optic.dsp.equalization.ffe

ffe(x, dx, param)

Decision-directed feedforward adaptive equalizer (FFE) for SISO receivers.

Parameters:

• x (np.array) – Input signal to be equalized.

• dx (np.array) – Desired (reference) signal.

• param (optic.utils.parameters object) –

  FFE parameters:

  • param.nTaps: number of feedforward taps [default: 5]

  • param.mu: step size [default: 0.0001]

  • param.SpS: samples per symbol [default: 1]

  • param.nTrain: number of training symbols [default: 1000]

  • param.prec: precision [default: np.float32]

  • param.M: modulation order [default: 4]

  • param.constType: constellation type (‘pam’, ‘qam’, etc.) [default: ‘pam’]

  • param.f: initial feedforward coeffs [default: None]

  • param.trainingMode: operation mode (‘data-aided’, ‘fulltime’) [default: ‘data-aided’]

  • param.preconvIters: number of pre-convergence iterations [default: 1]

Returns:

• yEq (np.array) – Equalized output signal.

• f (np.array) – Final feedforward filter coefficients.

Notes

• Training mode ‘data-aided’ uses the known training symbols for adaptation, while ‘fulltime’ continues to adapt using decision-directed mode even after the training phase.

• Pre-convergence iterations can help the algorithm to converge better by restarting the adaptation process after the initial training phase.

References

[1] S. Haykin, “Adaptive Filter Theory,” 5th ed., Pearson, 2013.