An improved system and method for communicating information on a transmission
medium is disclosed. The disclosed system and method provide improved communications
on the transmission medium in the presence of interference, which may take the
form of uncorrelated interference from different services on neighboring transmission
mediums. In one embodiment, the communications system includes a subscriber modem,
a central office modem; and a communications channel coupled between the subscriber
modem and the central office modem. The communications channel transports uplink
signals from the subscriber modem to the central office modem, and downlink signals
from the central office modem to the subscriber modem. At frequencies below a selected
frequency ME2F, the power spectral density of the transmitted uplink
signals is proportional to the power spectral density of the transmitted downlink
signals by a positive scale factor, and at frequencies above ME2F, the
power spectral density of the uplink signals is limited to one or more uplink frequency
bands and the power spectral density of the downlink signals is limited to one
or more downlink frequency bands that are disjoint from the uplink frequency bands.
Preferably, the total bandwidth of the uplink frequency bands above ME2F
is proportional to the total bandwidth of the downlink frequency bands above ME2F
by the same positive scale factor.