The simulation tool available in this page models the HAPs communication channel for fast moving trains using narrow beamwidth antennas in Ka band. The model is based on a land mobile satellite propagation channel model comprised of a finite state machine modelling a very slow channel variation and a set of probability density functions describing slow and fast variation of the channel attenuation. In the model we implemented three states: one for the line of sight (LOS) link conditions, one describing partially shadowed link and one to model the complete blocking of the signal. The ray tracing approach applied to the digital relief model (DRM) covering a representative railway track is used to obtain the state probability vector and matrix of the state transition probability for the final state machine taking into account the HAP visibility, the effects of attenuation due to high trees, and the distance between the HAP and the train. The probability density distributions and related set of parameters were obtained from publicly available literature for land mobile satellite channel models at Ka band. The atmospheric impairments such as rain fading and scintillation fading channel models are included in the model. Rain fading is modelled according to the modified DLR segment approach for generating channel attenuation time series, taking into consideration the specifics of stratospheric communication systems, namely the variable elevation angle and different carrier frequency. Additional fading due to scintillation, which may be harmful in deep fades caused by the rain, is modelled by adjusting the satellite scintillation channel model so that the amount of scintillation fading is correlated to the attenuation caused by the rain.
For the source code and examples of digital elevation model, send mail to: tomaz.javornik@ijs.si
T. Javornik, M. Mohorčič, A. Švigelj, I. Ozimek, G. Kandus, "Adaptive coding and modulation for mobile wireless access via high altitude platforms," Wirel. pers. commun., 2005, vol. 32, str. 301-317.
S. Plevel, T. Javornik, M. Mohorčič, G. Kandus, "Empirical propagation channel model for high altitude platform communication systems," 23rd AIAA International Communications Satellite Systems Conference (ICSSC-2005 [and] 11th Ka and Broadband Communications Conference, 25-28 September 2005, Rome, Italy. Joint conference 2005. Genoa: Istituto Internatinale dlle Comunicazione, 2005.
G. Kandus, M. Mohorcic, M. Smolnikar, E. Leitgeb and T. Javornik, "Modelling of atmospheric impairments in stratospheric communications, " Circuits, systems, signal & communications : proceedings of the 2nd WSEAS International Conference on Circuits, Systems, Signal and Telecommunications (CISST'08), Acapulco, Mexico, January 25-27, 2008, (Electrical and computer engineering series). [S. l.]: World Scientific and Engineering Academy and Society, 2008, str. 86-91.
Send mail to tomaz.javornik@ijs.si for a copy.
This work has been partially funded by the European Community through the 6th Framework Programme IST project CAPANINA (FP6-IST-2003-506745) and 6th Framework Programme IST project SatNEx (FP6-IST-027393).
Capanina: "Stratospheric broadband" www.capanina.org
Satnex: "Satellite Communications Network of Excellence" www.SatNEx.org
Helinet: "Network of Stratospheric Platforms for Traffic Monitoring, Environmental Surveillance and Broadband Services"