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 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: 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 bi-directional communication system is provided. The system includes a plurality of remote units communicatively coupled to a multipoint-to-point host unit through an orthogonal frequency division multiplexing waveform. The orthogonal frequency division multiplexing waveform comprises a plurality of tones transmitted by a plurality of remote units. A first remote unit of the plurality of remote units is configured to transmit a propagating signal that comprises a first type of information modulated onto a first tone of the plurality of tones, and a second type of information modulated onto a second tone of the plurality of tones. The first tone and the second tone are separated within the orthogonal frequency division multiplexing waveform by at least one guard tone.

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: Forward-looking tone allocation in multipoint-to-point communication using orthogonal frequency division multiplexing is provided. In one embodiment, a system comprises: 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 OFDM transmissions received at the host unit from the plurality of remote units; wherein the host unit allocates orthogonal tones within the system to the plurality of remote units; and wherein the host unit switches the tone allocation for at least one remote unit from a first tone to a second tone based at least in part on channel quality information for the second tone.

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 for multiple use subchannels are provided. In one embodiment, a bidirectional communication system comprises: a first remote for communicating with a host using orthogonal frequency division multiplexing (OFDM), the host communicatively coupled to a plurality of remotes in a multipoint-to-point configuration; wherein the first remote is configured to transmit up to a plurality of tones modulated with upstream information using OFDM; the first remote including a modulator for modulating the up to a plurality of tones with upstream information using OFDM, wherein the modulator is configured to adjust a carrier frequency of the plurality of tones such that when any tones are transmitted from the first remote and at least one other remote of the plurality of remotes, the orthogonality of the tones when received at the host is improved; and wherein both control data and payload data are transmitted on a first tone of the plurality of tones.

Abstract: Methods and systems for forward-looking tone allocation are provided. In one embodiment, a method for an orthogonal frequency division multiplexing (OFDM) multipoint-to-point communications system comprises: establishing communication between a plurality of remote units and a host unit, the remote units communicatively coupled to the host in a multipoint-to-point configuration; transmitting a plurality of tones from the remote units, such that tones from more than one remote unit are simultaneously received at the host, the tones modulated with upstream information using OFDM; adjusting at least one characteristic of at least one tone at least one remote unit, in response to adjustment commands from the host, such that the orthogonality of the simultaneously received tones is improved as received at the host unit; and dynamically switching modulation from at least a first tone of the plurality of tones to a second tone based on an error-rate history of the second tone.

Abstract: Methods and systems for tone hopping 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 modulated with upstream information using OFDM; adjusting at least one characteristic of the up to a 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 received at the host unit is improved; and dynamically switching modulation between tones of the up to a plurality of tones based on an error-rate history of at least one of the tones.

Abstract: A training premable in multipoint-to-point communication using orthogonal frequency division multiplexing (OFDM) 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 OFDM. 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. The host unit allocates orthogonal tones within the OFDM waveform to the plurality of remote units. At least one remote unit transmits a training sequence in at least one upstream OFDM signal to the host unit and the host unit uses the training sequence to assist in demodulating the upstream OFDM signal of the at least one remote unit.

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: Methods for contention-based bandwidth requests in orthogonal frequency division multiplexing systems are provided. In one embodiment, a method for 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; 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; determining when bandwidth is needed for an upstream transmission to the host unit; and transmitting a request for bandwidth to the host unit on a first tone of the plurality of tones, wherein access to the first tone is contention-based.

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

Abstract: Systems for contention-based access in multipoint-to-point communication using orthogonal frequency division multiplexing are provided. In one embodiment, a system comprises 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.

Abstract: Methods and systems for training sequences are provided. In one embodiment, a bi-directional communication system 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 plurality of remote units each transmit a training pattern to the host unit on at least one of the plurality of tones; and the multipoint-to-point host unit is configured to adjust demodulation of upstream information from the plurality of tones based on the training pattern.