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Using Collisions to improve Network protocols

By Gregg Bachmeyer for CMPE 257. Using Collisions to improve Network protocols. Overview . How to use collisions as beneficial part of a network protocol. Ask the right questions at the base station Break the system into parts Contention Base join May get congested

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Using Collisions to improve Network protocols

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  1. By Gregg Bachmeyer for CMPE 257 Using Collisions to improve Network protocols

  2. Overview • How to use collisions as beneficial part of a network protocol. • Ask the right questions at the base station • Break the system into parts • Contention Base join May get congested Preventing anyone from Joining/Sending Wireless client 2 Wireless client 3 Wireless client 1 Base station Wireless client 4 Wireless client 5

  3. Why It Might Be Important • Growing number of wireless devices may compete for network usage • Helps support power savings at client nodes, base station assume to be grid powered. • Most used networks appear to have access points. • Randomness can give random performance

  4. Scheduling Phases • Join/Notify • Schedule Query • Schedule Execution • Nodes Send and Receive • Dead Time Join / Notification Phase Schedule Query Schedule Execution Dead Time Join / Notification Phase ….

  5. Join Notification Phase • Base station send join notification • Nodes join • Nodes report on conflicts • Nodes report that they want to send (if joining) • If there is a collision the base station breaks MACaddress in 2 based on last digit and resends.

  6. Schedule Query • Base Station Has Nodes added into a tree. • Base Station Sends Schedule Query • Nodes respond with packets they want to send • If here is a collision the base station divides tree in half and resends Schedule Query 32-3D-56-28-BA-A5 82-3A-46-28-5A-A3 32-65-56-23-BA-B5 32-3D-56-28-B5-A1 32-3D-55-28-55-A2 56-3D-56-28-BA-FF

  7. Schedule Execution & Dead Time • Base station sends out schedule • Nodes wait for there time and send or receive. • The schedule can include areas of Dead Time so that frequencies can be shared. • Start from the beginning (Join/Notify Phase)

  8. Expectations • (better than 802.11)Large number of nodes with intermittent amount of data to send. Or nodes that have large number of packets to send at one time. • (worse than 802.11)Small number of nodes • (worse than 802.11)Nodes that only have one packet to send at a time. • (worse than 802.11)MAC addresses that are inversely sequential [but MAC addresses are changeable]

  9. Simulation Setup • NS-2 • 802.11 • Collision protocol • Increasing number of non-mobile wireless nodes (jump 30 nodes at a time) • Packet arrival at .0003 • TCP & AODV layers stacked above.

  10. Current Output (packet throughput in 10 sec period) • Note: this is current output, at time of presentation, I think that there are errors that are causing only one packet to arrive at a time that I am working on correcting.

  11. Expected Issues on Real Implemention • Possible large amount of overhead. • Fast processing on base station. • Current physical handling of collisions may prevent the possibility of the protocol working.

  12. Conclusion • The overhead of the protocol may be high for use today but its necessity for the future is possible. • There are many possible heuristics that should be considered or future research that may improve performance to help it compete with protocols used today.

  13. Questions

  14. References • VenkateshRajendran, KatiaObraczka, J.J. Garcia-Luna-Aceves. "DYNAMMA: A DYNAmic Multi-channel Medium Access Framework for Wireless Ad Hoc Networks", Proceedings of the 4th IEEE International Conference on Mobile Ad-hoc and Sensor Systems (MASS). Oct 2007. • John R. Vacca. "Wireless Data Demystified", McGraw-Hill Networking, 2002 • SourceForge. “Ns-2”

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