1. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 1 Multimedia Challenges for IEEE802.11 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: 2006-06-18 Authors:

2. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 2 Abstract A brief summary of the features required for a useable wireless network carrying audio-visual content in either the home or production environment, comparing these against the features available in the present IEEE802.11a/b/g core standards, the IEEE802.11e QoS extensions, and the proposed IEEE802.11n standard.

3. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 3 Multimedia Challenges for IEEE802.11 What are the requirements? In the home In the TV studio On location How does WiFi shape up? ChannelsDelay and jitter Throughput Quality of Service Error CorrectionUnicast vs Multicast Conclusions Where is more work needed?

4. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 4 What are the requirements? ●Potential uses ●Number of channels ●Delay/jitter ●Throughput ●Reliability

5. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 5 Uses around the home over WLAN Bedroom 1 Bedroom 2 Home CinemaKitchenFamily Room DSL Media Centre DVD player

6. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 6 Uses in a TV studio Up to twelve cameras ●One HD stream from each ●One HD stream to each ●1 or 2 SD/HD streams to all ●Camera control Other wireless uses ●Picture monitors ●Sound system ●Lighting ●Intercom ●Script/production network

7. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 7 Requirements for TV production Studio ●Six to twelve cameras ●Controlled environment ●Often a metal box ●Lots of multi-path ●Good for MIMO On location ●One to thirty cameras ●Public environment ●Laptops, mobile phones, … ●Long distances Production costs more than £10,000 per hour Loss of “one-off events” totally unacceptable ∴ E xclusive-use (licensed) frequencies are a necessity

8. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 8 Channels needed: flats ●Concrete flooring reduces transmission between floors ●3 to 5 other homes affected ●6 channels needed ●Assuming one per flat…..but the “building across the street” problem may double the number of channels required 7m

9. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 9 Channels needed: houses ●WiFi doesn’t stop at the garden fence… …if you reach all parts of your property, you also reach your neighbours ●5 to 7 homes affected ●8 channels needed ●Assuming one per house… 12m 36m 48m

10. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 10 Channels needed: TV production ●One per camera ●Two for “broadcast video” ●One for sound and lights ●One for “production team” Up to 20 channels in a studio Up to 40 channels on location… …but we (broadcasters) are used to paying for licensed channels!

11. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 11 Delay and synchronisation in the home over WLAN Bedroom 1 Bedroom 2 Home CinemaKitchenFamily Room DSL Media Centre DVD player

12. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 12 Lip-sync – Audio and Video Synchronisation over WLAN Bedroom 1 Bedroom 2 Home CinemaKitchenFamily Room DSL Media Centre DVD player

13. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 13 Delays in the TV Studio Delay is very disconcerting …to performers …to directors …to camera operators …to teleprompt operators We know that one frame (~30ms) of delay is too much

14. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 14 Summary of Requirements Similarities and Differences At home ●Multiple receivers ●Maybe multiple sources too ●Neighbouring properties ●Privacy ●Subscription sharing ●Moderate data rates ●“Last hop” ●Some delay tolerable ●100ms max ●Synchronisation important ●Good QoS TV production ●Multiple receivers and sources ●Each camera is a source ●Sometimes isolated ●Studios are metal boxes ●Golf courses aren’t! ●Very high data rates ●Cascaded codecs ●Very low delay tolerance ●1 frame (~30ms) is too much ●Synchronisation vital ●Excellent QoS

15. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 15 How does WiFi shape up? Frequency allocations Throughput Delay Error correction Quality of Service Unicast vs Multicast

16. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 16 2·4GHz band 12345678910111213 14 123 45678 910111213 14 Frequency allocations: 2·4GHz Band 802.11n Most of Europe France Spain USA Japan

17. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 17 Frequency allocations: 5GHz Band ●Typically twelve channels (depending on country and mode) ●Fewer users Better than 2·4GHz band …at the moment… So how many channels do we need?

18. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 18 Throughput ~600 Mbit/s 54 Mbit/s 11 Mbit/s 5 Mbit/s 6 Mbit/s 802.11b ~55% useable 802.11g ~45% useable 802.11n ~25% useable 450 Mbit/s overhead 150 Mbit/s useable 30 Mbit/s 24 Mbit/s

19. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 19 Re-try based error correction Delivered capacity Delay Desired capacity

20. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 20 Best Effort Video Audio Telephony Quality of Service High Low High “Priority” Data rate

21. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 21 Unicast vs Multicast Unicast ●Explicit acknowledgement ●Lost packets are re-sent ●Jitter and delay introduced ●Modulation rate optimised ●There is a “feedback path” ●Beamforming possible ●MIMO also works Multicast ●Blind transmission ●Lost packets are really lost ●Delay predictable ●Modulation assumes the worst ●11Mbit/s when 54Mbit/s would work ●Omni-directional transmission ●MIMO still works

22. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 22 Conclusions ●PHY layer ●More channels ●Licensed frequencies ●MAC layer ●More flexible Quality of Service ●Better handling of multicast ●Lower overhead and delay ●Application layer – with IEEE802.1as ●AV stream synchronisation ●Better delay management

23. doc.: IEEE 802.11-06/0892r1 Submission July 2006 Mike Ellis, BBCSlide 23 References ●11-05-0420-01-0wng-multicast-over-wlan ●11-05-0632-00-0wng-802.11-high-data-rate-multimedia-transmission ●11-05-1615-02-000k-qos-metrics ●11-06-0039-00-0wng-video-over-802-11 ●11-06-0322-00-000t-overview-video-use-cases ●11-06-0360-00-0wng-update-on-hd-video-over-wlan ●11-06-0632-00-0wng-proposed-multi-purpose-802-11-mac-extensions ●11-06-0691-00-0wng-mulitichanneldlp ●11-06-0713-01-0wng-mac-performance-improvement-using-random-aifsn ●11-06-0756-00-0wng-hd-video-and-multimedia-over-802-11-update