Abstract: A transmitter may comprise a symbol mapper circuit and operate in at least two modes. In a first mode, the number of symbols output by the mapper circuit per orthogonal frequency division multiplexing (OFDM) symbol transmitted by said transmitter may be greater than the number of data-carrying subcarriers used to transmit the OFDM symbol. In a second mode, the number of symbols output by said mapper circuit per orthogonal frequency division multiplexing (OFDM) symbol transmitted by said transmitter is less than or equal to the number of data-carrying subcarriers used to transmit said OFDM symbol. The symbols output by the symbol mapper circuit may be N-QAM symbols. While the circuitry operates in the first mode, the symbols output by the mapper may be converted to physical subcarrier values via filtering and decimation prior to being input to an IFFT circuit.

Abstract: A receiver may be operable to receive an inter-symbol correlated (ISC) signal, and generate a plurality of soft decisions as to information carried in the ISC signal. The soft decisions may be generated using a reduced-state sequence estimation (RSSE) process. The RSSE process may be such that the number of symbol survivors retained after each iteration of the RSSE process is less than the maximum likelihood state space. The plurality of soft decisions may comprise a plurality of log likelihood ratios (LLRs). Each of the plurality of LLRs may correspond to a respective one of a plurality of subwords of a forward error correction (FEC) codeword.

Abstract: An electronic receiver comprises a nonlinear distortion modeling circuit and a nonlinear distortion compensation circuit. The nonlinear distortion modeling circuit is operable to determine a plurality of sets of nonlinear distortion model parameter values, where each of the sets of nonlinear distortion model parameter values representing nonlinear distortion experienced by signals received by the electronic receiver from a respective one a plurality of communication partners. The nonlinear distortion compensation circuit is operable to use the sets of nonlinear distortion model parameter values for processing of signals from the plurality of communication partners. Each of the sets of nonlinear distortion model parameter values may comprises a plurality of values corresponding to a plurality of signal powers. The sets of nonlinear distortion model parameters may be stored in a lookup table indexed by a signal strength parameter.

Abstract: An OFDM receiver comprises a (FEC) decoder and a nonlinearity compensation circuit. The nonlinearity compensation circuit is operable to generate estimates of constellation points transmitted on each of a plurality of subcarriers of a received signal based on soft decisions from the FEC decoder and based on a model of nonlinear distortion introduced by a transmitter from which the received signal was received. The generation of the estimates may be based on a measure of distance between a function of the received signal and a synthesized version of the received signal. The generation of the estimates may comprise iterative processing of symbols of the received signal, and the iterative processing may comprise a plurality of outer iterations and a plurality of inner iterations.

Abstract: A single-carrier receiver comprises a (FEC) decoder and a nonlinearity compensation circuit. The nonlinearity compensation circuit is operable to generate estimates of constellation points transmitted on a received signal based on soft decisions from the FEC decoder and based on a model of nonlinear distortion introduced by a transmitter from which the received signal was received. The generation of the estimates may be based on a measure of distance between a function of the received signal and a synthesized version of the received signal. The generation of the estimates may comprise iterative processing of symbols of the received signal, and the iterative processing may comprise a plurality of outer iterations and a plurality of inner iterations.

Abstract: An orthogonal frequency division multiple Access (OFDMA) receiver may comprise a forward error correction (FEC) decoder and nonlinearity compensation circuitry. The OFDMA receiver may be configured to receive a signal that is a result of multiple concurrent, partially synchronized transmissions from multiple transmitters using different subsets of subcarriers. The nonlinearity compensation circuit may be operable to generate estimates of constellation points transmitted on each of a plurality of the subcarriers of the received signal. The generation of the estimates may be based on soft decisions from the FEC decoder, and models of nonlinear distortion introduced by the multiple transmitters.

Abstract: A modulator and demodulator pair may switch configurations without introducing errors as a result of the switch. Different configurations may, for example, correspond to different symbol rates and/or different amounts of controlled inter-symbol interference (ISI) introduced to the transmitted signal. For example, a first configuration may use be a near-zero ISI configuration (e.g., using Nyquist signaling) and a second configuration may introduce a significant (e.g., amount that would result in errors above a desired threshold if demodulation relied on symbol-by-symbol slicing) but controlled amount of ISI (e.g., using partial response or faster-than-Nyquist-rate signaling). Switching between modulator/demodulator configurations may be needed to maintain a stable link in the case of dynamic channels. At any given time, a modulator and demodulator pair may, for example, switch to a configuration that provides maximal throughput for the current channel conditions.

Abstract: A transmitter may comprise a symbol mapping circuit that is configurable to operate in at least two configurations, wherein a first of the configurations of the symbol mapping circuit uses a first symbol constellation and a second of the configurations of the symbol mapping circuit uses a second symbol constellation. The transmitter may also comprise a pulse shaping circuit that is configurable to operate in at least two configurations, wherein a first of the configurations of the pulse shaping circuit uses a first set of filter taps and a second of the configurations of the pulse shaping circuit uses a second set of filter taps. The first set of filter taps may correspond to a root raised cosine (RRC) filter and the second set of filter taps corresponds to a partial response filter.

Abstract: An electronic receiver may comprise nonlinear distortion modeling circuitry, interference estimation circuitry, and sequence estimation circuitry. The receiver may receive an orthogonal frequency division multiplexing (OFDM) symbol in the form of an electromagnetic signal. The nonlinear distortion modeling circuitry may generate a nonlinear distortion model that models nonlinear distortion introduced to the received electromagnetic signal en route to the sequence estimation circuitry. The interference estimation circuitry may estimate inter-subcarrier interference present in the received OFDM symbol based on the generated nonlinear distortion model. The estimating of the inter-subcarrier interference may comprise applying the nonlinear distortion model to one or more candidate vectors generated by the sequence estimation circuitry. The sequence estimation circuitry may sequentially process a plurality of received virtual subcarrier values of the OFDM symbol using the estimated inter-subcarrier interference.

Abstract: A receiver comprises a sequence estimation circuit and a soft-input-soft-output (SISO) decoder. The sequence estimation circuit comprises circuitry operable to generate first soft bit decisions for symbols of a received inter-symbol-correlated signal. The SISO decoder comprises circuitry operable to decode the first soft bit decisions to generate corrected soft bit decisions. The circuitry of the sequence estimation circuit is operable to generate, based on the corrected soft bit decisions, second soft bit decisions for the symbols of the received inter-symbol-correlated signal, which are improved/refined relative to the first soft bit decisions.

Abstract: One or more embodiments describe a decision feedback equalizer for highly spectrally efficient communications. A method may be performed in a decision feedback equalizer (DFE). The method may include initializing values of tap coefficients of the DFE based on values of tap coefficients of a partial response filter through which said transmitted symbols passed en route to said sequence estimation circuit. The method may include receiving estimates of transmitted symbols from a sequence estimation circuit, and receiving an error signal that is generated based on an estimated partial response signal output by the sequence estimation circuit. The method may include updating values of tap coefficients of the DFE based on the error signal and the estimates of transmitted symbols. The method may include generating one or more constraints that restrict the impact of the error signal on the updating of the values of the tap coefficients of the DFE.

Abstract: An OFDM receiver comprises a (FEC) decoder and a nonlinearity compensation circuit. The nonlinearity compensation circuit is operable to generate estimates of constellation points transmitted on each of a plurality of subcarriers of a received signal based on soft decisions from the FEC decoder and based on a model of nonlinear distortion introduced by a transmitter from which the received signal was received. The generation of the estimates may be based on a measure of distance between a function of the received signal and a synthesized version of the received signal. The generation of the estimates may comprise iterative processing of symbols of the received signal, and the iterative processing may comprise a plurality of outer iterations and a plurality of inner iterations.

Abstract: A receiver may be operable to generate estimates of transmitted symbols using a sequence estimation process that may incorporate a non-linear model. The non-linear model may be adapted by the receiver based on particular communication information that may be indicative of non-linearity experienced by the transmitted symbols. The receiver may generate a reconstructed signal from the estimates of the transmitted symbols. The receiver may adapt the non-linear model based on values of an error signal generated from the reconstructed signal, and the values of the error signal may be generated from a portion of the generated estimates that may correspond to known symbols and/or information symbols. The values of the error signal corresponding to the known symbols may be given more weight in an adaptation algorithm, and the values of the error signal corresponding to the information symbols may be given less weight in the adaptation algorithm.

Abstract: A transmitter comprises at least one nonlinear circuit, and a power spectral density (PSD) shaping circuit. The PSD shaping circuit is operable to receive a symbol of a modulated signal, wherein the symbol corresponds to a first one or more frequency bins. The PSD shaping circuit is operable to perform iterative processing of the symbol, wherein each iteration of the processing comprises: generation of a pre-distortion signal based on a model of the at least one nonlinear circuit, wherein the nonlinearly distorted signal corresponds to a second one or more frequency bins; and combination of the symbol, or a pre-distorted version of the symbol, with the nonlinearly-distorted signal. The generation of the pre-distorted signal may comprise generation of a nonlinearly-distorted signal, and adjustment of one or more components of the nonlinearly-distorted signal.

Abstract: A system may comprise circuitry that includes a sequence estimation circuit and a non-linearity modeling circuit. The circuitry may be operable to receive a single-carrier signal that was generated by passage of symbols through a partial response filter and through a non-linear circuit. The circuitry may be operable to generate estimated values of the symbols using the sequence estimation circuit and using the non-linearity modeling circuit. An output of the non-linearity modeling circuit may be equal to a corresponding input of the non-linearity modeling circuit modified according to a non-linear model that approximates the non-linearity of the non-linear circuit through which the received signal passed.

Abstract: A system may comprise a symbol mapper circuit that outputs C? quadrature amplitude modulation (QAM) symbols per orthogonal frequency division multiplexing (OFDM) symbol. The system may also comprise circuitry operable to process said C? QAM symbols using a circulant matrix to generate a particular OFDM symbol consisting of C+? subcarriers, where C? is a first integer, C is a second integer less than C?, and ? is an integer equal to the number of non-data-carrying subcarriers in the particular OFDM symbol. The circulant matrix may be a P×P matrix, where P is an integer less than C?. The system may comprise a nonlinear circuit that introduces nonlinear distortion to said particular OFDM symbol.

Abstract: A receiver is configured to receive a sample of an inter-symbol correlated (ISC) signal, the sample corresponding to a time instant when phase and/or amplitude of the ISC signal is a result of correlation among a plurality of symbols of a transmitted symbol sequence. The receiver may linearize the sample of the ISC signal. The receiver may calculate a residual signal value based on the linearized sample of the ISC signal. The receiver may generate an estimate of one or more of said plurality of symbols based on a slicing of the residual signal value. The linearization may comprise applying an estimate of an inverse of a non-linear model. The non-linear model may be a model of nonlinearity experienced by the ISC signal in a transmitter from which the ISC signal originated, in a channel through which the ISC signal passed en route to the receiver, and/or in a front-end of the receiver.

Abstract: An electronic receiver may comprise nonlinear distortion modeling circuitry, interference estimation circuitry, and sequence estimation circuitry. The receiver may receive an orthogonal frequency division multiplexing (OFDM) symbol in the form of an electromagnetic signal. The nonlinear distortion modeling circuitry may generate a nonlinear distortion model that models nonlinear distortion introduced to the received electromagnetic signal en route to the sequence estimation circuitry. The interference estimation circuitry may estimate inter-subcarrier interference present in the received OFDM symbol based on the generated nonlinear distortion model. The estimating of the inter-subcarrier interference may comprise applying the nonlinear distortion model to one or more candidate vectors generated by the sequence estimation circuitry. The sequence estimation circuitry may sequentially process a plurality of received virtual subcarrier values of the OFDM symbol using the estimated inter-subcarrier interference.

Abstract: A receiver may process a received signal to generate a processed received signal. The receiver may generate, during a sequence estimation process, an estimate of a phase error of the processed received signal. The receiver may generate an estimate of a value of a transmitted symbol corresponding to the received signal based on the estimated phase error. The generation of the estimate of the phase error may comprise generation of one or more phase candidate vectors. The generation of the estimate may comprise calculation of a metric based on the one or more phase candidate vectors. The calculation of the metric may comprise phase shifting the processed received signal based on the estimated phase error resulting in a phase-corrected received signal. The calculation of the metric may comprise calculating a Euclidean distance based on the phase-corrected received signal and one or more symbol candidate vectors.

Abstract: An electronic receiver comprises sequence estimation circuitry operable to implement a sequence estimation algorithm. In the sequence estimation algorithm, each of a plurality of possible current states of the signal may have associated with it a respective Nc possible prior states and a respective M state extensions, where Nc and M are integers greater than 1. Each iteration of the sequence estimation algorithm may comprise extending each of the plurality of possible current states of the signal by its respective Nc possible prior states and its respective M state extensions to generate a respective Nc×M extended states for each of the plurality of possible current states. Each iteration of the sequence estimation algorithm may comprise, for each of the plurality of possible current states of the signal, selecting M of the respective Nc×M extended states to be state extensions for a next iteration of the sequence estimation algorithm.