Energy-Efficient Routing Schemes for Underwater Acoustic Networks

Interest in underwater acoustic networks has grown rapidly with the desire to monitor the large portion of the world covered by oceans. Fundamental differences between underwater acoustic propagation and terrestrial radio propagation may call for new criteria for the design of networking protocols. In this paper, we focus on some of these fundamental differences, including attenuation and noise, propagation delays, and the dependence of usable bandwidth and transmit power on distance (which has not been extensively considered before in protocol design studies). Furthermore, the relationship between the energy consumptions of acoustic modems in various modes (i.e., transmit, receive, and idle) is different than that of their terrestrial radio counterparts, which also impacts the design of energyefficient protocols. The main contribution of this work is an in-depth analysis of the impacts of these unique relationships. We present insights that are useful in guiding both protocol design and network deployment. We design a class of energyefficient routing protocols for underwater sensor networks based on the insights gained in our analysis. These protocols are tested in a number of relevant network scenarios, and shown to significantly outperform other commonly used routing strategies and to provide near optimal total path energy consumption. Finally, we implement in ns2 a detailed model of the underwater acoustic channel, and study the performance of routing choices when used with a simple MAC protocol and a realistic PHY model, with special regard to such issues as interference and medium access.     

OFDM水声通信中最大多普勒频偏估计算法研究

在水声通信中,发射与接收端相对运动引起的多普勒频移会严重恶化OFDM系统传输效果.因此多普勒频移估计是水声通信的关键技术之一.本文采用的最大Doppler频移估计算法,是利用信道功率谱的分布对接收的导频信号进行频域差分检测来进行估计.这种方法复杂度低,精度较高,无需获得正确的信道时域冲击响应信息,也无需再对信号进行自相关运算,而且特别适用于低信噪比的水声通信系统.     

水声通信网络中的MACA-C介质访问控制协议

介质访问控制协议（Medium Access Control , MAC）是水声通信网络中的一种关键技术。与陆地无线通信系统使用无线电波有所不同,水声通信网络依靠水声进行通信。水声通信网络中的MAC协议设计面临许多挑战面,如:传播延迟大、带宽窄、电池不易更换或充电、节点发射功率受限等。因此,陆地无线通信系统的各MAC协议不能直接应用到水声通信网络。本文提出了一种适用于水声通信网络的MACA（MACA-C）协议,该协议主要将传输数据包和控制包结合使用,在每轮握手的过程中,该协议通过发送列的首数据包和RTS控制包来改善信道利用率。仿真结果也表明MACA-C能够达到较高的和稳定的吞吐量性能,同时在保持低碰撞率的前提下增加信道利用率。      

Low-Power Based Coherent Acoustic Modem for Emerging Underwater Acoustic Sensor Networks

Smart, small, inexpensive sensor nodes are used to construct underwater acoustic sensor networks. In addition, with the recent increase in the importance of underwater applications, the need for underwater communication has become more important. Hence, an acoustic modem capable of effective underwater communications has become more necessary for the sensor nodes to obtain underwater data. To develop an acoustic modem for effective underwater communications, some limitations must be overcome, such as the very short transmission range of radio waves, limited power supply, and high cost of commercial acoustic modems. Recently, low-power, low-cost acoustic modems have been developed. However, the data rates of these modems are so slow that sensor nodes cannot perform energy-efficient protocols. The objective of this work is to develop an acoustic modem capable of supporting high data rates. We introduce a coherent acoustic modem that uses waterproof ultrasonic sensors to process acoustic waves. The proposed modem is based on a low-power, low-cost, short-range concept, and it also supports a high data rate for energy-efficient MAC and routing protocols. Underwater experiments are conducted to evaluate the performance improvements of our modem. Experimental results show that our modem has the best performance among all recently developed low-power modems and that it is preferable to develop a coherent modem able to perform effective underwater communications.     

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。     

水声多径信道多普勒因子精确估计方法

由水下平台运动导致的多普勒效应是影响高数据率水声通信性能的主要因素,现有多普勒估计方法在复杂水声多径信道条件下估计精度急剧下降。针对此问题,提出了一种可自动匹配水声多径信道的精确多普勒频移估计方法。仿真结果表明：该方法可显著提高水声多径信道的多普勒频移估计精度,信道适应性强,在信噪比大于-5 dB时,估计精度始终保持在10^-4左右,满足高数据率水声通信对多普勒因子估计精度的要求。     

一种多速率水声传感器网络协商机制

在水下声通信传感器网络中,一个较短的链路可以比一个较长的链路提供更大的带宽。多速率水声传感器网络模型可以在不同长度的链路间动态选择传输速率,提高了带宽的利用率。针对多速率水声传感器网络的速率协商问题,提出了一种基于握手的多速率协商机制。这种协商机制适用于链路长度未知的多速率水声传感网,可以在保证网络连通率的前提下降低端到端延迟和单位比特的能量消耗。仿真验证结果表明,该协商机制可以有效提高水下声通信传感器网络的性能。     

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。     

Reinforcement Learning-Based Routing in Underwater Acoustic Sensor Networks

Wireless Personal Communications - Underwater acoustic sensor networks (UASNs) play an essential role in exploring the marine world applications in rivers, ponds, and oceans. In recent years,...     

Location-Free Void Avoidance Routing Protocol for Underwater Acoustic Sensor Networks

Wireless Personal Communications - The field of Underwater Acoustic Sensor Networks (UASNs) is one of the emerging areas of communication due to the number of marine applications. However, UASNs...     

一种应用于超宽带系统的宽带LNA的设计

结合切比雪夫滤波器,可以实现宽带输入匹配的特性和片上集成窄带低噪声放大器(LNA)的噪声优化方法。提出一套完整的基于CMOS工艺的宽带LNA的设计流程,并设计了一个应用于超宽带(UWB)系统的3~5 GHz宽带LNA电路。模拟结果验证了设计流程的正确性。该电路采用SMIC 0.18μm CMOS工艺进行模拟仿真。结果表明,该LNA带宽为3~5 GHz,功率增益为5.6 dB,带内增益波动1.2dB,带内噪声系数为3.3~4.3 dB,IIP3为-0.5 dBm;在1.8V电源电压下,主体电路电流消耗只有9 mA,跟随器电流消耗2 mA,可以驱动1.2 pF容性负载。     

Accurate Localization Under Correlated Errors for Underwater Acoustic Sensor Networks

Localization is an indispensable part for most underwater wireless sensor networks (UWSNs). In these networks, acoustic ranging signals are typically used. Because of the depth dependent sound speed, acoustic ray bends in water. This presents a unique problem making conventional localization algorithms assuming straight line distances between target and anchor nodes inaccurate. In this paper, authors present a Maximum Likelihood estimation scheme for accurate location estimation in UWSNs where there is correlation of range measurement errors. The method takes into account ray bending by making use of ray tracing, with sound speed profile as input. The performance of the scheme was studied by means of Monte-Carlo simulation and the results are reported. The Cramer-Rao lower bound of the scheme is also derived and reported.     

RIPT: A Receiver-Initiated Reservation-Based Protocol for Underwater Acoustic Networks

Although there are many MAC protocols that have been proposed for terrestrial wireless networks with a wide variety of aspects, these protocols cannot be applied directly in underwater acoustic networks due to the channel's uniqueness of having low data rate and long propagation delay. In order to achieve a high throughput, both characteristics must be taken into account in the MAC design. We propose a random access MAC protocol for multi-hop underwater acoustic networks based on receiver reservation, which we shall call the "Receiverinitiated Packet Train" (RIPT) protocol. It is a handshakingbased protocol that addresses the channel?s long propagation delay characteristic by utilizing receiver-initiated reservations, as well as by coordinating packets from multiple neighboring nodes to arrive in a packet train manner at the receiver. Our simulation results have confirmed that the RIPT protocol can achieve our goal of having high and stable throughput performance while maintaining low collision rate.     

Ultra Low Power CORDIC Processor for Wireless Communication Algorithms

We designed and implemented an ultra low power CORDIC processor which targets the implementation of advanced wireless communications algorithms based on Givens rotations and Householder reflections. We propose a modified CORDIC algorithm and architecture, and we elaborate on the low power architectural and algorithmic techniques for minimizing its power consumption. Our CORDIC implementation consumes, in rotate mode, on average 50 W @ 10 MHz under 1 V supply voltage in a .25 m technology.     

水声通信网的研究进展及其应用

随着现代"网络中心战"理论的完善,现代立体化信息战争已从传统的空天地战场延伸至海面以下战场。水声通信技术是构建水下通信网络的有效手段,是构建立体化战争、立体化作战平台的必要技术。首先分析了水下通信与水声网络的特点和发展现状。其次,结合美国海军在水声通信网络的实验研究成果,以及国内在该领域内取得的研究进展情况,展望了水声通信网络在现代海军建设中的应用前景。     

水下声传感器网络节点自定位研究

以无线传感器网络（WSN）水下应用为背景,针对水下环境的特殊性,提出了一种基于聚类的分布式无锚点网络节点自定位算法：采用分布式坐标计算,有利于网络节点能量的合理使用;同时,不需位置已知的锚节点,方便了水下环境的应用。仿真论证了影响算法精度的因素,并对比了LAR和MET两种坐标确定方法。对水下WSN应用研究具有重要的参考价值。     

水声网络及其军事应用研究

介绍了水声网络国内外发展动态,分析了其特点和关键技术,最后通过美海军目前正在实施的水下网络项目详细介绍了水声网络技术在军事领域的应用.     

A Distributed Energy-Aware Routing Protocol for Underwater Wireless Sensor Networks

The design of routing protocols for Underwater Wireless Sensor Networks (UWSNs) poses many challenges due to the intrinsic properties of underwater environments. In this paper we present DUCS (Distributed Underwater Clustering Scheme), a new GPS-free routing protocol that does not use flooding techniques, minimizes the proactive routing message exchange and uses data aggregation to eliminate redundant information. Besides, DUCS assumes random node mobility and compensates the high propagation delays of the underwater medium using a continually adjusted timing advance combined with guard time values to minimize data loss. The theoretical and simulation studies carried out demonstrate its effectiveness.