1. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 1 March 2002 CC/RR Alternatives HCF Adhoc Discussion Work Sheet V00.04 Bobby Jose, et.al bobby@ieee.org

2. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 2 March 2002 Outline CC/RR objections/concerns Changes Solution 1 Solution 2 Solution 3

3. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 3 March 2002 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.

4. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 4 March 2002 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.

5. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 5 March 2002 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.

6. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 6 March 2002 CC Frame octets: 226112*FbCount4 Frame Control Dur/IDBSSIDCCI Length Feed-back Count Feedback AID (2 octets) FCS Priority Mask Field Removed, AID Feedback

7. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 7 March 2002 RR Frame (option1) octets: 226 28 4 Frame Control Dur/IDBSSID AID/ C/S TXOP Req FCS MAC Header B0 to B10B11B12 to B15 AID (1-2007) rsrvC/S 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

8. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 8 March 2002 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. octets: 2262N*24 Frame Control Dur/IDBSSID AID/N TXOP Req FCS MAC Header

9. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 9 March 2002 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.

10. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 10 March 2002 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). octets: 2266N*24 Frame Control Dur/IDBSSID TATXOP Req FCS MAC Header

11. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 11 March 2002 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. octets: 11112*N QoS (category 1) TXOP Req (action 3) 00TXOP Req

12. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 12 March 2002 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.

13. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 13 March 2002 CC Format octets: 22614 Frame Control Dur/IDBSSIDCTOPFCS MAC Header CTOP Units of 128 us Duration value may be set to 0 or CTOP Prioritization Complicated

14. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 14 March 2002 RR Contention Opportunity

15. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 15 March 2002 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).

16. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 16 March 2002 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.

17. doc.: IEEE 802.11-02/289r0 Submission Bobby Jose,Slide 17 March 2002 References 1.Various Comments to Ballot 30, TGE 2.01/151,CC/RR Model and Simulations,Wei Lin, Mathew Sherman,AT&T. 3.01/223r1,CC/RR Performance Evaluation – Revisited, Javier del Prado and Sunghyun Choi,Philips Research. 4.02/248,Contention Free TXOP Request and Allocation Issues, Bobby.