Recently, we researched the maximum allowed transmission power (TX) power of Bluetooth Low Energy (BLE) devices, specifically in the European Union (EU) and the US. It turns out that navigating the regulations for the TX power in these markets isn’t as straightforward as you’d expect.

Our journey began when we questioned the maximum TX power limits for our LinkBlu software in the EU and US. For our software, we focus on Nordic Semiconductor’s BLE chips, and their documentation states that the maximum TX power is +10 dBm in the EU and up to +20 dBm in the US. However, when we explored other BLE chip vendors like Silicon Labs, we discovered their devices can transmit at up to +20 dBm, even within the EU.

Curious about this difference, we looked further and found the Bluetooth Low Energy – Regulatory Aspects Document (RAD) released by the Bluetooth SIG. This document sheds light on how different regulatory bodies interpret the different aspects of BLE, such as the transmission power.

Here is our understanding of this document and the regulations for the TX power in the EU and US.

EU (ETSI)

In the EU, wireless devices are regulated by the ETSI EN norms. The relevant standard for BLE is ETSI EN 300 328, which generally caps TX power at +20 dBm. But there’s a catch: to leverage this full power, BLE devices must use Adaptive Frequency Hopping Spread Spectrum (Adaptive FHSS). This isn’t the same as Bluetooth’s standard Adaptive Frequency Hopping (AFH), but you can extend AFH with “adaptivity” to comply with ETSI norms.

To meet “adaptivity” requirements and transmit at +20 dBm, BLE devices must:

• Hop across at least 15 different channels.
• Detect and avoid channels already in use by other devices.

Otherwise, BLE devices are limited to a maximum TX power of +10 dBm.

This insight explains the differences between Nordic Semiconductor and Silicon Labs. From what we can tell, Nordic’s default BLE chips likely lack Adaptive FHSS, thus limiting them to +10 dBm. In contrast, Silicon Labs‘ chips support it, allowing up to +20 dBm.

Excitingly, we’ve implemented “adaptivity” on Nordic’s BLE chips, enabling us to reach TX powers of +20 dBm and achieve communication ranges exceeding 1000 meters!

USA (FCC)

In the USA, wireless devices are regulated by the FCC.  For BLE devices, the relevant norm is mainly the FCC 47 CFR Part 15 – Radio Frequency Devices.

In contrast to the EU, the FCC rules are more relaxed. BLE devices can generally transmit at up to +30 dBm, with a couple of caveats:

• BLE channel 37 is limited to +18 dBm.
• BLE channel 38 is limited to +15.3 dBm.

Unlike the EU, the FCC doesn’t require frequency hopping to hit these max levels. The only other limiter is the Bluetooth specification itself, capping at +20 dBm.

Takeaway

Navigating the maximum TX power regulations for BLE devices is crucial for optimizing communication range while staying compliant. In the EU, the ability to use the full +20 dBm depends on Adaptive FHSS implementation, whereas in the US, the rules are more relaxed, allowing up to +30 dBm with only a few channel-specific restrictions.