Information-theoretic aspects of subchannel allocation in ADSL systems supporting down-stream wireline/wireless trunks

Abstract

An analytically, tractable information-theoretic model is proposed to determine optimal subchannel allocation in an ADSL system whose downstream modem has wireline and/or wireless trunks at its input. The relevant (downstream) ADSL modem at the central office is assumed to receive packets from different types of trunks, such as optical lines, copper cables and/or wireless links, or their concatenated version. From an information-theoretic point of view, this ADSL modem is modeled as a "demultiplexer" in the sense that it selects out a specific set of bits and assigns it to an appropriate subchannel consistent with the Hartley-Shannon law specified SNR-level of the subchannels. The pertinent analyses pursued in evaluating a subchannel allocation metric (SAM) refer to the following: microcellular-fed fiber with a specified BER as the incoming trunk on an ADSL system and FEXT-infested copper customer loop access lines. The resultant performance of downstream ADSL traffic on subchannels is ascertained by the metric, SAM. Simulated results are presented and discussed.