Questions on Queue State Element

1. Questions on Queue State Element Shugong Xu Sharp Laboratories of America, Inc. E-Mail: sxu@sharplabs.com Shugong Xu, Sharp Labs

2. Brief info. of QSE • Proposed around Sep, 2001; • Intended to be an alternative to TSPEC in the original proposal; • Passed by the 802.11e WG after withdrawing the proposal of removing TSPEC, in Austin meeting, Nov 2001. (doc# 01/597r1) • Will be included in the new draft. Shugong Xu, Sharp Labs

3. Some aspect of QSE • Based on aggregated traffic for one traffic category, instead of each single traffic as that in TSPEC; • Assume L3 entity for admission control; AP or HC do not need to have information on each traffic; • Measures queue size in units of time, not bytes; • NO reply for the Report Queue State frame; Shugong Xu, Sharp Labs

4. Questions from the aggregated traffic • What the FEC, ACK policy bits mean for aggregated traffic within one TC? • In one TC, there may be several TSs, in which some of them use FEC, some not. • Same thing happens for ACK policy bit. Shugong Xu, Sharp Labs

5. Questions from “No handshake” • NO reply for the Report Queue State frame. • No re-negotiation possible. • more congestion, more QSE, which is in the high priority. Shugong Xu, Sharp Labs

6. HC (AP) no information for TS • No policing possible; • Can we trust the stations for staying within the limit they have negotiated (via L3)? • High priority applications based on TCP, or proposed DCP (datagram control protocol) in IETF. Shugong Xu, Sharp Labs

7. Other open issues • The complexity left for the end-point application? Most probably the complexity will be in the MAC of end-point. And lots of design details need to make clear. The performance depends on implementation choices. Such as, • How large the sender buffer will be for one traffic category? Large diversity between traffics exists, which could lead the amount of the buffer requirement varying greatly. Making this even worse, it is hard to anticipate the traffic of future new applications. • What if the buffer for one certain TC very small? Shugong Xu, Sharp Labs

8. Other open issues (cont.) • Each traffic category should have one separated queue? • How often for sending the QSE? When to send one? • when to send the first QSE? the beginning of each traffic?(no queue built up yet) • How fine is fine for the mapping from queue length to time? Note here we have variable size frames. How to do this? packet by packet? or total bytes in the queue? Shugong Xu, Sharp Labs

9. Some other questions (fundamental) • Without knowing the necessary globe information or activity of other stations, can one end-point makes the decisions for how much time should be allocated to itself? What will happen if HC cannot support all the TXOP requests? • Anticipating traffic from an instantaneousqueue length? Without considering the changing rate of the queue length? How about busty traffic like VBR video? • The instantaneous queue length is NOT stable, even for CBR traffic. Which instance will be used for deciding TXOP? Shugong Xu, Sharp Labs

10. Final question • QSE cannot work alone, what we need to do to make it function with TSPEC? Shugong Xu, Sharp Labs