Abstract: Signal to noise ratio is used as an indicator for the quality of communication. Due to this feature SNR is very important for the modern wireless communication. In this paper make a study on the SNR value for different digital modulation schemes through fading channels and AWGN are proposed. The existing model SNR estimation methods were degraded the performance for higher level modulation scheme. The proposed estimator is based on the moments of received signals at the receiver section and performance evaluated on different channel and modulation conditions. For the performances analysis take the SNR power and switch the channel to a low transmission power. Digital modulations like Bi polar phase shift keying (BPSK), Quadrature amplitude modulation (QAM) and quadrature phase shift keying (QPSK) are performed on the blind SNR estimator. Amplitude phase shift keying (APSK) modulation is used for data aided SNR estimator. The SNR estimator works on the fading channels like Additive White Gaussian Noise AWGN, Nakagami and Rayleigh. The bit error rate (BER) at the receiver section is varied due to the effect of fading. In this paper a comparison on SNR in terms of BER is taken. This comparison is done under OFDM system with different data rate id.SNR estimator on the OFDM system improving the performance with various rate ids. Paper indicates the result that SNR estimator works better in lower SNR conditions which are applicable to different communication scenarios especially in the case of cognitive radio scenarios.

Keywords: SNR estimator, channels, Digital modulation, OFDM.