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Method for adaptive slicing

IP.com Disclosure Number: IPCOM000130137D
Publication Date: 2005-Oct-12
Document File: 4 page(s) / 76K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for adaptive slicing. Benefits include improved functionality and improved performance.

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Method for adaptive slicing

Disclosed is a method for adaptive slicing. Benefits include improved functionality and improved performance.

Background

              Several specifications regulate modem operation and functioning, including the following:

•             International Telecommunication Union - Telecommunication Standardization Sector (ITU‑T) Recommendation V.90, “A Digital Modem and Analogue Modem Pair for Use on the Public Switched Telephone Network (PSTN) at Data Signaling Rates of Up to 56000 Bit/s Downstream and Up to 33600 Bit/s Upstream,” September 1998

•             ITU-T Recommendation V.92, “Enhancements to Recommendation V.90,” November 2000, March 2002; “ITU-T Amendment 1 to Recommendation V.92 - Enhancements to Recommendation V.90,” July 2001

•             ITU-T Recommendation V.34, “A Modem Operating at Data Signalling Rates of Up To 33600 Bit/s For Use on the General Switched Telephone Network and on Leased Point-to-Point 2-Wire Telephone-type Circuits,” February 1998

              A typical circuit of a modem in a communication system encodes the signal and processes it through various states, such as in the following example (see Figure 1):

1.           110 - Symbol stream, created from the information bit stream
2.           120 - Transmitter (TX), where the signal is modulated

3.           125 - Communication channel

4.           130 - Receiver modem, processes the input signal and recovers the symbol stream

5.           155 - Recovered symbol stream

6.           170 - Decoder, restores the information bit stream from the recovered symbol stream

7.           140 - Adaptive filter, compensates for the linear distortion of the channel (125)

8.           160 - Clock recovery circuit, compensates for the clock difference between TX and RX sampling

General description

              The disclosed method is adaptive slicing (150) for improving the signal equalization process (165). The method compensates for a portion of the nonlinear distortions from the TX to the RX path.

      The method applies to V.34, V.90, V.92, and other modems that communicate using wired and/or wireless transmission channels over which an analog signal is transmitted. The disclosed method can be applied for pulse code modulated (PCM), quadrature amplitude modulated (QAM), digital phase shift keying (DPSK), orthogonal frequency division multiplexing (OFDM) signals.

Advantages

              The disclosed method provides advantages, including:
•             Improved functionality due to providing adaptive slicing

•             Improved functionality due to providing an apparatus and procedure for improving distortion immunity near the perimeter or center of a signal constellation

•             Improved functionality due to providing tracing of amplitude nonlinearity during connection
•             Improved performance (connect rate) due to reducing equalizer errors

•             Improved performance (connect rate) due to compensating nonlinear channel noise

Detailed description

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