共查询到19条相似文献,搜索用时 209 毫秒
1.
2.
3.
水声信道高速率数据传输技术 总被引:2,自引:0,他引:2
本文介绍近年来水声信道高速率数所传输技术的一些研究进展,并结合本所研究的水声数据遥测,数字语音通讯和视频图像传输实验样机,讨论了具有抗多途干扰的声传输系统在调制信号设计及信号处理上所采用的关键技术。 相似文献
4.
水声通信及组网的现状和展望 总被引:1,自引:0,他引:1
水声通信是海洋中无线信息传输的主要技术手段。水声通信技术在海洋环境监测、水下航行器/载人潜水器作业等方面有着广泛应用。同时,水声信道传输状态多变、海洋作业环境恶劣,对通信算法和设备可靠性有较高要求,水声通信及组网成为目前的研究热点。文中面向海洋环境监测领域,从水声通信物理层技术、网络技术及组网应用等方面进行介绍,并对未来技术趋势进行展望。 相似文献
5.
浅海水声信道的随机时–空–频特性给数据的可靠传输带来了重大挑战,低复杂度和理论上证明能到达香农限的极化码(Polar code)可以增强水声通信系统的鲁棒性。水下传输的图像、语音、文本、海洋监测数据和遥控指令具有不等重要性的特点,宽码率 Polar 码能够适应不同水声信道和不等重要性的信息传输。 目前 Polar 码在水声通信中的实验研究多为仿真分析,设计了宽码率 Polar 码在厦门港海域海试验证,在不同信噪比的实录环境噪声下进行分析。海试结果表明:在良好的信道条件下,宽码率 Polar 码的性能优异,0.25 码率的 BPSK 和 QPSK 在实录环境噪声信噪比为–1 和 4 时实现零误码,其低复杂度信道编译码机制和宽码率与水声信道相匹配,可有效提高水声数据传输的可靠性和有效性,为基于 Polar 码的稳健可靠水声通信系统提供海试实验验证。 相似文献
6.
7.
《中国海洋大学学报(自然科学版)》2017,(3)
针对压缩效率和重建质量无法兼顾的问题,提出一种基于WBCT变换(Wavelet-based contourlet transform)的水下图像高效压缩算法。首先根据水下图像和人类视觉系统的特点,在WBCT变换域提出了一种改进的人眼最小可觉察失真(JND)模型,以自适应去除水下图像中的视觉冗余。然后,对重要的低频系数采用定长量化和无损压缩;而对高频系数,采用基于WBCT树结构的变精度定长量化和位置差降编码策略进行编码。实验结果表明,提出的算法不仅具有较高的压缩效率,而且能获得视觉上较为满意的解码效果,适用于水下图像在甚低比特率下的压缩传输。 相似文献
8.
9.
水声通信中的鲁棒图像编码研究 总被引:2,自引:1,他引:2
由于受各种因素的影响,水下声信道是一种传输差错率较高的信道。标准化的图像编码系统(例如JPEC;H.263,MPEG等)使用了相似的压缩技术,它们往往存在严重的错误扩散,甚至单个错误比特就可能破坏整幅图像,所以一般不适合作为水下声信道图像传输的编码方案。文章针对常用的图像编码的缺点,利用定长编码技术,提出了一种高鲁棒性的图像压缩方案。实验表明在压缩率1.25比特/象素时,压缩后的图像仍然保持了较好的质量,并且能够较好地抵抗信道误码,提高了水下声信道图像传输的质量。 相似文献
10.
水下视频图像压缩一直是有限带宽水声信道实时传输海量视频数据的关键技术之一。本文首先介绍了目前水下机器人和水下视频图像压缩研究存在的主要问题,并综合分析了目前几种高效视频压缩方法的特点并探讨了进一步研究的方向。此外,根据水下视频的成像特点,提出了高效的全局与局部运动混合补偿方案和基于小波变换的预处理方法。初步实验结果表明:本文提出的预处理方法可以有效去除视频图像中存在的大量视觉冗余和空间冗余,提出的混合运动补偿方案可以获得很高的压缩编码效率;但必须进一步研究快速、有效的全局运动估计方法。 相似文献
11.
12.
The underwater acoustic image transmission system based on the high-speed DSP device TMS320C549 has been studied.We use Goertzel algorithm for source decoding and MFSK for modulation.Turbo code is used for channel coding and decoding.The purpose is to implement underwater video image data transmission. 相似文献
13.
In this paper, we investigate the performance of adaptive modulation (AM) orthogonal frequency division multiplexing (OFDM) system in underwater acoustic (UWA) communications. The aim is to solve the problem of large feedback overhead for channel state information (CSI) in every subcarrier. A novel CSI feedback scheme is proposed based on the theory of compressed sensing (CS). We propose a feedback from the receiver that only feedback the sparse channel parameters. Additionally, prediction of the channel state is proposed every several symbols to realize the AM in practice. We describe a linear channel prediction algorithm which is used in adaptive transmission. This system has been tested in the real underwater acoustic channel. The linear channel prediction makes the AM transmission techniques more feasible for acoustic channel communications. The simulation and experiment show that significant improvements can be obtained both in bit error rate (BER) and throughput in the AM scheme compared with the fixed Quadrature Phase Shift Keying (QPSK) modulation scheme. Moreover, the performance with standard CS outperforms the Discrete Cosine Transform (DCT) method. 相似文献
14.
15.
The reliable acoustic transmission of images that have been processed by a video bandwidth reduction technique such as Micro-Adaptive Picture Sequencing (MAPS) necessitates a robust coding scheme. This is due to the fact that errors effect compressed data more seriously than uncompressed data. For this reason image quality is a function of three system variables: image compression, channel noise, and error checking. A real-time simulation has been developed to determine the relationship between the three system variables. The simulator uses two 68000 microcomputers connected by a serial link; one does image compression and noise modeling while the other performs error checking and image reconstruction. The noise model uses 17 characteristics and operating parameters of the acoustic channel to corrupt the image data with single bit random errors. At the receiver the error checking can correct up to 90 percent of the most serious single bit errors. 相似文献
16.
矢量传感器是一种新型水声传感器。介绍了应用矢量传感器确定目标方位的理论和方法,给出了仿真和实验研究结果,讨论了矢量传感器具体体积小、输出信号多、抗各向同性干扰等特性。最后定性地分析了目标方位的方位估值误差。 相似文献
17.
针对 UUV 任务结束或能源不足时自主回收的需求,深入研究了 UUV 中远程水声定位与遥测遥控导引技术,完成了水声定位与遥测遥控导引系统方案设计,重点研究了 MFSK、OFDM、扩频等水声遥测遥控调制方式。 通过分析和对比,设计了一种正交混合扩频调制方式,并采用相干二维搜索技术,提高扩频技术多普勒补偿能力。 开展了湖上静态与动态跑船试验,试验数据结果表明:水声水平定位精度优于 0. 5%,水声遥测遥控系统解算误码率达到了 10-3 数量级,可有效引导 UUV 回收作业。 相似文献
18.
19.
The purpose of the current study is to introduce a set of mobile underwater positioning systems (MUPS) that will enable non-offshore vessels to execute underwater missions. Besides mobility, the system would also possess the advantage of having to use fewer acoustic instruments than conventional acoustic positioning systems. The method adopted by the system will involve the use of expendable and multi-functional bathythermographs (XBT) to measure the underwater acoustic speed and the depth of water at the same time. Then it must utilize the geometric relations formed by measuring the position of underwater targets at set intervals during navigation. In addition, since sound does not travel in a straight line when underwater, the iteration and convergence method must be used to perform corrections on the transmission speed and positional errors to obtain an accurate coordinate of the underwater target. After simulation testing, the positioning system established by the current study has proven to be fast in converging the error values along with high positioning accuracy of the system. The results of the study indicate that the MUPS built by the research institute can be utilized on a vessel, and will be very helpful in assisting the management of urgent underwater positioning missions. 相似文献