Question: In a Public Land Mobile Network (PLMN), when a User Equipment (UE) initiates a call without an existing radio connection, what is the sequence of resource allocations before the remote user answers?
Option 1: Signalling channel allocation → Traffic channel allocation → Call set-up information transfer
Option 2: Traffic channel allocation → Signalling channel allocation → Call set-up information transfer
Option 3: Call set-up information transfer → Signalling channel allocation → Traffic channel allocation (if needed)
Option 4: Simultaneous allocation of signalling and traffic channels followed by call set-up information transfer
Explanation: According to the principles of circuit telecommunication services in a PLMN, when initiating a call without an existing radio connection, the UE first requests and is allocated a signalling channel. Once this signalling channel is established, the UE can then transfer the necessary call set-up information. A traffic channel may be allocated at any point after this, but before the network confirms that the remote user has answered, highlighting the flexibility in when the traffic channel is allocated relative to the signalling channel and call set-up information transfer. Thus, the correct sequence starts with allocating a signalling channel, followed by transferring call set-up information, and then possibly allocating a traffic channel.