GSM / UMTS R4 Media Gateway -...

411-2231-330

GSM / UMTS

R4 Media GatewayOperations and Reference Guide

GSM18/MGW18 Standard 02.06 May 2006

GSM / UMTS

R4 Media GatewayOperations and Reference Guide

Document number: 411-2231-330Product release: GSM18/MGW18Document version: Standard 02.06 Date: May 2006

Copyright Country of printing Confidentiality Legal statements Trademarks

Copyright © 2003–2006 Nortel Networks, All Rights Reserved

Originated in the United States of America

NORTEL NETWORKS CONFIDENTIAL

The information contained herein is the property of Nortel Networks and is strictly confidential. Except as expressly authorized in writing by Nortel Networks, the holder shall keep all information contained herein confidential, shall disclose it only to its employees with a need to know, and shall protect it, in whole or in part, from disclosure and dissemination to third parties with the same degree of care it uses to protect its own confidential information, but with no less than reasonable care. Except as expressly authorized in writing by Nortel Networks, the holder is granted no rights to use the information contained herein.

Information is subject to change without notice. Nortel Networks reserves the right to make changes in design or components as progress in engineering and manufacturing may warrant.

* Nortel Networks, the Nortel Networks logo, the Globemark HOW the WORLD SHARES IDEAS, and Unified Networks are trademarks of Nortel Networks. DMS, DMS-HLR, DMS-MSC, MAP, and SuperNode are trademarks of Nortel Networks. GSM is a trademark of GSM MOU Association. Trademarks are acknowledged with an asterisk (*) at their first appearance in the document.

iiNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

411-2231-330 Standard 02.06 May 2006

iiiNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Publication historyThis section contains a high-level listing of updates and changes to this product documentation for this release cycle.

GSM / UMTS R4 Media Gateway Operations and Reference Guide GSM18/MGW18

iv Publication historyNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

May 2006NSS18/MGW18, Standard, 02.06.

October 2005NSS18/MGW18, Preliminary, 02.05.

October 2005NSS18/MGW18, Preliminary, 02.04. For Review.

October 2005NSS18/MGW18, Preliminary, 02.03.

September 2005NSS18/MGW18, Draft, 02.02.

December 2004NSS18/MGW18, Draft, 02.01.

October 2004NSS17/MGW17, Standard, 01.13.

September 2004NSS17/MGW17, Standard, 01.12.

August 2004NSS17/MGW17, Standard, 01.11. For review.

April 2004NSS17/MGW17, Standard, 01.10.

April 2004NSS17/MGW17, Standard, 01.09. For review.

March 2004NSS17/MGW17, Standard, 01.08. For review.

February 2004NSS17/MGW17, Standard, 01.07.

November 2003NSS17/MGW17, Preliminary Phase 5, 01.06.

September 2003NSS17/MGW17, Preliminary Phase 4, 01.05.

September 2003NSS17/MGW17, Preliminary Phase 3, 01.04.

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Publication history vNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

July 2003NSS17/MGW17, Preliminary Phase 2, 01.03.

June 2003NSS17/MGW17, Preliminary Phase 1, 01.02.


vi Publication historyNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

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viiNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

About this document 1This document explains GSM Bearer Independent Core Network (BICN) and Bearer Independent Call Control (BICC) Media Gateway (MGW) functionality, the general architecture of the GSM BICN network with the introduction of the media gateway, along with the services supported by the media gateway. In addition, this document presents the hardware configuration, interfaces, routers, and features, such as voice quality features, and hardware maintenance procedures. This document also presents the fault, configuration, and performance management information for the MGW.

Audience for this document 1This document is intended for Nortel Networks’s external customers.

Organization of this document 1This section provides a brief overview of this guide. Each major section of the document is described below:• Chapter 1, “Introduction to the Media Gateway” explains GSM BICN/

BICC Media Gateway (MGW) functionality. • Chapter 2, “Media Gateway overview” describes the general architecture

of the GSM BICN/BICC network with the introduction of the media gateway, along with the services supported by the media gateway.

• Chapter 3, “Media gateway and AN shelf layouts” presents information on the Media Gateway (MGW) hardware configuration and self layouts.

• Chapter 4, “Media gateway hardware components” presents information on the Media Gateway shelf assembly, control processors (CP) and functional processors (FP).

• Chapter 5, “Media Gateway timing synchronization” presents information on Media Gateway timing synchronization.

• Chapter 6, “Media Gateway APS hardware” presents information on Audio Provisioning Server (APS) hardware.

• Chapter 7, “Standard interfaces and routers” describes Media Gateway interfaces and IP addressing and routing.


viii About this documentNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

• Chapter 8, “Media Gateway Voice Engine functionality” presents Media Gateway (MGW) voice quality features.

• Chapter 9, “Media Gateway services” presents MGW services supported by the MGW, such as handover, tones, circuit-switched, data, announcements, continuity test, and tandem free operation.

• Chapter 10, “Media Gateway OA&M overview” presents high-level, overview information regarding R4 BICN Media Gateway fault, configuration, and performance management, and general and basic card maintenance information. For further detailed information non this topic, refer to Nortel Networks Technical Publication (NTP) refer to NTP 411-2231-331, R4 BICN Media Gateway OAM and Troubleshooting Guide.

Related documents 1The following is a list of related Media Gateway documentation: • 411-2231-014, R4 BICN Solution Overview• 411-2231-331, R4 BICN Media Gateway OAM and Troubleshooting

Guide

Software release applicability 1Nortel software releases for the Wireless product are developed and identified by the product lines. The GSM product line software is identified by the letters GSM and a 2-digit number and UMTS and a 2-digit number, such as GSM18/UMTS18, signifying the current release in the software stream.

Special text conventions in this document 1The “Square Brackets” symbols, '[' and ']' will be used to denote a reference to an external document. The number contained within the brackets will be the same as the number listed beside the intended reference.

Indication of hypertext links 1Hypertext links in this document are indicated in blue. If viewing a PDF version of this document, click on the blue text to jump to the associated section or page.

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Publication history ixNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Contents 2

About this document viiAudience for this document 1-viiOrganization of this document 1-viiRelated documents 1-viiiSoftware release applicability 1-viiiSpecial text conventions in this document 1-viiiIndication of hypertext links 1-viii

Introduction to the Media Gateway 1-1Node definitions 1-2

Gateway MSC 1-2Home Subscriber Server 1-2Mobile Station 1-2Visited Mobile Services-switching Center 1-3Base Station Subsystem 1-3Universal Terrestrial Radio Access Network 1-3Media Gateway 1-3

Media Gateway overview 2-1BICN network architecture 2-1What is the Media Gateway 2-3What are the different types of Media Gateways? 2-4

A-Interface Media Gateway 2-5Iu Media Gateway 2-5PSTN Media Gateway 2-5Connection Fabric Inter-working Function 2-5Circuit-Switched Data Media Gateway 2-5Nb Media Gateway 2-5Multi-Party Media Gateway 2-6

Aggregation node 2-6HIOP interface 2-8

Media gateway and AN shelf layouts 3-1Media Gateway shelf layouts 3-1Aggregation node shelf layouts 3-3

Media gateway hardware components 4-1Media gateway shelf assembly 4-1

Common backplane 4-4Fabric cards 4-4Media access control module 4-5Alarm/BITS module 4-6Cooling unit 4-6

Processors 4-7Types of redundancy 4-21


x Publication historyNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

CP3 4-222pGPDsk 4-224-port OC-3e/STM-1 ATM FP 4-2216-port OC-3/STM-1 ATM FP 4-234-port OC-3/STM-1 TDM FP 4-2312-port DS3 ATM FP 4-23Vsp4e 4-24

Media Gateway timing synchronization 5-1Network clock synchronization 5-1

Internal Timing Reference 5-1External Timing Reference 5-1Line Timing Reference 5-2Network Synchronization Strategy 5-2

Media Gateway APS hardware 6-1Audio Provisioning Server hardware 6-1

Hardware details 6-2

Standard interfaces and routers 7-1Interfaces 7-1

A interface (BSS - MSC Server, BSS - MGW) 7-2Iu interface 7-3Iu-CS (RNC - MSC, RNC - MGW) 7-4Nb Interface (MGW - MGW) 7-6Mc Interface (MSC Server - MGW) 7-8

MGW interface support summary 7-9IP addressing and routing 7-9

MSS Virtual Routers 7-9Virtual Router Access Point (VRAP) 7-10IP access mechanisms and media 7-11IP addresses 7-11IP based applications on the MGW 7-12IP Routing 7-12I/O aggregation 7-12MGW inter-shelf communication 7-13MSS services 7-13

Media Gateway Voice Engine functionality 8-1Digital signal processor 8-1

G.711 companding 8-1AMR speech codec 8-2Vocoder bypass for IDEN 8-4Voice quality enhancement features 8-4Tandem free operation in-path equipment compliancy 8-13

Media Gateway services 9-1AAL1 circuit emulation service 9-1

SS7 backhaul over structured AAL1 CES 9-1MF trunk support over unstructured AAL1 CES 9-3

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Publication history xiNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Circuit-switched data 9-3UMTS 64kbit UDI service 9-5

Multi-Party (Conferencing) 9-5Global text telephony 9-7Lawful intercept 9-8Compression in the core network (TrFO-Lite) 9-10Channel associated signaling 9-12Signaling backhaul 9-13

Broadband SS7 backhaul over IP 9-13Narrowband SS7 backhaul over IP 9-13

Media Gateway OA&M overview 10-1Fault management 10-1Configuration and performance management 10-2Performance management 10-2General and basic card maintenance overview 10-3

Multiservice Switch boards LEDs 10-3

List of terms and definitions 11-1


xii Publication historyNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

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1-1Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Introduction to the Media Gateway 1The Bearer Independent Core Network (BICN) provides a 3GPP Release 4 BICN-based solution for GSM and UMTS circuit-switched networks enabling: • Packet transport (AAL2/ATM) for voice and legacy circuit switched data

services.• Centralized call processing by way of an MSC Server, allowing bearer

processing to be scaled independently from control processing.• “Remote” switching of bearer traffic by way of media gateways, enabling

call server deployments that serve multiple geographically dispersed regions.

Note 1: In H.248 the term MGC is used to describe an entity that controls a MGW.

Note 2: Vsp4e is used to refer to the function processor (FP), 4pOC3ChSmIrVsp4e, in this document.

Figure 1-1 illustrates the R4 BICN network architecture from the 3GPP specifications (3GPP 23.205). It describes the R4 BICN Architecture from a standards perspective, and is not meant to depict the architecture and interfaces supported in this release of the Nortel Networks solution.


1-2 Introduction to the Media GatewayNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 1-1 3GPP R4 BICN network architecture

Node definitions 1Gateway MSC

If a network delivering a call to the PLMN cannot interrogate the HLR, the call is routed to an MSC. This MSC will interrogate the appropriate HLR and then route the call to the MSC where the mobile station is located.

Home Subscriber ServerThe Home Subscriber Server (HSS) is a network database used for permanent management of mobile subscribers within a Public Land Mobile Network (PLMN). It is a repository for identification, location, security, and user profile information (essentially an evolution of the GSM HLR that includes IMS functionality).

Mobile StationThe mobile station (MS) consists of the physical equipment used by a PLMN subscriber; it comprises the Mobile Equipment (ME) and the Subscriber Identity Module (SIM). The ME comprises the Mobile Termination (MT) which, depending on the application and services, may support various

IN Servicesand applications HSS

VMSC GMSC

MGW MGW PSTN/LegacyExternalBSS

CAP

DC

Mc

Nb

Mc

Bearer data transfer and bearer signaling (user plane)Signaling (control plane)

Nc

A

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Introduction to the Media Gateway 1-3Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

combinations of Terminal Adapter (TA) and Terminal Equipment (TE) functional groups.

Visited Mobile Services-switching CenterThe Visited Mobile-services Switching Center (VMSC) constitutes the interface between the radio system and the fixed networks. The VMSC performs all necessary functions in order to handle the circuit-switched services to and from the mobile stations.

Base Station SubsystemThe Base Station Subsystem (BSS) is the Access network serving the GSM network. The BSS is a system of base station equipment (transceivers, controllers, and so on) which is viewed by the MSC through an A-interface as being the entity responsible for communicating with Mobile Stations in a certain area.

Universal Terrestrial Radio Access NetworkThe Universal Terrestrial Radio Access Network (UTRAN) is the Access Network serving the UMTS network, and consists of Radio Network Controllers (RNC) and Node-B units (radio equipment). The UTRAN communicates with both the circuit network (MSC and MGW) and packet network (SGSN) through the Iu interface.

Media GatewayThe GSM/UMTS Media Gateway (MGW) provides media handling in the GSM and UMTS BICN networks. It supports bearer traffic connection, media adaptation (TDM and AAL2), voice compression, voice quality services, and subscriber services (Conferencing, GTT, and so on).


1-4 Introduction to the Media GatewayNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

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Media Gateway overview 2This chapter discusses the following topics: • BICN network architecture• What is the Media Gateway• What are the different types of Media Gateways?• Aggregation node

BICN network architecture 2Figure 2-1 and Figure 2-2 depict a high-level view of the Nortel Networks BICN network for GSM. The diagrams do not detail the placement of specific MGW personality types (especially the Multi-Party and CSD MGWs), but show both local and remote MGW sites, and the platforms involved in providing signaling backhaul, and a generalized view of connectivity between the nodes (using ATM and LAN clouds).

Note 1: The Universal Signaling Point (USP), which up to this point has only been briefly mentioned. The USP is a Nortel signaling gateway product. It is a node in the SS7 network that provides carrier-grade interworking between classical circuit-switched networks and call control elements in the packet-based world. It can be thought of as a replacement for the SS7 and TDM peripherals on the MSC.

Note 2: The term Media Gateway or MGW is used in the general sense to refer to all the media gateway personalities.


2-2 Media Gateway overviewNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 2-1 Core network product architecture (GSM)

The USP lacks a high-speed ATM interface, so a MSS 7000 node fronts the USP and performs ATM switching between electrical and optical interfaces in UMTS networks where the USP is acting as a broadband STP for ALCAP signaling over the Nb I/F.

DMS MSCDMS MSC

BSSBSS

MGWMGW(Central Office)(Central Office)

IWFIWF

MGW ShelvesMGW Shelves

TDM

TDM Trunks

Other Other MGWs MGWs

(Nb)(Nb)

ATMATM

LAN/WANLAN/WAN

Remote Site

PlatformsPlatforms

DMSDMS

MSS MSS 1500015000

MSS MSS 70007000

USPUSP

USPUSP

TDM Trunks PSTNPSTN

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Media Gateway overview 2-3Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 2-2 Core network product architecture (UMTS)

What is the Media Gateway 2The term MGW refers to one or more Multiservice Switch (MSS) 15000 shelves hosting 1 or more Voice Gateway Servers (VGS) and the required ATM and/or TDM interface cards. The MGW also optionally supports the 2pGPDsk FP to aggregate and ATM-encapsulate Mc traffic. All of the shelves hosting VGSs in the same geographic area are collectively referred to as a MGW. Therefore, a MGW is of arbitrary size and capacity, depending upon the number of shelves and the number of VGSs served.

The VGS supplies the media services in the MGW. A single VGS is hosted on a Voice Services Processor 4e (Vsp4e) FP, and performs the media adaptation and voice quality features for the bearer data. It also terminates the Mc interface, sending and receiving both callp and maintenance-related messages to the MSC Server. Each VGS has its own unique Mc interface and operates independently of the other VGSs in the MGW.

The interface cards consist of a pair of TDM FPs and ATM FPs. The TDM I/O cards provide AAL1-CES service for the backhaul of narrow-band SS7 signaling traffic. These FPs are optional, and are only required in networks utilizing AAL1-CES for signaling backhaul. For networks using IP for signaling backhaul, the TDM FPs are not required. The ATM FPs connect the MGW to the packet backbone and provide inter-shelf connectivity.

Note: All VGSs in a shelf share the resources of the I/O cards in that shelf.

DMS MSCDMS MSC

UTRANUTRAN

MGWMGW(Central Office)(Central Office)

MGW ShelvesMGW Shelves

TDM

TDM Trunks

Other Other MGWs MGWs

(Nb)(Nb)

ATMATM

LAN/WANLAN/WAN

Remote Site

PlatformsPlatforms

DMSDMS

MSS MSS 1500015000

MSSMSS70007000

USPUSP

USPUSP

IWFIWF

PSTNPSTN



What are the different types of Media Gateways? 2The Media Gateway family of products is composed of the following major components: • Media Gateway (MGW). The MGW consists of Voice Gateway Servers

(VGS), ATM interface cards, TDM interface cards (optional), and 2pGPDsk FPs (optional). The VGS provides media adaptation services (AAL2<->TDM), voice quality features, subscriber services (GTT and Conference call support), and also terminates the Mc interface. The ATM and TDM interface cards support the VGS input/output requirements, which include: — Narrow-band signaling to/from the BSS and MSC SS7 A-Interface— AAL2/ATM bearer data to/from the packet backbone— AAL1 CES-encapsulated A-Interface, ISUP, or MF trunk signaling

to/from the packet backbone — AAL5-encapsulated Mc traffic to/from the packet backbone.

The TDM interface cards, when present, support the AAL1-CES-encapsulated A-Interface and ISUP narrowband SS7 signaling. The Vsp4e TDM interface is not capable of AAL1-CES service, therefore the TDM interface cards are required in networks not using the signaling backhaul solution. In this configuration, the TDM Interface cards accept both signaling and bearer traffic. The TDM bearer traffic is hair-pinned via AAL1-CES back out the faceplate of the TDM Interface card to a mux, then on to the Vsp4e FP. The SS7 signaling traffic is sent on to the ATM I/O card via AAL1-CES.

The 2pGPDsk cards, when present, support an Ethernet interface to the CO IP WAN for H.248/UDP/IP traffic (the Mc interface) and for M2UA/SCTP/IP traffic (SS7 signaling backhaul). The 2pGPDsk FPs also encapsulates the Mc traffic into AAL5/ATM cells and routes the cells to the appropriate MGW.

• Aggregation Node (AN). The Aggregation Node is responsible for providing connectivity between the shelves comprising the MGW, and between the MGW and the external transport network. An AN shelf is optional in small MGW configurations and is only required when more than 2 MGW shelves exist at a site. The AN also supports the 2pGPDsk FPs for Mc traffic aggregation and routing. The AN is a standard Multi-Service Switch 15000 product with no Wireless specific applications.

In order to adequately describe the roles and characteristics of the MGW (or more appropriately a VGS), Media Gateway personalities have been defined in order to clarify the MGW’s role in the network solution.

411-2231-330 Standard 02.06 May 2006


Note: These “MGW personalities” represent different roles in the BICN solution, but are all hosted on the same hardware platform (Vsp4e FP). In addition, all personalities except the Multi-Party MGW may co-reside on a single Vsp4e. From a network operator perspective, they are all simply media gateways whose configuration and connectivity allow them to provide the necessary functionality.

A-Interface Media GatewayThe A-Interface Media Gateway (MGA) supports the GSM wireless access network and connects the GSM BSS to the ATM backbone. It also backhauls DTAP and BSSMAP narrow-band-SS7 signaling, via AAL1-CES or SCTP/IP to the MSC. An MGA may reside on a Vsp4e with any MGW personality type except the Multi-Party MGW.

Iu Media GatewayThe Iu Media Gateway (MGI) supports the UMTS wireless access network and connects the RNC to the ATM backbone via the Iu interface. It also backhauls RANAP broadband-SS7 signaling, via SCTP/IP, to the MSC. An MGImay reside on a Vsp4e with any MGW personality type except the Multi-Party MGW.

PSTN Media GatewayPSTN Media Gateway (MGP) supports PSTN access and connects the ATM backbone to the PSTN. In addition, it backhauls ISUP narrow-band-SS7 signaling, via AAL1-CES or SCTP/IP, to the MSC. An MGP may reside on a Vsp4e with any MGW personality type except the Multi-Party MGW.

Connection Fabric Inter-working FunctionThe Connection Fabric Inter-working Function (CFIWF) connects the ATM backbone to legacy TDM peripherals (SPM/DTC/PDTC) in support of hybrid calls (that is, terminate on a legacy TDM peripheral). A CFIWF may reside on a Vsp4e with any MGW personality type except the Multi-Party MGW.

Circuit-Switched Data Media GatewayThe Circuit-Switched Data Media Gateway (MGD) connects the ATM backbone to the GPP Inter-Working Function (IWF) via TDM links in support of circuit-switched data calls. An (MGD) may reside on a Vsp4e with any MGW personality type except the Multi-Party MGW.

Nb Media GatewayThe Nb Media Gateway (MGN) is a packet-to-packet Media Gateway that provides a 3GPP standards-conformant Nb interface between Media Gateways under different MSC Servers. The Nb MGW provides inter-working capabilities between the Nb’ interface used within an MSC Server region and the standards-conformant Nb interface employed between



MSC Servers. An MGM may reside on a Vsp4e with any MGW personality type except the Multi-Party MGW.

Multi-Party Media GatewayMulti-Party Media Gateway (MGM) is a packet-to-packet Media Gateway that supports the multiparty (conferencing) service and a Lawful Intercept Distribution Function (LIDF). This MGW supports 6-port conference bridges, along with an LIDF that performs multi-casting of intercepted call content. This MGW is a centralized resource in the network, and is dedicated solely to Conferencing and LIDF capabilities. Unlike the other MGW personalities, it cannot co-reside with any of the other personalities.

Figure 2-3 depicts the MGW personalities, and briefly describes the characteristics of each personality.

Figure 2-3 Media gateway personalities

Each of the Media Gateway personalities described above utilize the same hardware platform (Vsp4e) and the same I/O FPs. The Multi-Party MGW utilizes a special DSP load, while all other personalities share a common, non-Conferencing DSP load.

Aggregation node 2The Aggregation Node (AN) is a MSS 15000 shelf loaded with a standard software load. The AN may be used at the Central Office and at Remote Sites,

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but its use is optional at both of these geographic locations. When deployed at the Central Office, the AN is responsible for all inter-shelf I/O and external network connectivity for the local MGWs. The AN at the CO may also support the HIOP function, aggregating the Mc traffic to/from both the local and remote sites. This function resides in the MGW shelf if no AN is present. As noted earlier, the AN at the CO is optional for small configurations, but is required when more than 2 MGW shelves of capacity is needed.

The AN should be configured for maximum redundancy to avoid having a single point of failure. This implies that there should be two CP3s and all I/O FPs are provisioned as 1:1 Equipment Protection with 1+1 Line Protection via Automatic Protection Switching (APS) where applicable. The hardware portfolio for the AN includes: • CP3• 4-port OC-3/STM-1 ATM FP PQC12 Multi-Mode (MM)• 4-port OC-3/STM-1 ATM FP PQC12 Single-Mode (SM)• 16-port OC-3/STM-1 ATM FP PQC2 Single-Mode (SM)• 4-port OC-3/STM-1 TDM FP PQC12• 2-port General Processor with Disk FP• 12-port DS-3 ATM FP

The AN provides the following: • Aggregates all I/O between the network and the local MGW, maximizing

utilization of I/O connections at the network edge• Inter-shelf communication device for co-resident MGW shelves

providing adequate and deterministic communication characteristics such as connectivity, routing, redundancy, and latency.

• Isolates the MGW function from the network via a widely dispersed MSS 15000 product increasing the successful probability of inter-operability.

• Streamlines the opportunity to introduce new services along with the wireless application by concentrating the MSS base functionality within the MSS 15000 AN, (for example, Soft PVC).

Figure 2-4 shows an AN at the Central Office and an AN at a Remote Site in the a BICN network.



Figure 2-4 AN usage in a BICN network

In Figure 2-4, the AN at the CO provides the HIOP interface (Mc traffic aggregation), inter-shelf communication, and backbone connectivity for the local MGWs.

Note: The AN can also be used at large Remote Sites as shown above. In this capacity, the AN provides inter-shelf communication and backbone connectivity for the MGWs at the Remote Site.

HIOP interfaceThe HIOP Interface at the Central Office provides an Ethernet-based interface to the MSC Server’s HIOP for H.248 traffic.

The AN local to the MSC (or the MGW, if no AN is present) uses the 2pGpDsk FP to receive the IP-based H.248 signaling traffic from the MSC. The 2pGpDsk also provides encapsulation of the H.248/UDP/IP traffic into AAL5/ATM cells for transport to the MGWs over the packet network. Figure 2-5 the HIOP interface handling at the CO both with an AN (top diagram) and without an AN (bottom diagram), along the respective protocol stacks entering and leaving the AN or MGW.

411-2231-330 Standard 02.06 May 2006


Figure 2-5 HIOP interface at the CO

Mc at remote MGW sitesMedia Gateways at remote locations receive H.248 traffic via the ATM FP as AAL5/ATM encapsulated cells. The H.248 traffic is distributed to the MGW shelves, for configurations with an AN, or sent on directly to the Vsp4e FPs in AN-less configurations. This is depicted in Figure 2-6 (top diagram depicts the solution with an AN).

AN

CP

ATM FP0 ATM WAN ATM WAN

CP

2pGpDsk ATM FP

Mc CO LAN CO LAN

MSC MSC MSC MSC

HIOP

Ethernet

IP

UDP

H.248 (BER)

Ethernet

IP

UDP

H.248 (BER)

AAL5

OC-3

ATM

RFC 1483

IP

UDP

H.248 (BER)

AAL5

OC-3

ATM

RFC 1483

IP

UDP

H.248 (BER)

MGW

CP

ATM FP0ATM WAN ATM WAN

CP

2pGpDsk ATM FP

Mc

CO LAN CO LAN

VSP4

VSP4

HIOP

MSC MSC MSC MSC

To Local MGWs

To Remote MGWs



Figure 2-6 H.248 traffic at remote MGW sites

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Media gateway and AN shelf layouts 3This chapter presents the following topic: • Media Gateway (MGW) • Aggregation node (AN) shelf layouts

Media Gateway shelf layouts 3The MGW is designed to provide a Highly Available, Robust, and scalable architecture. The flexibility of the system makes it easy to configure according to each customer’s network needs.

The basic configuration for the MGW shelf is that the top cage contains I/O cards and the bottom cage contains the Vsp4e FPs (maximum of 8 Vsp4e FPs per shelf).

Note: The the bottom cage may contain additional I/O if needed (that is, if the top cage is full), but this reduces the number of Vsp4e FPs supportable in the shelf, and thus limits the MGW call capacity. In most configurations, the shelf I/O requirements can be satisfied solely with the I/O cards in the top cage, leaving the bottom cage fully available for Vsp4e FPs.

Table 3-1 and Figure 3-1 present the card lineup for the MGW.

Table 3-1 MGW layout description

Slots FP Function(s)

0 - 1 CP3 Shelf administration


3-2 Media gateway and AN shelf layoutsNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

2 - 7 Options:

16pOC3SmlrAtm

4pOC3MmAtm

4pOC3SmlrAtm

12pDS3Atm

4pOC3ChSmIrVsp4e

2pGPDsk

Filler

Inter-Shelf and Network Interface I/O

Network Interface I/O



SS7 Signaling Backhaul via AAL1 CES

CO LAN Interface

8 - 15 Options:

Vsp4

16pOC3SmlrAtm

4pOC3MmAtm

4pOC3SmlrAtm

12pDS3Atm

4pOC3ChSmIr

2pGPDsk

Filler

VGS






CO LAN Interface

Table 3-1 MGW layout description


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Media gateway and AN shelf layouts 3-3Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 3-1 MGW layout

The 16 slots of the MGW shelf are allocated in the following manner. Slots 0 and 1 host the CP3 cards. Slots 2 thru 7 host I/O cards. These can be 16pOC-3 ATM, 4pOC-3 ATM, 4pOC-3 TDM, 12pDS3 ATM, or the 2pGPDsk. The number and type of I/O cards chosen depends upon of the I/O bandwidth required and the network transport type.

The 16pOC-3, 4pOC-3 ATM, and 4pOC-3 TDM FPs, if present, are hot spared with APS, while the 12pDS3 requires a sparing panel to provide equipment protection. Line protection is not available on the 12pDS3. The 2pGPDsk is hot-spared with Ethernet line-protection switching.

Slots 8 through 15 contain Vsp4e FPs, filler packs, or any of the I/O FPs supported in the previous paragraph (16pOC-3 ATM, 4pOC-3 ATM, 4pOC-3 TDM, 12pDS3 ATM, and 2pGPDsk). The number of Vsp4e FPs supported depends upon the capacity required at the MGW site, and the number and type of I/O cards depends upon the I/O bandwidth required and transport type.

Aggregation node shelf layouts 3The Aggregation Node is responsible for all inter-shelf traffic at the local site and remote region, and provides MGW connectivity to the WAN. In addition, it aggregates, encapsulates, and routes H.248 signaling traffic between the MSC Server and MGWs hosted by the MSC-Server. The AN is an optional node and is only required when a site hosts more than 2 MGW shelves.



The shelf has been configured in the following manner.

Figure 3-2 AN layout

The card layout of the AN is shown above. Slots 2 thru 15 can host any of the supported ATM I/O FPs in support of both inter-shelf (4pOC3 and 16pOC3 ATM FPs) and backbone connectivity (4pOC3, 16pOC3 and 12pDS3 ATM FPs). The only requirements for ATM I/O FP deployment in the AN are the rules identified in the section on Cable Management.

Simply, the rules are as follows: • Optical-based FPs start on the left side of the shelf and fill to the right• Copper-based FPs start on the right side of the shelf and fill to the left

Table 3-2 AN layout description


0 - 1 CP3 Shelf administration

2 - 15 Options:

16pOC3SmlrAtm

4pOC3MmAtm

4pOC3SmlrAtm

12pDS3Atm

4pOC3ChSmlr

2pGPDsk

Filler






CO LAN Interface

411-2231-330 Standard 02.06 May 2006

Media gateway and AN shelf layouts 3-5Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

The AN may also contain a pair of 1:1 redundant 2pGPDsk FPs serving as the HIOP Interface. These provide the IP/Ethernet interface for the H.248/UDP/IP traffic to/from the HIOP.



411-2231-330 Standard 02.06 May 2006


Media gateway hardware components 4This chapter presents the following topics: • Media Gateway (MGW) shelf assembly• Media gateway processors• Types of redundancy

Media gateway shelf assembly 4The NEBS 2000 frame supports two shelf assemblies: an upper and a lower. Each shelf assembly contains a separate MSS 15000. The shelf is divided into two card cages, positioned one above the other. The card cages hold the processor cards that manage the node and provide interfaces for connection to high-speed data networks.

The MSS 15000 shelf assembly contains all the components that make up a single MSS 15000. The shelf assembly houses the following components: • Switching fabrics• Back-plane• Alarm/BITS termination• Power interface• MAC address modules• Cooling unit• Processors: control processors (CP) and function processors (FP)


4-2 Media gateway hardware componentsNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 4-1 A typical shelf assembly, front view

411-2231-330 Standard 02.06 May 2006

Media gateway hardware components 4-3Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 4-2 A typical shelf assembly, rear view

Each processor card slides into its allocated shelf slot, labeled 0 to 15, where its connector engages with a connector on the backplane. Shelf slots are allocated as follows: • Function processors can occupy any of slots 2 to 15• Control processors occupy slots 0 and 1only

The serial link architecture of the backplane allows for hot-swapping packs by isolating each card to a single fabric port, preventing card failures from propagating through the switching fabric. The back-plane also provides links between adjacent FPs for functions such as sparing, clock distribution, and distribution of -48/-60 V dc.

Ejector latches at the top and bottom of the front panel of each processor card secure it in place. A lock latch prevents tampering.



Slots not occupied by a function or control processor are fitted with blank cards to ensure proper cooling of the node, and for electro-magnetic interference (EMI) protection and safety compliances. Blank cards are labeled Blank.

Access to the function and control processors is from the front. The faceplate of each processor card contains connectors and an LED status indicator.

Common backplaneThe backplane is located at the rear of the shelf assembly between the processor cards and the fabrics. The backplane spans both card cages and extends over the full height and width of the shelf.

The backplane is a 20-layer printed circuit board containing 8 signal layers and 12 power/ground layers and is located between the processor cards and the fabrics. Each processor card connects to the backplane with four ZPACK connectors with a total of 658 pins per processor card slot, plus additional pins for the fabric card, MAC address module, alarm/BITS module, and the power interface modules (PIMs).

The backplane is referred to as the common backplane because it is the point across which all processor cards and fabric cards in a shelf inter-communicate. The backplane provides redundant 3.52 Gbit/s serial links between the processor cards and the fabric cards to support power and signal distribution. The high-speed lines on the backplane have a nominal impedance of 50 ohm and 100 ohm differential to reduce signal ringing and reflections caused by impedance mismatches. The serial link architecture of the backplane allows for hot-swapping packs by isolating each card to a single fabric port, preventing card failures from propagating through the switching fabric.

The backplane also provides links between adjacent FPs for functions such as sparing, clock distribution, and distribution of -48/-60 V dc.

The backplane can function in dual- or single-fabric mode. Dual-fabric mode is the standard mode used by the MSS 15000.

Fabric cardsThe fabric cards are located at the rear of the MSS 15000 shelf assembly. Each shelf contains two fabrics enclosed in a carrier module.

Each shelf contains two fabric cards, located one above the other at the rear of the shelf assembly. The upper and lower fabric cards are rotated 180 degrees relative to each other to minimize serial link lengths.

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Each fabric is an individual switch embedded in a chip set. Each card consists of a 254 mm tall by 406 mm wide PCB module. It provides 16 input ports and 16 output ports. A single fabric provides 3.52 Gbit/s bandwidth for each input and output port, for a total throughput of 56.3 Gbit/s. The fabrics provide eight high-speed serial links for each input and output port, with each line operating at 440 Mbit/s.

The fabric cards provide the shelf with two redundant 16x16 switching elements for interconnecting up to 16 processor cards. Both fabrics are used to carry traffic, although a single fabric can handle all traffic carried by a fully provisioned and configured MSS 15K. Under normal circumstances, each processor card transmits to and receives from half the processors on the upper fabric (usually labeled the X fabric) and half on the lower fabric (the Y fabric).

Power interface modulesFour power interface modules (PIMs) are located along the left side of the rear of the MSS 15000 shelf assembly.

Each PIM provides a point at which power cables from the BIP are connected. Each shelf assembly contains four PIMs: two for A power feeds and two for B feeds. Each PIM provides separate power filtering for the portions of the shelf it supports. The PIMs also provide termination for the shelf clocks and for the secondary control bus.

The Vsp4e FP, due to increased power consumption, requires a new 25-Watt BIP. Before a shelf is upgraded to contain Vsp4e FPs, the existing BIP must be replaced with the new BIP. New shelves are delivered with the new BIP.

Media access control moduleThe media access control (MAC) address module is located on the left side of the rear of the MSS 15000 shelf assembly, between the two fabric cards and between the PIMs of the upper and lower module cage.

The MAC address module is a field-replaceable unit (FRU) that provides the shelf with media access control (MAC) addresses for the control and function processors. The MAC address module contains a circuit board with an 87C51 8-bit micro controller and a Z-PACK connector used to provide an interface to the shelf backplane. The module contains the base MAC address and the range of MAC addresses available for assignment (based on the base address value). During the MSS boot sequence, the control processor takes the range stored in the MAC address module, divides this value by the number of functional processors, and distributes to each functional processor a base value and range.



Alarm/BITS moduleThe alarm/BITS module is located at the right side of the rear of the MSS 15000 shelf assembly, between the upper and lower fabric modules.

The alarm/BITS module is a field-replaceable unit (FRU) that terminates cables carrying alarm signals (from the cooling unit and BIP), and BITS signals, and passes the information over the shelf backplane to the control processors and expansion slots.

The alarm/BITS module contains the following connectors: • BITS ports• Cooling unit alarm connector• BIP alarm connector

Both E1 and DS-1 alarm/BITS modules are supported.

Cooling unitThe MSS NEBS 2000 frame has two cooling units located in the middle of the frame, between the upper and lower shelf assemblies. The upper cooling unit pushes air from the fan under the modules in the upper shelf assembly and out through the exhaust plenum under the BIP. The lower cooling unit pulls air in from the bottom of the frame, over the modules in the lower shelf assembly and out through the fan assembly.

Each cooling unit consists of three fans and a cooling unit backplane located in a common shelf. Temperature sensors located in the shelf assembly control each cooling unit.

MSS uses forced air for cooling internal assemblies. The intake draws air from both the base and front of the frame, and forces it vertically through the shelf where it exhausts to the rear of frame at the cable management section.

The NEBS 2000 frame is also equipped with air filters to prevent dust and other airborne contaminants from being drawn into the shelf assemblies by the cooling units.

Each cooling unit is equipped with LEDs to indicate the unit’s status. Table 4-1 lists the possible LED displays.

Table 4-1 Cooling unit LED indications

LED color Description

Green light on Unit on, no fault detected

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Processors 4Control processors (CP) and function processors (FP) are the processing elements for performing and managing MSS 15000 functions. In most cases, the software providing a service is split into control and function parts. In general, the control part runs on the CP; the function part runs on the FP.

Table 4-2 presents a summary of the CPs, FPs, and other associated equipment used in the MGW.

Red light on Fan fault, missing fan or temperature sensor detected. A FANFAIL signal is sent to the

alarm/ BITS module, and the remaining fans are switched to the high speed setting.

Table 4-2 MGW hardware summary

Card name Abbreviation Line rate per port MGW applications and shelf presence

Control Processor

Note: Delivered as part of an MSS15K cabinet or shelf assembly and is typically not ordered separately.

CP3 9.6 kbps (V.24)

100 Mbps

(100BaseT)

NM

Administration

2-Port General services Processor with Disk

2pGPDsk 100 Mbps HIOP Interface

AN

MGW

4-port 0C-3e/STM-1 Multimode ATM FP

4pOC3MmAtm 155.52 Mbps I/O

AN

MGW

Table 4-1 Cooling unit LED indications

LED color Description



4-Port OC3e/STM-1 Singlemode ATM FP

4pOC3SmIrAtm 155.52 Mbps I/O

AN

MGW

4-port OC-3/STM-1 TDM FP

4pOC3ChSmIrVsp4e 155.52 Mbps I/O

AN

MGW

16-Port OC3c/STM-1 Singlemode ATM FP

16pOC3SmIrAtm 155.52 Mbps I/O

AN

MGW

12-port DS3 ATM FP 12pDS3Atm 45 Mbps I/O

AN

MGW

Fabric Card

Note 1: Delivered as part of a 15000 cabinet or shelf assembly and is typically not ordered separately.

Note 2: The NTHR16CB/DA fabric card is replaced by the NTHR16EA fabric card. This fabric card can remain in existing shelves (that is, swap-out is not required).



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Fabric Card

Note 1: Delivered as part of a 15000 cabinet or shelf assembly and is typically not ordered separately.

Note 2: The NTHR16EA fabric card replaces the NTHR16CB/DA fabric card and should be used in all new shelf deployments.

Filler

Note: The NTHR64CA filler card replaces the NTHR64BA filler card. Filler card change-out is required for MG18.

Filler

Note: The NTPB25AA filler card is a new filler card used only in the CP Expansion slots. This filler card is required for MG18.

Cooling Unit Controller

Note: Delivered as part of a 15000 cabinet or shelf assembly and is typically not ordered separately.

Alarm BITS module DS1 120 ohms Balanced

DS3 Sparing Panel Equipment Sparing for 12pDS3 FP





CP3A Control Processor (CP):• Includes a Power PC processor, PQC ASICs for datapath frame

forwarding, and disk storage• Sequences function processor (FP) startup• Downloads new software onto FPs• Manages and monitors the status of the FPs, the fabric modules, and other

MSS 15000 hardware• Provides system timing for all other processors connected to the back-

plane• Monitors and processes alarms and the performance of real-time clocking

Breaker Interface Panel BIP Dual MSS15K shelf cabinet

Breaker Interface Panel BIP

Single MSS15K

cabinet

DS3 8W8 to 8W8 Mini Coax Cable Assy (2.5m)

DS3 8W8 to 8W8 Mini Coax Cable Assy (5m)

DS3 8W8 to 8W8 Mini Coax Cable Assy (15m)

DS3 DB9 Control Panel Sparing Cable Assy (2.5m)

DS3 DB9 Control Panel Sparing Cable Assy (5m)

DS3 DB9 Control Panel Sparing Cable Assy (15m)



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• Provides an interface which is used for network operator access, network monitoring, provisioning, and maintenance— Text interface devices connect directly to a V.24 port on the faceplate

of a control processor— Network manager devices connect via the 100BaseT port

• Provides sparing ability

Figure 4-3 CP3 faceplate



2-Port General services Processor with DiskThe 2-port General services Processor with Disk (2pGPDsk) is an MSS 15000 function processor that supports 2 100Base-T ports and has the capability of automatically spooling data to its internal 30 gigabyte hard drive.

Note: The hard-disk is not used in the MGW.

The 2pGPDsk FP provides the Fast Ethernet interface into the CO IP WAN. This FP is responsible for aggregating the IP traffic (H.248 and Sigtran signaling) and forwarding it to the 4p/16pOC3 ATM FP for encapsulation in AAL5/ATM cells for transport over the packet network (WAN).

Table 4-3 CP3 hardware summary

Processor MPC755 @ 266 MHz

DRAM 256 Mbytes

Disk 4 Gigabytes

Technology not applicable

Faceplate port(s) 1 - V.24 DCE 9.6 Kbps

1 - 100BaseT 100 Mbps

Mode not applicable

Connectors not applicable

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Figure 4-4 2pGPDsk faceplate

Table 4-4 2pGPDsk hardware summary


DRAM 512 Mbytes

Disk 30 Gigabytes

Technology PQC2

Faceplate port(s) 1 - V.24 DCE 9.6 Kbps

2 - 100BaseT 100 Mbps

Mode not applicable



4-port OC-3e/STM-1 ATM FPThe 4-port OC-3e/STM-1 Function Processor provides support for a variety of ATM services.

Figure 4-5 4pOC-3e/STM-1 ATM FP hood and faceplate

The applications on the 4pOC-3e/STM-1 Single-Mode ATM FP include: • Inter-Shelf and Network Interface I/O

The applications on the 4pOC-3e/STM-1 Multi-Mode ATM FP include: • Network Interface I/O

Connectors not applicable

Table 4-5 4-port OC-3e/STM-1 hardware summary


Table 4-4 2pGPDsk hardware summary

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16-Port OC3c/STM-1 Single-mode ATM FPThe 16-port OC-3/STM-1 supports a variety of IP and ATM services.

Figure 4-6 16-port OC-3c/STM-1 single-mode ATM FP hood and faceplate

The applications on the 16pOC-3/STM-1 include:• Inter-shelf and Network Interface I/O

DRAM 128 Mbytes

Disk not applicable

Technology PQC12

Faceplate port(s) 4 - OC-3/STM-1 155.52 Mbps per port

Mode Multi-Mode

Single-Mode

Connectors Duplex SC

Table 4-5 4-port OC-3e/STM-1 hardware summary



4 Port OC-3/STM-1 TDM FPThe 4-port OC-3/STM-1TDM FP supports DTAP/BSSMAP and ISUP. This FP does not support TDM bearer traffic, which instead uses the OC-3/STM-1 TDM port on the Vsp4e FP.

Table 4-6 16-port OC-3c/STM-1 hardware summary


DRAM 256 Mbytes

Disk not applicable

Technology PQC2

Faceplate Port(s) 16 OC-3/STM-1 155.52 Mbps per port

Mode Single-Mode

Connectors Duplex LC

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Figure 4-7 4-port OC-3/STM-1 TDM FP hood and faceplate

Table 4-7 4-port OC-3/STM-1/OC-3 TDM hardware summary

Processor PPC750 @ 300 MHz

DRAM 256 Mbytes

Disk not applicable

Technology PQC12

Faceplate port(s) 4 - OC-3/STM-1 155.52 Mbps per port

Mode Single-Mode

Connectors Duplex SC



12-Port DS3 ATM FPThe 12-Port DS3 ATM FP provides ATM over DS3 connectivity between the WAN and the node providing the network interface. This FP is optional, and is present only if DS3 connectivity to the WAN is required.

Figure 4-8 12-port DS3/E3 ATM FP faceplate

The applications on the 12p DS3 ATM FP include: • Network I/O

Table 4-8 12-port DS3 ATM FP hardware summary


DRAM 128 Mbytes

Disk not applicable

Technology PQC2

Faceplate Port(s) 12 - DS3 45 Mbps/port

Mode N/A

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4pOC3ChSmIrVsp4e4Optical TDM ports are added to the VSP4e card. This removes the need to use a different TDM card in conjuction with the VSP card to process TDM traffic. This results in a large footprint savings. The Vsp4e can assign TDM channels to any of DSP cores on the board. The Vsp4e is capable of supporting two OC-3/STM-1 I/O ports, but currently only 1 port is enabled. The Vsp4e also supports intra-card Line Protection by means of Automatic Protection Switching (APS).

The OC-3 port is multiplexed as follows: • OC-3/STS-1/VT/VT1.5/DS1

Each DS-1 is mapped into one VC-1.5 There are 4 VT1.5s mapped into one VT group, 7 VT Groups per STS-1 and 3 STS1s per OC-3. This yields 84 DS1s, or 2016 DS0s per Vsp4e.

Note: The Vsp4e card is uses the second TDM port on the card to support intra-card laps.

Figure 4-9 Channel structure over OC-3 hierarchy

Connectors 3 8W8 Miniature Coax Cable Connectors

4 DS-8 Sparing Panel Control I/F Connectors

Table 4-8 12-port DS3 ATM FP hardware summary



Each STM-1 port is multiplexed as follows: • STM-1/AUG/AU-4/VC-4/TUG-3/TUG-2/TU-12/VC-12/C-12/E1

Each E1 is mapped into one VC-12. Thus, there are up to 3 E1s in a TUG-2 structure and 21 E1s in a TUG-3 structure. An STM-1 signal contains up to 63 E1s or 1953 channels per Vsp4.

Figure 4-10 Channel structure over STM-1 hierarchy

VSP4e uses the PowerPC755 processor subsystem as used on many Multiservice Switch FPs. This is to ensure that the Multiservice Switch kernel and base software can be used unchanged. 256MB of memory is provided as a minimum, with the option of upgrading to 512MB.

In this release, Vsp4e supports only 50 T1 Janus DSPs.

Each DSP is capable of supporting up to 42 H.248 Contexts, yielding a maximum of 2100 H.248 contexts per Vsp4e.

Note: The Vsp4e FP capacity is limited by the available TDM ports (maximum of 2016 ports) and also by DSP CPU processing capabilities. The overall Vsp4e capacity is therefore dependent upon the MGW personality type(s) assigned to the Vsp4e.

Table 4-9 Vsp4e hardware summary


DRAM 512 Mbytes

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Types of redundancy 4Table 4-10 presents the types of redundancy for the MGW cards.

There are three types of redundancy: • Hot Standby: The Stand-by FP is loaded with the same provisioning

information as the Active FP. It also receives information from the Active FP on the state of current processes and stored information in a process known as “journaling”. If there is a failure of the Active FP, the Stand-by assumes the Active FP role and begins processing information. Because it has copies of the active information of the failed FP, there is minimal loss of service and minimal impacts to the network.

• Warm Standby: The Stand-by FP is loaded with the same software and provisioning information as the Active FP. It does not receive journaling information from the Active FP. If the Active FP fails, the Stand-by FP assumes the Active FP role and begins processing new transactions.

• Cold Standby: The Stand-by FP is loaded with the same provisioning information as the Active FP after reboot. It does not receive information from the Active FP on the state of current processes and stored information. If there is a failure of the Active FP, the Stand-by is booted and assumes the Active FP role and begins processing information. Because it does not have copies of the active information of the failed FP, any dynamic information is lost, which may result in the need to re-start any in progress information that depends on the application that was

SPM Dual PrPMC IBM 750FX @ 800 MHz

512 MB Total

Disk not applicable

Technology PQC12

Faceplate Port(s) 2 - OC3 Port 2 is not enabled

Mode N/A

Connectors Duplex LC

Table 4-9 Vsp4e hardware summary



running on the failed FP, (for example, Mobiles attached to the network, message queries waiting a response, and so on).

CP3Each shelf will be equipped with two CP3 cards. The CP3 cards run in a 1:1 warm spare mode.

2pGPDskThe 2pGpDsk FP supports 1:1 Equipment Protection with Ethernet hot switchover capabilities. Ethernet hot switchover provides an uninterrupted Ethernet connection by automatically switching over to a hot standby Ethernet port on a spare 2pGpDsk FP when the system detects a carrier failure on a port on the active FP.

The switchover time will be under 2.5 seconds. All data traffic on the Ethernet port will be lost during the switchover.

4-port OC-3e/STM-1 ATM FPEach 4-port OC-3e/STM-1 ATM FP is configured as 1:1 Equipment Protection with 1+1 Line Protection via Automatic Protection Switching (APS). In the case of a line failure, the APS will switch to the spare FPs port, while the Active FP continues to process the traffic. In the case of an FP failure, both the port and FP will switch over to the Spare FP. In the case of an upgrade, there is an immediate switchover form the Active to Spare FP. The switchover is specified to occur in less than or equal to 50 ms.

Table 4-10- FP redundancy summary

Functional processor Redundancy Type Standby Special consideration

CP3 1:1 Warm

4pOC-3/STM-1 ATM 1:1 Hot with APS 1+1 Line Protect on

4pOC-3/STM-1 TDM 1:1 Hot with APS 1+1 Line Protect on

16pOC-3/STM-1 ATM 1:1 Hot with APS 1+1 Line Protect on

2pGpDsk 1:1 Hot Ethernet Hot Switch-over

12pDS3 ATM 1:1 Hot Sparing Panel (NTHR37AB) is required for Equipment Sparing. No Line Sparing supported.

Vsp4 N+M Over-provisioning

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16-port OC-3/STM-1 ATM FPEach 16-port OC-3/STM-1 ATM FP is configured as 1:1 Equipment Protection with 1+1 Line Protection via Automatic Protection Switching (APS). In the case of a line failure, the APS will switch to the spare FPs port, while the Active FP continues to process the traffic. In the case of an FP failure, both the port and FP will switch over to the Spare FP. In the case of an upgrade, there is an immediate switchover form the Active to Spare FP. The switchover is specified to occur in less than or equal to 50 ms.

4-port OC-3/STM-1 TDM FPThe 4-port OC-3/STM-1 TDM FP is configured as 1:1 Equipment Protection with 1+1 Line Protection via Automatic Protection Switching (APS). In the case of a line failure, the APS will switch to the spare FPs port, while the Active FP continues to process the traffic. In the case of an FP failure, both the port and FP will switch over to the Spare FP. In the case of an upgrade, there is an immediate switchover form the Active to Spare FP. The switchover is specified to occur in less than or equal to 50 ms.

12-port DS3 ATM FPThe 12-port DS3 ATM FP supports 1:1 Equipment Protection for all 12 ports. This requires both the active and spare 12pDS3 to be connected to a Sparing Panel (NTHR37AB) mounted in the MSS frame (One Sparing Panel per pair of 12pDS3 FPs). When an equipment fault occurs, all 12 ports/lines are switched from the active 12pDS3 FP to the spare 12pDS3 FP. The switchover is specified to occur in less than or equal to 100 ms. The following illustration depicts the Sparing Panel.



Figure 4-11 12p DS3 sparing panel

Vsp4eVsp4e FPs are provisioned as N+M spared (M=1 for the cost-optimized configurations). Traffic from the Access Network should be divided between at least 2 Vsp4e FPs located on different shelves to allow for availability during network upgrades or failures. When Vsp4e serving the same access node are spread across multiple shelves (with traffic load-shared between the shelves), each shelf can be upgraded independently of all other shelves. While the total capacity of a MGW is reduced during a software upgrade, it can continue to process new circuit calls and in-progress calls on the shelves not being upgraded are unaffected. Similarly for redundancy, while in-

411-2231-330 Standard 02.06 May 2006


progress calls fail on a shelf that has a failure, the MGW overall continues to function normally with only reduced capacity.

The Vsp4e also supports 2 spare DSPs, which may be activated upon failure of any of the 50 active DSPs.



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Media Gateway timing synchronization5This chapter presents the information regarding timing synchronization.

Network clock synchronization 5This section discusses the following topics: • Internal Timing Reference• External Timing Reference• Line Timing Reference• Network Synchronization Strategy

Internal Timing ReferenceThe MSS has a Stratum 3 clocking including holdover capability. This is compliant with Bellcore GR-1244-CORE and meets the following characteristics: • Accuracy: +- 4.6x10-6 (+- [email protected] MHz / [email protected]))• Stability: +- 3.7x10-7/day for the initial 24 hours of holdover• Pull in range: +-4.6x10-6

External Timing ReferenceThe MSS 15000 can accept two external timing references sources (A and B), for redundancy purposes. These external timing reference sources should provide a better than stratum-3 timing reference. The chosen timing reference will then be provided on all outgoing links. These external timing reference sources should be DS1 digital timing reference in accordance with G703. These signals are framed, but they do not carry traffic. The DS1 is connected to a clocking BITS/Alarm module on the MSS 15000 Frame. In case of failure of the two external timing reference sources, the MSS 1500 will go to the Holdover Mode. In this mode, the stratum 3 Clock of the MSS 1500 continues to operate at its last adjusted frequency and does not update its frequency.


5-2 Media Gateway timing synchronizationNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Line Timing ReferenceThe MSS15K can also extract timing from an incoming traffic OC-3/STM-1 signal. Three incoming signals can be configured as ‘Primary Reference,’ ‘Secondary Reference’, ‘Tertiary Reference’ at provisioning time, for redundancy purpose. The chosen timing reference will be provided on all outgoing links. In case of failure of all of these incoming signals, the MSS15K will go to the Holdover Mode. In this mode, the stratum 3 Clock of the MSS15K continues to operates at its last adjusted frequency and does not update its frequency.

Network Synchronization StrategyIn GSM and UMTS BICN networks, it is recommended that the MSS 15000 nodes (AN and MGW) use a combination of external timing and line timing as described in the following sections.

OC-3/ATM based networkFor an OC-3 based network, all of the MSS 15000 shelves at the Central Office use an external timing reference, connected to its BITS/Alarm module. The AN or MGW Shelf then distributes the timing reference over its OC-3 ATM carriers to all remote sites. The remote AN and MGW shelves use Line Timing to extract the reference from the OC-3 carriers. The remote AN and MGWs, in turn, distribute the timing reference to the other co-resident shelves over OC-3 carriers. Figure 5-1 illustrates the shelf timing in an OC-3 ATM network.

Note: Figure 5-1 shows ANs in both the local and remote markets. If the ANs are not present, a MGW shelf performs the same function with respect to timing.

411-2231-330 Standard 02.06 May 2006

Media Gateway timing synchronization 5-3Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 5-1 Shelf timing in OC-3 ATM network

DS-3/ATM based networkTiming of the components at the CO can be accomplished in the manner discussed in the “OC-3/ATM based network”. However, the optical carriers at the CO and remote markets are separated by an intermediate electrical (DS3) packet network. Unchannelized DS3 carriers are asynchronous and not suitable for timing. Therefore timing from the CO cannot be propagated to the remote markets via these point-to-point DS3s.

There are a number of options available for synchronizing the remote markets: 1. Use line timing at the remote sites, whereby each MGW shelf obtains

timing from OC-3 ports connecting to the PSTN, BSS or UTRAN, assuming these are traceable to the operator’s Stratum 1 timing source.



Figure 5-2 Network synchronization for NA market electrical ATM network (Option 1)

2. Install a GPS receiver at each remote site, which will provide the BITS module of a MSS 15000 with a Stratum 1 timing source. This MSS 15000 can then provide the other MGW shelves in that remote market with their timing. Have GPS receivers at multiple sites in the network does not pose a problem as they all obtain timing from the same satellite(s), but this solution does add cost. This does not work well with multiple CBOs as they could be out of phase from one another.

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Media Gateway timing synchronization 5-5Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 5-3 Network synchronization for NA market electrical ATM network (Option 2)

3. Run T1s from the Office BITS at the CO to each remote market. The OPEX cost of these extra transmission facilities makes this option unattractive.



Figure 5-4 Network synchronization for NA market. electrical ATM network (Option 3)

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Media Gateway APS hardware 6This chapter presents the following topic: • Audio Provisioning Server (APS) hardware

Audio Provisioning Server hardware 6Note: The Universal Audio Server (UAS) is used to store announcements and we ftp the files from the UAS to the MGW. The UAS does not get involved with the playout of announcements during calls. That happens on the MGW.

The Audio Provisioning Server (APS) is built upon the Nortel Networks Interactive Provisioning Server platform (IPS). This platform provides a centralized location and Graphical User Interface (GUI) for configuring and administrating the audio database and audio files used by the Media Gateway (MGW). The MGW and the audio provisioner access the APS by one of the following methods: • Data entry using the Graphical User Interface provisioning tool

(Provisioner to APS)• Audio distribution via the provisioner process (APS to Application

Server/MGW) automatically on an hourly basis• Immediate audio distribution to a MGW node when initiated by a user

from the APS GUI• Manual export audio package distribution via ftp to gateways

(provisioner/administrator to APS)• MGW automatically requests an audio update from the APS upon its

return to service after being in an out of service state

There is no support for real-time audio updates coming from the Application Server/MGW to the APS.

The APS provides to the audio provisioner access to its functionality through the use of any standard Internet network browser such as Internet Explorer (version 5 or higher) or Netscape (version 4.7x or higher) from their desktop.


6-2 Media Gateway APS hardwareNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

The platform is a carrier grade compatible, Solaris-based server. This platform is based upon the NEBS-3 compliant Sun Microsystem Netra1 t1400 (DC power) Solaris-based server. This server is suitable for location in the central office telephony environment.

The APS server has many of the reliability, availability, and serviceability features found in most central office environments. The platform is specifically designed for use in telecommunications and service provider applications by providing a high performance CPU, high speed memory, PCI connectivity, ultra SCSI disks, and high speed interconnects. A supplied rack mounting kit is used to install the unit within a standard, telephony central office environment rack.

The platform provides redundant power supplies for high reliability, availability, and serviceability found in telephony central office environments. There are three power supply units (PSUs) spared as n+1 allowing an extra power supply for redundancy. These power supplies are hot swap capable. The server platform consists of a PCI based processor that provides four expansion slots with three 33 MHz PCI slots and one 33/66 MHz PCI slot.

The platform provides 4 internal 36 Gbyte hot swappable drives connected into the system through an ultra-SCSI interface. Easy to read LEDs exist on the front of the platform to provide a visual indication of power, faults, and alarm status. Additionally, two 10/100BaseT Ethernet interfaces are available for network connectivity.

Hardware detailsThe Audio Provisioning Server is based upon a Interactive Provisioning Server hardware platform provided by Nortel Networks.

Figure 6-1 IPS base system

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Media Gateway APS hardware 6-3Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

ConfigurationThe IPS system upon which the Audio Provisioning System is built is a fixed configuration.

Four internal 36 GByte SCSI disk drives are used to host an Oracle database which is replicated across the drives for reliability and robustness of the stored data.

Table 6-1 - Basic APS capability and standard configuration

Vendor: Nortel Network Information Services Interactive Provisioning Server (Sun Microsystems Netra t1400 server)

Power Input: Three (n + 1 redundant, hot swapable) DC power supplies 48/60 V DC nominal, 330W dual input

Processor: Two 64-bit UltraSparc II processors at 440 MHz (additional CPUs can be provisioned - future)

Cache: 16 Kbyte data and 16 Kbyte instruction on chip Secondary: 4Mbyte external (per installed processor module)

RAM: 2 Gbytes (expandable up to 4 Gbytes - future)

Memory Management:

MMU with 64 I-TLB entries and 64 D-TLB entries, 8192 hardware supported contexts

Base disk drive:

4 - 36 GBytes hot swappable internal ultra-SCSI drives

Serial: 2 RS-232C/RS-423 serial ports (DB25 connector)

Ethernet: 10 and 100BaseT fast Ethernet using a twisted-pair cable through an 8-pin RJ45 connector

DVD-ROM drive:

10x - internal SCSI drive

O/S: Solaris 8

Tape Drive: Internal 4mm DDS-3 12 Gbyte

Alarms: Critical, Major, Minor

Local Visual Displays:

Status LEDs for Power, Fault, and Alarms

Certifications: Telecordia NEBS level 3 certified and ETSI compliant


6-4 Media Gateway APS hardwareNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Headless OperationThe configuration of the Interactive Provisioning Server (IPS) allows the platform to operate as a headless server. Access to the platform is possible through a standard telnet session, a terminal connection into one of the RS-232C serial ports provided by the platform, or on a temporary basis through a local terminal connection via the second serial RS-232C port provided by the platform.

Note: Accessing the platform through a telnet session provides the flexibility to the user to utilize a windowing software package available on the local desktop.

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Standard interfaces and routers 7This chapter presents the Media Gateway (MGW) topics: • Interfaces• MGW interface support summary• IP addressing and routing

Interfaces 7The following are the BICN inter-nodal interfaces presented in Figure 1-1: • A Interface: the GSM signaling interface for call control between BSS

and MSC, and also transports PCM-encoded bearer traffic to the MGW.• Iu: the UMTS signaling interface for call control between the UTRAN

and MSC, and also transports AMR-compressed bearer traffic to the MGW. According to the standards, the Iu interface also consists of an interface to the UMTS packet network (that is, between the UTRAN and SGSN).

• Nb: is the 3GPP-defined interface for bearer control signaling and bearer transport between Media Gateways. In the Nortel configuration, Nb is the interface between MGWs residing under different Call Servers.

• Nb’: a Nortel-defined interface for bearer control signaling and bearer transport between Media Gateways under the same Call Server.

• Nc: the signaling interface for call control between call servers.• Mc: the media control interface between call servers/gateway controllers

and Media Gateways and is comprised of H.248 signaling. • C, D: MAP-based interfaces between the HSS and the V/GMSC and are

used to exchange the data related to the location of the mobile station and the management of the subscriber.

Note: The following sections are a summary of the protocols stacks for each MGW interface (the Nc, C, and D interfaces are MSC Server-only, are outside the scope of this document).


7-2 Standard interfaces and routersNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

A interface (BSS - MSC Server, BSS - MGW)The A interface is used to transport DTAP and BSSMAP signaling messages between the BSS and the MSC, and to transport bearer data between the BSS and the MGW. The figures below depict the protocol stacks for both the bearer and signaling planes of the A interface.

The A interface bearer plane data is handled by the Vsp4e FP. DSPs on the Vsp4e convert bearer data between TDM and AAL2/ATM packet formats and applies voice quality features to the bearer data. For more information on the media adaptation and VQ services performed by the DSPs.

Figure 7-1 A interface Bearer Plane protocol stack

The A-Interface Signaling plane consists of BSSMAP and DTAP signaling between the BSS and the MSC. The MGW provides a signaling backhaul service, receiving BSSMAP/DTAP messaging over narrowband SS7 from the BSS, and converting MTP2/MTP1 to M2UA/SCTP/IP for transfer to the USP over the packet network. The USP, in turn, converts MTP3/M2UA/SCTP to M3UA’\/UDP for transfer the MSC Server.

Figure 7-2 shows the A-Interface signaling backhaul and appropriate protocol stacks into and out of the A-Interface MGW.

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Standard interfaces and routers 7-3Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 7-2 A-interface signaling backhaul

The signaling plane of the A interface may also be transparently switched through the MGW via AAL1-CES (Circuit Emulation Service) to the DMS-MSC. The MGW does no interpretation or processing of this signaling data.

Iu interfaceThe Iu interface can be logically divided into the following areas:• Bearer Control Plane:

— consists of the Q2630.1 protocol used for establishing and removing CS bearer AAL2 channels over the ATM interface. This plane, along with the CS and PS Control Plane, utilizes broadband SS7 transport protocols.

• CS and PS Control Plane: — carry the RANAP signaling for both CS and PS domains. This plane,

along with the Bearer Control Plane, utilizes broadband SS7 transport protocols.

• PS Bearer Plane: — the GTP-U protocol for packet switched data. It utilizes IP over ATM

transport protocols.• CS Bearer Plane:



Note: The document deals with the Media Gateway, only the circuit-impacting protocol layers are considered here. Therefore, the PS Bearer Plane is not considered further.

Figure 7-3 Iu-interface control and bearer planes

Figure 7-4 Protocol layers between the RNC and MGW

Iu-CS (RNC - MSC, RNC - MGW)The Iu-CS interface consists of the Bearer Control Plane, CS Bearer Plane, and CS Control Plane.

Iu-CS Control PlaneThe Iu-CS Control Plane between the RNC and the MSC Server is SS7 based, and carries RANAP signaling between the RNC and the MSC. RANAP also encapsulates layer 3 messages sent between the UE and the MSC.

The main purpose of the Control Plane is to convey mobility management, call control, and RAB management messages between the UTRAN and MSC.

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The MGW receives the Control Plane signaling over broadband SS7 and converts the SAAL-NNI/AAL5 to M2UA/SCTP/IP for transfer to the USP over the packet network. The USP, in turn, converts MTP3b/M2UA/SCTP to M3UA’\/UDP.

Figure 7-5 shows the Iu-CS Control Plane signaling backhaul along with the appropriate protocol stacks.

Figure 7-5 Iu-CS signaling plane backhaul

Iu-CS Bearer PlaneThe Iu-CS Bearer Plane between the RNC and MGW is AMR/IuUP/AAL2. The MGW supports the AMR and AMR2 codecs. In addition, RLP framing for Circuit Switched Data (CSD) at 14.4kbp and straight Unrestricted Digital Information (UDI) for CSD at 64kbps are also supported, depending on the call type established.

Figure 7-6 Bearer protocol layers between the RNC and MGW



Bearer Control PlaneThe Bearer Control Plane is responsible for establishing and maintaining AAL2 bearer resources between the RNC and Iu MGW. It uses the ALCAP (Q2630) protocol to manage AAL2 paths and to establish and release connections within these paths.

Figure 7-7 Protocol stack for Iu bearer control signaling

Nb Interface (MGW - MGW)The Nb interface transports bearer control signaling and bearer information between Media Gateways. As defined in the 3GPP standards, the bearer control signaling for ATM-based networks is Q2630.2, which provides dynamic setup and teardown of AAL2 connections between Media Gateways.

Note: The AAL2 setup between MGWs under the same MSC is provided via local/remote descriptors transferred through the MSC Server (via H.248 messaging). Setup via Q2630.2 is not supported between MGWs under the same MSC.

Figure 7-8 depicts a network with two Call Servers and Nb Gateways connecting the two MSC regions.

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Figure 7-8 Nb protocol stacks

Figure 7-9 presents the Nb’ and Nb bearer data protocol stacks.

Figure 7-9 Protocol stack for Nb’ and Nb bearer information

The signaling plane for Nb’ is a proprietary mechanism that transfers the necessary bearer characteristics and profile information through the MSC Server to the peer Media Gateway.

The interface between Media Gateways under different Call Servers is the standards-defined Nb interface. This interface uses Q2630.2 to establish dynamic AAL2 links between Nb MGWs. The Nb bearer control protocol stack is illustrated in Figure 7-10.



Figure 7-10 Protocol stack for Nb bearer control signaling

Mc Interface (MSC Server - MGW)Mc is the control interface between the MSC Server and the Media Gateway. It is developed under the guiding influence of several standard specifications, including 3GPP 29.232, ITU Q.1950, and, in particular, ITU H.248. The Mc interface allows the MSC Server and Media Gateway to exchange both call processing and non-call processing (maintenance) messages via an open interface. Both text-based and binary Basic Encoding Rules (BER) ASN.1 formatting is supported on Mc. The MGW currently supports only binary BER ASN.1 formatting, as described in Annex A and Annex C of ITU H.248.

The H.248 traffic is encapsulated in RFC1483/AAL5/ATM cells for transfer to the MGW. Figure 7-11 depicts this protocol stack.

Figure 7-11 Mc Protocol stack

Note: The transport layer used on the Mc interface, UDP, is an accepted transport for H.248, but is not 3GPP compliant. Therefore, this interface is referred to as Mc throughout the remainder of this document.

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MGW interface support summary 7Table 7-1 summarizes the Media Gateway interfaces and the current level of support by the Nortel MGW.

IP addressing and routing 7MSS Virtual Routers

MSS virtual routers (VR) provide a software emulation of physical routers. A VR has two main functions: • Construction of routing tables describing the paths to networks or

subnetworks• Forwarding or switching packets to the final destination network or

subnetwork

VRs on a MSS node can perform the functions of independent physical routers, forwarding packets to the correct destination, while isolating traffic from other VRs in the same way that physical routers do. VRs also have independent IP routing tables that are isolated from each other.

The management VR is a MSS VR that provides a single point of external entry into the MSS node. You can use the management VR to manage all customer VRs that reside on the MSS node. The first VR you create on a MSS

Table 7-1- MGW interface support in MG18

Interface Supported Notes

Mc Partial Standards based, but not open in this release of the MGW. The Statements of Compliance (SoC) for 3GPP 29.232 and H.248.1 detail the current non-compliances.

Nb Partial Between Media Gateways under the same Call Server, the Nb’ interface is used. Nb’ employs a proprietary signaling interface.

The 3GPP standards-defined Nb interface is used between Media Gateways served by different Call Servers.

A Yes Signaling plane backhauled via M2UA/SCTP/IP, bearer plane supported on the Vsp4

Iu Yes Signaling plane backhauled via M2UA/SCTP/IP.

Bearer Plane and Bearer Control Plane supported on the VSP4.



node becomes, by default, the management VR. All VRs added after the management VR are considered customer VRs.

The VR has logical ports, call Protocol Ports, which link the VR to different media and types of media. Protocol Ports are assigned an IP address(es).

Virtual Router Access Point (VRAP)Virtual Router Access Point (VRAP) supports inter-working between VSP cards and the IP stack on the Virtual Router, allowing the MGW to utilize the IP functionality available on the MSS. This includes DiffServ or Class of Service (CoS) support on IP cards, ECMP, and IP network failure protection via redundant IP network connectivity.

Figure 7-12 presents the VSP IP connectivity (over SPVCs) at the CO without VRAP.

Figure 7-12 CO MGW IP connectivity without VRAP

With VRAP, the Vsp4s interface directly to a VR on the MGW shelf as shown in Figure 7-13.

Note: The VRAP eliminates the SPVCs between each Vsp4e card and the ATM I/O card, and also reduces the number of PVCs between the MGW shelf and the AN (1 PVC per shelf instead of 1 per Vsp4).

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Figure 7-13 CO MGW IP connectivity with VRAP

IP access mechanisms and mediaIP access can be achieved through the following interface protocols including: • Ethernet• ATM

Both the CP3 and the 2pGPDsk FPs offer 100BaseT Ethernet connectivity. Management functions on the MSS node may use the CP3 Ethernet media for external access. The 2pGPDsk FP serves as the HIOP interface to the MSC, offering an 100BaseT interface to the MSC and aggregating the IP-based H.248 signaling traffic.

The ATM Multi-Protocol Encapsulation (MPE) interface is an access service that allows IP encapsulation over ATM in accordance with RFC 1483. The ATM MPE service allows IP traffic to be transmitted across the ATM network using the ATM MPE media.

IP addressesA subnet may be provisioned against a VR. All IP media that link to that VR may acquire and own an IP address from the subnet. The applied network mask of n bits determines the quantity of IP addresses for a given subnet resulting in 2n addresses. Two of this set of addresses are reserved for: • Broadcast IP Address• Forwarding IP Address

leaving 2n - 2 addresses for the various IP media linked to that VR.



IP based applications on the MGWThe applications running in the MGW shelf requiring IP addresses are shown in Table 7-2.

IP RoutingThe MSS 15000 supports several IP routing techniques/protocols. However, only static routing is supported on the MGW and AN nodes.

I/O aggregationThe MGW supports the following types of physical interfaces: • ATM• TDM• Ethernet

The Aggregation Node supports an ATM WAN interface, utilizing either OC-3 or DS-3 connectivity.

All ATM I/O, including both ATM cell switching (AAL2, AAL5) and IPoATM (IP/AAL5/ATM), route via either the AN or MGW (depending upon which is present). TDM traffic exits the MGW via Vsp4e FP, and does not need to pass through the AN. The TDM interface FPs, if present, carry only SS7-based signaling, using the AAL1-CES service to transport the signaling

Table 7-2- IP based applications

Processor Clients # IP addresses

IP address type Applicable to

CP3 OA&M 1 Private-Routable All MSS 15000 shelves

Vsp4 SPM (H.248) 1 Private-Routable All MGW personalities

SSM (SIGTRAN)

1 Private-Routable MGWs supporting SIGTRAN backhaul

PDC (MTP3b) 1 Private-Internal MGWs supporting Iu or Nb interfaces

2pGPDsk HIOP I/F 1 Private-Routable All MGW and AN shelves hosting 2pGpDsk FPs.

4/16-port OC-3 ATM

SAAL-NNI 1 Private-Internal All ATM I/O cards hosting SAAL-NNI

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over the packet network to the MSC. This AAL1-CES encapsulated signaling traffic also routes via the AN (if present) or the MGW.

Each MGW shelf requires, at a minimum, one OC-3/STM-1 port for connectivity, not including redundancy. In some cases, the total shelf’s I/O bandwidth, bits per second (bps), and packets per second (pps) may not fully utilize the port(s) between the local shelves. The I/O port requirements toward the network will need to accommodate the aggregate I/O bandwidth (bps) and load (pps). Generally, the total port requirements at the network edge will be less than the port requirements at the MGW edge. This offers a cost savings opportunity ensuring that all network I/O connectivity is utilized to its fullest.

The next level of I/O aggregation is to consolidate the network I/O into larger bandwidth interfaces. Based upon traffic models, however, larger bandwidth interfaces (e.g. OC-12/STM-4) are not required at this time.

Ethernet I/O is supported by the 2pGpDsk FP, and serves as the HIOP interface in the AN/MGW local to the CO.

MGW inter-shelf communicationInter-shelf communication between the various shelves is performed via ATM links employing the 16pOC-3 FP and Single Mode version of the 4pOC-3 FP.

Note: The Multi-Mode version of the 4pOC-3 ATM FP is not used for inter-shelf communication in order to avoid the use of attenuators for the instances where it interfaces with a Single-Mode ATM FP. The Multi-Mode version may be used for the network interface.

On the network facing interfaces, the AN and MGW are engineered as needed to provide the necessary physical connectivity, services, and bandwidth required by the transport network and GSM traffic.

MSS servicesThe MSS 15000 is a multi-service switch supporting a rich set of both IP and ATM services. Many of these services are considered table-stakes, are found in the MGW, and are fundamental to the operation of the MGW such as: • IP Addressing Protocols• Virtual Routers• IP over ATM Multi-Protocol Encapsulation (MPE)• Permanent Virtual Circuits (PVC)• Static Routing



Private network-to-network interfaceMSS private network-to-network interface (PNNI) Version 1.0 standard protocol is used between ATM switches, and groups of private ATM switches. MSS PNNI includes two categories of protocols: • A protocol defined for distributing topology information between

switches and clusters of switches.• A protocol defined for signaling and used to establish point-to-point and

point-to-multipoint connections across the ATM network.

PNNI uses source routing. The first node in a connection decides the route that the call takes, and subsequent nodes forward the call setup message along this pre-determined route. If a subsequent node rejects the connection, call setup retraces the path to the originating node. The originating node uses alternate routing information and re-attempts call setup.

PNNI is utilized by the AN and MGW in the following situations: • Inter-shelf communication utilizing SVCs• Inter-shelf communication when used in conjunction with Soft PVCs.

Soft permanent virtual circuitsSoft permanent virtual circuits (SPVC) perform the following tasks: • Reduction of provisioning. The end points must be provisioned but any

ATM switched in the network do not as they would for PVCs. • Connectivity resiliency via dynamic rerouting upon ATM link/nodal

failure.

Dynamic rerouting is accomplished with the assistance of an ATM routing protocol. If the node is supporting User-to-Network Interface (UNI) or Interim Inter-switch Signaling Protocol (IISP) interfaces, you must configure network nodes for hop-by-hop routing and that effectively defeats at least one purpose for Soft PVCs. For network nodes supporting PNNIs, no additional configuration is required. SPVC and SPVP connections also support automatic route selection and connection establishment as well as re-establishment. In addition, for IPoATM traffic, Soft PVCs are only supported with PNNI. Therefore, only PNNI is supported with Soft PVC.

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Media Gateway Voice Engine functionality 8

This chapter presents voice quality features and a description of the digital signal processor (DSP).

Digital signal processor 8The DSPs residing on the Vsp4e FP are responsible for performing the media processing functions. This includes converting circuit bearer traffic (e.g. voice or circuit-switched data) between the formats used in wire-line PSTN and the formats used in wireless access networks. The DSPs also provide voice quality features described in subsequent sections. The key components of the DSP are: • G.711 u-law and A-law companding• AMR/AMR2 12.2 kbps transcoding for Iu interface supports (UMTS) and

for CN Compression (UMTS and GSM)• Text Telephony - Cellular Text Modem (CTM) support• Tandem Free Operation (TFO) In-Path Equipment Compliancy• Tones and Announcements• Handover Support• Lawful Intercept tapping• LI multi-casting• Conference Bridge• Vocoder bypass for Motorola Integrated Digital Enhanced Network

(IDEN)• Voice Quality Enhancement Features

G.711 compandingG.711 companding is based on logarithmic quantization techniques where low-level signals are encoded with higher resolution than high-level signals. Two encoding laws are recommended and they are commonly referred to as A-law and u-law (Mu-law).


8-2 Media Gateway Voice Engine functionalityNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

The G.711 decoder expands the 8-bit A-law samples to 13-bit uniform samples. Similarly, 8-bit u-law (Mu-law) samples are converted to 14-bit uniform samples. The G.711 encoder compresses 16-bit linear samples to 8-bit PCM companded format. Accordingly, A-law conversion will only consider the 13 significant bits, and u-law conversion will employ the 14 significant bits. By default, the even bits of the A-law samples are inverted after compression, as well as before expansion. This was performed since certain devices within the transmission system may rely on the data stream to extract a clock signal. Even-bit-inversion increases the likelihood of transitions in the encoded signal, thus allowing devices to extract a clock signal. Additional options are provided with A-law companding. As a result, there are four available bit-inversion choices for each PCM companding law: • No Bit Inversion (NBI)• Odd Bit Inversion (OBI)• Even Bit Inversion (EBI)• All Bit Inversion (ABI)

Independent provisioning for Packet and TDM G.711 companding law is provided. In this release of the MGW, the following companding options are supported on TDM interfaces: • u-law and a-law NBI• u-law and a-law OBI• u-law and a-law EBI• u-law and a-law ABI

In addition, packet-based networks also support the following companding options: • a-law EBI• a-law ABI• u-law

AMR speech codecIn 3GPP Release 4, the mandatory speech codec for narrowband speech signals is the Adaptive Multi Rate (AMR) speech codec. Wireless speech codecs (encoder/decoder) employ speech coding algorithms to account for limited bandwidth and transmission conditions found in wireless access media.

Depending on its personality, a media gateway can carry out the speech transcoding functions for the current call. Via the Iu or Nb interface, the Transcoding and Rate Adaptation Unit (TRAU) receives AMR encoded voice over ATM or IP packets from a network (UMTS network, core network or

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Media Gateway Voice Engine functionality 8-3Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

external network). These AMR encoded packets are encapsulated using the I.366.1 format (the I.366.2 format is not supported for AMR).

The AMR speech codec consists of a multi-rate narrowband speech codec, a source-controlled rate mechanism that employs a voice activity detector and a comfort noise generator, and an error concealment algorithm to mitigate the effects of transmission errors and lost packets.

The AMR speech codec is based on the Algebraic Code-Excited Linear Predictive (ACELP) coding model, using a 10th order linear prediction synthesis filter. The codec operates on speech frames of 20 ms corresponding to 160 samples at a sampling frequency of 8 kHz. The AMR codec is includes a set of eight fixed rate speech codecs that adapts its encoding rate in response to changing radio and traffic conditions or to the needs of the network operators. The following bit rates are supported on the Iu interface:• 12.2 kbps (GSM EFR)• 10.2 kbps• 7.95 kbps• 7.4 kbps (TIA IS-641)• 6.7 kbps• 5.9 kbps• 5.15 kbps• 4.75 kbps

At every 20 ms frame, the speech signal is analyzed to extract the parameters of the ACELP model. These parameters are then encoded and transmitted at the specified bit rate. At the decoder, the parameters are decoded and the speech signal is synthesized by filtering the reconstructed excitation signal through the LP synthesis filter.

Source Control Rate (SCR) operation, also known as Discontinuous Transmission (DTX), is a mechanism for the AMR speech codec to encode the input signal at a lower average rate by exploiting instances of speech inactivity in the signal. This will allow a reduction in overall interference and processing load in the network. The DTX mechanism requires the following components in the Transmit or encoder direction: • Voice activity detector (VAD): Background or comfort noise estimator for

transmission

In the Receive or decoder direction, a comfort noise generator (CNG) inserts background noise during periods where transmission is switched off.



In the event of lost AMR frames, normal AMR speech decoding would result in undesirable and annoying noise effects. To improve subjective quality, the lost speech frames are substituted with the extrapolation of previous good speech frames. The signal level is gradually attenuated over successive lost frames until the output is finally muted. This will indicate a breakdown in the transmission channel.

Vocoder bypass for IDENThe DSP supports vocoder bypass support in the Motorola integrated Digital Enhanced Network (iDEN). iDEN vocoder bypass is a Motorola proprietary vocoder bypass technique for disabling vocoding operation in the base station in iDEN mobile-to-mobile calls. The objective of the support is to provide transmission bandwidth reduction to all voice traffic and to support iDEN vocoder bypass operation for voice quality improvement in iDEN mobile-to-mobile calls.

Voice quality enhancement featuresThe Nortel MGW supports the following VQ features: • Echo Canceller (ECAN)• Comfort Noise Generator for Echo Canceller (ECNG)• Mobile Echo Control (MEC)• Background Noise Conditioning (BNC)• Automatic Gain Control (AGC)• Background Noise Reduction (BNR)• Packet Mobile Echo Control (Pkt-MEC)• Packet Automatic Gain Control (Pkt-AGC)• Packet Background Noise Conditioning (Pkt-BNC)• Artifact Concealment

The following sections describe the MGW’s Voice Quality features in more detail. Figure 8-1 and Figure 8-2 present the placement of the VQ features with respect to the MGW personality types for compressed and uncompressed networks.

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Figure 8-1 VQ feature positions in compressed (AMR) networks



Figure 8-2 VQ feature positions in uncompressed (G.711) networks

Automatic gain controlThe function of the Automatic Gain Control (AGC) feature is to keep the speech energy at a constant level with respect to a reference by applying an adaptive gain factor to the speech signal. The gain factor is computed and applied every frame in order to slowly (smoothly) adjust the speech signal to the desired level. The gain factor can be computed to either increase or reduce the speech energy. The AGC gain factor is updated only during voiced periods, and it is done gradually so that speech artifacts are avoided. During silence and noise, the gain factor must be frozen but is still applied. The AGC feature therefore requires, as an input, the result of a voice activity detection (VAD) scheme to know if the input frame is speech or silence. Depending on the selected target level, the AGC will also prevent saturation of speech signals. The AGC modules are placed in the MGWs so that both users benefit from an energy normalized speech signal.

The AGC operating parameters are shown in Table 8-1. The upper and lower limits of the AGC gain range can be changed in 1dB steps within the MGW provisioning. The target signal power is set to a default level of -19 dBm0 and can be configured within the MGW provisioning (it can be varied in 1dBm0 steps).

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The AGC computes the signal energy at each frame and an average is calculated over a longer period. The average power is compared to the target signal power. The gain is then increased or decreased accordingly, always within the allowed ranges and speeds.

The AGC feature can be enabled, or disabled within the MGW provisioning. By default, the AGC feature is disabled. The AGC features are compliant to the ITU-T Recommendation G.169.

Echo cancellerECAN componentThe function of the echo canceller (ECAN) is to cancel reflections typically introduced by 4-wire to 2-wire hybrid transformers used at the boundary of the PSTN to terminate local loops. The echo canceller models the echo path by means of an adaptive linear FIR filter. The echo canceller tracks the location of echoes and determines the impulse response of the echo path continuously. The signal that goes out to the PSTN side (referred to as the far-end signal) is passed through the FIR echo path model. The filter output, called the echo estimate, is subtracted from the sum total of the circuit echo and the signal coming in from the PSTN side (referred to as the near-end signal). Figure 8-3 shows the block diagram of a typical echo canceller.

Figure 8-3 ECAN block diagram

If speech of tone signals originating from the PSTN side (near-end speech) of the voice connection is detected, the filter adaptations are frozen in order to avoid divergence of the filters and subsequent degradation of the echo

Table 8-1- AGC operating parameters

Gain Range Default: -10 to 10dB

Range: -14 to 14dB

Target signal power Default: -19dBm0

Range: -30dBm0 to -9dBm0



canceller performance. This condition is known as double-talk. The device used to track the occurrence of double talk is referred to as the double-talk detector.

Note: Single talk occurs if the echo canceller determines that only signals from the reverse link (mobile) are present.

Because of computational limitations, the FIR filter may not completely remove the echo from its input signal (nearend + echo signal). A residual echo control mechanism, also known as a non-linear processor (NLP), is used to replace the output of the echo canceller with noise when the near-end talker is silent in order to eliminate residual echo. The residual echo control relies on the performance of the double talk detector.

Table 8-2 shows the specifications of the Vsp4e echo canceller.

Note: The Echo Canceller can be enabled or disabled on a per call basis by the MSC Server via H.248 messaging. In the Nortel solution, the MSC Server uses H.248 messaging only to disable ECAN (for CSD calls, for instance). The MSC Server does not enable ECAN on a per-call basis.

Comfort Noise Generator for Echo CancellerECAN cannot fully remove echo from the PSTN input in a mobile to landline call. To prevent the detection of residual echo during mobile single-talk, comfort noise is substituted into the affected landline speech. As the talker is preoccupied with speaking, they will not easily detect the artificial background noise.

The ECAN Comfort Noise Generator (ECNG) synthesizes noise that resembles the background noise of its input. When the ECAN signals ECNG

Table 8-2- Vsp4e ECAN specifications

Parameter Possible values

Operating mode Enabled or disabled

Hybrid detector Enabled or disabled

ECAN comfort noise generator Enabled or disabled

Tail length 64ms or 128ms

Minimum ERL 3dB or 6dB

Tail length offset (fixed delay) 0-16ms (only when Tail length set at 64ms)

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that certain samples contain only residual echo, ECNG replaces them with comfort noise.

The comfort noise is generated by passing white noise through a shaping filter. The filter transfer function is based on statistics collected during non-speech periods.

ECNG has been designed to be invoked with a variable frame length between 0 and 40 ms.

Mobile Echo ControlMobile Echo Control (MEC) is a technique developed to contain echo caused by the acoustic coupling between the speaker and the microphone of mobile user terminals and hands-free kits. MEC employs echo suppression to reduce the perception of echo by replacing the echo signal with a noise signal. The noise signal is intended to prevent any perception of discontinuity during echo suppression. The MEC feature consists of two components: a mobile echo detector, and a comfort noise generator.

The mobile echo detector component determines whether there is a noticeable echo in the signal received from the mobile user equipment in the uplink direction. The mobile echo detector also determines the presence of double-talk, wherein the mobile echo co-exists with mobile user speech activity. The mobile echo detection result is passed to the comfort noise generator. Upon detecting mobile echo, the comfort noise generator (CNG) will generate noise similar to the original background noise to replace the mobile echo. This is carried out through an adaptive technique that mimics the characteristics of the background noise in a continuous manner.

MEC is designed to remove the mobile echo whose delay is between x and x+140ms, where x is the programmable fixed delay, which can be initialized or/and modified by the operators through provisioning. Under the current implementation, the programmable fixed delay, x, can be selected between 0ms and 320ms. That is, MEC is designed to remove the echo whose delay is between 0ms and 460ms.

Mobile Echo Control (MEC) is implemented in the MGW so that it suppresses and replaces the echo of the downlink signal reflected back in the uplink signal due to acoustic coupling within the mobile user equipment. In this case, MEC will detect echo based on the encoded speech parameters from both the downlink and the uplink. When echo is detected, the original uplink encoded parameters are replaced by the comfort noise’s encoded parameters.

MEC can be enabled or disabled within the MGW provisioning. By default, MEC is disabled.



Background noise conditioningLPC based speech coding algorithms represent speech signals as combinations of excitation waveforms and a time-varying all pole filter which model effects of the human speech production (articulatory) system on the excitation waveforms. The excitation waveforms and the filter coefficients can be encoded more efficiently than the input speech signal to provide a compressed representation of the speech signal. In particular, the UMTS wireless system employs the Adaptive Multi-Rate (AMR) speech codec, which consists of a set of 8 LPC-based low bit-rate speech codecs ranging from 4.75 kbps to 12.20 kbps. To accommodate changes in spectral characteristics of the input speech signal, conventional LPC based codecs update the filter coefficients once every 10 ms to 30 ms (for the AMR speech codec, the frame update period is 20 ms). This rate of updating the filter coefficients has proven to be subjectively acceptable for the characterization of speech components, but can result in subjectively unacceptable distortions for background noise or other environmental sounds.

Such background noise is common in digital cellular telephony because mobile telephones are often operating in noisy environments. In mobile telephony applications, landside and mobile users have reported subjectively annoying “swishing” or “waterfall” sounds during non-speech intervals, or report the presence of background noise that “seems to be coming from under water.”

One effective solution to the problem of noise distortions occurring when LPC type codecs are used is the Background Noise Conditioning (BNC) voice quality enhancement feature. This solution involves the detection of background noise (or equivalently, the detection of the absence of speech), at which time the parameters of the speech encoder or decoder would be manipulated in order to emulate the effect of an LPC analysis using a very long analysis window. This process is supplemented with a low-pass filter designed to compensate for the slow roll-off of the LPC synthesis filter when the input signal consists of broadband noise.

Background Noise Conditioning is implemented as part of the media gateway so that it is available to the landline user in the case of mobile-to landline calls. BNC improves the perceptual quality of background noise, such as engine noise or traffic noise surrounding the mobile user that has been processed by the Adaptive Multi-Rate (AMR) speech encoder and decoder. The noise is then "conditioned" by directly replacing the original encoded parameters with the background noise conditioned (and low-pass filtered) encoded parameters.

The BNC feature can be disabled, or enabled with or without the low-pass filter from within the MGW provisioning. By default, the BNC feature is disabled in both modes.

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Background Noise ReductionMobile telephony is particularly susceptible to problems associated with noise and thus highly appropriate for the application of noise reduction technology. Wireless telephony by definition has a lower speech quality than a wireline phone, due to the speech coding process that reduces the perceived quality. If, in addition, the system encodes the noisy signal, then further degradation in its performance results, since speech coders rely on a model for the clean signal and normally that model is not suitable for the noisy signal.

In speech coding situations, noise reduction at the front end (i.e. prior to encoding) will remove a great deal of additive noise, and results in a better end-to-end perceived voice quality and robust speech coding operation. In certain situations however, it is not possible to apply noise reduction prior to encoding. In these cases, speech enhancement is still possible by placing the noise reduction stage after compressed speech has been received and decoded at the far end, or at some intermediate point in the network (for example at the base station, or the switching center).

Background Noise Reduction (BNR) increases the quality and intelligibility of corrupted speech in order to improve the performance of voice communication systems. In general, the noise-attenuated speech is perceived to be more comfortable and clear to the listener at the landline or mobile (in the case of a mobile-to-landline call or of a mobile-to-mobile call respectively), and causes less listener fatigue during long conversations.

The design of this type of BNR is more demanding in comparison to those implemented in the mobile terminals where noise-filtering takes place before all other speech processes and is much closer to the true input speech signal. However, the current implementation has the advantage of providing increased quality of service to the uplink listener with effective noise reduction capability while requiring no update of the mobile user equipment.

BNR can be enabled or disabled within the MGWW provisioning. By default, the BNR feature is disabled. It should be noted that when the BNR feature is enabled in a 5 ms MGW, the processing delay of the link on which BNR is located would be increased by 5 ms because the BNR algorithm is based on 10 ms framing.

Packet MECPacket MEC (Pkt-MEC) has the same functionality as MEC but it is used for AMR-AMR Traffic or when TFO is engaged (TFO is not supported in MG18). Pkt-MEC and MEC require the same input parameters and call the same mobile echo detector. If the mobile echo is detected, MEC will output comfort noise in PCM samples while Pkt-MEC outputs comfort noise in the format of AMR encoded parameters.



Packet AGCPacket AGC (Pkt-AGC) has the same functionality as AGC but it is used for AMR-AMR Traffic or when TFO is engaged (TFO is not supported in MG18). Pkt-AGC and AGC require the same input parameters. AGC will directly adjust the energy level of the PCM signal while Pkt-AGC will modify the gain vectors of the AMR encoded parameters.

Packet BNCPacket BNC (Pkt-BNC) has the same functionality as BNC but it is used for AMR-AMR Traffic or when TFO is engaged (TFO is not supported in MG18). Pkt-BNC and BNC require the same input parameters. BNC will directly use the average LPCs to synthesize the noise signal while Pkt-BNC encodes the average LPCs into the AMR parameters for noise frames.

Artifact concealmentAbrupt discontinuities of speech segments may occur on the downlink or uplink paths of the TRAU. These discontinuities occur due to many reasons such as the phase shift resulting from an RNC Iu time alignment request in order to minimize the downlink delay across all active channels processed by the DSP core, or by the phase shift caused by the ADOM feature in order to minimize the uplink delay. As a result, subjectively noticeable artifacts such as clicks and pops are introduced if the amount of the phase shift is not controlled properly. In order to mitigate these undesirable effects, this feature applies different concealment techniques to the speech signal depending on whether it is voiced or unvoiced or background noise so as to lengthen or shorten the speech segment.

In order to conceal these noticeable "clicks" and "pops", the pitch contour must be maintained smoothly throughout the voiced segments. No sudden jerk is allowed. Hence, for voiced segments, the amount of shift is restricted to be an integer multiple of a pitch period. Depending on whether the frame is short of samples or surplus of samples, the artifact concealment algorithm will either insert or drop samples. As a consequence, the entire alignment process may spread across multiple frames, unless the pitch period just happens to be exactly the same as the number of short or surplus samples.

For unvoiced speech, background noise, or silence segments, the above restriction imposed on shifts does not apply. In other words, the number of samples can be inserted or dropped at will because there is a lack of periodic structure. In this case, the entire process takes a single frame to complete.

The artifact concealment algorithm is hence composed of the following building blocks: • Voice activity detector (VAD)• Voiced and unvoiced detector

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• Insertion speech template buffer

Tandem free operation in-path equipment compliancyTandem Free Operation (TFO) is an in-band based communication protocol, which enables transference of native voice encoding end-to-end for mobile-to-mobile calls. (Speech decoding is still performed for the benefit of any inpath equipment usage, that is, lawful intercept.) After TFO is established, effective speech encoding is performed only at the terminals. As a result, voice quality degradation introduced by tandem speech encoding and decoding processes are avoided, and end-to-end voice quality is improved.

The Nortel Networks Media Gateway does not support TFO in MG18, but is TFO In-Path Equipment (IPE) compliant, meaning it conforms to the requirements for IPE in GSM 8.62 (and 3GPP 28.062). The MGW transparently passes the TFO speech frames and Inband Signaling (IS) used to establish the TFO service.



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Media Gateway services 9This chapter describes some of the capabilities of the Media Gateway (MGW). This includes subscriber services such as Conferencing, regulatory services such as Global Text Telephony and Lawful Intercept, and network-related features such as Compression in the Core Network (CN).

AAL1 circuit emulation service 9AAL1 CES service is an alternative to the USP-based signaling backhaul option. AAL1 CES service encapsulates individual DS0s onto ATM VCs for transport to a remote node in the ATM network. There are two applications of the AAL1-CES service:

• SS7 backhaul (e.g. BSSAP, potentially ISUP) - Up to eight DS0s in a DS1 can be targeted for structured CES. The DS0s are mapped to one or more AAL1 SVCs.

• MF backhaul - The entire DS1 is backhauled via unstructured clear-pipe (Ucp) CES. The DS1 is backhauled via a single AAL1 SVC.

SS7 backhaul over structured AAL1 CESFor SS7 backhaul support, the A-Interface MGW employs Structured AAL1 CES to transport the A-interface channelized SS7 links from a remote BSS to the MSC Server. Similarly, the PSTN MGW can be configured to transport ISUP signaling from the PSTN to the MSC Server. Structured AAL1 CES allows up to 8 DS0s per T1 to be stripped off and put on one or more AAL1 SVCs and backhauled to the CO via the ATM network.

Figure 9-1 shows AAL1 CES carrying BSSMAP/DTAP messaging from a remote BSS to the MSC Server via the packet network.


9-2 Media Gateway servicesNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 9-1 AAL1 CES backhauling SS7

Figure 9-1 shows an AN at the CO. If no AN is present, the AAL1-CES flows enter the MGW through the 4pOC-3 ATM FP and traverse the same path though the MGW to the SPM.

Note: The TDM bearer is hairpinned in the 4pOC-3 TDM FP as depicted Figure 9-2.

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Media Gateway services 9-3Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 9-2 TDM bearer and signaling flow

Figure 9-2, a T1 carrier supporting both SS7 signaling and TDM bearer is multiplexed to the 4pOC-3 TDM card. The channels carrying the signaling traffic (dashed line) are sent on to the MSC Server using AAL1 CES. Channels carrying TDM bearer (solid line) are hair-pinned at the shelf backplane, then looped back out of the 4pOC-3 TDM FP to the mux, where they are then sent to the VSP4’s optical TDM port.

Note: Carriers supporting TDM bearer only (no signaling) are sent directly to the VSP4.

MF trunk support over unstructured AAL1 CESMF CAS trunks (sometimes referred to as North American R1) may also be supported on the MGW via AAL1 CES service. This solution leverages the “AAL1 unstructured clear-pipe” (Ucp) CES capabilities of the 4p OC-3 TDM FP that terminates the MF trunk at the MG. With Ucp CES, the framing signal is transported along with the DS1 data as payload (no data link is extracted). The MGW does no processing on the MF payload.

Note: The entire DS1 must be dedicated to MF signaling, fractional DS1 configurations are not allowed.

Circuit-switched data 9The circuit-switched data solution employs a GPP IWF hosted off of a MGW to provide CSD services in GSM and UMTS networks. The CSD services supported are equivalent to those currently supported in NSS17 and UMTS03, the difference is that the IWF is hosted off of a MGW instead of the legacy ENET and TDM peripherals.

Remote MSS Local AN MSS

Local MSS



Figure 9-3 CSD bearer flow

From Figure 9-3, the following observations can be made: • The GPP IWF is hosted off of a MGW. This "IWF-hosting MGW" can be

any Vsp4-based MGW with TDM connectivity, and may simultaneously host any of the other MGW personalities except the Multi-Party MGW.

• The IWF-hosting MGW is inserted into the call between the Access and PSTN Media Gateways, and provides TDM connectivity to the IWF via mobile-side Universal IWF Trunk (UIT) and network-side UIT TDM trunks.

• The IWF-hosting Media Gateway is configured via H.248 messaging the same as the other MGW personalities.

• The MSC still controls the IWF via MIP messaging, but the MIP messaging is transferred through the HIOP rather than the EIU.

MSS7K

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UMTS 64kbit UDI serviceThe UMTS 64kbit UDI service does not require IWF support. The Iu Access MGW is capable of supporting this service with a standard voice call Bearer Context layout. The 64kbit UDI call is configured via H.248 commands from the MSC, with the TMR parameter indicating the call type. Thus, an MS->PSTN 64k UDI configuration is illustrated in Figure 9-4.

Figure 9-4 UMTS 64K UDI call

Multi-Party (Conferencing) 9Conferencing, also known as Multiparty (MPTY), allows for more than two parties to converse together on a call. This feature requires the use of a conferencing bridge that mixes the individual voice channels and outputs a separate channel for each participant.

Note: Each participant has a unique audio experience, that is, each terminal can receive a different stream.

Figure 9-5 Conferencing

Figure 9-5 that the output of the conference bridge to a particular voice circuit is different for each caller. Party A does not hear his own voice, likewise neither do B and C.



The output to a given listener is determined by examining the other speakers and their loudness levels. The two loudest speakers are then mixed together and played out to the listening party.

The MGW conferencing solution supports: • A dedicated Vsp4e providing a pool of conference bridges for use by the

MGC Up to 6 parties in a Conference call• Both GSM and UMTS networks• Call Split, Call Hold, and other standard-defined multi-party services• AMR/AMR2 12.2 and G.711 bearer. A given conference call may include

both bearer types.• Lawful Intercept Mono-Mode Call Content by combining the Received

and Transmitted Call Content into a single stream.• The Conferencing-dedicated Vsp4e may also be used to support the LI

Distribution Function, which provides fan-out of intercepted Communication Content

From a network perspective, the Conferencing architecture is as presented in Figure 9-6.

Figure 9-6 Conferencing architecture

The Multi-Party Vsp4e is treated as a centralized resource within the network, most likely residing at the Central Office. When the Conferencing service is

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initiated, the existing backbone connections are removed and all parties have their bearer routed over the backbone to this centralized pool of Conference bridges, as illustrated in Figure 9-6.

Global text telephony 9Hearing-impaired and speech-impaired persons have been using Text Telephony (TTY) equipment in the fixed network for many years to transmit text and speech through ordinary speech traffic channels. Modern digital cellular systems, however, do not provide satisfactory character error rates for text transmitted in the speech channel with the traditional modulation developed for the fixed network.

The FCC under the US Government has required an urgent solution for all emergency (911) calls for one specific text telephone protocol of the ITU-T V.18 standard, called “Baudot Code”. The FCC has mandated that carriers provide 911 service for TTY callers over their digital networks by December 31, 2001 and that this solution is deployed across carrier networks. The MGW meets this requirement for both ANSI and ETSI versions of Baudot coding.

The Nortel Networks Media Gateway employs the "All transcoder solution", meaning there are no special Cellular Text Modem-capable resources in the network (every DSP in the MGW is capable of supporting the CTM modem). GTT calls are carried as Baudot tones over G.711 in both compressed and uncompressed networks as shown in Figure 9-7.

Figure 9-7 GTT architecture

In Figure 9-7, a TTY device is connected to a CTM-capable mobile device. This mobile device provides the Baudot-to-CTM transcoding prior to transmission over the air interface. In the Core Network, the MGW serving



the RNC receives the text transmission in the form of CTM over AMR. The MGW first performs the AMR decoding, then the CTM signal detection. If no CTM signal is detected, the audio signals are passed through unmodified. CTM signals, when detected, are decoded and converted to Baudot-encoded text characters over G.711.

Lawful intercept 9Lawful Interception (LI) is the process by which a Law Enforcement Agency (LEA) is permitted to ask the operator to electronically “wire tap” a subscriber's telecommunication traffic. Interception of voice calls in a telecommunication provider's network is already a mandatory operating requirement in many countries. An operator who does not meet national lawful interception requirements is not allowed to offer service in these markets.

The MGW supports the following functionality: • the tapping of both transmitted and received communications in the same

physical location• interception of a targeted subscriber’s Call Content (both transmitted and

received)• bi-casting of Call Content from the interception point. The MGW has

only one receive tap and one transmit tap for a subscriber.• an LI Distribution function, which can multi-cast received call content up

to 20 times (1:20 fan-out). The LIDF is part of the Conferencing/LIDF MGW, a dedicated Vsp4e reserved for this personality.

• both Separated Call Content Delivery and Combined Call Content Delivery via use of a standard Conference bridge

Figure 9-8 depicts the UMTS/GSM network from a LI-centric point of view. The LI tapping is performed in the Access MGW (except for some call forwarding scenarios). The intercepted call content is bi-cast to the Conferencing/LIDF MGW via the packet network. At the Conferencing/LIDF MGW, the Call Content is fanned-out, or multi-cast, according to the number of LEAs interested in the intercepted data. The call content may also be combined into a single stream via a Conference bridge, depending upon the format expected by the various LEAs. Finally, the PSTN MGW receives the multi-cast call content, performs ATM->TDM media adaptation, and sends the CC to the LEA over TDM links.

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Figure 9-8 Lawful intercept architecture for internal replicator solution

Figure 9-9 shows a typical intercept scenario. In this mobile-to-PSTN call, the mobile subscriber’s call content is intercepted in the Access MGW (an A-Interface MGW in this case). The intercepted call content is sent on to the Multi-Party MGW, where it is replicated and combined, if necessary. From there, the call content is transmitted to a PSTN MGW which connects to the LEAs over TDM links.

Note: The voice bearer data is not impacted by the LI tap. The Access MGW bi-casts the bearer data, creating the received and transmitted call content streams, while the voice bearer data travels the normal Access->PSTN MGW path.



Figure 9-9 LI intercept configuration for mobile-to-ISUP call

Compression in the core network (TrFO-Lite) 9Digital voice compression is a technique for decreasing the number of bits used to transmit digital voice while maintaining an appropriate level of fidelity for the receiver who decompresses and listens to the transmitted voice.

On cellular systems where RF bandwidth is a scarce resource, voice compression techniques to remove this redundant information have been successfully applied for several decades. UMTS 3gpp specifications define two narrowband Codecs called Adaptive Multi-Rate (AMR) and AMR2 initially used between the mobile and the MSC. With the advent of the R4 version of the UMTS standards, AMR voice compression use is extended end-to-end. End-to-end use of voice compression takes advantage of the flexible bandwidth allocation provided by the voice packet paths defined in the R4 version of the UMTS standards.

The MGW optionally supports transmitting compressed bearer data over the packet backbone. This feature has been termed “TrFO-lite” as the design intent is to follow the out of band transcoder control standards: • 3GPP TS 23.153 “Out of band transcoder control; Stage 2”

TrFO-lite is a Nortel proprietary implementation of the 3GPP TrFO standard. It is a scaled down implementation delivering TrFO benefits but without the elaborate signaling supports. The design supports transmission bandwidth

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reduction for traffic exchange with Nortel TrFO-lite capable MGWs and also with TrFO standard compliant MGW in a limited scope.

The main objective of TrFO is to deliver transmission bandwidth reduction over packet core networks. Bandwidth reduction in TrFO-lite is achieved by supporting compression of traffic exchanged by MGWs over Nb’ and Nb interfaces. TrFO-lite supports AMR2 12.2 with DTX SID for typical voice traffic. It supports PSTN-to-PSTN and 2G/3G mobile-to-PSTN and mobile-to-mobile calls. In the case with 3G calls, successful TrFO-lite operation does not require AMR vocoding in the Iu MGW. AMR vocoders are inserted on the PSTN, Access, or Nb MGWs when required.

It is realized that there are standard and also implementation limitations where AMR compression is not viable over the packet network. TrFO-lite supports traffic exchange in non-AMR compressed format for standard call types including CSD, Fax, and GTT. TrFO-lite also supports the non-standard iDEN vocoder bypass traffic which requires traffic transmission in formats incompatible to AMR.

This feature supports bandwidth requirements determined at call setup and also determined dynamically in midcall because of different service requirements. It also supports dynamic bandwidth and call configuration updates required by call topology changes such as handover or by call type changes.

The MGW performs compression/decompression as directed by the MSC in the A-Codec field for the ephemeral termination. Figure 9-10 depicts a mobile-to-mobile call in an uncompressed network.

Figure 9-10 Mobile-to-mobile call without compression



In an uncompressed network, the AMR12.2-encoded bearer stream from the RNC is decompressed to a G.711-64kbps stream over the packet network. Re-encoding to AMR takes place at the far MGW.

In a compressed network, the AMR-encoders/decoders are essentially deactivated, allowing the AMR12.2-encoded bearer to pass over the packet backbone, resulting in bandwidth savings. A mobile-to-mobile call in a compressed network is shown in Figure 9-11.

Figure 9-11 Mobile-to-mobile call with compression

Channel associated signaling 9The MGW supports Channel Associated Signaling (CAS) for North American E911 emergency services over outgoing, non-compelled CAS trunks. The illustration below depicts a PSTN MGW using CAS to deliver E911 services to a Public Safety Answering Point (PSAP). When the MGW connects directly (not shown) to a PSAP, routing will be done by the MSC. When the MGW connects to a Selective Router (SR, a.k.a. 911 Tandem), routing will be done by the SR. In addition, Figure 9-12 shows the five connection models supported by this feature: • Type 2C Model A• Type 2C Model C• Type 2C Model D• Type 2C Model E• Point of Interface Type 8 (POI-T8)

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Figure 9-12 MGW E911 support using CAS

Signaling backhaul 9Broadband SS7 backhaul over IP

Broadband SS7 (MTP3b/SAAL/ATM) is the signaling transport used on the Iu interface. The Iu-CS Control Plane, which carries RANAP signaling, is handled by the MSC Server. A mechanism is needed to transport the RANAP signaling from the various remote RNCs to the centralized MSC Server. Since the XA-Core has no ATM interfaces, a conversion from ATM to IP/Ethernet is also required.

In support of these required services, the MGW provides an interworking function between broadband SS7 and SIGTRAN over IP. The USP accepts the SIGTRAN interface from the MGW and converts it to the proprietary interface required by the MSC.

Narrowband SS7 backhaul over IPThe MGW also supports narrowband SS7 (MTP3/MTP2/MTP1) backhaul over IP. Narrowband SS7 is used for control signaling on the GSM A interface and ISUP signaling on the PSTN interfaces. Narrowband SS7 is carried over IP in much the same way as bbSS7. MTP2 is terminated on the MGW and transported over M2UA/SCTP/IP.

The enables the MTP2 physical interface to be geographically separated from the MTP3 layer running on the USP.

HandoverIn cellular mobile systems, handover is the process of transferring a mobile calls in progress from one cell transmitter and receiver to another cell



transmitter and receiver without interruption of the call. During a handover operation, the Access MGW serves as the anchor point and bi-casts the bearer data on the original oath and on the newly established path to the Target Access MGW. Once the mobile is under the control of the new BSS/RNC, the original bearer path is removed and the bearer uses the new path that was established through the Target MGW.

Note: The original Access MGW remains active throughout the life of the call, but it does not transmit data to the Access Network. Instead, it transmits to the Access MGW that is currently serving the mobile station

Figure 9-13 presents the bearer path in the pre-handover, handover, and post-handover phases for a GSM Intra-MSC handover. A UMTS handover follows the same mechanism, with the BSS replaced by an RNC and the A-Interface MGW replaced by an Iu MGW.

Note: If this were Inter-MSC traffic instead of PSTN traffic, an Nb MGW would replace the PSTN MGW. The handover procedure itself would remain the same.

The pre-handover phase (top panel, Figure 9-13) depicts a normal two-party mobile-to-land call, with the bearer flowing from the BSS 1 to A-Interface MGW 1, then on to the PSTN MGW. (If this were Inter-MSC traffic instead of PSTN traffic, an Nb MGW would replace the PSTN MGW. The handover procedure itself would remain the same.)

In the handover phase (middle panel, Figure 9-13), BSS 2 (Target BSS) and A-Interface MGW 2 have been configured to accept the on-going call. A-Interface MGW 1, in turn, bi-casts bearer data to both BSS1 and A-Interface MGW 2. Bi-casting during this phase reduces the mute time over the handover by allowing the mobile station to begin receiving downlink data once it has tuned to the new channel.

Finally, the post-handover phase shows that the original connection between A-Interface MGW1 and BSS1 has been removed, and the bearer flow is now PSTN->A-Interface MGW1->A-Interface MGW2->BSS2->Mobile.

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Figure 9-13 Handover example for GSM network

Tone and announcementsThe MGW will generate, upon request from the MSC, audible tones (DTMF tones, call progress tones, and continuity tones) towards the specified TDM port or ephemeral termination. Tones may be played internally (towards the opposite termination) or externally (towards the external network), but not in both directions at the same time. (A direction of “both” is supported in H.248, but not supported on the MGW in MG18.) The MGW supports tones through a statically defined database of standardized tones. The tone definition database resides in the MGW and is hard coded and static. It contains numerous well-defined, standardized tone definitions for many countries. When the MGW receives a request to generate a standardized tone, the database is queried to determine the validity of the tone request. Once validated, the tone definition is retrieved and sent to the DSP for audible generation. For non-standardized feature tones, a proprietary tones package is employed. The GSM Service Tone Generation Package includes the Call Limit tone required for GSM services.

The following tone-sets are supported by the MGW: North America, Israel, Spain, China and Romania.



The MGW supports local playback of announcements to any TDM port or any ephemeral termination. Like tones, announcements can be played with an “internal” or “external” direction, but not “both”. Announcement audio data is stored in audio files. The audio files are created on the Audio Provisioning Server (APS) and exported to an external gateway, such as the MGW. The files are transferred from the APS to the CP disk on the MGW via FTP at MGW installation time. Once the audio files have been transferred, they are available on MGW (stored on disk on the CP) and announcements can be provisioned. When the provisioning is activated, the contents of the audio and index files are transferred to memory on the Vsp4e FP. The MGW waits for a command from the MSC Server to play an announcement on a specified channel. The requested announcement segment (G.711 voice packets) is streamed to the proper DSP for the channel. The DSP plays out the announcement in the specified direction.

New Announcement files may be transferred to an MGW at any time and swapped for the current Announcements file, without the interruption of currently playing Announcements using the old Announcements file. This must be done in a coordinated fashion with the required MSC datafill changes.

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Media Gateway OA&M overview 10This chapter presents a general description of Media Gateway (MGW) operations. administration, and maintenance: • fault, configuration, and performance management• general and basic card maintenance

The Multi-Service Switch (MSS) command line interface (CLI) or the Multi-Service Data Management (MDM) graphical user interface (GUI) provides a means for Configuration Management, Fault Management, and viewing of real-time performance statistics for the media gateway. The Magellan Data Provider (MDP) provides a means to collect spooled statistics for post processing and network performance analysis. Both MDM and MDP are part of the Preside Family of MSS OA&M management products.

Note: For detailed information regarding fault management, configuration management, performance management, and general and card maintenance procedures, refer to NTP 411-2231-331, R4 BICN Media Gateway OAM and Troubleshooting Guide. However, this chapters gives a brief overview of OA&M.

Fault management 10For detailed information regarding Multiservice Switch (MSS) alarms, refer to the NTP 241-5701-500, Multiservice Switch 6400, 7400, 15000, 20000 Alarms.

For the MGW, there are two aspects to fault management: • alarms:

— MGW alarms are used to report a fault, recovery from a fault, or a significant event that a network operator would be interested in knowing about. Typically only the component that detects the fault or is at the source of the fault generates an alarm.

• OSI states: — CCITT Recommendation X.731 defines three state attributes and six

qualifying status attributes that managed objects use to represent their


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state. The standard also defines a notification (State Change Notification) that is used to report changes in these attributes. The standard also prescribes guidelines on their use, and state diagrams indicating legal state combinations and transitions between them. The MGW has adopted a subset of applicable OSI State and Status values. State Change Notifications are a subset of OSI SCNs, and are only generated by specific components undergoing specific state changes.

Configuration and performance management 10The component description language (CDL), a data description language, is used to manage the components on the Media Gateway. The CDL is used, by the applications, to define the customer's administrative view of the application's services. This view consists of the components, their attributes (operational, collected, and provisionable) that can be viewed and/or modified, and all commands that are supported for the services.

Performance management 10The Media Gateway Performance Management (PM) supports two types of counters: • Operational Attributes:

— Operational Attributes are used for real-time performance management. They convey the number of times a particular event has occurred, such as the reception of a particular message or detection of a particular error. If a counter increments such that it exceeds its maximum allowed value, it is reset to zero. The Operator can view operational Attributes in real time via any applicable AM system. Operational Attributes are only accessible while the component they are defined within is accessible. For instance, many per mobile statistics are only accessible while a particular mobile is viewed as active within the system. Once the contexts related to the mobile are deleted, the statistics associated with that mobile are deleted.

Operational Attributes are not archived by the system. If the history of Operational Attributes is to be archived, a Collected Event must also be created which matches the Operational Attribute.

• Collected Events: — Collected Events are counters that are archived by the MSS every 15

minutes. The counters are reset at the beginning of each collection interval; so each Collected Event counter is only meaningful for the

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prior 15-minute collection interval. The archives are periodically collected for further analysis by the MDP. Collected Events are not accessible in real time. If real-time access is desired an Operational Attribute must also be created which matches the Collected Event.

General and basic card maintenance overview 10The Media Gateway (MGW) is configured and managed primarily by means of the Multiservice Data Manager (MDM) element manager, not by means of the DSM-MSC as with legacy TDM peripherals. There may be cases where DMS-MSC maintenance commands are required for a MGW but this will be secondary to MDM consultation.

The MGW is responsible for communicating its state, and the state of the TDM resources under its control, to the MSC Server by means of H.248 messaging. In the Nortel Networks solution, each VGS maintains its own individual maintenance state and communicates with the MSC Server over it’s own Mc interface.

Note: For detailed information regarding fault management, configuration management, performance management, and general and card maintenance procedures, and how these requirements are fulfilled by means of the H.248 Call Independent Procedures, refer to NTP 411-2231-331, R4 BICN Media Gateway OAM and Troubleshooting Guide. However, this chapters gives a brief overview of OA&M.

The following documents provide additional information about this topic:• Nortel Networks Technical Publication (NTP), 411- 1501-030,

Multiservice Switch 7400, 15000 Overview• 241-1501-200, Multiservice Switch 15000 Hardware Description• 241-1501-215, Multiservice Switch 15000 Hardware Maintenance Guide

Multiservice Switch boards LEDsThese are the different light-emitting diodes (LED) that appear when a card startups.


10-4 Media Gateway OA&M overviewNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

Figure 10-1 Control and function processor LEDs

Card is operational and spareFast pulsinggreen

Card is not faulty, but cannot operate (does not fit the configuration)

Solid amber

Card is active and in full serviceSolid green

Card is loaded but not activatedSlow pulsinggreen

Card is loading its software

Card is waiting for to load its softwareSlow pulsingred

Card is powered on and performing tests, or after 30s, is faulty

Solid red

Card is unpoweredNo colour

DescriptionStatus Indicator

Fast pulsingred

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A-1Nortel Networks Confidential Copyright © 2003–2006 Nortel Networks

List of terms and definitions A1:1 Equipment Sparing

This refers to redundancy scheme in which two FPs are used to behave as a single FP. The Active FP has a Stand-by FP. The Standby cannot be used while the Active FP is in service. Therefore, there is no load sharing of the standby FP. It remains idle until it becomes the Active FP. This functionality is based upon the Logical Processor functionality of the MSS product. Two physical FPs are provisioned as one Logical Processor. In the event of a failure of the active FP, the stand-by FP immediately becomes the Active Processor.

1+1 Line SparingThis refers to the redundancy scheme utilized by ATM Automatic Protection Switching (APS) in which information is simultaneously sent on both the active and spare links.

3GThird Generation

3GPPThird Generation Partnership Project

AAL 2\5ATM Adaptation Layer Type 2 \ Type 5

AESAATM End Station Address

AGCAutomatic Gain Control

AMRAdaptive Multi-Rate

ANAggregation Node


A-2 List of terms and definitionsNortel Networks Confidential Copyright © 2003–2006 Nortel Networks

APSAutomatic Protection Switching

APSAutomatic Protection Switching

ATMAsynchronous Transfer Mode

AuCAuthentication Center

BG[P]Border Gateway [Protocol]

BHCABusy Hour Call Attempts

BICCBearer Independent Call Control

BICNBearer Independent Core Network

BITSBuilding Integrated Timing Supply

BNRBackground Noise Reduction

BPSBits Per Second

BSCBase Station Controller

BSSBase Station Subsystem

C-PlaneControl plane

CACCall Admission Control

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CASChannel Associated Signaling

CDVTCell Delay Variation Tolerance

CIDChannel Identifier

CLPCell Loss Priority

CLRCell Loss Ratio

CMCall Management, Connection Management

CNCore Network

Cold StandbyThe Stand-by FP is loaded with the same provisioning information as the Active FP after reboot. It does not receive information from the Active FP on the state of current processes and stored information. If there is a failure of the Active FP, the Stand-by is booted and assumes the Active FP role and begins processing information. Because it does not have copies of the active information of the failed FP, any dynamic information is lost, which may result in the need to re-start any in progress information that depends on the application that was running on the failed FP. (e.g. Mobiles attached to the network, message queries waiting on a response, etc.)

CPControl Processor

CPECustomer Premises Equipment

CPSOCP Switchover

CPUCentral Processing Unit



CSCall Server, Circuit Service

CSDCircuit Switched Data

DCS Data Collection System

DMSDigital Multiplex Switch

DTXDiscontinuous Transmission

EBIEven Bit Inversion

ECANEcho Canceller

ECMPEqual Cost Multiple Paths

EFREnhanced Full Rate

EPEmission Priority, Equipment Protection

ERL[E]Echo Return Loss [Enhancement]. Ratio of the echo to the residual signal power in the absence of near-end speech.

FECForwarding Equivalence Class

FPFunctional Processor

FPSOFP Switchover

GMSCGateway MSC

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GPMGeneral Processing Module

GPSGlobal Product Support

GSMGlobal System for Mobile Communications

GTTGlobal Text Telephony (referred to as TTY in North America)

HIOP InterfaceA function performed by a pair of 2pGpDsk FPs in the Multiservice Switch (MSS) 15000 that is local to the MSC Server. The 2pGpDsk FPs provide an Ethernet interface to the MSC Server, with both port and FP redundancy, and forward the H.248/UDP/IP traffic to the ATM I/O for encapsulation into AAL5/ATM cells for transport to the G-MGs via the packet data network.

HLRHome Location Register

Hot StandbyThe Stand-by FP is loaded with the same provisioning information as the Active FP. It also receives information from the Active FP on the state of current processes and stored information in a process known as “journaling”. If there is a failure of the Active FP, the Stand-by assumes the Active FP role and begins processing information. Because it has copies of the active information of the failed FP, there is minimal loss of service and minimal impacts to the network.

HSMHitless Software Migration

HSSHome Subscriber Server

HzHertz

IETFInternet Engineering Task Force

IISPInterim Inter-switch Signaling Protocol



IPInternet Protocol

IPEIn-Path Equipment

IPoATMIP over ATM

IPSecIP Security

ISInband Signaling

ITUInternational Telecommunication Union

IWFInter-Working Function

JDRJitter Delay-buffer Reduction

kbpskilo-bits per second, where k = 1000 bits

LCMLocal Cache Manager

Load SharingLoad Sharing is a technique for providing N+M redundancy. N corresponds to the minimum number of equipments required to perform an engineered task but the system load is shared among N+M elements. Each unit runs up to N/(N+M) of its maximum capacity. If the load exceeds N, the additional element can handle this extra-load and allows the system to support up to N+M. When an element fails the overall capacity is limited until the failed unit is replaced. Note that in the most optimal solution, M=1.

MDMMulti-Service Data Manager

MEMobile Equipment

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MECMobile Echo Control

MGWMedia Gateway. A collection of Multi-Service Switch (MSS) 1500 shelves hosting various function processors (FP) for I/O connectivity and Vsp4e FPs running Voice Gateway Server (VGS) applications for media services support.

MHzMegahertz

MMMulti-Mode

MPEMulti-Protocol Encapsulation

MSMobile Station, Mobile Subscriber

MSCMobile-services Switching Center

MSSMulti-Service Switch (Passport re-branded)

MSS15KMultiservice Switch 15000

MTMobile Termination

MTBFMean Time Between Failure

N+1 Over-ProvisioningA redundancy scheme that includes one extra unit of hardware for a given function over the engineered requirement. Load sharing occurs across all the units of hardware such that the extra hardware participates in the normal processing of that function.

NEBSNetwork Equipment Building System



NLPNon-Linear Processor (see ECAN)

NSMNetwork Services Manager

NUSCMNortel UMTS Standard Call Model

OA&MOperations, Administration, and Maintenance

OSOperating System

OSPFOpen Shortest Path First

PARDAPsyco-Acoustic Rate Determination Algorithm

PCMPulse Code Modulation

PCRPeak Cell Rate

PDPatch Descriptor

PDCProcessor Daughter Card

PD[N]P[U]Packet Data [Network] Path [Unit]

PEProtocol Engine

PIDPath Identifier

PLMNPublic Land Mobile Network

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PNNIPrivate Network-to-Network Interface

POSPacket On SONET

PP15KSee MSS 15000

PPSPackets Per Second

PQCProgrammable Queue Controller

PSTNPublic Switched Telephone Network

PVCPermanent Virtual Circuit

PVGPassport Voice Gateway

QoSQuality of Service

RedundancyDuplication or repetition of elements in electronic or mechanical equipment to provide alternative functional channels in case of failure.

RIPRouting Information Protocol

RNCRadio Network Controller

SDSSoftware Distribution Site

SMSingle Mode

SOCSoftware Optionality Control



SPMSignal Processing Module

SPVCSoft PVC

SRFSpecialized Resource Function

SS7Signaling System #7

STPSignaling Transfer Point

TATerminal Adaptor

TCPTransmission Control Protocol

TDMTime Division Multiplexing

TDPTrigger Detection Point

TETerminal Equipment

TFOTandem Free Operation

TTYText Telephony

U-PlaneBearer plane, see UP

UDIUnrestricted Digital Information

UDPUser Datagram Protocol

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UMTSUniversal Mobile Terrestrial System

UEUser Equipment

UNIUser-to-Network Interface

UPUser Plane, see U-Plane

VCVirtual Circuit

VCCVirtual Channel Connection

VEVoice Engine

VLRVisitor Location Register

VGSVoice Gateway Server. An application that runs on a Voice Services Processor 4 (Vsp4) FP in the Media Gateway that provides bearer traffic connection, media adaptation (TDM and AAL2), and voice quality services (echo cancellation, background noise reduction, mobile echo control, and automatic gain control). The VGS also terminates the Mc interface from the MSC Server.

VMSVoice Mail System, Voucher Management System

VPCVirtual Point Code, also called Multiple Point Code

VPMVoice Processing Module

VRVirtual Router

Vsp2WVoice Services Processor 2 for Wireless



Vsp4Voice Services Processor 4

Warm StandbyThe Stand-by FP is loaded with the same software and provisioning information as the Active FP. It does not receive journaling information from the Active FP. If the Active FP fails, the Stand-by FP assumes the Active FP role and begins processing new transactions.

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Family Product Manual Contacts Copyright Confidentiality Legal

GSM / UMTSR4 Media GatewayOperations and Reference Guide

To order documentation from Nortel Networks Global Wireless Knowledge Services, call (1) (877) 662-5669

To report a problem in this document, call (1) (877) 662-5669 or send e-mail from the Nortel Networks Customer Training & Documentation World Wide Web site at http://www.nortelnetworks.com/td

Copyright © 2003–2006 Nortel Networks, All Rights Reserved

NORTEL NETWORKS CONFIDENTIALThe information contained herein is the property of Nortel Networks and is strictly confidential. Except as expressly authorized in writing by Nortel Networks, the holder shall keep all information contained herein confidential, shall disclose it only to its employees with a need to know, and shall protect it, in whole or in part, from disclosure and dissemination to third parties with the same degree of care it uses to protect its own confidential information, but with no less than reasonable care. Except as expressly authorized in writing by Nortel Networks, the holder is granted no rights to use the information contained herein.

Information is subject to change without notice. Nortel Networks reserves the right to make changes in design or components as progress in engineering and manufacturing may warrant.

* Nortel Networks, the Nortel Networks logo, the Globemark HOW the WORLD SHARES IDEAS, and Unified Networks are trademarks of Nortel Networks. DMS, DMS-HLR, DMS-MSC, MAP, and SuperNode are trademarks of Nortel Networks. GSM is a trademark of GSM MOU Association. Trademarks are acknowledged with an asterisk (*) at their first appearance in the document.Document number: 411-2231-330Product release: GSM18/MGW18Document version: Standard 02.06Date: May 2006Originated in the United States of America

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