Silvair Mesh

Among the formal announcements at the Bluetooth World Event has been our Silvair Mesh network. Mesh is the Smart Home Keyword in 2015 with the two most influential standard organizations (The Bluetooth SIG and the Thread Group) building their connected home vision around it. While capable of running on top of any radio transport, Silvair is different. It may even be a little counter intuitive for many network engineers.

The Silvair Mesh is based on source addresses and is designed to form loosely coupled broadcaster - subscribers relationships. We do not want to have any central network coordinator / hub / server on the network. Everything is distributed. Messages are multicast. Devices are autonomous and decide what to do - nobody tells them.

Let's take a light bulb as an example. The bulb can turn itself on or off, depending on various conditions. The simplest condition is a message from a switch. So the bulb listens to messages from a switch and whenever there is a "on" message, it turns itself on (and off for the "off" message). It can listen to several switches. For example if it is a bulb on a stairway, it will listen to the downstairs switch and to the upstairs switch. It identifies the switches based on their source addresses.

The lamp may also subscribe to messages from the switch by the door, marked "all off". There are many other devices subscribed to the "all off" switch. Whenever I leave the house, I hit the "all off" switch and all devices subscribed to the "off" message broadcasted by the "all off" switch turn themselves off.

You already see the many - to - many relationship. The "all off" switch even does not know who is listening to it. It just broadcasts the message and all devices subscribed to it act upon.

Then the stairway lamp may want to listen to motion sensors monitoring the stairway. Why use switches if the light can turn on automatically whenever there is motion detected? So the lamp is now subscribing to messages from three sources: the motion sensor, and three switches (upstairs, downstairs and the "all off"). It can even decide to turn off automatically after, say, 5 minutes of no motion being reported by the motion sensor. But may stay on longer when activated explicitly by the upstairs or downstairs switches. The logic is in the lamp. And of course will go off when the "all off" message is transmitted.

Finally the lamp may even know if it is dark outside. Either by knowing the time and geo-location and computing the position of the Sun over the horizon, or by subscribing to status messages from an ambient light sensor.

So to recap: sensors (switches, motion, ambient light, temperature...) are broadcasters. Like radio stations. They broadcast information they sense. To all who listen and want to use this information. Actors subscribe to the information they may consider relevant (or: they are configured to listen to). And act. Actors may combine several information sources and decide what to do. This broadcasters - subscribers model makes it possible to build the fully distributed system with complex logic algorithms, without a requirement for a central information processing unit (which is usually considered the central point of failure in a smart system).

What we have developed is completely opposite to the established systems like Z-Wave, where a switch knows exactly which lamp it controls. It is also counter - intuitive to many engineers (hey: no destination addresses in your messages?). But this is the approach we've taken based on several years of experience with building smart wireless systems. One we believe makes the difference.