Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Patent
1993-07-30
1998-05-12
Cumming, William
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
375224, H04Q 722
Patent
active
057521905
ABSTRACT:
A Supervisory Audio Tone (SAT) based Carrier-to-Interference (C/I) ratio measurement system uses the SAT tone to determine the desired signal to undesired interferers so that an intelligent hand-off decision can be made in a digital cellular communication system. The measurement is implemented by digital signal processors which allows additional signal processing and subsequently noise rejection over analog techniques. The received level of the desired SAT as well as the received levels of the SATs for the co-channel interferers is detected. The ratio of the desired SAT level to the sum of the undesired SAT levels provides the C/I measurement. By monitoring this C/I measurement, the base station can determine when to make a hand-off. This SAT based C/I measurement system also aids in the selection of a candidate cell to which the subscriber is handed-off. Surveillance receivers in the candidate cells make SAT based C/I measurements as well as Received Signal Strength Indication (RSSI) measurements. The cell with the most favorable channel conditions would be the cell to which the hand-off is made.
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Cooley David M.
Kaewell, Jr. John D.
Cumming William
Denson-Low Wanda
Hughes Electronics
Whelan John
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