Cellular Internet-of-Things (IoT) Communications over Unlicensed Band

Abstract

The mass deployments of Internet-of-Thing (IoT) devices may quick congest the cellular network, affecting the energy consumption of IoT devices and degrading the spectral efficiency of the cellular network. To tackle this problem, a promising issue is to extend the IoT communications into the unlicensed band. In this paper, we consider an uplink cellular IoT network where IoT devices can serve as the cluster head (CH) to aggregate the data from other IoT devices in the same cluster. To be specific, the IoT devices can either transmit the sensory data to the base station (BS) directly by cellular communications, or aggregate the data to a CH through Machine-to-Machine (M2M) communications before the CH uploads the aggregated data to the BS. To support the massive connection of IoT devices, the unlicensed spectrum is utilized for M2M communications. We first introduce the scheduled number maximization problem of IoT devices with the minimum transmit power, and then decouple it into two subproblems, which are solved by successive integer linear programming and convex optimization techniques, respectively. Simulation results show that the proposed unlicensed scheme can support more IoT devices than that only using licensed spectrum.