Multiple Frame Exchanges during EDCF TXOP

1. Multiple Frame Exchanges during EDCF TXOP Sunghyun Choi1, Javier del Prado1, Atul Garg1, Maarten Hoeben3, Stefan Mangold2, Sai Shankar1, and Menzo Wentink3 Philips1, Aachen University2, and Intersil3 sunghyun.choi@philips.com and mwentink@intersil.com S. Choi, Philips & M.M. Wentink, Intersil

2. Problem Statement • Per 802.11e/D2.0, it is clear that one cannot have multiple frame (i.e., MSDU) exchanges during a non-polled TXOP (or EDCF TXOP). • 802.11e/D1.2 was not very clear in that; see 01/534r0 for related discussion. • However, allowing the multiple frame exchanges (or EDCF TXOP Bursting) looks very attractive. • See 02/xxxr0 and the next for the details. S. Choi, Philips & M.M. Wentink, Intersil

3. Advantages of EDCF TXOP Bursting • Will reduce network overhead • Without bursting available, an ESTA must backoff after each MSDU transmission • Will increase bandwidth fairness among the same priority queues, virtually independent from the frame sizes. • Without bursting available, the ESTA with larger MSDUs will use the channel more • Should not affect the HCF polled access as the EDCF TXOP is limited by “CP TXOP Limit” in QoS Parameter Set element anyway. S. Choi, Philips & M.M. Wentink, Intersil

4. Proposed EDCF TXOP Bursting • During an EDCF TXOP, ESTA may transmit multiple frames (i.e., MSDUs) from the same queue • Once there is a transmission failure, the EDCF TXOP ends, and the ESTA goes into backoff. • Without a transmission failure, the ESTA goes to backoff after the final frame exchange. S. Choi, Philips & M.M. Wentink, Intersil

5. Duration and NAV Rules • EDCF bursting uses Duration rules similar to fragment bursting • Each MPDU protects up to the next frame exchange via Duration field. S. Choi, Philips & M.M. Wentink, Intersil

6. Normative Text Changes from D2.0 • Revise 9.10.2.2 as follows: • Title should read “Duration values within TXOPs” • Within the clause each “TXOP” is replaced by “polled TXOP” • Add the following paragraph at the end of 9.10.2.2: “Each frame during a TXOP obtained by winning EDCF contention contains duration information that defines the duration until the end of the next frame exchange sequence. Duration information from each frame shall be used to update the NAV to indicate busy until the end of the next frame exchange sequence.” • Replace the first sentence of 9.10.3 with: • “A TXOP obtained by winning EDCF contention may be used to send one or more frame exchange sequences of the frames in the same queue with total medium occupancy time not exceeding CP TXOP limit from the QoS parameter set element in the beacon.” S. Choi, Philips & M.M. Wentink, Intersil

7. Motion I • Move to empower the TGe editor to revise the non-polled TXOP usage by incorporating normative text changes on slide 6 of document 01/566r3 by changing wording on non-polled TXOP usage elsewhere in the TGe draft as may be necessary to make the revised TGe draft consistent with the above changes. S. Choi, Philips & M.M. Wentink, Intersil

8. EDCF TXOP Limit per UP • Replace the “CP TXOP Limit” in QoS Parameter Set element with eight “CP TXOP Limit [UP]’s” • Assuming that xxx[TC] in D2.0 be replaced by xxx[UP] according to the new definition of UP. • One per User Priority (UP) • Desirable along with the EDCF TXOP bursting • Will enable bursting size tuning per UP depending on the traffic types • Can achieve weighted bandwidth sharing among UPs S. Choi, Philips & M.M. Wentink, Intersil

9. Normative Text Changes from D2.0 • Replace the first sentence of 9.10.3 with: • “A TXOP obtained by winning EDCF contention may be used to send one or more frame exchange sequences of the frames in the same queue with total medium occupancy time not exceeding CP TXOP limit [UP] from the QoS parameter set element in the beacon, where UP is the user priority of the first frame transmitted in the TXOP.” S. Choi, Philips & M.M. Wentink, Intersil

10. Normative Text Changes from D2.0 • In Clause 7.3.2.14: • Replace the third paragraph with: “The CP TXOP limits [UP] field contains 16 octects which specify 8 time limits on TXOPs that are not granted by QoS (+)CF-Polls, for user priorities 0 through 7, respectively. Each CP TXOP limit is 2 octets in length and contains the unsigned integer number of 16-microsecond periods. All non-polled WSTA TXOPs during the CP last no longer than the period specified by the corresponding CP TXOP limit value. A CP TXOP limit [UP] value of 0 indicates that each non-polled TXOP of user priority UP during the CP can be used to transmit a single MPDU at any rate in the operational rate set of the QBSS. CP TXOP Limit [UP] values update the dot11CPTXOPLimit[UP] MIB values when received by a QSTA.” S. Choi, Philips & M.M. Wentink, Intersil

11. Normative Text Changes from D2.0 • In Clause 7.3.2.14 and Figure 42.6: • Replace “CP TXOP Limit” with “CP TXOP Limits,” “CP TXOP Limit [UP],” or “CP TXOP Limit [0] … CP TXOP Limit [7]” depending on the context • In Annex D: • Replace “dot11CPTXOPLimit” with “dot11CPTXOPLimit[0…7] S. Choi, Philips & M.M. Wentink, Intersil

12. Motion II • Move to empower the TGe editor to revise the non-polled TXOP usage by incorporating normative text changes on slides 9-11 of document 01/566r3 and by changing wording on non-polled TXOP usage elsewhere in the TGe draft as may be necessary to make the revised TGe draft consistent with the above changes. S. Choi, Philips & M.M. Wentink, Intersil