Channel initialization method

An initialization method and channel technology, applied in the direction of digital transmission system, electrical components, error prevention, etc., can solve the problems of low transmission rate, small amount of data, and the transmission rate of logging system cannot meet the requirements, so as to meet the requirements of large data amount. Transmission requirements, the effect of increasing the data transmission rate

Active Publication Date: 2008-06-18
CHINA NAT OFFSHORE OIL CORP +1
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Problems solved by technology

Before the 1960s, analog modulation methods such as frequency modulation and amplitude modulation were basically used to transmit analog quantities, the amount of transmitted data was very small, and the transmission rate was also very low.
[0007] However, as the real-time r

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[0028] The basic idea of ​​the present invention is to apply the multi-carrier technology, especially the OFDM (Orthogonal Frequency Division Multiplexing, Orthogonal Frequency Division Multiplexing) technology to the data transmission of the logging cable in order to improve the data transmission rate.

[0029] The multi-carrier technology realizes parallel data transmission and multi-channel data transmission through technologies such as frequency division multiplexing (FDM) with overlapping spectrum, so as to improve the data transmission rate. Among them, the discrete Fourier transform (DFT) is usually used to realize the FDM scheme.

[0030] Among various FDM technologies, the OFDM technology based on the multi-carrier scheme is one of the most promising modulation and demodulation technologies in the field of communication technology. OFDM divides a high-rate information stream into many low-rate streams and transmits them in parallel on a set of orthogonal sub-channels....

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Abstract

A channel initialization method includes the following steps: A1) a ground end modem and an underground end modem respectively send a first training sequence to each other; B1) the modem received the first training sequence finishes the training of channel activation, multi-carrier clock synchronization, multi-carrier symbol synchronization, multi-carrier frame synchronization, AGC parameter arrangement, transmission power adjustment, time-domain equalizer and frequency-domain equalizer; C1) the ground end modem and the underground end modem respectively send a second training sequence to each other; D1) the modem received the second training sequence carries out subchannel SNR estimation to the training sequence and carries out bit and energy distribution to each subchannel according to the estimated SNR value; E1) the ground end modem and the underground end modem respectively send a subchannel bit distribution information and a subchannel energy distribution information to each other.

Description

technical field [0001] The invention relates to a channel initialization method, in particular to a channel initialization method for well logging cables. Background technique [0002] A logging system usually includes two parts: ground equipment (surface equipment) and downhole equipment (downhole equipment). The ground equipment and downhole equipment are connected by logging cables. The downhole instrument needs to transmit the collected data to the ground equipment through the logging cable; and the ground equipment also needs to transmit data such as control instructions to the downhole instrument. [0003] Logging operations began in the 1920s to 1930s, and the logging system experienced development from analog to digital. At present, it has developed to the fifth generation imaging logging stage. With the development of logging tools, the demand for data transmission rate is gradually increasing. [0004] In order to meet the increasing demand for data transmission...

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Application Information

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IPC IPC(8): H04B3/50H04L1/00
Inventor 卢涛李群张菊茜张艺陈伟顾庆水伍瑞卿
Owner CHINA NAT OFFSHORE OIL CORP
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