Theory
How devices talk, and the trade-offs
IoT devices must send their data somewhere, but they do not all connect the same way. The choice matters because of trade-offs: some connections are fast but drain power, others sip power but send only tiny amounts of data slowly, and others reach far or barely at all.
This lesson compares four common options, Wi-Fi, Bluetooth, Zigbee, and LoRaWAN, along the axes that matter: range, data rate (speed), and power. On a smart farm, a distant field sensor and a barn camera need very different connections. Knowing the trade-offs lets you match the right connectivity to each device.
At a glance
| Technology | Range | Data rate and power |
|---|---|---|
| Wi-Fi | Moderate (a building) | High data rate, high power; for data-heavy devices near power |
| Bluetooth (BLE) | Short (metres) | Low-moderate data, low power; for wearables and nearby devices |
| Zigbee | Short to medium (mesh) | Low data rate, low power; mesh for smart-home sensors |
| LoRaWAN | Very long (kilometres) | Very low data rate, very low power; for remote sensors |
Theory
Wi-Fi, Bluetooth, Zigbee, LoRaWAN
Wi-Fi offers a high data rate over a moderate range (a building), but uses relatively high power, so it suits data-heavy devices (like a camera) that can be near mains power. Bluetooth (especially BLE, Bluetooth Low Energy) is short-range (metres) and low-power, ideal for wearables and nearby devices exchanging modest data.
Zigbee is low-power with a low data rate and forms mesh networks, where devices relay data for each other to extend coverage, common in smart-home sensors. LoRaWAN (Long Range WAN) reaches very far (kilometres) on very low power, but at a very low data rate, perfect for remote sensors that send small readings occasionally, like moisture probes scattered across a large farm.
Formula
The core trade-off: range and power vs data rate
There is a pattern behind these choices. Broadly, technologies that reach far on little power (like LoRaWAN) can only send small amounts of data slowly, while technologies with a high data rate (like Wi-Fi) need more power and cover less distance. You generally cannot have long range, low power, AND high speed all at once.
So you match the connection to the device's needs: a farm sensor sending a tiny moisture reading once an hour from a distant field wants LoRaWAN (far, low power, low data); a camera streaming images wants Wi-Fi (high data, more power, near mains). Choosing well means being clear about how much data, how far, and how much power each device has.
Quiz
For moisture sensors spread across a large farm, sending small readings occasionally on battery power over long distances, which connectivity fits best?
- Wi-Fi, because it is the fastest
- LoRaWAN, which offers very long range on very low power (at a low data rate), ideal for remote sensors sending small data
- Bluetooth, because it works over kilometres
- A wired ethernet cable to each sensor
Show the answer
LoRaWAN, which offers very long range on very low power (at a low data rate), ideal for remote sensors sending small data
LoRaWAN provides very long range (kilometres) on very low power, at a low data rate, which perfectly matches remote farm sensors that send small readings occasionally and run on batteries. Option A, Wi-Fi, has a high data rate but only moderate range and high power draw, poor for distant, battery-powered sensors. Option C is wrong: Bluetooth is SHORT range (metres), not kilometres, so it cannot reach across a farm. Option D, wiring each distant sensor with ethernet, is impractical and expensive across a large field. Match the need: far distance, low power, small data means LoRaWAN; a nearby data-heavy device (like a camera) would instead use Wi-Fi.
Think first
Why can you not just use one connectivity technology for everything?
Why not pick the 'best' connection and use it for all IoT devices? Then tap.
Show the answer
Because there is no single 'best' connection; each technology makes a different TRADE-OFF between range, data rate, and power, and no one option is good at all three at once, so different devices with different needs require different connections. The fundamental tension is physical: sending data FAST and sending it FAR both take energy, and doing either well tends to cost power or capacity elsewhere. So the technologies each optimise for a different priority. Wi-Fi maximises DATA RATE (great for a camera streaming images) but pays in high power and limited range, fine for a device plugged into mains near a router, terrible for a battery sensor in a distant field. LoRaWAN maximises RANGE and battery life (great for that distant sensor sending a tiny reading now and then) but can only carry small amounts of data slowly, useless for streaming video. Bluetooth optimises for SHORT-range, low-power personal devices like wearables; Zigbee for low-power mesh networks of many home sensors. If you forced everything onto one technology, you would cripple many devices: put the far-flung farm sensors on Wi-Fi and their batteries die and they are out of range; put the camera on LoRaWAN and it cannot send images at all. So the sensible approach is to CHOOSE the connectivity per device, asking how much data it must send, how far, and how much power it has, and often a real system uses SEVERAL technologies together (LoRaWAN for distant sensors, Wi-Fi for the camera, gateways bridging them). This is the same 'right tool for the job' principle seen throughout computing: the diversity of connectivity options exists precisely because IoT devices are diverse, and matching each device to the connection that fits its range, data, and power needs is how you build a system that actually works. One size cannot fit all when the trade-offs pull in different directions.
Summary
Key takeaways
- IoT devices connect in different ways, trading off range, data rate (speed), and power.
- Wi-Fi: high data rate, moderate range, high power; suits data-heavy devices near mains power (cameras).
- Bluetooth (BLE): short range (metres), low power; suits wearables and nearby devices.
- Zigbee: low power, low data rate, forms mesh networks; common in smart-home sensors.
- LoRaWAN: very long range (kilometres), very low power, very low data rate; ideal for remote sensors like farm probes.
- The core trade-off: long range and low power come at the cost of data rate; high data rate costs power and range.
- Memory hook: match the connection to the device, Wi-Fi for data-heavy near power, LoRaWAN for far-and-low-power, Bluetooth/Zigbee for short-range low-power.