Digital pre-distortion for orthogonal frequency division multiplexing (OFDM) signals

1. 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.

2. The method of claim 1 , further comprising generating a limiting indicator when the portion of the OFDM symbol exceeds the amplitude limiting threshold.

3. 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.

4. The method of claim 1 , wherein combining the OFDM symbol further comprises:

delaying the OFDM symbol by a period of time equal to a processing time required to generate the pre-distortion noise.

5. 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.

6. The system of claim 5 , wherein:

the peak detector generates a limiting indicator when the portion of the OFDM symbol exceeds the amplitude limiting threshold.

7. 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.

8. The system of claim 5 , further comprising:

a delay module that delays the OFDM symbol by a period of time equal to a processing time required to generate the pre-distortion noise.