Training Course_SRAN6.0_MBTS(V100R004C00)_Wireless Air Interface and RF Maintenance and Testing...

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Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.

Security Level: Internal

Wireless Air Interface and RF

Maintenance & Testing Guide

Wireless Product Service Dept.

SRAN6.0 Solution


About This Course

This course is based on the SRAN6.0 solution. Before learning

this course, you have received the training of the following

SRAN6.0 courses:

Product Overview

Operation and Maintenance


Training Objective

After learning this course, you should be able to:

Describe the basic principles of intermodulation interference

and CDMA network interference.

Explain how to troubleshoot interference problems by using the

wireless air interface and RF maintenance and testing

functions.

Explain principles of the wireless air interface and RF

maintenance and testing functions.

Know how to use the wireless air interface and RF

maintenance and testing functions.


Contents

Wireless Air Interface and RF Fault Detection

1. Background Information

2 Specification and Capacity

3 Offline Intermodulation Interference Test (GSM/UMTS/LTE)

4 Online Antenna Feeder PIM Test (GSM)

5 Offline Frequency Spectrum Scanning (GSM)

6 Online Frequency Spectrum Scanning (GSM)

7 Frequency Spectrum Scanning (UMTS/LTE)

8 CDMA Network Interference Detection (GSM)

9 Reference Documents & Abbreviation


Faults Caused by Interference

Man-made noise is one of the main interference sources for the mobile

communication system.

Interference within or between communication equipment can be overcome by

network planning and system optimization.

User Experience

· Incoming and outgoing call failure

· Interruption

· Noise

· Mute

· Call drop

Traffic Statistics Index

· The traffic statistics show level 2 or higher level interference bands.

· The SDCCH and TCH assignment failure rates are high.

· The call drop occurs frequently, or the call drop rate is high.

· The success ratio of handovers is low.

· The rate of high level/low quality statistics is high.

Drive Test Result

· Handovers fail frequently.

· High level and low quality.

Signaling Analysis

· The BER is higher than that of other cells.


Classification of System Interference Sources

Hardware Fault

· TRX fault

· RF front end or divider fault

· Spuriousness and intermodulation

· Interference from antenna feeder surge protector

Inter-Network Interference

· Radar station

· Simulation BTS

· CDMA BTS

· Cordless telephone set at M900 band

· Other intra-frequency radio equipment and interference units

Intra-Network Interference

· Co-channel or adjacent-channel interference

· Repeater interference

· Intermodulation interference

The discussing scope of this document: interference types discribed in red


Definition of Intermodulation Interference

Four-carrier intermodulation

3rd

orde

r

5th

orde

r

7th

orde

r

Two-carrier intermodulation, power increased

3rd

orde

r

5th

orde

r

7th

orde

r

Four carrier intermodulation, power increased

3rd

orde

r

5th

orde

r

7th

orde

r

Two-carrier intermodulation

3rd

orde

r

5th

orde

r

7th

orde

r

TX

sig

nal

TX

sig

nal

TX

sig

nal

TX

sig

nal

◆Frequency spectrum analyzer test result

◆Theoretical analysis

Antenna feeder intermodulation interference: The intermodulation interference mainly comes from the antenna feeder system. When the intermodulation product of the TX signals falls into the receiving band, it will interfere with the signals in the receiving band if its amplitude is large.

Standard requirement on antenna feeder intermodulation: When the input is 2*20 W, TX signal (dBm) - Intermodulation product (dBm) > 150 dBc

Receiving band Receiving band Receiving band Receiving band


Main Sources of Intermodulation Interference

Intermodulation interference caused by hardware faults Out-of-band spuriousness of the TRX or power amplifier of the BTS

exceeds the limit.

The transmit and receive distance of a duplexer at the RF front end is

too small.

Intermodulation interference caused by the antenna The antenna connector is unclean. There are mechanical damage,

internal silver plating damage due to dismantling, and scrap iron in the

connector.

The antenna connector is insecurely installed or sealed.

The antenna dipoles sealed in the protective cover are eroded.

The feeder parts from the input connector to the dipoles are corroded.


Method for Troubleshooting Intermodulation Interference

Current Method for Troubleshooting Intermodulation Interference SRAN6.0 Improvements

· Engineers can remotely determine whether the antenna feeder intermodulation interference exists at the site, and decide whether to go to the site for handling.

· Engineers can start the spectrum scanning remotely or locally, without carrying the spectrum analyzer.

Difficulties

· Engineers cannot remotely determine whether there is antenna feeder intermodulation interference at the site. They should go to the site for troubleshooting, leading to high cost and low efficiency.

· Engineers need to carry the spectrum analyzer for the troubleshooting, but the analyzer is very expensive and requires high professional skill.

Make preparations to expose potential problems

Check whether the connectors are loose

Replace the lower jumper and redo the feeder connector

Remove the surge protector and repeater

Replace the CDMA network filter

Check whether it is BTS main device intermodulation or antenna intermodulation

Replace parts (such as antennas) on the tower

Confirm that the interference problem is solved


Method for Troubleshooting CDMA Interference

A CDMA BTS and an adjacent GSM BTS use adjacent bands

SRAN6.0 Improvements

· Engineers can start CDMA interference detection directly through the maintenance terminal, and obtain the test result. No professional skill is required.

Difficulties

· The uplink frequency scanning function is required to test the levels of CDMA frequencies. Engineers determine whether the CDMA interference exists based on their experience. This operation requires high professional skill.

Basic Principles of CDMA Interference

The CDMA out-of-band leakage signals fall into the GSM receiver channel

The noise level of the GSM receiver is increased

There is interference with the receiving channel of GSM/UMTS 900 MHz, deteriorating the GSM

uplink channel


Maintenance and Testing Methods Provided by SRAN6.0Scenario Service Target Maintenance and Testing Methods Provided by SRAN6.0

Remote [Web LMT] Local [SMT]

Installation & Commissioning

of Antenna Feeders

Checking whether the project meets the requirements for PIM interference

Offline intermodulation interference test


Troubleshooting

Troubleshooting intermodulation interference

Online antenna feeder PIM test


Acquiring frequency spectrum information

Offline frequency spectrum scanning

Offline frequency spectrum scanning

Online frequency spectrum scanning -

Troubleshooting CDMA Interference

CDMA network interference detection -


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Specification and Capacity Applicable products

BTS3900/BTS3900A/BTS3900L/DBS3900 (GSM/UMTS/LTE) BTS3012/BTS3012II/BTS3012AE/BTS3006C/BTS3002E (GSM)

Note: For the BTS3012 series, only the new double-density DTRU supports this function. Note: For U and L, the V2/V3 platform supports offline FFT frequency spectrum scanning and

offline intermodulation interference detection. The V3 platform supports the online FFT frequency spectrum.

Matching versions BSC6900 BSC6900V900R013C00 and later M2000 iManager M2000-II V200R011C00 and later BTS BTS3900 V100R004C00 and later

License controlNone

Conflict of featuresThe RRU co-BCCH (GBFD-510104 multi-site cell) scenario does not support the wireless air interface and RF maintenance and testing function (GSM).


Contents












Offline Intermodulation Interference Test - Function Description

Basic principle (GSM) When the signals of RF frequencies f1 and f2 are sent simultaneously on the specified antenna

feeder port, check whether the levels of the 3rd order, 5th order, 7th order and higher-order intermodulation products that fall into the receiving band in the range from f1 to f2 can meet the requirements.

The counter decision thresholds of 3rd order, 5th order, and 7th order intermodulation products can be set.

The counter decision threshold of higher-order (higher than 7) intermodulation products is the same as that of the 7th order.

Basic principle (UMTS/LTE) Observe the difference between RTWP values before and during the intermodulation

interference test by controlling the transmit power of the cell, and check whether intermodulation interference exists. Significant RTWP difference indicates the existence of intermodulation interference.

The intermodulation interference is tested only when an antenna feeder port in the TRX module needs to send and receive signals. When the port just sends or receives signals, the intermodulation interference test is unnecessary and unavailable.


MRFU/GRFU


Applicable modules:

TRX Module Type Port A Port B

DRRU/DRFU Supported Not supported

MRRU/GRRU Supported Supported

MRFU/GRFU Supported Not supported

The offline intermodulation interference test can be performed on only one

antenna feeder port in a single cell at one time. The antenna feeder port to be tested should be able to transmit two carriers

simultaneously.

DRRU/DRFU MRRU/GRRU


Restrictions Carriers in other modes cannot be configured on the

corresponding TRX module of an antenna feeder port.

There is no critical alarm on the corresponding TRX module of an

antenna feeder port.

During the test, the entire cell is out of service. Before the test

starts, the BTS instructs the BSC to trigger the inter-cell service

switchover.

The high test frequency f1 and low test frequency f2 must fall into

the band that is supported by the module.

For a multi-carrier module, the bandwidth between f1 and f2 must

meet bandwidth requirements for instantaneous transmission.

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Offline Intermodulation Interference Test - Operation Method (GSM Remote)

Operate the Web LMT or M2000 to trigger the test.

Step 1: Run STR BTSRFTST in the MML window of the BSC6900 LMT to start the

offline intermodulation interference test. Set Test Type to PIMOFFLINE (offline

intermodulation interference test).

Step 2: When the test is complete, the test result is displayed on the LMT. The test

result and the original data for achieving the result are saved in a file by the BSC.

Note:

You can stop the test at

any time by

running STP BTSRFTST

during the test.


Offline Intermodulation Interference Test - Operation Method (UMTS Remote Terminal)

1. Run STR RFTEST on the NodeB LMT. Set Test Type to PIMOFFLINE.

2. The offline intermodulation interference test result is displayed.


Offline Intermodulation Interference Test - Operation Method (LTE Remote Terminal)

1. Run STR RFTEST on the LTE LMT. Set Test Type to PIMOFFLINE.

2. The offline intermodulation interference test result is displayed.


Step 1: Run PIM Offline Test on the SMT to start the test.

Step 2: When the test is complete, the SMT displays the test result.

Note: You can stop the test at any time by clicking Stop during the test.

Offline Intermodulation Interference Test - Operation Method (GSM Local Terminal)


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Online Antenna Feeder PIM Test - Function Description Basic principles

When multiple carriers are transmitted on the same antenna feeder port with antenna feeder PIM, the intermodulation product (level) is generated in the receiving band. The intermodulation product is a broadband signal.

You can check whether there is antenna feeder PIM by analyzing the uplink receiving level difference in cells during off-peak hours between scenarios with all carriers transmitting full power in the downlink and scenarios with some carriers transmitting power.

During the online antenna feeder PIM test, perform 10-second sampling of states for six times in the following sequence: power-transmitting, non-power-transmitting, power-transmitting, non-power-transmitting, power-transmitting, and non-power-transmitting, as shown in the following figure.

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Cell coverageBurst power transmitting

for 10 seconds

Cell coverageStop burst power transmitting

for 10 seconds


for 10 seconds


for 10 seconds

Cell coverageStop burst power transmitting for

10 seconds

Cell coverageStop burst power transmitting

for 10 seconds

Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved. Page 24

TRX Module Type Port A Port B

DRRU/DRFU Supported Not supported

MRRU/GRRU Supportedbut cannot determine whether it is port A or port B. You must use the offline intermodulation interference test function to further identify the port with intermodulation interference.

MRFU/GRFU Supported Not supported

DRRU/DRFU MRRU/GRRU MRFU/GRFU

Online Antenna Feeder PIM Test - Function Description


Restrictions

The test should be carried out in off-peak hours. It has no adverse

impact on the cell service.

Only one online antenna feeder PIM test can be performed

simultaneously in one cell. Multiple tests can be performed

simultaneously in multiple cells at a site.

Page 25

Online Antenna Feeder PIM Test - Function Description


Online Antenna Feeder PIM Test - Algorithm Description

Page 26

Number of groups of the valid data exceeding the Delta ≥ 2

Start

Report the existence of the PIM interference with

related data

Yes

Calculate the Delta based on the valid results of all

ARFCNs

Other ARFCNs need to be determined

Yes

No

Report the inexistence of the PIM interference with

related data

Determine the validity of ARFCN measurement

according to the ratio of full-power transmit times

Number of valid ARFCNs ≥ 1

Yes

Report the unreliability of the test result with

related data

No


Operate the Web LMT or M2000 to trigger the test and display the result.Step 1: Run STR BTSRFTST in the MML window of the BSC6900 LMT to start the offline intermodulation interference test. Set Test Type to PIMONLINE (online antenna feeder PIM test). Note: You can stop the test at any time by running STP BTSRFTS during the test.

Step 2: The whole test lasts about 60 seconds. The BTS reports the progress every 10 seconds. When the test is complete, the test result is displayed in the MML window, and the test result and the original data for achieving the result are saved in the OMU by the BSC.

Online Antenna Feeder PIM Test - Operation Method


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Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved. Page 29

Offline Frequency Spectrum Scanning - Feature Description Basic principles

To periodically measure the uplink receiving level of the specified

frequency in real time, you must specify the band range [f1, fk] to be

scanned and the tested carrier. The test timeslot is optional. If the

timeslot is not specified, the carrier-level scanning is performed. If the

test timeslot is specified, the channel-level scanning is performed.

Channel-level scanning: refers to the scanning of frequencies one

after another of the specified band by using the single timeslot of the

single carrier.

Carrier-level scanning: refers to the scanning of frequencies one

after another of the specified band by using all channels of the single

carrier.


Offline Frequency Spectrum Scanning - Feature Description

Channel-level scanning

Channel-level scanning interval: The round robin to multiple frequencies in the same timeslot is

implemented.

For the channel-level scanning, the tested carrier in the cell is out of service automatically;

meanwhile, the timeslots of all carriers (including the BCCH carrier) in the cell where the tested

carrier is located are out of service automatically. The timeslot downlink of the BCCH carrier is still

available.

Page 30

Cell operating timeslot

Cell scanning timeslot


Carrier-level scanning Carrier-level scanning interval: The round robin to multiple frequencies in all

timeslots is implemented.

For the carrier-level scanning, all non-BCCH carriers in the cell where the tested

carrier is located are out of service automatically.

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Offline Frequency Spectrum Scanning - Feature Description

Cell scanning timeslot


Offline Frequency Spectrum Scanning - Feature Description Restrictions

Only one offline frequency spectrum scanning test can be

performed simultaneously in one cell.

On the remote (Web LMT/M2000), multiple tests can be performed

simultaneously in multiple cells at a site. In a remote test, the BTS sends information (large amount) to the

BSC through the RSL link. To ensure availability of the RSL link, the

information will be partially discarded when the link is

congested.

On the SMT, only one offline frequency spectrum scanning test

can be performed at a site.

Page 32


Offline Frequency Spectrum Scanning - Operation Method (Remote)

Step 1: On the Monitor tab on the BSC6900 LMT, click GSM Monitoring in the

Monitor Navigation Tree pane, and then double-click Spectrum Scan Monitoring.

The Spectrum Scan Monitoring dialog box is displayed. In the Monitor Item drop-

down list, select Off-line Spectrum Scan, and then specify relevant information as

required. Click Submit. The remote offline spectrum scanning starts.


Offline Frequency Spectrum Scanning - Operation Method (Remote) ContinuedStep 2: After the remote offline spectrum scanning starts, the Spectrum Scan Monitoring

page is displayed on the Monitor Data tab. The maximum and average levels of main and

diversity are displayed. The reported frequency level ranges from -110 dBm to -47 dBm.


Offline Frequency Spectrum Scanning - Operation Method (Local)

Step 1: Start the LMT for cell operations, and then double-click the Frequency Scan

command on the right. In the displayed window, specify relevant information as required,

and then click Start. The local offline spectrum scanning starts.


Offline Frequency Spectrum Scanning - Operation Method (Local) ContinuedStep 2: After the local offline spectrum scanning starts, the scanning data is displayed in the

Frequency Scan Result Display window. The maximum and average levels of main and

diversity are displayed. The reported frequency level ranges from –110 dBm to –47 dBm.


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Online Frequency Spectrum Scanning - Feature Description Basic principles

When the online frequency spectrum scanning starts, the system measures the uplink receiving level of the test frequency periodically. The frequency and occasion are calculated according to the frequency hopping sequence during normal operation. The scanning result is not affected by the normal operation of other carriers in the same timeslot in the cell, as shown in the following figure.

Only the tested timeslot of tested carrier is out of service during the online frequency spectrum scanning.

Page 38

Carrier operating timeslot

Online scanning timeslot


Online Frequency Spectrum Scanning - Feature Description To ensure the normal service, the online frequency spectrum

scanning test can be performed on only one channel in one

carrier.

The test fails if the test does not meet the following

conditions:

Only one online frequency spectrum scanning test can be performed

simultaneously on one carrier.

There is no critical alarm in the corresponding module of the carrier.

There is no LAPD alarm in the tested carrier.

The corresponding channel type of the tested timeslot must be TCHF, TCHH, or

PDCH.

Page 39


Online Frequency Spectrum Scanning - Operation MethodStep 1: Start the BSC6900 LMT for monitor operations, and then choose Monitor >

GSM Monitor > Spectrum Scan Monitoring. The frequency spectrum time domain

scanning starts.


Online Frequency Spectrum Scanning - Operation Method (Continued)Step 2: After the offline spectrum scanning starts, the Spectrum Scan Monitoring page is displayed on the Monitor Data tab. The maximum and average levels of main and diversity are displayed. The reported frequency level ranges from -110 dBm to -47 dBm.


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Frequency Spectrum Scanning - Feature Description

Scanning types Online high-precision carrier scanning

Interference around the cell frequencies in use (including a few sidebands) is checked.

Online broadband carrier scanning

Continuous spectrums (including all frequencies in use, and intervals between these frequencies) in a certain range of spectrums are checked. Its scanning precision is lower than that of the online high-precision carrier scanning.

Full-band scanning

Services must be interrupted. It can scan all frequencies in the band range supported by the RF module. Its scanning spectrum width is greater than or equal to that of the online broadband carrier scanning, and its scanning precision is lower than that of the online high-precision carrier scanning.

Page 43


Frequency Spectrum Scanning - Feature Description

Application scenarios

Page 44

Functions Typical Application Scenarios

Adverse Impact on Services (in this mode or other modes)

Advantages Disadvantages

Online high-precision carrier scanning

There is a problem with the cell KPI. Collect information during the interference troubleshooting.

No adverse impact on local and peer services.

Services are not interrupted. The amount of data is small and the precision is high.

The states of frequencies that are not in use cannot be observed.

Online broadband carrier scanning

Use the spectrum function to check whether there is external interference when problems are found during service verification at the site in the engineering phase.

No adverse impact on local and peer services.

Services are not interrupted. Inter-frequency interference can be observed.

The precision is low.

Full-band scanning When there is a severe problem with the service KPI, the service is stopped. Collect interference information and ensure the precision.

Local and peer services are interrupted.

Wide scanning spectrum and high precision, without any adverse impact on services.

Services are interrupted (a request should be sent to the customer). The precision is low.

Note: Before the full-band scanning starts, all carriers on the RF module must be deactivated.


Frequency Spectrum Scanning - Operation Method (UMTS)-1

Step 1: In the Service navigation tree of the NodeB LMT, double-click FFT Frequency Scan. The FFT Frequency Scan dialog box is displayed. Set Cabinet No., Subrack No., and Slot No. to the numbers of the cabinet, subrack, and slot where the tested TRX board is located. Set Channel Type based on the application scenarios in section 2.1.2. Set Scanning Interval to the default value. Select Auto Save, and select a path for saving files, for example, D:\HW LMT\client\output.


Frequency Spectrum Scanning - Operation Method (UMTS)-2

Step 2: Click Yes in the Confirmation dialog box. The FFT frequency scanning starts. The

Chart tab displays the scanning result.


Frequency Spectrum Scanning - Operation Method (LTE)

Step: In the Service navigation tree of the NodeB LMT, double-click Spectrum Detect. In the

displayed dialog box, select the scan mode, and set Cabinet No., Subrack No., and Slot No. to

the numbers of the cabinet, subrack, and slot where the tested TRX board is located. Set other

parameters to default values. Click Submit.


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CDMA Network Interference Detection - Feature Description Basic principles

The CDMA interference to the GSM uplink can be decreased by modifying the

diminution factor of the tower mounted amplifier or adjustable attenuator in

other receiving channels, which is called CDMA interference suppression.

Delta: refers to the uplink receiving level average difference of the operating

frequencies in the idle channels when the CDMA interference suppression is

performed and not performed.

The BTS determines whether the CDMA network interference occurs by

comparing the Delta and the decision threshold.

Operating frequencies for comparison: If the number of operating frequencies

is greater than 8, 8 operating frequencies most adjacent to the CDMA band are

used for the decision. Otherwise, all configured operating frequencies are

used. If an operating frequency Delta exceeds the decision threshold, the

CDMA network intermodulation exists. Otherwise, the CDMA network

intermodulation does not exist.

Page 49


CDMA Network Interference Detection - Feature Description Restrictions

Only one CDMA network interference detection can be performed

simultaneously in one cell. Multiple tests can be performed

simultaneously in multiple cells at a site.

During the test, the diminution factor of the tower mounted amplifier

and adjustable attenuator in other receiving channels will be modified,

which will temporarily reduce the capability of resisting CDMA network

interference. However, the adverse impact on the service is low.

Page 50


Step 1: Run STR BTSRFTST in the MML window of the BSC6900 LMT to start the

CDMA network interference detection.

Note: You can stop the test at any time by running STP BTSRFTS during the test.

CDMA Network Interference Detection - Operation Method

Step 2: When the test is complete, the test result is displayed in the MML

window, and the test result and the original data for achieving the result are

saved in the OMU by the BSC for further analysis.


Contents












Reference Documents

1. "Wireless Air Interface and RF Maintenance and Testing Guide" in

Equipment Deployment Guide_GBSS13.0_BTS3900 Series Macro

Base Stations

2. GSM BSS Network Performance KPI (Interference Problem)

Optimization Manual

3. SingleRAN6.0 MBTS Equipment Deployment Guide Subject 14 -

RF Detection Capability Enhancement


Abbreviation

PIM: Passive Intermodulation

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Training Course_SRAN6.0_MBTS(V100R004C00)_Wireless Air Interface and RF Maintenance and Testing...

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Transcript of Training Course_SRAN6.0_MBTS(V100R004C00)_Wireless Air Interface and RF Maintenance and Testing...