Digital pre-distortion for orthogonal frequency division multiplexing (OFDM) signals
AssigneeMotorola Mobility LLC
InventorXiaoyong Yu
Life of this patent
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Abstract
A method (300) and a system (100) for processing an orthogonal frequency division multiplexing (OFDM) signal. At least one portion of an OFDM symbol (125) that exceeds an amplitude limiting threshold can be identified. The identified portion of the OFDM symbol (125) can be filtered to generate a pre-distortion noise (145). The OFDM symbol (125) and the pre-distortion noise (145) can be combined to generate a pre-distorted OFDM symbol (165).
Claims8
A method of processing an orthogonal frequency division multiplexing (OFDM) signal comprising:
- identifying at least one portion of an OFDM symbol that exceeds an amplitude limiting threshold;
- filtering the identified portion of the OFDM symbol to generate a pre-distortion noise, wherein filtering comprises filtering the identified portion of the OFDM symbol with a filter whose frequency response correlates to one or more of:
- a modulation index of at least one modulated subcarrier on which the OFDM symbol is received, and
- an inverse of a square root of a bit load index of at least one modulated subcarrier from which the OFDM symbol is generated;
- combining the OFDM symbol and the pre-distortion noise to generate a pre-distorted OFDM symbol;
- and
- outputting the pre-distorted OFDM symbol.
A method of processing an orthogonal frequency division multiplexing (OFDM) signal comprising:
- identifying at least a first portion and a second portion of an OFDM symbol that exceed an amplitude limiting threshold;
- filtering the identified portions of the OFDM symbol to generate a pre-distortion noise, wherein generation of the predistortion noise comprises solving a plurality of linear equations to generate a plurality of limiting noise variables, wherein a number of the linear equations solved corresponds to a number of portions of the OFDM symbol that are identified;
- combining the OFDM symbol and the pre-distortion noise to generate a pre-distorted OFDM symbol;
- outputting the pre-distorted OFDM symbol.
An OFDM signal processing system, comprising:
- a peak detector that identifies a portion of an OFDM symbol that exceeds an amplitude limiting threshold;
- a pre-distortion noise generator that filters the identified portion of the OFDM symbol and generates a pre-distortion noise, wherein filtering comprises filtering the identified portion of the OFDM symbol with a filter whose frequency response correlates to one or more of:
- a modulation index of at least one modulated subcarrier on which the OFDM symbol is received, and
- an inverse of a square root of a bit load index of at least one modulated subcarrier from which the OFDM symbol is generated;
- and
- an adder that combines the OFDM symbol and the pre-distortion noise to generate a pre-distorted OFDM symbol.
An OFDM signal processing system, comprising:
- a peak detector that identifies at least a first portion and a second portion of the an OFDM symbol that exceed an amplitude limiting threshold;
- a pre-distortion noise generator that filters the identified portions of the OFDM symbol and generates a pre-distortion noise, wherein the pre-distortion noise generator solves a plurality of linear equations to generate a plurality of limiting noise variables and a number of the linear equations solved corresponds to a number of portions of the OFDM symbol that are identified;
- and
- an adder that combines the OFDM symbol and the pre-distortion noise to generate a pre-distorted OFDM symbol.
Dependencies are inferred from the claim text.