OFDM水声通信关键技术研究
文献类型：学位论文
| 作者 | 黄建纯 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-05-26 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | OFDM MC-CDMA 峰均比抑制 信道估计 频率同步 |
| 学位专业 | 信号与信息处理 |
| 中文摘要 | 随着人类开发海洋步伐的加快，水声通信技术获得了飞速发展，其中的OFDM技术由于能将宽带信道的频率选择性衰落转换成各个子信道上的平坦衰落，可以简化接收机均衡器的设计，因此受到了研究人员的重视。 本文对OFDM的几个关键技术——峰均比抑制、信道估计和频率同步进行了理论分析和计算机仿真。由于水声信道中多普勒效应明显，因此频率同步问题是研究的重点。在对多普勒条件下OFDM信号性能进行分析的基础上，本文设计了一种OFDM水声通信方案，该方案将发射信号封装成特殊的帧结构，利用插入的定时信号和训练序列分两步对多普勒进行较为细致的补偿。为验证其性能，进行了相应的水池和海上试验，通过试验数据的分析表明该方案可行，即使在收发双方相对运动的情况下仍能对接收信号进行较好的频率同步。 考虑到水声通信常工作在低信噪比条件下，本文研究了将OFDM与扩频技术相结合的MC-CDMA技术，它能克服低信噪比条件下OFDM信号误码率偏高的问题。但传统的算法传输率很低，本文提出了一种提高传输率的改进方案，该方案将传输信息调制到扩频码的循环位移值上。由于扩频序列经过循环移位后相关性能不会发生变化，因此不影响系统的抗噪声特性，通过对空气声试验和海上试验数据的分析也验证了该方案在低信噪比条件下仍有良好的性能。 |
| 英文摘要 | Following the ocean exploration, UAC (Underwater Acoustic Communications) is developing rapidly. And OFDM (Orthogonal Frequency Division Multiplexing) is among the most attractive UAC techniques. By separating one frequency selective fading wideband channel into several flat fading narrowband sub-channels, OFDM can simplify the design of equalizer. Through theoretical analysis and computer simulations, this thesis studies several key techniques of OFDM, including PAPR (Peak to Average Power Ratio) reduction, channel estimation and frequency synchronization. Obvious Doppler effect in underwater acoustic channel makes frequency synchronization a key point in the study. A scheme for OFDM underwater communications is presented basing on the study of OFDM performance under Doppler effect. This scheme constructs signals into several frames, compensates Doppler precisely using time synchronization signals and training signals inserted in the frames. A set of pool experiments and sea experiments is conducted to testify performance of the scheme. The result of these experiments shows that the scheme can compensate Doppler effectively even when movement between transmitter and receiver presents. Because the receive signals of UAC often have low SNR, this thesis studies MC- CDMA (Multicarrier CDMA) too. By combining OFDM and spectrum spreading technique together, MC-CDMA is a solution to reduce the high bit error rate when OFDM signals are transmitted under low SNR. But the traditional MC-CDMA has a very low data rate. In this thesis, an improved scheme is presented to increase the data rate. It maps transmit information onto the cyclic shift value of spreading codes. Because the correlation property of spreading codes does not change after cyclic shift, good performance of traditional scheme is retained. The results of air experiments and sea experiments all show that the improved scheme has a good performance even under low SNR. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 86 |
| 源URL | [http://159.226.59.140/handle/311008/544]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 黄建纯. OFDM水声通信关键技术研究[D]. 声学研究所. 中国科学院声学研究所. 2009. |
入库方式： OAI收割
来源：声学研究所
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