Vision of Best Practices for IMS Implementation

Vision of Best Practices for IMS Implementation

Daniel Biga, Horacio Del Giorgio, Fernando Dufour, Ariel Serra
DOI: 10.4018/978-1-4666-7377-9.ch018
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The IMS technology is a framework architecture for delivering IP multimedia services, which allows voice and multimedia applications to communicate from multi-access scenarios (Wireless, PacketCable, DSL, etc.), thus allowing the convergence of fixed and mobile networks. The authors carry out an investigation into the current state of the art of this technology, focusing on its architecture, operating principles, and especially on the current state of development in Argentina. They make a forecast of what will happen in the next three years and their vision of what today are the best practices for its implementation.
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IMS Architecture Overview

The IMS is an umbrella that aims to integrate all the information and communications technologies for new services that can be implemented to make full and integrated use of the existing communications services.

The idea of the architecture is to define a model that separates the offered services (voice, video and data) from the access networks used for these services (fixed telephony, cellular networks, cable companies, etc.).

Considering that the services that can be implemented are varied and open to the creativity of designers, we shall introduce a simple example for easy understanding. Suppose we are talking with out mobile phone and we are arriving to our office, which has Wi-Fi equipment. IMS would allow our mobile phone leave the connection of the cellular network and continue it (like a normal handoff) through the Wi-Fi. In this case, the access network would be changing.

We may also want to come to our desk (in our home or office), and continue our communication from a Soft-Phone that we have in our Tablet or from a fixed telephone line. In this case, we are changing the terminal.

The above is only a minimum example of services that can be implemented on an IMS network. We hope they were easy-to-understand examples that allow us to visualize how the access network or the terminal will be irrelevant in the future.

The IMS architecture is designed in a structure of levels, planes or layers, and each layer having its network elements and functionalities. The layers are described below:

Access Layer

The access layer can represent all high speed access, such as xDSL (x Digital Subscriber Line), cable networks, Wi-Fi, WiMAX, LTE (Long Term Evolution), among others.

Transport Layer

The transport layer represents an IP network. This network can integrate QoS (Quality of Service) mechanisms with MPLS (Multi Protocol Label Switching), DiffServ (Differentiated Services), RSVP (Resource Reservation Protocol), among many others.

The transport layer is mainly compunded by routers (edge routers for access and core routers for transit).

Control Layer

The control layer is made of several Session Controllers, which are responsible for routing signaling between users and for the invocation of the services. These nodes are called CSCF (Call Session Control Function). In this layer, we can also find the HSS (Home Subscriber Server) and the MRF (Multimedia Resource Function), which is also known as IP Media Server (IP MS). The MRF is divided into two parts, the MRFC (MRF Control), located in the control layer, and the MRFP (MRF Processor), located at the transport layer. The interconnection between MFRC and MRFP is performed via the H.248 protocol.

Application Layer

The Application Layer introduces the applications (also known as value added services) offered to the users. Depending on the organization of the control layer of its IMS Stack, the Service Provider could offer integrated services by itself or eventually by third parties. This layer is compounded by the AS (Application Servers).

Key Terms in this Chapter

IMS: The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem is an architectural framework for delivering IP multimedia services.

Multimedia: Multimedia includes a combination of text, audio, dynamics and statics images with an interactivity content forms.

Information and Communications Technologies: Refers to all technologies that provide access to information through telecommunications. It is similar to Information Technology, but focuses mainly on communication technologies. In short, it is includes the Internet, wireless networks, cell phones, and other communication mediums.

Wireless Networks: Are computer networks that are not connected by cables of any kind. The bases of wireless systems are radio waves, an implementation that takes place at the physical level of network structure.

Telecommunications: Refers to the exchange of information by electronic and electrical means over a significant distance. Telecommunications devices include telephones, internet, fiber optics, satellites, radio and telegraph, for example.

Cellular Network: Is a radio network distributed over land through cells where each cell includes a fixed location transceiver known as base station. User equipment, such as mobile phones, is therefore able to communicate even if the equipment is moving through cells during transmission.

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