WiNGS Lab @ UW

The digital domain allows for much easier recovery of information from coherent systems. Even though radio channels are noisy and fading and difficult to work with, information can be recovered using approximation.

Warp website

Currently, a two-USRP GNURadio setup is being used, with either differential 8-PSK or straight 8- or 16-QAM.

• GNURadio: Feedback (non-feedforward) AGC that doesn't use std::max(), which should be more noise-resistant
• Error data using PSK/QAM
  • PSK should be taken before differential decoding and after differential encoding, to give numbers for the actual effect on constellation points, in addition to the actual values used
• Working QAM implementation:
  • GNURadio
    • Scrambler block? ('scrambling' can be on a bit level basis, i.e. each bit of a 16QAM gets scrambled independently, if that would aid us. Mason is admittedly unfamiliar with scrambling.)
  • WARP
• Streaming video
  • On GNURadio using IP Works, but laggy on Minis
  • On GNURadio using straight video transmission (benchmark_[tr]x.py) (currently sort-of-works but even worse than IP)
  • On WARP

MPEG Streaming on GR implementation details:

• Proposal is to take apart an MPEG stream, stripe out the I, P, B frames, send them over air, and then reassemble them into an MPEG stream at the other end. This means we need to:
  • Be able to parse an MPEG-2 file in python, read it in, save metadata, and start picking off I, P, B frames, etc
  • Be able to do the striping on separated I,P,B frames and metadata
  • Send this over the wireless link
  • destripe the data
  • reassemble into an MPEG-2 stream
  • output to some video player (through Python?)

What Steve is doing this week:

• Reading about how DSSS works, used in 802.11b,g to spread the signal in frequency. Open questions are:
  • How can this be used to put multiple bit streams with different error protection into one signal? (same error protection seems easy)
    • sub-thought: perhaps by spreading different bit streams by different amounts.
  • Is this implemented in GNU Radio? in WARP?
    • sub-question: where's the documentation for WARP?
• Assuming that QAM on GNU Radio is dead, unless a better AGC/phase error calculator works magically, given that we'll have WARP radios soon.
• Fighting occasionally with docuwiki syntax