doc.: ieee 802.11-06/0892r1 submission july 2006 mike ellis, bbcslide 1 multimedia challenges for...
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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.
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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
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