RSSI, noise and signal (on the wrt54g)

For a sensor network project I have been using a modified Linksys wrt54g (wrt54gs) wireless box. (For a podcast on modding the wrt54g wireless router to run your own software based on linux, you can also see the related podcast on iTunes.) The driver on these devices returns a measurement of signal strength called rssi (Recieved Signal Strength Indicator). To access it you run a sheel on the device and enter "wl rssi". In several places, this value is documented as being in dB, which is a logarithmic scale for measuring power. I don't believe it. (For those running openwrt, ddwrt or similar, download the "wl" application and try (wl rss and wl noise).

RSSI is a classic way (albeit ad hoc?) of measuring the signal strength for a wireless devices (such as an 802.11b access point). As far as I know, it is not usually reported in dB, but some more-or-less liner scale. In fact the wrt54g "wl" command itself claims that RSSI and NOISE are reported in dB, but observed data contradict this. Note also that...

  

Aqua robot V1.5 tests -- new amphibious legs

The next version of the Aqua underwater will be getting a workout in the McGill pool sometime soon with new legs. We have some problems with the calibration of the intertial measurement unit, but otherwise things are proceeding apace. The amphibious legs, which allow both walking and swimming to be accomplished efficiently are looking really good and this should be an exciting test.


(The legs shown here are the older swimming flippers and not the new still-confidential version 3 legs. Movie here.

These legs combine compliance and swimming factors to greatly exceed the performance of our prior legs. They have been on the drawing board and in prototype form for some time, and it will be important to really assess their performance accurately.

  

Dinner with poets

Last week Bernhard Beutler and his wife were in town from Germany. We invited them to supper as well as Sonja Scarstead (my father's last published), Pierre DesRuisseaux (translator of Louis Dudek poetry into French) and a few other people. On the whole, the crowd was composed of people with either a Louis Dudek connection or a German connection (or both). The not-strictly-literary crowd included renowed computer scientist Luc Devroye, his wife Bea, Mike and Corinna Langer and Geof Isherwood. Luc and Geof Isherwood (artist) developed a scintillating dynamic.