The development of assistive devices for automated sound recognition is an important field of research and has been receiving increased attention. However, there are still very few methods specifically developed for identifying environmental sounds. The majority of the existing approaches try to adapt speech recognition techniques for the task, usually incurring high computational complexity. This paper proposes a sound recognition method dedicated to environmental sounds, designed with its main focus on embedded applications. The pre-processing stage is loosely based on the human hearing system, while a robust set of binary features permits a simple k-NN classifier to be used. This gives the system the capability of in-field learning, by which new sounds can be simply added to the reference set in real-time, greatly improving its usability. The system was implemented in an FPGA based platform, developed in-house specifically for this application. The design of the proposed method took into consideration several restrictions imposed by the hardware, such as limited computing power and memory, and supports up to 12 reference sounds of around 5.3 s each. Experimental results were performed in a database of 29 sounds. Sensitivity and specificity were evaluated over several random subsets of these signals. The obtained values for sensitivity and specificity, without additional noise, were, respectively, 0.957 and 0.918. With the addition of +6 dB of pink noise, sensitivity and specificity were 0.822 and 0.942, respectively. The in-field learning strategy presented no significant change in sensitivity and a total decrease of 5.4% in specificity when progressively increasing the number of reference sounds from 1 to 9 under noisy conditions. The minimal signal-to-noise ration required by the prototype to correctly recognize sounds was between -8 dB and 3 dB. These results show that the proposed method and implementation have great potential for several real life applications.

The orthogonal array is an important object in combinatorial design theory, and it is applied to many fields, such as computer science, coding theory and cryptography etc. This paper mainly studies the existence of the mixed orthogonal arrays of strength two with seven factors and presents some new constructions. Consequently, a few new mixed orthogonal arrays are obtained.

This paper presents novel reconfigurable semi-systolic array architecture for the Smith-Waterman with an affine gap penalty algorithm to align protein sequences optimized for shorter database sequences. This architecture has been modified to enable hardware reuse rather than replicating processing elements of the semi-systolic array in multiple FPGAs. The proposed hardware architecture and the previously published conventional one are described at the Register Transfer Level (RTL) using VHDL language and implemented using the FPGA technology. The results show that the proposed design has significant higher normalized speedup (up to 125%) over the conventional one for query sequence lengths less than 512 residues. According to the UniProtKB/TrEMBL protein database (release 2015_05) statistics, the largest number of sequences (about 80%) have sequence length less than 512 residues that makes the proposed design outperforms the conventional one in terms of speed and area in this sequence lengths range.

This paper deals with a beamforming and cell ID detection technique for a mobile station (MS) with multiple antenna arrays in millimeter wave (mm-wave) cellular communication systems. Multiple antenna arrays, required to cover the entire space around the MS, can be used to estimate the direction of arrivals (DoAs) and cell IDs, form beams in the direction of DoAs, select a serving cell in a cooperative manner, and improve BER performance by signal combining. However, a signal may enter the overlapped region formed by two adjacent arrays in the MS, resulting in a double-counting problem during the cell searching period. In this paper, a beamforming and cell detection technique without double-counting is proposed to handle this problem, and they are evaluated by simulation in a simple scenario of an mm-wave cellular system with spatial channel model (SCM).

The Lyapunov stability theory-based adaptive filter (LST-AF) is a robust filtering algorithm which the tracking error quickly converges to zero asymptotically. Recently, the software module of the LST-AF algorithm is effectively used in engineering applications such as tracking, prediction, noise cancellation and system identification problems. Therefore, hardware implementation becomes necessary in many cases where real time procedure is needed. In this paper, an implementation of the LST-AF algorithm on Field Programmable Gate Arrays (FPGA) is realized for the first time to our knowledge. The proposed hardware implementation on FPGA is performed for two main benchmark problems; i) tracking of an artificial signal and a Henon chaotic signal, ii) estimation of filter parameters using a system identification model. Experimental results are comparatively presented to test accuracy, performance and logic occupation. The results show that our proposed hardware implementation not only conserves the capabilities of software versions of the LST-AF algorithm but also achieves a better performance than them.

The dramatic growth in wireless data traffic has triggered the investigation of fifth generation (5G) wireless communication systems. Small cells will play a very important role in 5G to meet the 5G requirements in spectral efficiency, energy savings, etc. In this paper, we investigate low complexity millimeter-wave communication systems with uniform circular arrays (UCAs) in line-of-sight (LOS) multiple-input multiple-output (MIMO) channels, which are used in fixed wireless access such as small cell wireless backhaul for 5G. First, we demonstrate that the MIMO channel matrices for UCAs in LOS-MIMO channels are circulant matrices. Next, we provide a detailed derivation of the unified optimal antenna placement which makes MIMO channel matrices orthogonal for 3×3 and 4×4 UCAs in LOS channels. We also derive simple analytical expressions of eigenvalues and capacity as a function of array design (link range and array diameters) for the concerned systems. Finally, based on the properties of circulant matrices, we propose a high performance low complexity LOS-MIMO precoding system that combines forward error correction (FEC) codes and spatial interleaver with the fixed IDFT precoding matrix. The proposed precoding system for UCAs does not require the channel knowledge for estimating the precoding matrix at the transmitter under the LOS condition, since the channel matrices are circulant ones for UCAs. Simulation results show that the proposed low complexity system is robust to various link ranges and can attain excellent performance in strong LOS environments and channel estimation errors.

The emerging three-dimensional (3D) technology is considered as a promising solution for achieving better performance and easier heterogeneous integration. However, the thermal issue becomes exacerbated primarily due to larger power density and longer heat dissipation paths. The thermal issue would also be critical once FPGAs step into the 3D arena. In this article, we first construct a fine-grained thermal resistive model for 3D FPGAs. We show that merely reducing the total power consumption and/or minimizing the power density in vertical direction is not enough for a thermal-aware 3D FPGA backend (placement and routing) flow. Then, we propose our thermal-aware backend flow named TherWare considering location-based heat balance. In the placement stage, TherWare not only considers power distribution of logic tiles in both lateral and vertical directions but also minimizes the interconnect power. In the routing stage, TherWare concentrates on overall power minimization and evenness of power distribution at the same time. Experimental results show that TherWare can significantly reduce the maximum temperature, the maximum temperature gradient, and the temperature deviation only at the cost of a minor increase in delay and runtime as compared with present arts.

Monopulse is a classical technique for radar angle estimation and still adopted for fast angle estimation in phased array antenna. The classical formula can be applied to a 2-dimentional phased array antenna if two conditions---the unbiasedness and the independence of the azimuth and the elevation estimate---are satisfied. However, if the sum and difference beams are adapted to suppress the interference under jamming condition, they can be severely distorted. Thus the difference beams become highly correlated and violate the conditions. In this paper, we show the numerical implementation of the generalized monopulse estimation using the distorted and correlated beams, especially for a subarray configured antenna. Because we use the data from the measured subarray patterns rather than the mathematical model, this numerical method can be easily implemented for the complex array configuration and gives good performance for the uncertainty of the real system.

Perfect arrays are widely applied to high-dimensional communications, time-frequency-coding, spatial correlation or map matching, built-in tests of VLSI-circuits, radar, and so on. The letter investigates perfect arrays over the 8-QAM+ constellation, and two constructions for yielding such arrays are presented. Furthermore, the family size of the proposed arrays is determined as well.

In this paper, a method is introduced that can detect the number of incident signals (NIS) even there are fewer antennas than NIS. Previous works on NIS detection methods assumed that the number of antennas always exceeded NIS. In the DOA estimation field, the DOA estimation is possible, even if NIS exceeds the number of antennas, by extending the degrees of freedom of array (DOFA) using a modified array configuration, such as a nested array (NA). The information of NIS is required in advance to accurately estimate DOA, however, it has not been investigated deeply when NIS is larger than the number of antennas. In this paper, a NIS detection method based on the DOFA extending process using NA is proposed. One of the important issues in NIS detection is the detection metric. As one of the simple metrics, the ratio of adjacent eigenvalues (RAE) has been used. However, the direct application of RAE may not achieve adequate NIS detection performance. Therefore, we propose a metric based on the modified ratio of adjacent eigenvalues (MRAE) avoids the issue of RAE. Numerical results show that the metric based on MRAE can achieve proper NIS detection performance even if NIS is larger than the number of antennas.

Orthogonal arrays have important applications in statistics and computer science, as well as in coding theory. In this letter, a new construction method of symmetric orthogonal arrays of strength t is proposed, which is a concatenation of two orthogonal partitions according to a latin square. As far as we know, this is a new construction of symmetric orthogonal arrays of strength t, where t is a given integer. Based on the different latin squares, we also study the enumeration problem of orthogonal partitions, and a lower bound on the count of orthogonal partitions is derived.

A semi-analytical method for a planar periodic array formed by a finite number of magnetized ferrite circular cylinders is presented using a model of layered cylindrical structures. The method uses the T-matrix approach and the extraction of the reflection and transmission matrices based on the cylindrical harmonic mode expansion. Based on the proposed method, plane wave scattering by the finite number of magnetized ferrite circular cylinders is numerically studied from the viewpoint of realization the electronic switching and electronic scanning effects by varying the applied magnetic field.

This paper investigates construction methods of perfect 16-QAM sequences and arrays, since such sequences and arrays play quite an important role in synchronization of communication systems making use of 16-QAM signals. The method used for obtaining the results is to establish a relationship between the known perfect quaternary sequences/arrays and the required ones so that the former is transformed into the latter. Consequently, the sufficient conditions for implementing the required transformations are derived, and several examples are given. Our methods can provide perfect 16-QAM sequences with lengths 2, 4, 8, and 16, which are given in Table A·1 and infinite families of perfect 16-QAM arrays, whose existing sizes up to dimension 5 and volume 2304 are listed in Tables A·2 and A·3.

This paper presents a simple 3-D array configuration for high-resolution 2-D Direction-Of-Arrival (DOA) estimation. Planar array structures like Uniform Rectangular Array (URA) or Uniform Circular Array (UCA) often well estimate azimuth angle but cannot well estimate elevation angle because of short antenna aperture in elevation direction. One may put more number of array elements to improve elevation angle estimation accuracy, however it will require very large hardware and software cost. This paper presents a simple 3-D array structure for high-resolution 2-D DOA estimation only by modifying the height of some array elements in a planar array. Based on the analysis of Cramer-Rao Lower Bound (CRLB) formulation and its dependency on the height of array elements, we develop a simple 3-D array structure which improves elevation angle estimation accuracy while preserving azimuth angle estimation accuracy.

In most software development environments, time, computing and human resources needed to perform the testing of a component is strictly limited. In order to deal with such situations, this paper proposes a method of creating the best possible test suite (covering the maximum number of 3-tuples) within a fixed number of test cases.

In this paper, we designed and fabricated large scale micro-light-emitting-diode (LED) arrays and silicon driver for single chip device for realizing as prototypes of heterogeneous optoelectronic integrated circuits (OEICs). The large scale micro-LED arrays were separated by a dry etching method from mesa structure to 16,384 pixels of 128 128, each with a size of 15 µm in radius. Silicon driver was designed the additional bonding pad on each driving transistor for bonding with micro-LED arrays. Fabricated micro-LED arrays and driver were flip-chip bonded using anisotropic conductive adhesive.

Dielectric rod arrays in a metallic waveguide alter the propagation modes and group velocities of electromagnetic waves. We have focused on TE30-to-TE10 mode converters and investigated how their behavior varies with frequency. A mode converter is proposed that passes the TE10 mode at frequencies lower than 2fc, and converts the TE30 mode into the TE10 mode for frequencies higher than 3fc.

A semi-analytical approach for analyzing the electromagnetic radiation of a line source in cylindrical electromagnetic bandgap (EBG) structure is presented. The cylindrical structure is composed of circular rods periodically distributed along concentrically layered circular rings. The method uses the T-matrix of a circular rod in isolation, the reflection and transmission matrices of a cylindrical array expressed in terms of the cylindrical waves as the basis, and the generalized reflection and transmission matrices for a layered cylindrical structure. Using the proposed method, the radiated field from a line source placed inside a three-layered cylindrical EBG structure with defects is investigated. The defects are created by removing the particular circular rods from each circular ring. The structure is prominent from the viewpoint of flexible design of the directive antennas. Numerical examples demonstrate that the cylindrical EBG structures are very effective at forming and controlling the directed beam in the radiated fields.

Two designs of wideband compact MIMO antenna using printed dipoles are proposed in this paper. One is a three-port orthogonal polarization antenna and the other is a cube-six-port antenna. Measured results for the antennas show that they resonate at 2.6 GHz and support a bandwidth of over 400 MHz. The worst mutual coupling for the three-port orthogonal polarization antenna is kept under -20 dB whereas that level of the cube-six-port antenna is -18 dB. A number of experiments are conducted on MIMO systems with these compact antennas and linear antenna arrays. Measured data are analyzed to examine channel characteristics, such as cumulative distribution functions (CDFs) of eigenvalues. Furthermore, the effect of different antenna configurations on channel capacity is highlighted and discussed. A high data rate capacity can be achieved with the compact antennas, particularly from the cube-six-port variant. These antennas might be applied in actual MIMO systems in wireless communications.

This paper proposes a channel capacity maximization method for Multiple-Input Multiple-Output (MIMO) antennas with parasitic elements. Reactive terminations are connected to the parasitic elements, and the reactance values are determined to achieve stochastically high channel capacity for the environment targeted. This method treats the S-parameter and propagation channel of the antenna, including the parasitic elements, as a combined circuit. The idea of the 'parasitic channel,' which is observed at the parasitic antenna, is introduced to simplify the optimization procedure. This method can significantly reduce the number of necessary measurements of the channel for designing the antenna. As a design example, a bidirectional Yagi-Uda array, which has two driven antennas at both ends of the linear array, is measured in an indoor environment. The resulting design offers enhanced channel capacity mainly due to its improved signal-to-noise ratio compared to the antenna without the parasitic antennas.