Apparatus and method for locating cellular telephones
First Claim
1. A method for determining the time difference of arrival, tdoa, of signals from a cellular telephone, cell phone, at a pair of base stations, comprising the steps of:
- substantially simultaneously sampling transmission signals from the cell phone at the pair of base stations in a plurality of cell phone channels having different frequencies;
correlating the corresponding signals sampled at the base stations for each channel to determine a tdoa therebetween for each channel;
averaging the tdoas determined for each channel;
subtracting the average tdoa from each of the determined channel tdoas to determine a residual phase tdoa for each channel;
determining an overall phase tdoa between the pair of base stations based upon the residual phase tdoas for each channel; and
adding the average tdoa to the overall phase tdoa to determine an overall tdoa between the pair of base stations.
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Accused Products
Abstract
A method for determining the time difference of arrival, tdoa, of signals from a cellular telephone, includes determining tdoas for a plurality of channels, averaging the tdoas from the channels, subtracting the average tdoa from the individual channel tdoas to determine residual channel tdoas and determining an overall residual tdoa from the residual channel tdoas. An apparatus and method for collecting cell phone transmission signals for performing tdoa calculations, includes receiving, digitizing and temporarily storing wideband transmission signals while monitoring a known reverse control channel for a predetermined cell phone number to be located, and permanently storing the delayed reverse control channel signal once the predetermined number is identified.
403 Citations
17 Claims
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1. A method for determining the time difference of arrival, tdoa, of signals from a cellular telephone, cell phone, at a pair of base stations, comprising the steps of:
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substantially simultaneously sampling transmission signals from the cell phone at the pair of base stations in a plurality of cell phone channels having different frequencies; correlating the corresponding signals sampled at the base stations for each channel to determine a tdoa therebetween for each channel; averaging the tdoas determined for each channel; subtracting the average tdoa from each of the determined channel tdoas to determine a residual phase tdoa for each channel; determining an overall phase tdoa between the pair of base stations based upon the residual phase tdoas for each channel; and adding the average tdoa to the overall phase tdoa to determine an overall tdoa between the pair of base stations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for collecting transmission signals at a first cell phone base station from a particular cell phone for the purpose of determining location of the cell phone using time difference of arrival, tdoa, comprising the steps of:
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receiving signals transmitted over all channels of a wideband, cell phone base station, operating spectrum including a known reverse control channel thereof; digitizing the received wideband spectrum signals; storing the digitized signals as digitized data in a delay memory; monitoring the known reverse control channel signal for a cell phone transmission including a predetermined phone number of a cell phone to be located; identifying a predetermined number from the monitoring of the reverse control channel; and storing data from the delay memory in response to the identifying of the predetermined number, including the portion of the received signal bearing the identifying data of the predetermined number. - View Dependent Claims (10, 11, 12, 13)
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14. An apparatus for collecting transmission signals at a first cell phone base station from a particular cell phone for the purpose of determining location of the cell phone using time difference of arrival, tdoa, comprising:
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means for receiving signals transmitted over all channels of a wideband, cell phone base station, operating spectrum including a known reverse control channel thereof; means for digitizing the received wideband spectrum signals; means for storing the digitized signals as digitized data in a delay memory; means for monitoring the known reverse control channel signal for a cell phone transmission including a predetermined phone number of a cell phone to be located; means for identifying the predetermined number from the monitoring of the reverse control channel; and means for storing data from the delay memory in response to the identifying of the predetermined number, including the portion of the received signal bearing the identifying data of the predetermined number. - View Dependent Claims (15, 16, 17)
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Specification