An integrated circuit which, in operation, performs a process to control a mobile node connectable to a master base station and to a secondary base station by using a split bearer split across the master base station and the secondary base station, wherein a Packet Data Convergence Protocol, PDCP, layer located in the mobile node is shared for the split bearer between the master base station and the secondary base station, the process comprising: determining, by the mobile node, whether a total buffer occupancy value of the PDCP layer in the mobile node exceeds a threshold; when the total buffer occupancy value exceeds the threshold, splitting by the mobile node a total buffer occupancy of the PDCP layer in the mobile node between the master base station and the secondary base station based on a split ratio, into both a first PDCP buffer occupancy value for the master base station and a second PDCP buffer occupancy value for the secondary base station; when the total buffer occupancy value does not exceed the threshold, splitting by the mobile node the total buffer occupancy of the PDCP layer in the mobile node between the master base station and the secondary base station based on a particular split ratio, into only one of the first PDCP buffer occupancy value for the master base station and the second PDCP buffer occupancy value for the secondary base station, wherein the particular split ratio is defined such that one of the first and second PDCP buffer occupancy values is equal to the total buffer occupancy of the PDCP layer in the mobile node for the split bearer, and such that the other one of the first and second PDCP buffer occupancy values is equal to zero, wherein said particular split ratio is 1 to 0 or 0 to 1; generating by the mobile node a first buffer status report for the master base station based on the first PDCP buffer occupancy value, and generating a second buffer status report for the secondary base station based on the second PDCP buffer occupancy value; and transmitting by the mobile node the first buffer status report to the master base station, and transmitting the second buffer status report to the secondary base station. determining, by the mobile node, whether a total buffer occupancy value of the PDCP layer in the mobile node exceeds a threshold; when the total buffer occupancy value exceeds the threshold, splitting by the mobile node a total buffer occupancy of the PDCP layer in the mobile node between the master base station and the secondary base station based on a split ratio, into both a first PDCP buffer occupancy value for the master base station and a second PDCP buffer occupancy value for the secondary base station; when the total buffer occupancy value does not exceed the threshold, splitting by the mobile node the total buffer occupancy of the PDCP layer in the mobile node between the master base station and the secondary base station based on a particular split ratio, into only one of the first PDCP buffer occupancy value for the master base station and the second PDCP buffer occupancy value for the secondary base station, wherein the particular split ratio is defined such that one of the first and second PDCP buffer occupancy values is equal to the total buffer occupancy of the PDCP layer in the mobile node for the split bearer, and such that the other one of the first and second PDCP buffer occupancy values is equal to zero, wherein said particular split ratio is 1 to 0 or 0 to 1; generating by the mobile node a first buffer status report for the master base station based on the first PDCP buffer occupancy value, and generating a second buffer status report for the secondary base station based on the second PDCP buffer occupancy value; and transmitting by the mobile node the first buffer status report to the master base station, and transmitting the second buffer status report to the secondary base station.