Leader based Multicast Date: 2007-3-14 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>. Yongho SEOK

Yongho SEOK

Abstract This document describes an example of leader-based multicast mechanism. First, we introduce the problems of the current 802.11 multicast mechanism. Second, we describe a specific leader-based multicast mechanism Third, we evaluate its benefits with experimental results. At the end of the presentation, there will be a motion to include normative text of this proposal in 802.11v draft. Yongho SEOK

Introduction Increasing quantity of WiFi enabled portable devices Growing availability of multimedia streaming Increasing WiFi coverage on public places The best option: Multicast Yongho SEOK

<Saturated Condition> Problem Current implementation of Multicast: Open Loop Transmission No CW adaptation No retransmission No rate adaptation Multicast transmission starts <Saturated Condition> Yongho SEOK

<Unsaturated Condition> Problem Current implementation of Multicast: Open Loop Transmission No CW adaptation No retransmission No rate adaptation 4th unicast stream starts Multicast transmission starts <Unsaturated Condition> Yongho SEOK

Proposed solution Leader-based Multicast: [Kuri and Kasera] -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] Yongho SEOK

Proposed solution Optional Retransmission 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 Yongho SEOK

Proposed solution Optional Retransmission When a multicast frame is retransmitted, the retransmitted multicast frame has a virtual BSSID AP: BSSID = A Retransmission BSSID = B STA1 STA2 Retransmitted Multicast MPDU (BSSID = B) STA4 STA3 Multicast MPDU (BSSID = A) STA5[Leader] Yongho SEOK

Proposed solution Optional RTS/CTS exchange AP sends RTS to Leader Leader sends back CTS to the AP STA1 STA2 STA4 STA3 CTS RTS STA5[Leader] Yongho SEOK

Proposed solution Leader Election Protocol -AP chooses one receiver as the Leader AP sends a Leader Request frame to the Leader The leader informs AP of its leadership acceptation (or rejection), by sending back to AP a Leader Response frame AP sends to the previous leader a Leader Release frame to stop acknowledging frames Yongho SEOK

Proposed solution Leader Election Protocol Leader Selection Algorithm -It is possible to utilize IEEE 802.11v multicast diagnostic capability E.g.: The station with the highest PER may be selected as the Leader of the group STA3 STA5[Old Leader] STA4[New Leader] STA2 STA1 Leader Response ACK STA3 STA5[Old Leader] STA4[New Leader] STA2 STA1 Leader Request ACK STA3 STA5[Old Leader] STA4[New Leader] STA2 STA1 ACK Leader Release Yongho SEOK

Experimentation: Controlled conditions 4 Experiments: 5 tests of 5 minutes of VBR video streaming Legacy Multicast without background traffic Legacy Multicast with TCP background traffic Leader based without background traffic. Leader based with TCP background traffic Yongho SEOK

Results Video Goodput for both mechanisms Leader based Legacy Multicast Yongho SEOK

Conclusion Leader based solution: Better throughput than Legacy multicast Can follow the VBR test video requirements Increases throughput with retransmissions on a loaded network Low complexity to be implemented Compatible with legacy 802.11 station Yongho SEOK

Motion Move to include normative text in document 11-07-0144-03-000v-normative-text-leader-based-multicast.doc into the TGv draft. Mover: Emily H. Qi Seconder: Result: Yongho SEOK

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 802.11 WLANs: An Experimental Study,” in 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. Y. Seok and T. Turletti, “Practical Rate-Adaptive Multicast Schemes for Multimedia over IEEE 802.11 WLANs,” INRIA Report, http://hal.inria.fr/inria-00104699. B. Metzler and E. H. Qi, “A Statistical Method to Leader-Based ACK for Reliable Multicast in WLAN,” INTEL Technical Report. *the one from MSWiM where the figures are from Yongho SEOK