1. A Medium Access Control Protocol with Reliable Multicast Support for Wireless Networks Thesis defense of: Vikram Shankar Advising Committee: Dr. Sandeep Gupta Dr. Arunabha Sen Dr. Joseph Hui

2. December 2002 Mobile Computing and Wireless Networking LabArizona State University Outline of Presentation Motivation System Model Related work Overview of IEEE 802.11 IEEE 802.11MX (multicast extension) Performance studies Conclusions

3. December 2002 Mobile Computing and Wireless Networking LabArizona State University Motivation Need for reliable multicast Group communication Whiteboard applications Why reliable multicast support at MAC layer? Utilize broadcast nature of wireless medium Local error recovery reduces end-to-end delays

4. December 2002 Mobile Computing and Wireless Networking LabArizona State University System Model Infrastructure-based as well as ad hoc Each node has two transceivers One for data channel One for busy tones Bit errors caused by: Channel noise Packet collisions We deal with one hop reliability only Assumptions: Multicast recipients are always within transmission range of sender Antenna is capable of picking up both data bits as well as tones

5. December 2002 Mobile Computing and Wireless Networking LabArizona State University Hidden Terminal Problem Translucent circles indicate transmission range of respective colored nodes Node Blue Node Orange Node Green

6. December 2002 Mobile Computing and Wireless Networking LabArizona State University Exposed Terminal Problem Node Blue Node Purple Node Green Node Orange Translucent circles indicate transmission range of respective colored nodes

7. December 2002 Mobile Computing and Wireless Networking LabArizona State University Use of RTS/CTS RTS CTS X RTS – Request-To-Send CTS- Clear-To-Send Node Green Node Orange Node Blue

8. December 2002 Mobile Computing and Wireless Networking LabArizona State University Use of RTS/CTS RTS CTS RTS Node Blue Node Orange Node Green Node Purple Translucent circles indicate transmission range of respective colored nodes

9. December 2002 Mobile Computing and Wireless Networking LabArizona State University Some Related Work… IEEE 802.11 Leader Based Protocol Probability Based Protocol Delay Based Protocol Parity Based Multicast Dual Busy Tone Multiple Access

10. December 2002 Mobile Computing and Wireless Networking LabArizona State University Leader Based Protocol RTS Leader Base Station

11. December 2002 Mobile Computing and Wireless Networking LabArizona State University Leader Based Protocol Base Station Leader CTS NCTS

12. December 2002 Mobile Computing and Wireless Networking LabArizona State University Leader Based Protocol DATA Leader Base Station

13. December 2002 Mobile Computing and Wireless Networking LabArizona State University Leader Based Protocol Base Station Leader ACK NAK

14. December 2002 Mobile Computing and Wireless Networking LabArizona State University Problems with Leader Based Protocol Leader Mobility reduces throughput “Capture Effect” may hide NCTS and NAK from distant nodes Incoming nodes may not have heard RTS/CTS exchange and may cause collision Sender has to know the multicast group members a priori

15. December 2002 Mobile Computing and Wireless Networking LabArizona State University IEEE 802.11 Modes of operation: Infrastructure-based Ad hoc Three access mechanisms: Basic CSMA/CA CSMA with RTS/CTS Polling Does not support reliable multicast

16. December 2002 Mobile Computing and Wireless Networking LabArizona State University IEEE 802.11

17. December 2002 Mobile Computing and Wireless Networking LabArizona State University Dual Busy Tone Multiple Access Node mobility causes problems In coming nodes may not have heard RTS/CTS exchange Unaware of current transmission Up to 60% of packets may be lost due to collision Use Transmit Busy tone while transmitting Use Receive Busy tone while receiving

18. December 2002 Mobile Computing and Wireless Networking LabArizona State University IEEE 802.11MX Salient features Multicast extension to IEEE 802.11 Remains compatible with IEEE 802.11 Multicast is NAK-based Use of tones instead of packets for NAK and NCTS Dual Busy tones to reduce packet collisions

19. December 2002 Mobile Computing and Wireless Networking LabArizona State University Slot Diagram

20. December 2002 Mobile Computing and Wireless Networking LabArizona State University State Diagram - Sender

21. December 2002 Mobile Computing and Wireless Networking LabArizona State University State Diagram - Receiver

22. December 2002 Mobile Computing and Wireless Networking LabArizona State University Results - Throughput

23. December 2002 Mobile Computing and Wireless Networking LabArizona State University Results - Reliability

24. December 2002 Mobile Computing and Wireless Networking LabArizona State University Conclusions IEEE 802.11MX was proposed as a reliable multicast extension to IEEE 802.11 Multicast is NAK-based NAKs and NCTSs are in the form of tones Provides the same reliability as Leader Based Protocol Has better throughput compared to Leader Based Protocol

25. December 2002 Mobile Computing and Wireless Networking LabArizona State University Future Work Addition of power saving strategies Currently working on reliable multicast protocol built over IEEE 802.11MX

26. December 2002 Mobile Computing and Wireless Networking LabArizona State University References ANSI/IEEE Standard 802.11 Wireless LAN medium control (MAC) and physical layer (PHY) specifications, In 1999 Edition. J. Deng, Z. J. Haas, “Dual Busy Tone Multiple Access (DBTMA): A New Medium Access Control for Packet Radio Networks”, In IEEE ICUPC’98, Italy, 1998. J. Kuri, S. Kasera, “Reliable Multicast in Multi-access Wireless LANs”, In Proceedings of INFOCOM’99, New York, March 99. Network Simulator – ns-2, Available via http://www.isi.edu/nsnam/ns/, [Accessed on Aug 02] http://www.isi.edu/nsnam/ns/ D. Towsley, J. Kurose, S. Pingali, “A Comparison of Sender- Initiated and Receiver-Initiated Multicast Protocols”, In IEEE Journal on Selected Areas in Communication, April 1997.

27. December 2002 Mobile Computing and Wireless Networking LabArizona State University Thank You!