1. Leader based Multicast
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Yongho SEOK

2. Yongho SEOK

3. Abstract
This document describes an example of leader-based multicast mechanism.
First, we introduce the problems of the current multicast mechanism.
Second, we describe a specific leader-based multicast mechanism
Third, we evaluate its benefits with experimental and simulation results.
At the end of the presentation, there will be a motion to include normative text ( r0) of this proposal in v draft.
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4. Introduction Increasing quantity of WiFi enabled portable devices
Growing availability of multimedia streaming
Increasing WiFi coverage on public places
The best option: Multicast
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5. Problem Current implementation of Multicast: Open Loop Transmission
No CW adaptation
No retransmission
No rate adaptation
Multicast transmission
starts
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6. Proposed solution Leader-based Multicast
AP chooses one receiver as the Leader
Leader sends back ACK to the AP
AP performs the backoff whenever ACK is not received
STA1
STA2
STA4
STA3
ACK
STA5[Leader]
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7. Proposed solution Leader-based Multicast (Optional Feature)
Each multicast group has a different retry limit according to the requirement of the multicast application
If the retry limit is set to 0, a retransmission of a multicast frame is not allowed
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8. Proposed solution Leader-based Multicast (Optional Feature)
AP sends RTS to Leader
Leader sends back CTS to the AP
STA1
STA2
STA4
STA3
CTS
RTS
STA5[Leader]
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9. Experimentation: Controlled conditions
Experimentation Scenario
4 Experiments: 5 tests of 5 minutes of VBR video streaming
Multicast without background traffic
Multicast with TCP background traffic
Leader-based multicast without background traffic.
Leader-based multicast with TCP background traffic
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10. Experimentation: Controlled conditions
Experimentation Scenario
No terminal mobility
Leader is fixed to STA5
<Mean receiving power value for each station>
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11. Results Video Goodput at STA5 Leader based Legacy Multicast
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12. Simulation: Mobile environments
Simulation Scenario (using NS-2)
4 Experiments: 20 tests of 8 minutes of CBR video streaming (average sending rate is 512Kbps)
Multicast without background traffic
Multicast with CBR background traffic
Leader-based without background traffic.
Leader-based with CBR background traffic
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13. Simulation: Mobile environments
Simulation Scenario (using NS-2)
Random mobility within a square (200m by 200m)
For a leader selection in mobile environments, a triggered multicast diagnostic report is utilized
Max frame loss rate
<Average frame loss ratio>
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14. Simulation: Mobile environments
Simulation Results
G_legacy(STA 1, t1, t2) : a goodput of STA 1 using multicast from t1 to t2
G_leader(STA 1, t1, t2) : a goodput of STA 1 using leader based multicast from t1 to t2
Gain is defined as G_leader(STA 1, t1, t2) – G_legacy(STA 1, t1, t2)
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15. Results Video Goodput in Mobile Environments 5 multicast receivers
STA 1
STA 4
Time
G_legacy
Gain
360
5.8464
370
9.1872
380
41.76
390
54.288
400
410
420
5.0112
430
2.5056
440
7.5168
450
4.176
460
470
25.056
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16. Results Video Goodput in Mobile Environments 5 multicast receivers
<No background traffic >
<With background traffic>
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17. Results Video Goodput in Mobile Environments 20 multicast receivers
<No background traffic>
<With background traffic>
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18. Conclusion Leader based multicast
Provide the fairness between multicast throughput and unicast throughput
Reduce network load by adapting multicast PHY rate
Low complexity to be implemented
Compatible with legacy station
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19. Motion
Move to include normative text in document v-normative-text-leader-based-multicast.doc into the TGv draft.
Mover: Yongho Seok
Seconder:
Result:
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20. References
J. Kuri and S.K. Kasera, “Reliable Multicast in Multi-access Wireless LANs,” ACM Wireless Networks, 2001.
D. Dujovne and T. Turletti, “Multicast in WLANs: An Experimental Study,” ACM MSWiM 2006.
J. Villalon, P. Cuenca, L. Orozco-Barbosa, Y. Seok and T. Turletti, “Cross-Layer Architecture for Adaptive Video Multicast Streaming over Multirate Wireless LANs,” IEEE JSAC, Vol. 25, No. 4, May, 2007.
J. Villalon, P. Cuenca, L. Orozco-Barbosa, Y. Seok and T. Turletti, “Auto Rate Selection for Multicast in Multi-rate Wireless LANs,” IET Communications, 2007.
S. Choi, N. Choi, Y. Seok, T. Kwon and Y. Choi, “Leader-based Rate Adaptive Multicasting for Wireless LANs, ” IEEE Globecom 2007.
Y. Seok and T. Turletti, “Practical Rate-Adaptive Multicast Schemes for Multimedia over IEEE WLANs,” INRIA Report,
B. Metzler and E. H. Qi, “A Statistical Method to Leader-Based ACK for Reliable Multicast in WLAN,” INTEL Technical Report.
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21. Proposed solution Leader Election Protocol
In order to join the LBMS, a non-AP STA shall transmit a LBMS Request frame containing the LBMS Request element
In order to leave the LBMS, a non-AP STA shall send a LBMS Request frame without containing the LBMS Request element of the corresponding multicast stream to leave the LBMS
To elect a leader for a multicast stream, the AP shall send a LBMS Report to the selected leader
To change a leader for a multicast stream, the AP shall send to the previous leader a LBMS Report frame except the multicast address of the corresponding multicast stream to stop acknowledging
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22. Proposed solution Leader Election Protocol Leader Selection Algorithm
It is possible to utilize IEEE v multicast diagnostic capability
E.g.: The station with the highest PER may be selected as the Leader of the group
STA1
STA2
Leader Report (G1, G2, G3)
ACK
STA4
(Leader for G1, G2, G3, G4)
STA4
(Leader for G1, G2, G3, G4)
STA3
Leader Report (G4)
ACK
STA5
(New leader for G4)
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23. Proposed solution Frame Sequence of Leader-based Multicast
RTS/CTS/Multicast Data
Multicast/Leader ACK
RTS/CTS/Multicast Data/Leader ACK
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