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Frequency domain echo canceller

An echo cancellation, frequency domain technology, applied in the field of OFDM-based systems, which can solve problems such as increasing periodic prefixes and reducing data rates

Inactive Publication Date: 2009-02-04
TELEFON AB LM ERICSSON (PUBL)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Unfortunately, increasing the length of the periodic prefix reduces the data rate

Method used

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Embodiment Construction

[0033] In the following description, specific details are set forth for purposes of illustration and not limitation, such as particular embodiments, protocols, data structures, and techniques, in order to provide a thorough understanding of the invention. It will be evident, however, that one skilled in the art to which this invention pertains can practice other embodiments without these specific details. In other instances, detailed descriptions of well-known methods, systems, and devices are omitted so as not to obscure the description of the present invention with unnecessary detail. Furthermore, in some of the figures a single functional block is represented. Those skilled in the art will recognize that these functions can be implemented by means of a single hardware circuit, a combination of software functions and a suitably programmed digital microprocessor or conventional computer, an application specific integrated circuit (ASIC) , and / or one or more digital signal pr...

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Abstract

An echo canceller reduces the echo signal generated when the transmitted signal leaks through a hybrid circuit to the receiver. The echo canceller estimates the echo signal from the transmitted signal and then subtracts the estimated echo signal from the received signal. In fact, the echo path channel in a DMT modem is much longer than the periodic prefix, so the received echo signal will suffer from ISI (Inter-Symbol Interference) and ICI (Inter-Carrier Interference). A conventional echo canceller designed for an ADSL modem uses a time-domain adaptive FIR filter, or uses a joint echo canceller implemented in the time and frequency domains. Implement a matrix adaptive echo canceller in the frequency domain. Various embodiments are disclosed.

Description

technical field [0001] The present invention relates to digital communication systems. One application of the invention is a system using a multi-carrier modulation method, eg DMT (Discrete Multi-Tone) DSL (Digital Subscriber Line) subscriber twisted pair for high speed data transmission. Another application of the invention is in OFDM (Orthogonal Frequency Division Multiplexing) based systems. Background technique [0002] see figure 1 , a DSL modem includes a transmitter 12 and a receiver 14 connected through a so-called hybrid circuit 16 to the user's twisted pair 18 (telephone line). The hybrid circuit 16 is a two-wire to four-wire interface which connects the subscriber twisted pair 18 to a four-wire modem (two wires for the transmitter and two wires for the receiver). An ideal hybrid circuit exactly matches the impedance of the subscriber line and transmits the transmitted signal only to the subscriber line and the received signal only to the receiver. [0003] One...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B3/23
CPCH04B3/23
Inventor F·林奎斯特A·费尔特纳P·费伦格
Owner TELEFON AB LM ERICSSON (PUBL)