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Low-Power Wide-Area Networks (LPWANs) are emerging as appealing solutions for several Internet of Things (IoT) applications, such as healthcare, smart cities and Industry 4.0, thanks to their ease of deployment, low energy consumption and large coverage range. LoRaWAN is one of the most successful LPWAN standards, as it supports robust long-distance communications using low-cost devices. To comply with the ETSI regulations, LoRaWAN can adopt as medium access control (MAC) layer either a pure ALOHA approach with duty-cycle limitations or a polite spectrum access technique, such as Listen Before Talk (LBT). The two approaches have their pros and cons that need to be carefully evaluated. The studies in the literature that so far have addressed an evaluation of MAC protocols for LoRaWAN refer to a previous and now obsolete version of the ETSI regulations, therefore they do not take into account the current limits on the timing parameters for polite spectrum access, such as that maximum time an end-node is allowed to be transmitting per hour. For this reason, the contribution of this work is two-fold. First, the paper discusses the restrictions that the current ETSI regulations impose on some timing parameters of the two kinds of MAC protocols for LoRaWAN. Second, the paper provides comparative performance assessments of the two protocols through simulations in realistic scenarios under different workload conditions.

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The Deterministic and Synchronous Multichannel Extension (DSME) of the IEEE 802.15.4 standard was designed to fulfill the requirements of commercial and industrial applications. DSME overcomes the IEEE 802.15.4 limitation on the maximum number of Guaranteed Time Slots (GTS) in a superframe and it also exploits channel diversity to increase the communication reliability. However, DSME suffers from scalability problems, as its multi-superframe structure does not efficiently handle GTS in networks with a high number of nodes and periodic flows. This paper proposes the enhanceD DSME (D-DSME), which consists of two extensions that improve the DSME scalability and reliability exploiting a GTS within the multi-superframe to accommodate multiple flows or multiple retransmissions of the same flow. The paper describes the proposed extensions and the performance results of both OMNeT simulations and experiments with real devices implementing the D-DSME.