This was a project focused on a very low power (less than 100mA@3V), short range digital wireless network to provide point to point (or point to multipoint) communication for the quadrocopter project.
The network was based on ZigBee module PAN4551 from Panasonic (equipped with 8bit HCS08 microntroller and ZigBee transciever – both from Freescale). The modules are equipped with a small ceramic antenna which conserves some space and whole module is so small it can be placed on a board. Attributes of the antenna should enable use of triangulation when there are more modules in known locations, and I suppose someone has definitely implemented it.
But the modules are no longer used because, well, there is a professional ZigBee modem available – XBee. No need of additional programming, just place and go!
Here is what remained from original network:
The first picture shows PC receiver (point to multi-point master). The second picture shows PAN4551 module on the original quadrocopter board.