The stage 1 description of LCS at the service level is provided in TS 22.071; the stage 2 LCS functional description, including the LCS system architecture and message flows, is provided in TS 23.271. Positioning functionality provides a means to determine the geographic position and/or velocity of the UE based on measuring radio signals. The position information may be requested by and reported to a client (e.g., an application) associated with the UE, or by a client within or attached to the core network. The position information shall be reported in standard formats, such as those for cell-based or geographical co-ordinates, together with the estimated errors (uncertainty) of the position and velocity of the UE and, if available, the positioning method (or the list of the methods) used to obtain the position estimate. Restrictions on the geographic shape encoded within the 'position information' parameter may exist for certain LCS client types. The EPS, including E-UTRAN, shall comply with any shape restrictions defined in LTE and, in a particular country, with any shape restrictions defined for a specific LCS client type in relevant national standards. For example, in the US, national standard J-STD-036-B restricts the geographic shape for an emergency services LCS client to minimally either an "ellipsoid point" or an "ellipsoid point with uncertainty circle and confidence" as defined in TS 23.032. It shall be possible for the majority of the UEs (active or inactive) within a network to use the LCS feature without compromising the radio transmission or signalling capabilities of the E-UTRAN. The uncertainty of the position measurement shall be network-implementation-dependent, at the choice of the network operator. The uncertainty may vary between networks as well as from one area within a network to another. The uncertainty may be hundreds of metres in some areas and only a few metres in others. In the event that a particular position measurement is provided through a UE-assisted process, the uncertainty may also depend on the capabilities of the UE. In some jurisdictions, there is a regulatory requirement for location service accuracy that is part of an emergency service. Further details of the accuracy requirements can be found in TS 22.071. The uncertainty of the position information is dependent on the method used, the position of the UE within the coverage area and the activity of the UE. Several design options of the E-UTRAN system (e.g., size of cell, adaptive antenna technique, pathloss estimation, timing accuracy, eNode B surveys) shall allow the network operator to choose a suitable and cost-effective UE positioning method for their market. There are many different possible uses for the positioning information. The positioning functions may be used internally by the EPS, by value-added network services, by the UE itself or through the network, and by "third party" services. The feature may also be used by an emergency service (which may be mandated or "value-added"), but the location service is not exclusively for emergencies. The E-UTRAN is a new radio system design without a pre-existing deployment of "legacy" UEs operating according to the radio interface. This freedom from legacy equipment enables the location service feature design to make use of appropriate techniques to provide the most accurate results. The technique must also be a cost-effective total solution, must allow evolution to meet evolving service requirements, and must be able to take advantage of advances in technology over the lifetime of E-UTRAN deployments. Design of the E-UTRAN positioning capability as documented in this specification includes position methods, protocols and procedures that are either adapted from capabilities already supported for UTRAN and GERAN, or created separately from first principles. The proportion of the latter is higher than if the UTRAN and GERAN capabilities had been designed to provide forward compatibility to other access types. In contrast to GERAN and UTRAN, the E-UTRAN positioning capabilities are intended to be forward compatible to other access types and other position methods, in an effort to reduce the amount of additional positioning support needed in the future. This goal also extends to user plane location solutions such as OMA SUPL ([17], [18]), for which E-UTRAN positioning capabilities are intended to be compatible where appropriate. As a basis for the operation of UE Positioning in E-UTRAN, the following assumptions apply:

• both TDD and FDD will be supported;
• the provision of the UE Positioning function in E-UTRAN and EPC is optional through support of the specified method(s) in the eNode B and the E-SMLC;
• UE Positioning is applicable to any target UE, whether or not the UE supports LCS, but with restrictions on the use of certain positioning methods depending on UE capability (as defined within the LPP protocol);
• the positioning information may be used for internal system operations to improve system performance;
• the UE Positioning architecture and functions shall include the option to accommodate several techniques of measurement and processing to ensure evolution to follow changing service requirements and to take advantage of advancing technology;
• LMU aspects are left for implementation and are not standardized in this release.

The E-UTRAN may utilise one or more positioning methods in order to determine the position of an UE. Positioning the UE involves two main steps:

• signal measurements; and
• Position estimate and optional velocity computation based on the measurements.

The signal measurements may be made by the UE or the eNode B. The basic signals measured for terrestrial position methods are typically the E-UTRA radio transmissions; however, other methods may make use of other transmissions such as general radio navigation signals including those from Global Navigation Satellites Systems (GNSSs). The positioning function should not be limited to a single method or measurement. That is, it should be capable of utilising other standard methods and measurements, as such methods and measurements are available and appropriate, to meet the required service needs of the location service client. This additional information could consist of readily available E-UTRAN measurements. The position estimate computation may be made by the UE or by the E-SMLC.

The standard positioning methods supported for E-UTRAN access are:

• network-assisted GNSS methods;
• downlink positioning;
• enhanced cell ID method;
• uplink positioning;
• WLAN method;
• Bluetooth method;
• Terrestrial Beacon System method;
• Sensor based methods:
  • Barometric Pressure Sensor;
  • Motion sensor.

Hybrid positioning using multiple methods from the list of positioning methods above is also supported. Standalone mode (e.g. autonomous, without network assistance) using one or more methods from the list of positioning methods above is also supported. These positioning methods may be supported in UE-based, UE-assisted/E-SMLC-based, eNB-assisted, and LMU-assisted/E-SMLC-based versions. Table 4.3-1 indicates which of these versions are supported in this version of the specification for the standardised positioning methods.

Sensor, WLAN, Bluetooth, and TBS positioning methods based on MBS signals are also supported in standalone mode, as described in the corresponding clauses.