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Multiple transmission windows for OFDM symbol

  • US 10,002,995 B2
  • Filed: 09/09/2014
  • Issued: 06/19/2018
  • Est. Priority Date: 09/09/2013
  • Status: Expired due to Fees
First Claim
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1. A method of generating an orthogonal frequency division multiplexing (OFDM) symbol for transmission in a communication channel containing one or more notches of forbidden frequencies, the method comprising:

  • receiving a plurality of information bits;

    mapping the plurality of information bits to a plurality of constellation symbols corresponding to a plurality of OFDM subcarriers in the OFDM symbol, the plurality of constellation symbols including;

    (i) a first set of constellation symbols corresponding to a first set of OFDM subcarriers in the OFDM symbol, wherein the first set of OFDM subcarriers includes i) one or more OFDM subcarriers in the one or more notches, and ii) one or more OFDM subcarriers adjacent to the one or more notches where the one or more OFDM subcarriers adjacent to the one or more notches include at least some of the plurality of information bits, and(ii) a second set of constellation symbols corresponding to a second set of OFDM subcarriers in the OFDM symbol, wherein the second set of OFDM subcarriers are further in frequency from the one or more notches than the first set of OFDM subcarriers;

    generating a first time-domain signal by performing an Inverse Discrete Fourier Transform (IDFT) based on the first set of constellation symbols;

    generating a second time-domain signal by performing an IDFT based on the second set of constellation symbols;

    modifying the first time-domain signal by applying a first windowing function corresponding to a first window transition width β

    1;

    modifying the second time-domain signal by applying a second windowing function having a second window transition width β

    2, wherein the first window transition width β

    1 is different than the second window transition width β

    2 such that β

    1≠

    β

    2;

    setting the first window transition width β

    1 to be longer than a guard interval width NGI such that β

    1>

    NGI;

    setting the second window transition width β

    2 to be shorter than the guard interval width NGI such that β

    2<

    NGI; and

    generating an output signal to include a sum of the first time-domain signal and the second time-domain signal, the output signal corresponding to the OFDM symbol.

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