Hand Hygiene

The six motes (numbered 2-7) were placed 2m apart with radios facing each other, at a height of 42.5″ from the ground on 2.5″ PVC pipes, level to about 1.5 degrees. The channel was set to 11 (2405 MHz), determined to be quite in the lab on that day. The motes were first synchronized. During each trial interval, each mote broadcast a signal at strength 20 and listened for a broadcast from its pair. The timing of each broadcast within the interval was randomized. After the broadcast interval, the motes rebroadcast at full power an acknowledgement of the signal received and the strength of the received signal. This acknowledgement was received by a listener. The number of packets acknowledged was recorded, along with the mean and standard deviation of the power of the received signal.

Here is the data.

[iframe http://spreadsheets.google.com/pub?key=tTVrUa8kCXzt1KH-CfjpUfw&output=html 500 600]

Discussion:
The results do not support the idea that the motes have two separate groups that communicate within their group, but not outside the group.

We were surprised that the communication had either a poor or an intermediate level of reliability (1 in 6 or 1 in 2). We were also surprised that the reliability seemed to be, at best, around 50%.

We’re going to double check the code for errors, as a higher success rate seemed likely. Hopefully the software will also account for the inter-mote reliability.