Version:1.0
VIETTEL Cameroon -- RADIO DEPARTMENT INSTRUCTION Solving alarm 2G Nokia "RSSI detected Rx signal difference exceeding threshold"
Issued Date: 25/01/2017
Page: 1-6
MODIFICATION MONITORING TABLE
No
Page
Editor
Modification Content
Inspector
Effective Date
Approver
Signature
Issued time: Effective date: 25/01/2017 25/01/2017
Radio/VTC
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Version:1.0
VIETTEL Cameroon -- RADIO DEPARTMENT INSTRUCTION Solving alarm 2G Nokia "RSSI detected Rx signal difference exceeding threshold"
Issued Date: 25/01/2017
Page: 1-6
TABLE OF CONTENTS
Table of Contents 1.
PURPOSE .................................................................................................................................................. 3
2.
SCOPE OF APPLICATION ...................................................................................................................... 3
3.
REFERENCE DOCUMENTS...................................................................................................................3
4.
CONTENT ................................................................................................................................................. 3 4.1 Introduce about the RSSI alarm ............................................................................................................... 3 4.1.1 What is the RSSI alarm ..................................................................................................................... 3 4.1.2 Detect RF module and corresponding port having problem ............................................................. 4 4.1.3 Analysis............................................................................................................................................. 5 4.2
Troubleshooting the alarm .................................................................................................................. 6
4.2.1
Detect the Port in RF Module having problem by Analysis step of 4.1.3 ................................... 6
4.2.2
Check if there is a power combining on the sector: ..................................................................... 6
4.2.3
Request NOC to send technician on site implement:...................................................................6
Issued time: Effective date: 25/01/2017
Radio/VTC
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Version:1.0
VIETTEL Cameroon -- RADIO DEPARTMENT INSTRUCTION Solving alarm 2G Nokia "RSSI detected Rx signal difference exceeding threshold"
Issued Date: 25/01/2017
Page: 1-6
1. PURPOSE Instruct how to troubleshot and correct Alarm “ RSSI detected Rx signal difference exceeding threshold”, it should be used during monitoring of BTS Alarm.
2. SCOPE OF APPLICATION This instruction is applied to engineers of BSS in Technical De partment, NOC, Branch and all the engineers of Viettel Cameroon in charge of RAN in Nokia Area.
3. REFERENCE DOCUMENTS NED library – Nokia document.
4. CONTENT The RSSI Alarm can be due to: -
Mismatch of power combining (between Software Configuration and Hardware Connections on site).
-
Issue of Jumper and Connections between RF module and Antenna.
4.1 Introduce about the RSSI alarm 4.1.1 What is the RSSI alarm Each antenna is connected to RF module by 2 jumpers. -
1 Jumper transmit and receive signal (TxRx): this i s main Rx signal, it usually connects to port 1/3/5 of RF module.
-
1 Jumper receive signal (Rx only): this is Rx diversity, it usually connects to port 2/4/6 of RF module.
In the case combine power, both 2 jumper connect to odd port in RF module (1/3/5) and each of them play the role TxRx signal, other jumper is Rx diversi ty for this jumper and reverse. BTS will monitor the signal level it received in both port of cell: -
Good signal is in range -75dBm
-90
-
Bad signal is in range -100 dBm
-110
dBm dBm.
When the different between Rx level of main and diversity is exceeding 10dB, this alarm will appear. Eg. Rx main =-85dBm, Rx Div = -110dBm)
Schema 1: Back view of RF module(FXDB)
Issued time: Effective date: 25/01/2017
Radio/VTC
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Version:1.0
VIETTEL Cameroon -- RADIO DEPARTMENT INSTRUCTION Solving alarm 2G Nokia "RSSI detected Rx signal difference exceeding threshold"
Issued Date: 25/01/2017
Page: 1-6
Schema 2: Example Design Power Combining AD0067B (S1 on port 01&03; S2 on port 01&03)
4.1.2 Detect RF module and corresponding port having problem
Connect to the site by BTS Site Manager
Go to Supervision
You can see 3 group: Reliable, Newest, Raw
RSSI
Comparison value
We should check in Reliable. If after impact (change port in RF) we can observe Raw to se e the situation for short period.
Schema 3: Example of site with RSSI Alarm. Issued time: Effective date: 25/01/2017
Radio/VTC
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Version:1.0
VIETTEL Cameroon -- RADIO DEPARTMENT INSTRUCTION Solving alarm 2G Nokia "RSSI detected Rx signal difference exceeding threshold"
Issued Date: 25/01/2017
Page: 1-6
4.1.3 Analysis The case normal configuration:
In this case BTS 242 connect to port 3&4 of RF module including TRx 5,6,7,8,15,18.
The main Rxlevel is good (-89dBm) in Port 3.
The Div Rxlevel is bad (-120dBm) in port 4.
Conclusion: Port 4 have problem make Diversity receive signal i s bad
Schema 4: Checking RSSI Comparison value.
The case combine power:
In this case: cell BTS 203 is combine in Port 3 of RF module 1 and Port 3 of RF module 2.
TRx 5,6,7,8 is configured in Port 3 RF 1; TRx 13,14,15 is configured in Port 3 of RF 2.
In RSSI Comparison: First TRx group Tx in Port 3 RF module 1 have good Main Rxlevel
(-90dBm), bad Diversity Rxlevel (-110 dBm)
Second TRx group Tx in Port 3 RF module 2, the Main Rxlevel is bad (-110dBm) and Div Rxlevel is good (-90dBm)
Conclusion: The jumper and connection in port 3 of RF module 1 is OK, the problem is in Port 3 of RF
module 2.
Schema 5: Checking RSSI Comparison value
Issued time: Effective date: 25/01/2017
Radio/VTC
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Version:1.0
VIETTEL Cameroon -- RADIO DEPARTMENT INSTRUCTION Solving alarm 2G Nokia "RSSI detected Rx signal difference exceeding threshold"
Issued Date: 25/01/2017
Page: 1-6
4.2 Troubleshooting the alarm 4.2.1 Detect the Port in RF Module having problem by Analysis step of 4.1.3 4.2.2 Check if there is a power combining on the sector: 4.2.2.1 Check if the Soft configuration don’t respect the Design as the corresponding CR
correct
it
4.2.2.2 If Soft configuration follow the design: Call region to check the connection on site and correct as in the design. Then align with BSS.
4.2.2.3 Check if alarm is clear If Alarm still not clear, move to 4.2.3 Notice: BSS
need to be sure all the port in RF Module is all connect exactly as the design of Radio
Department.
4.2.3 Request NOC to send technician on site implement: 4.2.3.1 Check if jumper distorted change jumper. 4.2.3.2 Re-connect jumpers to corresponding port having bad Rxlevel, connect it correctly and tightly. Then hard reset RF module, soft reset cell. Check alarm. 4.2.3.3 If the alarm still not clear, change jumper and repeat step 4.2.3.2. 4.2.3.4 If still not clear, change RF module and repeat step 4.2.3.3.
Issued time: Effective date: 25/01/2017
Radio/VTC
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