Switching between antenna subset selection and quasi-orthogonal space-time block code in presence of correlation

We address the problem of adaptive modulation and coding scheme (AMCS) for a multi-input multioutput (MIMO) system in presence of time-varying transmitting correlation. Antenna subset selection and quasiorthogonal space-time block code (QOSTBC) have different error performances with different signal-to-noise ratios (SNRs) and in different spatial correlation scenarios. The error performance can be improved by selecting an appropriate transmission scheme to adapt to various channel conditions. The maximum distance criterion is the simplest and very effective algorithm for the antenna subset selection without needs of complex calculation and channel state information at transmitter (CSIT). The minimum error performance criteria and the simplified linear decision strategy are developed for constant transmission rate traffic to select the optimal transmission scheme. It can dramatically decrease algorithm complexity for obtaining error probability according to the known quantities comparing with using instant CSIT. Simulation results show that, remarkable performances including low SNR and weak spatial correlation at the expense of simple calculation and almost no bandwidth loss by adopting AMCS can be achieved. The proposed AMCS improves robustness of slowly varying spatial correlated channels.     

一种改进的GSM/GPRS网络信道分配策略

在对GSM／GPRS(global system for mobile communications／general packet radio service)蜂窝系统现有典型信道分配策略FRA(fixed resource allocation)和DRA(dynamical resource allocation)及其排队策略进行分析的基础上，提出了基于DRA的改进策略DMC—DRA(dynamical minimum channels of packets for DRA)．新策略能动态改变GPRS包下限信道数，在FRA和DRA之间折衷，提高信道利用率、包传输时间、呼叫阻塞率等综合性能．     

基于能效的D2D通信系统中资源复用策略研究

针对D2D通信(device-to-device communication)与传统蜂窝通信共存下的能效资源复用问题,联合考虑蜂窝用户和D2D用户对的QoS约束,结合电路消耗功率,提出一种基于能效的D2D用户对与蜂窝用户最优匹配的资源复用和功率分配策略,分析了D2D用户对复用蜂窝用户资源的最优功率的存在性,并用分式规划理论求解了该最优功率的闭合表达式.仿真结果表明,相比已有算法,所提的能效资源复用策略的D2D用户的总能效最优,并且该总能效在低QoS要求下相比最大化和速率算法提高36.25%,高QoS要求下略高于基于节能的功率分配算法,同时还具有1.7~3 Mbit/s的和速率.      

A high-performance low cost inverse integer transform architecture for AVS video standard

A high-performance, low cost inverse integer transform architecture for advanced video standard (AVS) video coding standard was presented. An 8×8 inverse integer transform is required in AVS video system which is compute-intensive. A hardware transform is inevitable to compute the transform for the real-time ap-plication. Compared with the 4×4 transform for H.264/AVC, the 8×8 integer transform is much more complex and the coefficient in the inverse transform matrix Ts is not inerratic as that in H.264/AVC. Dividing the Ts into matrix S8 and R8, the proposed architecture is implemented with the adders and the specific CSA-trees instead of multipliers, which are area and time consuming. The architecture obtains the data processing rate up to 8 pixels per-cycle at a low cost of area. Synthesized to TSMC 0.18 μm COMS process, the architecture attains the operating frequency of 300 MHz at cost of 34 252 gates with a 2-stage pipeline scheme. A reusable scheme is also introduced for the area optimization, which results in the operating frequency of 143 MHz at cost of only 19 758 gates.     

A low-cost testbed of underwater mobile sensing network

Comprised by a swarm of acoustically linked and cooperative autonomous underwater vehicles (AUVs) with onboard sensors, an underwater mobile sensing network (UMSN) will be a complementary means to fixed observatory networks, e.g. seafloor observatory networks and moored buoy arrays. It has obvious advantages over a single large AUV in higher efficiency due to parallel observation, stronger robustness to vehicle failures and lower cost. Although an UMSN can be viewed as a counterpart of wireless mobile sensing networks for air and terrestrial applications, it is much more challenging due to poor performance of underwater acoustic communication, poor performance of underwater positioning and high degree of uncertainty in vehicle dynamics and underwater environment. In order to verify key technologies involved in an UMSN, e.g. cooperation of multi-AUVs based on acoustic communication, a low cost testbed has been developed for experimental study. The design of both hardware and software is introduced. Also the results of a functional test for verification of the effectiveness of the testbed are presented.     

��ʽ�������䷽��ѡ��Ľ����ط���

为了深入研究多式联运运输方案优化问题,将问题抽象成为组合优化问题,并将交叉熵方法应用于多式联运问题的研究.探讨综合运输的背景下,寻求运输成本、转运费用等最小化的运输方案,提出了针对多式联运运输方案选择问题的交叉熵算法,并给出了计算步骤和相应的计算方法.在计算过程中,为了验证本文提出算法的有效性,采用节点扩展的网络图描述多式联运网络,进而转化为最短路问题进行求解.结果表明,运输成本、转运费用对运输方案起到关键作用,并且提出的交叉熵算法能够很快收敛.     

Simultaneous localization and mapping of autonomous underwater vehicle using looking forward sonar

A method of underwater simultaneous localization and mapping (SLAM) based on on-board looking forward sonar is proposed. The real-time data flow is obtained to form the underwater acoustic images and these images are pre-processed and positions of objects are extracted for SLAM. Extended Kalman filter (EKF) is selected as the kernel approach to enable the underwater vehicle to construct a feature map, and the EKF can locate the underwater vehicle through the map. In order to improve the association efficiency, a novel association method based on ant colony algorithm is introduced. Results obtained on simulation data and real acoustic vision data in tank are displayed and discussed. The proposed method maintains better association efficiency and reduces navigation error, and is effective and feasible.     

Efficient and provably-secure certificateless proxy re-encryption scheme for secure cloud data sharing

In current cloud computing system, large amounts of sensitive data are shared to other cloud users. To keep these data confidentiality, data owners should encrypt their data before outsourcing. We choose proxy reencryption （PRE） as the cloud data encryption technique. In a PRE system, a semi-trusted proxy can transform a ciphertext under one public key into a ciphertext of the same message under another public key, but the proxy cannot gain any information about the message. In this paper, we propose a certificateless PRE （CL-PRE） scheme without pairings. The security of the proposed scheme can be proved to be equivalent to the computational Dire- Hellman （CDH） problem in the random oracle model. Compared with other existing CL-PRE schemes, our scheme requires less computation cost and is significantly more efficient. The new scheme does not need the public key certificates to guarantee validity of public keys and solves the key escrow problem in identity-based public key cryptography.     

Application of method of fundamental solutions in solving potential flow problems for ship motion prediction

A novel panel-free approach based on the method of fundamental solutions (MFS) is proposed to solve the potential flow for predicting ship motion responses in the frequency domain according to strip theory. Compared with the conventional boundary element method (BEM), MFS is a desingularized, panel-free and integration-free approach. As a result, it is mathematically simple and easy for programming. The velocity potential is described by radial basis function (RBF) approximations and any degree of continuity of the velocity potential gradient can be obtained. Desingularization is achieved through collating singularities on a pseudo boundary outside the real fluid domain. Practical implementation and numerical characteristics of the MFS for solving the potential flow problem concerning ship hydrodynamics are elaborated through the computation of a 2D rectangular section. Then, the current method is further integrated with frequency domain strip theory to predict the heave and pitch responses of a containership and a very large crude carrier (VLCC) in regular head waves. The results of both ships agree well with the 3D frequency domain panel method and experimental data. Thus, the correctness and usefulness of the proposed approach are proved. We hope that this paper will serve as a motivation for other researchers to apply the MFS to various challenging problems in the field of ship hydrodynamics.     

基于语义相似度的话题关联检测方法

为有效识别任意两篇报道的相似性,提出了一种基于语义相似度的话题关联检测算法.该算法首先通过计算特征词之间的相对熵作为两篇报道中特征词之间的语义相似度;其次,通过计算平均语义相似度获得特征词和报道之间的关联度;最后,结合特征词在语料库中的TF-IF(term frequency-inverse document frequency)权重计算两篇报道之间的关联度,实现报道之间的关联度检测.本文提出的方法与现有的向量空间模型方法和仅依赖于平均点互信息的方法进行了比较,并通过TDT4中文语料进行测评,结果表明,基于语义相似度的关联检测方法能够更好地利用文本的语境信息,提高了现有检测系统的性能,其最小DET(detection error tradeoff)代价降低了3%.      

水下隧道开挖面三维渗流场解析及涌水量预测分析

开挖面前方地层水压力及渗水量值是水下隧道工程重要参数,也是开挖面支护力设计、超前堵水加固参数设计的重要指标. 针对以往二维渗流模型分析水下隧道开挖面前方三维渗流场的局限性问题,首先,建立考虑开挖面前方渗流等势面为空间曲面的水下隧道三维渗流解析模型;其次,推导以开挖面所在平面为分界线的全部未开挖区半地层空间的水头分布函数,得出开挖面渗水量及前方地层孔隙水压力计算公式;最后,分析超前加固厚度、土体与超前加固渗透系数相对值等因素对开挖面前方水压力及渗水量的影响. 分析结果表明:与以往考虑开挖面正前方为二维渗流场的理论模型相较,三维解析模型能更好地反映开挖面前方空间渗流形态,且涌水量与水压力计算结果误差在5%以内;当掌子面前方加固范围为2倍洞室直径,超前加固区与地层相对渗透系数取值50,为安全合理的超前堵水加固参数.      

无线感测网络上节能的事件驱动数据汇集机制

针对无线感测网络上动态改变的事件,设计一套有效率的数据汇集机制.采用网格架构,建立数据汇集树将事件数据传送至汇集点.在初始建立数据汇集树架构时便尽量减少多余的回传节点,以减少感测点的能量消耗.而在事件产生变动时,可应事件变化的调整机制让树架构依然有效率的运作.本文提出的方法与无线感测网络中的3个数据汇集技术EADA、Dual-Tree-Based和Range Query做比较,仿真结果显示本文的方法能够有效的延长网络存活时间,且在总能量消耗及系统开销（overhead）皆有良好表现.     

A High-performance Low Cost Inverse Integer Transform Architecture for AVS Video Standard

A high-performance, low cost inverse integer transform architecture for advanced video standard (AVS) video coding standard was presented. An 8×8 inverse integer transform is required in AVS video system which is compute-intensive. A hardware transform is inevitable to compute the transform for the real-time ap-plication. Compared with the 4×4 transform for H.264/AVC, the 8×8 integer transform is much more complex and the coefficient in the inverse transform matrix Ts is not inerratic as that in H.264/AVC. Dividing the Ts into matrix S8 and R8, the proposed architecture is implemented with the adders and the specific CSA-trees instead of multipliers, which are area and time consuming. The architecture obtains the data processing rate up to 8 pixels per-cycle at a low cost of area. Synthesized to TSMC 0.18 μm COMS process, the architecture attains the operating frequency of 300 MHz at cost of 34 252 gates with a 2-stage pipeline scheme. A reusable scheme is also introduced for the area optimization, which results in the operating frequency of 143 MHz at cost of only 19 758 gates.     

Practical identity-based aggregate signature from bilinear maps

A new identity-based(ID-based) aggregate signature scheme which does not need any kind of interaction among the signers was proposed to provide partial aggregation.Compared with the existing ID-based aggregate signatures, the scheme is more effcient in terms of computational cost.Security in the random oracle model based on a variant of the computation Diffe-Hellman(CDH) problem is captured.     

潜艇用新型铅酸蓄电池万用放电模型研究

铅酸蓄电池是常规潜艇水下航行的核心动力,为优化动力系统工作性能,需要建立放电模型.但铅酸蓄电池内部是十分复杂的电化学反应,随机性较大,蓄电池性能受各种不确定性因素影响,蓄电池模型具有明显的非线性特征,并且随着蓄电池充放电周期的增加,蓄电池的性能也发生较大的变化.文中在研究蓄电池放电特点的基础上,考虑蓄电池建模的各种方法,采用前馈神经网络方法,建立了可以模拟蓄电池非线性和时变性的模型.检验结果表明,该模型能够较好地反映蓄电池的特性.     

不均匀地质条件下地震动目标定位方法

针对不均匀地质条件下地震动信号传播速度差异造成定位精度较低的问题,通过将位置域的传播速度转换为时延域的等效传播速度,提出了一种基于时延-等效传播速度检索表的到达时间差(TDOA)目标定位方法.对等腰直角三角形传感器阵列的定位盲区进行了仿真分析,为消除定位盲区,提出了五元十字阵传感器布置方法;进行了场地试验,对运动车辆进行目标定位,对基于时延-等效传播速度检索表的TDOA定位方法与固定传播速度TDOA定位方法的定位结果进行了比较,结果表明,前者的定位效果远优于后者.      

考虑随机需求和时间约束LIRP联合协同优化

针对多节点多层次多功能的供应链管理中整体效益亟待提高的问题,结合某连锁超市的单一供应商、多分销中心、多零售店所构成二级分销网络,建立以系统总成本和供货时间为目标的多目标选址-库存-路径问题(location-inventory-routing problem,LIRP)集成规划模型.利用线性加权法将其转化为单目标规划模型,提出遗传算法和节约里程法相结合的两阶段启发式算法并求解模型,第1阶段用遗传算法求解选址-库存问题,第2阶段用节约里程算法求解车辆路径规划问题.并结合某连锁超市实例,对不同总成本权重下的不同决策方案的分销网络进行LIRP集成优化,优化后的系统方案比原文献的总里程减少了3 606.9 km,系统总成本减小了6 526.2元,缺货成本降低了124.6元,只有19.7元,验证了模型和算法的有效性.     

基于可控量子隐形传态的代理签名方案

提出了一种量子代理签名方案．基于可控量子隐形传态，采用3粒子纠缠态作为量子信道，不同于经典的基于计算复杂性的代理签名方案，本方案利用量子隐形传态的物理特性来实现签名及验证，具有无条件安全性．     

Pre-emptive channel borrowing and traffic overflowing channel allocation scheme for multimedia overlay networks

This paper proposes a channel allocation scheme for multimedia wireless networks, in which a twolayer macro-cell or micro-cell architecture is considered. Macro-cells are used to access high-mobility services; while micro-cells, which are overlaid by the macro-cells, are used to cater low-mobility services. To analyze the scheme, a multidimensional Markov traffic model is firstly developed, in which traffic characteristic of two special periods of time is considered. And then, a pre-emptive channel-borrowing scheme combined with trafficoverflowing strategy for multimedia (voice, video or data) networks is proposed, in which handoff requests can not only borrow channels from adjacent homogenous cells, but also be overflowed to heterogeneous cells. Priority strategies are also dedicated to high-mobility services for they can pre-empt channels being used by low-mobility services in macro-cells. To meet the high quality of service (QoS) requirements of video services and increase the channel utilization ratio, video services can be transformed between real-time services and non-real-time services as necessary. Simulation results show that our schemes can decrease the blocking probabilities and improve the channel utilization.     

Iterative algorithm of steered minimum variance and its application in weak targets detection

The steered covariance matrix (STCM) and its inverse matrix should be calculated in each beam for steered minimum variance (STMV). The inverse matrix needs complex computation and restricts its application in engineering. Combining the integration character of one-phase regressive filter with the iterative formula of inverse matrix, an STMV iterative algorithm is proposed. The computational cost of the iterative algorithm is reduced approximately to be 2/M times of the original one when there are M sensors, and is more advantaged for the realization of the algorithm in real time. Simulation results show that the STMV iterative algorithm can preserve the characters of STMV on high azimuth resolution and weak target detection while the computational cost reduced sharply. The analysis on sea trial data proves that the proposed algorithm can estimate each target’s azimuth even when the source powers differ in large scales or their bearings are very approximate.