City center high-elevation angle propagation measurements at L band for land mobile satellite systems

A land mobile satellite system (LMSS) propagation experiment at 1.8 GHz was performed at the Athens city center during June 1996 for high-elevation angle channels. The transmitter platform used was a helicopter dying in predetermined paths to simulate high-elevation angle (60 degrees, 70 degrees, and 80 degrees) communication. A land vehicle specially prepared to accommodate the receiver system was performing the channel recordings. Four narrow streets with large building blocks were selected as representatives, and the statistical analysis presented includes cumulative distributions functions, level crossing rate (LCR), average duration of fades (AFD), and fade and unfade duration distributions. This paper also attempts a comparison of the measured data statistics with statistical models and provides least-square fit formulas for characteristic measures. The results show considerable increase of the fade depth compared to suburban and rural environments. In general, the fade depth decreases with the increasing elevation angle, and the overall analysis indicates the strong dependence of the signal attenuation on the width of the streets, average building height, and vegetation at the edges of the streets.