Theoretical Analysis of Effects of Atmospheric Turbulence on Bit Error Rate for Satellite Communications in Ka-Band

Abstract

In electromagnetic wave propagation through the earth’s atmosphere like satellite communications, it is known that random fluctuations of the dielectric constant of atmosphere affect propagation characteristics of electromagnetic waves (Fante, 1975; 1980; Ishimaru, 1997; Rytov et al., 1989; Strohbehn, 1977; Tatarskii, 1961; 1971; Tatarskii et al., 1993; Uscinski, 1977; Wheelon, 2003). The random fluctuations, called atmospheric turbulence, cause spot dancing, wave form distortion, scintillations of the received intensity, the decrease in the spatial coherence of wave beams etc. These effects make the received power decrease, and result in the degradation in the performance on satellite communication links. Fig. 1 shows the image of spot dancing and wave form distortion of wave beams. Fig. 2 presents the image of the decrease in the spatial coherence of transmitted waves due to a wave front distortion. The effects of atmospheric turbulence are not negligible in satellite communications in high carrier frequencies at low elevation angles. For example, tropospheric scintillation, caused by turbulence in the lowest layer of atmosphere, has been observed in satellite communications in Ku-band at low elevation angles (Karasawa, Yamada & Allnutt, 1988; Karasawa, Yasukawa & Yamada, 1988). Therefore, it becomes important to consider the effects of atmospheric turbulence appropriately in the design of such satellite communication systems. Somemodels to predict tropospheric scintillation have been developed for applications up to around 14 GHz in the carrier frequency on the basis of both theoretical and empirical studies (Ippolito, 2008). However, because a carrier frequency becomes higher according to the increase in the required channel capacity of satellite communication links in the next generation, the analysis of the effects of atmospheric turbulence should be done for applications at the higher carrier frequencies such as Ka-band, a millimeter wave and an optical wave. Some studies are conducted for satellite communications in such frequencies (Marzano et al., 1999; Matricciani et al., 1997; Matricciani & Riva, 2008; Mayer et al., 1997; Otung, 1996; Otung & Savvaris, 2003; Peeters et al., 1997). We study the effects of atmospheric turbulence on satellite communications in such high frequencies by the theoretical analysis of the moments of wave fields given on the basis of a multiple scattering method (Tateiba, 1974; 1975; 1982). We investigate the method to estimate 2