1. doc.: IEEE 802.11-01/413r0 Submission S. Choi, Philips Research July 2001 Slide 1 Can EDCF Support QoS? Sunghyun Choi Philips Research-USA Briarcliff Manor, New York sunghyun.choi@philips.com

2. doc.: IEEE 802.11-01/413r0 Submission S. Choi, Philips Research July 2001 Slide 2 Outline Introduction Some known problems with EDCF Admission control for QoS networks Can EDCF support QoS?

3. doc.: IEEE 802.11-01/413r0 Submission S. Choi, Philips Research July 2001 Slide 3 References IEEE 802.11e QoS draft D1

4. doc.: IEEE 802.11-01/413r0 Submission S. Choi, Philips Research July 2001 Slide 4 Something Known Already AIFS –AIFS[TC] >= PIFS –There is no much room to give higher priority than the legacy stations using DIFS IBSS –The default CWmin[TC] = CWmin and AIFS[TC]=DIFS –Without a mechanism to update the values, how can we support prioritized access in IBSS?

5. doc.: IEEE 802.11-01/413r0 Submission S. Choi, Philips Research July 2001 Slide 5 Admission Control for QoS Network Admission control is a crucial mechanism for QoS support in any network –The network will admit a connection only if the requested resources are available in the network including the destination node. Packet scheduling and/or traffic policer are also needed during the network run-time –This will prevent a node to put more traffic than the amount agreed during the admission control stage.

6. doc.: IEEE 802.11-01/413r0 Submission S. Choi, Philips Research July 2001 Slide 6 Simple Example Wireless network with 10 Mbps Each QoS connection requests 1 Mbps Admission control will not admit more than 10 connections into the network Packet scheduling and traffic policer will force each connection to use up to 1 Mbps Both will ensure all the admitted connections to enjoy at least the pre-agreed 1 Mbps

7. doc.: IEEE 802.11-01/413r0 Submission S. Choi, Philips Research July 2001 Slide 7 HC Can Do It! HC should grant TXOPs (i.e., poll ESTAs) and transmit downlink frames based on the pre- agreement during the admission control phase Therefore, an ESTA cannot transmit more traffic than the amount agreed during CFBs as long as the HC does not allow so HC can even protect ESTAs from legacy STAs for QoS support

8. doc.: IEEE 802.11-01/413r0 Submission S. Choi, Philips Research July 2001 Slide 8 With EDCF... With EDCF, one does not need to go through admission control to get bandwidth Even if admission control is done, there is no way to restrict the traffic amount to the pre- agreed amount Actually, for uplink and downlink traffic, EAP can work for both admission control and traffic shaper But, for side traffic, it is not possible since EAP is not involved

9. doc.: IEEE 802.11-01/413r0 Submission S. Choi, Philips Research July 2001 Slide 9 With EDCF … (Cont.) Even with admission control and voluntary traffic policer in each ESTAs, QoS support becomes really difficult when legacy STAs exist –Since legacy STAs will not be involved with admission control and traffic policer

10. doc.: IEEE 802.11-01/413r0 Submission S. Choi, Philips Research July 2001 Slide 10 What EDCF Can (Not) Do? Can provides prioritized access –Relative quality (delay & throughput) differentiation among TCs –Can we say this QoS support? Cannot provide any absolute quality guarantee –Not even in a probabilistic manner –Not even in a perfect channel condition