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Jiyoung et al.Slide 1
doc.: IEEE 802.11-06/1687
Submission
Nov 2006
Multicast Issues for Multimedia ApplicationMulticast Issues for Multimedia Application
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Date: 2006-11-10
Name Compay Address Phone E-mail
Jiyoung Huh LG Electronics [email protected]
Yongho Seok LG Electronics
Jaeyoung Lee LG Electronics
Donghee Shim LG Electronics [email protected]
Jiyoung et al.Slide 2
doc.: IEEE 802.11-06/1687
Submission
Nov 2006
AgendaAgenda• Overview• Issue1 – Reliability • Issue2 – Fairness • Issue3 – Rate Adaptation• Issue4 – Multicast Group Management• Conclusion• Straw Poll
Jiyoung et al.Slide 3
doc.: IEEE 802.11-06/1687
Submission
Nov 2006
OverviewOverview• High quality multimedia is being key application for high data
rate 802.11 technology, e.g. 802.11n• Use of multicast for various home network environments seems
to be one of key applications with high data rate 802.11
Home Server
AV Streaming
Jiyoung et al.Slide 4
doc.: IEEE 802.11-06/1687
Submission
Nov 2006
Issue 1 - ReliabilityIssue 1 - Reliability
• Unreliable Multicast– No ACK mechanism and retransmission
mechanism– No mechanism like RTS/CTS to solve the
hidden node problem
• For the use of 802.11 multicast for multimedia data transfer, reliability becomes more important
Jiyoung et al.Slide 5
doc.: IEEE 802.11-06/1687
Submission
Nov 2006
Issue 2 - FairnessIssue 2 - Fairness
• No Backoff procedure– Always fixed contention window size– On each collision
• Unicast packet: binary exponential back-off• Multicast packet: no back-off
Contention for a unicast flow and a multicast flow
Jiyoung et al.Slide 6
doc.: IEEE 802.11-06/1687
Submission
Nov 2006
Issue 3 – Rate AdaptationIssue 3 – Rate Adaptation
• The lowest PHY data rate– Channel access probability of all hosts is equal– Strong influence of a slow host on overall
WLAN performance1 Mb/s rate
A
LAN
Access Point
server
B
WLAN802.11b
11 Mb/s rate
11 Mb/s rate
A
• Need any PHY rate adaptation mechanism for multicast
Jiyoung et al.Slide 7
doc.: IEEE 802.11-06/1687
Submission
Nov 2006
Issue 4 – Multicast Group ManagementIssue 4 – Multicast Group Management
• No mechanism for multicast group management– No discrimination between Multicast packet
and Broadcast packet– Inefficiency of the use of DTIM for all
broadcast and multicast packet• All STAs shall wake up every DTIM
AP
TIM TIM TIMDTIM DTIM
DTIMCount
(0)
DTIMPeriod
(3)
BitmapControl
(Bit 0: 1)
Partial VirtualBitmap
DTIMCount
(0)
DTIMPeriod
(3)
BitmapControl
(Bit 0: 1)
Partial VirtualBitmap
AP buffers multicast framefor Multicast Group1
AP buffers multicast framefor Multicast Group2
Jiyoung et al.Slide 8
doc.: IEEE 802.11-06/1687
Submission
Nov 2006
ConclusionConclusion
• IEEE 802.11 is working on high data rate e.g. in TGn.
• One of killer applications for the use of available high data rate is high quality multimedia, e.g. AV streaming with MEPG 2
• In addition to unicast AV streaming, multicast use cases are feasible in Home Network environments
• However, multicast in 802.11 is not enough as well as have several problems for supporting various user scenarios, especially high quality multimedia use case
• Currently 802.11 doesn’t have any TG/SG to focus on multicast investigating multicast problems and possible solutions
Jiyoung et al.Slide 9
doc.: IEEE 802.11-06/1687
Submission
Nov 2006
Straw PollStraw Poll
• Require mechanisms that solve the multicast-related problems and new study group to discuss these
Good idea: Bad idea:
Jiyoung et al.Slide 10
doc.: IEEE 802.11-06/1687
Submission
Nov 2006
ReferenceReference
• IEEE Std802.11, 1999 edition (R2003)• M. Heusse, F. Rousseau, G. Berger-Sabbatel,
and A. Duda, “Performance Anomaly of 802.11b,” in Proc. of IEEE INFOCOM, April 2003
