Systems and methods for scanning by remotes in multipoint-to-point
communication using orthogonal frequency division multiplexing are
provided. In one embodiment, a system comprises a host unit; and a
plurality of remote units using a multiple access scheme to communicate
at the same time with the host unit using orthogonal frequency division
multiplexing (OFDM); wherein at least one remote unit scans a band of
frequencies for a downstream signal from the host unit; wherein the host
unit sends an adjustment signal to the at least one remote unit
instructing the at least one remote unit to adjust the timing of
transmissions from the remote unit to improve orthogonality of an OFDM
waveform received at the host unit; and wherein the host unit allocates
orthogonal tones within the OFDM waveform to the plurality of remote
units.