What constitutes a useful experimental result?

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

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

Question:  What constitutes a useful experimental result?

Answer:  They are always useful!

New question:  What is the lifetime of an experimental result?

Answer:  Can affect parameters/optimization  Can affect theoretical limits  Can affect future hardware design

Parameter/Optimization  Characterize bit-error probability  Changes phy-layer coding techniques Hardware

Parameter/Optimization  Characterize Rx/Tx switch times  Change CSMA backoff times Hardware

Validate/Invalidate Assumptions  Characterize link quality distribution  Change network layer choices Hardware

Validate/Invalidate Assumptions

Influencing hardware design

Collision Detection and Recovery A B

Pream Sync

  Recovers stronger last packets Identifies collision

Data Crc Pream Sync Data Crc

A Stronger-First Collision Detection

Pream Sync Data Detection Term

B

Pream Sync Data Term

Effect on Protocols Revisit fundamental protocol design decisions   NACKs Broadcast: reliability A B NACK C

Effect on Protocols Revisit fundamental protocol design decisions    NACKs Broadcast: reliability TDMA: association

Effect on Protocols Revisit fundamental protocol design decisions      NACKs Broadcast: reliability TDMA: association CSMA: spatial reuse RTS/CTS: spatial reuse

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

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

Changing hardware design  Wireless collision detection  New capabilities  Protocol requirements affect hardware design Hardware

Changing hardware design  This is possible   802.11 generations ~1 2yrs Laptop lifetime ~2-3yrs