Local DAA Ground Station

Description

The Local DAA Ground Station (LDGS) is a functional entity introduced in 3GPP Release 19 as part of the Direct Access to Application (DAA) framework. It is specified in 3GPP TS 23.255 (Architecture for enabling DAA), TS 24.257 (Protocol for DAA), and TS 29.257 (Signalling for DAA). LDGS acts as a localized gateway or ground station that provides direct access to application services, potentially via satellite links or local radio access, bypassing traditional core network paths to reduce latency and improve efficiency. It is particularly relevant for edge computing and localized service scenarios.

Architecturally, LDGS is deployed at the edge of the network, close to the user equipment (UE) or at a satellite ground station. It interfaces with the 5G core network functions such as the User Plane Function (UPF) and the Session Management Function (SMF) to establish and manage DAA sessions. The LDGS may also interact with the Application Function (AF) to discover and connect to application servers. When a UE requests a DAA service, the request is routed to the LDGS, which then establishes a direct data path to the application server, potentially using local breakout or satellite links. This reduces the need for traffic to traverse the entire core network, lowering latency and backhaul costs.

The operation of LDGS involves several key procedures. First, the UE initiates a DAA session request, which is sent to the SMF. The SMF selects an appropriate LDGS based on the UE's location, service requirements, and network policies. The LDGS then sets up the user plane connection, which may involve establishing a PDU session or a dedicated DAA bearer. The LDGS also handles mobility events, ensuring that the DAA session continues seamlessly as the UE moves. It supports various access technologies, including 5G NR, satellite, and potentially Wi-Fi, providing flexibility in deployment.

LDGS is designed to support a wide range of applications, including immersive media, industrial IoT, and public safety. It enables direct communication between UEs and application servers without the need for complex core network traversal, making it ideal for latency-sensitive and bandwidth-intensive services. Security is a critical aspect, with mechanisms for authentication, authorization, and encryption applied to the DAA sessions. The LDGS also supports charging and policy enforcement, ensuring that service usage is properly accounted for.

In summary, LDGS is a key enabler of the DAA architecture, providing localized access to application services. It leverages edge computing and satellite integration to deliver low-latency, high-throughput services, aligning with the 5G vision of ubiquitous connectivity and enhanced mobile broadband.

Purpose & Motivation

LDGS was created to address the growing demand for low-latency, high-bandwidth application services that require direct access to application servers without traversing the entire mobile core network. Traditional architectures route all user traffic through centralized core network functions, which can introduce significant latency and backhaul costs, especially for edge applications. The DAA framework, with LDGS as a key component, enables local breakout and direct access, reducing latency and improving user experience.

The function solves the problem of inefficient traffic routing for localized services by providing a ground station that can be deployed at the edge or integrated with satellite systems. This is particularly important for applications such as augmented reality, virtual reality, and industrial automation, where milliseconds of latency matter. LDGS also supports satellite access, extending coverage to remote areas where terrestrial infrastructure is limited.

Furthermore, LDGS facilitates the integration of satellite and terrestrial networks, enabling seamless service continuity across different access types. It aligns with 3GPP's broader goals of network slicing, edge computing, and non-terrestrial networks (NTN). By introducing LDGS in Rel-19, 3GPP provides a standardized way to implement DAA, ensuring interoperability and scalability across vendors and operators.