Rician fading
The model behind Rician fading is similar to that for Rayleigh fading, except that in Rician fading a strong dominant component is present. This dominant component can for instance be the lineofsight wave. Refined Rician models also consider that
 that the dominant wave can be a phasor sum of two or more dominant signals, e.g. the lineofsight, plus a ground reflection. This combined signal is then mostly treated as a deterministic (fully predictable) process, and that
 the dominant wave can also be subject to shadow attenuation. This is a popular assumption in the modelling of satellite channels.
Besides the dominant component, the mobile antenna receives a large number of reflected and scattered waves.


Phasor Diagram of Rician fading signal

Java Applet: Phasor diagram of one direct and 4
scattered waves (in blue),
resulting an approximately
Ricefading envelope (in black).

Signal Model


Hear a discussion of the basic model behind Ricain and Rayleigh fading.

We model a narrowband propagation channel by considering
a sinusoidal transmitted carrier
s(t) = cos w_{c}t
This signal received over a Rician multipath channel can be expressed as
v(t) = C cos w_{c}t
+ S^{N}_{n=1} r_{n} cos (w_{c}t + f_{n})
where
C
is the amplitude of the lineofsight component
r_{n}
is the amplitude of the nth reflected wave
f_{n}
is the phase of the nth reflected wave
n = 1 .. N identify the reflected, scattered waves.
Rayleigh fading is recovered for
C= 0
PDF of signal amplitude
The derivation of the probability density function of amplitude is
more involved than for Rayleigh fading, and a Bessel function occurs in the mathematical expression.
It has been proposed to approximate this expression by the model for Nakagami fading, however,
the behaviour of Nakagami and Rician fading in deep fades is essentially different. Approximations that focus on the behavior near the mean value,
will divert by orders of magnitude in predicting the probability of deep fades.
Rician factor
The Rician Kfactor is defined as the ratio of signal power in dominant component over the (localmean) scattered power.
In the expression for the received signal, the power in the
lineofsight equals C^{2}/2.
In indoor channels with an unobstructed lineofsight between transmit and receive antenna the Kfactor is between, say, 4 and 12 dB.
Rayleigh fading is recovered for K = 0 (infinity dB).
See also: Rician distribution, measuring the Kfactor.
Rician Channels
Examples of Rician fading are found in