Method and apparatus for tracking identity-code changes in a communications system
First Claim
1. A method of tracking identity-code changes in a communications system in which a plurality of user stations can simultaneously conduct respective communication transactions during which signalling messages are exchanged with operational elements of the remainder of the communication system over at least one signalling path of a signalling subsystem of said communications system, said signalling messages including first messages sent by said user stations and each including an identity code associated with the user station sending that message, and second messages specifying corresponding identity codes for particular user stations;
- said method comprising the steps of;
(a) monitoring said signalling subsystem to detect said first message in passage from a user station to said remainder of the communications system;
(b) extracting from the said first message detected in step (a), said identity code included therein, the extracting effected independently of an operational element to which said first message is being sent;
(c) further monitoring said signalling subsystem to detect a said second message related to the same communication transaction as the first message detected in step (a) and passing to/from the same user station;
(d) extracting from said second message detected in step (c), said identity code included therein, said extracting effected independently of the user station/operational element to which the second message is being sent; and
(e) associating the identity code extracted in step (b) with the identity code extracted in step (d) thereby to indicate correspondence therebetween.
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Accused Products
Abstract
In a mobile radio network such a GSM network, an operative identity code is passed by a mobile station to the fixed network part at the start of each communication transaction. This operative identity code will either be the unique identity code (IMSI) assigned to the mobile-station user or, more usually, a temporary, substitute, identity code (TMSI) allocated by the fixed network part with a view to obscuring the identity of the user to anyone monitoring the network radio traffic. Whilst the fixed network infrastructure knows the association between a temporary identity code (TMSI) and the corresponding unique identity code (IMSI) of a user, this information is generally not readily accessible. To enable the current temporary identity code (TMSI) of a user to be readily tracked without burdening the network infrastructure, a monitoring arrangement is provided which monitors network signalling messages to link the different messages associated with a particular user mobile station that separately give the current operative identity code (line "c") and assign a successor operative identity code to that user (line "h"). In one embodiment applicable to a GSM network, messages on the A interface that carry identity code information for a particular user during a communication transaction are linked through the local references of the SCCP connection established for the transaction. In a second embodiment, also applicable to GSM, messages on the Abis interface are monitored and linked through the channel numbers contained in these messages.
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Citations
19 Claims
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1. A method of tracking identity-code changes in a communications system in which a plurality of user stations can simultaneously conduct respective communication transactions during which signalling messages are exchanged with operational elements of the remainder of the communication system over at least one signalling path of a signalling subsystem of said communications system, said signalling messages including first messages sent by said user stations and each including an identity code associated with the user station sending that message, and second messages specifying corresponding identity codes for particular user stations;
- said method comprising the steps of;
(a) monitoring said signalling subsystem to detect said first message in passage from a user station to said remainder of the communications system; (b) extracting from the said first message detected in step (a), said identity code included therein, the extracting effected independently of an operational element to which said first message is being sent; (c) further monitoring said signalling subsystem to detect a said second message related to the same communication transaction as the first message detected in step (a) and passing to/from the same user station; (d) extracting from said second message detected in step (c), said identity code included therein, said extracting effected independently of the user station/operational element to which the second message is being sent; and (e) associating the identity code extracted in step (b) with the identity code extracted in step (d) thereby to indicate correspondence therebetween. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
- said method comprising the steps of;
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19. Apparatus for tracking identity-code changes in a communications system in which a plurality of user stations can simultaneously conduct respective communication transactions during which signalling messages are exchanged with operational elements of the remainder of the communication system over at least one signalling path of a signalling subsystem of said communications system, said signalling messages including first messages sent by said user stations and each including an identity code associated with the user station sending that message, and second messages specifying corresponding identity codes for particular user stations;
- said apparatus comprising;
first monitoring means for monitoring said signalling subsystem to detect said first message, in passage from a user station to said remainder of the communications system; first extracting means for extracting from a said first message detected by said first monitoring means, the said identity code included therein, second monitoring means for further monitoring said signalling subsystem to detect a said second message related to the same communication transaction as said first message detected by said first extracting means and passing to/from the same user station, and second extracting means for extracting from a said second message detected by said second monitoring means, the identity code specified in that second message as the identity code corresponding to the identity code extracted by the first extraction means and means for associating the identity code extracted by the first extracting means with the identity code extracted by the second extracting means to thereby indicate their correspondence, said apparatus being functionally independent off said user stations and said operational elements of the communications system.
- said apparatus comprising;
Specification