Performance Evaluation of Radio Frequency Interference Measurements from
Microwave Links in Dense Urban Cities
Abstract
Radio frequency interference (RFI) constitutes a significant problem in
achieving a good quality of service in radio links. Several techniques
have been proposed to identify and mitigate RFI in wireless networks.
However, most of these techniques are not generalized for all
propagation environments due to their varying geographical features. The
need for extensive frequency scan measurements on the links to identify
the available channels, evaluate the performances of the links, and
detect RFI in the channels becomes imperative. In this study,
performance evaluation of frequency scan measurements from active
microwave links comprising eighteen base stations is presented. The
measurements equipment comprises a spectrum analyzer and a 0.6-meter
antenna dish. The frequency scans were taken at 6GHz, 7GHz, and 8GHz
with full azimuth coverage of the horizontal and vertical polarization.
Measured data were processed to determine the available frequencies and
RFI in the channels. The histogram and probability density function of
the frequency scans were computed. The cumulative distribution functions
were determined, and the statistical error characteristics of the
frequency scans for the estimated normal distribution and the estimated
fitness curve were derived. The short-time Fourier transform of the
noisy signal was obtained, and the signal without noise was recovered
using the inverse short-time Fourier transform. Analysis of the scanned
signals before and after the noise removal is demonstrated. The denoised
signals compare favorably with related results in the preliminary
literature. Overall, the frequency scans would be highly useful in
evaluating RFI measurements and spectrum planning.