77535012 rssi overwiev troubleshooting

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Page 1: 77535012 RSSI Overwiev Troubleshooting

© 2006 AT&T Knowledge Ventures.  All rights reserved. AT&T is a registered trademark of AT&T Knowledge Ventures.

RSSI troubleshooting

Page 2: 77535012 RSSI Overwiev Troubleshooting

April 8, 2023Page 2© 2006 AT&T Knowledge Ventures.  All rights reserved.

AT&T is a registered trademark of AT&T Knowledge Ventures.

RSSI Troubleshooting

Purpose of this presentation

The purpose of this presentation is to point out the main sources that are susceptible to cause 3G UL interference, as well as the best practices that can help finding and solving them.

The UL RSSI counters are Ericsson performance indicators designed to identify cells that experience abnormal high or low interference levels. Site visits might still be required and could potentially provide additional important information

The site design and parameter configurations play an important part in RSSI troubleshooting. Components that impact the UL RSSI are, for example:

Indoor Distributed Antenna System (DAS)

Ericsson Diplexer-Duplexer units (DDU)

Receive Antenna Interface Tray (RX-AIT)

Enhanced Uplink (EUL) represents an important step towards mobile broadband services. Ensuring the UL interference is kept under control, will ensure no serious limitation exists over services performance in P5MD.

Page 3: 77535012 RSSI Overwiev Troubleshooting

April 8, 2023Page 3© 2006 AT&T Knowledge Ventures.  All rights reserved.

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RSSI Troubleshooting

Some Frequent Asked Questions

What is UL RSSI?

Received Signal Strength Indicator of the total wideband received power within the entire channel bandwidth

Note that RSSI does not distinguish between own, other, or any other unwanted internal or external interference

How is UL RSSI measured in the Ericsson system?

The RSSI is measured every 100 ms. An average value is then calculated every second and stored as a PDF step range, [65] long (-110 to -65 dBm, with the resolutions 0.5 dBm and 5 dBm).

Counter “pmaverageRSSI”, MO Class “Carrier” and incremented on the RBS level

How high is the actual noise floor for an unloaded system?

The expected uplink interference level in an unloaded system is given by thermal noise (kTB = -174 dBm/Hz) plus the ASC Noise Figure of the Node B (~2 dB)

Thus the Receiver Noise Density = -174 + 2 = -172 dBm/Hz.

The total effective noise = -172 + 10*log(3,840,000) = -106 dBm

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RSSI Troubleshooting

Some Frequent Asked Questions (continue)

What impact will my traffic load have on the RSSI?

If the system load (Mpole) is increased to 50%, a 3dB Noise rise can be expected

This means we can expect a uplink interference level of -106 + 3 = -103 dBm

How does the system configurable parameters affect the RSSI?

No TMA: ValueReported = ValueMeasured in RBS + ULAttenuationMO:AntFeederCable

With TMA: ValueReported = ValueMeasured in RBS + ULAttenuationMO:AntFeederCable – ULGainMO:ExternalTMA

So if we assume a RBS without a TMA, and the ULAttenuation set to 3 dB, then we should investigate if the RSSI increase over -103 + 3 = -100 dBm

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RSSI Troubleshooting

What is new in P5MD?

RBS P5ED

RBS P5MD

RNC P5MD

New

New

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April 8, 2023Page 6© 2006 AT&T Knowledge Ventures.  All rights reserved.

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RSSI Troubleshooting

Selecting sites for troubleshooting

Investigate sites with reported RSSI values outside the normal* range:

*The normal range depends on the market design and traffic load

Normal

Low RSSI

This example site is considered “deaf” since all samples are below -110 dBm

High RSSI

This example site has to many high RSSI samples

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RSSI Troubleshooting

Low RSSI

Possible reasons for sites experiencing a Low UL RSSI

1. No IP communication (unable to ftp xml from the site)

2. Component failures:

i. Cable, connectors and/or diplexers

ii. Antenna

iii. TMA

iv. RX-AIT

v. Distributed antenna system (DAS)

3. Incorrect parameter settings

4. Incorrect installation

Sites that are not integrated or locked, won’t show any counter values

Page 8: 77535012 RSSI Overwiev Troubleshooting

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Case L1

TMA not powered

Notes

The TMA power to this site was not enabled, causing a low RSSI. This was corrected on 6/19

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RSSI Troubleshooting

High RSSI

Possible reasons for sites experiencing a High UL RSSI

1. Internal Causes

i. RBS Internal Interference (Case H1)

ii. Faulty diplexers (Case H2, H3)

iii. Faulty Antenna/TMA (Case H4)

iv. Incorrect parameter settings (Case H5)

v. Incorrect installation (Case H6, H7, H8, H9)

vi. Traffic load (Case H10)

2. External Causes

i. GSM Interference (Case H11)

ii. High sites (Case 12)

iii. External interference (Case 13)

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Case H1

RBS Internal Interference

RF Cable connection

Notes

In order to eliminate possible interference created internally to the RBS, the RF jumper ports can be connected to a spectrum analyzer or a dummy load

If the RSSI values of the site returns to normal, it means interference is generated external to the RBS

In case of the RBS3202, the set of connectors H1, H2 and H3 are related to Rx Diversity, while J1, J2 and J3 are the ones with Tx/Rx combined. In the case of the RBS3206, the lower cables are the ones with the Rx Diversity, while the upper ones are the Tx/Rx branch

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Case H2

Faulty Diplexers

SFL RSSI tracker during Rollout

Notes

A faulty diplexer can cause unwanted interference on the uplink.

The SFL team found a specific RSS diplexer model that increased the uplink interference. Once these were replaced, the UL RSSI recovered

Vs.

Befo

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Case H3

Faulty Diplexers

Notes

The Tampa team found a bad diplexer on 6/9, and replaced it. The average RSSI remained within the normal range afterward

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Case H4

Faulty Antenna/TMA

Notes

A TMA or an Antenna can also be a source of interference. TMAs are usually replaced, while Antennae don’t typically fail.

Troubleshooting can commence using dummy loads and/or a spectrum analyzer to isolated the source of interference

RBS

TMA

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Case H5

Incorrect parameter settings

Notes

When using a RX-AIT or/and a TMA, it is important to ensure the configurations are set correctly in the RBS

Typically, the RX-AIT uplink gain is 10 dB for 1900 MHz and 20 dB for 850 MHz. The attenuator loss is typically 4 dB, unless it is a 850 MHz installation with a TMA, where the attenuation will be 15 dB

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Case H5

Incorrect parameter settings

A Cluster in Charlotte got the ULAttenuator values fixed to include the 6 dB gain

If a site reports 6 dB lower RSSI than other cells, it could be that that RX-AIT is down

6 dB

6 dB

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Case H5

Incorrect parameter settings

TMA

DlAttenuationMO:AntFeederCable = Feeder_loss

UlAttenuationMO:AntFeederCable = Feeder_Loss

DlAttenuationMO:ExternalTMA = TMA_Ins_Loss

ULGainMO:ExternalTma = 12 dB (typical value)

DlAttenuationMO:AntFeederCable = Feeder_Loss + RXAIT_Losses_DL

ULAttenuationMO:AntFeederCable = Feeder_Loss + RXAIT_Losses_UL – RXAIT_Gain

DlAttenuationMO:ExternalTma = TMA_Ins_Loss

ULGainMO:ExternalTma = 12 dB (typical value)

TMA

DlAttenuationMO:AntFeederCable = Feeder_Loss + RXAIT_Losses_DL + Jumper_loss

ULAttenuationMO:AntFeederCable = Feeder_Loss + RXAIT_Losses_UL + Jumper_loss

ULGainMO:ExternalTma = RXAIT_Gain (need to define the TMA object)

TMA

DlAttenuationMO:AntFeederCable = Feeder_loss + Jumper_loss

UlAttenuationMO:AntFeederCable = Feeder_Loss + Jumper_loss

TMA

System configuration calculations

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Case H6

Faulty installation

Notes

During the design of the antenna sharing solution it was identified that the RX path to the UMTS receiver would require 15dB attenuation to prevent the receivers from being over powered.

These attenuators were never installed for this example site. This resulted in the average RSSI of -88dBm on all affected sectors.

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Case H7

Faulty installation

Notes

The Tampa team added the correct attenuator pads, and this moved the UL RSSI to the expected range

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Case H8

Faulty installation

GA6363

LGC Neutral Host

1900 MHz

GA6363 & GA6364 - Hartsfield-Jackson Atlanta International Airport

RU

RU

RU

3206 x 19003 sectors (X, Y, Z)1 RU per sector

RU

RU

RU

GA63643206 x 1900

3 sectors (X, Y, Z)1 RU per sector

FU

FU

FU

FU

FU

FU

Attenuator

30 dB50 W

Attenuator

30 dB50 W

Notes:1) LGC will need to be on-site duringcommissioning to set proper levels2) No Rx Diversity - the A branch is usedfor Tx & the B branch is used for Rx3) DL TX Power is limited to the amountspecified for each zone (+5 dBm). Thesecond attenuator (xx dB) will need to bemeasured on site and ordered then inorder to be exact. The second attenuator

Attenuator

30 dB50 W

Concourse A(+5 dBm)

Tx Rx

T Gates(+5 dBm)

Tx Rx

Atrium(+8 dBm)

Tx Rx

Concourse B(+5 dBm)

Tx Rx

Concourse C(+5 dBm)

Tx Rx

Concourse D(+5 dBm)

Tx Rx

Concourse E(+5 dBm)

Tx Rx

Tunnel(+8 dBm)

Tx Rx

Attenuator

30 dB50 W

Attenuator

xx dB2 W

2 to 1Splitter

2 to 1Splitter

2 to 1Splitter

2 to 1Splitter

Attenuator

xx dB2 W

Attenuator

30 dB50 W

Attenuator

30 dB50 W

Attenuator Specifications:Meca 650-30-1F430 dB, 50 WN-type connections

Attenuator

30 dB50 WFemale

NMale

Female NMale

Splitter Specifications:Meca 802-4-1.500VN-type connections

2 to 1SplitterFemale

NMale

Male NFemale

Attenuator

xx dB2 W

Attenuator

xx dB2 W

Attenuator

xx dB2 W

Attenuator

xx dB2 W

Attenuator

xx dB2 WFemale

NMale

Female NMale

Attenuator Specifications:Meca 612-xx-1xx dB, 2 WN-type connections

Notes

This Atlanta design called for an attenuator to be installed with the Distributed Antenna System (DAS). This was never completed, resulting in a high UL RSSI

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Case H9

Faulty installation

Notes

This site example had cabling problems affecting GSM as well. The Tampa team corrected it, and this restored the UL RSSI

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Case H10

Impact of Traffic load on the UL Interference

Increase in RSSI

Notes

If the noise rise is higher than 3-4 dB while the load is less than 50-60%, then further investigation should be performed. Neighboring cells and external interference are examples that may cause the increase

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Case H11

GSM Interference

200kHz GSM spikes will impact the RTWP on UMTS

TelCel, a mexican operator, was using the same band as Cingular’s UMTS network

High interference

Mexican border

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Case H11

GSM Interference (continue)

-101.57

-103.42

-99.52

-96.13

-99.23

-97.13

-98.73

-96.13

-99.33

-101.82

-105.00

-103.00

-101.00

-99.00

-97.00

-95.00

-93.00

-91.00

-89.00

-87.00

-85.00

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UL RSSI measured by sites experiencing GSM interference

Ave. UL RSSI measured by sites with configuration issues

Ave. Network UL RSSI

Notes

Narrow band GSM interference is easily identified by the fact that the reported UL RSSI follows a similar pattern to the GSM traffic profile

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Case H12

High sites

Mount Soledad – High site (2400ft)

Notes

High sites normally share the tower with multiple technologies. Unwanted coupling is always a risk if minimum separation between antennas are not maintained.

Containing this site is almost impossible due to it’s relative height. This sector was measuring UL RSSI at -97dBm while the surrounding sites were reporting the noise floor at -104dBm.

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Case H13

External interference

1500 ft broadcast tower was identified as the cause for this network wide harmonic interferer

San Antonio

Notes

More than 280 sectors were affected in San Antonio

Ave. RSSI was generally acceptable, but the No. samples >= “-90.5 to -90 dBm” indicated that there was an external interferer present

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High and Low UL RSSI measurements usually points towards a problem within the system setup or equipment functionality

Hourly and daily statistics can help to indicate if the interference is constant, or trend with 2G and/or 3G traffic load

It is important to ensure all system parameters and the installation are implemented correctly, before searching for an external interferer

Conclusions

Summary