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Content for  TS 33.107  Word version:  16.0.0

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19  Lawful Access Location Services (LALS) |R13|Word‑p. 223

19.1  General

LALS provides lawful access to the target's location using the Location Services (LCS) capabilities defined in the TS 23.271 and OMA MLP TS [76]. The present clause details the stage 2 Lawful Interception architecture and functions that are needed to provide the LCS information to the DF2 for a target of interception for subsequent delivery to the LEMF. Commercial LCS shall meet Clause 8 security requirements and provide priority to Lawful interception requests.
For LALS the subscriber location privacy settings shall be overridden.
Depending on national requirements and LCS capabilities of the network operator, the location information provided by LALS may vary in location information types (mobile network location format, location shape and geo-coordinates, civic address, or a combination of those), in the set of additional location parameters (map data, motion state, speed, etc.), as well as in the accuracy of provided location information.
The parameters controlling the LALS output are either delivered per authorization over HI1/X1 interface or pre-configured in the LI-LCS client.
There are two types of the location interception defined in the present specification: the Target Positioning and the Enhanced Location for IRI.
The Target Positioning is used to determine the target's location independently of the services used by the target.
The Enhanced Location for IRI is used to determine the LCS-based location of the target when specific user service events related to the target occur.
The authorizations for Target Positioning and for Enhanced Location for the same target may be independent of each other and may be overlapping in time or combined in a single intercept authorization by LEA.
There may be multiple active LALS authorizations from different LEAs at any given time.
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19.2  Target PositioningWord‑p. 224

19.2.0  General

There are two Target Positioning provision variants supported in the current specification - the Immediate Location and the Periodic Location.
Figure 19.2.1 shows the architecture for the LALS where the LI LCS Client provides the target's location and associated information towards the DF2 over the X2 interface fulfilling the Target Positioning ADMF authorization delivered over X1_1 interface.
[not reproduced yet]
Figure 19.2.1: LALS Model for Target Positioning
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19.2.1  Immediate Location Provision

The authorization for Immediate Location provision is delivered to LI LCS Client over X1_1 interface. Upon receiving the authorization the LI LCS Client initiates a Location Immediate Request (LIR, see TS 23.271) with the LCS Server/GMLC over Le interface and reports the acquired location to the DF2 over X2.
During the period of active authorization for Immediate Location the LI LCS client may receive and process additional Immediate Location requests from AMDF over the X1_1.
The resulting Immediate Location intercept product is delivered over X2 to the DF2 and propagated to the LEMF over HI2.
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19.2.2  Periodic Location ProvisionWord‑p. 225
The authorization for Periodic Location provision is delivered to LI LCS Client over X1_1 interface.
During the Periodic Location authorization the LI LCS Client shall produce the LALS Reports with the specified periodicity.
The periodicity shall be controlled by the LI LCS Client. The LI LCS Client shall issue a series of Location Immediate Requests (LIR, see TS 23.271) at required time intervals.
The LI LCS Client provides the acquired location reports to the DF2 over X2.
The Request for Periodic Location from ADMF to LI LCS Client may be accompanied by a set of parameters defining the time interval for reporting, report periodicity, etc. The description of the service response parameters is provided in clause 19.4. The Periodic Location intercept product is delivered over X2 to the DF2 and propagated to LEMF over HI2.
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19.3  Enhanced Location for IRI

19.3.1  General

The Enhanced Location for IRI refers to a capability providing LCS-based location information when specific user service events related to the target of interception occur. An example of such service events are the events of IMS session initiation and termination.
Figure 19.3.1-1 depicts the architecture of Enhanced Location acquisition and delivery for the case when the LTF is associated with an IRI ICE.
[not reproduced yet]
Figure 19.3.1-1: LALS Model for Enhanced Location for IRI (ICE/LTF option)
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Figure 19.3.1-2 depicts the architecture of Enhanced Location acquisition and delivery for the case when the LTF is associated with a DF2.
[not reproduced yet]
Figure 19.3.1-2: LALS Model for Enhanced Location for IRI (DF/LTF option)
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19.3.2  LALS Triggering FunctionWord‑p. 226
The LALS Enhanced Location architecture in Figures 19.3.1-1 and 19.3.1-2 depicts the LALS Triggering Function (LTF). LTF is associated with an IRI ICE or with a DF2/MF and is responsible for triggering the LI LCS Client when a specific event related to the target is observed at the IRI ICE, or received at the DF2.
The request for Enhanced Location reporting for IRI is delivered from ADMF to either an ICE over X1_1 or to a DF2 over X1_2 interface along with other parameters of IRI intercept authorization/activation. The ICE(s) or the DF2 then arm the LTF(s).
The ICE nodes that may have an associated LTF include P/S-CSCF, IMS AS, HLR, HSS, MSC Server, MME, S/GGSN, P/S-GW.
The LTF triggers the LI LCS Client over the LALS_T interface.
The LALS intercept product is delivered to DF2 from the LI LCS client over X2 interface asynchronously with the associated IRI event reports generated by an IRI ICE. To enable correlation between the LALS Reports and the associated IRI Events the LTF shall include the Correlation Identifier from the IRI Event, if available, into the LALS_T trigger.
The LALS_T interface for the LALS intercept trigger shall adhere to the security requirements outlined in Clause 8.
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19.4  X2-interface for Target Positioning and Enhanced Location

19.4.1  General

The following information needs to be transferred from the LI LCS Client to the DF2 in order to allow a DF2 to perform its functionality:
  • target identity;
  • other target identities, if available;
  • event date/time;
  • target location and extended location parameters, if available;
  • date/time of Location (if target location provided);
  • correlation information (in case of Extended Location for IRI reporting);
  • error code, if the positioning fails.

19.4.2  LALS Information ElementsWord‑p. 227
A set of possible elements as shown in Table 19.4.2-1 are used to generate the reports.
Element
Description

Observed IMSI
IMSI of the target.
Observed Other Identities
Other Identities of the target (MSISDN, IMEI, SIP-URI, TEL-URI)
Event date
Date of the report generation by the LI LCS Client
Event time
Time of the report generation by the LI LCS Client
Network Element Identifier
Unique identifier of the LI LCS Client
Location Information
Geographical Location and/or Civic Location
Time of Location
Date/Time of location. The time when location was obtained by the location source node.
Extended Location Parameters
Additional location information and associated QoS information
Correlation Identifier
Correlation information to allow the DF2 and/or LEMF to correlate LALS events with the triggering IRI events for the Enhanced Location for IRI
Additional location information and associated QoS information

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19.4.3  Structure of LALS Records

19.4.3.1  Target Positioning Reporting

This record will be generated when a response to the LIR (Location Immediate Request) is received from LCS for either Immediate or Periodic Target Positioning service.
If the target cannot be located, i.e. no response is received from the LCS in a predefined period or the LCS indicates failure to position the target, the record will contain an error code instead of the location information.
The information elements shown in Table 19.4.3.1-1, if available, will be delivered to the DF2 by the LI LCS Client.
Information Element

Observed IMSI
Observed Other Identities
Event Time
Event Date
Network Element Identifier
Location Information
Time of Location
Extended Location Parameters
Location Error Code

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19.4.3.2  Triggered Location ReportingWord‑p. 228
This record is generated when an LCS response to LI LCS request triggered by an IRI ICE is received (for Enhanced Location for IRI service). The elements, shown in Table 19.4.3.2-1 will be delivered to the DF2, if available. This record contains a Correlation Identifier parameter allowing to correlate the Location Reports with the corresponding IRI events.
If the target cannot be located, i.e. no response is received from the LCS in a predefined period after the triggering or the LCS server indicates failure to position the target, the record will contain an error code instead of the location information.
Information Element

Observed IMSI
Observed Other Identities
Event Time
Event Date
Network Element Identifier
Location Information
Time of Location
Extended Location Parameters
Correlation Identifier

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