In the paper, a novel method, which exploits both the Orthogonal Frequency Division Multiplexing (OFDM)-Code Division Multiple Access (CDMA) technique and the time reversal mirror technique, is investigated to realize...In the paper, a novel method, which exploits both the Orthogonal Frequency Division Multiplexing (OFDM)-Code Division Multiple Access (CDMA) technique and the time reversal mirror technique, is investigated to realize multi-user underwater acoustic communication. By taking advantages of these two techniques, the proposed method has the capability of effectively suppressing multi-path interference, reducing the error rate, enhancing the processing gain and improving user capacity. Simulations verify the correctness and effectiveness of the proposed method.展开更多
为了提高水声通信的性能,提出了一种联合运用 M 元扩频(MSS)通信和 Pattern时延差编码(PDS)水声通信体制,并采用单阵元被动式时间反转镜(PTRM)来实现声信道均衡的深海远程水声通信方案。该方案的 M 元扩频-Pattern 时延差编码通信技术...为了提高水声通信的性能,提出了一种联合运用 M 元扩频(MSS)通信和 Pattern时延差编码(PDS)水声通信体制,并采用单阵元被动式时间反转镜(PTRM)来实现声信道均衡的深海远程水声通信方案。该方案的 M 元扩频-Pattern 时延差编码通信技术既能胜任远程水声通信,又能提高通信速率;单阵元被动式时间反转镜信道均衡技术既可抑制多途扩展产生的码间干扰,又能提高信噪比。根据深海声道特性分析,该方案将通信固定节点置于声道轴以获取会聚增益,提高通信距离。计算机仿真结果证明,所提出的深海远程水声通信方案具有很好的鲁棒性和可行性。展开更多
Microwave-induced thermo-acoustic tomography (MITAT) is a promising technique with great potential in biomedical imaging. It has both the high contrast of the microwave imaging and the high resolution of the ultrasoun...Microwave-induced thermo-acoustic tomography (MITAT) is a promising technique with great potential in biomedical imaging. It has both the high contrast of the microwave imaging and the high resolution of the ultrasound imaging. In this paper, the proportional relationship between the absorbed microwave energy distribution and the induced ultrasound source distribution is derived. Further, the time reversal mirror (TRM) technique based on the pseudo-spectral time domain (PSTD) method is applied to MITAT system. The simulation results show that high contrast and resolution can be achieved by the TRM technique based on PSTD method even for the received signals with very low signal-to-noise ratio (SNR) and the model parameter with random fluctuation.展开更多
Pattern time delay shift coding(PDS) scheme is introduced and combined with spread spectrum tech-nique called SS-PDS for short which is power-saving and competent for long-range underwater acoustic networks.Single-ele...Pattern time delay shift coding(PDS) scheme is introduced and combined with spread spectrum tech-nique called SS-PDS for short which is power-saving and competent for long-range underwater acoustic networks.Single-element virtual time reversal mirror(VTRM) is presented in this paper and validated by the lake trial results.Employing single-element VTRM in multiuser communication system based on SS-PDS can separate different users' information simultaneously at master node as indicated in the simulation results.展开更多
将被动时间反转镜(PTRM)技术与双向判决反馈均衡器(DFE)相结合,设计并实现了高可靠性的单载波水声通信解码方案。接收端采用PTRM压缩信道多途结构,聚焦信号能量;利用双向DFE将传统DFE和反向DFE输出结果合并,进一步降低错误判决的概率,...将被动时间反转镜(PTRM)技术与双向判决反馈均衡器(DFE)相结合,设计并实现了高可靠性的单载波水声通信解码方案。接收端采用PTRM压缩信道多途结构,聚焦信号能量;利用双向DFE将传统DFE和反向DFE输出结果合并,进一步降低错误判决的概率,提高系统稳健性。在时不变浅海水声信道环境中,开展的水声通信试验数据处理结果表明:与传统DFE相比,双向DFE能够获得一定的处理增益,5 km、7 km和10 km通信距离上的均衡后输出信噪比分别提高了2.74 d B、2.36 d B和1.54 d B,有效改善了解码性能。展开更多
文摘In the paper, a novel method, which exploits both the Orthogonal Frequency Division Multiplexing (OFDM)-Code Division Multiple Access (CDMA) technique and the time reversal mirror technique, is investigated to realize multi-user underwater acoustic communication. By taking advantages of these two techniques, the proposed method has the capability of effectively suppressing multi-path interference, reducing the error rate, enhancing the processing gain and improving user capacity. Simulations verify the correctness and effectiveness of the proposed method.
文摘为了提高水声通信的性能,提出了一种联合运用 M 元扩频(MSS)通信和 Pattern时延差编码(PDS)水声通信体制,并采用单阵元被动式时间反转镜(PTRM)来实现声信道均衡的深海远程水声通信方案。该方案的 M 元扩频-Pattern 时延差编码通信技术既能胜任远程水声通信,又能提高通信速率;单阵元被动式时间反转镜信道均衡技术既可抑制多途扩展产生的码间干扰,又能提高信噪比。根据深海声道特性分析,该方案将通信固定节点置于声道轴以获取会聚增益,提高通信距离。计算机仿真结果证明,所提出的深海远程水声通信方案具有很好的鲁棒性和可行性。
基金Supported by the National Natural Science Foundation of China(Grant No.60771042)the National Hi-Tech Research and Development Program("863"Project)(Grant No.2007AA12Z159)+2 种基金111Project(Grant No.B07046)SiChuan Excellent Youth Foun-dation(Grant No.08ZQ026-039)Program for New Century Excellent Talents in University of China and Program for Changjiang Scholars
文摘Microwave-induced thermo-acoustic tomography (MITAT) is a promising technique with great potential in biomedical imaging. It has both the high contrast of the microwave imaging and the high resolution of the ultrasound imaging. In this paper, the proportional relationship between the absorbed microwave energy distribution and the induced ultrasound source distribution is derived. Further, the time reversal mirror (TRM) technique based on the pseudo-spectral time domain (PSTD) method is applied to MITAT system. The simulation results show that high contrast and resolution can be achieved by the TRM technique based on PSTD method even for the received signals with very low signal-to-noise ratio (SNR) and the model parameter with random fluctuation.
基金Supported by the National Natural Science Foundation of China (Grant No.60802060)Research Fund for the Doctoral Program of Higher Education (Grant No.200802171061)
文摘Pattern time delay shift coding(PDS) scheme is introduced and combined with spread spectrum tech-nique called SS-PDS for short which is power-saving and competent for long-range underwater acoustic networks.Single-element virtual time reversal mirror(VTRM) is presented in this paper and validated by the lake trial results.Employing single-element VTRM in multiuser communication system based on SS-PDS can separate different users' information simultaneously at master node as indicated in the simulation results.
文摘将被动时间反转镜(PTRM)技术与双向判决反馈均衡器(DFE)相结合,设计并实现了高可靠性的单载波水声通信解码方案。接收端采用PTRM压缩信道多途结构,聚焦信号能量;利用双向DFE将传统DFE和反向DFE输出结果合并,进一步降低错误判决的概率,提高系统稳健性。在时不变浅海水声信道环境中,开展的水声通信试验数据处理结果表明:与传统DFE相比,双向DFE能够获得一定的处理增益,5 km、7 km和10 km通信距离上的均衡后输出信噪比分别提高了2.74 d B、2.36 d B和1.54 d B,有效改善了解码性能。
