I’ll copy & paste your post here, and reply within each bullet point.
1.Yes the Problem is not related to all the cells, But 20-40 % of cells of all the BSC have this Problem, Though if compare with ZTE the problem is there with only 2-3% cells.
2.Drops are Increasing when Traffic is Increasing, Highest in the Busy Hour i.e 19th Hour.
Drops Start getting Double from 300 Drops to 600 & Increase so on from 7:00 AM till 22:00 Hrs in night.
— that seems to indicate a high frequency load due to high traffic load. In other words, interference. Check out TCH drops on the same TRX than the one carrying SDCCH. If AMR is enabled, then TCH will be much more resistant to interference than SDCCH, and will face less drops, rending the comparison useless. So you can check the average DL & UL RXQUAL through RMS on each TRX. For the 40% cells having high SD Drop, do you see a higher average RXQUAL ? (.8 is ok, 1.2 is really bad.. decimals are important!) Check out the UL FER too.
3.Mean Holding Time i.e(SDCCH_occy_total / SDCCH_allocated) from NPO is 4.1 to 4.2 every day in Busy Hour.
— That is very acceptable. How high is the SD Drop % on those cells ?
4.Also, SDCCH Is mainly Configured on BCCH TRX, But will check for few cases & if configured on TCH, will shift & check the case.
— ALU system will preferably use the SD timeslot located on the “highest” TRX. Only when this SD TS is full, then it will use a “lowest” SD TS. At busy hour, that is probably the case, and more and more SDCCH TS are being used. I let you find out the best methodology to change TRX location. There must always be at least 1 SD TS on TRX0.
5.Checked with many cells, SD Assignment & TCH Assignment are good for these Poor SD Drop cases, Even TCH Cong is not there.
— You could try to work on power control here. Try to inhibit power control for a longer time (SDCCH PC INIHBIT, or something similar). Instead of 3s, put 6s….
6.We are Using Adhoc Freq Plan, Based on Optimized Frequency Plan generated from Measurements.. No degradation Observed because of this.
— Not until now, isn’t it ? Were the SD Drops fine when you first deployed adhoc fp ?
7.I am not able to get the SDCCH Drops due to Location Update failures, Can you help me with counters/indicators.(Also I learned somewhere that LOC Updates does not happen on SDCCH in Dedicated Mode) so how it will Impact in SDCCH Drops.
— Look for counters which are named *LU*. Then drag and drop counters into the indicators tab, to get all related indicators.
8.These are the drops, Happening due to radio Link Timeout or Lapdm timer expiry, So as Immediate remedy , Are there any Timer or parameter which can be increased to resolve this slightly.
— Yes, there is a “timer”, it is the same than for TCH (radio link timeout). Not really a timer, but i guess you are familiar with that.
But it reminds me about ‘lapdm”. Could you check the LAPD RSL congestion ? (can be seen in the NPO object “lapd bts-bsc”, very few counters there). If RSL is congested, that might lead to delays, and possibly SDCCH drops. It is a very long shot 🙂