Smart cities need smart technology to improve the lives of its residents and to streamline the whole operation and maintenance of urban infrastructure.

And while you can’t necessarily use the same technology everywhere – geographical features, financial challenges, cultural considerations and technical issues all come into play when thinking about how to implement the smart city. What is clear is that the Internet of Things (IoT) will play a key role.

The IoT enables sensors and other connected devices to send data off for processing, either locally or in the cloud. The insights this results in can then be used to initiate appropriate actions. Using the IoT, you can connect every element in the city, from parking spaces to utility meters, to ultimately improve the way people, goods and utilities are moved around our urban areas.

Of course, connecting every street lamp, traffic light, energy meter, parking space, rubbish bin and more to the cloud – not to mention all the electrical appliances in every home and workplace – results in an enormous density of kit. And this raises big technical questions. How do you link all of these devices together in a way that’s energy-efficient, reliable and economically sustainable? What kind of network technology and topology do you need?

Mesh and capillary networks

Mesh networks are an obvious choice for smart cities. Instead of each device connecting directly to the cloud, nodes in the network connect to one another. Smart street lamps, for instance, linked using a mesh network, can exchange information about levels of ambient light in their immediate vicinity, or whether there are people or vehicles nearby. This will mean the network of lights can adjust itself dynamically, to improve safety and energy-efficiency.

Another approach is to use capillary networks. Here, a local mesh network connects to the cloud through some kind of gateway, usually via a low-bandwidth cellular technology. In our smart street lamp example, a capillary network could enable the local authority to remotely monitor the lighting network, visualise the data online and manually control the lights, if required.

Diagram showing a possible configuration for a wired-wireless mesh network, connected upstream via a VSAT link (click to enlarge) By David Johnson, Karel Matthee, Dare Sokoya, Lawrence Mboweni, Ajay Makan, and Henk Kotze (Wireless Africa, Meraka Institute, South Africa) - Building a Rural Wireless Mesh Network: A do-it-yourself guide to planning and building a Freifunk based mesh network, CC BY-SA 2.5, Link Click to enlarge





Mesh and capillary networks are particularly valuable when data volumes are fairly low and latency isn’t a major consideration. They provide broad geographical coverage that can penetrate into locations that would otherwise be difficult to reach, because data only needs to be passed short distances between individual nodes. And when keeping tabs on local events, having wireless connections between every node means you don’t need as many connections to the cloud. This helps reduce power consumption, thereby preserving battery lives and reducing the need for maintenance.

Moreover, mesh networks can easily scale. This is particularly true of flat mesh networks that use self-forming and self-healing architectures. In these networks, adding devices over time as needs evolve, is straightforward.

Choosing the right connectivity kit

Rolling out an effective and durable mesh network, however, can be challenging. Issues include node interoperability, network coverage, scalability and security. One part of the solution is to choose appropriate hardware. For example, the NINA Bluetooth Low Energy series of modules supports a number of mesh technologies, including Bluetooth Mesh, Thread and Wirepas Mesh. For the connection between the mesh network and the cloud, the SARA series of cellular modules enables smart city developers to use technologies such as LTE Cat M1 or Narrowband IoT.

So while different smart cities will require different technologies, some features are likely to be common across the majority. Mesh and capillary networking are two of these, and by choosing components that support the major technologies in these areas, smart city planners will minimise the challenges they’ll face around the scalability, interoperability and longevity of their connected networks.

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