Prediction of data stream parameters in atmospheric turbulent wireless communication links.

A unified approach for calculation of information data stream parameters in the atmospheric optical communication channel is presented based on irradiance fluctuations of optical wave propagation through turbulence and on a generalized Ricean K-parameter distribution. The effects of turbulence are described via the well-known Kolmogorov scheme of turbulent structure relaxation in terms of stochastic scintillation theory described by the gamma-gamma distribution along with measurements of the values of the refractive index structure parameter, C(n)(2). The relation between the Ricean parameter K and the signal scintillation parameter sigma(I)(2) is considered to develop a unified description of the corresponding probability density function (pdf) of signal fading within an atmospheric wireless communication link. Through the corresponding pdf and parameter K, signal data stream parameters such as the signal-to-noise ratio (SNR), bit error rate (BER), and capacity of the optical atmospheric channel (C) are estimated. Such an approach permits the reliable prediction of the effects of fading caused by different levels of turbulence and agrees with experimental data observed at different atmospheric levels, at the heights of both 100-200 m and above 1-2 km. It is shown that at heights of 100-200 m, effects of fading, caused by turbulence, occur much more frequently than those at the heights of 1-2 km. Data stream parameters such as channel capacity, SNR, and spectral efficiency become stronger at higher altitudes, while at the same time the BER becomes relatively negligible.