水下无线光自动对准系统的设计与实现

水下无线光通信(UOWC)具有保密性好、容量大、传输速度快等优点,可应用于水下信息传输、资源勘查等领域,通信链路的快速建立和持续稳定是水下无线光通信实际应用的基本条件。在平台扰动和海水信道杂质干扰的条件下,如何实现远距离的快速对准是水下无线光通信必须解决的问题。针对水下无线光通信过程中系统发射端和接收端之间的链路由于干扰问题引起底层平台不断移动而无法对准的问题,搭建了一个基于激光二极管(LD)的水下无线光自动对准系统,该系统具有自动对准控制的特点,即系统在底层平台移动的情况下,依然可以实现链路的对准。     

水下无线通信技术发展研究

水下无线通信是水下通信技术的重要分支,是进行水下监测、水下开发和开展水下军事斗争的关键支撑。为了争夺水下资源和增强水下作战能力,水下无线通信已成为世界大国竞相发展的重要通信技术之一。文章首先介绍了水下无线电磁波通信、水声通信等水下无线通信的发展现状,接着对水下光通信、引力波通信、中微子通信、水下量子通信等水下无线通信的发展进行了展望,最后分析了水下无线通信技术发展面临的问题。     

Performance Evaluation of Short Range Underwater Optical Wireless Communications for Different Ocean Water Types

This paper has presented our interesting in wireless underwater communications for different ocean water types. Recent interest in ocean exploration has brought about a desire for developing wireless communication techniques in this challenging environment. Due to its high attenuation in water, a radio frequency (RF) carrier is not the optimum choice. Acoustic techniques have made tremendous progress in establishing wireless underwater links, but they are ultimately limited in bandwidth. In traditional communication systems, constructing a link budget is often relatively straight forward. In the case of underwater optical systems the variations in the optical properties of ocean water lead to interesting problems when considering the feasibility and reliability of underwater optical links. The main focus of this paper is to construct an underwater link budget which includes the effects of scattering and absorption of realistic ocean water. As well as we have developed the underwater optical wireless communication systems to have shorter ranges, that can provide higher bandwidth (up to several hundred Mbit/s) communications by the assistant of exciting high brightness blue LED sources, and laser diodes suggest that high speed optical links can be viable for short range application. The received signal power, signal to noise ratio, bit error rate, transmitted signal bandwidth, and transmission bit rates are the major interesting parameters for different ocean water mediums as a criteria of the best signal transmission characteristics of short wireless optical communications over wide range of the affecting parameters.     

一种水下信息网络教学实验系统设计

本文结合陆上无线网络原理,提出了一种水下信息网络教学实验系统设计方案。该实验系统分为水下和陆上两部分,基于水声通信机的水下声学网络通过浮标网关节点实现了与陆上无线传感器网络信息的交互,进而构成立体式水下信息网络教学实验平台。该系统不仅能够进行相关学科的教学演示,同时也能够作为该方向的基础科研平台。     

基于光电倍增管的自动增益控制技术研究

为了压缩水下无线光通信系统中接收光信号的动态范围、提高有效通信距离,从自动增益控制技术的基础理论入手,利用光电倍增管增益可随工作电压改变的特性,设计出基于光电倍增管实现的自动增益控制电路,其数字控制部分以单片机为核心,并在空气中模拟水下实验。结果表明,该电路可以对接收光信号实现40dB的压缩,提高了水下无线光通信的有效范围。     

水下无线传感器网络MAC协议分析

在水下无线传感器网络中,MAC (Medium Access Control)协议为相互竞争的用户之间公平地分配信道资源.介绍了水声通信的特点以及在此环境下设计MAC协议所面临的主要问题,归纳水下无线传感器网络MAC协议的设计原则和分类方法.通过分析当前典型的各类MAC协议的主要机制,详细比较这些协议的特点、性能差异和...     

A new compact multichannel receiver for underwater wireless communication networks

In this letter it is shown that by taking advantage of the particle velocity, in addition to the pressure, multichannel reception can be accomplished in underwater acoustic wireless channels. Theoretical formulation and Monte Carlo simulations are provided for a vector sensor equalizer that measures the pressure and the velocity at a single point in space. These results demonstrate the usefulness of small-size vector sensors as multichannel equalizers for underwater acoustic wireless systems and sensor networks.     

潜水员水下近距离简易通信系统的设计

介绍了基于单片机的潜水员水下简易通信系统的设计与实现,给出了它的硬件原理图和软件程序框图。该系统采用短消息通信,并且通过语音播放收到的消息。硬件部分采用ATMEL公司的AT89S52作为主控芯片,实现了FSK调制解调,并控制ISD公司的ISD4002语音芯片进行话音的录放。系统利用水下电流场,完成了潜水员间的水下近距离简易通信。     

A Slotted-FAMA based MAC Protocol for Underwater Wireless Sensor Networks with Data Train

Underwater wireless sensor networks are significantly different from terrestrial wireless sensor networks in that sound is mainly used as the communication medium. The limited bandwidth, long propagation delay and high bit error rate pose great challenges in Media Access Control (MAC) protocol design for underwater wireless sensor networks. In this paper, we propose a Slotted-FAMA based MAC protocol for underwater wireless sensor networks with data train, called SFAMA-DT. It improves the channel utilization by forming a train of data packets of multiple transmission pairs during each round of simultaneously handshakes, which overcomes the multiple RTS attempts problem of Slotted-FAMA in high traffic environments and greatly reduces the relative proportion of time wasted due to the propagation delays of control packets. Our simulations show that the SFAMA-DT is able to achieve much higher throughput than the Slotted-FAMA protocol.     

Monte Carlo–based channel estimation and performance evaluation for UWOC links under geometric losses

Underwater wireless optical communication has been studied and proposed as a potential technology for various underwater applications including monitoring and surveillance using wireless sensor networks. In this context, we present a statistical model using an exhaustive Monte Carlo approach for an underwater wireless optical communication link between sensor nodes in a data mulling environment. This work provides insights into the science of photon transport underwater, its utilization in a communication system, evaluation, and optimization of underwater communication. We characterize the temporal channel behavior taking into account multiple scattering of photons involving the constraints of detector aperture diameter, field‐of‐view (FOV), and link distance for an aligned point‐to‐point link. We analyze the designed model in terms of total received power and bit error rate for clear ocean waters. Our simulation results show that the detector aperture and FOV has an impact towards a successful communication in the distance from 5 to 20 m. In addition, results show that the FOV is an affecting factor only in the presence of larger aperture sizes of the detector.     

大动态能量自适应蓝/绿激光探测方法

针对水下无线光通信链路中近距功率饱和与远距功率不足导致的光信号采集失效的难题,提出一种大动态能量自适应蓝/绿激光探测方法。该方法在水下无线光通信系统中加入由电控液晶光阀、可调增益光电倍增管及FPGA板卡组成的增益可控探测模块,该模块在链路功率和探测器增益两个维度对通信链路形成闭环调控,以保证光电倍增管始终工作在最优状态,从而实现水下远距离、高速、大动态范围无线光通信。     

水下无线光通信中的FDPIM性能研究

为了改善脉冲位置调制需要符号同步和数字脉冲间隔调制、双头脉冲间隔调制、多幅度脉冲间隔调制符号长度不固定所引起的接收发机结构复杂和调制器速率不固定等问题,提出将定长数字脉冲间隔调制应用于水下无线光通信系统。分析了带宽需求、传输容量,并与其它调制方式进行了比较;在给出水下无线光通信信道模型的基础上,推导了该信道中定长数字脉冲间隔调制方式的误包率表达式。结果表明,定长数字脉冲间隔调制适用于水下无线光通信系统。     

Energy Efficient Mobility Enhancement in LTE Pico–Macro HetNet Systems

Wireless Personal Communications - Unlike terrestrial environment, the underwater environment possess additional and complicated challenges for wireless communication. For the underwater wireless...     

一种改进的OFDM水下可见光无线通信系统

在水下直流偏置光无线通信正交频分复用(UOWC-DCO-OFDM)系统中,为了保证光信号在发射端具有较低峰均比(PAPR)并在水下可进行远距离低误比特率传输,采用了子载波预留、最小二乘算法(TR-LSA)与压扩变换相结合的方法,同时运用优化的神经网络对水下环境进行信道估计,并基于该方法在接收端设计信道均衡器,以应对水下...     

Fuzzy-based unequal clustering protocol for underwater wireless sensor networks

Underwater wireless sensor network (UWSN) is a network made up of underwater sensor nodes, anchor nodes, surface sink nodes or surface stations, and the offshore sink node. Energy consumption, limited bandwidth, propagation delay, high bit error rate, stability, scalability, and network lifetime are the key challenges related to underwater wireless sensor networks. Clustering is used to mitigate these issues. In this work, fuzzy-based unequal clustering protocol (FBUCP) is proposed that does cluster head selection using fuzzy logic as it can deal with the uncertainties of the harsh atmosphere in the water. Cluster heads are selected using linguistic input variables like distance to the surface sink node, residual energy, and node density and linguistic output variables like cluster head advertisement radius and rank of underwater sensor nodes. Unequal clustering is used to have an unequal size of the cluster which deals with the problem of excess energy usage of the underwater sensor nodes near the surface sink node, called the hot spot problem. Data gathered by the cluster heads are transmitted to the surface sink node using neighboring cluster heads in the direction of the surface sink node. Dijkstra's shortest path algorithm is used for multi-hop and inter-cluster routing. The FBUCP is compared with the LEACH-UWSN, CDBR, and FBCA protocols for underwater wireless sensor networks. A comparative analysis shows that in first node dies, the FBUCP is up to 80% better, has 64.86% more network lifetime, has 91% more number of packets transmitted to the surface sink node, and is up to 58.81% more energy efficient than LEACH-UWSN, CDBR, and FBCA.     

一种用于水声通信网的多址接入协议

由于传输介质的不同，使得水声通信具有一些有别于电磁波通信的特点。本文针对水声信号传播时延长带来的效率低的问题，为水下环境中的通信网提出了一种新型的冲突避免多址接入协议，该协议通过减少不必要RTS／CTS握手次数，降低了这种预约形式所造成的资源浪费，提高了网络效率。仿真结果显示，该协议在水声环境下，能获得较好的网络性能。     

水下无线光通信系统研究进展

水下无线光通信作为一种新兴的高速水下无线通信技术,在海洋生态环境监测、资源勘测以及军事作战等方面的作用不可小觑,并已成为全世界竞相争夺的关键性技术。对目前常用的3种水下无线通信方式进行比较,介绍了水下无线光通信的信道特性,并阐述水下无线光通信系统中光源、调制、信道编码以及探测等关键技术的研究进展。总结了水下无线光通信技术的发展趋势,为未来水下无线光通信系统的深入研究和实用化提供了参考。     

水下无线传感器网络中一种安全定位算法

提出一种基于阵列传输结构的无线传感器网络安全定位算法（USA）。该算法主要解决水下无线传感器网络（UWSN）面临的一些安全威胁问题。以提高无线传感器网络安全性,特别是位置信息的安全性为设计目标。利用节点协作形成的阵列作为天线阵列进行相互通信,在不增加额外硬件成本的同时,还获得阵列天线给无线传感器网络带来的优势,如减小多径效应、提高接收端的信噪比、增加系统容量等。USA算法基于这种阵列结构使网络得到很高安全特性,特别是,对Wormhole攻击具有非常好的抵御性能。仿真实验证明该算法的有效性。     

基于超声波的水下无线能量传输初探

近年来,无线能量传输已成为一个热点的应用研究方向,而围绕水下机器人,水下探测器等特殊目标的无线供电方式研究却鲜有报道。对基于超声波共振方式的水下无线能量传输的原理、可行性进行了初步的分析探讨,给出了实现的原理框图及实现方式。通过理论推导重点分析了传输效率和传输功率与频率、距离的关系。研究表明当选取超声波传输频率20 k Hz时,在距离40 m以内可达到10%以上的传输效率,具有一定的实际应用价值。     

水声网络中Aloha协议与MACA协议的比较分析

浅海水声信道的快衰落、长延时使水声网络媒介访问控制（MAC）层协议的性能受到了较大的负面影响。为了能更好地将无线传感器网络的MAC协议适用于水声网络,本文着重对Aloha协议和冲突避免多址接入（MACA）协议进行改进分析,借助通信网络仿真工具OPNET,比较两者在吞吐量、时延、能量损耗和分组丢失率4方面的性能结果。仿真结果表明：与Aloha协议相比,MACA协议能更好地提高性能,有利于在水声网络中使用。