In this letter, we analyze the performance of limited feedback beamforming in a distributed antenna system. We propose a novel codebook design scheme to maximize a lower bound of the averaged effective signal-to-noise ratio (SNR), which is a function of the power of the signal and noise, the number of antennas, and the number of total feedback bits for characterizing the quantized channel vector. Simulations verify that the proposed scheme can provide effective capacity improvement.

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A useful optimization problem to help solve various base station layout problems in multihop wireless networks is formulated. By solving the proposed generalized formula, the relation between the permissible largest number of hops and the minimum base station density necessary to cover an entire service area while guaranteeing a specified QoS is easily calculated. Our formula is extendable to other allocation problems by replacing parameters. The energy-cost transformation and scope of the multihop effect are also presented.

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This letter reports a high-performance Ka-band equilateral triangular microstrip patch (ETMP) antenna suspended on a thin dielectric membrane. The membrane is released using a silicon bulk-micromachining technique. A set of closed-form expressions to calculate the resonant frequency of the proposed antenna on the micromachined substrate is also presented. The measured performance of the antenna structure is verified using the finite element method (FEM) based Agilent High Frequency Structure Simulator (version 5.5). The fabricated antenna exhibited a wide -10dB return loss bandwidth of 1.2GHz at 35.4GHz. The measured antenna cross-polarization level is less than -15dB in both the E- and H-planes.

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Spatial filtering is a useful method to suppress undesired reflection from unwanted scatters in Radar Cross Section (RCS) measurements. Actually, it is difficult to prepare an ideal field which satisfies the far-field criterion for RCS measurements of large targets. We applied the filtering method to a bistatic RCS measurement in a near field and investigated the validity of that method by varying the scanning angular span. Electromagnetic simulations show that predicted RCS profiles from near-field data with unwanted scatters closely matched far-field reference data of the test target. In conclusion, the results show that the method is effective for bistatic RCS measurements in practical field enviroments.

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A new unsupervised classification method is proposed for polarimetric SAR images to keep the spatial coherence of pixels and edges of different kinds of targets simultaneously. We consider the label scale variability of images by combining Inhomogeneous Markov Random Field (MRF) and Bayes' theorem. After minimizing an energy function using an expansion algorithm based on Graph Cuts, we can obtain classification results that are discontinuity preserving. Using a NASA/JPL AIRSAR image, we demonstrate the effectiveness of the proposed method.

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A C-band polarimetric radar on Okinawa Island successfully observed large-scale bird migrations over the western Pacific Ocean. The birds generated interesting polarimetric signatures. This paper describes the signatures and speculates bird behavior.

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In this letter, we propose effective feature vectors to improve the performance of voice activity detection (VAD) employing a support vector machine (SVM), which is known to incorporate an optimized nonlinear decision over two different classes. To extract the effective feature vectors, we present a novel scheme that combines the a posteriori SNR, a priori SNR, and predicted SNR, widely adopted in conventional statistical model-based VAD.

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A new sinusoidal modeling approach for the analysis-by-synthesis (AbS) of parameters that characterize a linear combination of damped sinusoids is proposed. In addition to the typical sinusoidal parameters, two different damping factors, which represent the time-varying nature of speech, were used to efficiently reduce the modeling error. Even though the proposed model does not employ the overlap-adding synthesis or smoothly interpolative synthesis scheme, it shows substantially better modeling performance in the synthesis of voiced and transient segments.

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