1. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 1 802.11 MAC extensions for high rate Video Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at.http:// ieee802.org/guides/bylaws/sb-bylaws.pdfstuart.kerry@philips.compatcom@ieee.org Date: 2005-07-17 Authors:

2. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 2 Abstract In this presentation we identify the requirements for video transmission over 802.11 networks. We come to the conclusion that the recently completed 802.11e amendment for QoS appears to be inadequate for end- to-end QoS for high quality video over 802.11. We survey work done at other organizations such as the IETF. Some MAC-level solutions to the end-to-end QoS problems are outlined. These solutions require further standardization work beyond 802.11e.

3. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 3 Outline 802.11e and its limitations Potential solutions to the 802.11e limitations Current work in media-independent and media- dependent packet-based FEC Relevant work at IETF Conclusions

4. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 4 802.11e and its limitations 802.11e is an almost complete “QoS amendment” Priorities are assigned only within a session There is no prioritization of traffic ‘within’ an AV stream Current prioritization provides latency and average throughput enhancement Scheduling and admission control are still largely left to vendors Different applications have specific jitter, latency and retransmission requirements. They are still not part of TSPEC

5. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 5 Potential MAC-level solutions Truly dynamic prioritization Operational profile (TSPEC) may be developed for standard DLNA formats Admission control and scheduling schemes should be standardized for AV clients Jitter requirements should be specified in the TSPEC together with block ACK length, retransmissions, and aggregation size. Content specific dynamic link rate adaptation may be specified A separate direct link transmission mode may be defined for hi-speed transmission of video

6. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 6 Potential solutions to the limitations of 802.11e (cont.) Two-dimensional QoS model –Priority is one dimension –PER is another dimension This two-dimensional model requires media-specific methods

7. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 7 End-to-end QoS support for multimedia over 802.11 Media-specific –Packets belonging to one media class can be assigned different priorities depending on each packet’s contribution to overall QoS –Adjust FEC and power control depending on media type and class An adaptive MAC is necessary to determine the resources (throughput and battery power) for multimedia delivery.

8. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 8 MAC enhancements for multimedia over 802.11 Adaptive congestion control –Reduce packet loss and delay –Rate control and rate adaptive encoding MAC-level FEC

9. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 9 Media Independent FEC Given k data packets Generate n-k parity packets Transmit n packets Any subset of k received packets suffices to reconstruct the data. The exact position of missing packets is unknown. IETF RFC 2733: An RTP Payload Format for Generic Forward Error Correction

10. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 10 Media-independent FEC advantages and disadvantages Advantages –it is media independent –Efficient for multicast Disadvantages: –Delay is increased (up to n packets) –Decoder complexity –Relationship between FEC and congestion control generally not very well understood

11. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 11 Media-specific FEC Send a lower-resolution redundant packet Advantages: –Low latency –Less redundancy Disadvantage –Lower quality –Decoder complexity

12. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 12 Priority Encoding Transmission Specify different priorities for different data segments According to assigned priority use different FEC Early detection of packet loss is the key

13. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 13 Hybrid error control (ARQ/FEC) How do you choose the right amount of redundancy? Hybrid error conrtol –No redundancy after the first transmission –Redundant packets are sent afterwards Efficient for multicast Further research is necessary

14. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 14 Relevant prior work RTP: Transport protocol for real-time applications: IETF RFC 1889 –Source identification –Packet loss detection –Inter-media synchronization –Intra-media synchronization RTCP: RTP plus periodic retransmission of control packets

15. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 15 Conclusions 802.11e provides basic QoS, but is inadequate for high end multimedia applications More work is carried out by IETF and others Further MAC-level solutions are necessary –Dynamic prioritization –Generalized TSPEC –Content-specific techniques

16. doc.: IEEE 802.11-05/0632r1 Submission July 2005 Clifford Tavares, Hitachi America Ltd.Slide 16 References J. Kowalski, “Link measurement results give thumbs-up to MAC FEC,” doc. 802.11-01/422r0, July 2001. S. Choi, “New OFDM SERVICE field format for.11e MAC FEC,” doc. 802.11-02/051r0, January 2002. C. Padhye, K. Christensen, and W. Moreno, “A new adaptive FEC loss control algorithm for voice over IP applications,” IEEE Performance Computing and Communications Conf., Feb. 2000 Q. Zhang, W. Zhu, Y.-Q. Zhang, “End-to-end QoS for video delivery over wireless Internet,” Proc. IEEE, vol. 93, pp. 123-134, Jan. 2005. S. Choi, “IEEE 802.11e MAC-level performance evaluation and enhancement, IEEE Globecom 2002.