Pushing Bistatic Wireless Sensing toward High Accuracy at the Sub-Wavelength Scale

Abstract

Contactless sensing using wireless communication signals has garnered significant attention due to its non-intrusive nature and ubiquitous infrastructure. Despite the promise, the inherent bistatic deployment of wireless communication introduces clock asynchronism, which leads to unknown phase offsets in channel response and hinders fine-grained sensing. State-of-the-art systems widely adopt the cross-antenna channel ratio to cancel these detrimental phase offsets. However, the channel ratio preserves sensing feature accuracy only at integer-wavelength target displacements, losing sub-wavelength fidelity. To overcome this limitation, we derive the first quantitative mapping between the distorted ratio feature and the ideal channel feature. Building on this foundation, we develop a robust framework that leverages channel response amplitude to recover the ideal channel feature from the distorted ratio. Real-world experiments across Wi-Fi and LoRa demonstrate that our method can effectively reconstruct sub-wavelength displacement details, achieving nearly an order-of-magnitude improvement in accuracy.

Figures (7)

• Figure 1: Illustration of ideal channel responses.
• Figure 2: The rotation feature of the channel ratio is distorted under sub-wavelength-scale variations.
• Figure 3: Illustration of $\left\vert H_{2}\right\vert_{\text{max}}$ and $\left\vert H_{2}\right\vert_{\text{min}}$.
• Figure 4: Framework Overview.
• Figure 5: Examples of displacement estimates.