Participating Operator

Description

A Participating Operator (PO) is a network operator entity that participates in a cooperative agreement to share network resources with one or more other operators. This concept is central to network sharing architectures defined by 3GPP, which allow multiple operators to utilize common infrastructure—most commonly the Radio Access Network (RAN)—while maintaining independent core networks and subscriber management. A PO is distinct from the Primary Network Operator (PNO) for a given subscriber; a single operator can act as the PNO for its own subscribers and simultaneously be a PO in a sharing agreement for a geographical area where it does not have its own RAN deployment.

The technical implementation involves several key components. In a Multi-Operator Core Network (MOCN) sharing model, multiple POs connect their independent core networks (each with its own MME, S-GW, P-GW in 4G, or AMF, SMF, UPF in 5G) to a shared RAN node (e.g., an eNodeB or gNB). The shared RAN broadcasts the Public Land Mobile Network (PLMN) IDs of all participating operators. When a User Equipment (UE) camps on this cell, it sees multiple PLMNs as available. The UE, based on its configuration and network selection policies, selects one PLMN (its PNO) and initiates a connection. The RAN node, using the selected PLMN ID, routes the signaling to the corresponding PO's core network element. This requires enhancements to RAN protocols (e.g., S1-AP, NG-AP) to carry multiple PLMN IDs and to correctly route initial messages.

In a Gateway Core Network (GWCN) sharing model, the sharing is deeper, extending to some core network nodes like the MME in LTE. Here, POs share not only the RAN but also a common MME pool. The shared MME must be able to interface with the HSS/UDM of each PO. This requires the MME to support multiple network identities and to correctly route subscriber authentication requests to the appropriate home network. Specifications such as TS 23.251 detail these architectures. The PO's role is also critical in spectrum sharing scenarios, like Licensed Shared Access (LSA) or Citizens Broadband Radio Service (CBRS), where an operator (the PO) may gain temporary access to spectrum resources owned by another entity.

The concept extends to 5G network slicing and non-public networks. In a network slice instance provisioned for an enterprise, the enterprise or a third-party service provider could be a PO, participating in the slice's operation and management. For neutral host networks in buildings or campuses, a neutral host operator builds the RAN infrastructure, and multiple mobile network operators become POs by connecting their core networks to it. The PO framework enables cost reduction (by sharing CapEx and OpEx), faster deployment (especially in rural areas), and improved coverage, all while allowing operators to maintain brand identity, independent subscriber management, and control over their core services and policies.

Purpose & Motivation

The Participating Operator concept was developed to facilitate and standardize network sharing, which emerged as a critical strategy for operators to manage the escalating costs and complexities of deploying and maintaining dense radio networks, especially with the transition to 3G, 4G, and 5G. Building duplicate RAN infrastructure in every region is economically inefficient and spectrally wasteful. The PO model provides a standardized framework that allows operators to collaborate on infrastructure while remaining competitors in the service layer, addressing both economic and regulatory needs.

Historically, before formal 3GPP network sharing standards, operators engaged in bilateral site sharing or roaming agreements, which were often limited in scope and technically cumbersome. The introduction of standardized sharing architectures like MOCN (from Release 6 onwards) and GWCN provided a clear technical blueprint. This allowed an operator to act as a PO in an area where it lacked coverage, gaining immediate service presence by participating in another operator's RAN. Conversely, an operator with excess RAN capacity could host other POs, turning infrastructure into a revenue stream. This was particularly important for new market entrants and for covering rural or low-density areas where the business case for a standalone network was weak.

The creation of the PO role was also motivated by spectrum policy and technology evolution. With the auctioning of high-frequency spectrum for 5G (e.g., mmWave), which has limited propagation, dense network deployment becomes necessary but prohibitively expensive for a single operator. Sharing through the PO model makes such deployments viable. Furthermore, for technologies like Network Function Virtualization (NFV) and network slicing, the PO concept allows for flexible service-based participation in a shared physical infrastructure. It solves the problem of how to maintain operational and commercial separation in a technically converged environment, enabling innovation like neutral hosts and private network operators to participate in the mobile ecosystem.