Guard section length detection method and system

• US 20080074991A1
• Filed: 08/17/2007
• Published: 03/27/2008
• Est. Priority Date: 09/21/2006
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Ting, Pang-Ah, Chen, Chin-Hung, Kuo, Chun-Chun, Wen, Chao-Kai
• Granted Patent: US 7,860,178 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2666 Acquisition of further OFDM parameters, e.g. bandwidth, subcarrier spacing, or guard interval length
• CPC Class Codes: H04L 27/2676 Blind, i.e. without using known symbols

Abstract

A guard section length detection method is disclosed. In the method, a guard section length detection method is used in an OFDM system. The OFDM symbol includes a data interval having a first length, and a guard section having a guard section length. The method detects a first symbol boundary and a second symbol boundary, and determines the guard section length based on a length between the first symbol boundary and the second symbol boundary.

Claims

1. A guard section length detection method used in an OFDM system, wherein an OFDM symbol comprises a data interval having a first length, and a guard section having a plurality kinds of guard section lengths, comprising:

detecting a first symbol boundary;

detecting a second symbol boundary; and

determining the guard section length based on a length between the first symbol boundary and the second symbol boundary.

2. The method as claimed in claim 1, wherein the first symbol boundary is determined by a local maximum signal correlation value.

3. The method as claimed in claim 1, wherein the position of the second symbol boundary is determined by two maximum signal correlation values.

4. The method as claimed in claim 1, wherein the position of the second symbol boundary is determined by at most five maximum signal correlation values.

5. The method as claimed in claim 1, wherein the guard section length is ¼

, ⅛

, 1/16 or 1/32 of the first length.

6. A guard section length detection system used in an OFDM system, wherein an OFDM symbol comprises a data interval having a first length, and a guard section having a plurality kinds of guard section lengths, comprising:

a first boundary detection unit receiving an OFDM signal for detecting a first symbol boundary;

a second boundary detection unit receiving the input OFDM signal from the first boundary detection unit to detect a second symbol boundary; and

a guard section length detection unit for determining the guard section length based on the length between the first symbol boundary and the second symbol boundary.

7. The system as claimed in claim 6, the second boundary detection unit thereof comprising:

a delay unit receiving and delaying the OFDM signal by a predetermined length; and

a signal correlation unit calculating a signal correlation value based on the OFDM signal and the delayed OFDM signal.

8. The system as claimed in claim 7, further comprising a conjugate complex number generating unit receiving the delayed OFDM signal and generating a corresponding conjugate complex number.

9. The system as claimed in claim 7, further comprising a position detection unit receiving the signal correlation value and outputting a position data in response to the received signal correlation value being a local maximum value or a maximum value.

10. The system as claimed in claim 6, further comprising a signal correlation unit calculating a plurality of signal correlation values based on the guard section lengths.

11. The system as claimed in claim 10, further comprising a position detection unit receiving the signal correlation value and outputting the second symbol boundary in response to the received signal correlation value being a local maximum value or a maximum value.

12. A guard section length detection method for an OFDM system wherein an OFDM symbol comprises a data interval having a first length, and four kinds of guard sections respectively called ¼

mode, ⅛

mode, 1/16 mode and 1/32 mode guard sections, comprising;

detecting a first symbol boundary;

determining the four OFDM symbol lengths of the four guard sections;

calculating signal correlation values at the positions having a distance of at least two OFDM symbol lengths from the first symbol boundary; and

determining an actual guard length in response to the signal correlation value being a local maximum value or a maximum value.

13. The method as claimed in claim 12, wherein a sliding window is used to calculate signal correlation values.

14. The method as claimed in claim 13, wherein a length of the sliding window is set to a 1/32 mode guard section.

15. The method as claimed in claim 12, wherein the first symbol boundary is determined by a local maximum signal correlation value.

16. A guard section length detection method for an OFDM system, comprising:

detecting a first guard section in a first packet;

detecting a second guard section in a second packet;

if the first guard section length and the second guard section length are the same, the guard section length for the OFDM system is the first guard section; and

if the first guard section length and the second guard section length are not the same, detecting a third guard section in a third packet. If the third guard section length is the same as either the first or the second guard section length, the guard section length for the OFDM system is the third guard section.

17. The method as claimed in claim 16, wherein if the OFDM system defines N guard section lengths, the maximum number of guard section length detections is (N+1).