Broadcast models: DTT, Satellite and CDN

Digital artwork of a satellite

Broadcast is changing, this is undeniable. And one of the areas in which we have seen a progressive evolution has been in the means by which the images reach our homes. In TM Broadcast, three of the most common types of transmission will be looked at in depth: DTT, satellite and CDN.

By Yeray Alfageme, Business Technology Manager Olympic Channel



Towards the end of the 20th century, we experienced a transformation in the method through which television images entered our homes. We shifted from receiving analogue images through an antenna on the roof to these being digital, thus DTT, Digital Terrestrial Television came into being. This change was a considerable increase in both the quality of the images received, bidding farewell to seeing images with noises with strange shadows, along with the coverage, less signal and less power was now needed with meaning this could reach more places spread over our geography, as well as in the product on offer, since in the same radio-electric space, digital technology allows the chance to house many more channels.

The increase in the quality of the image was evident, without going into the subsequent definition increase with the arrival of HD. This was possible thanks to the fact that digital TV signals are less prone to interference and digital receivers allow for the reception of the signal in a sturdier manner than their analogue counterparts. The change was perhaps not so stark in the cities, although areas of the same ones that did not have an optimal reception were now able to enjoy a higher quality image, as well as in the rural environment, places with typically worse coverage of television signal experienced a dramatic change for the better in most cases. And it can be stated that in most cases as there were places, until the television distribution network improved, where the image could barely be made, since with little signal and quality, analogue television allowed for the reception of images, even if intermingled with noise and signal losses, to receiving nothing, as is the case in a good digital environment, the TV signal today or may be viewed or not, there is no middle ground.

There was also an automatic increase in geographical coverage with the change in technology since much less power is needed to receive it. An analogue TV channel needed around 90 dB to be able to be received with optimum quality while a digital channel is enough with 60 or even 40 dB to be able to be viewed, always perfectly. This meant that many corners would be able to receive a signal that failed to arrive beforehand. As we are dealing with a terrestrial network, whose means of transmitting the signal are located on land, there is significant dependence on the proximity and quality with which the signal is received from our nearest transmitter and depending on the topology of the terrain this also makes the network somewhat expensive, since in complicated environments multiple broadcaster points are required to be able to cover this area properly. As we will see later, this is one of the major differences between DTT and the other means of transmission that under examination.

Digital map of the Earth with digital connectionsA further improvement was in the range on offer, since the number of channels that we can have thanks to the implementation of digital technology is much greater than with the former analogue channels. An analogue TV channel in standard definition, remember that there were countries such as Japan that started to broadcast channels in high definition before making the leap to digital technology, occupying a bandwidth of 8 MHz. This analogue transmission channel was renamed multiplex, since it allowed more than one digital transmission service to be included in the same, with which it was possible to broadcast up to 5 digital channels and certain radio services, in the same radio-electric space where previously there was solely space for a single television channel. We never did manage to multiply the offer by five, they were around three times the number of channels on view, since the implantation was progressive and initially there was not the same space for the digital channels as for the analogue channels, yet today we can indeed talk about a significant increase once the transition to the digital world has ended and even with the implementation of high definition channels, which obviously require greater bandwidth, it can be said that we enjoy 5 times more channels of television in the DTT than with the former analogue network.

However, there are certain aspects of DTT networks that must be taken into account when using this type of system for signal distribution. Normally they are public property, which implies that they are highly regulated environments and the creation of new services, such as channels, is usually slow and tedious. In addition, as we forwarded beforehand, its implementation is expensive, and this is one of the reasons that they are publicly owned. As they are signal broadcasters located on land, the investment in the signal distribution network to them and the number of issuers needed to cover a large audience are expensive and difficult to implement in most cases.

These two aspects mainly make methods such as satellite or content distribution networks, CDN as its acronym in English, more convenient in certain cases.



Simultaneously with the terrestrial distribution of television, both analogue and digital, another method of making the images burst into our homes, the satellite, appeared. Initially, it was a much more global method since a single broadcaster allows for the covering a much wider area of coverage and, due to the modulation method used, the loss of quality was minimal.


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