White Paper

Nokia MSC Server SystemThe fi rst true mobile soft switch and backbone independent

Multimedia Gateway for GSM/EDGE and WCDMA networks

2

White Paper

Contents

Introduction 2

Facing the future with Nokia MSC Server System 3Safe interworking with existing networks 3New interfaces and protocols 4

Cutting costs with the MSC Server System 4Fewer sites 4Transmission savings 5Savings by mobile optimized VoIP 5Field proven quality and resiliency 5Long-term investment protection 6

Optimal solution for all operators 6

Abbreviations 7

Introduction

The mobile industry is facing new challenges in today’s turbulent business environment. Although networks are growing, the revenue per minute from mobile phone calls is decreasing, while the implementation of EDGE and WCDMA networks demands an economic balancing act from industry players.

In this challenging environment, operators need a solution that can answer four vital questions: • How can I maximise voice revenue?• How can I reduce operational costs?• How can I protect existing network

investments?• How can I deploy WCDMA while

increasing profi tability in GSM?

To solve these challenges, Nokia has introduced the MSC Server solution, a common circuit switched core for both GSM/EDGE and WCDMA. When subscribers migrate from GSM to WCDMA, the same core network elements can be used throughout the migration. No changes in the elements or the network topology are needed, keeping the cost and risk to a minimum.

3

White Paper

Facing the future with Nokia MSC Server System

Safe interworking with existing networks

The MSC Server System supports all existing interfaces with legacy network elements. For example, Intelligent Networks (with INAP or CAP) and GSM/PSTN networks (with ISUP) can be connected to the MSC Server System in a similar way to their connections with MSC systems. Also, interfaces with

The MSC Server System is independent of the transmission backbone and is specifi ed in the 3G Partnership Program’s Release 4 specifi cations (3GPP Rel4). It separates call control and signaling (control plane) and traffi c (user plane) into separate network elements. The MSC Server (MSS) handles call control and signaling, while the Multimedia Gateway (MGW) takes care of switching and carries the actual traffi c.

This division allows a totally new style of structure for the core network. Call control can be amalgamated into very large centers, while the actual voice traffi c fl ow can be optimized by locating the MGWs close to traffi c hot spots and the interconnection points closer to other networks.

The Nokia MSC Server System provides a state of the art system compliant with 3GPP Rel4 standards, which offer the fi rst real possibility of implementing Voice over IP (VoIP) in the mobile environment in a standardized way. This allows operators to achieve the benefi ts of VoIP safely without the limitations of proprietary solutions. It also ensures a safe interworking of the mobile VoIP core network with the existing network infrastructure.

In the Nokia implementation, the MSC Server has similar call control and signaling functions as the MSC, allowing an existing Nokia MSCi to be upgraded to an MSC Server. The element can operate as both a MSC and a MSC Server simultaneously, safeguarding the existing MSC investment.

Nokia MSC Server System supports both GSM/EDGE and and WCDMA radio networks. Looking further ahead, 3GPP will standardize IP multimedia voice calls. The Nokia MSC Server System will interconnect voice calls with SIP between the IP Multimedia Subsystem (IMS) domain and existing circuit switched domains. The investment in the Nokia MSC Server System will bring substantial returns well into the IP Multimedia era.

Nb

MSCServer

MGW MGW

GSM BSS3G RAN

PSTN

GSM BSS3G RANPSTN

HLR

Nb

Nc

BICC

MAP

McMc

SIGTRANH.248

IP, TDM or ATM

IP MultimediaSubsystem

IN & otherapplication servers

SIPCAP/INAP

Figure 1. 3GPP Rel4 MSC Server architecture and main interfaces.

Figure 2. The MSC Server System integrates safely into the existing network. From the existing network’s point of view, the MSC Server System uses the same fi eld-proven interfaces and protocols as the MSC System, ensuring safe interworking with both single vendor and multi-vendor networks.

NetworkManagement Billing

IN (CAP/INAP)

RAN (RANAP)BSS (BSSAP)

HLR (MAP)

MSC (ISUP)

PSTN (ISUP)

HLR (MAP)

MSC (ISUP)

PSTN (ISUP)

IN (CAP/INAP)

RAN (RANAP)BSS (BSSAP)

NetworkManagement Billing

MSCServer

SIGTRAN H.248/Megaco

MGWMSC

GSM BSS (A interface) and WCDMA RAN (Iu-CS interface) networks are identical with today’s fi eld proven interfaces and protocols. This ensures that MSC Server System is compatible with today’s networks, including those with elements from several vendors. The similarity between the current MSC System and the MSC Server System is illustrated in Figure 2.

4

White Paper

Voice Mail Systems and Short Message Service Centers (SMSC) connect to the MSC Server System with the same interfaces currently used. In the case of the integrated MSC Server, the connection can remain in the MSC Server without changes. For a new standalone MSC Server, the VMS and SMSC can be connected via the MGW with ISUP. If the SMSC supports SIGTRAN, a direct connection from the MSC Server by SIGTRAN is also possible. Figure 3 illustrates the options for connecting an SMSC.

New interfaces and protocols

3GPP Rel4 technical specifi cations defi ne the functional entities and the interfaces needed to support the mobile service. The main new interfaces are:• Mc interface (MSC Server – MGW) • Nc interface (MSC Server – MSC Server)• Nb interface (MGW – MGW)

The main protocols introduced by 3GPP Rel4 are H.248/Megaco, SIGTRAN and Bearer Independent Call Control (BICC). H.248/Megaco is a control protocol used by the MSC Server to control the MGW over the Mc interface.

SIGTRAN is used to transport C7 signaling over the IP network. It is also used between the MGW and MSC Server to transport PSTN and GSM / UMTS Radio Network signaling to the MSC Server over the Mc interface. Thus the MGW acts as an integrated Signaling Gateway. In the CS domain, SIGTRAN can also be used between the MSC Server and HLR and IN/SCP.

BICC is used for call control between two MSC Servers in the Nc interface, allowing a backbone independent Control Plane and User Plane.

The Nokia MSC Server System supports Session Initiation Protocol (SIP), connecting the MSS to IP Multimedia Core elements and other SIP capable network elements.

Cutting costs with the MSC Server System

number of sites needed. Also, access costs can be kept low by local switching at distributed MGWs, which can be located in existing BSC and/or RNC sites. Thus the total number of sites can be minimized. Site cost savings are illustrated in Figure 4.

Site numbers and total fl oor space requirement are also reduced through the improved capacity per footprint ratios of the Nokia MSC Server – BHCA/footprint – and MGW-Erlang/footprint.

TDM E1 / MAP

SMSC connection options• E1 connection to Integrated MSC Server• E1 connection to MGW• SIGTRAN connection to Integrated or

Standalone MSC Server

SIGTRAN capable SMSC• Connection directly to MSS

by SIGTRAN

Non SIGTRAN capable SMSC• Connection by C7 over TDM• SIGTRAN from MGW to MSC Server

MGW MGW

MSS

SIGTRAN

H.248 & SIGTRAN

A

SMS path(SIGTRAN connected SMSC)

SMS path(TDM connected SMSC)

H.248 & SIGTRAN

Figure 3. An SMSC connection to an MSC Server can use the same interfaces and protocols as SMSC connection to a traditional MSC.

The Nokia MSC Server System provides key benefi ts that increase revenue as well as decrease costs.

Fewer sitesThe separation of the user plane and control plane allows the respective elements to be located independently of each other. MSC Servers can be concentrated on a few sites at the most convenient location, reducing the

Only signalling between MSS and MGW• Number and location of MSS sites is

independent of traffic

=> Number of sites can be reduced

MGW (switching)

MSS (control)

Iu-CS

MGW seldom requires a site visit• MGW elements can be located to

existing BSC/RNC sites

=> No dedicated sites required

MSS and MGW are compact in size• Footprint 1/3 of typical MSC footprint

=> Floorspace cost minimized

Signalling only

A

PSTN

Backbone

Figure 4. Site cost is reduced due to the optimal location of elements and the reduced fl oor space needed.

5

White Paper

Transmission savings

The MSC Server System saves transmission costs by local switching for calls managed by a single, local MGW. Increasing the capacity of the call control element leads to increasing distances between call control and traffi c hot spots. With MSC systems, this may lead to expensive inter-city transmission connections, even for local mobile-to-mobile or mobile-to-PSTN calls, due to the fact that all traffi c needs to be transported to the MSC to be switched. With MSC Server Systems, the distributed MGWs can perform local switching, removing the need to carry local traffi c over long distances. This is illustrated in Figure 5.

The Nokia MSC Server System also saves transmission bandwith capacity compared what is needed by traditional switching systems. This is possible by an integrated voice compression feature that is compatible with all transmission technologies (TDM, IP and ATM). Furthermore, transmission capacity savings can be combined with optimal voice quality by Transcoder Free Operation (TrFO) or Tandem Free Operation (TFO) with Nokia specifi c enhancements. Transmission backbone capacity can be shared based on traffi c needs.

Savings by mobile optimized VoIP

In a Nokia MSC Server network, the TDM point-to-point connections of MSC networks can be replaced by Ethernet interfaces to the IP backbone. Traffi c changes can be accommodated in the interfaces without modifi cations and the laborious confi guration familiar from TDM connections is also unnecessary. The routing of traffi c and signaling is provided by the backbone. This ease of operation of the IP based network will dramatically reduce the required O&M work.

The IP based network will also remove the need for a transit layer. IP transport in the backbone allows traffi c interfaces to be shared, rather than requiring dedicated TDM interfaces for each traffi c direction. Together with the fl exible

operation of IP compared to TDM, this enables even large networks without a transit MSC layer, without compromising network operability.

The differences between MSC and MSC Server networks are illustrated in Figure 6.

Non-real-time (non-voice) packet data will grow signifi cantly during the coming years, along with GPRS and WCDMA. The MSC Server System is important in this development as it provides the voice call (and WCDMA real time video call) services in these networks. MSC Server, which supports all current transport technologies, including TDM and ATM, allows the operator to consolidate voice and data transport networks into a single IP based transport network.

Field proven quality and resiliency

Mobile telecommunications networks have grown from niche applications to the preferred carrier of all voice and data. To facilitate the cost-effective operation of large networks, the network elements must offer fi eld proven technology, high capacity, low energy consumption and small fl oor space.

In the Nokia solution, the MSC Server and the Multimedia Gateway are based on the fi eld proven resilient DX 200 and IPA2800 platforms. The Nokia MSC Server System provides the highest proven capacity in the market. The processing capacity is the real operational capacity measured with a heavy usage profi le that includes IN services. In addition to

Figure 5. Separation of call control and switching enables high capacity control elements and localized switching. This eliminates long transmission legs in local calls.

MSC Server System• Local traffic is switched

locally in MGWs• MSC Server capacity can

be maximized withoutaccess cost increaseMGW

MSC System• High MSC capacity increases

access transmission cost• Difficult to reduce the

number of MSCs

City B

MSC

MSC Server

City A

BSS/RAN

BSS/RAN

PSTN

H.248

MSC

MSC

MSC

MSC

MSC

MSC

MSC

MSC

MSC

TDMfor voice

TDMfor voice

TMSC

TMSC

MSCIP for all

voice, data andsignalling

MultimediaGateways

MSCServers

Figure 6. MSC network and MSC Server network. The MSC Server System uses the multi-service IP network to transport traffi c and signaling.

6

White Paper

Optimal solution for all operators

In today’s challenging market situation, mobile network operators must cut investment while ensuring they are not left behind by as networks evolve. The MSC Server System meets both these needs by providing a cost-effective optimized circuit switched core solution that will evolve to accommodate IP Multimedia.

An investment in the Nokia MSC Server System allows easy and safe migration from GSM to WCDMA radio access and to the pure IP Multimedia core through simultaneous support of existing and new core interfaces and standards.

The Nokia MSC Server System guarantees service continuity, ensures investments are fully protected and maintains value for operators developing a mobile network to keep ahead in the competition.

Looking further ahead, the advent of 3GPP Release 6 or Release 7 wilI standardize IP multimedia voice calls. The Nokia MSC Server will interconnect voice calls with SIP between the IP Multimedia domain and existing circuit switched domains, such as today’s large circuit switched GSM/WCDMA networks and PSTN. Voice migration from circuit switched to IP Multimedia will happen gradually, yet the investment in the Nokia MSC Server System will bring substantial returns well into the IP Multimedia era.

the resilient platforms, the Nokia MSC Server System employes system-wide multi-layer resilience mechanisms for both voice and signaling. This ensures that there is no single point of failure in the entire Nokia MSC Server System.

Long-term investment protection

The current Nokia MSCi elements can be upgraded to MSC Servers in a simple way by activating the MSC Server software, fully safeguarding the existing MSCi investment.

The MSC Server System supports GSM/EDGE and WCDMA subscribers simultaneously and can dynamically allocate any share of its capacity between them. This means that full use can be made of the MSC Server investment even with a purely GSM network. Numbers of WCDMA subscribers are expected to grow rapidly – when they do, MSS capacity can be used for WCDMA by adding interfaces to RNCs. In terms of WCDMA migration as well as migration to VoIP, the MSC Server System is a safe investment.

3GPP Rel 6 or Rel 7 will fully standardize IP multimedia voice calls in future. MSC Server will be the system needed for interconnecting voice calls between the IMS domain and existing circuit switched (CS) domains, such as today’s large circuit switched GSM/WCDMA networks and PSTN. Voice migration from CS to IMS will happen gradually and investments in MSC Server Systems will be relevant well into the IP Multimedia era.

The Nokia MSC Server System is the optimal solution for all kinds of operators, regardless of their current situation and network structure.

For greenfi eld operators, the Nokia MSC Server System is an ideal solution as it provides best-in breed products and high capacities. As the Nokia MSC Server System has been developed on fi eld proven Nokia platforms, the operator gets the latest technology together with high quality and availability. Also, since the Nokia MSC Server System has all the interfaces for interconnecting with GSM, WCDMA and PSTN networks, Nokia can provide a fl exible solution to meet differing needs.

For the existing Nokia GSM/EDGE customer, the Nokia MSC Server System provides an easy migration to the 3GPP Release 4 architecture, as the existing MSCis can be fully re-used. The Nokia MSC Server System also uses the current TDM based architecture where applicable. Furthermore, the network can be split, allowing certain regions to be built with the MSC Server System while other regions continue with traditional switching architecture.

For Nokia WCDMA customers, the migration to MSC Server architecture is even easier as the current network elements, 3G MSC and MGW, can be fully reused in the MSC Server architecture. Nokia 3GPP Release 99 network elements can be upgraded to MSC Server System network elements with a simple software upgrade and in some cases with minor hardware changes.

For operators currently using circuit switched core infrastructure from another telecommunications vendor, the Nokia MSC Server System is a feasible solution for expansion. Nokia has a long experience of multi-vendor integration and interoperability testing, guaranteeing a seamless expansion with the Nokia MSC Server System based on open interfaces.

7

White Paper

Abbreviations

The contents of this document are copyright © 2004 Nokia. All rights reserved. A license is hereby granted to download and print a copy of this document for personal use only. No other license to any other intellectual property rights is granted herein. Unless expressly permitted herein, reproduction, transfer, distribution or storage of part or all of the contents in any form without the prior written permission of Nokia is prohibited.

The content of this document is provided “as is”, without warranties of any kind with regards its accuracy or reliability, and specifi cally excluding all implied warranties, for example of merchantability, fi tness for purpose, title and non-infringement. In no event shall Nokia be liable for any special, indirect or consequential damages, or any damages whatsoever resulting form loss of use, data or profi ts, arising out of or in connection with the use of the document. Nokia reserves the right to revise the document or withdraw it at any time without prior notice.

Nokia and Nokia Connecting People are registered trademarks of Nokia Corporation. Nokia product names are either trademarks or registered trademarks of Nokia. Other product and company names mentioned herein may be trademarks or trade names of their respective owners.

INAPIntelligent Network Application Protocol. A signalling protocol between Service Switching Point and Service Control Point. It enables Intelligent Network services.

IP Internet protocol. A communication protocol specifi ed by the Internet Engineering Task Force (IETF).

ISUPISDN User Part. This portion of the signaling system manages the telephone call, including calling party number information, call status checking, trunk management, system messaging.

MAPMobile Application Part. An open interface specifi ed by ETSI. The MAP functions mainly concern the information exchange between switches and registers in GSM networks related to the possibility for a mobile station to roam.

MGWMultimedia Gateway. Network element that together with MSC Server forms the MSC Server System. It takes care of switching and carries the actual traffi c. Multimedia Gateway is defi ned in 3GPP Release 4 specifi cations.

MSSMSC Server. Network element that together with Multimedia Gateway forms the MSC Server System. It handles call control and signaling. MSC Server is defi ned in 3GPP Release 4 specifi cations.

PSTNPublic Switched Telephone Network. Regular phone lines.

SIGTRANSIGTRAN is a set of protocols defi ned to transport SS7 messages over IP networks.

3GPPThird Generation Partnership Project. A group of organizational partners that have agreed to co-operate in the formulation of technical specifi cations for third generation mobile systems based on further evolved GSM core networks and radio access technologies.

ATMAsynchronous Transfer Mode. An international CCITT standard for high-speed packet-switched networks that operates at digital transmission speeds above 1.544 Mbps.

BHCABusy Hour Call Attempt. How many call setups are made in an hour. Example value 3600 bhca means that new call attempt is made after every second.

BICCBearer Independent Call Control. An Inter-MSC Server signaling protocol specifi ed by ITU-T and 3GPP. The use is defi ned in 3GPP Release 4 specifi cations.

CAPCAMEL Application Protocol. A signalling protocol between Service Switching Point and Service Control Point. It enables Intelligent Network services for roaming subscribers.

H.248/MegacoMSC Server uses this protocol to control Multimedia Gateway over the Mc interface. It is defi ned in 3GPP Release 4 specifi cations.

IMSIP Multimedia Subsystem. Enables operators to deploy person-to-person multimedia services in 2G and 3G networks.

SIPSession Initiation Protocol. A signaling protocol for Internet conferencing, telephony, presence, events notifi cation and instant messaging.

SMSCShort Message Service Centre. Network element through which short messages are transmitted and in which they can be stored for later transmission if the receiver is not reached.

TDMTime Division Multiplexing. A type of multiplexing that combines data streams by assigning each stream a different time slot in a set.

TFOTandem Free Operation. Confi guration of a voice or multimedia call for which transcoders are physically present in the communication path but transcoding functions are disabled or partially disabled in order to avoid multiple transcoding. The objective of avoiding multiple transcoding is to improve the speech quality in calls.

TrFOTranscoder Free Operation. Confi guration of a speech or multimedia call for which no transcoder device is physically present in the communication path and hence no control or conversion or other functions can be associated with it. The purpose of TrFO is to remove unnecessary speech encoding completely from the speech path.

UMTSUniversal Mobile Telecommunication System. Third generation mobile system.

VoIPVoice over IP. Technology to carry voice communication over a data network based on the Internet protocol.

NOKIA CORPORATIONNetworksP.O. Box 300FIN-00045 NOKIA GROUP, FinlandPhone: +358 (0) 7180 08000www.nokia.com

No

kia

cod

e: 1

1129

– 1

204

Ind

ivis

ual

/Lib

ris

Cop

yrig

ht

© 2

004

No

kia.

All

rig

hts

res

erve

d. N

oki

a an

d N

oki

a Co

nn

ecti

ng

Peo

ple

are

reg

iste

red

tra

dem

arks

of

No

kia

Corp

ora

tio

n.

Oth

er p

rod

uct

an

d c

om

pan

y n

ames

men

tio

ned

her

ein

may

be

trad

emar

ks o

r tr

ade

nam

es o

f th

eir

resp

ecti

ve o

wn

ers.

Pr

od

uct

s ar

e su

bje

ct t

o c

han

ge

wit

ho

ut

no

tice

.