Question: In an AM RLC entity, when the SOend field has a value of '111111111111111' (for a 15-bit configuration), what does it indicate about the missing portion of the AMD PDU with SN = NACK_SN?
Option 1: The first byte of the Data field is missing.
Option 2: The missing portion includes all bytes to the last byte of the AMD PDU.
Option 3: Only the header of the AMD PDU is affected.
Option 4: There are no missing bytes in the AMD PDU.
Explanation: A special SOend value of '111111111111111' signifies that the entire portion of the AMD PDU, from the start up to the last byte, has been detected as lost at the receiving end of the AM RLC entity, crucial for efficient retransmission and maintaining data integrity in wireless communications.