TCH Congestion Analysis

 

What should I check?

• Check if TCH congestion exists and if the SDCCH mean holding time is high. Check CLS and Assignment to Worse cell parameter settings.

Where do I look for it?

• Use STS Counters and look into time congestion to see how severe is the TCH Congestion. The formula is:

TCH TIME CONGESTION OF TOTAL MEASUREMENT INTERVAL	=	TFTCONGS	X 100 %
		PERLEN * 60

• If activated, check CLS and Assignment to worse cells parameters from CNA.

Why do I need to check this?

• TCH congestion causes the mobiles to stay extra long time on the SDCCH.  Increase TCH capacity if required.  Utilize the features for traffic distribution such as CLS and Assignment to Worse Cell.

SMS Usage

What should I check?

• Check SMS activity.

Where do I look for it?

• Check STS counters for SMS on SDCCH. Counters are CSMSDWN and CSMSUP.

Why do I need to check this?

• Extensive SMS usage increases the SDCCH traffic and could cause congestion if badly dimensioned SDCCH channels. Re-dimension the SDCCH channels with consideration taken to SMS usage.

Too Frequent Periodic Registration

What should I check?

• Check Random Access Distribution. Check the timer T3212 in the BSC.

Where do I look for it?

• STS Object Type RANDOMACC for Random Access and look into CNA for T3212 setting.

Why do I need to check this?

• To prevent intervals of Location Updating which is too short that it affects Random Access Performance to deteriorate.

Increasing Traffic Demand

What should I check?

• Check if it’s short-term traffic growth and whether combined SDCCH is used.

Where do I look for it?

• Compare the traffic trends and refer to planning on how SDCCH is dimensioned.

Why do I need to check this?

• The high traffic could be related to an occasional event or due to a long-term growth. If it’s a special one-time event of surge in traffic, then it shouldn’t cause too much concerned. But if the trends continue, then SDCCH might need to be re-dimensioned by increasing the number of SDCCH channels. Note that an increase may lead to the need for new transceivers. If combined SDCCH is used, non-combined channel configuration should be introduced.

Cell Broadcast Used

What should I check?

• Check if Cell Broadcast is active.

Where do I look for it?

• Run BSC command RLCCP.

Why do I need to check this?

• CBCH is the cell broadcast channel and indicates whether or not a CBCH shall be included in one of the SDCCH/8 sub-channels for the cell or channel group. It is defined per cell or per channel group. If it is active, check if the network uses it. If it is not used, remove Cell Broadcast.

Long Mean Holding time

What should I check?

• Check SDCCH Mean Holding Time.

Where do I look for it?

• STS counter for SDCCH Mean Holding time. The formula is:

SDCCH MEAN HOLDING TIME	=	CTRALACC*PERLEN*60	X 100 %
		CNSCAN*CMSESTAB

Why do I need to check this?

• If the mean holding time is too long, this can possibly generates a higher traffic load.

SDCCH Dimensioning

What should I check?

• Check how SDCCH is dimensioned.

Where do I look for it?

• Check the SDCCH settings from CNA parameters.

Why do I need to check this?

• As no of subscribers steadily increase, previous SDCCH dimensioning plan might be insufficient. Review SDCCH dimensioning requirement to existing demands.

Bad use of Adaptive Configuration of Logical Channels

What should I check?

• Check if ACSTATE is on or off. If it’s on, check the parameter settings.

Where do I look for it?

• Run RLACP in BSC for ACSTATE status and use CNA to check these feature parameter settings.

Why do I need to check this?

• By using the Adaptive Configuration of Logical Channels feature, the basic SDCCH configuration in a cell will be under-dimensioned. If this feature is not used correctly, it will cause SDCCH congestion.