Towards Seamless Single Receiver Backscatter with Uncontrolled Ambient OFDM WiFi

OFDM WiFi backscatter with uncontrolled ambient signals is a promising approach for realizing passive Internet of Things (IoT) systems. However, existing OFDM backscatter systems are often limited by coarse modulation granularity, typically constrained to the packet or OFDM symbol levels, and commonly require dual receivers for data demodulation. To address these challenges, we propose DFTScatter, a novel sub-symbol level backscatter system that utilizes a single receiver for demodulation. DFTScatter leverages the Discrete Fourier Transform (DFT) shift theorem to achieve sub-symbol level modulation through frequency domain cyclic shifts. This method enhances data transmission efficiency and operates within a single-symbol bandwidth, thereby optimizing spectrum utilization. Additionally, we introduce a single-receiver decoding technique that exploits invariant frequency domain information of the reflected signals for accurate demodulation. Extensive experiments demonstrate that DFTScatter outperforms existing methods and effectively operates with various ambient OFDM WiFi signals, including WiFi 3/4/5/6, paving the way for scalable, low-cost IoT ecosystems in smart cities, healthcare, industrial automation, and beyond.