Shared Network

Description

A Shared Network is a deployment arrangement in which two or more mobile network operators (MNOs) jointly use parts or all of their network infrastructure. Rather than each operator building and operating a fully independent network, the operators cooperate on selected network elements — which can range from passive infrastructure (sites, towers, power, backhaul) to active equipment (base stations, RNCs, MSCs, SGSNs/MMEs, HSS, and even spectrum) — while retaining their own subscriber bases, SIMs, and often their own core network functions. The concept is defined in 3GPP TR 22.951 ('Service aspects and requirements for network sharing') and the vocabulary is maintained in TR 21.905.

3GPP defines several distinct network sharing architectures. In the Gateway Core Network (GWCN) architecture, the shared radio access network connects to a shared core network node (for example, a shared MSC or SGSN), which then connects to the individual operators' core networks. In the Multi-Operator Core Network (MOCN) architecture, the shared radio access network connects directly to each operator's separate core network through distinct interfaces (Iu-CS/Iu-PS or S1), allowing each operator to keep full control of its core. A further variant, the RAN sharing model, shares only the radio access network while the core networks remain entirely independent.

Operationally, network sharing depends on the ability of a shared RAN node to select the correct core network or Public Land Mobile Network (PLMN) for each subscriber. This is typically achieved using the Shared Network Area (SNA) concept and the Network Resource Identifier (NRI), which helps route mobile-originated and mobile-terminated traffic to the right operator's core. For the UE, the broadcast system information carries multiple PLMN identities, so a subscriber of any participating operator can select the shared cell as its home network. Roaming and handover procedures are extended so that a UE can move between shared and non-shared cells without losing service.

From a regulatory and commercial perspective, network sharing has become an important tool for meeting coverage obligations, particularly in rural and underserved areas, and for reducing the environmental footprint of mobile networks. Regulators in many markets explicitly permit or even encourage it, subject to competition safeguards. However, sharing raises questions about differentiation, spectrum usage rights, and infrastructure ownership, which is why 3GPP provides several architectures with different degrees of sharing.

In the 5G era, the concept continues to evolve. 5G supports RAN sharing through mechanisms such as multiple PLMN broadcast, network slicing, and the support of Neutral Host operators, allowing several operators to use the same 5G RAN while each maintains its own slice, policies, and core. The term 'Shared Network' therefore remains relevant across all generations, covering a spectrum of cooperation from passive site sharing up to full active RAN and core sharing.

Purpose & Motivation

Network sharing exists to solve the economic and practical problem of deploying mobile networks in a competitive but resource-constrained environment. Building a nationwide radio access network requires enormous capital expenditure on sites, towers, power, transmission, and equipment, and it is often not economically viable for every operator — especially new entrants or smaller operators — to replicate this infrastructure. Sharing allows operators to divide these costs, accelerate coverage rollout, and reach areas where a single operator's business case would fail.

Historically, before 3GPP standardized shared network architectures, operators used bilateral commercial agreements, often only for passive infrastructure such as towers. This lacked standardized interfaces and procedures, making multi-operator access to a shared RAN difficult and error-prone. 3GPP TR 22.951 addressed this gap by defining standard architectures (GWCN, MOCN, RAN sharing) and procedures, such as shared network area handling and NRI-based core network selection, so that equipment from different vendors and operators could interoperate.

The concept also supports regulatory goals. Universal service obligations, rural coverage mandates, and environmental targets often favor shared infrastructure over duplicated deployments. At the same time, sharing must not eliminate competition, so 3GPP architectures preserve operator control over core networks, subscriber data, and services, allowing operators to share costs while still differentiating on tariffs and value-added services.