文档介绍：Abstract
Abstract
With slight cable core, convenient application in logging and low price, the single-
core cable has been widely used in oil field logging as the medium connecting ground
and down-hole instruments, both for transmitting data and providing electricity.
However, as a result of its structure and length, the single-core cable only has a narrow
transmission bandwidth. Besides, due to its slow transmission speed and the
complicated logging environment, data accuracy of single-core cable transmission can
be hardly reached. With the development of information processing and sensor
technology, the data volume delivered of logging is on the rise, which presents higher
requirements for cable transmission. Therefore, it es a significant issue to study
cable transmission technology with high capacity, high efficiency and high accuracy.
Against such a background, this thesis makes a model with PSpice for 5000-
kilometer-long single-core cable and analyzes the signal channel transmission
characteristics and noise features of the cable. Thus, it uses 100 kHz bandwidth to
conduct convolutional encoding and error control coding of Viterbi coding to data
delivered, in the hope of enhancing error correcting capability of transferred data. As the
high-band signal of the transmission cable weaken seriously, this pares three
different digital modulation methods and employs OFDM multi-carrier modulation
scheme to allocate the data to several sub-bands to improve band efficiency and
transmission speed.
As the cable has a rather narrow channel bandwidth, symbol disturbance will
frequently occur, when it es serious, even destroying the orthogonality of the sub-
carrier. This research studies signal channel estimation and symbol timing estimation.
Since synchronization is an essential step of the OFDM system, this thesis uses
maximum likelihood estimation method of cyclic prefix, so as to ensure accuracy and
avoiding inserti