A DSP-based research prototype reverse channel transmitter/receiver for ADSL

The asymmetric digital subscriber line (ADSL) is an emerging technology for the transport of asymmetric DS1-rate services over a single copper twisted-pair in the local loop plant. One of the key ingredients to the ADSL system is the upstream low bit-rate control channel. The architecture and laboratory implementation of the low bit-rate upstream control channel is described. The system was first computer modeled, and then the transmitter/receiver were implemented around programmable digital signal processing chips (DSP) such as the TI TMS320C40. Experimental results indicate that the system is functional to loops of 18 kft