UC San Diego

My dissertation develops novel wireless devices that utilize the electromagnetic wave backscattering phenomenon to enable low-power and long-range applications in wireless communication and sensing domains.

We show the advantages of using smart surfaces for both outdoor and indoor wireless connectivity solutions. We present a passive smart surface prototype equipped with antenna elements and phase shifters to backscatter wireless signals in the environment. When this smart surface is deployed with an access point, it creates a virtual access point, resulting in strong multipath effects that enhance MIMO multiplexing.

Furthermore, we explore how backscattering can enable new connectivity solutions for low-power wireless devices. We prototype a backscatter tag integrated circuit to demonstrate low-power connectivity by embedding data on ambient WiFi signals. We develop a hierarchical wake-up receiver for the backscatter tag to synchronize with ambient WiFi signals and modulate data while maintaining low power consumption. This hierarchical wake-up scheme reduces the bit error rate in the decoded backscattered data and extends the deployable range of the backscatter tag.

We also introduce Beamscatter to facilitate backscatter tag deployment in a wide-area mesh network. Beamscatter employs a multiple-antenna backscatter tag framework to enhance the tag's reachability from an access point. We present a low-power hardware architecture that enables steering the backscattered signal toward an arbitrary direction.

Finally, we demonstrate the application of backscatter tags in assisting traffic infrastructure sensing using automotive radars. By deploying backscatter tags on traffic infrastructure like roadside signs, we make them detectable by frequency-modulated continuous wave radars from long ranges. We propose a tag modulation scheme that differentiates scattered signals from closely situated tags, enabling vehicles to distinguish between traffic infrastructures.