Optimization of the DTT network in ISDB-T/Tb environments

IP, OTT, DTO (download-to-own) and access to mobile content are major trends in developed markets and a growing option in many other regions. But how to optimize these networks?

There is no doubt that today the world of content distribution is a rapidly changing scenario. IP, OTT, DTO (download-to-own) and access to mobile content are major trends in developed markets and a growing option in many other regions. However, before dismissing traditional broadcast television, it is worth remembering that for the vast majority around the world, IP is, at best, part of our world of fragmented delivery and not the primary way in which television content is received. Proven and trusted broadcast delivery (whether analog or digital, satellite, cable or terrestrial) continues to predominate in large areas of the world. In the open signal world, digital terrestrial delivery is today the most effective method, especially when regional content is required.

According to a Digital TV Research report from July 2013, the number of homes that will receive DTT signals in 2018 will be more than double that of 2013, equivalent to 553 million worldwide. The number of households receiving primarily DTT (those without a cable, IPTV or satellite subscription and that essentially use DTT) will also double in that period to 380 million. And half of the content comes from regional television channels.

Enensys is known in the DVB world for its network optimization and regionalization technologies. These address encoding/multiplexing and streaming, and are designed to create optimized networks that in turn enable more efficient monetization opportunities. This is vital in the DTT environment. His most recent successes include installations with Thai PBS for the launch of a DTT network; Thai TV5 and also with Televisa.

For some time now, Enensys has been exploring the Latin American markets and evaluating where its products can provide real benefit in an ISDB-T/ISDB-Tb environment, compared to DVB-T/T2. It has also put a lot of effort into the reengineering process, once the initial assessment is complete. As a result, it has developed OneBeam, one of its leading DTT solutions to help LatAm markets reduce Capex and Opex. However, the system has evolved from its DVB iteration to address ISDB-T-specific issues.

One of the key issues that OneBeam addresses is the specific nature of the broadcast transport stream (BTS) in ISDB-T. This in turn requires specific equipment that is not interoperable to receive signals. Due to the way ISDB-T is designed, there can also be significant bandwidth inefficiencies within a transport stream.

In a normal ISDB-T environment, a specific BTS has to be generated in the broadcast header, with proprietary compression mechanisms, to cope with highly specialized ISDB-T streams. For example, cable operators require additional proprietary equipment to decode and read the BTS signal. Furthermore, ISDB-T requires a 32 Mbit/s stream, regardless of the number of channels or services included, being an expensive option when content is delivered via satellite for DTT headends, as is the general case in Latin America from a geographical perspective.

In the context of ISDB-Tb, OneBeam offers the possibility of using a standardized transport stream (MPEG-2) within the distribution network. As a result, no proprietary equipment is required to access or monitor the content stream. Regional content is more easily managed through a central location, while standard CAM systems can be used to protect the content stream. Bandwidth usage can also be optimized more effectively, as the system only sends the content that is being used over the distribution network.

The same MPEG-2 transport stream can be delivered via satellite as through the DTT network. This means that services can be easily monitored across the delivery network due to the standardized MPEG signal. It also means that operators have a delivery network with multiple services. At each transmission site they can easily select the services that are required, thus utilizing a distribution network across multiple regions, enabling regionalization. The BTS that is generated at the final transmission site is where the content is, which is adapted for SFN and associated with the different related layers that exist within the ISDB-T stream. In this case, OneBeam acts as a deterministic BTS generator.

Using OneBeam, a normal broadcast signal can be used in the distribution network. This in turn offers an efficient and easy-to-manage option for enabled contributions, affiliate contributions, analog broadcast (using IRD with analog output) or digital broadcast in MFN and SFN environments.

In the context of ISDB-Tb, OneBeam allows four different services (cable operator contribution, affiliate contribution, analog terrestrial transport streams and digital terrestrial signals) to be managed within a single transport stream, providing significant cost savings and additional monetization opportunities.

Each affiliated television station needs to receive content in a format that can be easily reused and also insert its own local content. That's why local broadcasters need a dedicated delivery network with standard MPEG transport stream. Cable operators also benefit from this flexibility and there are a large number of operators throughout the region. They can also use the distribution network in the same way as local affiliates.

Even in an analogue disconnection situation, terrestrial analogue delivery is still required and, by using the distribution network we have described above, there is no need for a separate analogue distribution network. Finally, we have the distribution of services to a DTT network in the best possible quality. All of these applications can use the same distribution network, with associated cost savings, because standardized MPEG-2 receiving equipment can be used to receive the transport stream.

Ku band can also be used to deliver the same stream via satellite, providing as an additional benefit the ability to simultaneously offer a TDH service. This can be used to cover existing gaps, allow broadcasters to reach more customers and offer a greater variety of television services to existing customers, all without the need for two separate networks for DTT and DTT.