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Synchronization techniques in multipoint-to-point communication using orthogonal frequency division multiplexing

  • US 7,420,914 B2
  • Filed: 09/13/2007
  • Issued: 09/02/2008
  • 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 upstream OFDM signals from at least two of the remote units combine to a unified OFDM waveform at the host unit;

    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 performs a first analysis of at least one transmission characteristic of the upstream signal from at least one of the remote units in order to determine a first adjustment to the upstream signal within the OFDM communication system;

    wherein the host unit generates and transmits a first adjustment signal to the at least one remote unit to perform the first adjustment;

    wherein after the first analysis the host unit performs a second analysis of the at least one transmission characteristic of the upstream signal from the at least one remote unit in order to determine a second adjustment to the upstream signal within the OFDM communication system; and

    wherein the host unit generates and transmits a second adjustment signal to the at least one remote unit to perform the second adjustment.

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