Systems and methods for orthogonal frequency divisional multiplexing

A method for quality based assessments of orthogonal channels for remote service units of an OFDM based multiple access system, the method comprising:

• monitoring a subset of orthogonal carriers within an OFDM waveform associated with at least one communication channel, wherein the subset of orthogonal carriers comprises less than all of the orthogonal carriers within the OFDM waveform;
• determining a quality measurement for the subset of orthogonal carriers;
• communicating a notification message regarding the quality measurement for the subset of orthogonal carriers;
• and
• adjusting a frequency of upstream carriers of the OFDM waveform to maintain orthogonality within the OFDM waveform.

A method for quality based allocation of orthogonal channels for remote service units of an OFDM based multiple access system, the method comprising:

• determining a channel quality measurement for a first portion of an OFDM waveform, said first portion comprising less than all the payload bearing orthogonal tones within the waveform;
• determining a channel quality measurement for a second portion of the OFDM waveform different than the first portion, said second portion comprising less than all the payload bearing orthogonal tones within the waveform;
• and
• receiving an allocation of only a portion of upstream orthogonal tones, said allocation based at least in part on the channel quality measurements for said first and second portions;
• receiving frequency and timing adjustment information for maintaining orthogonality of the upstream orthogonal tones.

A remote service unit for a multiple access OFDM communication system, the remote service unit comprising:

• a transceiver for receiving an OFDM waveform, the OFDM waveform having references signals distributed throughout, the references signals for adjusting demodulation of the OFDM waveform;
• an FFT engine coupled to the transceiver, the FFT engine producing frequency domain data samples representing information carried by the OFDM waveform;
• an FFT engine coupled to the transceiver, the FFT engine producing time domain data samples representing upstream information for transmission by the transceiver on a subset of orthogonal carriers of the OFDM waveform;
• a mapper that that receives payload data mapped onto an in-phase (1) and quadrature-phase (Q) constellation based on an output from the FFT engine, wherein the mapper maps said payload data into a at least one baseband payload signal;
• and
• a controller that receives reference data based on at least one of the reference signals, wherein the controller makes adjustments for demodulating the payload data based on the reference data.

A remote service unit for a multiple access OFDM communication system, the remote service unit comprising:

• a transceiver for receiving an OFDM waveform, the OFDM waveform having reference signals transmitted over a plurality of reference tones distributed within the OFDM waveform, the references signals for adjusting demodulation of the signals transmitted over the OFDM waveform;
• an FFT engine communicatively coupled to the transceiver;
• a mapper communicatively coupled to the FFT engine, the mapper using a constellation map to demodulate data from signals transmitted over the OFDM waveform;
• and
• a controller that makes adjustments to the data demodulation based on the receipt of the reference signals;
• wherein the transceiver transmits upstream OFDM signals using only a portion of the orthogonal tones within an upstream OFDM waveform based on an allocation of said portion received from a host unit.

A remote service unit for a scalable multiple access OFDM communication system, the remote service unit comprising:

• a multi-carrier modem for accessing an OFDM waveform having a first bandwidth, wherein the multi-carrier modem provides access to a subset of channels available in a second bandwidth of the OFDM waveform, wherein the second bandwidth is smaller than the first bandwidth;
• an n-point FFT engine producing time domain samples of data for modulation onto OFDM carriers within the second bandwidth, the n-point FFT having a number of n-points selected for producing the time domain samples based on a size of the second bandwidth;
• and
• a controller for controlling OFDM carrier spacing of the OFDM carriers modulated by the n-point FFT engine, wherein the controller maintains OFDM carrier spacing of the OFDM carriers modulated by the n-point FFT engine based on a carrier spacing criteria for the first bandwidth.

A remote service unit for a scalable multiple access OFDM communication system, the remote service unit comprising:

• a multi-carrier modem for accessing an OFDM waveform having a first bandwidth, wherein the multi-carrier modem provides access to a subset of channels available in a second bandwidth of the OFDM waveform, wherein the second bandwidth is contained within the first bandwidth;
• an n-point FFT engine producing time domain samples of data for modulation onto OFDM carriers within the second bandwidth, the n-point FFT having a number of n-points selected for producing the time domain samples based on a size of the second bandwidth;
• and
• a controller for controlling OFDM carrier spacing of the OFDM carriers modulated by the n-point FFT engine, wherein the controller maintains OFDM carrier spacing of the OFDM carriers modulated by the n-point FFT engine based on a carrier spacing criteria for the first bandwidth.

A remote service unit for a multipoint-to-point communication system utilizing a guard band within an OFDM waveform, the remote service unit comprising:

• a transceiver communicatively coupled with a host unit in a multipoint-to-point configuration, the transceiver configured to communicate with the host unit via an orthogonal frequency division multiplexing (OFDM) waveform;
• a multi-carrier modulator coupled to the transceiver and configured to modulate upstream information onto the orthogonal frequency division multiplexing waveform;
• wherein the multi-carrier modulator modulates upstream information onto a plurality of OFDM subcarriers of the OFDM waveform;
• and
• wherein a first OFDM subcarrier of the plurality of distinct OFDM subcarriers is spectrally separated in frequency from a second OFDM subcarrier of the plurality of distinct OFDM subcarriers by a guard band region within the OFDM waveform.

A remote service unit synchronized within a multipoint-to-point communication system, the remote service unit comprising:

• a transceiver communicatively coupled with a host unit in a multipoint-to-point configuration, the transceiver configured to communicate with the host unit via an orthogonal frequency division multiplexing (OFDM) waveform;
• a multi-carrier modulator coupled to the transceiver and configured to modulate upstream information onto the orthogonal frequency division multiplexing waveform;
• wherein the multi-carrier modulator modulates upstream information onto a plurality of distinct OFDM subcarriers of the OFDM waveform;
• wherein transmissions on the distinct OFDM subcarriers are synchronized to orthogonally overlap with distinct transmissions from at least one other remote service unit to form the OFDM waveform.

A method for quality based assessments of orthogonal channels for remote service units of an OFDM based multiple access system, the method comprising:

• monitoring a first subset of orthogonal carriers within an OFDM waveform associated with at least one communication channel, wherein the first subset of orthogonal carriers comprises less than all of the orthogonal carriers within the OFDM waveform;
• monitoring a second subset of orthogonal carriers within the OFDM waveform associated with at least one communication channel, wherein the second subset of orthogonal carriers comprises less than all of the orthogonal carriers within the OFDM waveform, wherein the second subset of orthogonal carriers includes different orthogonal carriers that the first subset of orthogonal carriers;
• determining a first quality measurement for the first subset of orthogonal carriers;
• determining a second quality measurement for the second subset of orthogonal earners;
• communicating a notification message regarding the quality measurements for the first subset of orthogonal carriers and the second subset of orthogonal carriers;
• and
• adjusting a frequency of upstream carriers of the OFDM waveform to maintain orthogonality within the OFDM waveform.