ISACoT: Integrating Sensing with Data Traffic for Ubiquitous IoT Devices

The intention of leveraging Radio-Frequency (RF) resources for diverse sensing purposes has grown increasingly keen, thanks to the ever-expanding deployment of IoT devices using RF communications to maintain connectivity. Whereas the original idea was to integrate sensing and communications (a.k.a. ISAC) for individual IoT devices, most proposals in the past decade simply converted such devices (e.g., Wi-Fi or LoRa) into RF sensors without attending to their communication nature. Therefore, we argue that the device architecture has to be overhauled so as to achieve the ISAC ambition. To this end, we propose ISA-CoT as the framework for enabling ISAC over IoT devices. We categorize ISACoT's extensions over existing devices into four aspects, namely time, frequency, space, and protocol. We argue that, as the multistatic communication infrastructure of IoT is adverse to device-free sensing (e.g., lack of precise time synchronization), the keystone of ISACoT should be operating sensing in a monostatic mode (like radar). We tackle the fundamental time aspect based on Wi-Fi first, but leave the other three as challenges for exploration. For each of the three aspects, we present our proposals along with verification experiments, while putting forward challenges along with potential solutions. In particular, the protocol aspect discusses how ISACoT can be generalized to other IoT protocols beyond Wi-Fi.