High SDCCH congestion

[dacoder]

In our customers network, they have enabled a feature called Dynamic Cell Power Off. Under this, during night hour, for dual band cells, if the traffic of 900 band cell is below certain threshold, then the corresponding 1800 band cell is switched off.
The problem we are seeing is the SDCCH congestion rate is very high(>15%) in 1800 cells before they are switched off. Suppose if cell X(1800 band) is switched off at 2am then we see high SDCCH congestion during 1am.Such congestion was not seen before this feature was enabled. Also no SDCCH congestion is seen in 900 band after 1800 is switched off. What could be the reason for this?

We are using Huawei vendor.

Thanks

[mobilek530]

Hi

You are using Different BCCH for 900 and 1800?

regards

[m121]

I am not familiar with Huawei and this feature, but I guess that SDCCH congestion is due LU.
Probably system forces them to make location update. For what reason I don't know, but probably to move them all to 900Mhz cell or simply count how many MS there are camping (probably second treshold: 1.traffic, 2.number of subscribers)
To confirm this you must check feature's specifications provided by vendor.

Also a question - are you using any Cellreselection offsets for DCS band or any other parameters that limits MS camping on DCS?
I ask this to confirm that probably you have many MS camping in DCS and they all are accessing SDCCH at the same time for some reason.

Also it would be very nice if you camped with TEMS in cell that are switched off at night to see what messages MS receive at that time.

[dacoder]

Hi

You are using Different BCCH for 900 and 1800?

regards

Yes, we are using different BCCH for 900 and 1800 bands.

[mobilek530]

It is recommended to use BCCH for 900 only. When 1800 switch off, its lead all mobiles to search the network and do retransmission.

Try Single BCCH , problem will be closed.


Regards

Add Repu and thanks

[dacoder]

I am not familiar with Huawei and this feature, but I guess that SDCCH congestion is due LU.
Probably system forces them to make location update. For what reason I don't know, but probably to move them all to 900Mhz cell or simply count how many MS there are camping (probably second treshold: 1.traffic, 2.number of subscribers)
To confirm this you must check feature's specifications provided by vendor.

Also a question - are you using any Cellreselection offsets for DCS band or any other parameters that limits MS camping on DCS?
I ask this to confirm that probably you have many MS camping in DCS and they all are accessing SDCCH at the same time for some reason.

Also it would be very nice if you camped with TEMS in cell that are switched off at night to see what messages MS receive at that time.

I was also suspicious if it was due to LU, but i found very less LU requests in that cells and all those requests were successful as well.

Regarding Cellreselection offset for DCS band, I need to check it. Not sure right now.

Thanks

[mashi123]

the feature that u activate should not make any effect on SDCCH stat
I think this happened due to another reason , please check the SDCCH traffic distribution is it all due to LU?
try to deactivate this feature in one cell and monitor the impact
logically doesn't make any since i don't think they are related

[fahmi]

In our customers network, they have enabled a feature called Dynamic Cell Power Off. Under this, during night hour, for dual band cells, if the traffic of 900 band cell is below certain threshold, then the corresponding 1800 band cell is switched off.
The problem we are seeing is the SDCCH congestion rate is very high(>15%) in 1800 cells before they are switched off. Suppose if cell X(1800 band) is switched off at 2am then we see high SDCCH congestion during 1am.Such congestion was not seen before this feature was enabled. Also no SDCCH congestion is seen in 900 band after 1800 is switched off. What could be the reason for this?

We are using Huawei vendor.

Thanks

Hi dacoder,
please what's new for this problem ? did you solve it ?
thans a lot

[the.rf.consultant]

I encountered this problem before...

Check your static SDCCH allocation, if you have assigned it to CHGR-1, 2, 3 and so on. Move it to CHGR-0 because this one is not affected by this feature.

[kilisuci_kdr]

I encountered this problem before...

Check your static SDCCH allocation, if you have assigned it to CHGR-1, 2, 3 and so on. Move it to CHGR-0 because this one is not affected by this feature.
Hi,
Do you have any reason/document that why is not affected in CHGR-0 in your problem?

[the.rf.consultant]

Because this power saving feature only turns off the hopping TRX on CHGR-1, 2, 3 and so on and not the BCCH carrying TRX which is located on CHGR-0.


So if you put your static SDCCH on your hopping TRX, once the feature turns off this TRX's during off-peak/low traffic hours it also lessen your SDCCH resources thereby SDCCH congestion is the result.