Patent ID: 9178740
Filing Date: 2015-11-03
Classification: H04L

Abstract:
1. A method comprising: (a) using a modulator to quadrature amplitude modulate a signal including a set of subcarriers with a set of data to produce an Orthogonal Frequency Division Multiplexing (OFDM) modulated symbol vector; and using processing circuitry to (b) limit the magnitude of the modulated symbol vector to produce a first limited OFDM modulated symbol; (c) demodulate the first limited OFDM modulated symbol to recover distorted Quadrature Amplitude Modulation (QAM) constellations; (d) constrain points in the distorted QAM constellations recovered from the first limited OFDM modulated symbol to produce constrained QAM constellations wherein: points at corners of the distorted QAM constellations are constrained both in-phase and in-quadrature to values greater than or equal to a first minimum threshold; points along edges, said points along edges not including any points at corners of the distorted QAM constellations are constrained to either in-phase values greater than or equal to a second minimum threshold value and in quadrature to a first predetermine range of values on either side of the undistorted constellation point, or in-quadrature to values greater than or equal to a third minimum threshold value and in phase to a second predetermine range of values on either side of the undistorted constellation point; and internal points of the distorted QAM constellations are constrained to both in-phase or in-quadrature values less than or equal to a third predetermined range of values on either side of the undistorted constellation point; (e) modulate an OFDM symbol vector with the constrained QAM constellations to produce a modified modulated OFDM symbol; and (f) output the modified modulated OFDM symbol.