EQUALIZERS FOR MULTIPLE INPUT MULTIPLE OUTPUT CHANNELS AND PAM SYSTEMS WITH CYCLOSTATIONARY INPUT SEQUENCES

We study minimum mean square error (MMSE) linear and decision feedback (DF) equalizers for multiple input/multiple output (MIMO) communication systems with intersymbol interference (ISI) and wide-sense stationary (w.s.s.) inputs. To derive these equalizers, we work in the D-transform domain and use prediction theory results. Partial-response MMSE equalizers are also found. As an application, we consider a pulse amplitude modulation (PAM) communication system with ISI and cyclostationary inputs. The MMSE linear and DF equalizers are determined by studying an equivalent MIMO system. The resulting filters are expressed in compact matrix notation and are time-invariant, whereas the corresponding single input/single output filters are periodically time-variant. We also consider MMSE equalizers for a wide-sense stationary process obtained from a cyclostationary input process by introducing a "random phase." To aid in the performance evaluation of various equalizers, we derive their mean square errors. Mean square errors and error rates of several equalizers are compared for a simple example. We also evaluate mean square errors of the derived equalizers for a run-length encoded sequence used in magnetic recording.