Why mesh networks matter at the edge
Mesh networks are essential ingredients in almost every IoT platform, as they use short-range wireless standards to communicate with each other and send their data to the “outside world.” So, it’s important to understand how they differ from their counterparts, and why their characteristics make them so well suited for IoT.
There are three basic architectures for creating a network: star, point-to-point, and mesh, the latter being the most useful for short-range IoT solutions. A star network requires that all devices connected to pass through a central hub, which creates a single point of failure. That is, if the hub goes down so does everything connected to it, a major problem. However, if any node on the network fails, no others are affected, and devices can be added or removed at will.
Although star-type networks are comparatively easy to install and troubleshoot, they require more cable to cover a given area, high RF output power, and don’t scale well. Consequently, except for special cases they are of little value in connecting edge devices in an IoT network
A point-to-point topology consists of two endpoints that communicate with each other, such as two microwave radios. In a point-to-multipoint network one endpoint serves others (a “one-to-one” scenario). Both architectures are the foundation of wide-area telecommunications networks as well as fixed wireless access delivery of broadband and voice communications and can span large distances and be beneficial for IoT in special situations for connecting devices at the edge to the Internet.
The mesh network is arguably the only type with characteristics suitable for connecting devices at the edge of the network where the data is generated. Unlike the star topology, devices in a mesh network can communicate directly with each other rather than first to a hub. This is one of the most important benefits of the architecture along with its ability to “self-heal” so that if one node fails communication can be rerouted around allowing the network to continue to operate, increasing reliability as well.
Mesh networks are also inherently easy and more cost-effective to scale because only short distances between devices are required, which allows radios with a very low RF output to be used, dramatically increasing the operating life for devices using the coin cell battery for power.
Every wireless technology designed for short-range communication has mesh networking capability, including (recently) Bluetooth 5. Wi-Fi mesh networks of recently appeared for extending coverage and maintaining data rates in homes and offices, but has the technology was never designed for this purpose, has disadvantages that currently make it less desirable than others for IoT.
So which short-range technology has the best mesh capabilities? There are variances between how each technology implements the networks, but all get the job done. So, the “best” solution depends on what other metrics are most important toyou and whether one appears for various reasons better suited to your application. Other factors include how many vendors support to technology with the most comprehensive application-specific portfolios, and whether you intend to use one technology for all edge devices in a specific location.
Technologies based on the IEEE 802.15.4 like ZigBee and Thread have the benefits of this standard baked into them such as the ability to serve “typical” edge devices in which low power consumption, simplicity, and low data rates are the key metrics. The standard has been around since 2000, so it predates every other short-range wireless solution except Wi-Fi, which is one reason why ZigBee has the greatest market share. Both ZigBee and Thread IP-based so they use the same protocol as the Internet.
Z-Wave is a proprietary solution that has gained quite a following with more than 2,500 products supporting it, and Bluetooth 5 is the latest entry as it gained mesh capability only in mid-2017 (although a proprietary solution with this capability was available for several years). Like the others, Bluetooth has its own advantages and disadvantages but has one unique benefit: the ability to support beacons.
The above technologies and other less-prominent competitors have been pegged as being useful for specific applications, but this should be taken with a tablespoon of salt as some of these “recommendations” come from supporting one (or two) above the others. As always, it pays to learn as much as possible about these technologies and make a decision based on your knowledge.