Convergence and IP Multimedia Sub-System

8.1 Introduction to Convergence

The communications world is moving towards always-on and always-connected conditions for people who want to be connected to the world – real time. Both the means of communications, fixed and wireless, have undergone a sea-change. PSTN and ISDN are not only being used for voice but low-cost connectivity to the Internet world. Mobile communications have seen technology changing from first generation to the third generation and beyond (e.g. HSPA, LTE, etc.). And on top of this, we are witnessing a convergence of these two (fixed and mobile) worlds. Convergence is a word that may mean different things to different people. Convergence is happening on the service and application side, handset and communication devices, content and media, Internet and mobile; fixed and mobile networks, etc. But fundamentally, there are three types of convergence, as shown in Figure 8.1.

  • Device Convergence.
  • Network Convergence.
  • Service Convergence.

Figure 8.1 Types of convergence.


A mobile device is no more just used for voice communication. It is used for data and can be used for viewing television programmes, etc. So also is the case with computers – no more just a data upload/download machine, it can be very much used for voice communications. Service industries are as well not just about using one technology for one device ...

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