Multiplex communications – Generalized orthogonal or special mathematical techniques – Quadrature carriers
Patent
1997-07-25
1999-11-30
Nguyen, Chau
Multiplex communications
Generalized orthogonal or special mathematical techniques
Quadrature carriers
370208, 370486, 375260, H04J 1100
Patent
active
059954833
ABSTRACT:
A multi-point communications system is set forth herein. The communications system includes a transmitter for transmitting OFDM/DMT symbols over a predetermined number of bins across a transmission medium. The OFDM/DMT symbols are generated using at least one timing signal. At least one of the predetermined number of bins includes pilot tone sub-symbols generated from a pilot tone having a frequency corresponding to the at least one timing signal. The communications system also includes a receiver for receiving the OFDM/DMT symbols from the transmission medium. At least one frequency multiplexer is disposed along the transmission medium that frequency multiplexers the OFDM/DMT symbols and a transmission from at least one other transmission source. A mixer is disposed along the transmission medium between the frequency multiplexer and the receiver for mixing the OFDM/DMT symbols for receipt within a passband of the receiver. The receiver includes a frequency demodulator for performing frequency carrier demodulation of the received symbols in response to a first timing signal and a digital demodulator for digitally demodulating the received symbols using a second timing signal. The receiver uses the pilot tone sub-symbols received from the transmitter to adjust the frequency of the first timing signal for carrier synchronization. The second timing signal is separate from the first timing signal. The timing signal of the transmitter is synchronized to the second timing signal, preferably in a preceding downstream synchronization process.
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Kapoor Samir
Marchok Daniel J.
Boortalary Forood
Nguyen Chau
Tellabs Operations Inc.
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