CONTENTION-BASED ACCESS IN MULTIPOINT-TO-POINT COMMUNICATION USING ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING

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; and

wherein remote unit access to at least one orthogonal tone within the OFDM waveform is contention based.

2 . The OFDM communication system of claim 1 wherein the at least one orthogonal tone is permanently assigned to carry control data.

3 . The OFDM communication system of claim 1 wherein access to the at least one orthogonal tone within the OFDM waveform is always contention based.

4 . The OFDM communication system of claim 1 wherein the at least one contention based orthogonal tone carries at least one request for bandwidth from at least one requesting remote unit to the host unit.

5 . The OFDM communication system of claim 4 wherein the at least one requesting remote unit retransmits its request for bandwidth in the event there is a collision on the at least one contention based orthogonal tone.

6 . The OFDM communication system of claim 1 wherein the OFDM waveform received at the host unit concurrently includes a first set of at least one orthogonal tone, access to the first set being contention based and a second set of at least one orthogonal tone, access to the second set being allocated by the host unit.

7 . The OFDM communication system of claim 6 wherein the first set carries control data and the second set carries payload data.

8 . The OFDM communication system of claim 6 wherein access to the first set is always contention based and wherein access to the second set is always allocated by the host unit.

9 . 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 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 remote unit access to at least one orthogonal tone within the OFDM waveform is contention based.

10 . The system of claim 9 wherein the at least one orthogonal tone is permanently assigned to carry control data.

11 . The system of claim 9 wherein the at least one contention-based orthogonal tone carries at least one request for bandwidth from at least one requesting remote unit to the host unit.