We derive a closed-form expression for the outage probability (OP), which is an important performance metric used to measure the probability that the target error rate performance of wireless systems exceeds a specified value, of multiple-input multiple-output (MIMO) amplify-and-forward (AF) relaying systems with best antenna selection under independent, but not necessarily identical distributed Nakagami-m fading. To gain further insights on the performance, the asymptotic approximation for OP, which reveals the diversity gain, is presented. We show that the diversity gain is solely determined by the fading severity parameters and increases with number of antennas at all nodes.

High-performance FFT processor is indispensable for real-time OFDM communication systems. This paper presents a CORDIC based design of variable-length FFT processor which can perform various FFT lengths of 64/128/256/512/1024/2048/4096/8192-point. The proposed FFT processor employs memory based architecture in which mixed radix 4/2 algorithm, pipelined CORDIC, and conflict-free parallel memory access scheme are exploited. Besides, the CORDIC rotation angles are generated internally based on the transform of butterfly counter, which eliminates the need of ROM making it memory-efficient. The proposed architecture has a lower hardware complexity because it is ROM-free and with no dedicated complex multiplier. We implemented the proposed FFT processor and verified it on FPGA development platform. Additionally, the processor is also synthesized in 0.18 µm technology, the core area of the processor is 3.47 mm2 and the maximum operating frequency can be up to 500 MHz. The proposed FFT processor is better trade off performance and hardware overhead, and it can meet the speed requirement of most modern OFDM system, such as IEEE 802.11n, WiMax, 3GPP-LTE and DVB-T/H.

This paper proposes an asymptotic method for calculating the received intensity of multi-path millimeter waves transmitted over an undulating surface. This method is a generalization of the asymptotic method that the authors previously derived, based on a quartic phase function approximation, from the physical optics integral expression of the received intensity. The applicability of the previous method is limited to ratios of transmission distance (D) to surface undulation wavelength (λs) of roughly less than 2. This is because the method is based on a quartic phase function approximation. In this paper, this limitation is resolved through this method's generalization, which is achieved by incorporating a technique for calculating the diffraction integral with a higher-degree phase function by using the steepest descent technique with a procedure for systematically identifying the active saddles of the phase function. Numerical examples demonstrate that the proposed asymptotic method can attain calculation accuracy comparable with the physical optics method, even in the case of large D/λs values.

Reinforcement learning (RL) is a flexible framework for learning a decision rule in an unknown environment. However, a large number of samples are often required for finding a useful decision rule. To mitigate this problem, the concept of transfer learning has been employed to utilize knowledge obtained from similar RL tasks. However, most approaches developed so far are useful only in low-dimensional settings. In this paper, we propose a novel transfer learning idea that targets problems with high-dimensional states. Our idea is to transfer knowledge between state factors (e.g., interacting objects) within a single RL task. This allows the agent to learn the system dynamics of the target RL task with fewer data samples. The effectiveness of the proposed method is demonstrated through experiments.

The need for the OpenGL-family of the 3D rendering API's are highly increasing, especially for graphical human-machine interfaces on various systems. In the case of safety-critical market for avionics, military, medical and automotive applications, OpenGL SC, the safety critical profile of the OpenGL standard plays the major role for graphical interfaces. In this paper, we present an efficient way of implementing OpenGL SC 3D graphics API for the environments with hardware-supported OpenGL 1.1 and its multi-texture extension facility, which is widely available on recent embedded systems. Our approach achieved the OpenGL SC features at the low development cost on the embedded systems and also on general personal computers. Our final result shows its compliance with the OpenGL SC standard specification. From the efficiency point of view, we measured its execution times for various application programs, to show a remarkable speed-up.

The end-to-end performance of dual-hop multiple-input multiple-output (MIMO) decouple-and-forward relaying with orthogonal space-time block code (OSTBC) transmission over Nakagami-m fading is analyzed. By considering the multiple antennas at all nodes, we derive exact closed-form and asymptotic expressions for the outage probability and symbol error rate, which enables us to evaluate the exact performance and reveals the diversity gains of the considered system. In addition, the closed-form approximation and asymptotic expressions for the ergodic capacity are also derived. We show that OSTBC transmission over relay systems yields a unit order of multiplexing gain despite the fact that full diversity order, which is equal to the minimum fading severity between the two hops, is achieved.

In this letter, we consider a control problem of a chain of integrators by output feedback under sensor noise. First, we introduce a measurement output feedback controller which drives all states and output of the considered system to arbitrarily small bounds. Then, we suggest a measurement output feedback controller coupled with a switching gain-scaling factor in order to improve the transient response and retain the same arbitrarily small ultimate bounds as well. An example is given to show the advantage of the proposed control method.

In this paper, we discuss the stochastic modeling for operational software reliability measurement, assuming that the testing environment is originally different from the user operation one. In particular, we introduce the concept of systemability which is defined as the reliability characteristic subject to the uncertainty of the field operational environment into the model. First we introduce the environmental factor to consistently bridge the gap between the software failure-occurrence characteristics during the testing and the operation phases. Then we consider the randomness of the environmental factor, i.e., the environmental factor is treated as a random-distributed variable. We use the Markovian imperfect debugging model to describe the software reliability growth phenomena in the testing and the operation phases. We derive the analytical solutions of the several operational software reliability assessment measures which are given as the functions of time and the number of debuggings. Finally, we show several numerical illustrations to investigate the impacts of the consideration of systemability on the field software reliability evaluation.

At the stage of software debugging, the effective interaction between software debugging engineers and fault localization techniques can greatly improve fault localization performance. However, most fault localization approaches usually ignore this interaction and merely utilize the information from testing. Due to different goals of testing and fault localization, the lack of interaction may lead to the issue of information inadequacy, which can substantially degrade fault localization performance. In addition, human work is costly and error-prone. It is vital to study and simulate the pattern of debugging engineers as they apply their knowledge and experience to this interaction to promote fault localization effectiveness and reduce their workload. Thus this paper proposes an effective fault localization approach to simulate this interaction via feedback. Based on results obtained from fault localization techniques, this approach utilizes test data generation techniques to automatically produce feedback for interacting with these fault localization techniques, and then iterate this process to improve fault localization performance until a specific stopping condition is satisfied. Experiments on two standard benchmarks demonstrate the significant improvement of our approach over a promising fault localization technique, namely the spectrum-based fault localization technique.

In this letter, an improved statistical simulation model with a new parameter computation method is proposed for Rayleigh fading channels. Compared with the existing simulators, the proposed model yields much higher simulation efficiency, while it can still obtain adequate approximations of the desired statistical properties.

This paper presents a response time acceleration technique in a high-gain capacitive-feedback frontend amplifier (FA) for high output impedance sensors. Using an auxiliary amplifier as a unity-gain buffer, a sample-and-hold capacitor which is used for band-limiting and sampling the FA output is driven at the beginning of the transient response to make the response faster and then it is re-charged directly by the FA output. A condition and parameters for the response time acceleration using this technique while maintaining the noise level unaffected are discussed. Theoretical analysis and simulation results show that the response time can be less than half of the case without the acceleration technique for the specified settling error of less than 0.5%.

Performance of CSMA/CA wireless communication is severely affected by hidden terminal (HT) problem that results in failure of carrier sense and causes packet error due to collision. However, no mathematical analysis method for the HT problem has been available that takes into account actual radio environments including both fading and capture effect. This paper presents an analysis method that enables to well predict the probability of successful communication (PSC) and communication efficiency for CSMA/CA unicast communication including the interaction of data and ACK packets. Analysis of the PSC with two-dimensional HT distribution makes it easy to understand the influence of HT location and carrier sense level. Also it is shown that there is considerable difference on the PSC between fading and fading-free environments. The obtained results as well as the proposed analysis method are quite useful in CSMA/CA network design for WLAN and sensor network applications.

A loosened connector between interconnected electric devices causes an increase in electromagnetic radiation when the devices operate in high-frequency bands. To develop a high-frequency circuit equivalent to a connector with contact failure, we previously investigated the parasitic elements caused by failure at the contact boundary. From the results of that study, the inductance and resistance at a connection contact boundary are increased by the loosening of a connector. Furthermore, the increase in inductance is the dominant factor in increasing the intensity of the electromagnetic radiation. In this paper, to suppress electromagnetic radiation resulting from a loose contact, we formulate the contact performance requirement needed to maintain a good contact condition when a small loosening has occurred at the interconnection. To this end, we investigate the mechanism of increase in the inductance by loosening the connector.

A facial components based facial expression recognition algorithm with sparse representation classifier is proposed. Sparse representation classifier is based on sparse representation and computed by L1-norm minimization problem on facial components. The features of “important” training samples are selected to represent test sample. Furthermore, fuzzy integral is utilized to fuse individual classifiers for facial components. Experiments for frontal views and partially occluded facial images show that this method is efficient and robust to partial occlusion on facial images.

The non-homogeneous Poisson process (NHPP) has been applied successfully to model nonstationary counting phenomena for a large class of problems. In software reliability engineering, the NHPP-based software reliability models (SRMs) are of a very important class. Since NHPP is characterized by its rate (intensity) function, which is known as the software failure rate of NHPP-based SRM, it is of great interest to estimate accurately the rate function from observed software failure data. In the existing work the same authors introduced a Haar-wavelet-based technique for this problem and found that the Haar wavelet transform provided a very powerful performance in estimating software failure rate. In this paper, we consider the application potentiality of a Daubechies wavelet estimator in the estimation of software failure rate, given the software failure time data. We give practical solutions by overcoming technical difficulties in applying the Daubechies wavelet estimator to the real software failure time data.

The wireless sensor network (WSN) is a technology that senses environmental information and provides appropriate services to users. There are diverse application areas for WSNs such as disaster prevention, military, and facility management. Despite the many prospective applications, WSN s are vulnerable to various malicious attacks. In false report attacks, a malicious attacker steals a few sensor nodes and obtains security materials such as authentication keys from the nodes. The attacker then injects false event reports to the network through the captured nodes. The injected false reports confuse users or deplete the limited energy of the nodes in the network. Many filtering schemes have been proposed to detect and remove false reports. In the statistical en route filtering (SEF) scheme, each node shares authentication keys selected from a global key pool. Due to the limited memory, each node is able to store only a small portion of the global key pool. Therefore, the routing paths of the event reports significantly affect the filtering (i.e., detecting) probability of false reports. In this paper, we propose a method to determine the routing paths of event reports both hop by hop and on demand at each node. In this method, each node chooses the next node on the path from the event source to the sink node based on the key indexes of its neighbor nodes. Experiments show that the proposed method is far more energy efficient than the SEF when the false traffic ratio (FTR) is ≥ 50% in the network.

Non-negative matrix factorization (NMF) is widely used for music transcription because of its efficiency. However, the conventional NMF-based music transcription algorithm often causes harmonic confusion errors or time split-up errors, because the NMF decomposes the time-frequency data according to the activated frequency in its time. To solve these problems, we proposed an NMF with temporal continuity and harmonicity constraints. The temporal continuity constraint prevented the time split-up of the continuous time components, and the harmonicity constraint helped to bind the fundamental with harmonic frequencies by reducing the additional octave errors. The transcription performance of the proposed algorithm was compared with that of the conventional algorithms, which showed that the proposed method helped to reduce additional false errors and increased the overall transcription performance.

We performed the (NH4)2S surface treatments before Al2O3 deposition to improve the Al2O3/III-Nitride interface quality in Al2O3/AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs). Interface state density at the Al2O3/GaN interface was decreased by the (NH4)2S treatment. The hysteresis width in ID-VGS and gm-VGS characteristics of the Al2O3/AlGaN MOSHFETs with the (NH4)2S treatment was smaller than that without the (NH4)2S treatment. In addition, transconductance (gm) decrease at a large gate voltage was relaxed by the (NH4)2S treatment. We also performed ultraviolet (UV) illumination during the (NH4)2S treatment for further improvement of the Al2O3/III-Nitride interface quality. Interface state density of the Al2O3/GaN MOS diodes with the UV illumination was smaller than that without the UV illumination.

This paper proposes a novel routing algorithm that constructs position-based k-disjoint paths to realize greater resiliency to patterned failure. The proposed algorithm constructs k-disjoint paths that are spatially distributed by using the hop-count based positioning system. Simulation results reveal that the proposed algorithm is more resilient to patterned failure than other routing algorithms, while it has low power consumption and small delay.

Cooperative relay selection, in which one of multiple relays is selected to retransmit the source signal to the destination, has received considerable attention in recent years, because it is a simple way to obtain cooperative diversity in wireless networks. The exact expression of outage probability for a decode-and-forward cooperative relay selection with multiple source and destination antennas over Rayleigh fading channels was recently derived in [9]. In this letter, we derive the exact expressions of outage probability and diversity-multiplexing tradeoff over independent and non-identically distributed Nakagami-m fading channels as an extension of [9]. We then analyze the effects of various parameters such as fading conditions, number of relays, and number of source and destination antennas on the outage probability.