Content for TS 36.305 Word version: 18.0.0
5 E-UTRAN UE Positioning Architecture
5.1 UE Positioning Operations
5.2 E-UTRAN Positioning Operations
5.2.1 Downlink Position Method Support
5.2.2 Uplink Position Method Support
5.2.3 Assistance Information Broadcast Support
5.3 Functional Description of Elements Related to UE Positioning in E-UTRAN
5.3.1 User Equipment (UE)
5.3.2 eNode B
5.3.3 Evolved Serving Mobile Location Centre (E-SMLC)
5.3.4 Location Measurement Unit (LMU)
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5 E-UTRAN UE Positioning Architecture p. 17
Figure 5-1 shows the architecture in EPS applicable to positioning of a UE with E-UTRAN access.
The MME receives a request for some location service associated with a particular target UE from another entity (e.g., GMLC or UE) or the MME itself decides to initiate some location service on behalf of a particular target UE (e.g., for an IMS emergency call from the UE) as described in TS 23.271. The MME then sends a location services request to an E-SMLC. The E-SMLC processes the location services request which may include transferring assistance data to the target UE to assist with UE-based and/or UE-assisted positioning and/or may include positioning of the target UE. For the Uplink method, the E-SMLC processes the location services request which includes transferring configuration data to the selected LMU(s). The E-SMLC then returns the result of the location service back to the MME (e.g., a position estimate for the UE and/or an indication of any assistance data transferred to the UE). In the case of a location service requested by an entity other than the MME (e.g., UE or E-SMLC), the MME returns the location service result to this entity.
The SLP is the SUPL entity responsible for positioning over the user plane. Further details of the relationship of the user-plane positioning entities to the E-UTRAN control-plane positioning architecture are described in Annex B.
An eNodeB may control several TPs, such as remote radio heads, or PRS-only TPs for support of PRS-based TBS.
5.1 UE Positioning Operations p. 18
To support positioning of a target UE and delivery of location assistance data to a UE with E-UTRAN access in EPS, location related functions are distributed as shown in the architecture in Figure 5-1 and as clarified in greater detail in TS 23.271. The overall sequence of events applicable to the UE, E-UTRAN and E-SMLC for any location service is shown in Figure 5.1-1.
Note that when the MME receives Location Service Request in case of the UE is in ECM-IDLE state, the MME performs a network triggered service request as defined in TS 23.401 in order to establish a signalling connection with the UE and assign a specific eNodeB. The UE is assumed to be in connected mode before the beginning of the flow shown in the Figure 5.1-1; that is, any signalling that might be required to bring the UE to connected mode prior to step 1a is not shown. The signaling connection may, however, be later released (e.g. by the eNode B as a result of signaling and data inactivity) while positioning is still ongoing.
Step 1a.
Location procedures applicable to E-UTRAN occur in steps 3a, 3b and 3c in Figure 5.1-2 and are defined in greater detail in this specification. Steps 1a and 5a are also applicable to E-UTRAN support because of a capability to tunnel signalling applicable to steps 3a and 3b. Other steps in Figure 5.1-2 are applicable only to the EPC and are described in greater detail and in TS 23.271.
Steps 3a and 3b can involve the use of different position methods to obtain location related measurements for a target UE and from these compute a location estimate and possibly additional information like velocity. Positioning methods supported in this release are summarized in clause 4.3 and described in detail in clause 8.
The case that the eNode B functions as an LCS client is not supported in this version of the specification.
Either: the UE requests some location service (e.g. positioning or delivery of assistance data) to the serving MME at the NAS level.
Step 1b.
Or: some entity in the EPC (e.g. GMLC) requests some location service (e.g. positioning) for a target UE to the serving MME .
Step 1c.
Or: the serving MME for a target UE determines the need for some location service (e.g. to locate the UE for an emergency call).
Step 2.
The MME transfers the location service request to an E-SMLC.
Step 3a.
The E-SMLC instigates location procedures with the serving eNode B for the UE - e.g. to obtain positioning measurements or assistance data.
Step 3b.
In addition to step 3a or instead of step 3a, for downlink positioning the E-SMLC instigates location procedures with the UE - e.g. to obtain a location estimate or positioning measurements or to transfer location assistance data to the UE.
Step 3c.
For uplink positioning (e.g., UTDOA), in addition to performing step 3a, the E-SMLC instigates location procedures with multiple LMUs for the target UE - e.g. to obtain positioning measurements.
Step 4.
The E-SMLC provides a location service response to the MME and includes any needed results - e.g. success or failure indication and, if requested and obtained, a location estimate for the UE.
Step 5a.
If step 1a was performed, the MME returns a location service response to the UE and includes any needed results - e.g. a location estimate for the UE.
Step 5b.
If step 1b was performed, the MME returns a location service response to the EPC entity in step 1b and includes any needed results - e.g. a location estimate for the UE.
Step 5c.
If step 1c occurred, the MME uses the location service response received in step 4 to assist the service that triggered this in step 1c (e.g. may provide a location estimate associated with an emergency call to a GMLC).
5.2 E-UTRAN Positioning Operations p. 20
Separately from location service support for particular UEs, an E-SMLC may interact with elements in the E-UTRAN in order to obtain measurement information to help assist one or more position methods for all UEs. An E-SMLC may also interact with elements in E-UTRAN to provide location assistance data information for broadcasting.
5.2.1 Downlink Position Method Support p. 20
An E-SMLC can interact with any eNodeB reachable from any of the MMEs with signaling access to the E-SMLC in order to obtain location related information to support the downlink position method, including PRS-based TBS. The information can include timing information for the TP in relation to either absolute GNSS time or timing of other TPs and information about the supported cells and TPs including PRS schedule.
Signalling access between the E-SMLC and eNodeB is via any MME with signalling access to both the E-SMLC and eNodeB.
5.2.2 Uplink Position Method Support p. 20
An E-SMLC can interact with the Serving eNodeB for the UE in order to retrieve target UE configuration information to support the uplink positioning method. The configuration information may include information required by the LMUs in order to obtain uplink time measurements; see clause 8.5.2. The E-SMLC can indicate to the serving eNodeB the need to direct the UE to transmit SRS signals (up to the maximum SRS bandwidth applicable for the carrier frequency) for uplink positioning. If the requested resources are not available, the eNB may assign other resources (or no resources e.g. if none are available) and report the resource allocation to the E-SMLC.
The E-SMLC can also request multiple LMUs to perform uplink time measurements and report the results.
5.2.3 Assistance Information Broadcast Support p. 20
An E-SMLC can interact with any eNodeB reachable from any of the MMEs with signalling access to the E-SMLC in order to provide location assistance data information for broadcasting. The information can include positioning System Information Blocks (posSIBs) together with assistance information meta data and broadcast periodicity.
Signalling access between the E-SMLC and eNodeB is via any MME with signalling access to both the E-SMLC and eNodeB.
5.3 Functional Description of Elements Related to UE Positioning in E-UTRAN p. 20
5.3.1 User Equipment (UE) p. 20
The UE may transmit the needed signals for uplink-based UE Positioning measurements and may make measurements of downlink signals from E-UTRAN and other sources such as different GNSS and TBS systems, WLAN access points, Bluetooth beacons, UE barometric pressure and motion sensors. The measurements to be made will be determined by the chosen positioning method.
The UE may also contain LCS applications, or access an LCS application either through communication with a network accessed by the UE or through another application residing in the UE. This LCS application may include the needed measurement and calculation functions to determine the UE's position with or without network assistance. This is outside of the scope of this specification.
The UE may also, for example, contain an independent positioning function (e.g., GPS) and thus be able to report its position, independent of the E-UTRAN transmissions. The UE with an independent positioning function may also make use of assistance information obtained from the network.
5.3.2 eNode B p. 21
The eNode B is a network element of E-UTRAN that may provide measurement results for position estimation and makes measurements of radio signals for a target UE and communicates these measurements to an E-SMLC.
The eNode B makes its measurements in response to requests from the E-SMLC (on demand or periodically).
The eNode B may configure the target UE to transmit periodic SRS with multiple transmissions (see 5.2.2) during uplink positioning.
An eNode B may serve several TPs, including for example remote radio heads and PRS-only TPs for PRS-based TBS positioning.
An eNode B may broadcast location assistance data information, received from an E-SMLC, in positioning System Information messages.
5.3.3 Evolved Serving Mobile Location Centre (E-SMLC) p. 21
The E-SMLC manages the support of different location services for target UEs, including positioning of UEs and delivery of assistance data to UEs. The E-SMLC may interact with the serving eNode B for a target UE in order to obtain position measurements for the UE, including uplink measurements made by the eNode B and downlink measurements made by the UE that were provided to the eNode B as part of other functions such as for support of handover. The E-SMLC may also interact with the serving eNode B to indicate to the serving eNode B the need to direct the UE to transmit SRS (see 5.2.2) signals to enable the uplink positioning method and to acquire the target UE configuration data needed by the LMUs to calculate the timing of these signals.
The E-SMLC will select a set of LMUs to be used for the UTDOA positioning. The E-SMLC interacts with the selected LMUs to request timing measurements.
The E-SMLC may interact with a target UE in order to deliver assistance data if requested for a particular location service, or to obtain a location estimate if that was requested.
The E-SMLC may interact with multiple eNode B's to provide location assistance data information for broadcasting. The assistance data information for broadcast may optionally be segmented and/or ciphered by the E-SMLC. The E-SMLC may also interact with MMEs to provide ciphering key data information to the MME as described in greater detail in TS 23.271.
For positioning of a target UE, the E-SMLC decides on the position methods to be used, based on factors that may include the LCS Client type, the required QoS, UE positioning capabilities, and eNode B positioning capabilities. The E-SMLC then invokes these positioning methods in the UE and/or serving eNode B. The positioning methods may yield a location estimate for UE-based position methods and/or positioning measurements for UE-assisted and network-based position methods. The E-SMLC may combine all the received results and determine a single location estimate for the target UE (hybrid positioning). Additional information like accuracy of the location estimate and velocity may also be determined.
5.3.4 Location Measurement Unit (LMU) p. 21
The Location Measurement Unit (LMU) makes measurements and communicates these measurements to an E-SMLC. All positioning measurements obtained by an LMU are supplied to the E-SMLC that made the request.
A UE Positioning request may involve measurements by multiple LMUs.
