Phaser: A Phase-Shifting Antenna for Low-Power Directional Communication

Team: Octav Chipara, Leo Selavo, and Dhruv Vyas

The wireless sensor network community has extensively studied low-power communication when nodes are equipped with omnidirectional antennas. However, in contrast to omnidirectional antennas, smart directional antennas can be controlled by software to transmit signals in a preferential direction to create multiple radiation patterns. The diversity of radiation patterns can be exploited to selectively increase (or decrease) the signal at a receiver and improve spatial reuse. This basic capability can be a foundation for building the next generation of low-power wireless stacks that can extend the reach of low-power wireless communication by improving throughput, energy-efficiency, and reliability. We have developed a novel mote platform called PHASER that supports directional communication for wireless sensor networks. PHASER provides directional communication by controlling the phase the signal transmitted to each of its two antennas. PHASER is well-suited for wireless sensor networks as it does not require heavyweight signal processing techniques and consumes minimal additional energy. The net effect of controlling the phase of the signals is that they generate patterns of constructive and destructive interference as signals propagate. The video below shows the impact that changing the phases has on the antenna patterns.