Among many others, LoRa/LoRaWAN is one of the most widely employed technologies to support Internet of Things applications for low-power and long-range wireless devices. LoRaWAN is a medium access control (MAC) layer protocol based on the traditional Aloha algorithm which reveals a great degraded throughput when a large number of devices attempt to communicate over the shared channel at the same time. Aiming at this scalability issue, we propose to introduce the distributed queueing (DQ) algorithm into the MAC protocol over the LoRa physical layer, named DQ-LoRa. The details of DQ-LoRa are provided about the frame structure and access procedure, followed by the performance evaluations on system throughput, average delay, and energy consumption. Our analytical results show that the maximum throughput of DQ-LoRa is independent of the number of devices, and the delay is insensitive to the number of random access minislots for device contending. The numerical computation shows the gain of throughput up to 2.6-fold, and the savings of energy and latency up to 48% and 54%, respectively, in comparing DQ-LoRa with a pure Aloha system.
