Can WiFi Backscatter Achieve the Range of RFID? Nulling to the Rescue (Presentation Video)

RFID and WiFi backscatter systems use similar techniques to enable battery-free wireless communication. Despite their similarities, existing WiFi backscatter systems achieve a much shorter range than RFID systems. The main reason for this limitation is self-interference. In particular, in any backscatter communication, the reader needs to transmit and receive at the same time. RFID systems do this by using full-duplex hardware. Unfortunately, existing WiFi devices do not have full-duplex capabilities. Therefore, to enable backscatter communication using existing WiFi devices, today's WiFi backscatter systems use two WiFi devices where one transmits and the other one receives. However, since the tag's reflection is very weak compared to the query signal, it is very challenging to detect and extract the tag's reflection from the query signal. This problem is known as self-interference. In this paper, we propose a novel approach for eliminating this problem in WiFi backscatter systems without any hardware modifications on existing WiFi devices. Our empirical evaluations show that our technique improves the range of in-channel WiFi backscatter systems to that of RFID in both line-of-sight and non-line-of-sight scenarios. Moreover, our approach enables WiFi backscatter communication even in scenarios where the tag has no LOS path to any WiFi device. None of existing WiFi backscatter systems work in this scenario.
Ali Abedi (University of Waterloo), Omid Abari (UCLA),
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The idea was very cool.