MULTIPOINT-TO-POINT COMMUNICATION USING ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING
A bidirectional communication system is provided. The system includes a first remote unit for communicating with a host unit using orthogonal frequency division multiplexing. The host unit is communicatively coupled to a plurality of remote units in a multipoint-to-point configuration. The first remote unit is configured to transmit up to a plurality of tones and the first remote unit includes a modulator for modulating the plurality of tones with upstream information using orthogonal frequency division multiplexing such that when any tones are transmitted from the first remote unit and at least one other remote unit of the plurality of remote units, the tones are substantially orthogonal when received at the host unit.
1 . A host unit for a bi-directional communication system, the host unit comprising:
a modem to communicate with a plurality of remote units using a fast Fourier transform to accomplish orthogonal frequency division multiplexing, the plurality of remote units communicatively coupled to the modem in a multipoint-to-point configuration;
the modem receiving an orthogonal frequency division multiplexing waveform, the orthogonal frequency division multiplexing waveform comprising a plurality of tones transmitted by the plurality of remote units;
a control circuit, coupled to the modem, that is configured to generate adjustment information for a first remote unit of the plurality of remote units; and
wherein the control circuit provides the adjustment information to the modem for transmission to the first remote unit so that when any tones are transmitted from the first remote unit and at least one other remote unit of the plurality of remote units, the tones are substantially orthogonal when received at the modem.
2 . The host unit of claim 1 , wherein the controller adjusts transmission characteristics of each of the plurality of remote units to assist the plurality of remote units in generating tones within the orthogonal frequency division multiplexing waveform that are orthogonal at the host unit.
3 . The host unit of claim 1 , wherein the controller adjusts each of the plurality of remote units to achieve alignment within a predefined margin at the host unit of any upstream transmissions from the plurality of remote units.
4 . The host unit of claim 1 , wherein the controller adjust at least one of frequency, amplitude and timing for the plurality of remote units.
5 . The host unit of claim 1 , wherein the modem communicates with the plurality of remote units over a wireless system.
6 . A remote unit for a bi-directional communication system, the remote unit comprising:
a modem communicatively coupled with a multipoint-to-point host unit via an orthogonal frequency division multiplexing waveform in a multiple access scheme;
wherein the modem is adjusted by the multipoint-to-point host unit to modulate at least one tone of a plurality of tones in the orthogonal frequency division multiplexing waveform to be orthogonal with other tones in the orthogonal frequency division multiplexing waveform at the host unit.
7 . The remote unit of claim 6 , wherein the modem comprises a multi-carrier modem for modulating the at least one tone with upstream information so that when received at the host unit, the plurality of tones are orthogonal to the host unit.
8 . The remote unit of claim 6 , wherein the modem implements the orthogonal frequency division multiplexing based on a fast Fourier transform.
9 . The remote unit of claim 6 , and further including a controller that adjusts the manner in which transmissions are transmitted from the modem on at least one tone of the orthogonal frequency division multiplexing waveform so that the plurality of tones in the orthogonal frequency division multiplexing waveform are orthogonal at the host unit.
10 . The remote unit of claim 9 , wherein the controller adjusts at least one of carrier frequency, amplitude and timing for the tones of the orthogonal frequency division multiplexing waveform transmitted by the modem.
11 . A bidirectional communication system, comprising:
a host unit having a modem;
a plurality of remote units, communicatively coupled with the host unit in a multipoint-to-point configuration;
wherein the plurality of remote units are configured to use a multiple access communication scheme to transmit using a plurality of tones in an orthogonal frequency division multiplexing (OFDM) waveform so that tones from the plurality of remote units are received at the host unit modem substantially orthogonal within an OFDM waveform.
12 . The system of claim 11 , wherein the host unit modem modulates and demodulates tones based on a fast Fourier transform.
13 . The system of clam 11 , wherein the host unit is communicatively coupled with the plurality of remote units over a distribution network.
14 . The system of claim 13 , wherein the distribution network is one of a hybrid fiber/coax network and a wireless system.
15 . The system of claim 11 , wherein host unit further includes a controller that adjusts at least one transmission characteristic of at least one of the plurality of remote units to assist in achieving orthogonality of the plurality of tones in the OFDM waveform when received at the host unit.
16 . The system of claim 15 , wherein the controller adjusts at least one of carrier frequency, power, and timing of at least one of the plurality of remote units.
17 . The system of claim 15 , wherein the controller analyzes a signal from the at least one of the plurality of remote units to determine which transmission characteristics to adjust.