EDITORIAL BOARD
Editor-In-Chief
Bui Thu Lam, Le Quy Don Technical University
Deputy Editor-In-Chief
Tran Xuan Nam, Le Quy Don Technical University
Pham The Long, Le Quy Don Technical University
Editors
Nguyen Binh, Posts and Telecommunications Institute of Technology
Dinh The Cuong, Directorate of Information Technology
Luong Chi Mai, Vietnam Academy of Science and Technology
Huynh Quyet Thang, Hanoi University of Science and Technology
Nguyen Huu Thanh, Hanoi University of Science and Technology
Vu Duc Thi, Vietnam National University, Hanoi
Nguyen Thanh Thuy, Vietnam National University, Hanoi
Dao Thanh Tinh, Le Quy Don Technical University
Scientific Secretary
Nguyen Van Giang, Le Quy Don Technical University
Table: Issue 7
ID Paper
Title
Author
Page
Abstract
07.01
Question classification by combination of multiple features.
Nguyen Van Tu, Le Anh Cuong, Nguyen Ha Nam
5-14
Question classification plays an important role in automated question answering systems. The task of question classification is to predict the entity type for answering a natural language question. Question classification can be done using the approaches including rule-based methods and machine learning-based methods. Different lexical, syntactical and semantic features should be extracted automatically from the input (i.e. the questions) to use for the classification. In this paper we combine lexical, syntactical and semantic features to question classification. We also propose a new feature type which we call question pattern. We found that by combining this new features with the lexical, syntactical and semantic features can significantly improve the accuracy of question classification. We tested our proposed approach using a Support Vector Machines as the classifier and using TREC dataset. The achieved classification accuracy is greater than the previous studies on the same question taxonomy and dataset.
07.02
An analytical method of general muticlass queueing network G/G/J.
Nguyen Trung Dung, Ha Manh Tien.
15-31
In this paper, we present the combining technique between disintegration and synthesization to evaluate a general multiclass queueing network with multi-directional information flow as a combining network of directional queueing networks. This technique enables us to study the general queueing network as the simple component networks.
07.03
New digital signature scheme based on integer factorization and finding root problem.
Hoang Thi Mai, Luu Hong Dung.
32-41
In this paper, we propose a new type of digital signature scheme based on a two hard problems - the prime factorization of a large integer number and finding root based on ring $Z_{n=p.q}$, (p, q - large prime numbers). The result of this research can be applied to develop signature schemes that there are high level of security in many applications in reality.
07.04
Low area ASIC implementation of logarithm approximation for digital signal processing.
Hoang Van Phuc, Sai Van Thuan, Pham Cong Kha
42-57
This paper presents an efficient ASIC implementation of the hardware logarithm approximation which can be used for emerging digital signal processing applications. By employing the quasi-symmetrical logarithm approximation method, the modified barrel shifter circuit and the optimized leading one detector and encoder, the proposed approach can reduce the hardware area and improve the logarithm computation speed significantly while achieve the similar accuracy compared with other implementations. The ASIC implementation results using a 0.18-$\mu$m CMOS technology standard library are also presented and discussed.
07.05
Estimation of the effect of nonlinear distortion by high power amplifiers in MIMO 2×nR STBC systems.
Nguyen Tat Nam, Nguyen Quoc Binh, Nguyen Thanh.
58-73
At that time, reseaches on the effects of nonlinearity in Multiple Input-Multiple Output Space-Time Block Coding (MIMO STBC) mainly focus on evaluation on the effect of high power amplifier (HPA) in terms of solid state power amplifier (SSPA) or soft envelope limiter (SEL). The investigation of the effect of nonlinear distortion caused by HPA using travelling wave tube amplifier (TWTA) has just been carried out for space-time trellis codes \cite{Sulyman08}. In this paper, we suggest using the parameter distance degradation ($dd$) of HPA to estimate effects of nonlinearity in MIMO $2 \times n_{R}$ STBC using TWTA. Then, we introduce empirical formulas that allow quick estimating effects of any TWTA in MIMO $2 \times n_{R}$ STBC systems using the $dd$ parameter. Besides we also point out the change of optimal operating point of the same HPA investigated in single input-single output (SISO) and MIMO $2 \times n_{R}$ STBC.
07.06
A cross-layer cooperative MAC protocol with adaptive relay selection.
Hoang Quang Trung, Tran Xuan Nam.
74-88
Cooperative communication has been known as an effective solution to improve performance of wireless networks. In the cooperative wireless networks, the design issue of the medium access control (MAC) protocol is considered an important and challenging task. In this paper, we propose an effective cross-layer cooperative MAC protocol which can support adaptive relay selection. The proposed protocol is designed based on the PHY-MAC cross-layer approach to achieve two main goals: (i) enhancing the received signal quality based on the effective cooperative diversity scheme, and (ii) improving the system throughput and the packet transmission latency performance by using an adaptive relay selection procedure. Simulation results proved that our proposed protocol outperforms the previous cooperative protocol as well as the traditional protocol in terms of network performance.
07.07
New method for determining the bias point drift of electrooptics modulator.
Bui Dang Thanh
89-96
This paper presents a drift measurement method of the electrooptics modulator (EOM) bias point. The EOM is a key component that is used in optical communication systems. When the bias point is on the best linear range of transfer function, the modulation quality is the most effectively. In fact, the EOM is not perfectly stable with time and the transfer function is drifted caused by many effects such as temperature changes, inherent phototrefractive coefficient, optical coupling efficiency. The drift of the transfer function lead to performance decrease of the application systems where the EOM works as a key component. By applying a sinusoidal signal at low-frequency to the bias electrode and analyse the second harmonic component in the EOM output, we can determine the drift of the transfer function. Besides examining the calculations, we have also successfully implemented measurement circuit based on PSoC microcontroller.