Intel Corporation

Cirrus Logic Inc.

Vedavalli Gomatam Krishnan

Sigang Qiu

Jeffrey Allan Green

Bo A Zhang

Wesley Hamilton Smith

Mandayam Krishnan

Xuefeng Jiang

Karl I Nordling

Prashant Pratap Tawade

Fred Schuckert

Don Carmon

Singang Qiu

A Digital Impairment detection scheme which is designed for providing reliable estimate of digital impairments such as PAD, and CODEC type in the presence of digital impairments such as Robbed Bit Signalling and non G.711 complaint network CODECs and analog impairments such as IMD, noise and changing line conditions. This estimate is used to derive optimum transmit symbol constellations for a modem connected digitally to a trunk so as to maximize its data transmission rate.

Pad and CODEC detection

Embodiments of the invention provide methods for determining the characteristics of a local loop using the multi-carrier tones of a DSL activation process. For one embodiment, one or more sets of downstream multi-carrier tones of a digital subscriber line activation process are received at an extended voice-band modem and are capable of transmitting upstream multi-carrier tones of the digital subscriber line activation process over a local loop. The downstream carrier tones and the upstream carrier tones are folded into a first multi-tone signal and a second multi-tone signal, respectively, each having a plurality of component signals within the spectrum band of the extended voice-based modem. The total signal power of the first multi-tone signal is divided by the power of one of the plurality of component signals of the second multi-tone signal to determine a ratio value. The ratio value is used to determine a characteristic of the local loop.

Methods and apparatuses for determining loop characteristics using an extended voice-band modem

An Inter-modulation distortion measurement and correction method which could be applied over a communication channel that is a combination of either or both analog and digital channels. This method is applicable for a communication system between a modem pair.

Inter-modulation distortion compensation

A technique is proposed to accurately estimate the Network CODEC levels for each PCM code a server modem generates. These levels are affected by the digital impairments such as Digital attenuation PAD in the trunk, the Robbed Bit Signaling, the type of CODEC (&#x3bc;-law or a-law&#x2014;or non standard), and by analog impairments such as loop distortion, noise, inter-modulation distortion, echo. At client modem equalizer output good estimates for these levels are derived. By detecting RBS pattern of the trunk, and using averages of decode levels of similar RBS slots, more accurate data points are obtained. By further replacing these levels with the closest CODEC receive levels, good accuracy is obtained. Non-monotonic points are detected and eliminated. An upper limit is set for constellation points to avoid saturation of the receiver. IMD correction is applied to the decode levels. Ideal points that are not signaled, are added if possible. When PAD-detection or Codec detection fails, PAD is set to 0 dB and the constellation is based on originally received and averaged data points. Techniques are presented for V.90 type modem constellation generation.

Receiver codec super set constellation generator

Lower bandwidth technology is used to determine whether a communication channel can support higher bandwidth technology. A signal generator generates a series of test signals that are associated with the higher bandwidth technology. The test signals are sampled to produce aliases that can be analyzed with lower bandwidth technology. Modem parameters are accessed from a modem's memory. The modem parameters are compared with a database containing information about whether a set of modem parameters indicates that a telephone local can support broadband devices.

Use of lower bandwidth technology to determine channel capability for supporting higher bandwidth technology

A method of generating a data constellation at a client modem is provided whereby an optimum distance between data constellation data points may be calculated for a predetermined, acceptable error probability. An iterative process may be carried out using proposed data constellations which may be used to provide factors for calculating corrected constellations. Once a constellation is generated to satisfy the required probability of error, the constellation may be re-evaluated using CRC errors and detected noise variance at the client modem. Based upon predetermined levels of noise variance and CRC error, the constellation may be regenerated to operate at either a higher bit rate or a lower bit rate.

Constellation generation and re-evaluation

A technique is proposed to accurately estimate the Network CODEC levels for each PCM code a server modem generates. These levels are affected by the digital impairments such as Digital attenuation PAD in the trunk, the Robbed Bit Signaling, the type of CODEC (&mgr;-law or a-law&mdash;or non standard), and by analog impairments such as loop distortion, noise, inter-modulation distortion, echo. At client modem equalizer output good estimates for these levels are derived. By detecting RBS pattern of the trunk, and using averages of decode levels of similar RBS slots, more accurate data points are obtained. By further replacing these levels with the closest CODEC receive levels, good accuracy is obtained. Non-monotonic points are detected and eliminated. An upper limit is set for constellation points to avoid saturation of the receiver. IMD correction is applied to the decode levels Ideal points that are not signaled, are added if possible . When PAD-detection or Codec detection fails, PAD is set to 0 dB and the constellation is based on originally received and averaged data points. Techniques are presented for V.90 type modem constellation generation.

Receiver CODEC super set constellation generator

A Digital Impairment Learning sequence which is designed for providing reliable estimate of digital impairments such as PAD, RBS, and CODEC type in the presence of analog impairments such as IMD, noise and changing line conditions. This estimate is used to derive optimum transmit symbol constellations for a modem connected digitally to a trunk so as to maximize its data transmission rate.

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Raleigh, NC, United States of America

Vedavalli Gomatam Krishnan