Using Simulations for Evaluation of Measurements on Adsl2+ Lines

The ADSL2+ lines are gradually replacing the first generation of ADSL in homes and small offices connecting to the Internet. Since there is a need to estimate the transmission speed, we have used MATLAB Web Server to design a simulator of xDSL lines that is available at our web pages. This paper compares simulations with measurement results and proposes a methodology for evaluation of measurements based on the suggestions from Slovak Telecom in connection with the practical introduction of ADSL2+ technology in 2006. The original analogue telephone lines use xDSL digital systems to a lesser or greater extent. Let us focus on the trend in the metallic access networks field and the potential possibilities for further development. Apart from the evolution of ADSL (Asymmetric Digital Subscriber Line) standards the transfer methods for the very high speed VDSL (Very-high-speed Digital Subscriber Line) are being optimized. An ADSL line transmits digital signals at various transfer speeds in opposing directions of transfer. For the connection of larger companies, especially those, which operate their own application and web servers, ADSL connection is not suitable although the SHDSL (Single-pair High-bit-rate Digital Subscriber Line) connection can be used. Allocation of bands for transfer directions downstream and upstream and also the total width of the band is dependent on the ADSL variant given by the ITU-T standard. According to the recommendation of the ITU-T G.992.1 today’s systems use a frequency band of up to 1.104 MHz. The lower part of the spectrum is of course used for telephone channels and for this reason it counts on the coexistence of ADSL in one conduit with the original analogue telephone connection (ADSL/POTS), which is preserved thanks to separation filters (adapter, splitter). Apart from this, ADSL can also coexist with the basic ISDN-BA connection (ADSL/ISDN).