Question: In a UTRAN Iub interface (Node B Application Part - NBAP), under FDD mode, what triggers a Radio Link Failure procedure with the cause 'Invalid CM Settings' when a transmission gap pattern sequence is activated with an SF/2 downlink compressed mode method?
Option 1: The Node B receives an incorrect Transmission Gap Pattern Sequence code for any Radio Link on the primary serving cell only.
Option 2: A UE switches from F-DPCH to another downlink configuration without updating the Node B Communication Context.
Option 3: The Transmission Gap Pattern Sequence is activated for the HS-DSCH Primary Serving Cell but not for all other serving cells listed in the COMPRESSED MODE COMMAND message.
Option 4: The Node B detects a mismatch in the SF/2 downlink compressed mode method between two adjacent Radio Links.
Explanation: This is correct because, according to the specifications, if a Transmission Gap Pattern Sequence for affected HS-DSCH Serving Cells is activated on the HS-DSCH Primary Serving Cell but not for all other serving cells (as indicated in the COMPRESSED MODE COMMAND message), the Node B must reject the procedure and trigger a Radio Link Failure with the specified cause. This ensures consistency across all serving cells to maintain reliable communication.