초록 ▼

A transmission system is disclosed which permits the receiving end to demodulate multi-valued modulated symbols successfully under fading conditions and reduces the amount of transmitted reference data to improve data transmission efficiency. At the transmitting end, a multiplexing section, a modula

A transmission system is disclosed which permits the receiving end to demodulate multi-valued modulated symbols successfully under fading conditions and reduces the amount of transmitted reference data to improve data transmission efficiency. At the transmitting end, a multiplexing section, a modulating section, and a transmitting section are provided. In transmitting an OFDM transmission frame, null symbols and reference symbols are placed in the beginning portion of the frame and QPSK symbols are placed in an information symbol data region in the frame with equal spacings in time and frequency. At the receiving end, a receiving section, a demodulation section, an equalizing section, and a demultiplexing section are provided. An error detector detects amplitude and phase errors of each carrier from the reference symbols, and a variation detector detects variations in the amplitude and phase of a received signal from the QPSK symbols. The carrier amplitude and phase errors are corrected by a correction information producing section on the amplitude and phase variations of the received signal detected by the variation detector to produce correction information. The equalizing section equalizes the demodulated symbol data according to the correction information.

대표청구항 ▼

[ What is claimed is:] [9.] For use with an orthogonal frequency division multiplexing transmission system for radio transmission of information from a transmitter to a receiver by orthogonal frequency division multiplexing modulation using multiple carriers, said receiver comprising:receiving means

[ What is claimed is:] [9.] For use with an orthogonal frequency division multiplexing transmission system for radio transmission of information from a transmitter to a receiver by orthogonal frequency division multiplexing modulation using multiple carriers, said receiver comprising:receiving means for receiving and quadrature demodulating an orthogonal frequency division multiplexing modulated signal to recover an orthogonal demodulated signal, said orthogonal frequency division multiplexing modulated signal including a transmission frame in which a plurality of slots are two-dimensionally arranged along time and frequency axes, reference symbols are inserted into predetermined restricted slots, and PSK information symbols subjected to at least PSK modulation and information symbols subjected to digital modulation with a higher multi-value level than said PSK modulation are inserted into the other slots in a predetermined positional relation with respect to each other;orthogonal frequency division multiplexing demodulation means for orthogonal frequency division multiplexing demodulating said quadrature demodulated signal from said receiving means to obtain a demodulated signal;equalizing means for equalizing the amplitude and phase of each symbol in said demodulated signal from said orthogonal frequency division multiplexing demodulation means;error detecting means for detecting amplitude errors and phase errors of said multiple carriers from said reference symbols in said demodulated signal output from said orthogonal frequency division multiplexing demodulation means;variation detecting means for detecting variations in amplitude and phase of a received signal from said PSK information symbols in said demodulated signal equalized by said equalizing means; andcorrecting information producing means for producing correcting information from said amplitude errors and phase errors of said multiple carriers detected by said error detecting means and said variations in amplitude and phase of said received signal detected by said variation detecting means,wherein said equalizing means is responsive to said correcting information from said correcting information producing means to correct the amplitude and phase of said symbols in said demodulated signal output from said orthogonal frequency division multiplexing demodulation means.