Patent ID: 6252914
Filing Date: 2001-06-26
Classification: H04L,H04M

Abstract:
A radio communication system having a terminal and a base station connected to each other through a propagation path and capable of reducing deterioration of transmission quality between the terminal and the base station due to multipath fading in the propagation path, the base station comprising:a frequency converter for frequency-converting data sent from the terminal through the propagation path into a base band signal and outputting the signal;a sample quantizer for sample-quantizing the base band signal output from the frequency converter;an automatic equalizer for equalizing distortions of the propagation path about the base band signal sample-quantized by the sample quantizer, estimating a characteristic of the propagation path in accordance with the base band signal sample-quantized by the sample quantizer, and outputting an estimated result;a demodulator for demodulating the base band signal whose distortions are equalized by the automatic equalizer;a predistortion section for adding the inverse of the characteristic of the propagation path to data to be transmitted to the terminal in accordance with the estimated result from the automatic equalizer; anda modulator for modulating the data to which the inverse characteristic of the propagation path is added by the predistortion section, wherein the automatic equalizer comprises:a Fourier transform circuit for transforming the base band signal sample-quantized by the sample quantizer into a frequency-region signal;a propagation-path-characteristic estimation section to which frequency-region signals output from the Fourier transform circuit are input to estimate a transfer function of the propagation path in accordance with a reference signal regularly inserted into data sent from the terminal and a signal corresponding to the reference signal among the frequency-region signals output from the Fourier transform circuit, in order to estimate a propagation path characteristic of the propagation path;a complex divider for computing the inverse characteristic of the propagation path characteristic by applying complex-division to the propagation path characteristic estimated by the propagation-path-characteristic estimation section,a complex multiplier for multiplying the frequency-region signals output from the Fourier transform circuit with the inverse characteristic computed by the complex divider;a selector for outputting the multiplication result computed by the complex multiplier when the base station receives data from the terminal and, after the base station receives the data transmitted from the terminal, outputting the computation result computed by the complex divider; andan inverse Fourier transform circuit for inverse-Fourier-transforming the multiplication result computed by the complex multiplier or the computation result computed by the complex divider, input via the selector.