LAC update in dedicated Mode

[Piscean21]

Experts,
How is LAC updated in dedicated Mode??Which channel is used for this purpose???

[forumuser-2008]

Experts,
How is LAC updated in dedicated Mode??Which channel is used for this purpose???

Location update occur in Idle Mode in SDCCH channel.

[redrooster]

Location update occur in Idle Mode in SDCCH channel.

As forumuser-2008 mentioned, LAC only occur whilst in Idle Mode, upon reselecting a cell with a different LAC is moved to dedicated mode (RACH's) then the Location Area Update is sent typically on the SDCCH (2G). Once complete the mobile returns to Idle and cell selections/reselections.

redrooster

[Piscean21]

I think my question was not clear.I want to ask, if a user during a call crosses LAC boundary how is LAC updated then??And if call waiting option is enabled,will other users making call to the same number find it "Not Responding" until LAC updates???

[timedomain]

Location update is done after conversation is finished, ur location is known in dedicated mode, in case of a new call system knows your place already because u have a dedicated channel

[Piscean21]

Can you plz elaborate how location is known to system in this case when LAC is not still updated?

[s52d]

Can you plz elaborate how location is known to system in this case when LAC is not still updated?

Anchor MSC magically knows which terminals are in dedicated mode ;-)

Knowing LA is needed for routing of pages towards idle terminal:
as terminal is in the dedicated mode, it is not listening to the paging ch, nor answering.
Thus, VLR does not need to know LA:
VLR knows terminal is busy and how to communicate with it.

[PaleNxtTel]

we need to know the LAC only for paging thats mean we need it only in the idle mode. the when the terminal hooked up in a call the BSC knows which cell serving the MS so we don't need the LAC any more !!

Can you plz elaborate how location is known to system in this case when LAC is not still updated?