Proximity Services Enabled User Equipment

Description

A ProSe-enabled UE is a User Equipment that satisfies the functional and performance requirements defined by 3GPP for Proximity Services (ProSe). ProSe, introduced in Release 12, enables devices in close proximity to discover each other and communicate directly, either through the network or over a direct radio link known as the PC5 interface (sidelink). The ProSe-enabled UE is the fundamental endpoint capability that makes these services possible. Unless explicitly stated otherwise, the term encompasses all ProSe-enabled UEs, whether they are used for public safety applications or commercial use cases.

The architecture supporting a ProSe-enabled UE involves several key functional entities. The ProSe Function in the core network provides provisioning, authorization, and configuration for ProSe discovery and communication. The ProSe Application Server (ProSe AS) supports application-layer functions, while the ProSe Application ID and ProSe Restricted Code are used to identify and restrict discovery. On the radio side, the UE must support the PC5 interface, which operates using dedicated sidelink resources. In network-covered scenarios, the eNodeB/gNodeB allocates resources for sidelink transmission; in partial or out-of-coverage scenarios, the UE may use pre-configured resources. The UE also supports the PC3 interface towards the ProSe Function for provisioning and the PC1 interface towards the ProSe Application Server for application-level signaling.

ProSe Discovery can be either open or restricted. Open discovery allows any ProSe-enabled UE to discover another, while restricted discovery requires explicit permission from the announcing UE. ProSe Communication can be one-to-one or one-to-many. One-to-one communication uses unicast sidelink, while one-to-many uses groupcast or broadcast. The ProSe-enabled UE must handle radio resource management for sidelink, including synchronization, resource selection, and power control. It also supports relay functionality, where a UE in coverage can act as a relay for a UE out of coverage, extending network reach for public safety operations.

From a security perspective, the ProSe-enabled UE must support authentication and authorization with the ProSe Function, and it must protect user data and signaling over the PC5 interface. Security procedures include mutual authentication, integrity protection, and ciphering of sidelink signaling and user data. The UE also supports privacy features such as changing ProSe Application IDs to prevent tracking. In Release 12, ProSe was primarily designed for public safety use cases, but later releases expanded support for commercial applications, including wearable devices, social networking, and vehicle-to-everything (V2X) communications.

The ProSe-enabled UE is central to several advanced 3GPP features. In V2X, the UE supports sidelink communication for vehicle-to-vehicle, vehicle-to-infrastructure, and vehicle-to-pedestrian scenarios. In 5G, ProSe evolved into 5G ProSe, which supports enhanced sidelink and relay capabilities, including UE-to-network relaying and UE-to-UE relaying. The ProSe-enabled UE also plays a role in mission-critical services, where direct communication is essential when network infrastructure is unavailable or congested. Overall, the ProSe-enabled UE is a versatile device capability that enables direct communication, enhances network coverage and capacity, and supports critical public safety and commercial applications.

Purpose & Motivation

The ProSe-enabled UE concept was created to enable direct device-to-device communication and discovery, addressing the limitations of traditional cellular networks that route all traffic through the core network. Before ProSe, devices in close proximity could not communicate directly without infrastructure support, which was inefficient for local services and problematic for public safety scenarios where network coverage might be unavailable. The ProSe-enabled UE provides a standardized way to identify devices capable of these advanced services, ensuring interoperability and consistent behavior across vendors and networks.

Public safety was a primary motivation for ProSe. First responders need reliable communication in disaster areas where cellular infrastructure may be damaged or overloaded. The ProSe-enabled UE allows them to communicate directly with each other, forming a self-contained network. Additionally, commercial applications such as social networking, proximity-based advertising, and multiplayer gaming benefit from low-latency direct links. The term also simplifies specification references by defining a common baseline for UEs that support ProSe, avoiding the need to repeatedly list requirements.

The evolution of ProSe-enabled UEs reflects the growing demand for direct communication in 5G and beyond. While the definition text has remained stable across releases, the underlying capabilities have expanded significantly, including support for new frequency bands, enhanced sidelink features, and integration with network slicing and edge computing. The ProSe-enabled UE remains a cornerstone for mission-critical and commercial proximity services.