These will in turn
create more detailed requirements given in the actual application.
1. Minimize BER
2. Minimize required power, Eb/No
3. Maximize transmission bit rate, Rb
4. Minimize occupied BW
5. Minimize system complexity
6. Maximize system efficiency
On many occasions, not all of the above goals can be optimally solved jointly; however, in a practical
system, not being optimal in all planes of the above goals will not prove to be catastrophic or
even problematic for that matter. As we progress through this book, we will touch each goal when the
relevant signal processing topics are discussed. Let us begin with the first goal [80??“82].
2.3.1 BER Performance
In this subsection, we will present the BER performance of a few commonly used modulation
schemes. We do this since they are most often used as a point of reference and they have simple,
110 CHAPTER TWO
I-Channel
Q-Channel
FIGURE 2.102 Star QAM signal constellation diagram.
mathematically tractable, closed form expressions. The way this figure of merit is presented is BER
versus the received SNR. As discussed in Chap. 1, this can also be plotted against any normalized
SNR value as well. Since their BER behavior has an exponentially decaying response, it is meaningful
to plot their performance on a log scale.
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