Gigabit data rates over copper telephone lines

July 10, 2014 // By Graham Prophet
The next milestone in the build-out of the broadband access network is called Fibre-To-The-Distribution Point (FTTdp). This concept calls for running optical fibre to a distribution point that can be flexibly installed relatively close to the customer premise.

The existing copper infrastructure is used to complete the access line to, and within, the building. To determine how 1-2 Gbit/sec data rates can actually be achieved in such environments, researchers from Fraunhofer ESK will be working with Lantiq and InnoRoute GmbH until 2016 as part of the FlexDP research project.

Achieving high access data rates requires utilisation of the higher frequency ranges on the phone lines. This is possible only if the copper line segment of the data transmission channel is relatively short. With this in mind, Fraunhofer ESK is analysing the channel properties within these high frequency ranges as part of the FlexDP project. Lantiq and InnoRoute will use the results of this work to eventually develop a reverse powered, flexible distribution point installed closer to the customers' premises. Through a combination of research, implementation and testing, the partners are laying the groundwork for the practical application of FTTdp.

Measuring channel properties in the 300 MHz frequency range

VDSL2 uses frequencies up to 30 MHz. With the aim of achieving still higher data rates, Fraunhofer ESK is examining the use of frequencies up to 300 MHz. Apart from the transmission characteristics of the line, background noise and sporadic impulse interference are important factors that impact transmission speeds. Higher frequency ranges permit the deployment of new transmission schemes such as, which operates up to 212 MHz and is currently in the standardisation stage. By extending the currently used spectrum, data rates of up to 2 Gbit/sec are theoretically possible, but only if the channel characteristics are consistently taken into consideration.

In order to gain a realistic picture of the situation in Germany, Fraunhofer ESK researchers identified and measured the various types of cables used in the country and examined typical customer premise wiring installations. Based on this preparatory work and with new measurements in the 300 MHz extended frequency range, engineers will develop a simulation environment allowing them