From the perspective of user needs, with the continuous improvement of living standards, people's demand for communication services is not only a normal voice call, but also differentiated, personalized, diversified information, entertainment, audiovisual and other rich value-added services application. Scientific research shows that when humans receive information, the visual acceptance rate is 83%, while the auditory acceptance rate is only 13%, so video communication will be more efficient. With the continuous development of communication technology, the broadbandization of communication networks has become an obvious development trend. Following this trend, telecom operators can provide users with a richer mobile video service.
The 3G Mobile Communications Standards Organization (3GPP) proposed the technical architecture of the IP Multimedia Subsystem (IMS) in the R5 version. Its core idea is to introduce a subsystem supporting IP multimedia services in the 3G network. The technical characteristics of IMS at the protocol level are separation of control and application. The control layer uses Session Initiation Protocol (SIP). The application layer supports various application layer protocols above IP, such as RTP, FTP, SMTP, etc. At the network level, IMS uses the principle that the bearer network and the control network are separated. Due to the above technical characteristics, the introduction of multimedia services on the IMS network is more advantageous than the 3GR4 network, and it is easy to directly transplant Internet services into the 3G mobile communication network. Therefore, IMS has become an important factor driving the development of mobile value-added services. Video sharing (VS) service is one of the typical services in IMS system.
The VS service in the IMS network is a data service for IMS users to communicate better. The VS service allows users to share one-way real-time video with the other party at any time during the call. The video sharing does not affect the user's voice. Communication. In addition, users can terminate the video sharing function at any time and return to normal voice calls. The VS service also supports multi-point video sharing. The main difference between VS service and traditional video phone service is: VS service is a unidirectional video stream; VS service can share video with offline users. In the offline video sharing mode, the initiating user saves the video clip on the VS server. Once the user is found online, the VS server can push the video clip to the user terminal. The VS-based service can provide a better service experience than the VT-based service, and is therefore valued by the 3GPP and OMA organizations.
The IMS service architecture of IMS is composed of 4 parts: IMS terminal, IMS core network, VS application server, and support system. The IMS mobile terminal provides a user operation interface for using the VS service, including functions such as VS service initiation, video playback, video storage, and VS service response. In supporting the video sharing service, the IMS core network involves P-CSCF, S-CSCF, I-CSCF and other network elements. The role of these network elements is to complete the session control function between SIP mobile terminals, including the establishment of the session and the session. Save, session release, etc.
The VS application server is the most critical functional entity in the VS business system, and its functions include signaling and media flow control of the VS business request. In addition, in order to enable terminals with different encoding capabilities to communicate with each other, the VS application server also has the function of media encoding conversion. Another important function of the VS application server is to implement business billing. It supports multiple flexible billing methods based on business billing, event billing, time billing and flow rate billing, and can generate billing bills. The functions of the support system are mainly to realize the VS service ordering, service cancellation, and collection and collection of bills.
As a typical service in IMS, VS will be promoted vigorously with the deployment of IMS networks. At this time, IMS end users based on the SIP protocol will appear, combined with business processes (taking the VS business scenario in voice calls as an example). The implementation steps are as follows: establishing a voice call between IMS users; after establishing a session, before any party initiates a video sharing service request in this process, the capability interaction is performed first, and the information of the capability interaction includes the media stream supported by the IMS call to be made Type, corresponding codec format, IP address and port number, whether the terminal can support video sharing services, Personal ME IdenTIfier information, user terminal (UE) version, etc .; according to the ability to interact with content, any party can initiate an IMS domain call request. In addition to the basic call information, the call request message should also include the service capabilities to support the video sharing service; the IMS network and the VS application server complete the routing work, and reserve network resources for the current call; establish a one-way video service between users , That is, video sharing; users release video calls; users release voice calls.
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