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Doc.: IEEE 802.11-07/2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 1 Topics for VTS PAR(s) Date: 2007-08-07 Authors:

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Presentation on theme: "Doc.: IEEE 802.11-07/2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 1 Topics for VTS PAR(s) Date: 2007-08-07 Authors:"— Presentation transcript:

1 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 1 Topics for VTS PAR(s) Date: Authors:

2 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 2 Abstract This presentation suggests some topics that could form the basis of one or more PARs for the Video Transport Streams task group. These topics are based on previous inputs to IEEE that highlighted issues with the current MAC.

3 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 3 Introduction Checking the 8941 documents on the document server from the last three years, 21 presentations seemed to be related to the work of the VTS study group and described specific limitations with The following slides group these presentations in to five known issues themes Following this is a proposal of four topics for the VTS task group that covers these themes

4 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 4 Known Issues with MAC Jitter –Video and voice traffic is jitter sensitive – MAC level retransmissions, DCF/EDCA channel access rules and 11n AMPDU cause non-deterministic delays EDCA scalability –Multiple streams all sharing the same AC HCCA and PCF with overlapping BSS –Collisions during controlled access phase

5 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 5 Known Issues with MAC Compatibility with –Support for 802.1avb stream reservation –Reflection issues with routing –Packet based behaviour (priority, drop eligibility) Multicast –QoS for multicast streams –Delivery of A/V to multiple devices simultaneously (e.g. display + speakers)

6 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 6 Jitter Video and voice traffic is jitter sensitive – MAC level retransmissions, DCF/EDCA channel access rules and 11n AMPDU cause non-deterministic delays Jitter can be smoothed by buffering, but this is undesirable for video and voice traffic Use an FEC to reduce / remove retransmissions? Use a deterministic channel access method (HCCA/PCF) ? 05/0632r MAC extensions for high rate Video 05/0910r for video transmission 06/0322r0 - Video Use Cases 06/0360r0 - Update on HD Video over WLAN 07/0676r0 - Video over Research 07/2256r2 - Minutes of VTS Study Group

7 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 7 EDCA Scalability Multiple streams all sharing the same AC As number of streams increase, likelihood of collisions increase –Collisions cause exponential back-off and rate adaptation Adjust EDCA TXOP_limit based on actual / predicted video frame type? Modify AIFSN? 05/0632r MAC extensions for high rate Video 05/0910r for video transmission 06/0039r1 - On video over /0713r1 - MAC improvement using random AIFSN 06/0892r1 - Multimedia Challenges for IEEE /0105r0 - Requirements towards video over /0400r1 - Audio/Video Streaming over /2157r1 - Limitation of EDCA and HCCA for Video Transmission

8 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 8 HCCA and PCF with overlapping BSS Collisions during controlled access phase can cause large number of packets to be lost and time on the medium to be lost Maybe a (partial?) solution in TGv ? 05/0505r0 - Access Point Coordination 06/0691r0 - Multi-channel Direct Link Protocol for HD Video 07/0676r0 - Video over Research 07/2115r0 - Access Point Collaboration 07/2157r1 - Limitation of EDCA and HCCA for Video Transmission

9 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 9 Compatibility with Support for 802.1avb stream reservation protocol Reflection issues with routing IEEE 802.1Qad added support for discard eligibility –The ability of a system (a network node, a station, an access point) to selectively drop frames when congested. 06/0144r1 - Video Testing Methodology 06/0898r Amendments to Support CE Applications 06/1021r1 - WLAN for Next Generation AV 07/0693r0 - Supporting Drop Eligibility in IEEE MAC 07/2233r0 - Wireless Bridge Common Practices

10 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 10 Multicast e standard does not provide QoS for multicast For multicast transmission to several speakers, not only the speakers must be synchronized among themselves, but they must be synchronized with the video as well 05/0420r1 - Multicast over WLAN 06/0892r1 - Multimedia Challenges for IEEE /0898r Amendments to Support CE Applications 07/0105r0 - Requirements towards video over

11 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 11 Proposed PAR Topics Based on analysis of documents from the last 3 years, the following topics should be addressed by the VTS task group Improved support Modified ACK & FCS behaviour Modified EDCA BSS overlap

12 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 12 Improved support MAC layer enhancements to: Add support for 802.1avb stream reservation protocol Add support for 802.1Qad discard eligibility Specify four address behaviour?

13 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 13 Modified ACK & FCS behaviour MAC layer enhancements to provide a hook for higher- layer error handling techniques –E.g. video decoder error concealment, application level FEC –Allows frames with payload bit-errors to be used –Allows choice of error handling technique (e.g. FEC algorithm) –Still allows frame headers to be validated –Possibly integrated with block-ACK? Removal of retransmissions could provide a solution for jitter Could also be used to improve quality of multicast delivery

14 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 14 Modified EDCA MAC layer enhancements to EDCA QoS mode for AIFSN and TXOP values –Improve the scalability of EDCA by modifying AIFSN Random? Based upon information in the packet? –Use 802.1q information to modify TXOP?

15 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 15 BSS overlap Management layer enhancements to allow overlapping BSS to avoid CAP collisions –No MAC layer modifications –Ideally, no modifications to non-AP STAs –Allow exchange of TSPECs between APs? –Inter-BSS admission control? This topic needs collaboration with TGv –cf ECSA in TGn, TGv and TGy

16 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 16 Conclusions This presentation describes four topics that could be addressed by a VTS task group Each topic has had several independent submissions describing the need for an solution Each topic could have a very narrow scope to enable timely delivery of a technical solution

17 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 17 References (1/2) 05/0505r0 - Access Point Coordination 05/0632r MAC extensions for high rate Video 05/0910r for video transmission 06/0039r1 - On video over /0144r1 - Video Testing Methodology 06/0322r0 - Video Use Cases 06/0360r0 - Update on HD Video over WLAN 06/0691r0 - Multi-channel Direct Link Protocol for HD Video 06/0713r1 - MAC improvement using random AIFSN# 05/0420r1 - Multicast over WLAN 06/0892r1 - Multimedia Challenges for IEEE802.11

18 doc.: IEEE /2294r1 Submission August 2007 Alex Ashley, NDS LtdSlide 18 References (2/2) 06/0898r Amendments to Support CE Applications 06/1021r1 - WLAN for Next Generation AV 07/0105r0 - Requirements towards video over /0400r1 - Audio/Video Streaming over /0676r0 - Video over Research 07/0693r0 - Supporting Drop Eligibility in IEEE MAC 07/2115r0 - Access Point Collaboration 07/2157r1 - Limitation of EDCA and HCCA for Video Transmission 07/2233r0 - Wireless Bridge Common Practices 07/2256r2 - Minutes of VTS Study Group


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