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(12) United States Patent ao) Patent No.: us 6,549,561 B2
Crawford (45) Date of Patent: *Apr. 15,2003
(54) OFDM PILOT TONE TRACKING FOR WIRELESS LAN
(75) Inventor: James A. Crawford, San Diego, CA (US)
(73) Assignee: Magis Networks, Inc., San Diego, CA (US)
( * ) Notice: Subject to any disclaimer, the term ol this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
This patent is subject to a terminal disclaimer.
(21) Appl. No.: 09/935,243
(22) Filed: Aug. 21, 2001
(65) Prior Publication Data
US 2002/0176483 Al Nov. 28, 2002
Related U.S. Application Data
(63) Continuation-in-part of application No. 09/790,429, filed on Feb. 21, 2001.
(51) Int. CI.7 H04J 11/00; H04L 27/22
(52) U.S. CI 375/137; 375/326; 375/328;
(58) Field of Search 375/134, 137,
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FOREIGN PATENT DOCUMENTS
EP 0 822 682 Al * 2/1998
European Telecommunications Standards Institute 2000 (ETSI); "Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Physical (PHY) Layer"; Technical Specification; http://www.etsi.org ; pp. 1-40; ETSI TS 101 475 VI.1.1 (2000-04).
(List continued on next page.)
Primary Examiner—-Young T. Tse
(74) Attorney, Agent, or Firm—Fitch, Even, Tabin & Flannery
A pilot phase tracking loop for an OFDM receiver including a phase rotator for receiving an incoming signal, which is coupled to a Fourier transform, which is coupled to a pilot phase error metric for determining a phase error estimate associated with a received OFDM symbol, e.g., a data symbol. The pilot phase error metric is coupled to a loop filter, which is coupled to an oscillator, which is coupled back to the phase rotator. The phase rotator rotates the incoming signal by the filtered phase error estimate for subsequent OFDM symbols to reduce the phase noise of the signaling output from the phase rotator. Thus, the phase noise introduced by a radio portion of the OFDM receiver and an OFDM transmitter is compensated for by the pilot phase error estimation in the baseband portion of the OFDM receiver and improved OFDM signal tracking is accomplished under poor SNR conditions.
29 Claims, 13 Drawing Sheets
IEEE Computer Society; "Draft Supplement to Standard [for] Information Technology-Telecommunications and Information Exchange Between Systems-Local and Metropolitan Area Networks-Specific Requirements-Part II: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: High Speed Physical Layer in the 5 Ghz Band"; IEEE P802.11a/D7.0; Supplement to IEEE Standard 802.11-1999; (1999); pp. 1-90. U.S. patent application Ser. No. 09/790,429, Crawford, filed Feb. 21, 2001.
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