Mica Sensorboard Time of Flight data

This data was collected to answer two questions:

  1. How useful is the acoustic time of flight estimate from the mica sensorboard
  2. To what extent is calibration required to make TOF useful

The data resides in the tinyos cvs in /tinyos-1.x/tools/matlab/contrib/kamin/acousticTimeOfFlight.  All data was collected on the ping-pong table testbed on the south side of the Intel Lab at Berkeley.  The code in /analysis subdirectory will help calibrate and plot the tof data, although this code is unsupported.  The easiest way to calibrate the data is the understand the calibration code in the chipconRssi sibdirectory and apply it to the time of flight estimates.

The MICA mote is essentially an Atmel 103 microcontroller in conjunction with a RFM TR1000 radio transceiver and is about the size of two AA batteries. Connected to each mote is a MICA sensor board which, among other things, contains a Sirius PS14T40A 4.3KHz sounder and a Panasonic WM-62A microphone, whose band-passed output is wired to a National Semiconductor LMC567CM tone detector whose center frequency is set to about 4.5KHz.

In our experiments we use 32 nodes in a 30cm x 30cm grid. The motes are situated atop a large table in an 8 x 4 formation spanning a total area of 210cm x 90cm, as seen in. All motes are in the same orientation. Both the sounder and microphone point directly upwards. The sounder is located in the center of the board while the microphone is in one corner.   The testbed setup and the mica sensorboard are shown here.

    

Although this experimental setup does not test all combinations of paired distances and relative orientations, it does provide a nice sampling of that space. A total of 24 distances ranging from 30cm to 210cm are measured using this setup. While all motes are in the same orientation on the table, they are not all in the same orientation relative to each other. A total of 992 transmitter/receiver pairs are used, although each at only one distance and orientation. The acoustic transmission frequencies are distributed evenly from 4.2KHz to 4.5KHz while the tone detector center frequencies are distributed between 4.4KHz and 4.6KHz.

To generate the data, each transmitter sent several localization beacons allowing all other nodes to make a single distance estimate. Each node therefore generated up to 31 distance estimates.   This experiment was repeated five times, each time with the nodes in different spots on the grid.  Therefore, each pair generated about 5 distance estimates at different distances.  To understand the data format, read the comments in the file called "convertTOF_DISTANCEtoRangingData.m".  To see plots of this data, look at on the calibration papers mentioned on the home page.   However, note that the data set located here is newer and more complete.