Linear and decision feedback equalizers which are communication receivers used in computer systems having an ISI receiver system and analysis paradigm to provide the ability of estimating the performance of these receivers under mismatched channel conditions. The mean square error (MSE) performance of linear and decision feedback equalizers in the presence of arbitrary channel mismatch is presented. A generic equalizer which has feed-forward and feedback taps which are optimized for a mean square error (MSE) criterion. The ability to rapidly predict MSE performance also leads to the real-time adaptation of the equalizer complexity to improve MSE performance, optimal truncation of channel impulse response based on an MSE criterion, and assessing the impact of assuming white noise in a colored noise environment. With the system and method there is a determination of the spectral characteristics of the communication channel during training and/or decoding. These are either known in advance via models and/or experimentation, or they are estimated and/or measured on-line on a periodic schedule. Once this data is obtained, the MSE estimation paradigm is used to predict the MSE performance of the linear or DFE receiver. Among the areas of application is the area of optical and wireless communication systems, such as mobile cellular systems, satellite systems, and wireless indoor networks. Since the physical channel in wireless systems is susceptible to many variations, the receiver is usually operating with inaccurate channel estimates.