DECISION FEEDBACK EQUALIZATION FOR DIGITAL CELLULAR RADIO

摘要

An adaptive Decision Feedback Equalizer (DFE) (40) for adigital cellular mobile radio channel demodulator (30)employs a Complex Fast-Kalman Adaptation algorithm (56) totrack channel variations Sensitivity to sample timing jitteris reduced by providing the DFE with fractionally spacedfeed-forward taps (50'). Deficiencies inherent in using areduced precision implementation are overcome by adding adither signal to sets of operation in the algorithm, thedither signal comprising an appropriately selected Gaussianrandom variable. For small delay spreads of approximately onethird of a symbol duration or less, a resulting degradationin Bit Error Rate is avoided by switching the DFE out of thecircuit or by reducing the number of taps of the DFE. Fordelay spreads of less than 40 microseconds and greater thanapproximately 10 microseconds, a (2,3) fractionally spacedDFE provides an adequate compromise between complexity andperformance.