NGN, softswitching and IMS position in the gradual progress tactics of the network
First, NGN, softswitching and IMS (1) NGN NGN refers to the network based on technology of dividing into groups, can offer the multiple operation including telecommunications service, can utilize many kinds of broadband and conveyance technology with QoS holding capacity, associative function of the business and bottom layer are separate while conveying correlation technique, can let users insert different business providers freely, can support common and excursively, thus provide the network that concerted sum can be ubiquitous for user and insert the business. NGN adopts layered structure, including business storey, control layer, transport layer and subscriber station, can offer many kinds of types of traffic to have pronunciation, data, multimedia,etc.. (2) Softswitching Softswitching can be interpreted as a kind of stratification, open NGN architecture, it is one of NGN key control layer technology. Softswitching in practice " Control " ,But not " exchange " ,Because " exchange " Embody in the bearing bed more, so " the softswitching network is that the speech network of future generation or future generation divides into groups in the communication network " Statement proper. The technical basic fixed position of softswitching taking controlling and bearing the weight of separating as essential feature offers 5 kinds of speech businesses such as traditional long distance in a network based on IP technology. Flexible arrangement and high integration density of softswitching are the enormous reducing that operators have brought construction cost of network and maintenance cost, but because receive the restrictions of a great deal of respects such as terminal ability, QoS, security and business interface canonicalization, comparatively mature softswitching (including fixed softswitching and 3GPPR4) at present Application only for too, herein, business of lasting the ones new yet it. (3) IMS IMS( IPMultimediaSubsystem) Namely IP multimedia subsystem, is organized by 3GPP standard to propose, offer the universal network framework of business of the multimedia in the network based on IP on the basis of R5 edition, contents such as the core architecture, Network Element Function, interface and procedure of the main definition IMS of R5 edition,etc.; R6 edition has carried on IMS completely, such characteristics as intercommunication norm and WLAN which has increased some IMS business characteristics, IMS and other networks are inserted; R7 has strengthened and made fixed canonicalization moving and merging, requires IMS to support fixed access ways such as xDSL, cable,etc.. IMS technology has further decomposed the control layer function, has realized conversation controlled entity CSCF (CallSessionControlFunction) And bear the weight of controlled entity MGCF (Media Gateway Control Function) The separation functionally, make the network framework more open, more flexible, so IMS is in fact " softer " than traditional softswitching . IMS business, control with it, bearing the weight of the horizontal framework totally separated, concentrated user's attribute, with inserting the characteristic of having nothing to do etc., have solved the problem that soft swapper also can't be solved at present on one hand, such as business interface, flexible IP multimedia provision that user's excursive support, standard are open,etc.; On the other hand, it inserts independence, make IMS become fixed to merge the foundation of the gradual progress with the mobile network too. The intersection of IMS and business structure, purpose of IMS set up, have no relations with inserting, can mobile network and integration core network that fixed network shares. In wireless access technology, IMS is besides GSM/GPRS and WCDMA, WLAN can be inserted too through SIPProxy. In addition, LAN and xDSL access technology of the fixed network can be inserted to IMS. IMS has offered with that of ISDN/PSTN traditional circuit switched network on-linely each other and made. In this way, the terminal station that IMS provides service includes stationary telephone terminal, multimedia intelligent terminal, soft terminal station of the PC,etc. besides movable termination. IMS can offer the business merged for using differently and meeting the users who start with section, but insert the characteristic different from moving and inserting and having fixedly eventually, apply IMS system based on that mobile communication develops to the fixed net to also need to carry on a large number of improvements, the standardized work still shoulders heavy responsiblities. Basic thought and goal of softswitching that the circle puts forward are concerted that IMS and fixed net that the mobile communication circle puts forward communicate, hope to set up integration and open network platform based on IP. Second, IMS system are studied (1) IMS architecture The designs of IMS architecture and CSCF have utilized soft swapper, has realized business and control looks separation, call control and media transmit and separate. Though IMS is the system that 3GPP is developed for moving the multimedia service of customer access, but because it has merged the technology of IP land in an all-round way, and carry on close cooperation on and other organizations during the course of developing, make IMS not merely limited to only serving the mobile subscriber actually. IMS architecture. In IMS architecture, the bottom is a bearing bed, used for offering access and transmission of IMSSIP conversation, it must be based on packet switch to bear the weight of the network. Bearing the weight of the way by moving the packet network of Fig. 2 has described as the example IMS users carry on IMS conversation way through the mobile phone, the master bearing bed apparatus has SGSN (GPRS business supports the node) , GGSN (gateway GPRS business supports the node) And MGW ( Media gateway) . Among them SGSN and GGSN can re-utilize the apparatus of the network now, does not need hardware staging, can support IMS when disposing only through doing relevantly. MGW responsible for media flow in the intersection of IMS and land and CS ' Circuit switching) The function entity of intercommunication of land, mainly solve the intercommunication problem of the pronunciation. No matter which kind of access way to adopt specifically, so long as because of IP technology, all signallings of IMS user can be well conveyed to the control layer. The intermediate layer is a control layer of the signalling, made up of control server of the network, take charge of managing and call out or conversation is set up, revised and released, the signalling of all IP multimedia business is controlled and finished on this floor. The master function entity is CSCF, HSS (HomeSubscriberServer, user's server of home country) , MGCF,etc.,these network element carry out different role,such as signalling control server, database, media gateway server,etc., finish the treatment function of the aspect of signalling in coordination, such as the setting-up, release of SIP conversation. This layer is only responsible for IMS signalling, the final IMS traffic flow does not pass this floor, totally make the route and realize end-to-end communication through the bearing bed of the bottom layer. The upper layer is the application layer the most, made up of application and content server, is responsible for offering IMS value-added service to user, the main network element a series of offers the Application Platforms of business of multimedia through CAMEL, OSA/Parlay and SIP technology. The operator can develop some application based on SIP by oneself, connect with IMS system through the interface of standard SIP; If the operator needs to connect application of the third party SP, IMS all right and canonial API, for instance OSAAPI connects, carries on authenticating and management,etc. to SP business that the third party does not believe in through OSA/ParlayGW. (2) Advantage of IMS 1. IMS packet network because of adopt, there are natural advantages in the support of the data traffic, can meet high-speed broadband and low-cost need of new business.