Wireline 5G Cable Access Network

Description

The Wireline 5G Cable Access Network (W-5GCAN) is a standardized architecture within 3GPP that facilitates the convergence of cable broadband networks, primarily those based on Data Over Cable Service Interface Specification (DOCSIS) standards, with the 5G Core network. Similar to W-5GAN and W-5GBAN, it classifies cable access as a trusted non-3GPP access type. The key network function enabling this integration is a Cable Access Gateway Function, which performs the critical role of protocol adaptation between the DOCSIS cable network domain and the 5G Core domain.

This gateway function interfaces with the Cable Modem Termination System (CMTS) or Converged Cable Access Platform (CCAP) in the cable network. It intercepts control and data traffic from cable modems (CM) and embedded Multimedia Terminal Adapters (eMTAs). The gateway translates cable-specific provisioning, authentication, and management protocols (such as DOCSIS MAC management messages and PacketCable signaling) into 5G-native signaling over the N2 interface to the AMF. For the user plane, it establishes GTP-U tunnels over the N3 interface to a UPF, effectively routing subscriber data traffic directly into the 5G Core's data network, bypassing the traditional cable modem termination system's routing functions.

The technical process involves the cable modem or gateway being recognized as a 5G UE with a subscription in the UDM. During initial provisioning or service flow establishment, the Cable Access Gateway Function facilitates 5G-AKA authentication. Once authenticated, the SMF establishes a PDU Session for the device. The cable network's QoS parameters (e.g., DOCSIS service flows with specific latency and bandwidth guarantees) are mapped to 5G QoS Flows under the control of the PCF. This allows the cable operator to apply the rich policy control, charging, and network slicing capabilities of the 5G Core to its fixed broadband subscribers, creating a seamless service experience across cable and mobile access.

Purpose & Motivation

W-5GCAN was created to address the strategic need for cable network operators (Multi-System Operators or MSOs) to participate in the 5G ecosystem using their extensive Hybrid Fiber-Coaxial (HFC) infrastructure. Historically, cable networks provided broadband internet, voice, and video using entirely separate core networks (PacketCable for voice, DOCSIS for data) from mobile operators. This separation prevented the offering of converged services and resulted in duplicated network functions for authentication, policy, and charging.

The primary problem W-5GCAN solves is the technological silo between the DOCSIS/PacketCable world and the 3GPP mobile world. It provides a clear, standards-based path for cable operators to modernize their networks by adopting a 5G Core, thereby gaining access to advanced 5G capabilities like network slicing for enterprise services, edge computing integration, and unified policy frameworks. This is particularly motivated by cable operators' expansion into mobile services (via MVNO or own radio) and the desire to offer a consistent "wireless-like" experience over their fixed network.

Introduced in Release 16, W-5GCAN leverages the same convergence principles as W-5GAN but tailors them to the specific protocols, QoS models, and operational practices of the cable industry. It addresses limitations of previous convergence attempts by providing native support for cable-specific features like multicast video delivery within a 5G PDU Session context. This enables cable operators to compete effectively with fiber and mobile operators by offering a unified, next-generation service portfolio anchored by their existing coaxial plant.