| Budget Amount *help |
¥14,400,000 (Direct Cost: ¥14,400,000)
Fiscal Year 2004: ¥4,000,000 (Direct Cost: ¥4,000,000)
Fiscal Year 2003: ¥5,200,000 (Direct Cost: ¥5,200,000)
Fiscal Year 2002: ¥5,200,000 (Direct Cost: ¥5,200,000)
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| Research Abstract |
Optical fiber networks are rapidly spreading, but the construction of the end parts has been a bottleneck. The horizontal drilling technique gathers attention because of its low-cost and speed. In using this technique, we need to locate and control the drilling head. However, artificial noise has prevented the commercial use of this technique in urban areas. We propose a communication scheme which has a high efficiency in low bit rate by making use of characteristics of the artificial noise.
Firstly, we found that the artificial noise often has discrete line spectra, and its distribution changes with places and times. In this paper, we propose a one-way communication scheme which uses the OFDM and selectively uses low-noise channels. Here we define the ratio of power which gives the same bit-error-rate to the simple OFDM and proposed schemes as gain. In this scheme, we must communicate all data in one-way from undergrond. We thus need to send the channel selection information at the sam
… More
e time.
We obtain a high gain by selecting low noise channels compared a scheme without channel selection. We obtain a gain of 3-8dB by using amplitude modulation.
Secondly, we propose a scheme with phase modulation. In this scheme, we deal with two kinds of information data sets. One is the channel selection information, and the other is the error correction information. These information have different error rates with each other. Then we apply the UQPSK(Unbalanced QPSK), in which the symbols representing these two kinds of data are located asymmetrically, and obtained the maximum gain of 11.5dB. Next, we optimized the parameters of UQPSK, and showed that we can obtain the highest gain with this scheme.
Finally, we applied a synchronization scheme which makes use of correlation of signals after channel selection, and showed that we can achieve an accurate synchronization. Moreover, we confirmed the stability of the proposed UQPSK scheme against the types of noise by simulations using pseudo-artificial noise. Less
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