Implementation of a Real-Time Satellite Channel Simulator

This paper is focused upon implementation aspects of a real-time simulator applicable to narrowband land mobile satellite channels. The satellite channel is mainly affected by shadowing. If a direct signal component exists (line of sight (LOS) conditions), the channel is in a so-called good/clear state and the probability density function (pdf) of the signal amplitude is Rician distributed. The shadowed state (bad/blocked state) is modeled by a Rayleigh distribution of the signal amplitude whereat, with respect to the relative slow shadowing process, the mean power of the Rayleigh fading component is lognormal distributed. The transitions between blocked and LOS periods modeled by a two state Markov chain. In order to regard the multipath propagation, the core software procedure of the simulator is a Rayleigh fading generator incorporating a flexible (user definable) spectrum shaping to take into account Doppler effects due to mobility of the user and movements of the satellite. The real-time channel simulator is a useful tool to demonstrate the influence of the channel on mobile communication in laboratory or teaching purposes. In response to experimenters concerns, arbitrary RF-modules can be connected to the I/Q connectors of the simulator. The baseband channel simulator software runs on a high-performance TMS320C6701 DSP platform