6.1IoT and wireless communication

Selecting a wireless technology for an IoT device is not simply a matter of "just use Wi-Fi." Range, data volume, power consumption, and installation cost (wiring or not) trade off against each other, and the core of the practice is for an embedded designer to choose the wireless standard best suited to the use case. Because the device is network-connected, design decisions around embedded security—detecting tampering at boot and safely updating firmware in the field—are also unavoidable.

6.1.1Short-range wireless: BLE, Wi-Fi, Zigbee

• BLE (Bluetooth Low Energy) links devices over a range of a few to a few tens of meters at extremely low power consumption. It suits wearables and beacons that must run on a coin-cell battery for years, but its data rate is low and it is unsuited to large transfers such as file uploads.
• Wi-Fi delivers high-speed, high-volume communication over a range of tens of meters. It has the advantage of connecting directly to an existing home or office LAN, but its power consumption is high, making it unsuited to battery-powered sensor nodes meant to run for years (it fits mains-powered devices instead).
• Zigbee is a short-range, low-power standard similar in scale to BLE, but its distinguishing feature is that it can form a mesh network. Because each node can also relay traffic, many sensor nodes can be spread across a wide area beyond the reach of a single radio, suiting multi-point sensing inside a factory or building.