ADSL compatible discrete multi-tone apparatus for mitigation of T1 noise
First Claim
1. A discrete multi-tone transmitter that is suitable for transmitting digital data over a twisted pair communication line on a multiplicity of subcarriers having different frequencies, the transmitter comprising:
- an encoder for encoding digital information, the encoder being capable of encoding digital information at speeds in excess of six megabits per second;
a modulator for modulating the encoded digital information onto a multiplicity of subcarriers in a discrete multi-tone signal, 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 1.6 MHz, the modulation being arranged to take into consideration at least detected line quality parameters and a permissible power mask parameter, and wherein the modulation is capable of dynamically updating both the subchannels used and the amount of data transmitted on each subchannel during transmission in order to accommodate real time changes in specific parameters; and
an adder for appending a cyclic prefix to the discrete multi-tone signal before it is applied to the transmission line.
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Abstract
An improved discrete multi-tone transmission scheme is describe that contemplates encoding digital data and modulating the encoded data onto a discrete multi-tone signal having a total bandwidth of at least 1.6 MHz. The modulation system is capable of dynamically updating the subcarriers used and the amount of data transmitted on each subcarrier during transmission in order to accommodate real time changes in the line quality over particular subcarriers. In one preferred embodiment of the invention the multi-tone encoding and modulation is done in substantial compliance with the ATIS North American Asymmetric Digital Subscriber Lines standard although a total of 512 subchannels each having a bandwidth of approximately 4.3125 kHz are used. In this system, the subchannels that occur at frequencies above those set forth in the standard are treated similarly to those within the standard range in terms of subcarrier selection criteria. This embodiment contemplates the use of a discrete multi-tone signal having an available bandwidth of 2.208 MHz. The described system permits transmission of digital data at transmission rates of 6 Mbps over telephone lines at distances of two miles even on lines that experience significant T1 crosstalk noise. In one application of the invention, it may be used with ordinary telephone lines such as twisted pair lines to transmit data to remote receivers located up to six thousand feet from the transmitter at digital data transmission rates of at least ten million bits per second (10 Mbps). With more subchannels provided, the number of subchannels available for upstream communications may also be increased.
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Citations
20 Claims
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1. A discrete multi-tone transmitter that is suitable for transmitting digital data over a twisted pair communication line on a multiplicity of subcarriers having different frequencies, the transmitter comprising:
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an encoder for encoding digital information, the encoder being capable of encoding digital information at speeds in excess of six megabits per second; a modulator for modulating the encoded digital information onto a multiplicity of subcarriers in a discrete multi-tone signal, 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 1.6 MHz, the modulation being arranged to take into consideration at least detected line quality parameters and a permissible power mask parameter, and wherein the modulation is capable of dynamically updating both the subchannels used and the amount of data transmitted on each subchannel during transmission in order to accommodate real time changes in specific parameters; and an adder for appending a cyclic prefix to the discrete multi-tone signal before it is applied to the transmission line. - View Dependent Claims (2, 3, 4, 5, 6, 7, 13, 14, 19)
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8. 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:
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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 1.6 MHz, the demodulation being arranged to receive modulation information as part of the discrete multi-tone signal, wherein the demodulator is capable of dynamically 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. - View Dependent Claims (9, 10)
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11. 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:
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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 1.6 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. - View Dependent Claims (12, 15, 16, 17, 18, 20)
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Specification