Patent ID: 7489623
Filing Date: 2009-02-10
Classification: G06F,H03M,H04B,H04H,H04J,H04K,H04L,H04M,H04N,H04W,Y02D

Abstract:
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 control data is sent between the host unit and at least one remote unit using a first modulation scheme on at least one orthogonal tone within the OFDM communication system; wherein payload data is sent between the host unit and the at least one remote unit using a second modulation scheme on at least one orthogonal tone within the OFDM communication system; wherein the first modulation scheme is different than the second modulation scheme; and wherein the first modulation scheme is a form of phase shift keying and the second modulation scheme is a form of quadrature amplitude modulation (QAM).