Bluetooth® Low Energy (LE) for wearables, peripherals and IoT

Bluetooth® Low Energy (LE)

Bluetooth® Low Energy testing

Bluetooth® LE - the future of Bluetooth® technology

Bluetooth® Low Energy (LE) technology, introduced in Bluetooth® 4.0, revolutionized the landscape by providing an ultra-low-power solution tailored for peripherals and wearables. Bluetooth® LE is ideal for applications that require spontaneous small data communications - for example, smartwatches, sport trackers or medical devices. The first version of Bluetooth® LE had a maximum data rate of 1 Mbits/s, which was significantly lower than the 3 Mbits/s offered by Bluetooth® Classic. However, it also consumed only half the power, and it introduced fast pairing through dedicated advertising channels.

With Bluetooth® 5.0, the application range of Bluetooth® LE was further expanded into the IoT space. New features, such as a higher rate of 2 Mbits/s, long-range coding and enhanced advertising capabilities, were added. This version increased the number of devices per ad hoc network. In conjunction with the Bluetooth® Mesh specification, this paved the way for new opportunities in home automation and industrial applications.

Subsequent versions continued to enhance Bluetooth® technology. Bluetooth® 5.1 improved direction-finding capabilities with features such as angle of arrival (AoA) and angle of departure (AoD), and Bluetooth® 5.2 introduced native audio support and smart power control. All of this shows that Bluetooth® LE is the long-term future of Bluetooth® technology.

Overview of Bluetooth® LE

Bluetooth® LE operates as an adaptive frequency-hopping (AFH) spread spectrum system within the globally available ISM bands at 2.4 GHz. It employs Gaussian frequency shift keying (GFSK) modulation with a symbol rate of 1 or 2 Msym/s (LE 1M, LE 2M). This frequency-hopping mechanism spans across 37 general-purpose RF channels, ensuring robust and efficient communication.

Comparison of LE 1M and LE 2M
Comparison of LE 1M and LE 2M

For extended-range applications, Bluetooth® 5.0 introduced LE coded channels in conjunction with LE 2M. These channels offer two optional coding schemes: S=8, where eight symbols represent a single bit, and S=2, where two symbols represent a single bit. The S=8 scheme is specifically applied to the header part of both LE coded channels.

Comparison of Bluetooth 5.0 and 4.2.
Comparison of Bluetooth® 5.0 and 4.2.

In addition to supporting advertising communication through primary and secondary advertising channels, Bluetooth® LE also supports asynchronous communication links (ACL). The purpose of these links is controlling signaling and best effort traffic. Moreover, Bluetooth® LE introduces connected isochronous streams (CIS) and broadcast isochronous streams (BIS), which are both specifically dedicated to LE audio applications.

Bluetooth® LE testing - physical layer

Several factors play a crucial role in determining overall communication performance:

  • Antenna design
  • Power supplies
  • Coexistence with other wireless communication chips, such as LTE and WLAN
  • Final housing

Throughout and following the design phase, it is important to conduct thorough tests to ensure the accuracy of the transmitted information and achieve the desired performance benchmarks.

There are RF testing methods for Bluetooth® LE devices. One approach involves utilizing a vendor-specific control interface, commonly employed for fully automated tests in research, development and production.

For compliance testing of Bluetooth® LE devices, the Bluetooth® Special Interest Group (SIG) has standardized the direct test mode (DTM). This mode enables testing of the Bluetooth® LE transmitter and receiver, with control facilitated through a dedicated wired test interface.

Bluetooth LE direct test mode setup for RFPHY qualification
Bluetooth® LE direct test mode setup for RFPHY qualification

The direct test mode requires a cable connector on the implementation under test (IUT) for test control. Two specified options include a USB or RS232 connection to the host control interface (HCI) of the IUT or a dedicated 2-wire UART connection to the IUT. This test setup ensures highly reliable and secure control of the IUT.

Bluetooth® LE physical layer test items typically encompass:

  • Transmitter tests, which cover aspects such as transmit power, power density spectrum, spurious emission and modulation accuracy
  • Receiver tests, which assess sensitivity and blocking performance
  • Introduction of new features, such as direction-finding
Transmitter tests vs. receiver tests

The industry is exploring options to facilitate convenient over-the-air (OTA) testing for Bluetooth® LE devices, which often lack the provision for a wired connection. Rohde & Schwarz address this by offering two possibilities:

  • Utilizing the primary advertising channels for both RX and TX measurements
  • Employing a standard Bluetooth® LE connection for testing - especially useful for evaluating the performance of applications such as audio/video streaming or data transfer

We have also developed a dedicated test solution to further enhance the testing capabilities over a Bluetooth® channel. It supports DTM-like test control through an adapted Bluetooth® link layer protocol, a methodology that will be supported by Bluetooth® SIG in an upcoming release.

Bluetooth LE DTM-like test control over radio for RFPHY qualification
Bluetooth® LE DTM-like test control over radio for RFPHY qualification

High-efficiency solutions for Bluetooth® LE testing

Rohde & Schwarz test and measurement solutions support Bluetooth® BR, EDR and LE, in-line with the latest Bluetooth® core specifications. We cover the entire product development cycle, and this comprehensive support is complemented by an extensive portfolio for digital design, low power applications and over the air (OTA) testing.

The R&S®CMW wireless communication test platform is a versatile solution that supports Bluetooth® testing up to version 5.x. It covers Bluetooth® LE DTM, as specified by Bluetooth® SIG, as well as full stack signaling. Additionally, it provides a robust test automation tool and already supports DTM-like test control for Bluetooth® LE devices over a Bluetooth® radio link, eliminating the need for a wired test control interface.

Bluetooth® test functions are available across all major Rohde & Schwarz test instruments, including signal generators and analyzers. These instruments offer comprehensive support for Bluetooth® as well as for other non-cellular and cellular standards.

Want to discuss your specific Bluetooth® LE test cases with our experts?

Bluetooth® Low Energy test solutions

R&S®SMBV100B vector signal generator

Support for Bluetooth® BR/EDR/LE with excellent EVM performance at high output power levels

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R&S®FSV3000 signal and spectrum analyzer

Bluetooth® BR/EDR/LE testing at the push of a button - fast speeds and high throughput

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R&S®CMW270 wireless connectivity tester

Bluetooth® LE testing in both non-signaling and signaling modes - approved by Bluetooth® SIG

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R&S®TS8997 regulatory test system for wireless devices

Reliable regulatory testing for wireless devices in ISM bands based on ETSI and FCC

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R&S®CMW100 communications manufacturing test set

Leading multi-DUT and multitechnology RF tester optimized for production lines

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R&S®CMW-Z10 shielded box

Excellent shielding effectiveness and coupling characteristics for Bluetooth® OTA testing

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Bluetooth® LE testing Knowledge+

Webinar: Redefining testing for Bluetooth® Low Energy

This webinar provides an overview of the latest Bluetooth® LE developments and demonstrates related test solutions.

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

Discover the latest in Bluetooth® LE and learn about related test challenges and solutions

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Poster: Connecting almost everything with Bluetooth® Low Energy

Overview of Bluetooth® Low Energy technology aspects including physical layer options, direction finding, power control and audio streaming.

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Flyer: Unplug! Bluetooth® Low Energy testing reinvented

Introduction of the world’s first radio controlled Bluetooth® Low Energy Test Mode – the easiest and most accurate way of testing Bluetooth® Low Energy

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Application note: Bluetooth® Low Energy over-the-air advertiser testing

Detailed guide to Bluetooth® LE RF OTA RX and TX measurements using advertising channels

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

Overview of Bluetooth® technologies, focused on the physical layer in-line with version 5.1

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Application note: Bluetooth® adaptive frequency hopping on an R&S®CMW

Guide to adaptive frequency hopping for improved Bluetooth® BR/EDR signaling performance

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Application brochure: Bluetooth® testing with the R&S®CMW

In-depth overview of Bluetooth® technology and testing Bluetooth® devices with R&S®CMW500

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Application note: Advanced Bluetooth® RF tests with R&S®CMWrun

Detailed guide on requirements and setups for Bluetooth® RF tests using the R&S®CMWrun

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Application card: Conducted multi-standard in-device coexistence testing

Introduction to RF coexistence testing for automotive infotainment systems

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Application card: The smarter way to test BLE transmit signals

How to use the R&S®FPC spectrum analyzer to verify and decode BLE transmit signals

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

Explanation of direct test mode mechanisms for testing Bluetooth® Low Energy devices

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Application card: Bluetooth® LE devices – complete RF characterization

How to use the R&S®CMW to design and verify Bluetooth® Low Energy circuits and modules

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