Applies a flat fading profile to the input complex waveform. The faded waveform can be used to test receiver immunity to fading channels.
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.
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.
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.
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,
, corresponding to each path are shown in the following equation:
The normalized power coefficients can then be represented by:
for k = 1,...,N.
For the selective Rician profile, the power in the line-of-sight (LOS) path is given by:
The normalized power coefficients can then be represented by the following equation:
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:
for k = 1,...,N and l = 1,...,L, where L is the profile length.
The time array,
, 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:
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:
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,
, 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,
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.
Installed By: LabVIEW Communications System Design Suite (introduced in 1.0)
Where This Node Can Run:
Desktop OS: Windows
FPGA: Not supported
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