US00RE37669E
(io) Patent Number: US RE37,669 E
(45) Date of Reissued Patent: Apr. 23,2002
(54) METHOD AND APPARATUS FOR HAND-OFF OF CALL IN PROGRESS
(75) Inventor: Minori Kawano, Amagasaki (JP)
(73) Assignee: Mitsubishi Denki Kabushiki Kaisha, Tokyo (JP)
(21) Appl. No.: 08/154,250
(22) Filed: Nov. 18, 1993
Related U.S. Patent Documents
Reissue of:
(64) Patent No.: 5,067,171
Issued: Nov. 19, 1991
Appl. No.: 07/167,634
Filed: Mar. 11, 1988
(30) Foreign Application Priority Data
Mar. 31, 1987 (JP) 62-79942
(51) Int. C I. I104Q 7/22
(52) U.S. CI 455/436; 455/525
(58) Field of Search 455/33.2, 33.3,
455/33.4, 52.1, 52.2, 52.3, 56.1, 54.1, 54.2, 226, 1, 23, 436, 437, 438, 439, 442, 443, 525, 513; 379/59, 60, 63
(56) References Cited
U.S. PATENT DOCUMENTS
4,485,486 A * 11/1984 Webb et al 455/438 X
4,531,235 A * 7/1985 Brasen 455/226.2 X
4,619,002 A * 10/1986 Thro 455/226.2
4,704,734 A * 11/1987 Menich et al 455/436 X
4,718,081 A * 1/1988 Brenig 455/438
4,751,725 A * 6/1988 Bonta et al 455/438 X
4,759,051 A * 7/1988 Han 455/436 X
OTHER PUBLICATIONS
"Cellular Handoff Procedure", Oct. 1984 by Astronet Corp.* "Handoff Procedure in Nordic NMT System", published Mar. 3, 1983.*
Astronet Corp. "Cellular Handoff Procedure", Engineering Bulletin 011, Oct. 1984.*
Nordic Systems, "Handoff Procedure in Nordic NMT System", Mar. 1983.*
* cited by examiner
Primary Examiner—Fan Tsang
Assistant Examiner—Philip J. Sobutka
(74) Attorney, Agent, or Firm—Pennie & Edmonds LLP
(57) ABSTRACT
A method and apparatus for a hand-off of a call-in-progress according to the present invention is arranged such that both a first ratio of a length of time, in which a measured value of SNR is below a predetermined "threshold" to a total length of the measuring time, and a second ratio of a length of time, in which a measured value of RSSI is below a predetermined "threshold", to a total length of the measuring time are detected and that the first ratio functions mainly when the "threshold" of RSSI is predetermined to a relatively low value; and the second ratio functions mainly when the "threshold" of RSSI is predetermined to a relatively high value, thereby optimizing the hand-off timing.
79 Claims, 5 Drawing Sheets
