Noise suppression characteristics of InP-based monolithically integrated guided wave balanced photodiodes

Measurements were made of the noise suppression and signal enhancement properties of dual In/sub 0.53/Ga/sub 0.47/As-InP metal-semiconductor-metal (MSM) photodiodes integrated with a leaky mode In/sub 0.52/Al/sub 0.48/As waveguide directional coupler, and an electro-optic phase shifter. The experiments were done with a 1.3- mu m laser as the local oscillator. A noise suppression of 11 dB and signal enhancement of 1.3 dB were recorded for the MSM photodiodes.<>     

An investigation on TCP large initial window

Transport layer implicates a position where satellite networks form one integrated component of hybrid Internet architecture in today's advance technology. However, the Internet has emerged with an important new class of applications that exhibits significant variations of transmission rate over time. Variable‐rate traffic poses a new challenge for transmission control protocol that provides congestion control, especially for applications that need to share the limited capacity of a bottleneck over a long delay Internet path (e.g. paths that include satellite links). Variable‐rate traffic can be produced by persistent transmission control protocol connections and can be impacted by the initial window at the start or during the restart of a session. Current transport research issues are identified related to larger initial window to highlight the expected performance benefits and derive the implications on the design of geostationary satellite Internet systems as the network evolves toward a next‐generation Internet. Copyright © 2013 John Wiley & Sons, Ltd.     

Fusion function placement for Active Networks paradigm in wireless sensor networks

Active Networks paradigm integrated with distributed data fusion has the potential to significantly reduce energy dissipation in wireless sensor networks, where energy conservation is the most challenging issue. This work aims to minimize energy cost when distributed data fusion is deployed for the Active Networks computing paradigm. First we propose an optimal solution for mapping task graph of distributed data fusion application into network. Optimal solution uses an exhaustive search algorithm for finding the placements with minimized power consumption. However, optimal solution has high computational complexity—O(mn ^k ), where n denotes the number of network nodes, m is the number of fusion functions, and k is the maximum number of children a fusion function has in task graph and its children are also fusion functions. Then, an approximate solution with low complexity (O(mlog n + log² m)) is proposed called P2lace, which includes two phases, task graph partition and task graph placement. Finally, an extensive evaluation compares approximate solution with optimal solution. The results show that approximate solution is scalable with different task graph characteristics and network size and only causes slightly more transmission cost than optimal solution. And the algorithm without optimizing is shown to be applicable to the network, where the sink node does not have global information of entire network.     

Elimination of truncation and round off error and enhancement of stability using a new split loop DPLL

In contrast with the conventional split loop digital phase lock loop, a new loop is presented in this paper that differs from the earlier version principally by design aspects. It incorporates an additional phase modulation input along with its frequency modulation input in the digital controlled oscillator. It is capable of eliminating the deleterious effects of rounding and truncation error with faster signal accusation. Higher loop stability is also achievable using the new split loop digital phase lock loop. Furthermore, radio frequency filtering is done using an In phase and Quadrature phase (IQ) voltage controlled oscillator to avoid interaction between the loop filter and the radio frequency filter. Copyright © 2011 John Wiley & Sons, Ltd.     

A networked mobile sensor test-bed for collaborative multi-target tracking applications

This paper presents the design, architecture, implementation, and experimental results from a networked mobile sensor test-bed developed for collaborative sensor tracking applications. The test-bed comprises a fleet of networked mobile sensors, an indoor localization system, a control, debugging and management infrastructure, and a tiered wireless ad hoc network for seamless integration of the above three components and the existing wireless infrastructure. First, the software and hardware architectural details of a swarm capable autonomous vehicle (SCAV) system for our collaborative applications are presented. Second, the details of an indoor self-localization and Kalman filter based navigation system design for the SCAV platform are presented. Third, as an example multi-sensor application, a collaborative multi-target tracking problem and a heuristics-based networked solution are formulated. Finally, the performance of the collaborative tracking framework is evaluated on the laboratory test-bed for characterizing the impacts of localization and navigation errors on the distributed tracking performance. The experimental study also characterizes the tradeoff between the tracking performance and the consumed wireless bandwidth. The experimental results demonstrate a number of counterintuitive results due to various errors in sensor localization and navigation.     

Retesting Defective Circuits to Allow Acceptable Faults for Yield Enhancement

Journal of Electronic Testing - Applications like Recognition, Mining, and Synthesis (RMS) with error-resilience properties can use circuits that produce acceptable results. In other words, the...     

Design and simulation of a novel GaN based resonant tunneling high electron mobility transistor on a silicon substrate

For the first time, we have introduced a novel GaN based resonant tunneling high electron mobility transistor (RTHEMT) on a silicon substrate. A monolithically integrated GaN based inverted high electron mobility transistor (HEMT) and a resonant tunneling diode (RTD) are designed and simulated using the ATLAS simulator and MATLAB in this study. The 10% Al composition in the barrier layer of the GaN based RTD structure provides a peak-to-valley current ratio of 2.66 which controls the GaN based HEMT performance. Thus the results indicate an improvement in the current-voltage characteristics of the RTHEMT by controlling the gate voltage in this structure. The introduction of silicon as a substrate is a unique step taken by us for this type of RTHEMT structure.     

A simple unsupervised MRF model based image segmentation approach

A simple technique has been suggested to obtain optimal segmentation based on tonal and textural characteristics of an image using the Markov random field (MRF) model. The technique takes an initially over segmented image as well as the original image as its inputs and defines an MRF over the region adjacency graph (RAG) of the initially segmented regions. A tonal-region based segmentation technique due to Kartikeyan and Sarkar (1989) has been used for initial segmentation. The energy function has been defined over the first order cliques of the MRF. The essence of this approach is primarily based on quantitative values of the second order statistics, on region characteristics and consequently deciding upon the action of merging neighboring regions using the F-statistic. The effectiveness of our approach is demonstrated with wide variety of real life examples viz., indoor, outdoor and satellite and a comparison of its output with that of a previous work in the literature has been provided.     

Health and wellness monitoring through wearable and ambient sensors: exemplars from home-based care of elderly with mild dementia

Monitoring and timely intervention are extremely important in the continuous management of health and wellness among all segments of the population, but particularly among those with mild dementia. In relation to this, we prescribe three design principles for the construction of services and applications. These are ambient intelligence, service continuity, and micro-context. In this paper, we provide three exemplars from our research and development activities that illustrate the use of these design principles in the construction of services and applications. All the applications are drawn from the field of care for mild dementia patients in their living quarters.