Reshaping WiFi ISAC with High-Coherence Hardware Capabilities

WiFi shows great promise for integrated sensing and communication (ISAC), but its wider application is hampered by two pivotal challenges: the low-quality channel state information (CSI) and inadequate hardware capabilities. This article introduces a paradigm shift with high-coherence hardware capabilities to fundamentally overcome these two challenges. Our approach is realized through four key break-throughs. First, we uncover a novel category of CSI error sources, termed CODEs, which pose core challenges for WiFi ISAC. The CODEs stem from the WiFi hardware design, and addressing them requires hardware-level modifications. Then, we propose a list of high-coherence hardware capabilities aimed at eliminating these errors. Our analysis indicates that the majority of these capabilities can be implemented at the firmware level, with a minority requiring chip-level changes. Next, we introduce two robust and synergistic incentives to encourage vendors to integrate these capabilities into their hardware: the 802.11bf standard and its certification program, and the large-scale carrier-grade purchasing. Finally, we present two demonstrations: a sub-nanosecond level time-of-flight (ToF) estimation system and a WiFi-based phased array. Both demonstrations show that remarkable sensing precision is achievable with the proposed high-coherence capabilities.