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: 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 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 multiframe alignment in a multipoint-to-point orthogonal frequency division multiplexing (OFDM system are provided. In one embodiment, an (OFDM) communication system comprises: a host unit; a plurality of remote units that access the host unit using an orthogonal frequency division multiple access scheme; wherein each of the remote units modulates upstream information into an OFDM signal modulated using a Fourier transform; wherein the host unit receives upstream OFDM signals from a plurality of the remote units, wherein portions of the upstream OFDM signals arrive at the host unit at the same time; and wherein the host unit causes at least one remote unit to align symbols with symbols transmitted from another remote unit based on a predefined multiframe pattern.

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 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: Systems and methods for orderwire modulation in a multipoint-to-point orthogonal frequency division multiplexing (OFDM) system are provided.

Abstract: Systems and methods for course and fine synchronization are provided. In one embodiment, a method comprises establishing communication between a first remote of a plurality of remote units and a host, the plurality of remote units coupled to the host in a multipoint-to-point configuration; transmitting up to a plurality of tones from the first remote, the tones modulated with upstream information using orthogonal frequency division multiplexing (OFDM); making a first adjustment in a manner in which transmissions are transmitted from the first remote on at least one of the tones, the first adjustment varying the alignment of the transmissions received at the host; and making a second adjustment in the manner in which transmissions are transmitted from the first remote on the at least one of the tones, the second adjustment varying the alignment of the transmissions received at the host, wherein the second adjustment is finer the first adjustment.

Abstract: Systems and methods for bidirectional communication are provided. In one embodiment, a bidirectional communication comprises 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 allocate up to a plurality of the plurality of tones to a first remote unit of the plurality of remote units based on a characteristic of upstream information transmitted by the first remote unit.

Abstract: Systems and methods for multiframe alignment in a multipoint-to-point orthogonal frequency division multiplexing (OFDM) system are provided. In one embodiment, a method for communicating a multiframe comprises: receiving at a host a plurality of upstream symbols transmitted from a plurality of remote units, the upstream symbols transmitted on a plurality of orthogonal carriers modulated using an inverse Fourier transform; and adjusting a transmission timing of at least two of the plurality of remote units so that symbols transmitted from the at least two of the plurality of remote units and associated with frames of a predetermined multiframe structure are received at the host in a sequence based on the predetermined multiframe structure.

Abstract: Systems and methods for round-trip-delay adjustment in a multipoint-to-point orthogonal frequency division multiplexing (OFDM) system are provided. In one embodiment, a method for a remote unit to request bandwidth in an Orthogonal Frequency Division Multiplexing (OFDM) multi-point to point system comprises: transmitting a signal from a remote unit having a request for bandwidth to a host unit on a first tone, the signal from the remote unit configured to combine with a signal from at least one other remote unit on a different tone to form a coherent OFDM waveform; determining when a collision has occurred on the first tone between the signal transmitted by the remote unit and a signal from at least one other remote unit; and when a collision occurs, re-transmitting the request for bandwidth on the first tone.

Abstract: Systems and methods for ranging in a multipoint-to-point orthogonal frequency division multiplexing (OFDM) system are provided. In one embodiment, a method for ranging comprises: receiving at a host a plurality of upstream symbols transmitted from a plurality of remote units, the upstream symbols transmitted on a plurality of orthogonal carriers modulated using an inverse Fourier transform; comparing a phase of at least one ranging symbol received from at least one of the plurality of remote units with a reference generated by the host; transmitting an adjustment instruction instructing the at least one of the plurality of remote units to vary a phase of transmissions transmitted from the at least one of the plurality of remote units based on a difference in phase between the at least one ranging symbol and the reference generated by the host.

Abstract: Systems and methods for round-trip-delay adjustment in a multipoint-to-point orthogonal frequency division multiplexing (OFDM) system are provided. In one embodiment, a method for multipoint-to-point communication comprises: receiving at a host a plurality of upstream symbols transmitted from a plurality of remote units, the upstream symbols transmitted on a plurality of orthogonal carriers modulated using an inverse Fourier transform; and determining respective round trip path delay values associated with each of at least two of the plurality of remote units.

Abstract: A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system is provided. The system includes a plurality of remote units and a host unit that includes a demodulator. 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. 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. Portions of upstream OFDM signals from at least two of the remote units arrive at the host unit at the same time. The host unit demodulator demodulates the portions of the upstream OFDM signals.

Abstract: Systems and methods for orderwire modulation in a multipoint-to-point orthogonal frequency division multiplexed (OFDM) system are provided. In one embodiment, a system comprises: a host; a plurality of remotes using an orthogonal frequency division multiple access scheme to communicate at the same time with the host; wherein the host sends a timing adjustment signal to at least one of the remotes instructing the at least one remote to adjust the timing of transmissions from the at least one remote to improve orthogonality of a combined orthogonal frequency division multiplexed (OFDM) waveform received at the host; wherein a first remote transmits a first upstream signal to the host on a first orthogonal tone; and wherein the host demodulates payload data from at least one orthogonal tone based on a first modulation scheme, and demodulates control data from at least one orthogonal tone based on a second modulation scheme.

Abstract: Systems and methods for contention based tones in a multipoint-to-point orthogonal frequency division multiplexing system are provided. In one embodiment, a multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprises: a host unit; a plurality of remote units that access the host unit using an orthogonal frequency division multiple access scheme; wherein each of the remote units modulates upstream information into an OFDM signal modulated using a Fourier transform; wherein the host unit receives upstream OFDM signals from a plurality of the remote units, wherein portions of the upstream OFDM signals arrive at the host unit at the same time; wherein a first remote unit transmits a first upstream signal to the host unit on a first orthogonal tone; and wherein the first remote unit retransmits the first upstream signal to the host unit in the event a collision occurs on the first orthogonal tone.