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An orthogonal forward selection (OFS) algorithm based on leave-one-out (LOO) criteria is proposed for the construction of radial basis function (RBF) networks with tunable nodes. Each stage of the construction process determines an RBF node, namely, its center vector and diagonal covariance matrix, by minimizing the LOO statistics. For regression application, the LOO criterion is chosen to be the LOO mean-square error, while the LOO misclassification rate is adopted in two-class classification application. This OFS-LOO algorithm is computationally efficient, and it is capable of constructing parsimonious RBF networks that generalize well. Moreover, the proposed algorithm is fully automatic, and the user does not need to specify a termination criterion for the construction process. The effectiveness of the proposed RBF network construction procedure is demonstrated using examples taken from both regression and classification applications. Index Terms--Classification, leave-one-out (LOO) statistics, orthogonal forward selection (OFS), radial basis function (RBF) network, regression, tunable node.

This paper presents a method for creating orthoimage in the urban area of extremely high buildings. The proposed method in this paper is different from the traditional methods, which improved the accuracy by increasing the number and/or improved the geometric distribution of ground control points. This proposed method first established a mathematical model of constraint condition on the building edges, such as perpendicularity, and then the established constraint conditions are merged into the orthorectification model. A test field located in downtown of Denver, CO, has been used to evaluate our methods. The experiments of comparing the accuracy achieved by our method and other methods are conducted. The experimental results demonstrated that the proposed method can improve the accuracy of 2-5 ft for those buildings of over 100 m high and even 5-7 ft for those buildings over 100 m high in the margin of imagery. Index Terms--Image orientation analysis, image registration, orthogonal functions, rectifiers.

A general framework for the design of low complexity timing error detectors (TEDs) for orthogonal space-time block code (OSTBC) receivers is proposed. Specifically, we derive sufficient conditions for a difference-of-threshold-crossings timing error estimate to be robust to channel fading. General expressions for the S-curve, estimation error variance and the signal-to-noise ratio are also obtained. As the designed detectors inherently depend on the properties of the OSTBC under consideration, we derive and evaluate the properties of TEDs for a number of known codes. Simulations are used to assess the system performance with the proposed timing detectors incorporated into the receiver timing loop operating in tracking mode. While the theoretical derivations assume a receiver with perfect channel state information and symbol decisions, simulation results include performance for pilot-symbol-based channel estimation and data symbol detection errors. For the case of frequency-flat Rayleigh fading and QPSK modulation, symbol-error-rate results show timing synchronization loss of less than 0.3 dB for practical timing offsets. In addition it is shown that the receiver is able to track timing drift with a normalized bandwidth of up to 0.001. Index Terms--Synchronization, symbol timing estimation, timing error tracking, orthogonal space-time block coding.

A blind carrier phase synchronization algorithm is proposed for high-order M-ary quadrature amplitude modulation-orthogonal frequency division multiplexing (M-QAM-OFDM) systems, which has recovered residual frequency offset (RFO) in the presence of intercarrier interference (ICI). The studies have shown that the algorithm is superior to the conventional decision-directed (DD) scheme for high-order M-QAM-OFDM systems.

A new algorithm based on the properties of the orthogonal-frequency-division-multiplexing (OFDM) PSD for carrier tracking in OFDM is discussed. Results suggest the achievement of highly accurate frequency offset estimate.

A direct technique for collective evaluation of optimal Hermite-Gaussian-like eigenvectors of matrix F is discussed. Findings reveal that the proposed method is faster than the orthogonal procrustes algorithm (OPA).

A theoretical analysis of the whitened adaptive beamformer orthogonal rejection test (W-ABORT) detector is discussed for both matched and mismatched signals. Results reveal excellent mismatch signals rejection capabilities of W-ABORT.

A low-complexity partial transmit sequence (PTS) technique is described for reducing the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal. This new method has reduced the multiplicative complexity, while providing PAPR reduction that is similar to other methods such as original PTS (O-PTS), and has lower additive complexity.

A multichannel extension of ALLIANCES (ALLow Improved Access in the Network via Cooperation and Energy Savings) is described, which has exploited multipath diversity in addition to cooperation diversity. The relationship between achievable diversity and parameters such as collision order, number of relays, channel length and number of carriers per subchannel is analyzed.

A new carrier frequency offset (CFO) mitigation algorithm is described for multi-transmitter cooperative orthogonal frequency-division multiplexing (OFDM) transmissions. The algorithm is shown to be an efficient preprocessing procedure from the cooperative encoding/decoding details.

Orthogonal designs are developed with quaternion elements to be used as a basis for orthogonal space-time-polarization block codes.

This paper derives exact expressions for the average error performance of M-ary orthogonal signals with noncoherent equal-gain diversity combining over nonidentical generalized Rician, Nakagami-m, Nakagami-q, and implicitly Rayleigh fading channels. The assumption of generalized distributed fading envelopes implies that the received average signal-to-noise ratios (SNRs) and/or the fading parameters can have arbitrary nonidentical values. The derived expressions are precisely given in terms of either one-fold integral or rapidly convergent infinite series, which can be readily evaluated numerically. In addition, they can be usefully used to study the impact of arbitrary correlation among diversity branches on the system average error performance. Index Terms--M-ary orthogonal signals, noncoherent equal-gain combining, nonidentical fading channels.

A substantially better compressed sensing (CS) reconstruction performance with the basis pursuit (BP) and the orthogonal matching pursuit (OMP) algorithms is obtained after optimization of the choice of projection. The projections seem beneficial for BP and OMP with a reduction of the error rate by a factor of 10 and beyond.

A new generalized discrete multiwavelet transform (DMWT) structure is described in which the prefilter is embedded into the first stage of the transform. The findings suggest better performance and low computational complexity of the proposed DMWT structure on application to vector-based image coding applications.

This paper presents simple tight upper bound expressions for the average symbol error probability and bit error probability of coherent M-ary biorthugnnal signals over fading channels with diversity reception. The upper hounds, which do not involve numerical integration and are expressed with only elementary functions, can he efficiently evaluated. In addition, they are valid for different diversity-cumbining techniques, as well as for arhitrarily correlated and/or nonidentically distributed channels. The tightness of the derived upper bounds is clarified under various channel conditions. Numerical results are also provided to demonstrate the impact of nonidentical channels on the system average error performance. Index Terms--Average error performance, biorthogonal signals, diversity reception, fading channels.

Orthogonal space-time block coding (OSTBC) in multiple-antenna wireless systems has recently emerged as one of the most promising reliability-enhancing technologies for high-speed, high-quality data services. In this paper, we propose a technique to achieve joint channel estimation and symbol detection for OSTBC in frequency-selective fading channels. The key observation is that a multiple-input-single-output system, which is using OSTBC, can be transformed into an equivalent single-input-multiple-output system using the implicit redundancy in OSTBC. This allows a probabilistic method, known as the Baum-Welch algorithm, to be applied at each output branch. As each output branch is a function of the same input, redundant information may be exchanged between the multiple branches to improve detection performance. The proposed technique does not require multiple antennas at the receiver and only has moderate computational complexity. Furthermore, the Cramer-Rao lower bound (CRB) is also developed to facilitate performance analysis. Simulation results are provided to demonstrate the performance of the proposed algorithm. Index Terms--Channel estimation, Cramer-Rao lower bound (CRB), iterative receivers, orthogonai space-time block coding (OSTBC), symbol detection.

Due to its spectral efficiency and robustness over mulitipath channels, orthogonal frequency-division multiplexing (OFDM) has served as one of the major modulation schemes for high-speed communication systems. In the future, wireless OFDM systems are expected to operate at high carrier frequencies, high speed, and high throughput for mobile reception, where fast time-varying fading channels are encountered. Channel variation destroys the orthogonality among the subcarriers and leads to intercarrier interference (ICI). ICI poses a significant limitation on wireless OFDM systems. The aim of this paper is to find an efficient method of providing reliable communications using OFDM in fast time-varying fading channels. It is observed that ICI power arises from a few adjacent subcarriers. This observation motivates us to design low-complexity Q-tap ICI equalizers. To employ these equalizers, channel state information is also required. In this paper, we also design a pilot-aided minimum mean square error (MMSE) channel estimation scheme for a time-varying wide-sense stationary uncorrelated scatters channel model. The MMSE channel estimator utilizes the statistical channel properties to achieve computational efficiency. Simulation results show that our proposed low-complexity ICI suppression scheme, which incorporates the Q-tap equalizer with the MMSE channel estimator, can significantly improve the performance of OFDM systems in fast time-varying fading channels. Index Terms--Fading channels, intercarrier interference (ICI), minimum mean square error (MMSE), orthogonal frequency-division multiplexing (OFDM), Q-tap equalizer, wide-sense stationary uncorrelated scatters (WSSUS).

In this paper, we analyze from a geometric perspective the meaningful relations taking place between belief and probability functions in the framework of the geometric approach to the theory of evidence. Starting from the case of binary domains, we identify and study three major geometric entities relating a generic belief function (b.f.) to the set of probabilities P: 1) the dual line connecting belief and plausibility functions; 2) the orthogonal complement of P; and 3) the simplex of consistent probabilities. Each of them is in turn associated with a different probability measure that depends on the original b.f. We focus in particular on the geometry and properties of the orthogonal projection of a b.f. onto P and its intersection probability, provide their interpretations in terms of degrees of belief, and discuss their behavior with respect to affine combination. Index Terms--Bayesian belief functions (b.f.), commutativity, geometric approach, intersection probability, orthogonal projection, theory of evidence.

Linear phase requirements are relaxed and new sets of Walsh-like nonlinear phase binary orthogonal user codes are obtained for asynchronous and asynchronous spread spectrum multiuser communications. These new binary sets with good performance and flexible code lengths have helped in improving the spread spectrum multiplexing capabilities of future wireline and wireless code division multiple-access (CDMA) communications systems.

The performance of an approximately multiaccess interference (MAI)-free multiaccess precoded multiuser orthogonal frequency division multiplexing (PMU-OFDM) system in a mobile environment, where the channel response changes within one OFDM symbol due to the Doppler effect, is analyzed. The results have shown that the performance of PMU-OFDM is better than OFDMA in a mobile environment in terms of bit error probability (BEP) performance.

A novel approach is described for concurrent extraction of target range and Doppler information in radar systems. Based on the proposed orthogonal signal processing approach, the processing results have displayed the technical feasibility of implementing the signal processing scheme in radar systems consisting of orthogonal coding signals.

We address the problem of comparing sets of images for object recognition, where the sets may represent variations in an object's appearance due to changing camera pose and lighting conditions. Canonical Correlations (also known as principal or canonical angles), which can be thought of as the angles between two d-dimensional subspaces, have recently attracted attention for image set matching. Canonical correlations offer many benefits in accuracy, efficiency, and robustness compared to the two main classical methods: parametric distribution-based and nonparametric sample-based matching of sets. Here, this is first demonstrated experimentally for reasonably sized data sets using existing methods exploiting canonical correlations. Motivated by their proven effectiveness, a novel discriminative learning method over sets is proposed for set classification. Specifically, inspired by classical Linear Discriminant Analysis (LDA), we develop a linear discriminant function that maximizes the canonical correlations of within-class sets and minimizes the canonical correlations of between-class sets. Image sets transformed by the discriminant function are then compared by the canonical correlations. Classical orthogonal subspace method (OSM) is also investigated for the similar purpose and compared with the proposed method. The proposed method is evaluated on various object recognition problems using face image sets with arbitrary motion captured under different illuminations and image sets of 500 general objects taken at different views. The method is also applied to object category recognition using ETH-80 database. The proposed method is shown to outperform the state-of-the-art methods in terms of accuracy and efficiency. Index Terms--Object recognition, face recognition, image sets, canonical correlation, principal angles, canonical correlation analysis, linear discriminant analysis, orthogonal subspace method.

The study explains and describes the power law behavior that is exhibited by the operational rate-distortion (RD) functions of most of the natural images on being compressed with the state-of-the-art wavelet coders at moderately high rates.

The two-channel filter banks with directional vanishing moments (DVM) can easily annihilate information along a given direction and are widely being used in image approximation and denoising, as they provide better visual quality with less ringing artifacts.

An approach based on the empirical mode decomposition (EMD) technique and proper orthogonal decomposition is proposed to examine dynamic trends and phase relationships between key system signals from measured data. Drawing on the EMD approach, and the method of snapshots, a technique based on the notion of proper orthogonal modes, is used to express an ensemble of measured data as a linear combination of basis functions or modes. This approach improves the ability of the EMD technique to capture abrupt changes in the observed data. Analytical criteria to describe the energy relationships in the observed oscillations are derived and a physical interpretation of the system modes is suggested. It is shown that in addition to providing estimates of time dependent mode shapes, the analysis also provides a method to identify the modes with the most energy embedded in the underlying signals. The method is applied to conduct post-mortem analysis of measured data of a real event in northern Mexico and to transient stability data. Index Terms--Empirical eigen functions, inter-area oscillations, mode shape, phasor measurement units.

A technique, which is based on wavelets derived from a slant matrix of order 3, is proposed for displaying gray shades in root-mean-square responding displays. It is shown that it is not necessary to compute the orthogonal transform repeatedly and the number of time intervals to complete a cycle is 25% less than that of Haar wavelets.

The linear equalization of biorthogonal modulation (BOM) signals is analyzed and two blind adaptive equalization algorithms are proposed for BOM. The convergence properties of these algorithms are discussed and their performance is demonstrated with numerical simulations.

The main purpose of this paper is to describe a novel ultrasonic motor which is suitable for small information devices. With a bending mode of a bimorph structure having relatively large displacement, the input voltage and frequency could be reduced. The overall shape of the motor is very simple, so it could be manufactured and miniaturized with ease. From the simulated results, such as mode and harmonic analysis, resonance mode, operating frequency, and displacement are determined. Finally, the experimental results are compared with the simulated. Index Terms--Finite element analysis, orthogonal bimorph, ultrasonic motor.

The application of bit-interleaved coded modulation and iterative decoding (BICM-ID) in orthogonal-frequency-division-multiplexing (OFDM) systems with signal space diversity (SSD) over frequency-selective Rayleigh-fading channels is investigated. The results have shown that the best error performance of BICM-ID for OFDM with SSD can be achieved with low-complexity receiver, using optimal grouping and rotation matrix.

In this paper, a highly efficient blind band-edge filter-based technique is introduced for the estimation of carrier frequency offsets that are much larger than the subcarrier spacing in orthogonal-frequency-division-multiplexing (OFDM) systems. The proposed scheme is shown to have a high accuracy and an acquisition range that is much larger than the subcarrier spacing limitation inherent to other synchronization techniques. The performance of the proposed system as well as other well-referred techniques is assessed over additive white Gaussian noise and frequency-selective fading channels using different pulse shaping filters. Index Terms--Band-edge filters (BEFs), blind estimation, carrier frequency offset (CFO), orthogonal frequency division multiplexing (OFDM).

In this paper, we propose a robust space-time block coded (STBC)-based transmit diversity scheme with low decoding complexity against spatially transmit-correlated fading channels compared with the conventional STBC orthogonal frequency-division multiplexing (STBC-OFDM) schemes. The proposed scheme is comprised of Alamouti code for spatial diversity and a simple mapping process with subcarrier selection for frequency diversity. Proceeding from a detailed analysis of the rank and determinant of the channel correlation matrix, we present a proper subcarrier selection scheme satisfying the conditions for robustness against spatial transmit correlation. Furthermore, when the receiver employs a low-complexity decoder such as a zero-forcing decoder, the proposed scheme shows improved performance compared with the existing space-frequency coded OFDM schemes. Index Terms--Fourth-order diversity gain, space-time block coded orthogonal frequency-division multiplexing (STBC-OFDM), spatial transmit correlation.

Deliberate digital clipping is a simple and efficient way of controlling the peak-to-average power ratio of orthogonal frequency division multiplexing (OFDM) systems. However, a clipping is a nonlinear process that may lead to significant distortion and performance loss. An iterative time-domain decision-aided clipping compensation framework is proposed to mitigate the distortion caused by the intentional clipping with the additional constraint of out-of-band noise filtering, and it is compared with the existing frequency-domain scheme. It incorporates the simple additive distortion model and the minimum mean-square distortion (MMSD) model, with the options of hard and soft symbol estimation. Extensive simulation results are provided for the performance comparison among different schemes. The MMSD-distortion-model-based frequency-domain clipping compensation gives the best performance and is applied to scalable video transmission with a multiband OFDM. Simulations demonstrate an effective mitigation of the performance loss by the applied compensation algorithm. Index Terms--Digital clipping, iterative cancellation, iterative compensation, iterative reconstruction, multiband orthogonal frequency division multiplexing (OFDM), OFDM, scalable video.

Orthogonal-frequency-division-multiplexing (OFDM) techniques allow the transmission of high data rates over broadband radio channels subject to multipath fading without the need for powerful channel equalization. However, they are very sensitive to nonlinear effects due to the high peak-to-average power ratio (PAPR) owned by their transmitted signals. This paper proposes an efficient technique for reducing the PAPR of OFDM signals. The proposed technique is data-independent and, thus, does not require new processing and optimization for each transmitted OFDM block. The reduction in PAPR of the OFDM signal is obtained through a proper selection of a precoding scheme that distributes the power of each modulated symbol over the OFDM block. The obtained results show that this precoding scheme is an attractive solution to the PAPR problem of OFDM signals. It is shown, through computer simulations, that the PAPR of precoded OFDM signals approaches that of single-carrier signals. The good improvement in PAPR given by the present technique permits the reduction of the complexity and cost of the transmitter significantly. The precoding schemes also take advantage of the frequency variations of the communication channel and can provide considerable performance gain in fading-multipath channels. Index Terms--Bandwidth efficiency, diversity gain, fading multipath, low complexity, orthogonal-frequency-division-multiplexing (OFDM), peak-to-average power ratio (PAPR), power efficiency, precoding.

By combining multiple-input multiple-output (MIMO) communication with the orthogonal frequency division multiplexing (OFDM) modulation scheme, MIMO-OFDM systems can achieve high data rates over broadband wireless channels. In this paper, to provide a bandwidth-efficient solution for MIMO-OFDM channel estimation, we establish conditions for channel identifiability and present a blind channel estimation technique based on a subspace approach. The proposed method unifies and generalizes the existing subspace-based methods for blind channel estimation in single-input single-output OFDM systems to blind channel estimation for two different MIMO-OFDM systems distinguished according to the number of transmit and receive antennas. In particular, the proposed method obtains accurate channel estimation and fast convergence with insensitivity to overestimates of the true channel order. If virtual carriers (VCs) are available, the proposed method can work with no or insufficient cyclic prefix (CP), thereby potentially increasing channel utilization. Furthermore, it is shown under specific system conditions that the proposed method can be applied to MIMO-OFDM systems without CPs, regardless of the presence of VCs, and obtains an accurate channel estimate with a small number of OFDM symbols. Thus, this method improves the transmission bandwidth efficiency. Simulation results illustrate the mean-square error performance of the proposed method via numerical experiments. Index Terms--Blind channel estimation, cyclic prefix, multiple-input multiple-output (MIMO) system, orthogonal frequency division multiplexing (OFDM), subspace method, virtual carrier.

The possibility of predicting ocean-surface wind field a few days ahead from satellite scatterometer observations in the Arabian Sea has been explored in this paper. The prediction technique is based on a combination of empirical orthogonal function (EOF) analysis and genetic algorithm (GA). The space-time distributed satellite data (zonal or meridional wind field) have been decomposed into a set of spatial eigenmodes ranked by their temporal variance. The associated temporal amplitude functions have been used by the GA for carrying out forecasts with lead times varying from one to five days. The GA finds the analytical equations that best describe the behavior of the different temporal amplitude functions in the EOF decomposition. Later, the predicted wind field has been generated as a linear combination of the dominant spatial modes weighted by the corresponding predicted amplitudes. The technique has been tested using independent validation data sets. It has been further tested by comparing the forecast fields with buoy data. The performance of GA is comparable to that of persistence forecast for the first two days of forecast, while it is better than that of persistence for three- to five-day-ahead forecasts. Index Terms--Arabian Sea, empirical orthogonal function (EOF) analysis, forecasting ocean-surface wind, genetic algorithm (GA), QuikSCAT scatterometer.

An algorithm is presented for the construction of orthogonal Latin hypercubes along with the explanation of a method that improves the space-filling properties of the resultant Latin hypercubes at the expense of inducing small correlations between columns in the design matrix. These methods provide flexibility in fitting models for the Department of Defense analysts while exploring high-dimensional computer simulations.

A simple subspace-based blind channel estimation technique is developed for orthogonal frequency-division multiplexing (OFDM) system by using nonredundant linear block precoding. The presented technique is capable of implementing channel estimation even if the number of the transit antennas is greater than or equal to the number of the receive antennas.

The time-domain equalization for quasi-orthogonal space-timeblock codes (QO-STBC) is investigated by using the inherent quasi-orthogonality to design low-complexity receivers. The diversity gains are presented for the proposed scheme through pairwise error probability (PEP) derivation and analysis, which are confirmed by Monte Carlo simulations.

In this paper, we have investigated the design parameters for efficient stirring in reverberation chambers. We have measured the efficiency of the stirrer in terms of the lowest possible frequency for which it gives a certain number of uncorrelated samples. Rotating stirrers, when rotated about their axes, generate cylindrical volumes. The impact of a change of the stirrer diameter is approximately cubic compared with the change of the stirrer height. The efficiency of stirrers that are translated is proportional to the stepping increment and to the square root of the area of projection of the stirrer on a plane orthogonal to the direction of translation. Index Terms--Efficient stirring, mode stirring, reverberation chamber, uncorrelated samples.

Functional data can be clustered by plugging estimated regression coefficients from individual curves into the k-means algorithm. Clustering results can differ depending on how the curves are fit to the data. Estimating curves using different sets of basis functions corresponds to different linear transformations of the data. k-means clustering is not invariant to linear transformations of the data. The optimal linear transformation for clustering will stretch the distribution so that the primary direction of variability aligns with actual differences in the clusters. It is shown that clustering the raw data will often give results similar to clustering regression coefficients obtained using an orthogonal design matrix. Clustering functional data using an [L.sup.2] metric on function space can be achieved by clustering a suitable linear transformation of the regression coefficients. An example where depressed individuals are treated with an antidepressant is used for illustration. KEY WORDS: Allometric extension; Canonical discriminant analysis; Orthogonal design matrix; Principal component analysis.