A method performed by a Base Station, BS, for communication with a User Equipment, UE, the UE having a Packet Data Convergence Protocol, PDCP, entity and two Radio Link Control, RLC, entities associated with the PDCP entity, the two RLC entities comprising a first RLC entity and a second RLC entity, the first RLC entity being configured as a primary RLC entity, the method comprising: configuring the PDCP entity with a duplication function that is not activated; determining to configure the UE to operate in a duplication mode under a Carrier Aggregation, CA, architecture or under a Dual Connectivity, DC, architecture; in response to determining to configure the UE to operate in the duplication mode under the CA architecture, configuring the UE with a specific Information Element, IE, which is associated with the two RLC entities, without appending an uplink data split threshold, wherein when the uplink data split threshold is not configured in the UE and the duplication function is not activated the PDCP entity is configured to submit a PDCP Data Protocol Data Unit, PDU, only to the first RLC entity; and in response to determining to configure the UE to operate in the duplication mode under the DC architecture, configuring the UE with the specific IE with the uplink data split threshold, wherein when the uplink data split threshold is configured in the UE and the duplication function is not activated the UE is configured to perform a set of operations based on the uplink data split threshold, the set of operations comprising: submitting, by the PDCP entity, the PDCP Data PDU to the first RLC entity when a total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is less than the uplink data split threshold; and submitting, by the PDCP entity, the PDCP Data PDU to the first RLC entity or the second RLC entity when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is equal to or larger than the uplink data split threshold. configuring the PDCP entity with a duplication function that is not activated; determining to configure the UE to operate in a duplication mode under a Carrier Aggregation, CA, architecture or under a Dual Connectivity, DC, architecture; in response to determining to configure the UE to operate in the duplication mode under the CA architecture, configuring the UE with a specific Information Element, IE, which is associated with the two RLC entities, without appending an uplink data split threshold, wherein when the uplink data split threshold is not configured in the UE and the duplication function is not activated the PDCP entity is configured to submit a PDCP Data Protocol Data Unit, PDU, only to the first RLC entity; and in response to determining to configure the UE to operate in the duplication mode under the DC architecture, configuring the UE with the specific IE with the uplink data split threshold, wherein when the uplink data split threshold is configured in the UE and the duplication function is not activated the UE is configured to perform a set of operations based on the uplink data split threshold, the set of operations comprising: submitting, by the PDCP entity, the PDCP Data PDU to the first RLC entity when a total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is less than the uplink data split threshold; and submitting, by the PDCP entity, the PDCP Data PDU to the first RLC entity or the second RLC entity when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is equal to or larger than the uplink data split threshold. submitting, by the PDCP entity, the PDCP Data PDU to the first RLC entity when a total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is less than the uplink data split threshold; and submitting, by the PDCP entity, the PDCP Data PDU to the first RLC entity or the second RLC entity when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is equal to or larger than the uplink data split threshold.