Overview

In the past three months, we explored two innovative approaches to integrating LoRaWAN with Delay-Tolerant Networking (DTN) protocols. While LoRaWAN excels in energy-efficient, long-range communication, its reliance on consistent backhaul connectivity limits its reliability in disrupted scenarios. With a store-and-forward mechanism, messages can be recovered during network outages, a common challenge in remote environments. Integrating DTN protocols creates a robust solution for environments with intermittent connectivity, such as rural IoT deployments, disaster recovery, or Direct-to-Satellite IoT. To achieve this, this article covers two key integrations:

1. µD3TN LoRaWAN Integration: Embedding µD3TN nodes between LoRa gateways and The Things Network (TTN) to enable store-and-forward capabilities¹.

2. LoRa-DTN7 CLA Integration: Utilizing DTN7’s LoRa-specific Convergence Layer Adapter (CLA) to ensure interoperability with µD3TN².

Several studies have explored integrating LoRa with DTN for communication in challenging scenarios. For instance, Höchst et al.³ demonstrated the integration of LoRa modules with DTN7, enabling device-to-device messaging and infrastructure-less communication during crises​. Similarly, Schmidt et al.⁴ presented the Bundle Protocol over LoRa (BPoL), which combines DTN with LoRa to create a robust, disruption-tolerant communication network suited for disaster scenarios​. The work by Kuntke et al.⁵ proposed using LoRaWAN gateways as DTN nodes for rural emergency communication, enabling peer-to-peer messaging with commodity hardware​. These foundational works provided insights into LoRa-DTN interoperability, motivating us to extend this exploration by practically integrating LoRa with µD3TN for enhanced reliability and scalability in IoT environments.

Approach 1: µD3TN LoRaWAN Integration

Objective: This approach integrates µD3TN nodes between LoRa gateways and TTN to enable reliable, delay-tolerant data transmission. This approach aims to enhance the resilience and reliability of IoT communications in rural, disaster-prone, and remote areas.

Architecture: µD3TN nodes act as intermediaries between LoRa gateways and TTN, enabling data to persist during connectivity interruptions. The TTN was selected for the final implementation due to its default compatibility with the RAKWireless UDP Packet Forwarder, providing a more straightforward and practical solution than the added complexity of ChirpStack. The workflow ensures bidirectional data flow:

• Uplink Path: End device sensor data is captured at the gateway, encapsulated in bundles, and sent to TTN via µD3TN nodes (LoRa End Device → Gateway → µD3TN Node A → µD3TN Node B → TTN).

• Downlink Path: Packets from TTN are processed by µD3TN nodes and transmitted back to the end devices (TTN → µD3TN Node C → µD3TN Node D → Gateway → LoRa End Device).

Implementation: The hardware setup includes a Raspberry Pi 3 with a RAK2287 concentrator and Heltec LoRa 32 V3 devices. Software components include µD3TN for bundle transfers, a Dockerized UDP Packet Forwarder⁶ for gateway-to-node communication, and scripts for data handling.

Results: The µD3TN integration enabled uninterrupted uplink and downlink traffic routing, with metrics such as strong signal quality (SNR: 12, RSSI: -21 dBm) and reliable activation via OTAA. The store-and-forward mechanism ensures data integrity, even in disruptive scenarios. To observe the complete workflow, refer to the screenshots section within the repository¹, available in the docs/workflow_captures.md folder on GitHub.

Approach 2: LoRa-DTN7 CLA Integration

Objective: This method leverages DTN7’s LoRa-specific CLA to encapsulate LoRa data into DTN bundles. The goal is to ensure reliable transmission and seamless interoperability between LoRa devices and µD3TN nodes.

Architecture: This approach combines DTN7’s LoRa-specific CLA⁷ with µD3TN to enable reliable data flow over LoRa links. Data is initially bundled at a DTN7 node and passed through the LoRa CLA, which encapsulates the bundles for transmission. A WebSocket bridge (the relevant code can be found in the repository², specifically in the src/websockets folder) facilitates interaction between the LoRa CLA and µD3TN, ensuring compatibility and seamless integration. µD3TN processes the received bundles for application delivery, creating a robust and interoperable communication system.

Implementation: The DTN7 LoRa CLA encapsulates DTN bundles for LoRa transmission, with the WebSocket bridge managing the transmission (LoRa_TX) and reception (LoRa_RX) of data. Once received, the CLA_MTCP layer in µD3TN adapts the bundles for further application processing and delivery. This streamlined workflow ensures compatibility across the DTN7 and µD3TN ecosystems while maintaining data reliability in environments with intermittent connectivity.

Results: The DTN7 CLA successfully transmitted DTN bundles over LoRa and forwarded them to µD3TN nodes. This experiment validated the potential of a custom LoRa CLA for µD3TN, paving the way for more scalable and interoperable IoT solutions. To observe the workflow, see the screenshots in the section within the repository², located in docs/workflow_captures.md.

Conclusions and Outlook

Integrating LoRa with Delay-Tolerant Networking (DTN) protocols has showcased a transformative potential for IoT communications in scenarios with intermittent connectivity, such as rural deployments, disaster recovery, and satellite-enabled networks. By combining LoRa’s energy-efficient, long-range capabilities with DTN’s resilience and data persistence, two validated approaches have emerged:

• µD3TN LoRaWAN Integration: This method introduced µD3TN nodes between LoRa gateways and TTN, enabling reliable store-and-forward functionality. It effectively managed UDP message handling while ensuring seamless integration with TTN.

• DTN7 LoRa-DTN7 CLA Integration: This approach enhanced protocol interoperability and scalability by encapsulating LoRa data into DTN bundles. It also highlighted LoRa’s potential role within modular DTN-based architectures, paving the way for future network expansion and adaptability.

Key Takeaways

• Enhanced Resilience: Both approaches demonstrated robust data persistence and delivery, mitigating the effects of network disruptions.

• Cross-Protocol Compatibility: The seamless integration of DTN7, µD3TN, and LoRaWAN underscored the feasibility of unified communication systems.

• Scalability: The DTN7 CLA integration with µD3TN lays the groundwork for a dedicated LoRa CLA, offering opportunities to streamline further and scale IoT solutions.

Outlook: Future efforts will focus on real-world testing under disrupted connectivity scenarios, such as satellite delays or extended rural deployments. Exploring direct UDP packet forwarding over LoRa to µD3TN nodes will further enhance system robustness. Optimizing these integrations for Direct-to-Satellite IoT applications promises to unlock scalable and reliable communication pathways for global IoT networks.

Acknowledgment

This work has been performed during the secondment of Germán Scapin of the Universidad Nacional de Río Cuarto as part of the MISSION project under the Marie Sklodowska-Curie grant no. 101008233 (“Models in Space Systems: Integration, Operation and Networking”). We thank Germán for his valuable contributions.