基于频分多址的双信道水声通信网介质访问控制协议

在水下传感器网络中,有效解决隐藏终端与暴露终端问题,可以提高网络吞吐量和延长网络生存周期。文章提出了一种基于频分多址(Frequency Division Multiple Access, FDMA)方式的双信道载波侦听多路访问(Carrier Sense Multiple Access,CSMA)协议,将水声信道分成控制信道与数据信道,分别进行控制报文与数据报文的传递。仿真结果表明,此协议可以有效地解决由于隐藏终端与暴露终端引起的控制报文与数据报文的冲突,比单信道的CSMA协议性能有较大提升。实验结果表明,在双信道条件下,通信节点可以成功解码在时域上重叠的控制报文与数据报文,具有工程可实现性。     

水声通信网竞争式介质访问控制协议的研究

水声通信网介质访问控制(Media access control,MAC)协议决定了节点共享水声信道资源的方式,它直接影响到水声信道的利用率和网络的整体性能。本文简要介绍了Aloha、MACA-U和UW-CSMA/CA三种竞争式MAC协议的基本原理,并基于NS2仿真平台,在集中式单跳网络和分布式多跳网络两种拓扑结构中对Aloha、MACA-U和UW-CS/MACA三种竞争式MAC协议的吞吐量、平均端对端时延、冲突率和协议开销等性能进行对比,并分析数据包长度对三种协议性能的影响,为实用MAC协议的设计提供了有效的参考数据和策略。     

水声通信网络快速重构路由协议技术的研究

本文针对水声通信特点,在按需距离矢量(AODV)路由协议的基础上,提出了一种旨在缩短路由重构时间的按需距离矢量(RB-AODV)路由协议。该协议解决了水声通信网络中,由中间节点的移动而引起的路由失效问题。通过检测到移动节点的中间节点进行本地路由修复重构的过程,避免了由源节点重新启动路由发现过程,从而大大节省了信道带宽。仿真结果表明,该RB-AODV路由协议可以降低丢包率、增大网络吞吐量,缩短路由重构时间并提高信道利用率。     

联合空时编码的水声多用户节点协同并行传输多址接人协议设计

针对水声信道长传播时延特点导致水声通信网吞吐量低的问题,提出了一种多节点协同并行传输的多址接入协议。该协议由接收端发起预约,在距离认知的基础上对预约节点划分协同传输小区,从而构建多用户节点的多输入多输出集中式网络架构;采用空时码对数据包编码,并合理规划数据包的发送时刻,使同一小区的多个用户节点发送的数据包在设定时间偏差范围内同时到达接收端,而不同小区的数据包以包链形式到达,实现多用户节点的无干扰、高效并行传输。仿真实验结果表明,与已有的其它两种协议相比,设计的协议通过空时复用的方法大幅缩短了平均端到端时延,显著提升了归一化网络吞吐量。      

水声通信网络定向搜索AODV协议研究

水声通信网络是水声研究的一个热点问题。由于水下声网络带宽窄、传播延迟大、能量受限等特点,无线电网络中一些成熟的路由协议,如DSDV、AODV等的应用受到了很大的限制。本文结合按需距离矢量(AODV)路由协议和地理位置协议,提出了一种适用于水下网络的路由协议——定向搜索AODV(DSAODV)路由协议。DSAODV协议利用地理位置信息约束路由请求分组(RREQ)寻找路由的范围,降低了路由寻径的开销,减少了网络拥塞。仿真结果表明,DSAODV协议在吞吐量、协议开销等方面都优于AODV协议。     

一种基于分层的量子分组传输方案及性能分析

大规模量子通信网络中,采用量子分组传输技术能有效提升发送节点的吞吐量,提高网络中链路的利用率,增强通信的抗干扰性能.然而量子分组的快速传输与路由器性能息息相关.路由器性能瓶颈将严重影响网络的可扩展性和链路的传输效率.本文提出一种量子通信网络分层结构,并根据量子密集编码和量子隐形传态理论,给出一种基于分层的量子分组信息传输方案,实现端到端的量子信息传输.该方案先将量子分组按照目的地址进行聚类,再按聚类后的地址进行传输.仿真结果表明,基于分层的量子分组信息传输方案能够有效减少量子分组信息在量子通信网络中的传输时间,并且所减少的时间与量子路由器性能与发送的量子分组数量有关.因此,本文提出的量子分组信息传输方案适用于大规模量子通信网络的构建.     

基于量子远程传态的无线自组织量子通信网络路由协议

针对复杂结构的无线量子通信网络,提出了无线自组织量子通信网络概念并设计其路由协议．该路由协议为按需路由协议,路由度量基于相邻节点问的纠缠粒子对数目．需要发送携带信息的量子态的节点发起路由请求和建立过程,由目的节点根据路由度量选择路径．目的节点选择路径后,沿所选路径发送路由应答信息至源节点并通知路径中其他节点．信息传输过程中,若所选路径中相邻节点问无线信道或者量子信道中断,将重新发起一个路由发现过程．建立新路由．路径中节点收到路由应答信息后,利用纠缠交换和两端逼近方法,从路径两端向中间节点方向进行纠缠交换,建立量子信道后,通过量子远程传态传输携带信息的量子态,从而实现无线自组织量子通信网络中任意两节点问信息的传递．     

基于最短路径长度的空间网络路由

以通信网、电力网、交通网为代表的很多复杂网络以传输负载为基本功能.在这些网络中,网络的吞吐量是衡量网络传输性能的重要指标,如何提升网络的吞吐量是研究热点之一.不少研究人员提出了不同的路由算法,通过调节传输路径来提高网络吞吐量.但之前的研究很少考虑网络中节点的空间位置.本文针对空间网络提出了一种高效的路由策略,通过节点位置得到路径长度;采用该算法,负载从源节点沿着最短长度的路径传输到目标节点.为了检验算法的有效性,采用网络从自由流状态转变成拥塞状态的相变点Rc来衡量网络的吞吐量.在匀质和异质空间网络上的仿真表明,与传统的最少跳数路由策略相比,本文提出的基于最短路径长度的路由算法能有效提高空间网络的吞吐量.     

基于Cayley图上量子漫步的匿名通信方案

信息安全是信息化社会国家安全的基石与命脉,而匿名量子通信是保护信息安全的重要通信方式之一.利用量子漫步随机性有效解决身份信息泄露等敏感问题,本文提出一种基于Cayley图上量子漫步的匿名通信方案.首先,通信双方隐藏自身身份信息,发送方Alice通过逻辑或操作匿名选择接收方Bob.其次,可信第三方与通信双方利用BB84协议生成和分发安全密钥, Alice根据安全密钥对信息序列进行加密,获得盲化信息; Bob利用联合Bell态测量和安全密钥进行签名,可信第三方验证签名信息.再次,可信第三方依据傅里叶变换计算Bob量子漫步的位置概率分布函数,将概率最大值对应的位置信息转换为确认帧发送给Alice;Alice利用量子降维压缩算法减少传输信息比特数,并利用安全密钥完成信息加密后将信息传输至确认帧表示的位置, Bob利用量子漫步搜索位置节点获取传输信息,完成匿名量子通信.最后,对方案进行安全分析,并给出200个节点Cayley图的数值仿真结果,漫步10步时,第6个节点的概率最大为45.31%.根据仿真结果,本方案通信过程中Bob漫步10步时被窃听到具体位置的概率近似为6×10~(–7)%.     

水下声音网络中基于簇的按需时间共享MAC协议

水下声音网络中基于调制解调器的商用系统具有传输率低、前同步码长两大特征,严重降低了媒介访问控制协议(MAC)的性能;针对上述问题,分析了调制解调器特征对当前水下声音网络两种主流MAC协议(随机访问MAC,握手MAC)的影响,提出了一种基于簇的按需时间共享MAC协议(COD-TS);该协议采用簇技术实现了局部调度和按需响应特性;文章首先给出单跳网络的COD-TS协议的含义,提出相应的吞吐量模型;然后,实现方案多跳场景的扩展;仿真结果表明,相比于已有的Slotted ALOHA和RTS/CTS等协议而言,本文方案的吞吐量更优。     

MAC protocol with delay-aware adaptive round time for split light-trail

Light-trail (LT) has been considered as an attractive solution for optical networks to support emerging services such as video-on-demand, pseudo-wires, and data-centers. The media access control (MAC) protocol is essential for LT networks because LT is a shared-medium. Recently, in order to enhance the throughput, a regular LT can be split into several sub-LTs at the split nodes where traffic undergoes optical-electronic-optical conversation. To deal with the split LT, a novel MAC protocol named Delay-aware adaptive round time for split LT (DAARTS) is developed on the basis of DAART MAC protocol and the schemes of splitting LT. To estimate the performance of the developed MAC protocol, ART, DAART and DAARTS protocols are simulated and compared in the scenarios of three different traffic patterns. Simulation results show that, for traffic 1 and traffic 2, DAARTS has stable throughput performance and can obtain almost 40.83% and 106.64% throughput improvement compared with DAART, respectively. In other words, DAARTS can further enhance the throughput of LT networks.     

Underwater acoustic localization by principal components analyses based probabilistic approach

In this paper, the underwater localization is given from wireless acoustic communication signals by probabilistic pattern recognition in eigenspace of PCA (principal components analyses). It should be emphasized that our underwater localization is from existing wireless acoustic communication signals, but not from additional localization systems. Our underwater localization scheme is based on fingerprinting and contains two stages, i.e., the off-line (i.e., training) and on-line (i.e., predicting) stages. In general, the received acoustic signals fluctuate seriously in underwater environments. To reduce the complexity and noise effects, all received signals are projected onto the eigenspace of PCA. Each projected feature is assumed to have Gaussian probabilistic distributions. Therefore, the location information can be easily obtained by probabilistic pattern recognition of projected features in PCA space. Note that our underwater localization scheme is not affected by reflected signals. To illustrate such a benefit, experiments were conducted in a bounded water pool where reflected signals exist near the walls. Experimental results show that the proposed underwater localization scheme is efficient and accurate. The proposed localization scheme is useful for underwater acoustic communication networks, and then in underwater technologies.     

Pattern时延差编码四信道水声通信技术研究

本文所研究的是基于Pattern时延差编码（PDS）体制下的水声通信技术.PDS水声编码体制利用Pattern码片出现在码元窗的时延差值进行时延编码,通过码元分割,有效的降低了水声信道的多途干扰;通过频率分割划分四个通信信道,增加通信速率至1000bit/s.在接收端利用带通滤波器来实现通信信道分割,每个信道再应用拷贝相关器实现码元分割并估计出时延差值,完成译码.仿真实验表明,该系统适合于大量不同水声信道高可靠性工作,为水声通信网络化打下坚实基础.     

高速空间激光通信系统在空天信息网中的应用

 针对高速空间激光通信系统应用时面临的主要问题：节点高速运动的跟踪瞄准和与组网载荷协同工作,提出将高速空间激光通信系统作为节点主要通信载荷的双通信载荷结构,并设计了高速空间激光通信系统与组网载荷协同工作机制和协议模型,依据协议模型进行了原理样机开发与试验。试验结果表明,提出的协同工作机制与协议模型能很好地适用于高速空间激光系统,支持超高速率数据传输,最高MAC层协议数据速率可达1.772 Gb/s,平均处理时延20 μs。     

Design and performance evaluation of successive interference cancellation based Slotted Aloha MAC protocol

As a result of densification, the performance of the wireless networks has become highly interference-limited and energy inefficient. To overcome this problem, interference mitigation techniques such as Successive Interference Cancellation (SIC) can be used to decode multiple packets simultaneously at the receiver. In this context, we analyze a SIC-based Slotted Aloha (SIC-SA) Medium Access Control (MAC) protocol for wireless networks. We derive expressions for packets decoding probability and optimal transmission probability of the nodes of the SIC-SA MAC protocol. Our derivation is based on the order statistics of Independent and Identical/non-Identical exponentially distributed received-signal-powers from the nodes under the Rayleigh channel condition. Throughput, delay, and energy efficiency of the SIC-SA MAC protocol have been derived and validated against simulation. The effect of path loss exponent, SINR threshold, and the number of nodes on the performance of SIC-SA have been studied. The performance of SIC-SA in a network of nodes distributed randomly according to the Poisson Point Process has been analyzed. Extension of our analysis to Power Domain Non-Orthogonal Multiple Access (NOMA) has been demonstrated. We also analyzed the impact of imperfect estimation of channel state information and imperfect SIC at the receiver. Results show an improvement in performance metrics of SIC-SA over the traditional Slotted Aloha.     

基于水声传感器网络的多路径协同多跳通信研究

针对水声网络高误码、大时延的特点,借鉴提出了一种多路径协同多跳通信协议,该协议通过多路径、多节点的协同多跳中继通信以及冗余判决,来完成网络中端对端的远程数据传输。通过数值仿真试验分析表明:与普通的点对点直接通信和单路径多跳中继通信方式相比,此协议具有低误码、高能效的特点(距离与能量相同时,误码率低一至两数量级;限定误码率时,每比特能耗降低一个数量级),能够减少数据重发几率,提高网络的通信效率和工作寿命,特别适于水声传感器网络应用。     

Fairness and throughput performance of infrastructure IEEE 802.11 networks with hidden-nodes

The fairness behavior and throughput performance of IEEE 802.11 distributed coordination function and request-to-send/clear-to-send channel access scheme in the presence of hidden nodes are investigated. A mathematical model which accurately predicts a user’s throughput performance and packet collision probability in non-saturated traffic and asymmetric hidden node environments is developed. The model allows us to see many interesting results in networks with hidden nodes. In an asymmetric hidden node network environment, the network fairness performance depends on the traffic load. In low traffic conditions, users get their fair share of the resources. However, in moderate-to-high traffic conditions, users that experience less number of hidden nodes dominate the network, causing badly located stations in a network to starve. In addition, the performance of request-to-send/clear-to-send channel access scheme, which is developed as a solution to hidden node problem, in networks with hidden nodes, is also estimated. It is shown that request-to-send/clear-to-send contention resolution scheme greatly improves the network fairness performance in hidden node scenarios. The developed model enables us to more accurately estimate the performance of practical wireless local area networks, where hidden node occurrence is common. Theoretical analysis presented in the paper is validated with simulation results.