Pctel, Inc.

General Datacomm, Inc.

William Hanna

Yuri Goldstein

Yuri Okunev

Vitaly Drucker

Paul D Cole

Val Maizenberg

A method of providing a high bit rate DMT signal includes providing information on a plurality of DMT tones, with at least two of the plurality of DMT tones sending information in parallel. Of the tones sending information in parallel, at least one has a SNR too low to be individually used for the number of bits it is transmitting. Accordingly, the tones are coherently &ldquo;combined&rdquo; at the receiver in order to generate a SNR sufficient together to carry, at the desired BER, the number of bits being transmitted in parallel. Two or more tones which alone cannot carry a single bit of information may be used together to provide a sufficient SNR at the receiver to transmit one or more bits. Similarly, two or more tones which alone cannot carry two bits of information, may be used together via parallel transmission to provide a sufficient SNR at the receiver. Further, the bit-carrying capacity of a first tone which can carry one or more bits may be increased by transmitting an increased number of bits in parallel with one or more additional tones which cannot carry any bits of information. According to another embodiment of the invention, rather than sending two or more DMT tones in parallel, one or more DMT tones are repeated over a plurality of DMT symbols, and &ldquo;combined&rdquo; coherently in order to generate a SNR sufficient together to carry the number of bits being carried by the repeated tone.

Method and apparatus for data transmission using discrete multitone technology

A PCM modem equalizer includes an RBS estimator and decision modulator in conjunction with an adaptive equalizer such as a conventional decision feedback equalizer (DFE). The RBS estimator and decision modulator receives error signals from the second summer in the equalizer, receives the estimated R signals from the first summer of the equalizer, and outputs a gain correction signal which is applied to the output of the reference generator before the reference generator output is applied to the feedback equalizer and the second summer. The methods of the invention are based on the recognition that the effects of RBS can be detected in the amplitude modulation of the main training sequence stream. The modulation will occur in a periodic repetitive pattern of length 6*T where T is the symbol interval. Therefore, the invention applies a corrective gain to the decision in each time slot in a periodic manner having the same period 6*T. For each time interval T.sub.k over a period of 6*T, the symbol present at the time interval is sampled and a respective corrective gain g(6k-j) is applied to it, where j has the values 0 through 5. The gain applied to each of the six time slots is adaptively updated over a training period until each of the six gain coefficients is optimized.

PCM modem equalizer with adaptive compensation for robbed bit signalling

A spectral and power shaping mapper for high data rate signaling modem functions in a first mode having spectral and power shaping and using convolutional encoding, a second mode having power shaping, a third mode having power shaping using convolutional encoding, and a fourth mode having straight-forward mapping. Based on data rates and other criteria, incoming bits are grouped together, with a first subgroup of bits used in the first mode to generate two sign vectors (and in the other modes a single vector), a second subgroup of bits used in conjunction with an appended bit in the first, second and third modes to generate at least two magnitude manipulation vectors, and a third subgroup of bits used in a modulus converter to generate a plurality of quotients. The quotients and magnitude manipulation vector(s) are used to select one, two or four sequences of constellation points from a multidimensional constellation depending on mode. The sequences of selected points are combined with the sign vector(s) to generate, one, two or four sequences of octets for a shaping selector. In the first and third modes, the shaping selector employs a convolutional encoder state machine which uses criteria such as lowest cost paths and/or lowest average power in order to select which sequence of octets to output. In the second mode, selection is based on power only. In the fourth mode, the generated octets are output as there is no choice of octets.

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Wolcott, CT, United States of America

William Hanna