Patent US5239667A successfully refreshed from Google Patents.
US5239667A
Expired / Lapsed
US
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Method of controlling handoff in cellular mobile radio communications system
Assignee: NEC Corp
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Filing: 1991-01-31
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Granted: 1993-08-24
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Expires: 2011-01-31
Abstract
Abstract When communication is established using a mobile radio terminal, the speed at which the terminal is moving is measured by monitoring the Rayleigh fading of the signal strength. Using this velocity indicative parameter, a threshold level which is used to determine if a handoff is required or not, can be adjusted in a manner which renders the decision process more accurate and minimizes the number of unwarranted handoffs.
Inventors
- 👤 Toshihito Kanai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 06:34
CPC Classifications
H; H04; H04W; H04W36/00; H04W36/24; H04W36/30; H04W36/302
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
156 words
A method of controlling handoff in a cellular mobile radio communications system at a mobile unit, comprising the steps of: (a) detecting a first signal strength level of a signal transmitted from a first land site with which said mobile unit communicates, and further detecting a second signal strength level of a signal transmitted from a second land site with which said mobile unit establishes no communication; (b) detecting a level crossing rate which is the number indicating that said first signal strength level crosses a predetermined level within a predetermined time duration; (c) detecting a signal strength level difference by subtracting said first signal strength level from said second signal strength level; (d) changing a threshold level in accordance with the level crossing rate detected; and (e) comparing said signal strength level difference with said threshold and issuing a handoff request in the event that said signal strength level difference is more than said threshold.
Claim 2
Independent Claim
156 words
A method of controlling handoff in a cellular mobile radio communications system at a mobile unit, comprising the steps of: (a) detecting a first signal strength level of a signal transmitted from a first land site with which said mobile unit communicates, and further detecting a second signal strength level of a signal transmitted from a second land site with which said mobile unit establishes no communication; (b) detecting a level crossing rate which is the number indicating that said first signal strength level crosses a predetermined level within a predetermined time duration; (c) detecting a signal strength level difference by subtracting said first signal strength level from said second signal strength level; (d) changing a threshold level in accordance with the level crossing rate detected; and (e) comparing said signal strength level difference with said threshold and issuing a handoff request in the event that said signal strength level difference is more than said threshold.
Claim 3
Dependent Claim
41 words
A method as claimed in claim 1, further comprising step of deriving a maximum Doppler frequency from said level crossing rate and said first signal strength level, and wherein said predetermined time duration is changed according to said maximum Doppler frequency.
Claim 4
Independent Claim
231 words
A method of controlling handoff in a cellular mobile radio communications system at a land site comprising the steps of: (a) detecting, at a first land site, a first signal strength level of a signal transmitted from a mobile unit with which said first land site communicates, and further detecting, at a second land site, a second signal strength level of a signal transmitted from said mobile unit with which said second land site establishes no communication; (b) detecting, at said first land site, a level crossing rate which is the number indicating that said first signal strength level crosses a predetermined level within a predetermined time duration; (c) changing, at said first land site, a threshold level in accordance with the level crossing rate detected; (d) allowing said first land site to apply said first signal strength level and said threshold level to a control unit for controlling said first and second land sites, and allowing said second land site to apply said second signal strength level to said control unit; and (e) detecting, at said control unit, a signal strength level difference by subtracting said first signal strength level from said second signal strength level; and (f) comparing, at said control unit, said signal strength level difference with said threshold and issuing a handoff request in the event that said signal strength level difference is more than said threshold.
Claim 5
Independent Claim
231 words
A method of controlling handoff in a cellular mobile radio communications system at a land site comprising the steps of: (a) detecting, at a first land site, a first signal strength level of a signal transmitted from a mobile unit with which said first land site communicates, and further detecting, at a second land site, a second signal strength level of a signal transmitted from said mobile unit with which said second land site establishes no communication; (b) detecting, at said first land site, a level crossing rate which is the number indicating that said first signal strength level crosses a predetermined level within a predetermined time duration; (c) changing, at said first land site, a threshold level in accordance with the level crossing rate detected; (d) allowing said first land site to apply said first signal strength level and said threshold level to a control unit for controlling said first and second land sites, and allowing said second land site to apply said second signal strength level to said control unit; and (e) detecting, at said control unit, a signal strength level difference by subtracting said first signal strength level from said second signal strength level; and (f) comparing, at said control unit, said signal strength level difference with said threshold and issuing a handoff request in the event that said signal strength level difference is more than said threshold.
Claim 6
Dependent Claim
41 words
A method as claimed in claim 3, further comprising step of deriving a maximum Doppler frequency from said level crossing rate and said first signal strength level, and wherein said predetermined time duration is changed according to said maximum Doppler frequency.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-08-23 | 1997-02-22 | 1997-08-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-08-23 | 2001-02-22 | 2001-08-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-08-23 | 2005-02-22 | 2005-08-24 | $7700.00 | Window Closed / Lapsed |