MGW-MediaGateway.ppt

8/14/2019 MGW-MediaGateway.ppt

http://slidepdf.com/reader/full/mgw-mediagatewayppt 1/4

- 1 -

Media Gateway

The Media Gateway (MGw) connects the Core Network (MSC Server and SGSN) to the WCDMA RAN (RNC). It also

connects to external networks such as the PSTN, the Internet/Intranet as wellas other mobile networks.

The MSC servers handle the signaling and control the MGw media streaming resources (transcoders for AMR, echo cancellersetc.) via the Gateway Control Protocol (GCP).

The MGw provides interfaces to ATM-based transit networks. For the packet domain, the SGSN will keep a server combined

with MGw functionality. The MGw is therefore only acting as a cross connection between the RNC and the SGSN.

The Media Gateway for Mobile Networks (M-MGw) makes interconnection between different networks and transport technologies

possible for WCDMA and GSM.

With M-MGw, the layered network architecture can be fully implemented for circuit-switched traffic. MSC Servers remotely controlthe M-MGw R3 using the Gateway Control Protocol (GCP) that is based on the ITU-T H.248 standard. The M-MGw allows

circuit-switched payload and signaling traffic to be carried over a TDM, IP or ATM backbone network. The ATM based WCDMA

packet-switched user and control traffic is cross-connected by the M-MGw to the SGSN node.



- 2 -

Media Gateway …..continued

In the layered architecture servers handle the Control Layer; Gateways, IP routers and/or ATM switches handle the Connectivity

Layer (user plane) traffic. Consequently, the different levels in the network hierarchy are separated, and communicate over well-

specified interfaces.

The M-MGw located in the Connectivity layer manipulates the network resources as instructed by the MSC or GMSC/Transit

servers. The M-MGw

itself is a self-contained network element that provides all the necessary functionality for handling and setting up the Connectivity

layer at the borders between different networks.

The M-MGw connects the Mobile Core Network with external networks such as UMTS/WCDMA and GSM Radio Access

Networks, PSTN networks or other mobile networks.

The M-MGw contains a full set of speech and data resources for performing modifications and additions on the Connectivity

Layer. It also contains transport resources for performing protocol and Connectivity Layer conversions between different

networks, and provides Signaling Gateway functionality for performing bearer conversions of control protocols.

Depending on network topology and the traffic cases that the M-MGw is handling, the node can assume different roles in the

Mobile Core Network. It is not necessary to have several physical M-MGw nodes to take care of these different situations; one

node can have a number of roles in the network.

Functionality

Functions Related to Media Stream Handling

– The M-MGw contains a set of functions needed to support the circuit-switched speech services in WCDMA and GSM. With thehelp of these functions, the M-MGw can adapt the circuit-switched speech for transfer over different networks. Speech codingfrom PCM coded voice to Adaptive Multi-Rate (AMR) coded voice in WCDMA can be mentioned as an example.



- 3 -

Media Gateway…..continued

Functionality…..continued

Functions Related to Media Stream Handling…..continued

– On ATM and IP bearers, the payload is delivered to/from M-MGw in packages that contain several speech samplesaccompanied by addressing information used by the bearer in question.

– These packages are called frames. In order to be able to carry out its task, the M-MGw R3 will have to extract the payloadfrom the frames on incoming bearer, carry out the media stream processing (e.g. speech coding or echo cancellation), andthen pack the resulting payload on frames needed on the outgoing bearer.

– The Media Stream Handling functionality is implemented as pooled devices that can be configured to support any of theindividual functions listed below.

– With the help of this unique M-MGw capability, the operator can maximize the use of scarce network resources, such as echocancellers.

– The fundamental Media Stream Handling functions are:

Speech Coder including AMR2; the default speech coding/decoding algorithm for WCDMA.

All modes of the AMR2 speech codec are supported

Echo Canceller Multi-Party Call

Tone Sender

DTMF Sender/Receiver

Interactive Messaging

The Code Answer and Tone Sender (CAT), used for maintenance purposes

Continuity Check (CC), used to test the integrity of the speech path

– Four Voice Quality Enhancement functions are also available:

Mobile Crosstalk Control (MCC) that cancels acoustic echo generated at MS side Noise Reduction feature, effectively reduces background noise when calling from noisy environments

Signaling Gateway Function

– The Signaling Gateway functionality enables seamless communication between TDM, ATM and IP based signaling networks.

– The Signaling Gateway functionality makes it possible to perform signaling bearer conversion (MTP3B/SAAL-NNI,MTP3/MTP2 and M3UA/SCTP) in the M-MGw R3 at the network edges, thus allowing unified signaling bearers to be usedwithin the core network.



- 4 -

Media Gateway…..continued

Functionality…..continued

Signaling Gateway Function…..continued

– The Signaling Gateway functionality enables seamless communication between TDM, ATM and IP based signaling networks.

– The Signaling Gateway functionality makes it possible to perform signaling bearer conversion (MTP3B/SAAL-NNI,MTP3/MTP2 and M3UA/SCTP) in the M-MGw at the network edges, thus allowing unified signaling bearers to be used withinthe core network.

– The Signaling Gateway can, for instance, relay control signaling to the MSC Server and between MSC Servers by performingconversion of lower layer control protocols. MTP Level Signaling Transfer Point (STP) and SCCP Relay Point (SRP)functionality is included in the SS7 Signaling Gateway.

Radio Access Network Interfaces

– The WCDMA Radio Access Network is connected to the M-MGw over Iu interface that defines the payload framing used in thecommunication towards the WCDMA Radio Network Controllers.

– M-MGw also supports the physical connection between two Radio Network Controllers (Iur interface).

– Introducing the GSM A-interface gives the possibility to interface 2G BSS directly via the M-MGw. The physical HW related tothe A-interface TDM devices is located in the M-MGw, but the MSC Server controls the call using the GCP protocol.

– All required signalling is relayed through the Signalling Gateway functionality in the M-MGw R3 to the MSC Server.

– Operators who have licenses for both 2G and 3G, such as STC, now have the ability to integrate transport solutions for bothGSM and WCDMA traffic over a common ATM or IP backbone network, thus optimizing transport of traffic.

– This will result in lower operational expenditure during migration from 2G to 3G networks as well as subsequent networkoperation.

Documents

MGW-MediaGateway.ppt