Minimum intersymbol interference methods for time domain equalizer design

During initialization, discrete multitone receivers train a time domain equalizer (TEQ) to shorten the channel impulse response to a preset length, ν+1. G. Arslan et al. report a minimum intersymbol interference (Min-ISI) method for TEQ design (see IEEE Trans. Sig. Process., vol.49, no.12, p.3123-35, 2001). Min-ISI TEQs give the highest bit rates among single-FIR TEQs amenable to real-time implementation on programmable fixed-point digital signal processors (DSPs). The Min-ISI method, however, has several disadvantages: (1) sensitivity to transmission delay; (2) inability to design TEQs longer than ν+1 taps; (3) sensitivity to the fixed-point computation in the Cholesky decomposition. We develop an alternate Min-ISI cost function, from which we derive: (1) a fast search method for the optimal transmission delay; (2) extensions to design arbitrary-length Min-ISI TEQs; (3) an iterative Min-ISI method. The iterative Min-ISI method avoids Cholesky decomposition, designs arbitrary length TEQs, and achieves the bit rate performance of the original Min-ISI method.