Public land mobile network

In telecommunication, apublic land mobile network(PLMN) is a combination of wireless communication services offered by a specific operator in a specific country.A PLMN typically consists of several cellular technologies likeGSM/2G,UMTS/3G,LTE/4G,NR/5G, offered by a single operator within a given country, often referred to as acellular network.

PLMN code

A PLMN is identified by a globally unique PLMN code, which consists of aMCC (Mobile Country Code) and MNC (Mobile Network Code).Hence, it is a five- to six-digit number identifying a country, and a mobile network operator in that country, usually represented in the form 001-01 or 001–001.

A PLMN is part of a:

• Location Area Identity (LAI)(PLMN and Location Area Code)
• Cell Global Identity (CGI)(LAI and Cell Identifier)
• IMSI(seePLMN code and IMSI)

Leading zeros in PLMN codes

Note that an MNC can be of two-digit form and three-digit form with leading zeros. It is administered by the respective national numbering plan administrator.From PLMN assignments, it is apparent that such dualities of two-digit and three-digit MNCs with the same number value are avoided (see thelist of mobile country codes and mobile network codes). An example for an actual three-digit/two-digit MNC with leading zeros is inBermuda MCC,350-007 and 350-00, 350-01.

PLMN code and IMSI

TheIMSI,which identifies a SIM or USIM for one subscriber, typically starts with the PLMN code. For example, an IMSI belonging to the PLMN 262-33 would look like 262330000000001. Mobile phones use this to detectroaming,so that a mobile phone subscribed on a network with a PLMN code that mismatches the start of the USIM's IMSI will typically display an "R" on the icon that indicates connection strength.

PLMN services

A PLMN typically offers the following services to a mobile subscriber:

• Emergency calls to local Fire/Ambulance/Police stations.
• Voice calls to/from any other PLMN ( "cellular network" ) orPSTN( "landline"/VoIP).
• Short message service(SMS) services to/from any other PLMN orSIPservice (the original form oftextingon a mobile phone, now often replaced byMessaging apps).
• Multimedia Messaging Service(MMS) services to/from any other PLMN or SIP service.
• Unstructured Supplementary Service Data(USSD) for operator specific interactions (e.g. dialing "*#100#" to indicate the current balance).
• Internet data connectivity for arbitrary services, e.g. viaGPRSinGSM,IuPSinUMTS,orLTE.

The availability, quality and bandwidth of these services strongly depends on the particular technology used to implement a PLMN.