SDCCH Congestion Analysis.

Low Availability

What should I check?

• SDCCH Availability.

Where do I look for it?

• STS Counters on SDCCH availability. The formula is:

Available SDCCHs of Total Number of Defined SDCCHs	=	CAVAACC	X 100 %
		CAVASCAN * CNUCHCNT

• Run BSC commands to see if the channels are manual, control or automatic blocked.

Why do I need to check this?

• We need to check this area to make sure that there is no hardware problem as faulty equipment can affect SDCCH availability. If needed, the O&M procedures need to be reviewed.

Location Area Border Cell & CRH

What should I check?

• Check site position and location area border, Location Update Performance and parameter CRH.

Where do I look for it?

• Refer to site database for site info.
• Location Update performance should come from the MSC.
• You can run BSC command RLSSP to check CRH value.

Why do I need to check this?

• If the cell is situated on a misplaced Location Area border, this means that unnecessary many normal Location Updating are performed. If the site is located close to major road or railway, consider moving the Location Area border.
• The CRH is the hysteresis value used when the MS in idle mode crosses a LA border. The default value for this parameter is 4. If a high number of Location Updating occurs in a Location Area border cell, a higher CRH can be set in order to reduce the number of Location Updating.

TCH Congestion

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:

Note that if the feature “Adaptive configuration of logical channels” is active the formulahave no meaning. Then S_AV_NR is recommended to be used instead.