Blind channel identification using the constant modulus adaptive algorithm

A technique is presented for identifying the impulse response of a nonminimum phase channel based solely on observations of the channel output. The technique uses a two-step estimation procedure whereby the channel input is first estimated and then used in conjunction with the observed channel output to determine a least-squares model of the actual channel. Estimation of the channel input is accomplished through equalisation, demodulation, and remodulation of the channel output. The constant-modulus adaptive algorithm (CMA) is used in the equalization process. The technique is applicable to channels carrying quadrature amplitude modulation (QAM), frequency modulation (FM), and frequency-shift keyed (FSK) modulation. In addition to identifying the channel response, the technique also generates an estimate of the additive cochannel interference.<>