Location-quality-aware policy optimisation for relay selection in mobile networks

Relaying can improve the coverage and performance of wireless access networks. In presence of a localisation system at the mobile nodes, the use of such location estimates for relay node selection can be advantageous as such information can be collected by access points in linear effort with respect to number of mobile nodes (while the number of links grows quadratically). However, the localisation error and the chosen update rate of location information in conjunction with the mobility model affect the performance of such location-based relay schemes; these parameters also need to be taken into account in the design of optimal policies. This paper develops a Markov model that can capture the joint impact of localisation errors and inaccuracies of location information due to forwarding delays and mobility; the Markov model is used to develop algorithms to determine optimal location-based relay policies that take the aforementioned factors into account. The model is subsequently used to analyse the impact of deployment parameter choices on the performance of location-based relaying in WLAN scenarios with free-space propagation conditions and in an measurement-based indoor office scenario.     

Defense against Sybil attacks and authentication for anonymous location-based routing in MANET

In MANET, providing authentication and security to location-based routing is a big task. To overcome this problem, in this paper, we proposed a defense against Sybil attacks and authentication for anonymous location-based routing in MANET. Each random forwarder has a table of RSS values estimated from the previous message exchanges across a zone to detect the Sybil attack. The difference in RSS values of two neighboring nodes is estimated based on which the node’s arrival angle into the zone is detected. Depending on the arrival angle, the nodes can be categorized as safety zone and caution zone. The messages exchanged between the RFs and senders can be protected by means of group signature. Finally, misrouting packet drop attack is detected and eliminated by using ant colony optimization technique. By simulation results, we show the proposed technique reduces the packet drop due to attacks, thereby increasing the delivery ratio.     

Effects of incorporating salts with various alkyl chain lengths on carrier balance of light-emitting electrochemical cells

Recently, solid-state light-emitting electrochemical cells (LECs) have attracted much attention since they have advantages such as low operation voltages, simple device structure and balanced carrier injection. Salts are commonly added in the emissive layer of LECs to provide additional mobile ions and thus to accelerate device response. However, in addition to modified ionic property, carrier balance of LECs would also be tailored by salt additives. In this work, we improve device efficiency of LECs by incorporating imidazole-based salts bearing various alkyl chain lengths. As the alkyl chain length of the added salt increases, the device current decreases and the recombination zone approaches the anode. These results reveal that hole transport in the emissive layer of LEC containing a salt with a larger size would be impeded more significantly than electron transport. When doped with a salt possessing a proper size, nearly doubled device efficiency as compared to that of the neat-film device can be obtained due to improved carrier balance. This work demonstrates a feasible strategy to improve device performance of LECs and clarifies the physical insights of the effect of salt size on carrier balance of LECs.     

基于BCMCS的精密定位信息移动广播方案设计

主要研究在CDMA2000 1xEV-DO网络中建立基于BCMCS的移动广播网络方案,具体内容包括了BCMCS的介绍,广播方案的网络拓扑、基本流程图和关键技术等。方案将应用于定位信息分发业务当中,实现将从大众导航与位置服务信息处理服务中心获得的精密定位信息实时送达到用户移动终端上,解决定位信息分发业务无法实现大规模用户和快速实时送达的不足,实现更高效的传输。     

Location-aware routing protocol with dynamic adaptation of request zone for mobile ad hoc networks

One possibility direction to assist routing in Mobile Ad Hoc Network (MANET) is to use geographical location information provided by positioning devices such as global positioning systems (GPS). Instead of searching the route in the entire network blindly, position-based routing protocol uses the location information of mobile nodes to confine the route searching space into a smaller estimated range. The smaller route searching space to be searched, the less routing overhead and broadcast storm problem will occur. In this paper, we proposed a location-based routing protocol called LARDAR. There are three important characteristics be used in our protocol to improve the performance. Firstly, we use the location information of destination node to predict a smaller triangle or rectangle request zone that covers the position of destination in the past. The smaller route discovery space reduces the traffic of route request and the probability of collision. Secondly, in order to adapt the precision of the estimated request zone, and reduce the searching range, we applied a dynamic adaptation of request zone technique to trigger intermediate nodes using the location information of destination node to redefine a more precise request zone. Finally, an increasing-exclusive search approach is used to redo route discovery by a progressive increasing search angle basis when route discovery failed. This progressive increased request zone and exclusive search method is helpful to reduce routing overhead. It guarantees that the areas of route rediscovery will never exceed twice the entire network. Simulation results show that LARDAR has lower routing cost and collision than other protocols. Tzay-Farn Shih was with Department of Electrical Engineering, National Taiwan University. Tzay-Farn Shih received the B.S. degree in Information Management from Chinese Culture University, Taiwan, in 1992, the M.S. degree in Computer Science Engineering from Tatung University, Taiwan, in 1996, and the Ph.D. degree in Electrical Engineering from National Taiwan University, Taiwan, in 2006. He is presently an assistant professor of Computer Science and Information Engineering at Chaoyang University of Technology, where he initially joined in August 2006. He is currently an overseas member of the Institute of Electronics, Information and Communication Engineers (IEICE). His current research interests include computer simulation, computer networks routing protocol, wireless networks, Mobile Ad Hoc networks and sensor networks. Hsu-Chun Yen was born in Taiwan, Republic of China, on May 29, 1958. He received the B.S. degree in electrical engineering from National Taiwan University, Taiwan, in 1980, the M.S. degree in computer engineering from National Chiao-Tung University, Taiwan, in 1982, and the Ph.D. degree in computer science from the University of Texas at Austin, U.S.A., in 1986. He is presently a Professor of Electrical Engineering at National Taiwan University, where he initially joined in August 1990. From August 1986 to July 1990, he was an Assistant Professor of Computer Science at Iowa State University, Ames, Iowa, U.S.A. His current research interests include Petri net theory, formal methods, design and analysis of algorithms, and complexity theory. Dr. Yen is an editor of International Journal of Foundations of Computer Science (IJFCS, World Scientific Publisher).     

The mechanical stress resistance capability of stress buffer structures in analog devices

In this research, we showed that the different stress buffer configurations in the analog device will change the magnitude of the mechanical stress effect on the device surface, which will cause the variation in the output voltage characteristic of the device as well. And, the experimental results reveal that the different stress buffer configurations provide the difference of the mechanical stress resistance capability on the LDO (Low Drop Out) analog device. The stress buffer structure can reduce the stress effect to the LDO analog device effectively, i.e., the variation of the output voltage character of the LDO analog device will be larger if there is no stress buffer structure on the LDO analog device. Our results could be a reference for the design of an analog device and its packaging to improve the performance of the analog device.     

Location Awareness—Improving Distributed Multimedia Communication

Multimedia creation and consumption is highly intensive and makes up the majority of Internet traffic nowadays. End-users are able to share their digital content with each other and to build communities based on interests, which often differ drastically according to location. Distributing these media using a central server can be quite expensive for a content provider. Distributed (peer-to-peer like) systems share costs evenly among participants. Thus, distributed multimedia systems will be more important in the future. The global distribution of end-users aggravates high-quality delivery of multimedia content. In this paper, we argue that geographical location-awareness greatly helps distributed multimedia communication. It increases the quality of multimedia content delivery and at the same time satisfies the growing need for more personalized, location-based services. In this paper, as a proof of concept, we introduce an overlay structure for distributed multimedia systems (and similar systems), which is location-aware and uses the locations of its nodes to optimize node-to-node communication for performance and delay. At the same time, the system enables location-based services.     

Image capture: simulation of sensor responses from hyperspectralimages

This paper describes the design and performance of an image capture simulator. The general model underlying the simulator assumes that the image capture device contains multiple classes of sensors with different spectral sensitivities and that each sensor responds in a known way to irradiance over most of its operating range. The input to the simulator is a set of narrow-band images of the scene taken with a custom-designed hyperspectral camera system. The parameters for the simulator are the number of sensor classes, the sensor spectral sensitivities, the noise statistics and number of quantization levels for each sensor class, the spatial arrangement of the sensors and the exposure duration. The output of the simulator is the raw image data that would have been acquired by the simulated image capture device. To test the simulator, we acquired images of the same scene both with the hyperspectral camera and with a calibrated Kodak DCS-200 digital color camera. We used the simulator to predict the DCS-200 output from the hyperspectral data. The agreement between simulated and acquired images validated the image capture response model and our simulator implementation. We believe the simulator will provide a useful tool for understanding the effect of varying the design parameters of an image capture device.     

电子器件的失效分析

为了研究材料晶体形态与器件性能的关系及其形成机理，寻求提高器件质量的依据，利用显微设备、电子探针等对电子器件引脚可焊接性极差的失效现象进行了分析.     

An asymmetric post-processing for correspondence problem

This paper presents a novel approach that performs post-processing for stereo matching. We improve the performance of stereo matching by performing consistency check and adaptive filtering in an iterative filtering scheme. The consistency check is only done with asymmetric information so that very few additional computational loads are necessary. The information in the valid pixels is propagated into invalid pixels through the adaptive filtering. The proposed post-filtering method can be used in various methods for stereo matching. We demonstrate the validity of the proposed method by applying it to hierarchical belief propagation and semi-global matching. The performance of the post-processing method for hierarchical belief propagation is comparable to state-of-the-art methods in the Middlebury stereo datasets. In order to verify the performance of asymmetric consistency check, we compare it with other reliability estimation methods in the proposed post-processing scheme. Moreover, in order to verify the performance of post-filtering method in noisy environment, the proposed post-filtering method is applied to the stereo images denoised by NL-means algorithm. We find that the iterative filtering scheme reduce an error which may be caused in stereo matching for the denoised images and improve the performance of stereo matching.     

基于位置的流量经营实现方案分析

话音经营时代,运营商纷纷推出了分区话音计费业务.流量经营时代,基于位置的流量营销将具有更广阔的市场空间.本文基于运营商的智能网络架构,详细研究了基于位置的流量经营所需的网络侧关键技术:用户位置获取和基于位置的差异化计费,以期对运营商开展位置流量业务提供参考.     

Parametric manufacturing yield modeling of GaAs/AlGaAs multiplequantum well avalanche photodiodes

GaAs/AlGaAs multiple quantum well (MQW) avalanche photodiodes (APD's) are of interest as an ultra-low noise image capture mechanism for high-definition systems. Since literally millions of these devices must be fabricated for imaging arrays, it is critical to evaluate potential performance variations of individual devices in light of the realities of semiconductor manufacturing. Specifically, even in a defect-free manufacturing environment, random variations in the fabrication process will lead to varying levels of device performance, Accurate device performance prediction requires precise characterization of these variations. This paper presents a systematic methodology for modeling the parametric performance of GaAs MQW APD's. The approach described requires a model of the probability distribution of each of the relevant process variables, as well as a second model to account for the correlation between this measured process data and device performance metrics. The availability of these models enables the computation of the joint probability density function required for predicting performance using the Jacobian transformation method. The resulting density function can then be numerically integrated to determine parametric yield. Since they have demonstrated the capability of highly accurate function approximation and mapping of complex, nonlinear data sets, neural networks are proposed as the preferred tool for generating the models described above. In applying this methodology to MQW APD's, it is shown that using a small number of test devices with varying active diameters, barrier and well widths, and doping concentrations enables prediction of the expected performance variation of APD gain and noise in larger populations of devices. This approach compares favorably with Monte Carlo techniques and allows device yield prediction prior to high volume manufacturing in order to evaluate the impact of both design decisions and process capability     

A Comparative Analysis of Flat,Hierarchical and Location-Based Routing in Wireless Sensor Networks

In this article, we are going to discuss the comparison of three different categories of routing principles, namely, flat routing, hierarchical routing and location-based routing in Wireless Sensor Networks. Under the flat routing strategies, we are going to discuss 1-D flooding and 2-D flooding. Under the hierarchical category, we will explore spanning tree and under the location-based routing category, we will use angle-based dynamic path construction. For all these four algorithms, on the basis of a precise energy modelling and MAC layer modelling, comparison is made out on the basis of energy consumption and delay incurred for the transmission of data from the sensing nodes via the forwarding nodes and ultimately converging at the sink node. Also, retransmission probability, an important criterion, is taken into consideration and its effect on energy consumption and end-to-end delay is observed.     

一种Enlighten-GAN网络的指纹超分辨率重建方法北大核心CSCD

将低分辨率(LR)图像重建为高分辨率(HR)图像的主流模型是生成对抗网络(GAN)。然而,由于基于GAN的方法利用从其他图像中学习到的内容来恢复高频信息,在处理新的图像时往往会产生伪影。由于,指纹图像的特征比自然图像更加复杂。因此,将以前的网络应用于指纹图像,尤其是中等分辨率的图像,会导致收敛不稳定伪影效果更加严重。针对以上弊端,本文提出了一种Enlighten-GAN超分辨率方法,来解决指纹图像的重建问题。具体来说,我们设计了启发块来控制网络收敛到一个可靠的点,并利用自我监督分层感知损失以改进损失函数提升网络性能。实验结果证明Enlighten-GAN方法在指纹图像的重建效果性能上具有更加卓越的效果。     

An energy‐aware transmission mechanism for WiFi‐based mobile devices handling upload TCP traffic

This paper presents an energy‐aware transmission mechanism that improves the throughput and reduces the energy consumption of mobile devices in wired‐cum‐wireless TCP networks. The proposed mechanism places an agent at the base station, which identifies the cause of packet losses in the underlying network. When the mobile device acts as a TCP source, it adjusts the size of the congestion window adaptively according to the cause of packet losses with the aids of the agent in order to improve the transmission performance. In addition, the proposed mechanism lets the communication device to stay in sleep mode after completing the transmission in order to reduce the energy consumption. As a result, the cooperation between the mobile device and the agent improves the transmission performance as well as the energy efficiency greatly. To evaluate the performance of the proposed mechanism, we analyzed the effect of TCP on the communication device for mobile devices and present a power model. With extensive simulations based on the power model, we demonstrate that the proposed mechanism significantly improves the transmission performance, and reduces the energy consumption over a wide range of both wired and wireless packet losses. Copyright © 2008 John Wiley & Sons, Ltd.     

Quality measurement and use of pre-processing in image compression

Traditional quality measures for image coding, such as the peak signal-to-noise ratio, assume that the preservation of the original image is the desired goal. However, pre-processing images prior to encoding, designed to remove noise or unimportant detail, can improve the overall performance of an image coder. Objective image quality metrics obtained from the difference between the original and coded images cannot properly assess this improved performance. This paper proposes a new methodology for quality metrics that differentially weighs the changes in the image due to pre-processing and encoding. These new quality measures establish the value of pre-processing for image coding and quantitatively determine the performance improvement that can be thus achieved by JPEG and wavelet coders.     

Enhancing localization accuracy of collaborative cognitive radio users by internal noise mitigation

Location information of mobile primary users is one of the essential requirements for an underlay cognitive radio user to utilize the licensed spectrum efficiently. The performance of various location-based applications such as global navigation satellite system, device to device communication in dense urban 5G network also depends on the localization accuracy. In this paper, a collaborative localization scheme based on received signal strength has been proposed. The weighted centroid localization algorithm has been applied in the proposed network scenario to compute location coordinates of the mobile primary user. Since the channel noise effects are random and unavoidable, this paper has focused on the mitigation of the internal noise by designing a suitable reconfigurable FIR filter after the demodulator stage of a cognitive radio receiver circuit to improve precision of signal measurement during primary user localization. The localization error rate has come down to (1.3–1.62) % after internal noise mitigation. The enhancement in the localization accuracy improves the overall spectrum utilization efficiency and reduces the miss detection and false detection probabilities in the proposed underlay network.

     

Mining user preferences of new locations on location-based social networks: a multidimensional cloud model approach

In recent years, the prevalent of location-based social networks contributes massive data for location recommendation. Although collaborative filtering (CF) algorithm has been widely employed for location recommendation, it suffers the data sparsity and the high time complexity as it estimates the similarity of users by the common locations. In this paper, we extend the two-dimensional cloud model to the multidimensional cloud model and utilize it to the measure the similarity of user preferences and user behaviors. This method not only considers the multiple attributes of users (e.g., the diversity of user preferences), but also alleviates the sparsity of location recommendation based on CF algorithm to some extent. Then we integrate the similarity of user preferences, social ties and user behaviors into CF algorithm, which is expected to mine user preferences of new locations (MUPNL) more precisely. Furthermore, in order to improve the efficiency of the MUPNL algorithm, we parallelize it with Mapreduce framework. Experimental results on Yelp academic dataset demonstrate the good performance of the distributed MUPNL algorithm in accuracy and efficiency.     

基于监督对比学习正则化的高分辨率SAR图像建筑物提取方法

近年来,高分辨合成孔径雷达(SAR)图像的智能解译技术在城市规划、变化监测等方面得到了广泛应用.不同于光学图像,SAR图像的获取方式、图像中目标的几何结构等因素制约了现有深度学习方法对SAR图像地物目标的解译效果.该文针对高分辨SAR图像城市区域建筑物提取,提出了基于监督对比学习的正则化方法,其主要思想是增强同一类别像...     

Effective Phase-Shifter Cost as a Selection Criterion

In order to select a phase shifter for a given application, it is necessary to weigh a number of performance factors such that the device selected will result in the lowest overall system cost. This may be accomplished by defining an effective phase-shifter cost in terms of the initial cost of the phase shifter and driver, and dollar factors resulting from insertion loss, phase error, and quantization level.