3com Corporation

Mark A Waldron

Scott A Lery

Vladimir G Parizhsky

Andrew L Norrell

Carl H Alelyunas

A method and device for generating a constellation of Pulse Code Modulation (PCM) levels to represent digital data in a communication system. The constellation of Pulse Code Modulation levels are selected to have a total number of PCM levels and an upper power limit that optimizes noise performance. PCM levels are selected to increase the minimum spacing between PCM levels as great as possible while staying within the upper power limit for a constellation having a desired number of PCM levels. To minimize the power level of the selected constellation, constellation points are selected starting from PCM levels at linear values near zero to PCM levels at higher linear values. To improve noise performance, the number of occurrences of the minimum distance between PCM levels is also reduced without exceeding the upper power level. To reduce occurrences of the minimum distance between constellation points, PCM levels at the minimum distance from the previously selected PCM level may be skipped. The number of PCM levels spaced at the minimum distance is thus reduced to an optimum number without exceeding the upper power level.

Method and device for generating signal constellations in PCM space for high speed data communication

An improved DC compensation method for use in conjunction with telephony signalling. The method includes defining a frame that includes at least two n-bit codewords. An unsigned codeword is then identified within the frame by applying a rule to the codewords in the defined frame. Next, a sign bit is appended to the unsigned codeword, thereby producing a DC compensating codeword. The sign bit is selected based upon a weighting function of the linear values associated with previously transmitted codewords. The remaining unsigned codewords in the frame are assigned sign bits from user data.

Frame-based spectral shaping method and apparatus

A method of detecting the presence of signal impairments that introduce distortion in one or more time slots of a communication link by comparing a received training sequence of signal points with hypothetical received signal points, where the hypothetical points are predistorted versions of the training sequence, and are based on the known, predetermined training sequence of signal points. A detection matrix is formed where one dimension of the matrix corresponds to a time slot within a frame, preferably six time slots to a frame, and the other dimension corresponds to a particular impairment, or combination of impairments. The individual signal impairments are generally one or more of the following: robbed bit signaling where the robbed bit is replaced with a logic `0`; robbed bit signaling where the robbed bit is replaced with a logic `1`; robbed bit signaling where the robbed bit is replaced with a logic `1/2`; 3 dB digital attenuator; 6 dB digital attenuator. The hypotheses are based on individual impairments and combinations/permutations of these impairments. The minimum value of each column (corresponding to a time slot within the frame) of the detection matrix indicates the type of impairment in that time slot.

Method of detecting network impairments for high speed data

Method and device for generating signal constellations in PCM space for

A method for storing a constellation of Pulse Code Modulation (PCM) levels in a condensed representation. The constellation of PCM levels is stored in a condensed representation that can be expanded to the full constellation. A 16 bit binary word stores the full constellation of selected points. The 6 most significant bits represent a number of PCM linear values at the minimum spacing between PCM linear values that should not be selected in the constellation. The 10 least significant bits represent the minimum spacing between PCM linear values selected in the constellation from the condensed representation. Using the number of PCM linear values at the minimum spacing between PCM linear values that should not be selected in the constellation, the minimum spacing between PCM linear values, and the number of selected constellation points, the full constellation can be generated from the condensed representation.

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Gurnee, IL, United States of America

Mark A Waldron