Utilization-Weighted Algorithm for Spreading Factor Assignment in LoRaWAN

Long Range Wide Area Network (LoRaWAN) is one of the leading low power wireless networks that can support thousands of Internet of Things (IoT) devices. To enhance the scalability of LoRaWAN, this paper proposes the UtilizationWeighted (UW) algorithm, which is the spreading factor management algorithm designed based on the M/D/1 queue theory. The main concept of this algorithm is channel utilization balancing that helps form groups of nodes assigned with different spreading factors (SFs). The simulations are performed under two scenarios that are similar and various uplink time interval among SFs. The results show that our UW algorithm can outperform the traditional Min-airtime method in both scenarios. The packet received rate (PRR) of the UW algorithm is clearly higher than that of the Min-airtime method for all number of nodes and time intervals. Especially in the various time interval simulation of the networks of 120, 600, and 1,200 nodes, the maximum PRR improvements occur at 1, 3, and 5 times of the minimum time interval between uplinks, T
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, respectively, and are around 34%, 36%, and 35%, respectively.