Improving LoRaWAN downlink performance in the EU868 spectrum

LoRaWAN is one of the most widely used Internet of Things protocols. It is developed driven by the easiness of the deployment and the support of any type of application. However, LoRaWAN has been made mostly for uplink transmissions rather than downlink traffic. As it has been shown by many studies in the literature, it suffers from very poor performance even with moderate downlink traffic. This is mainly due to the radio duty cycle restrictions applied on gateways but also due to the half-duplex nature of LoRa transceivers. To mitigate the problem of the reduced downlink performance, this paper proposes different channel, band, and downlink window schemes taking into account the recently announced Band 47b in the EU868 spectrum which adds four extra downlink channels with a total radio duty cycle of 10%. The main issue that is tackled is how the additional downlink time can be used effectively in the new schemes. The advantages and disadvantages of each scheme are discussed and ranked based on the easiness of their integration into the native LoRaWAN and the number of modifications they require. Extensive simulation results are presented and are compared to the baseline. The results reveal that schemes which require more changes to the protocol exhibit higher performance gains. More specifically, if a 10% duty cycle channel is applied in the first receive window, a higher than 200% performance gain in terms of packet delivery ratio and energy consumption can be achieved.