The first choice is that of distance. Devices that are used in buildings can often use short-range networks and take advantage of the greater simplicity and lower power consumption of protocols tuned to this environment. The installer can generally count on nearby gateways being present that can relay data to the internet. Sensors for smart farming or for monitoring utility services need much greater range as any gateway device or base station may be several kilometres away.
In the short-range sector, there are two technologies that are establishing dominant positions in wireless communications. Both benefit from already being mass-market successes in the consumer electronics market. And they continue to enjoy a continuing programme of enhancements.
Although its parent protocol was developed for personal area networks centred on the phone, the creation of Bluetooth Low Energy has opened the door to a much wider range of applications. Previously, IoT devices were faced with a choice of niche protocols such as Zigbee for home automation or 6LowPAN for industrial automation. Bluetooth Low Energy now offers compatibility with 6LowPAN and supports several of the key features originally developed for Zigbee.
One of those features is mesh networking. Bluetooth has had the Scatternet option since 2013, which let nodes switch between master and slave modes to make them more flexible. For example, a smart node might collect data from several simple slave devices and then relay that data onto a smartphone by temporarily acting as a slave. The mesh networking capability now available in Bluetooth makes it possible to extend the range of a single gateway seamlessly by using intermediate nodes as staging points for packets.