A low complexity SNR estimator for QPSK modulation in AWGN channel

A low complexity non-data-aided (NDA) signal-to-noise ratio (SNR) estimator is proposed for quadrature phase shift keying (QPSK) signals in complex additive white Gaussian noise (AWGN) channel. The novel SNR estimator utilizes the constant amplitude characteristics of the in-phase and quadrature components of QPSK modulation to evaluate the signal power and the noise power separately. The estimation mean and normalized mean square error (NMSE) of the proposed SNR estimator are investigated by Monte Carlo simulations. Results demonstrate that, compared with M₂M₄ algorithm and Ijaz´s method, the proposed estimator saves about 80% and 50% multiplications, respectively. Furthermore, the proposed method performs better than other NDA SNR estimators at the same computational complexity.