[Paper Review] Scalability analysis of large-scale LoRaWAN networks in ns-3

Floris Van den Abeele, Jetmir Haxhibeqiri+2 more|arXiv (Cornell University)|May 16, 2017

IoT Networks and Protocols4 citations

TL;DR

This paper presents an ns-3 module for simulating large-scale LoRaWAN networks with a physics-based LoRa error model derived from baseband bit error rate simulations. It reveals that downstream traffic severely degrades confirmed upstream message delivery ratios, and while increasing gateway density helps, duty cycle limitations prevent full mitigation, highlighting a critical scalability bottleneck in LoRaWAN design.

ABSTRACT

As LoRaWAN networks are actively being deployed in the field, it is important to comprehend the limitations of this Low Power Wide Area Network technology. Previous work has raised questions in terms of the scalability and capacity of LoRaWAN networks as the number of end devices grows to hundreds or thousands per gateway. Some works have modeled LoRaWAN networks as pure ALOHA networks, which fails to capture important characteristics such as the capture effect and the effects of interference. Other works provide a more comprehensive model by relying on empirical and stochastic techniques. This work uses a different approach where a LoRa error model is constructed from extensive complex baseband bit error rate simulations and used as an interference model. The error model is combined with the LoRaWAN MAC protocol in an ns-3 module that enables to study multi channel, multi spreading factor, multi gateway, bi-directional LoRaWAN networks with thousands of end devices. Using the lorawan ns-3 module, a scalability analysis of LoRaWAN shows the detrimental impact of downstream traffic on the delivery ratio of confirmed upstream traffic. The analysis shows that increasing gateway density can ameliorate but not eliminate this effect, as stringent duty cycle requirements for gateways continue to limit downstream opportunities.

Motivation & Objective

• To develop a high-fidelity ns-3 module for simulating large-scale, multi-gateway, multi-channel LoRaWAN networks with realistic interference modeling.
• To investigate the scalability limits of LoRaWAN under high device density and varying traffic patterns, particularly the impact of downstream traffic on upstream performance.
• To evaluate how gateway density and network parameter allocation affect end-to-end delivery ratios in confirmed and unconfirmed message traffic.
• To provide a publicly available, open-source ns-3 module to enable reproducible and extensible research on LoRaWAN performance and coexistence.

Proposed method

• The authors constructed a LoRa error model using extensive complex baseband bit error rate simulations to accurately represent link-level reliability across different spreading factors and coding rates.
• This error model was integrated into an ns-3 module that implements the full LoRaWAN MAC layer for Class A end devices, including support for confirmed and unconfirmed messages.
• The module supports multi-gateway, multi-channel, bi-directional communication and includes a simple network server for message routing and scheduling.
• Interference is modeled by treating all simultaneous transmissions as noise, with path loss and frequency reuse considered via the ns-3 SpectrumPhy model for accurate coexistence studies.
• The simulation framework enables dynamic parameter tuning, such as data rates, duty cycles, and retransmission strategies, to assess their impact on network scalability.
• The study uses a 600-second simulation period to evaluate performance across varying numbers of end devices and gateways under different traffic loads.

Experimental results

Research questions

• RQ1 How does downstream traffic impact the packet delivery ratio (PDR) of confirmed upstream messages in large-scale LoRaWAN networks?
• RQ2 To what extent can increasing gateway density mitigate the performance degradation caused by downstream traffic?
• RQ3 How do different traffic patterns—confirmed vs. unconfirmed messages—affect overall network scalability and reliability?
• RQ4 What role do duty cycle limitations play in constraining downlink capacity and upstream performance?
• RQ5 How does the presence of multiple gateways and varying spreading factors influence interference and network capacity?

Key findings

• Confirmed upstream messages experience a significant drop in delivery ratio when downstream traffic is present, with PDR remaining low even in four-gateway deployments.
• The impact of downstream traffic on upstream PDR is negligible under low-load conditions, but becomes critical when downstream data rates approach the 10% RDC limit in the RW2 channel.
• Increasing gateway density delays but does not eliminate the performance degradation caused by downstream traffic, due to persistent duty cycle constraints on gateways.
• The difference in downstream PDR between confirmed and unconfirmed messages is minimal, except in single-gateway scenarios with high traffic load (μ = 10).
• The study confirms that the limited downlink capacity in LoRaWAN, particularly in the RW2 channel, is a major bottleneck for scalable network operation.
• The ns-3 module enables accurate simulation of interference, coexistence with other sub-GHz technologies, and future extension with features like ADR and network management.