Above we
showed as M increases this gap becomes narrower.
5.2.4 Optimum Combining (OC)
In the previous three subsections, three antenna combining/selection techniques were presented, all
of which improve the system performance. One of the major assumptions used in these sections was
that interference was at least, negligible. However, for interference-limited systems or systems that
get peak traffic interference, the above techniques are, in fact, not optimal. In this section, we will
present the optimal combining receiver and show how this receiver can have a subset, the MRC
receiver discussed above. Optimal combining is a form of smart antenna technology. There are basically
two categories: The first is called beam forming (BF), here the antennas are physically located close
to each other. Here the weights are controlled to form antenna patterns (or beams) in the direction of
the desired signal and nulls in the direction of the interfering signals. The second category is optimal
combining; here the antennas are physically located far apart where antenna patterns are avoided, but
array signal processing rules apply [59??“62].
Prior to presenting the mathematical equations describing the optimal combining antenna weights,
we would like to present the following adaptive antenna array (AAA) block diagram (see Fig.
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