Changes between Version 41 and Version 42 of Old/Dailyupdates


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Timestamp:
Jun 29, 2007, 2:15:13 PM (17 years ago)
Author:
aniket
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  • Old/Dailyupdates

    v41 v42  
    3939Today was an educational day. We have been reviewing our statistics and reading up on signal processing. We ran an experiment and collected some data to use to work out our statistical algorithms. The experiment was as followed: We set up an access point out in the hall way and had a robot drive strait passed it, never stopping but collecting signal strength and position data the whole way through. Two trials were run - in one the source was right at the beginning of the robot's motion, and at another the source was midway between the robots start and end points.
    4040
    41 We found an interesting fact in MadWifi's documentation - the scale we use to measure signal strength (dbm) was specifically chosen to be linear with distance. We went ahead and performed a least square regression and fit a line  to the data from the first test. The line fit well but something is wrong with my code that calculates RMS value - I will debug that.
     41We found an interesting fact in !MadWifi's documentation - the scale we use to measure signal strength (dbm) was specifically chosen to be linear with distance. We went ahead and performed a least square regression and fit a line  to the data from the first test. The line fit well but something is wrong with my code that calculates RMS value - I will debug that.
    4242
    4343Next, looking at the second test, we found a very distinct U shaped pattern in signal strength with distance. We estimated the location of the minimum with our eyes and fit two LSLs (least square regressions). Rather than eyeball it, I thought we should find the code that finds the location along the distance axis which calculates the lowest over all square regressions (summing the regressions from the two lines). It takes a large amount of computer power (approx 15sec) to compute the total regression for every possible location, but in the end we see another distinct U-shaped curve with a minimum right about at the location of the access point.