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| Titel |
{A Review of Working Group 2 (Advanced Terrestrial Systems) of the COST 296 Action} |
| VerfasserIn |
E. M. Warrington, E. Tulunay |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024204
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| Zusammenfassung |
| E.M. Warrington, E. Tulunay, N.M. Abbasi, J. Azevedo, L. Bertel, A. Bourdillon, E. Benito,
C. Bianchi, A. Casimiro, L. Economou, Y. Erhel, S.M. Feeney, S.D. Gunashekar,
H. Haralambous, D. Lemur, F. Marie, J.P. Monilie, M. Muriuki, M. Oger M. Pietrella,
V. Rannou, H. Rothkaehl, S. Saillant, S. Salous, O. Sari, A.J. Stocker, H.J. Strangeways,
Y. Tulunay and N.Y. Zaalov
This paper deals with the research undertaken during the COST 296 Action in Working
Group 2 on Advanced Terrestrial Systems. The Working Group comprised three work
packages covering various topics: Radar and Radiolocation, HF/MF Communications, and
Spectrum Management. Results from this Working Group are presented in this paper, and
may be summarised as follows.
Aspects of HF propagation
The propagation characteristics of radio signals are important parameters to consider
when designing and operating radio systems. From the point of view Working Group 2 of the
COST-296 Action, interest lies with effects associated with propagation via the ionosphere of
signals within the HF band. Several aspects were covered:
The directions of arrival and times of flight of signals received over a path
oriented along the trough have been examined and several types of propagation
effects identified. Of particular note, combining the HF observations with
satellite measurements has identified the presence of irregularities within the
floor of the trough that result in propagation displaced from the great circle
direction. An understanding of the propagation effects that result in deviations
of the signal path from the great circle direction are of particular relevance to the
operation of HF radiolocation systems.
Inclusion of the results from the above mentioned measurements into a
propagation model of the northerly ionosphere (i.e. those regions of the
ionosphere located poleward of, and including, the mid-latitude trough) and the
use of this model to predict the coverage expected from transmitters where the
signals impinge on the northerly ionosphere.
Development of inversion techniques enabling backscatter ionograms obtained
by an HF radar to be used to estimate the ionospheric electron density profile.
This development facilitates the operation of over the horizon HF radars by
enhancing the frequency management aspects of the systems.
Various
propagation prediction techniques have been tested against measurements made
over the trough path mentioned above, and also over a long-range path between
Cyprus and the UK.
The effect of changes in the levels of ionospheric disturbances on the operational
availability at various data throughput rates has been examined for the trough
path mentioned earlier.
Utilization of antenna arrays in HF systems
Various radio systems are based on arrays of antennas and associated signal processing
techniques. Classically, radio direction finding operates with a multi-channel receiving
system connected to an array of receiving antennas. More recently, MIMO architectures have
been proposed to increase the capacity of radio links by the use of antenna arrays at both
the transmitter and receiver ends of the link. Several aspects were covered within
COST-296:
Experimental work carried out to characterise the HF channel from the point
of view of HF-MIMO systems. Considering various array geometries and a
diversity of the transmitting antennas, the correlation coefficients of the different
transmitter-receiver paths were estimated to investigate the effectiveness of a
MIMO structure for HF radio links.
The dependence of the inter element correlation relatively to the sensors spacing
within MIMO systems. Simulations were carried out with a model of the HF
channel.
Sensitivity analysis of different structures of antenna array for direction finding
applications. Better robustness of heterogeneous arrays to model errors by
comparison to classical homogeneous structures was demonstrated.
Computation of antenna array weighting factors to reduce the sidelobe levels and
to create nulls in the direction of interfering signals.
HF Spectrum Management
A long-term joint UK–Swedish–German project has previously been undertaken on the
measurement and analysis of HF spectral occupancy over northern Europe. The
results from that research were shared at COST 296 with research focussed in four
areas:
Procedures for measuring and modelling spectral occupancy, with final
stable-day and stable-nighttime models for northern Europe, when using
calibrated monopole antennas.
Preliminary investigation into the possible application of artificial neural
networks to predict spectral occupancy in the HF spectrum. In particular, a study
of the development of a single ITU allocation model for the diurnal variation of
HF spectral occupancy over Linköping, Sweden was undertaken.
Application of Neural Networks as a means of optimising the reliability of
HF groundwave communication systems by predicting the detrimental effect of
interference from other users.
Application of Neural Networks as a means of optimising the reliability of
HF communication systems by predicting the detrimental effect of interference
from other users and its variability due to the ionosphere. In particular, the
development of a long-term interference prediction model for the HF spectrum
was developed. |
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