Most existing studies of spectrum usage have been performed by actively sensing the energy levels in specific RF bands including cellular bands. In this paper, we provide a unique, complementary analysis of cellular primary usage by analyzing a dataset collected inside a cellular network operator. One of the key aspects of our dataset is its scale - it consists of data collected over three weeks at hundreds of base stations. We dissect this data along different dimensions to characterize and model primary usage as well as understand its temporal and spatial variations. Our analysis reveals several results that are relevant if dynamic spectrum access (DSA) approaches are to be deployed for cellular frequency bands. For instance, we find that call durations show significant deviations from the often- used exponential distribution, which makes call-based modeling more complicated. We also show that a random walk process, which does not use call durations, can often be used for modeling the aggregate cell capacity. Furthermore, we highlight some applications of our results to improve secondary usage of licensed spectrum.

http://www.tkn.tu-berlin.de/fileadmin/fg112/Papers/dyspan08_measurement-study.pdf

Primary Users in Cellular Networks: A Large-Scale Measurement Study

This paper presents the development of Neural Network models to predict the likelihood of interference experienced by Broadcast users in the HF spectrum (3-30 MHz). The models are based upon several years of measurements recorded at Linkoping (Sweden) across the HF band, covering a substantial part of a sunspot cycle. The dataset used for the model development is a result of a long-term project being undertaken jointly by the University of Manchester and by the Swedish Defence Research Establishment, to measure systematically and to analyze the occupancy of the entire HF spectrum. The measure of occupancy used is congestion, which is defined as the fraction of channels within a certain frequency allocation with signals exceeding a given threshold. The procedures for measuring and modeling congestion as a function of solar activity, time of day, day of year and incident field strength threshold are briefly presented. The accuracy of the predictions produced by the developed models demonstrate their ability to successfully capture the 24-hour, seasonal and long-term trend in the variability of congestion. These models can be used to advise operators on typical interference occupancy levels and assist the HF broadcast service in the planning of frequency usage and management by assessing the interference effect to short-wave broadcasting in an effort to alleviate spectral congestion in the HF broadcast bands.

24-Hour Neural Network Congestion Models for High-Frequency Broadcast Users

The high frequency (HF) radio channel is highly variable and unpredictable. On the other hand, being largely utilized around the globe, the HF spectrum is densely occupied, characterized by significant levels of interference. Therefore, spectral congestion is always a severe issue to be addressed. One year data (June 2012–June 2013) of HF spectral occupancy measurements collected by a dedicated measurement system installed in Cyprus have been examined in order to characterize and model the HF interference environment over the eastern Mediterranean region. An investigation into the short-term temporal variability of HF spectral occupancy for selected indicative allocations has been conducted. With a view to extend the data analysis from descriptive to predictive and from qualitative to quantitative, time series analysis has been applied to model the HF spectral occupancy of the indicative ranges in the HF spectrum. We categorized different time series models for different occupancy patterns. Analysis for three broadcast allocations covering three different portions of the HF spectrum namely, lower (5.950–6.200 MHZ), middle (11.650–12.050 MHZ), and upper (17.550–17.900 MHZ), is presented. Results of this investigation are expected to be useful for radio system design and frequency management strategies.

HF Spectral Occupancy Time Series Models Over the Eastern Mediterranean Region

The performance of systems using high frequency (HF) radio waves, such as over-the-horizon radars (OTHR), can be strongly affected by external interferers at great distances (thousands of kilometers) from the systems receiver. However, the propagation of interference has complex behavior and is known to vary with location, time, season, sunspot number, and radio frequency. Understanding how the level of interference varies with all of these factors is important for the design of new systems such as next generation OTHR. By combining databases of known transmitters, ray-tracing propagation, and a model ionosphere, a model of the behavior of interference at HF has been developed.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015RS005856

Modeling the interference environment in the HF band

This paper presents an analysis of the characteristics of HF (1.6-30 MHz) spectral occupancy and describes the development of neural network models to predict the likelihood of interference in the HF spectrum over a significant part of Northern Europe. The analysis and developed models are based upon several years of 24-h measurements recorded at four sites in Northern Europe over a substantial part of the previous sunspot cycle. The measure of occupancy used is congestion, which is defined as the fraction of channels within a certain frequency allocation with signals exceeding a given threshold.

24-h HF Spectral Occupancy Characteristics and Neural Network Modeling Over Northern Europe

A long-term joint UK-Swedish-German project has been undertaken on the measurement and analysis of HF spectral occupancy over northern Europe. This has resulted in an extensive database of spectral occupancy measurements made at four sites over a complete sunspot cycle, and mathematical models for spectral occupancy have been developed. The procedures for measuring and modelling spectral occupancy are briefly presented, with final stable-day and stable-night models for northern Europe, when using calibrated monopole antennas. Accuracy of fit and examples of extrapolation in time and in space are presented.

Models of HF spectral occupancy over a sunspot cycle

Since 1982, a long term programme has been undertaken at UMIST to measure and analyse spectral occupancy across the entire HF band 1.6-30 MHz. The aim of the work is to provide experimental data and mathematical models, showing how occupancy varies with frequency, time, bandwidth, threshold level, type of user allocation, antenna, and geographical location. From 1982 to 1989, the measurement site was RSRE, Pershore, Worcestershire, a rural site in central England which was available at the times of the solstices. In 1989, a dedicated measurement system was installed at the Radiocommunications Agency monitoring site, at Baldock, Hertfordshire. A data link between UMIST and Baldock enables system control and transfer of results. In 1990, an identical measurement system was set up by the Swedish National Defence Research Establishment at LinkSping, Sweden, and an agreement made for the simultaneous operation of the two sites, and for data exchange. In 1993 a third system was installed by UMIST and DRA at the antenna site of Rohde and Schwarz near Munich, Germany, again linked to UMIST for control and data transfer. These three sites are approximately at the corners of an equilateral triangle of side length 11000 km, and provide effective measurement of spectral occupancy over northern Europe. The introduction of automatic systems has meant that occupancy measurements are not restricted to the solstices, and this paper is based on results taken at more frequent time intervals.

https://ieeexplore.ieee.org/iel3/1166/7915/00336999.pdf

Recent work on the measurement and analysis of spectral occupancy at HF

Stable day and stable night European occupancy models are presented, with examples of their extrapolation and interpolation properties to predict occupancy both outside and inside the area covered by the measurement sites. An investigation into the possible long-term change of the utilisation of the HF spectrum is also presented and observations are made on the effects of the 1999 eclipse.

Aspects of HF spectral occupancy

http://ieeexplore.ieee.org/iel3/3160/13851/00640040.pdf

S. Boberg

Papers

Models of HF spectral occupancy over a sunspot cycle

Recent work on the measurement and analysis of spectral occupancy at HF

Aspects of HF spectral occupancy

The mapping of HF spectral occupancy over northern Europe