Mobile phones are not used only for talking these days. Now they are equipped with memory cards and large screens capable of displaying millions of colors, they have become multimedia devices. This situation has pushed network operators to provide more and more multimedia-based services like MMS (Multimedia Messaging System), Internet access and videocall via the UMTS (Universal Mobile Telecommunications System) network, etc. We can listen to the radio, mp3s or even read the news using our cell phone – it seems to incorporate all the possible media services. And what about motion picture- based services?
We could say that video streaming over 3G networks is a relevant example, but to be honest, its quality and price does not make it attractive. There is a need for a technology suitable for providing high quality audio/video transmission to complete the scope of multimedia services in handheld devices.
The audio/video transmission itself is not a problem; what then is? Why can’t we provide that kind of service? The main concept of the existing networks is the answer. The cellular architecture causes radio bandwidth limitations, which is an important issue here. Moreover, batteries in mobile devices seem to be another problem – constant radio receiver usage generates high power consumption and causes fast battery exhaustion.
The Internet Protocol Datacasting (IPDC) is being developed the limitations I have highlighted above. It carries IP datagrams over a broadcast network, thus it is suitable for transmitting any data, not just high quality audio/video streams.
In this article I discuss the system architecture for IPDC with reference digital video.
In order to enable any multimedia services, first we need a primary source. Thus, the Content Creation block is the starting element of the system in the model – the element responsible for content provisioning.
The Content Creation element is strictly connected to the Service Application module, which gathers data along with the related metadata from various Content Creation elements, offering them to users. It also has some security features; it is responsible for coding and service metadata provisioning to the Electronic Service Guide ESG). An important part of this module is the point of interaction with end terminals. This basically enables uplink communication and, in this way, also interactivity. There can be as many Service Application entities as there are services provided by IPDC. The next part of the system is responsible for Service Management and can be divided into the following four functional entities:
Service Configuration and Resource Allocation: this takes care of bandwidth allocation for Service Applications and binding a service to localization.
• Service Guide Provisioning Application: its main role is ESG aggregation from different Service Application entities. There can be more than one application in the Service Management module.
• Security/Service Protection Provision: its role is access control and management.
• Some location services can be provided to the Service Application module by the Service Management module.
The module responsible for security is of primary importance. The main IPDC feature, as we are transmitting over a broadcast network, is that the signal can be received by every user in the transmitter area. This means that even unauthorized terminals can receive the signal. If any user has access to every service, non-free services are useless. Therefore, an appropriate security system (Digital Rights Management) is important.
The next module, the Broadcast Network, has two main features. First of all, it is responsible for multiplexing various Service Applications. Secondly, it handles security issues. However, when discussing the Broadcast Network module, the most important aspect to mention is the DVB-H-based data broadcast. It offers many improvements for data transmission to mobile devices, time slicing and encapsulation in particular. Thanks to this, terminal battery consumption is reduced, making the service attractive since the user does not need to recharge the terminal so often. The Interactive Network is another element in the discussed architecture. As the name implies, it is a network element that enables terminal interaction with the system by providing an uplink connection to Service Application and Service Management entities. However, it is possible that some of the mentioned architecture elements do not enable such functionality. In this case, any interaction is impossible. Generally, interaction is a welcome feature. It increases security and makes new services possible.
