OFDM pilot tone tracking for wireless LAN

(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;

370/206; 370/210

(58) Field of Search 375/134, 137,

375/144, 145, 148, 149, 226, 326, 327, 328, 340, 341, 349, 260; 370/206, 207,

208, 210

(56) References Cited

U.S. PATENT DOCUMENTS

5,170,415 A * 12/1992 Yoshida et al 329/304

5,577,072 A * 11/1996 Moon et al 375/261

5,799,047 A * 8/1998 Dobrica 375/350

5,930,305 A * 7/1999 Leib 329/304

5,940,450 A * 8/1999 Koslov et al 375/326

6,035,003 A * 3/2000 Park et al 370/208

6,181,258 Bl * 1/2001 Summers et al 340/870.02

6,218,896 Bl * 4/2001 Becker et al 329/304

6,310,926 Bl * 10/2001 Tore 375/261

FOREIGN PATENT DOCUMENTS

EP 0 822 682 Al * 2/1998

OTHER PUBLICATIONS

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

(57) ABSTRACT

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

OTHER PUBLICATIONS

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.

U.S. patent application Ser. No. 09/935,081, Crawford, filed Aug. 21, 2001.

Baoguo Yang, et al., "Timing Recovery For OFDM Transmission", IEEE Journal of Selected Areas In Communications, Nov. 2000, pp. 2278-2291, vol. 18, No. 11, IEEE. Jihoon Choi, et al., "Carrier Frequency Offset Compensation For Uplink Of OFDM-FDMA Systems", IEEE Communications Letters, Dec. 2000, pp. 414-416, vol. 4, No. 12, IEEE.

Dusan Matic, et al., "OFDM Synchronisation Based On The Phase Rotation Of Sub-Carriers", IEEE Journal, 2000, pp. 1260-1264, IEEE.

Stefan A. Fechtel, "Performance OF OFDM Carrier And Sampling Frequency Synchronization On Stationary And Mobile Channels", International Conf. On Consumer Electronics 2000, IEEE Journal, Jun. 13-15, 2000, pp. 18-19, IEEE.

Navid Lashkarian, et al., "Globally Optimum ML Estimation Of Timing And Frequency Offset In OFDM Systems", IEEE Journal, pp. 1044-1048, IEEE. Hyoung-Kyu Song, et al., "Frequency-Offset Synchronization and Channel Estimation For OFDM-Based Transmission", IEEE Communciations Letters, Mar. 2000, pp. 95-97, vol. 4, No. 3, IEEE.

Sebastien Simoens, et al., "A New Method For Joint Cancellation Of Clock And Carrier Frequency Offsets In OFDM Receivers Over Frequency Selective Channels", Center de Recherche Motorola Paris, Espace Technologique SaintAubin 99193, Gif-sur Yvette France, pp. 390-394, IEEE VTC2000, IEEE.

Fred Daneshgaran, et al., "ML Symbol Synchronization For Multichannel Modulation: Analysis And Implementation", ECE Department, California State University, Los Angeles, pp. 1-5.

Timothy M. Schmidl, et al., "Robust Frequency And Timing Synchronization For OFDM", IEEE Transactions On Communications, Dec. 1997, pp. 1613-1621, vol. 45, No. 12, IEEE.

Hui Liu, et al., "A High-Efficiency Carrier Estimatior For OFDM Communications", IEEE Communications Letters, Apr. 1998, vol. 2, No. 4, pp. 104-106, IEEE.

Keukjoon Bang, et al., "A Coarse Frequency Offset Estimation In An OFDM System Using The Concept Of The Coherence Phase Bandwidth", IEEE, pp. 1135-1139, IEEE.

Paul H. Moose, "A Technique For Orthogonal Frequency Division Multiplexing Frequency Offset Correction", IEEE Transactions On Communications, Oct. 1994, vol. 42, No. 10, pp. 2908-2914, IEEE.

Paul Koufalas, "State Variable Approach To Carrier Phase Recovery And Fine Automatic Gain Control On Flat Fading Channels", Aug. 30, 1996, Submitted to the School of Physics and Electronic Systems Engineering of the Faculty of Information Technology of the University of South Australia for the Degree of Master of Electronic Engineering by Research, University of South Australia.

* cited by examiner