Performance of Physical-Layer Network Coding in Asymmetric Two-Way Relay Channels

In this paper, we study the performance of physical-layer network coding in asymmetric two-way relay channels using four different cases having different poor channels:phase asymmetry, downlink asymmetry, uplink asymmetry and node asymmetry. The decision and mapping rule for symmetric and asymmetric cases are studied. The performance in terms of bit error rate for each case will be studied and analysed by computer simulation. Analytical and simulation results show that uplink asymmetry is the worst case;intra-phase asymmetry and unreliable uplink channels will more severely affect the performance degradation, which is caused by channel asymmetry.

MSMSE-based optimal beamforming design and simplification on AF MIMO two-way relay channels

An optimal cooperative beamforming for the amplify-and-forward (AF) MIMO two-way relay channels was designed. Supposing the channel state information (CSI) was perfectly known by the receiver and transmitter as well as the relay, optimal beamforming vectors (matrices) of all nodes were jointly designed based on the criterion of minimizing the sum mean square errors (MSMSE). The analysis result shows that the performance effect of transmitting and receiving beamforming pairs is to maximize the receive signal-to-noise ratio (SNR) at two communication nodes, and the rank of the optimal relay beamforming matrix is no larger than two when there is only one data stream at each source node. A simplified algorithm was put forward to accomplish the design based on the analysis conclusions. Simulation results provide that the system performance, which is characterized in terms of bit error rates (BER), is significantly improved by cooperative beamforming, and the performance of the simplified method is not only very close to the optimal one but also with faster iteration speed and much lower computational complexity.

Energy efficiency enhancement of two-way amplifier forward relaying with channel estimation error

In order to save energy consumption of two-way amplifier forward(AF) relaying with channel estimation error, an energy efficiency enhancement scheme is proposed in this work. Firstly, through the analysis of two-way AF relaying mode with channel estimation error, the resultant instantaneous SNRs at end nodes is obtained. Then, by using a high SNR approximation, outage possibility is acquired and its simple closed-form expression is represented. Specially, for using the energy resource more efficiently, a low-complexity power allocation and transmission mode selection policy is proposed to enhance the energy efficiency of two-way AF relay system. Finally, relay priority region is identified in which cooperative diversity energy gain can be achieved. The computer simulations are presented to verify our analytical results, indicating that the proposed policy outperforms direct transmission by an energy gain of 3 dB at the relative channel estimation error less than 0.001. The results also show that the two-way AF relaying transmission loses the two-way AF relaying transmission loses its superiority to direct transmission in terms of energy efficiency when channel estimation error reaches 0.03.

Diversity-multiplexing tradeoff of half-duplex multi-input multi-output two-way relay channel with decode-and-forward protocol

A multi-input multi-output(MIMO) separated two-way relay channel(STWRC) is considered,where two users exchange their messages via a relay node.When each link is quasi-static Rayleigh fading,the achievable diversity-multiplexing tradeoff(DMT) of the half-duplex STWRC is analyzed.Firstly,the achievable DMT of the STWRC with static decode-and-forward(DF) protocol is obtained.Then,a dynamic decode-and-forward(DDF) protocol for the STWRC is proposed,where the relay listening time varies dynamically with the channel qualities of the links between two users and the relay.Finally,the achievable DMT of the proposed DDF protocol is derived in a case-bycase manner.Numerical examples are also provided to verify the theoretical analysis of both protocols.

Optimal cooperative beamforming design schemes for AF MOMO two-way relay channels

In this paper,beamforming parameters in multiple input multiple output(MIMO) two-way relay channels(TWRCs) are designed.We investigate three communicating scenarios,in which,the source nodes are all equipped with multiple antennas.In the first scenario,one pair of source nodes are communicating with each other under the help of a single multi-antenna equipped relay.A centralized scheme is correspondingly developed where the optimal relay beamforming(RaB) is jointly designed with the transmit beamformings(TBs) and the receive beamformings(RcBs) at both source nodes to minimize the sum of mean square errors(SMSE).In the second scenario,one pair of users in the first scenario is extended to multi-pair of source nodes.We derive a general expression of the optimal RaB matrix of this scenario in the second scheme,and based on which,a RaB matrix is designed to cancel the inter-pair interference(IPI) and to minimize the intra-pair SMSE.At last,we consider a distributed scenario where multiple single-antenna equipped relays are helping the communication between one pair of source nodes.In the scheme associated with this scenario,beamformings are developed under relay total power constraint and relay individual power constraint,respectively.The simulation results reveal that beamformings at source and relay nodes significantly improve the performance in the sense of average bit error rate(BER).The proposed multi-pair scheme has made superior progress in BER performance because it not only can cancel the IPIs but also can balance the useful signal and the noise at each user.Moreover,in one-pair scenarios,the performance of the centralized scheme is better than the distributed one,but the latter is nevertheless much more practical.

Integrated Scheduling Optimization of Two-Way Channel Ships Entering and Leaving Ports and Tugboat Distribution

According to the passage rules of ships in the bidirectional channel,the realistic conditions of the limited number of tugboats in the port are taken into account.This paper studies the problems faced in the integrated scheduling optimization in terms of ship arrival and departure and tugboat allocation in two-way channel.A mixed integer programming model with minimum waiting time was established,and a heuristic algorithm was designed to solve the problem.Experimental results show that the model and algorithm in this paper can effectively solve such problems and provide support for port management.

Physical Experiments to Investigate the Effects of Street Bottom Heating and Inflow Turbulence on Urban Street-Canyon Flow

The effects of street bottom heating and inflow turbulence on urbanstreet-canyon flow are experimentally investigated using a circulating water channel. Threeexperiments are carried out for a street canyon with a street aspect ratio of 1. Results from eachexperiment with bottom heating or inflow turbulence are compared with those without bottom heatingand appreciable inflow turbulence. It is demonstrated that street bottom heating or inflowturbulence increases the intensity of the canyon vortex. A possible explanation on how street bottomheating or inflow turbulence intensifies the canyon vortex is given from a fluid dynamicalviewpoint.

Opportunistic Relaying Schemes for Amplify and Forward Bidirectional Relay Channels with Multi antenna Sources

We consider a two-way relay network where the Amplify-and-Forward (AF) protocol is adopted by all relays in this paper.The network consists of two multi-antenna source nodes and multiple distributed single-antenna relays.Two opportunistic relaying schemes are proposed to efficiently utilize the antennas of the source nodes and the relay nodes.In the first scheme,the best relay is selected out by a max-min-max criterion before transmitting.After that,at each source,only the antenna with the largest channel gain between itself and the best relay is activated to transmit and receive signals with full power.In the second scheme,assisted by the best relay which is selected by the typical max-min criterion,both source nodes use all their antennas to exchange data,and match filter beamforming techniques are employed at both source nodes.Further analyses show that all schemes can achieve the full diversity order,and the conclusions are not only mathematically demonstrated but numerically illustrated.System performance comparisons are carried out by numerical methods in terms of rate sum and outage probability,respectively.The beamforming assisted scheme can be found to be superior to the antenna selection scheme when accurate Channel State Information (CSI) is available at the transmitters.Otherwise,the latter is very suitable.

Automatic Classification of Superimposed Modulations for 5G MIMO Two-Way Cognitive Relay Networks

To promote reliable and secure communications in the cognitive radio network,the automatic modulation classification algorithms have been mainly proposed to estimate a single modulation.In this paper,we address the classification of superimposed modulations dedicated to 5G multipleinput multiple-output(MIMO)two-way cognitive relay network in realistic channels modeled with Nakagami-m distribution.Our purpose consists of classifying pairs of users modulations from superimposed signals.To achieve this goal,we apply the higher-order statistics in conjunction with the Multi-BoostAB classifier.We use several efficiency metrics including the true positive(TP)rate,false positive(FP)rate,precision,recall,F-Measure and receiver operating characteristic(ROC)area in order to evaluate the performance of the proposed algorithm in terms of correct superimposed modulations classification.Computer simulations prove that our proposal allows obtaining a good probability of classification for ten superimposed modulations at a low signal-to-noise ratio,including the worst case(i.e.,m=0.5),where the fading distribution follows a one-sided Gaussian distribution.We also carry out a comparative study between our proposal usingMultiBoostAB classifier with the decision tree(J48)classifier.Simulation results show that the performance of MultiBoostAB on the superimposed modulations classifications outperforms the one of J48 classifier.In addition,we study the impact of the symbols number,path loss exponent and relay position on the performance of the proposed automatic classification superimposed modulations in terms of probability of correct classification.

PERFORMANCE ANALYSIS OF TWO-WAY AMPLIFY-AND-FORWARD RELAYING SYSTEM WITH MULTIPLE INTERFERERS AT THE RELAY

In this paper,we investigate the performance of the two-way Amplify-and-Forward(AF) relaying systems in an interference-limited Rayleigh fading environment.More specifically,assuming the presence of Rayleigh faded multiple interferers at the AF relay and noisy sources,an approximate closed-form expression for the Overall Outage Probability(OOP) and an integral expression for the average Symbol Error Probability(SEP) are derived.The analysis results are verified through com-parison with the Monte Carlo simulation results.

Experiments on Development of Channel Pattern in the Process of River Reformation

The changing of flow conditions caused by construction of hydro-projects will result in river's refor- mation and development of channel pattern.In this paper,the development of channel pattern in the process of reformation is studied by means of flume experiments.Influence of slope,grain size,angle-of-inflow,dis- charge and discharge process are comprehensively analyzed according to the experimental data.It was found that the channel would be widened as the river slope or discharge increased and grain s...

煤矿充水因素评价及涌水量预测

为真实掌握煤矿的涌水量和充水条件,在对煤矿水文地质分析的基础上,首先对充水条件和充水因素进行评价,得出煤矿的充水通道主要为导水裂隙带,基于层次分析得出通道条件的权重因子为0.2667最大,为该煤矿的充水的首要条件;在对煤矿历年涌水量观测结果分析的基础上,采用大井法对涌水量进行预测,综合分析最终得出该煤矿正常涌水量为462 m^(3)/h,最大涌水量为693 m^(3)/h。

支流入汇对干流航道通航条件影响模拟研究

自然河流由于支流的汇入,在交汇区与干流相互混掺顶托,改变了原有的水流形态,形成复杂的水流结构,对内河船舶航运的操纵性和安全性均造成一定影响。采用数值模拟试验方法,基于分离式(MMG)水动力模型,系统地研究了不同交汇角、汇流比以及干支流河道宽度比情况下交汇区船舶通航条件,即船舶航行时的漂角和偏航距离因素,并以此为基础,基于Design-Export响应面分析软件,得出了无量纲化后的最大偏航距离与交汇角、汇流比以及干支流宽度比之间的响应函数。

感应流道式自动控流阀控水原理及性能分析

基于计算流体力学方法(有限体积法),针对一种感应流道式自动控流阀的控制原理及其内部流体流动特征进行研究。结果表明:该自动控流阀对流体黏度具有较强的识别能力,见水后自动控流阀能够有效自动关闭,当原油黏度大于2 mPa·s,该自动控流阀即可开启生产;感应流道的长度与流体黏度敏感性呈正相关,感应流道截面大小对流体黏度敏感性影响较大;与浮板式AICD和螺旋通道型AICD试验结果对比发现,相同条件下自动控流阀产油量更高,控水效果更好。研究结果对感应流道式自动控流阀的优化设计提供了理论依据。

多种勘探手段在某灰岩矿山导水通道探测中的应用

为解决某灰岩矿山日趋严重的涌水问题,开展了专项水文地质勘查工作,通过地质调查、物探、钻探、井下电视、连通试验等多种工作手段相结合,基本查明了矿区内地下水来源及主要导水通道的发育情况,为后期的涌水治理提供了依据。

Deflt3D模型在鄱阳湖码头工程防洪评价中的应用

采用Delft3D二维数学模型模拟鄱阳湖入江水道水流,结合港区3座码头涉河建设方案,合理进行矩形网格划分,利用实测的上游五河来水及下游湖口站水位资料进行率定和验证,确定模拟河段糙率系数和涡黏系数。选用2种边界条件,计算码头建设前后水位和流速变化数值,经过数据处理,形成工程建设前后水位和流速差值等值线图,得出港区3座码头最大壅水高度为0.95 cm,流速增加最大值为0.17 m/s,即工程建设对鄱阳湖入江水道壅水和流速影响均不大。这表明Delft3D可定量分析新建码头对鄱阳湖入江水道壅水和行洪能力的影响,为得到合理的防洪评价结论提供有力的技术支撑。

董家河煤矿23502工作面底板出水水源及水害防治技术研究

董家河煤矿23502工作面形成后切眼出现底板涌水,严重威胁工作面的安全回采。针对工作面底板出水水源不清、出水通道不明的问题,通过对5号煤层底板充水含水层涌水水源分析,探究了底板涌水通道的形成,并通过物探、钻探、水化学、水位、注浆加固改造等手段,实现23502工作面采前侧向补给截流。23502工作面切眼底板涌水主要水源为奥灰水,主要通道为董家河断层的侧向补给及垂向裂隙补给,因此需要通过一定的工程技术手段,切断奥灰水对K_(2)的侧向补给,垂向进行奥灰的局部注浆加固,从而实现三采区董家河邻断层工作面的水量可控和安全回采。

蒸汽发生器下封头对核主泵入口流场影响

为了研究AP1000蒸汽发生器（SG）下封头对反应堆冷却剂泵（RCP）入口流场的影响,将SG下封头与RCP统一建模,采用CFD方法对其耦合模型进行全三维流场计算,分别研究了在稳态和瞬态情况下SG下封头对RCP入口流场的影响.稳态计算时,将均匀入流下缩尺泵的数值计算结果与试验结果进行对比,以验证数值计算方法的正确性;瞬态计算时,进行了时间步长无关性验证,以准确分析压力脉动特性.结果表明：在SG下封头的影响下,RCP入口处产生了周向不均匀的轴向速度并且形成了2个回转方向相反的旋涡;瞬态下,核主泵入口处形成了2个低压区,与均匀入流情况相比,监测点的压力系数标准差增幅达53%~90%;SG下封头使RCP入流产生预旋,且与叶轮形成较大的冲角,使得RCP扬程、效率分别下降了1.5%~7.7%,2.6%~4.1%.

水厂虹吸滤池进水流道水力特性的数值模拟

在计算流体力学(CFD)的基础上,采用重正化群(RNG)湍流模型建立虹吸滤池虹吸流动过程的仿真模型,对真空负荷加载过程及真空负荷去除之后的水流流动过程进行模拟,探讨了真空负荷对虹吸过滤启动和虹吸发展过程的影响。结果表明,所建模型能有效地仿真虹吸滤池的进水虹吸管在特定压力启动负荷下的水力特性,当真空度为进水渠液面与虹吸管顶部中心线之间的水头高度(-5 000 Pa)时,能够较快地促使虹吸产生。

太湖流域直湖港支流龙延河水系鱼类集群现状

分别于2009年8月和2010年5月对直湖港支流龙延河水系的鱼类集群现状及其影响因素进行研究.结果表明,研究区域有多种鱼类存在,共采集到31种,隶属于5目9科22属;春、夏两季鱼类集群的种类数没有明显差异,但春季的鱼类多度和生物量均显著高于夏季;主干支流、次级支流和支流末端等不同区位的鱼类组成也有一定差异;水体透明度、溶解氧与鲫、圆尾斗鱼、叉尾斗鱼多度显著正相关,而氮、磷等营养盐浓度与似鳊、餐条、鲫鱼等种类的多度呈负相关;水体营养盐浓度过高及相应的溶解氧、透明度降低均对鱼类群落产生了不利影响.