A Medium Access Control Protocol with Reliable Multicast Support for Wireless Networks

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. Outline of Presentation • Motivation • System Model • Related work • Overview of IEEE 802.11 • IEEE 802.11MX (multicast extension) • Performance studies • Conclusions Mobile Computing and Wireless Networking Lab

3. 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 Mobile Computing and Wireless Networking Lab

4. 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 Mobile Computing and Wireless Networking Lab

5. Hidden Terminal Problem Node Orange Node Blue Node Green Translucent circles indicate transmission range of respective colored nodes Mobile Computing and Wireless Networking Lab

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

7. Use of RTS/CTS CTS Node Orange CTS Node Blue X Node Green RTS RTS – Request-To-Send CTS- Clear-To-Send Mobile Computing and Wireless Networking Lab

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

9. Some Related Work… • IEEE 802.11 • Leader Based Protocol • Probability Based Protocol • Delay Based Protocol • Parity Based Multicast • Dual Busy Tone Multiple Access Mobile Computing and Wireless Networking Lab

10. Leader Based Protocol Base Station RTS Leader Mobile Computing and Wireless Networking Lab

11. Leader Based Protocol Base Station NCTS CTS Leader Mobile Computing and Wireless Networking Lab

12. Leader Based Protocol Base Station DATA Leader Mobile Computing and Wireless Networking Lab

13. Leader Based Protocol Base Station NAK ACK Leader Mobile Computing and Wireless Networking Lab

14. 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 Mobile Computing and Wireless Networking Lab

15. 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 Mobile Computing and Wireless Networking Lab

16. IEEE 802.11 Mobile Computing and Wireless Networking Lab

17. 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 Mobile Computing and Wireless Networking Lab

18. 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 Mobile Computing and Wireless Networking Lab

19. Slot Diagram Mobile Computing and Wireless Networking Lab

20. State Diagram - Sender Mobile Computing and Wireless Networking Lab

21. State Diagram - Receiver Mobile Computing and Wireless Networking Lab

22. Results - Throughput Mobile Computing and Wireless Networking Lab

23. Results - Reliability Mobile Computing and Wireless Networking Lab

24. 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 Mobile Computing and Wireless Networking Lab

25. Future Work • Addition of power saving strategies • Currently working on reliable multicast protocol built over IEEE 802.11MX Mobile Computing and Wireless Networking Lab

26. 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] • 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. Mobile Computing and Wireless Networking Lab

27. Thank You! Mobile Computing and Wireless Networking Lab