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Communication system

  • US 7,542,729 B2
  • Filed: 10/05/2007
  • Issued: 06/02/2009
  • Est. Priority Date: 03/26/1992
  • Status: Expired due to Fees
First Claim
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1. A signal transmission apparatus comprising:

  • a modulator operable to modulate first carriers by a first data stream according to an m-level PSK or an m-level QAM to produce first modulated carriers, and modulate second carriers by a second data stream according to an n-level PSK or an n-level QAM to produce second modulated carriers, wherein adjacent two carriers of the first and second carriers are quadrate with each other, and wherein n is an integer greater than m;

    a converter operable to convert the first modulated carriers into a first OFDM symbol according to Orthogonal Frequency Division Multiplexing, and add a first guard interval to the first OFDM symbol to produce a first OFDM signal, and to convert the second modulated carriers into a second OFDM symbol according to Orthogonal Frequency Division Multiplexing, and add a second guard interval to the second OFM symbol to produce a second OFDM signal, wherein time periods of the first and second guard intervals are selectable; and

    a transmitter operable to transmit the first OFDM signal and the second OFDM signal.

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