A globally admissible off-line modulus restoral algorithm for low-order adaptive channel equalisers

We present an off-line algorithm to recover the binary input sequence to a nonminimum phase communication channel using only the second- and fourth-order moments at the channel output. The algorithm, originally motivated by the well-known constant modulus algorithm (CMA), estimates the equaliser parameters directly without assuming that the channel input is an independent sequence. Consistency of the estimates for the channel inverse impulse response is established by means of a uniqueness theorem. An effective method for determining whether the equaliser has too many taps is proposed and illustrated by simulation examples.