The case for a DVB-H mobile TV flexible satellite distribution architecture

DVB-T was ratified by the European Telecommunications Standards Institute (ETSI), in early 1997 and is in wide use in Europe today.

DVB-H (Digital Video Broadcasting—Handheld) is a leading standard for broadcasting video to handheld receivers. It became an ETSI standard in November 2004. DVB-H is based on DVB-T but modified to the more demanding power consumption requirements of handheld, battery-powered receivers.

It can offer a downstream channel at high data rates which can be used standalone or as an enhancement of mobile telecoms networks which many typical handheld terminals are able to access anyway.

Technical challenges in the generic DVB-H chain
The key technical challenge for DBV-H is that within an SFN (Single Frequency Network) all towers must broadcast the identical signal to within 100ns accuracy. This means that the latter part of the distribution path must be totally deterministic, up to every single bit transmitted.

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Figure 1: Simplified view of generic mobile TV data flow.

Although not as stringent in its requirement for synchronization, the rest of the distribution path also benefits from having as similar a path as possible, especially to transmitters in the same SFN.

Beyond the boundary of the SFN, issues such as handover from one SFN to another (MFN handover) can be engineered to be smoother when the signals are deterministically related to each other.

In the illustration below, loss-free handover is illustrated by the way that the wheel is transmitted by the two SFNs. The blue cell is broadcasting the left half then the right half, while the red cell broadcasts the middle first and then the edges. This means that handover from one to another can be performed with no loss of image.

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Figure 2: Loss free handoff.

However, significant network planning and coordination are needed to ensure that this occurs.

One of the ways to ensure central content processing and a homogenous management model, similar to the existing digital TV broadcasting systems, is to have a centralized, hierarchical distribution network made up of common equipment at each level and broadcasting a common signal throughout.

However, although it simplifies the technical network design, a single signal has a number of commercial (and possibly regulatory) drawbacks, as it removes the possibility of localization.

Localized content, however, is widely believed to be important to mobile TV's commercial success. Studies have shown revenue can be optimized by allotting between 15% and 20% of the data stream to local content and advertising.

With this in mind, it is important to understand how amenable the various DVB-H network architecture options are to including local content. In other words, the advantages of realizing additional revenue from local content must be weighted against the capital and operating costs of its inclusion for the different network architectures.