The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 29, 2007
Filed:
May. 13, 2002
Srikanth Gummadi, Santa Rosa, CA (US);
Peter A. Murphy, Santa Rosa, CA (US);
Richard G. C. Williams, San Diego, CA (US);
Srikanth Gummadi, Santa Rosa, CA (US);
Peter A. Murphy, Santa Rosa, CA (US);
Richard G. C. Williams, San Diego, CA (US);
Texas Instruments Incorporated, Dallas, TX (US);
Abstract
A method for estimating carrier frequency offset (CFO) and sampling frequency offset (SFO) in an Orthogonal Frequency Division Multiplexing (OFDM) system having a plurality of pilot tones. The absolute phase angle for each pilot tone is measured, and estimates of the CFO and the SFO are derived using a weighted least-squares methodology. More particularly, the phase of each pilot tone is measured for a number (n) of symbol times; for each of the pilot tones, the slope of a phase angle change from symbol time to symbol time is estimated using a best least-squares fit of the measured phases to a straight line; and a weighted least-squares best-fit straight line is determined to find an estimated phase angle differential value (α(i)) for each pilot tone; wherein a slope of the best-fit straight line yields an estimate of the SFO, and an intercept with the best-fit straight line yields an estimate of the CFO. The plurality of pilot tones may have frequencies which are symmetrically disposed about a reference frequency, and there may be four pilot tones. The OFDM communications system is suitably a wireless LAN (WLAN) implementing a standard such as IEEE 802.11a or HiperLAN/2. Corresponding apparatus is also described.