Helpful A-Z glossary listing key terms and their definition.

  • 2G is short for second-generation wireless telephone technology. Second-generation 2G cellular telecoms networks were commercially launched on the GSM standard.
  • 3G is the third-generation of mobile telecommunications technology. This is based on a set of standards used for mobile devices and mobile telecommunications use services and networks that comply with the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union. 3G finds application in wireless voice telephony, mobile internet access, fixed wireless internet access, video calls and mobile television.


The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations, known as the Organisational Partners. The initial scope of 3GPP was to make a globally applicable, third-generation (3G) mobile phone system specification. This was to be based on evolved Global System for Mobile Communications (GSM) specifications within the scope of the International Mobile Telecommunications-2000 project of the International Telecommunication Union (ITU). The scope was later enlarged to include the development and maintenance of:

  • GSM and related “2G” and “2.5G” standards including GPRS and EDGE;
  • UMTS and related “3G” standards including HSPA;
  • LTE and related “4G” standards; and
  • An evolved IP Multimedia Subsystem (IMS) developed in an access independent manner.


4G, short for fourth-generation, is the fourth generation of mobile telecommunications technology, succeeding 3G and preceding 5G. A 4G provides mobile broadband internet access and over some networks voice services (known as VoLTE). Potential and current applications include amended mobile web access, IP telephony, gaming services, high-definition mobile television, video conferencing, 3D television and cloud computing.


5G (5th generation mobile networks or 5th generation wireless systems) denotes the next major phase of mobile telecommunications standards beyond the current 4G/IMT-Advanced standards. 5G has speeds beyond what 4G can offer.

Read more about our work on 5G here.

Advanced Communications

Advanced Communications is a GSMA term that refers to enhanced calling and messaging features such as VoLTE, VoWiFi, ViLTE and RCS. Although designed principally for an all-IP world, on 4G and in the future 5G networks, some features will work on existing 3G networks.

All-IP communications

Internet Protocol (IP) is the most successful technology for data transmission worldwide. The introduction of all-IP considerably simplifies communication, with all services – including fixed network telephony – run over the same network. The switch-over to IP is currently taking place all over the world and means that landlines, televisions, mobile phones and the internet – plus all related services – will communicate consistently via IP, that is, in a single language.


Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session. The circuit functions as if the nodes were physically connected, as with an electrical circuit.


Evolved Multimedia Broadcast Multicast Services (eMBMS) is a point-to-multipoint interface specification for existing and upcoming 3GPP cellular networks, which is designed to provide efficient delivery of broadcast and multicast services, both within a cell as well as within the core network. For broadcast transmission across multiple cells, it defines transmission via single-frequency network configurations. Target applications include mobile television and radio broadcasting, as well as file delivery and emergency alerts.

Enriched calling

The GSMA term, which refers to calls that have enhanced features such as VoLTE, ViLTE and RCS. Read more


GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile) 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 phones, first deployed in Finland in July 1991. As of 2014, it has become the default global standard for mobile communications – with over 90 per cent market share, operating in over 219 countries and territories.

HD voice

The GSMA supports a universal HD voice logo that gives the consumer confidence that a defined quality of experience is provided when making an end-to-end HD voice call. It provides organisations with the opportunity to clearly identify and promote HD voice-enabled devices and services to a global audience. Read more


The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS) is an architectural framework for delivering IP multimedia services. Historically, mobile phones have provided voice call services over a switched-circuit-style network, rather than strictly over an IP packet-switched network. Alternative methods of delivering voice or other multimedia services over IP have become available on smartphones (e.g. VoIP or Skype), but they have not become standardised across the industry. IMS is an architectural framework to provide such standardisation.


Interconnection is the physical linking of a carrier’s network with equipment or facilities not belonging to that network. The term may refer to a connection between a carrier’s facilities and the equipment belonging to its customer, or to a connection between two (or more) carriers. Read more


LTE Advanced is a mobile communication standard and a major enhancement of the Long-Term Evolution (LTE) standard. It was formally submitted as a candidate 4G system to ITU-T in late 2009, as meeting the requirements of the IMT-Advanced standard, and was standardised by the 3rd Generation Partnership Project (3GPP) in March 2011 as 3GPP Release 10.


LTE, an abbreviation for Long-Term Evolution, commonly marketed as 4G LTE, is a standard for wireless communication of high-speed data for mobile phones and data terminals. It is based on the GSM/EDGE and UMTS/HSPA network technologies, increasing the capacity and speed using a different radio interface together with core network improvements. The standard is developed by the 3GPP (3rd Generation Partnership Project).

LTE is the natural upgrade path for carriers with both GSM/UMTS networks and CDMA2000 networks. The different LTE frequencies and bands used in different countries will mean that only multi-band phones will be able to use LTE in all countries where it is supported.

Native devices

Native devices refer to devices that have out-of-the-box compatibility with IP-networks.

Future Network Programme

The GSMA’s Future Networks Programme works with the mobile industry to deliver a collaborative, coordinated way of accelerating the development of all-IP mobile communications. Ultimately, the programme aims to create a world in which all-IP global networks let mobile users enjoy seamless, secure, enriched communications, on any device. Read more


In broadcasting, over-the-top content (OTT) refers to the delivery of audio, video, and other media over the internet without the involvement of a multiple-system operator in the control or distribution of the content. The internet provider may be aware of the contents of the Internet Protocol packets but is not responsible for, nor able to control, the viewing abilities, copyrights, and/or other redistribution of the content.


A private branch exchange (PBX) is a telephone exchange or switching system that serves a private organisation and performs concentration of central office lines or trunks and provides intercommunication between a large number of telephone stations in the organisation.


Quality of Service (QoS) is the overall performance of a telephony or computer network, particularly the performance seen by the users of the network.

Rich Communications Services (RCS)

RCS (sometimes referred to as RBM or RCS Business Messaging) services – such as instant messaging, chat, live video and file sharing – work across all networks and on any Android device, and mark a transition from circuit-switched technology to an all-IP world that is changing the way people communicate. Read more


Roaming helps ensure that a travelling wireless device (typically a mobile phone) is kept connected to a network without breaking the connection. In wireless telecommunications, traditional roaming is a general term referring to the ability for a cellular customer to automatically make and receive voice calls, send and receive data, or access other services, including home data services, when travelling outside the geographical coverage area of the home network, by means of using a visited network. For example: should you travel beyond your cell phone company’s transmitter range, your cell phone would automatically hop onto another phone company’s service, if available. Read more


Software-Defined Networking (SDN) is a new approach to designing, building, and managing networks. The SDN method centralises control of the network by separating the control logic to off-device computer resources.


Long-Term Evolution Time-Division Duplex (LTE-TDD), also referred to as Time-Division Long-Term Evolution (TD-LTE), is a 4G telecommunications technology and standard co-developed by an international coalition of companies, including China Mobile, Datang Telecom, Huawei, Nokia Solutions and Networks, Qualcomm, Samsung and ST-Ericsson. It is one of two variants of the Long-Term Evolution (LTE) technology standard, the other being Frequency-Division Long-Term Evolution (LTE-FDD).

Video over LTE (ViLTE)

ViLTE, an acronym for Video over LTE, is a conversational, i.e. person-to-person, video service based on the IP Multimedia Subsystem (IMS) core network. It has specific profiles for the control and media planes of the video service and uses LTE as the radio access medium. Read more

Voice over LTE (VoLTE)

VoLTE, an acronym for Voice over LTE, which is based on the IP Multimedia Subsystem (IMS) network, with specific profiles for control and media planes of voice service on LTE. VoLTE will facilitate far richer, multi-media voice services, increasing the service quality (by offering HD Voice) and interest delivered to consumers. Read more

Voice over Wi-Fi (VoWi-Fi)

VoWi-Fi stands for Voice over Wi-Fi. VoLTE calls get transferred seamlessly and completed over a Wi-Fi connection where applicable. Read more


Voice over IP (VoIP) is a methodology and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the internet.

VoLTE roaming

VoLTE calling different carriers, providing the same level of call quality.