Bit rate maximizing window and equalizer design for DMT-systems

The classical equalizer structure in a discrete multi tone (DMT) receiver, as e.g. in asymmetric digital subscriber line (ADSL), consists of a (real) time domain equalizer (TEQ) combined with complex 1-tap frequency domain equalizers (FEQ´s). In addition, receiver windowing can be added in front of the demodulating DFT to improve the spectral containment of the DFT-filters. In this paper, a framework is developed for the combined design of an equalizer and a window that maximizes the achievable bit rate. This general framework allows to treat equalizer-only and window-only designs as well, which appear as special cases in a natural way. This bit rate maximizing design can serve either as a practical design method, or as an upper bound for existing (suboptimal) methods. For the same achievable bit rate it will also be shown that equalizer taps can be exchanged for window coefficients to obtain a complexity reduced receiver.