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Orthogonal frequency-division multiplexing (OFDM) is one of the most successful digital communication techniques. Nevertheless, the decrease in inter-symbol interference in quadrature amplitude modulation (QAM) over dispersive channels is still challenging. Different researches recently proposed the idea of using unsupervised learning as an alternative to the classic approaches to equalization of OFDM channels. In those purposes, the identification of a received QAM symbol is possible by the comparison of its position on the in-phase/quadrature (IQ) plane relative to the positions of previously arrived symbols, generally processed by the Kohonen’s Self-Organizing Map (SOM) algorithm. This work presents the SOM unsupervised learning method executed on an embedded system applied to QAM symbols identification. The system is implemented on an FPGA, a configurable digital circuit able to meet the low power and parallel process requirements of mobile applications. Also, in order to extend the classical set of experiments to evaluate our system, this paper proposes a theoretical model of the time-varying scheme representing the transition between different channel characteristics, obtained from real measurements available on a public repository. The model is employed to verify our purpose under dynamically both changing and realistic conditions. On the assumption that it is provided enough IQ symbols for the initial training process, the hardware implementation of SOM is able to track and identify the time-varying distorted QAM constellation. No knowledge of channel characteristics is necessary. The system spends only some microseconds at start-up to reach about 100% performance, and no dedicated training phase is needed afterward. [ABSTRACT FROM AUTHOR]

A challenging issue in photoacoustic biomedical imaging is to take into account the presence of dispersive acoustic media, since these are prone to induce amplitude attenuation and scattering of the photoacoustic frequency components. These perturbations are largely the cause for which the photoacoustic tomographic image reconstruction from projections lacks a plane-wave transport formalism. Attending this problem, we further develop an analytic formalism of the transport and its numerical implementation accounting for dispersive acoustic media. We differentiate three variations of an acoustically perturbing media. Our object of interest is a numerical description of the light absorption map of a coronal human breast image. Then, we analyze conditions for which the propagation of photoacoustic perturbations can obey the generalized Heaviside telegraph equation. In addition, we provide a study of the causality consistency of the wave propagation models. We observe transport implications due to the presence of dispersive acoustic media and derive model adjustments that include attenuation and diffusion approximations within the two-dimensional forward problem. Next, we restore the inverse problem description with the deduced perturbation components. Finally, we solve the nonlinear inverse problem with a numerical strategy for a filtered backprojection reconstruction. At a stage prior to the image reconstruction, we compensate for the effect of acoustic attenuation and diffusion to calculate the inversions of the wave perturbations located within the projections. In this way, we manage to significantly reduce reconstruction artifacts. In consequence, we prevent the use of some additional image processing of noise reduction. We demonstrate a feasible strategy on how to solve the stated nonlinear inverse problem of photoacoustic tomography accounting for dispersive acoustic media. In particular, we emphasize efforts to achieve an analytical description, and thus an algorithm is placed, for imaged sound perturbations to be cleaned from acoustic scattering in a simplified manner. [ABSTRACT FROM AUTHOR]

Filter bank multicarrier (FBMC) has emerged as the favourite multicarrier communication technique since it meets the demands of the next-generation standards, especially for communication under doubly dispersive channels. In order to combat the undesirable channel effects like inter symbol interference and inter carrier interference, the prototype filters used in FBMC systems must satisfy orthogonality conditions and be well localized simultaneously in both time and frequency domains. Even though conventional doubly localized filters are optimum in the absence of channel, they fail to satisfy orthogonality and localization criteria under doubly dispersive channels. In the present study, an adaptive filter design method is proposed in which the prototype filter is designed as the weighted sum of a time-limited Nyquist filter, a band-limited Nyquist filter, and doubly localized Gaussian filter based on the analysis of discrete ambiguity function (DAF). The filter is designed to vary its characteristics according to the maximum time and frequency domain dispersions of the channel, so that signal-to-interference ratio is maximized. In order to ensure distortion-less transmission, the perfect reconstruction criterion for distortion-less transmission is mapped to specific conditions for DAF according to two-dimensional channel scattering function. The superiority in performance of the proposed adaptive filter is analysed in terms of signal-tointerference ratio and bit error rate, and is compared with the conventional filters for various channel scattering conditions. [ABSTRACT FROM AUTHOR]

Rigorous justification is presented for a recently introduced method to construct leaky-mode expansions of electromagnetic fields excited inside a spherical cavity filled with a dispersive, lossy medium. In a departure from the traditional approaches, our construction does not rely on Green’s functions, rather it starts from a judiciously chosen auxiliary meromorphic function. Convergence of both the series expansions and of the over-completeness relations for the leaky modes is proven for a realistic model of chromatic dispersion. [ABSTRACT FROM AUTHOR]

A hybrid 2-D and 3-D discontinuous Garlerkin time-domain (DGTD) method is proposed for transient analysis of multiple arbitrarily shaped antipads in a dispersive parallel-plate pair. In the proposed hybrid method, the domains where only the zeroth-order parallel-plate mode exists are modeled by the 2-D DGTD, and the remaining domains are modeled by the 3-D DGTD. Each element is independent with others, thus easily parallelizable. Because higher order modes will propagate in the parallel-plate pair, the spatial domain decomposition should be time-dependent. For domain decomposition criterion at time step \text t\text {n} , the electromagnetic field distribution at the previous time step \text t\text {n-1} is analyzed to identify the zeroth-order parallel mode domain. Compared with the classical static distance criterion, this new adaptive criterion makes the approximation error under control, thus enhancing the stability. The accuracy and flexibility of the hybrid method have been validated by comparison with commercial software. Its enhancement of efficiency and stability is also demonstrated. [ABSTRACT FROM AUTHOR]

Millimeter wave (mmWave) communications use large transmission bandwidth and experience severe propagation conditions. This forces the communication system to operate in the so-called wideband regime, where signals must be increasingly “peaky” in order to attain a large fraction of the peak unconstrained wideband capacity. This paper investigates the capacity of the noncoherent channels as a function of bandwidth for signals with average and peak power constraints operating in the millimeter spectrum. Upper and lower bounds on capacity are provided, and the impact of features peculiar to mmWave channels is investigated. Numerical results for a scenario based on recent experimental campaigns are provided. It is shown that the rate achievable by a typical user in a mmWave cell with “non-peaky” signaling can be bounded away from the peak unconstrained wideband capacity. This suggests to reconsider the role of signaling “peakedness” in future mmWave communications. [ABSTRACT FROM PUBLISHER]

In this work, we exploit the space/time duality in optics to implement a temporal lenticular lens allowing to simultaneously sample and magnify an arbitrary-shaped optical signal. More specifically, by applying a sinusoidal phase-modulation, the signal under test is propagated through a discrete dispersive element that samples and magnifies its initial waveform. Thanks to this temporal lenticular lens, optical sampling associated to an intensity magnification factor of 3.6 is experimentally demonstrated at a repetition rate of 10 GHz. [ABSTRACT FROM AUTHOR]

In this paper, we perform numerical analysis about the influence of the wavelength dependence of birefringence (WDB) in the Supercontinuum (SC) and dispersive wave (DW) generation. We study different birefringence profiles such as constant, linear, and parabolic. We see that, for a linear and parabolic profile, the generation of SC practically does not change, while this does so when the constant value of the birefringence varies. Similar situation happens with the generation of dispersive waves. In addition, we observe that the broadband of the SC increases when the Stimulated Raman Scattering (SRS) is neglected for all WDB profiles. [ABSTRACT FROM AUTHOR]

This paper presents dispersive optical solitons that are governed by the Schrödinger–Hirota equation (SHe) with power law nonlinearity. Optical solitons and solitary wave solutions are sought for the SHe with power law nonlinearity in the sense of the Bäcklund transformation. Some general and specific solitons of the SHe are obtained in this work. [ABSTRACT FROM AUTHOR]

This paper presents a novel formulation for dispersive media computation in finite-difference time-domain (FDTD). Motivated by conventional recursive convolution (RC) methods in handling convolution integral, the method name quadratic RC (QRC) makes improvement in the approximation of electric field in convolution integral. The electric field is approximated by quadratic function determined by the fields at three time steps at current, next and former. Via quadratic interpolation, the convolution integral result is approximated by the linear combination of three electric fields, rather than two fields in trapezoidal RC (TRC) or piecewise linear RC (PLRC) and one field in constant RC (CRC). Because three electric fields are required for the convolution integral, the method needs two more back level storage of the electric fields to fulfill the recursion process. Numerical demonstrations of Debye and Drude slab's transmission and reflection coefficients demonstrate the efficiency and accuracy of the novel method. [ABSTRACT FROM AUTHOR]

This paper proposes a new prototype filter design method based on the time-frequency constellation for filter bank multicarrier (FBMC) systems in highly doubly dispersive channels. Maximal spectral efficiency, complex orthogonality and a well-localised pulse shaping in time and frequency domains are three criteria in the prototype filter design. Satisfying these criteria simultaneously is a challenging issue in the FBMC system design. In order to meet these criteria as much as possible, we consider an FBMC system in which the complex-valued data symbols are transmitted via a selected time-frequency constellation with maximal spectral efficiency. Based on the selected constellation and channel statistic properties, the prototype filter is designed by maximising a new utility function called signal to weighted interference ratio (SWIR), which is defined according to the channel time and frequency dispersions. Because the SWIR is a nonlinear utility function, its maximisation is not straightforward. In this paper, for prototype filter design, a reliable, robust and fast converging algorithm called evolutionary cooperatively coevolving particle swarm optimisation is used to maximise the SWIR. The FBMC system, which uses the proposed prototype filter design method, can be combined with the MIMO techniques efficiently because of its capability of sending complex-valued symbols. Simulation results show that the performance and bandwidth efficiency of the proposed method are superior to those of other techniques, for both cases of single antenna and multiple antennas, in highly doubly dispersive channels. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The problem of influence maximization in social networks has attracted much attention. However, traditional centrality indices are suitable for the case where a single spreader is chosen as the spreading source. Many times, spreading process is initiated by simultaneously choosing multiple nodes as the spreading sources. In this situation, choosing the top ranked nodes as multiple spreaders is not an optimal strategy, since the chosen nodes are not sufficiently scattered in networks. Therefore, one ideal situation for multiple spreaders case is that the spreaders themselves are not only influential but also they are dispersively distributed in networks, but it is difficult to meet the two conditions together. In this paper, we propose a heuristic clustering (HC) algorithm based on the similarity index to classify nodes into different clusters, and finally the center nodes in clusters are chosen as the multiple spreaders. HC algorithm not only ensures that the multiple spreaders are dispersively distributed in networks but also avoids the selected nodes to be very “negligible”. Compared with the traditional methods, our experimental results on synthetic and real networks indicate that the performance of HC method on influence maximization is more significant. [ABSTRACT FROM AUTHOR]

ABSTRACT Retrodirectivity and invisibility are two opposite concepts in the radar context. The former looks for an evident identification, while the latter aims to remain unnoticed. Here, we present a new structure based on inverted conical surfaces to provide both effects depending on the conical aperture value: 90° for retrodirective applications and 120° for invisible and Wi-Fi/Li-Fi applications. Results of the study carried out to confirm the behavior of the two structures are also presented, including measurements to compare performance with commercial prototypes in the case of retrodirectivity. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2570-2577, 2016 [ABSTRACT FROM AUTHOR]

Linear prediction methods, based on a Hankel data matrix, suffer from subspace leakage and degraded resolution when applied to data models that do not result in a mode matrix with Vandermonde structure, such as the constant- Q model. In the absence of noise, the Vandermonde structure ensures the equivalence between the number of backscattered signals and the rank of the data matrix. This paper first identifies the origin of subspace leakage residing in subspace-based and linear prediction methods when applied to data of the constant- Q model. Second, it proposes a frequency-distortion technique, based on the extension theorems, for suppressing the leakage and preserving the time resolution performance of these methods. The effectiveness of the distortion technique is then demonstrated on GPR simulated data by extending the damped MUSIC algorithm to the joint parameter estimation of the constant- Q model. [ABSTRACT FROM AUTHOR]

A general closed-form representation is introduced for representing the isofrequency dispersion curve (IDC) of an anisotropic, spatially, and frequency dispersive metasurface (MTS) constituted by a dense periodic texture of metallic elements printed on a grounded substrate. The formulation is restricted to printed elements isolated from each other (namely, patches and not slots) whose geometry exhibits at least two axes of symmetry. The expression is valid for the dominant TM surface wave (SW) until the limit of the Floquet–Bloch (FB) region and generalizes our previous formulation to arbitrary direction of propagation. This generalization permits a closed-form representation of the IDCs and of the group velocity as a function of two parameters only; these are the equivalent quasi-static capacitances along the symmetry directions of the geometry. The limit of validity of the closed-form representation has been defined and the formulation has been tested by full-wave analysis. The present formulation simplifies the design of MTS antennas and flat transformation optics devices. [ABSTRACT FROM PUBLISHER]

In this paper, we consider joint beamforming, power, and channel allocation in a multiuser and multichannel underlay multiple-input–single-output (MISO) cognitive radio network (CRN). In this system, the primary users' spectrum can be reused by secondary-user transmitters (SU-TXs) to maximize spectrum utilization, whereas intrauser interference is minimized by implementing beamforming at each SU-TX. After formulating the joint optimization problem as a nonconvex mixed-integer nonlinear programming problem, we propose a solution that consists of two stages. In the first stage, a feasible solution for power allocation and beamforming vectors is derived under a given channel allocation by converting the original problem into a convex form with an introduced optimal auxiliary variable and a semidefinite relaxation approach. In the second stage, two explicit searching algorithms, i.e., genetic algorithm (GA) and simulated annealing (SA)-based algorithm, are proposed to determine suboptimal channel allocations. Simulation results show that the beamforming and power and channel allocation with SA algorithm can achieve a close-to-optimal sum rate while having lower computational complexity compared with the beamforming and power and channel allocation with the GA algorithm. Furthermore, our proposed allocation scheme has significant improvement in achievable sum rate compared with the existing zero-forcing beamforming. [ABSTRACT FROM AUTHOR]

Adaptive time-domain equalizer (TDE) is an important module for digital optical coherent receivers. From an implementation perspective, we analyze and compare in detail the effects of error signal feedback delay on the convergence performance of TDE using either least-mean square (LMS) or constant modulus algorithm (CMA). For this purpose, a simplified theoretical model is proposed based on which iterative equations on the mean value and the variance of the tap coefficient are derived with or without error signal feedback delay for both LMS- and CMA-based methods for the first time. The analytical results show that decreased step size has to be used for TDE to converge and a slower convergence speed cannot be avoided as the feedback delay increases. Compared with the data-aided LMS-based method, the CMA-based method has a slower convergence speed and larger variation after convergence. Similar results are confirmed using numerical simulations for fiber dispersive channels. As the step size increases, a feedback delay of 20 clock cycles might cause the TDE to diverge. Compared with the CMA-based method, the LMS-based method has a higher tolerance on the feedback delay and allows a larger step size for a faster convergence speed. [ABSTRACT FROM AUTHOR]

Breathtaking innovations in optical imaging have opened new exciting avenues for science, industry, and medicine over the last few decades. One of such innovations is optical time-stretch imaging--an emerging method for ultrafast optical imaging that builds on temporally stretching broadband pulses by using dispersive properties of light in both spatial and temporal domains. It achieves continuous image acquisition at an ultrahigh frame rate of 10-1000 million frames per second by overcoming technical and fundamental limitations that exist in traditional imaging methods. By virtue of its inherent affinity with optical signal processing, optical time-stretch imaging can be combined with various optical techniques such as amplification, nonlinear processing, compressive sensing, and pattern correlation to realize unique capabilities that are not possible with the traditional imaging methods. Applications enabled by such capabilities are versatile and include surface inspection, surface vibrometry, particle analysis, and cell screening. In this paper, we review the principles and limitations of conventional optical imaging, the principles and applications of optical time-stretch imaging, and discuss our future perspective. [ABSTRACT FROM AUTHOR]

In this paper, we propose a broadband single-carrier (SC) spatial modulation (SM)-based multiple-input–multiple-output (MIMO) architecture relying on a soft decision (SoD) frequency-domain equalization (FDE) receiver. We demonstrate that conventional orthogonal-frequency-division-multiplexing (OFDM)-based broadband transmissions are not readily suitable for the single-radio-frequency-assisted SM-MIMO schemes since this scheme exhibits no substantial performance advantage over single-antenna transmissions. To circumvent this limitation, a low-complexity SoD FDE algorithm based on the minimum mean square error (MMSE) criterion is invoked for our broadband SC-based SM-MIMO scheme, which is capable of operating in a strongly dispersive channel having a long channel impulse response at moderate decoding complexity. Furthermore, our SoD FDE attains a near-capacity performance with the aid of a three-stage concatenated SC-based SM architecture. [ABSTRACT FROM PUBLISHER]

This paper studies the second-order coding rates for memoryless channels with a state sequence known non-causally at the encoder. In the case of finite alphabets, an achievability result is obtained using constant-composition random coding, and by using a small fraction of the block to transmit the empirical distribution of the state sequence. For error probabilities less than 0.5, it is shown that the second-order rate improves on an existing one based on independent and identically distributed random coding. In the Gaussian case (dirty paper coding) with an almost-sure power constraint, an achievability result is obtained using random coding over the surface of a sphere, and using a small fraction of the block to transmit a quantized description of the state power. It is shown that the second-order asymptotics are identical to the single-user Gaussian channel of the same input power without a state. [ABSTRACT FROM AUTHOR]

The reflection, transmission, and absorption coefficients of Terahertz wave from one dimensional stratified media containing dispersive single walled carbon nanotubes (SWCNTs) are presented with the propagation matrix method. Firstly, the propagation matrix for the whole stratified media slab is obtained by applying electromagnetic waves in each stratified media to the boundary conditions of continuous tangential fields. The reflection and transmission coefficients are got by solving the propagation matrix expressed in the matrix recursion form. Then the accuracy of the propagation matrix method is verified by comparing with numerical results of the Finite-Difference Time-Domain method in reference. The effects to reflection and transmission coefficients of stratified media containing SWCNTs caused by the working frequency, thickness of SWCNTs and silicon dioxide substrate are investigated in detail. [ABSTRACT FROM AUTHOR]

Vehicular Ad hoc NETworks (VANETs) belong to a class of complex networks due to constant addition and deletion of nodes. Stimulating cooperation in these networks is a research challenge due to this uncertainty. The reason is that the node behavior is highly influenced by the neighborhood structure. Game theory has been significantly used to model ad hoc networks and optimize cooperation. However, in vehicular interactions, apart from the individual node behavior, networking properties play a vital role in the evolution of cooperation. This paper presents a public goods game (PGG) group interaction model for vehicular networks. We analyze how networking properties can impact the diffusion of cooperation. Simulation results show that higher network connectivity induces higher clustering in the network. This influences the probability of nodes receiving common packets from the neighborhood. The average path length proportional to clustering impacts the benefit sharing in the neighborhood. Results show that cooperation diffusion in these networks cannot be forced but evolves with different networking conditions. [ABSTRACT FROM PUBLISHER]

It is widely recognized that orthogonal frequency division multiplexing (OFDM) signals are very prone to nonlinear distortion effects, which can lead to significant performance degradation. However, recent results have showed that nonlinear distortion effects do not necessarily mean performance degradation and can actually lead to performance improvements relative to conventional linear OFDM schemes. In this paper, we consider the effects of bandpass memoryless nonlinear devices on OFDM signals and study the optimum asymptotic performance for both nondispersive channels and severely time-dispersive channels. We present analytical methods for obtaining the Euclidean distance between two OFDM signals that are subjected to different nonlinear characteristics. These results are then employed for obtaining the average asymptotic gain relative to conventional linear OFDM schemes in nondispersive channels and the gain distribution for severely time-dispersive channels with Rayleigh-distributed fading on the different multipath components. Our analytical results, which are shown to be very accurate, indicate that the optimum detection of OFDM schemes with strong nonlinear distortion effects allows significant gains when compared with conventional linear OFDM schemes. [ABSTRACT FROM PUBLISHER]

We report on peer-to-peer (ground-based) wireless channel characteristics for an urban environment in two public-safety bands. Results were based upon measurements taken in Denver in June 2009. The public-safety bands we investigated were the 700 MHz and 4.9 GHz bands, both planned for public-safety and ?emergency-responder? applications. Heretofore, characterization of an urban environment in these bands has not been done. Specifically, an estimation of the distributions of both the number of multipath components and their delays has not been made for these bands, this environment, and our low antenna heights. Our measurements employed a vector network analyzer, from which both path loss and delay dispersion characteristics were obtained for link distances up to approximately 100 m. Log-distance models for path loss are presented, and dispersive channel models are also described. Our dispersive channel models employed a statistical algorithm for the number of multipath components, previously used only in indoor settings. By employing a transmitter-antenna positioner, we introduced spatial diversity into the measurement system, which enabled analysis of the dispersion characteristics of the angle of departure, also new for this ground-ground channel. The channel models should be useful for public-safety communication system designers. [ABSTRACT FROM AUTHOR]

This paper considers the problem of minimum cost communication of correlated sources over a network with multiple sinks, which consists of distributed source coding followed by routing. We introduce a new routing paradigm called dispersive information routing (DIR), wherein the intermediate nodes are allowed to split a packet and forward subsets of the received bits on each of the forward paths. This paradigm opens up a rich class of research problems, which focus on the interplay between encoding and routing in a network. Unlike conventional routing methods such as in [1], DIR ensures that each sink receives just the information needed to reconstruct the sources it is required to reproduce. We demonstrate using simple examples that the proposed approach offers better asymptotic performance than conventional routing techniques. We show that, under certain assumptions on the cost function, the problem of finding the minimum cost under DIR essentially reduces to characterizing an achievable rate region for a new multiterminal information theoretic setup. While it is possible to derive an achievable region for this setup using prior results from general multiterminal source coding [3], these techniques do not exploit the underlying problem structure and thereby lead to suboptimal regions. In this paper, we propose a new coding scheme, using principles from multiple descriptions encoding [2], and show that it strictly improves upon a corresponding variant of coding scheme in [3]. We further show that the new coding scheme achieves the complete rate region for certain special cases of the general setup and thereby achieves the minimum communication cost under this routing paradigm. [ABSTRACT FROM PUBLISHER]

.A hybrid four-hole AsSe2-As2S5 microstructured optical fiber (MOF) is fabricated by the rod-in-tube drawing technique. The core is made of AsSe2 glass and the cladding is made of As2S5 glass. The material refractive indices of the core and the cladding are ~2.832 and ~2.219 at the wavelength of ~2.8 lm, respectively. The calculated zero-dispersion wavelength of the AsSe2-As2S5 MOF is 2.759 lm. Soliton self-frequency shift with a soliton central wavelength from 2.986 to 3.419 lm is observed when the AsSe2-As2S5 MOF is pumped by an optical parametric oscillator at the pump wavelength of ~2.8 μm. At the same time a blue-shift dispersive wave is emitted by the soliton. [ABSTRACT FROM AUTHOR]

In this letter, we describe the formation and the evolution of Brillouin precursor fields through human tissues by using a frequency-domain analysis technique and a multi-pole Cole–Cole model to characterize the dielectric properties of the human body tissues, in a frequency band designated by the FCC for ultra wide band medical applications, which extends from 0.5 to 20 GHz. A 3D representation of the human body model has been implemented by employing a discretized mesh of cuboids with a resolution of 8 mm3in which the frequency dispersive material parameters for different tissues have been considered. The dispersive propagation is analyzed for the purposes of radar imaging and intra-body communications. The performance of a classical rectangular pulse, a Brillouin pulse and a medium-matched waveform is described. The results show the potential application of this type of communication scheme in order to improve the achievable measurement range and provide better signal to noise ratios. [ABSTRACT FROM AUTHOR]

The concept of space mapping is applied, for the first time, to the design of microwave dispersive delay structures (DDSs). DDSs are components providing specified group delay versus frequency responses for real-time radio systems. The DDSs considered in this paper are formed by cascaded coupled C-sections. It is first shown that aggressive space mapping does not provide sufficient accuracy in the synthesis of DDSs. To address this issue, we propose a predistortion space mapping technique. Compared to aggressive space mapping, this technique provides enhanced accuracy, while compared to output space mapping, it provides greater implementation simplicity. Two full-wave and one experimental examples are provided to illustrate the proposed predistortion space mapping technique. [ABSTRACT FROM AUTHOR]

This paper investigates the signal-to-interference ratio and the achievable rates of underwater acoustic (UA) OFDM systems over channels where time and frequency dispersion are high enough that (i) neither the transmitter nor the receiver can have a priori knowledge of the channel state information and (ii) intersymbol/intercarrier interference (ISI/ICI) cannot be neglected in the information-theoretic treatment. The goal of this study is to obtain a better understanding of the interplay between interference and the achievable transmission rates. Expressions for these rates take into account the "cross-channels" established by the ISI/ICI and are based on lower bounds on mutual information that assume independent and identically distributed input data symbols. In agreement with recent statistical analyses of experimental shallow-water data, the channel is modeled as a multivariate Rician fading process with a slowly time-varying mean and with potentially correlated scatterers, which ismore general than the common wide-sense stationary uncorrelated scattering model. Numerical assessments on real UA channels with spread factors around 10-1 show that reliable OFDM transmissions at 2 to 4 bits/sec/Hz are achievable provided an average signal-to-noise ratio of 15 to 20 dB. [ABSTRACT FROM AUTHOR]

An underwater optical wireless communication (UOWC) system is considered. For such system, a zero-padding (ZP) block-transmission scheme is presented to reduce the influence of inter-symbol-interference. Simulation results, which are based on the existing experimental data of channel pulse response, show that ZP system is effective especially for serious dispersive channel with high data rates and thus, potentially applicable to the high data rate UOWC systems. [ABSTRACT FROM AUTHOR]

Based on a novel composite right/left-handed unit cell, a wideband frequency- scanning network with a large scanning angle ranging towards both negative and positive elevation angles is proposed. The measured results show that the insertion loss variation of the designed frequencyscanning network is 7.2 ± 1 dB when the frequency ranges from 4.33 to 8.53 GHz and the phase differences of adjacent output ports scan from -50° to 50° when the frequency ranges from 4.76 to 8.26 GHz (53.8%). The proposed network can be used in wideband systems that require a large scanning angle range. [ABSTRACT FROM AUTHOR]

A compact patch antenna periodically loaded by air gaps is presented. The gaps are arranged to create EBG cells, which affect the dispersivebehaviours of the patch (as a transmission line). This causes waves totravel faster along the patch, and increases the cumulative radiationfrom the structure. The proposed antenna is compared with its conventional counterpart, considering the efficiency, electrical/physical sizeand the potential to achieve an electrically small footprint. Experimental results validate the analyses. [ABSTRACT FROM AUTHOR]

Based on the use of auxiliary differential equations, a unified split-step precise integration time-domain (SS-PITD) method is proposed for modelling wave propagation in linear dispersive media. The unification of this method is achieved by using a general expression to represent the Debye, Lorentz and Drude dielectric medium models. Moreover, due to the introduction of the SS scheme, the original two-dimensional (2D) or 3D electromagnetic problem reduces to a set of 1D sub-problems which can be efficiently solved by using the conventional PITD algorithm. It leads to a great reduction in the requirement of computation time and storage space. The proposed method is verified with a numerical example and compared with the finite-difference time-domain method. [ABSTRACT FROM AUTHOR]

We present a method to measure the spectrally-resolved transmission matrix of a multiply scattering medium, thus allowing for the deterministic spatiospectral control of a broadband light source by means of wavefront shaping. As a demonstration, we show how the medium can be used to selectively focus one or many spectral components of a femtosecond pulse, and how it can be turned into a controllable dispersive optical element to spatially separate different spectral components to arbitrary positions. [ABSTRACT FROM AUTHOR]