%0 Journal Article %J IEEE Transactions on Communications %D 2009 %T Cramer-Rao Lower Bound and EM Algorithm for Envelope-Based SNR Estimation of Nonconstant Modulus Constellations %A Wilfried Gappmair %A R. López-Valcarce %A C. Mosquera %B IEEE Transactions on Communications %V 57 %P 1622 - 1627 %8 june %G eng