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StatusOngoing
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Status date2012-02-01
The objectives of the project are to study the characteristics of fading from satellite systems using angle diversity (spatial diversity) for different reception scenarios and to develop a suitable channel model.
The project covers a measurement campaign, statistical analysis and the development of a model capable of air-interface designs and performance analysis.
Two measurement campaigns are planned:
- Measurements in the U.S. using the S-DARS satellites (XM Satellite Radio and Sirius Satellite Radio),
- Measurements in Europe using a MEO satellite to emulate different elevations and azimuth angles.
The activity is supported by ICO Global Communications (ICO). ICO provides access to their MEO satellite, which is fully operational and only partly used for other applications. This allows the transmission of sequences from the satellite suitable for wideband channel measurements.
The goal is the development of an enhanced multistate channel model covering the effects of multi-satellite systems with angle diversity.
Today, terrestrial repeaters are installed in areas where the satellite cannot provide a sufficient QoS. With angle diversity it may be feasible to cover many of these areas without terrestrial repeaters. A key issue is therefore the selection of environments and usage scenarios where a satellite system with angle diversity can provide a sufficient QoS and is not already covered by a single satellite system.
Two main benefits from angle diversity are expected:
- Increase overall availability (reach high availability without CGC),
- Reduce required satellite power for given availability.
The project shall provide:
- Statistical data for the justification of the expected gain from angle diversity for different usage scenarios,
- Achannel model for evaluation of systems supporting diversity combining of signals from several satellites.
The main goal of the project is the development of a model useful for verification of systems with:
- Time diversity/interleaving,
- Diversity combining of several signals.
The efficiency of angle diversity is strongly dependent on the correlation of fades in the respective diversity propagation paths. Consequently, the main goal is to extend an existing LMS model to include angle diversity. The LMS model typically includes a statistical approach based on a Markov-model to generate time series. The channel model can be split into a slow or “large-scale fading model” (LSFM) and a fast or “small scale fading model” (SSFM). The slow fading model can, for example, be implemented by a Markov-model. For each state transition the key parameters of the fading channel (mean signal level, Rice factor, etc.) are selected using a statistical model using for each state a different distribution.
The fast fading effects are typically implemented by well-known models and assumptions like the Wide Sense Stationary – Uncorrelated Scattering (WSSUS). The goal of the project is to develop a LSFM1 (representing signal 1) and LSFM2 (representing signal 2). Special focus will be on the correlation between LSFM2 and LSFM1.
The gain resulting from the angle diversity depends highly on the satellite constellation parameters (elevation, azimuth angles) and the environment (narrow or wide streets, etc). Accordingly, it is planned to make the measurements for different elevations, azimuth and separation angles. Especially for GEO stationary satellites the trade-off between high separation angle and better elevation becomes relevant. If the separation angle is increased orbital positions have to be selected resulting in a lower elevation. Therefore, special attention shall be put on the parameter range relevant for Europe. A first set of data is already available from measurements in the U.S. Many of the scenarios in the U.S. may not be typical for Europe. Therefore, a measurement campaign in Europe is considered as essential to ensure that the model covers scenarios typical for Europe.
The project started with a literature, experiment and data review, after the requirements for the experiment and the measurement equipment and a preliminary design were reviewed at the Preliminary Design Review in April 2008.
The Critical Design Review included complete measurement campaign planning and measurement equipment design, and also a preliminary integration and testing of the equipment. The measurements were scheduled between August and December 2008 with the first results reviewed by end of October. After that, data analysis and model development will happen with a preliminary model by March 2009. The activity concludes with a Final Review in October 2009.
The project has been extended by a CCN for three purposes:
- To consolidate the single and multi-satellite channel generative time series modelling,
- To further evaluate two aspects of channel modelling: the influence of the antenna pattern on the modelling and the improvement of scenario classification by the introduction of semi-automatic micro-environment classification,
- To analyse an optimal European angle-diversity scenario case, based on the simulation of angular satellite and time diversity.
The MiLADY project was finished in October 2009. The final presentation has been held in September 2010 together with the two other projects funded by ESA: J-ORTIGIA and Channel Measurement Equipment (CME). The MiLADY CCN has been finalized in 2011; the final presentation has been held during the ESA propagation workshop in December 2011.
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The first measurement campaign in the US was carried out successfully in September 2008. Measurement data were recorded for a total of 3700 km of drive tests along the US East coast. The campaign started in Jacksonville, Florida and ends up in Portland, Maine (see below). Signals from 4 visible satellites in S-band at 2.3 GHz were recorded in parallel.
During the project, the objective of the second measurement campaign was refocused and the originally planned MEO experiments were replaced by GPS measurements in Europe. The GPS satellite system has the advantage, that it provides a multi-satellite constellation for simultaneous measurements of L-band signals at 1575 MHz (8 signals in average), thus allowing analysing many different angle diversity constellations. A disadvantage is the fact, that the channel impulse response cannot be measured, preventing the analysis of the wideband characteristics of the propagation channel. Different routes were selected in the centre and the vicinity of Erlangen, covering multiple environments such as urban and suburban.
Each of the roads was driven multiple times to obtain a significant amount of satellite orbit positions for angle diversity analysis.
The new MiLADY LMS narrowband channel model for SISO and MISO (angle diversity) satellite constellations as depicted in the figure below has been developed within the CCN. The MiLADY model extends the latest 2-state SISO model as described in [Prieto10] by modifying the generator architecture and by extending the model databases. After the consolidation of the MiLADY SISO model, it has been further extended to support MISO satellite constellations.
The key characteristics of the MiLADY SISO and MISO narrowband channel model are:
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- Support of different environments: urban, suburban, open/highway, heavy tree shadowing (HTS) and commercial environment classes.
- Support of nearly any satellite constellation regarding the number of satellites (1..n), the individual elevations (10° ... 90°) and the angular separations of the satellites (0..180°). The correlation between multiple satellite signals is realized in the state sequence generator (SSG) and small scale fading module (SSFM). After comparing different approaches for the correlated state sequence generation, the SSG has been implemented using a semi-Markov model for the first two satellites and a Master-slave approach for more than two satellites. The chosen approach provides an accurate modeling of the satellite correlation and the state duration statistics with a limited required number of database parameters and a limited model complexity. In the SSFM, the lognormal fading of several satellite signals is implemented by a correlated Loo generator using linear correlation coefficients.
- Modern satellite broadcasting systems (e.g. DVB-SH) introduce long time interleaving in the range of several seconds to increase the QoS during mobile reception. The model is optimized for system simulations without and with long time interleaving due to the improvements in the state sequence generator and the statistical Loo parameter modeling.
- It has been observed in the measurement data, that the dependency of the state probabilities on the relative driving direction is as significant as the dependency from the elevation. As a consequence, the model supports individual SISO SSG parameter sets for different driving directions (0..10°, 10..30°, 30..60°, 60..90°) with respect to the satellite.
Further detailed information about the measurement campaigns and the analysis results can be found in several publications about the MiLADY project:
- E. Eberlein, A. Heuberger, T. Heyn, “Channel models for systems with angle diversity – The MiLADY project”, ESA Workshop on Radiowave Propagation Models, Tools and Data for Space Systems, ESTEC Noordwijk, the Netherlands, December 2008
- D. Arndt, A. Ihlow, A. Heuberger, T. Heyn, E. Eberlein, “Land Mobile Satellite Channel Characteristics from the MiLADY Project”, 10th workshop digital broadcasting, Ilmenau, Germany, September 2009
- D. Arndt, A.Ihlow, A. Heuberger, T.Heyn, E.Eberlein, “Mobile Satellite Broadcasting with Angle Diversity – Performance Evaluation based on Measurements”, IEEE BMSB symposium, Shanghai, March 2010
- T. Heyn, E. Eberlein, D. Arndt, B. Matuz, F. Lázaro Blasco, R. Prieto-Cerdeira, J. Rivera-Castro, “Mobile Satellite Channel with Angle Diversity: the MiLADY Project”, EuCAP conference, Barcelona, April 2010
- D. Arndt, A. Ihlow, A. Heuberger, T. Heyn, E. Eberlein, “QoS Prediction for Mobile Satellite Broadcasting with Angle Diversity Based on Measurements”, IEEE BMSB symposium,Erlangen, 2011
- T. Heyn, D. Arndt, E.Eberlein, “MiLADY CCN Executive Summary”, ESA Workshop on Radiowave Propagation Models and Data for Space Systems, ESTEC, Noordwijk, the Netherlands, December 2011
- D. Arndt, T. Heyn, E. Eberlein, R. Prieto-Cerdeira, “State Modeling of the Land Mobile Satellite Channel with Angle Diversity”, EuCAP 2012, Prague
- D. Arndt, A. Ihlow, T. Heyn, A. Heuberger, R. Prieto-Cerdeira, E. Eberlein, “State Modelling of the Land Mobile Propagation Channel for Dual-Satellite Systems”, submitted for publication to EURASIP Journal on Wireless Communications and Networking, Special Issue on Satellite Communication Systems and Networking, 2012
- D. Arndt, T. Heyn, R. Prieto-Cerdeira, E. Eberlein, “Extended Two-State Narrowband LMS Propagation Model for S-Band”, submitted for publication to IEEE BMSB symposium, Seoul, Korea, June 2012
- The MiLADY CCN final report is available on request.
References:
- Prieto10: R. Prieto-Cerdeira, F. Perez-Fontan, P. Burzigotti, A. Bolea-Alamanac, I. Sanchez-Lago, “Versatile two-state land mobile satellite channel model with first application to DVB-SH analysis”, INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING Int. J. Satellite Communication Network. 2010; 28:291–315