Predetection filter design for practical digital communication systems

A recent approach by P. Galko and S. Pasopathy (see IEEE Trans. Inform. Theory, vol.34, p.77-92, Jan. 1988) to filter design for linear receivers allows the calculation of the asymptotically optimal predetection filter for most modulation methods and sources of distortion that may affect signals during transmission. Here, a technique that overcomes some of the practical difficulties encountered in applying the approach to realistic signals is presented. The methods are illustrated by determining the asymptotically optimal filters for bandlimited duobinary MSK and for duobinary MSK in the presence of an adjacent channel interferer. For the cases studied, asymptotic gains as high as 4.6 dB are observed for adjacent channel interference, and 1.12 dB for bandlimiting.<>