CDMA Core Network Evolution. 3GPP2 LMSD and the Packet MSC

Transcription

1 CDMA Core Network Evolution 3GPP2 LMSD and the Packet MSC January 2005

2 Table of Contents 1 Introduction GPP2 LMSD and MMD Evolution LMSD Evolution LMSD Evolution Benefits LMSD Architecture and Entities Nortel LMSD Solution Summary and Program Status Nortel Packet MSC The Value of a Packet-based MSC The Differentiation of Nortel Packet MSC Nortel P-MSC Roll out Strategy P-MSC Solution and Timing P-MSC with Gateway Functionality (MTX Generally Available) P-MSC with Serving Functionality (MTX 13 mid-2005) P-MSC with TrFO-Phase 1 and RTO-Phase 1 (MTX 14 mid-2006)... 14

3 1 Introduction 1.1 3GPP2 LMSD and MMD Evolution 3GPP2 offers Operators two complementary migration paths in order to optimize the current CDMA Core Network deployments. Circuit Core Packet Core Optimizing by Packetizing Voice Transport (P-MSC) Optimizing by Standardizing Services Framework All IP IP Core Path to an optimized Core Network Figure 1 LMSD and MMD Evolution LMSD (Legacy MS Domain) Evolution LMSD evolution is focused on packetizing the existing Circuit Core Network and providing the associated cost reduction benefits such as: Reduced footprint and power consumption, Distributed architecture with centralized call processing and reduction of operational centers, Transport and transcoding optimization, These additional benefits derived from the evolution from circuit TDM networks to packet needs to be accomplished while preserving the breadth of high value subscriber and operational features of the existing Circuit Core Network. A small sample of those features would be as followings: 3WC, Group Ringing, Color Ring Back Tone, OTAPA, Network Optimization,

4 Nortel Confidential 2 MMD (Multimedia Domain) Evolution MMD Evolution is focused on standardizing the Services Framework over the Packet Core Network, allowing Operators to: Leverage MMD network and investment to converge across different Access Technologies besides CDMA such as GSM/UMTS W-LAN, DSL and Wireline Rationalize clients and application strategy, Reduce time to market with a new Application, Facilitate the creation and implementation of innovative applications allowing for differentiation in the market place. Better control network access and simplify subscriber provisioning Initially, the MMD solution will be leveraged for non real time applications as the CDMA implementations do not yet allow for the key requirements associated with real time apps such as End to End QoS. As those issues get solved on the CDMA Network, the MMD infrastructure will then be leveraged to implement real time applications such as Voice. At that stage, Operators will have a mixed environment with voice being handled over the Circuit Core and the Packet Core Network. The remainder of this document will cover in more detail the evolution plans for Nortel CDMA Core Network to both LMSD and MMD.

5 Nortel Confidential 3 2 LMSD Evolution 2.1 LMSD Evolution Benefits The LMSD allows for packetizing the voice transport within the existing Circuit Switched Domain, by introducing a split architecture, where the bearer and signaling are separated, and the bearer is transported directly between media gateways over the packet network: Figure 2 LMSD Architecture Benefits By moving to such architecture, Operators achieve major savings. Capital Expenditure Reduction CAPEX savings are enabled by centralizing call processing and distributing media gateways within network regions, hence using the full capacity of the processors and sharing it efficiently between the regions.

6 Nortel Confidential 4 MSC Processor Offload (up to 17% capacity recovery verified in lab tests) is enabled by gateway application in a distributed packet architecture by extending processor life of existing MSCs, thereby stretching existing MSC investments and delaying new real estate expenses, thereby reducing capital expenditure and RF network redesign (Base station re-homing and network border cell redesign) required by new MSC introduction. Reduction in ports required for inter-machine or tandem trunking, a substantial reduction in port utilization of packet versus circuit switched ports and increased simplification of the existing transport network as the service provider moves from a complex mesh to a scalable star configuration between MSCs Operational Expenditure Reduction OPEX savings enabled by both central office optimization and transport optimization.: Transport optimization enabled by avoiding the trombone path of traffic routing back to a distant MSC for routing through the network; local traffic stays local which provides further saving on operational expenditure. Nortel accomplishes this intelligent routing through the application of Dynamic Packet Trunks (DPT). Transcoding optimization enabled by the ability to minimize the need of transcoding on Mobile to Mobile Calls (Transcoder Free Operation,TrFO), on Mobile to Land and Land to Mobile Calls (Remote Transcoder Operation, RTO) Footprint & Power Savings enabled by the reduction of frames required in a packet-based MSC implementation in comparison to a circuit MSC Fewer nodes and sites need to be operated as the architecture allows consolidating several regions onto a single node, hence leading to a reduction of operational staff requirements and real estate / leasing fees.

7 Nortel Confidential LMSD Architecture and Entities Below the 3GPP2 architecture for all IP network is represented. LMSD entities are within dotted lines: Legacy MS Domain Support HLRe MSCe SCPe Figure 3 All IP Standards Architecture Described next is each of these components, along with the name of the Nortel product that delivers the respective function. Also included is the interface protocol for connecting these components together.

8 Nortel Confidential 6 The LMSD Support entity contains the following functional network components: Home Location Register emulation (HLRe), Mobile Switching Center emulation (MSCe), and Service Control Point emulation (SCPe). The LMSD performs the call control, mobility management, and service management functions for non-ip (i.e., legacy) mobiles. The MSCe within the LMSD provides call control, services, WIN triggers, and controls the connections for bearer channels in a Media Gateway connected to a BSC in the Access Network (i.e., the A2 interface from IOS). The HLRe is similar to a legacy HLR, but differs in that it supports IP interfaces and supports roaming to the packet data (multimedia) domain. The primary signaling interfaces are 13, 14, 39, and 48, which are defined as follows: Interface 13, which is the SS7 ISUP interface to the PSTN. Interface 14, which is the ANSI-41 interface to the Public Land Mobile Network (PLMN). Interface 39, which is H.248 (MEGACO) control interface to the Media Gateway Interface 48, which is the A1 signaling interface between the access network and the MSCe. MSC Emulation (MSCe) In Nortel s implementation, the MSCe is the MSC Server. The MSC Server comes in two flavors: - In Nortel s first release, the MSC Server 1000 is based on the XA-Core platform to allow for a smooth evolution of the existing CDMA base to a packetized Core. It is implemented through the simple addition of a HIOP card to the existing XA-Core frame. - In the following release, for greenfield opportunities, the MSC Server 2000 will also be available on an off the shelf commercial hardware and the MSC Server 2000 will consist of a Call Agent (CA) which resides on a blade. Media Gateway Control Function (MGCF) The MGCF is used to control the MGW via a standardized IP interface, called H.248. The MGCF manages the resources within the MGW, and allocates and de-allocates them as necessary. The primary signaling interfaces supported by the MGCF are 17, 26 and 30, which are defined as follows: Interface 17, which is the SIP interface to the Call Session Control Function (CSCF) Interface 26, which is the SS7 ISUP interface to the PSTN Interface 30, which is H.248 control interface to the Media Gateway

9 Nortel Confidential 7 Nortel s implementation of the MGCF consists of the Gateway Controller Cards (GWC) which is a component of the MSC Server. This implementation is similar to the Wireline solution used in a packetized architecture. Media Gateway (MGW) The MGW is used to carry the user traffic in the network, and provide the interface between the packet domain and the circuit domain for the bearer path. The MGW contains DSPs for vocoding the bearer traffic, and may also contain modem functions. The primary signaling interfaces supported by the MGW are 27, 30, 33, 34, 36, 38, 39 and 40, which are defined as follows: Interface 27, which is the bearer path interface to the access network. Interface 30, which is H.248 (MEGACO) control interface from the Media Gateway Control Function (MGCF) Interface 33, which is the bearer path interface to the Media Resource Function Processor Interface 34, which is the bearer path interface to the PSTN Interface 36, which is the bearer path interface to the PDSN/FA (referred to as the Access Gateway in the NAM) Interface 38, which is the bearer path interface to the Mobile IP Home Agent (HA) function Interface 39, which is the H.248 (MEGACO) control interface from the MSCe in the LMSD Interface 40, which is the bearer path interface to the Border Router Nortel Packet Voice Gateway (PVG) based on the industry leading Passport or Media Gateway 15000, and is Nortel s implementation of the MGW. The Wireline Call Server Solution (CS2K) also uses the PVG as the MGW in a packetized deployment. Media Resource Function Controller (MRFC) The MRFC works with the Media Resource Function Processor (MRFP) to provide tones, announcements, conference bridge facilities, CALEA (Legal Intercept) capabilities, etc. The MRFC is very similar to the MGCF in function, in that it requests and manages media resources. The primary signaling interfaces supported by the MRFC are 24 and 25, which are defined as follows: Interface 24, which is the SIP interface to the Call Session Control Function (CSCF) Interface 25, which is H.248 (MEGACO) control interface to the Media Resource Function Processor (MRFP) Nortel s implementation of the MRFC consists of Gateway Controller Cards (GWC) and the MSC Server working in unison to perform this function. The Wireline Call Server Solution (CS2K) also uses GWC cards to provide the MRFC function in a packetized deployment.

10 Nortel Confidential 8 Media Resource Function Processor (MRFP) The MRFP works with the Media Resource Function Controller (MRFC) to provide tones, announcements, conference bridge facilities, CALEA (Legal Intercept) capabilities, etc. The MRFP contains various components to provide these functions (e.g., DSPs, recording devices, etc.). The primary signaling interfaces supported by the MRFP are 25, 32, 33, 37, and 42, which are defined as follows: Interface 25, which is the H.248 (MEGACO) control interface from the Media Resource Function Controller (MRFC) Interface 32, which is the bearer path interface to the PDSN/FA (referred to as the Access Gateway in the NAM) Interface 33, which is the bearer path interface to the Media Gateway Interface 37, which is the bearer path interface to the Mobile IP Home Agent (HA) function Interface 42, which is the bearer path interface to the Border Router The Nortel Media Server 2000 (MS 2000) is Nortel s implementation of the MRFP. The Wireline Call Server Solution (CS2K) also uses the MS 2000 as the MRFP in a packetized deployment.

11 Nortel Confidential Nortel LMSD Solution Summary and Program Status Nortel s LMSD Evolution is delivered via the CDMA Packet Mobile Switching Center solution (P-MSC). It consists of four key network elements: the Mobile Switching Center Server 1000 (MSC Server 1000); the Media Gateway (MG 15000); the Universal Signaling Point (USP); and, the Media Server 2000 Series (MS20x0) audio server. Together these elements transform the circuit switched Mobile Telephone Exchange (MTX) into a broadband, packetbased solution Nortel Packet MSC Nortel s wireless packet solution benefits from our expertise as a leader in Voice over Packet (VoP) and CDMA networks. Our complete CDMA Packet MSC (P-MSC) platform uses fieldproven % available platforms. This solution integrates our proven Passport-based Media Gateway based Media Gateways, DMS-based HLR, and our investment-protected CDMA Broadband STP that through a simple software upgrade becomes the required VoP Signaling Gateway via our Universal Signaling Point. Nortel P-MSC provides the value of network packetization to wireless operators in both Serving and Gateway applications. Wireless operators are positioned for a reduction in capex and opex through central office (CO) footprint and utility reduction as well as MSC transport optimization, in addition to gaining operational IP experience required for future IP Multimedia Domain deployments The Value of a Packet-based MSC Packet-based MSC solutions allow wireless operators to manage costs while growing their subscriber base. This occurs through inter-machine trunk port savings from a substantial reduction in port utilization of packet versus circuit switched ports and increased simplification of the existing transport network as the service provider moves from a complex mesh to a scalable star configuration between MSCs. Reduced central office footprint helps reduce power consumption and other associated operating costs. Separation of control and bearer planes allows for flexible and remote deployment of the call servers (Packet MSC) and the access network. This also avoids the trombone path of traffic routing back to a distant MSC for routing through the network; local traffic stays local which provides further saving on operational expenditure. Nortel accomplishes this intelligent routing through the application of Dynamic Packet Trunks (DPT). Nortel s current live deployments of the gateway application allows for MSC Offload (up to 17% capacity recovery verified in lab tests) in a distributed packet architecture by extending processor life of existing MSCs, thereby stretching existing MSC investments and delaying new real estate expenses, thereby reducing capital expenditure and RF network redesign (Base station re-homing and network border cell redesign) required by new MSC introduction.

12 Nortel Confidential The Differentiation of Nortel Packet MSC Along with this compelling value of packet-based solutions Nortel Packet MSC offers the following differentiation with the deployment of our 2 nd P-MSC release planned for customer deployment in early 2005: Feature Richness Leverage same feature set available of Circuit MSC with minor exceptions by porting 25 years of telephony feature set. o Preserve the Breadth of Subscriber Feature Offering e.g. 3WC, Group Ringing, Color Ring Back Tone o Preserve Valuable Operational Tools e.g. OTAPA, Network Optimization o Consistent back office interfaces such as FCAPS and Billing as compared with current TDM MSC deployments Network Flexibility Choice of packet bearer support VoIP (GigE or AAL5) and VoATM (AAL2) Integrated HLR or Standalone HLR Allows for concurrent operation of TDM and Packet North American and International PSTN variants, IOS, ATM, IP, TDM Open standard architecture with protocols such as SIP-T, IS41, ISUP variants for call signaling; H.248 for Gateway control to enable systems integration of third party network elements. Investment protection enables the service provider to move a significant step towards a 3GPP2 all-ip network. Nortel s P-MSC solution evolves to perform the MSCe (MSC Emulation), RSGW, TSGW and MGW functions in the 3GPP2 all-ip network Network Robustness Five 9s reliability of solution, Six 9s on many of the distributed elements NEBS Level 3 compliant Central Office chassis Online upgrade or hitless software migration, Hot card insertion/protection Proven call-processing architecture delivers network capacity with scalability. A single Packet MSC system in a gateway application scales up to 2 million BHCA of voice traffic under one set of translations and one SS7 point-code. This will increase to 3 million in our 3rd release. (Note: BHCA obtained is dependent upon call model.) Experienced Voice over Packet deployments and Carrier grade products with VoP solutions being implemented by carriers such as Sprint, Qwest, and Verizon since A complete end to end solution from a single vendor e.g. MGW, SGW, MRF provides improved network reliability, availability and time to revenue, critical for large-scale service deployment and cost effective management.

13 Nortel Confidential Nortel P-MSC Roll out Strategy P-MSC Solution and Timing Nortel has a phased approach to its introduction of the P-MSC Solution: Phase 1 (MTX 12, 2004): P-MSC (Gateway) focused on packetizing PSTN originated traffic and releasing processing capacity on Serving MSCs Phase 2 (MTX 13, mid-2005): P-MSC (Serving) extending the packetization to mobile originating traffic Phase 3 (MTX 14, mid-2006): P-MSC (TrFO-Phase 1, RTO- Phase 1) further increase the benefits of packet architecture through transcoding and transport optimization, further central office consolidation with the delivery of even higher P-MSC densities P-MSC with Gateway Functionality (MTX Generally Available) Network Growth Challenges Multi-MSC Markets require each MSC to be connected to every other MSC in the region directly, so that incoming calls from the PSTN can be routed from the Home MSC to the Serving MSC (MSC-S) if the subscriber is currently outside of his Home MSC area. This creates substantial overhead messaging between the MSCs in the market, using CPU processing which could be better served on other activities. Adding an incremental MSC in this environment has an exponentially diminishing return on capital expenditure. With every new MSC, more of the capacity of each switch in the network is devoted to talking to every other switch via inter-machine trunks (IMT), consequently reducing the individual capacity of all MSCs. The other significant capital expenditure impact of adding an incremental MSC is the increased number of trunk ports required to support the increased IMT traffic. Also when a new MSC is added to the network, a new border area is introduced and this long before being required due to BSC capacity limitations. This requires time-consuming and expensive network redesign to ensure the quality of service is maintained. Finally, subscriber usage patterns are changing to include far more incoming calls as Wireline replacement is gaining momentum. As this trend continues more calls will travel from the Home MSC to the Serving MSC, creating more IMT messaging. This ultimately will further impact MSC capacity,, require more IMT circuits and introduce more handoff border areas. Introducing a P-MSC with Gateway application into multi-msc markets can help address the architectural shortcomings described above and offers additional benefits in IMT circuit cost reduction.

14 Nortel Confidential 12 Packet MSC (Gateway) Benefits The P-MSC Gateway offers a next generation packet-based ANSI-41 Gateway MSC functionality. The P-MSC Gateway serves as the originating MSC (MSC-O) for all mobile terminated traffic from the PSTN. In this function, the P-MSC provides ANSI-41 gateway functionality, WIN termination triggers and Legal Intercept functionality. Therefore all incoming calls are routed to the P-MSC and then directed to the Serving MSC (MSC-S) where the subscriber is currently located. Removing this function from the MSC-S that manages the mobile traffic creates a significant improvement in capacity for handling BSC-generated traffic. In this configuration, the Serving MSCs are also connected to the P-MSC (Gateway) over the packet network, instead of meshing the MSCs together with IMT trunks. The P-MSC solution deployed in this phase assumes an XA-Core based MSC Server Region 4 Multi-MSC Market PST Region 1 Region 4 HLR PSTN PVG PVG PV Region 1 PVG Region 3 Region 2 Region 3 Region 2 Figure 4 Leveraging Packet MSC with Gateway Functionality Nortel P-MSC Gateway solution provides benefits to the service provider in the following ways: Inter Switch Inter Machine trunk Cost Port Savings Through a substantial reduction in port pricing of packet versus circuit switched ports and increased simplification of the existing transport network as the service provider moves from a mesh to star configuration between MSCs. MSC Offload: up to 17% capacity recovery in distributed packet architecture extends processor life of existing MSCs, thereby stretching existing TDM investments and delaying new real estate expenses, thereby reducing capital expenditure and RF network redesign due to the introduction of a new border cell with a new Serving MSC. The P-MSC with Gateway functionality is commercially deployed today in the United States with a major Operator and has confirmed the benefits highlighted above.

15 Nortel Confidential P-MSC with Serving Functionality (MTX 13 mid-2005) In this phase Nortel extends the P-MSC Solution to support the Serving functionality, hence allowing to extend the packetization to Mobile originated traffic in addition to PSTN traffic. The P-MSC solution deployed in this phase still assumes an XA-Core based MSC Server The XA-Core is the processor front-end currently used within Nortel s leading TDM-MSC, the DMS-MTX. The P-MSC solution is therefore a smooth evolution from existing MTX and will have a consistent feature set with what is available on the Circuit MTX including consistent billing interfaces and OAM to the back office. Existing Customers will have the option to implement a cap and grow strategy, whereby they keep their existing TDM peripherals (DTC, SPM) while growing new traffic on the PVGs. With this step of the Evolution, Operators will be able to leverage the benefits of packetization and the distributed Architecture, in particular transport optimization will begin occurring as local traffic stays local instead of being backhauled all the way back to the switch site. They will also start benefiting from more flexibility in network design as capacity is becoming centralized, ready to be shared across remote regions. Region 2 HLR ANSI-41 Local PSTN MSC Server Region 1 USP BSC H.248 H.248 Local PSTN Inter Region Traffic MG BSC MG Long Distance Centralized call processing Fully utilize MSC Server processing power Figure 5 Packet MSC (Serving) Local Traffic stays local Mobile to Mobile Land to Mobile Mobile to Land

16 Nortel Confidential P-MSC with TrFO-Phase 1 and RTO-Phase 1 (MTX 14 mid-2006) This 3 rd phase of the P-MSC has two focuses: Introduce a new platform choice for the MSC Server, the MSC Server 2000 which is targeted at Greenfield Opportunities Further distribution of MGWs via the support of multiple BSCs per P-MSC Further expand packetization benefits by limiting transcoding requirements while optimizing transport New Platform for MSC Server to complement existing Portfolio Nortel has selected for its Softswitch portfolio the new generation architecture defined in the PICMG 3.x series of specification (ATCA), which is targeted at building high end carrier grade equipment. For the OS, Nortel will be using Nortel Carrier Grade Linux, which we are already using on other platforms today like the Call Server 2000 Compact (CS2Kc) 1 delivering a Nortel proven and high availability SW which we can then smoothly port onto the new HW. The ATCA based MSC Server 2000 will leverage all the feature sets and software code available today on the XA-Core Solution. Using general purpose HW should allow our Operators to benefit from the following: Benefit from latest industry technology advancements for HW Nortel is confident that its implementation will differentiate itself. Even though the specifications define the architecture, every vendor s solution will be different as the components are not mandated only the interoperability requirements. Nortel has built expertise in implementing a general purpose solution with its Wireline VoIP deployments (CS2Kc) and is leveraging this same expertise to build its ATCA platform. Reduced Footprint and Power Consumption The ATCA based solution will have an even smaller footprint and power consumption than the XA-Core based Solution. The ATCA based solution will be supporting much higher BHCA capacity than the XA-Core (1M BHCA) based solution and should allow our Operators to address smoothly their fast growing network requirements. Faster time to Market with features In Wireline, the team has now become very reactive to the market requirements and moved to 1 release every six months since they introduced the general purpose solution. Nortel is confident that the Wireless loads will also see an increased flexibility provided by the introduction of the general purpose solution. In addition, removing proprietary aspects (HW and OS should increase Nortel s ability to leverage easily work from one group to another group across lines of business. 1 The Nortel CS2Kc is currently deployed as a Wireline packet tandem for one example.

17 Nortel Confidential Increased BSC/MGW distribution per Packet MSC In 2005, the Nortel Packet MSC solution will support the remote operation of Base Station Controllers (BSC) which allow for the distribution of MGWs. Operators will be able to leverage the benefits of packetization and the distributed Architecture, in particular transport optimization will begin occurring as local traffic stays local instead of being backhauled all the way back to the switch site. In this release in 2006, Nortel will support an increased number of distributed BSCs and MGWs as operators build out or move to packet within their secondary regions TrFO and RTO TrFO/RTO Introduction The introduction of multiple codec types within the call path, both at the mobile and the Base Station Controller (BSC), results in transport inefficiencies and voice quality degradation due to multiple transcoder operations. While wireless CODECs have improved significantly, additional transcoding and delays are imminent with the introduction of voice over packet transport networks (e.g. G.726-compressed voice over ATM Adaptation Layer 2). Additionally, as networks evolve to packet-based transport technologies to take advantage of reduced transport costs, the optimization of potential delays in call setup and Quality of Service (QoS) issues become more critical. Today s mobile-mobile calls sit on the edge of maximum allowable bearer path end to end delay (E-to-E delay), where any shift in equilibrium will cause user dissatisfaction, primarily due to poor voice quality. Given this set of problems, Nortel has revisited a basic question from the days of analog wireless communications and first generation CODECs: is it possible to maintain end-to-end native wireless format in a mobile to mobile call? Additionally, can a vendor extend this technology concept to other call types (e.g. mobile to land, land to mobile)? Nortel Experience Beginning in 1995, Nortel was the first vendor to design, implement, and deploy Tandem Free Operation (TFO) for wireless calls supported over TDMA networks. TFO was designed and standardized to improve voice quality for calls traveling across TDM circuit networks. Nortel holds essential patents of TFO protocol design, and has played a significant role in the adoption of this technology in ETSI, 3GPP, and 3GPP2 standards. The benefits of TFO are as follows: A vocoder-specific feature with minimal impact to and dependence on other network components (MSC, peripherals, etc) Enhanced speech quality by reducing/removing unnecessary transcoding Increased vocoder hardware density (increase in the ratio of calls per resource) may be attainable on the terminating BSC Provisions for vocoder negotiation No impact to call set-up (timing or message flow)

18 Nortel Confidential 16 Relatively simple implementation of legal intercept, conferencing, & DTMF tones due to the in-band signaling nature of the technology - TFO standard meets the CALEA/Lawful Intercept requirements with the availability of PCM frames in addition to the compressed speech frames at the BSC vocoder A mature standard with the last release (ANSI/TIA-895-A) approved for publication in October 2002 Transcoder Free Operation (TrFO) TrFO achieves voice quality improvements in a similar manner as TFO; through the use of Vocoder by-pass on the BSC to maintain the device CODEC data from end to end. Nortel will implement the TrFO solution in 2 phases. TrFO-Phase 1 is being implemented in order to meet time to market requirements while still providing most of the benefits of TrFO. Transcoder Free Operation Phase 1 (TrFO-Phase 1) TrFO-Phase 1 is a subset of the standards based TrFO solution. Out of band signaling is used for CODEC negotiation during call setup via SIP-T between the wireless call servers. During call set up signaling, EVRC and G.711 are offered as the voice core network transport CODECs. If EVRC is unavailable from end to end, the call falls back to G.711 for the voice core network transport CODEC. Media Gateways are required on both the originating and terminating BSCs. The benefits of TrFO-Phase 1 are as follows: Reduced transmission bandwidth (native wireless compressed voice) Increased vocoder hardware call density (vocoder savings) Enhanced speech quality (by the removal of in network transcoding) Enhanced speech quality (by the delay reduction associated with not performing in network transcoding) Standards alignment on external interfaces to allow for interworking yy interface for bearer between media gateways is standards compliant zz interface for signaling between call servers is standards compliant Time to market by the use of proprietary internal solution interfaces Figure 7 below illustrates the architecture for a packetized voice core mobilemobile call, with TrFO-Phase 1:

19 Nortel Confidential 17 Legend Signaling - Circuit Signaling - Packet Bearer - Circuit TrFO-Phase 1 Network Architecture USP ANSI-41 Over SS7 HLR SS7 Network Bearer - Packet BTS BSC Interface ANSI-41 Over M3UA A1 Interface NOIS MSC Server SIP-T MSC Server A1 Interface NOIS H.248 H.248 EBSC MGW MGW EBSC EVRC TDM EVRC RTP UDP IP L2 L1 EVRC TDM TrFO End To End Native Device CODEC (Mobile To Mobile) Figure 7 - TrFO-Phase 1 (Mobile to Mobile) Remote Transcoder Operation (RTO) RTO is motivated by the desire to reduce network transport bandwidth requirements on calls between a TrFO capable mobile network and the PSTN. A TrFO-like architecture between wireless and PSTN networks allows the operator to attain this savings. RTO is used primarily in the case of mobile-to-land and land-to-mobile calls. These categories constitute the largest percentage of wireless calls today. -end of document-