Bearer Independent Core Network

Description

The Bearer Independent Core Network (BICN) is a fundamental architectural principle within 3GPP standards that defines a core network (CN) structure independent of the specific radio access technology and its associated circuit-switched (CS) or packet-switched (PS) bearers. Its primary objective is to create a unified core network layer that can serve multiple radio access networks (RANs), such as GSM EDGE Radio Access Network (GERAN), UMTS Terrestrial Radio Access Network (UTRAN), and later evolved UTRAN (E-UTRAN for LTE), without being tied to their native transport mechanisms. This is achieved by abstracting the core network functions from the underlying bearer services, treating the access network primarily as a source of IP packets or a connectivity pipe. The architecture emphasizes a clear separation between the control plane (signaling) and the user plane (data traffic), which is a precursor to more formalized control and user plane separation (CUPS) seen in later releases.

At its core, BICN leverages the IP Multimedia Subsystem (IMS) as the primary service delivery platform for real-time multimedia services, moving away from traditional circuit-switched telephony. The core network nodes, such as the Mobile Switching Center (MSC) and Serving GPRS Support Node (SGSN), evolve to support IP-based transport for both signaling and user data. For example, the MSC can evolve into an MSC Server (for control) and a Media Gateway (MGW) for user plane traffic, interconnected via standardized interfaces like the Mc interface (using protocols like H.248). Similarly, the SGSN and Gateway GPRS Support Node (GGSN) utilize fully IP-based Gn and Gp interfaces. This allows a single, consolidated packet-switched core to handle voice (via Voice over IP in the IMS), video, and data services, regardless of whether the user is connected via GSM, UMTS, or LTE.

The key architectural enablers of BICN include the use of IP as the universal transport layer and the definition of interworking functions (IWFs) and media gateways to handle legacy circuit-switched traffic. The IMS provides the call session control and application servers for service logic, while the bearer-independent core provides the transport and mobility management. This architecture reduces operational complexity by allowing operators to manage a single, converged core network for all access types, streamlining network expansion and service deployment. It forms the evolutionary foundation for the fully IP-based Evolved Packet Core (EPC) in 4G and the 5G Core (5GC), which fully realize the bearer-independent, service-based architecture vision.

Purpose & Motivation

BICN was introduced to address the growing complexity and cost of operating multiple, separate core networks for different generations of radio access technology (2G GSM, 3G UMTS). Prior to BICN, operators had to maintain parallel circuit-switched cores for voice and SMS and packet-switched cores for data, each with its own specific nodes, interfaces, and transport networks. This led to high capital and operational expenditures, inefficient resource utilization, and slow service deployment across different access networks. The industry needed a path to consolidate network infrastructure and simplify the introduction of new multimedia services.

The driving motivation was the transition to all-IP networks. As data services grew and IP became the ubiquitous protocol for communication, 3GPP defined BICN to enable a single, IP-based core network capable of supporting all services—voice, video, and data—over any access technology. This solved the problem of service silos, where a service like video calling might work on 3G but not on 2G. By making the core network 'bearer independent,' it allowed operators to evolve their networks flexibly, reusing core assets while upgrading radio access. It also positioned IMS as the future-proof service layer, ensuring network longevity and paving the way for fixed-mobile convergence.

Historically, BICN provided the critical architectural bridge from 2G/3G dual-domain networks to the flat, all-IP architecture of 4G LTE/EPC. It addressed the limitations of tight coupling between radio bearers and core network protocols, enabling more efficient traffic routing, simplified network management, and the economic benefits of a unified transport and service platform. This concept was essential for reducing time-to-market for new IP-based services and for managing the co-existence of legacy and next-generation access during long migration periods.

Key Features

• Decouples core network functions from specific radio access technologies (GERAN, UTRAN)
• Enables a unified IP-based core network for multiple access types
• Facilitates clear separation of control plane and user plane functions
• Supports service delivery through the IP Multimedia Subsystem (IMS) for multimedia
• Utilizes media gateways and interworking functions for legacy circuit-switched compatibility
• Reduces operational complexity and cost through network consolidation

Evolution Across Releases

Defining Specifications