Blind receivers for nonlinearly modulated signals in multipath

Classical blind channel equalization methods may not be suitable for system s with nonlinear modulation (e.g., continous phase-modulated signals) becau se the input to the channel may not be i.i.d. due to the modulator's memory . Moreover, the nonlinear characteristics of the modulator further complica te the channel estimation task. In this correspondence, we derive blind max imum likelihood channel estimation algorithms for nonlinearly modulated sig nals using a hidden Markov model (HMM) formulation. The proposed method imp lements a stochastic maximum likelihood approach and is well suited for sho rt data records appearing in TDMA systems. Cramer-Rao bounds are derived, a nd some illustrative simulations are presented.