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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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By gregg bachmeyer for cmpe 257

By Gregg Bachmeyer

for CMPE 257

Using Collisions to improve Network protocols


Overview
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


Why it m ight b e i mportant
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


Scheduling phases
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

….


Join notification phase
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.


Schedule query
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


Schedule execution dead time
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)


Expectations
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]


Simulation setup
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.


Current output packet throughput in 10 sec period
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.


Expected issues on r eal i mplemention
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.


Conclusion
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.



References
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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