MULTIFRAME ALIGNMENT IN MULTIPOINT-TO-POINT COMMUNICATION USING ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING
First Claim
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; and
wherein each remote unit times its upstream signal transmission so that when multiple upstream signals arrive at the host unit, multiframes of the multiple upstream signals are aligned.
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Accused Products
Abstract
A bidirectional communication system is provided. In one embodiment, a system comprises a host unit including a multicarrier demodulator and a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit multicarrier demodulator using orthogonal frequency division multiplexing (OFDM). Each of the plurality of remote units transmits to the host unit using a multiframe pattern, each multiframe of the multiframe pattern being at least a predetermined plurality of consecutive symbols in duration. The host unit determines a timing error for at least one of the remote units; and the host unit sends a timing adjustment signal to the at least one remote unit so that multiframes received at the host unit from the plurality of remote units are aligned at the host unit.
131 Citations
10 Claims
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1. A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprising:
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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; and
wherein each remote unit times its upstream signal transmission so that when multiple upstream signals arrive at the host unit, multiframes of the multiple upstream signals are aligned. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A system comprising:
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a host unit including a multicarrier demodulator;
a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit multicarrier demodulator using orthogonal frequency division multiplexing (OFDM);
wherein each of the plurality of remote units transmits to the host unit using a multiframe pattern, each multiframe of the multiframe pattern being at least a predetermined plurality of consecutive symbols in duration;
wherein the host unit determines a timing error for at least one of the remote units; and
wherein the host unit sends a timing adjustment signal to the at least one remote unit so that multiframes received at the host unit from the plurality of remote units are aligned at the host unit. - View Dependent Claims (8, 9, 10)
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Specification