Pulse or digital communications – Equalizers – Automatic
Reexamination Certificate
1998-11-30
2001-09-11
Pham, Chi (Department: 2631)
Pulse or digital communications
Equalizers
Automatic
C708S323000
Reexamination Certificate
active
06289045
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a training method in a time domain equalizer and a digital data transmission apparatus including an improved training apparatus in a digital data transmission system.
2. Description of the Related Art
In general, there are two types in a digital data transmission system, i.e., one being a single-carrier transmission system which transmits data signals by using a single carrier, and the other being a multi-carrier transmission system which transmits the data signals by dividing them into a plurality of bit-strings, by encoding the plurality of bit-strings, and by using a plurality of carriers. Although the present invention can be applied to both single-carrier and multi-carrier transmission systems, the following explanations will be given in the training method in the time domain equalizer and the digital data transmission apparatus including the improved training apparatus in the multi-carrier transmission system.
Further, the multi-carrier transmission system usually can be applied to a transmission system called an asymmetric digital subscriber line (ADSL). A detailed structure of the above transmission system has been disclosed, for example, in the document published by John A. C. Bingham, titled “Multicarrier Modulation for Data Transmission: An idea whose Time Has Come”, dated May 1990, in the IEEE Communication magazine.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a training method which can easily correct DC components contained in the channel target characteristic and the characteristic in the time domain equalizer so as to become zero after a window process was provided to tap coefficients.
Another object of the present invention is to provide a training apparatus, provided in a digital data transmission apparatus, which can easily correct DC components, contained in the channel target characteristic and the characteristic in the time domain equalizer, so as to become zero after a window process was provided to tap coefficients.
In accordance with a first aspect of the present invention, there is provided a training method in a time domain equalizer provided in a digital data transmission system for updating tap coefficients in the time domain equalizer so that an error between the tap coefficients and channel target characteristic becomes zero, the training method including steps of: obtaining a first sum of the tap coefficients of the channel target characteristic before a rectangular window is provided to the tap coefficients, and storing the first sum in a memory; obtaining a second sum of the tap coefficients of the channel target characteristic after the rectangular window was provided to the tap coefficients; subtracting the second sum from the first sum, and dividing a resultant value of subtraction by the numbers of the tap coefficients existing within the rectangular window; and obtaining each of tap coefficients of the channel target characteristic by adding a divided value to each tap coefficient existing within the rectangular window.
In accordance with a second aspect of the present invention, there is provided a training method in a time domain equalizer in a digital data transmission system for updating tap coefficients in the time domain equalizer so that an error between the tap coefficients and channel target characteristic becomes zero, the training method including steps of: obtaining a first sum of the tap coefficients in the time domain equalizer before a rectangular window is provided to the tap coefficients, and storing the first sum in a memory; obtaining a second sum of the tap coefficients in the time domain equalizer after the rectangular window was provided to the tap coefficients; subtracting the second sum from the first sum, and dividing a resultant value of subtraction by the numbers of the tap coefficients existing within the rectangular window; and obtaining each of tap coefficients in the time domain equalizer by adding a divided value to each tap coefficient existing within the rectangular window.
In accordance with a third aspect of the present invention, there is provided a training apparatus provided in a digital data transmission apparatus for updating tap coefficients in a time domain equalizer so that an error between the tap coefficients and channel target characteristic becomes zero, the training apparatus including: a first unit for obtaining a first sum of the tap coefficients of the channel target characteristic before a rectangular window is provided to the tap coefficients, and storing the first sum in a storage unit; a second unit for obtaining a second sum of the tap coefficients of the channel target characteristic after the rectangular window was provided to the tap coefficients; a third unit for subtracting the second sum from the first sum, and dividing a resultant value of subtraction by the numbers of the tap coefficients existing within the rectangular window; and a fourth unit for obtaining each of tap coefficients of the channel target characteristic by adding a divided value to each tap coefficient existing within the rectangular window.
In accordance with a fourth aspect of the present invention, there is provided a training apparatus provided in a digital data transmission apparatus for updating tap coefficients in a time domain equalizer so that an error between the tap coefficients and the channel target characteristic becomes zero, the training apparatus including: a first unit for obtaining a first sum of the tap coefficients in the time domain equalizer before a rectangular window is provided to the tap coefficients, and storing the first sum in a storage unit; a second unit for obtaining a second sum of the tap coefficients in the time domain equalizer after the rectangular window was provided to the tap coefficients; a third unit for subtracting the second sum from the first sum, and dividing a resultant value of subtraction by the numbers of the tap coefficients existing within the rectangular window; and a fourth unit for obtaining each of tap coefficient in the time domain equalizer by adding a divided value to each tap coefficient existing within the rectangular window.
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Awata Yutaka
Hasegawa Kazutomo
Miyoshi Seiji
Fujitsu Limited
Helfgott & Haras, P.C.
Pham Chi
Phu Phuong
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