Rician fading


Rician fading or Ricean fading is a stochastic model for radio propagation anomaly caused by partial cancellation of a radio signal by itself — the signal arrives at the receiver by several different paths, and at least one of the paths is changing. Rician fading occurs when one of the paths, typically a line of sight signal or some strong reflection signals, is much stronger than the others. In Rician fading, the amplitude gain is characterized by a Rician distribution.
Rayleigh fading is the specialised model for stochastic fading when there is no line of sight signal, and is sometimes considered as a special case of the more generalised concept of Rician fading. In Rayleigh fading, the amplitude gain is characterized by a Rayleigh distribution. Rician fading itself is a special case of two-wave with diffuse power fading.

Channel characterization

A Rician fading channel can be described by two parameters. The first one,, is the ratio between the power in the direct path and the power in the other, scattered, paths:
The second one,, is the total power from both paths, and acts as a scaling factor to the distribution:
The received signal amplitude is then Rice distributed with the following parameters:
The resulting PDF then is:
where is the 0th order modified Bessel function of the first kind.