Average-adjusted (MA) models
MA means "moving average "
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We assume that the signal whose PSD we want to estimate is the input of an MA filter, and we estimate the output's power from this PSD.

Figure 6: MA parametric estimation of the DSP.
Let x(k) be a time series. We consider that it is an MA process of order p if we can express its value at time t as a linear combination of random errors (white noise).
Mathematically, we translate this as:
\(\forall\ t:x(k)=\epsilon_k+\sum_{1}^{p}{a_i\epsilon_{k-i}}\) (39)
The noise \(\epsilon_k\) being white with power \(\sigma_u^2\) and (𝛼1, ..., 𝛼p) of the real numbers.