Media gateway
Encyclopedia
A Media gateway is a translation device or service that converts digital media streams between disparate telecommunications networks such as PSTN, SS7, Next Generation Networks (2G
, 2.5G and 3G
radio access networks) or PBX. Media gateways enable multimedia
communications across Next Generation Networks over multiple transport protocols such as Asynchronous Transfer Mode
(ATM) and Internet Protocol
(IP).
Because the media gateway connects different types of networks, one of its main functions is to convert between different transmission and coding techniques (see also Transcode
). Media streaming functions such as echo cancellation
, DTMF, and tone sender are also located in the media gateway.
Media gateways are often controlled by a separate Media Gateway Controller
which provides the call control and signaling functionality. Communication between media gateways and Call Agent
s is achieved by means of protocols such as MGCP or Megaco
(H.248) or Session Initiation Protocol
(SIP). Modern media gateways used with SIP are often stand-alone units with their own call and signaling control integrated and can function as independent, intelligent SIP end-points.
Voice over Internet Protocol (VoIP) media gateways perform the conversion between TDM
voice to a media streaming protocol (usually Real-time Transport Protocol
, RTP), as well as a signaling protocol used in the VoIP system.
Mobile access Media Gateways connect the radio access networks of a public land mobile network PLMN to a Next Generation Core network
. 3GPP
standards define the functionality of CS-MGW and IMS-MGW for UTRAN
and GERAN
based PLMNs.
2G
2G is short for second-generation wireless telephone technology. Second generation 2G cellular telecom networks were commercially launched on the GSM standard in Finland by Radiolinja in 1991...
, 2.5G and 3G
3G
3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 specifications by the International Telecommunication Union...
radio access networks) or PBX. Media gateways enable multimedia
Multimedia
Multimedia is media and content that uses a combination of different content forms. The term can be used as a noun or as an adjective describing a medium as having multiple content forms. The term is used in contrast to media which use only rudimentary computer display such as text-only, or...
communications across Next Generation Networks over multiple transport protocols such as Asynchronous Transfer Mode
Asynchronous Transfer Mode
Asynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
(ATM) and Internet Protocol
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
(IP).
Because the media gateway connects different types of networks, one of its main functions is to convert between different transmission and coding techniques (see also Transcode
Transcode
Transcoding is the direct digital-to-digital data conversion of one encoding to another, such as for movie data files or audio files. This is usually done in cases where a target device does not support the format or has limited storage capacity that mandates a reduced file size, or to convert...
). Media streaming functions such as echo cancellation
Echo cancellation
'The term echo cancellation is used in telephony to describe the process of removing echo from a voice communication in order to improve voice quality on a telephone call...
, DTMF, and tone sender are also located in the media gateway.
Media gateways are often controlled by a separate Media Gateway Controller
Media Gateway Controller
A Media Gateway Controller is a system used in certain Voice over IPtelephony architectures. An MGC controls a number of dumb terminals, the Media Gateways...
which provides the call control and signaling functionality. Communication between media gateways and Call Agent
Call Agent
In a telecommunications system, a Call Agent is a Media Gateway Controller when used in the context of MGCP. It is concerned with the handling of specific services to users. MGCP is a server client protocol developed by Cisco, to make Industry Standard. MGCP is the only Server Client Voice...
s is achieved by means of protocols such as MGCP or Megaco
Megaco
Megaco is a gateway control protocol. and an implementation of the Media Gateway Control Protocol architecture for controlling media gateways in Internet Protocol networks and the public switched telephone network...
(H.248) or Session Initiation Protocol
Session Initiation Protocol
The Session Initiation Protocol is an IETF-defined signaling protocol widely used for controlling communication sessions such as voice and video calls over Internet Protocol . The protocol can be used for creating, modifying and terminating two-party or multiparty sessions...
(SIP). Modern media gateways used with SIP are often stand-alone units with their own call and signaling control integrated and can function as independent, intelligent SIP end-points.
Voice over Internet Protocol (VoIP) media gateways perform the conversion between TDM
Time-division multiplexing
Time-division multiplexing is a type of digital multiplexing in which two or more bit streams or signals are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent...
voice to a media streaming protocol (usually Real-time Transport Protocol
Real-time Transport Protocol
The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...
, RTP), as well as a signaling protocol used in the VoIP system.
Mobile access Media Gateways connect the radio access networks of a public land mobile network PLMN to a Next Generation Core network
Core network
A core network, or network core, is the central part of a telecommunication network that provides various services to customers who are connected by the access network. One of the main functions is to route telephone calls across the PSTN....
. 3GPP
3GPP
The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...
standards define the functionality of CS-MGW and IMS-MGW for UTRAN
Utran
Utran is a census town in Surat district in the Indian state of Gujarat.-Geography:Utran is located at . It has an average elevation of 12 metres .-Demographics:...
and GERAN
GERAN
GERAN is an abbreviation for GSM EDGE Radio Access Network. The standards for GERAN are maintained by the 3GPP...
based PLMNs.