Performance of fractionally spaced linear and decision-feedback equalizers for multitone systems

When OFDM or multitone modulation is used, the channel dispersion is usually circumvented by means of the technique of guard time. As an alternative it is possible not to use a guard time but design receivers able to equalize the intersymbol interference (ISI) and inter-carrier interference (ICI). In the present paper we show how to design fractionally spaced linear or decision-feedback MIMO equalizers for multitone systems without guard time. Full complexity and reduced complexity solutions are investigated. The design is made for an MMSE criterion and the steady-state performance is analyzed. The performance of these detectors is investigated for BPSK modulation of the tones. In addition the robustness of the fractionally spaced detectors against timing errors is demonstrated