A team of developers has created an open source wireless tracking system for following people around buildings.

The creators of the OpenBeacon system sold 900 tags at €10 (US$13) each to attendees at the Chaos Communication Congress in Berlin. The volunteers agreed to be tracked during the four-day event; some attendees bought multiple tags to experiment with later.

OpenBeacon uses chips from Nordic Semiconductor that transmit and receive over the 2.4GHz frequency, which is available for unlicensed use in many countries. At the conference, the chips communicated with nearby base stations which sent data back to a central server. There were 23 base stations positioned around the conference centre.

The developers of OpenBeacon worked with partners to create a three dimensional model of the conference center and anyone could use touch-screen monitors that displayed the location of attendees on the model. Touching an attendee on the screen displayed a profile that the person could voluntarily add.

The OpenBeacon team used the congress as a showcase for the tracking technology and its implications. "At first look, you don't see anything special about the data moving around the building," said Milosch Meriac, one of the creators of OpenBeacon. However, an analysis of data collected over several days and about many people could lead to assumptions about relationships between people who may have gathered in similar spaces repeatedly, he noted.

"We wanted to make this analysis transparent so that people are more aware of what data they're willing to give away," he said. On the last day of the conference, OpenBeacon released all the data gathered over the four days so anyone could access and analyse it.

There are already many types of commercial systems that could be used for tracking people or things but Meriac hoped to solve several shortcomings in those systems. He and a friend initially developed OpenBeacon after looking for a possible way to solve crowd control problems that often occur when millions of Muslim pilgrims visit Mecca each year.

They decided that RFID (radio frequency identification) wouldn't be very helpful because the tags can only be read by passing through gates. Requiring millions of people to funnel through specific areas might only exacerbate the problem.

Other tracking systems based on Wi-Fi exist but they often have battery-life limitations and higher costs, Meriac said.

OpenBeacon tracking devices transmit and then sleep, cutting back on power consumption. The devices could run for several months before requiring a new battery.

The OpenBeacon devices could be distributed to 10,000 pilgrims travelling to Mecca, for example. Their identities wouldn't be important but crowd control monitors could note when many of the tagged pilgrims converge in one spot, implying that potentially many other untagged people are also in the same area, and then they could work to divert or otherwise alleviate the congestion, Meriac said.

The firmware, drivers and hardware design for the tracking devices are released under GNU/GPL open source licenses. The base station designs are not currently available as open source because they were designed closely with a vendor.

Meriac hopes that other contributors will develop mesh protocols for the system so that the devices can communicate with each other rather than only with a central base station.