The demand for video on-demand (VOD) and catch-up services has skyrocketed in just a few years. For cable TV operators, VOD services are a double edged sword – while they can be a lucrative revenue stream, they also require lots of bandwidth because each user typically needs their own unicast stream. However, our research shows that there is an ingenious way to significantly improve bandwidth efficiency and provide VOD services to a much larger number of users with current cable networks. This can be achieved by combing innovations from Over-the-top (OTT) technology to digital television services.

 

Cable networks are ideal for providing high-quality live television services. Integrated digital televisions are convenient for users and digital television networks are very cost-efficient for free and pay-TV services. However, there is much to learn from OTT. One of the key factors OTT services’ success has been the low barrier for introducing new innovations and compelling services such as catch-up and movies on-demand.

 

We see that between broadcast digital television and OTT on-demand video exists a market for guaranteed high-quality on-demand video. In essence, the target is to deliver the same compelling services as OTT directly to television sets, but with the assured quality associated with broadcast HD television services. In principle, both OTT and digital TV technologies can be utilized to implement such services. Why not take the best of both worlds?

 

Adaptive streaming is one of the key innovations OTT has introduced. OTT services are delivered over unmanaged, heterogeneous networks, and therefore the delivery technology must adapt to changing delivery conditions. Adaptive streaming uses long buffer sizes, and client side control of streaming bandwidth to cope with temporal variation in the delivery capacity.

 

VOD services in cable networks face a similar problem. The required bandwidth changes considerably with time causing non-uniform daily and weekly loads. Networks with unicast services therefore have significant unused capacity needed only during the peak hours. The cable operators need to perform costly network upgrades to handle peak loads, resulting in unused network capacity.

 

This excess bandwidth, combined with the fact that there is ample storage and network capacity available in modern set top boxes and integrated digital televisions, can be utilized to provide VOD services efficiently in cable networks. The networking efficiency is improved with two separate means:

 

1. Video is transported faster than real-time to consumers’ TV sets and set-top-boxes in order to fully utilize the network during the off-peak periods. The transport and playback resemble the progressive video download of Internet video services. The faster transport will decrease the peak time load because more transports will be completed prior to the peak. Additionally, trick modes such as fast forwarding can be performed locally.

 

2. Multicast-approach is used to transport fractions of titles to more than one receiver. This makes sense because typically most of the traffic is made up of a small number of highly popular content, and it is highly likely that several clients in the same network segment are transporting the same title. For a new transport there is an opportunity to join earlier transports to receive later parts of the movie using bandwidth efficient multicast, and simultaneously receive the earlier parts from a new, dedicated stream. Because services in DVB-C networks are transported in multi-program transport streams, digital cable networks are inherently suitable for multicasting.

 

Combining these two will make the world of a difference for cable operators, by making VOD much more efficient. Our research and simulations show that the number of served subscribers can be increased manyfold when compared to traditional VOD transport, leading to lower capital investment costs and better service for consumers. Furthermore, constructing such a system for DVB networks is in principle relatively simple. The best inventions usually are.