77535012-RSSI-Overwiev-Troubleshooting[1].ppt
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Transcript of 77535012-RSSI-Overwiev-Troubleshooting[1].ppt
© 2006 AT&T Knowledge Ventures. All rights reserved. AT&T is a registered trademark of AT&T Knowledge Ventures.
RSSI 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.
April 8, 2023Page 3© 2006 AT&T Knowledge Ventures. All rights reserved.
AT&T is a registered trademark of AT&T Knowledge Ventures.
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
April 8, 2023Page 4© 2006 AT&T Knowledge Ventures. All rights reserved.
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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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April 8, 2023Page 5© 2006 AT&T Knowledge Ventures. All rights reserved.
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RSSI Troubleshooting
What is new in P5MD?
RBS P5ED
RBS P5MD
RNC P5MD
New
New
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
April 8, 2023Page 7© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 8© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 9© 2006 AT&T Knowledge Ventures. All rights reserved.
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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)
April 8, 2023Page 10© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 11© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
re
Aft
er
Vs.
Befo
re
Aft
er
Vs.
Befo
re
Aft
er
April 8, 2023Page 12© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 13© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 14© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 15© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 16© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 17© 2006 AT&T Knowledge Ventures. All rights reserved.
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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.
April 8, 2023Page 18© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 19© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 20© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 21© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 22© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 23© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
1:0
0 A
M
2:0
0 A
M
3:0
0 A
M
4:0
0 A
M
5:0
0 A
M
6:0
0 A
M
7:0
0 A
M
8:0
0 A
M
9:0
0 A
M
10
:00
AM
11
:00
AM
12
:00
PM
1:0
0 P
M
2:0
0 P
M
3:0
0 P
M
4:0
0 P
M
5:0
0 P
M
6:0
0 P
M
7:0
0 P
M
8:0
0 P
M
9:0
0 P
M
10
:00
PM
11
:00
PM
12
:00
AM
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.
April 8, 2023Page 25© 2006 AT&T Knowledge Ventures. All rights reserved.
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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
April 8, 2023Page 26© 2006 AT&T Knowledge Ventures. All rights reserved.
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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