不确定干扰约束下外集卡提箱策略

为提高集装箱码头作业效率,降低不确定干扰因素对外集卡提箱作业的影响,提出以滚动窗口策略处理干扰因素的方法,并建立以作业延误惩罚成本与场桥移动成本最小化为目标的混合整数模型,采用遗传算法（GA）进行求解。首先,利用滚动窗口策略得到在无干扰因素情况下的外集卡提箱作业调度方案;其次,当出现干扰因素时触发滚动窗口再调度机制对外集卡提箱作业顺序重新安排;最后,计算出各滚动窗口内最优的调度方案,提出总计划时间内最优作业方案。通过对不同情景下的案例求解结果进行对比分析,实验结果表明在无干扰情况下,滚动窗口策略下的最小作业成本比传统作业方式下降低了9%,而在干扰情况下滚动窗口策略优于传统作业方式15%,进而验证了算法的有效性以及滚动窗口策略对外集卡提箱作业的优越性。     

A sensitive data aggregation scheme for body sensor networks based on data hiding

Body sensor networks (BSNs) enable the pervasive, long-term, and real-time monitoring in any environment and without restriction of activity. Security and privacy are extremely critical issues of BSNs, as sensitive information is transmitted through the wireless network. This paper proposes a novel sensitive data aggregation scheme based on data hiding for BSNs, namely SDAS. SDAS adopts the packet combination based on the sensitive data aggregation tree built in each BSN to reduce the transmission energy consumption by eliminating transmitted redundancy. After lossless compression, the compressed sensitive data are embedded into various ordinary data in the combined packet by using a lightweight data hiding algorithm to prevent the disclosure of the sensitive data and avoid arousing the attention of attackers. Extensive analysis demonstrates that our proposed scheme can ensure a high level of security and privacy of the sensitive data without affecting the ordinary data quality, while delivering low power consumption.     

无线传感器网络中一种抗无线局域网干扰的信道分配机制

无线传感器网络(WSN)易受到与其共享信道的无线局域网(Wifi)干扰,造成通信可靠性及吞吐量下降.当具有不同优先级的多个WSN受到Wifi干扰时,如何按优先级分配信道,并兼顾整体通信可靠性及吞吐量是一个重要问题.针对该问题,作者提出了一种抗Wifi干扰的信道分配机制EasiCAP(Channel Allocation for wireless sensor networks with Priority).该机制利用基于干扰强度和活跃比率的干扰特征模型(External Interference Model,EIM)度量WSN中各信道的Wifi干扰;同时,采用以接收端为中心的模型(Internal Interference Model,IIM)度量各WSN之间的干扰.然后,各WSN根据EIM和IIM度量的结果,采用局部化贪婪信道分配算法独立、实时地选择信道,通过保持信道、切换信道及抢占信道操作实现按优先级分配信道,并尽可能降低所有网络所受干扰之和.实际测量和仿真结果表明,EasiCAP可为各WSN提供与其优先级相对应的通信可靠性和吞吐量;而且该机制下的平均通信可靠性及吞吐量也比现有方法高.此外,EasiCAP未带来过大的开销.     

An interval centroid based spread spectrum watermarking scheme for multi-flow traceback

Network flow watermarking schemes have been proposed to trace network attacks in the presence of stepping stones or anonymized channels. Most existing interval-based watermarking schemes are not only ineffective in tracing multiple network flows in parallel due to severe inter-flow interference in practice but also vulnerable to the newly introduced watermarking attacks. By combining the Interval Centroid Based Watermarking (ICBW) modulation approach with the Spread Spectrum (SS) watermarking coding technique, we herein propose an Interval Centroid Based Spread Spectrum Watermarking scheme (ICBSSW) for efficiently tracing multiple network flows in parallel. Based on our proposed theoretical model, a statistical analysis of ICBSSW, with no assumptions or limitations concerning the distribution of packet times, proves its effectiveness and robustness against inter-flow interference. ICBSSW can thwart multi-flow attacks by utilizing multiple Pseudo-Noise (PN) codes as random seeds for randomizing the location of the embedded watermark across multiple flows. The experiments using a large number of synthetically generated secure shell (SSH) traffic flows demonstrate that ICBSSW can efficiently trace multiple flows simultaneously and achieve robustness against inter-flow interference. Furthermore, our approach can be applied to other interval-based flow watermarking schemes besides ICBW for effective and efficient multi-flow traceback.     

分布式MIMO 系统的迭代空时检测算法

针对未来无线通信系统中广义分布式天线阵的架构,提出了一种适用于分布式多输入多输出（MIMO） 系统的LST-STBC 空时编码方案．该方案通过具有差错控制编码的分层空时（LST）结构与基于正交设计的分组空 时码（STBC）的有效结合,同时获得了分集和复用增益．针对提出的空时编码结构,接收端采用基于软干扰抵消和 最小均方误差（MMSE）的迭代检测算法,通过检测和译码软信息的迭代,有效降低了系统的误码率．仿真结果表 明,文中提出的基于接收端迭代检测的空时编码方案能有效提高分布式MIMO 系统的传输速率和传输质量．     

A framework for collaborative computing and multi-sensor data fusion in body sensor networks

Body Sensor Networks (BSNs) have emerged as the most effective technology enabling not only new e-Health methods and systems but also novel applications in human-centered areas such as electronic health care, fitness/welness systems, sport performance monitoring, interactive games, factory workers monitoring, and social physical interaction. Despite their enormous potential, they are currently mostly used only to monitor single individuals. Indeed, BSNs can proactively interact and collaborate to foster novel BSN applications centered on collaborative groups of individuals. In this paper, C-SPINE, a framework for Collaborative BSNs (CBSNs), is proposed. CBSNs are BSNs able to collaborate with each other to fulfill a common goal. They can support the development of novel smart wearable systems for cyberphysical pervasive computing environments. Collaboration therefore relies on interaction and synchronization among the CBSNs and on collaborative distributed computing atop the collaborating CBSNs. Specifically, collaboration is triggered upon CBSN proximity and relies on service-specific protocols allowing for managing services among the collaborating CBSNs. C-SPINE also natively supports multi-sensor data fusion among CBSNs to enable joint data analysis such as filtering, time-dependent data integration and classification. To demonstrate its effectiveness, C-SPINE is used to implement e-Shake, a collaborative CBSN system for the detection of emotions. The system is based on a multi-sensor data fusion schema to perform automatic detection of handshakes between two individuals and capture of possible heart-rate-based emotion reactions due to the individuals’ meeting.     

A Joint Source-Channel Video Coding Scheme Based on Distributed Source Coding

Recently, several error resilient schemes have been proposed to tackle the error propagation problem in the motion-compensated predictive video coding based on a promising technique—distributed source coding (DSC). However, these schemes mainly apply the distributed source codes for channel error correction, while under-utilizing their capability for data compression. A channel-aware joint source-channel video coding scheme based on DSC is proposed to eliminate the error propagation problem in predictive video coding in a more efficient way. It is known that near Slepian–Wolf bound DSC is achieved using powerful channel codes, assuming the source and its reference (also known as side-information) are connected by a virtual error-prone channel. In the proposed scheme, the virtual and real error-prone channels are fused so that a unified single channel code is applied to encode the current frame thus accomplishing a joint source-channel coding. Our analysis of the rate efficiency in recovering error propagation shows that the joint scheme can achieve a lower rate compared with performing source and channel coding separately. Simulation results show that the number of bits used for recovering from error propagation can be reduced by up to 10% using the proposed scheme compared to Sehgal–Jagmohan–Ahuja's DSC-based error resilient scheme.      

Adaptive frequency hopping and power control based on spectrum characteristic of error sources in Bluetooth systems

In this paper, we propose a new adaptive frequency hopping (AFH) and power control (PC) scheme to mitigate co-channel interferences and channel noise in the Bluetooth systems. We consider a two-step interference mitigation scheme exploiting the spectrum characteristic of the interference source and channel noise. Good channels without IEEE 802.11x based wireless local area networks (WLAN) interference are first estimated by considering wideband characteristic of WLAN. Then, channel noise and interference from other Bluetooth devices in good channels are, respectively, mitigated by PC and AFH based on narrowband characteristic of Bluetooth. The performance of the proposed scheme is verified by computer simulation. Simulation results show that the proposed mitigation scheme significantly outperforms conventional schemes.     

基于协作中继的多点广播码分多址信息系统设计

为了提高多群多点广播中继网络系统的性能,提出一种改进的协作中继多点广播码分多址(CDMA)系统设计。该方案利用协作中继辅助的分布式波束形成 实现单天线基站多播,获得了较好的空间分集增益。在该系统中,多个基站利用多个中继节点向多个目的地的各个小组传播消息;利用CDMA技术来减少中继节点以及目的地节点的多址干扰(MAI)障碍,同时每个中继节点作为线性预编码波束合成器,可以在合适的代码空间重塑基站信号;对线性波束形成矩阵进行优化,使得中继节点的功率最小化,从而满足QoS在信号干扰噪声比方面的要求。系统性能仿真对比实验的结果表明,提出的改进方案明显优于传统的正交复用方案(FDMA / TDMA)。     

TuLP: A Family of Lightweight Message Authentication Codes for Body Sensor Networks简

A wireless sensor network （WSN） commonly whilst a body sensor network （BSN） must be secured with requires lower level security for public information gathering, strong authenticity to protect personal health information. In this paper, some practical problems with the message authentication codes （MACs）, which were proposed in the popular security architectures for WSNs, are reconsidered. The analysis shows that the recommended MACs for WSNs, e.g., CBC- MAC （TinySec）, OCB-MAC （MiniSec）, and XCBC-MAC （SenSee）, might not be exactly suitable for BSNs. Particularly an existential forgery attack is elaborated on XCBC-MAC. Considering the hardware limitations of BSNs, we propose a new family of tunable lightweight MAC based on the PRESENT block cipher. The first scheme, which is named TukP, is a new lightweight MAC with 64-bit output range. The second scheme, which is named TuLP-128, is a 128-bit variant which provides a higher resistance against internal collisions. Compared with the existing schemes, our lightweight MACs are both time and resource efficient on hardware-constrained devices.     

Contention based scheduling for femtocell access points in a densely deployed network environment

The proliferation of new data intensive devices has caused an enormous burden on wireless systems. A femtocell network is a promising new technology developed to meet these demands. Since each femtocell network consists of uncoordinated subnetworks that work independently, the interference between subnetworks can result in a significant degradation of the overall network capacity. In this paper, we address the interference problem between uncoordinated femtocell access points (FAPs) and propose a distributed FAP scheduling scheme in a densely deployed femtocell network where FAPs interfere with each other. In contrast to previous works that have focused on dynamic power and frequency management, our approach focuses on time sharing through FAP contention. Depending on the outcome of contention, our method selects a winning FAP to be the sole user of the next time frame. The approach operates in a fully distributed manner with help from mobile nodes (MNs). To implement this scheme, we develop a new synchronous frame structure, which uses special common control channels. Through simulations, we observe that the proposed scheme doubles the network capacity compared to the legacy non-contending scheme, and could serve as the basis for future standards on femtocell networks.     

LTE下行时变信道参考信号映射

为解决在时变环境下LTE下行传输时各参考信号之间的存在载波间干扰的问题,提出了一种新的适用于3GPP长期演进(LTE)下行时变信道下的参考信号映射方法,与3GPP LTE标准参考信号(RS)映射相比,该方案具有更优的性能.该方案通过加入虚子载波来保护参考信号(也就是导频符号),有助于减弱载波间干扰(ICI)在导频子载波的影响.另外,该方案允许通过一个简单的估计来得到ICI增益参数,通过对所提方法与标准映射的归一化均方误差性能和误码率性能在不同移动速度环境的仿真比较,在时变环境下,该方案性能明显优于标准方案.     

Distributed space-time-frequency coding for cooperative OFDM systems

A distributed space-time-frequency (STF) coding scheme is proposed for cooperative OFDM (C-OFDM) systems with three terminals over quasi-static frequency-selective Rayleigh fading channels. The outage probability is derived and its tight closed-form lower bound is presented. Asymptotic analysis indicates that the proposed scheme can achieve both spatial and multipath (frequency) diversity. The theoretical analysis of the proposed STF coded scheme is further implemented by the distributed group STF block coding (D-GSTFBC) scheme based on the subcarrier grouping technique. Simulation results confirm the previously introduced theoretical analysis.     

Enhancing multi-hop communication over multi-radio multi-channel wireless mesh networks: A cross-layer approach

The multi-channel multi-radio technology represents a straightforward approach to expand the capacity of wireless mesh networks (WMNs) in broadband wireless access scenarios. However, the effective leveraging of this technology in WMNs requires (i) enhanced MAC protocols, to coordinate the access to multiple channels with a limited number of radio interfaces, and (ii) efficient channel allocation schemes, to mitigate the impact of co-channel interference. The design of channel assignment schemes and MAC protocols is strictly interrelated, so that joint design should be considered to optimize the mesh network performance. In this paper, a channel assignment and fast MAC architecture (CAFMA) is proposed, which exploits the benefits provided by the multi-channel multi-radio technology to (i) enhance the performance of multi-hop communications, (ii) maximize the resource utilization, and (iii) support differentiation of traffic classes with different quality of service (QoS) requirements. CAFMA is designed with a cross-layer approach and includes (1) a novel MAC scheme, which provides multi-channel coordination and fast data relaying over multi-hop topologies, and (2) a distributed channel allocation scheme, which works in cooperation with the routing protocol. Simulation results confirm the effectiveness of CAFMA when compared with other single-layer and cross-layer solutions for multi-radio multi-channel WMNs.     

一种改进的被动雷达直达干扰抑制方案

研究被动雷达系统中直达信号干扰的抑制问题.针对实际场景中系统主通道与参考通道之间存在频域与时域上的链路差异,提出一种改进的直达干扰抑制方案.利用最大似然原理对参考通道与主通道的频差进行补偿,使用分层搜索的方法降低算法复杂度,进而基于解卷积的算法对时域失真进行恢复.仿真结果显示,与现有方案相比,所提出方案能够克服通道链路差异带来的不利影响,精确重构出主通道中的直达干扰信号,实现更佳的干扰抑制效果,具有很好的实用价值.     

On the immersed interface method for solving time-domain Maxwell's equations in materials with curved dielectric interfaces

This paper deals with accurate numerical simulation of two-dimensional time-domain Maxwell's equations in materials with curved dielectric interfaces. The proposed fully second-order scheme is a hybridization between the immersed interface method (IIM), introduced to take into account curved geometries in structured schemes, and the Lax-Wendroff scheme, usually used to improve order of approximations in time for partial differential equations. In particular, the IIM proposed for two-dimensional acoustic wave equations with piecewise constant coefficients [C. Zhang, R.J. LeVeque, The immersed interface method for acoustic wave equations with discontinuous coefficients, Wave Motion 25 (1997) 237-263] is extended through a simple least squares procedure to such Maxwell's equations. Numerical results from the simulation of electromagnetic scattering of a plane incident wave by a dielectric circular cylinder appear to indicate that, compared to the original IIM for the acoustic wave equations, the augmented IIM with the proposed least squares fitting greatly improves the long-time stability of the time-domain solution. Semi-discrete finite difference schemes using the IIM for spatial discretization are also discussed and numerically tested in the paper.     

How to Effectively Use Multiple Channels in Wireless Mesh Networks

Operating on a frequency band occupying several nonoverlapping channels, IEEE 802.11 is now widely used in wireless mesh networks (WMNs). Many multichannel MAC protocols are proposed to improve the spatial reuse in the network under the assumption that the transmissions on nonoverlapping channels do not interfere with each other. Some joint routing and channel assignment algorithms are also designed to increase the network throughput based on the premise that we can switch between different channels freely. Although simulations show that great improvements on network throughput can be observed in both cases, two fundamental questions remain: 1) Can we really use multiple nonoverlapping channels freely in WMNs? 2) If we can, what will be the cost when we switch channels dynamically and frequently? In this paper, by conducting extensive experiments on our testbed, we attempt to answer these questions. We find that in spite of interference between both overlapping and nonoverlapping channels, we can still use multiple channels in mesh networks under certain conditions but with care. We also show that the channel switching cost is actually very significant in WMNs. We recommend not to switch the channels too frequently when designing the channel assignment algorithms, and those channel assignment algorithms selecting one channel for each packet are not really beneficial.     

基于多对一Gale-Shapley算法的D2D通信资源分配

针对D2D通信复用异构蜂窝网络上行信道产生的干扰问题和频谱资源优化问题进行研究,提出一种基于多对一Gale-Shapley算法的D2D通信资源分配方案。本方案允许多个D2D用户共享一个蜂窝用户信道资源,通过设置信干噪比（SINR）门限保证用户的通信服务质量（QOS）。根据信道分配情况,构建D2D用户和信道的偏好列表,最大化系统总容量。仿真结果表明,该方案收敛较快,复杂度较低,能够有效保证用户的通信服务质量,系统总容量接近最优解。本研究为实现D2D用户和蜂窝用户的频谱资源共享,提高频谱利用率提供了一种有效方案。     

一种用于CDMA系统的信道估计与检测方案

在DS/CDMA系统中,多用户检测技术可以减小多址干扰和远近效应,但一般情况下,多用户检测总是假设接收机对信道特性已知。本文提出一种慢衰落信道中的有效的联合信道估计和干扰抵消方法,这种方法需要很少的导频符号来进行信道估计,而且实现简单,可以用在较快衰落信道中。     

Dynamic Resource Allocation for Robust Distributed Multi-Point Video Conferencing

This paper proposes a distributed multi-point video conferencing system over packet erasure channels, where the aggregation of multiple video streams and resource allocation are performed in a distributed manner. Video stream combiners, which are located in different geographical areas and serve as portals for conferees, aggregate incoming streams supplied by local users with other streams aggregated from nearby video stream combiners. A packet-division multiple-access (PDMA)-based error protection scheme is proposed to be performed at each video stream combiner to minimize the maximal expected video distortion among aggregated streams. The proposed error protection scheme for multi-stream aggregation also supports user preference. In order to deliver video streams to end users with different preferred quality, a consensus algorithm is proposed to adaptively perform resource allocation based on user preference. Simulation results show that the proposed multi-stream aggregation and error protection scheme has significant gains over traditional multi-stream error protection schemes for a multi-point video conferencing system.