Method for handling state variables of a PDCP 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 handling state variables of a PDCP entity in wireless communication system, the method comprising: delivering an PDCP SDU associated with a first COUNT to upper layer and starting, by the PDCP entity, a reordering timer, when an out-of-order PDCP PDU with the first COUNT value is received from lower layer; updating a value of a first state variable to the first COUNT value+1, when the reordering timer starts; and when the reordering timer expires, updating, by the PDCP entity, a value of a second state variable based on a second COUNT value of a first PDCP SDU which has not been delivered to upper layers, among PDCP SDUs with COUNT values which are equal to or larger than the first state variable.
1. A method for a receiving device operating in a wireless communication system, the method comprising:
based on receiving an out-of-order Packet Data Convergence Protocol (PDCP) Protocol Data Unit (PDU) with a first COUNT value from a lower layer:
delivering, by a PDCP entity, an PDCP Service Data Unit (SDU) associated with the first COUNT value to upper layers;
starting, by the PDCP entity, a reordering timer;
updating, by the PDCP entity, a value of a first state variable to the first COUNT value +1; and
based on expiry of the reordering timer:
updating, by the PDCP entity, a value of a second state variable based on a second COUNT value of the first PDCP SDU which has not been delivered to upper layers within a reordering window, among PDCP SDUs with COUNT values which are equal to or higher than the first state variable.
2. The method according to claim 1 , wherein the first state variable indicates a COUNT value following a COUNT value associated with a PDCP PDU which triggered the reordering timer.
3. The method according to claim 1 , wherein the first COUNT value associated with the out-of-order PDCP PDU is higher than a third state variable indicating a COUNT value of a next PDCP SDU expected to be received in a reordering window associated with the reordering timer.
4. The method according to claim 1 , wherein the PDCP entity configured with out-of-order delivery delivers the PDCP SDU associated with the out-of-order PDCP PDU to the upper layers as soon as the out-of-order PDCP PDU is received from the lower layer.
5. The method according to claim 1 , wherein the out-of-order PDCP PDU is received from the lower layer in a reordering window, and the value of the second state variable indicates a lower edge of the reordering window.
6. The method according to claim 1 , wherein the reordering timer starts based on the reordering timer not already running.
7. A receiving device configured to operate in a wireless communication system, the receiving device comprising:
a Radio Frequency (RF) transceiver; and
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:
based on receiving an out-of-order Packet Data Convergence Protocol (PDCP) Protocol Data Unit (PDU) with a first COUNT value from a lower layer:
delivering, by a PDCP entity, an PDCP Service Data Unit (SDU) associated with the first COUNT value to upper layers;
starting, by the PDCP entity, a reordering timer;
updating, by the PDCP entity, a value of a first state variable to the first COUNT value +1; and
based on expiry of the reordering timer:
updating, by the PDCP entity, a value of a second state variable based on a second COUNT value of the first PDCP SDU which has not been delivered to upper layers within a reordering window, among PDCP SDUs with COUNT values which are equal to or higher than the first state variable.
8. The receiving device according to claim 7 , wherein the first state variable indicates a COUNT value following a COUNT value associated with a PDCP PDU which triggered the reordering timer.
9. The receiving device according to claim 7 , wherein the first COUNT value associated with the out-of-order PDCP PDU is higher than a third state variable indicating a COUNT value of a next PDCP SDU expected to be received in a reordering window associated with the reordering timer.
10. The receiving device according to claim 7 , wherein the PDCP entity configured with out-of-order delivery delivers the PDCP SDU associated with the out-of-order PDCP PDU to the upper layers as soon as the out-of-order PDCP PDU is received from the lower layer.
11. The receiving device according to claim 7 , wherein the out-of-order PDCP PDU is received from the lower layer in a reordering window, and the value of the second state variable indicates a lower edge of the reordering window.
12. The receiving device according to claim 7 , wherein the reordering timer starts based on the reordering timer not already running.
13. An apparatus configured to control a receiving device operating in a wireless communication system, the apparatus comprising:
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:
based on receiving an out-of-order Packet Data Convergence Protocol (PDCP) Protocol Data Unit (PDU) with a first COUNT value from lower layer:
delivering, by a PDCP entity, an PDCP Service Data Unit (SDU) associated with the first COUNT value to upper layers;
starting, by the PDCP entity, a reordering timer; and
updating, by the PDCP entity, a value of a first state variable to the first COUNT value +1; and
based on expiry of the reordering timer:
updating, by the PDCP entity, a value of a second state variable based on a second COUNT value of the first PDCP SDU which has not been delivered to upper layers within a reordering window, among PDCP SDUs with COUNT values which are equal to or higher than the first state variable.
14. The apparatus according to claim 13 , wherein the first state variable indicates a COUNT value following a COUNT value associated with a PDCP PDU which triggered the reordering timer.
15. The apparatus according to claim 13 , wherein the first COUNT value associated with the out-of-order PDCP PDU is higher than a third state variable indicating a COUNT value of a next PDCP SDU expected to be received in a reordering window associated with the reordering timer.
16. The apparatus according to claim 13 , wherein the PDCP entity configured with out-of-order delivery delivers the PDCP SDU associated with the out-of-order PDCP PDU to the upper layers as soon as the out-of-order PDCP PDU is received from the lower layer.
17. The apparatus according to claim 13 , wherein the out-of-order PDCP PDU is received from the lower layer in a reordering window, and the value of the second state variable indicates a lower edge of the reordering window.
18. The apparatus according to claim 13 , wherein the reordering timer starts based on the reordering timer not already running.