#### Question 5.6 Question 5.7

## BER performance for FSK

The theoretical performance for coherent and non-coherent FSK is shown here for an Additive White Gaussian Noise limited channel. If the FSK symbol frequencies are chosen to be orthogonal such that the two coherent detectors can in essence operate independently of each other, then the BER performance for coherent FSK is identical to that for coherent ASK. It can be seen that the Eb/N0 penalty of the simpler non-coherent detection method is only about 1 dB at practical bit error rates. As a result, the simpler, non-coherent FSK forms the basis of many low end (for example, 1200 bps) telephone and radio modems in the market-place. Interestingly, the non-coherent performance of FSK is not nearly as bad as that for ASK. |