Plotting the performance of M-ary systems on the Shannon diagram
demonstrates that none of them are able to deliver the theoretical maximum capacity
predicted by the ShannonHartley equation, being adrift
in most cases by 4 dB or more.
In order to get closer to the Shannon limit we need to introduce Coding of the data, allowing us to detect and correct data
errors. A simple introduction to coding and its benefits is given in the next chapter.
It is clear that M-ary FSK allows us to exchange bandwidth efficiency to improve the
power efficiency of the modem, but the uncoded performance falls very short of the ideal
-1.6 dB Eb/N0 performance limit.
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