METHOD AND APPARATUS FOR ENHANCING RLC FOR FLEXIBLE RLC PDU SIZE

• US 20080212561A1
• Filed: 02/04/2008
• Published: 09/04/2008
• Est. Priority Date: 02/02/2007
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Marinier, Paul, Terry, Stephen E., Miller, James M., Pani, Diana, Grandhi, Sudheer A.
• Granted Patent: US 8,498,284 B2
• Time in Patent Office: Days
• US Class Current: 370/346
• CPC Class Codes: H04L 43/0882 Utilisation of link capacity
• CPC Class Codes: H04L 43/10 Active monitoring, e.g. heartbeat, ping or trace-route
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/225 Determination of shaping rate, e.g. using a moving window
• CPC Class Codes: H04L 47/27 Evaluation or update of window size, e.g. using information derived from acknowledged [ACK] packets
• CPC Class Codes: H04L 47/365 Dynamic adaptation of the packet size
• CPC Class Codes: H04W 28/0252 per individual bearer or channel dynamic wireless traffic scheduling H04W72/12
• CPC Class Codes: H04W 28/10 Flow control between communication endpoints
• CPC Class Codes: H04W 74/06 using polling
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]
• CPC Class Codes: H04W 92/12 between access points and access point controllers

Abstract

Enhancements are provided for the radio link control (RLC) protocol in wireless communication systems where variable RLC packet data unit (PDU) size is allowed. When flexible RLC PDU sizes are configured by upper layers, radio network controller (RNC)/Node B flow control, RLC flow control, status reporting and polling mechanisms are configured to use byte count based metrics in order to prevent possible buffer underflows in the Node B and buffer overflows in the RNC. The enhancements proposed herein for the RLC apply to both uplink and downlink communications.

Claims

1. A method for enhancing radio link control (RLC) operations in an RLC entity configured to support flexible packet data unit (PDU) size comprising defining and managing window size based on byte count based window size metrics.

2. The method of claim 1 wherein the defining and managing of window size is based on window size metrics that include at least one of a number of bytes and a number of blocks where each block is a fixed number of bytes.

3. The method of claim 2, wherein the defining and managing of window size is further based on packet data unit (PDU) sequence numbers.

4. The method of claim 1 further comprising including the window size metrics in RLC control and status PDUs.

5. The method of claim 1 further comprising:

receiving a maximum RLC PDU payload size from higher layers; and

inferring a maximum RLC PDU size from the maximum RLC PDU payload size.

6. The method of claim 1 further comprising receiving a maximum RLC PDU size from higher layers.

7. The method of claim 1 further comprising receiving and negotiating the byte count based window size metrics during at least one of setup, configuration and reconfiguration procedures for a radio bearer.

8. The method of claim 1 further comprising applying the byte based window size metrics in all messaging that updates a window for flow control during a connection.

9. The method of claim 8 wherein the applying the window size metrics in all messaging is such that the messaging includes at least one of a Window Size super-field (SUFI) and a Move Receiving Window (MRW) SUFI in RLC control and status PDUs.

10. The method of claim 1 wherein the RLC entity is operating in acknowledged mode (AM).

11. The method of claim 1 further comprising receiving radio bearer information elements from a radio resource control (RRC) entity including at least one of:

CHOICE Downlink RLC mode information including a new indicator for flexible RLC PDU size mode in addition to other RLC modes;

an information element indicating flexible RLC PDU size mode;

downlink RLC PDU size information indicating one of an RLC Scale parameter in octets or a maximum RLC PDU size in flexible RLC PDU size mode; and

protocol parameters signaled by the RRC including Poll_PDU, Poll_SDU, Configured_Tx_Window_Size, and Configured_Rx_Window_Size, wherein the protocol parameters are specified and interpreted in at least one of a number of PDUs and units of bytes.

12. The method of claim 11 further comprising:

receiving RLC PDUs for transmission; and

retaining the received RLC PDUs and not submitting them to lower layers when a window utilization exceeds a maximum window size in bytes or when a received RLC PDU sequence number exceeds a maximum window size in number of PDUs.

13. The method of claim 11 further comprising receiving from the RRC entity a Window Size super field (SUFI) referring to an octet quantity in an RLC STATUS PDU.

14. The method of claim 13 wherein the Window Size SUFI is specified in a number of PDUs further comprising deriving a window size in octets by multiplying the number of PDUs with an RLC scale parameter in octets.

15. The method of claim 13 wherein the Window Size SUFI is specified in units of bytes as a new SUFI WINDOW_BYTES with type, length and value components.

16. The method of claim 1 further comprising performing RLC flow control using byte count based metrics.

17. The method of claim 1 wherein the RLC entity is configured as an RLC transmission entity in a transmitter further comprising updating an RLC transmission window upon execution of an RLC transmission operation if one or more PDUs were positively acknowledged by a receiver, or if one or more PDUs were negatively acknowledged by the receiver as a result of the receiver exceeding a maximum number of retries, or as a result of a timer based discard in the transmitter.

18. The method of claim 17 wherein the updating an RLC transmission window includes:

removing one or more PDUs from a utilized transmission window and increasing a lower end of the utilized transmission window;

determining parameters;

TxWMAX equal to a length in bytes of a maximum window size;

TxWUTIL equal to one of a length in bytes of the utilized transmission window, or a length in bytes of packets that are acknowledged within a window bounded by transmission state variables V(A) and V(T);

TxL equal to one of a length in bytes of the one or more PDUs that are discarded due to RLC SDU discard procedure or a length in bytes due to reception of one or more acknowledgements; and

TxN equal to a length in bytes of a next one or more PDUs to be transmitted for the first time;

computing a window length (WL) quantity WL=TxWUTIL−

TxL+TxN; and

if WL is less than TxWMAX, transmitting the next one or more PDUs and increasing an upper end of the utilized transmission window.

19. The method of claim 1 wherein the RLC entity is configured as an RLC reception entity further comprising updating an RLC reception window upon execution of an RLC reception operation if the RLC reception entity receives one or more PDUs with sequence number following that of a last in-sequence PDU received or a Move Receiving Window (MRW) instruction from an RLC transmission entity.

20. The method of claim 19 wherein the updating an RLC reception window includes:

increasing a lower end of a utilized reception window;

determining parameters;

RxWMAX equal to a length in bytes of a maximum window size;

RxWUTIL equal to a length in bytes of the utilized reception window;

RxD equal to a length in bytes of one or more PDUs that are removed from the RLC reception window due to in-order reception; and

RxN equal to a length in bytes of a next one or more PDUs to be received for the first time;

computing a window length (WL) quantity WL=RxWUTIL+RxN-RxD; and

if WL is less than RxWMAX, receiving the next one or more PDUs and increasing an upper end of the utilized reception window.

21. The method of claim 1 further comprising creating RLC PDUs every interval of time by:

defining parameters;

Current_Credit equal to an amount of data that can be transmitted based on MAC link adaptation in an uplink, and a result of a remaining credit allocation plus a received new credit allocation in octets in a downlink;

Available_Data equal to data available to be transmitted in RLC PDU format in octets;

Leftover_Window equal to a length of a window bounded by state variables VT(S) and VT(MS) in an RLC transmitter represented in octets;

computing parameter;

X=Min{Current_Credit, Available_Data, Leftover_Window} wherein Min{•

}

returns a minimum value from a set; and

generating a PDU of length X.

22. The method of claim 21 further comprising:

defining parameters;

Maximum_RLC_PDU_size equal to a maximum RLC PDU size as configured by upper layers; and

Minimum_RLC_PDU_size equal to a parameter configured by the upper layers that specifies one of a minimum RLC PDU size or a minimum RLC PDU payload size; and

generating a PDU of size within the Minimum_RLC_PDU_size and Maximum_RLC_PDU_size.

23. A method of claim 22 further comprising:

computing parameters;

N=Floor{X/Maximum_RLC_PDU_size}; and

L=X mod Maximum_RLC_PDU_size, where Floor{•

} returns a nearest lower integer value and a mod b returns a modulo b division of a; and

generating N PDUs of length equal to Maximum_RLC_PDU_size.

24. The method of claim 23 further comprising:

generating another RLC PDU of length L if X is not equal to Leftover_Window or Current_Credit;

generating another RLC PDU of length L if X is equal to Leftover_Window or Current_Credit, and L is greater than Minimum_RLC_PDU_size or if X is equal to Available_Data; and

generating another RLC PDU of length Minimum_RLC_PDU size if X is equal to Leftover_Window or Current_Credit, and L is not greater than Minimum_RLC_PDU_size.

25. The method of claim 24 further comprising storing generated RLC PDUs in a buffer for transmission.

26. The method of claim 21 wherein the interval of time is defined by a multiple of 1 or more times a transmission time interval (TTI).

27. The method of claim 21 wherein the interval of time is defined by time instances when data is available for transmission or requested from lower layers.

28. The method of claim 21 wherein Maximum_RLC_PDU_size and Minimum_RLC_PDU_size are not configured by upper layers.

29. The method of claim 1 further comprising maintaining state variables wherein the state variables are specified and interpreted in terms of a number of PDUs and units of bytes.

30. The method of claim 29 wherein the RLC entity is configured as an RLC transmission entity comprising:

maintaining state variable Maximum_Tx_Window_Size representing a maximum transmission window size in octets;

updating state variable Maximum_Tx_Window_Size to an octet quantity specified by a Window Size superfield (SUFI) in a received RLC status PDU;

maintaining the following state variables;

send state variable VT(S), acknowledge state variable VT(A), maximum send state variable VT(MS), and transmission window size state variable VT(WS); and

updating the state variables VT(S), VT(A), VT(MS) and VT(WS) based on the state variable Maximum_Tx_Window_Size in octets.

31. The method of claim 29 wherein the RLC entity is configured as an RLC reception entity comprising:

maintaining state variable Maximum_Rx_Window_Size representing a maximum reception window size in octets;

receiving state variable Maximum_Rx_Window_Size from upper layers;

maintaining the following state variables;

receive state variable VR(R), highest expected state variable VR(H), and maximum acceptable receive state variable VR(MR); and

updating the state variables VR(R), VR(H), and VR(MR) based on the state variable Maximum_Rx_Window_Size in octets.

50. A wireless transmit/receive unit (WTRU) comprising an RLC entity configured to perform a method as in claim 1.

51. A Node B comprising an RLC entity configured to perform a method as in claim 1.

52. A radio network controller (RNC) comprising an RLC entity configured to perform a method as in claim 1.

32. A method for enhancing radio link control (RLC) operations in an RLC entity configured to support flexible packet data unit (PDU) size comprising defining and managing RLC polling mechanisms using byte count based metrics.

33. The method of claim 32 further comprising triggering a poll in an acknowledge mode data (AMD) PDU when a utilized window size in octets is greater than a system configured threshold in bytes.

34. The method of claim 32 further comprising triggering a poll in an AMD PDU each time a total amount of transmitted data exceeds a known pre-determined amount of octets or data blocks.

35. The method of claim 32 further comprising:

using a protocol parameter Poll_Window to poll a receiver when window-based polling is configured by upper layers; and

triggering a poll for each acknowledge mode data (AMD) PDU when a transmission window percentage K is greater than or equal to the Poll_Window, where K is the defined as;

K=utilized_window/Maximum_—

Tx_Window_Size in octets

where utilized_window is a length in octets of a window bounded by state variables VT(A) and VT(S).

36. The method of claim 32, wherein protocol parameters Poll_PDU and Poll_SDU are received at the RLC transmission entity from the upper layers to indicate a PDU count interval.

37. The method of claim 32 wherein a protocol parameter Poll_Bytes in octets is configured to indicate a byte count interval between polling further comprising:

maintaining by the RLC transmission entity a variable Poll_Octets counter of a total number of bytes transmitted in PDUs since transmission of a last PDU that triggered a polling request; and

when the Poll_Octets counter becomes greater than or equal to the value of Poll_Bytes, triggering by the RLC transmission entity a polling request in a PDU that makes the Poll_Octets counter exceed Poll_Bytes and resetting the Poll_Octets counter.

38. The method of claim 37 wherein the Poll_Octets counter counts a total number of bytes of a first transmission of each acknowledged mode data (AMD) PDU.

39. The method of claim 37 wherein the Poll_Octets counter counts a total number of bytes of all PDUs transmitted including retransmissions.

40. The method of claim 37 wherein triggering the polling request includes setting a polling bit in the PDU that makes the Poll_Octets counter exceed Poll_Bytes.

41. The method of claim 37 wherein triggering the polling request includes sending a POLL PDU to a receiver.

42. The method of claim 37 wherein the last PDU that triggered a polling request is due to a Poll_Bytes mechanism.

43. The method of claim 37 wherein the last PDU that triggered a polling request is due to Poll_PDU or Poll_SDU.

44. The method of claim 32 further comprising triggering a poll in an acknowledge mode data (AMD) PDU when a utilized window size in octets is greater than a system configured threshold percentage of a maximum window size.

45. The method of claim 32 further comprising triggering a status report when utilized receive window size is above a certain system configured threshold percentage of a maximum window size.

46. The method of claim 32 further comprising triggering a status report in an when a utilized receive window size in octets is greater than a system configured threshold in bytes.

47. The method of claim 32 wherein a Protocol parameter Poll_Window is received at an RLC transmission entity from upper layers further comprising:

using Poll_Window to poll a receiver when window-based polling is configured by upper layers; and

triggering a poll by the transmitter for each acknowledge mode data (AMD) PDU when a value J is greater than or equal to the Poll_Window, where J is the defined as;

$J=\frac{\left(4096+\mathrm{VT}<br><br>\left(S\right)+1-\mathrm{VT}<br><br>\left(A\right)\right)<br><br>\mathrm{mod}<br><br><br><br>4096}{\mathrm{VT}<br><br>\left(\mathrm{WS}\right)}\times <br><br>100$

where 4096 is a modulus for acknowledged mode (AM) and VT(S), VT(A) and VT(WS) are state variable.

48. The method of claim 47 further comprising:

triggering a poll for each AMD PDU when a value K is greater than or equal to the protocol parameter Poll_Window, where K is defined as;

$K=\frac{\mathrm{Sum}<br><br><br><br>\mathrm{of}<br><br><br><br>\mathrm{RLC}<br><br><br><br>\mathrm{PDU}<br><br><br><br>\mathrm{sizes}<br><br><br><br>\mathrm{from}<br><br><br><br>\mathrm{VT}<br><br>\left(A\right)<br><br><br><br>\mathrm{to}<br><br><br><br>\mathrm{VT}<br><br>\left(S\right)}{\mathrm{Maximum}<br><br><br><br>\mathrm{Transmit}<br><br><br><br>\mathrm{Window}<br><br><br><br>\mathrm{Size}}\times <br><br>100.$

49. The method of claim 47 wherein the protocol parameter Poll_Window is in terms of number of bytes, further comprising:

triggering a poll for each AMD PDU when a value K is greater than or equal to the protocol parameter Poll_Window, where K is defined as;

K=Sum of RLC PDU sizes from VT(A) to VT(S).

53. A wireless transmit/receive unit (WTRU) comprising an RLC entity configured to perform a method as in claim 32.

54. A Node B comprising an RLC entity configured to perform a method as in claim 32.

55. A radio network controller (RNC) comprising an RLC entity configured to perform a method as in claim 32.

56. A method for radio network controller (RNC)/Node B flow control of downlink data when flexible radio link control (RLC) packet data unit (PDU) size is supported comprising signaling credit allocations in bytes.

57. The method of claim 56 wherein the signaling of credit allocations in bytes includes adding to a frame information specifying a number of bytes of credit.

58. The method of claim 57 further comprising omitting from a frame information specifying a number of PDUs of credit.

59. The method of claim 56 occurring in a Node B.

60. A method for RNC/Node B flow control of downlink data when flexible radio link control (RLC) packet data unit (PDU) size is supported comprising receiving credit allocations in bytes.

61. The method of claim 60 wherein the receiving of credit allocations in bytes includes receiving a frame containing information specifying a number of bytes of credit.

62. The method of claim 60 further comprising storing a maximum size of PDU in bytes, wherein the receiving of credit allocations in bytes includes:

receiving a frame containing information specifying a number of PDUs of credit; and

multiplying the number of PDUs of credit by the maximum size of PDU in bytes.

63. The method of claim 60 further comprising:

storing a mapping of PDU SN to an associated length in bytes; and

transmitting PDUs without exceeding the received credit allocations.

64. The method of claim 60 occurring in an RNC.

65. The method of claim 64 wherein the RNC is a serving RNC (SRNC).

66. The method of claim 64 wherein the RNC is a drift RNC (DRNC).

67. A radio link control (RLC) entity configured to:

enhance RLC operations in order to support flexible packet data unit (PDU) size with a maximum RLC PDU size; and

define and manage window size based on byte count based window size metrics.

68. The RLC entity of claim 67 configured to define and manage window size based on window size metrics that include at least one of a number of bytes, and a number of blocks where each block is a fixed number of bytes.

69. The RLC entity of claim 68 configured to define and manage window size further based on packet data unit (PDU) sequence numbers.

70. The RLC entity of claim 67 further configured to include the window size metrics in RLC control and status PDUs.

71. The RLC entity of claim 67 further configured to:

receive a maximum RLC PDU payload size from higher layers; and

infer a maximum RLC PDU size from the maximum RLC PDU payload size.

72. The RLC entity of claim 67 further configured to receive a maximum RLC PDU size from higher layers.

73. The RLC entity of claim 67 further configured to receive and negotiate the byte count based window size metrics during at least one of setup, configuration and reconfiguration procedures for a radio bearer.

74. The RLC entity of claim 67 further configured to apply the byte based window size metrics in all messaging that updates a window for flow control during a connection.

75. The RLC entity of claim 74 configured to apply the window size metrics in all messaging such that the messaging includes at least one of a Window Size super-field (SUFI) and a Move Receiving Window (MRW) SUFI in RLC control and status PDUs.

76. The RLC entity of claim 67 further configured to operate in acknowledged mode (AM).

77. The RLC entity of claim 67 further configured to receive radio bearer information elements from a radio resource control (RRC) entity including at least one of:

CHOICE Downlink RLC mode information including a new indicator for flexible RLC PDU size mode in addition to other RLC modes;

an information element indicating flexible RLC PDU size mode;

downlink RLC PDU size information indicating one of an RLC Scale parameter in octets or a maximum RLC PDU size in flexible RLC PDU size mode; and

protocol parameters signaled by the RRC including Poll_PDU, Poll_SDU, Configured_Tx_Window_Size, and Configured_Rx_Window_Size, wherein the protocol parameters are specified and interpreted in at least one of a number of PDUs and units of bytes.

78. The RLC entity of claim 77 further configured to:

receive RLC PDUs for transmission; and

retain the received RLC PDUs and not submit them to lower layers when a window utilization exceeds a maximum window size in bytes or when a received RLC PDU sequence number exceeds a maximum window size in number of PDUs.

79. The RLC entity of claim 77 further configured to receive from the RRC entity a Window Size super field (SUFI) referring to an octet quantity in an RLC STATUS PDU.

80. The RLC entity of claim 79, wherein the Window Size SUFI is specified in a number of PDUs, further configured to derive a window size in octets by multiplying the number of PDUs with an RLC scale parameter in octets.

81. The RLC entity of claim 79 wherein the Window Size SUFI is specified in units of bytes as a new SUFI WINDOW_BYTES with type, length and value components.

82. The RLC entity of claim 67 further configured to perform RLC flow control using byte count based metrics.

83. The RLC entity of claim 67 configured as an RLC transmission entity in a transmitter further configured to update an RLC transmission window upon execution of an RLC transmission operation if one or more PDUs were positively acknowledged by a receiver, or if one or more PDUs were negatively acknowledged by the receiver as a result of the receiver exceeding a maximum number of retries, or as a result of a timer based discard in the transmitter.

84. The RLC entity of claim 83 configured to update an RLC transmission window by:

removing one or more PDUs from a utilized transmission window and increasing a lower end of the utilized transmission window;

determining parameters;

TxWMAX equal to a length in bytes of a maximum window size;

TxWUTIL equal to one of a length in bytes of the utilized transmission window, or a length in bytes of packets that are acknowledged within a window bounded by transmission state variables V(A) and V(T);

TxL equal to one of a length in bytes of the one or more PDUs that are discarded due to RLC SDU discard procedure or a length in bytes due to reception of one or more acknowledgements; and

TxN equal to a length in bytes of a next one or more PDUs to be transmitted for the first time;

computing a window length (WL) quantity WL=TxWUTIL—

TxL+TxN; and

if WL is less than TxWMAX, transmitting the next one or more PDUs and increasing an upper end of the utilized transmission window.

85. The RLC entity of claim 67 configured as an RLC reception entity further configured to update an RLC reception window upon execution of an RLC reception operation if one or more PDUs with sequence number following that of a last in-sequence PDU received or a Move Receiving Window (MRW) instruction from an RLC transmission entity are received.

86. The RLC entity of claim 85 configured to update an RLC reception window by:

increasing a lower end of a utilized reception window;

determining parameters;

RxWMAX equal to a length in bytes of a maximum window size;

RxWUTIL equal to a length in bytes of the utilized reception window;

RxD equal to a length in bytes of one or more PDUs that are removed from the RLC reception window due to in-order reception; and

RxN equal to a length in bytes of a next one or more PDUs to be received for the first time;

computing a window length (WL) quantity WL=RxWUTIL+RxN−

RxD; and

if WL is less than RxWMAX, receiving the next one or more PDUs and increasing an upper end of the utilized reception window.

87. The RLC entity of claim 67 further configured to create RLC PDUs every interval of time by:

defining parameters;

Current_Credit equal to an amount of data that can be transmitted based on MAC link adaptation in an uplink, and a result of a remaining credit allocation plus a received new credit allocation in octets in a downlink;

Available_Data equal to data available to be transmitted in RLC PDU format in octets;

Leftover_Window equal to a length of a window bounded by state variables VT(S) and VT(MS) in an RLC transmitter represented in octets;

computing parameter;

X=Min{Current_Credit, Available_Data, Leftover_Window} wherein Min{•

}

returns a minimum value from a set; and

generating a PDU of length X.

88. The RLC entity of claim 87 further configured to:

define parameters;

Maximum_RLC_PDU_size equal to a maximum RLC PDU size as configured by upper layers; and

Minimum_RLC_PDU_size equal to a parameter configured by the upper layers that specifies one of a minimum RLC PDU size or a minimum RLC PDU payload size; and

generate a PDU of size within the Minimum_RLC_PDU_size and Maximum_RLC_PDU_size.

89. The RLC entity of claim 88 further configured to:

compute parameters;

N=Floor{X/Maximum_RLC_PDU_size}; and

L=X mod Maximum_RLC_PDU_size, where Floor {•

} returns a nearest lower integer value and a mod b returns a modulo b division of a; and

generate N PDUs of length equal to Maximum_RLC_PDU_size.

90. The RLC entity of claim 89 further configured to:

generate another RLC PDU of length L if X is not equal to Leftover_Window or Current_Credit;

generate another RLC PDU of length L if X is equal to Leftover_Window or Current_Credit, and L is greater than Minimum_RLC_PDU_size or if X is equal to Available_Data; and

generate another RLC PDU of length Minimum_RLC_PDU size if X is equal to Leftover_Window or Current_Credit, and L is not greater than Minimum_RLC_PDU_size.

91. The RLC entity of claim 90 further configured to store generated RLC PDUs in a buffer for transmission.

92. The RLC entity of claim 89 wherein the interval of time is defined by a multiple of 1 or more times a transmission time interval (TTI).

93. The RLC entity of claim 89 wherein the interval of time is defined by time instances when data is available for transmission or requested from lower requested from lower layers.

94. The RLC entity of claim 89 wherein Maximum_RLC_PDU_size and Minimum_RLC_PDU_size are not configured by upper layers.

95. The RLC entity of claim 67 further configured to maintain state variables wherein the state variables are specified and interpreted in terms of a number of PDUs and units of bytes.

96. The RLC entity of claim 95 configured as an RLC transmission entity and further configured to:

maintain state variable Maximum_Tx_Window_Size representing a maximum transmission window size in octets;

update state variable Maximum_Tx_Window_Size to an octet quantity specified by a Window Size superfield (SUFI) in a received RLC status PDU;

maintain the following state variables;

send state variable VT(S), acknowledge state variable VT(A), maximum send state variable VT(MS), and transmission window size state variable VT(WS); and

update the state variables VT(S), VT(A), VT(MS) and VT(WS) based on the state variable Maximum_Tx_Window_Size in octets.

97. The RLC entity of claim 95 configured as an RLC reception entity and further configured to:

maintain state variable Maximum_Rx_Window_Size representing a maximum reception window size in octets;

receive state variable Maximum_Rx_Window_Size from upper layers;

maintain the following state variables;

receive state variable VR(R), highest expected state variable VR(H), and maximum acceptable receive state variable VR(MR); and

update the state variables VR(R), VR(H), and VR(MR) based on the state variable Maximum_Rx_Window_Size in octets.

116. A wireless transmit/receive unit (WTRU) comprising the RLC entity of claim 67.

117. A Node B comprising the RLC entity of claim 67.

118. A radio network controller (RNC) comprising the RLC entity of claim 67.

98. A radio link control (RLC) entity configured to:

enhance RLC operations in order to support flexible packet data unit (PDU) size with a maximum RLC PDU size; and

define and manage RLC polling mechanisms using byte count based metrics.

99. The RLC entity of claim 98 further configured to trigger a poll in an acknowledge mode data (AMD) PDU when a utilized window size in octets is greater than a system configured threshold in bytes.

100. The RLC entity of claim 98 further configured to trigger a poll in an AMD PDU each time a total amount of transmitted data exceeds a known pre-determined amount of octets or data blocks.

101. The RLC entity of claim 98 configured as an RLC transmission entity, further configured to:

using a protocol Poll_Window to poll a receiver when window-based polling is configured by upper layers; and

trigger a poll for each acknowledge mode data (AMD) PDU when a transmission window percentage K is greater than or equal to the Poll_Window, where K is the defined as;

K=utilized_window/Maximum_—

Tx_Window_Size in octets

where utilized_window is a length in octets of a window bounded by state variables VT(A) and VT(S).

102. The RLC entity of claim 98 further configured to receive protocol parameters Poll_PDU and Poll_SDU from the upper layers to indicate a PDU count interval.

103. The RLC entity of claim 98 configured to receive a protocol parameter Poll_Bytes in octets indicating byte count interval between polling, further configured to:

maintain a variable Poll_Octets counter of a total number of bytes transmitted in PDUs since transmission of a last PDU that triggered a polling request; and

when the Poll_Octets counter becomes greater than or equal to the value of Poll_Bytes, trigger a polling request in a PDU that makes the Poll_Octets counter exceed Poll_Bytes and resetting the Poll_Octets counter.

104. The RLC entity of claim 103 wherein the Poll_Octets counter counts a total number of bytes of a first transmission of each RLC acknowledged mode data (AMD) PDU.

105. The RLC entity of claim 103 wherein the Poll_Octets counter counts a total number of bytes of all PDUs transmitted including retransmissions

106. The RLC entity of claim 103 configured to trigger the polling request by setting a polling bit in the PDU that makes the Poll_Octets counter exceed Poll_Bytes.

107. The RLC entity of claim 103 configured to trigger the polling request by sending a POLL PDU to a receiver.

108. The RLC entity of claim 103 wherein the last PDU that triggered a polling request is due to a Poll_Bytes mechanism.

109. The RLC entity of claim 103 wherein the last PDU that triggered a polling request is due to Poll_PDU or Poll_SDU.

110. The RLC entity of claim 98 further configured to trigger a poll in an acknowledge mode data (AMD) PDU when a utilized window size in octets is greater than a system configured threshold percentage of a maximum window size.

111. The RLC entity of claim 98 further configured to trigger a status report when a utilized receive window size is above a certain system configured threshold percentage of a maximum window size.

112. The RLC entity of claim 98 further configured to trigger a status report when a utilized receive window size in octets is greater than a system configured threshold in bytes.

113. The RLC entity of claim 98 configured to receive a Protocol parameter Poll_Window from upper layers, further configured to:

use Poll_Window to poll a receiver when window-based polling is configured by upper layers; and

trigger a poll for each acknowledge mode data (AMD) PDU when a value J is greater than or equal to the Poll_Window, where J is the defined as;

$J=\frac{\left(4096+\mathrm{VT}<br><br>\left(S\right)+1-\mathrm{VT}<br><br>\left(A\right)\right)<br><br>\mathrm{mod}<br><br><br><br>4096}{\mathrm{VT}<br><br>\left(\mathrm{WS}\right)}\times <br><br>100$

where 4096 is a modulus for acknowledged mode (AM) and VT(S), VT(A) and VT(WS) are state variable.

114. The RLC entity of claim 113 further configured to:

trigger a poll for each AMD PDU when a value K is greater than or equal to the Poll_Window, where K is defined as;

$K=\frac{\mathrm{Sum}<br><br><br><br>\mathrm{of}<br><br><br><br>\mathrm{RLC}<br><br><br><br>\mathrm{PDU}<br><br><br><br>\mathrm{sizes}<br><br><br><br>\mathrm{from}<br><br><br><br>\mathrm{VT}<br><br>\left(A\right)<br><br><br><br>\mathrm{to}<br><br><br><br>\mathrm{VT}<br><br>\left(S\right)}{\mathrm{Maximum}<br><br><br><br>\mathrm{Transmit}<br><br><br><br>\mathrm{Window}<br><br><br><br>\mathrm{Size}}\times <br><br>100.$

115. The RLC entity of claim 113 wherein the protocol parameter Poll_Window is in terms of number of bytes, further configured to:

trigger a poll for each AMD PDU when a value K is greater than or equal to the protocol parameter Poll_Window, where K is defined as;

K=Sum of RLC PDU sizes from VT(A) to VT(S).

119. A wireless transmit/receive unit (WTRU) comprising the RLC entity of claim 98.

120. A Node B comprising the RLC entity of claim 98.

121. A radio network controller (RNC) comprising the RLC entity of claim 98.

122. A radio link control (RLC) entity configured to:

perform radio network controller (RNC)/Node B flow control of downlink data when flexible radio link control (RLC) packet data unit (PDU) size is supported; and

signal credit allocations in bytes.

123. The RLC entity of claim 122 configured to signal credit allocations in bytes by adding to a frame information specifying a number of bytes of credit.

124. The RLC entity of claim 123 further configured to omit from a frame information specifying a number of PDUs of credit.

125. A Node B comprising the RLC entity of claim 122.

126. A radio link control (RLC) entity configured to:

perform RNC/Node B flow control of downlink data when flexible radio link control (RLC) packet data unit (PDU) size is supported; and

receive credit allocations in bytes.

127. The RLC entity of claim 126 configured to receive credit allocations in bytes by receiving a frame containing information specifying a number of bytes of credit.

128. The RLC entity of claim 126 further configured to:

store a maximum size of PDU in bytes;

receive a frame containing information specifying a number of PDUs of credit; and

multiply the number of PDUs of credit by the maximum size of PDU in bytes.

129. The RLC entity of claim 126 further configured to:

store a mapping of PDU SN to an associated length in bytes; and

transmit PDUs without exceeding the received credit allocations.

130. A radio network controller (RNC) comprising the RLC entity of claim 126.

131. The RNC of claim 130 configured as a serving RNC (SRNC).

132. The RNC of claim 130 configured as a drift RNC (DRNC).