TIMING AND SYMBOL 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 of upstream OFDM signals;
wherein the upstream signals from the remote units each include a plurality of symbols; and
wherein each remote unit times its upstream signal transmission so that when multiple upstream signals arrive at the host unit the symbols of the multiple upstream signals are aligned.
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Accused Products
Abstract
A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system is provided. The system includes a plurality of remote units and a host unit that includes a demodulator. 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. 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. Portions of upstream OFDM signals from at least two of the remote units arrive at the host unit at the same time. The host unit demodulator demodulates the portions of the upstream OFDM signals. The upstream signals from the remote units each include a plurality of symbols and each remote unit times its upstream signal transmission so that when multiple upstream signals arrive at the host unit the symbols of the multiple upstream signals are aligned.
136 Citations
22 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 of upstream OFDM signals;
wherein the upstream signals from the remote units each include a plurality of symbols; and
wherein each remote unit times its upstream signal transmission so that when multiple upstream signals arrive at the host unit the symbols of the multiple upstream signals are aligned. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. 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 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 symbols received at the host unit from the plurality of remote units are aligned. - View Dependent Claims (10, 11, 12)
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13. 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 the host unit participates in controlling the transmission timing of the upstream signals from the remote units to assist in demodulating said portions at the host unit. - View Dependent Claims (14, 15, 16, 17, 18)
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19. 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;
wherein the upstream signal transmissions from the plurality of remote units are synchronized in time to improve orthogonality of the upstream signals at the host unit; and
wherein the host unit and at least one remote unit participate in synchronizing the timing of the upstream OFDM signal transmissions. - View Dependent Claims (20, 21, 22)
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Specification