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CC/RR Alternatives HCF Adhoc Discussion Work Sheet V00.04

CC/RR Alternatives HCF Adhoc Discussion Work Sheet V00.04. Bobby Jose, et.al bobby@ieee.org. Outline. CC/RR objections/concerns Changes Solution 1 Solution 2 Solution 3. Issues. Key objections can be classified as follows[1]. EDCF is sufficient for reservation requests.

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CC/RR Alternatives HCF Adhoc Discussion Work Sheet V00.04

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  1. CC/RR AlternativesHCF Adhoc Discussion Work Sheet V00.04 Bobby Jose, et.al bobby@ieee.org Bobby Jose,

  2. Outline • CC/RR objections/concerns • Changes • Solution 1 • Solution 2 • Solution 3 Bobby Jose,

  3. Issues Key objections can be classified as follows[1]. • EDCF is sufficient for reservation requests. • EDCF is sufficient for many cases, however there are situations in which DCF is loaded, and higher priority access is needed. • Complexity (Requiring New Hardware) • Overhead of current mechanism. Bobby Jose,

  4. Changes • Support multiple traffic per RR • Min required CCOP per DTIM is now a MIB variable which may be set to zero • Allow RR to be transmitted during any TXOP not just as a response to CC • Change the access mechanism from slotted access to (E)DCF (TBD: performance analysis). • Allow controlled contention to be scheduled ( time based), allowing for software implementation, increased robustness. Bobby Jose,

  5. Solution1 • Retain current slotted access of CC/RR • Allow multiple traffic categories in RR- fixed size RR in response to CC (only 8 traffic tc or ts, not both or allow all 16). • Allow RR to be transmitted during any TXOP • No immediate ack for RR, acknowledgement through CC. • Min CCOP a MIB variable which may be set to 0 by the HC. Bobby Jose,

  6. octets: 2 2 6 1 1 2*FbCount 4 FrameControl Dur/ID BSSID CCILength Feed-backCount FeedbackAID(2 octets) FCS CC Frame Priority Mask Field Removed, AID Feedback Bobby Jose,

  7. B0 to B10 octets: 2 2 6 B11 2 B12 to B15 8 4 AID(1-2007) rsrv C/S Frame Control Dur/ID BSSID AID/ C/S TXOP Req FCS MAC Header RR Frame (option1) Based on HCF adhoc resolutions, each byte indicates TXOP request per tc or ts, 4 bits to choose ( a bit for each two bytes). Other options considered : to have either TS or TC in the same packet Bobby Jose,

  8. octets: 2 2 6 2 N*2 4 Frame Control Dur/ID BSSID AID/N TXOP Req FCS MAC Header RR Frame (option2)  N = aNumTIDPerRR ( MIB) variable, or choose a value 4, 8, 16 and keep fixed, when RR is transmitted in a CCOP. N chosen by sender when RR transmitted otherwise. TXOP request consist of N QOS control fields, N can be found from length. Keeps QOS control field based request and RR based request uniform. Retain special semantics of values in QOS control field. Supporting FEC for RR frames. Bobby Jose,

  9. Solution 2 • Remove CC/RR. • TXOP Reservation Requests transmitted using a new mgmt frame with immediate ack. variable size, include upto 16 traffic types. • TXOP Request Frame may be sent during any TXOP. • Highest priority using EDCF. Bobby Jose,

  10. octets: 2 2 6 6 N*2 4 Frame Control Dur/ID BSSID TA TXOP Req FCS MAC Header TXOP Req Frame (option1) Use Control Frame RR,  TA field introduced, TXOP Req consists of N QOS Control Fields N derived from length. No need for sequence control, contents are cumulative in nature. Supporting FEC (TBD) . Bobby Jose,

  11. octets: 1 1 1 1 2*N QoS(category1) TXOPReq(action 3) 0 0 TXOP Req TXOP Req Frame (option2) Use Management Information Element or Action TXOP Req consists of N QOS Control Fields N derived from length. AID derived from SA. Bobby Jose,

  12. Solution 3 • Instead of the slotted access scheme, use (E)DCF as the access scheme for contention among RR’s in the controlled contention period (Contention Opportunity) created by the CC. • This allows for an (E)DCF contention period in the CFP during which only stations with TXOP request contend for channel. • New TXOP request frame with immediate acknowledgement. (variable length). • PIFS and a small backoff may be used • Note: PIFS access may be yielded by HC for a well defined period. Bobby Jose,

  13. octets: 2 2 6 1 4 FrameControl Dur/ID BSSID CTOP FCS MAC Header CC Format CTOP Units of 128 us Duration value may be set to 0 or CTOP Prioritization Complicated Bobby Jose,

  14. RR Contention Opportunity Bobby Jose,

  15. Issues • PIFS access/Back off Values (CW) • NAV Rules • Performance/Choosing CTOP duration. • Overlapping Subnets • Loss of CC -> Lost of CTOP (Same Problem exists for Slotted Access). Bobby Jose,

  16. Solution 3a • TXOP Request Controlled Contention period is defined as an offset from TBTT. • Signaled through action frame with countdown (increased robustness). • Preferred location just before cf end in a cfp. • PIFS access and smaller backoff may be used during this period. • New (variable size) frame for TXOP request. • Implement using software, existing hardware. Bobby Jose,

  17. References • Various Comments to Ballot 30, TGE • 01/151,CC/RR Model and Simulations,Wei Lin, Mathew Sherman,AT&T. • 01/223r1,CC/RR Performance Evaluation – Revisited, Javier del Prado and Sunghyun Choi ,Philips Research. • 02/248,Contention Free TXOP Request and Allocation Issues, Bobby. Bobby Jose,

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