SDCCH Drop During Location Update !!

[PaleNxtTel]

Dears ...

I have a problem in the SDCCH Drop in E******* equipment. More than 50% of the SDCCH Drop due to Drop During Location Update. I reduced the coverage area but no results. I tried to play with the CRO and CRH but no effect and still the same issue. The transmission is clear and no HW fault. Could this be related to signaling ? or related to core ? any idea ?


Thanks,

[electron]

Hi,


Do not you have lac island on this cell/site?


Cheers
Dears ...

I have a problem in the SDCCH Drop in E******* equipment. More than 50% of the SDCCH Drop due to Drop During Location Update. I reduced the coverage area but no results. I tried to play with the CRO and CRH but no effect and still the same issue. The transmission is clear and no HW fault. Could this be related to signaling ? or related to core ? any idea ?


Thanks,

[Jerry]

SDCCH congestion may cause the LU failed. Check if it is there.

[PaleNxtTel]

Hi Electron,

what do you mean by "LAC Island" ?


Hi,


Do not you have lac island on this cell/site?


Cheers

[PaleNxtTel]

Hi Jerry,

There is no congestion in the infected cells.


SDCCH congestion may cause the LU failed. Check if it is there.

[chronix_ray]

Hi,

I am also having this same issue. The location update is increased without doing anything any my SDCCH drops increased also. What should I do or check?

Br//

[luganomu]

PalexNxTel

Hw alarm to check if problem is on some cells
1.RF performance alarm
2.VSWR
3. RX cable disconnected

Apart from Alarm please do the following
1. LAC audit- make sure you clear all the planning mistake like
i] introducing one site with different lac with nearby site
ii] Site in improper BSC
2. LAC border review

You should check if the top worst cells in CLUNDROP are either BSC border/ LAC border. remember one BSC can have more than one LAC
BR

[Osman Nayeem]

Dear,

I just want to share something from my experience:

1. SDCCH Drop during LAC update is always close or more than 50% in E/// system in normal situation.
2. If the Cell is in LAC border, shift all the SDCCH TS to CHGR0, you will find good improvement.
3. Please check ICM band for any interference issue.
4. If the cell is not in LAC border, please check the drop rate for each SD TS from MOTS data. And then shift the SDCCH with better performing channel group.

Thanks!

[Optimustron]

Hi, I experienced from 2 or 3 years before that issue like Osman tell you, but some times it's hard to solve, I checked it out all things he mentioned and sometimes it works, i.e. move SDCCH's to CHGR0 and you see immediately the change in performance for SDCCH DROP RATE. At this time I have a sector that is far away from our location that is having this issue and I made all the possible changes to solve the problem, I'll keep trying to solve this and if we finally resolve this problem I'll tell you. By the way try the procedure from Osman because almost all the time it works, Best regards,

[Optimustron]

Hi friends, I finally have good news about the case I told you, almost at the end I reduced the coverage of the sector putting more downtilt to that sector but It did't work then I check again the KPI's, I see that the reasons of SDCCH DROP was "OTHERS", I only have 3 normal reasons, Excesive TA, Low Signal and Bad Quality I don't have the CLUNDROP from the new versions of BSS, then I check the entire parametrization of the sector and I found that somebody put a very high value of ACCMIN and of course BSRXMIN and MSRXMIN, the valuas was 75 for ACCMIN and MSRXMIN and 78 for BSRXMIN, I suspected that these values caused the SDCCH DROP then in despite of the high traffic of the sector I changed it to 90 and voila it works very well. Please check it maybe it's the same case or you can increase the power if you can because is almost the same that changing the ACCMIN to lower values. Best regards,

[PaleNxtTel]

Dear Optimustron

good work my friend :) in my case I checked ACCMIN, TALIM, PC parameters, OFFSETP, CRO, CRH and sure physical coverage and still having the same issue :(



Hi friends, I finally have good news about the case I told you, almost at the end I reduced the coverage of the sector putting more downtilt to that sector but It did't work then I check again the KPI's, I see that the reasons of SDCCH DROP was "OTHERS", I only have 3 normal reasons, Excesive TA, Low Signal and Bad Quality I don't have the CLUNDROP from the new versions of BSS, then I check the entire parametrization of the sector and I found that somebody put a very high value of ACCMIN and of course BSRXMIN and MSRXMIN, the valuas was 75 for ACCMIN and MSRXMIN and 78 for BSRXMIN, I suspected that these values caused the SDCCH DROP then in despite of the high traffic of the sector I changed it to 90 and voila it works very well. Please check it maybe it's the same case or you can increase the power if you can because is almost the same that changing the ACCMIN to lower values. Best regards,

[Optimustron]

Did you check interference?, or maybe channel definition?, how many SDCCH's per TRX is defined in your network? Check command RXCDP and look for unused slots if you have at least one is a configuration issue. Check RXMOP command too and look for CELL=ALL, if you have at least one change it to rigth value, by the way you can have CHGR=ALL in /order to put more than 1 SDCCH per TRX up to the maximum number of TRXs in a specific sector. I hope this can help you, best regards,

[samuraial]

Check with Core side if the problem is with one or more IMSI in those cells.
We had some issue regarding SDCCH drops with some sim box that were causing the issue.

Also as someone stated check if the problem is in LAC borders and if they are defined correctly in core/bsc.

B/R

[Optimustron]

Today We discovered another reason for high SDCCH DROP RATE, previously I made the same things I do in the past however again It didn't work, then I check configuration for alarms and misconfiguration and all of that was ok, I reset the entire site and made a software download with command RXPLI but I got the same results, then we check the conections and voila we discoverd that this site have an expansion cabinet and a load was missing we put a new load and now the site is working right, the SDCCH DROP RATE disappears, please check the load/termination in the last cabinet for us this was the second cabinet. I hope this can help you, best regards,

[PaleNxtTel]

Hi Samuraial

Thank you for ur reply :)

I checked with the core but they said there it nothing wrong but I dont think they check the IMSI !! is there is a specific way to check the IMSI from the core ?


Check with Core side if the problem is with one or more IMSI in those cells.
We had some issue regarding SDCCH drops with some sim box that were causing the issue.

Also as someone stated check if the problem is in LAC borders and if they are defined correctly in core/bsc.

B/R

[PaleNxtTel]

Optimustron u r the best :)

thanks for ur recommendations. I'll check and let u know the results.


Today We discovered another reason for high SDCCH DROP RATE, previously I made the same things I do in the past however again It didn't work, then I check configuration for alarms and misconfiguration and all of that was ok, I reset the entire site and made a software download with command RXPLI but I got the same results, then we check the conections and voila we discoverd that this site have an expansion cabinet and a load was missing we put a new load and now the site is working right, the SDCCH DROP RATE disappears, please check the load/termination in the last cabinet for us this was the second cabinet. I hope this can help you, best regards,

[samuraial]

You should have a platform in Core that can check the cell and within all the users that attach/connect/disconnect etc etc.
From there you can see if the failures came from one IMSI only or from different ones.

B/R

[a00bcd]

Today We discovered another reason for high SDCCH DROP RATE, previously I made the same things I do in the past however again It didn't work, then I check configuration for alarms and misconfiguration and all of that was ok, I reset the entire site and made a software download with command RXPLI but I got the same results, then we check the conections and voila we discoverd that this site have an expansion cabinet and a load was missing we put a new load and now the site is working right, the SDCCH DROP RATE disappears, please check the load/termination in the last cabinet for us this was the second cabinet. I hope this can help you, best regards,



Dear Optimustron,

What do you mean by Load missing?

regards,

[Optimustron]

I mean that in the last cabinet you need to put a load in order to finish the communication bus between cabinets, this is a termination load that is tipical in all kind of electronics that is planned to have expansions that load is generally colocated at the final stage, I'm attaching two images of that load, like you see this is a female RJ45 connector with resistors that finish the load in order to end properly the communications bus in the last cabinet of a cell site. I'm going to make some of this loads because the Field Service people have dificulties to get this termination loads and they are expensive in despite the simple that they are, by the way I'm going to dissamble one of this to see the value of the resistor and I'm going to measure too to cross check that value.

3582635827

An you see in the picture there is a male connector too, the load is only the metallic piece and inside is the female connector and the loads. Excuse me for the long explain and I didn't explain what I mean with load is missing, the load was missing because it didn't have that load then they attached a new one in that site.

Best regards,

[a00bcd]

Dear Optimustron,

Thank you very much for the detailled explanation, but as I never be involved in an expansion operation of cabinet, could you please give more details about this operation and how to connect two cabinets, what's the utility of RJ45 cable in this operation,

if you have a document explaining this it would be great.

B regards,

[Optimustron]

I have added some extracts and documents from E******* for these installations, I hope this can help you, best regards,
35832, 35833, 35834, 35835, 35836