Question: What does the Acknowledgement SN (ACK_SN) field in an RLC STATUS PDU indicate for an AM RLC entity?
Option 1: The Sequence Number (SN) of the next RLC Data PDU to be transmitted.
Option 2: The SN of the next not received RLC Data PDU, excluding those reported as missing or partially missing in the STATUS PDU.
Option 3: The total number of RLC Data PDUs successfully received by the peer entity.
Option 4: The length of the RLC window for the AM RLC entity.
Explanation: The ACK_SN field points to the next RLC Data PDU that has not been received (and is not reported as missing or partially missing with NACK_SN, SOstart, and SOend in the STATUS PDU), helping the transmitting side understand which PDUs are still pending receipt confirmation from its peer for efficient retransmission and sequence management.