Effects of cell correlations in a matched-filter PN codeacquisition for direct-sequence spread-spectrum systems

Rapid pseudonoise (PN) code acquisition with matched-filter correlators has been very popular in direct-sequence (DS) spread-spectrum systems. Conventionally, the analysis of this acquisition method is based on the assumption that the detections among cells are independent. However, there may be strong correlations among cell detections for the case that the cell size is less than a chip duration. In this paper, the mean acquisition time performance of the acquisition method is analyzed with the cell correlations being taken into account. Numerical results show that depending on the threshold value and other system parameters, the effect of cell correlations may be over 20% of the mean acquisition time for signal-to-noise ratios (SNR) of practical interest. The analytical results are substantiated by computer simulations     

Fabrication of diamond micro-structures by ink-jet printed diamond seeding and microwave plasma assisted chemical vapor deposition

Ink-jet printing has the advantage of easy formation of micro-patterns on rigid as well as flexible surfaces without needing conventional lithographic processes. By means of printing in selected areas, diamond seeding in designed patterns and areas is achieved. Properly designed ink with a desirable composition helps the formation of patterned structures with tailored functions. Ink containing nano-diamond particles was designed and used to print micro-structures, which were applied for further CVD growth of diamond by means of microwave plasma CVD. Promising applications of this technique are discussed.     

Identification of a threshold value for the DEMATEL method using the maximum mean de-entropy algorithm to find critical services provided by a semiconductor intellectual property mall

To deal with complex problems, structuring them through graphical representations and analyzing causal influences can aid in illuminating complex issues, systems, or concepts. The DEMATEL method is a methodology which can confirm interdependence among variables and aid in the development of a chart to reflect interrelationships between variables, and can be used for researching and solving complicated and intertwined problem groups. The end product of the DEMATEL process is a visual representation—the impact-relations map—by which respondents organize their own actions in the world. In order to obtain a suitable impact-relations map, an appropriate threshold value is needed to obtain adequate information for further analysis and decision-making. In the existing literature, the threshold value has been determined through interviews with respondents or judged by the researcher. In most cases, it is hard and time-consuming to aggregate the respondents and make a consistent decision. In addition, in order to avoid subjective judgments, a theoretical method to select the threshold value is necessary. In this paper, we propose a method based on the entropy approach, the maximum mean de-entropy algorithm, to achieve this purpose. Using a real case to find the interrelationships between the services of a Semiconductor Intellectual Property Mall as an example, we will compare the results obtained from the respondents and from our method, and show that the impact-relations maps from these two methods could be the same.     

Channel Assignment and Hand-off Policies in Cluster-Based Micro/ Picocellular Wireless Networks

In this paper, we consider cluster-based micro/picocellular networks with overlapped cell-clusters. Channel assignment and hand-off policies are essential and important policies in cellular wireless networks. The issue of how different channel assignment and hand-off policies in the overlapped areas affect the overall system performance has not yet been studied in the literature. This paper provides a thorough study and understanding of this issue. We propose two cluster channel assignment policies, namely, partitioned and shared cluster channel assignment policies, and two hand-off policies, namely, boundary and early hand-off policies. The proposed cluster channel assignment policies and hand-off policies are combined to obtain three different strategies, namely, partitioned-boundary, partitioned-early, and shared-boundary strategies. Extensive simulations are used to study the performance of the strategies. Our results show that the partitioned-early and shared-boundary strategies produce significantly lower hand-off dropping and forced termination probabilities than the partitioned-boundary strategy. The partitioned-early and shared-boundary strategies yield similar performance.     

Modeling VOC Emissions in the High-Purity Oxygen Activated Sludge Process

Mass balances for volatile organic compounds (VOCs) were added to a structured mathematical model of the high-purity oxygen activated sludge (HPO-AS) process. The model was sized to correspond to two large existing HPO-AS treatment plants. The stripping of ten different VOCs was modeled and compared to stripping from conventional air activated sludge process. The results show that the covered aeration tanks can reduce stripping by more than 90%, depending on the specific VOC. If biodegradation is considered, the HPO-AS process degrades more than the conventional process due to the higher liquid-phase concentrations that result because of reduced stripping. The increase in biodegradation depends on the VOCs degradability but should increase to nearly 100% for highly volatile but biodegradable VOCs.     

A CPM-Based Construction Quality Inspection and Decision-Aid System

This article adopted the concept of decision support to establish a CPM-based construction quality inspection and decision-aid system (CQIDS) to improve ineffective field quality inspection processes. The system consists of two main subsystems: the database subsystem and the decision subsystem. The database subsystem contains information about quality specifications, shop drawings, checklists, and corrective actions that comprises a multimedia network. The decision subsystem contains statistical algorithms to facilitate in situ quality data analysis. Moreover, in order to execute quality management in a timely fashion, quality management timetables are generated automatically from the CQIDS and sent to field quality supervisors by integrating quality management activities within the project's own CPM network.     

Code-modulated path-sharing multi-antenna receivers: theory and analysis

Conventional multi-antenna receiver front-ends require multiple RF/baseband chains and analog-to-digital converters (ADC). This increases power consumption and chip area substantially. In this letter, we introduce a new Code-Modulated Path-Sharing Multi-Antenna (CPMA) receiver architecture suitable for any multi-antenna scheme including spatial multiplexing, spatial diversity, and beamforming. The receiver uses code modulation to distinguish the antenna signals before combining them in the analog domain. The combined signal propagates through shared-path blocks and all the original signals are later recovered in the digital domain for further processing. Due to the spread spectrum nature of code modulation, a larger bandwidth is needed for the blocks in the shared path. To alleviate this effect, the use of non-orthogonal coding is examined. An effective channel matrix is derived and the system capacity is evaluated in terms of the cross-correlation between signature codes. Implementation and code selection issues are discussed. Analysis and simulation results indicate that by properly selecting non-orthogonal code sets, the spreading factor, and therefore, the overall analog signal bandwidth is reduced while incurring minimal performance degradation.     

Improvement of CSO/CTB performances employing up-converted and polarization modulation techniques

A two-wavelength wavelength-division multiplexing (WDM) community antenna television (CATV) transport system that employed up-converted and polarization modulation techniques to reduce the composite second-order (CSO) distortion and optical nonlinearities is proposed and demonstrated. In contrast to a two-wavelength WDM CATV transport system using the intensity modulation technique, good performances of CSO and composite triple beat were obtained, accompanied by acceptable carrier-to-noise ratio value in our proposed system over a 100-km single-mode fiber transmission.     

Influence of number of simulated particles on DSMC modeling of micro-scale Rayleigh-Bénard flows

Two-dimensional micro-scale Rayleigh-Bénard flows are investigated numerically using direct simulation Monte Carlo method. An enclosure of length-to-height aspect ratio of AS = 4 is taken to explore the influence of initial setting of simulated molecules. The simulation domain is divided into 81 × 21 sampling cells and the range of Rayleigh number from 3000 to 10 000 corresponds to the convection state. Cases of 8, 10, 12, 14, 16 and 24 simulated particles in each collision cell are examined. It is shown that flow patterns with three-, four- or five-roll modes may appear depending on the number of simulated particles.     

Backhaul and Routing Assignments with End-to-End QoS Constraints for Wireless Mesh Networks

In scalable last-mile broadband networks such as wireless mesh networks (WMNs), quality-of-service (QoS) concerns are vital to multimedia applications such as video-conferencing and voice over IP (VoIP). Crucial decisions involve the number of backhauls that are to be deployed as well as the optimal assignment of paths and bandwidths. We focus on cost effectiveness and QoS requirements to develop a solution based on Lagrangean Relaxation and the subgradient method. Our approach satisfies QoS demands and minimizes costs more effectively than general algorithms, as demonstrated by our experimental results.