Boosting Reliability and Energy-Efficiency in Indoor LoRa

Abstract

LoRa (Long Range) is a promising communication technology for enabling the next-generation indoor Internet of Things applications. Very few studies, however, have analyzed its performance indoors. Besides, these indoor studies investigate mostly the RSSI (received signal strength indicator) and SNR (signal-to-noise ratio) of the received packets at the gateway, which, as we show, may not unfold the poor performance of LoRa and its MAC (medium access control) protocol – LoRaWAN – indoors in terms of reliability and energy-efficiency. In this paper, we evaluate the performance of LoRaWAN and use its key insights to boost the reliability and energy-efficiency in indoor environments by proposing LoRaIN (LoRa Indoor Network), a new link-layer protocol that can be effectively used for indoor deployments. The approach to boosting the reliability and energy-efficiency in LoRaIN is underpinned by enabling constructive interference with specific timing requirements for different pairs of channel bandwidth and spreading factor and relaying precious acknowledgments to the end-devices with the assistance of several booster nodes. The booster nodes do not need any special capability and can be a subset of the LoRa end-devices. To our knowledge, LoRaIN is the first protocol for boosting reliability and energy-efficiency in indoor LoRa networks. We evaluate its performance in an indoor testbed consisting of one LoRaWAN gateway and 20 LoRaWAN end-devices. Our extensive evaluation shows that when 15% of the end-devices operate as booster nodes, the reliability at the gateway increases from 62% to 95%, and the end-devices are approximately 2.5x energy-efficient.