  Low-Power Wide-Area Network (LPWAN) is an emerging communication standard for
Internet of Things (IoT) that has strong potential to support connectivity of a
large number of roadside sensors with an extremely long communication range.
However, the high operation cost to manage such a large-scale roadside sensor
network remains as a significant challenge. In this article, we propose Low
Operation-Cost LPWAN (LOC-LPWAN), a novel optimization framework that is
designed to reduce the operation cost using the cross-technology communication
(CTC). LOC-LPWAN allows roadside sensors to offload sensor data to passing
vehicles that in turn forward the data to a LPWAN server using CTC aiming to
reduce the data subscription cost. LOC-LPWAN finds the optimal communication
schedule between sensors and vehicles to maximize the throughput given an
available budget. Furthermore, LOC-LPWAN optimizes the fairness among sensors
by preventing certain sensors from dominating the channel for data
transmission. LOC-LPWAN can also be configured to ensure that data packets are
received within a specific time bound. Extensive numerical analysis performed
with real-world taxi data consisting of 40 vehicles with 24-hour trajectories
demonstrate that LOC-LPWAN reduces the cost by 50% compared with the baseline
approach where no vehicle is used to relay packets. The results also show that
LOC-LPWAN improves the throughput by 72.6%, enhances the fairness by 65.7%, and
reduces the delay by 28.8% compared with a greedy algorithm given the same
amount of budget.
