With more and more tiny devices being embedded at all scales and in different physical environments, there are increasing challenges to manage energy resources and communication resource limits. One recent area of research involves the exploitation of existing ambient radio frequency (RF) signals, both for energy harvesting and for device-to-device communications. The authors of this paper have designed a novel communication and energy harvesting primitive and prototype that uses ambient RF TV signals and backscattering communication. The advantages of such a design are that these devices don’t need any extra energy sources, and their communication systems are an order of magnitude more power efficient than traditional radio communications. This ambient backscatter communication system is more efficient than, but different from, a radio frequency identification (RFID) system (which requires an RFID reader) in the sense that it does not need to expend extra energy on inter-device communication. This design prototype has been able to achieve a data rate of 1 kilobit per second (kbps) over distances of 2.5 feet (outdoors) and 1.5 feet (indoors).
The paper presents details about the system of RF TV signals that is exploited by the proposed backscatter system, and the hardware and component designs of the ambient backscattering transmitter and receiver. The two main functional designs of the receiver are: the extraction of backscatter information from ambient RF signals with a conventional digital receiver, and ultra-low-power receiver design using analog components with decoding. After the hardware was designed, the researchers designed the full network communication stack with modulation and bit encoding, packet transmission detection, packet formatting, and carrier sensing. Further key functionalities include multiple bit rates, collision avoidance, and the reduction of overhead for request-to-send/clear-to-send (RTS-CTS) for hidden terminals. The complete prototype is evaluated with performance parameters such as the ratio of received power, the bit error rate (BER) with distance, carrier sensing (energy detection and preamble correction), and interference. Finally, the prototype is tested with two key ubiquitous applications that were previously infeasible: smart passive cards for billing and inventory management in retail.
Overall, this paper makes a significant technical contribution and is recommended for readers interested in the future of low-power device-to-device communication and RF energy harvesting systems for smart environments, ubiquitous computing, pervasive computing, and applications for the Internet of Things.