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Interference Analysis

As use of the radio spectrum has become more intense, radio systems have also become larger and more complex. There is also an increasing trend towards regulatory liberalisation, whereby traditional technology and service-specific licences are being replaced with spectrum usage rights that are largely technology and service neutral. Consequently, co-existence between these systems is more difficult to analyse, both because of the presence of multiple interference sources and the increasingly dynamic nature of the interference environment. In many cases, the complexity is further compounded by the statistical nature of the radio-wave propagation on the wanted and interfering paths. At Aegis we offer a comprehensive interference analysis service for all types of radiocommunication systems.

The solution of complex spectrum sharing problems demands the availability of appropriate tools: our work is supported by the Aegis Spectrum Engineering Toolkit. It has been used as a key element of work undertaken for clients such as the UK Office of Communications (Ofcom), Eutelsat and Airspan; it enables us to model interference arising between any two or more radio applications, operating at any frequency from 9 kHz to beyond 100 GHz, whether space-based or terrestrial, fixed or mobile.

Proven software is only part of the solution, however. It is also necessary to have a thorough understanding of the different approaches that can be used for interference analysis, and for a practical knowledge of which approach is most suitable for a given sharing scenario.

The traditional approach to interference analysis has tended to use an aggregation of worst-case assumptions. Often, the worst-case situation has been modelled by taking the most pessimistic value for each of a number of parameters involved in an interference analysis. These pessimistic values have then been aggregated even though, statistically, they are not likely to occur at the same time.

However, this cautious approach, while certainly helping to prevent interference, resulted in systems being over-protected. Today, the increasing demand for spectrum, combined with an ever more complex interference environment, means that greater consideration has to be given to the statistical effects of the different parameters involved in any interference analysis, in order that the spectrum may be used with maximum efficiency. Many of the parameters used in interference analysis can be characterised by some sort of statistical behaviour, but the relationship between these parameters needs to be considered in an appropriate fashion if the overall effect is not to be exaggerated.

Analysis techniques that we use include:

  • time-based simulation (used to obtain both the magnitude and the duration of interference events between non-geostationary satellite networks, for example)
  • Monte Carlo simulation, based on a large number of trials (as used, for example, in our simulation of interference between multimedia wireless systems)
  • modelling based on the convolution of independent statistical functions (used to derive the probability of interference from a tracking Earth station into rain-faded fixed radio relay links, for example)
  • mathematical analysis, for more straightforward interference scenarios.

To discuss how Aegis can help your organisation to solve its spectrum sharing, interference analysis and propagation modelling problems, contact us at enquiry-2015@aegis-systems.co.uk.

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See also:

Aegis Spectrum Engineering Toolkit | Frequency Management | Propagation Modelling


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