A method for a network device of a powerline communications network includes selecting between a default preamble signal and a network-specific preamble signal specific to the network but not to a neighboring network and transmitting at least user data in conjunction with the selected preamble signal. Another method for a network device of a powerline communications network includes tuning a sensor to detect network-specific preamble signals specific to the network but not to a neighboring network and receiving at least user data associated with the preamble signals.