PERFORMANCE EVALUATION OF A MULTICHANNEL TRANSCEIVER SYSTEM FOR ADSL AND VHDSL SERVICES

We study the performance of a multichannel modulation method for two contemplated subscriber line data services known as asymmetric digital subscriber lines (ADSL) and very high-speed digital subscriber lines (VHDSL). In the ADSL case, we find that over all unloaded North America subscriber lines in our test set, an unidirectional 1.536 Mb/s data rate service from the end office to the customer premises is possible on a single twisted pair at an error rate of 10(-7) with at least a 6 dB margin using coded multichannel modulation with sufficient transmit power. Furthermore, we find that the proposed ADSL service can co-exist with basic-rate access ISDN (or voiceband analog services) on the same twisted pair with our proposed system. In the VHDSL case, data rates in excess of 100 Mb/s can be transmitted reliably, at an error rate of 10(-7), using uncoded multichannel modulation on a single twisted pair over a relatively short distance (less-than-or-equal-to 150 feet) with a sufficiently high sampling rate (almost-equal-to 24 MHz) and transmit power. In this study, the dominant line impairments in the ADSL environment include intersymbol interference (ISI), far-end crosstalk (FEXT) from other ADSL services, spill-over near-end crosstalk (FEXT) from baseband services in the same wire bundle, spill-over far-end baseband signal on the same twisted pair due to imperfect filtering, and additive white Gaussian noise (AWGN) from such sources as electronic and thermal noises. In the VHDSL environment, ISI, FEXT and NEXT from other VHDSL services in the same wire bundle, as well as AWGN, are included. Finally, we show that a cost-effective multichannel transceiver design that has been suggested for high-speed digital subscriber lines (HDSL) service will also work well for the proposed ADSL and VHDSL services with only minimal modifications.