bluuebunny/crossref_metadata_2025_split huggingface dataset:
ACO-Based Multi-User Detection in Cooperative CDMA Networks
Authors: Jahromi Ali Jafarnia , Abdizadeh Mohammad T. 
Published: May 2016

In this paper, the cooperative diversity is investigated in the uplink of a Code Division Multiple Access (CDMA) network in which users cooperate by relaying each other’s messages toward the Base Station (BS). It is assumed that the spreading waveforms are not orthogonal and hence, Multiple Access Interference (MAI) exists at the relay nodes as well as the BS. MAI degrades the signal quality at both relays and BS and decreases the cooperative diversity gain. To alleviate this problem, an Ant Colony Optimization (ACO) based Multi-User Detector (MUD) has been proposed to efficiently combine the received signals from the direct and relay paths and sub-optimally extract transmitted bits at the BS. The computational complexity of proposed algorithm is significantly lower than that of the Maximum Likelihood (ML) detector. More explicitly, for a cooperative network supporting 15 users, the computational complexity of the proposed ACO algorithm is a factor of 103 lower than that of the optimum Bayesian detector. Simulation results show that the performance of the proposed ACO-based detector can closely approach the maximum diversity in terms of BER and efficiently cancel the MAI at the BS.
Bit-Interleaved Coded Modulation Systems with Iterative Decoding and Partial Reusing QAM Signal Points
Authors: Tuan Nguyen Quang , Trinh Do Quoc , Nam Tran Xuan , Cuong Dinh The 
Published: May 2016

A new method of reusing a subset of an M-QAM signal constellation is presented for Bit-Interleaved Coded Modulation systems with Iterative Decoding (BICM-ID). In addition to the remapping of high-energy signals to low-energy signals in order to save the average signal energy as a shaping technique known so far, a new scheme of remapping low-energy signals to high-energy signals is proposed in order to gain the equivalent distance when decoding bits, often called the Squared Euclidean Weights (SEW). Numerical analysis and simulation results show that the partial reuse of the signals in the BICM-ID system with 16-QAM can improve the system performance in terms of lowering the bit error rate in the error floor region.
Theoretical Foundations of Mobile Flexible Networks
Authors: Debbah Mérouane 
Published: May 2016

The general framework of Mobile Flexible Networks (MFN) is to design dense self-organizing, self-healing and self-energy harvesting secure networks where terminals and base stations interact and self-adapt in an intelligent manner without the need of a central controller or with the right amount of regulation to let the agents in the network exploit fully the degrees of freedom. The design depends mainly on the mobility pattern as in highly mobile environments, intelligence at the terminal reduces the cost of signaling whereas for fixedling whereas for fixed (non-mobile) networks, all the intelligence can be put on the network side. One of the big challenges is to find how to optimally split the intelligence between cognitive terminals and cognitive networks. In this paper, we discuss the challenges ahead and provide some research directions to develop the theoretical foundations of these networks.
On the Practical Implementation of VFDM-based Opportunistic Systems: Issues and Challenges
Authors: Maso Marco , Cardoso Leonardo S. , Bastug Ejder , Linh-Trung Nguyen , Debbah Mérouane , Ozdemir Ozgur 
Published: May 2016

Vandermonde-subspace frequency division multiplexing (VFDM) is a physical layer technique for cognitive two-tiered networks, allowing for the coexistence of an orthogonal frequency division multiplexing (OFDM) legacy system and a cognitive secondary system in a time division duplex mode. It consists of a linear null-space precoder used by the secondary transmitter to effectively cancel the interference towards one or more primary receivers, while guaranteeing a non-negligible rate to a served secondary receiver. In this work, we propose an implementation of an experimental test-bed using the new SDR4All platform developed at the Alcatel-Lucent Chair on Flexible Radio (SUPELEC) to take a step towards a proof of concept of a VFDM-based system. We focus on the secondary link, where an opportunistic transmitter/receiver pair communicates over moderately frequency selective channels, characterized by very short root mean square (r.m.s.) delay spreads and non uniform power delay profiles (PDP). The obtained results show the practical feasibility of a VFDM transmission over a secondary link. However, a significant bit error rate (BER) loss with respect to the previously shown achievable theoretical performance is evident. A thorough analysis of the structure of the VFDM precoder is carried out and the impact of the channel characteristics on the performance of the opportunistic system is discussed. Numerical findings demonstrate that the potential BER drop can be addressed by designing a suitable flexible receiver able to deal with the effect induced by non uniform PDP and short r.m.s. delay spread channels.
Standard-Compliant Content Adaptation in IPTV Systems
Authors: Thang Truong Cong , Kang Jung Won , Pham Ngoc Nam , Pham Anh T. 
Published: May 2016

IPTV, which is based on the universal IP infrastructure, has the inherent nature of heterogeneity in terms of content, networks, terminals, and users. An important solution to cope with such heterogeneity is content adaptation. This paper reviews the standardization issues related to content adaptation in IPTV standards. We first describe the basic architecture of content adaptation and its integration into the ITU-T IPTV architecture. Then typical methods of content adaptation in practical IPTV systems are discussed in detail. Especially, we highlight the standard metadata tools that are potential to support adaptation methods within ITU-T IPTV architecture. Some recent developments in other standard bodies are also discussed.
Improving the Performance of Concatenated Convolutional Codes in the Error Floor Region
Authors: Dinh The Cuong , Tran Xuan Nam , Huynh Huu-Tue 
Published: May 2016

The idea of the Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) is applied to classic schemes of both parallel and serial concatenation of convolutional codes (PCCC and SCCC) with Binary Phase Shift Keying (BPSK) modulation. Simulation results show that slightly modified PCCC and SCCC schemes provide significant improved performance of the encoder in the error floor region in terms of much lower bit error rate (BER).
A Hybrid of T-Dipole and Quasi-Yagi Antenna for Dual-band WLAN Access Point
Authors: Ta Son Xuat , Park Ikmo , Dao-Ngoc Chien 
Published: May 2016

In this paper, a hybrid of T-dipole and quasi-Yagi antenna is presented for using in dual-band Wireless Local Area Network (WLAN) access point. The antenna is made up of combination of T-dipole and quasi-Yagi antenna structures, which are distinctly designed to operate at 2.4 and 5.5 GHz frequency bands. A simply integrated balun that consists of a curved microstrip line and a circular slot to allow broadband characteristic is used to feed the antenna. The final antenna design presents measured bandwidths (RL ≤ − 10 dB) of 2.35 – 2.55 GHz and 4.30 – 6.56 GHz which cover completely the two bands of WLAN. Simulated and measured results of peak gain and radiation patterns in both E- and H-plane validate potential of the design.
Minimalist Self-Organization in Wireless Networks
Authors: Roy Sébastien , Leroux Philippe 
Published: May 2016

Many fields of human endeavour, such as biology and the theory of complex systems, are now embracing the concept of self-organization based on local actions leading to a desirable global emergent behavior. While many examples, both natural and artificial, can be found of such self-organized systems, the relationship between the local rules and the global behavior remains elusive and no systematic procedure is known to engineer a specific global result. Given the increasing pervasiveness of wireless networks of all sorts, including ad hoc networks competing within narrow unlicensed bands and wireless sensor networks, self-organization could constitute the next defining paradigm in wireless communications. It can be shown that a set of heuristic principles can be leveraged to engineer a self-organized connection-oriented wireless network with minimal complexity. Such a system requires no centralization of information, yet achieves a nearly optimal global state with only a modest amount of local signaling. It will naturally and jointly balance the many parameters related to radio resource management, exhibiting great adaptability, fault tolerance and scalability.
Blind Identification for Communication Signals: An Approach Exploiting Sampling Phase Diversity
Authors: Racine Emmanuel , Grenier Dominic 
Published: May 2016

This paper presents a second-order blind channel estimation algorithm for digital communication signals under natural asynchronous conditions where no synchronization exists between transmitting and receiving antennas. The approach exploits sampling phase diversity provided by the cyclostationary nature of the received signals as an advantageous means of constructing multiple sets of distinct autocorrelation matrices evaluated at equals time lags. Channel estimation is then performed via joint diagonalization of a set of differential autocorrelation target matrices, avoiding the need of noise power or statistical distribution estimation. A broad set of simulation experiments is presented in distinctive signal contexts as a means of supporting and evidencing the potential of the proposed estimation method.
Improving Delay-Based Data Dissemination Protocol in VANETs with Network Coding
Authors: Mirani Farhan H. , Busson Anthony , Adjih Cedric 
Published: May 2016

In vehicular ad hoc networks (VANETs), for a large number of applications, the destination of relevant information such as alerts, is the whole set of vehicles located inside a given area. Therefore dissemination with efficient broadcast is an essential communication primitive. One of the families of broadcast protocols suitable for such networks, is the family of delay-based broadcast protocols, where farthest receivers retransmit first and where transmissions also act as implicit acknowledgements. For lossless networks, such protocols may approach the optimum efficiency. However with realistic loss models of VANET wireless communication, their performance is noticeably degraded. This is because packet losses have a double effect: directly on the amount of successfully received packets and indirectly with implicit acknowledgement misses. In this article, in order to combat the effects of packet losses, we combine delay-based broadcast with network coding, through a new protocol: Delay-based Opportunistic Network Coding protocol (DONC). By design, DONC aims at cancelling the twofold effects of packet and implicit acknowledgement losses. We describe the details of the DONC protocol, and we study its behavior, with realistic models and simulations. Results illustrate the excellent performance of the protocol.
Lattice-Reduction-Aided Detection with Successive Interference Cancelation for Multiuser Space-Time Block Coded Systems
Authors: Nguyen Tien Duc , Le Quang Duc , Tran Xuan Nam , Fujino Tadashi 
Published: May 2016

Effective detectors with low-complexity are considered for the Alamouti’s multiuser space-time block coded (STBC) systems. Viewing the noiseless received signals from Q users as a lattice with basis vectors being the columns of the total channel matrix H, we apply lattice reduction to transform the original basis into a nearly orthogonal one which improves the decision regions against noise. Then, linear detection using zero-forcing (ZF) and minimum-mean-square-error (MMSE) methods is performed on the transformed basis to detect transmitted signals from the Q users. These lattice-reduction-aided (LRA) linear detectors significantly improve BER of the linear detectors and, more importantly, allow us to achieve full diversity at high Eb/N0 regions.
Interference Analysis for OFDM Transmissions in the Presence of Time-Varying Channel Impairments
Authors: Nguyen-Duy-Nhat Vien , Nguyen-Le Hung , Tang-Tan Chien 
Published: May 2016

This paper is concerned with the detrimental effect of phase noise on the performance of orthogonal frequency division multiplexing (OFDM) transmissions over time-selective channels. In the literature, most of the existing papers analyze the performance of OFDM systems in the presence of either time-selective channels or phase noise. Unlike the existing studies, this paper formulates an approximate expression of signal-to-interference-plus-noise ratio (SINR) at an OFDM receiver in the presence of both phase noise and time-selective channel response. The formulated SINR expression can be used as a guideline in determining appropriate OFDM transmission settings under a given quality-of-service (QoS) requirement. To illustrate the tightness of the approximate SINR formulation, empirical and theoretical values of SINR under different OFDM system settings are presented in this paper.
A Comprehensive Model for Performance Analysis of APD-based FSO Systems using M-PPM Signaling in Atmospheric Turbulence
Authors: Pham Hien T. T. , Dang Ngoc T. 
Published: May 2016

In this paper, a model of Gaussian pulse propagation over atmospheric turbulence channel is used to comprehensively analyze the performance of APD-based free-space optical communication (FSO) systems using M-PPM signaling. This model is able to simultaneously take into account all effects of atmospheric turbulence including attenuation, intensity fluctuation, and pulse broadening, which has not been considered in previous works. In addition, the impacts of APD shot noise, background noise, and thermal noise are included in our analysis. The numerical results show that the main factor that limits the system performance is intensity fluctuation. However, when M is large enough, optical pulse is so short that the effect of pulse broadening becomes dominant. By using APD receiver, bit-error rate is improved significantly. Finally, based on channel capacity, we are able to determine the maximum transmission length of the system.
A Comparative Survey on 3D Models Retrieval Methods
Authors: Ali Sarah , Tran Trung-Thien , Laurendeau Denis 
Published: May 2016

In computer vision many studies have been conducted in order to perform the matching and comparison of 3D models of objects. The main goal of matching is to group the models into different categories according to their similarity in order to allow their retrieval for recognition purposes and for further usage. So, in most of the cases, the comparison is run on a large dataset containing various models whether they belong to the same type of object or not and generally having similar or different shapes and poses. The objects’ nature and characteristics are important factors to be taken into consideration before performing the comparison step. We distinguish between two main categories of objects: rigid objects and deformable objects whose treatment and handling differ in the modeling as well as in the comparison phases. In this paper, we will be focusing on the comparison of deformable objects, and thus dealing with objects whose shapes might vary in different instances. For this purpose two main approaches used in the retrieval of 3D deformable models will be reviewed and implemented: the spectral approach and the bag-of-features approach. The deformation or variation in shape involves different aspects depending on the type of object. It could be a change in the posture of an articulated or bendable model, or it could result from a variation (loss or gain) in the total mass leading to a change in the surface and thus in the shape of the object. Even more complex situations occur when both cases are combined together.
On The Performance of Underlay Relay Cognitive Networks
Authors: Ho-Van Khuong , Bao Vo Nguyen Quoc 
Published: May 2016

The bit error rate (BER) performance of underlay relay cognitive networks in the presence of Rayleigh fading is thoroughly analyzed in this paper. New exact and asymptotic analytic expressions under consideration of both interference power constraint and maximum transmit power constraint are derived in closed-form and are extensively corroborated by Monte-Carlo simulations. These expressions facilitate in evaluating effectively the network performance behaviour in key operation parameters as well as in optimizing system parameters. A multitude of analytical results expose that underlay relay cognitive networks experience the performance saturation phenomena while their performance considerably depends on the number of hops for the linear network model. Additionally, optimum relay position is significantly dependent of maximum transmit power, maximum interference power, and licensee location. Moreover, the appropriate order of locating unlicensees with different maximum transmit power levels can dramatically improve the network performance.
Improved Time and Frequency Synchronization Algorithm for 802.11a Wireless Standard based on the SIGNAL Field
Authors: Nguyen Cong Luong , Mokraoui Anissa , Duhamel Pierre , Linh-Trung Nguyen 
Published: May 2016

Time and frequency synchronization in the IEEE 802.11a OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system is addressed in this paper. Usually synchronization algorithms rely only on training sequences specified by the standard. To enhance the synchronization between stations, we propose to extract known information by both the transmitter and the receiver at the IEEE 802.11a physical layer to be then exploited by the receiver in addition to the training sequences. Indeed the parts of the identified SIGNAL field are either known or predictable from the RtS (Request to Send) control frame when the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism is triggered jointly to bit-rate adaptation algorithms to the channel. Moreover the received RtS control frame allows the receiver to estimate the channel before time synchronization stage improving then the performance of the proposed synchronization algorithm. Simulation results show that the performance of the proposed synchronization algorithm is improved as compared to existing algorithms.
A New Decoding Algorithm based on Equivalent Parity Check Matrix for LDPC Codes
Authors: Hung Nguyen Tung 
Published: May 2016

The article introduces a new LDPC decoding algorithm based on Equivalent Parity Check Matrix. Simulation results show that the new LDPC decoding algorithm can improve LDPC decoding performance. Compared to some other improvements, the new LDPC decoding algorithm, which is simpler, can detect errors and be applied to LDPC codes for great-length LDPC codes.
A Novel Non-Stationary Channel Model Utilizing Brownian Random Paths
Authors: Borhani Alireza , Pätzold Matthias 
Published: May 2016

This paper proposes a non-stationary channel model in which real-time dynamics of the mobile station (MS) are taken into account. We utilize Brownian motion (BM) processes to model targeted and non-targeted dynamics of the MS. The proposed trajectory model consists of both drift and random components to capture both targeted and non-targeted motions of the MS. The Brownian trajectory model is then employed to provide a non-stationary channel model, in which the scattering effects of the propagation area are modelled by a non-centred one-ring geometric scattering model. The starting point of the motion is a fixed point in the propagation environment, whereas its terminating point is a random point along a predetermined drift. The drift component can be controlled by a so-called drift parameter. Tracking the MS on the proposed Brownian path allows us to derive the local angles-of-arrival (AOAs) and local angles-of-motion (AOMs), which are expressed by stochastic processes rather than random variables. We compute the first-order densities of the AOA and AOM processes in closed form. The local power spectral density (PSD) of the Doppler frequencies and the autocorrelation function (ACF) of the complex channel gain are also provided. Given a walking speed scenario, the analytical results are demonstrated and explained in depth. It turns out that the proposed Brownian path model results in a non-stationary non-isotropic channel model. The proposed geometry-based channel model is very useful for the performance analysis of mobile communication systems under non-stationary conditions.
Jointly Optimal Precoder and Power Allocation for an Amplify-and-Forward Half-Duplex Relay System
Authors: Rodríguez Leonardo J. , Tran Nghi H. , Le-Ngoc Tho 
Published: May 2016

This paper investigates the optimal precoder design and power allocation between the source and relay for a half-duplex single-relay non-orthogonal amplify-and-forward (NAF) system. Based on the pair-wise error probability (PEP) analysis, an optimal class of 2 × 2 precoders is first derived for the traditional power allocation scheme, where one-third of the system power is spent at the relay node, while two-thirds are spent at the source node. Different from optimal unitary precoders proposed earlier, the derived class of precoders indicates that the source should spend all its power transmitting a superposition of the symbols in the broadcast phase, while being silent in the cooperative phase, for optimal asymptotic performance. We then further address the problem of jointly optimal precoder and power allocation for the system under consideration. It is shown that the total power should be equally distributed to the source and the relay, and the source should again spend no power during the cooperative phase for the best asymptotic performance. Analytical and simulation results reveal that the proposed precoders not only exploit full cooperative diversity, but also provide significant coding gain over the optimal unitary precoders. For instance, a coding gain of around 1dB can be attained at the practical BER level of 10 − 5 for various modulation schemes.
High Performance Direction Finding Algorithm Based on Phase Locked Loop
Authors: Thanh Han Trong , Yem Vu Van 
Published: May 2016

Using Phase Locked Loop based single channel Direction Finding (DF) system to estimate the bearing angle or the coordinates of an incoming radio signal(s) has much more advantages than multiple receiver system does in many practical scenarios such as mobile communication. This method utilizes a bank of Phase Locked Loops (PLLs) to calculate the differential phase of signal received by an M-element uniform circular antenna array with a commutative switch followed by single channel Software Defined Radio (SDR) receiver. One important factor when using conventional phase locked loop is the requirement of the small convergence rate of the algorithm compared to the switching cycle. In order to achieve small convergence rate, we propose a method for DOA estimation with low computation complexity that improves significantly the performance of conventional PLLs system. An analysis of the challenges of computation complexity in this algorithm is presented. The simulation results for DOA estimation using the proposed structure with low complexity are shown to verify the performance of the system.