1. Reliable multicast with QoS support in IEEE 802.11
September 2007
Date:
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2. Multicast benefits Bandwidth-conserving technology
September 2007
Multicast benefits 3 2 4 AP 1 5
Bandwidth-conserving technology
Simultaneous delivery of the same data stream to multiple recipients
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3. Multicast-based audio/video applications
September 2007
Multicast-based audio/video applications TV
Home video
Gaming
Video conferencing
Corporate communications
Distance learning
News
etc.
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4. Wireless TV & video multicast around the home
September 2007
Wireless TV & video multicast around the home
over WLAN
Bedroom 1
Bedroom 2
Home Cinema
Kitchen
Family Room
DSL or LAN
Media Centre
video player
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5. September 2007
Multicast problems in
Noise, interference, obstacles, etc. may cause high Packet Error Rate
No error recovery mechanism (ARQ) for multicast traffic in IEEE MAC
Legacy multicast does not ensure reliable data flow and can’t support QoS
Best effort service only
HD multimedia streaming requires high transmission rate
multicast stream is transmitted at the lowest PHY rate in legacy
No rate adaptation mechanism
Not appropriate for most of multimedia applications
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6. Existed reliable multicast solutions
September 2007
Existed reliable multicast solutions
Joy Kuri and Sneha Kumar Kasera, “Reliable Multicast in Multi-access Wireless LANs,” Wireless Networks, Vol. 7,  no. 4, pp. 359 – 369, August 2001
Leader Based Protocol (LBP) was proposed
Question “How to select a leader?” is not answered
Han-Chieh Chao, S.W. Chang, J.L. Chen “Throughput Improvements Using the Random Leader Technique for the Reliable Multicast Wireless LANs,” Lecture Notes In Computer Science, Proc. of the First ICN–Part 1 Vol. 2093, pp. 708 – 719, 2001
Channel conditions are not taken into account
Min-Te Sun, Lifei Huang, Anish Arora, Ten-Hwang Lai, “Reliable MAC Layer Multicast in IEEE Wireless Networks,” Proc. ICCP’02
Batch Mode Multicast MAC protocol (BMMM) was proposed
ACK is requested from every recipient
This is most reliable method but overhead and delay are too large
Yongho Seok, Diego Dujovne, Thierry Turletti, Pedro Cuenca, “Leader based Multicast Proposal,” IEEE /0144r2, January 2007
Leader is the recipient operating in the worst channel conditions (lowest SNR)
For other recipients Packet Loss Ratio (PLR) may be too high
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7. Comparative analysis of LBP and BMMM
September 2007
Comparative analysis of LBP and BMMM
LBP:
the only recipient (i.e. leader) sends ACK in reply to data frame
high throughput and short delay
high Packet Loss Ratio (PLR) for non-leader recipients, i.e. low reliability
BMMM:
every recipient sends ACK in reply to data frame in turn
all recipients are leaders
low PLR, i.e. high reliability
low throughput and long delay
Neither LBP nor BMMM can meet performance and reliability
requirements of different applications and different traffic categories
Different applications require different QoS !!!
Our goal is to make new multicast method that can support any QoS
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8. Multicast with QoS support
September 2007
Multicast with QoS support
QoS indices:
Maximal PLR
Minimal throughput
Maximal delay
where i=1,..,N is the recipient’s number
To provide QoS for any kind of video applications, we propose new multicast scheme with variable number J of leaders
Example:
LBP with J =1 leader:
New multicast with J > 1:
more time is needed to transmit data packet → longer delay and lower throughput
with increasing J, the probability that all leaders receive the packet correctly decreases → the number of packet retransmissions increases → lower PLRmax
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9. Choice of the number of leaders, based on QoS requirements
September 2007
Choice of the number of leaders, based on QoS requirements
Video QoS requirements:
J values highlighted with green meet QoS requirements on PLR
J values highlighted with green meet QoS requirements on throughput
J values highlighted with green meet QoS requirements on delay
All QoS requirements are met inside the blue box. If no, PHY data rate might be decreased.
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10. How to select multiple leaders?
September 2007
How to select multiple leaders?
We can use:
Random Leader Technique
Multiple recipients operating in the worst channel conditions
Other selection schemes..?
How many leaders are needed?
Based on application QoS requirements (TBD)
Based on recipients’ SNR/BER/PER (TBD)
etc..?
How data rate should be selected?
Based on application QoS requirements (TBD)
etc..?
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11. Thanks for your kind attention!
September 2007
Thanks for your kind attention!
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12. September 2007
Call for interest
Who’s interested in getting together to work on this?
What should be the next steps:
Development of multiple-leaders-based multicast mechanism ?
Design and investigation of leader selection schemes ?
Rate adaptation scheme ?
Preparation the normative text ?
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