Multiple Operator Core Network

Description

MOCN is a standardized 3GPP network sharing architecture defined to allow two or more mobile network operators (MNOs) to share a common Radio Access Network (RAN). In this model, the shared RAN, comprising NodeBs in UMTS or eNodeBs/gNBs in LTE/5G, is connected to the separate core networks of each participating operator. The shared RAN broadcasts multiple Public Land Mobile Network (PLMN) identities, allowing User Equipment (UE) to discover and select their home operator's network. A key architectural component is the RAN node's ability to route initial UE access requests to the correct core network based on the selected PLMN ID, typically using mechanisms like RAN-based Network Node Selection Function (RAN-NNSF) or core network assistance.

The operational flow begins when a UE, capable of network selection, identifies the available PLMNs from the system information broadcast by the shared cell. Upon selecting its home PLMN, the UE initiates a connection. The RAN node (e.g., a gNB in 5G) uses the selected PLMN ID, often in conjunction with the Network Slice Selection Assistance Information (NSSAI) in 5G, to determine the appropriate core network operator and route the Non-Access Stratum (NAS) signaling accordingly. This routing is critical and is managed over shared interfaces like the N2 (NG-C) interface in 5G, where a single RAN node maintains separate logical connections to the Access and Mobility Management Functions (AMFs) of different operators.

MOCN involves several key technical components: the shared RAN hardware and software, the broadcast of multiple PLMN IDs in system information blocks (SIBs), and the RAN's PLMN-aware routing function. It also requires support in the UE for multi-PLMN selection. The shared RAN must manage radio resources (like carriers and cells) in a way that can serve subscribers from all sharing operators, potentially with agreed-upon service level agreements (SLAs) on capacity partitioning or prioritization. From a core network perspective, each operator's network remains entirely independent, handling subscriber authentication, policy control, charging, and data routing separately. This separation ensures operational autonomy and security while maximizing the efficiency of the expensive RAN infrastructure.

Purpose & Motivation

MOCN was created to address the high capital expenditure (CAPEX) and operational expenditure (OPEX) associated with deploying and maintaining dense radio access networks, especially as mobile data demand exploded. Historically, each operator deployed its own exclusive RAN, leading to infrastructure duplication, increased site acquisition costs, and higher energy consumption. For new market entrants or smaller operators, these costs presented a significant barrier to entry and competitive service rollout. MOCN provides a standardized solution for RAN sharing, enabling operators to pool their resources.

The primary problems MOCN solves are inefficient spectrum utilization and redundant infrastructure. By sharing physical sites, antennas, and baseband units, operators can significantly reduce deployment and maintenance costs. It also allows for faster network rollout, particularly in rural or underserved areas where the business case for a single operator might be weak. Furthermore, in scenarios where spectrum is scarce, MOCN can enable operators to share licensed spectrum bands, leading to better overall spectral efficiency and improved user experience through combined coverage and capacity.

Before MOCN, operators could engage in site sharing (sharing physical mast and power) but lacked a standardized method for deep RAN sharing, including shared radio equipment and spectrum. Proprietary solutions existed but led to vendor lock-in and interoperability issues. 3GPP's standardization of MOCN, starting in Release 6, provided a vendor-neutral, interoperable framework. This was crucial for regulatory acceptance and for enabling complex operational models like national roaming or joint ventures, ensuring fair competition while promoting network densification and overall industry sustainability.