here: http://yehar.com/dsp/deip.pdf And don't worry about the pink elephant...
How it is possible to estimate change ( deterioration) SNR on an output of cubic interpolation at various number of samples on a symbol, for qpsk signal? How much will be worse snr (for cubic interpolation) in case of 4 samples on a symbol in comparison of 10 samples on a symbol, for qpsk signal? Whether there is any technique for the answer to a question?