This is an interesting topic and i also faced this problem lets see some more definition…
Actually i missed one thing in my last message
t3110 is a mobile side timer
t3111 is a network side timer
you can define t3111 in parameters you can find and according to that value t3110 is defined same value. Siemens default is 0.5 second.
Here is the siemens definition about t3111 and it says if you put high value call release will take more time
T3111: This timer is used to delay the radio channel deactivation in
the BSC after release of the main signalling link on the Um. During
the call release procedure the BSC sends the CHANNEL RELEASE
message. After receipt of the CHANNEL RELEASE message the MS
sends a DISCONNECT message to the BTS to disconnect the
FACCH. Subsequently the BTS acknowledges the DISCONNECT
message towards the MS by an UA and informs the BSC by sending
the RELEASE INDICATION message. On receipt of the RELEASE
INDICATION the BSC stops timer T3109 and starts timer T3111. On
expiry of T3111 the BSC deactivates the radio channels by sending
the RF CHANNEL RELEASE message to the BTS. The sole purpose
of timer T3111 is to let some time for the acknowledgement of the
disconnection (by an UA) and to protect the channel in case of loss of
the acknowledge frame.
Note: The higher the value of T3111 is the longer the call release
procedure takes. Thus T3111 has an impact on the feature ‘Queuing’
(see also parameters EQ (SET BTS [OPTIONS]) and BSCT11PUB
(SET BSC [TIMER])): the longer the release procedure for an existing
call takes, the later a queued TCH request can be served. A released
TCH is ‘available’ for a queued TCH request if the BSC has received
the RF CHANNEL RELEASE ACKNOWLEDGE for the released
TCH. As a higher value of T3111 leads to a delay of the RF
CHANNEL RELEASE message it simultaneously leads to an
extension of the queuing time. Therefore it is recommended to set
T3111 to the default value (HLFSEC-1).