All wireless networking technologies have a limited range. That’s just the way the physics work. But there are a growing number of scenarios where devices, spread across a large area, need to be able to communicate with each other using a highly reliable, low-power wireless technology. Think about the smart home, and even more so, the smart commercial building like offices and hotels. Imagine wanting to control all the lights in a hotel or collect temperature data wirelessly from the most distant points in your office block over Bluetooth® technology.
Bluetooth Smart technology has a great many attractive qualities for product and solution designers, including its native support by 96% of smartphones and its ultra-low energy requirements. It’s become the wireless networking technology of choice for countless scenarios.
But what can you do when its “maximum range” is just not enough?—create a mesh network.
About Mesh Networks
A mesh network has a topology whereby all devices can communicate with all other devices in the network, either directly if in range, or indirectly via one or more intermediate “nodes” if they are not. This is in contrast to other network types that often feature a central hub like a router, through which all traffic must flow. Mesh networks have no such central hub and offer multiple ways of getting data from one device to another. This makes for an inherently reliable network design.
Mesh networks can use “routing” to select a specific path through the network from one device to another or an approach called “flooding” where every message is sent to every device in range and they, in turn, relay the message to each device they can reach. In this way, messages get relayed to all devices in the network. One advantage of a flooding based approach over routing is that less memory and processing power is required and therefore, less energy.
Mesh networks usually allow subsets of devices in the mesh to be members of named groups, which can be addressed collectively. In our diagram above, imagine node 1 is a Bluetooth Smart light switch, nodes 2-6 are Bluetooth Smart lights in the same room, while nodes 7-10 are lights in another room and node 11 is another switch. With the light switch suitably configured, we could switch on or off all of the lights in room 2 from room 1 (and don’t forget, room 2 could in fact be hundreds of meters away from room 1).
Conceptually, this works if the light switch emits a message using the mesh protocol over Bluetooth Smart that means “Group ‘room 2’ lights switch on now!” The message would go from the switch to the other in-range devices in room 1. Since they are not members of the room 2 group, the lights ignore the message and pass it on to the next lights, including those on the nearest edge of room 2. Those lights respond to the command and switch on because they are members of the room 2 group and then relay the message on to the remainder of the devices in room 2 where again, they would be processed and relayed.
Bluetooth and Mesh Networks
Many companies are working to define protocols that allow mesh networks to be created from widely dispersed collections of Bluetooth devices. One common implementation is CSRmesh, from Cambridge Silicon Radio (CSR). Their protocol works on top of Bluetooth 4.0 and many companies have already selected it for a number of products, such as the avi-on smart home lighting products. Developers interested in learning more about CSRmesh can obtain a developer kit from CSR. Zuli is another company experimenting with Bluetooth mesh. The Zuli network allows Bluetooth devices to “mesh” and extend the range in the home while getting around interference from thick walls and metal appliances. It also exploits user presence detection in the mesh which makes for other, interesting possibilities. In June, Samsung announced a Bluetooth Smart LED light bulb that uses a Bluetooth mesh network to connect the user to the light. As you can see, there are many Bluetooth mesh options out there.
The future of Bluetooth Mesh
The Bluetooth SIG recently launched a study group to examine the subject of mesh networks with a view of defining an industry standard Bluetooth mesh protocol. When the process completes, this will be big, big news for manufacturers and developers everywhere, opening the door to some incredible new products and applications.