Digital network lecturer4

Editor's Notes

• #8: Media Gateways are the interface between IMS and the legacy PSTN world. This allows calling between the richly featured multimedia IMS environment to the existing voice networks. The interworking between legacy endpoints and the IMS network allow those endpoints to access the features and functions that IMS can provide. Of course, this functionality may be limited by the capabilities of the endpoint. For example, network based features may be available to the legacy endpoint, but not multimedia. IMS defines common support for Classes of Service, Quality of Service, security and other attributes. However, standards are still evolving in many of these areas. Since IMS is built upon IP, it supports the flexibility and scalability to support mobility, portability, service creation, etc. All of these together may provide operational and financial improvements beyond existing networks. IMS defines how to develop subscriber databases which include User Profiles that enumerate identity, services, security levels, etc. IMS defines common session control that applies to any media. So the way a voice call is set up is identical to how a video call is set up. Based upon the class of service, different resources may be allocated in the network. IMS specifies common OAM&P environment that allows the evolution of operation support systems. IMS, in its self, does not define services. However, it defines how services are accessed. These services may be inherent in the IMS network or can provide gateways to existing service platforms.
• #9: IMS is designed to be applicable to the evolution of all types of networks. The major wireless carriers have committed to IMS as their next generations network. All of the U.S. major wireline carriers have embraced IMS in their evolution path. Cable network companies have not embraced IMS as of yet since Cable Labs has just defined IP-based network topology that was pre-IMS. It is thought that as cable networks evolve, they too will embrace IMS. One major advantage of IMS’s commonality is that carriers from each discipline can purchase equipment based upon the same standards, thereby potentially decreasing the cost to provide duplicate networks for different media services.
• #10: IMS is being defined as the convergence vehicle for all types of access connectivity. IMS allows typical Centrex customers to migrate to IP-based Centrex services and provides direct connectivity from the myriad of IP PBXs that are being deployed. IMS provides a natural evolution as LECs deploy their broadband access to the home as well as providing cable providers a standardized approach for network evolution. This theme extends to the introduction of WiFi or WiMax technologies that are inherently IP based. It is recognized that not all end points will be SIP enabled. Therefore, legacy systems can take advantage of the IMS services by entering the network through signaling and media gateways. As shown in the wireless cloud, a network can evolve such that it can take advantage of existing access techniques while evolving to IP connectivity that can natively interconnect to the IMS core.
• #13: UE sends SIP INVITE, which is tunneled through the RAN and BPN, to the P-CSCF. P-CSCF queries DNS for the address of a CSCF in the home network. P-CSCF forwards SIP INVITE to the I-CSCF in the Home Network I-CSCF retrieves the information needed to select the S-CSCF. I-CSCF forwards SIP INVITE to the S-CSCF in the Home Network. S-CSCF retrieves authentication vectors from the HSS, and selects one of the vectors. A “SIP 401 unauthorized” is sent back to the UE with authentication data. This message rejects the initial REGISTER. UE sends a new INVITE, with authentication data calculated by the UE, to the S-CSCF. The message flow is similar to steps 1 through 5. The S-CSCF performs authentication. If authentication is successful, the name of the S-CSCF is stored in the HSS. S-CSCF retrieves profile information and filter criteria from the HSS over the Cx interface. S-CSCF sends SUBSCRIBE message to the P-CSCF.
• #18: This example illustrates how IMS multimedia calls may be coordinated between parties. The first is a voice call originated by User A. The second is a video call originated by User B and the third is a data call originated by User A. The voice call originates from user A and enters the IMS network X at the P-CSCF The P-CSCF passes the call to the S-CSCF The S-CSCF interrogates the Application Server for originating services The S-CSCF forwards the call to the I-CSCF of network Y. The I-CSCF interrogates the HSS to determine the S-CSCF and passes the call to it. The S-CSCF interrogates the Application Server for terminating services. The S-CSCF passes the call to the P-CSCF assigned for the user and the voice call is completed. Now a video call is set up from User B to User A and the signaling path is reversed. Finally, User A sets up a data call to User B using the same signaling path.
• #21: Complex and Close Service Environment Too complex Service Creation Environment The 3rd AS can’t be introduced Operator have to upgrade the network nodes to support new services Separated Networks Different network for different services Common service enablers can’t be shared Simple services, simple experience - IP over everything Everything over IP - Much lower cost With wider bandwidth, it can support some real-time service Client-to-Server mode Fast provide abundant services Simplify network Multimedia user’s experience
• #23: The legacy services are provides by different networks. Each service has its different profile, and user shall sign on to each services. IMS focus on user only have one identification, one profile, one address book, and single sing-on. What more, use can customize every service. Such as ring back tone, call ID, smart routing etc. One fundamental assumption is that the business landscape in coming years will contain a wide variety of person-to-person and person-to-content applications, sometimes handled and managed individually by the end user, but probably normally bundled and provided by the operator or operator federations. Obviously, the end users expect convenience and ease of use; one major element here is the ability to provide Single Sign On functionality
• #25: 用户体验：多种终端应用开发
• #28: PS only：管道命运
• #30: SIP Modularity IMS is based on SIP. SIP is very modular. Many different functions supported by SIP are separate, modular, orthogonal components, which over time can be swapped in and out of IMS. This is especially important when mechanisms for accomplishing these functions will evolve over time. The QOS The authentication Signaling Compression A key feature of SIP is its ability to separate the notion of a session from the protocol used to invite a user to a session. SIP just issues invitations; it does not know anything about the session itself. The Benefit： IMS is a future-proof architecture. Network Capability Extension very easy. The core network is not changed when new services and new mechanisms are introduced. Common Function IMS core network provide common function by defining how service requests are routed, how charging is performed, how QOS is assured and how service composition is enabled. The CSCF don’t support service logic. The CSCF can route SIP messages very effectively. Benefit Provide a Unified routing mechanism, service interoperability is supported. Enable the service can be decomposed. Enables operators eliminate the costly and complex traditional network structure of overlapping functionality for charging, routing and provisioning. Service Enabler Service enabler: A service in the IMS service framework that can be used as basic building block functionalities giving support to other Application Server in order to create more complex services. IMS facilitates the creation and delivery of multimedia services based on service enabler. Presence Group List Management Messaging Server Benefit: Service enablers: Write once, use many The enablers developed for successful applications can become ’global enablers’ that are automatically included in new applications and services.
• #31: GSM/UMTS and WiFi multi-mode terminal can make telephony calls with VoIP via WLAN access, or with CS voice via GSM/UMTS access, in order to achieve cheaper tariff and better coverage; Solution compliant with 3GPP Rel7 VCC specification standard, with IMS domain HOAS as the anchoring point; Same MSISDN number can be shared for WiFi and Cellular coverage for the same subscriber; Bi-directional in-call handover between CS and IMS with excellent performance supported; Multimedia and IP Centrex services can be enjoyed by end users over WiFi access;