OFDM speed estimation

• US 9,100,278 B2
• Filed: 03/01/2013
• Issued: 08/04/2015
• Est. Priority Date: 08/17/2012
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Beauregard, Stephen J.
• Primary Examiner(s): Vlahos, Sophia
• Application Number:
  US13/782,888
• Publication Number:
  US 20140050257A1
• Time in Patent Office: 886 Days
• Field of Search: 342/104, 342/111, 342/112, 342/116, 342/461
• US Class Current: 1/1
• CPC Class Codes: G01S 11/10 using Doppler effect
• CPC Class Codes: G01S 5/02585 at least one of the measurements being a non-radio measurement
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 43/00 Arrangements for monitoring or testing data switching networks
• CPC Class Codes: H04W 64/006 with additional information processing, e.g. for direction or speed determination

Abstract

Techniques are provided for deriving speed estimates by performing a convolution of the output of the Fast Fourier Transform (FFT) stage from different time windows in an orthogonal frequency-division multiplexing (OFDM) modulation scheme. Such techniques enable speed estimation to be performed in the frequency domain, requiring little or no modification to existing OFDM systems.

Claims

1. A method for estimating speed using an orthogonal frequency division multiplexing (OFDM) receiver, the method comprising:

receiving a radio frequency (RF) signal at the OFDM receiver, the OFDM receiver having a fast Fourier transform (FFT) stage;

storing a first output of the FFT stage in a memory, the first output corresponding to the RF signal at a first time;

convolving the first output with a second output of the FFT stage, the second output corresponding to the RF signal at a second time;

determining one or more observables of the convolution; and

estimating a speed based on the one or more observables.

2. The method of claim 1, wherein the memory comprises a First In, First Out (FIFO) buffer.

3. The method of claim 1, wherein one or more observables includes at least one of:

a width,

a Doppler shift, or

an amplitude.

4. The method of claim 1, wherein estimating the speed includes using heuristics.

5. The method of claim 1, wherein estimating the speed includes performing a mathematical analysis of the one or more observables.

6. The method of claim 1, wherein the RF signal is received from at least one of:

a cellular network,

a broadcast OFDM network, or

a Local Area Network (LAN).

7. An orthogonal frequency division multiplexing (OFDM) receiver comprising:

an antenna configured to receive a radio frequency (RF) signal;

a fast Fourier transform (FFT) module configured to provide;

a first output corresponding to the RF signal at a first time; and

a second output corresponding to the RF signal at a second time;

a memory, coupled with the FFT module, configured to store the first output; and

a convolution module, coupled with the FFT module and the memory, configured to convolve the first output and the second output; and

a speed estimation module configured to;

determine one or more observables of the convolution of the first output and the second output; and

estimate a speed based on one or more observables.

8. The OFDM receiver of claim 7, wherein the memory comprises a First In, First Out (FIFO) buffer.

9. The OFDM receiver of claim 7, wherein functionality of at least one of the FFT module, the convolution module, or the speed estimation module is provided with a digital signal processor.

10. The OFDM receiver of claim 7, wherein the antenna is configured to receive the RF signal from at least one of:

a cellular network,

a broadcast OFDM network, or

a Local Area Network (LAN).

11. The OFDM receiver of claim 7, wherein the speed estimation module is configured to estimate the speed using heuristics.

12. The OFDM receiver of claim 7, wherein the speed estimation module is configured to estimate the speed with a mathematical analysis of the one or more observables.

13. A device comprising:

means for receiving a radio frequency (RF) signal at an OFDM receiver, the OFDM receiver having a fast Fourier transform (FFT) stage;

means for storing a first output of the FFT stage, the first output corresponding to the RF signal at a first time;

means for convolving the first output with a second output of the FFT stage, the second output corresponding to the RF signal at a second time;

means for determining one or more observables of the convolution; and

means for estimating a speed based on the one or more observables.

14. The device of claim 13, wherein the means for storing the first output of the FFT stage comprise a First In, First Out (FIFO) buffer.

15. The device of claim 13, wherein the means for determining the one or more observables include means for determining at least one of:

a width,

a Doppler shift, or

an amplitude.

16. The device of claim 13, wherein the means for estimating the speed include means for estimating the speed using heuristics.

17. The device of claim 13, wherein the means for estimating the speed include means for performing a mathematical analysis of the one or more observables.

18. The device of claim 13, wherein the means for receiving the RF signal include means for receiving the RF signal from at least one of:

a cellular network,

a broadcast OFDM network, or

a Local Area Network (LAN).

19. A non-transitory machine-readable storage medium comprising instructions that, when executed by a processor, perform functions including:

receiving a radio frequency (RF) signal at an OFDM receiver, the OFDM receiver having a fast Fourier transform (FFT) stage;

storing a first output of the FFT stage, the first output corresponding to the RF signal at a first time;

convolving the first output with a second output of the FFT stage, the second output corresponding to the RF signal at a second time;

determining one or more observables of the convolution; and

estimating a speed based on the one or more observables.

20. The non-transitory machine-readable storage medium of claim 19, wherein the instructions for storing the first output of the FFT stage comprise instructions for utilizing a First In, First Out (FIFO) buffer.

21. The non-transitory machine-readable storage medium of claim 19, wherein the instructions for determining the one or more observables include instructions for determining at least one of:

a width,

a Doppler shift, or

an amplitude.

22. The non-transitory machine-readable storage medium of claim 19, wherein the instructions for estimating the speed include instructions for estimating the speed using heuristics.

23. The non-transitory machine-readable storage medium of claim 19, wherein the instructions for estimating the speed include instructions for performing a mathematical analysis of the one or more observables.

24. The non-transitory machine-readable storage medium of claim 19, wherein the instructions for receiving the RF signal include instructions for receiving the RF signal from at least one of:

a cellular network,

a broadcast OFDM network, or

a Local Area Network (LAN).