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 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 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 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 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 bidirectional communication system is provided. In one embodiment, a system comprises a host; and a plurality of remote units, wherein a plurality of tones is shared among the plurality of remote units in order to communicate with the host using orthogonal frequency division multiplexing, wherein the plurality of tones is shared in a manner that permits at least two of the remote units to transmit to the host at any one time using the plurality of tones. The host causes at least one remote unit to adjust a timing of symbols transmitted on at least one of the plurality of orthogonal tones in order to improve an alignment of multiframes received at the host.

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: Systems and methods for ranging and round trip delay adjustment in a multipoint-to-point orthogonal frequency division multiplexing (OFDM) system are provided. In one embodiment, a multipoint-to-point, OFDM communication system comprises: a host units; a plurality of remote units that access the host using an orthogonal frequency division multiple access scheme; wherein each of the remote units modulates upstream information into an OFDM signal modulated using an inverse Fourier transform; wherein the host receives upstream OFDM signals from a plurality of the remote units, wherein portions of the upstream OFDM signals arrive at the host at the same time; wherein the host detects a round trip delay between the host and each remote unit; and wherein the host transmits at least one timing adjustment signal to at least one of the remote units based at least in part on at least one of the detected round trip delays.

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: Methods and systems for remote band scanning in multipoint-to-point orthogonal frequency division multiplexing communication are provided. In one embodiment, a method for a remote unit of an orthogonal frequency division multiplexing 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, wherein establishing communication includes the first remote unit scanning a frequency range for a signal from the host unit; and transmitting up to a plurality of tones from the first remote unit based on the signal from the host unit, the up to a plurality of tones modulated with upstream information using orthogonal frequency division multiplexing.

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 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 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 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, 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.