July 2006

Mike Ellis, BBC

Slide 1

doc.: IEEE 802.11-06/0892r1

Submission

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 <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, 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 <stuart.kerry@philips.com> 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 <patcom@ieee.org>.

Date: 2006-06-18

Name Company Address Phone email Mike Ellis BBC Kingswood Warren,

Woodland Way, Tadworth, Surrey, KT20 6NP, UK

+44 (0) 1737 839 663

mike.r.ellis@ieee.org

Alex Ashley NDS UK One London Road Staines, Middlesex, TW18 4EX, UK

+44 (0) 1784 848 770

aashley@nds.com

Authors:

July 2006

Mike Ellis, BBC

Slide 2

doc.: IEEE 802.11-06/0892r1

Submission

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.

July 2006

Mike Ellis, BBC

Slide 3

doc.: IEEE 802.11-06/0892r1

Submission

Multimedia Challenges for IEEE802.11

What are the requirements?In the home

In the TV studio

On location

How does WiFi shape up?Channels Delay and jitter

Throughput Quality of Service

Error Correction Unicast vs Multicast

ConclusionsWhere is more work needed?

July 2006

Mike Ellis, BBC

Slide 4

doc.: IEEE 802.11-06/0892r1

Submission

What are the requirements?

●Potential uses

●Number of channels

●Delay/jitter

●Throughput

●Reliability

July 2006

Mike Ellis, BBC

Slide 5

doc.: IEEE 802.11-06/0892r1

Submission

Uses around the home

over WLAN

Bedroom 1Bedroom 2

Home CinemaKitchen Family Room

DSL

Media Centre

DVD player

July 2006

Mike Ellis, BBC

Slide 6

doc.: IEEE 802.11-06/0892r1

Submission

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

July 2006

Mike Ellis, BBC

Slide 7

doc.: IEEE 802.11-06/0892r1

Submission

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

∴ Exclusive-use (licensed) frequencies are a necessity

July 2006

Mike Ellis, BBC

Slide 8

doc.: IEEE 802.11-06/0892r1

Submission

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

7m

July 2006

Mike Ellis, BBC

Slide 9

doc.: IEEE 802.11-06/0892r1

Submission

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

July 2006

Mike Ellis, BBC

Slide 10

doc.: IEEE 802.11-06/0892r1

Submission

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!

July 2006

Mike Ellis, BBC

Slide 11

doc.: IEEE 802.11-06/0892r1

Submission

Delay and synchronisation in the home

over WLAN

Bedroom 1Bedroom 2

Home CinemaKitchen Family Room

DSL

Media Centre

DVD player

July 2006

Mike Ellis, BBC

Slide 12

doc.: IEEE 802.11-06/0892r1

Submission

Lip-sync – Audio and Video Synchronisation

over WLAN

Bedroom 1Bedroom 2

Home CinemaKitchen Family Room

DSL

Media Centre

DVD player

July 2006

Mike Ellis, BBC

Slide 13

doc.: IEEE 802.11-06/0892r1

Submission

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

July 2006

Mike Ellis, BBC

Slide 14

doc.: IEEE 802.11-06/0892r1

Submission

Summary of RequirementsSimilarities 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

July 2006

Mike Ellis, BBC

Slide 15

doc.: IEEE 802.11-06/0892r1

Submission

How does WiFi shape up?

Frequency allocations

Throughput

Delay

Error correction

Quality of Service

Unicast vs Multicast

July 2006

Mike Ellis, BBC

Slide 16

doc.: IEEE 802.11-06/0892r1

Submission

2·4GHz band1 2 3 4 5 6 7 8 9 10 11 12 13 141 2 3 4 5 6 7 8 9 10 11 12 13 14

Frequency allocations: 2·4GHz Band

802.11n

Most of Europe

France

SpainUSA

Japan

July 2006

Mike Ellis, BBC

Slide 17

doc.: IEEE 802.11-06/0892r1

Submission

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?

July 2006

Mike Ellis, BBC

Slide 18

doc.: IEEE 802.11-06/0892r1

Submission

Throughput

~600 Mbit/s54 Mbit/s11 Mbit/s5

Mbit/s6 Mbit/s

802.11b

~55% useable

802.11g

~45% useable

802.11n

~25% useable

450 Mbit/soverhead

150 Mbit/suseable

30 Mbit/s

24 Mbit/s

July 2006

Mike Ellis, BBC

Slide 19

doc.: IEEE 802.11-06/0892r1

Submission

Re-try based error correctionDeliveredcapacity

Delay

Desired capacity

Desired capacity

July 2006

Mike Ellis, BBC

Slide 20

doc.: IEEE 802.11-06/0892r1

Submission

Best Effort

Video

Audio

Telephony

Quality of Service

High

LowLow High

“Priority”

Data rate

July 2006

Mike Ellis, BBC

Slide 21

doc.: IEEE 802.11-06/0892r1

Submission

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

July 2006

Mike Ellis, BBC

Slide 22

doc.: IEEE 802.11-06/0892r1

Submission

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

July 2006

Mike Ellis, BBC

Slide 23

doc.: IEEE 802.11-06/0892r1

Submission

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