REV Journal on Electronics and Communications
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Band Selection for Hyperspectral Images Using Non-Negativity Constraints
Get PDFThis paper presents a new factorization technique for hyperspectral signal processing based on a constrained singular value decomposition (SVD) approach. Hyperpectral images typically have a large number of contiguous bands that are highly correlated. Likewise the field of view typically contains a limited number of materials and the spectra are also correlated. Only a selected number of bands, the extreme bands that include the dominant materials spectral signatures, are needed to express the data. Factorization can provide a means for interpretation and compression of the spectral data. Hyperspectral images are represented as non-negative matrices by graphic concatenation, with the pixels arranged into columns and each row corresponding to a spectral band. SVD and principal component analysis enjoy a broad range of applications, including, rank estimation, noise reduction, classification and compression, with the resulting singular vectors forming orthogonal basis sets for subspace projection techniques. A key property of non-negative matrices is that their columns/rows form non-negative cones, with any non-negative linear combination of the columns/rows belonging to the cone. Data sets of spectral images and time series reside in non-negative orthants and while subspaces spanned by SVD include all orthants, SVD projections can be constrained to the non-negative orthants. In this paper we utilize constraint sets that confine projections of SVD singular vectors to lie within the cones formed by the spectral data. The extreme vectors of the cone are found and these vectors form a basis for the factorization of the data. The approach is illustrated in an application to hyperspectral data of a mining area collected by an airborne sensor
Efficient Image Watermarking Using Filtered DWT-Blocks for Quantization of Significant Differences
Get PDFIn the paper, a robust blind watermarking method is introduced for gray-scale images based on wavelet tree quantization with an adaptive threshold in the extraction. Every block of 2×2 coefficients of High-Low subbands of the Wavelet tranform are grouped in a block through the parent-child relationship of the wavelet tree. Every scrambled binary watermark bit is embedded into each block based on the difference value of two largest coefficients. The watermark is recovered by comparing the difference values in each block to an adaptive threshold. The accuracy of an extracted watermark depends on the threshold which is determined by minimizing the sum of weighted within-class variance. The performance of the proposed watermarking method is represented through experimental results under various types of attack such as, Histogram Equalization, Cropping, Low-pass Filtering, Gaussian noise, Salt & Pepper noise and JPEG compression. In additions, the proposed method is also compared to recent methods in the extraction performance
Geographic-based Routing in Smart Grid’s Neighbor Area Networks
Get PDFNeighbor area network (NAN), also known as smart meter communication network, is one of the most important segments of smart grid communications network (SGCN). This paper studies the performance of greedy perimeter stateless routing (GPSR), a representative implementation of geographic-based routing class, in the NAN scenario and investigates the feasibility of this routing protocol in supporting SG applications. Specifically, packet transmission delay and reliability of GPSR in an IEEE 802.15.4-based wireless mesh NAN with practical system parameters are measured by simulations. The results show that, at the data rate required for conventional SG applications including smart metering, real-time pricing and demand response, the delay can always be maintained below 70 ms (in 95th-percentile perspective) while packet delivery ratio is higher than 90%. However, due to that fact that more advanced applications that require information exchange at higher rates and more stringent delays are emerging in SG, the performance of GPSR in NAN scenarios using radio technologies that can support higher loads and/or larger network scales needs to be studied
Noncoherent Receiver for Decode-and-Forward Cooperative Systems with Multi-Antenna Equipped Destination
Get PDFThis paper studies a maximum energy selection receiver for an adaptive decode-and-forward (DF) cooperative wireless system with multiple-antenna equipped destination. In particular, the destination selects the maximum output from all the outputs of the square-law detectors to perform the detection of the transmitted information. A close-form expression for the bit-error-rate (BER) is analytically derived when the system is deployed with binary frequency-shift keying (BFSK) modulation. The thresholds used at the relays to address the issue of error propagation are optimized to minimize the BER. While finding the optimal thresholds requires information on the average signal-to-noise ratios (SNRs) of all the transmission links in the system, the approximate thresholds at each relay that require only information on the average SNR of the source-corresponding relay are investigated. It is also derived that the system achieves a full diversity order with the approximate thresholds. Finally, both analytical and simulation results are provided to verify our analysis
An Improved White Space Prediction Algorithm for Cognitive Radio Systems
Get PDFCognitive radio (CR) is a promising technology to enhance the current low usage of limited frequency resources. TV white space (TVWS) - TV bands at a particular time in a particular geographic area that are not being used by licensed services - is perceived as the most suitable frequency bands for CR. This paper proposes a new prediction TVWS algorithm for CR systems based on the ITU 1546.1 and the Okumura-Hata models. The proposed algorithm is verified with the data of 22 provinces in the South of Vietnam. The numerical results confirm the advantage of the proposed algorithm as well as the possibility of TVWS CR networks
High Performance Direction Finding Algorithm Based on Phase Locked Loop
Get PDFUsing Phase Locked Loop based single channel Direction Finding (DF) system to estimate the bearing angle or the coordinates of an incoming radio signal(s) has much more advantages than multiple receiver system does in many practical scenarios such as mobile communication. This method utilizes a bank of Phase Locked Loops (PLLs) to calculate the differential phase of signal received by an M-element uniform circular antenna array with a commutative switch followed by single channel Software Defined Radio (SDR) receiver. One important factor when using conventional phase locked loop is the requirement of the small convergence rate of the algorithm compared to the switching cycle. In order to achieve small convergence rate, we propose a method for DOA estimation with low computation complexity that improves significantly the performance of conventional PLLs system. An analysis of the challenges of computation complexity in this algorithm is presented. The simulation results for DOA estimation using the proposed structure with low complexity are shown to verify the performance of the system
Group Scheduling for MultiChannel in OBS Networks
Get PDFGroup scheduling is a scheduling operation of optical burst switching networks in which the burst header packets arriving in each timeslot will schedule their following bursts simultaneously. There have been many proposals for group scheduling (such as OBS-GS, MWIS-OS and LGS), but they consider mainly to schedule the arriving bursts which have the same wavelength on an output data channel. Another suggestion is GreedyOPT which considers the group scheduling for multichannel with the support of full wavelength converters, but it is not optimal. This article proposes another approach of group scheduling which is more optimal and has a linear complexity
Analysis and Simulation of MRC Diversity Reception in Correlated Composite Nakagami-Lognormal Fading Channels
Get PDFThe physical meaning of the composite Nakagami-lognormal fading model is not well understood by many researchers using the model. The signal power transfer and transform at the interface between the global lognormal shadowing sub-channels and the local Nakagami multipath sub-channels in the presence of correlation between these diversity sub-channels is rather complex. This is the main reason why a thorough analysis or a simulation model is absent to date for the case of correlated composite Nakagami-lognormal diversity channels. This paper presents a novel technique for the estimation of the probability density function (PDF) of the signal-to-noise (SNR) at the output of a maximum ratio combining (MRC) receiver operating in correlated composite diversity fading channels. The PDF is estimated using the recently proposed two-point lossless moment generating function (MGF) matching technique and a closed-form expression for the bit-error rate (BER) for QPSK signal is consequently presented using the Gauss-Hermite polynomial approximation. The paper also presents the complex Monte-Carlo simulation model for the MRC reception and BER counting in correlated composite Nakagami-lognormal fading channels
A Novel Non-Stationary Channel Model Utilizing Brownian Random Paths
Get PDFThis paper proposes a non-stationary channel model in which real-time dynamics of the mobile station (MS) are taken into account. We utilize Brownian motion (BM) processes to model targeted and non-targeted dynamics of the MS. The proposed trajectory model consists of both drift and random components to capture both targeted and non-targeted motions of the MS. The Brownian trajectory model is then employed to provide a non-stationary channel model, in which the scattering effects of the propagation area are modelled by a non-centred one-ring geometric scattering model. The starting point of the motion is a fixed point in the propagation environment, whereas its terminating point is a random point along a predetermined drift. The drift component can be controlled by a so-called drift parameter. Tracking the MS on the proposed Brownian path allows us to derive the local angles-of-arrival (AOAs) and local angles-of-motion (AOMs), which are expressed by stochastic processes rather than random variables. We compute the first-order densities of the AOA and AOM processes in closed form. The local power spectral density (PSD) of the Doppler frequencies and the autocorrelation function (ACF) of the complex channel gain are also provided. Given a walking speed scenario, the analytical results are demonstrated and explained in depth. It turns out that the proposed Brownian path model results in a non-stationary non-isotropic channel model. The proposed geometry-based channel model is very useful for the performance analysis of mobile communication systems under non-stationary conditions