Maximum likelihood SNR estimation for non-coherent FSK-based cooperative networks over correlated Rayleigh fading channels

This paper addresses the problem of signal-to-noise ratio (SNR) estimation for a virtual multi-input single-output (MISO) communication system employing non-coherent M-ary frequency shift keying (NCMFSK) modulation scheme. The transmitted signals from L different nodes undergoing correlated Rayleigh fading with additive white Gaussian noise (AWGN) are combined at a single receiving node via equal gain combining (EGC) scheme. Maximum likelihood (ML) estimation technique is used for deriving the closed-form expressions for data aided (DA) and non-data aided (NDA) estimators. Cramer-Rao bound (CRB) has also been derived to evaluate the performance of the derived estimators. Numerical results have been shown for various parameters such as number of transmitting nodes, modulation order, and varying number of symbols.