Assessment of organizational reliability capability

A reliability capability assessment process can assist OEMs and system integrators in assessing prospective suppliers for their ability to design and manufacture reliable products before they are delivered for use, and on an ongoing basis, help a company in identifying shortcomings in its reliability program, which can be rectified by subsequent improvement actions. The assessment can also help to establish reliability management practices for use by designers, suppliers, customers, and independent authorities. The assessment method may be used to evaluate the reliability capability of all types of electronics-related industries that perform activities influencing the reliability of a product. It can produce increased customer satisfaction, provide competitive opportunities, and shorten the product development cycle. In summary, a reliability capability assessment can be used for: 1) specifying or planning reliability practices if product development is implemented internally; 2) evaluating reliability practices to determine the extent to which a supplier is capable of providing a product that meets the reliability requirements/needs; and 3) improving reliability practices if the current reliability practices have been evaluated and improvement is desired or required.     

Designing a green optical network unit using ARMA-based traffic prediction for quality of service-aware traffic

The optical access networks (OANs) provide an attractive solution to the bandwidth bottleneck problem of the last mile. However, it has been proved (Baliga et al. in J Lightwave Technol 27(13):2391–2403, 2009; Baliga et al. in IEEE Commun Mag 49(6):70–77, 2011) that the OAN consumes a significant ratio of the total energy consumed in an optical networking scenario. This has provided incentive for inspection of energy-efficient schemes for OANs. It has been demonstrated in the literature that energy consumption figures of an OAN can be improved by either designing efficient hardware or employing better media access control (MAC) protocols. In this paper, we design a MAC protocol for OANs to ensure energy-efficiency in the presence of quality of service (QoS)-aware traffic. The proposed scheme incorporates traffic prediction-based selection of different sleep (energy-efficient) modes of operation, of the optical network units—ONUs (OAN end units). It also implements switching between different sleep modes to maintain high QoS with significant energy-efficiency figures. The discussed scheme requires processing at the ONU only and can work independent of the entire OAN (ONU assisted). Thus, our proposal is an attractive solution for the already deployed networks or even in green field deployment.     

EEFFL: energy efficient data forwarding for forest fire detection using localization technique in wireless sensor network

Wireless Networks - Early prediction of a forest fire is one of the critical research challenges of the wireless sensor network (WSN) to save our ecosystem. In WSN based forest fire detection...     

Vector Quantization Based QoS Classification for Admission Control in CDMA Systems

Optimal power control is of great importance for CDMA systems and it can be controlled to provide the desired quality of service (QoS) to mobile hosts in a cellular radio system. The power levels of all the mobile hosts are determined and constantly tuned in order to achieve the required SINR (signal to interference and noise ratio) which changes dynamically. The SINR of all the K mobiles in a cell can be expressed in the form of a k-dimensional vector. It helps determine the operating point of the system and hence it is constantly monitored and updated due to the variability in the wireless channel conditions and user mobility. We view this continuously changing vector as the motion of a point in a higher dimensional Euclidean space, called the QoS space. We apply vector quantization technique to shrink the infinite-point space to a finite-point space by partitioning the former into N regions such that the points within a region reflect almost similar system performance and are identified by what we call a QoS index. We show how the system operating point can be mapped to one of the QoS indices. The location of the point or the region of operability in the QoS space conveys the system status in terms of the current load and the QoS being delivered. The dynamism in the system's input conditions due to wireless link characteristics and user mobility acts like an opposing force against which the system has to operate. The system reacts to all such changes preventing it from going into a region with an undesirable QoS index. We show how the apriori knowledge of the operating region helps in decision making pertaining to call admission and resource allocation in CDMA systems. Mainak Chatterjee received his Ph.D. from the department of Computer Science and Engineering at the University of Texas at Arlington in 2002. Prior to that, he completed his B.Sc. with Physics (Hons) from the University of Calcutta in 1994 and M.E. in Electrical Communication Engineering from the Indian Institute of Science, Bangalore. He is currently an Assistant Professor in the department of Electrical and Computer Engineering at the University of Central Florida. His research interests include resource management and quality-of-service provisioning in wireless and cellular networks, sensor networks, CDMA data networking, media access control protocols, Internet traffic, and applied game theory. Sajal K. Das is a Professor of Computer Science and Engineering and also the Founding Director of the Center for Research in Wireless Mobility and Networking (CReWMaN) at the University of Texas at Arlington (UTA). His current research interests include resource and mobility management in wireless networks, mobile and pervasive computing, wireless multimedia and QoS provisioning, sensor networks, mobile Internet protocols, distributed processing and grid computing. He has published over 250 research papers, directed numerous funded projects, and holds 5 US patents in wireless mobile networks. He received the Best Paper Awards in ACM MobiCom'99, ICOIN-2001, ACM MSWIM-2000, and ACM/IEEE PADS'97. Dr. Das is also a recipeint of UTA's Outstanding Faculty Research Award in Computer Science in 2001 and 2003, and UTA's College of Engineering Excellence in Research Award in 2003. He serves on the Editorial Boards of IEEE Transactions on Mobile Computing, ACM/Kluwer Wireless Networks, Parallel Processing Letters, Journal of Parallel Algorithms and Applications. He served as General Chair of IEEE PerCom-2004, CIT-2003 and IEEE MASCOTS-2002; General Vice Chair of IEEE PerCom-2003, ACM MobiCom-2000 and HiPC 2000-01; General Chair of ACM WoWMoM 2000-02; Program Chair of IWDC-2002, WoWMoM 1998-99; TPC Vice Chair of ICPADS-2002; and as TPC member of numerous IEEE and ACM conferences. He is the Vice Chair of IEEE TCPP and TCCC. Prior to 1999, Dr. Das was a professor of computer science at Univeristy of North Texas where he twice (1991 and 1997) received the Student Association's Honor Professor Award for best teaching and scholarly research. He received B.Tech. degree in 1983 from Calcutta University, M.S. degree in 1984 from Indian Institute of Science, Bangalore, and PhD degree in 1988 from the University of Central Florida, Orlando, all in Computer Science.     

Sensitivity analysis of handoff algorithms on CDMA forward link

We analyze the performance of different handoff algorithms on the forward link or downlink of a code-division multiple-access (CDMA) cellular system. Unlike the reverse link, soft handoff on the forward link requires additional resources such as CDMA codes and transmit power and also causes additional interference. If handoff requests can be processed and completed instantaneously, transmission from the base station with the best link to the user would achieve a significant fraction of the macrodiversity gain without utilizing additional resources. However, in practical systems, there is a nonzero handoff completion delay and soft handoff provides the required robustness to delays, although it comes at the expense of additional network resources. Thus, there is a tradeoff between the extent of soft handoff required and the handoff execution delay. We compare the performance of hard and soft handoff schemes and study their sensitivity to the delay in the execution of the handoff. Outage probability and the total average power required are used as performance metrics. We present an analytical framework to study this tradeoff and also discuss simulation results with field data. The results provide insights on the conditions under which soft handoff can be eliminated and on the effect of relevant handoff thresholds on the performance.     

Highly coherent electronically tunable waveguide extended cavity diode laser

A frequency agile extended cavity diode laser using an integrated Bragg reflector in a Ti : Fe : LiNbO/sub 3/ waveguide is developed and characterized. The laser emits up to 7 mW in the 1.5-/spl mu/m telecommunication window. The emission spectrum exhibits a 18-kHz linewidth, >40-dB sidemode suppression ratio, and a wavelength stability of /spl plusmn/1 pm over hours. Very fast mode hop-free frequency tuning is achieved through the electrooptic effect, with a tuning slope of 55.5 MHz/V.     

Gecko‐Inspired Dry Adhesive for Robotic Applications

Most geckos can rapidly attach and detach from almost any kind of surface. This ability is attributed to the hierarchical structure of their feet (involving toe pads, setal arrays, and spatulae), and how they are moved (articulated) to generate strong adhesion and friction forces on gripping that rapidly relax on releasing. Inspired by the gecko's bioadhesive system, various structured surfaces have been fabricated suitable for robotic applications. In this study, x–y–z asymmetric, micrometer‐sized rectangular flaps composed of polydimethylsiloxane (PDMS) were fabricated using massively parallel micro‐electromechanical systems (MEMS) techniques with the intention of creating directionally responsive, high‐to‐low frictional‐adhesion toe pads exhibiting properties similar to those found in geckos. Using a surface forces apparatus (SFA), the friction and adhesion forces of both vertical (symmetric) and angled/tilted (x–y–z asymmetric) microflaps under various loading, unloading and shearing conditIons were investigated. It was found that the anisotropic structure of tilted microflaps gives very different adhesion and tribological forces when articulated along different x–y–z directions: high friction and adhesion forces when articulated in the y–z plane along the tilt (+y) direction, which is also the direction of motion, and weak friction and adhesion forces when articulated against the tilt (–y) direction. These results demonstrate that asymmetric angled structures, as occur in geckos, are required to enable the gecko to optimize the requirements of high friction and adhesion on gripping, and low frictional‐adhesion on releasing. These properties are intimately coupled to a (also optimum) articulation mechanism. We discuss how both of these features can be simultaneously optimized in the design of robotic systems that can mimic the gecko adhesive system.     

High Precision,Electrochemical Detection of Reversible Binding of Recombinant Proteins on Wide Bandgap GaN Electrodes Functionalized with Biomembrane Models

We report a novel hybrid charge sensor realized by the deposition of phospholipid monolayers on highly doped n‐GaN electrodes. To detect the binding of recombinant proteins with histidine‐tags, lipid vesicles containing chelator lipids were deposited on GaN electrodes pre‐coated with octadecyltrimethoxysilane monolayers. Owing to its optical transparency, GaN allows the confirmation of the fluidity of supported membranes by fluorescence recovery after photo‐bleaching (FRAP). The electrolyte‐(organic) insulator‐semiconductor (EIS) setup enables one to transduce variations in the surface charge density ΔQ into a change in the interface capacitance ΔC _p and, thus, the flat‐band potential ΔU _FB. The obtained results demonstrate that the membrane‐based charge sensor can reach a high sensitivity to detect reversible changes in the surface charge density on the membranes by the formation of chelator complexes, docking of eGFP with histidine tags, and cancellation by EDTA. The achievable resolution of ΔQ ≥ 0.1 μC/cm² is better than that obtained for membrane‐functionalized p‐GaAs, 0.9 μC/cm², and for ITO coated with a polymer supported lipid monolayer, 2.2 μC/cm². Moreover, we examined the potential application of optically active InGaN/GaN quantum dot structures, for the detection of changes in the surface potential from the photoluminescence signals measured at room temperature.     

Minimum symbol error rate multiuser detection using an effective invasive weed optimization for MIMO/SDMA–OFDM system

Space division multiple access–orthogonal frequency division multiplexing system has become a potential wireless communication system by offering high spectral efficiency, performance and capacity. This article deals with minimum symbol error rate (MSER)‐based multiuser detection (MUD) technique for the space division multiple access–orthogonal frequency division multiplexing system using an efficient invasive weed optimization (IWO) algorithm. The IWO algorithm is used for finding optimal weights such that the probability of error is directly minimized rather than minimizing the mean square error. Because of this, the MSER MUD is able to detect users even in overload scenario, where the number of users is more than the number of receiving antennas, unlike several classical detection techniques. The IWO is inspired from the nature of invasive colonization of weeds and relatively simple compared with other optimization techniques. The bit error rate performance of the proposed IWO‐aided MSER MUD is found to be better than minimum means square error and differential evolution algorithm‐aided MSER MUDs. Simulation results show that the proposed IWO MSER achieves faster convergence and lower complexity compared with the differential evolution MSER MUD. Copyright © 2013 John Wiley & Sons, Ltd.     

Design of efficient lightweight strategies to combat DoS attack in delay tolerant network routing

Delay tolerant networks (DTNs) are characterized by delay and intermittent connectivity. Satisfactory network functioning in a DTN relies heavily on co-ordination among participating nodes. However, in practice, such co-ordination cannot be taken for granted due to possible misbehaviour by relay nodes. Routing in a DTN is, therefore, vulnerable to various attacks, which adversely affect network performance. Several strategies have been proposed in the literature to alleviate such vulnerabilities—they vary widely in terms of throughput, detection time, overhead etc. One key challenge is to arrive at a tradeoff between detection time and overhead. We observe that the existing table-based reactive strategies to combat Denial-of-service (DoS) attacks in DTN suffer from two major drawbacks: high overhead and slow detection. In this paper, we propose three secure, light-weight and time-efficient routing algorithms for detecting DoS attacks (Blackhole and Grey-hole attacks) in the Spray & Focus routing protocol. The proposed algorithms are based on use of a small fraction of privileged (trusted) nodes. The first strategy, called TN, outperforms the existing table-based strategy with 20–30 % lesser detection time, 20–25 % higher malicious node detection and negligible overhead. The other two strategies, CTN_MI and CTN_RF explore the novel idea that trusted nodes are able to utilize each others’ information/experience using their long range connectivity as and when available. Simulations performed using an enhanced ONE simulator reveals that investing in enabling connectivity among trusted nodes (as in CTN_RF) can have significant performance benefits.