## The Shannon limit – how close can we get? |
Question 6.10

#### 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 Shannon–Hartley 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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