Abstract: Systems and methods for orthogonal frequency division multiplexing are provided. In one embodiment, a multi-carrier modem comprises: a transmitter configured to modulate symbols onto at least one of a plurality of the spectrally overlapping carrier signals; a processor coupled to the transmitter, wherein the processor outputs data for transmission by the transmitter, wherein the processor applies an inverse Fourier transform to the data transmitted by the transmitter; the processor modulating a first carrier of the plurality of spectrally overlapping carrier signals based on a first modulation scheme while modulating a second carrier of the plurality of spectrally overlapping carrier signals based on a second modulation scheme.

Abstract: Systems and methods for orthogonal frequency division multiplexing are provided.

Abstract: Systems and methods for orthogonal frequency division multiplexing are provided. In one embodiment, a multi-carrier modem comprises: a receiver configured to de-modulate symbols from at least one of a plurality of spectrally overlapping carrier signals; a transmitter configured to modulate symbols onto at least one of a plurality of the spectrally overlapping carrier signals; a processor coupled to the transmitter, wherein the processor outputs data for transmission by the transmitter, wherein the processor applies an inverse Fourier transform to the data transmitted by the transmitter; and a controller programmed to instruct a transmitter to transmit one or more timing adjustments to at least one of the plurality of remote units based on detected variations in transmissions received from the at least one of the plurality of remote units.

Abstract: Systems and methods for orthogonal frequency division multiplexing are provided. In one embodiment, a multi-carrier modem comprising: a receiver configured to receive symbols from at least one of a plurality of spectrally overlapping carrier signals to produce an output; a transmitter configured to modulate symbols onto at least one of a plurality of the spectrally overlapping carrier signals; a processor coupled to the receiver, wherein the processor applies a Fourier transform to the output from the receiver; and a controller programmed to instruct the transmitter to transmit at least one symbol comprising a ranging pattern when a predetermined instruction is received by the receiver.

Abstract: Systems and methods for orthogonal frequency division multiplexing are provided. In one embodiment, a multi-carrier modem comprising: a receiver configured to de-modulate symbols from at least one of a plurality of spectrally overlapping carrier signals; a transmitter configured to modulate symbols onto at least one of a plurality of the spectrally overlapping carrier signals; a processor coupled to the transmitter, wherein the processor outputs data for transmission by the transmitter, wherein the processor applies an inverse Fourier transform to the data transmitted by the transmitter; and a controller programmed to instruct the transmitter to transmit a coarse timing adjustment followed by at least one secondary timing adjustment, wherein the secondary timing adjustment is a fine tuning adjustment with respect to the coarse timing adjustment.

Abstract: Systems for tone hopping in a multipoint-to-point orthogonal frequency division multiplexing (OFDM) communication system are provided. In one embodiment, a bidirectional communication system comprises: a first remote unit for communicating with a host unit using OFDM, the host unit communicatively coupled to a plurality of remote units in a multipoint-to-point configuration; the first remote unit including a modulator for modulating up to a plurality of tones with upstream information using orthogonal frequency division multiplexing, wherein the modulator is configured to adjust at least one characteristic of the plurality of tones 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 orthogonality of the tones when received at the host unit is improved. The first remote unit switches modulation between tones of the plurality of tones to reduce the impact of using any corrupted tones.

Abstract: Systems and methods for orthogonal frequency division multiplexing are provided. In one embodiment, a method for communication comprises receiving baseband user data; modulating the baseband user data onto a first plurality of parallel streams based on a first modulation constellation; modulating non-user data onto a second plurality of parallel streams based on a second modulation constellation, wherein the first modulation constellation provides a higher bit-rate than the second modulation constellation; applying an inverse Fourier transform algorithm to the first plurality of parallel streams and the second plurality of parallel streams to produce a set of complex time-domain samples; and transmitting a radio frequency transmission signal based on the set of complex time-domain samples.

Abstract: Systems and methods for orthogonal frequency division multiplexing are provided. In one embodiment, a multi-carrier modem comprises: a receiver configured to de-modulate symbols from at least one of a plurality of spectrally overlapping carrier signals; a transmitter configured to modulate symbols onto at least one of a plurality of the spectrally overlapping carrier signals; and a processor coupled to the transmitter, wherein the processor outputs data for transmission by the transmitter, wherein the processor applies an inverse Fourier transform to the data transmitted by the transmitter, the processor programmed to multiplex upstream information onto an allocated number of the plurality of spectrally overlapping carrier signals based on an allocation instruction received be the receiver.

Abstract: A bidirectional communication system is 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 orthogonal frequency division multiplexing (OFDM). The host unit repeatedly performs an analysis of a transmission characteristic of at least one upstream signal from at least one remote unit. The at least one remote unit makes adjustments to the transmission characteristic based on the analyses performed by the host unit to assist the host unit in demodulating a plurality of upstream signals from the plurality of remote units.

Abstract: A bidirectional communication system is provided. In one embodiment, a system comprises a host unit including a multicarrier demodulator and a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit multicarrier demodulator using orthogonal frequency division multiplexing (OFDM). Each of the plurality of remote units transmits to the host unit using a multiframe pattern, each multiframe of the multiframe pattern being at least a predetermined plurality of consecutive symbols in duration. The host unit determines a timing error for at least one of the remote units; and the host unit sends a timing adjustment signal to the at least one remote unit so that multiframes received at the host unit from the plurality of remote units are aligned at the host unit.

Abstract: Systems for contention-based bandwidth requests in orthogonal frequency division multiplexing (OFDM) systems are provided. In one embodiment, a bidirectional communication system comprises: a multipoint-to-point host; and a plurality of remotes communicatively coupled to the multipoint-to-point host through an OFDM waveform; wherein the multipoint-to-point host is configured to receive the OFDM waveform, the OFDM waveform comprising a plurality of tones transmitted by the plurality of remotes, wherein the plurality of tones are simultaneously received at the host from at least two of the plurality of remotes; wherein a first remote is configured to transmit a request for bandwidth to the host on a first tone of the plurality of tones, wherein access to the first tone is contention based; and wherein the multipoint-to-point host transmits information on at least one tone based on whether the host successfully receives the request for bandwidth from the first remote of the plurality of remotes.

Abstract: Methods for multiple use subchannels are provided. In one embodiment, a method for an orthogonal frequency division multiplexing (OFDM) multipoint-to-point communications system comprises: establishing communication between a first remote unit of a plurality of remote units and a host unit, the plurality of remote units communicatively coupled to the host unit in a multipoint-to-point configuration; transmitting up to a plurality of tones from the first remote unit, the up to a plurality of tones modulated with upstream information using OFDM; adjusting a carrier frequency of the up to a plurality of tones such that when any tones are transmitted from a first remote unit and a least one other remote unit, the orthogonality of the tones when received at the host unit is improved; and transmitting both control data and payload data on at least one of the up to a plurality of tones from the first remote unit.

Abstract: Systems and methods for bidirectional communication are provided. In one embodiment, a multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprises: a plurality of remote units, a host unit; wherein the host sends an adjustment signal to a remote instructing the remote to adjust the timing of transmissions from the remote to improve orthogonality of the OFDM waveform received at the host, wherein the host sends an adjustment signal to a remote instructing the remote to adjust the frequency of transmissions from the remote to improve orthogonality of the OFDM waveform received at the host, wherein payload data is transmitted between a remote and the host over a first orthogonal tone within the OFDM communication system during a first time interval, and wherein control data is transmitted between a remote and the host over the first orthogonal tone within the OFDM communication system during a second time interval.

Abstract: Systems and methods for scanning by remotes in multipoint-to-point communication using orthogonal frequency division multiplexing 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 orthogonal frequency division multiplexing (OFDM); wherein at least one remote unit scans a band of frequencies for a downstream signal from the host unit; wherein the host unit sends an adjustment signal to the at least one remote unit 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; and wherein the host unit allocates orthogonal tones within the OFDM waveform to the plurality of remote units.

Abstract: A bi-directional communication system is provided. The system includes a multipoint-to-point host unit and a plurality of remote units communicatively coupled to the multipoint-to-point host unit through an orthogonal frequency division multiplexing waveform. The multipoint-to-point host unit is configured to receive the orthogonal frequency division multiplexing waveform, the orthogonal frequency division multiplexing waveform comprising a plurality of tones transmitted by the plurality of remote units. The multipoint-to-point host unit is configured to adjust transmissions from at least one of the plurality of remote units based on the orthogonal frequency division multiplexing waveform so that the plurality of tones transmitted by the plurality of remote units are substantially orthogonal when received at the multipoint-to-point host unit.

Abstract: A method for an orthogonal frequency division multiplexing multipoint-to-point communications system is provided. The method includes establishing communication between a first remote unit of a plurality of remote units and a host unit, the plurality of remote units communicatively coupled to the host unit in a multipoint-to-point configuration, transmitting up to a plurality of tones from the first remote unit, the up to a plurality of tones modulated with upstream information using orthogonal frequency division multiplexing, and receiving information from the host unit to adjust transmission of the up to a plurality of tones from the first remote unit 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, all of the tones are substantially orthogonal when received at the host unit.

Abstract: A method for an orthogonal frequency division multiplexing multipoint-to-point communications system is provided. The method includes establishing communication between a first remote unit of a plurality of remote units and a host unit, the plurality of remote units communicatively coupled to the host unit in a multipoint-to-point, multiple access configuration, transmitting up to a plurality of tones from the first remote unit, the up to a plurality of tones modulated with upstream information using orthogonal frequency division multiplexing, and receiving information from the host unit to adjust a carrier power for tones transmitted by the first of remote unit so that the tones are substantially orthogonal when received at the host unit.

Abstract: 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 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, the up to a plurality of tones modulated with upstream information using orthogonal frequency division multiplexing. The first remote unit is configured to receive information from the host unit to adjust a carrier frequency of tones transmitted by the first remote unit, and is configured to adjust the carrier frequency based on the received information from the host unit.

Abstract: A bidirectional communication system is provided. In one embodiment, a system comprises a plurality of remote units; a multipoint-to-point host unit communicatively coupled with a plurality of remote units in a multi-point to point configuration, the multipoint-to-point host unit including a multi-carrier modem configured to communicate with the plurality of remote units via an orthogonal frequency division multiplexing waveform; wherein the multipoint-to-point host unit is configured to estimate a round trip path delay correction associated with at least one of the plurality of remote units; and wherein the multipoint-to-point host unit is configured to adjust the round trip path delay associated with the at least one of the plurality of remote units.

Abstract: A method is provided. The method includes sharing upstream bandwidth capacity among a plurality of remote units in a manner that permits at least two of the remote units to transmit to a host at any one time using the upstream bandwidth capacity, the upstream bandwidth capacity comprising a plurality of orthogonal tones generated using inverse fast Fourier transforms, and causing at least one remote unit to adjust the manner in which symbols are transmitted therefrom on at least one of the plurality of orthogonal tones in order to improve the alignment of symbols received at the host.