Nodes in sensor fields and in autonomous swarms of mobile robots need to communicate; this usually requires individual nodes to either consume a significant amount of energy, carefully position themselves, precisely align carrier phase, or use complex coding. We propose allowing multiple independent and mobile wireless transmitters to share the power-consumption burden by combining lowpower transmissions into a unified higher-power transmission. This is not a distributed beamforming or spacetime coding approach. Instead, all nodes simultaneously broadcast the same symbol on the same channel without using different code books and without aligning carriers. This paper briefly describes a modulation scheme (RandomPhase Frequency Shift Keying, RPFSK), a synchronization scheme (Ensemble), and a node selection scheme which make this possible. It then describes an RPFSK demodulator design in detail for Ensemble nodes. It also covers both baseband and over-the-air test results.
Tingting Meng, Peter M. Athanas