IMS-MGW (IMS media gateway)
Introduction
The IMS (IP Multimedia Subsystem) is a framework that enables the convergence of various multimedia services on the IP network. It is an all-IP network architecture that provides a standardized way to deliver multimedia services such as voice, video, and data over the internet. One of the key components of the IMS architecture is the IMS Media Gateway (IMS-MGW).
IMS Media Gateway
An IMS-MGW is a device that provides the conversion between the IP-based IMS network and the traditional PSTN/ISDN network. The IMS-MGW is responsible for handling the media traffic between these two networks, enabling communication between IMS and non-IMS devices. The IMS-MGW provides several functions, including media conversion, signaling conversion, and media processing.
Media Conversion
The IMS-MGW is responsible for converting the media streams between the IMS network and the PSTN/ISDN network. The IMS network uses packet-based media (RTP/UDP/IP), while the PSTN/ISDN network uses circuit-based media (TDM). The IMS-MGW converts the packet-based media into circuit-based media, and vice versa. This conversion enables communication between IMS devices and traditional PSTN/ISDN devices.
Signaling Conversion
In addition to media conversion, the IMS-MGW also performs signaling conversion between the IMS network and the PSTN/ISDN network. The IMS network uses SIP (Session Initiation Protocol) for signaling, while the PSTN/ISDN network uses SS7 (Signaling System 7). The IMS-MGW translates the SIP messages into SS7 messages and vice versa. This conversion enables the signaling messages to be properly processed by both the IMS network and the PSTN/ISDN network.
Media Processing
The IMS-MGW also provides media processing functions, such as echo cancellation, noise reduction, and tone detection. These functions are necessary to ensure the quality of the voice calls between IMS and non-IMS devices. The media processing functions are performed in real-time, which means that the media traffic is processed as it is being transmitted.
IMS-MGW Architecture
The IMS-MGW is a complex device that consists of several components. The following are the main components of the IMS-MGW:
Media Gateway Controller (MGC)
The MGC is responsible for controlling the IMS-MGW. It provides the interface between the IMS network and the IMS-MGW. The MGC communicates with the IMS network using SIP and with the IMS-MGW using MGCP (Media Gateway Control Protocol).
Media Gateway (MG)
The MG is the physical device that performs the media conversion, signaling conversion, and media processing functions. The MG communicates with the MGC using MGCP.
Signaling Gateway (SG)
The SG is responsible for providing the signaling conversion function. It translates the SIP messages from the IMS network into SS7 messages for the PSTN/ISDN network, and vice versa. The SG communicates with the MGC using SIP and with the PSTN/ISDN network using SS7.
Media Gateway Function (MGF)
The MGF is responsible for providing the media processing functions. It performs functions such as echo cancellation, noise reduction, and tone detection. The MGF communicates with the MG using MGCP.
IMS-MGW Deployment Scenarios
There are several deployment scenarios for the IMS-MGW. The following are some of the common scenarios:
IMS-to-PSTN/ISDN
In this scenario, the IMS-MGW is deployed to enable communication between the IMS network and the PSTN/ISDN network. The IMS-MGW provides media conversion and signaling conversion between these two networks.
- PSTN/ISDN-to-IMS
In this scenario, the IMS-MGW is deployed to enable communication between the PSTN/ISDN network and the IMS network. The IMS-MGW provides media conversion and signaling conversion between these two networks.
IMS-to-IMS Interconnect
In this scenario, the IMS-MGW is deployed to enable communication between two different IMS networks. The IMS-MGW provides media conversion and signaling conversion between these two networks.
Emergency Services
In this scenario, the IMS-MGW is deployed to enable emergency calls to be made from the IMS network to the PSTN/ISDN network. The IMS-MGW provides media conversion and signaling conversion, as well as the necessary features to ensure that the emergency call is handled correctly.
Conclusion
The IMS-MGW is a critical component of the IMS architecture that enables communication between the IP-based IMS network and the traditional PSTN/ISDN network. The IMS-MGW provides media conversion, signaling conversion, and media processing functions. The IMS-MGW is a complex device that consists of several components, including the Media Gateway Controller, Media Gateway, Signaling Gateway, and Media Gateway Function. There are several deployment scenarios for the IMS-MGW, including IMS-to-PSTN/ISDN, PSTN/ISDN-to-IMS, IMS-to-IMS Interconnect, and Emergency Services. The IMS-MGW plays a critical role in enabling the convergence of various multimedia services on the IP network, and it is expected to play an even more important role in the future as more and more services move to the IP network.