Location-based trigger for lawful interception
Original Publication Date: 2002-Oct-25
Included in the Prior Art Database: 2002-Oct-25
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Rescue services and law enforcement agencies need information about people present on a scene as early as possible. These people may be victims, witnesses or malefactors. Till now, no technical means for obtaining this information exist. In order to get a good idea of the number and identity of people present on a certain scene, a location-based trigger for existing lawful interception (LI) features is suggested. By this a list of mobile phones can be created, which gives the desirable information. When location-based LI is activated on a area of interest an Intercept Related Information (IRI) record is generated for each mobile phone inside the area under observation and for each mobile phone entering or leaving this area. An IRI record is also generated when a mobile phone inside this area is switched on or off and when a communication is originated or received. If desired and allowed under national law, this communication can also be re-corded automatically. The generated IRI records (and possibly the recorded content of communica-tion) provide useful information to the rescue workers and/or law enforcement officers, and may also constitute important evidence for later investigations or courts of law. There are several implementation methods to ensure the LI-trigger: 1. During call establishment, the mobile switch recognises the mobile phone is located within an active location-based LI measure area and therefore triggers LI-functions. 2. The subscriber or mobile phone individual LI mark is set. a) The mobile switch autonomously issues the LI marks and keeps them up-to-date as phones enter or leave the targeted area by relocation or (de-)activation. b) An Interception Management System (IMS) issues the “start LI measure” commands for the targets. Similar functionality is triggered by the IRI records, resulting in “start LI measure” or “stop LI measure” commands towards the mobile switch. The query for a list of mobile subscribers inside a particular geographical area may be an existing functionality. Using this function and activating LI on each found subject results in a similar functional-ity. However, in this solution the mobile switch does not inform the IMS by means of an IRI record when a mobile phone enters or leaves the targeted area or is switched on or off. This functionality has to be emulated by periodically repeating the query and adapting the activated individual LI measures. The time-frame between two queries constitutes a gap in the implementation in which newly arrived or activated phones are missed, while mobile subscribers which have left the scene remain unlawfully under observation. Assuming the query is indeed an existing function, this solution could be fully im-plemented in the IMS, without requiring new or changed Mobile Switch functionality. The location-based trigger for lawful interception can be extended to wire-line communications, based on a database with geographical coordinates of fixed phones.