Binh Van Nguyen

Loop-interference suppression strategies using antenna selection in full-duplex MIMO relays

Loop-interference (LI) from relay transmission to reception reduces the channel capacity and makes the relay system unstable in full-duplex (FD) multi-input multi-output (MIMO) relay systems. conventional schemes to suppress LI still have drawbacks: 1) incur a dispensable signal-to-noise ratio (SNR) loss in low SNR regions; 2) increase the system complexity due to the requirement of weighting matrices; and 3) make insufficient practical sense due to varying signal-to-interference ratios (SIRs). In this paper, we propose a new LI suppression scheme using transmit antenna selection in order to solve the above problems. Simulation results show that the proposed scheme outperforms a conventional scheme, especially in low SNR and high SIR regions, even though the proposed scheme has a lower complexity.

Dependence of Outage Probability of Cooperative Systems with Single Relay Selection on Channel Correlation

The relay selection method is a promising technique for improving the performance of cooperative systems. Most of the existing studies assume that wireless channels are statistically independent. However, in reality, channel correlation is more likely to be non-negligible. In this study, we investigate the dependence of the performance of cooperative systems with single relay selection in equally correlated environments. A tight upper bound of the system outage probability is given as a function of the channel correlation coefficients. We show that even though the system performance is considerably degraded in the high signal-to-noise ratio (SNR) region when the channel correlations are sufficiently large, yet less than one, the system still achieves a diversity order equal to the number of available relays.

A novel relay selection with power allocation-based mechanism in interference environment

In this paper, the behavior of relay networks in interference environments is investigated. It has been shown that the effect of interference during Amplify-and-Forward process at relays bounds the diversity slope of the system at a well-defined static point. Moreover, the conventional relay selection criteria are also shown to be inefficient. To help our systems to improve its performance, the power allocation issue is taken into account with relay selection. However, solving a jointly optimization problem, optimizing transmitted power and maximizing the received SNR corresponding with the potential relay simultaneously, are difficult. In other words, it requires high complexity manipulation procedures. By proposing a power allocation and a relay selection separately, then combining these two methods, we form a new relay selection with power allocation-based mechanism that is less complex and has comparable performance with the optimal process.

On the Antijamming Performance of the NR-DCSK System

This paper investigates the antijamming performance of the NR-DCSK system. We consider practical jamming environments including broadband jamming (BBJ), partial-time jamming (PTJ), tone jamming (TJ), and sweep jamming (SWJ). We first analytically derived the bit error rates of the system under the BBJ and the PTJ. Our results show that the system performances under these two jamming environments are enhanced as increases, where is the parameter of the NR-DCSK modulation scheme denoting the number of times a chaotic sample is repeated. In addition, our results demonstrate that, for the PTJ, the optimal value of the jamming factor is close to zero when the jamming power is small; however, it increases and approaches one as the jamming power enlarges. We then investigate the performance of the system under the TJ and the SWJ via Monte-Carlo simulations. Our simulations show that single-tone jamming causes a more significant performance degradation than multitone jamming. Moreover, we point out that the system performance is significantly degraded when the starting frequency of the sweep jammer is close to the carrier frequency of the transmitted signals, the sweep bandwidth is small, and the sweep time is half of the transmitted bit duration.

Diagnosis of shockable rhythms for automated external defibrillators using a reliable support vector machine classifier

Abstract Sudden cardiac arrest is mainly caused by ventricular fibrillation and ventricular tachycardia, which are known as shockable rhythms. In this paper, a detection algorithm of shockable rhythms including support vector machine (SVM) model uses the public electrocardiogram (ECG) databases for training and testing. The databases are the Creighton University Ventricular Tachyarrhythmia Database (CUDB) and the MIT-BIH Malignant Ventricular Arrhythmia Database (VFDB). At first, to compose a set of good features, we extend a well-known set of 2 good features such as Count2 and VF-filter Leakage Measure (Lk). We supplemented 5 more good features, selected based on a binary genetic algorithm-based feature selection, among 11 new input candidate features. All the combinations of 7 good features are estimated for their performance on the training and the testing data using the SVM models to identify 6 combinations of the final feature pool. 5-Folds cross validation is then implemented carefully to validate the performance of the SVM classifier using final feature pool on separated and entire 5s-segment databases. The final combination of 4 features, which includes Count2, Lk, Threshold Crossing Interval (TCI), and Centroid Frequency (CF), is addressed by the highest validation performance of the corresponding SVM model. The Count2 shows the proportion of the signal, which is above the mean absolute values of the output of an integer coefficient recursive bandpass filter computed for every 1 s time interval. The Lk represents the output of a narrow bandstop filter, which is applied to the ECG signal with the central frequency being the mean signal frequency. The TCI shows the average time between the fixed thresholds, which are computed for every 1s-segment using the pulses converted from the ECG signal. The CF is the frequency, which bisects vertically the area under the power spectrum. For the proposed algorithm, the average accuracy of 95.9%, sensitivity of 91.7%, and specificity of 96.8% are archived on the evaluation data of the entire database. Comparing to the performance of the SVM model using a combination of the Count2 and the Lk, we report a significant improvement for the accuracy of the SVM model using the final feature combination in average, i.e. 2.6%, 22.4%, and 2.7% on the evaluation data of the entire database, the CUDB, and the VFDB, respectively. Furthermore, existence of ventricular ectopic beats in the input data shows a negligible influence on the final performance of classification.

Performance Analysis of Amplify-and-Forward Systems with Single Relay Selection in Correlated Environments

In this paper, we consider amplify-and-forward (AnF) cooperative systems under correlated fading environments. We first present a brief overview of existing works on the effect of channel correlations on the system performance. We then focus on our main contribution which is analyzing the outage probability of a multi-AnF-relay system with the best relay selection (BRS) scheme under a condition that two channels of each relay, source-relay and relay-destination channels, are correlated. Using lower and upper bounds on the end-to-end received signal-to-noise ratio (SNR) at the destination, we derive corresponding upper and lower bounds on the system outage probability. We prove that the system can achieve a diversity order (DO) equal to the number of relays. In addition, and importantly, we show that the considered correlation form has a constructive effect on the system performance. In other words, the larger the correlation coefficient, the better system performance. Our analytic results are corroborated by extensive Monte-Carlo simulations.

A relay selection scheme with interference cancellation at the receiver

In this work, we consider the relay selection (RS) method for an Amplify-and-Forward (AnF) relaying system in multi-cell environments. The selection scheme aims to maximize the instantaneous received signal-to-noise and interference ratio (SINR). We propose an idea of combining RS with interference cancellation (IC) at the receiver. Furthermore, we analyze the system outage probability performance with the proposed scheme. We use approximation approach to simplify the derivation of the probability distributed function (PDF) of the received SINR. The system outage probability bound is also given. Simulation results validate our analysis, and show that our scheme greatly improves the system outage probability as well as bit-error-rate (BER) performances.