Multiplex communications – Generalized orthogonal or special mathematical techniques – Quadrature carriers
Patent
1996-03-21
1998-06-23
Hsu, Alphus H.
Multiplex communications
Generalized orthogonal or special mathematical techniques
Quadrature carriers
370482, 375264, 375266, 375269, 375308, 375331, H04L 2726, H04L 2734
Patent
active
057712247
ABSTRACT:
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.
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Ishikawa Tatsuya
Okita Shigeru
Seki Takashi
Taga Noboru
Hsu Alphus H.
Kabushiki Kaisha Toshiba
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