Public land mobile network
Encyclopedia
A public land mobile network (PLMN) is a regulatory term in telecommunications. A PLMN is a network
that is established and operated by an administration or by a recognized operating agency (ROA) for the specific purpose of providing land mobile
telecommunications services to the public.
A PLMN is identified by the Mobile Country Code (MCC) and the Mobile Network Code
(MNC). Each operator providing mobile services has its own PLMN. PLMNs interconnect with other PLMNs and Public switched telephone network
s (PSTN) for telephone communications
or with internet service provider
s for data
and internet
access of which links are defined as interconnect links between providers. These links mostly incorporate SDH digital transmission networks via fibre optic on land and digital microwave links.
Access to PLMN services is achieved by means of an air interface
involving radio
communications between mobile phone
s or other wireless
enabled user equipment and land based radio transmitters
or radio base stations
or even fibre optic distributed SDH network between mobile base stations and central stations via SDH equipment (ADMs) with integrated IP network services.
(PSTN) in order to route calls.
The PSTN is the world's collection of interconnected voice-oriented public telephone networks, in much the same way that the Internet is the concentration of the world's public IP-based packet-switched networks. It is both commercially- and government-owned. PSTN service may be informally called Plain Old Telephone Service
or POTS. This aggregation of circuit-switching
telephone networks has evolved greatly from the days of Alexander Graham Bell
, and in the late 20th century became almost entirely digital in nature — except for the final link from the central (local) telephone office to the user (the local loop
). It also extends into mobile as well as fixed telephones.
The PSTN also furnishes much of the Internet's long-distance infrastructure and, for the majority of users, the access network
as well. Because Internet Service Providers (ISPs) pay the long-distance carriers for access to their infrastructure, and share the circuits among many users through packet switching
, the end Internet user avoids having to pay usage tolls to anyone other than their ISP.
Many observers believe that the long-term future of the PSTN is to be just one application of the Internet — however, the Internet has some way to go before this transition can be made. For example, the Quality of Service
(QoS) guarantee is one aspect that needs to be improved for Voice over IP
(VOIP) technology.
The PSTN is largely governed by technical standards created by the ITU-T
, and uses E.163/E.164 addresses (usually called telephone number
s) for addressing. A number of large private telephone networks are not connected to the PSTN, and are used for military purposes (such as the Defense Switched Network
). There are also private networks run by large companies which are linked to the PSTN, but only through controlled gateways such as private branch exchanges.
PLMN is network that is established and operated by an administration or by a recognized operating agency (ROA) for the specific purpose of providing land mobile telecommunications services to the public. A PLMN may be considered as an extension of a fixed network, e.g. the Public Switched Telephone Network (PSTN) or as an integral part of the PSTN. This is just one view-point on PLMN. PLMN mostly refers to the whole system of hardware and software which enables wireless communication, irrespective of the service area or service provider. Sometimes separate PLMN is defined for each country or for each service provider. Its case is same as that of PSTN. Sometimes it refers to the whole circuit-switched system, or else specific to each country.
PLMN is not a term specific to GSM. In fact GSM can be treated as an example of a PLMN system. These days (as of January, 2006) much discussions are going on to form the structure of UMTS PLMN for the third generation systems. Access to PLMN services is achieved by means of an air interface involving radio communications between mobile phones or other wireless enabled user equipment and land based radio transmitters or radio base stations PLMNs interconnect with other PLMNs and PSTNs for telephone communications or with internet service providers for data and internet access.
A public land mobile network may be defined as a number of mobile services switching centre areas within a common numbering plan and a common routing plan. With respect to their functions, the PLMNs may be regarded as independent communications entities, even though different PLMNs may be interconnected through the PSTN/ISDN for the forwarding of calls or network information. The MSCs of a PLMN can be interconnected similarly to allow interaction. A PLMN may have several interfaces with the fixed network (e.g. one for each MSC). Inter-working between two PLMNs may be performed via an international switching centre. The PLMN is connected via an NCP to the PSTN/ISDN. If there are two mobile service suppliers in the same country, they can be connected through the same PSTN/ISDN.
and software).
(BSS), and the operation and support system (OSS).
There are three viewpoints of interoperability between PLMN and PSTN:
Telecommunications network
A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections...
that is established and operated by an administration or by a recognized operating agency (ROA) for the specific purpose of providing land mobile
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
telecommunications services to the public.
A PLMN is identified by the Mobile Country Code (MCC) and the Mobile Network Code
Mobile Network Code
A Mobile Network Code is used in combination with a Mobile Country Code to uniquely identify a mobile phone operator/carrier using the GSM/LTE, CDMA, iDEN, TETRA and UMTS public land mobile networks and some satellite mobile networks...
(MNC). Each operator providing mobile services has its own PLMN. PLMNs interconnect with other PLMNs and Public switched telephone network
Public switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...
s (PSTN) for telephone communications
Telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...
or with internet service provider
Internet service provider
An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
s for data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
and internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
access of which links are defined as interconnect links between providers. These links mostly incorporate SDH digital transmission networks via fibre optic on land and digital microwave links.
Access to PLMN services is achieved by means of an air interface
Air interface
In mobile or wireless communication, the air interface is the radio-based communication link between the mobile station and the active base station...
involving radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
communications between mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s or other wireless
Wireless
Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...
enabled user equipment and land based radio transmitters
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
or radio base stations
Base station
The term base station can be used in the context of land surveying and wireless communications.- Land surveying :In the context of external land surveying, a base station is a GPS receiver at an accurately-known fixed location which is used to derive correction information for nearby portable GPS...
or even fibre optic distributed SDH network between mobile base stations and central stations via SDH equipment (ADMs) with integrated IP network services.
Public switched telephone network
Public Land Mobile Networks need to connect to the Public Switched Telephone NetworkPublic switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...
(PSTN) in order to route calls.
The PSTN is the world's collection of interconnected voice-oriented public telephone networks, in much the same way that the Internet is the concentration of the world's public IP-based packet-switched networks. It is both commercially- and government-owned. PSTN service may be informally called Plain Old Telephone Service
Plain old telephone service
Plain old telephone service is the voice-grade telephone service that remains the basic form of residential and small business service connection to the telephone network in many parts of the world....
or POTS. This aggregation of circuit-switching
Circuit switching
Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the...
telephone networks has evolved greatly from the days of Alexander Graham Bell
Alexander Graham Bell
Alexander Graham Bell was an eminent scientist, inventor, engineer and innovator who is credited with inventing the first practical telephone....
, and in the late 20th century became almost entirely digital in nature — except for the final link from the central (local) telephone office to the user (the local loop
Local loop
In telephony, the local loop is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the carrier or telecommunications service provider's network...
). It also extends into mobile as well as fixed telephones.
The PSTN also furnishes much of the Internet's long-distance infrastructure and, for the majority of users, the access network
Access network
An access network is that part of a telecommunications network which connects subscribers to their immediate service provider. It is contrasted with the core network, which connects local providers to each other...
as well. Because Internet Service Providers (ISPs) pay the long-distance carriers for access to their infrastructure, and share the circuits among many users through packet switching
Packet switching
Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network...
, the end Internet user avoids having to pay usage tolls to anyone other than their ISP.
Many observers believe that the long-term future of the PSTN is to be just one application of the Internet — however, the Internet has some way to go before this transition can be made. For example, the Quality of Service
Quality of service
The quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
(QoS) guarantee is one aspect that needs to be improved for Voice over IP
Voice over IP
Voice over Internet Protocol is a family of technologies, methodologies, communication protocols, and transmission techniques for the delivery of voice communications and multimedia sessions over Internet Protocol networks, such as the Internet...
(VOIP) technology.
The PSTN is largely governed by technical standards created by the ITU-T
ITU-T
The ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....
, and uses E.163/E.164 addresses (usually called telephone number
Telephone number
A telephone number or phone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short — as few as one, two or three digits — and were given orally to a switchboard operator...
s) for addressing. A number of large private telephone networks are not connected to the PSTN, and are used for military purposes (such as the Defense Switched Network
Defense Switched Network
The Defense Switched Network is a primary information transfer network for the Defense Information Systems Network . The DSN provides the worldwide non-secure voice, secure voice, data, facsimile, and video teleconferencing services for DOD Command and Control elements, their supporting...
). There are also private networks run by large companies which are linked to the PSTN, but only through controlled gateways such as private branch exchanges.
Specifications
A GSM PLMN may be described by a limited set of access interfaces and a limited set of GSM PLMN connection types to support the telecommunication services described in the GSM 02-series of specifications.PLMN is network that is established and operated by an administration or by a recognized operating agency (ROA) for the specific purpose of providing land mobile telecommunications services to the public. A PLMN may be considered as an extension of a fixed network, e.g. the Public Switched Telephone Network (PSTN) or as an integral part of the PSTN. This is just one view-point on PLMN. PLMN mostly refers to the whole system of hardware and software which enables wireless communication, irrespective of the service area or service provider. Sometimes separate PLMN is defined for each country or for each service provider. Its case is same as that of PSTN. Sometimes it refers to the whole circuit-switched system, or else specific to each country.
PLMN is not a term specific to GSM. In fact GSM can be treated as an example of a PLMN system. These days (as of January, 2006) much discussions are going on to form the structure of UMTS PLMN for the third generation systems. Access to PLMN services is achieved by means of an air interface involving radio communications between mobile phones or other wireless enabled user equipment and land based radio transmitters or radio base stations PLMNs interconnect with other PLMNs and PSTNs for telephone communications or with internet service providers for data and internet access.
A public land mobile network may be defined as a number of mobile services switching centre areas within a common numbering plan and a common routing plan. With respect to their functions, the PLMNs may be regarded as independent communications entities, even though different PLMNs may be interconnected through the PSTN/ISDN for the forwarding of calls or network information. The MSCs of a PLMN can be interconnected similarly to allow interaction. A PLMN may have several interfaces with the fixed network (e.g. one for each MSC). Inter-working between two PLMNs may be performed via an international switching centre. The PLMN is connected via an NCP to the PSTN/ISDN. If there are two mobile service suppliers in the same country, they can be connected through the same PSTN/ISDN.
Objectives of a GSM PLMN
The general objective of a PLMN is to facilitate wireless communication and to interlink the wireless network with the fixed wired network. The PLMN was specified by the European Telecommunications Standard Institute (ETSI) following up with their GSM specification. Even as times changed, the GSM PLMN objectives conceptually remained the same.- To give access to the GSM network for a mobile subscriber in a country that operates the GSM system.
- To provide facilities for automatic roaming, locating and updating of mobile subscribers.
- To provide the subscriber a wide range of services and facilities, both voice and non voice, that are compatible with those offered by existing networks like PSTN and ISDN.
Services
- Bearer Services : These services give the subscriber the capacity required to transmit appropriate signals between certain access points (user-network interfaces).
- Tele Services : Provide subscriber with necessary capabilities including terminal equipment function to communicate with other subscribers.
- Supplementary Services : Modify or supplement basic telecommunication services and are offered together or in association with basic communication services.
Architecture
GSM architecture is basically the PLMN architecture itself as the subject is GSM PLMN. Various interfaces between the GSM subsystems are to be considered, along with the signaling system and the various components (both hardwareHardware
Hardware is a general term for equipment such as keys, locks, hinges, latches, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts. Household hardware is typically sold in hardware stores....
and software).
Subsystems
The GSM PLMN is divided into signaling network and mobile network. Each of these has various subsystems, which are grouped under three major systems: the Network and Switching Subsystem (NSS), the Base Station SubsystemBase Station Subsystem
The base station subsystem is the section of a traditional cellular telephone network which is responsible for handling traffic and signaling between a mobile phone and the network switching subsystem...
(BSS), and the operation and support system (OSS).
Operation and Support System (OSS)
The operations and maintenance center (OMC) is connected to all equipment in the switching system and to the BSC. The implementation of OMC is called the operation and support system (OSS). The OSS is the functional entity from which the network operator monitors and controls the system. The purpose of OSS is to offer the customer cost-effective support for centralized, regional, and local operational and maintenance activities that are required for a GSM network. An important function of OSS is to provide a network overview and support the maintenance activities of different operation and maintenance organizations.Additional functional elements
Other functional elements shown are as follows:- message center (MXE)-The MXE is a node that provides integrated voice, fax, and data messaging. Specifically, the MXE handles short message service, cell broadcast, voice mail, fax mail, email, and notification.
- mobile service node (MSN)-The MSN is the node that handles the mobile intelligent network (IN) services.
- gateway mobile services switching center (GMSC)-A gateway is a node used to interconnect two networks. The gateway is often implemented in an MSC. The MSC is then referred to as the GMSC.
- GSM interworking unit (GIWU)-The GIWU consists of both hardware and software that provides an interface to various networks for data communications. Through the GIWU, users can alternate between speech and data during the same call. The GIWU hardware equipment is physically located at the MSC/VLR.
There are three viewpoints of interoperability between PLMN and PSTN:
- PLMN can be treated as an integral part of PSTN, extending the services offered by PSTN to wireless networks.
- PSTN can be treated as an integral part of PLMN, through which it facilitates call routing.
- PLMN and PSTN can be treated as two separate systems, which depends on each other or connects to each other for the purpose of call routing.