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Discrete Fourier transform equipment of ADSL system

A digital user loop, discrete Fourier technology, applied in the field of data communication, can solve problems such as not being able to meet the requirements well, and achieve the effects of solving the shortage of hardware resources, reducing the amount of calculation, and simplifying the calculation

Inactive Publication Date: 2003-12-31
南通国邦科技发展有限公司
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Problems solved by technology

In the ADSL system, since there are many modules involved in DMT, how to save hardware resources becomes one of the most important issues, and the existing technology cannot meet the requirements well, so there is an urgent need for DFT devices suitable for ADSL systems to achieve effective The purpose of controlling hardware resources and quickly completing modulation and demodulation in real time

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  • Discrete Fourier transform equipment of ADSL system
  • Discrete Fourier transform equipment of ADSL system
  • Discrete Fourier transform equipment of ADSL system

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Embodiment Construction

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0025] The DMT system in the ADSL system includes two directions of modulation and demodulation, such as figure 1 shown. In the modulation direction, the data to be sent is first allocated to bits, and the data of different bits is allocated to 256 channels according to the transmission performance of the channel. After the bit allocation, the data is constellation coded, and then its gain is adjusted. , and then modulate the signal to 256 channels through I-DFT, and then send it out after processing such as adding cyclic prefix and clipping; The signals of each channel are processed and demodulated by F-DFT, and then frequency-domain equalization, constellation decoding, bit de-allocation and other processing are performed on it to complete the DMT demodulation. It can be seen from the above process that demodulation is the reverse process ...

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Abstract

The invention provides a fourier transformation apparatus in the ADSL system that can be used for the modems of 256 communication channels, Being capable of accomplishing the 512 point DFT (I-DFT AND F-DFT) processing, the apparatus comprises a double port RAM, rotational factor module, sequential control module, read-write address producing module and butterfly-type calculation module. After the data preparation of the front level input double port RAM is ready, the sequential control module starts the read-write address producing module to begin to read-write data and the rotational factor, the butterfly-type calculation module performs the butterfly-type computation according to data and the rotational factor, the immediate data is stored in the double port RAM. The invention solves the problem of insufficient hardware resources, nearly 50% of operand can be saved

Description

technical field [0001] The present invention relates to the field of data communication, in particular to a discrete Fourier transform (DFT) device in an asymmetrical digital subscriber loop (ADSL for short) system. Background technique [0002] The ADSL system adopts advanced digital modulation and signal processing technology. While transmitting telephone services on ordinary telephone lines, it provides high-speed broadband data services and video services with up to 640kbit\s and 8Mbit\s speeds at the same time. Its key technology Discrete Multi-Tone (DMT) modulation technology in high-speed channels. In the ADSL system, the 1MHz bandwidth is divided into 256 sub-channels through DMT technology, and the bandwidth of each sub-channel is 4.3125kHz, and then according to the channel attenuation characteristics and noise conditions, the input data is adaptively allocated to each sub-channel. [0003] The structure diagram of DMT system in ADSL system is as follows: figure ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L12/28H04L27/00H04M11/06
Inventor 高芳李建宇
Owner 南通国邦科技发展有限公司
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