Undersökning av modulationsscheman för existerande bredbandsteknologier
In this thesis some different modulation schemes for xDSL-techniques are compared. The investigated techniques are ADSL, G.lite, ADSL2, HDSL, SHDSL and VDSL. The modulation methods used are DMT, CAP and different versions of PAM. Several broadband techniques also use Trellis Coded Modulation (TCM) to increase the coding gain of the transmission. For each one of the different modulation methods the signal-to-noise ratio is calculated for generating a bit error rate probability of 10-7. This is the error rate that is demanded for several of the investigated standards. Comparison is also made of the transmission capacity of the channel and how sensitive the technique is for interference in a part of the frequency band. To compare the different modulation techniques, simulations of the modulations were made. The simulations were made with MatLab and Simulink. Unfortunately Simulink only supports one- and two-dimensional TCM. Therefore no good simulations of ADSL and ADSL2 with TCM were made, because those techniques use four-dimensional TCM.