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Suboptimum Receivers

A binary communication system employs the following signals to communicate two equally likely messages over an additive white Gaussian noise channel with spectral height $\frac{N_0}{2}$:

\begin{displaymath}\begin{array}{l}
s_0(t) = \left\{
\begin{array}{cl}
\frac{2At...
...leq t < T$ }\\
0 & \mbox{else}
\end{array}\right.
\end{array}\end{displaymath}

1.
Draw a block diagram of the optimum receiver.
2.
Compute the probability of error achieved by your receiver from part (a).
3.
Consider now the following suboptimum receiver:

\begin{picture}(100,30)
\setlength{\unitlength}{1mm}
%\put(0,10){\vector(1,0){1...
...90,10){\vector(1,0){10}}
\put(98,11){\makebox(0,0)[b]{$\hat{b}$ }}
\end{picture}
Find the distribution of R for both cases, s0(t) was transmitted and s1(t) was transmitted.
4.
Find the probability of error of the suboptimum receiver.
5.
Assume that the transmitted signal is amplified with a gain $\alpha$ when the receiver in part (c) is used. How must $\alpha$ be chosen so that the performance of the receiver in part (c) equals the performance of the optimum receiver without amplification.
6.
Bonus: Express the result in part (e) in terms of a loss of SNR measured in dB.



Prof. Bernd-Peter Paris
2002-04-22