Radiated Wireless Coexistence testing

A step by step HOW TO guide to perform manual and automated wireless coexistence testing

At the end of the year 2020, there were over 20 Billion internet of things (IoT) products in the world operating using the licensed and unlicensed frequency bands. This growth trend is projected to keep steady over the coming years as more and more people adopt to a smarter and more connected lifestyle. This will result in a much busier and challenging RF environment than the one we have today. In order to understand the complexity of the RF spectrum, a white paper was published in 2021 from Rohde & Schwarz, which featured RF spectrum activity at multiple locations observed at different times of the day. The locations were selected based on population densities and the amount of known RF transmitters & their frequencies at those locations. It was also concluded that the ISM bands on average have higher channel utilization since most IoT devices take advantage of the unlicensed spectrum. The paper recommended, that while performing wireless coexistence testing, the test conditions should reflect the operational RF environment that the device is intended to operate in. Otherwise, the characterization of RF performance would only reflect ideal case which doesn’t exist in real world operation. Since it is not always possible to test all devices in the real world, relevant test methodologies need to be setup to replicate the real world as much as possible.

This will help us get a better understanding of how the receiver of the RF device will behave under different RF conditions. It is also recommended to perform measurements in order to understand the behavior of the device in the future when the spectrum will get even more challenging. Therefore, a through characterization of the capability of the RF receiver to handle in-band and out-of-band interference signals in also of interest.

In terms of regulatory compliance requirements for ensuring wireless coexistence performance, the ANSI C63.27 is currently the only published test standard that provides guidance on how to perform coexistence testing on devices. The test complexity is based up on risk imposed on the user’s health in the event of a failure caused by an or a plurality of interference signal. The standard also gives device manufacturers guidance regarding test setups, measurement environments, interference signal types and strategy, performance quality measurement parameters for physical layer using key performance indicator (KPI) and application layer parameters for end-to-end functional wireless performance (FWP).

In this application note, the guidance provided by the ANSI C63.27-2021 version regarding test setup, measurement parameter and interference signal have been followed. It will give the reader a clear idea on how to configure standardized test instruments from R&S in order to generate the wanted signal as well as unintended interference signals and conduct measurement to monitor device performance in terms of PER, ping latency and data throughput.

This application note provides step-by-step instruction on how to perform measurements using conducted and radiated methodology. Both manual and automated instrument configuration approach is explained in this document.

The automation scripts are written using python scripting language and are available for download with this application note, free of charge. Official R&S python packages required to run the scripts are available on the PYPI database.