ADSL compatible discrete multi-tone apparatus

A discrete multi-tone receiver for receiving a first set of multi-tone encoded digital information over a communication line that may take the form of a twisted pair communication line, the receiver comprising:

• a demodulator for demodulating the encoded digital information from a multiplicity of subcarriers in a discrete multi-tone signal at data rates in excess of six megabits per second, each subcarrier corresponding to an associated tone and an associated subchannel, wherein the available subcarriers for the discrete multi-tone encoded signal have a combined bandwidth of at least 8.8 MHz, the demodulation being arranged to receive modulation information as part of the discrete multi-tone signal, wherein the demodulator is capable of dynamic updating during reception in response to changed modulation information in order to accommodate real time changes in the modulation scheme, the demodulator being arranged to strip the cyclic prefix from the discrete multi-tone signal;
• a decoder for decoding the demodulated digital information in real time;
• an encoder for encoding a second set of digital information;
• and
• a modulator for modulating the encoded second set of digital information onto a multiplicity of subcarriers in a second discrete multi-tone signal, each subcarrier in the second discrete multi-tone signal corresponding to an associated tone and an associated subchannel, wherein the available subcarriers for the second discrete multi-tone encoded signal have a combined bandwidth that is significantly less than the bandwidth of the subcarriers that are available to the first discrete multi-tone encoded signal.

A method of transmitting digital information from a source over a potentially noisy communication line that may take the form of a twisted pair communication line using a discrete multi-tone transmission scheme having a multiplicity of tones wherein the digital information is encoded and modulated onto a multiplicity of subcarriers, each subcarrier corresponding to an associated tone, the method comprising the steps of:

• monitoring the communication line to determine at least one line quality parameter indicative of noise levels at each of a multiplicity of subchannels that correspond to associated ones of said tones;
• encoding a digital data stream;
• forming a discrete multi-tone encoded signal from the encoded digital data stream using a discrete multi-tone modulator, wherein the available subcarriers for the discrete multi-tone encoded signal have a combined bandwidth of at least 8.8 MHz, the encoding and modulation being arranged to take into consideration the detected line quality parameters, and a permissible power mask parameter, and wherein the modulation system is capable of dynamically updating both the subchannels used and the data transmission rate over each subchannel used during transmission in order to accommodate real time changes in specific parameters;
• appending a cyclic prefix to the discrete multi-tone encoded signal;
• transmitting the discrete multi-tone encoded signal and its cyclic prefix over the communication line to a remote location.