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MT Generate Fading Profile (MT Rayleigh Fading Profile (Jakes)) (G Dataflow)

Version:
    Last Modified: February 7, 2018

    Generates a Rayleigh flat-fading profile with an envelope that statistically obeys the Rayleigh distribution, using the Jakes fading model.

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    profile length

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

    Default: 1000

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    sampling frequency

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

    Default: 1

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    doppler spread

    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.

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    Note  

    The inverse of the Doppler spread T c = 1 / 16 π f m (known as the coherence time) is the time duration over which the channel impulse response is essentially invariant.

    Default: 0.01

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    seed in

    The initial state for generating the fading profile. If seed in is set to -1, the generated fading profile is randomly chosen during every call when reset? is set to TRUE. Otherwise, the generated fading profile returns the same set of fading coefficients when reset? is set to TRUE. The seed in value is used only for the first call or when reset? is set to TRUE.

    Default: -1

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    error in

    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.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Default: No error

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    fading variance

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

    Default: 1

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    reset?

    A Boolean that determines whether the fading profile generation is reset on subsequent calls to this node.

    TRUE Resets the fading profile generation on every call to this node.
    FALSE Continues generating the fading profile from the previous iteration on subsequent calls.

    Default: TRUE

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    fading profile

    Complex-valued coefficients of the generated fading profile size that equals profile length. Wire this parameter to MT Apply Fading Profile to apply this fading profile to a baseband I/Q signal.

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    seed out

    The internal state of the node at the end of generation of the fading profile for the current iteration.

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    error out

    Error information.

    The node produces this output 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.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Rayleigh Distribution Equation

    The Rayleigh distribution describes a flat-fading channel characterized by a single-tap impulse response with a time-varying envelope that is Rayleigh-distributed. This model describes the statistical time-varying nature of the received envelope of a flat fading channel or the envelope of an individual multipath component. The Rayleigh distribution has a probability density function (PDF) given by the following equation:

    p ( r ) = r σ 2 exp ( r 2 2 σ 2 ) u ( r )

    where r is the specified fading variance.

    Jakes Model Equation

    The Jakes model is a deterministic method that simulates time-correlated Rayleigh fading waveforms. The model assumes that N equal-strength rays arrive at a moving receiver with uniformly distributed arrival angles, such that ray n experiences a Doppler shift defined by the following equation:

    ω n = ω m cos ( α n )

    where

    ω n = 2 π f m

    and

    α m = 2 π ( n 0.5 ) N represents the arrival angle of the ray n.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: Not supported

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


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