Current Issue : April - June Volume : 2015 Issue Number : 2 Articles : 8 Articles
Computation offloading is an effective way to alleviate the resource limited problem of mobile devices. However, the offloading is\nnot an always advantageous strategy for under some circumstances the overhead in time and energy may turn out to be greater\nthan the offloading savings. Therefore, an offloading decision scheme is in demand for mobile devices to decide whether to offload\na computation task to the server or to execute it in a local processor. In this paper, the offloading decision problem is translated into\na dynamic executionmode selection problem, the objective of which is to minimize the task execution delay and reduce the energy\nconsumption ofmobile devices. A novel executionmode adjustment mechanism is introduced to make the execution process more\nflexible for real-time environment variation. Numerical results indicate that the proposed scheme can significantly reduce the task\nexecution delay in an energy-efficient way....
In this paper we propose a high performance parallel strategy/technique to implement the fast direct solver based on hierarchical\nmatrices method. Our goal is to directly solve electromagnetic integral equations involving electric-large and geometrical-complex\ntargets, which are traditionally difficult to be solved by iterative methods. The parallel method of our direct solver features both\nOpenMP shared memory programming and MPl message passing for running on a computer cluster. With modifications to the\ncore direct-solving algorithm of hierarchical LUfactorization, the new fast solver is scalable for parallelized implementation despite\nof its sequential nature.The numerical experiments demonstrate the accuracy and efficiency of the proposed parallel direct solver\nfor analyzing electromagnetic scattering problems of complex 3D objects with nearly 4 million unknowns...
Microstrip antenna has gained the attention of the researchers for its many salient features. The present day is the age of wireless communication. The potential application of Microstrip Antenna (MSA) for the wireless and personal commutation is the hot topic of interest of the researchers around the globe. As per Microstrip Patch Antenna offer low profile, low cost and low volume. But inherently MPA have narrow bandwidth so to enhance bandwidth various techniques are engaged. This review paper shows some commonly engaged techniques to reduce return loss of Micro strip patch antenna....
As technology advances andmore demands are on satellite services, rain-induced attenuation still creates one of themost damaging\neffects of the atmosphere on the quality of radio communication signals, especially those operating above 10GHz. System designers\ntherefore require statistical information on rain-induced attenuation over the coverage area in order to determine the appropriate\ntransmitter and receiver characteristics to be adopted. This paper presents results on the time-varying rain characterization and\ndiurnal variation of slant path rain attenuation in the Ka-band frequency simulated with synthetic storm techniques over a\nsubtropical location in South Africa using 10-year rain rate time-series data. The analysis is based on the CDF of one-minute\nrain rate; time-series seasonal variation of rain rate observed over four time intervals: 00:00ââ?¬â??06:00, 06:00ââ?¬â??12:00, 12:00ââ?¬â??18:00, and\n18:00ââ?¬â??24:00; diurnal fades margin; and diurnal variation of rain attenuation. Comparison was also made between the synthesized\nvalues and measured attenuation data. The predicted statistics are in good agreement with those obtained from the propagation\nbeacon measurement in the area. The overall results will be needed for an acceptable planning that can effectively reduce the fade\nmargin to a very low value for an optimum data communication over this area....
A modified method for the beam tilt-angle estimation of monopole end-fire array mounted on finite ground plane is proposed. In\nthe simplified model, the monopole array and ground plane are approximated to two line sources of transverse and longitudinal\nelectric current, respectively. It is deduced that the beamtilt angle is a function about the length of ground plane in front of array La????,\nthe length of monopole array Lg, and the phase constant ??. After verifying the optimizing principle of monopole end-fire array,\na 10-element monopole Yagi-Uda antenna satisfying Hansen-Woodyard condition is designed and measured for the analysis. By\ncomparison and analysis, the value of ?? is demonstrated to be the key point of the proposed method. And a slow wave monopole\narray is proved to be able to achieve a low beam tilt angle from end-fire with only a short-length ground plane....
Two designs of frequency triplers, which use planar transitions as baluns and an anti parallel diode pair to achieve wide bandwidth,\nare presented.The ultra wide band transitions are utilized for input and output impedance matching of the frequency triplers.The\ndesign process and operation principles are described in this paper. The implemented frequency triplers exhibit flat response over\nwide frequency range of 3 to 9GHz. The proposed Type A frequency tripler shows conversion loss of ?18 dB with above 30 dB even\nharmonics suppression.With Type B frequency tripler, conversion loss of ?17 dB and above 25 dB even harmonic suppression are\nachieved....
In this paper software based design and analysis has been carried out for a rectangular microstrip patch antenna using three different shapes of substrate materials. Three individual microstrip antennas are designed and compared. A rectangular patch (11.86 mm x 9.06 mm) mounted on three different substrate shapes like square, rectangular and circular. All design uses Roger RT/Duriod 5880 substrate material. The designed antennas are analyzed by finite element method (FEM) based HFSSTM EM simulator software. The designed antennas have applications in X-Band (8-12 GHz). The results of three antennas are compared in terms of return loss, VSWR and return loss bandwidth at particular frequency....
Low SNR condition has been a big challenge in the face of distributed compressive sensing MIMO radar (DCS-MIMO radar) and\nnoise in measurements would decrease performance of radar system. In this paper, we first devise the scheme of DCS-MIMO\nradar including the joint sparse basis and the joint measurement matrix. Joint orthogonal matching pursuit (JOMP) algorithm is\nproposed to recover sparse targets scene.We then derive a recovery stability guarantee by employing the average coherence of the\nsensing matrix, further reducing the least amount of measurements which are necessary for stable recovery of the sparse scene in\nthe presence of noise. Numerical results show that this scheme of DCS-MIMO radar could estimate targets� parameters accurately\nand demonstrate that the proposed stability guarantee could further reduce the amount of data to be transferred and processed.We\nalso show the phase transitions diagram of the DCS-MIMO radar system in simulations, pointing out the problem to be further\nsolved in our future work....
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