Short-Range IoT Communication Technologies
What the exam tests
Questions on ZigBee, Wi-Fi, Bluetooth/BLE, and RFID: standards, topology, power, range, and fit.
Core rules
- ZigBee: IEEE 802.15.4, 2.4 GHz, low rate (250 kbps), mesh; roles coordinator, router, end device; good for many low-power sensors but not IP-native without 6LoWPAN.
- Wi-Fi: IEEE 802.11, high throughput, mains-powered AP/station model; easy IP integration but high power and contention.
- Bluetooth: classic for audio/high-rate; BLE for low-power peripherals using GATT services/characteristics and advertising; piconet with one master.
- RFID: passive tags harvest reader energy and backscatter; LF/HF/UHF differ in range and environment; UHF gives meters but is affected by metal and liquid.
Worked example
A warehouse wants to track pallets moving through dock doors, with no battery changes for five years. Passive UHF RFID fits: tags are battery-free, door readers give event reads, and the ERP receives dock-in/dock-out events. BLE beacons would need batteries and give coarse location; ZigBee needs a mesh and higher infrastructure; Wi-Fi tags are power-hungry.
Traps
- Saying ZigBee is IP-based; it is not, unless a 6LoWPAN adaptation layer is used.
- Confusing BLE range with classic Bluetooth range; both are short, and walls reduce them.
- Choosing UHF RFID for liquid-filled containers without testing; HF is often better near metal or liquid.