One use case for Radio Link Quality APIs is how third-party call quality diagnostics tools can be enhanced by knowing what’s going on at the first three feet. Specifically, how can IT troubleshoot the Bluetooth link between headset and USB adapter? 
The Radio Link Quality API provides key information that can be used to gain true insights into the Bluetooth radio link:
  • Quality impairment score (QIS) is a measure of the user’s average call quality based on the percentage of packet errors and related data. The higher the impairment score, the lower the quality of the user’s average call experience. For example, a QIS of 0 for a given user would indicate that all calls were free from any detectable errors, while a QIS of 100 for a user would indicate that all calls suffered a complete loss of call audio. QIS is reported once for every call.
  • Receive signal strength indication (RSSI) is a measure of the absolute strength of the Bluetooth signal at the headset. It measures the amount of power received at the headset antenna measured in dBm. dBm (sometimes dBmW or decibel-milliwatts) is an abbreviation for the power ratio in decibels (dB) of the measured power referenced to one milliwatt (mW). The RSSI is reported every four seconds during a call.
  • Link figure of metric (LFOM) is a calculated guess on what the user is hearing based on the radio link quality. For each packet of data across the link there is an indication of any corruption in the data. This information is used to calculate sample error rates, which are then further processed over a period of time, creating the LFOM metric. Zero means that there were no valid data across the link; five means there were no errors. The LFOM is reported every four seconds during a call.
With more people working remotely, in locations such as coffee shops and airport lounges, these three measurements now make it possible to quickly determine if the environment and its associated interference on the Bluetooth radio link is the root cause of the user’s audio issues.