Method for handoff in wireless communication systems using pattern recognition

(54) METHOD FOR HANDOFF IN WIRELESS COMMUNICATION SYSTEMS USING PATTERN RECOGNITION

(75) Inventors: Ravi Narasimhan, Los Altos; Donald C. Cox, Stanford, both ol CA (US)

(73) Assignee: The Board of Trustees of the Leland Stamford Junior University, Stamford, CA (US)

( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.

(21) Appl. No.: 09/392,975

(22) Filed: Sep. 9, 1999

(51) Int. C I. II04Q 7/20

(52) U.S. CI 455/436; 455/522; 455/432;

455/422; 455/442; 455/438

(58) Field of Search 455/522, 422,

455/442, 432, 436, 438

(56) References Cited

U.S. PATENT DOCUMENTS

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5,570,349 * 10/1996 Bustamante et al 370/18

5,657,487 8/1997 Doner 455/456

5,754,945 5/1998 Lin et al 455/33.2

5,884,187 * 3/1999 Ziv et al 455/522

5,901,354 * 5/1999 Menich et al 455/442

5,920,549 7/1999 Brackert et al 370/331

* cited by examiner

Primary Examiner—Daniel Hunter

Assistant Examiner—Lana Le

(74) Attorney, Agent, or Firm—Lumen IPS, Inc

(57) ABSTRACT

A handoff technique for wireless communication systems uses pattern recognition of signal strength data to anticipate handoffs and reduce the total number of handoffs in the system. A criterion for system performance is used in determining the necessity for handoff. A window of signal samples from nearby base stations constitutes a pattern vector which is classified using a probabilistic neural network or other learning machine. The use of averaged signals and the sequencing of classes allow for a small number of training vectors for the pattern classifier. Substantially increased performance requires only one training vector per class. Simulation results indicate that, for a given probability of failure, the pattern recognition based handoff technique yields fewer handoffs than the conventional hysteresis rule.

9 Claims, 6 Drawing Sheets