Efficient uplink scheduling mechanisms for dual connectivity
The present disclosure mainly relates to improvements for the buffer status reporting and the logical channel prioritization procedures performed in the UE, in scenarios where the UE is in dual connectivity and the PDCP layer of the UE is shared in the uplink for MeNB and SeNB. According to the present disclosure, a ratio is introduced according to which the buffer values for the PDCP are split in the UE between the SeNB and the MeNB according to said ratio.
1. A communication system comprising:
a mobile node;
a master base station; and
a secondary base station; wherein
the mobile node comprises:
circuitry, which, in operation,
connects to the master base station and to the secondary base station via a split bearer that is split between the master base station and the secondary base station in a Packet Data Convergence Protocol (PDCP) layer;
determines whether a total buffer occupancy of the PDCP layer in the mobile node exceeds a threshold;
responsive to the total buffer occupancy exceeding the threshold, splits the total buffer occupancy of the PDCP layer 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;
responsive to the total buffer occupancy not exceeding the threshold, splits the total buffer occupancy of the PDCP layer based on a defined split ratio into a first PDCP buffer occupancy value for the master base station and a second PDCP buffer occupancy value for the secondary base station, wherein the defined split ratio is configured such that one of the first and second PDCP buffer occupancy values is equal to the total buffer occupancy, and the other one of the first and second PDCP buffer occupancy values is equal to zero; and
a transmitter, which is coupled to the circuitry and which, in operation, transmits a first buffer status report based on the first PDCP buffer occupancy value to the master base station responsive to the first buffer occupancy value being more than zero, and a second buffer status report based on the second PDCP buffer occupancy value to the secondary base station responsive to the second buffer occupancy value being more than zero.
2. The communication system according to claim 1 , wherein the defined split ratio is configured by a Radio Resource Control (RRC) message.
3. The communication system to claim 2 , wherein the transmitter transmits all uplink data, processed by the PDCP layer, to either the master base station or to the secondary base station depending on the defined split ratio, with an exception of Radio Link Control (RLC) uplink data being transmitted to the master base station and to the secondary base station, respectively.
4. The communication system according to claim 1 , wherein the defined split ratio is 1:0 or 0:1.
5. The communication system according to claim 1 , wherein transmission of the first buffer status report to the master base station and transmission of the second buffer status report to the secondary base station are independent of each other.
6. The communication system according to claim 1 , wherein the threshold is configured by a Radio Resource Control (RRC) message.
7. A method performed by a communication system comprising a mobile node, a master base station and a secondary base station, the method comprising:
the mobile node connecting to the master base station and to the secondary base station via a split bearer that is split between the master base station and the secondary base station in a Packet Data Convergence Protocol (PDCP) layer;
the mobile node determining whether a total buffer occupancy of the PDCP layer in the mobile node exceeds a threshold;
responsive to the total buffer occupancy exceeding the threshold, the mobile node splitting the total buffer occupancy of the PDCP layer 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;
responsive to the total buffer occupancy not exceeding the threshold, the mobile node splitting the total buffer occupancy of the PDCP layer based on a defined split ratio into a first PDCP buffer occupancy value for the master base station and a second PDCP buffer occupancy value for the secondary base station, wherein the defined split ratio is configured such that one of the first and second PDCP buffer occupancy values is equal to the total buffer occupancy, and the other one of the first and second PDCP buffer occupancy values is equal to zero;
the mobile node transmitting a first buffer status report based on the first PDCP buffer occupancy value to the master base station responsive to the first buffer occupancy value being more than zero; and
the mobile node transmitting a second buffer status report based on the second PDCP buffer occupancy value to the secondary base station responsive to the second buffer occupancy value being more than zero.
8. The method according to claim 7 , wherein the defined split ratio is configured by a Radio Resource Control (RRC) message.
9. The method according to claim 8 comprising:
the mobile node transmitting all uplink data, processed by the PDCP layer, to either the master base station or to the secondary base station depending on the defined split ratio, with an exception of Radio Link Control (RLC) uplink data being transmitted to the master base station and to the secondary base station, respectively.
10. The method according to claim 7 , wherein the defined split ratio is 1:0 or 0:1.
11. The method according to claim 7 , wherein transmission of the first buffer status report to the master base station and transmission of the second buffer status report to the secondary base station are independent of each other.
12. The method according to claim 7 , wherein the threshold is configured by a Radio Resource Control (RRC) message.