Question: During a normal handover in E-UTRAN, how does the target eNB handle downlink PDCP SDUs forwarded by the source eNB with a PDCP SN, in relation to those it has already transmitted to the UE?
Option 1: The target eNB retransmits all forwarded PDCP SDUs to ensure duplication.
Option 2: The target eNB uses the PDCP SN to avoid duplicate transmissions, discarding any forwarded SDU it has already sent to the UE.
Option 3: The target eNB only transmits forwarded PDCP SDUs with a higher SN than those it has sent, ignoring lower or equal SNs.
Option 4: The target eNB forwards all received PDCP SDUs from the source eNB to the UE without checking for duplicates.
Explanation: This is because the 'in-order delivery and duplicate elimination' function at the PDCP layer ensures in-sequence delivery. By using the PDCP SN, the target eNB can identify and discard any forwarded SDUs it has already transmitted to the UE, preventing duplicates and maintaining sequence integrity. This behavior aligns with efficient handover procedures, minimizing unnecessary retransmissions.