OFDM receiving method of OFDM receiver

An OFDM receiving method for receiving an OFDM signal via a plurality of space paths using a plurality of receiver antennas, the OFDM signal being transmitted from a plurality of transmitter antennas and including a plurality of subcarriers orthogonal to each other, the subcarriers including a data carrier which is assigned transmit data and a pilot carrier which is assigned a known phase and a known amplitude, the method comprising:

• a first step of OFDM-demodulating each of the OFDM signals received by the plurality of receiver antennas into a plurality of receive subcarriers;
• a second step of estimating propagation coefficients of the plurality of space paths based on the plurality of receive subcarriers;
• a third step of calculating an inverse matrix of a propagation matrix whose elements are the estimated propagation coefficients;
• a fourth step of performing interference cancellation for the plurality of receive subcarriers by using the inverse matrix, and estimating transmit subcarriers multiplexed in space;
• a fifth step of calculating a reliability of the inverse matrix;
• a sixth step of extracting the pilot carrier from the estimated transmit subcarriers, and weighting the extracted pilot carrier according to the reliability;
• and
• a seventh step of estimating an instantaneous variation of a demodulation error and a temporal variation of the demodulation error for each estimated subcarrier based on the weighted pilot carrier, and correcting the estimated propagation coefficients based on the instantaneous variation and the temporal variation;
• an eighth step of demodulating the estimated transmit subcarriers to obtain transmit data;
• a ninth step of re-modulating the demodulated transmit data to produce a plurality of subcarriers;
• a tenth step of multiplying the plurality of re-modulated subcarriers by the corrected propagation coefficients to produce a replica signal;
• and
• an eleventh step of producing a subtracted signal obtained by subtracting the replica signal from the plurality of receive subcarriers,
• wherein a loop process of performing the third to eleventh steps using the subtracted signal as a new set of receive subcarriers is repeated a number of times equal to the number of receive subcarriers.

An OFDM receiver for receiving an OFDM signal via a plurality of space paths using a plurality of receiver antennas, the OFDM signal being transmitted from at least one transmitter antenna and including a plurality of subcarriers orthogonal to each other, the subcarriers including a data carrier which is assigned transmit data and a pilot carrier which is assigned a known phase and a known amplitude, the receiver comprising:

• a plurality of OFDM demodulating sections for OFDM-demodulating the OFDM signals received by the plurality of receiver antennas each into a plurality of receive subcarriers;
• a transmission path estimating section for estimating propagation coefficients of the plurality of space paths based on the plurality of receive subcarriers;
• an inverse matrix calculating section for calculating an inverse matrix of a propagation matrix whose elements are the estimated propagation coefficients;
• an interference canceling section for performing interference cancellation for the plurality of receive subcarriers by using the inverse matrix, and estimating transmit subcarriers multiplexed in space;
• a reliability calculating section for calculating a reliability of the inverse matrix;
• a weighted calculation section for extracting the pilot carrier from the estimated transmit subcarriers, and weighting the extracted pilot carrier according to the reliability;
• and
• a variation estimating section for correcting an error included in the plurality of receive subcarriers based on the weighted pilot carrier.

An OFDM receiver for receiving an OFDM signal via a plurality of space paths using a plurality of receiver antennas, the OFDM signal being transmitted from a plurality of transmitter antennas and including a plurality of subcarriers orthogonal to each other, the subcarriers including a data carrier which is assigned transmit data and a pilot carrier which is assigned a known phase and a known amplitude, the receiver comprising:

• a plurality of OFDM demodulating sections for OFDM-demodulating the OFDM signals received by the plurality of receiver antennas each into a plurality of receive subcarriers;
• a transmission path estimating section for estimating propagation coefficients of the plurality of space paths based on the plurality of receive subcarriers;
• an equal number of demodulation stages to the number of receive subcarriers;
• a reliability calculating section for calculating a reliability of an inverse matrix obtained in the plurality of demodulation stages;
• a weighted calculation section for extracting the pilot carrier from the transmit subcarriers estimated in the plurality of demodulation stages, and weighting the extracted pilot carrier according to the reliability;
• and
• a variation estimating section for estimating an instantaneous variation of a demodulation error and a temporal variation of the demodulation error for each estimated subcarrier based on the weighted pilot carrier, and correcting the estimated propagation coefficients based on the instantaneous variation and the temporal variation,
• wherein the plurality of demodulation stages each include:
• an inverse matrix calculating section for calculating an inverse matrix of a propagation matrix whose elements are the estimated propagation coefficients;
• an interference canceling section for performing interference cancellation for the plurality of receive subcarriers by using the inverse matrix, and estimating transmit subcarriers multiplexed in space;
• a data demodulating section for demodulating the estimated transmit subcarriers to obtain transmit data;
• a data modulating section for re-modulating the demodulated transmit data to produce a plurality of subcarriers;
• a replica producing section for multiplying the plurality of re-modulated subcarriers by the corrected propagation coefficients to produce a replica signal;
• and
• a calculation section for producing a subtracted signal obtained by subtracting the replica signal from the plurality of receive subcarriers, and outputting the produced subtracted signal, as a new set of receive subcarriers, to the interference canceling section of a subsequent demodulation stage.

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• a step of correcting the estimated transmit subcarriers according to the estimated instantaneous variation of the demodulation error;
• a step of estimating a temporal variation of a demodulation error of a pilot carrier by using the weighted pilot carrier;
• a step of estimating a temporal variation of the demodulation error for each subcarrier by interpolating the estimated temporal variation in a frequency direction;
• and
• a step of correcting the estimated propagation coefficients based on the estimated temporal variation of the demodulation error for each subcarrier.