Patent EP0625863A2 successfully refreshed from Google Patents.
EP0625863A2
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Dual stage RSSI handoff trigger
Assignee: Nortel Networks Ltd
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Filing: 1994-04-18
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Granted: —
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Expires: 2014-04-18
Abstract
Abstract An appropriate handoff trigger is determined in a cellular system by maintaining both a long term representation of the received signal strength and a short term measurement of the current signal strength. The long term representation is used as the initial trigger for a handoff condition. The averaging process removes the effects of short term fades in the signal that may cause a premature handoff decision due to these fluctuations. This initial trigger is then qualified by examining the short term current, value of the signal. The actual handoff trigger is only realized when both values indicate that the handoff threshold has been exceeded. This approach eliminates the occurrence of false handoff triggers caused by the historical bias that may exist from the long term averaging process. The short term signal strengths value is reported as the mobile station's signal for comparisons to the signal strength measured on the adjacent cells. Since this value represents the current measure of the signal, it provides a truer comparison with the current measurements made on the adjacent cells, and virtually eliminates delayed handoff realizations due to the long term average historical bias.
Inventors
- 👤 Steven J. Willhoff
- 👤 Paul S. Meche
- 👤 John S. Mayes
- 👤 Lance Miguel Labauve
- 👤 Mark Bruce Pyle
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 15:46
CPC Classifications
H; H04; H04B; H04B17/00; H04B17/30; H04B17/382; H04W; H04W36/00; H04W36/24; H04W36/30; H04W36/302
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
119 words
A method of correctly determining, in a cellular system, when a phone call on a mobile station on a particular voice channel in one cell site should be handed off to a voice channel in another cell site, the method comprising the steps of: comparing a first signal value indicative of a long term averaged signal strength of a received signal from said mobile station, to a predetermined threshold value; comparing a second signal value indicative of a short term value of said received signal strength to said threshold value if said first signal value is below said threshold value; and determining that a handoff condition exists if both said first and second signal values are below said threshold.
Claim 2
Dependent Claim
43 words
A method as recited in claim 1 further comprising the step of: sending a handoff request to a controller after determining that a handoff condition exists, said handoff request including said second signal value for comparisons to adjacent cell sites signal strength levels.
Claim 3
Dependent Claim
30 words
The method of claim 1 wherein a time period over which said first signal value is averaged is longer than a time period over which said second signal is averaged.
Claim 4
Dependent Claim
37 words
The method of claim 1 wherein a time period over which said second signal value is averaged is correlated to a time period over which a signal strength value is measured by locate/receive devices of adjacent cells.
Claim 5
Independent Claim
164 words
A method of correctly determining, in a cellular system, when a phone call on a mobile station on a particular voice channel in one cell site should be handed off to a voice channel in another cell site, the method comprising the steps of: (a) determining if a long term sample rate window average of a received signal strength indicator (RSSI) is less than a handoff threshold; (b) if said long term sample rate window average is less than said handoff threshold, determining if a short term average of said RSSI is less than said handoff threshold; (c) if both said long term sample rate window average and said short term average is less than said handoff threshold, send a handoff request to a controller; and (d) if said short term average is not less than said handoff threshold, continuing checking with every sample taken until one of both said short and long term averages are less than said handoff threshold, or call releases.
Claim 6
Dependent Claim
42 words
The method as recited in claim 5 further comprising the steps of: setting a handoff guard timer after sending said handoff request; and returning to step (a) if said handoff guard timer expires before a handoff command is received from said controller.
Claim 7
Independent Claim
106 words
A method of correctly determining, in a cellular system, when a phone call on a mobile station on a particular voice channel in one cell site should be handed off to a voice channel in another cell site, the method comprising the steps of: comparing a first signal value indicative of a long term averaged signal strength of a received signal from a mobile station, to a predetermined threshold; comparing a second signal value indicative of a short term value of said received signal to said threshold; and determining that said handoff condition exists if both said first and second signal values are below said threshold.
Claim 8
Independent Claim
156 words
A method of correctly determining, in a cellular system, when a phone call on a mobile station on a particular voice channel in one cell site should be handed off to a voice channel in another cell site, the method comprising the steps of: sampling signals received from said mobile station to determine a signal strength of said received signals at predetermined intervals and outputting a received signal strength indication (RSSI) sample at said predetermined intervals; calculating a long term average of said samples at said predetermined intervals once a predetermined number of said samples have been received; calculating a short term average of said samples; comparing said long term average to a predetermined threshold value; comparing said short term average to said threshold value if said long term average is below said threshold value; and determining that said handoff condition exists if both said long term and short term averages are below said threshold value.
Claim 9
Dependent Claim
167 words
A voice channel apparatus for correctly determining, in a cellular system, when a phone call on a mobile station on a particular voice channel in one cell site should be handed off to a voice channel in another cell site, said apparatus comprising: a receive channel for receiving signals from said mobile station; a cell controller interface for receiving a threshold value from a cell controller; a controller, receiving samples representing a signal strength of said received signals from said receive channel, said controller maintaining a long and short term buffer and storage locations for a long term average of said long term buffer and a short term average of said short term buffer, said controller including a processor which determines a handoff condition when both said long term average and said short term average are less than said threshold value, said controller sending a handoff request, including said short term average, to said cell controller through said cell controller interface upon determination of said handoff condition.
References Cited (Backward Citations)
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