Detection and prevention of channel grabbing in a wireless communications system
First Claim
1. In a wireless telephone network, a method of detecting an unauthorized access to a communication channel assigned to an authorized wireless telephone during an ongoing communication with the authorized telephone, comprising the steps of:
- (a) monitoring a signal received from the communication channel during the ongoing communication;
(b) detecting in the received signal an unexpected shift from an expected predetermined value or a lack of shift to an expected predetermined value; and
(c) determining that an unauthorized access to the communication channel of the authorized telephone by an unauthorized wireless telephone has occurred based on the unexpected shift from the expected predetermined value or the lack of shift to the expected predetermined value is detected.
1 Assignment
0 Petitions
Accused Products
Abstract
A method and system for detecting a voice channel grab by a pirate in a cellular telephone network. Initially, RF signals transmitted to and from an authorized cellular telephone over the control and voice channels are monitored to track call processing activities and obtain various data that are used to detect potential voice channel grabbing attempts. The data may include such things as RSSI, change power output messages and responses, and hook-flash signal. From the data, the system looks for two events. A first event is an unexpected change or an absence of an expected change in the voice channel RF signal indicating that the pirate may be transmitting on the voice channel. The first event may be any one or more of the following: (1) a sudden upward shift in the voice channel RSSI; (2) an unexpected phase shift of either the RF signal or the SAT signal contained in the RF signal; and (3) an absence of an expected shift in the RSSI that corresponds to the change power level message from the network. The second event is receipt of a message indicative of a request to establish a new telephone connection such as a hook-flash message initiating a call conference. When the unexpected change in the RF signal and the message indicative of the request to establish the new telephone connection are detected, the system determines that the voice channel assigned to the authorized cellular telephone has been grabbed by the pirate. When the system determines that the channel grab has occurred, it prevents the pirate from establishing the new telephone connection by preventing receipt of dialed digits or terminating the connection on the voice channel.
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Citations
43 Claims
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1. In a wireless telephone network, a method of detecting an unauthorized access to a communication channel assigned to an authorized wireless telephone during an ongoing communication with the authorized telephone, comprising the steps of:
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(a) monitoring a signal received from the communication channel during the ongoing communication; (b) detecting in the received signal an unexpected shift from an expected predetermined value or a lack of shift to an expected predetermined value; and (c) determining that an unauthorized access to the communication channel of the authorized telephone by an unauthorized wireless telephone has occurred based on the unexpected shift from the expected predetermined value or the lack of shift to the expected predetermined value is detected. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. In a wireless telephone network, a method of detecting an unauthorized access to a communication channel of a given control site in the telephone network assigned to an authorized wireless telephone, the method comprising the steps of:
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(a) receiving a signal from the communication channel of the given control site; (b) detecting a shift or lack of shift in the received signal indicative of transmission of a signal on the communication channel by an unauthorized wireless telephone; (c) detecting in the received signal a communication indicative of a request for a new telephone connection within the same control site; and (d) determining that an unauthorized access to the communication channel by an unauthorized wireless telephone has occurred when both the shift or lack of shift in the received signal and the communication indicative of the request for the new telephone connection within the same control site are detected. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. In a wireless telephone network, a system for detecting an unauthorized access to a communication channel within a cell and assigned to an authorized wireless telephone, comprising:
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a data decoder connected to the communication channel receiver and operable to extract data contained in the received signal; and a processor connected to the communication channel receiver for receiving a strength indicator signal and the data decoder for receiving the extracted data, the processor being operable to detect in the received signal a shift or lack of shift indicative of transmission of a signal on the communication channel by an unauthorized wireless telephone and to detect from the extracted data a communication indicative of a request to establish a new telephone connection within the same cell as the communication channel, the processor being operable to determine the unauthorized access to the communication channel by the unauthorized wireless telephone when both the shift or lack of shift in the received signal and the communication indicative of the request to establish the new telephone connection are detected. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. In a cellular telephone network including a voice channel receiver generating a strength indicator signal indicative of the strength of a signal received from the voice channel, a system for detecting an unauthorized access to the voice channel within a cell and assigned to an authorized cellular telephone having an established telephone connection thereon, the system comprising:
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a message decoder connected to the voice channel receiver and operable to extract messages contained in the received signal; a processor connected to the voice channel receiver for receiving the strength indicator signal and the message decoder for receiving the extracted messages; a memory; and a process stored in the memory and running on the processor to detect in the received signal an unexpected shift or lack of an expected shift indicative of transmission of a signal on the voice channel by an unauthorized cellular telephone and to detect from the extracted messages a message indicative of a request to establish a new telephone connection within the same cell as the voice channel, the process being executable to determine the unauthorized access to the voice channel by the unauthorized cellular telephone when both the shift or lack of shift in the received signal and the message indicative of the request to establish the new telephone connection are detected. - View Dependent Claims (41, 42)
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43. In a wireless telephone network, a method of detecting an unauthorized access to a communication channel assigned to an authorized wireless telephone during an ongoing communication with the authorized telephone, comprising the steps of:
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monitoring a signal received from the communication channel; detecting at least two of the following events (i) to (iii); (i) an upward shift in the signal strength of the received signal beyond an expected predetermined signal strength value, (ii) a lack of downward shift in the signal strength of the received signal to an expected predetermined signal strength value indicative of a failure of the authorized wireless telephone to respond to a power down message, and (iii) a phase shift in the received signal beyond a predetermined range of phase shift values; and determining that an unauthorized access to the communication channel of the authorized telephone by an unauthorized wireless telephone has occurred when at least two of the events (i) to (iii) are detected.
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Specification