1 / 20

MAC Reliable Broadcast in Ad Hoc Networks Ken Tang, Mario Gerla

MAC Reliable Broadcast in Ad Hoc Networks Ken Tang, Mario Gerla University of California, Los Angeles (ktang, gerla@cs.ucla.edu). Overview. Ad hoc network introduction Medium access control (MAC) protocol Broadcast limitation Broadcast Medium Window (BMW) protocol

hashley
Download Presentation

MAC Reliable Broadcast in Ad Hoc Networks Ken Tang, Mario Gerla

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MAC Reliable Broadcast in Ad Hoc Networks Ken Tang, Mario Gerla University of California, Los Angeles (ktang, gerla@cs.ucla.edu)

  2. Overview • Ad hoc network introduction • Medium access control (MAC) protocol • Broadcast limitation • Broadcast Medium Window (BMW) protocol • The broadcast medium window • Example • Simulation results • Conclusion

  3. Base Base Base Instant infrastructure, multi-hop wireless ad hoc networks Ad Hoc Network Introduction Standard base station cellular networks

  4. Overview • Ad hoc network introduction • Medium access control (MAC) protocol • Broadcast limitation • Broadcast Medium Window (BMW) protocol • The broadcast medium window • Example • Simulation results • Conclusion

  5. An Example of Random Access Scheme (IEEE 802.11) – Unicast Mode 2 6 1 0 4 5 RTS CTS 3 DATA Steps: ACK A. Collision avoidance Remote B. Node 0 transmits RTS to node 4 C. Node 4 transmits CTS and node 6 attempts an RTS D. Node 0 transmits DATA E. Node 4 transmits ACK

  6. MAC Broadcast Limitation • Reliable unicast • RTS/CTS to acquire the channel • ACK to make sure data is received • What about broadcast? • Send data and pray!

  7. An Example of Random Access Scheme (IEEE 802.11) – Broadcast Mode 2 6 1 0 4 5 3 DATA Steps: A. Collision avoidance B. Node 0 transmits DATA

  8. Overview • Ad hoc network introduction • Medium access control (MAC) protocol • Broadcast limitation • Broadcast Medium Window (BMW) protocol • The broadcast medium window • Example • Simulation results • Conclusion

  9. Broadcast Medium Window (BMW) • Ad hoc multicast routing protocols rely on MAC broadcast to achieve multicasting • Typical ad hoc MAC layer protocols (e.g., IEEE 802.11) are very “lossy” in the broadcast mode • We propose a novel scheme, Broadcast Medium Window (BMW) to provide robust (but not 100% reliable) MAC broadcasting

  10. The Broadcast Medium Window • Conventional window protocol (e.g., TCP) transmits packets in sequence to a single destination • The “broadcast window” protocol transmits packets by increasing sequence numbers to ALL neighbors • The window protocol “visits” each neighbor in Round Robin order to retransmit packets which the node missed in the broadcast transmission

  11. seqno = 1 seqno = 0 - 1 seqno = 0 seqno = 0 - 1 seqno = 0 seqno = 0 seqno = 2 seqno = 0 - 2 Broadcast Medium Window (BMW) Protocol Example 2 1 0 4 3 RTS CTS DATA ACK

  12. Overview • Ad hoc network introduction • Medium access control (MAC) protocol • Broadcast limitation • Broadcast Medium Window (BMW) protocol • The broadcast medium window • Example • Simulation results • Conclusion

  13. Simulation Results • GloMoSim/QualNet network simulator • (http://www.scalable-networks.com) • Application • CBR (512B) • Transport • UDP multicast traffic • Routing • ODMRP • MAC • 802.11 • BMW • Channel • 2Mbps • free-space

  14. On-Demand Multicast Routing Protocol (ODMRP) S S S S D D D D • Sources build routes on demand by flooding • Sources flood JOIN QUERY to multicast receivers • Multicast receivers respond with JOIN REPLY to sources

  15. Traffic Rate Experiment 4 3 0 1 2 9 8 5 6 7 14 13 10 11 12 19 15 18 16 17 24 23 20 21 22 • 25 nodes in grid topology, 3 sources and 6 members • BMW outperforms 802.11 • Under high rate, BMW and 802.11 are comparable • BMW reverts to 802.11 unreliable broadcast

  16. Sources Experiment 4 3 0 1 2 9 8 5 6 7 14 13 10 11 12 19 15 18 16 17 24 23 20 21 22 • 5 members, 2 packets per second, vary number of sources • BMW improves upon 802.11 with moderate number of sources • Under large number of senders, performances are comparable • Large number of senders also implies high network load • BMW reverts to 802.11 again

  17. Members Experiment 4 3 0 1 2 9 8 5 6 7 14 13 10 11 12 19 15 18 16 17 24 23 20 21 22 • 3 sources, 2 packets per second, vary number of members • BMW achieves 100% reliability • 802.11 gradually degrades as the number of members increases

  18. Uniform Experiment • More realistic ad hoc scenario • 25 nodes placed in 1000m x 1000m • Randomly select 5 sources and 5 members • Vary traffic rate • BMW consistently outperforms 802.11

  19. Overview • Ad hoc network introduction • Medium access control (MAC) protocol • Broadcast limitation • Broadcast Medium Window (BMW) protocol • The broadcast medium window • Example • ODMRP with congestion control • Simulation results • Conclusion

  20. Conclusion • Free-space model is very conservative • BMW benefit more from detailed channel model • Drawback of BMW • Increase latency as neighbors and packet loss increase • Solution • Reduce transmit power -> reduce power consumption • Port BMW concept directly into ODMRP • More efficient due to knowledge of forwarding group members

More Related