Systems, devices and techniques for receiving a signal comprising a quadrature duobinary modulated signal include performing channel equalization of the received signal using a constant multi-modulus to obtain a set of channel estimation coefficients and a stream of symbols, partitioning, based on modulus, the stream of symbols into three partitions, estimating carrier frequency based on the partitioned stream of symbols, recovering a phase of the signal using a maximum likelihood algorithm, and decoding the partitioned stream of symbols to recover data.