Scanning of sector and cosecant beams generated by a circular aperture

A method of scanning a one-dimensional shaped pattern generated by a circular aperture is presented. It is shown that the desired beam shape can be retained in the desired scan plane by superposing on the nonlinear phase distribution applied along and parallel to the meridian plane, a linear phase progression along the perpendicular direction. Analysis carried out using the stationary phase method of evaluating the integral reveals that the gradient of the linear phase progression is a function of position along the meridian plane of the aperture. Expressions for the phase functions are derived. Computed results on the phase distribution and the radiation pattern are presented.     

Routing Correlated Data in Wireless Sensor Networks: A Survey

Sensory data gathered from sensor nodes in physical proximity tend to exhibit strong correlation. To minimize such redundancy and hence curtail the load in wireless sensor networks with a goal to conserve energy, effective in-network fusion schemes have been extensively proposed in the literature. To this end, routing schemes supporting data fusion are extremely important as they dictate where and when sensory data streams shall intersect with each other and thus fusion will be performed. In this article we briefly articulate this problem and classify recently proposed routing schemes supporting data fusion in wireless sensor networks into three categories: routing-driven, coding-driven, and fusion-driven. We also give an overview of various algorithms in each category by summarizing their design approaches, benefits, and drawbacks.     

A Distance Based Communication Mode Selection Mechanism for M2M Communications Over Cellular Networks

The implementation of machine-to-machine (M2M) communications in fifth-generation (5G) cellular networks can facilitate with several benefits like enhancement of bandwidth utilization, accommodating large number of users and decreasing traffic load on evolved node B (eNB). Integration of location information of unknown machine in communication mode selection mechanism is the key feature of this research. In this paper, a distance based communication mode selection mechanism using non-orthogonal resource sharing scheme is adopted in the proposed system model. Under the proposed mechanism, the expressions of throughput and RBs utilization policy are derived, which are the key parameters to evaluate the performance in the proposed network. Depending on the mode selection condition, such as threshold distance and threshold SINR between M2M users and regular cellular users, a UE can automatically choose its communication mode in the network. It is supposed that selection of mode before data transfer can improve the system performance. On the other hand, designing of efficient distance assisted proposed resource blocks (RBs) utilization policy reduces the traffic load on the eNB. Extensive simulations are carried out for evaluating the performance of the proposed mechanisms. The system performance is compared with various changeable parameters, such as throughput, mode selection threshold SINR, threshold distance and RBs. Besides, the proposed mechanism provides better network performance as well as reduces the traffic load in the proposed network.

     

Capacitance of dielectric coated cylinder of finite axial lengthand truncated cone isolated in free space

The capacitance of dielectric coated metallic cylinder and truncated cone are evaluated using the method of moments based on the pulse function and point matching. The analysis is based on the boundary condition for the potential on the conductor surface and the normal component of the displacement density at the dielectric-free space interface. The total free charge on the conductor surface is found from the inversion of a matrix partitioned into submatrices. Numerical data on the capacitance and charge distribution are presented     

Effect of Lead-Free Soldering on Key Material Properties of FR-4 Printed Circuit Board Laminates

The transition to lead-free soldering of printed circuit boards (PCBs) using solder alloys such as SnAgCu has resulted in higher temperature exposures during assembly compared with eutectic SnPb solders. The knowledge of PCB laminate material properties and their dependence on the material constituents, combined with their possible variations due to lead-free soldering temperature exposures, is an essential input in the laminate selection process. This paper provides laminate selection guidelines that were arrived at by assessing key material properties (glass transition temperature, coefficient of thermal expansion, decomposition temperature, and water absorption), and their responses to lead-free soldering assembly conditions. A range of commercially available FR-4 PCB laminate materials, classified on the basis of glass transition temperature (high, mid, and low), curing agents (dicyandiamide and phenolic), flame retardants (halogenated and halogen-free), and fillers (presence or absence) were studied. The laminate material properties under investigation were measured as per the IPC-TM-650 test methods before and after exposure to multiple lead-free soldering cycles. Combinatorial property analysis was conducted to investigate the causes behind variations in material properties.     

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.     

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.