METHOD AND APPARATUS FOR PCDP DISCARD

• US 20090103478A1
• Filed: 09/29/2008
• Published: 04/23/2009
• Est. Priority Date: 10/01/2007
• Status: Active Grant

• Current Assignee: InterDigital Patent Holdings, Inc. (InterDigital, Inc.)
• Original Assignee: InterDigital Patent Holdings, Inc. (InterDigital, Inc.)
• Inventors: Sammour, Mohammed, Terry, Stephen E.
• Granted Patent: US 8,855,047 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04L 1/1874 Buffer management
• CPC Class Codes: H04L 1/188 Time-out mechanisms
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]
• CPC Class Codes: H04L 47/32 by discarding or delaying data units, e.g. packets or frames
• CPC Class Codes: H04L 69/04 Protocols for data compression, e.g. ROHC
• CPC Class Codes: H04L 69/28 Timers or timing mechanisms used in protocols
• CPC Class Codes: H04L 69/324 in the data link layer [OSI layer 2], e.g. HDLC
• CPC Class Codes: H04W 28/0205 at the air interface dynamic wireless traffic scheduling H04W72/12
• CPC Class Codes: H04W 80/02 Data link layer protocols

Abstract

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.

Claims

1. A method for discarding a packet data convergence protocol (PDCP) packet or a radio link control (RLC) packet comprising:

measuring and checking a time elapsed since a reference event occurred; and

discarding a PDCP packet if the elapsed time reaches or exceeds a threshold.

2. The method of claim 1 wherein the PDCP packet includes at least one service data unit (SDU) or protocol data unit (PDU).

3. The method of claim 1 wherein the measuring and checking, and the discarding is performed by a PDCP entity.

4. The method of claim 1 wherein the reference event is at least one of receiving a packet from an upper layer, storing a packet in a buffer, removing a packet from a buffer, sending a packet to a lower layer, or performing a PDCP procedure, PDCP function or PDCP action on a packet.

5. The method of claim 1 further comprising:

sending an indication of the discarded PDCP packet to lower layers.

6. The method of claim 5 further comprising:

discarding an RLC packet corresponding to the indicated PDCP packet, wherein the RLC packet includes at least one service data unit (SDU) or protocol data unit (PDU).

7. A method for discarding a packet data convergence protocol (PDCP) packet or a radio link control (RLC) packet comprising:

starting a timer; and

discarding a PDCP packet upon expiration of the timer.

8. The method of claim 7 wherein the PDCP packet includes at least one service data unit (SDU) or protocol data unit (PDU).

9. The method of claim 7 wherein the starting of the timer and the discarding is performed by a PDCP entity.

10. The method of claim 9, wherein the starting of the timer is performed upon receiving a PDCP SDU from an upper layer.

11. The method of claim 9, wherein the starting of the timer is performed upon sending a PDCP PDU to a lower layer.

12. The method of claim 9 wherein the starting of the timer is performed upon occurrence of at least one of receiving a packet from an upper layer, storing a packet in a buffer, removing a packet from a buffer, sending a packet to a lower layer, or performing a PDCP procedure, PDCP function or PDCP action on a packet.

13. The method of claim 7 further comprising:

sending an indication of the discarded PDCP packet to lower layers.

14. The method of claim 13 further comprising:

discarding an RLC packet corresponding to the indicated PDCP packet, wherein the RLC packet includes at least one service data unit (SDU) or protocol data unit (PDU).

15. The method of claim 7, wherein a separate timer is started for every PDCP packet.

16. The method of claim 7, wherein a threshold value of the timer is configured by another layer.

17. The method of claim 7, wherein a threshold value of the timer is configured by a radio resource control (RRC) layer.

18. The method of claim 7, wherein a threshold value of the timer is configured on a per-radio bearer (RB) basis.

19. The method of claim 7, wherein the timer and a radio link control (RLC) discard timer are coordinated.

20. A method for discarding a packet data convergence protocol (PDCP) service data unit (SDU) or protocol data unit (PDU) comprising:

recording or storing a time of occurrence of a reference event; and

discarding a PDCP SDU/PDU if the difference between a current time and the recorded time reaches or exceeds a pre-configured time threshold.

21. The method of claim 20 wherein the reference event is at least one of receiving a packet from an upper layer, storing a packet in a buffer, removing a packet from a buffer, sending a packet to a lower layer, or performing a PDCP procedure, PDCP function, or PDCP action on a packet.

22. The method of claim 20 further comprising:

sending an indication of the discarded PDCP SDU/PDU to lower layers.

23. The method of claim 22 further comprising:

discarding an RLC SDU corresponding to the indicated PDCP SDU/PDU.

24. The method of claim 20 further comprising:

discarding a RLC SDU corresponding to the PDCP SDU/PDU if the difference between a current time and the recorded time reaches or exceeds a pre-configured time threshold.

25. A method for discarding a packet data convergence protocol (PDCP) service data unit (SDU) or protocol data unit (PDU) comprising:

associating a timestamp with a PDCP SDU upon its reception from upper layers;

storing a time of reception from upper layers in the timestamp; and

discarding the associated PDCP SDU/PDU if the difference between a current time and the timestamp reaches or exceeds a pre-configured time threshold.

26. A method for discarding a packet data convergence protocol (PDCP) service data unit (SDU) or protocol data unit (PDU) comprising:

associating a timestamp with a PDCP SDU/PDU upon its sending to lower layers;

storing a time of sending to the lower layers in the timestamp; and

discarding the associated PDCP SDU/PDU if the difference between a current time and the timestamp reaches or exceeds a pre-configured time threshold.

27. A method for discarding a radio link control (RLC) service data unit (SDU) or protocol data unit (PDU) comprising:

setting a timer using an initial value determined or signaled by a packet data convergence protocol (PDCP) entity; and

discarding a RLC SDU/PDU upon expiration of the timer.

28. The method of claim 27 wherein the setting of the timer and the discarding is performed by a RLC entity.

29. The method of claim 28, wherein the setting of the timer is performed upon receiving the RLC SDU from an upper layer.

30. A method for discarding a radio link control (RLC) service data unit (SDU) or protocol data unit (PDU) comprising:

recording or storing a time of occurrence of a reference event that is at least one of a packet data convergence protocol (PDCP) entity receiving a packet from an upper layer, the PDCP entity storing a packet in a buffer, the PDCP entity removing a packet from a buffer, or the PDCP entity performing a PDCP procedure, PDCP function, or PDCP action on a packet;

discarding a RLC SDU/PDU corresponding to the packet if the difference between a current time and the recorded time reaches or exceeds a certain (pre-configured) time threshold.

31. A method for discarding a radio link control (RLC) service data unit (SDU) or protocol data unit (PDU) comprising:

associating a timestamp with a RLC SDU upon its reception from upper layers;

storing a time of reception from upper layers in the timestamp; and

discarding the associated RLC SDU/PDU if the difference between a current time and the timestamp reaches or exceeds a time threshold wherein the threshold is determined or signaled by a PDCP entity.

32. A method of coordinating a packet data convergence protocol (PDCP) discard with a radio link control (RLC) discard comprising:

setting a first timer upon reception of a PDCP SDU from upper layers;

buffering the PDCP SDU/PDU in a PDCP entity; and

sending the PDCP SDU/PDU to lower layers for transmission with an indication of the time spent in the PDCP entity or an indication of the first timer'"'"'s value.

33. The method of claim 32 further comprising:

initializing a second timer with the indicated value;

starting the second timer upon reception of a RLC SDU corresponding to the PDCP SDU/PDU from upper layers; and

discarding the RLC SDU corresponding to the PDCP SDU/PDU if the second timer expires.

34. A method of coordinating a packet data convergence protocol (PDCP) discard with a radio link control (RLC) discard comprising:

associating a timestamp with a PDCP SDU upon its reception from upper layers;

storing a time of reception from upper layers in the timestamp; and

sending a PDCP PDU corresponding to the PDCP SDU to lower layers for transmission with a value of the timestamp.

35. The method of claim 34 further comprising:

receiving a RLC SDU corresponding to the PDCP PDU;

receiving the timestamp value;

checking the timestamp value against a current time; and

discarding an associated RLC SDU/PDU if the difference between a current time and the timestamp value reaches or exceeds a pre-configured time threshold.

36. A method of coordinating a packet data convergence protocol (PDCP) discard with a radio link control (RLC) discard comprising:

determining whether to discard a packet based on a trigger event;

discarding a packet; and

signaling an indication of the discarded packet.

37. The method of claim 36 further comprising:

receiving the indication of the discarded packet; and

discarding a packet corresponding to the indicated discarded packet.

38. A method for packet data convergence protocol (PDCP) discard comprising:

signaling information via a primitive and its respective parameters; and

discarding a PDCP service data unit (SDU) using the signaled information.

39. The method of claim 38 wherein the signaling is performed by a transmitting radio link control (RLC) entity and the discarding is performed by a transmitting PDCP entity.

40. The method of claim 39 wherein the information includes an identifier of the PDCP SDU to be discarded.

41. The method of claim 39 wherein the information includes at least one of the following:

a discard signal for an SDU triggered by any RLC event;

a discard signal for an SDU triggered by an RLC SDU discard event;

a successful delivery notification indicating the delivery of the SDU to a peer RLC entity was successful based on information from the RLC automatic repeat request (ARQ) Status Reports or hybrid automatic repeat request (HARQ) acknowledgement (ACK)/nonacknowledgement (NACK) feedback;

or

a failed delivery notification/signal.

42. A method for radio link control (RLC) discard comprising:

signaling information via a primitive and its respective parameters; and

discarding a RLC service data unit (SDU) using the signaled information.

43. The method of claim 42 wherein the signaling is performed by a transmitting packet data convergence protocol (PDCP) entity and the discarding is performed by a transmitting RLC entity.

44. The method of claim 43 wherein the information includes an identifier of the RLC SDU to be discarded.

45. The method of claim 43 wherein the information includes at least one of:

a discard signal for an SDU triggered by any PDCP event;

a discard signal for an SDU triggered by a PDCP SDU discard event;

a discard signal for an SDU triggered by a PDCP SDU timer based discard event;

or

a discard signal for an SDU triggered by an acknowledgement (ACK) indication in a received PDCP Status Report.

46. A method for packet data convergence protocol (PDCP) discard comprising:

receiving acknowledgement (ACK) or nonacknowledgement (NACK) information via receiving a PDCP status report; and

discarding a PDCP SDU/PDU based on the received PDCP status report information.

47. A method for packet data convergence protocol (PDCP) discard comprising:

receiving acknowledgement (ACK) or nonacknowledgement (NACK) information via receiving a PDCP status report; and

discarding a PDCP SDU/PDU if an ACK indication for the PDCP SDU/PDU is received in the PDCP Status Report.

48. The method of claim 47 further comprising:

sending an indication of the discarded PDCP SDU/PDU to lower layers.

49. The method of claim 48 further comprising:

discarding an RLC SDU/PDU corresponding to the indicated PDCP SDU/PDU.

50. A method for packet data convergence protocol (PDCP) discard comprising:

discarding a PDCP SDU/PDU based upon a timer-based discard trigger; and

sending information on the SDU/PDU that has been discarded or cannot be transmitted or retransmitted;

52. The method of claim 50 wherein a PDCP Control PDU carries the information.

51. A method for packet data convergence protocol (PDCP) reordering or in-sequence delivery comprising:

receiving information on a packet that has been discarded or cannot be transmitted or retransmitted; and

submitting a previously buffered packet to upper layers without waiting for the packet indicated in the information.

53. The method of claim 51 wherein a PDCP Control PDU carries the information.

54. A method for packet data convergence protocol (PDCP) packet processing at the transmitter comprising:

receiving a packet from an upper layer; and

assigning a PDCP sequence number (SN) to the packet before inserting the packet into a PDCP transmit buffer.

55. A method for packet data convergence protocol (PDCP) packet processing at the transmitter comprising:

receiving a packet from an upper layer;

inserting the packet into a PDCP transmit buffer; and

assigning a PDCP sequence number (SN) to the packet after removing the packet from the PDCP transmit buffer.

56. A wireless transmit/receive unit (WTRU) configured to discard a packet data convergence protocol (PDCP) service data unit (SDU) or protocol data unit (PDU) comprising:

a PDCP entity configured to measure and check a time elapsed since a reference event occurred; and

the PDCP entity configured to discard a PDCP packet if the elapsed time reaches or exceeds a threshold, wherein the PDCP packet includes at least one service data unit (SDU) or protocol data unit (PDU).

57. The WTRU of claim 56 wherein the reference event is at least one of receiving a packet from an upper layer, storing a packet in a buffer, removing a packet from a buffer, sending a packet to a lower layer, or performing a PDCP procedure, PDCP function or PDCP action on a packet.

58. The WTRU of claim 56 further comprising a PDCP entity configured to send an indication of the discarded PDCP packet to a RLC entity.

59. The WTRU of claim 58 further comprising the RLC entity configured to discard a RLC packet corresponding to the indicated PDCP packet, wherein the RLC packet includes at least one service data unit (SDU) or protocol data unit (PDU).

60. A wireless transmit/receive unit (WTRU) configured to discard a packet data convergence protocol (PDCP) service data unit (SDU) or protocol data unit (PDU) comprising:

a PDCP entity configured to start a timer; and

the PDCP entity further configured to discard a PDCP packet upon expiration of the timer.

61. The WTRU of claim 60 wherein the PDCP packet includes at least one SDU or PDU.

62. The WTRU of claim 61 further comprising:

the PDCP entity configured to start the timer upon receiving a PDCP SDU from an upper layer.

63. The WTRU of claim 61 further comprising:

the PDCP entity configured to start the timer upon sending a PDCP PDU to a lower layer.

64. The WTRU of claim 61 wherein the PDCP entity is configured to start the timer upon the occurrence of at least one of receiving a packet from an upper layer, storing a packet in a buffer, removing a packet from a buffer, sending a packet to a lower layer, or performing a PDCP procedure, PDCP function or PDCP action on a packet.

65. The WTRU of claim 60 further comprising:

the PDCP entity further configured to send an indication of the discarded PDCP packet to a RLC entity.

66. The WTRU of claim 65 further comprising:

the RLC entity configured to discard an RLC packet corresponding to the discarded PDCP packet, wherein the RLC packet includes at least one service data unit (SDU) or protocol data unit (PDU).

67. The WTRU of claim 60 further comprising:

the PDCP entity configured to start a separate timer for every PDCP packet.

68. The WTRU of claim 60, wherein a threshold value of the timer is configured by another layer.

69. The WTRU of claim 60, wherein a threshold value of the timer is configured by radio resource control (RRC) layer.

70. The WTRU of claim 60, wherein a threshold value of the timer is configured on a per-radio bearer (RB) basis.

71. The WTRU of claim 60, wherein the timer and a radio link control (RLC) discard timer are coordinated.

72. A wireless transmit/receive unit (WTRU) configured to discard a packet data convergence protocol (PDCP) service data unit (SDU) or protocol data unit (PDU) comprising:

a transmitting PDCP entity configured to record or store a time of occurrence of a reference event; and

the transmitting PDCP entity further configured to discard a PDCP SDU/PDU if the difference between a current time and the recorded time reaches or exceeds a pre-configured time threshold.

73. The WTRU of claim 72 further comprising the transmitting PDCP entity configured to record or store the reference event wherein such reference event comprises at least one of a reception of a packet from an upper layer, a storing of a packet in a buffer, a removal of a packet from a buffer, a sending of a packet to a lower layer, or a performance of a PDCP procedure, PDCP function, or PDCP action on a packet.

74. The WTRU of claim 72 further comprising:

the transmitting PDCP entity configured to send an indication of the discarded PDCP SDU/PDU to a transmitting RLC entity.

75. The WTRU of claim 74 further comprising:

the transmitting RLC entity configured to discard an RLC SDU corresponding to the indicated PDCP SDU/PDU.

76. The WTRU of claim 72 further comprising:

a transmitting RLC entity configured to discard a RLC SDU corresponding to the PDCP SDU/PDU if the difference between a current time and the recorded time reaches or exceeds a pre-configured time threshold.

77. A wireless transmit/receive unit (WTRU) configured to discard a packet data convergence protocol (PDCP) service data unit (SDU) or protocol data unit (PDU) comprising:

a transmitting PDCP entity configured to associate a timestamp with a PDCP SDU upon its reception from upper layers;

the transmitting PDCP entity configured to store a time of reception from upper layers in the timestamp; and

the transmitting PDCP entity configured to discard the associated PDCP SDU/PDU if the difference between a current time and the timestamp reaches or exceeds a pre-configured time threshold.

78. A wireless transmit/receive unit (WTRU) configured to discard a packet data convergence protocol (PDCP) service data unit (SDU) or protocol data unit (PDU) comprising:

a transmitting PDCP entity configured to associate a timestamp with a PDCP SDU/PDU upon its sending to lower layers;

the transmitting PDCP entity configured to store a time of sending to the lower layers in the timestamp; and

the transmitting PDCP entity configured to discard the associated PDCP SDU/PDU if the difference between a current time and the timestamp reaches or exceeds a pre-configured time threshold.

79. A wireless transmit/receive unit (WTRU) configured to discard a radio link control (RLC) service data unit (SDU) or protocol data unit (PDU) comprising:

a RLC entity configured to set a timer using an initial value determined or signaled by a packet data convergence protocol (PDCP) entity; and

the RLC entity configured to discard a RLC SDU/PDU upon expiration of the timer.

80. The WTRU of claim 79, wherein the RLC entity is configured to set the timer upon receiving the RLC SDU from an upper layer.

81. A wireless transmit/receive unit configured to discard a radio link control (RLC) service data unit (SDU) or protocol data unit (PDU) comprising:

a RLC entity configured to record or store a time of occurrence of a reference event that is at least one of a packet data convergence protocol (PDCP) entity receiving a packet from an upper layer, the PDCP entity storing a packet in a buffer, the PDCP entity removing a packet from a buffer, or the PDCP entity performing a PDCP procedure, PDCP function, or PDCP action on a packet;

the RLC entity configured to discard a RLC SDU/PDU corresponding to the packet if the difference between a current time and the recorded time reaches or exceeds a pre-configured time threshold.

82. A wireless transmit/receive unit configured to discard a radio link control (RLC) service data unit (SDU) or protocol data unit (PDU) comprising:

an RLC entity configured to associate a timestamp with a RLC SDU upon its reception from upper layers;

the RLC entity configured to store a time of reception from upper layers in the timestamp; and

the RLC entity configured to discard the associated RLC SDU/PDU if the difference between the current time and the timestamp reaches or exceeds a time threshold wherein the threshold is determined or signaled by a PDCP entity.

84. The WTRU of claim 82 further comprising:

a RLC entity configured to initialize a second timer with the indicated value;

the RLC entity configured to start the second timer upon reception of a RLC SDU corresponding to the PDCP SDU/PDU from upper layers; and

the RLC entity configured to discard the RLC SDU corresponding to the PDCP SDU/PDU if the second timer expires.

83. A wireless transmit/receive unit (WTRU) configured to coordinate a packet data convergence protocol (PDCP) discard with a radio link control (RLC) discard comprising:

a transmitting PDCP entity configured to set a first timer upon reception of a PDCP SDU from upper layers;

the transmitting PDCP entity configured to buffer the PDCP SDU/PDU in a PDCP entity; and

the transmitting PDCP entity configured to send the PDCP SDU/PDU to lower layers for transmission with an indication of the time spent in the PDCP entity or an indication of the first timer'"'"'s value.

85. A wireless transmit/receive unit (WTRU) configured to coordinate a packet data convergence protocol (PDCP) discard with a radio link control (RLC) discard comprising:

a transmitting PDCP entity configured to associate a timestamp with a PDCP SDU upon its reception from upper layers;

the transmitting PDCP entity configured to store a time of reception from upper layers in the timestamp; and

the transmitting PDCP entity configured to send a PDCP PDU corresponding to the PDCP SDU to lower layers for transmission with a value of the timestamp.

86. The WTRU of claim 85 further comprising:

a RLC entity configured to receive a RLC SDU corresponding to the PDCP PDU;

the RLC entity configured to receive the timestamp value;

the RLC entity configured to check the timestamp value against a current time; and

the RLC entity configured to discard an associated RLC SDU/PDU if the difference between a current time and the timestamp value reaches or exceeds a pre-configured time threshold.

87. A wireless transmit/receive unit (WTRU) configured to coordinate a packet data convergence protocol (PDCP) discard with a radio link control (RLC) discard comprising:

a transmitting PDCP entity configured to determine whether to discard a packet based on a trigger event;

the transmitting PDCP entity configured to discard a packet; and

the transmitting PDCP entity configured to signal an indication of the discarded packet.

88. The WTRU of claim 87 further comprising:

a RLC entity configured to receive the indication of the discarded packet; and

RLC entity configured to discard a packet corresponding to the indicated discarded packet.

89. A wireless transmit/receive unit (WTRU) configured to discard packet data convergence protocol (PDCP) packets comprising:

a radio link control (RLC) entity configured to signal information via a primitive and its respective parameters; and

a transmitting PDCP entity configured to discard a PDCP service data unit (SDU) using the signaled information.

90. The WTRU of claim 89 wherein the RLC entity is configured to signal information that includes at least one of:

an identifier of the PDCP SDU to be discarded;

a discard signal for an SDU triggered by any RLC event;

a discard signal for an SDU triggered by an RLC SDU discard event;

a successful delivery notification indicating the delivery of the SDU to a peer RLC entity was successful based on information from the RLC automatic repeat request (ARQ) Status Reports or hybrid automatic repeat request (HARQ) acknowledgement (ACK)/nonacknowledgement (NACK) feedback;

or

a failed delivery notification/signal.

91. A wireless transmit/receive unit configured to perform radio link control (RLC) discard comprising:

a packet data convergence protocol (PDCP) entity configured to signal information via a primitive and its respective parameters; and

the RLC entity configured to discard a RLC service data unit (SDU) using the signaled information.

92. The WTRU of claim 91 wherein the information includes at least one of:

an identifier of the RLC SDU to be discarded;

a discard signal for an SDU triggered by any PDCP event;

a discard signal for an SDU triggered by a PDCP SDU discard event;

a discard signal for an SDU triggered by a PDCP SDU timer based discard event;

or

a discard signal for an SDU triggered by an acknowledgement (ACK) indication in a received PDCP Status Report.

93. A wireless transmit/receive unit (WTRU) configured to perform packet data convergence protocol (PDCP) discard comprising:

a transmitting PDCP entity configured to receive acknowledgement (ACK) or nonacknowledgement (NACK) information via receiving a PDCP status report; and

the transmitting PDCP entity configured to discard a PDCP SDU/PDU based on the received PDCP status report information.

94. A wireless transmit/receive unit (WTRU) configured to perform packet data convergence protocol (PDCP) discard comprising:

a transmitting PDCP entity configured to receive acknowledgement (ACK) or nonacknowledgement (NACK) information via receiving a PDCP status report; and

the transmitting PDCP entity configured to discard a PDCP SDU/PDU if an ACK indication for the PDCP SDU/PDU is received in the PDCP Status Report.

95. The WTRU of claim 94 further comprising:

the transmitting PDCP entity configured to send an indication of the discarded PDCP SDU/PDU to lower layers.

96. The WTRU of claim 95 further comprising:

the transmitting PDCP entity configured to discard an RLC SDU/PDU corresponding to the indicated PDCP SDU/PDU.

97. A wireless transmit/receive unit (WTRU) configured to perform packet data convergence protocol (PDCP) discard comprising:

a transmitting PDCP entity configured to discard a PDCP SDU/PDU based upon a timer-based discard trigger; and

the transmitting PDCP entity configured to send information on the SDU/PDU that has been discarded or cannot be transmitted or retransmitted.

99. The WTRU of claim 97 wherein a PDCP Control PDU carries the information.

98. A wireless transmit/receive unit (WTRU) configured to perform packet data convergence protocol (PDCP) reordering or in-sequence delivery comprising:

a receiving PDCP entity configured to receive information on a packet that has been discarded or cannot be transmitted or retransmitted; and

the receiving PDCP entity configured to submit a previously buffered packet to upper layers without waiting for the packet indicated in the information.

100. The WTRU of claim 98 wherein a PDCP Control PDU carries the information.

101. A wireless transmit/receive unit (WTRU) configured to perform packet data convergence protocol (PDCP) packet processing at the transmitter comprising:

a transmitting PDCP entity configured to receive a packet from an upper layer; and

the transmitting PDCP entity configured to assign a PDCP sequence number (SN) to the packet before inserting the packet into a PDCP transmit buffer.

102. A wireless transmit/receive unit (WTRU) configured to perform packet data convergence protocol (PDCP) packet processing at the transmitter comprising:

a transmitting PDCP entity configured to receive a packet from an upper layer;

the transmitting PDCP entity configured to insert the packet into a PDCP transmit buffer; and

the transmitting PDCP entity configured to assign a PDCP sequence number (SN) to the packet after removing the packet from the PDCP transmit buffer.