Adaptive Uplink Rate Control for Confirmed Class A Transmission in LoRa Networks

Long-range wide-area networks (LoRaWANs) have been designed to provide low-power long-range communication service to Internet-of-Things (IoT) applications. To efficiently support a massive number of IoT devices in a wide area with limited resources, the LoRaWAN utilizes various adaptation techniques, including rate and power control. In this article, we propose a very simple and energy-efficient rate control scheme for LoRa uplink transmission. With the proposed scheme, a LoRa end device increases its rate (rate_up) when recognizing that the uplink channel quality gets better and, when recognizing the transmission failure under an uncongested network situation, the device decreases the rate (rate_down) or increases the transmission power. The proposed scheme also has a simple mechanism for avoiding the repeated alternation between rate_up and rate_down, called a ping-pong situation. We evaluate the performance of the proposed scheme, by modeling it as a continuous-time Markov chain. In addition, we compare the performances of the proposed scheme and some existing schemes by using simulation. The simulation results demonstrate that the proposed scheme greatly outperforms the others, in the transmission success probability, effective transmission rate, frame transmission delay, and energy consumption.