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Soner Bekleric Title of Thesis: Nonlinear Prediction via Volterra Ser

Soner Bekleric Title of Thesis: Nonlinear Prediction via Volterra Ser

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2.3. LINEAR PREDICTION 12<br />

In my thesis I have adopted the least squares approach to estimate the coef-<br />

ficients <strong>of</strong> linear and non-linear prediction systems but bear in mind that other<br />

method (at least for the linear prediction problem) are also plausible. In the follow-<br />

ing section I will discuss three methods to estimate the coefficients a(i), i = 1 . . . p<br />

from the data x(n): the Yule-Walker method, Burg’s algorithm, and the least<br />

squares approach.<br />

2.3.1 Forward and backward prediction<br />

Off-line processing allows computation <strong>of</strong> forward and backward prediction oper-<br />

ators. In other words, I can use past samples <strong>of</strong> data to predict future samples<br />

and/or I can use future samples <strong>of</strong> data to predict past samples. This allows us to<br />

formulate a problem with two systems <strong>of</strong> equations. One for forward prediction,<br />

and, the other for backward prediction,<br />

x f p<br />

n = a<br />

i=1<br />

f<br />

i xn−i + εn, (2.12)<br />

x b p<br />

n = a<br />

i=1<br />

b ixn+i + εn . (2.13)<br />

2.3.2 Estimating AR coefficients <strong>via</strong> Yule-Walker Equations<br />

I can write equation (2.6) as follows<br />

X(z) = E(z)<br />

, (2.14)<br />

A(z)<br />

and the autocorrelation in the z domain (Ulrych and Sacchi, 2005) is

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