Within the NGN concepts the standardization institutions are solving the following issues and problems:
There are many conceptual models and reference architectures for both the converged networks and VoIP architectures. Therefore, we have tried to find common features and to define a suitable conceptual model for NGN.
An objective of the conceptual model [4] is to determine functional layers (covering similar functionalities), their entities, reference points (interfaces) and information flows between them. Such a model then can be mapped more easily into the physical reference architecture (and it is independent of the physical entities, i.e. components of the architecture).
In most analyzed cases the NGN conceptual model layers are from the point of view of functionalities divided into independent parts as follows: access (some reference architectures do not include it directly into the NGN model or replace it by the adaptation one), transport (transmission, switching), control (call/sessions control) and application (services).
The access layer provides the infrastructure, for example an access network between the end user and the transport network. The access network can be both wireless and fixed and it can be based on various transport media.
The transport layer ensures the transport between the individual nodes (points) of the network, to which are connected access networks. It connects physical elements deployed in the individual layers It also enables the transport of different types of traffic, media (signaling, interactive data, real-time video, voice communication, etc.)
The control layer includes the control of services and network elements. This layer is responsible for set-up/establishing, control and cancelling of the multimedia session. It ensures the control of sources as well, depending on the service requirements. One of the fundamental NGN principles is the separation of control logic from the switching hardware.
The service layer offers the basic service functions, which can be used to create more complex and sophisticated services and applications. It controls the progress of the service based on its logic.
In the NGN it is required that the network control is not determined only by the terminal equipment applications, but that the network intelligence may carry out control over the network at all levels of the reference model. The network management reference model implies the following tasks for the network intelligence it has to ensure:
As it has already been stated, the next generation networks are a vision of a converged network, meeting all the requirements for a converged universal packet network of the future. The main aim is to explain the deployment and functions of the individual components within the network intelligence and to give a brief characteristic of the individual layers of an NGN conceptual model. After introducing the first real solutions, the next generation networks are becoming a reality, not just a concept. That is why it is appropriate to look into their evolution and to outline their future trends and the open issues to be solved as well. Migration scenarios of different types of networks platforms are based on the idea to integrate TDM (Time Division Multiplexing) and IP (Internet Protocol) platforms into one converged NGN platform (from the point of network infrastructure, as well as services, Figure below) [4], [5]. The separation of processes of service control and providing from the physical network architecture and extension of telephone and multimedia services are two different NGN aspects.
New concepts and architectures of new generation of ICT (Information and Communication Technology) based on converged ICT and NGN offer to operators new opportunities to implement and provide wide spectrum of multimedia services and applications [6].
Therefore operators can move from vertical silo architecture where each type of service has dedicated access, transport, control and application infrastructure per service to horizontally oriented architecture more independent from provided services. The main idea of NGN based IPTV is to include functionalities and infrastructure required for any of multimedia NGN services specially here the IPTV type of services to NGN architecture.
Table shows some of the main parameters and features of network concepts: NGN, PSTN/IN (Public Switched Telephone Network/Intelligent Network) and Internet (simplified and generalized interpretation).
PSTN/IN |
Internet |
NGN |
|
Multimedia services |
NO |
YES |
YES |
QoS support |
YES (Voice) |
NO |
YES |
Network intelligence |
YES |
NO |
YES |
Intelligent terminal equipment |
NO |
YES |
YES |
Integrated supervision and control |
YES |
NO |
YES |
Reliability |
high |
low |
high |
Service creation |
complex |
ad-hoc |
systematic |
Simplicity of services use |
medium |
high |
high |
Modularity |
low |
medium |
high |
Time of service introduction |
long |
short |
short |
Openness of architecture |
small |
high |
high |