Novel data-aided SNR estimation algorithm for QPSK signal in AWGN channel was presented.The analytical and simulated results show that the new SNR estimator performs better than ML-DA estimators

especially in the condi-tion of low SNR

it is more precise and more reliable

and is not sensitive to phase errors of the receiver.Finally

the ori-gin of the new estimator’s error was explored and some suggestions were made on its application.