VARIABLE ERROR CORRECTION IN MULTIPOINT-TO-POINT COMMUNICATION USING ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING
Variable error correction for a multipoint-to-point orthogonal frequency division multiplexing (OFDM) system are provided. In one embodiment, a system comprises: a host unit; 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 allocates orthogonal tones within the system to the plurality of remote units; 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 at least one remote unit to improve orthogonality of an OFDM waveform received at the host unit; and wherein at least one of the remote units transmits an upstream OFDM signal to the host unit using variable error correction in which the remote unit applies at least one of a plurality of available levels of error correction.
1 . A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprising:
a plurality of remote units; and
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 at least one remote unit to improve orthogonality of the OFDM waveform received at the host unit; and
wherein at least one of the remote units transmits an upstream OFDM signal to the host unit using variable error correction in which the remote unit applies at least one of a plurality of available levels of error correction.
2 . The OFDM communication system of claim 1 wherein the at least one remote unit applies a first level of error correction during a first time period and wherein the at least one remote unit applies a second level of error correction during a second time period, the second time period being after the first time period.
3 . The OFDM communication system of claim 1 wherein the level of error correction is chosen based at least in part on one of type of data being transmitted and a desired degree of data integrity.
4 . The OFDM communication system of claim 1 wherein the at least one remote unit varies the level of error correction by adjusting at least one of a multiframe length and a number of error-correcting symbols per multiframe.
5 . The OFDM communication system of claim 1 wherein the host unit transmits an instruction to the at least one remote unit designating the level of error correction to be applied by the at least one remote unit to upstream transmissions.
6 . A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprising:
a plurality of remote units; and
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 at least one remote unit to improve orthogonality of the OFDM waveform received at the host unit; and
wherein at least two different orthogonal tones used simultaneously within the OFDM communication system carry upstream signals having different levels of error correction.
7 . A system comprising:
a host unit;
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 allocates orthogonal tones within the system to the plurality of remote units;
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 at least one remote unit to improve orthogonality of an OFDM waveform received at the host unit; and
wherein at least one of the remote units transmits an upstream OFDM signal to the host unit using variable error correction in which the remote unit applies at least one of a plurality of available levels of error correction.
8 . The system of claim 7 wherein the host unit transmits an instruction to the at least one remote unit designating the level of error correction to be applied by the remote unit to the upstream OFDM signal.
9 . The system of claim 7 wherein the at least one remote unit applies a first level of error correction during a first time period and wherein the at least one remote unit applies a second level of error correction during a second time period, the second time period being after the first time period.
10 . The system of claim 7 wherein at least two remote units transmit simultaneously to the host unit, each of the at least two remote units using a level of error correction that is different than the level of error correction used by the other of the at least two remote units.