high SDCCH congestion

[almoqbali36]

hi all

some cells in the network have sudden high SDCH congestion.
i check SD raffic at that day but no increase in traffic and there is no TX issue in the cell.
this happend to some cells like ones or twic a month but for differnt cell.

please any one can explain why?

E******* vendor

[plannerguy]

Hi

Nearby sites may had outages...


Regards
Plannerguy

[almoqbali36]

but there is no increas in SD traffic !

[kaizzer545]

What about transmission if its not stable users wont register normally in network using constantly SDCCH channel in otherwise what about SMS traffic give us more details about ir

BR

[rishi]

waht about directed retry u can try to implement it on that congested cell

[auto_art]

hi all

some cells in the network have sudden high SDCH congestion.
i check SD raffic at that day but no increase in traffic and there is no TX issue in the cell.
this happend to some cells like ones or twic a month but for differnt cell.

please any one can explain why?

E******* vendor

a lot is needed to analyse here. pl share site data & config.

have u turned ACSTATE on??

[jainapurvab]

Check below stats

1) TA report- this will indirectly suggest call requests from far ranges if surrounding cell coverage is affected.

2) BCCH and BSIC or BCC plan. co BCCH-BSIC plan in between any cells can cause Phentom request and thus SD congestion.

3)check any surrounding BSC shifting for LAC update.

Apurva Jain.
R.F. Engineer.

[_lisi4king]

Check below stats

1) TA report- this will indirectly suggest call requests from far ranges if surrounding cell coverage is affected.

2) BCCH and BSIC or BCC plan. co BCCH-BSIC plan in between any cells can cause Phentom request and thus SD congestion.

3)check any surrounding BSC shifting for LAC update.

Apurva Jain.
R.F. Engineer.

Can you describe in detailes Phentom request? How is it possible? What do you make on your network to avoid this problem?

[moayash]

What about transmission if its not stable users wont register normally in network using constantly SDCCH channel in otherwise what about SMS traffic give us more details about ir

BR

[jainapurvab]

Can you describe in detailes Phentom request? How is it possible? What do you make on your network to avoid this problem?

According to GSM spesification,

RACH is identified by BTS using 3 parameters.

-BCCH, BSIC(spesifically BCC) and delay which get refelcted in guard burst in RACH(thats why RACH guard bits are 68.25 approx and from this TA is calculated before synch.)

Think of two neighbor cells having same BCCH and BSIC.
GSM specification has same protocol for access burst sent for target cell during handover synch after receiving handover commanad from source cell AND channel request on RACH.

If network is synch. 4 burst are sent during handover which is also heard to BTS having same BCCH and BSIC.In reply BTS assumes new channel req. on RACH and forwards to BSC for allocation which in turns allocates false channels.

NOTE: SINCE NEW STANDARDS SUGGESTS THAT T3101 TIMER IS NOT SUITABLE FOR SDCCH DROP because this are triggered by above channel request procedures and some times ghost requests due to noise in receiver end. HENCE THIS COUNTER IS NOT SEEN IN SDCCH DROP,(btw check yr KPI whether its using couter or not-if yes then it will introduce SD drop also in phentom req.)

Hope this clearifies...

Apurva Jain.
RF,India.
GTL LTD.