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EDCF Access Categories

EDCF Access Categories. Menzo Wentink, Intersil; Sunghyun Choi, Javier del Prado, Sai Shankar Philips Research USA; Atul Garg, Philips Semiconductors mwentink@intersil.com and sunghyun.choi@philips.com. Introduction.

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EDCF Access Categories

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  1. EDCF Access Categories Menzo Wentink, Intersil; Sunghyun Choi, Javier del Prado, Sai Shankar Philips Research USA; Atul Garg, Philips Semiconductors mwentink@intersil.com and sunghyun.choi@philips.com M.M. Wentink, Intersil & S. Choi, Philips

  2. Introduction Priority, Priority Parameter, Delivery Priority, TCs, Queues and EDCF Parameters M.M. Wentink, Intersil & S. Choi, Philips

  3. Status as of 802.11e/D1.3 (1) • Priority parameter = TC (from 0 to 15) • provided in the MA-UNIDATA.request • Priority (from 0 to 7) • extracted from the Priority Parameter • indirectly in the Delivery Priority of the TSPEC • Delivery Priority (from 0 to 7) • mapped from Priority using dot11PriorityMapping M.M. Wentink, Intersil & S. Choi, Philips

  4. Status as of 802.11e/D1.3 (2) 16 Priority Parameters or TCs 8 Priorities 8 Delivery Priorities <= 8 Physical Queues EDCF Parameters (AIFS, CWmin,…) M1 M2 M3 M.M. Wentink, Intersil & S. Choi, Philips

  5. Status as of 802.11e/D1.3 (2) • Mapping M1 using table dot11PriorityMapping • Mapping M2 not specified • Mapping M3 between access parameters (i.e., AIFS[i], Cwmin[i], PF[i]) and queues is currently problematic • this was noted earlier by Sunghyun Choi • see next slides! • more details about the problems can be found in submissions by Choi, et al. (01/534) and Wentink (01/541) • the solution outlined in this proposal supersedes the solutions in the above mentioned documents M.M. Wentink, Intersil & S. Choi, Philips

  6. Problematic Descriptions in D1.3 • 9.1.3.1: • “An ESTA or EAP may implement fewer than 8 physical queues and shall provide a mapping from traffic categories and delivery priorities to the available queues by means of the dot11PriorityMapping table in the MAC MIB.” • 9.2.3.4: • “An ESTA that provides fewer than 8 output queues shall use the TxAIFS [TC] slot boundary for queue [i] where TC is the highest priority TC assigned to queue [i]. • What happens if an ESTA has only one queue? • All frames will be served using TC=7 AIFS !!! • This does not sound reasonable at all !!! M.M. Wentink, Intersil & S. Choi, Philips

  7. Problematic Descriptions in D1.3 • 9.2.4: • The enumeration of implemented queues determines which access parameters should be used: “queue i uses CWmin[i]" • 9.2.3.4: • “An ESTA that provides fewer than 8 output queues shall use the TxAIFS [TC] slot boundary for queue [i] where TC is the highest priority TC assigned to queue [i]. • So which access parameters should be used for queue i when there are <8 queues? M.M. Wentink, Intersil & S. Choi, Philips

  8. Proposed Solution M.M. Wentink, Intersil & S. Choi, Philips

  9. Proposed Solution (1) • Delete the concept of Delivery Priority • confusing with Priority • doesn’t appear to have any use in the draft • Introduce the concept of Access Category (AC) • an Access Category represents a single virtual DCF • Let 4 ACs be normative, for EAP and ESTA • in absence of certain types of traffic, the corresponding queue does not have to be implemented • i.e. no burden on dedicated application terminals, like phones • Note 4 ACs does not limit the number of queues to 4. M.M. Wentink, Intersil & S. Choi, Philips

  10. Proposed Solution (2) • Simplify M1 and M2 into one unique mapping M0: • see tables on next slides Priority Access Category M0 • Let the QoS Parameter Set element contain 4 sets of access parameters • M3is now a trivial one-to-one mapping between access parameters and ACs M.M. Wentink, Intersil & S. Choi, Philips

  11. Proposed Solution (3) 16 Priority Parameters or TCs 8 Priorities M0 4 ACs (↔ 4x EDCF parameters) M.M. Wentink, Intersil & S. Choi, Philips

  12. Proposed Solution – M0 • Priority to Access Category mapping, alt. II • dedicated AC for voice, video • no ‘lower-than-best-effort’ AC, but this does not exclude a ‘lower-than-best-effort’ priority. bk = background sp = spare be = best effort ee = excellent effort vi = video cl = controlled load vo = voice nc = network control M.M. Wentink, Intersil & S. Choi, Philips

  13. Normative Text Changes and Motion M.M. Wentink, Intersil & S. Choi, Philips

  14. To clause 3, add the following definition: Access Category (AC) • An enhanced variant of the DCF that contends for TXOPs using one set of EDCF channel access parameters from the QoS Parameter Set element in the beacon. Each ESTA shall contain four ACs. Collisions between contending ACs within an ESTA are resolved within the ESTA such that the higher AC receives the TXOP and the lower colliding AC(s) behave as if there were an external collision on the WM. M.M. Wentink, Intersil & S. Choi, Philips

  15. Replace 3.57 with: • 3.57 enhanced access point (EAP) • An access point (AP) that implements the access point functionality required for the QoS facility. An EAP differentiates among 8 traffic categories within the traffic to/from each associated ESTA, provides at least 4 access categoriestransmit queuesfor differing priorities or other categories of QoS traffic, and supports the hybrid coordination function (HCF). M.M. Wentink, Intersil & S. Choi, Philips

  16. Revise 6.1.1.1 as follows: • 6.1.1.1 Interpretation of priority • replace delivery category with access category • add: The default dot11PriorityMapping is: M.M. Wentink, Intersil & S. Choi, Philips

  17. Revise 6.1.1.2 as follows: second paragraph: • Priority parameter and TCID field values 0 through 7 are interpreted as delivery priorities. Outgoing MSDUs with priority values 0 through 7 are handled by MAC entities at ESTAs in accordance with thecorresponding access category local significance of the specified delivery priority, and use the current, local default values for all other QoS parameters. third paragraph: • replace delivery priority with priority M.M. Wentink, Intersil & S. Choi, Philips

  18. Revise 7.3.2.14 as follows: • 7.3.2.14 QoS Parameter Set element • Replace TC with AC • Replace traffic category(ies) with access category(ies) • Replace 8 with 4 • Replace 7 with 3 M.M. Wentink, Intersil & S. Choi, Philips

  19. Revise 9.1.3.1 as follows: M.M. Wentink, Intersil & S. Choi, Philips

  20. Revise 9.2.3.4 as follows: change first part of the paragraph: • The Arbitration Interframe Space shall be used by ESTAs to transmit Data type frames (MPDUs) and Management type frames (MMPDUs). An ESTA using the EDCF shall obtain a TXOP for a particular queue access category i if the ESTA's carrier sense mechanism (see 9.2.1) determines that the medium is idle at the TxAIFS[i] slot boundary (see 9.2.10) after a correctly-received frame, and the backoff time for access category queue i has expired. An ESTA that provides fewer than 8 output queues shall use the TxAIFS[TC] slot boundary for queue[i] where TC is the highest priority TC assigned to queue[i]. replace “[TC]” with “[AC]”. M.M. Wentink, Intersil & S. Choi, Philips

  21. Other revisions: replace queue(s) with access category(ies), in clauses • 9.2.4 Random backoff time • 9.2.5.1 Basic access • 9.2.5.2 Backoff procedure • 9.2.5.3 Recovery procedures and retransmit limits • 9.2.5.4 Setting and resetting the NAV replace ‘7’ with ‘3’ in clauses • 9.10 HCF • Annex D M.M. Wentink, Intersil & S. Choi, Philips

  22. Motion • Move to empower the TGe editor to incorporate the concept of access categories, based on normative text changes as suggested on slides 14 - 21 of document 01/565r1, and by changing wording in the TGe draft as may be necessary to make the revised TGe draft consistent with the above changes. M.M. Wentink, Intersil & S. Choi, Philips

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