High SD Drops OTHER REASONS

[ejamhas]

Dear Seniors,

I am facing high SD Drop on many cells due to other reasons. I have checked for H/W Alarms, LAPD and DIP stats. No issues found there...

Need your expert opinion to resolve this issue.

Please help... :(

Many many thanks in advance.

[fannakhosr]

Hi
what about the CONFACT (CONCENTRATION FACTOR) value if it is 4 then there may be signaling congestion in the ABIS, another thing , do you check the value of SD drop due to TCH congestion, if it is high then you need to expand the capacity of TCH's

[ejamhas]

Hi Fanna,

Many thanks for your response. Yes the CONFACT is 4. There are not SD Drops due to TCH Congestion.
I am not sure on how to check for the signaling congestion on ABIS. Could you please help me out on this...

Thanks again.


Hi
what about the CONFACT (CONCENTRATION FACTOR) value if it is 4 then there may be signaling congestion in the ABIS, another thing , do you check the value of SD drop due to TCH congestion, if it is high then you need to expand the capacity of TCH's

[fannakhosr]

OK
I need more information regarding your case , is your cell is multi band cell, if so you have to revise the synchronisation settings (TF modes,... etc) try also to monitor intracell HO and OL to UL handover, if the SD drop rises suddenly that means there is some thing not OK, do you have Tems visualization SW, if so you could find the problem of (reversion to old channel) if so feed back me again.
with respect to signaling congestion on Abis you can check the support team, but generally there is the RXASP:moty= rxotg to get the alarm list, most likely this alarm related to the busy hour.

[ejamhas]

Hi Fanna!

I am really thankful to you for your help.

Yes the cells are MBC. Can you please elaborate which sync. settings I need to check. SD Drops keep on fluctuating and the drops due to other reasons is 80% and above. Sorry I don't have TEMS Visualization.

Please let me know what information you need.

Once again many thanks for your help.




OK
I need more information regarding your case , is your cell is multi band cell, if so you have to revise the synchronisation settings (TF modes,... etc) try also to monitor intracell HO and OL to UL handover, if the SD drop rises suddenly that means there is some thing not OK, do you have Tems visualization SW, if so you could find the problem of (reversion to old channel) if so feed back me again.
with respect to signaling congestion on Abis you can check the support team, but generally there is the RXASP:moty= rxotg to get the alarm list, most likely this alarm related to the busy hour.

[fannakhosr]

you are welcome my friend, what I mean by synchronisation as you know we have tow cabinets, one for 900 and the other for 1800 how could we link them to work to gether, most likely through a cable called ESB cable, try to check it with your maintinance team you could easily change it, again I need to know about the call setup scinario, if you havn't tems vis, if possible you have tems investigation logfile, I will try to give you document about MBC and synchronisation

[radenmohawk]

you are welcome my friend, what I mean by synchronisation as you know we have tow cabinets, one for 900 and the other for 1800 how could we link them to work to gether, most likely through a cable called ESB cable, try to check it with your maintinance team you could easily change it, again I need to know about the call setup scinario, if you havn't tems vis, if possible you have tems investigation logfile, I will try to give you document about MBC and synchronisation

Please share document about MBC and synchronization, because i'll get MBC project. I would like to know what the commonly problem on MBC implementation.

[fannakhosr]

Ok, I will do that soon

[auto_art]

what is traffic on a particular site. if site is having 4/4/4 config u should go with confact 2 instead of 4.!

[auto_art]

what is traffic on a particular site. if site is having 4/4/4 config u should go with confact 2 instead of 4.! definately ur SD drop will reduce. & try shifting of channel group.!

[iamsasuke]

Hi,

What are the breakdown for your SDDrop? have you included SDDROP due to location update. I faced this kind of problem before w/ "Other Reasons" was so high but when i breaked it down including LU drops, other reasons was cut more than half. Meaning LU has a big contribution on SDDROP. You can try to check border cells and increase CRH

thankx,

[adewijaya]

Dear Seniors,

I am facing high SD Drop on many cells due to other reasons. I have checked for H/W Alarms, LAPD and DIP stats. No issues found there...

Need your expert opinion to resolve this issue.

Please help... :(

Many many thanks in advance.

E******* SDCCH drops due to 'OTHER'. It is well known T200 time out is one of the events to trigger
There are 2 known formulas for the SDCCH Drop:
CNDROP/CMSESTAB
and
(CNDROP-CNRELCONG)/CMSESTAB
The second formula corresponds to the TCH Congestion excluded. So, the first formula really goes off the limit when there is congestion.
The reason counters are the following:
CDISTA: Excessive TA, that is if the TA value at a dropped connection is higher than or equal to the cell parameter TALIM.
CDISSS: Low signal strength in downlink and/or uplink per cell (CDISSS or CDISSSSUB), that is if the signal strength is less than the BSC exchange properties LOWSSUL and LOWSSDL in uplink or downlink respectively, or in both the uplink and downlink.
CDISQA: Bad quality in downlink and/or uplink (CDISQA or CDISQASUB), that is if the radio link quality is less than the BSC exchange properties BADQUL and BADQDL in uplink or downlink respectively, or in both the uplink and downlink.
As you can see the Reasons also depend on the parameter configuration of the TALIM, LOWSSDL, LOWSSUL, BADQDL and BADQUL. Maybe you can check the values and consider to move a couple of them and after check the new distribution.
Drops due to 'OTHER' reason is normally around 70% - 75% in the E******* networks that I have seen.
The SDCCH Drop can be improved by:
- Adjusting the LA border so the interaction is minimum.
- Using parameters such as the ACCMIN, CCHPWR and/or MAXTA. But be careful with the coverage and some complaints.
- Better antenna performance. Remember to use electrical tilt (if possible) instead of too much mechanical.
- In you have a MSC in Pool and High SDCCH Drop check if there is any issue with the synchrony.
- Turned off the SDCCH HO (SCHO) and it worked in some sectors. Maybe you can try that.

[ramsriniv]

Hi,

Also see whether you have recently upgraded to new Version of BSC. If you go to G10B, you might see high SD drops. I do know that there is a patch for the same. Alternatively you can play with T200 timer, but beware of long setup time. Have you checked the basic DL interference?

Thanks
Ram

[ejamhas]

Hi adewijaya & ramsriniv!

Thank you very much for helping me out and elaborating the issue. Can you also please tell me how to check the T200 timer values? What is the OSS command to check its values?


Thanks again for your help:victory:


Cheers:)

[ramsriniv]

Hi,
You can check this in Alex library, although i longer work for E/// if i remember correctly the value is like 240 ms, this assuming signalling delay is set normal. The value can be as high as 1400 ms if signalling delay is set long. Check also T3122 and T3126. Most of the timers are changed cell level and also BSC level, although i have not as such changed when i was with E///. You can ask these questions in E/// KB. Usually the timer are set as integers which correspond to seconds. You can find all this in Alex, sorry i do not have much on this.

If you play with your timers, you might end up shifting your SD drops to TCH other reason drops. Also check if there is some kind of rail route/BSC/LAC border. Also ensure the correct SD's are set as per TRX guidelines and also check for high SD traffic. Finally if BTSPS is enabled, you may want to disable it for few days to see if your SD drops go away.

Cheers
Ram

[tungbill123456]

hi all!
SDr hight ORTHER because cell in LAC boundarry Rxlever verry low. You can't change LAC.OK

[rezapa]

Hi,
1. Try making a cell reload, CF reload or TG reload (better to make a TG reload in night time, as it's the lowest level of reloading). It works quite often, specially with 2206 RBSs.
2. Reduce CONFACT to 2 or even 1. I've had this problem on a high traffic indoor cell. Although there was no TCH congestion or drop (12 TRXs were configured), SD drops were high and it got solved only after reducing LAPD concentration.
3. Moving BCCH carrier from one TRX to another. Or move all SDCCH channels to one TRX and then try changing the TRX that carries SDs. Sometimes you can find that one TRX is faulty. Always make sure that the TRX which carries SDs has LAPD concentration of 1 (use RXCDP).
4. Check antenna and feeder system. I'm not quite sure yet, but I am suspicious that sometimes after rainstorms, this problems happens for many cells overnight and goes away after a few days of trying everything. It "might be" due to water leakage into feeders (not sure).

[radenmohawk]

E******* SDCCH drops due to 'OTHER'. It is well known T200 time out is one of the events to trigger
There are 2 known formulas for the SDCCH Drop:
CNDROP/CMSESTAB
and
(CNDROP-CNRELCONG)/CMSESTAB
The second formula corresponds to the TCH Congestion excluded. So, the first formula really goes off the limit when there is congestion.
The reason counters are the following:
CDISTA: Excessive TA, that is if the TA value at a dropped connection is higher than or equal to the cell parameter TALIM.
CDISSS: Low signal strength in downlink and/or uplink per cell (CDISSS or CDISSSSUB), that is if the signal strength is less than the BSC exchange properties LOWSSUL and LOWSSDL in uplink or downlink respectively, or in both the uplink and downlink.
CDISQA: Bad quality in downlink and/or uplink (CDISQA or CDISQASUB), that is if the radio link quality is less than the BSC exchange properties BADQUL and BADQDL in uplink or downlink respectively, or in both the uplink and downlink.
As you can see the Reasons also depend on the parameter configuration of the TALIM, LOWSSDL, LOWSSUL, BADQDL and BADQUL. Maybe you can check the values and consider to move a couple of them and after check the new distribution.
Drops due to 'OTHER' reason is normally around 70% - 75% in the E******* networks that I have seen.
The SDCCH Drop can be improved by:
- Adjusting the LA border so the interaction is minimum.
- Using parameters such as the ACCMIN, CCHPWR and/or MAXTA. But be careful with the coverage and some complaints.
- Better antenna performance. Remember to use electrical tilt (if possible) instead of too much mechanical.
- In you have a MSC in Pool and High SDCCH Drop check if there is any issue with the synchrony.
- Turned off the SDCCH HO (SCHO) and it worked in some sectors. Maybe you can try that.

Do you have experience to get/print or change timers as like T200/T8/T10/etc at E******* network? Please share.... :o

[rezapa]

Hi,

What are the breakdown for your SDDrop? have you included SDDROP due to location update. I faced this kind of problem before w/ "Other Reasons" was so high but when i breaked it down including LU drops, other reasons was cut more than half. Meaning LU has a big contribution on SDDROP. You can try to check border cells and increase CRH

thankx,
In that case I'd recommend not to simply increase CRH, but rather revise it. Too low CRH causes too many unnecessary LA updates. But CRHs as high as 10 or more may also cause more SD drops because in such cases, MS remains on the old cell although it might have gone deeply inside the area of new LA. This in turn, can result in SD drops or TCH drops due to quality (camping and initiating the call on a worse cell).
CRH is best kept between 4-10.