Proximity Services Discovery

Description

ProSe Discovery is a broad term that encompasses all processes used to determine that a ProSe-enabled UE is in proximity of another ProSe-enabled UE. Introduced in Release 12, it is a fundamental enabler for Proximity Services (ProSe) in 3GPP networks. The discovery process can be direct (using E-UTRA or WLAN technology without network involvement) or network-assisted (using E-UTRAN or EPC infrastructure). This flexibility allows ProSe Discovery to operate in various scenarios, including in-coverage, out-of-coverage, and partial coverage.

The core purpose of ProSe Discovery is to allow UEs to become aware of each other's presence so that they can subsequently engage in ProSe Communication or other proximity-based services. The discovery process involves the exchange of discovery messages between UEs or between a UE and the network. These messages contain information such as UE identity, application identity, and proximity criteria. The discovery can be triggered by the UE itself (UE-initiated) or by the network (network-initiated).

ProSe Discovery can be categorized into two main types: Direct Discovery and Network-Assisted Discovery. Direct Discovery, as defined in ProSe Direct Discovery, uses direct radio signals between UEs (via PC5 interface) to discover each other. Network-Assisted Discovery uses the E-UTRAN or EPC to facilitate discovery; for example, the network may track UE locations and inform UEs when they are in proximity. The latter is often used when direct discovery is not feasible, such as when UEs are not within direct radio range but are still close enough for proximity services.

The architecture for ProSe Discovery includes the ProSe Function, which is responsible for authorization, provisioning, and policy control. The ProSe Function interacts with the HSS to authenticate and authorize UEs for discovery, and with the EPC to manage mobility and session continuity. The UEs must be ProSe-enabled and may need to be registered with the ProSe Function to participate in discovery. The discovery process may also involve the ProSe Application Server, which can provide application-specific information and manage discovery requests.

Security and privacy are critical aspects of ProSe Discovery. The specifications define mechanisms to protect the privacy of UEs, such as using temporary identifiers and restricting discovery to authorized parties. The ProSe Function manages the security parameters and ensures that only authorized UEs can discover each other.

ProSe Discovery has evolved over releases to support new technologies and use cases, including 5G and WLAN integration. It is a key technology for public safety, social networking, and IoT applications, enabling devices to find each other and communicate efficiently.

Purpose & Motivation

ProSe Discovery was created to provide a standardized way for UEs to determine proximity to each other, enabling a wide range of proximity-based services. Before its introduction, there was no standardized mechanism in 3GPP networks for UEs to discover nearby devices; such functionality was either application-specific or not supported. ProSe Discovery solves this by defining a common framework that can be used across different applications and scenarios, ensuring interoperability and efficient use of network resources.

The motivation for ProSe Discovery came from the need for public safety communication, where devices must be able to discover each other even when network coverage is unavailable. It also addressed commercial demands for social networking, local advertising, and other proximity-based services. By providing both direct and network-assisted discovery methods, ProSe Discovery offers flexibility and robustness, allowing operation in various coverage conditions.

ProSe Discovery builds on the existing E-UTRA and EPC infrastructure, leveraging the ProSe Function and PC5 interface to enable efficient discovery. It represents a significant step towards more autonomous and context-aware communication in cellular networks, paving the way for advanced D2D and IoT services.