The Art of Signal Processing in Backscatter Radio for μW (or Less) Internet of Things: Intelligent Signal Processing and Backscatter Radio Enabling Batteryless Connectivity

Backscatter (or simply scatter) radio is based on reflection principles, where each tag modulates information on top of an illuminating signal, by simply connecting its antenna to different loads; modulation of information is based on the modifications of the tag antenna-load reflection coefficient, requiring in principle only a switch and omitting powerconsuming signal conditioning units, such as mixers, amplifiers, oscillators, and filters. The ultralow-power nature of backscatter radio, in conjunction with the recent advances in multiple access and achieved communication ranges (on the order of hundreds of meters to kilometers), due to intelligent signal processing, elevate backscatter radio as the de facto communication principle e for nW (or less)-level consumption, last-mile connectivity, and Internet of Things (IoT) networking. This article is an update to the state-of-the-art advances in the emerging backscatter radio domain, focusing on the signal processing engine, including ambient illumination from existing signals, as well as unconventional backscatter radio-based IoT technologies that could revolutionize environmental sensing and agriculture. Finally, the offered research methodology and techniques in short-packet, channel-encoded (or not), coherent (or not) sequence detection will assist researchers in radio-frequency identification (RFID)/backscatter radio as well as other domains of the telecommunications industry.