Method for performing a re-establishment of a PDCP entity associated with UM RLC entity in wireless communication system and a device therefor
The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for performing a re-establishment of PDCP entity associated with UM RLC entity in wireless communication system, the method comprising: when a re-establishment of a Packet Data Convergence Protocol (PDCP) entity is triggered, stopping and resetting, by the PDCP entity, a reordering timer of the PDCP entity if the reordering timer of the PDCP entity is running; and delivering, by the PDCP entity, all stored PDCP Service Data Unit (SDU) to upper layers in ascending order of associated COUNT values.
1. A method performed by a receiving device operating in a wireless communication system, the method comprising:
determining that a Packet Data Convergence Protocol (PDCP) re-establishment has been triggered for re-establishment of a PDCP entity of the receiving device; and
based on the PDCP re-establishment being triggered:
for unacknowledged mode (UM) data radio bearers (DRBs):
stopping and resetting a reordering timer;
delivering all stored PDCP data units to an upper layer in ascending order of associated COUNT values after performing header decompression; and
setting, by the PDCP entity, an RX_DELIV state variable and an RX_NEXT state variable of the PDCP entity to an initial value, wherein the RX_DELIV state variable and the RX_NEXT state variable are receive state variables for the PDCP entity,
wherein a first PDCP data unit not delivered to the upper layer is indicated by the RX_DELIV state variable, and
wherein a next PDCP data unit expected to be received is indicated by the RX_NEXT state variable.
2. The method according to claim 1 , wherein the first PDCP data unit not delivered to the upper layer is the first missing PDCP data unit within a reordering window.
3. The method according to claim 1 , wherein setting, by the PDCP entity, the RX_DELIV state variable and the RX_NEXT state variable to the initial value comprises setting the RX_DELIV state variable and the RX_NEXT state variable to a value of 0.
4. The method according to claim 1 , further comprising:
starting the reordering timer based on receiving a PDCP data unit with a COUNT value higher than a value of the RX_NEXT state variable.
5. The method according to claim 1 , wherein determining that the PDCP re-establishment has been triggered comprises:
receiving, from the upper layer of the receiving device, a request for the PDCP re-establishment.
6. The method according to claim 1 , wherein stopping and resetting the reordering timer comprises:
stopping and resetting the reordering timer in a state in which the reordering timer is running.
7. The method according to claim 1 , wherein a last PDCP data unit delivered to the upper layer is further indicated by the RX_DELIV state variable.
8. A receiving device configured to operate in a wireless communication system, the receiving device comprising:
a Radio Frequency (RF) module;
at least one processor; and
at least one computer memory operably connectable to the at least one processor and storing instructions that, when executed by the at least one processor, perform operations comprising:
determining that a Packet Data Convergence Protocol (PDCP) re-establishment has been triggered for re-establishment of a PDCP entity of the receiving device,
based on the PDCP re-establishment being triggered:
for unacknowledged mode (UM) data radio bearers (DRBs):
stopping and resetting a reordering timer;
delivering all stored PDCP data units to an upper layer in ascending order of COUNT values after performing header decompression; and
setting, by the PDCP entity, an RX_DELIV state variable and an RX_NEXT state variable of the PDCP entity to an initial value, wherein the RX_DELIV state variable and the RX_NEXT state variable are receive state variables for the PDCP entity,
wherein a first PDCP data unit not delivered to the upper layer is indicated by the RX_DELIV state variable, and
wherein a next PDCP data unit expected to be received is indicated by the RX_NEXT state variable.
9. The receiving device according to claim 8 , wherein the first PDCP data unit not delivered to the upper layer is the first missing PDCP data unit within a reordering window.
10. The receiving device according to claim 8 , wherein setting, by the PDCP entity, the RX_DELIV state variable and the RX_NEXT state variable to the initial value comprises setting the RX_DELIV state variable and the RX_NEXT state variable to a value of 0.
11. The receiving device according to claim 8 , wherein the operations further comprise:
starting the reordering timer based on receiving a PDCP data unit with a COUNT value higher than a value of the RX_NEXT state variable.
12. The receiving device according to claim 8 , wherein determining that the PDCP re-establishment has been triggered comprises:
receiving, from the upper layer of the receiving device, a request for the PDCP re-establishment.
13. The receiving device according to claim 8 , wherein stopping and resetting the reordering timer comprises:
stopping and resetting the reordering timer in a state in which the reordering timer is running.
14. The receiving device according to claim 8 , wherein a last PDCP data unit delivered to the upper layer is further indicated by the RX_DELIV state variable.