Dual band microstrip patch antenna for MIMO system

This work targets design of microstrip patch antenna that will resonate at two different band of frequencies which can be used as elements of array for MIMO system. The proposed dual band antenna operates at ISM band (2.37Ghz-2.48Ghz) and Wimax band (3.46 GHz-3.56 GHz).Bandwidth of operation offered by the given microstrip antenna in ISM band is around 110 Mhz while in Wimax band is 110 Mhz.

The designed dual band antenna was optimized using simulation tool CAD-FEKO_v6.2 which works on Method of Moments. Antenna was manufactured on FR4 substrate having εr= 4.4.The results obtained from simulating antenna with the help of simulation software matches with results of manufactured antenna obtained from Antritsu vector network analyzer.

Nonmechanical Laser Beam Steering Based on Polymer Polarization Gratings: Design Optimization and Demonstration

We present a wide-angle, nonmechanical laser beam steerer based on polymer polarization gratings with an optimal design approach for maximizing field-of-regard ($F!O!R$ ). The steering design offers exponential scaling of the number of steering angles, called suprabinary steering. The design approach can be easily adapted for any 1-D or 2-D (e.g., symmetric or asymmetric FOR) beam steering. We simulate a system using a finite difference and ray tracing tools and fabricate coarse beam steerer with 65$^{circ}$ $F!O!R$ with $sim$ 8$^{circ}$ resolution at 1550 nm.

We demonstrate high optical throughput (84$%$ –87$%$) that can be substantially improved by optimizing substrates and electrode materials. This beam steerer can achieve very low sidelobes and supports comparatively large beam diameters paired with a very thin assembly and low beam walk-off. We also demonstrate using a certain type of LC variable retarder that the total switching time from any steering angle to another can be 1.7 ms or better.

RF performance of InGaAs-based T-gate junctionless field-effect transistors which applicable for high frequency network systems

The T-gate InGaAs-based JLFET’s which has high frequency RF characteristics have been demonstrated by TCAD tool. To achieve advanced performance of RF characteristics, the T-gate structure is applied, also. By T-gate structure we decrease gate resistance (RG) and achieve a higher maximum oscillation frequency (fmax) compare with planar-type structure.

However, the increase of parasitic gate capacitance degrades current gain cut-off frequency (fT) and this trade-off between parasitic components and optimal device structure will be discussed.

An Improved Empirical Model for Retrieving Bottom Reflectance in Optically Shallow Water

Satellite remote sensing has become an essential observing system to obtain comprehensive information on the status of coastal habitats. However, a significant challenge in remote sensing of optically shallow water is to correct the effects of the water column. This challenge becomes particularly difficult due to the spatial and temporal variability of water optical properties. In order to model the light distribution for optically shallow water and retrieve the bottom reflectance, a parameterized model was proposed by introducing an important adjusted factor g. The synthetic data sets generated by HYDROLIGHT were utilized to train a neural network (NN) and then to derive the adjustable parameter values. The parameter g was found to vary with water depth, water optical properties, and bottom reflectance. Specifically, it revealed two obvious patterns among the different benthic habitat types.

In coral reef, seagrass, and macrophyte habitats, g exhibited a remarkable peak at about 550 nm. The peak has a value of about 2.47-2.49. In white sand or hardpan habitats, g spectra are relatively flat. The semi-empirical model was applied to calculate the bottom reflectance from the new weighting factor, the downward diffuse attenuation coefficient, and the irradiance reflectance just below the sea surface collected in Sanya Bay in 2008 and 2009. Good agreement between the predicted and measured values demonstrated that the weighting factor g is an effective tool to modify the model for interpreting and predicting bottom reflectance without the need for any localized input (R2 > 0.79).

Tropospheric scintillation estimation using 10 years meteorological data

This paper presents estimation of tropospheric scintillation based on ITU-R model from previous 10 years meteorological data. Scintillation As(p) is critical in designing of microwave links for achieving optimal performance. There are many phenomenons that cause degradation to signal during transmission through the earth’s atmosphere one of them is scintillation.

Scintillation estimation is based on measurements of surface temperature T and relative humidity RH. Input parameter for ITU-R scintillation estimation model is the monthly average of wet part of refractivity Nwet. MATLAB software tool is employed to show the results for tropospheric scintillation in various seasons for time percentage p and frequencies ranging from 4GHz to 20GHz.

Recent open source wireless sensor network supporting simulators: A performance comparison

Any common methodology for functionality research in the field of communication systems engineering is network simulation. There is always the overriding worry when utilizing simulation that the results may not reflect appropriate behavior. Therefore, it is important to recognize the particular strengths and also flaws of such simulators. There are a variety of network simulators, as an illustration, NS-2, NS-3, OMNET++, SWAN, OPNET, Jist, and also GloMoSiM and so forth.

As a result, the selection of any network simulator for assessing investigation function is really a critical activity for researchers. The leading emphasis in this research is usually to examine the particular advanced, open source network simulators based on the parameters, CPU usage, memory usage, computational time period, and also scalibility by simulating a wireless sensor network routing protocol, to identify a best network simulator to the investigation area.

How Tangential Problems Limit Value Creation in IT-Based Service Systems

Service systems create value through interactions among people and technology. Though information technology (IT), such as those that support electronic commerce, are key resources in IT-based service systems, it is the people in the system, the computer system administrators, who play the most critical role in making these systems work. In our ethnographic studies of IT service delivery, we found that system administrators typically spend much time troubleshooting. We observed that while configuration and performance work is often guided by explicit procedures or plans, troubleshooting work is not. Problems are handled case-by-case.

Our observations also reveal that a substantial fraction of time spent troubleshooting is on issues related only tangentially to the primary problem. These tangential problems divert time and energy from the primary problem. Although tangential problems tax the overall service system, there may be opportunities to identify and remediate them to improve overall service delivery and value co-creation.

Proportional Sharing in Distributed Dynamic Spectrum Access-Based Networks

Dynamic spectrum access (DSA) is a promising technology to alleviate the exhaustion of spectral resources. To realize DSA, new technologies that enable fast discovery of the unused spectrum along with efficient spectrum management must be developed. In this paper, we propose a novel scanning algorithm and access etiquette to provide secondary devices differentiated spectrum access in a fully distributed manner.

The proposed solution does not use any common control channel or require any a prior knowledge of primary devices’ usage pattern. More importantly, hardware limitation such as imperfect sensing or lack of strict synchronization between secondary devices are taken into account in our design. A mathematical model and an Opnet-based implementation are also developed to evaluate the performance of the proposed solution in DSA networks.

Analytic Performance Model for State-Based MAC Layer Cooperative Retransmission Protocols

Cooperative retransmission can significantly improve link reliability over lossy and time-varying wireless links. However, comparing retransmission protocols is challenging, and generally requires simplistic assumptions specific to each protocol. In this paper, we develop a general model to evaluate cooperative retransmission protocols with distributed, slot-based contention algorithms. Specifically, we propose to calculate the relay time-out probabilities at a MAC time-slot scale, formulate retransmission outcomes as functions of the time-out probabilities, and derive the probability of a retransmission process for every data frame.

We also propose a Markov extension of our model to characterise the dependency between retransmissions of multiple frames. This enables our model to analyse continuous retransmissions of successive frames. Validated by QualNet simulations, our model can analytically predict the probabilities of cooperative retransmissions with an accuracy of 1%. As a result, direct comparisons between cooperative retransmission protocols become tangible, without implementing the full protocol in a state-based simulator.

OPART: Towards an Open Platform for Abstraction of real-time communication in cross-domain applications

Developing real-time communication in various application fields such as robotics, factory automation, etc. is one the most important steps achieving a deterministic system. However, the development of this step is very complex and requires low level and advanced knowledge about the real-timecommunication systems. This complexity decelerates the developing process specially in cross-domain applications e.g. surgical control applications in Networked Medical Systems (NMS) requiring real-time communication and deterministic system behavior.

General complexities developing real-timecommunication systems are classified. The architecture of an Open Platform for Abstraction of Real-Time Communication (OPART) is introduced for reducing these complexities. The architecture of OPART is based on the Ethernet-based real-time communication protocol openPOWERLINK. An experimental setup of OPART using a medical sensor and actuator is demonstrated.