###### Abstract  
Long-range wireless area networks (LoRaWAN) typically use a simple star topology. However, some nodes may experience connectivity issues with the gateway due to signal degradation or limited coverage, often resulting from challenging environments in sectors such as agriculture, industry, smart cities, smart grids, and healthcare, where LoRaWAN-based IoT solutions have expanded. The main contribution of this paper is the implementation of a hybrid topology for LoRaWAN networks that remains fully transparent to current spec LoRaWAN servers and IoT applications. It enables the coexistence of mesh (multi-hop) and star (single-hop) communication schemes, dynamically adapting a node's transmission mode based on physical link quality metrics. Additionally, the user interface allows for customizing network topology and parameters. Experimental proof-of-concept tests were conducted on a campus-wide testbed. Results showed that all devices successfully switched topology mode in 100% of the instances, enabling data transmission across all three scenarios under test. Network performance metrics were evaluated, with latencies ranging from 0.5 to 3.2 s for both single-hop and multi-hop transmissions. Additionally, improvements in RSSI and SNR were observed, validating the efficiency of the proposed solution. These results demonstrate the feasibility and effectiveness of our approach in extending network connectivity to areas beyond the gateway's coverage. hybrid topologies; LoRa; LoRaWAN; mesh +
Footnote †: journal: Applied sciences  
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1222 allow for reaching communication distances of 5 km in urban areas and up to 20 km in rural areas [3]. The small number of control messages in the MAC layer results in reduced energy consumption and delay [4]. Furthermore, the literature indicates that data rates range from 250 bit/s to 21.9 kbit/s [5], also establishing a maximum data rate of 50 kbit/s when using FSK modulation [3]. These characteristics ensure good performance for telemetry IoT applications that do not require frequent real-time transmissions. The support of bidirectional communications opens the door to new functionalities for remote and intelligent device control and configuration [6]. The excellent performance of LoRaWAN networks not only in outdoor environments but also in indoor facilities enables its adoption as a robust wireless communication technology in factories and other industrial buildings [7]. Moreover, as depicted in the physical layer specifications, LoRa uses the ISM (industrial, scientific, and medical) band which, along with the low cost of the available certified devices, facilitates the easy deployment of LoRaWAN networks. All these advantages have led to the development of LoRaWAN-based IoT added-value solutions in multiple sectors, including smart cities [8], smart grids [9], agriculture [10], localization [11], industry [12], and medical applications [13], among many others [14]. Nevertheless, LoRaWAN as it is currently specified also has some drawbacks. One of the main disadvantages is network size limitations. This is due to the duty cycle that, in the case of Europe, is established at 1% [15]. The characteristics of conventional star topology may lead to difficulties in providing service to inaccessible areas and zones without enough power supply infrastructure. In addition, battery-operated end devices with low power availability may need to reduce their transmission power, which could result in a lack of connectivity with the gateway. LoRaWAN specifications contemplate the star topology as the main form of network configuration for LoRaWAN end devices, but it can benefit from the implementation of other forms of network topologies, such as tree, cluster, or mesh networks. This would create the possibility of reaching more distant areas while still routing packets to the gateway, addressing, as a result, some of LoRaWAN's current issues.