Checkout coverage of our long range backscatter system on Economist. https://www.economist.com/news/science-and-technology/21728866-long-range-frugal-new-chip-could-be-just-what-smart-city-needs-clever-way Also check out other coverage: https://spectrum.ieee.org/tech-talk/telecom/wireless/lowpower-sensors-use-backscatter-to-transmit-data-several-kilometers  

Our recent work on LoRa backscatter breaks the long held belief that backscatter is a short-range communication system.   http://longrange.cs.washington.edu/