Radio Frequency Interference Measurements in WLAN Networks

External radio frequency interference signals are causing malfunctions and disruptions to indoor and outdoor WLAN devices degrading their Quality of Service (QoS). This study aims to help hospitals to ensure that their WLAN networks function without interference. To address this issue, this study adds to the knowledge of how to detect and measure interference signals from external sources and what kind of measurement equipment can be used for interference measurements. In practice, there were some challenges in data gathering in a hospital environment due to confidentiality and technical measurement test setup reasons. Instead of performing measurements in hospital premises, an experimental WLAN network was constructed in a sales office environment for interference and data bandwidth measurement purposes. The study is divided in a theoretical framework and a practical part. The theoretical part focuses on explaining typical RF-interference signal characteristics and WLAN standards physical layer properties. The typical structure of hospital WLAN networks and properties of modern spectrum analyzer and measurement antennas were also described in theory. In the practical part of the study, a microwave oven and a Bluetooth loudspeaker were used as external interferer sources inside the experimental WLAN network. The frequency, power level, RF-bandwidth of interference signals and WLAN network data bandwidth were measured with a spectrum analyzer and a network performance software tool. The results of this study shows that an external interference source, such as a microwave oven or a Bluetooth device can cause problems to the WLAN network physical layer signal, and in the worst case dramatically decrease networks quality of service and performance. A modern real time spectrum analyzer in combination with a highly directive measurement antenna are the most effective choice of measurement equipment for detecting and measuring wideband, narrowband and periodical spurious interference signals in the WLAN networks