A recent article has been published that talks about wireless location tracking. Location is often referred to as the "holy grail" for wireless solutions since it allows motes to be deployed in a truly ad-hoc manner. There are multiple methods for figuring out where a mote is--the most commonly used method is GPS. GPS chipsets have significantly advanced in the last 10 years, where the power consumption is low and the accuracy is very high. Integrating GPS with motes is more commonplace and provides a very good solution for outdoor deployments with a clear view of the sky.

For indoor situations, the options are less abudant and less accurate. Companies like Rosum offer location positioning based on TV signals, but these only work well in metropolitan areas. Why is that a problem? Well, as the article points out, determining the location of a person in burning building or a mine is not possible using traditional techniques. Instead, the motes must rely on each other to figure out their location. This approach is the most difficult, the least accurate, but has extremely promising uses.

We're constantly tracking the new location technologies that are coming on to the market. Some companies are proposing ultra-wideband which uses a slew of different frequencies to address the issues with a single signal bouncing around like in the case of WiFi. But the most fundamental is to measure and calibrate the strength of signal received from other motes. Basically each mote listens to its neighbors and then computes the distance based on how loud its neighbors are talking. Not very accurate, but sometimes knowing within 10-20m where someone is located is more than enough to rescue them from a dangerous situation.

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