More and more objects are connected to our surroundings. The electronics of these objects often provide many possibilities, but they are especially powerful when they are interconnected with each other inside homes, offices and others communal areas. This can be done in several ways, some of which especially enable their integration in an easy, yet powerful manner.
Years ago the Bluetooth Special Interest Group began to work on a variant of the popular Bluetooth connection protocol in order to provide communication between these devices, also known as mesh networks. This network topology does not require a central point and the nodes are all connected to each other (or at least many of them with many others). Therefore, expanding the network is as easy as adding more devices. Using Bluetooth, which is cheap and energy efficient, is interesting in terms of other ‘centralised’ alternatives like Wi-Fi or devices which require a physical cable, such as Ethernet. It is highly useful to integrate it in the Internet of Things because of the aforementioned reasons and because many devices have Bluetooth, such as smartphones, tablets, PCs, and smartwatches. It has a very fast response time (less than 6 milliseconds) and is optimised to send small information packages at a low speed and with low energy consumption. There are more and more electronic devices in our homes and offices that include it: smart light bulbs, thermostats, presence detectors, shutters and alarms, among others.
How do these mesh networks work? First of all, it is necessary to distinguish between nodes and messages. Each Bluetooth device is a network node and messages are relayed between them, which are information packages that travel along different routes until reaching their destination. In this sense, mesh networks have a smart function, almost like the Internet, using different paths or hopping from node to node until reaching their destination. Standard networks can contain up to 32,767 nodes in the same network, with 4096 subnets and secure transmissions.
Due to this peculiar way of working, adding devices is simplified, even though some devices will need a connection to a local intranet or external Internet. For example, if a new light bulb is added, it can be connected to other light bulbs or appliances that act as close nodes, normally up to dozens or hundreds of metres away. An order from a mobile like ‘switch office light on’ will reach its destination without the light bulb even being connected to a Wi-Fi router.
Mesh networks are also interesting because each node can send and receive information in both directions. Therefore, in actual fact, a light bulb can act as a ‘presence sensor’ if it is configured to detect the presence of other devices close to it, such as mobile phones. Consequently, the air conditioning can be switched on when a certain number of smartphones are in range (maybe indicating a meeting) or the lights in a room can automatically switch off when people leave.
Other places where mesh networks can be particularly attractive due to their usability and low cost are shops, car parks and warehouses. Galleries and museums are using them to detect the presence of visitors and even interact with them. Even advertising campaigns have been sent to smartphones close to certain devices.