Interference Analysis
As use of the radio spectrum has become more intense, radio
systems have also become larger and more complex. 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
Radiocommunications Agency, 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.
This cautious approach certainly helps to prevent interference,
but it also results 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-2008@aegis-systems.co.uk.
See also:
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