- This topic has 13 replies, 1 voice, and was last updated 8 years, 4 months ago by cellular.
7th December 2009 at 07:56 #60010benaiadGuest
The customers claim that the call fails often when they are in the 5th floor or higher in a building7th December 2009 at 08:11 #60011positive telcoGuest
Is there IBS to cover indoor are?
If not,is nearest site taller than building or not?
Thank you9th December 2009 at 07:45 #60012benaiadGuest
Thanks ” positive telco “,
can you explain me what is “lonly island”
may be I’ve to eliminate it!10th December 2009 at 08:34 #60013vijuGuest
multiserver issue13th December 2009 at 07:52 #60014all_8Guest
interference or trx faulty is one of reason of call drop13th December 2009 at 09:27 #60015MakGuest
As the customer is at 5th Floor or higher floor. You have to check the following things:-
2.Multiserver(How many cells are serving that area and what are the frequencies of that.
3. It can be due to multiserver frequency interference.
4.it can be because of overshooting cells. either you have to downtilt or define handover.13th December 2009 at 10:30 #60016all_8Guest
Thanks Mak , but benaiad you might be have to check this reasons:
• Drop Reason, Low Signal Strength Uplink (%).
• Drop Reason, Low Signal Strength Downlink (%).
• Drop Reason, Bad Quality Uplink (%).
• Drop Reason, Bad Quality Downlink (%).
• Drop Reason, Excess TA (%).
\BR13th December 2009 at 10:36 #60017aymenGuest
please, can you give us more details about multiserver “Mak”
BR aymen13th December 2009 at 13:11 #60018MakGuest
Could you pls tell me what is average clutter height and site height in that area.14th December 2009 at 04:17 #60019ArtGuest
Old values: HOP = ON, HSN = 0 => Results in
cyclic hopping (HOP is the Ericsson cell level
parameter to enable hopping)
New values: HOP = ON, HSN = (63 – BSIC) =>
Results in random hopping
The dropped call rate (DCR) decreased by
approximately 20 percent.
Thank you SIR Michael Pipikakis15th December 2009 at 12:40 #60020brouneGuest
The following are main types of call drop:
1． RF loss call drop (i.e. radio link fault call drop);
2． Handover failure call drop;
3． LAPD call drop.
3.1.1 RF Loss Call Drop
The RF loss call drop is shown in Fig. 3.1 1.
Fig. 3.1 1 RF Loss Call Drop
The RF loss call drop is divided into two parts: uplink and downlink.
1． Downlink failure
According to GSM specification, MS has a timer S (T100), when MS starts the call, the timer is assigned with an initial value (i..e. radio_link_timeout) that is broadcasted on BCCH.
When MS cannot correctly decode a SACCH message (four SACCH BLOCK), S is decreased by 1; when MS correctly decodes a SACCH message, S is increased by 2.
S will not exceed the initial value defined by radio_link_timeout. When S is zero, MS will abandon the radio resource connection and enter idle mode, and a call drop occurs.
2． Uplink failure
The uplink failure parameter monitored by system is link_fail.
When the site cannot correctly decode a SACCH message, the timer in HDPC (the timer’s maximum value is defined by link_fail) is decreased by 1; when the site correctly decodes a SACCH message, the timer is increased by 2 (the timer’s value will exceed the value defined by link_fail).
When the timers’ value is zero, the site stops transmitting downlink SACCH and starts the rr_t3109 timer (rr_t3109>T100). When T100 of MS is timeout, MS returns to idle mode and call drop occurs. The site releases the radio channel when the rr_t3109 timer is timeout. Besides, BSC has to send a Clear request message to MSC.
Either uplink failure or downlink failure will cause stopping sending SACCH to the opposite end, and this will start the radio resource releasing procedure of the opposite end. Each time link_fail occurred on TCH will be counted as a RF_LOSSES_TCH.15th December 2009 at 12:43 #60021all_8Guest
may be your message has some missing words…!
BR all15th December 2009 at 16:23 #60022MakGuest
As you have said your call drop is happening because of RLT timer expiry. Means your MS is not able to decode the Sacch frame. So your RLT counter will start and goes to 0 than after call drop happen.
I Think it can be because of either high interference or this cell can be stand alone cell.27th June 2012 at 13:55 #60023cellularGuest
Hi. Can somebody plz tell me whether the T10 timer comes into play during call setup, or is it for handovers only? I want to improve the TCH Asgn Success Rate so will increasing T10 value help? It is currently set to 16 in the network.