Image Source: Mouser Electronics
By Mike Rohrmoser, Vice President of Product Management, OEM Solutions, Digi International
Take a walk through any city, and it’s easy to overlook the technology working in the background. While you’re taking in the sights, intelligent lighting is guiding your way. To track air quality, thousands of sensors monitor it. And, should you take a tumble and fall into a river, lifebelts should be available thanks to clever lifebelt holders that register when one has been removed. None of this is a forward-looking projection of the future capabilities of the Internet of Things (IoT) and smart cities. They are real applications running today in the world’s metropoles, such as London, Paris, and Miami, proving that millions of devices can be successfully connected in massive wireless mesh networks (Figure 1).
Figure 1: Smart city applications, from utility monitoring and smart lighting to parking, are possible thanks to the massively networked wireless mesh technology Wi-SUN. (Source: Digi International Inc.)
Low-power wide-area networks (LPWANs) are typically comprised of wireless nodes that, in addition to their application function, perform different roles within the network. Some simply connect to the network. Others can manage the network, enabling new nodes to be added. Then there are the gateway devices, translating between the wireless mesh protocol and the backhaul link to a cloud service. However, these technologies often have limits on the maximum number of nodes supported or data throughput, making it difficult to scale for larger deployments, let alone cities.
One key issue for most of these wireless technologies is the lack of support for IP-based addressing, a staple of Internet communication. Instead, the cloud backend communicates with an IP-addressed gateway that translates the message to its nodes using its own addressing and protocol. The struggle for those developing these protocols is balancing the memory footprint and protocol complexity with the limited resources of a microcontroller that may be battery-powered.
There is, however, a relative newcomer to this space that manages to strike the right balance between IPv6 support and the needs of small, low-power embedded nodes. Wireless Smart Ubiquitous Network (Wi-SUN) is a sub-GHz mesh networking technology built on IEEE 802.15.4g standards that is equally at home in both moderate and massive IoT deployments (Figure 2).
Figure 2: The Wi-SUN Alliance includes over 300 members. (Source: Digi International Inc.)
Like other sub-GHz, self-forming and self-healing wireless alternatives operating in the unlicensed frequency bands, a border router (BR) provides gateway-like access to the wide area network. On the sub-GHz side, devices act as full-function nodes (FFN, with parent and child nodes) or leaf nodes (LFN, terminal nodes). LFNs can also act as router nodes if required, automatically rerouting in the event of interference or node failures. Key to Wi-SUN’s resilience is support for multiple BRs, enabling an established mesh network to migrate, as configured, to a different BR and maintain a link to the WAN.
Digi has pulled together the necessary technology blocks to simplify the implementation of Wi-SUN deployments from node to cloud. Starting with building nodes, the first element is the Digi XBee Wi-SUN Modules range (Figure 3). Built around a Silicon Labs EFR32 SoC with built-in Secure Vault, through-hole, surface-mount, and micro-mount modules are available, simplifying evaluation while also offering variants suited to different application form factors. Two functional options are available. The first are the Leaf Node (LFN) modules, which can achieve 10-year battery life for remote sensing and optionally support Bluetooth® Low Energy. Full Function Node (FFN) modules require permanent power and provide the high throughput necessary with data rates up to 2.4 Mbps.
Figure 3: Wi-SUN LFNs and FFNs can be implemented using the range of Digi XBee modules. Different form factors target rapid integration, high-volume, and space-constrained applications. (Source: Digi International Inc.)
Key to their capability is support for MicroPython, enabling edge intelligence to be deployed within the node. This reduces reliance on a cloud backend and ensures real-time responses to local events based on sensor data. Security is also ensured thanks to pre-injected certificates, allowing nodes to join networks securely out of the box without complex provisioning.
For successful deployment, developers have the Digi XBee® Hive Wi-SUN Border Router (Figure 4). Built on Digi Accelerated Linux[1] with the integrated Digi TrustFence® security framework,[2] the router also leverages Silicon Labs Secure Vault capabilities, creating a complete security ecosystem at every network level.
Its multicore processor architecture (dual Cortex-A7 @ 650 MHz + Cortex-M4 @ 209 MHz) delivers the performance needed for advanced applications. Multiple connectivity options, including LTE Cat 1 cellular, dual-band Wi-Fi 5 with Bluetooth 5.2, 10/100 Mbit Ethernet, and software-selectable RS232/RS485 serial interfaces, ensure reliable backhaul connectivity regardless of site conditions.
Python 3 is also supported, providing a command-line interface (CLI) enabling local data processing, real-time decision-making, and automated task execution, reducing bandwidth costs and improving response times. There are also managed Linux LXC containers, enabling the deployment of custom applications using Digi’s Containers-as-a-Service functionality.[3]
Figure 4: WAN connectivity is provided with the Digi XBee Hive Border Router, running Linux and supporting both containers and Python 3 applications. (Source: Digi International Inc.)
Finally, Wi-SUN networks can be competently managed with the Digi Remote Manager[4] (Figure 5). Serving as a cloud-based command centre for Wi-SUN networks, it includes centralised network configuration and monitoring, automated PKI certificate management, OTA firmware and software updates, real-time alerts and reports on network health, and open APIs for third-party system integration.
Figure 5: The final element of the end-to-end Wi-SUN solution is Digi Remote Manager, simplifying provisioning, OTAs, and network management. (Source: Digi International Inc.)
With significant, large-scale, mission-critical deployments of Wi-SUN worldwide, the reliability and robustness of this wireless mesh technology have been proven. Regardless of whether you target utility metering, smart lighting, EV charging, parking, or environmental sensors, Digi’s Wi-SUN solutions provide a well-thought-out, end-to-end approach to rolling out the technology. With global regulatory approvals in the US, Canada, Europe, India, and Japan, and industrial operating temperature ranges, Wi-SUN can be deployed worldwide at any scale.
Mike Rohrmoser is VP of Product Management for OEM Solutions, now in his second tenure at Digi International. He is a seasoned global technology executive with over two decades of experience in product strategy, technology leadership, product innovation, industry solutions, and ecosystem development. Prior to Digi, Mike led IoT initiatives as a Global IoT Partner Segment Lead at Amazon Web Services (AWS). At AWS, he helped drive digital transformation across key industries by delivering scalable, secure IoT solutions from edge to cloud with the AWS Partner ecosystem and by accelerating the adoption of Generative AI technologies. Throughout his career, Mike has created significant innovation across IoT, including launching industry-first products like the Digi TrustFence® embedded security framework. His unique blend of expertise spans embedded systems, wireless connectivity, security, cloud technology, IoT, and AI/ML.
Sources
[1] https://www.digi.com/solutions/by-technology/dal-operating-system [2] https://www.digi.com/solutions/by-technology/trustfence [3] https://www.digi.com/products/iot-software-services/value-added-services/digi-containers [4] https://www.digi.com/products/iot-software-services/digi-remote-manager
DIGI is a leading global provider of mission-critical machine-to-machine (M2M) and Internet of Things (IoT) connectivity products and services. DIGI helps customers create next-generation connected products and deploy and manage critical communications infrastructures.