Question: During a PDCP re-establishment for an LWA (LWIP Adaptation) bearer mapped on RLC AM, where the LWA configuration is retained without a WT change, what action does the UE take regarding the transmission of a LWA end-marker PDCP Control PDU?
Option 1: The UE discards all pending PDCP Data PDUs and directly transmits the LWA end-marker PDCP Control PDU to the RLC entity.
Option 2: The UE waits for an acknowledgement from the network before submitting the LWA end-marker PDCP Control PDU to lower layers.
Option 3: The UE compiles and submits the LWA end-marker PDCP Control PDU to lower layers after the last associated PDCP Data PDU has been submitted, ensuring its successful transmission (e.g., via repeated transmissions if necessary).
Option 4: The UE only transmits the LWA end-marker PDCP Control PDU if explicitly instructed by upper layers during the re-establishment procedure.
Explanation: This is correct because, according to the specifications for handling a PDCP re-establishment under these conditions, the UE must ensure that the LWA end-marker PDCP Control PDU is transmitted after the associated PDCP Data PDU and take measures (like repeated transmissions) to guarantee its successful delivery. This approach maintains data integrity and ensures a seamless handover process without WT change for LWA bearers on RLC AM.