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

multimedia gateway for GSM/EDGE and WCDMA networks

2ContentsExecutive summary 3

Introduction 3

The technology behind the MSC Server System 4Safe interworking with existing network 4New interfaces and protocols 4

Bene ts of the solution 5Fewer sites 5Transmission savings 5Field proven quality 5Savings by mobile optimized VoIP 6Long-term investment protection 6

Nokias value proposition 6

Conclusions 7

Abbreviations 7

3radio networks. Core network capacity can be dynamically shared between these two radio access networks, giving best use of the circuit core investment as subscribers migrate to WCDMA. The Nokia MSC Server System supports all the signaling interfaces of existing networks, allowing safe integration with both single and multi-vendor networks.

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 todays 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.

IntroductionThe mobile industry is facing new challenges in todays turbulent business environment. Networks are growing, but the revenue per minute of mobile phone call is decreasing. Implementation of EDGE and WCDMA networks demands an economical balancing act from industry players. In this challenging environment, operators need the best solution to the following questions: how can I maximise voice revenue? how can I protect existing network

investments?

how can I deploy WCDMA while increasing pro tability in GSM?

To solve these challenges, Nokia introduces the MSC Server solution, a common circuit switched core for GSM/EDGE and WCDMA.

The MSC Server System is a circuit core network architecture, independent of transmission backbone and speci ed in the 3G Partnership Programs Release 4 speci cations (3GPP Rel4). It separates call control and signaling (control plane) and traf c (user plane) into separate network elements: MSC Server (MSS) and Multimedia Gateway (MGW). This division enables a totally new style of structure for the core network. Call control can be centralized into very large centers and the actual voice traf c ow can be optimized by locating the MGWs close to traf c hot spots and the interconnection points closer to other networks.

3GPP Rel4 speci cations offer the rst real possibility to implement Voice over IP (VoIP) in the mobile environment in a standardized way. This allows operators to achieve the bene 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. The IP based backbone architecture brings the operational exibility and cost savings of VoIP to mobile networks.

The Nokia MSC Server System provides a state of the art system compliant with 3GPP Rel4 standards, based on eld proven Nokia DX 200 and IPA2800 technologies.

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

Executive summary

The mobile business environment is fundamentally changing. Non-real-time data traf c is growing while revenues per voice minute have stagnated. The industry demands more ef cient business and much more cost-effective networks. The Nokia MSC Server System is a highly cost-effective core network solution that has very low cost-of-ownership to help operators meet these demands today and stay ahead of their competitors.

The Nokia MSC Server System uses a circuit core network architecture, independent of the transmission backbone, as speci ed in the 3GPP Release 4 speci cations. It is a major development in the implementation of the core network for voice and SMS services. As well as todays TDM and ATM backbone solutions, it supports IP for both traf c and signaling. This makes it ideal for integrating voice services in growing IP based multiservice networks.

The Nokia MSC Server System separates call control and signaling and the actual traf c into distinct network elements: the MSC Server and the Multimedia Gateway. This split architecture enables a new style of core network structure that brings savings in both OPEX and CAPEX and thus cuts the production cost of each voice minute.

Lower OPEX arises from operational manpower and site cost savings, achieved through optimized mobile VoIP and transmission cost savings. Site costs can be minimized because of the higher capacity/footprint of the Nokia MSC Server System, which is up to three times better than traditional MSC Systems. The high capacity of the elements also means that fewer sites are needed, reducing network maintenance and upgrades workloads.

The simpli ed layout of the circuit core network eliminates the need for transit MSCs in MSC Server VoIP networks. The 3GPP Release 4 architecture allows optimum network expansions call control and traf c capacity can be expanded separately, minimizing the excess buffer capacity in the network, further saving CAPEX.

From day one, Nokia MSC Server will support both GSM/EDGE and WCDMA

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

4The technology behind the MSC Server SystemThe 3GPP Rel4 compliant MSC Server System consists of MSC servers (MSS) and Multimedia Gateways (MGW). The MSC Server is responsible for call control and signaling, while the MGW takes care of switching and carries the actual traf c.

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. In order to fully safeguard the existing MSC investment, the element can operate as both a MSC and a MSC Server simultaneously.

Safe interworking with existing networkThe MSC Server System supports all existing interfaces with legacy network elements. For example, Intelligent Networks (with INAP or CAP) and GSM/PSTN (with ISUP) networks can be connected to MSC Server System in a similar way to their connections with MSC systems. Also, interfaces with GSM BSS (A interface) and WCDMA RAN (Iu-CS interface) networks are identical with todays eld proven interfaces and protocols, ensuring that MSC Server System is compatible with todays 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.

Voice Mail Systems (VMS) and Short Message Service Centers (SMSC) connect to the MSC Server System with the same interfaces as 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 a SMSC.

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

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

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. A SMSC connection to a MSC server can use the same interfaces and protocols as SMSC connection to a traditional MSC.

New interfaces and protocols

3GPP Rel4 technical speci cations de ne the functional entities and the interfaces needed to support the mobile service. The main new interfaces are the following: 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 that is used by the MSC server to control the MGW over the Mc interface.

Sigtran is used to transport C7 signaling over the IP network. Sigtran 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 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 supports Session Initiation Protocol (SIP), connecting the MSS to Nokia IP Multimedia Core elements.

5Bene ts of the solution

In this changing industry it is critical to ensure service continuity, exploit opportunities and emphasize the importance of reducing operational costs in safeguarding the nal pro t margin. 3GPP Release 4 architecture, implemented with the compliant Nokia MSC Server System, provides key bene ts that increase revenue as well as decrease costs to help the operator meet these challenges.

Fewer sitesSeparation of user plane and control plane enables the respective elements to be located independently of each other. This means that MSC Servers can be concentrated on a few sites at the most convenient location, reducing the number of sites needed. Access costs can be kept low by local switching in 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.

The capacity per footprint ratios of Nokia MSS (BHCA/footprint) and MGW (Erlang/footprint) are signicantly improved compared to a typical MSC. Thus MSC Server System optimizes the number of sites and the total oor space requirement.

Transmission savings The MSC Server System saves transmission costs by local switching when the call is managed by a single, local MGW. Increasing the capacity of the call control element leads to increasing distances between call control and traf 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 in MSC systems all traf c is transported to the MSC to be switched. With MSC Server Systems, the distributed MGWs can do local switching, removing the need to carry local traf c over long distances.

This is illustrated in Figure 5.

The Nokia MSC Server System also saves transmission bandwidth capacity. Transmission in traditional systems is based on dedicated 64kbit/s connections, whereas the MSC Server System can make use of a packet based transmission network. Transcoder Free Operation (TrFO) and Tandem Free Operation (TFO) with Nokia speci c enhancements reduce the transmission bandwidth requirement to less than 20 kbit/s per traf c direction. This backbone capacity can be shared based on traf c needs.

Field proven qualityMobile 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

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

BB

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

elements must offer eld proven technology, high capacity, low energy consumption and small oor space.

In the Nokia solution, the MSC Server and the Multimedia Gateway are based on the eld proven DX 200 and IPA2800 platforms. The Nokia MSC Server System provides the highest proven capacity in the market, with an initial capacity of 600,000 subscribers plus an additional 200,000 telemetric subscribers. Only 5.1 kW / 4.5 square meters is needed for the maximum capacity standalone Nokia MSC Server. The processing capacity is 600,000 BHCA, measured with a heavy usage pro le that includes IN services. These capacities are operational today in Nokias DX 200 MSC in commercial networks. DX 200 MSCs today serve more than 180 Million subscribers in more than 80 networks worldwide.

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

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

6The Nokia Multimedia Gateway provides TDM, ATM, and IP connectivity, removing the need for a separate PSTN gateway. The Nokia Multimedia Gateway also has integrated announcement, tone generation, conference call, and STP functionalities.

Nokia MSC Server System supports both GSM/EDGE and WCDMA radio networks. 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.

Savings by mobile optimized VoIPIn a Nokia MSC server network, the TDM point-to-point connections of MSC networks can be replaced by Ethernet interfaces to the IP backbone. Traf c changes can be accommodated in the interfaces without modi cations and the laborious con guration familiar from TDM connections is also unnecessary. The routing of traf 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 enables shared traf c interfaces instead of dedicated TDM interfaces for each traf c direction. Together with the 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 signi 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.

Nokias value proposition

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

For green 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 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 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 MSCi installed base 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 where certain regions may be built with the MSC Server System and other regions continue with traditional switching architecture. The Nokia integrated MSC Server combines the current MSC and MSC Server technologies and can act as an MSC Server while also having TDM connections to BSS and PSTN. For Nokia WCDMA customers, the migration to MSC

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. This will fully safeguard 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 with a purely GSM network. WCDMA subscribers are expected to grow rapidly and MSS capacity can then be taken into WCDMA use 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 IP Multimedia (IMS) domain and existing circuit switched (CS) domains, such as todays large circuit switched GSM/WCDMA networks and PSTN. Voice migration from CS to IMS will happen gradually and investments in MSC Server Systems will have a lifetime well into the IP Multimedia era.

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 traf c and signaling.

7expansions enabled by the 3GPP Release 4 architecture minimizes the capital expenditure.

Operational costs are reduced by savings in site costs due to compact high capacity elements and free location of the elements. An IP based VoIP network is easier to operate than a TDM based network, which brings savings in O&M work. Due to this simple operation, the transit layer and its associated costs can also be avoided, even in large networks.

The MSC Server System is compatible with IP, TDM and ATM networks, so regardless of the operators chosen backbone technology, the Nokia MSC Server System is the best solution. Since the Nokia MSC Server System supports TDM, ATM and IP interfaces concurrently it existing transmission technology to be used, while at the same time it makes possible a gradual migration to SIP based VoIP. MSC Server will be an important part of the IP multiservice networks by integrating voice to the IP based networks and services.

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

The Nokia MSC Server System guarantees service continuity, ensures full investment protection and maintains value when developing a mobile network to keep ahead in the competition.

Abbreviations3GPPThird Generation Partnership Project. A group of organizational partners that have agreed to co-operate in the formulation of technical speci cations for third generation mobile systems based on further evolved GSM core networks and radio access technologies

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

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

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 speci ed by the Internet Engineering Task Force (IETF).

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.

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 expanding the current network. Nokia has a long experience in multi-vendor integration and interoperability testing, guaranteeing a seamless expansion with the Nokia MSC Server System based on the open interfaces.

ConclusionsIn the current challenging market situation, mobile network operators must both invest less than in the past, while ensuring they will not be left behind by continuing network evolution. The MSC Server System serves both of these needs by providing a cost effective optimized circuit switched core solution that will evolve to accommodate IP Multimedia.

The MSC Server System brings capital and operational cost savings. Capital cost is saved by common MSS/MGW elements for GSM/EDGE and WCDMA. This makes it possible to roll out WCDMA coverage, while keeping the number of elements to a minimum. Also, optimum network

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