What constitutes a useful experimental result?

1
What constitutes a useful experimental result?

• Kamin Whitehouse
• University of Virginia
• Wireless Networking Workshop
• May 20, 2008

2
A double standard

• This experiment must use a radio like 802.11
• This experiment applies only to one radio
• We need to bridge the gap between
  hardware/protocols
• Hardware-specific protocols have little value

3

• Question
• What constitutes a useful experimental result?
• Answer
• They are always useful!

4

• New question
• What is the lifetime of an experimental result?
• Answer
• Can affect parameters/optimization
• Can affect theoretical limits
• Can affect future hardware design

5
Parameter/Optimization

• Characterize bit-error probability
• Changes phy-layer coding techniques

Hardware
6
Parameter/Optimization

• Characterize Rx/Tx switch times
• Change CSMA backoff times

Hardware
7
Validate/Invalidate Assumptions

• Characterize link quality distribution
• Change network layer choices

Hardware
8
Validate/Invalidate Assumptions
9
Influencing hardware design
10
Collision Detection and Recovery
A

• Recovers stronger-last packets
• Identifies collision

B
11
Stronger-First Collision Detection
A
B
12
Effect on Protocols

• Revisit fundamental protocol design decisions
• NACKs
• Broadcast reliability

13
Effect on Protocols

• Revisit fundamental protocol design decisions
• NACKs
• Broadcast reliability
• TDMA association

14
Effect on Protocols

• Revisit fundamental protocol design decisions
• NACKs
• Broadcast reliability
• TDMA association
• CSMA spatial reuse
• RTS/CTS spatial reuse

15
Effect on Protocols

• Revisit fundamental protocol design decisions
• NACKs
• Broadcast reliability
• TDMA association
• CSMA spatial reuse
• RTS/CTS spatial reuse
• CSMA/CD aggressiveness
• Rapid Flooding latency

16
Measurements

• We need to evaluate effectiveness
• 15 of receptions were in a collision
• Up to 40-50 transmissions collided somewhere
• 92 (100) of stronger-last collisions can be
  recovered
• 84 of stronger-last collisions can be detected
• Both txr identifies can be recovered in 80 of
  detections

17
Changing hardware design

• Wireless collision detection
• New capabilities
• Protocol requirements affect hardware design

Hardware
18
Changing hardware design

• This is possible
• 802.11 generations 1-2yrs
• Laptop lifetime 2-3yrs