Hybrid Self-Organizing Network

Description

Hybrid SON is a self-organizing network (SON) architecture introduced in 3GPP Release 19, where SON algorithms are distributed and executed across two or more of the following layers: the Network Function (NF) layer, the Domain layer, or the 3GPP Cross Domain layer. This multi-layer approach contrasts with traditional SON deployments where algorithms are confined to a single layer, such as within a single network function or a single management domain. By distributing SON functions across layers, Hybrid SON enables more flexible, scalable, and coordinated automation of network operations, including optimization, configuration, and healing.

The architecture of Hybrid SON is defined in 3GPP specifications 28.313 (Self-Organizing Networks (SON) Policy Network Resource Model (NRM) Integration Reference Point (IRP)) and 32.500 (Telecommunication management; Self-Organizing Networks (SON); Concepts and requirements). These specifications outline the management framework, policy models, and requirements for SON operations across different layers. The NF layer refers to SON functions embedded within individual network functions, such as a gNB or AMF, which can perform local optimizations. The Domain layer encompasses SON functions that operate within a specific management domain, such as Radio Access Network (RAN) or Core Network (CN) domain, coordinating across multiple NFs. The 3GPP Cross Domain layer involves SON functions that span multiple domains, enabling end-to-end optimization across RAN, CN, and other domains.

In operation, Hybrid SON allows SON algorithms to be placed at the most appropriate layer based on factors such as scope, latency requirements, and complexity. For example, fast, localized decisions like antenna tilt optimization might be executed at the NF layer, while broader coordination like load balancing across multiple cells could be handled at the Domain layer. Cross-domain functions, such as end-to-end QoS optimization or network slicing adjustments, would reside at the 3GPP Cross Domain layer. This layered execution ensures that SON functions can interact and coordinate, avoiding conflicts and ensuring consistent policies. The management system, as per 28.313, provides the necessary integration reference point for policy-based control, allowing the operator to define SON policies that govern the behavior across layers.

Key components of Hybrid SON include SON functions (e.g., Mobility Load Balancing, Mobility Robustness Optimization, Energy Saving, Coverage and Capacity Optimization), which are instantiated at different layers. The coordination between layers is managed through standardized interfaces and policy frameworks. For instance, the Domain layer may aggregate information from multiple NF-layer SON functions and provide directives to the Cross Domain layer. This hierarchical coordination is essential to prevent oscillations and ensure stable network performance. The 3GPP management architecture, with its element manager (EM), domain manager (DM), and network manager (NM), provides the structural basis for these layers.

Hybrid SON is particularly relevant in 5G and beyond networks, where complexity and heterogeneity are high due to diverse services, network slicing, and multi-vendor deployments. It enables operators to automate network management more effectively, reducing operational expenditure (OPEX) and improving network efficiency. By leveraging multi-layer SON, networks can adapt dynamically to changing conditions, such as traffic variations, interference, or failures, ensuring service continuity and quality. As networks evolve towards 6G, Hybrid SON is expected to play a crucial role in enabling autonomous network operations.

Purpose & Motivation

Hybrid SON exists to address the limitations of traditional, single-layer SON solutions in increasingly complex and heterogeneous networks. Traditional SON, as defined in earlier 3GPP releases, typically confined SON algorithms to a single layer, such as within a network function (e.g., eNB/gNB) or within a single management domain. While effective for localized optimizations, this approach struggled to coordinate across multiple domains and network functions, leading to suboptimal performance, conflicts between SON functions, and inability to achieve end-to-end optimization. As networks evolved towards 5G with network slicing, multi-vendor deployments, and diverse service requirements, the need for a more holistic, multi-layer SON framework became evident.

The motivation for Hybrid SON was to enable SON algorithms to be executed at the most appropriate layer, leveraging the strengths of each layer while ensuring coordination. By allowing SON functions to operate at the NF, Domain, and 3GPP Cross Domain layers, Hybrid SON provides flexibility to handle both fast, localized optimizations and slower, network-wide optimizations. This layered approach also facilitates the integration of SON with emerging technologies like network slicing and edge computing, where cross-domain coordination is essential. Furthermore, Hybrid SON aligns with the 3GPP management framework, enabling standardized policy-based control and interoperability across vendors.

Historically, SON was introduced in 3GPP Release 8 for LTE, focusing on self-configuration, self-optimization, and self-healing. Over releases, SON capabilities expanded, but the architectural model remained largely centralized or distributed within a single layer. Hybrid SON, introduced in Release 19, represents a significant evolution by formally defining a multi-layer SON architecture. It addresses the limitations of previous approaches by providing a standardized way to distribute and coordinate SON functions across layers, thereby enhancing automation, scalability, and end-to-end network performance. This is particularly important for 5G-Advanced and future 6G networks, where autonomous operation is a key goal.