Choosing a wireless link for battery-powered devices

Radio choice drives battery size, BOM cost, certification effort and the recurring cost of running a fleet. It is worth deciding with numbers rather than habit.

Ask three questions first

• How many bytes per day does the device really need to send?
• Is there a phone, gateway or existing network nearby?
• Who pays for connectivity over the product's lifetime?

Short range: BLE and Zigbee

Bluetooth Low Energy suits devices that talk to a phone or a nearby gateway and can run for years on a coin cell. Zigbee adds mesh networking for building and home automation, at the cost of needing a coordinator.

Local network: Wi-Fi

Wi-Fi is convenient where infrastructure already exists, but association and DHCP make each wake-up expensive. It fits mains-powered products, or battery devices that report rarely and can use connection-reuse features.

Wide area: NB-IoT and LoRa

NB-IoT uses operator networks with deep indoor coverage, ideal for meters, at the cost of a SIM and data plan. LoRaWAN offers very low power and private or community networks, with small payloads and duty-cycle limits.

Measure, don't estimate

Datasheet averages hide transmit peaks, retries and the cost of a poor signal. Profile the real current waveform with the final antenna in the final enclosure before committing to a battery size.