Question: What action does a transmitting Unacknowledged Mode (UM) Radio Link Control (RLC) entity take when notified of a transmission opportunity by the lower layer if the RLC SDU exceeds the indicated RLC PDU size?
Option 1: Discard the RLC SDU to prevent fragmentation
Option 2: Send the RLC SDU as is, relying on lower layer fragmentation
Option 3: Segment the RLC SDU into smaller UMD PDUs, updating RLC headers as necessary
Option 4: Buffer the RLC SDU indefinitely until a larger transmission opportunity arises
Explanation: In Unacknowledged Mode (UM), reliability is not guaranteed, but efficient use of resources is crucial. Segmenting the RLC SDU into smaller UMD PDUs when a transmission opportunity is limited ensures that data is transmitted within the constraints provided by the lower layer, minimizing potential losses and optimizing network resource utilization. Updating RLC headers as needed maintains the integrity of the segmented data for proper reassembly at the receiving end.