Page 39 - Use cases and requirements for the vehicular multimedia networks - Focus Group on Vehicular Multimedia (FG-VM)

Figure 12 – Diagram of the satellite broadcast system with CA support

10.2 Use cases
The conditional access system shown in Figure 12 has several drawbacks. In the following use cases,
the limits of the above conditional access system are analysed and solutions to improve the system
performance with converged networks are described.

10.2.1 Use case A – VMS with flexible EMM
Consider a live television broadcast service delivered solely by satellite networks. In such a case, the
scrambled multimedia data for each channel, ECM for each channel, and EMM for each terminal
should be transmitted over the satellite broadcast channel. Typically, the size of an EMM is about
dozens of bytes. If tens of thousands of new users are trying to activate their devices in a short period
of time, then the bandwidth required for the transmission of the EMMs for these new devices may
not be available in a satellite broadcast channel. As a result, some of these users may experience
service activation delay or failure.
For a service operator with access to converged networks, such circumstance could be avoided by
offloading the EMM transmission to the cellular communication network. The architecture of the
multimedia system with flexible EMM transmission is illustrated in Figure 13, where the scrambled
data and ECMs are transmitted over satellite broadcast channel and the EMMs are transmitted over
cellular communication networks.

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