THE LAND MOBILE SATELLITE COMMUNICATION CHANNEL - RECORDING, STATISTICS, AND CHANNEL MODEL

The communication channel between the MARECS satellite at 26-degrees-W and a cruising van was measured and recorded in European areas exhibiting satellite elevations from 13 to 43 deg. Different environments and mobile antennas were tested. Results of an extensive statistical evaluation include spectra of the fading amplitude, probability density, and distribution of the received signal power, as well as the percentage of time for fade and nonfade periods. Based on the physical phenomena of multipath fading and signal shadowing, an analog model of the land mobile satellite channel is developed which can readily be used for software and hardware fading simulation. The most important parameter of this model is the time-share of shadowing A, ranging from less than 1% on southern highways to 89% in the city of Stockholm. The Rice-factor c, which characterizes the channel during unshadowed periods, can vary from 3.9 to 18.1 dB. For analytical purposes the land mobile satellite channel can be represented by a digital two-state Gilbert-Elliott model. For DPSK modulation with a 10 dB signal-to-noise ratio in the satellite link, the mean bit error probability in the unshadowed channel state is typically in the range of 10(-4)-10(-2), while it is around 0.3 in the shadowed channel state. With regard to data transmission, block error probability density (probability of m errors occurring in a block of n bits), error gap distribution, and block error probability are discussed. The results show good agreement between the recorded channel and the channel models. Moreover, if the transmission scheme is suitably adapted to the channel behavior, reliable and efficient data transmission via the land mobile satellite channel should be achievable.