Bluetooth Low Energy is rapidly becoming one of the most widely deployed wireless technologies, finding use in a wide range of applications such as asset tracking, fitness monitoring, location services, and remote sensing. BLE devices are often small and ruggedized, and in many cases fully encapsulated in a protective housing to protect against environmental effects. This packaging adds a unique challenge for design and test engineers: How can the wireless performance be verified without any RF or digital connections?
One alternative is over-the-air (OTA) BLE testing, which provides rapid parametric verification of transmitter and receiver performance. Both transmitter and receiver are equally important, but validating OTA performance of the receiver in BLE is especially challenging and requires a new measurement methodology. This article examines new measurement techniques developed specifically to determine BLE OTA packet error rate (PER) and receiver sensitivity.
OTA testing solves two key challenges
Challenge #1: In typical non-OTA testing, a digital communication method such as UART or USB connection is used to control the device under test (DUT). For receiver tests, the device will be set up to start receiving packets, a test system will then send a known number of packets, and the device will be queried to determine how many packets were successfully received. The information allows the test system to calculate PER, which is an industry standard method to quantify receiver performance. For OTA testing, there’s no direct wired communication and the challenge is to design a new method to determine if packets were properly received.
Solution #1: To determine PER without a wired connection, an OTA test solution must make use of standard BLE over-the-air protocol messages to determine if packets are received. BLE devices transmit on three specific advertising frequencies, which are spaced across the 2.4-GHz band.