Bluetooth® Low Energy (LE) direction finding

Bluetooth® LE version 5.1 adds new positioning capabilities to enhance coverage and accuracy particularly in indoor environments and requires thorough testing


Positioning is a typical requirement in today’s electronic devices such as smartphones, cars and wearable IoT devices. In many situations, methods based on satellite (GNSS) or cellular networks (OTDOA) fail because of lacking coverage or accuracy. Bluetooth® based positioning services try to compensate for this deficiency or provide improvement, especially in indoor scenarios. Today’s Bluetooth® location service solutions use received signal strength indication (RSSI) measurements to estimate the distance between the two devices for proximity services or triangulation based on several RSSI measurements for positioning.

Bluetooth® version 5.1 adds two new direction finding techniques: AoA and AoD

In order to further enhance the positioning service capabilities, a Bluetooth® LE direction finding (DF) feature was defined in version 5.1. It supports two methods for determining the direction of a Bluetooth® signal by using an antenna array with two or more antennas on a stationary peer device:

  • Angle of arrival (AoA) estimation on a peer device is typically used for asset tracking. A Bluetooth® transmitter using a single antenna sends a special direction finding signal. The receiving peer device uses an antenna array to measure the phase difference to estimate the relative signal direction.
  • Angle of departure (AoD) estimation on a moving LE device is typically used for wayfinding applications. A stationary Bluetooth® transmitter uses a switched antenna array to send DF enabled packets. The receiving device receives the signals from the transmitting device on a single antenna and is able to measure the delay differences used to estimate the relative signal direction.

Your Bluetooth® direction finding test challenges

The accuracy of the AoA/AoD estimation is strongly dependent on the power stability quality and frequency drift quality of the DF signal transmitting device and the capabilities of the receiving device to accurately sample the I/Q data from the received signals. The Bluetooth® SIG has defined 23 new test cases for four different test setups, which are supported by the R&S®CMW wireless communications test platform.


Save the date | 13-Feb-2020

Webinar: Everything you need to know about Bluetooth® Low Energy (LE) in 2020

Bluetooth®LE is among the most successful wireless technologies for the internet of things (IoT). Over the last decade, the use cases have evolved from connecting PC peripherals to full communications with wearable devices, and even more. The latest releases (5.0, 5.1, 5.2) of the Bluetooth® specification open the door to even more applications in the IoT area, such as smart homes, smart buildings and indoor location services.

The webinar will introduce the latest features you should know about, such as long range or direction finding, and explain related test challenges and solutions. It will also highlight a novel solution of a radio-controlled test mode, which will redefine the way of testing upcoming Bluetooth® LE devices.

Test cases for Bluetooth® direction finding

Test cases 1 Ms/s PHY 2 Ms/s PHY
TRM/BV Output power, with AoD constant tone extension #15 -
Carrier frequency offset and drift with AoD constant tone extension (CTE) #16 #17
TRM/PS/BV TX power stability; AoD transmitter #01, #02 #03, #04
TRM/ASI/BV Antenna switching integrity; AoD transmitter #05, #06 #07, #08
RCV/IQC/BV I/Q samples coherency; AoD receiver #01, #02 #03, #04
I/Q samples coherency; AoA receiver #05 #06
RCV/IQDR/BV I/Q samples dynamic range; AoD receiver #07, #08 #09, #10
I/Q samples dynamic range; AoA receiver #11 #12

Benefits of Rohde & Schwarz Bluetooth® direction finding test solutions

  • One-box test solution for Bluetooth® direction finding
  • Coexistence testing such as NB-IoT together with Bluetooth® is only possible with the R&S®CMW wireless communications test platform
  • Fully approved test platform by Bluetooth® SIG

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Related resources

White paper: From cable replacement to the IoT – Bluetooth 5.1

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Application note: Tests of Bluetooth Low Energy 5.1 indoor navigation - direction finding

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Application note: Bluetooth® LE RF test for IoT applications

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Application note: Configuration of the R&S®CMW for Bluetooth Low Energy direct test mode (DTM)

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