Blind SNR estimation for QAM constellations based on the signal magnitude statistics
Stefanos Dris, Christos Spatharakis, Paraskevas Bakopoulos, Ioannis Lazarou, H. Avramopoulos · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2013
We present a novel non-data-aided algorithm that uses only the magnitude of the received signal for accurate estimation of the signal-to-noise ratio (SNR) in M-QAM optical coherent digital receivers. The Koay inversion method that only works with constant-modulus signals, is extended through analytically exact expressions so as to allow application to any multi-level, complex modulation scheme. Performance is evaluated via simulation for formats up to 64-QAM and is shown to be superior than the decision-directed error vector magnitude (EVM) method at low SNR, while outperforming schemes based on the method of moments at high SNR.