US 2004/0174936 A1 · Receiver codec super set constellation generator

Abstract

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 (μ-law or a-law—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.

Claims26

Dependent claims

A method for generating multiple unique real non-linear constellations each representing different time slots corresponding to a set of network CODEC linear output levels for each digital PCM code from the server modem, said method comprising the steps of:

receiving, in an analog modem, the linear output of a network CODEC converted from PCM coded data transmitted by a network server modem, the linear data comprising a number of data points in a predetermined number of slots,
averaging, in the analog modem, the linear data, for each digital PCM code, for each of the time slots, to generate a statistical estimate of the linear data corresponding to the real non-linear constellation points to produce estimated real non-linear constellation points,
converting, using a first converting algorithm, to map the estimated real non-linear constellation points to the network CODEC linear output levels,
matching, in the analog modem, for selecting closest ideal CODEC output levels for a selected type of network CODEC, and
converting, using an inverse the first converting algorithm, to re-map the closest ideal CODEC output levels back to real non-linear constellation points.

2 more elements

Dependencies are inferred from the claim text.

Receiver codec super set constellation generator

Life of this patent

Receiver codec super set constellation generator

Life of this patent

Abstract

Claims26