Phase noise canceling OFDM receiver

• US 20070086533A1
• Filed: 10/14/2005
• Published: 04/19/2007
• Est. Priority Date: 10/14/2005
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Lindh, Lars
• Granted Patent: US 7,733,993 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 2027/0032 at baseband and passband
• CPC Class Codes: H04L 2027/0055 single phase
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2679 Decision-aided

Abstract

A receiver includes, in series, at least one receive antenna, a buffer, and arithmetic logic block, a symbol detector, and a phase noise estimator. A further feedback loop couples an output of the phase noise estimator to an input of the arithmetic logic block for providing an estimate of phase noise. The buffer is for storing the received signal. The arithmetic logic block, such as a multiplier, is for removing the estimate of phase noise, received via the feedback loop, from the buffered signal. The symbol detector is for estimating a symbol from the output of the arithmetic logic block. The phase noise estimator estimates phase noise from two inputs received from the symbol detector: the estimated symbol and the remainder signal. Preferably, the phase noise estimator performs an IFFT on these two inputs and Kalman filters the result. Iteratively estimating the phase noise improves precision substantially.

Claims

1. A method for processing a received signal comprising:

receiving a signal over a plurality of orthogonal subcarriers and storing the signal in a buffer;

estimating a symbol from the buffered signal

determining decision noise from the buffered signal and the estimated symbol;

estimating phase noise from the decision noise and the estimated symbol; and

canceling the estimated phase noise from the buffered signal and estimating a phase noise corrected estimated symbol therefrom.

2. The method of claim 1, further comprising:

determining a next iterative decision noise from the buffered signal and the phase noise corrected estimated symbol;

estimating a next iterative phase noise from the next iterative decision noise and the phase noise corrected estimated symbol;

accumulating all estimated phase noise for the buffered signal;

and wherein canceling the estimated phase noise comprises canceling the accumulated estimated phase noise from the buffered signal and estimating an iteratively phase noise corrected estimated symbol therefrom.

3. The method of claim 2 further comprising repeating the determining and estimating elements of claim 2 for at least one additional iteration.

4. The method of claim 1, further comprising:

storing the phase noise corrected estimated symbol;

determining a next iterative decision noise from the received signal and the phase noise corrected estimated symbol;

estimating a next iterative phase noise from the next iterative decision noise and the phase noise corrected estimated symbol;

canceling the next iterative phase noise from a phase of the phase noise corrected estimated symbol to yield an iteratively phase noise corrected estimated symbol.

5. The method of claim 1, wherein the estimated phase noise comprises computing an inverse Fourier transform on the decision noise and on the estimated symbol.

6. The method of claim 5, wherein estimating the phase noise further comprises Kalman filtering a difference between the inverse Fourier transforms of the decision noise and the estimated symbol.

7. A receiver comprising:

means for receiving a signal over a plurality of orthogonal subcarriers;

a buffer having an input coupled to an output of the at least one antenna for storing the received signal;

an arithmetic logic block having an input coupled to an output of the buffer for canceling an estimate of phase noise from the buffered signal;

a symbol detector having an input coupled to an output of the arithmetic logic block for estimating a symbol from the output of the arithmetic logic block;

a phase noise estimator having a first input for receiving the estimated symbol from the symbol detector and a second input for receiving a remainder signal from the symbol detector;

a feedback loop coupling an output of the phase noise estimator to an input of the arithmetic logic block for providing the estimate of phase noise.

8. The receiver of claim 7, wherein the feedback loop comprises in series an adder and a phase noise accumulator.

9. The receiver of claim 7 further comprising a second feedback loop coupling an output of the arithmetic logic block with an input of the buffer for replacing the signal stored in the buffer with a signal modified by the arithmetic logic block.

10. The receiver of claim 7, wherein the phase noise estimator operates to compute an inverse Fourier transform on the estimated symbol and the remainder signal.

11. The receiver of claim 10, wherein the phase noise estimator further comprises at least one Kalman filter for filtering the results of the inverse Fourier transforms to yield the estimate of phase noise.

12. The receiver of claim 7 wherein the means for receiving comprises at least one receive antenna.

13. The receiver of claim 12 disposed within a mobile station.

14. An apparatus comprising:

means for estimating a symbol from a buffered received signal;

means for iteratively estimating phase noise from the estimated symbol and a remainder signal; and

means for canceling the iteratively estimated phase noise from the buffered received signal.

15. The apparatus of claim 14, wherein:

the means for estimating a symbol comprises a symbol estimator;

the means for iteratively estimating phase noise comprises a phase noise estimator and a feedback loop coupling an output of the phase noise estimator to an input of the symbol estimator, said phase noise estimator comprising circuitry for executing an inverse Fourier transform on the estimated phase noise and the remainder signal; and

the means for canceling the iteratively estimated phase noise comprises a multiplier having an input coupled to the feedback loop and an output coupled to the symbol estimator.

16. A program of machine-readable instructions, tangibly embodied on an information bearing medium and executable by a digital data processor, to perform actions directed toward processing a received signal, the actions comprising:

estimating a symbol from a buffered received signal;

determining decision noise from the received signal and the estimated symbol;

estimating phase noise from the decision noise and the estimated symbol; and

canceling the estimated phase noise from the buffered signal, and estimating a phase noise corrected estimated symbol therefrom.

17. The program of claim 16, wherein the actions further comprise:

determining a next iterative decision noise from the buffered received signal and the phase noise corrected estimated symbol;

estimating a next iterative phase noise from the next iterative decision noise and the phase noise corrected estimated symbol;

accumulating all estimated phase noise for the buffered signal;

and wherein canceling the estimated phase noise comprises canceling the accumulated estimated phase noise from the buffered signal and estimating an iteratively phase noise corrected estimated symbol therefrom.

18. The program of claim 17, wherein the actions further comprise repeating the determining and estimating elements of claim 17 for at least one additional iteration.

19. The program of claim 16, wherein the actions further comprise:

storing the phase noise corrected estimated symbol;

determining a next iterative decision noise from the received signal and the phase noise corrected estimated symbol;

estimating a next iterative phase noise from the next iterative decision noise and the phase noise corrected estimated symbol; and

canceling the next iterative phase noise from a phase of the phase noise corrected estimated symbol to yield an iteratively phase noise corrected estimated symbol.

20. The program of claim 16, wherein estimating phase noise comprises computing an inverse Fourier transform on the decision noise and on the estimated symbol.

21. The program of claim 20, wherein estimating the phase noise further comprises Kalman filtering a difference between the inverse Fourier transforms of the decision noise and the estimated symbol.

22. The program of claim 16, wherein the actions further comprise correcting a frequency offset of the received signal with the estimated phase noise.

23. A program of machine-readable instructions, tangibly embodied on an information bearing medium and executable by a digital data processor, to perform actions directed toward processing a received signal, the actions comprising:

estimating a symbol from a signal received over a plurality of orthogonal frequency division multiplexed subcarriers;

iteratively estimating phase noise from the estimated symbol and a remainder signal by an inverse Fourier transform;

canceling the iteratively estimated phase noise from the signal.

24. A receiver comprising:

a symbol detector, for estimating from a received signal, an estimated frequency domain symbol and a frequency domain decision noise;

means for converting the estimated frequency domain symbol and the frequency domain decision noise to the time domain;

a Kalman filter for estimating phase noise from the time domain converted estimated symbol and decision noise; and

a recursive feedback loop for canceling from the received signal an accumulation of phase noise estimates from the Kalman filter.

25. The receiver of claim 24, wherein the means for converting comprises a processor that executes an inverse fast Fourier transform.

26. A method of processing a received signal comprising:

estimating from a received signal a frequency domain symbol and a frequency domain decision noise;

converting the estimated frequency domain symbol and the frequency domain decision noise to the time domain;

filtering the time domain converted estimated symbol and decision noise to achieve a phase noise estimate;

iteratively estimating, converting, and filtering as recited above to achieve at least one iterative estimate of phase noise; and

canceling from the received signal the phase noise estimate and the at least one iterative estimate of phase noise.