Method for a simple 802.11e HCF implementation

• US 20040184475A1
• Filed: 03/21/2003
• Published: 09/23/2004
• Est. Priority Date: 03/21/2003
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Meier, Robert
• Granted Patent: US 7,801,092 B2
• Time in Patent Office: Days
• US Class Current: 370/449
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 74/06 using polling
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A Hybrid Coordination Function (HCF) implementation wherein an access point'"'"'s existing (E)DCF transmit queues are augmented by at least one strict priority HCF transmit queue. The HCF queues are only used to schedule downlink data and CF-Poll transmissions are used for admitted downlink flows and for uplink flows. The 802.1D user priority value is used to select the HCF queue for an admitted flow. The strict priority HCF transmit queues are always serviced first, in priority order before any other (E)DCF transmit queue. The channel is considered busy to (E)DCF transmit queues while the strict priority queues are being serviced. An admissions control mechanism is used to control data flows and prevents the strict priority traffic from starving (E)DCF traffic. A single, simple AP scheduler is used for scheduling both polling times and station wakeup times.

Claims

1. A method for controlling channel access by an access point, the steps comprising:

creating a strict priority queue, the strict priority queue is used to queue at least one of a poll and a data transmission;

inserting at least one of a poll and a data transmission into the strict priority queue; and

servicing the strict priority queue prior to servicing a (E)DCF transmit queues.

2. The method of claim 1 wherein the access point is an 802.11 access point.

3. The method of claim 1 wherein the strict priority queue is a first in first out queue.

4. The method of claim 1, the steps further comprising assigning a fixed size to all transmission opportunities.

5. The method of claim 1 wherein the creating step creates multiple strict priorities queues, wherein each queue is mapped to a specific traffic class.

6. The method of claim 5 wherein the traffic class is at least one selected from the group consisting of a voice management queue and a network management queue.

7. The method of claim 5 wherein at least one strict priority queue receives only a set of admitted frames that are subject to admission control, wherein the set of admitted frames that are subject to admission control is established in the access point via a signaling protocol.

8. The method of claim 1 further comprising binding an egress quality of service classifier by the access point to a target MAC address of an 802.11 station with an admitted traffic stream, and identifying downlink frames for the admitted traffic stream by the access point.

9. The method of claim 8 wherein the egress quality of service classifier comprises at least one of the group consisting of an internet protocol address, an internet protocol type, and a UDP/TCP protocol port identifier that uniquely identify an application traffic stream.

10. The method of claim 9 wherein the egress quality of service classifier parameters are obtained by a quality of service signaling protocol.

11. The method of claim 9 wherein egress quality of service classifier parameters are automatically derived by the access point.

12. The method of claim 11 further comprising snooping the data packets by the access point to derive the egress quality of service classifier parameters.

13. The method of claim 6 further comprising determining a traffic class for a traffic stream by a quality of service signaling protocol.

14. The method of claim 1 further comprising establishing a periodic polling schedule for a station, and placing a poll in a strict priority transmit queue at each scheduled polling period.

15. The method of claim 1 further comprising

establishing a wakeup schedule for a power-save station, wherein the wakeup schedule coincides with the power station'"'"'s polling schedule;

transferring active frames buffered for the station to an active transmit queue after a scheduled wakeup time; and

indicating to the power-save station when data transfer is completed.

16. The method of claim 15 further comprising sending a poll frame to the power save station following a scheduled wakeup time, wherein the poll frame contains a field to inform the power-save station when there are buffered frames waiting to be transferred.

17. The method of claim 15 further comprising sending a data frame to the power-save station with a field indicating when there are more queued frames.

18. The method of claim 14 wherein polling times are scheduled to minimize at least one of latency and contention.

19. The method of claim 18 wherein the polling times are scheduled distinct from beacon transmissions.

20. The method of claim 18 wherein polling times are scheduled to minimize a time period the station must be awake.

21. The method of claim 14, the establishing step further comprising synchronizing the polling schedule with a standard 802.11 timer synchronization function.

22. The method of claim 14 wherein the polling schedule comprises a start time and an inter-poll period, wherein the start time is a timer synchronization function timer value and the inter-poll period is an integral multiple of timer synchronization function time units.

23. The method of claim 15 wherein the establishing step further comprises synchronizing the wakeup schedule for the power-save station to a standard 802.11 timer synchronization function timer.

24. The method of claim 23 further comprising defining a service schedule by a start time and an inter-service period, wherein the start time is a timer synchronization function timer value and the inter-poll period is an integral multiple of timer synchronization function time units.

25. The method of claim 15, the establishing step further comprising receiving polling requirements via a signaling protocol.

26. The method of claim 25, the establishing step further comprising establishing a service schedule based on a timer wheel, the timer wheel comprising clock ticks that are an integral of a timer synchronization function time unit, each clock tick comprising a bucket, the bucket comprising a linked list with an entry for each station to be served at the corresponding clock tick.

27. The method of claim 14, the establishing step further comprising receiving polling requirements via a signaling protocol.

28. The method of claim 27, the establishing step further comprising establishing a service schedule based on a timer wheel, the timer wheel comprising clock ticks that are an integral of a timer synchronization function time unit, each clock tick comprising a bucket, the bucket comprising a linked list with an entry for each station to be served at the corresponding clock tick.

29. The method of claim 15 further comprising sending a downlink data transmission queued in the transmit queue, the downlink data transmission comprising a buffered frame and a poll.

30. The method of claim 29 wherein the station is an interactive voice station.

31. The method of claim 14 further comprising sending a downlink data transmission queued in the transmit queue, the downlink data transmission comprising a buffered frame and a poll.

32. The method of claim 31 wherein the station is an interactive voice station.

33. The method of claim 1 wherein the strict priority queue is only used for data and poll frames for an admitted interactive voice stream and network management traffic.

34. A method for controlling access by an access point, the steps comprising

allocating a fixed transmission window to a target station, the transmission window of sufficient size to enable the target station to send a queued frame in response to a poll;

establishing a polling schedule;

allocating a maximum amount of uplink data based on an application data rate; and

polling the station according to the polling schedule when the uplink data sent by the target station does not exceed an admitted data rate.

35. The method of claim 34, the polling step further comprising transmitting a poll, the poll comprising a duration field, wherein the duration field is set to the fixed transmission window.

36. The method of claim 34 further comprising sending a frame to reduce the channel reservation when the access point does not receive an expected response from the target station.

37. The method of claim 34 further comprising reclaiming a channel by the access point when the access point does not receive an expected response from the target station.

38. The method of claim 34 wherein:

the allocating step further comprises allocating a token bucket for a data stream with a predetermined number of tokens, wherein the sum of the tokens represent a maximum allowed burst for the data stream; and

the polling step further comprises;

adding a token to the token bucket each time a service timer for the data stream expires, and

removing tokens from the token bucket each time a data frame is successfully transferred.

39. The method of claim 38 wherein the polling step is suspended when the token bucket has no tokens.

40. The method of claim 38 wherein downlink frames are not queued in a strict priority queue when the token bucket has no tokens.

41. The method of claim 38 wherein the data stream is selected from the group consisting of an uplink data stream and a downlink data stream.

42. A method for controlling channel access by an 802.11 access point, the steps comprising:

creating a strict priority queue, the strict priority queue is used to queue at least one of a poll and a data transmission;

assigning a fixed size to all transmission opportunities;

inserting at least one of a poll and a data transmission into the strict priority queue;

establishing a periodic polling schedule for a station, and placing a poll in a strict priority transmit queue at each scheduled polling period; and

servicing the strict priority queue prior to servicing a (E)DCF transmit queues;

wherein the strict priority queue is a first in first out queue;

wherein the strict priority queue receives frames that are subject to admission control, wherein the frames that are subject to admission control is established in the access point via a signaling protocol.

43. The method of claim 42 further comprising

establishing a wakeup schedule for a power-save station, wherein the wakeup schedule coincides with the power station'"'"'s polling schedule;

transferring active frames buffered for the station to an active transmit queue after a scheduled wakeup time; and

indicating to the power-save station when data transfer is completed.

44. The method of claim 43 further comprising sending a poll frame to the power save station following a scheduled wakeup time, wherein the poll frame contains a field to inform the power-save station when there are buffered frames waiting to be transferred.

45. The method of claim 43 further comprising sending a data frame to the power-save station with a field indicating when there are more queued frames.

46. The method of claim 42 wherein polling times are scheduled to minimize at least one of latency and contention.

47. The method of claim 46 wherein the polling times are scheduled distinct from beacon transmissions.

48. The method of claim 46 wherein polling times are scheduled to minimize a time period the station must be awake.

49. The method of claim 42, the establishing step further comprising synchronizing the polling schedule with a standard 802.11 timer synchronization function.

50. The method of claim 42 wherein the polling schedule comprises a start time and an inter-poll period, wherein the start time is a timer synchronization function timer value and the inter-poll period is an integral multiple of timer synchronization function time units.

51. The method of claim 43 wherein the establishing step further comprises synchronizing the wakeup schedule for the power-save station to a standard 802.11 timer synchronization function timer.

52. The method of claim 51 further comprising defining a service schedule by a start time and an inter-service period, wherein the start time is a timer synchronization function timer value and the inter-service period is an integral multiple of timer synchronization function time units.

53. The method of claim 43, the establishing step further comprising receiving polling requirements via a signaling protocol.

54. The method of claim 53, the establishing step further comprising establishing a service schedule based on a timer wheel, the timer wheel comprising clock ticks that are an integral of a timer synchronization function time unit, each clock tick comprising a bucket, the bucket comprising a linked list with an entry for each station to be served at the corresponding clock tick.

55. The method of claim 54, the establishing step further comprising receiving polling requirements via a signaling protocol.

56. The method of claim 55, the establishing step further comprising establishing a service schedule based on a timer wheel, the timer wheel comprising clock ticks that are an integral of a timer synchronization function time unit, each clock tick comprising a bucket, the bucket comprising a linked list with an entry for each station to be served at the corresponding clock tick.

57. The method of claim 42 wherein the signaling protocol comprises allocating a token bucket for a data stream with a predetermined number of tokens where the sum of the tokens represent a maximum allowed burst for the data stream;

and the admission control comprises

adding a token to the token bucket each time the timer expires and where the number of tokens corresponds to the mean data rate, and

removing tokens from the token bucket each time a data frame is successfully transferred.

58. The method of claim 57 wherein the servicing step is suspended when the token bucket has no tokens.

59. The method of claim 57 wherein downlink frames are not queued in a strict priority queue when the token bucket has no tokens.

60. The method of claim 57 wherein the data stream is selected from the group consisting of an uplink data stream and a downlink data stream.