Enhanced Time Slotted LoRaWAN for Node Mobility: A Joint Selection of Data Rate, Time Slot and Channel

Long Range Wide Area Network (LoRaWAN) offers a wide range communication with low power consumption at the cost of low throughput. Although this technology is well suited to IoT applications, it faces scalability and reliability limitations because it is based on the Aloha random access protocol on one hand and on random choice of a channel and a spreading factor (SF) on the other hand. LoRaWAN recommends the use of Adaptive Data Rate (ADR) mechanism to optimize the global network utilization by adjusting the node's configuration (Spreading Factor, Transmission Power, Data rate, etc.). However, ADR is defined for fixed nodes and doesn't handle the node's mobility. We proposed in previous work, an enhanced ADR mechanism (E-ADR) that takes into account the movement of the device and its position to define the optimal data rate to use. Despite the performance improvement of LoRaWAN thanks to E-ADR, collisions are happened due to simultaneous transmissions with the same configuration (channel, SF). A best practice to reduce collisions and improve performance in mobile networks is the use of time slotted communication. Several research papers proposed time slotted schemes for LoRaWAN, however none of them considered the case of mobile nodes. Therefore, in this work, we propose ETS-LoRaWAN (Enhanced Time Slotted LoRaWAN), a dynamic collision free time slotted approach to determine respectively the best SF according to the node's position, the time slot, and the channel to use. Our experimental results show performance improvement of ETS-LoRaWAN compared to Aloha LoRaWAN by reducing the Packet Loss Ratio (PLR) and the energy consumption.