Bluetooth® Classic - BR/EDR

Bluetooth® Classic vs. Bluetooth® Low Energy

Bluetooth® Classic radio, or Bluetooth® BR/EDR, supports wireless point-to-point communication. It has become the standard radio used by headphones, wireless speakers and ICE systems as well as for hands-free calling applications. Despite the successful introduction of Bluetooth® Low Energy (Bluetooth® LE) and especially LE Audio, Bluetooth® Classic will play still an important role, with most devices supporting both Bluetooth® Classic and Bluetooth® LE.

For the synchronization and header part of the EDR packets, Gaussian frequency shift keying (GFSK) modulation is adopted, where the GFSK modulation is the same used for the basic rate packets with a bandwidth bit period product (BT) of 0.5 and a modulation index between 0.28 and 0.35. The higher modulation schemes of π/4-DQPSK and 8DPSK are used for the data part of EDR packets as shown below.

Bluetooth® Classic supports two transport schemes based on:

• Synchronous communication-oriented links (SCO), which are used for interactive voice communication
• Asynchronous communications links (ACL), which are used for packet data and audio/video streaming application

Your Bluetooth® test challenges

Bluetooth® device developers use ready-to-go chipsets or modules for easy integration. However, each device design is slightly different. There are several factors in the final design that may influence overall performance: antenna design, power supplies, other wireless communications chips or the final housing. Therefore, it is necessary to test each Bluetooth® device to verify the performance and ensure conformance with the Bluetooth® Special Interest Group (SIG) standards and regulatory requirements. This is especially important because Bluetooth® operates in the unlicensed spectrum and has to work with other radio technologies that use the same spectrum.

Physical layer testing of Bluetooth® Classic devices

There are several RF testing methods for Bluetooth® Classic devices. Testing can be controlled by a vendor-specific control interface, which is often used for fully automated tests in R&D and production. The Bluetooth® SIG standardized test mode is for BR/EDR device compliance testing. This mode enables Bluetooth® transmitter and receiver testing in both conducted and over-the-air (OTA) setups.

When testing, the tester and the implementation under test (IUT) form a Bluetooth® piconet, where the tester acts as the central device and has full control over the test sequence via a control interface using the link management protocol (LMP). The IUT acts as peripheral and is set at the beginning via an IUT specific local interface in test mode (TM) for security reasons.

Typical Bluetooth® physical layer test items comprise transmitter tests that cover transmit power, power density spectrum, spurious emission or modulation accuracy, as well as receiver tests for sensitivity or blocking performance.

This is also reflected in the test cases specified by the Bluetooth® SIG for RF qualification as shown on the table below.

When evaluating the performance of applications such as audio streaming, data transfer or hands-free calling, it is useful to have a fully functional Bluetooth® connection between the tester and DUT along with the possibility of applying related profiles, e.g., A2DP for audio streaming or the hands-free profile (HFP) for interactive speech communication.