ADAPTIVE MODULATION 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;
wherein a first upstream signal on a first orthogonal tone within the OFDM communication system is modulated using a first modulation scheme;
wherein a second upstream signal on a second orthogonal tone within the OFDM communication system is modulated using a second modulation scheme; and
wherein the first modulation scheme is different than the second modulation scheme.
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Accused Products
Abstract
Systems for adaptive modulation in multipoint-to-point communication using orthgonal frequency division multiplexing (OFDM) are provided. In one embodiment, a system comprises: a host unit; and a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit using OFDM; 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 an OFDM waveform received at the host unit; wherein the host unit allocates tones within the OFDM waveform to the plurality of remote units; wherein different modulation schemes are used on different tones within the OFDM waveform; and wherein the host unit allocates tones within the OFDM waveform based on at least one of type of data to be transmitted and error rate requirement.
146 Citations
7 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;
wherein a first upstream signal on a first orthogonal tone within the OFDM communication system is modulated using a first modulation scheme;
wherein a second upstream signal on a second orthogonal tone within the OFDM communication system is modulated using a second modulation scheme; and
wherein the first modulation scheme is different than the second modulation scheme. - View Dependent Claims (2, 3, 4, 5)
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6. A system comprising:
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a host unit; and
a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit using orthogonal frequency division multiplexing (OFDM);
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 an OFDM waveform received at the host unit;
wherein the host unit allocates orthogonal tones within the OFDM waveform to the plurality of remote units;
wherein different modulation schemes are used on different orthogonal tones within the OFDM waveform; and
wherein the host unit allocates orthogonal tones within the OFDM waveform based at least in part on at least one of type of data to be transmitted and error rate requirement. - View Dependent Claims (7)
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Specification