- This topic has 24 replies, 1 voice, and was last updated 11 years, 4 months ago by JACK.
18th September 2004 at 11:40 #39811fredGuest
How can I solve the call drop broplem in GSM. What cause them and their probable solution1st October 2004 at 06:52 #39812Mohammad YasinGuest
its a too big issue to be discussed so if u can tell a probable cause than may i can help you1st October 2004 at 10:17 #39813VuyofGuest
1)A call may drop when you move from a zone of coverage to a zone of no coverage.This is always the case when the mobile subscriber moves across cells that do not overlap to each other so the gap causes the drop since there is no coverage at that point.To solve this problem you can use a Booster to extend the DL coverage of one of the cells to overlap OR you use a repeater to give coverage to that gap.
2)You can also have drop calls in an urban area where the uplink is not matched to the downlink thus causing signals not to be able to reach the BTS since the RX Lev is low.To solve this,networks must always be balanced DL=UL (balanced Network) or you use TMAs to improve on the UL sensitivity of the BTS and also the RX Lev.
If you have any doubts or querry do not hesitate to contact me>you can send me your email ID so that I can send you more on this.
Vuyof17th October 2004 at 12:23 #39814fredGuest26th February 2007 at 03:19 #39815chillGuest
I have a problem on the HI CALL Drop Rate of some of my sites. most of the reasons are TCH Dropped due to Low SS Uplink. my sites already have TMA since we have far fetch sites.
can you please help me on what to do? what parameters i should adjust to lessen the call drop?
I have already adjust ACCMIN and BSRXMIN but mo effect.
Please help.26th February 2007 at 07:32 #39816pixGuest
how is located the main traffic spot compared to your site ? (which timing advance, which dl and ul rxlev ?)
according to what you’re explaining, it seems your subscribers do not receive a good coverage (DL RXLEV < -90dBm) In this situation, you can either re-positionate your antenna (so they are aligned with the area they are meant to cover), change your antenna (more gain, more directivity). Are you using Rx-diversity ? You cannot increase coverage by tweaking parameters though, all solutions needs to be more "physical". You can try "synthetized frequency hopping" or "radio hopping", maybe you'll get benefit from "frequency diversity". It can add up to 3dB to your UL and DL, by lessen the fast fading attenuation.26th February 2007 at 08:11 #39817chillGuest
thanks for the info…base on the stats, drop due to TA is not that significant neither on quality. but rather, its all base on signal strength. thats why iam trying to limit the accessibility of the subcribers by adjusting ACCMIN bust still drop calls are still high.
we’re using RX diversity.and the sites are already synthesized hopping.
does adjusting my antenna tilt would help lessen drop call?28th February 2007 at 04:04 #39818TufailGuest
Watz the avg TA in those sites.
Tufail28th February 2007 at 15:53 #39819patrickGuest
you can explain me call drop what’s it means, the cause of call drop and how can solve the problem28th February 2007 at 18:31 #39820PixGuest
i experienced some cases like yours : the cell is covering a road until a certain point, after which there is no more coverage. So, subscribers are driving on the road, making calls, but the call drop after a certain point because of low UL Rx Lev & no neighbors available.
Are there neighbors in your area that should “capture” the subscribers with a low SS ? If yes, you might wan to trigger HO due to low level faster. If no, then i think it is natural to drop the call if ppl are too far away.
If the TA is very low (ppl nearby the site), you might have a antenna design issue, or TX/RX hardware issue. Setting a downtilt at 0° (or 2° if you prefer, at most) is a good idea to maximize the coverage.
I think, first of all, you should perform a drive-test in those areas and see what is really happening. Or get some Abis traces (or radio statistics) to show the distribution of timing advance compared to the UL RXLEV and DL RXLEV.
Pix1st March 2007 at 02:29 #39821FeGuest
Check first if there is alarm, use ZEOH to determine what alarm, drop calls cause can be determine through alarms of the site.1st March 2007 at 16:01 #39822tarun sharmaGuest
what are all resons behind call drop give full details2nd March 2007 at 19:49 #39823pixGuest
a call drop occurs when the radio link timeout timer has expired (too many erroneous SACCH frames received in a row)
this can happen in the UL or in the DL…
up to you to find all the possible reasons for that to happen 🙂
pix7th March 2007 at 18:53 #39824tarun sharmaGuest
what are soft parameters?8th March 2007 at 09:31 #39825chillGuest
the evg TA for some sites are 4-6.