Many IoT devices will support both WiFi and Bluetooth as the cost of supporting both is often only marginally higher than that for a WiFi-only transceiver. This can be leveraged to ease tasks such as installation. First, a simple Bluetooth connection to an app hosted by a mobile device can be used to set up the device. Once configured, it can switch to using the WiFi protocol for data transfers.
A further option that has emerged recently is DECT Ultra Low Energy (ULE). It has the advantage over many of the IoT short-range protocols of having dedicated RF spectrum instead of shared access to the 2.4 GHz ISM band. DECT ULE’s range can extend as far as 300m outdoors and 50m indoors.
The DECT protocol lets multiple gateways cooperate to extend the range of a single network much further than the core 300m. Although DECT was originally developed for wireless telephony, the ULE version provides low-power communication for IoT sensor nodes.
In the short-range environment, the gateway is normally managed by the user. In the low-power wide-area networking (LPWAN) environment, the gateway can be privately owned but access can also be through public networks. A protocol that offers the choice of either is LoRA.
Based on a transceiver design by semiconductor supplier Semtech, LoRA employs unlicensed spectrum and provides users with the option to deploy their own gateways or have their devices communicate with third-party networks. Some cities have deployed networks based on LoRA that are free to access and service providers have appeared that rent access to their gateways.
To avoid interference problems from other users on the same RF band, LoRA uses a spread-spectrum modulation scheme supporting datarates from 300 b/s to 50 kb/s. The range can be up to 10 km and the use of comparatively low frequencies makes it possible to reach devices buried below ground, such as water meters.