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Tech Featureswith standard-based protocols andinterfaces between them.● Strong networking and accesscapabilityNGN support multiple accesstechnologies tailored to differentapplication environments such asFTTC, FTTZ, FTTB, FTTH, FTTO,DSL, hybrid fiber coaxial (HFC),CDMA WLL, and wireless.● Flexible creation of services andimproved time-to-marketNGN provides a fully open serviceplatform architecture which allowsInternet service providers (ISPs), evencustomers themselves to develop newservices.● Operation Expenditure (OPEX)r e d u c t i o n w i t h c e n t r a l i z e dmanagementmigration strategy.the access layer, Multi-Service AccessPSTN has an evolutionary path as Network (MSAN) and Multi-Serviceillustrated in Fig. 2. Of course, some Access Gateway (MSAG) are favoredoperators can utilize IMS architectures solutions as they can provide variousto optimize their networks if the PSTN narrowband and broadband services.reconstruction pressure is not intense. It’s worth noting that Stage 2 is notFig. 2 General evolution path for fixed networksEvolutionary phases of fixednetworksI n t h e s e c o n d h a l f o f 2 0 0 5 ,migration from PSTN to NGN hasentered a substantive stage. Manymainstream operators especiallythose in China, Russia, India, Brazil,Malaysia, Pakistan are embarkingon NGN migration projects. Thesemovements to NGN are motivatedby the need to support end users’demands, to exploit the synergies thatnew technologies bring as well as theneed to replace the legacy obsoletenetwork. Regardless of their differentmotivations, operators all emphasizeon the open architecture, flexiblecreation of new services, all kindsof broadband access networks, andabundant bandwidth, and Softswitchis the first step in their PSTN networkStage 1: Construct an IP Backbonenetwork based on Softswitch networktechnology. Fixed operator willimplement an open NGN architectureto take advantage of the new marketdemands, optimizing the legacynetwork while replacing obsoletePSTN equipment. NGN can accessmultiple types of services includingthe traditional voice service. TheSoftswitch network will coexist andinterwork with the PSTN network atthis stage.S t a g e 2 : F i x e d n e t w o r kintellectualization stage. Introducingthe Smart HLR (SHLR), operatorscan bring next generation value-addedservices to legacy users. To meet therequirements of emerging broadbandmultimedia services, intelligentterminal devices will be employed. Atan essential step for those operatorswhose networks have a small capacityand a simple structure. For them, thenetwork-wide intellectualization canbe implemented in Stage 1.Stage 3: Evolution from Softswitchto IMS. As IMS technology isgradually getting mature and usersincreasingly demand multimediaservices, it’s inevitable that Softswitchwill be substituted by IMS. Basedon a layered architecture, IMSand Softswitch in fact have a lotin common. Both have the samefunctional model, and the same SIParchitecture–both support intelligentdevices and allow operators todeliver multimedia services. The IMSarchitecture was initially proposedfor use in mobile networks by 3GPP,and now being adapted for use in10ZTE TECHNOLOGIES