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In telecommunication, a public land mobile network (PLMN) is a combination of wireless communication services offered by a specific operator in a specific country. [1] [2] A PLMN typically consists of several cellular technologies like GSM/2G, UMTS/3G, LTE/4G, NR/5G, offered by a single operator within a given country, often referred to as a cellular network.
A PLMN is identified by a globally unique PLMN code, which consists of a MCC (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:
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 [3] . From PLMN assignments, it is apparent that such dualities of two-digit and three-digit MNCs with the same number value are avoided (see the list of mobile country codes and mobile network codes). An example for an actual three-digit/two-digit MNC with leading zeros is in Bermuda MCC, 350-007 and 350-00, 350-01.
The IMSI, 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 detect roaming, 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.
A PLMN typically offers the following services to a mobile subscriber:
The availability, quality and bandwidth of these services strongly depends on the particular technology used to implement a PLMN.
The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation (2G) digital cellular networks used by mobile devices such as mobile phones and tablets. GSM is also a trade mark owned by the GSM Association. GSM may also refer to the Full Rate voice codec.
General Packet Radio Service (GPRS), also called 2.5G, is a packet oriented mobile data standard on the 2G cellular communication network's global system for mobile communications (GSM). GPRS was established by European Telecommunications Standards Institute (ETSI) in response to the earlier CDPD and i-mode packet-switched cellular technologies. It is now maintained by the 3rd Generation Partnership Project (3GPP).
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP, UMTS is a component of the International Telecommunication Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing cdmaOne technology. UMTS uses wideband code-division multiple access (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators.
The international mobile subscriber identity is a number that uniquely identifies every user of a cellular network. It is stored as a 64-bit field and is sent by the mobile device to the network. It is also used for acquiring other details of the mobile in the home location register (HLR) or as locally copied in the visitor location register. To prevent eavesdroppers from identifying and tracking the subscriber on the radio interface, the IMSI is sent as rarely as possible and a randomly-generated TMSI is sent instead.
A SIM card is an integrated circuit (IC) intended to securely store an international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephone devices. Technically the actual physical card is known as a universal integrated circuit card (UICC); this smart card is usually made of PVC with embedded contacts and semiconductors, with the SIM as its primary component. In practice the term "SIM card" is still used to refer to the entire unit and not simply the IC.
Mobility management is one of the major functions of a GSM or a UMTS network that allows mobile phones to work. The aim of mobility management is to track where the subscribers are, allowing calls, SMS and other mobile phone services to be delivered to them.
Network switching subsystem (NSS) is the component of a GSM system that carries out call out and mobility management functions for mobile phones roaming on the network of base stations. It is owned and deployed by mobile phone operators and allows mobile devices to communicate with each other and telephones in the wider public switched telephone network (PSTN). The architecture contains specific features and functions which are needed because the phones are not fixed in one location.
Unstructured Supplementary Service Data (USSD), sometimes referred to as "quick codes" or "feature codes", is a communications protocol used by GSM cellular telephones to communicate with the mobile network operator's computers. USSD can be used for WAP browsing, prepaid callback service, mobile-money services, location-based content services, menu-based information services, and as part of configuring the phone on the network. The service does not require a messaging app, and does not incur charges.
MSISDN is a number uniquely identifying a subscription in a Global System for Mobile communications or a Universal Mobile Telecommunications System mobile network. It is the mapping of the telephone number to the subscriber identity module in a mobile or cellular phone. This abbreviation has several interpretations, the most common one being "Mobile Station International Subscriber Directory Number".
GSM frequency bands or frequency ranges are the cellular frequencies designated by the ITU for the operation of GSM mobile phones and other mobile devices.
The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS) is a standardised architectural framework for delivering IP multimedia services. Historically, mobile phones have provided voice call services over a circuit-switched-style network, rather than strictly over an IP packet-switched network. Various voice over IP technologies are available on smartphones; IMS provides a standard protocol across vendors.
The universal integrated circuit card (UICC) is the smart card used in mobile terminals in 2G (GSM), 3G (UMTS), 4G (LTE), and 5G networks. The UICC ensures the integrity and security of all kinds of personal data, and it typically holds a few hundred kilobytes. The official definition for UICC is found in ETSI TR 102 216, where it is defined as a "smart card that conforms to the specifications written and maintained by the ETSI Smart Card Platform project". In addition, the definition has a note that states that "UICC is neither an abbreviation nor an acronym". NIST SP 800-101 Rev. 1 and NIST Computer Security Resource Center Glossary state that, "A UICC may be referred to as a SIM, USIM, RUIM or CSIM, and is used interchangeably with those terms", though this is an over-simplification. The primary component of a UICC is a SIM card.
An Access Point Name (APN) is the name of a gateway between a mobile network and another computer network, frequently the public Internet.
An international mobile subscriber identity-catcher, or IMSI-catcher, is a telephone eavesdropping device used for intercepting mobile phone traffic and tracking location data of mobile phone users. Essentially a "fake" mobile tower acting between the target mobile phone and the service provider's real towers, it is considered a man-in-the-middle (MITM) attack. The 3G wireless standard offers some risk mitigation due to mutual authentication required from both the handset and the network. However, sophisticated attacks may be able to downgrade 3G and LTE to non-LTE network services which do not require mutual authentication.
An IP Multimedia Services Identity Module (ISIM) is an application residing on the UICC, an IC card specified in TS 31.101. This module could be on a UMTS 3G or IMS VoLTE network. It contains parameters for identifying and authenticating the user to the IMS. The ISIM application can co-exist with SIM and USIM on the same UICC making it possible to use the same smartcard in both GSM networks and earlier releases of UMTS.
The ITU-T Recommendation E.212 defines mobile country codes (MCC) as well as mobile network codes (MNC).
In telecommunications, a femtocell is a small, low-power cellular base station, typically designed for use in a home or small business. A broader term which is more widespread in the industry is small cell, with femtocell as a subset. It typically connects to the service provider's network via the Internet through a wired broadband link ; current designs typically support four to eight simultaneously active mobile phones in a residential setting depending on version number and femtocell hardware, and eight to sixteen mobile phones in enterprise settings. A femtocell allows service providers to extend service coverage indoors or at the cell edge, especially where access would otherwise be limited or unavailable. Although much attention is focused on WCDMA, the concept is applicable to all standards, including GSM, CDMA2000, TD-SCDMA, WiMAX and LTE solutions.
SIM Application Toolkit (STK) is a standard of the GSM system which enables the subscriber identity module to initiate actions which can be used for various value-added services. Similar standards exist for other network and card systems, with the USIM Application Toolkit (USAT) for USIMs used by newer-generation networks being an example. A more general name for this class of Java Card-based applications running on UICC cards is the Card Application Toolkit (CAT).
Cell Global Identity (CGI) is a globally unique identifier for a Base Transceiver Station in mobile phone networks. It consists of four parts: Mobile Country Code (MCC), Mobile Network Code (MNC), Location Area Code (LAC) and Cell Identification (CI). It is an integral part of 3GPP specifications for mobile networks, for example, for identifying individual base stations to "handover" ongoing phone calls between separately controlled base stations, or between different mobile technologies.
Cellular network standards | |||||||||
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| 0G radio telephones (1946) | |||||||||
| 1G (1979) |
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| 2G (1991) |
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| 2G transitional (2.5G, 2.75G, 2.9G) |
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| 3G (1998) IMT-2000 (2001) |
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| 3G transitional (3.5G, 3.75G, 3.9G) |
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| 4G (2009) IMT Advanced (2013) |
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| 5G (2018) IMT-2020 (2021) |
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