Fault management provides the following basic functions:
l Fault detection
After detecting faults, a fault detection unit reports the faults to the fault management module. Then, the fault management system reports alarms for these faults to the U2000 or local maintenance terminal (LMT) after processing the faults on each layer. Fault detection units can detect faults of all MOs including software and hardware, such as TRXs, ports, channels, boards, base stations, cells, links, and signaling messages.
l Fault collection
Fault collection is the most important external interface of fault management. It collects faults reported by fault detection units and processes in a centralized manner.
l Duplicate fault filtering, fault transient rule, and fault toggle rule
There are two filtering stages: primary filter and secondary filter. In the primary filter, fault detection units filter duplicate faults and other faults using the transient rule and toggle rule.
In the secondary filter, alarms to be reported are filtered.
– Transient rule
Faults or alarms of short duration can be filtered based on the alarm or fault generation delay. Only the faults or alarms whose duration exceeds the threshold of the generation delay comply with the transient rule and are reserved for next filtering.
As shown in Figure 7-3, the duration of fault 1 or alarm 1 is shorter than the delay threshold T, so fault 1 or alarm 1 is discarded. The duration of fault 2 or alarm 2 is longer than T, so alarm 2 or an alarm for fault 2 can be reported.
Base Station Controller Equipment Reliability Feature
Parameter Description 7 Fault Management
Figure 7-3 Principles of the transient rule
– Toggle rule
The toggle rule applies to the faults that frequently occur and has oscillation characters.
Figure 7-4 shows the principles of the toggle rule.
Figure 7-4 Principles of the toggle rule
If the number of duplicate faults exceeds a threshold in a period T1, the duplicate faults are filtered using the toggle rule. After that, one fault and an alarm for the fault are reserved, and alarms for other duplicate faults are filtered. The fault detection units determine oscillation termination conditions once oscillation starts. If the number of duplicate faults is within the threshold in T2, the oscillation ends, which means that the fault does not occur.
l Fault troubleshooting
Fault troubleshooting involves device status switchover, fault isolation, and automatic fault rectification. Base stations and controllers filter faults and automatically rectify them based on preset policies. If required, the preset policies can be modified by adjusting parameters.
When faults fail to be automatically rectified and manual interventions are required, alarms are reported.
l Alarm mapping
Alarm mapping is one of the core processes in fault management and aims to isolate fault information from the alarms reported to users. Alarms presented to users are in a uniform format and easy to understand. Alarm mapping forces faults to map reported alarms. Faults and events occur in the system and involve system details. Alarms provide fault analysis results and are displayed in a uniform and simple format. You can rectify faults based on alarms. Rather than obtaining system details, you only need to locate the units where faults occur and that can be replaced or modified.
l Alarm box management
Alarm box management provides functions, such as specifying the severity of alarms to be reported to the alarm box, resetting the alarm box, and querying the alarm box version.
After you specify concerned alarms to be reported to an alarm box, the alarm box provides audible and visual notifications for you to rectify faults in a timely manner.
l Alarm correlation
Alarm correlation is one of the core processes in fault management. This function filters out non-root faults and presents root faults to users. A root fault generally triggers multiple correlative faults. If alarm correlation is not performed, multiple alarms are reported, which affects fault location.
Certain critical alarms, such as service-related alarms, cannot be masked based on alarm correlation even if the critical alarms are generated for correlative faults that include physical device faults or data transmission faults. These alarms carry the serial numbers of their root alarms. In this way, the U2000 can present alarm correlations to maintenance personnel for fast fault location and troubleshooting.
l Supporting common alarms in the SingleRAN solution
In a GSM/UMTS dual-mode base station, if two common alarms with the same information are detected and the alarms are for GSM and UMTS, respectively, an alarm for only one RAT can be displayed. This prevents redundant work order dispatches. The RAT displayed in the alarm varies according to the multi-RAT priority settings.
l Alarm synchronization between a base station and the U2000
Alarm synchronization between a base station and the U2000 consists of two stages:
– Alarm synchronization between the base station and the controller: The controller queries active alarms from the base station, issues a command to the base station to check for alarms that have not been synchronized, and updates alarm records on the controller based on the check result.
– Alarm synchronization between the controller and the U2000.
l Alarm severity change
Based on 3GPP specifications, the severity of an uncleared alarm can be changed. After the severity is changed, an alarm severity change message is reported.
l User-defined alarms
Base stations and controllers can be connected to external environment monitoring devices to monitor the environment and device status, such as the temperature, humidity, voltage, theft, and smoke. You can define alarms on base stations and controllers for faults related to the status of the environment and devices. You can also set parameters for these alarms, such as the alarm name, severity, and network management type. In this way, you can dynamically monitor the environment and devices.
l Alarm masking
With this function, you can mask specified alarms by alarm ID or object.
– Masking alarms by alarm ID
If Shielded Flag of a specified alarm ID is set to Shielded, all the active alarms of the alarm ID are cleared. During alarm masking, the specified alarm will not be reported even if the fault persists. If the fault is not rectified after alarm masking is disabled, alarms of the specified alarm ID are reported.
– Masking alarms by object
You can mask a specified alarm or all alarms for a certain board, port, or digital signal processor (DSP), or mask a specified alarm for all objects.
l Fault log
Base Station Controller Equipment Reliability Feature
Parameter Description 7 Fault Management
Fault logs are classified into local fault logs and central fault logs. Local fault logs record faults on faulty boards and are stored in a nonvolatile storage device. Central fault logs record the information about all faults, based on which you can obtain all the fault information about an NE.