Target Device

Description

The term "Target Device" refers to the device that is being positioned in a location services (LCS) context. It is a generic term used in 3GPP specifications to denote the entity whose location is being determined, which can be a User Equipment (UE) in a cellular network or a SUPL Enabled Terminal (SET) in the Secure User Plane Location (SUPL) architecture. The Target Device is the endpoint of positioning procedures and may initiate or respond to location requests. It is defined in specifications such as TS 36.355 (LTE Positioning Protocol), TS 37.355 (NR Positioning Protocol), and their associated SUPL specifications (TS 36.855, TS 37.857).

In the control plane architecture, the Target Device is typically a UE that communicates with the Evolved Serving Mobile Location Centre (E-SMLC) or the Location Management Function (LMF) in 5G. The positioning procedures involve the exchange of assistance data and location measurements between the Target Device and the positioning server. The Target Device may perform measurements on downlink signals (e.g., OTDOA, A-GNSS) or transmit uplink signals (e.g., for UTDOA). The location calculation can be performed either by the Target Device (UE-based) or by the network (UE-assisted).

In the user plane architecture, the Target Device is a SET that communicates with a SUPL Location Platform (SLP) over a user plane connection (e.g., IP). The SUPL protocol enables the exchange of positioning data and allows the SET to compute its location or send measurements to the SLP. The Target Device in SUPL can be a mobile phone, a tablet, or any device with SUPL support. The term "Target Device" is used to abstract the specific type of device, emphasizing its role as the object of positioning rather than its technology.

The Target Device is a key concept in location-based services, emergency calling (e.g., E911), and network optimization. Its location is determined using a variety of positioning methods, including GNSS, OTDOA, E-CID, and barometric pressure sensing. The accuracy and latency requirements for positioning vary by use case, and the Target Device must support the necessary capabilities. The 3GPP specifications define the protocols and procedures for interaction between the Target Device and the positioning server, ensuring interoperability across different vendors and networks.

Across releases, the definition of Target Device has remained consistent, reflecting its stable role in positioning architectures. The term is used in both LTE and 5G specifications, and it is expected to continue to be relevant as positioning technologies evolve. The Target Device is thus a fundamental concept in the 3GPP location services framework.

Purpose & Motivation

The term "Target Device" was introduced to provide a clear and unambiguous reference to the entity being positioned in location services. In early positioning systems, there was no standardized terminology, leading to confusion between the device being positioned and other network elements. The Target Device concept solves this by defining a single term that encompasses both UEs in cellular networks and SETs in SUPL, allowing specifications to describe positioning procedures without being tied to a specific access technology or architecture.

The Target Device abstraction is essential for the development of interoperable positioning solutions. It allows the same positioning protocols (e.g., LPP, SUPL) to be applied to different types of devices and networks. For example, the LTE Positioning Protocol (LPP) can be used to position a UE in an LTE network, while the SUPL protocol can be used to position a SET over a user plane connection. By referring to the Target Device, specifications can define procedures that are independent of the underlying transport and access technology.

Furthermore, the Target Device concept supports the separation of positioning functionality between the device and the network. Depending on the positioning method, the Target Device may perform measurements, compute its location, or both. This flexibility is crucial for optimizing performance and power consumption. The Target Device is also the point at which location privacy and security are enforced, as it may control whether its location is shared with external clients. The term thus encapsulates both the technical and policy aspects of positioning.