Fazley RabbiThe connection an IoT device uses decides where it can work, how long its battery lasts and what happens when the power or network drops. There is no single best option. Wi-Fi suits devices inside a building that already has reliable internet. Mobile data suits devices in places with no Wi-Fi. LoRa suits low-power sensors spread over a large area, such as a farm. Bluetooth suits short links to a phone or a nearby hub. Most projects decide on four things: distance, power, how much data, and what already exists on site. Settle it early: changing the radio later usually means a new circuit board, and sometimes a new enclosure and power supply.
The four options at a glance
| Wi-Fi | Mobile data (SIM) | LoRa | Bluetooth | |
|---|---|---|---|---|
| Typical reach | One building or yard | Anywhere with mobile coverage | Long distances over open land, less through buildings | A room or a few metres |
| Power use | Fairly high | Moderate to high | Very low | Low |
| Size of each message | Large is fine | Large is fine | Very small only | Small |
| What you need on site | A router with internet | A SIM and a data plan | A LoRa gateway with internet | A phone or hub nearby |
| Ongoing cost | Usually your existing internet | A recurring data plan per device | Mostly the gateway's internet | Usually none |
The table is a rough guide. Real range depends on walls, trees, metal sheds, antennas and where the device is mounted.
Wi-Fi: simple when the building already has it
Wi-Fi is the natural choice for shops, offices, server rooms and cold rooms inside a building with steady internet. Boards such as the ESP32 have Wi-Fi built in, which keeps the hardware simple and affordable.
Its weak points are practical rather than technical:
- Concrete walls and metal doors weaken the signal, so a device at the back of a warehouse may struggle.
- The router switches off in a power cut unless it is on a UPS or other backup.
- Someone changes the Wi-Fi password and every device goes silent.
A small habit helps: put IoT devices on their own network, or at least use a password that is written down and not changed casually.
Mobile data: for places without internet
A device with a SIM module sends data over the mobile network, just as a phone does. This suits generator rooms, delivery vehicles, a pump house at the edge of town, or a warehouse in a district town with no broadband.
Things to check:
- Each device needs its own SIM and a data plan that someone keeps recharged.
- Coverage varies. Test the signal at the exact spot where the device will sit; inside a tin-roofed shed it can be much weaker than outside.
- Ask your operator which network types they plan to keep supporting in your area, because older networks are being switched off in many countries.
Mobile data does not depend on your building's internet, which helps during outages, but the device itself still needs power.
LoRa: long range, tiny messages, long battery life
LoRa is a radio technology that sends small messages over long distances while using very little power. A sensor in a fish pond or a field can run on batteries for a long time and report to a gateway placed where there is power and internet, such as the farm office. One gateway can serve many sensors. This is why LoRa often appears in fish farm water monitoring and similar outdoor projects.
The trade-offs:
- Only small messages: a temperature or a water level, not photos.
- You need at least one gateway, and that gateway needs a dependable internet link.
- The radio must use a frequency band permitted in Bangladesh. Confirm this with the equipment supplier or the telecom regulator before buying.
LoRaWAN is a widely used network standard built on top of LoRa.
Bluetooth: short range, works with phones
Bluetooth, especially Bluetooth Low Energy, covers short distances with low power. It fits when a technician reads a device through a phone app, for handheld devices, or for sensors that talk to a nearby hub which then forwards the data over Wi-Fi or mobile data. On its own, it is not a way to reach the internet.
How to choose for your site
Answer these questions for each device:
- How far is it from the nearest reliable internet connection?
- Does it have mains power, or must it run on batteries or solar?
- How much data does each reading carry, and how often? A temperature every few minutes is tiny; a camera image is not.
- What should happen if it cannot connect for an hour? Should it store readings and send them later?
- How many devices are there, and how spread out are they?
Mixing is normal. A farm might use LoRa sensors in the ponds, a gateway with mobile data in the office, and Wi-Fi for a screen at the owner's desk. Whatever carries the signal, the messages on top often use MQTT. Whichever link you choose, design the device to retry, store readings while the link is down, and raise an alert when it goes quiet. And because no connection works without power, read about designing IoT for power cuts too.
Your next step
Before buying hardware, walk the site with a phone. Check Wi-Fi and mobile signal where each device will sit, note the power points and measure the distances. Then try two or three devices at the hardest spots in a small pilot; it will tell you more than any datasheet. If you want help planning it, my IoT device development service covers exactly this.