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MT Apply Fading Profile (MT Apply Flat Fading Profile) (G Dataflow)

Version:
    Last Modified: February 7, 2018

    Applies a flat fading profile to the input complex waveform. The faded waveform can be used to test receiver immunity to fading channels.

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    Note  

    This node normalizes the fading profile to ensure that the power in the input complex waveform is equal to the fading variance. The Modulation Toolkit 4.0 version of MT Apply Flat Fading does not apply this normalization algorithm.

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    input complex waveform

    The modulated complex baseband waveform data.

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    t0

    Trigger (start) time of the Y array.

    Default: 0.0

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    dt

    Time interval between data points in the Y array.

    Default: 1.0

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    Y

    The complex-valued signal-only baseband modulated waveform. The real and imaginary parts of this complex data array correspond to the in-phase (I) and quadrature-phase (Q) data, respectively.

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    fading profile

    The sample-by-sample profile to be applied to the input complex waveform. At each call, this node begins applying this fading profile from the index point where it left off on the previous iteration unless reset? is set to TRUE. Wire the fading profile parameter of MT Generate Fading Profile to this parameter.

    Setting the right fading profile length

    fading profile input complex waveform fading profile input complex waveform fading profile input complex waveform fading profile reset? input complex waveform
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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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    reset?

    A Boolean that determines whether this node begins applying the fading profile at the index point where it left off on the last iteration.

    TRUE Applies the fading profile at index point 0.
    FALSE Does not apply the fading profile at index point 0.

    Default: TRUE

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    output complex waveform

    The faded modulated complex baseband waveform data returned by this node. This parameter is always the same size as the input complex waveform, regardless of the size of the fading profile.

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    t0

    Time of the first value in the Y array.

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    dt

    Time interval between data values in the Y array.

    Default: 1.0

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    Y

    The complex-valued signal-only baseband modulated waveform. The real and imaginary parts of this complex data array correspond to the in-phase (I) and quadrature-phase (Q) data, respectively.

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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.

    Normalizing the Rician Fading Profile

    To match the output complex waveform power to the specified fading variance, this VI first normalizes the power array of the power delay profile, and the amplitude corresponding to power element is then multiplied by the corresponding fading profile, fkl, where l = 1, 2 …, L, and L is the profile length.

    For the selective Rayleigh profile, the power coefficients, C k 2 , corresponding to each path are shown in the following equation:

    C k 2 = 10 P k 10

    The normalized power coefficients can then be represented by:

    C ¯ k 2 = C k 2 k = 1 N C k 2

    for k = 1,...,N.

    For the selective Rician profile, the power in the line-of-sight (LOS) path is given by:

    P L O S = ( k + 1 ) × P 1

    The normalized power coefficients can then be represented by the following equation:

    C ¯ k 2 = C k 2 ( k L O S + 1 ) × C 1 2 + k = 2 N C k 2

    By multiplying these power coefficients with the generated fading profile, fkl, for each path, we can obtain the amplitude, akl, to apply to the Rician profile as shown in the following equation:

    a k l = C ¯ k × f k l

    for k = 1,...,N and l = 1,...,L, where L is the profile length.

    The time array, τ k , is approximated to an integer multiple of the sampling duration, dt, to obtain the integer delay, nk. The integer delay is applied to the input complex waveform as shown by the following equation:

    n k = τ k d t

    The input complex waveform is then delayed for each path by yk[n] = x[n - nk], where n = 1,...,M and M is the input complex waveform size.

    Finally, yk[n] is point-by-point multiplied with amplitude coefficients to obtain the output complex waveform as shown by the following equation:

    y [ n ] = k = 1 N a k l × x [ n n k ]

    In MT Apply Selective Fading Profile, the power from the power delay profile, set for each path, is applied to the corresponding fading profile generated by MT Generate Fading Profile. The power delay profile is specified in terms of power, Pk, and time, τ k , for each path, where k = 1, 2…,N. The delay in the power delay profile is approximated to an integer multiple of the sampling duration, τ k d t for each path, for k = 1,…N, where N is the total number of paths. The input complex waveform is delayed by this amount and then multiplied by the corresponding attenuated fading profile. All these paths are summed to calculate the received signal, y(t), as illustrated by the following figure.


    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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