Og 103 test and analysis of gsm electromagnetic background issue1.0

HUAWEI TECHNOLOGIES CO., LTD.

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HUAWEI Confidential

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Test and Analysis of GSM

Electromagnetic Background

ISSUE 1.0

HUAWEI TECHNOLOGIES CO., LTD. Page 2HUAWEI Confidential

Foreword

In the GSM system, to extend the capacity, perform frequency reuse. If the frequency reuse is more aggressive, the network capacity becomes more large. If the reuse distance is shorter, the interference becomes stronger.

The interference has obvious impacts on call quality, call drop rate, handover, and congestion. If there is a strong interference in the band, clear frequency or apply for new frequency.


Purpose

Interference source of electromagneti

c background

Test methods of electromagnetic bac

kground

Use of spectrum test instrument

After learning this course, you should be

familiar with:


Contents

Training.huawei.com

Chapter 1 Impacts of Electromagnetic Interference on System

Chapter 2 Interference Source of Electromagnetic Background

Chapter 3 Introduction to Interference Test Tool

Chapter 4 Test Methods of Electromagnetic Background

Chapter 5 Use of YBT250


Channel interval: 200kHz

890 915 935 960

Duplex distance: 45 MHz

GSM 900 :

1710 1785 1805 1880

Duplex distance: 95 MHz

GSM 1800 :

Frequency of GSM System

EGSM: Uplink: 880MHz - 915MHz Downlink: 925MHz - 960MHz

RGSM: Uplink: 876MHz - 915MHz Downlink: 921MHz - 960MHz


Impacts of Electromagnetic Interference on System

Impacts on Calls

If calls are failed, the calling parties hear beeps, and then hear call

drop sounds. (The prompt tones of different mobile phones may be

different.)

In the courses of calls, voice discontinuity, noise, silence, and call drop

often occur.

Impacts on System

Failures of SDCCH assignment and TCH assignment

Frequent call drop or high call drop rate

Low handover success rate

Much statistics of high level and low quality in the receiver level

performance measurement and the quality performance measurement


Contents







Category of Interference Source

Nature Noise

Atmospheric noise

Galaxy noise

Sun noise (quiet period)

Human Noise

Interferences of automobiles or the engine systems

Interferences of communication equipment

Interferences of electrical power cables

Interferences of industrial equipment, scientific equipment, medical equipment, and home appliances


Ambient Noise


Analysis of Interference Source

Equipment Faults

Faults of TRX, CDU, or Splitter

Out-of-band Spurious emission and intermodulation

Network Interference

Intra-frequency and neighboring-frequency interferences owning to improper frequency planning

Repeater interference

Intermodulation interference

Off-net interference

Radar, intra-frequency radio equipment, interference generator, Cordless Telephone, analog BTS, and CDMA BTS


Contents







Tools for Testing Interference

Spectrum Analyzer

Antenna

Low-noise

amplifier/attenuator


Tools for Testing Interference Spectrum Analyzer

The spectrum analyzer is used to test the features of frequency do

mains of signals, including spectrum, adjacent-channel power, fast ti

me-domain sweep, parasitic radiation, and intermodulation attenuati

on.

Key indexes

− F0

− Sensitivity

− RBW

− VBW

− SPAN

− ATT

− RefLv

− RMS

− Sweep Time



Specifications of Various Spectrum Analyzers

Model Operating Band Sensitivity (1Hz)

Minimum resolution band

HP8591E 30Hz-1.8GHz -145dBm 30Hz




YBT250 30-2500MHz -132dBm 1KHz



Antenna

Omni-directional antenna: Being convenient for measuring interferen

ce and not being convenient for locating interference

Directional antenna: Being used for searching interference source; T

he searching capability is determined by the directionality and gain.

Directional antenna:

− Flat-antenna

− Yagi antenna

− Log-periodic antenna



Low-Noise Amplifier (LNA)

It is used for testing the receiver sensitivity of test appliance.

The LNA with 30dB gain and 5dB noise factor can be used.

LNA needs external power supply. Some appliances are equipped with built-in

LNA, such as YBT250.

In a cascading network, if the front of the system is configured with high-gain

amplifier, the noise factor of the system is determined by the first-class noise factor.

Attenuator

It is used for attenuating the power of input signals to protect spectrum analyzer

against strong signals.


Contents








Section 1 Preparation Section 1 Preparation

Section 2 Setting of Basic Parameters

Section 3 Measurement Course

Section 4 Data Processing


Preparations Being familiar with the planning of local radio frequency band and usage of radio equipment

Pilot office

− The available frequencies are not confirmed. The test frequency band is distributed temporarily. For the noise test, you should sweep the full frequency band or choose several available frequency bands based on the local frequency resources.

Commercial stage

− The available frequencies are confirmed. To eliminate the interferences in bands, mainly test the available frequency bands of carriers.


Preparations Confirming time and place of test

Test for electromagnetic interference of uplink

− Test place: position of installing antenna

− Test angle: North by east 0°, 120°, and 240°

− Available antenna: Portable antenna and BTS antenna

Test for electromagnetic interference of downlink

− Test place: typical positions in the cell

− Test angle: North by east 0° ， 120° ， 240°

− Portable antenna

− Testing the places with strong interferences


Preparations

Ensure that the following tools are ready:

Spectrum Analyzer

GPS satellite receiver

Compass

Antenna

Vehicle


Preparations Ensure the following tools are available:

If a spectrum analyzer has weak receiver sensitivity, the low-noise amplifier (LNA) is required.

Check whether connectors are matching and whether meters can be supplied power all the time.

Antenna type Model of connector

Portable omni-directional mini antenna

N-shaped male connector

Yagi antenna N-shaped male connector

Common BTS antenna DIN female connector

7/8 feeder DIN female connector

Small jumper DIN male connector

Common spectrum analyzer N-shaped female connector



Section 1 Preparation

Section 2 Setting of Basic ParametersSection 2 Setting of Basic Parameters




Set the basic parameters that are listed in the following table:

Setting of Basic Parameters

Parameter Description Remarks

Fo Setting based on test results Central frequency of

tested spectrum

SPAN Setting based on test results Width of tested

spectrum

Trace Choosing MaxHold or Average based on accidental interference or continuous interference

Maximum value or average value

RefLvl Setting based on the tested signals; making signals in the middle of spectrum analyzer

Reference level





Section 3 Measurement CourseSection 3 Measurement Course



Test CourseConfirming Test Azimuth

Choose the position where the antenna is installed. Often make tests in t

hree azimuths. If the azimuth of antenna is confirmed, ensure the azimut

h of test antenna is the same as that of BTS antenna.

Search Interference

Search for interference in the uplink band, and then in the downlink

band.

Operations

− Enter the noise test interface of the YBT250, and then set Fo and SPAN.

− Fill in the record table, save data file, and check whether interferences exist.

Judging principle: Check whether there are interference waves that

are higher than the back noise


Test Course Confirming Interference

In the course of searching interferences, if interferences exist, make test for confir

ming the interferences.

To confirm interferences, proceed as follows:

− Enter the interface of testing YBT250, and then set Fo to the central freque

ncy that nears to interferences and set SPAN to 3×interference. Analyze the

distribution of signal spectrum. Confirm the interference signals. Record the

strengths of signals and azimuth angle and elevation of directional antenna

beam.

− Search new test point along the direction of antenna beam. Then, perform t

he preceding step to find interference source.

− If two places in different directions may have interference sources, the inter

section of the two places is the position where the interface source is. Thus,

perform search near the intersection.


Test Course Downlink Drive Test

Drive slowly on the main streets where the signals of cell are covered.

If you find strong interferences, make downlink pointing test to confirm

interference source.

To confirm interference source, proceed as follows:

− Enter the noise test interface of the

− Set the Fo and SPAN. Drive at less than 15KM/H speed to perfor

m interference search.

− In the course of searching, if you find interferences, confirm the in

terferences.






Section 4 Data ProcessingSection 4 Data Processing


Data Processing

Filling test results

After constructing the test region,

fill in the Electromagnetic Interfe

rence Test Table.

After constructing the entire netw

ork, fill in the Electromagnetic In

terference Test Report.


FAQs-Question

Whether the interference level obtained

from the electromagnetic interference test

is the actual interference level that affects

the BTS or mobile station?


FAQs-Answer

Because the test system and the actual syst

em may use different antennae and feeders,

confirm the interference level of BTS or mobi

le station based on test data.


FAQs-Answer

Test System

Antenna gain: 3dBi

Feeder loss: 1dB

Interference level: -90dBm

BTS System

Antenna gain: 10dBi

Feeder loss: 2dB

Interference level: － 90 － (3 － 1)+(10 － 2) ＝－84dBm


Contents







Use of YBT250

Connecting System

Switching on

Test

Test Setting

Test Result


Use Description of YBT250 Before carrying out survey, use proper appliance to

make noise test.

Use the YBT250 of Tektronix

Features of the YBT250

Being convenient for taking

Integrated system with built-in LNA


Use Description of YBT250

Connecting System

The YBT250 is configured with yagi directional antenna.

Use portable mini antenna to make electromagnetic background

test.

The YBT250 is equipped with battery or can be connected exter

nal power.

Switching on

Press Power and enter the Windows CE operating system.

Use the touch screen of the YBT250 to enter the test interface.


Use Description of YBT250 Test

The YBT250 has three test functions:

BTS information test

Noise test

Interference source searching

The noise test has two kinds of shown modes:

− Spectrum mode

− Spectrogrum mode



The Spectrum mode is used for real-time test.

− Confirming the frequency band for test and setting the Fo of the central frequency

− Modifying SPAN

− Checking the spectrum figure, modifying Fo and SPAN, and checking for interferences

− Options of the TRACE menu

▪ Normal, Max Hold, Min Hold, Max/Min Hold

− Saving the spectrum figure

Note: Set RefLvl and ensure that the test level is not more than

70dB

(Proper level of YBT250: 70dB)



The Spectrogrum mode is used to check whether interferences exist in the frequency bands. The horizontal axis represents frequency band and the vertical axis represents time.

Operations:

− Setting automatic storage option and file name

− Setting the frequency band (Fo, SPAN)

− Opening the saved file and checking for interference

To check interference value, export the file:

− Exporting the figure

− Exporting data and saving it as a *.txt file, or a *.csv file


Use Description of YBT250 Setting Measurement Parameters

− Fo: central frequency of tested signals, MHz

− SPAN: 100MHz, 10MHz, and 5MHz

− RBW: Setting automatically based on SPAN

− MaxHold/Average: Maximum value, average value

− RefLvl: Setting based on interference level

Output

Electromagnetic Interference Test Table

Electromagnetic Interference Test Report


Use Description of YBT250


Summary

In this course, we have learnt:

Impacts of interference on the mobile network syste

m

Source of interference

Test method of electromagnetic background

Use of YBT250

Thank Youwww.huawei.com

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Og 103 test and analysis of gsm electromagnetic background issue1.0