Definition
PLMN (Public Land Mobile Network) is the unique identifier for mobile network operators, consisting of MCC (Mobile Country Code) and MNC (Mobile Network Code). For example, China Mobile's PLMN is 46000, where 460 is the MCC and 00 is the MNC. HPLMN refers to the Home PLMN, i.e., the network of the SIM card's subscribed operator; VPLMN refers to the Visited PLMN, i.e., the local operator's network accessed when the device is roaming. PLMN Selection is used for roaming network selection, determining which networks the device will preferentially connect to in cross-border scenarios.
Working Principle
When IoT devices are powered on or enter a new area, they scan the list of available PLMNs and select an access network according to the PLMN Selection strategy. The priority order is usually: HPLMN, the preferred networks in the Preferred Network List, and other Roaming Partner networks. PLMN selection directly affects roaming charges, connection quality, and compliance: accessing different VPLMN may correspond to different Rate Card and Roaming Policy, and the platform needs to configure and issue network selection strategies in ICMP to balance cost and experience.
Application in cross-border ICMP
In the International IoT Cloud Platform (ICMP), PLMN is the basic dimension for connection management. The platform needs to maintain a global PLMN mapping table, linking MCC+MNC with operators, countries, and tariff levels. In the Global Dashboard, devices can be filtered by PLMN to view distribution, usage, and failure rates; in Usage Analytics, roaming costs and traffic distribution can be analyzed by PLMN. SimtoLink ICMP supports configuring the Preferred Network List according to PLMN Selection, allowing customized network selection strategies for different regions and different customers, achieving intelligent roaming and cost optimization.
Relationship with the roaming ecosystem
PLMN is the basis for roaming agreements and settlement. When an operator signs a roaming agreement with Roaming Partner, the accessible PLMN list and billing rules are agreed upon. The ICMP platform needs to interface with the operator's BSS to obtain the relationship between PLMN and tariffs, Quota, and Suspension policies. When a device connects to a certain VPLMN, the platform charges and calculates usage based on the PLMN information in the CDR, supporting Usage Aggregation and Unified Invoice output.