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 sometimes considered a special case of Rician fading for when there is no line of sight signal. In such a case, the Rician distribution, which describes the amplitude gain in Rician fading, reduces to a Rayleigh distribution. Rician fading itself is a special case of two-wave with diffuse power (TWDP) 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 Probability [density function] is:
where is the 0th order modified Bessel function of the first kind.