  Wireless Sensor Networks (WSNs) are being used in various applications such
as structural health monitoring and industrial control. Since energy efficiency
is one of the major design factors, the existing WSNs primarily rely on
low-power, low-rate wireless technologies such as 802.15.4 and Bluetooth. In
this paper, we strive to tackle the challenges of developing ultra-high-rate
WSNs based on 802.11 (WiFi) standard by proposing Sensifi. As an illustrative
application of this system, we consider vibration test monitoring of spacecraft
and identify system design requirements and challenges. Our main contributions
are as follows. First, we propose packet encoding methods to reduce the
overhead of assigning accurate timestamps to samples. Second, we propose energy
efficiency methods to enhance the system's lifetime. Third, we reduce the
overhead of processing outgoing packets through network stack to enhance
sampling rate and mitigate sampling rate instability. Fourth, we study and
reduce the delay of processing incoming packets through network stack to
enhance the accuracy of time synchronization among nodes. Fifth, we propose a
low-power node design for ultra-high-rate applications. Sixth, we use our node
design to empirically evaluate the system.
