IMS (IP Multimedia Subsystem), Next Very Interesting Services in 3G (WCDMA Rel.5)

What Is IMS

• IP Multimedia Subsystem is a Session Initiation Protocol (SIP)-based IP Multimedia infrastructure that provides a complete architecture and framework for real-time and non-real-time IP multimedia services on the top of Packet Switched (PS) core while still preserving the Circuit Switched (CS) telephony services.
  

• IMS provides the necessary IMS Capabilities: service control, security functions (e.g. authentication, authorization), routing, registration, SIP compressionand QoS support, charging.
  

• IMS is also expected to bring the strengths of wireless and fixed-line worldstogether. In 3GPP’s words: “The IMS should enable the convergence of, and access to, voice, video, messaging, data and web-based technologies for the wireless user, and combine the growth of the Internet with the growth in mobile communications.”

Main advantages to network and users

• Deliver person-to-person real-time IP-based multimedia communications as well as person-to-machine communications
• IMS enables applications in mobile devices to establish P2P connections
• Quality of Service (QoS) provides some type of guaranteed level transmission
• Easy user setup of multiple services in a single session or multiple simultaneous synchronized sessions

Sample Application

As shown in Figure 4.9, without IMS, participants are notified through e-mail and/or phone calls. The presentation is e-mailed and/or faxed out in advance so that mobile users that have access to a printer can print the document and view it while on the audio conference. Those individuals with access to a PC can view it during the call, seeing the presentation pages as the host scrolls through his presentation. Because the mobile device is not IMS capable, it does not allow users to participate in the conference while simultaneously attending to other messages or communications. Consequently, one participant must leave the call to attend to other urgent business. Another participant becomes aware that based upon the content of the presentation, she needs to change work plans and to contact “Dave” to discuss the revisions. However, she is not able to make that call while the information is fresh in her mind, but must wait until after the broadcast is finished.

In Figure 4.10, IMS simplifies the invitation process for the host by notifying all participants through one interface using e-mail and visual voicemail. In addition, through the Presence capability, participants busy in other activities can be automatically added into the conference when they are available. Because graphics and audio are integrated, mobile participants can view the presentation in real-time as the host pages through each slide. The interactivity of audio and graphics capability allows one participant to easily attend to other urgent business without leaving the meeting, and for other participants to discuss the contents of the broadcast without leaving the call or disturbing other participants.

This Posting combined from some articles about IMS.