Logical Channel during Authentication (2G)

[Stealth]

Dear experts,

What logical channel does GSM use during authentication process (the exchange of Triplet Key), during location update?

Thanks in advance for your answer

[alb_elezi]

The SDCCH is used to transfer all call set-up information, e.g. authentication details, callers number, etc.

[Stealth]

The SDCCH is used to transfer all call set-up information, e.g. authentication details, callers number, etc.

But authentication during location update is carried on when the MS is in idle mode.

I thought SDCCH occurs when a call is initiated.

Please advise...
Correct me if I'm wrong...

[zeezzoo]

whenever there's signaling (location update , call setup , .... ) ==> you are in connected mode and you should have SDCCH (or TCH in case of very early assignment activated)

[Stealth]

whenever there's signaling (location update , call setup , .... ) ==> you are in connected mode and you should have SDCCH (or TCH in case of very early assignment activated)

Alright. Thanks.

[alb_elezi]

But authentication during location update is carried on when the MS is in idle mode.

I thought SDCCH occurs when a call is initiated.

Please advise...
Correct me if I'm wrong...

Taken from the docs:

The MS listens to the beacon and checks if the LAI (location area identity) of the cell matches with the LAI stored in its SIM
(from previous location update). The location update happens when they are different. In that case the MS requests for
location update service. Like all other service requests it gets an SDCCH data channel for this service. On the SDCCH the
MS sends a message to inform the network its new location (new LAI). The MSC undergoes through the authentication
procedure first. Then the MSC updates its VLR. If the MS is new to this MSC (that is, location change causes the change of
MSC) the MSC interacts with HLR to get all the required information about the MS, and gets its VLR a new entry for the
MS. The HLR by that time updates its data for that MS and also sends message to the MSC, where the MS was located
before, asking to update its VLR. The MSC returns an acknowledgment message to the MS. The network then releases the
SDCCH channel.