US5422933A
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US
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Method and system for effecting handoff in a cellular communication system
Assignee: Raytheon Co
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Filing: 1993-09-09
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Granted: 1995-06-06
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Expires: 2013-09-09
Abstract
Abstract A method and system for handing off an on-going communication from a serving cell to a neighboring cell of a cellular communication system having scanning receivers associated with each base transceiver station. A dynamic threshold is calculated for effecting the handoff in accordance with various operating conditions. The current mobile minimum attentuation level, (MT) the minimum permissible attenuation level of a serving (MS) cell and a neighboring cell (MN), together with the RF signal strength of the mobile unit at the neighboring cell (RSSI-NBR) and the serving cell (RSSI-SRV) are used in calculating a dynamic threshold (RSSI-THP).
Inventors
- 👤 Charles A. Barnett
- 👤 Stanley E. Kay
- 👤 Lou King
- 👤 Ashok D. Mehta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 13:27
CPC Classifications
H; H04; H04W; H04W36/00; H04W36/0005; H04W36/0083; H04W36/0085; H04W36/00838; H04W36/24; H04W36/30; H04W36/304
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
98 words
A method of handing off an on-going communication of a mobile unit from a serving cell to a neighboring cell of a cellular communication system, comprising: handing off the communication to a neighboring cell at times when the scanning receiver signal strength of the mobile unit at the neighboring cell is greater than a determined cell selection threshold for the neighboring cell; and determining the cell selection threshold using the current attenuation level of the mobile unit, a minimum permissible attenuation level permitted by the serving cell, and a minimum permissible attenuation level permitted by the neighboring cell.
Claim 2
Independent Claim
98 words
A method of handing off an on-going communication of a mobile unit from a serving cell to a neighboring cell of a cellular communication system, comprising: handing off the communication to a neighboring cell at times when the scanning receiver signal strength of the mobile unit at the neighboring cell is greater than a determined cell selection threshold for the neighboring cell; and determining the cell selection threshold using the current attenuation level of the mobile unit, a minimum permissible attenuation level permitted by the serving cell, and a minimum permissible attenuation level permitted by the neighboring cell.
Claim 3
Dependent Claim
77 words
The method of claim 1 wherein the step of determining the cell selection threshold, comprises the substeps of: determining the cell selection threshold at times when the current attenuation level of the mobile unit is greater than the minimum attenuation level permitted by the serving cell, and reporting the neighboring cell to the base station controller at times when an RF signal strength of the mobile unit at the neighboring cell exceeds the determined cell selection threshold.
Claim 4
Dependent Claim
72 words
The method of claim 1 wherein the step of determining the cell selection threshold, comprises the substeps of determining the cell selection threshold at times when the current attenuation level of the mobile unit is less than the minimum attenuation level permitted by the neighboring cell; and reporting the neighboring cell to the base station at times when an RF signal strength of the neighboring cell exceeds the determined cell selection threshold.
Claim 5
Dependent Claim
50 words
The method of claim 2 wherein the step of determining the cell selection threshold comprises the substeps of calculating the threshold to correspond to a value representing the minimum attenuation level permitted by the serving cell less the current attenuation level of the mobile unit combined with the nominal threshold.
Claim 6
Dependent Claim
53 words
The method of claim 3 wherein the step of determining the cell selection threshold comprises the substep of determining the threshold to correspond to the RF signal strength of the traffic channel of the serving cell plus the current mobile attenuation level subtracted from the minimum attenuation level permitted by the neighboring cell.
Claim 7
Dependent Claim
45 words
The method of claim 1 wherein the step of determining the cell selection threshold comprises the substeps of utilizing the nominal cell selection threshold at times when the current mobile attenuation level is not greater than the minimum attenuation level permitted by the serving cell.
Claim 8
Dependent Claim
59 words
The method of claim 3 wherein the step of determining the cell selection threshold, comprises the substeps of: utilizing a value corresponding to the traffic channel RF strength of the serving cell as the cell selection threshold at times when the current mobile unit attenuation level is not less than the minimum attenuation level permitted by the neighboring cell.
Claim 9
Dependent Claim
41 words
The method of claim 2 wherein the step of determining the cell selection threshold comprises the substep of determining the cell selection threshold to correspond to the value of the RF signal strength of the traffic channel plus a hysteresis constant.
Claim 10
Dependent Claim
62 words
The method of claim 8 wherein the substep of determining the selected cell threshold occurs at times when the RF signal strength of the serving cell plus the hysteresis constant is greater than a threshold value that correspond to the nominal threshold value plus the minimum attenuation level permitted by the serving cell less the current attenuation level of the mobile unit.
Claim 11
Dependent Claim
73 words
The method of claim 1 wherein the step of determining the cell selection threshold, comprises the substeps of: determining the cell selection threshold at times when the current attenuation level of the mobile unit is not greater than the minimum attenuation level of the serving cell; and reporting the neighboring cell to the base station controller at times when an RF signal strength of the neighboring cell exceeds the determined cell selection threshold.
Claim 12
Dependent Claim
55 words
The method of claim 10 wherein the step of determining the cell selection threshold comprises the substeps of determining the threshold to correspond to a value represented by the traffic channel signal strength of the serving cell plus the hysteresis constant at times when the determined threshold is greater than the nominal cell selection threshold.
Claim 13
Independent Claim
155 words
A system for effecting handoff of a mobile telephone communication from a serving cell to a neighboring cell of a cellular communication system having a plurality of mobile switching centers coupled to a telephone network, a plurality of base station controllers coupled to each mobile switching center, and a plurality of base transceiver stations, each defining an individual cell, and a plurality of scanning receivers for each base transceiver station for scanning neighboring cells, the system comprising: means for handing off the communication to a neighboring cell at times when the scanning receiver signal strength of the mobile unit at the neighboring cell is greater than a cell selection threshold for the neighboring cell; and means for determining the cell selection threshold in accordance with a current attenuation level of the mobile unit, as compared to a minimum attenuation level permitted by the serving cell and a minimum attenuation level permitted by the neighboring cell.
Claim 14
Independent Claim
155 words
A system for effecting handoff of a mobile telephone communication from a serving cell to a neighboring cell of a cellular communication system having a plurality of mobile switching centers coupled to a telephone network, a plurality of base station controllers coupled to each mobile switching center, and a plurality of base transceiver stations, each defining an individual cell, and a plurality of scanning receivers for each base transceiver station for scanning neighboring cells, the system comprising: means for handing off the communication to a neighboring cell at times when the scanning receiver signal strength of the mobile unit at the neighboring cell is greater than a cell selection threshold for the neighboring cell; and means for determining the cell selection threshold in accordance with a current attenuation level of the mobile unit, as compared to a minimum attenuation level permitted by the serving cell and a minimum attenuation level permitted by the neighboring cell.
Claim 15
Dependent Claim
78 words
The system of claim 12 wherein the means for determining the cell selection threshold, comprises: means for determining the cell selection threshold at times when the current attenuation level of the mobile unit is greater than the minimum attenuation level permitted by the serving cell, and means for reporting the neighboring cell to the base station controller at times when an RF signal strength of the mobile unit at the neighboring cell exceeds the determined cell selection threshold.
Claim 16
Dependent Claim
71 words
The system of claim 12 wherein the means for determining the cell selection threshold, comprises: means for determining the cell selection threshold at times when the current attenuation level of the mobile unit is less than the minimum attenuation level permitted by the neighboring cell; and means for reporting to the base station controller at times when an RF signal strength of the neighboring cell exceeds the determined cell selection threshold.
Claim 17
Dependent Claim
50 words
The system of claim 13 wherein the means for determining the cell selection threshold includes means for calculating the threshold to correspond to a value representing the current attenuation level of the mobile unit subtracted from the minimum attenuation level of the serving cell combined with a filed nominal threshold.
Claim 18
Dependent Claim
52 words
The system of claim 14 wherein the means for determining the cell selection threshold comprises: means for calculating the threshold to correspond to the RF signal strength of the traffic channel of the serving cell plus the current mobile attenuation level subtracted from the minimum attenuation level permitted by the neighboring cell.
Claim 19
Dependent Claim
44 words
The system of claim 12 wherein the means for determining the cell selection threshold comprises, means for utilizing the nominal cell selection threshold at times when the current mobile attenuation level is not greater than the minimum attenuation level permitted by the serving cell.
Claim 20
Dependent Claim
58 words
The system of claim 14 wherein the step of determining the cell selection threshold, comprises: means for utilizing a value corresponding to the traffic channel RF strength of the serving cell as the cell selection threshold at times when the current mobile unit attenuation level is not less than the minimum attenuation level permitted by the neighboring cell.
Claim 21
Dependent Claim
40 words
The system of claim 13 wherein the means for determining the cell selection threshold comprises means for calculating the cell selection threshold to correspond to the value of the RF signal strength of the traffic channel plus a hysteresis constant.
Claim 22
Dependent Claim
62 words
The system of claim 19 wherein the means for calculating the cell selection threshold occurs at times when the RF signal strength of the serving cell plus the hysteresis constant is greater than a threshold value that corresponds to the nominal threshold value plus the minimum attenuation level permitted by the serving cell less the current attenuation level of the mobile unit.
Claim 23
Dependent Claim
75 words
The method of claim 12 wherein the means for determining the cell selection threshold, comprises: means for determining the cell selection threshold at times when the current attenuation level of the mobile unit is not greater than the minimum attenuation level permitted by the serving cell; and means for reporting the neighboring cell to the base station controller at times when an RF signal strength of the neighboring cell exceeds the determined cell selection threshold.
Claim 24
Dependent Claim
54 words
The system of claim 21 wherein the means for determining the cell selection threshold comprises means for calculating the threshold to correspond to a value represented by the traffic channel signal strength of the serving cell plus the hysteresis constant at times when the calculated threshold is greater than the nominal cell selection threshold.
References Cited (Backward Citations)
US4613900A
Cited
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| 3.5 Years (Year 4) | 1998-06-05 | 1998-12-05 | 1999-06-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-06-05 | 2002-12-05 | 2003-06-06 | $3760.00 | Window Closed / Lapsed |
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