Decoding Error-Correction Codes Utilizing Bit-Error Probability ...
Decoding Error-Correction Codes Utilizing Bit-Error Probability ...
Decoding Error-Correction Codes Utilizing Bit-Error Probability ...
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If one equates the first and last expressions for R(τ), given in (2.20), then the two-sided<br />
spectral density is related to the one-sided spectral density as follows:<br />
⎧<br />
⎪⎨<br />
G(f) =<br />
⎪⎩<br />
1<br />
2 G 1(f), if f > 0<br />
1<br />
2 G 1(−f), if f < 0,<br />
(2.21)<br />
where G 1 (f) and G(f) are the original one-sided and modern two-sided definition of power<br />
spectral density, respectively. The graphical interpretation of the one and two-sided power<br />
spectral density for an<br />
½´µ<br />
arbitrary stochastic process is illustrated<br />
´µ<br />
in Figure 2.1.<br />
<br />
¾<br />
Figure 2.1: One and two-sided power spectral density for an arbitrary process<br />
2.3 The Complex Process z(t), Associated with the Real<br />
Process x(t)<br />
The complex WSS stochastic process z(t), associated with the real process x(t), is defined<br />
by the one-sided spectral representation,<br />
z(t) = 2<br />
∫ ∞<br />
0<br />
e i2πft dX(f). (2.22)<br />
For this definition to be consistent with the real process, it is demonstrated next that<br />
x(t) = Re{z(t)} = z(t) + z∗ (t)<br />
. (2.23)<br />
2<br />
11