Towards SISO Bistatic Sensing for ISAC

TL;DR

This paper introduces WiDFS 3.0, a lightweight SISO sensing framework that accurately estimates delay and Doppler in low-cost, single-antenna ISAC systems despite phase offsets, outperforming traditional multi-antenna methods.

Contribution

It proposes a novel SISO sensing approach with self-referencing and delay-domain beamforming to resolve phase and Doppler ambiguities, enabling robust sensing with minimal hardware.

Findings

WiDFS 3.0 achieves high-accuracy delay and Doppler estimation.

It outperforms conventional multi-antenna methods in delay accuracy.

The framework generalizes well across different scenarios.

Abstract

Integrated Sensing and Communication (ISAC) is a key enabler for next-generation wireless systems. However, real-world deployment is often limited to low-cost, single-antenna transceivers. In such bistatic Single-Input Single-Output (SISO) setup, clock asynchrony introduces random phase offsets in Channel State Information (CSI), which cannot be mitigated using conventional multi-antenna methods. This work proposes WiDFS 3.0, a lightweight bistatic SISO sensing framework that enables accurate delay and Doppler estimation from distorted CSI by effectively suppressing Doppler mirroring ambiguity. It operates with only a single antenna at both the transmitter and receiver, making it suitable for low-complexity deployments. We propose a self-referencing cross-correlation (SRCC) method for SISO random phase removal and employ delay-domain beamforming to resolve Doppler ambiguity. The resulting unambiguous delay-Doppler-time features enable robust sensing with compact neural networks. Extensive experiments show that WiDFS 3.0 achieves accurate parameter estimation, with performance comparable to or even surpassing that of prior multi-antenna methods, especially in delay estimation. Validated under single- and multi-target scenarios, the extracted ambiguity-resolved features show strong sensing accuracy and generalization. For example, when deployed on the embedded-friendly MobileViT-XXS with only 1.3M parameters, WiDFS 3.0 consistently outperforms conventional features such as CSI amplitude, mirrored Doppler, and multi-receiver aggregated Doppler.