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Training premable in multipoint-to-point communication using orthogonal frequency division multiplexing

  • US 7,394,753 B2
  • Filed: 06/25/2007
  • Issued: 07/01/2008
  • Est. Priority Date: 02/06/1995
  • Status: Expired due to Fees
First Claim
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1. A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprising:

  • a plurality of remote units;

    a host unit that includes a demodulator;

    wherein each of the remote units transmits an upstream OFDM signal using a multiple access scheme to the host unit demodulator using at least one of a plurality of orthogonal tones within an OFDM waveform;

    wherein the host unit receives the upstream OFDM signals from a plurality of the remote units, the tones of the upstream signals being substantially orthogonal when received at the host unit;

    wherein portions of upstream OFDM signals from at least two of the remote units arrive at the host unit at the same time;

    wherein the host unit demodulator demodulates said portions;

    wherein the host unit sends an adjustment signal to at least one of the remote units instructing the at least one remote unit to adjust the timing of transmissions from the remote unit to improve orthogonality of the OFDM waveform received at the host unit;

    wherein at least one remote unit transmits a preamble prior to at least a portion of payload data in at least one upstream OFDM signal; and

    wherein the host unit uses the preamble to assist in demodulating the upstream OFDM signal of the at least one remote unit.

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