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Future satellite systems such as satellite mobile broadcast systems are interested in offering coverage from the satellite component to a wide range of environments, including indoor. Reliable propagation models are required. The satellite to indoor (and reverse) environment at S band is characterised by severe attenuation of the signals and strong multipath effects due to reflection and diffraction, which makes this environment more stringent than most of the other typical Land Mobile Satellite (LMS) environments. The situation is also different from the terrestrial propagation channel due to the different elevation angles and power margins. As opposed to the terrestrial mobile and LMS cases, the development of precise prediction methods for satellite to indoor propagation environment lacks experimental data.
This project aims to provide simple statistical models, giving guidance to system designers. First an experimental campaign will provide a relevant dataset, then both narrowband and wideband propagation will be investigated. Applications refer both to satellite communication channels as well as to navigation systems, where to some extent at least a partial service by satellite systems may be provided.
Firstly, the project meets the demand for suitable experimental data allowing reliable satellite to indoor propagation modelling at S-band.
Secondly, a new satellite to indoor propagation model will be established that is useful for designers of communication as well as of navigation systems.
Both items, provision of the dataset as well as establishment of the propagation model are considered to have a special importance since there are hardly any comparable results available.
For the satellite to indoor environment there is a significant lack of experimental data that does not allow giving precise prediction methods. Based on the wide and profound expertise of the project team, the flight campaign significantly enhances the basis of experimental data available, with an optimum of experimental configuration (type of channel sounder, etc.) achieved.
The subsequently developed satellite to indoor propagation model marks an important step forward, it will be an easily applicable tool for system designers.
Experimental Data Set
An experimental data set will be part of this project's result. A helicopter substitutes the satellite with a multi-dimensional channel sounder on-board, measuring the real world radio channel both in time domain and in spatial domain. Indoor reception in buildings open to the public is of special interest, such as shopping malls or office towers. Detailed documentation on building structures and the experimental environment is included.
New Satellite to Indoor Propogation Model:
This project aims to develop a new statistical channel model valid for both narrow and wideband conditions based on the observed behaviour of the channel during a measurement campaign.
Depending on the amount of details used as model input, two modes of model operation are proposed. If the description of the building and surrounding are not given in very much detail, coarse propagation estimates per room or part of the building will be provided. This mode can be denominated as a general or site-independent mode.
If details are given on the building inner structure, its furnishings, and the surrounding buildings, detailed coverage maps can be calculated. This mode can be denominated site-specific mode. The output would be plotted in the form of a "coverage" map (received power, delay spread, ...).
Output parameters can be: received powers, mean, 90% percentile, basic losses, delay spreads, coherence bandwidths, power delay profiles, distribution of angles of arrival, etc.
The model can also be utilised in link level simulations. Thus, the model will also be fitted with a generative module capable of producing time series either narrowband (complex envelope, I and Q, slow and fast variations) or wideband in the form of tapped delay-lines (TDL). ASCII output will allow an easy interface with link level simulators such as TOPSIM, COSSAP, Simulink or Matlab. Basis of modelling are information on individual (clusters of) multipath rays together with their angle of arrivals, as obtained from the Channel Sounder measurements with multiple patch RX antenna.
click for larger image
|(Clusters of) rays, obtained from Channel Sounder measurements with multipIe patch RX antenna. A strong line-of-sight component is visible, together with reflections coming approx. from the back of the RX antenna. Measurements taken at Graz Airport (Austria) on Oct. 18, 2006.|
Focus is on principles of building penetration and indoor propagation models.
Experimental Measurement Campaign:
The satellite is substituted by a helicopter equipped with a multi-dimensional channel sounder. Buildings open to the public are of special interest, like airports, shopping malls or office towers.
Super-resolution algorithms allow the identification of individual echoes from the measured delay profiles and a full description of the signal.
Data will be categorized according to environment and building type in order to develop adequate model parameter sets.
Actual Modelling Work:
The new satellite to indoor channel model will be established and verified.
The Review of Models has resulted in proposing a statistical model quantifying building entry loss from external walls for the analysis of overall received power. In the delay axis the existence of clusters of diffuse multipath echoes shall be taken into account.
The Experimental Measurement Campaign has yielded a unique data set, describing the channel in igloo configuration for indoor locations within six buildings - two airports, shopping mall, standard and high rise office building and residential home.
3D Surface / Building Models have been obtained by high-resolution stereographic aerial photography.
Analysis during Postprocessing steps clearly shows how clusters of multipath echoes can be identified and angles of arrival be determined.
The measured data from eight different locations in six different buildings has been analyzed for extracting parameters like building entry loss and time / space spreading. A well recognised channel model due to Saleh and Valenzuela has been simplified for this purpose. Geometrical information like the entry angle of the TX-RX path on the outer building surface or the length of the TX-RX path in the building has been determined for all single measurements.
The project was finalised in January 2008.