A novel phase based SNR estimation method for constant modulus constellations

A novel signal-to-noise ratio (SNR) estimation algorithm for digital communication systems is presented. Lack of knowledge of both the current channel´s transfer function and the current noise power is a typical property of systems, which transmit over multipath time varying channels. In order to overcome this impediment we designed a SNR estimation method that only makes use of the phases of the received signal and the ones of the transmitted signal or an estimate of them without regarding the channel´s transfer function. It is shown that the SNR calculation formula provides an excellent estimate for SNR values higher than 10dB and constellation schemes with constant modulus. Moreover, the method´s enhanced performance in comparison to the well-known M₂M₄ moment based estimator when a relatively small number of symbols is used for the SNR estimation is shown through simulation results. It is finally explained how the new phase based estimator can be beneficially used in orthogonal frequency division multiplexing (OFDM) systems with faulty frame synchronization or/and a frequency offset.