GateWay Core Network

Description

The GateWay Core Network (GWCN) is a specific model of network sharing defined in 3GPP, detailed in TS 23.251. In this architecture, two or more participating operators (each with their own PLMN ID) share a common set of core network nodes, which act as a gateway for all their respective radio access networks (RANs). The shared core network typically includes critical nodes like the Mobile Switching Center (MSC), Serving GPRS Support Node (SGSN), and potentially the Home Location Register (HLR) or Home Subscriber Server (HSS). Each operator maintains its own independent RAN, broadcast on its unique PLMN identity, but all subscriber traffic is routed through and processed by the shared core infrastructure.

Operationally, when a user attaches to a cell broadcasting Operator A's PLMN, the connection is established through the shared RAN and then handed over to the common GWCN nodes. The GWCN identifies the user's home operator based on the International Mobile Subscriber Identity (IMSI) and applies the appropriate policies, services, and charging rules for that operator. The MSC and SGSN in the GWCN are configured to handle subscribers from all sharing partners, requiring robust subscriber data management and policy segregation mechanisms. Key interfaces, such as the Iu interface between the RNC and the core, connect to the shared nodes.

This architecture relies on careful configuration to ensure logical separation of traffic, billing, and operational support systems (OSS). The shared core nodes must support multiple PLMN contexts and route signaling and user data to the correct operator-specific backend systems (like charging gateways). The GWCN model is more integrated than other sharing models like the Multi-Operator Core Network (MOCN), as it involves sharing the core network gateways themselves, leading to higher cost savings but also greater integration complexity and mutual dependency between the operators.

Purpose & Motivation

GWCN was developed primarily to address the high capital expenditure (CAPEX) and operational expenditure (OPEX) associated with deploying and maintaining independent core networks, especially for new market entrants or operators in rural areas. Prior to network sharing standards, each operator needed a full, duplicate set of network infrastructure, which was economically inefficient and slowed down network rollout. The GWCN model provided a standardized way for operators to collaborate and share the most expensive parts of the network—the core switching and packet routing nodes—while still competing on services and retaining their brand identity via their own radio spectrum and PLMN.

It solved the problem of infrastructure redundancy and underutilization. By sharing the MSC and SGSN, operators could achieve significant cost savings on site rental, hardware, power, and maintenance. This was particularly motivated in the era of 3G/UMTS rollout, where costs were high. The model also facilitated faster coverage expansion, as operators could leverage a shared core to serve areas where building an independent core was not viable. It represented a strategic shift from purely competitive infrastructure to collaborative infrastructure in certain geographical or economic contexts, as formalized by 3GPP standards to ensure interoperability and clear operational boundaries.