SPECTRUM SENSING FOR OFDM SIGNALS BY UTILIZING PILOT TONES

• US 20100202574A1
• Filed: 12/06/2007
• Published: 08/12/2010
• Est. Priority Date: 07/13/2007
• Status: Active Grant

• Current Assignee: InterDigital Madison Patent Holdings (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Chen, Hou-Shin, Gao, Wen
• Granted Patent: US 8,433,006 B2
• Time in Patent Office: Days
• US Class Current: 375/343
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

An apparatus comprises a downconverter for providing a signal that may be a received orthogonal frequency division multiplexed (OFDM) symbols from a selected channel, each OFDM symbol comprising N subcarriers at least some of which are pilot subcarriers; and a processor that (a) correlates the received OFDM symbols for providing at least one correlated value, (b) generates a metric value as a function of the at least one correlated value and (b) compares the metric value to a threshold value for detecting if an incumbent signal is present.

Claims

1. A method for use in a wireless endpoint, the method comprising:

selecting one of a number of channels;

downconverting a received signal on the selected channel for providing received orthogonal frequency division multiplexed (OFDM) symbols, each OFDM symbol comprising N subcarriers at least some of which are pilot subcarriers;

correlating the received OFDM symbols for providing at least one correlated value;

generating a metric value as a function of the at least one correlated value; and

comparing the metric value to a threshold value for detecting if an incumbent signal is present.

2. The method of claim 1, wherein the correlating step coherently combines the received OFDM symbols.

3. The method of claim 1, wherein the correlating step correlates two received OFDM symbols.

4. The method of claim 1, wherein the correlating step correlates two received OFDM symbols that have the same index difference.

5. The method of claim 1, wherein the metric value is represented by a parameter T, where

$T=\underset{d}{\max }$



Q d 

[ v ] 

.

6. The method of claim 1, wherein the metric value is represented by a parameter T, where

$T=\underset{d}{\max }$

∑

v 



Q d 

[ v ] 

α

v .

7. The method of claim 1, wherein the metric value is represented by a parameter T, where

$T=\underset{d}{\max }$



∑

v = 1 V - β



Q d 

[ v ] 

Q d 

[ v + β

] * α

v 

.

8. The method of claim 1, wherein the incumbent signal is a Digital Video Broadcasting (DVB) signal.

9. The method of claim 1, further comprising the step of:

marking an available channel list to indicate that the selected channel is available for use if no incumbent signal is present.

10. Apparatus comprising:

a downconverter for providing a signal that may be a received orthogonal frequency division multiplexed (OFDM) symbols from a selected channel, each OFDM symbol comprising N subcarriers at least some of which are pilot subcarriers; and

a processor that (a) correlates the received OFDM symbols for providing at least one correlated value, (b) generates a metric value as a function of the at least one correlated value and (b) compares the metric value to a threshold value for detecting if an incumbent signal is present.

11. The apparatus of claim 10, wherein the processor coherently combines the received OFDM symbols.

12. The apparatus of claim 10, wherein the processor correlates two received OFDM symbols.

13. The apparatus of claim 10, wherein the processor correlates two received OFDM symbols that have the same index difference.

14. The apparatus of claim 10, wherein the metric value is represented by a parameter T, where

$T=\underset{d}{\max }$



Q d 

[ v ] 

.

15. The apparatus of claim 10, wherein the metric value is represented by a parameter T, where

$T=\underset{d}{\max }$

∑

v 



Q d 

[ v ] 

α

v .

16. The apparatus of claim 10, wherein the metric value is represented by a parameter T, where

$T=\underset{d}{\max }$



∑

v = 1 V - β



Q d 

[ v ] 

Q d 

[ v + β

] * α

v 

.

17. The apparatus of claim 10, wherein the incumbent signal is a Digital Video Broadcasting (DVB) signal.

18. The apparatus of claim 10, further comprising:

a memory for storing an available channel list to indicate that the selected channel is available for use if no incumbent signal is present.