20081 Loss of E1/T1 Signals (LOS)

Description

A Loss of E1/T1 Signals (LOS) alarm is generated if the E1/T1 port of the BSC does not receive any pulse over a certain period. Then, the BSC sends an RAI signal to the peer NE.

Attribute

Alarm ID	Alarm Severity	Alarm Type
20081	Major	Fault

Parameters

ID	Name	Meaning
1	Subrack No.	Subrack No.
2	Slot No.	Slot No.
3	Cpu No.	CPU No.
4	Port No.	The number of the port
5	Site No.	The IDs of all sites whose OMLs are on the faulty E1/T1. If BTS are cascade connected,a maximum of 4 sites are shown.Only Abis E1/T1 alarm has this parameter.
6	Site Name	The Names of all sites whose OMLs are on the faulty E1/T1. If BTS are cascade connected,a maximum of 4 sites are shown.Only Abis E1/T1 alarm has this parameter.
7	Alarm Attribute	0=Normal, Alarms period are longer than the Transient Threshold. 1=Transient Count, The times and the period of the alarms whose periods are shorter than the Transient Threshold are summed up. If the sum result is longer than the Alarm Occurrence Period Threshold or Alarm Occurrence Times Threshold, an alarm so called Transient Count Alarm is triggered. Because Transient Count Alarm is based on accumulative result, the recovery of the alarm may occur at least one Summing Cycle later. The Summing Cycle can be query by MML "LST STATSLDWIN".

Impact on the System

If the active board is faulty, the services carried on the port of the board are disrupted.
If the standby board is faulty, the services are not affected.

System Actions

When the active interface board is faulty, an active/standby switchover is performed if the standby board allows a switchover. Otherwise, no handling is performed.
When the standby interface board is faulty, no handling is performed.
When the faulty interface board works in independent mode, no handling is performed required.

Possible Causes

The E1/T1 cable is faulty or improperly connected to the BSC interface board.
The transmission equipment or transmission link between the BSC interface board and the peer NE is faulty.
The BSC or the peer equipment are improperly grounded.
The BSC interfaced board is faulty.
The board of the peer NE is faulty.

Procedure

Check the E1/T1 cable between the BSC interface board and the peer equipment.
1. Check whether the E1/T1 cable between the BSC and the peer equipment is correctly connected.
  Y => The E1/T1 cable is correctly connected. Go to c.
  
  N => The E1/T1 cable is incorrectly connected. Go to b.
2. Connect the E1/T1 cable properly. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Go to c.
3. Check whether the E1/T1 cable between the BSC interface board and the peer equipment is loosened, detached, or damaged.
  Y => If the E1/T1 cable is loosened or detached, Go to d. If the E1/T1 cable is damaged, Go to f.
  
  N => The E1/T1 cable is properly connected. Go to e.
4. Connect the E1/T1 cable securely to the BSC interface board and the peer equipment. Then, check whether the alarm is cleared.
  Y=> The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Go to e.
5. Identify the first connection point (such as the DDF) connected to the BSC and perform a loopback on the TX and RX of the BSC. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. Both the BSC interface board and the E1/T1 cable connected to the BSC interface board are normal. Go to 3.
  
  N => The alarm is not cleared. The BSC interface board is faulty or the E1/T1 cable connected to the BSC interface board is faulty. Go to f.
6. Replace the E1/T1 cable. Then, check whether the alarm is cleared.
  Y=> The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Replace the E1/T1 cable with the original one. Go to 2.
Check the BSC interface board.
1. Reset the BSC interface board. Wait five to ten minutes after the board is started and check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Go to c.
2. Remove and then reinstall the BSC interface board. Wait five to ten minutes after the board is started and check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Go to d.
3. Replace the BSC interface board. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Replace the BSC interface board with the original one. Go to 3.
Check whether the BSC and the peer equipment are properly grounded.
1. Check whether the BSC and the peer equipment are properly grounded.
  Y => The BSC and the peer equipment are properly grounded. Go to 4.
  
  N => The BSC and the peer equipment are improperly grounded. Go to b.
2. Ground the BSC and the peer equipment properly. Wait 10 minutes. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Go to 4.
Check the peer NE.
1. Check the type of board that generates the alarm.
  Y => If the board is an Ater interface board, Go to b. If the board is an Abis interface board, Go to e.
  
  N => The board is of another type. Go to i.
2. Perform a physical loopback on the E1/T1 port of the peer GEIUT towards the GEIUT that generates the alarm. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The peer GEIUT is faulty. Go to c.
  
  N => The alarm is not cleared. The transmission equipment or transmission link between the local and peer GEIUTs is faulty. Contact the transmission engineers. The alarm handling is complete.
3. Remove and then reinstall the peer GEIUT. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Go to d.
4. Replace the peer GEIUT. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Contact Huawei Customer Service Center.
5. Query the BTS information according to the alarm location information.
6. In the BTS, perform a loopback on the E1/T1 port of the E1 lightning protection board towards the BSC. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The E1 lightning protection board or the TMU in the BTS is faulty. Go to g.
  
  N => The alarm is not cleared. The transmission equipment or transmission link between the BSC and the BTS is faulty. Contact the transmission engineers. The alarm handling is complete.
7. Remove and then reinstall the E1 lightning protection board or the TMU. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Go to h.
8. Replace the E1 lightning protection board or replace the TMU. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  
  N => The alarm is not cleared. Contact Huawei Customer Service Center.
9. Contact the maintenance engineers of the peer NE. On the peer NE side, perform a loopback on the port of the peer NE towards the BSC. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The interface board of the peer NE is faulty. Contact the maintenance engineers of the peer NE. The alarm handling is complete.
  
  N => The alarm is not cleared. The transmission equipment or transmission link between the BSC and the peer NE is faulty. Contact the transmission engineers. The alarm handling is complete.