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.

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.

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.

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.

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.

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.

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.

The general LCS control plane architecture in the EPS applicable to a target UE with E-UTRAN access is defined in TS 23.271.

The LTE-Uu interface, connecting the UE to the eNode B over the air, is used as one of several transport links for the LTE Positioning Protocol.

The S1-MME interface between the eNode B and the MME is transparent to all UE-positioning-related procedures. It is involved in these procedures only as a transport link for the LTE Positioning Protocol. For eNode B related positioning procedures, the S1-MME interface transparently transports both positioning requests from the E-SMLC to the eNode B and positioning results from the eNode B to the E-SMLC. For delivery of broadcast location assistance data information, the S1-MME interface transparently transports the assistance data information from the E-SMLC to the eNode B for broadcasting and feedback information from the eNode B to the E-SMLC. The S1-MME interface is also used by an MME to provide ciphering keys to UEs for use in deciphering broadcast location assistance data information which was ciphered by an E-SMLC.

The SLs interface, between the E-SMLC and the MME, is transparent to all UE related and eNode B related positioning procedures. It is then used only as a transport link for the LTE Positioning Protocols LPP and LPPa. The SLs interface supports location sessions instigated by the MME as defined in TS 23.271. LPP and LPPa transport are then supported as part of any location session.

The SLm interface between the E-SMLC and an LMU is used for uplink positioning. It is used to transport SLmAP protocol messages over the E-SMLC-LMU interface. Network sharing should be supported. (Details FFS).

The LTE Positioning Protocol (LPP) is terminated between a target device (the UE in the control-plane case or SET in the user-plane case) and a positioning server (the E-SMLC in the control-plane case or SLP in the user-plane case). It may use either the control- or user-plane protocols as underlying transport. In this specification, only control plane use of LPP is defined. User plane support of LPP is defined in [17] and [18]. LPP is a point to point positioning protocol with capabilities similar to those in UMTS RRC (TS 25.331) and GERAN RRLP (TS 44.031). Whereas RRLP supports positioning of a target MS accessing GERAN and RRC supports positioning of a target UE accessing UTRAN, LPP supports positioning and location related services (e.g. transfer of assistance data) for a target UE accessing E-UTRAN. To avoid creating new positioning protocols for future access types developed by 3GPP, and to enable positioning measurements for terrestrial access types other than E UTRAN, LPP is in principle forward-compatible with other access types, even though restricted to E-UTRAN access in this specification. LPP further supports the OMA user plane location solution SUPL 2.0, as defined in the OMA SUPL 2.0 standards ([17], [18]), and is intended to be compatible with the successor protocols of SUPL 2.0 as well. LPP messages are carried as transparent PDUs across intermediate network interfaces using the appropriate protocols (e.g., S1-AP over the S1-MME interface, NAS/RRC over the Uu interface). The LPP protocol is intended to enable positioning for LTE using a multiplicity of different position methods, while isolating the details of any particular positioning method and the specifics of the underlying transport from one another. The protocol operates on a transaction basis between a target device and a server, with each transaction taking place as an independent procedure. More than one such procedure may be in progress at any given moment. An LPP procedure may involve a request/response pairing of messages or one or more "unsolicited" messages. Each procedure has a single objective (e.g., transfer of assistance data, exchange of LPP related capabilities, or positioning of a target device according to some QoS and use of one or more positioning methods). Multiple procedures, in series and/or in parallel, can be used to achieve more complex objectives (e.g., positioning of a target device in association with transfer of assistance data and exchange of LPP related capabilities). Multiple procedures also enable more than one positioning attempt to be ongoing at the same time (e.g., to obtain a coarse location estimate with low delay while a more accurate location estimate is being obtained with higher delay). An LPP session is defined between a positioning server and the target device, the details of its relation with transactions are described in clause 4.1.2 of TS 36.355. A single LPP transaction may be realised as multiple procedures; e.g., a single transaction for provision of assistance data might comprise several Provide Assistance Data messages, with each such message constituting a separate procedure (since there is no "multiple unsolicited messages" procedure type). For the 3GPP EPS Control Plane solution defined in TS 23.271, the UE is the target device and the E-SMLC is the server. For SUPL 2.0 support, the SUPL Enabled Terminal (SET) is the target device and the SUPL Location Platform (SLP) is the server. The protocol does not preclude the possibility of future developments in control plane and user plane solutions (e.g., possible successors of SUPL 2.0, as well as possible future 3GPP control plane solutions). All LPP operations and procedures are defined with respect to the target and server, and thus the LPP operations and procedures defined here with respect to a UE and an E-SMLC can also be viewed in this more generic context by substituting any target for the UE and any server for the E-SMLC. LPP further supports multiple positioning methods as defined in clause 4.3. LPP supports hybrid positioning, in which two or more position methods are used concurrently to provide measurements and/or a location estimate or estimates to the server. LPP is forward compatible with the later addition of other position methods in later releases (e.g., position methods associated with other types of terrestrial access). LPP also supports RRC broadcast of location assistance data information using data types defined in relation to LPP which are embedded in positioning SIBs. This enables an E-SMLC and a UE to support broadcast location assistance data using the same data structures which are used for point to point location. The operations controlled through LPP are described further in clause 7.1.

The RRC protocol is terminated between the eNode B and the UE. In addition to providing transport for LPP messages over the Uu interface, it supports transfer of measurements that may be used for positioning purposes through the existing measurement systems specified in TS 36.331. The RRC protocol also supports broadcasting of location assistance data via positioning System Information messages.

The LTE Positioning Protocol Annex (LPPa) carries information between the eNode B and the E-SMLC. It is used to support the following positioning functions:

• E-CID cases where assistance data or measurements are transferred from the eNode B to the E-SMLC;
• data collection from eNodeBs for support of downlink OTDOA positioning;
• retrieval of UE configuration data from the eNodeBs for support of uplink (e.g., UTDOA) positioning;
• exchange of information between E-SMLC and eNodeBs for the purpose of assistance data broadcasting.

The LPPa protocol is transparent to the MME. The MME routes the LPPa PDUs transparently based on a short Routing ID corresponding to the involved E-SMLC node over S1 interface without knowledge of the involved LPPa transaction. It carries the LPPa PDUs over S1 interface either in UE associated mode or non-UE associated mode.

The S1-AP protocol, terminated between the MME and the eNode B, is used as transport for LPP and LPPa messages over the S1-MME interface. The S1-AP protocol is also used to instigate and terminate eNode B related positioning procedures.

Figure 6.4.1-1 shows the protocol layering used to support transfer of LPP messages between an E-SMLC and UE. The LPP PDU is carried in NAS PDU between the MME and the UE.

Figure 6.4.2-1 shows the transfer of an LPP PDU between an E-SMLC and UE, in the network- and UE-triggered cases. These two cases may occur separately or as parts of a single more complex operation.

Figure 6.5.1-1 shows the protocol layering used to support transfer of LPPa PDUs between an E-SMLC and eNode B. The LPPa protocol is transparent to the MME. The MME routes the LPPa PDUs transparently based on a short Routing ID which corresponds to the involved E-SMLC node over the S1 interface without knowledge of the involved LPPa transaction. It carries the LPPa PDUs over S1 interface either in UE associated mode or non-UE associated mode.

Figure 6.5.2-1 shows LPPa PDU transfer between an E-SMLC and eNode B to support positioning of a particular UE.

Figure 6.5.3-1 shows LPPa PDU transfer between an E-SMLC and eNodeB when related to gathering data from the eNodeB for positioning support for all UEs.

Figure 6.5.4-1 shows LPPa PDU transfer between an E-SMLC and eNode B to support broadcast of assistance data.

Figure 6.5.4-2 shows LPPa PDU transfer between an eNode B and E-SMLC for providing feedback to the E-SMLC on assistance data broadcasting.

The SLmAP protocol, terminated between the E-SMLC and the LMU is used to support the following functions:

• delivery of target UE configuration data from the E-SMLC to the LMU
• request positioning measurements from the LMU and delivery of positioning measurements to the E-SMLC.

The SLmAP protocol is directly between the E-SMLC and the LMU.

Figure 6.Y.1-1 shows the protocol layering used to support transfer of SLmAP messages between an E-SMLC and LMU.