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Yes, you need a way to measure it, and there are potentially a number of ways to do it depending on your system, the signal modulation, and the receiver architecture.
e.g., if it is a PSK system and the receiver maintains lock, SNR can be estimated by taking statistics on the error vectors after bit slicing.
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Thanx
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measure it...
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"Slow fading" refers to comparison with respect to Symbol Rate, SR.
There are Large and Small Scale Fading, see "Fading Manifestations and Mitigation Techniques"
https://ortenga.com/blog/#Fading
Small Scale fading is a random variable, so you cannot predict SNR at each point in time, but rather know the distribution function, Rayleigh or Rician.
Best regards,
Shahram Shafie
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Got it. thnx Shafie
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The SNR is a random variable in a fading environment, so have to think of it in terms of a distribution, from which you can derive summary statistics (e.g. mean SNR). In a practical implementation, one would typically estimate it from a pilot channel (where the transmitted information is known). For typical fading profiles used in simulations (e.g. Rayeligh) you can derive it analytically.