Geometry-Aware LoRaWAN Gateway Placement in Dense Urban Cities Using Digital Twins

TL;DR

This work addresses LoRaWAN gateway placement in dense urban environments by leveraging a geometry-accurate digital twin (DT) of Sunway City and a GPU-accelerated ray tracing engine to predict sub-GHz propagation. It formulates a budgeted maximum coverage problem over eight candidate rooftop gateways using a LoRa link budget with a robust threshold of $\gamma_{\mathrm{thr}}=-10\,\mathrm{dB}$ and solves it by greedy selection, producing coverage, redundancy, and gateway association maps. Key findings show that a single rooftop covers $20.35\%$ of the DT, while six carefully chosen rooftops yield $44.07\%$ coverage with $26.58\%$ redundancy, revealing significant shadowing and non-circular service regions shaped by urban morphology. The study demonstrates that DTs coupled with ray tracing can bridge the gap between expensive real-world trials and planning, enabling operators to assess sufficiency of planned gateways and identify the need for additional sites in similar dense-city scenarios.

Abstract

LoRaWAN deployments rely on rough range estimates or simplified propagation models to decide where to place/mount gateways. As a result, operators have limited visibility into how rooftop choice, streets, and building shadowing jointly affect coverage and reliability. This paper addresses the problem of gateway placement in dense urban environments by combining a geometry accurate Digital Twin (DT) with a GPU accelerated ray tracing engine. Existing studies optimize placement on abstract grids or tune models with sparse measurements; few works evaluate LoRaWAN gateways on a full 3D city model using a realistic link budget. In this paper, we develop a DT with ITU radio materials and evaluate eight candidate rooftops for RAK7289 WisGate Edge Pro gateways under a sub-GHz link budget derived from the data sheet. For each rooftop, we obtain Signal-to-Noise Ratios (SNR) on a 5 meter grid, derive robust and edge coverage indicators, and apply a greedy maximum coverage algorithm to rank sites and quantify the benefit of incremental densification. Results show that a single rooftop gateway covers one fifth of the full Sunway twin (i.e., the DT) at a robust SNR threshold, and that six sites still leave large areas of single gateway or out of coverage cells in surrounding residential streets. The findings from this paper shows that DT and ray tracing tools enable network operators to bridge the gap of expensive real-world trials and planning to identify if the planned LoRaWAN gateway is sufficient or additional sites are required.

Figures (6)

• Figure 1: Overview of the Sunway City Twin.
• Figure 2: LoRaWAN path gain map over the DT. Red markers denote candidate rooftop gateways and blue markers denote sensor locations.
• Figure 3: Fraction of the DT that is covered by at least one gateway (i.e., blue) and by at least two gateways (i.e., orange) as a function of the number of deployed gateways selected from the candidate rooftops. Coverage is defined with respect to the robust SNR threshold of $-10$ dB.
• Figure 4: Number of gateways that cover each grid cell at the robust SNR threshold. White triangles indicate candidate rooftop locations.
• Figure 5: Standalone robust coverage fraction when each candidate rooftop is used alone as a LoRaWAN gateway.