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Last Modified: February 7, 2018

Generates a Rician selective-fading profile for the multipath channel. The envelope for the first path statistically obeys the Rician distribution, while the envelope for the remaining paths obey the Raleigh distribution implemented using the Gans model.

The number of complex-valued fading profile samples (having Rician-distributed envelopes) to generate.

**Default: **1000

The system sample rate, in hertz (Hz). This rate is the product of the *symbol rate* × *samples per symbol*.

**Default: **1

The desired input Doppler spread *f* _{ m } of the channel, in hertz (Hz).

This parameter denotes the measure of the spectral broadening caused by the time rate of change of the channel. Doppler spread is defined as the range of frequencies over which the received Doppler spectrum is essentially nonzero. When a pure sine tone at frequency *f* _{ c } is transmitted, the received signal spectrum, called the Doppler spectrum, has components in the range (*f* _{ c } - *f* _{ m }) to (*f* _{ c } + *f* _{ m }). The Doppler spread is related to the mobile velocity *v*, carrier frequency *f* _{ c }, and the speed of light *c* by the relation *f* _{ m } = *v* *f* _{ c }/*c*.

**Default: **0.01

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an **error in** input and an **error out** output so that the node can respond to and communicate errors that occur while code is running. The value of **error in** specifies whether an error occurred before the node runs. Most nodes respond to values of **error in** in a standard, predictable way.

**Default: **No error

The desired ratio, in dB, of the dominant line-of-sight (LOS) path to the scattering component. A large positive value of *k* represents a strongly additive white Gaussian noise channel, while a large negative value of *k* represents a Rayleigh fading (predominantly scattering) channel.

Mathematical definition of Rician parameter *k*

Mathematically, the Rician parameter **k** is defined as:

$K\left(dB\right)\text{\hspace{0.17em}}=\text{\hspace{0.17em}}10\times \mathrm{log}\left(\frac{Power[LOS\text{\hspace{0.17em}}component]}{Power[scattering\text{\hspace{0.17em}}component]}\right)$

The Rician fading profile is generated by adding a DC specular component to a Rayleigh distributed scattering component. *var* denotes the requested **fading variance**, which is the variance of the underlying Rayleigh fading profile. The amplitude (A) of the specular DC component is given by the following formula:

$A=\sqrt{\mathrm{var}\times K}$

By varying *K*, you can parameterize the extent of the scattering component relative to the LOS component of fading. For a strongly Gaussian channel, *K* approaches infinity, while *K* < 0 indicates a strongly scattering (Rayleigh fading) channel.

**Default: **0

The number of paths in the simulated multipath channel. A fading profile is generated for each of these paths.

**Default: **1

The desired variance of the complex-valued Rician distributed fading profile.

**Default: **1

A two-dimensional array of complex-valued coefficients. The number of rows corresponds to the number of paths in the channel, and the number of columns is equal to the profile length. Wire this parameter to MT Apply Fading Profile to apply this fading profile to a baseband I/Q signal.

The internal state of the node at the end of generation of the fading profile for the current iteration. When **reset?** is set to FALSE, this state is used to continue the fading profile generation at the beginning of the next iteration.

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

**error in** input and an **error out** output so that the node can respond to and communicate errors that occur while code is running. The value of **error in** specifies whether an error occurred before the node runs. Most nodes respond to values of **error in** in a standard, predictable way.

The Rician fading profile describes a time-varying channel with an envelope that follows a Rician distribution. The channel can be characterized by a single-tap impulse response comprising a dominant line-of-sight (LOS) path superimposed on a random multipath. The limiting case of a Rician fading channel (when the LOS path is much weaker than the random multipath) is the Rayleigh fading channel. The Rician distribution is given by:

$p\left(r\right)=\frac{r}{{\sigma}^{2}}\mathrm{exp}(-\frac{{r}^{2}+{A}^{2}}{2{\sigma}^{2}}){I}_{0}\left(\frac{Ar}{{\sigma}^{2}}\right)u\left(r\right)$

where *A* denotes the peak amplitude of the dominant signal, *I*_{0}() denotes the modified Bessel function of the first kind and zero-order, and *r* is the specified **fading variance**.

The Gans model generates the Rayleigh fading profile by passing quadrature Gaussian I/Q components through a Doppler filter with a U-shaped power spectral density profile. For the selective fading model, the implementation ensures that the generated fading profile for all paths is uncorrelated.

**Where This Node Can Run: **

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application