Method and apparatus for PCDP discard
A method and apparatus for discarding a packet data convergence protocol (PDCP) service data unit (SDU) are disclosed. A PDCP layer sets a timer and discards a PDCP SDU upon expiration of the timer. The timer may be set upon receiving the PDCP SDU from an upper layer or upon submitting the PDCP SDU to a lower layer for transmission. The timer and a radio link control (RLC) discard timer may be coordinated. Alternatively, the PDCP layer may discard the PDCP SDU based on a notification from an RLC layer or based on a PDCP status report.
1. A method for discarding one or more of a packet data convergence protocol (PDCP) packet or a radio link control packet, the method comprising:
a PDCP entity receiving a PDCP service data unit (SDU) from upper layers;
the PDCP entity starting a PDCP discard timer upon receiving the PDCP SDU from upper layers;
the PDCP entity processing the PDCP SDU to form a PDCP protocol data unit (PDU);
the PDCP entity sending the PDCP PDU to a radio link control (RLC) entity for transmission;
the PDCP entity discarding the PDCP SDU based on either the PDCP discard timer expiring or receiving a PDCP status report that acknowledges receipt of the PDCP SDU by a receiving PDCP entity; and
the RLC entity discarding an RLC SDU corresponding to the PDCP PDU based on either receiving an indication of PDCP discard from the PDCP entity or re-establishment of RLC.
2. The method as in claim 1 , wherein a value for the PDCP discard timer associated with the PDCP SDU is preserved during a PDCP re-establishment procedure.
3. The method as in claim 1 , further comprising the RLC entity discarding a RLC PDU corresponding the RLC SDU based on the re-establishment of RLC.
4. The method as in claim 1 , further comprising the RLC entity discarding at least one RLC SDU and at least one RLC PDU based on reaching a maximum number of automatic repeat request (ARQ) retransmissions.
5. The method as in claim 1 , wherein a threshold value of the PDCP discard timer is configured by a radio resource control layer on a per-radio bearer basis.
6. A wireless transmit receive unit (WTRU) comprising:
a PDCP entity configured to:
receive a PDCP service data unit (SDU) from an upper layer entity,
start a PDCP discard timer upon receiving the PDCP SDU from the upper layer entity,
process the PDCP SDU to form a PDCP protocol data unit (PDU),
send the PDCP PDU to a radio link control (RLC) entity for transmission, and
discard the PDCP SDU based on either the PDCP discard timer expiring or receiving a PDCP status report that acknowledges receipt of the PDCP SDU by a receiving PDCP entity; and
the RLC entity configured to discard an RLC SDU corresponding to the PDCP PDU based on either receiving an indication of PDCP discard from the PDCP entity or re-establishment of RLC.
7. The WTRU as in claim 6 , wherein the PDCP entity is further configured to preserve a value for the PDCP discard timer associated with the PDCP SDU during a PDCP re-establishment procedure.
8. The WTRU as in claim 6 , wherein the RLC entity is further configured to discard a RLC PDU corresponding the RLC SDU based on the re-establishment of RLC.
9. The WTRU as in claim 6 , wherein the RLC entity is further configured to discard at least one RLC SDU and at least one RLC PDU based on reaching a maximum number of automatic repeat request (ARQ) retransmissions.
10. The WTRU as in claim 6 , wherein a threshold value of the PDCP discard timer is configured by a radio resource control layer entity on a per-radio bearer basis.