This is machine translation

Translated by Microsoft
Mouseover text to see original. Click the button below to return to the English verison of the page.

Note: This page has been translated by MathWorks. Please click here
To view all translated materals including this page, select Japan from the country navigator on the bottom of this page.

Rayleigh Noise Generator

Generate Rayleigh distributed noise


Rayleigh Noise Generator will be removed in a future release. Use the MATLAB Function block and randn function instead.


Noise Generators sublibrary of Comm Sources


The Rayleigh Noise Generator block generates Rayleigh distributed noise. The Rayleigh probability density function is given by


where σ2 is known as the fading envelope of the Rayleigh distribution.

The block requires you to specify the Initial seed for the random number generator. If it is a constant, then the resulting noise is repeatable. The sigma parameter can be either a vector of the same length as the Initial seed, or a scalar. When sigma is a scalar, every element of the output signal shares that same value.

Initial Seed

The Initial seed parameter initializes the random number generator that the Rayleigh Noise Generator block uses to add noise to the input signal. For best results, the Initial seed should be a prime number greater than 30. Also, if there are other blocks in a model that have an Initial seed parameter, you should choose different initial seeds for all such blocks.

You can choose seeds for the Rayleigh Noise Generator block using the Communications System Toolbox™ randseed function. At the MATLAB® prompt, enter


This returns a random prime number greater than 30. Entering randseed again produces a different prime number. If you supply an integer argument, randseed always returns the same prime for that integer. For example, randseed(5) always returns the same answer.

Attributes of Output Signal

The output signal can be a frame-based matrix, a sample-based row or column vector, or a sample-based one-dimensional array. These attributes are controlled by the Frame-based outputs, Samples per frame, and Interpret vector parameters as 1-D parameters. See Sources and Sinks for more details.

The number of elements in the Initial seed parameter becomes the number of columns in a frame-based output or the number of elements in a sample-based vector output. Also, the shape (row or column) of the Initial seed parameter becomes the shape of a sample-based two-dimensional output signal.



Specify σ as defined in the Rayleigh probability density function.

Initial seed

The initial seed value for the random number generator.

Sample time

The period of each sample-based vector or each row of a frame-based matrix.

Frame-based outputs

Determines whether the output is frame-based or sample-based. This box is active only if Interpret vector parameters as 1-D is unchecked.

Samples per frame

The number of samples in each column of a frame-based output signal. This field is active only if Frame-based outputs is checked.

Interpret vector parameters as 1-D

If this box is checked, then the output is a one-dimensional signal. Otherwise, the output is a two-dimensional signal. This box is active only if Frame-based outputs is unchecked.

Output data type

The output can be set to double or single data types.

See Also




[1] Proakis, John G., Digital Communications, Third edition, New York, McGraw Hill, 1995.

Introduced before R2006a

Was this topic helpful?