  Despite the proliferation of mobile devices in various wide-area Internet of
Things applications (e.g., smart city, smart farming), current Low-Power
Wide-Area Networks (LPWANs) are not designed to effectively support mobile
nodes. In this paper, we propose to handle mobility in SNOW (Sensor Network
Over White spaces), an LPWAN that operates in the TV white spaces. SNOW
supports massive concurrent communication between a base station (BS) and
numerous low-power nodes through a distributed implementation of OFDM. In SNOW,
inter-carrier interference (ICI) is more pronounced under mobility due to its
OFDM based design. Geospatial variation of white spaces also raises challenges
in both intra- and inter-network mobility as the low-power nodes are not
equipped to determine white spaces. To handle mobility impacts on ICI, we
propose a dynamic carrier frequency offset estimation and compensation
technique which takes into account Doppler shifts without requiring to know the
speed of the nodes. We also propose to circumvent the mobility impacts on
geospatial variation of white space through a mobility-aware spectrum
assignment to nodes. To enable mobility of the nodes across different SNOWs, we
propose an efficient handoff management through a fast and energy-efficient BS
discovery and quick association with the BS by combining time and frequency
domain energy-sensing. Experiments through SNOW deployments in a large
metropolitan city and indoors show that our proposed approaches enable mobility
across multiple different SNOWs and provide robustness in terms of reliability,
latency, and energy consumption under mobility.
