Patent ID: 6122246
Filing Date: 2000-09-19
Classification: H04L

Abstract:
A communications system comprising:a transmitter for transmitting OFDM/DMT symbols over a predetermined number of bins across a transmission medium, the OFDM/DMT symbols being generated using at least one timing signal, at least one of the predetermined number of bins including a pilot tone sub-symbol having a frequency corresponding to the sampling clock signal; anda receiver for receiving the OFDM/DMT symbols from the transmission medium, the receiver demodulating the received symbols using at least one timing signal, the receiver having a first pilot tone search mode of operation in which the receiver adjusts its timing signal to scan the frequency range corresponding to the predetermined number of bins looking for the pilot tone sub-symbol and identifies the frequency of the bin including the pilot tone sub-symbol by identifying a known spectral pattern, the receiver further having a subsequent second pilot tone acquisition mode in which the receiver adjusts its timing signal to receive the identified bin containing the pilot tone sub-symbol and measures phase differences between successive pilot tone sub-symbols to thereby perform a further adjustment of the timing signal so that the pilot tone sub-symbols are received within a frequency range sufficient for subsequent phase locked loop processing thereof.