On the Uplink Traffic Distribution in Time for Duty-cycle Constrained LoRaWAN Networks

In the recent years, the LoRaWAN Low Power Wide Area Network (LPWAN) technology became a critical connectivity enabler for many Internet of Things (IoT) grade monitoring applications and has attracted substantial attention from Academy, Industry, and businesses. One of the most widespread assumption relative to the LoRaWAN and the basis for many studies has been the uniformity of distribution in time of uplink packet transmissions by the different machine devices composing the network. However, recent experimental studies revealed that this implication does not always hold in real-life networks composed of multiple devices, which operate under duty-cycle restrictions. This study dives deeper to identify the reason underlying this effect, which can potentially create negative consequences for the performance of the whole network. Specifically, the paper starts by detailing the key aspects of LoRaWAN procedures and mechanisms and hypothesize that non-uniform distribution of UL transmissions may be caused by a cumulative effect of (i) over-the-air activation (OTAA) procedure, (ii) duty-cycle restrictions and their implementation, and (iii) periodic UL traffic. This hypothesis is validated and confirmed through simulations using the specially-developed model, which captures the details of OTAA and subsequent data transmissions in LoRaWAN. After demonstrating this effect and validity of our hypothesis, several approaches, which can enable to mitigate it, are identified and pinpointed.