Title:Low PS RAB setup Success Ratw due to UL IuB Congestion

ID:

Information Type :Troubleshooting Cases

Update time:14 November 2011 8.15pm

Author:

Product Family:Network Planning and DesignProduct:RNC V200R011C00

Fault Type:Tool Instrument Problem

Keywords:PS RAB setup Success Rate due to UL IuB Congestion.

Permission level: Huawei Partners Permission

Phenomenon

Description:During a concert event, low PS RAB setup success rate is detected due to UL IuB Congestion. However, the UL IuB utilization is less than 30% of tatal UL IuB bandwidth and there is no alarm indication

Alarm Information:Null

Cause Analysis:Initial assumption is the UL IuB congestion because the bandwidth is not enough but from the utilization counter, it shows only 30% of the bandwidth is used, further investigation suspected the E1 configuration problem but after discuss with wireless team and found that was not the real cause and the real cause was the E1 link has been down but there is no alarm indication.

Handling Process:1. Checking the counter using OMSTAR

From the statistic, it is clear that the congestion occur while the concert is started (about 6-7pm)

2. CHR analysis show nothinh special but just the UL IuB congestion

3. Check the transmission rate of the E1 link (VS.IMALNK.PEAK.TXRATE)

From the statistic above, it shows that total of 12 E1s were configured but 2 E1s link have no transmission rate during the concert was on going.However, there was no alarm triggered. Therefore the reason of congestion is the E1 transmission poblem.

Suggestions and

summary:The reason of no alarm triggered is till unknown. Besides, when querrying the counter of bandwidth utilisation, it shows that the usage is low. This is because the formula for the counter is total bandwidth used divided by the total bandwidth configured but even the E1 have been down, it still counted in as total bandwidth configured. I suggested that there is a counter that can check the efficient(active) bandwidth by considering the transmission rate of the E1 link. As a conclusion, the congestion is mainly caused by E1 link down and there is no alarm indication

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