scope:

The present document describes the data content of a Lawful Interception interface in a TETRA system. It provides the requirements and specification of the interface within a TETRA system for the purpose of providing data to Law Enforcement Agencies (LEAs) in the area of Lawful Interception (LI) of communications.

The present document describes the internal LI interface of a TETRA network, and does not specify the means by which data is delivered to the LEA or to its designated Law Enforcement Monitoring Facility (LEMF). However the internal LI interface is defined in such a way that data may be carried transparently on most networks.

NOTE: In this context "internal" means within the boundary of the TETRA infrastructure. The boundary may extend in such a manner that the TETRA LI function is remote from other components of the SwMI, or it may be co-located with other SwMI components.

The general reference model of figure 1 shows that the overall LI interface lies between the LEMF and the TETRA infrastructure (SwMI) and is composed of both the Handover Interface (described in ES 201 671 [8] and/or TS 102 232 [11]) and the internal interception interface. The subject of the present document is the internal LI interface that lies between the TETRA infrastructure and the mediation function.

The provision of a Lawful Interception interface for TETRA is a national option, however where it is provided it shall be provided as described in the present document.

The Handover Interface may be the subject of national regulation and therefore the mediation function may be a matter of national regulation.

The present document describes the data content of the information flows of the intercepted activity from the TETRA system using ASN.1 but without respect to the encoding rules which are determined by the handover interface adopted.

The present document is structured as follows:

• clause 4 outlines the essential requirements for the TETRA LI interface;

• clause 5 presents the structural and behavioural models of the LI interface;

• clause 6 presents the data model and allocation behaviour in the LI interface.

The present document applies to TETRA services where access to the communication of TETRA Subscriber Identities (TSIs) is available in a network (Switching and Management Infrastructure (SwMI) or Radio Packet Data Infrastructure (RPDI)). Whilst this does not prohibit lawful interception of TETRA Direct Mode Operation (DMO) it removes the liability of network operators and service providers to provide a result of interception when communication does not make use of their networks.

The present document describes the normal and exceptional operation in each of the three operational phases of T-LI:

1) Setup:

The actions taken within the TETRA network to establish the monitoring of a target and the interception communications paths for delivery.

2) Monitoring:

The monitoring of target activity and its delivery.

3) Cleardown:

The removal of a monitor facility against a target and the cleardown of the interception communications paths.

The present document does not describe the means of transporting data from the TETRA network to the LEA, but describes only the means of capturing and encoding the activities of a target within the TETRA network and delivering this data to the mediation function.

The present document does not define the operations or technical requirements of the Handover Interface that takes data from the mediation function to the Law Enforcement Monitoring Facility (LEMF).

The present document does not define the operations or technical requirements of the LEMF.

NOTE 1: The present document presupposes some familiarity with the operation of TETRA systems and of lawful interception.

NOTE 2: The present document suggests a barrier to external manipulation of the TETRA infrastructure by means of a mediation function.