PRACH Improvement

[mounir34]

dears
please the PRACH SR in my network is almost 65 % , and almost failure is false alarm
and we have already open the feature false alarm detection under SON but the problem still persist
please any sugestion to improve it

thanks

[linhhy]

dears
please the PRACH SR in my network is almost 65 % , and almost failure is false alarm
and we have already open the feature false alarm detection under SON but the problem still persist
please any sugestion to improve it

thanks

PRACH SR comes with Random access and handover. Check counter to make sure which one is failed. I belieave it comes from handover area, where having too many handover failure between overshot cells.

[mounir34]

dear
the below formula used for troubleshooting ,
GroupA False Alarm Rate is the main failure




Contention Preamble Response Rate =(L.RA.GrpA.Resp + L.RA.GrpB.Resp) / (L.RA.GrpA.Att + L.RA.GrpB.Att) * 100



Non Contention Preamble Response Rate= L.RA.Dedicate.Resp / L.RA.Dedicate.Att * 100



Contention Resolution Ratio=(L.RA.GrpA.ContResolution + L.RA.GrpB.ContResolution) / (L.RA.GrpA.Resp + L.RA.GrpB.Resp) * 100



Contention Preamble False Alarm Rate =(L.RA.GrpA.Att-L.RA.GrpA.ContResolution+L.RA.GrpB.Att-L.RA.GrpB.ContResolution)/(L.RA.GrpA.Att+L.RA.GrpB.Att)*100



GroupA False Alarm Rate= (L.RA.GrpA.Att - L.RA.GrpA.ContResolution) / L.RA.GrpA.Att * 100



GroupB False Alarm Rate= (L.RA.GrpB.Att - L.RA.GrpB.ContResolution) / L.RA.GrpB.Att * 100



Non Contention Preamble False Alarm Rate= (L.RA.Dedicate.HO.Att - L.RA.Dedicate.HO.Msg3Rcv) / L.RA.Dedicate.HO.Att * 100










PRACH SR comes with Random access and handover. Check counter to make sure which one is failed. I belieave it comes from handover area, where having too many handover failure between overshot cells.

[mounir34]

dear
also another question the PRACH SR is almost 65% ,is it normal ? if no how to improve based on abouve KPI,thx


PRACH SR comes with Random access and handover. Check counter to make sure which one is failed. I belieave it comes from handover area, where having too many handover failure between overshot cells.

[mounir34]

dear
please check below the PRACH SR is very low ,any suggestion,thx

40875
PRACH SR comes with Random access and handover. Check counter to make sure which one is failed. I belieave it comes from handover area, where having too many handover failure between overshot cells.

[sak2e]

Dears,

Check from the counters which have been mentioned above, identify which is contributed GrpA or BrpB ?

If caused by GrpA -> Due to some UEs are located farther than the parameter Cellradius. For this case what you can do is reduce the overshooting issue by downtilting or expand the cell radius let say from 10 km to 15 km.

If caused by GrpB -> Most probably due to collision of root sequence. Please check the planning parameter like rootsequenceidx and cellradius. Sample case the cellradius is 10km but minimum delta between RSI less then 8, while based on planning it requires minimum 8 root sequence.

Just check first, then we can discuss more detail..

[mounir34]

yes Sir is caused by GroupA that why we increase the Cell Reduis to 10km before it was 8km
but also after increase cell reduis we noticed slight improvement in PRACH SR but also Outgoing HO degraded


Dears,

Check from the counters which have been mentioned above, identify which is contributed GrpA or BrpB ?

If caused by GrpA -> Due to some UEs are located farther than the parameter Cellradius. For this case what you can do is reduce the overshooting issue by downtilting or expand the cell radius let say from 10 km to 15 km.

If caused by GrpB -> Most probably due to collision of root sequence. Please check the planning parameter like rootsequenceidx and cellradius. Sample case the cellradius is 10km but minimum delta between RSI less then 8, while based on planning it requires minimum 8 root sequence.

Just check first, then we can discuss more detail..

[mounir34]

dears
do you have some parameters to improve the PRACH SR or features
because we have increase Cell reduis also we activated the RACH Optimization feature but SR still low,
thanks

Dears,

Check from the counters which have been mentioned above, identify which is contributed GrpA or BrpB ?

If caused by GrpA -> Due to some UEs are located farther than the parameter Cellradius. For this case what you can do is reduce the overshooting issue by downtilting or expand the cell radius let say from 10 km to 15 km.

If caused by GrpB -> Most probably due to collision of root sequence. Please check the planning parameter like rootsequenceidx and cellradius. Sample case the cellradius is 10km but minimum delta between RSI less then 8, while based on planning it requires minimum 8 root sequence.

Just check first, then we can discuss more detail..

[giegala]

yes Sir is caused by GroupA that why we increase the Cell Reduis to 10km before it was 8km
but also after increase cell reduis we noticed slight improvement in PRACH SR but also Outgoing HO degraded

you have to redo rootsequenceindex planning - the step in rootsequenceindex between cell should match cell radius.
You most likely have overlap between preambles between cells on the same site. Therefore you have incorrect decoding of Prach, which leads also to poor HO SR. That is cell with poor HOSR will have overlap of upper part of preambles with cell that has poor PRACH SR in group A (which are located at the bottom part of preamble list).