Why Sub-GHz IPv6 Mesh Networking for the Internet of Things?

Sub-GHz mesh networking makes your IoT system solid, scalable, and free from WiFi interference.

Fredrik Rosendal, Thingsquare CTOBy Fredrik Rosendal, Thingsquare CTO – January 30, 2020

Mesh networking is a way to add unlimited range to your IoT systems. By running the mesh network on the sub-GHz frequency bands, you avoid all the interference from WiFi and Bluetooth.

At Thingsquare, we use sub-GHz IPv6 mesh networking with all our customer projects.

Today we look at the benefits of using sub-GHz mesh networking for the Internet of Things and how we do it in the Thingsquare IoT platform.

But first, what is mesh networking in the first place?

What is Sub-GHz Meshing?

Mesh networking is a way to do wireless networking where the devices in the network help each other to send messages. If one device is far away, the others will help it by relaying its messages.

In a mesh network, there are many paths to go through the network. If one way fails, there is another path ready to take over.

It is called mesh networking because the devices in the network create a network with connections between all the nodes in the network – just like a mesh fence.

A sub-GHz network runs on a wireless frequency that is below 1 GHz. This is different from WiFi and Bluetooth networks, which both use the same 2.4 GHz frequency band.

On the sub-GHz band, there is no interference from by WiFi and Bluetooth – which means increased performance.

Why Sub-GHz Meshing?

There are many reasons to use sub-GHz mesh networking, compared to the alternatives:

  • There is no range limit: just add more devices to extend the network
  • There is no per-message fee
  • The network is hard to break
  • You avoid interference from WiFi and Bluetooth.

The most common alternatives to sub-GHz mesh networking are the non-meshed sub-GHz technologies like LoRa, Sigfox, and NB-IoT, and the 2.4 GHz mesh networking technologies based on WiFi, Bluetooth Low-Energy (BLE), and Thread. These technologies lack either mesh support, or suffer from interference on the 2.4 GHz band.

Let’s look at the benefits of sub-GHz meshing.

Benefit 1: Unlimited Range

With a mesh network, you can extend the range almost indefinitely, simply by adding more nodes to the network.

As you would imagine, this is useful in large-scale, out-door scenarios such as street lighting, agriculture, or smart cities.

And it is actually even more useful in in-door setups, because in-door wireless networks are often hampered by its limited range. Doors and walls will reduce the wireless signal strength. But mesh networking does not need a very strong signal strength, because devices help each other out.

Benefit 2: No Per-Message Cost

Many long-range sub-GHz systems like LoRa and Sigfox use the traditional phone subscription model, where you pay a subscription for each device or for each message.

With such models, every message sent costs real money. This makes it difficult to predict the cost over time.

A mesh network does not have a cost for each message. Instead, you simply connect the mesh network to the Internet and pay for a regular Internet connection.

Benefit 3: It is Self-Healing

Because of the way mesh networks are formed, they are very fail safe. If one node fails, another node can take its place in the mesh.

if the mesh network notices that a certain area of the network begins to work poorly, the network will automatically switch over to a different part of the network. The performance network will even improve over time, as the network learns the best paths.

Benefit 4: You Avoid WiFi Interference

Today, WiFi is everywhere. Particularly in areas where there are lots of people. And WiFi causes interference.

Because sub-GHz networking uses a lower wireless frequency (915 MHz or 868 MHz, depending on the country), there is no interference from WiFi.

And because the regulations for the sub-GHz frequency bands require devices to play nice with each other, there is very little interference from other devices too.

Because the regulations for the sub-GHz frequency bands require devices to play nice with each other, there is very little interference from other devices

Thingsquare IoT Sub-GHz Meshing

The Thingsquare IoT platform uses sub-GHz networking for communication between the wireless nodes. Built to be future-proof, the system uses standard IPv6 protocols that have no limitations in terms of network size. We have successfully run networks of thousands of nodes in each network.

  • Network separation
  • Future-proof protocols
  • Redundancy
  • Low-power operation

Network Separation Improves Scalability

In theory, a single mesh network can support an unlimited number of nodes. In practice, however, the required application data rate will limit the number of nodes in each network.

As a rule of thumb, we recommend dimensioning each network so that the access point will receive no more than one message per second, on average. That means that a system where each node reports data every minute should have no more than 60 nodes in each network.

To support higher data rates, the Thingsquare IoT mesh supports multiple networks running at the same physical location.

Networks are separated in two ways. First, each network has a separate channel hopping schedule, which means they will mostly be physically unable to hear each other. Second, each network has a separate network-wide encryption keys. This means that in the off-chance that two networks are on the same frequency, they will not be confused by each other’s messages.

Future-Proof Protocols

The Thingsquare IoT mesh system is designed on the standard next-generation Internet Protocol suite, IPv6. These protocols have evolved over a long period of time and have been battle-proven and hardened over time.

The Thingsquare IoT mesh use the IPv6 stack of protocols:

  • IPv6: the latest generation of the Internet Protocol (IP), with 6lowpan header compression to reduce overhead
  • RPL mesh routing: the IETF standard protocol for building and maintaining the mesh structure

The mesh connects to the Internet via one or more access points. These access points connect the IPv6 network inside the mesh to the IPv4 network on the Internet. The access points allow only outgoing, encrypted connections from the mesh. Any communication to the outside world uses TLS standard security protocols.

Redundancy

As a safety measure, the Thingsquare IoT mesh provides redundancy in several ways:

  • The mesh provides multiple routes through the network, in case anything should happen
  • It is possible to deploy several access points in each mesh
  • To further increase redundancy, we recommend deploying multiple mesh networks, with multiple access points, on the same deployment

Redundancy is crucial particularly in large-scale operations, because of the law of large numbers. Given enough devices, unlikely events become likely.

Battery Operation

We use a unique combination of techniques that allow devices to run in a range of operating modes:

  • High performance: Devices in high performance mode never turn off their radios and are therefore always accessible, but need to be connected to a power source. This mode is useful for systems such as street lights, where all devices always have power.
  • Responsive: In responsive mode, devices sleep for 95% of the time, but wake up 8 times per second to communicate. This allow devices to run on batteries, while participating in the mesh.
  • Lifetime: Devices in lifetime mode sleep 99% of the time or more and do not participate in the mesh. This is used for devices running on very small batteries, such as coin cells, or that are powered by solar cells.

This range of operating modes allow us to run mesh networks where devices are powered by coin cell batteries and even solar cells.

Conclusions

Sub-GHz mesh networking is a crucial technology for many IoT systems. Mesh networking brings stability, long range, and fail safe operation to IoT networks. The sub-GHz frequency band completely avoids interference from WiFi and Bluetooth, further improving performance.

The Thingsquare IoT platform uses a future-proof and scalable sub-GHz meshing technology, based on the IPv6 protocol stack. This makes us able to quickly deploy and run large-scale applications and customer projects in range of situations.

Interested in hearing how sub-GHz mesh networking can help you reach your own IoT goals? Get in touch with us and we’ll be happy to schedule a demo!


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