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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}
{c}
s_0(t) = \left\{
\begin{array}
{cl}
A \sqr...
 ...$0 \leq t < T$}\\ 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)
\put(0,10){\vector(1,0){12}}
\put(6,11){\makebox(0,0)[b...
 ...t(90,10){\vector(1,0){10}}
\put(98,11){\makebox(0,0)[b]{$\hat{b}$}}\end{picture}

where g(t) is given by

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

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 and compare with that of the optimum receiver.
Hint: $\sin^2 x = \frac{1}{2}(1-\cos 2x).$

Prof. Bernd-Peter Paris
3/3/1998