Adaptive Multi-Channels Allocation in LoRa Networks

• Published in: IEEE access Vol. 8; pp. 214177 - 214189
• Main Authors: Yu, Yi, Mroueh, Lina, Duchemin, Diane, Goursaud, Claire, Vivier, Guillaume, Gorce, Jean-Marie, Terre, Michel
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bandwidth; Bandwidths; Cascading style sheets; Channels; Chirp; Chirp Spread Spectrum modulation; Data recovery; Electric power distribution; Engineering Sciences; Interference; Internet of Things; Logic gates; LoRa network; Low Power Wide Area Network (LPWAN); Modulation; Nodes; Power consumption; Power management; Repetition; Resource management; Rural areas; spatial Poisson Point Process; Spread spectrum; Statistical analysis; stochastic geometry; Urban areas; Wide area networks
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2020.3040765

In this paper, we consider an IoT dedicated network corresponding to a non licensed LoRa Low Power Wide Area Network. The LoRa network operates in the unlicensed 868 MHz band within a total bandwidth of 1 MHz divided into 8 orthogonal channels of 125 kHz each. Despite the high level of interference, this network offers long range communications in the order of 2 to 5 km in urban areas and 10 to 30 km in rural areas. To efficiently mitigate this high level of interference, LoRa network essentially relies on a Chirp Spread Spectrum (CSS) modulation and on repetition diversity mechanisms. The LoRa CSS modulation spreads the signal within a band of 125 kHz using 6 possible spreading factors (from 7 to 12) to target data rates (starting from 5 kbps for the closest node to 300 bps for the furthest ones). The repetition diversity mechanisms enable the data recovery when the transmission is subject to bad channel conditions or/and high interference levels. Although the CSS modulation protects edge-cell's devices from the high level of interference induced by nodes in the proximity of the gateway, it fails to protect nodes at the edge of a given SF region and several trials are required to recover the packet. In this paper, we propose an adaptive multi-channels allocation policy that attributes multiple adjacent channels of 125 kHz for nodes situated at the edge of SF zones. We study the impact of this adaptive sub-band allocation on the gateways' intensities, the rate distribution and the power consumption. Our results are based on a statistical characterization of the interference in the network as well as the outage probability in a typical cell.