Spectrum Sharing for Internet of Things System in Periodic Transmission

This paper focuses on future Internet of things (IoT) devices equipped with a low-cost oscillator. An IoT system consists of many wireless devices and a base station (gateway) and is designed to collect multiple pieces of useful information. Each IoT device transmits signals periodically at regular intervals and is equipped with a low-cost oscillator. In previous work, using computer simulation, we have shown that collisions occur between packets transmitted by the IoT devices, as a result of the poor frequency stability caused by the cheap oscillator. Moreover, we have previously proposed an algorithm that enables an IoT device to modify its communication cycle: a regular packet transmission is delayed by predicting the interval between received packets at a gateway. However, packets from the device whose transmission timing is modified collide with the following packets from other IoT devices, and the total number of modifications is greatly increased by this algorithm. The work reported in this paper aims to suppress packet collisions more effectively than the previous algorithm. The performance of the new algorithm is confirmed by simulation.