  The research on Wi-Fi sensing has been thriving over the past decade but the
process has not been smooth. Three barriers always hamper the research: unknown
baseband design and its influence, inadequate hardware, and the lack of
versatile and flexible measurement software. This paper tries to eliminate
these barriers through the following work. First, we present an in-depth study
of the baseband design of the Qualcomm Atheros AR9300 (QCA9300) NIC. We
identify a missing item of the existing CSI model, namely, the CSI distortion,
and identify the baseband filter as its origin. We also propose a distortion
removal method. Second, we reintroduce both the QCA9300 and software-defined
radio (SDR) as powerful hardware for research. For the QCA9300, we unlock the
arbitrary tuning of both the carrier frequency and bandwidth. For SDR, we
develop a high?performance software implementation of the 802.11a/g/n/ac/ax
baseband, allowing users to fully control the baseband and access the complete
physical-layer information. Third, we release the PicoScenes software, which
supports concurrent CSI measure?ment from multiple QCA9300, Intel Wireless Link
(IWL5300) and SDR hardware. PicoScenes features rich low-level controls, packet
injection and software baseband implementation. It also allows users to develop
their own measurement plugins. Finally, we report state-of-the-art results in
the extensive evaluations of the PicoScenes system, such as the >2 GHz
available spectrum on the QCA9300, concurrent CSI measurement, and up to 40 kHz
and 1 kHz CSI measurement rates achieved by the QCA9300 and SDR. PicoScenes is
available at https://ps.zpj.io.
