June 5, 2020
By Sergio Licardie, VP of Advanced Technologies and Innovation at Aviat Networks
The FAS expert system is designed to use several rules to determine if interference is happening in any of the radio links registered for monitoring in the application. As part of the overall design and implementation efforts, Aviat has conducted many laboratory tests that were intended to determine the effects of different types of interferer signals in point to point microwave links. These tests allowed not only for a better understanding of how the performance parameters of the radio link were being affected in the presence of interference; but also to the creation, validation, and refinement of the rules that were implemented in the FAS expert system. As we understand more about the impact interferers can cause to the radio links, the expert system rules will be refined, and new rules will be added. This process will be part of the overall expert system learning and evolution.
The built-in rules of the expert system use several performance parameters to be able to identify interference uniquely from other radio link impairments. In essence, the main signature of interference consists of a strong received signal level (RSL) accompanied by one or more degraded performance indicators, like SNR, BER, ES/SES, or Alarms in the link. These considerations not only allow the expert system to detect interference but to classify it in up to 5 levels of severity:
The expert system will apply several rules to determine which type of interference is being detected or if this detected instance may be considered a false positive (unconfirmed interference):
The purpose of this document is to describe the laboratory tests executed to understand, create, validate, and refine the rules designed and implemented in the expert system. We will focus specifically on the WiFi interference tests as those are the most critical at this point due to the imminent opening by the FCC of the 6 GHz frequency band to WiFi and other unlicensed uses. While we have conducted numerous WiFi interferer tests in our labs, we will only present in this document one of the most representative sets capturing the different interference levels and the effects that they create in the PTP microwave link.