Universal WiFi Backscatter With Ambient Space-Time Streams

Since backscatter communication has the advantage of low power, it is promising to be widely used in IoT applications. For a space-time stream backscatter, we envision it can efficiently leverage ready-to-use multiform space-time streams in the environment. Previous works have struggled to achieve this because they use various tag-data modulations on various types of ambient space-time stream signals. What’s worse is that it is challenging to identify the properties of a space-time stream in a passive way. To this end, we present STScatter, a WiFi backscatter that is universally applicable for ambient space-time streams. Besides, STScatter achieves efficient tag-data modulation at the symbol-level, allowing space-time stream backscatter to reach high tag-data throughput with multiform excitation. Additionally, unlike previous systems that decoded tag data from both the original ambient and backscattered signal, STScatter can decode ambient data and backscattered data simultaneously from the backscattered signal. STScatter was prototyped using commercial FPGAs and SDRs. Our extensive experiments show that the STScatter is transmitter-agnostic and universal with different ambient space-time streams. STScatter can achieve a goodput of up to 455.9 kbps in single-stream excitation and 460.0 kbps in multi-stream excitation, which is 4.2x and 157.5x better than MOXcatter. Besides, STScatter successfully uses signals from various types of WiFi hardware for excitation and achieves an average tag-data goodput of 293.62 kbps with real-life file-downloading traffic generated by a household WiFi router.