A Day at the Beach  - Pushing Bluetooth Range to the Extremes

Published on February 25, 2020

A Day at the Beach  - Pushing Bluetooth Range to the Extremes

Supercharging the Personal Area Network - An Exercise in Bluetooth Range

Bluetooth, now approaching its 12th generation at Bluetooth 5.2, has been carefully developed and segmented to cater to a growing number of use cases and applications. Bluetooth Class is the categorization which separates Bluetooth products by their transmit power, which has an effect on power consumption and overall range. They range from Class 1 (with an average range of ~320 feet) to Class 3 (~1.5 feet), and they have very different purposes and uses for different customers.

Most consumer products fall into Class 2, which requires a maximum permitted power of up to 4dBm (1.5 mW) and achieves a typical range of 65 feet. This is the Bluetooth Class which most of us associate with the devices we use daily: headsets, wireless keyboards and mice, and other typical consumer items that occupy the Personal Area Network (PAN).

But other applications outside the consumer space, such as those found in medical and industrial environments, often require higher range and therefore higher power consumption to push Bluetooth data across larger environments, or to overcome signal loss in harsher RF  environments.

We wanted to see what the absolute limits of our BL654 Bluetooth LE module, and to do so, we set up a highly specialized test to push those traditional boundaries. One fine day in North Somerset, UK, we brought loads of RF / test equipment to Brean Down with the goal of seeing exactly how far we could sustain a Bluetooth LE link, and the conditions that would maximize that range.

The BL654’s Big Day Out

Brean Down is a peninsula that projects into the Bristol Channel, about 2 km or 1.5 miles in length, and where it connects to mainland is the beginning of Brean Beach, which extends for 7 km north to south. This is where our experiment began.

Conditions were dry and warm, full sun, with a temperature maximum of 29°C and relative humidity no greater than 66%.

The goal was to connect two BL654 development kits, and then slowly draw them apart, adjusting conditions when signal dropped to sustain the longest possible connection. The hardware required, therefore, were two BL654 development kits (part number 455-00001), a tripod for the stationary development board, and a tripod on a trolley for the moving board. The tripods would be 1.25 meters above the ground for the first test, and 2.5 meters above the ground for the second test. Both boards ran the Nordic Long Range demo application, available here from Nordic’s Github page and described in their blog post on the subject.

The full details of the test, plus more photographs and detailed results, can be found in our BL654 range testing application note.

Key Takeaways - Achieving Long Range for Bluetooth

Again, it’s worth noting that this test setup is completely unlike most Bluetooth LE applications in practice. You’ll rarely be able to rely on devices with direct line of site, with little interference nearby, and your devices will rarely have their antennas pointed directly at each other, as well.

But with all of that said, we were able to achieve a link as far out as 1.9 km (1.18 miles) between the two devices. This is after optimizing for a few factors, which included:

  1. Devices at 2.5 meters above ground achieved a better range than at 1.25 meters
  2. Devices communicating at 125 kbps with coded PHY achieved better range than at 1 mbps without coded PHY.

In fact, Coded PHY had practically a doubling effect at increasing range. Increasing the height of the tripods by double ALSO doubled the connection range.

Our Latest: The BL654PA Is Our Highest Power Bluetooth Module Ever

For applications where much more power and range are required, Ezurio (formerly Laird Connectivity) provides a version of the BL654 with an onboard power amplifier to significantly impact range. The BL654PA Long Range Bluetooth Module includes Skyworks part # SKY66112-11, which produces +18 dBm output power, a full +10 dBm more than the base BL654 module. That output power is also fully programmable with the onboard smartBASIC firmware image, which means you can adaptively adjust power to your requirements via a hostless, event-driven application in smartBASIC. And while we don’t have full data on the greatest range that the BL654PA can achieve (yet) , it’s fair to assume that the range will be significantly longer than the already improbably 1.9 km range that the BL654 achieved at +8 dBm.

Learn more about our BL654PA module.