A Dynamic Building Path Based on Method of Mobile Agent Referral Networks

The mobile agent is a computer program that is able to migrate continuously among hosts in a net- work and use host service to meet its task. The host, known as workplace, can be regarded as a proxy of social member. The sequence of workplaces on which the mobile agent completed its tasks is called path. In this paper, we propose a dynamic building method of mobile agent path with minimum payment based on referral. By referral, the next workplace of mobile agent can be recommended by the current workplace provider based on his acquaintance knowledge. The simulation results on a random network model show that the more acquaintance relationships there are on the referral network, the more efficiently the mo- bile agent path can be built, and the fewer costs need to be paid on the path.     

A Probability Driven Quadri-Stage Contention Protocol for Mobile Ad Hoc Networks

The paper proposes a new contention based Time division multiple access （TDMA） Medium access control （MAC） protocol in wireless ad hoc networks, which can be termed Quadri-stage contention protocol （QSCP）. The QSCP protocol is free of both the ＂hidden terminal＂ and the ＂exposed terminal＂ problems. It is distributive and arbitrarily scalable. In the dedicated contention stage, nodes exchange their ＂Normalized accumulation and dissipation rate of payload （NADROP）＂ messages in 2-hop neighborhood, and then run a contention probability calculation algorithm to decide the probability of sending a contention frame. The algorithm guaran- tees that the number of time slot reserved by a node is proportional to its NADROP value, which can remarkably improve the end-to-end throughput when network load is heavy, and is more efficient in energy consumption. The simulation results demonstrate that QSCP performs better than the existing protocols.     

Coupled-fed Printed PIFA for Internal Eight-Band LTE/GSM/UMTS Mobile Phone

A coupled-fed printed PIFA （Pla- nar Inverted-F antenna） for eight-band operation cov- ering the LTET00/2300/2500 and GSM850/900/1800/ 1900/UMTS2100 bands in the mobile phone is presented. The proposed antenna comprises a driven W-mouopole and two coupled folded-strips. The folded strip which is coplaner with the T-monopole is called strip 1 and the folded-strip on the back of the system circuit board is called strip 2. The strip 1 is short-circuited to the system ground through an inductance and the Strip 2 is short-circuited to the system ground plane of the mobile phone directly. The driven T-monopole and the strip 1 contribute a wide band for the antenna＇s upper band （1710-2690MHz）, whereas the strip 2 generates a resonant mode for the anteuna＇s lower band （698-960MHz）. The antenna＇s two wide op- erating bands are achieved and controlled by tuning the width of the T-monopole, the gap g3 between the strip 1 and the T-monopole, and the dimensions of the strip 2 on the back of the system circuit board. Details of the pro- posed antenna are described, and the obtained results are presented and discussed.     

Distributed In-Time Multiple Coverage Holes Healing Protocol

Coverage holes often appear in wireless sensor networks due to sensor failure or the inheritance of sensor＇s random distribution. In the hybrid model, mobile sensors in the network are acquired to heal coverage holes by their mobifity. When multiple coverage holes appear in the sensor network and each of them has a time requirement （in which the coverage hole has to be healed）, conflicts for the requests of the same mobile sensor may arise. A distributed multiple mobile sensor schedufing protocol （DMS） is proposed in this paper to solve this problem by finding mobile sensors in the time response zone defined by the time requirement of each coverage hole. Simulation results show that DMS can well schedule the mobile sensors to move to multiple coverage holes within the time requirement.     

基于RSSI的精确室内定位算法

无线传感器网络的关键问题是实现节点的精确定位。为了解决基于RSSI的无线传感器网络三角形质心定位算法在有些情况不适用的问题,本文提出一种新型的基于RSSI的精确室内定位算法,此算法提出了虚拟信标节点的概念并用此来修正未知节点位置。实验表明,该算法具有较高的定位精度,能满足大多数的应用场合,具有一定的实用价值。     

Optimal trajectory determination of a single moving beacon for efficient localization in a mobile ad-hoc network

An ad hoc network of small robots (sensor nodes) adjusting their positions to establish network connectivity would be able to provide a communication infrastructure in an urban battlefield environment. A sensor node would be capable of moving to a particular position to establish network connectivity, provided it knows its current position, positions of other sensor nodes and the radio propagation characteristics of the sensor area.In this paper, we present a pseudo formation control based trajectory algorithm to determine the optimal trajectory of a moving beacon used in localization of the sensor nodes in real-time. The trajectory and the frequency of transmission of the GPS based position information of the moving beacon influences the accuracy of localization and the power consumed by the beacon to localize. Localization accuracy and reduction in the number of position information messages can be achieved, in real-time, by determining the optimal position from where the beacon should transmit its next position information. This will decrease the time required to localize, and power consumed by the beacon in comparison to random or predetermined trajectories.We first show that optimal position determination is a pseudo formation control problem. Next, we show the pseudo formation control problem formulated as an unconstrained optimization problem under the free space propagation model. We further present the modeling of the beacon incorporating the trajectory algorithm based on the pseudo formation control in a discrete event simulator. Simulation results, comparing the performance of localization with pseudo formation control based trajectory against random waypoint and predetermined trajectories for the beacon are presented. The simulation results show that the localization accuracy is significantly improved along with reduction in the number of position information messages transmitted when the beacon traverses along the pseudo formation control based trajectory.     

Optimization of Lip Contour Estimation

Developing algorithms based on lip con- tour estimation is a distinctive trend in lip segmentation which is the first step of visual speech recognition. In order to establish an optimized estimation of lip contour that is complex enough to describe the principal features of the lip but at the same time simple enough to be implemented, the selection of lip model, estimator as well as parame- ters for features of lips, including the horizontal length of snake of feature points and horizontal distance between these feature points will be optimized. Experimental result demonstrates that the optimized estimation method of lip contour provides more accurate and more stable results of lip segmentation.     

A Key Pre-distribution Scheme for Wireless Sensor Networks Using Hexagonal Deployment knowledge

To insure security for the messages sent among sensor nodes, it is important to establish keys for encryption to nodes which have had no prior direct contact with each other in wireless sensor networks. To solve the problem above, several key pre-distribution schemes have been proposed. In this paper, we present a novel key pre-distribution scheme using hexagonal deployment knowledge, in which the q-composite keys scheme has been improved. By using hexagonal division over the deploy- ment region, the probability of sharing common keys be- tween each sub-region and its neighboring sub-regions are equal, so the keys for encryption can be generated efficiently. The analytic results show that the scheme we pre-sented can achieve a higher connection probability of any two neighboring nodes than previous schemes, and net- work resilience against node capture can be substantially improved.     

基于连通度和加权校正的移动节点定位算法

移动节点定位问题是无线传感器网络中的研究重点。针对移动节点定位误差大的问题,提出一种基于连通度和加权校正的移动节点定位算法。在未知节点移动过程中,根据节点间连通度大小选取参与定位的信标节点,利用加权校正方法修正RSSI测距信息,然后用最小二乘法对未知节点进行位置估计。仿真分析表明,节点通信半径和信标密度在一定范围内,该算法表现出良好的定位性能,定位精度明显提升。     

Time Delay Estimation Based on Entropy Estimation

Abstract--This paper presents a novel time delay estimation （TDE） method using the concept of entropy. The relative delay is estimated by minimizing the estimated joint entropy of multiple sensor output signals. When estimating the entropy, the information about the prior distribution of the source signal is not required. Instead, the Parzen window estimator is employed to estimate the density function of the source signal from multiple sensor output signals. Meanwhile, based on the Parzen window estimator, the Renyi＇s quadratic entropy （RQE） is incorporated to effectively and efficiently estimate the high-dimensional joint entropy of the multichannel outputs. Furthermore, a modified form of the joint entropy for embedding information about reverberation （multipath reflections） for speech signals is introduced to enhance the estimator＇s robustness against reverberation.     

An Intra-PAN Mobility Management Scheme for IPv6 over Low-Power Wireless Personal Area Networks

This paper proposes an intra-PAN mobility management scheme for IPv6 over Low-power wireless personal area networks （6LoWPAN） on the basis of ＂networkbased＂ idea. We developed a tree-like network architecture which includes coordinate nodes for packet routing. All of the control messages are designed to transmit in link layer, and the sensor nodes are free to consider care-of address and the mobile nodes are unnecessary to deal with any mobility handoff messages. The simulation results show that this scheme efficiently cuts down the signaling cost and reduces the energy consumed by fixed nodes which can extend the life time of the whole Personal area networks （PAN）.     

Relay Node Placement with Base Stations in Wireless Sensor Networks Fault-Tolerant

It has been proposed to deploy relay nodes for the sake of prolonging Wireless sensor networks （WSN） lifetime, such that sensors transmit the sensed data to them which in turn delivers the data to base stations. For survivability requirements, relay placements which considers fault tolerant ability have been noticed and studied. While related works are limited or most existing works don＇t take factors such as fault tolerance, or base stations into account comprehensively in two tired WSN. We focus on fault tolerant relay node placement in two-tiered het- erogeneous WSN with base stations. As far as we know, fault tolerance contains two fundamental aspects, for one is multi-coverage and the second is multi-path. It is a NP- hard problem and figure out an approximation, whose approximation ratio is enhanced to be （18＋ε）. While a sub-problem approximation is also described as supplementary. Experimental results verify that the number of relay nodes deployed by our algorithm is somewhat superior to existed relay node placement solutions.     

Dynamic Collaborative Support Vector Machine for Target Classification in Wireless Sensor Networks

Target classification is a significant topic addressed in Wireless sensor networks （WSNs）. The distributed learning for target classification is desired for highly-constrained WSN since the processing ability, energy and bandwidth are strictly limited. This paper presents a dynamic data fusion based collaborative Support vector machine （SVM） for target classification in WSN. With the collaboration of multiple sensor nodes, the dynamic collaborative SVM can independently select the optimal set of sensor nodes according to the estimated energy consumption and information contribution. Then the training process of SVM is incrementally carried out in the dynamic data fusion framework with the consideration of tradeoff between energy consumption and information contribution. Because of the purposeful sensor nodes selection strategy, the dynamic collaborative SVM can conquer the inevitable missing rate and false rate of samples in WSN and save the energy for prolonging the lifetime of WSN. Furthermore, the dynamic collaborative SVM can also improve the robustness in target classification, and achieve the tradeoff between the performance and the cost. The experimental results demonstrate that the proposed dynamic collaborative SVM can effectively implement target classification in WSN. It is also verified that the proposed dynamic collaborative SVM has outstanding performance in energy efficiency and time delay.     

传感网络中基于移动信标的网格扫描定位算法

节点定位是传感网络最基本的技术之一,对此提出一种基于移动信标的网格扫描定位算法(Mobile Beacon Grid-Scan,MBGS)。该算法在网格扫描定位算法基础上,利用一个移动信标巡航整个传感区域,产生大量的虚拟信标,提高网络信标覆盖率,然后普通节点利用这些信标信息减小其可能区域(Estimative Rectangle,ER),并把新可能区域网格坐标质心作为其最新估计坐标。仿真结果表明,与Bounding Box、质心定位算法以及传统的网格扫描定位算法相比,MBGS定位方法的定位精度更高,算法性能更加稳定。     

Opportunistic Data Aggregation in Low-Duty-Cycle Wireless Sensor Networks with Unreliable Links

This paper proposes an opportunistic data aggregation algorithm to support the data collection in low-duty-cycle Wireless sensor networks （WSNs） with unreliable links. In this algorithm, each sensor selectively waits for some certain time to maximize the number of packets that it can aggregate from its downstream nodes, then transmits the aggregated result to an adaptively selected upstream node following an optimal forwarding sequence. Simulation results show that the algorithm can significantly increase the data aggregation efficiency, and reduce energy consumption and message overhead.     

Range-Free Mobile Sensor Localization and a Novel Obstacle Detection Technique

Mobile sensor localization is a challenging problem in wireless sensor networks. Due to mobility, it is difficult to find exact position of the sensors at any time instance. The aim of localization is to minimize positioning errors of the mobile sensors. In this paper we propose two range-free distributed localization algorithms for mobile sensors with static anchors. Both the algorithms depend on selection of beacon points. First we assume that mobile sensors move straight during localization which helps us to provide an upper bound on localization error. Certain applications may not allow sensors to move in a straight line. Obstacles may also obstruct path of sensors. Moreover beacon point selection becomes difficult in presence of obstacles. To address these issues, we propose another localization algorithm with an obstacle detection technique which selects correct beacon points for localization in presence of obstacles. Simulation results show improvements in performance over existing algorithms.     

Defending Against Sybil Attacks Based on Received Signal Strength in Wireless Sensor Networks

Sybil attacks is a particularly harmful attack against Wireless sensor networks （WSN）, in which a malicious node illegitimately claims multiple identities, and forges an unbounded number of identities to defeat redundancy mechanisms. This paper proposes using received signal strength of the nodes to defend against Sybil attacks when the Jakes channel was established. Aiming at improving the detection accuracy and reducing power consumption, we put forward the mutual supervision between head nodes and member nodes to detect Sybil attacks together, and compared the related detection scheme for Sybil attacks. The simulation results show that our scheme consumes lower power, and the detection accuracy is over 90%.     

Jitter Detection for Synchronization Control in Wireless Multimedia Sensor Networks

Collaborative in-network processing operations in Wireless multimedia sensor networks （WMSNs） often require effective synchronization control. Extensive researches in the traditional networks mainly focus on the synchronization control with the buffer management in the receiver. However, for WMSNs, the chaotic transport channel and low bandwidth introduce serious jitter. Jitter degrades the timing relationship among packets in a single media stream and between packets from different media streams and, hence, creates multimedia synchronization problems. Moreover, too much jitter will also degrade the performance of the streaming buffer. By only employing the buffer management scheme in the receiver, we can hardly satisfy the synchronization requirement of the in-network processing. In this study, we propose an active jitter detection mechanism for the synchronization control in WMSNs. This mechanism will improve the quality of service in multimedia networking by discarding the jitter-corrupted packets immediately and balancing the delay and jitter actively. We implement the proposed scheme in the practical WMSNs platform. The experiment results show that our scheme can reduce the average packet jitter effectively and improve the synchronization controlling performance significantly.