antenna and basestation testing challenges - rohde & · pdf fileantenna and basestation...

Antenna and

Basestation Testing Challenges

Olaf HeischSenior DirectorTarget Account Managementfor Infrastructure Services

Agenda in brief ….

� The Basestation and BTS evolution steps

� BTS Installation and Antenna Measurements

� PIM (Passive Intermodulation) Basestation Testing

� Over - the - Air Measurements

� IR (Interference Hunting ) Spectrum Clearance

� Questions & Answers

1992 – 2002

BTS in a Cabinet Solution

In consequence: HetNet architecture becomes reality and drives

several rollout projects, whether for indoor (DAS/Small Cell) or

Macro MSR-BTS scenarios

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

Mobile Networks

Field Service ProjectsPacket Transport Build & Expansion

Building & Upgrading IP/Optical/Microwave for RAN

Managed ServicesHotline Support & Site Security

Benchmarking & Drive TestingNetwork Verification against competition & Optimization

Interference HuntingDetection and suppression of non-wanted/non-allowed signals

Reporting FunctionsData Analysis and Data preparation for Management

Antennas

Tower Mounted Amplifier and/or RRH

RF/Fiber Cables

BTS / BBU

RF Cables

Performance of the Site

Radio Quality=

Service Quality

Connectors

Measurements are key for the service quality!

Site Installation is fundamental for Radio Networks

Three Step Site Measurement Concept

Antennas

Tower Mounted Amplifier and/or RRH

RF/Fiber Cables

BTS / BBU

RF Cables

Connectors

Antennas as most important component

ı Antennas are the most important component inany mobile network site.

ı An ideal transmit antenna converts all incomingconducted power into radiated power with nopower reflected back to the transmitter.

ı Antennas must be properly matched to theiroperational band for maximum efficiency.

ı Incorrectly installed or damaged antennas can havea severe performance impact.

ı Antennas must also be oriented properly in both azi muth and elevation for optimum coverage and efficiency.

ı Wind load, weather behavior (lightning protection) and aging changes Antenna efficiency.

ı Testing before installation is needed & result repo rting is required by MNO’s.

Why do we need Cable and Antenna Measurements today?

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

ı To ensure high quality of installed baseı To prevent push of responsibility due to

many contractors/vendors involve� Cable & antenna provider/installer� Base station vendors

ı Minimize later trouble shooting

ı 3 Sector Site to 6 Sector BTS incl. RET,4X4 MIMO, integrated TMA

Filter and amplifier measurements as of today

ı Filters often used on base stations to keep out other signals (band-pass-filter, duplexer, s.o.).

ı Amplifiers (such as TMAs) may be used in some cases as well.

ı Note that to test an amplifier, we may have to inje ct some kind of DC power (bias) in order to power up the device.

ı LNAs are sometimes used when making measurements as well.

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

Cable and Antenna Measurements, still needed …

Legacy / Installed BaseMacro BS BTS + RRH

1 Port measurementsı Feeder / Jumper Return Loss / VSWRı Distance to Fault (DTF)ı Antenna VSWRı Cable insertion loss

2 Port measurementsı Antenna decouplingı TMA gain test

Can bevery long and complex in an

In-Building-Solution

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.

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).

Aligned Test Setup and Test Result Reporting

becomes time extensive factor � Wizard and Report GeneratorCentralized configuration

WIZARD guided measurements execution

Standardizedreporting

Aligned Test Setup and Test Results

R&S Mobile View 1.0 for Android is live, via google play store.

https://play.google.com/store/apps/developer?id=Rohde+%26+Schwarz+GmbH+%26+Co.+KG&hl=en

Aligned Test Setup and Test Results

R&S Mobile View 1.0 for Android is live, via google play store.

R&S Mobile View currently supports instrument series FSH, ZVH and FPH.

QualiPoc Android

Site Acceptance Reportı Site Acceptance appears on a separate monitor on

QualiPoc if option is licensed

ı Site Acceptance consists out of 3 parts:� Project : Contains project related information

� Sectors : Contains the sector technology and if cell locking shall be used, also channel and cell information

� Job : Select the job containing all the tests that shall run in order to check this site

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QualiPoc Android

Site Acceptance ReportJob – supported test typesThe following basic tests are available for site acceptance tests:ı Call to answering stationı Call to any number

ı FTP DL and ULı HTTP DL and UL

ı PING

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Measuring call setup time

Measuring data throughput

Measuring round trip time (RTT)

QualiPoc Android

Site Acceptance ReportSite Acceptance Report contains the following information:

ı Project informationı Measurement summaryı Results per sector ı Chart of recorded RF parameters

� LTE: SINR, RSRP, RSRQ� WCDMA: Aggr. Ec/Io, Aggr. RSCP� GSM: RxLev, C/I

ı KPI classification with all specified thresholds

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LTE/LTE-A Frequency Bands (FDD) and IntermodulationsE-UTRA

OperatingBand

Uplink (UL) operating band Downlink (DL) operating band

FUL_low – FUL_high [MHz] FDL_low – FDL_high [MHz]

1 1920 – 1980 2110 – 2170

2 1850 – 1910 1930 – 1990

3 1710 – 1785 1805 – 1880

4 1710 – 1755 2110 – 2155

5 824 – 849 869 – 894

6 830 – 840 875 – 885

7 2500 – 2570 2620 – 2690

8 880 – 915 925 – 960

9 1749.9 – 1784.9 1844.9 – 1879.9

10 1710 – 1770 2110 – 2170

11 1427.9 – 1447.9 1475.9 – 1495.9

12 699 – 716 729 – 746

13 777 – 787 746 – 756

14 788 – 798 758 – 768

17 704 – 716 734 – 746

E-UTRA Operating

Band

Uplink (UL) operating band Downlink (DL) operating band

FUL_low – FUL_high [MHz] FDL_low – FDL_high [MHz]

18 815 – 830 860 – 875

19 830 – 845 875 – 890

20 832 – 862 791 – 821

21 1447.9 – 1462.9 1495.9 – 1510.9

22 3410 – 3490 3510 – 3590

23 2000 – 2020 2180 – 2200

24 1626.5 – 1660.5 1525 – 1559

25 1850 – 1915 1930 – 1995

26 814 – 849 859 – 894

27 807 – 824 852 – 869

28 703 – 748 758 – 803

29 N/A 717 – 728

30 2305 – 2315 2350 – 2360

31 452.5 – 457.5 462.5 – 467.5

32 N/A 1452 – 1496

LTE/LTE-A Frequency Bands (TDD)

E-UTRA OperatingBand

Downlink (DL) / Uplink (UL) operating band

Flow – Fhigh [MHz]

33 1900 – 1920

34 2010 – 2025

35 1850 – 1910

36 1930 – 1990

37 1910 – 1930

38 2570 – 2620

39 1880 – 1920

40 2300 – 2400

41 2496 – 2690

42 3400 – 3600

43 3600 – 3800

44 703 - 803

Intermodulation Aspects from a BTS perspective

ı Linearity is Key – The Basestation 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

BTS PA & RF Frontend is driving factor for intermodulation in field

Pin

Pout 1dB Compression Point

1dB CP - 3dB � Powertage Working Point GMSK (GSM)

1dB CP - 6dB � 8 PSK (EDGE)

1dB CP - 9dB � WCDMA (QAM)

1dB CP - 10dB (min)

� OFDM (LTE, 256QAM � 30-35dB)

In case of less linearity…Co-Channel & Adjecent Channel Interference

Pin

Pout

Working pointLTE channel

f0

RF-Filter

f

PIM Uplink/Downlink

Source: “PIM Testing Best Practices White Paper”

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)

BTS and PIM

Passive Intermodulation

PIM is probably an issue when:

• By increasing the output power of the BTS, the noise level in the receiver path increases significantly (factor of 3).

• For every dB more on the transmitted signal,the received signal increases by approx.. 3 dB

BTS affected by PIM

Interference

Noise level increases

Quality of Service reduced

Reduced coverage

Low data rates

Drop calls

No service at all

Lost revenue

$$$

Why are operators concerned regarding PIM and bad VSWR ???

Passive Intermodulation (PIM) Testing due to non-linear-componentsı 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.

ı In FDD networks multiple tones in the DL frequency range can generate interference in the UL band. � Receiver sensitivity goes down!

PIM symptoms

Performance issues reportedby the network:

ı Low signal to noise ratioı Noise floor increaseı Reduced data ratesı Dropped callsı Reduced coverage ı Non-accessibility

� No VSWR issues found by field teams

Source: R&S®NPA Network Problem Analyzer

What is a PIM Analyzer?

How to work out PIM issues? Cable&Antenna Tester + PIM AnalyzerModels Transmit (TX) Frequency MHz Receive (RX) Frequency MHz

700 732 – 766 698 – 722 (L)779.5 – 804.5 (U)

700A 758 – 803 703 – 748

800 791 – 821 832 – 862

850 869 – 894 824 – 849

900 925 – 960 876 – 915

Dual Band 1821 1805 – 1880 1710 – 17851920 – 1980

Dual Band 1921 1930 – 19902110 – 2155

1870 – 19101710 – 1755

2600 2620 – 2690 2500 – 2570

One-Port measurements for 2 X 40W Output Poweron battery operation needed:

• PIM measurements• Distance to PIM• Reporting functions (HTML&PDF)

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

Conducted vs. OTA measurements

Con

duct

ed

mea

sure

men

ts • Cable loss power• Distance to fault• Reflected power (VSWR, return loss)• Transmitted power• Insertion loss• Gain• Decoupling• Passive intermodulation

Ove

r th

e A

ir m

easu

rem

ents • Spectrum monitoring

• Interference hunting• Demodulation of pilot channels• DL resource block allocation• MIMO measurements• Carrier agregation measurements• Functional testing

R&S®ZVH R&S®FSHR&S®FPH R&S®PR100 QualiPoc Android R&S®TSMA

April 2017Antenna and base station testing challenges

PiMPro Tower

36

R&S®ZPH

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

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

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

Spectrum � Interference Hunting & Clearance

Interferences – almost everything is possible

Interference Hunting

ı Interference hunting is the process of identifying and locating sources of interference.

ı Analysis of the signal can provide important clues as to its origin / location.

ı In almost all cases, radiolocation(direction finding) will be necessaryto establish the physical locationof the source.

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

ı Other systems involved to 1st step very often

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

ı Frequency identified and demodulated

ı Stage 3 : Walking aroundı Last few hundred meters/ sweep devicesı Areas of interest / Hand-held directional antennas

ı Access to objects needed ☺

Tools for Interference Hunting

ı Handheld instruments fall into two categories

ı Monitoring receivers : FFT-basedı Spectrum analyzers : Swept / heterodyne-based

ı Dedicated direction-finding systems can be useful in a number of cases

ı Antennas (vehicle and handheld)

ı Accessories (Filters, LNAs, etc.)

Monitoring Receivers vs. Spectrum Analyzers

ı Speed crucial in interference huntingı Monitoring Receivers : 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(e.g. for decoding acc. 3GPP)

Direction findingı Automatic direction finding systems can

determine the likely location of a signal source using one or more DF methodologies (integrated real time algorithm)

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

ı Very helpful in locating short-duration interferers or distant interferers.

ı Good multipath resistance also allows use in urban environments.

Direction finding

Thank you