by gregg bachmeyer for cmpe 257 n.
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Using Collisions to improve Network protocols

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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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  • 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


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




Schedule Execution



Join / Notification



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







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)
  • (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.
  • 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.
  • 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”