctu

re

2011 2014 2017 2020

5G Take Off• Cellular• M2M• D2D

predictions based on historical trend

3G Peakincl.

TD-SDMA

4G PeakLTE

4.5 G PeakLTE-A

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Increasing Number of BTS Rollout & Installationı Market Estimation 2015 to 2020

� 30-40 Frequencies � today� 70-80 Frequencies � 2020 (incl.. Small Cell)

2015 WORLD ���� 1.5 Mio BTS p.a.2020 WORLD ���� 3.5 Mio BTS p.a.

• VSWR• Intermodulation• RF-Spectrum Uplink

BTS integrated test casescauses changes for

• Interferences• Network Planning• Optical

Small Cell BTScauses new complex network behavior • Optical & Platform

Active Antenna & 4X4 MIMO causes optical installations

Mobile Networks

Field Service ProjectsRAN Expansion & Modernization & Swap

Increasing RAN site capacity by adding new equipment and SW

Small Cell BuildE2E solution, from planning to rollout as traffic increase

RAN BuildBuilding new RAN sites and/or networks incl. full site rollout

Multi Vendor RolloutRAN&Microwave project management in a shared environment

Fiber Network RolloutPlanning, designing & building E2E fiber networks

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Base station with Remote Radio Head (RRH)

ı Base band unit separated from the RF / RRH by a fiber optic link

ı RRH should be installed close to the antenna (shorter RF jumper cables)

ı RF connected measurements become more difficult in RRH⇒ OTA measurements becoming more

popular⇒ Cable and antenna measurements still

needed, shorter feeder but more complex setup

RF feeder cable

BB

Fiber optical cable

RRH

OTA

RF /Coax cablingOptical cabling

TMA = Tower Mounted AmplifierRRH = Remote Radio Head

Why do we need Cable and Antenna Measurements?

ı To ensure cable and antenna are properly installed before connecting to base station

ı To prevent push of responsibility due to many contractors/vendors involve� Cable & antenna provider� Cable & antenna installer� Base station vendors� Integrators

ı Ease of trouble shooting later

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What can go wrong ….. Antennas� Poor antenna isolation/matching� Loose connectors� Transport or weather damages

TMA and Ext. Components� Gain problems� Internal Filter problems� A&E handling problems

Cables� Poor or corroded cable connection� Poor isolation or ground� Damaged or broken cables� Unpaired or interchanged cables

Connectors� Improperly installed connectors� Weather (entrapped moisture) problems

Antenna analysis example

ı Response is most commonly displayed as VSWR (voltage standing wave ratio) or magnitude.

ı For magnitude, we want the maximum return loss dB (most negative value).

ı For VSWR, we want a value as close to 1 (perfect match) as possible.

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Distance to Fault / Cable Length Measurements

ı Cables can be damaged during manufacturing, deliver y, or installation. Installation faults are not-uncommon, indoors or outdoors.

ı Damaged cables may cause loss of signal, high level s of reflected power, interference, and other issues.

ı By injecting a pulse into one end of the cable and measuring the reflected power vs. time, we can determine where the fault (or “normal” end of the cable) is.This is also a “network analyzer” measurement.

Distance to Fault example

ı Distance to fault measurement results can be provided graphically or in a table.

ı The parameters of interest are both the location of the fault (meters) and the magnitude of the returned signal (in dB).

ı A “fault” is usually defined by the magnitude of the reflection (e.g. connectors create lower level reflections than true faults).

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Intermodulation Aspects from a BTS perspective

ı Linearity is Key – The Base station itselfı Active Intermodulation due to PA’sı Intermodulation due to BTS RF Frontendı Intermodulation of Duplexer or Combiner

ı Passive Intermodulation ı Components along the site installationı Bias-Tee’s & Jumperı Lightning Protectionı Splitterı Add-On Filters

Passive Intermodulation (PIM) Testing

ı Passive intermodulation (PIM) is a type of interfer ence that is generated when RF signals encounter a non-linear device.

ı Typically these are damaged or corroded base statio n components (the “rusty bolt”) but can be generated by a wide variety of objects.

ı To test for PIM, a pair of signals with a given fre quency spacing is injected into the DUT. Intermodulation products will be generated at known frequencies if PIM is present.

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PIM sources some reality

Loose connectors, poorly terminated cable, cracked/dry solder joints, deterioration over time, corrosion, wind vibration, etc.....

COMPANY CONFIDENTIAL

PIM example

ı A portable PIM tester is used to inject two signals(f1 and f2) into the system under tests

ı The tester calculates the location of the higher or der intermodulation products and measures the levels at those frequencies to see if PIM is present

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Over-The-Air (OTA) Measurements for Outdoor & Indoor

It‘s all about Link-Budget

Mobile-SensitivityBTS

TMA

UL Path-LossCable-Loss

TXoutDL Path-Loss

RX-Sensitivity

Mobile TXout

Examples Path Loss R=5Km:

900 MHz ���� 105dB

1800 MHz ���� 112dB

2100 MHz ���� 113dB

2600 MHZ ���� 115dB

3500 MHz ���� 117dB

Example Downlink:

TX_out (40Watt) ���� 46dBm

Cable_Loss ���� -3dB

Antenna_Gain ���� 12dB

DL_(900MHz/R=5Km) ���� -105dB

Diversity_Gain ���� 3dB

Signal to Noise Ratio ���� -9dB

_______________________________________

Mobile_RX_Level ���� -56dBm

Mobile_Sensitivity ���� -100dBm

________________________________________

System Margin DL ���� 44dB

needed for … Indoor coverageFading margin

Multipath conditions

S/N 3dB � GMSK (GSM)

S/N 6dB � 8 PSK (EDGE)

S/N 9dB � WCDMA (UMTS)

S/N 10dB (minimum)

� OFDM (LTE, 16QAM up to 256QAM)

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Over-The-Air (OTA) MeasurementStandard Spectrum Measurements

ı Spectrum emission mask

ı Occupied Bandwidth

ı Spurious emissions

ı Power on pulsed signals (TDMA-Power)

ı Harmonic distortion

ı ACLR

ı AM modulation depth

ı Channel Power

Over-The-Air (OTA) MeasurementRF Measurements - LTE

ı Measurement of:ı Constellation diagramı BTS Scannerı Resources allocation

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Over-The-Air (OTA) MeasurementRF Measurements - LTE (Carrier Aggregation/MIMO)

ı For LTE FDD / LTE TDD ı Measures 2 or 3 carriers over the air (OTA)ı User is setting Frequency and Bandwidthı Main RF parameters displayed ı Pass indication is displayed if Cell ID is same ı Antenna values are greyed out if results are out

of range (one of the antennas is not received)

ı Application: quick check whether the CA feature is working OK during base station installation and maintenance

Test Smartphones – TX/RX functional BTS test

Tailored Android based phones for Integration tests at site installationsDAS network verificationRF planning/verification and optimizations tasks

Intuitive User InterfaceExtensive set of service tests:ı forcing functionı call tests, voice quality (including POLQA, PESQ, and SQuad08)ı data testsı video streamingı video quality (non-referenced)

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Network Scanning Tools

ı Non-intrusive passive Scannersı Subscribed UEs / Mobiles

���� Combination is best

What about…ı Detection of crossed feeders, broken feeders…ı System internal interference optimization (pilot pollution)ı Uplink / Downlink interference detection (Spectrum measurement)ı Decoding of BCH information (missing neighbors, configuration

issues)ı Coverageı ……

Scanner example: Automatic Channel Detection

Multi-Band andMulti-Technology

Networks

Network overview

GSM, UMTS, LTE, CDMA/EV-DO, TETRA, WIMAX

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Some Scanner examples

Interferences ?

Strongest Cell = Serving Cell ?BCH demodulation

Spectrum UL/DL ?

Cyclic Prefix

Spectrum � Interference Hunting & Clearance

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Interferences - ANYTHING is Possible

Steps in Interference Hunting

ı Stage 1 : Identify general areaı What cells / sectors are being affected?ı Area usually < 10 km radius

ı Stage 2 : Driving aroundı Vehicle mounted antenna or direction-finding systemı Try to get within ~ 100 m radius

ı Stage 3 : Walking aroundı Last few hundred metersı Sweep devices / areas of interestı Hand-held directional antennas

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Monitoring Receivers vs. Spectrum Analyzers

ı Speed crucial in interference hunting

ı Monitoring Receivers : use FFT-based processing : very, very fast

ı Spectrum Analyzers : use swept / heterodyne architecture : very configurable, but slower

ı Generally speaking, monitoring receivers are superior for interference hunting due to speed and sensitivity

ı Spectrum analyzers provide good performance and additional non-IH measurement capabilities

Direction finding

ı Automatic direction finding systems can determine the likely location of a signal source using one or more DF methodologies.

ı Systems normally consist of a DF receiver, specially-designed antenna, and control / processing SW.

ı Very helpful in locating short-duration interferers or distant interferers. Good multipath resistance also allows use in urban environments.

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Thank you – any questions?Installation, Service & Maintenance

• Signal Analysis of LTE (FDD/TD-LTE), WCDMA/HSPA+, cdma2k/EVDO,

• Over-The-Air (OTA)• Interference Hunting• CAT, VNA

Spectrum-/Signal Analyser& OTA

• Reflection / VSWR• Distance-to-Fault• Cable Loss• Spectrum Analysis• ACLR, SEM, OBW• Power Meter • Antenna Isolation• PIM

Cable & Antennatester

• Interference Detection & Location

• Direction Finding• Spectrum

Clearance

Interference & Spectrum Clearance

• Real Time Testing• Functional Testing

in Field• User Experience

Test• RF & Quality Test• Multi Vendor Test

BTS Functional test

• Non intrusive OTA Network Testing

• Pilot Pollution• Radio Channel

quality analysis

Network Scanner

COMPANY CONFIDENTIAL