We have spoken with Bruno Jacobfeuerborn, CTO of Deutsche Telekom AG and Director of Technology in Germany, about the possibilities provided by the new ultra-bandwidth access technology XG-FAST.
Telekom and Nokia have demonstrated in a laboratory experiment that the new ultra-bandwidth access technology XG-FAST can be used to achieve data throughput speeds of over 10 gigabits per second (Gbit/s) with copper cable. This means that it would take less than ten seconds to download a two-hour HD movie, while a thousand photos could be uploaded in less than two seconds. These tests were carried out in Telekom’s cable test facility in Darmstadt.
Conversation is abuzz with terms such as vectoring, super vectoring, G.fast and XG-FAST. Can you explain the differences between them?
Bruno Jacobfeuerborn: For vectoring and super vectoring, the multifunctional cabinets – the big gray boxes at the side of the road – have to be equipped with fiber connections. Vectoring and super vectoring are technologies that ensure that the data transmission speed does not decrease during the last mile, which is copper.
For G.fast or XG-FAST, the fiber optic cable has to go even further – beyond the multifunctional cabinet and right to the customer. In this case, a fiber optic cable needs to be laid up to or even actually into the customer’s building. We refer to this as FTTB - Fiber to the Building.
How does XG-FAST work?
Jacobfeuerborn: XG-FAST, and also G.fast, use the last section of the available copper network to achieve speeds similar to those reached when transmitting data using fiber. During the XG-FAST test run in our cable test facility in Darmstadt, a peak download speed of more than 11 Gbit/s was achieved using two 50-meter-long, bundled pairs of a high-quality cable.
On top of this, XG-FAST also supports 1 Gbit/s symmetrical services spanning distances of up to 70 m using just one wire pair of a standard-quality cable. Inside buildings, therefore, operators could provide near-fiber speeds simply using existing telephone lines, without having to lay any new cables. This would mean shorter installation times and less expense for the end customer.
With 50 or 70 meters we don’t get far with broadband build-out outside buildings. So is XG-FAST an in-house technology?
Jacobfeuerborn: From our current viewpoint, yes. Nevertheless, we should not underestimate the possibilities. A particularly large amount of time and money is required to cover the last mile, referred to in technical jargon as network levels 3 and 4 – in other words, transmitting data from the multifunctional cabinet into the customer’s home and distributing it inside the building.
Is that the end of FTTH - Fiber To The Home - for Deutsche Telekom then?
Jacobfeuerborn: No, it's not. Deutsche Telekom aims to provide as many people as possible with as fast an Internet connection as possible, as quickly as possible. For this purpose, we are using the entire range of technical options in both fixed network and mobile telephony – which may supplement one another in some use cases and under certain conditions. Moreover, we are driving technological evolution. Regardless of whether mobile telephony or the fixed network is involved, we always strive to get the most out of resources. FTTH is an option that we are already actively using, for instance, for new property developments. However, those who commit themselves to a particular technology early on and are hell-bent on sticking to it are making a strategic error. They underestimate the dynamism of technological evolution and often also lose sight of aspects such as economic viability or the supply/demand ratio.
When do we want to implement XG-FAST?
Jacobfeuerborn: This question cannot be answered at this point in time. It is simply too soon. The technology is in an early phase of development. However, XG-FAST shows that new possibilities keep emerging for those who look for them. XG-FAST will provide us with another technology option which we can use to offer high transmission speeds while at the same time bringing our fiber infrastructure closer to our customers. But we have to proceed one step at a time. Thanks to vectoring, we will be able to supply around 80 percent of German households with over 50 MBit/s by 2018. Then, with super vectoring, the rate will increase to over 250 MBit/s. In parallel, we are building out our FTTH infrastructure, for example, in newly developed areas. We thus have a large toolbox which allows us to use different technologies in a targeted manner, as required. The framework conditions here include, of course, regulatory measures as well as future technological developments. Just think, for instance, of 5G, the new communications standard that we are currently helping to shape.
Does copper reach its limits with XG-FAST?
Jacobfeuerborn: No, XG-FAST shows that technology keeps evolving. I personally find the current fiber debate much too dogmatic and theoretical. It’s not about choosing between fiber and copper. XG-FAST provides a way of integrating the existing copper network into a fiber infrastructure. Our aim is to provide our customers with maximum bandwidths as quickly and efficiently as possible - no matter whether this is done using fiber or a combination of fiber and copper.