Question: Upon expiry of `t-PollRetransmit` in an AM (Acknowledged Mode) RLC entity, what action(s) does the transmitting side take if both buffers are empty or no new RLC data PDU can be sent due to window stalling?
Option 1: Immediately send a new RLC data PDU with a sequence number (SN) set to VT(S).
Option 2: Consider an AMD PDU with SN = VT(S) – 1 for retransmission, or any unacknowledged AMD PDU, and include a poll in a subsequent RLC data PDU.
Option 3: Reset the transmission and retransmission buffers to clear pending PDUs.
Option 4: Consider an AMD PDU with SN = VT(S) – 1 for retransmission, or any AMD PDU lacking positive acknowledgement, and include a poll in the same RLC data PDU as described in the protocol's polling mechanism.
Explanation: Upon expiry of `t-PollRetransmit`, if conditions (empty buffers or window stalling) are met, the transmitting side of an AM RLC entity must consider specific PDUs for retransmission (either with SN = VT(S) – 1 or any without positive acknowledgement) and, crucially, include a poll in the RLC data PDU to solicit an acknowledgement from the receiver, aligning with efficient link management principles in wireless communications. This ensures that the transmitter can assess the need for further retransmissions based on the receiver's response.