【作者】 邓敏；

【导师】 郭银景； 王正杰；

【作者基本信息】 山东科技大学 ， 信号与信息处理， 2009， 硕士

【摘要】 透地通信系统是彻底解决抢险、救灾的唯一有效途径,但是实现起来有一定难度,其中主要是由大地信道的复杂特性所导致的,不同介质层的吸收、反射、透射、折射情况复杂,限制了大地信道在通信系统中的应用。本文在此背景下研究透地通信系统。本文针对透地通信的困难,根据OFDM技术的优点,提出一种较好的解决透地通信问题的新方案。本文给出了基于OFDM的声波透地通信系统的设计方案,充分利用地层这一非空间资源实现声波透地通信,其最大特点是以性能优良的OFDM已调波作为媒体,将OFDM调制技术应用于透地救灾通信中,提高透地通信系统中声波的穿透能力。本文研究了声波透地通信系统中的OFDM编码方案及子载波间交织算法,采用Turbo码编码方式及基于IDS和最小距离的交织算法来纠错,提高系统的抗干扰能力。本文重点探讨了声波透地通信系统中信道探测方案和最佳接收方案的设计。在分析和总结大地信道特性的基础上,对大地信道的建模作了一定程度的分析和讨论,选择了Chirp和CHEC联合探测的方法找到最佳频段,进行子信道划分后,再用误码计数探测信道性能。对于最佳接收问题,把时间分集的思想融入到Rake接收机中,大地信道中出现的时延扩展看作是被传信号的再次发送,按照最大比合并准则对多径信号进行加权合并,使之复合成加强的信号。最后对透地通信系统进行了仿真。基于OFDM的声波透地通信还有很长的一段路要走,还要进行更深入的研究。随着技术的发展,当声波透地通信技术成熟后,声波透地通信的应用范围会越来越广。更多还原

【Abstract】 Through-the-Earth communication system is recognized as the only effective way to solve the problems of rescue and relief work. However, it seems that there were certain difficulties to put it into practice, because the characteristics of the earth channel are very complex. Further application of earth channel in the communication systems is restricted by complex absorption, reflection, transmission and refraction circumstances of different stratigraphic layers. Through-the-Earth communication system is researched in this paper in this background.A new proposal solving Through-the-Earth communication system problems is put forward in this paper on basis of analyzing and summarizing the transmission characteristics of the earth channel. A design scheme of sound waves Through-the-Earth communication system based on OFDM is proposed. The communication through the earth is realized in this system by taking advantage of the sound wave transmission in the layers, and making full use of the aspatial resources, that is, the stratum. The biggest characteristic of the system is that it can use the OFDM modulated waves as the media, and apply the OFDM modulation technology to the disaster relief communications. So the penetrability of the waves in Through-the-Earth communication system is raised.OFDM coding strategy and interweave algorithm among OFDM subcarriers are researched in this paper. Turbo coding and interweave algorithm based on IDS and minimum distance are used to correct errors in sound waves Through-the-Earth communication system, the use of them raises the disturbance resistilility.The design of channel detection strategy and optimum reception strategy in sound waves Through-the-Earth communication system is mainly discussed in this paper. The model of the earth channel is analyzed, and after that, Chirp and CHEC detection are selected to be used as the way of united detection to find the best frequency band on basis of analyzing and summarizing the characteristics of the earth channel. After dividing the sub-channels, counting error detection is used to probe the channel performance. To the optimum reception, the idea of time diversity is integrated into the Rake receiver, delay spread in the earth channel can be regarded as retransmission of the signals. These multipath signals are combined according to the maximum ratio combining law, and after that, they will become the strongest signals. In the end, sound waves Through-the-Earth communication system is simulated. The simulation shows the effictiveness of the proposed approach.There is still a long way to go for sound waves Through-the-Earth communication system based on OFDM, which needs more intensive research. With the development of science and technology, the applied range of sound wave Through-the-Earth communication system will become wider and wider, after Through-the-Earth communication system technology getting matured.更多还原