PLMN

A Public Land Mobile Network (PLMN) is the mobile communications network operated by a mobile network operator to provide wireless voice and data services to mobile subscribers. A PLMN encompasses the radio access network that reaches the user equipment and the core network that handles signaling, authentication, routing, and data transport. PLMNs operate under regional or international standards and interconnect with other networks through roaming agreements.

Identity and addressing are central to PLMNs. Each PLMN is identified by a combination of a Mobile Country Code (MCC) and a Mobile Network Code (MNC), collectively known as the PLMN code. The MCC denotes the country, while the MNC identifies the operator within that country. Devices store this information in the SIM or eSIM as part of the IMSI, which is used to locate and authenticate the subscriber within the PLMN.

Home and visiting networks are key concepts. The Home PLMN (HPLMN) is the operator that issues the subscriber’s SIM and manages authentication and billing. When a subscriber travels outside the HPLMN, the network they access is typically a Visited PLMN (VPLMN) via roaming arrangements. The VPLMN cooperates with the HPLMN to provide service, enforce policies, and handle inter-operator billing.

PLMNs support multiple generations of mobile technology, including 2G GSM, 3G UMTS, 4G LTE, and 5G NR. Each generation introduces new core network architectures, such as the EPC in 4G and the 5G core in 5G, while maintaining the PLMN’s role as the operator’s service provider and roaming partner.