Semi-Automatic Generation of Transformation Rules in Model Driven Engineering: The Challenge and First Steps

W. Alouini,O. Guedhami,S. Hammoudi,M.Gammoudi,D. Lopes 보안공학연구지원센터 2011 International Journal of Software Engineering and Vol.5 No.1

Flexible Proportional-Rate Scheduling for OFDMA System

Leith, A.,Alouini, M-S,Dong In Kim,Xuemin Shen,Zhiqiang Wu IEEE 2013 IEEE transactions on mobile computing Vol.12 No.10

<P>In this paper, we study the sum-rate maximization algorithms for downlink and uplink orthogonal frequency division multiple access (OFDMA) systems under proportional-rate constraint (PRC) and minimum-rate constraint. We develop a low-complexity weighted channel signal-to-noise ratio (w-SNR)-based ranking scheme for user selection on each subchannel in OFDMA combined with waterfilling (WF) power allocation. Both offline and online optimization algorithms are developed to optimize the SNR weight vector to maximize the sum rate while satisfying several constraints, such as PRC. The offline weight optimization technique relies on the analytical throughput results developed in this paper, and the online weight adaptation method tracks the user rates and meets the PRC using a subgradient search. Furthermore, we introduce a novel SNR operating region test to enhance the multiuser diversity gain and the sum rate. The proposed schemes have a low complexity, which is linear to the numbers of users and subchannels. Simulation results verify the accuracy of the developed analytical rates and fairness formulas, and show that the proposed w-SNR schemes can achieve higher sum rates than several benchmark schemes that provide the PRC with either short-term or long-term fairness.</P>

Bit Error Probability of Noncoherent M-ary Orthogonal Modulation over Generalized Fading Channels

Simon, Marvin K.,Alouini, Mohamed-Slim The Korean Institute of Communications and Informa 1999 Journal of communications and networks Vol.1 No.2

Using a method recently reported in the literature for analyzing the bit error probability (BEP) performance of noncoherent Mary orthogonal signals with square-law combining in the presence of independent and identically distributed Nakagami-m faded paths, we are able to reformulate this method so as to apply to a generalized fading channel in which the fading in each path need not be identically distributed nor even distributed ac-cording to the same family of distribution. The method leads to exact expressions for the BEP in the form of a finite-range integral whose integrand involves the moment generating function of the combined signal-to-noise ratio and which can therefore be readily evaluated numerically. The mathematical formalism is illustrated by applying the method to some selected numerical examples of interest showing the impact of the multipath intensity profile (MIP) as well as the fading correlation profile (FCP) on the BEP performance of M-ary orthogonal signal over Nakagami-m fading channels. Thses numerical results show that both MIP and FCP induce a non-negligible degradition in the BEP and have therefore to be taken into account for the accurate prediction of the performance of such systems.

Performance Analysis of Two-Way Amplify and Forward Relaying with Adaptive Modulation over Multiple Relay Network

Kyu-Sung Hwang,Young-Chai Ko,Alouini, Mohamed-Slim IEEE 2011 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.59 No.2

<P>In this letter, we propose two-way amplify-and-forward relaying in conjunction with adaptive modulation in order to improve spectral efficiency of relayed communication systems while monitoring the required error performance. We also consider a multiple relay network where only the best relay node is utilized so that the diversity order increases while maintaining a low complexity of implementation as the number of relays increases. Based on the best relay selection criterion, we offer an upper bound on the signal-to-noise ratio to keep the performance analysis tractable. Our numerical examples show that the proposed system offers a considerable gain in spectral efficiency while satisfying the error rate requirements.</P>

Joint Statistics of Partial Sums of Ordered Exponential Variates and Performance of GSC RAKE Receivers over Rayleigh Fading Channel

Sung Sik Nam,Hasna, M. O.,Alouini, M-S IEEE 2011 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.59 No.8

<P>Spread spectrum receivers with generalized selection combining (GSC) RAKE reception were proposed and have been studied as alternatives to the classical two fundamental schemes: maximal ratio combining and selection combining because the number of diversity paths increases with the transmission bandwidth. Previous work on performance analyses of GSC RAKE receivers based on the signal to noise ratio focused on the development of methodologies to derive exact closed-form expressions for various performance measures. However, some open problems related to the performance evaluation of GSC RAKE receivers still remain to be solved such as the exact performance analysis of the capture probability and an exact assessment of the impact of self-interference on GSC RAKE receivers. The major difficulty in these problems is to derive some joint statistics of ordered exponential variates. With this motivation in mind, we capitalize in this paper on some new order statistics results to derive exact closed-form expressions for the capture probability and outage probability of GSC RAKE receivers subject to self-interference over independent and identically distributed Rayleigh fading channels, and compare it to that of partial RAKE receivers.</P>

An MGF-Based Unified Framework to Determine the Joint Statistics of Partial Sums of Ordered i.n.d. Random Variables

Nam, Sung Sik,Yang, Hong-Chuan,Alouini, Mohamed-Slim,Kim, Dong In Institute of Electrical and Electronics Engineers 2014 IEEE transactions on signal processing Vol. No.

<P>The joint statistics of partial sums of ordered random variables (RVs) are often needed for the accurate performance characterization of a wide variety of wireless communication systems. A unified analytical framework to determine the joint statistics of partial sums of ordered independent and identically distributed (i.i.d.) random variables was recently presented. However, the identical distribution assumption may not be valid in several real-world applications. With this motivation in mind, we consider in this paper the more general case in which the random variables are independent but not necessarily identically distributed (i.n.d.). More specifically, we extend the previous analysis and introduce a new more general unified analytical framework to determine the joint statistics of partial sums of ordered i.n.d. RVs. Our mathematical formalism is illustrated with an application on the exact performance analysis of the capture probability of generalized selection combining (GSC)-based RAKE receivers operating over frequency-selective fading channels with a non-uniform power delay profile.</P>

Codebook-Based Interference Alignment for Uplink MIMO Interference Channels

이현호,박기홍,고영채,Mohamed-Slim Alouini 한국통신학회 2014 Journal of communications and networks Vol.16 No.1

In this paper, we propose a codebook-based interferencealignment (IA) scheme in the constant multiple-input multipleoutput(MIMO) interference channel especially for the uplink scenario. In our proposed scheme, we assume cooperation among basestations (BSs) through reliable backhaul links so that global channelknowledge is available for all BSs, which enables BS to computethe transmit precoder and inform its quantized index to theassociated user via limited rate feedback link.We present an upperbound on the rate loss of the proposed scheme and derive the scalinglaw of the feedback load tomaintain a constant rate loss relativeto IA with perfect channel knowledge. Considering the impact ofoverhead due to training, cooperation, and feedback, we addressthe effective degrees of freedom (DOF) of the proposed scheme andderive the maximization of the effective DOF. From simulation results,we verify our analysis on the scaling law to preserve the multiplexinggain and confirm that the proposed scheme is more effectivethan the conventional IA scheme in terms of the effective DOF.

Performance analysis of joint switched diversity and adaptive modulation

Haewoon Nam,Young-chai Ko,Alouini, Mohamed-slim IEEE 2008 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.7 No.10

<P>In this paper, a simple and practical system based on a switched diversity scheme with adaptive modulation is presented. This system provides a reduced number of channel estimation while offering the optimum spectral efficiency given by a selection diversity system. In addition, the switching threshold is easily manipulated so as to make an efficient use of the tradeoff between spectral efficiency and channel estimation overhead. An extension of switched diversity into a multiuser scheduling is later also considered. This switch-based multiuser access scheme results in a lower average feedback load than that for the optimal selection-based multiuser scheme. Numerical results show that we can obtain a trade-off between spectral efficiency and the feedback load by choosing the switching threshold appropriately.</P>

Low Complexity Transmit Antenna Selection with Power Balancing in OFDM Systems

Ki-Hong Park,Young-Chai Ko,Alouini, M IEEE 2010 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.9 No.10

<P>In this paper, we consider multi-carrier systems with multiple transmit antennas under the power balancing constraint, which is defined as the constraint that the power on each antenna should be limited under a certain level due to the linearity of the power amplifier of the RF chain. Applying transmit antenna selection and fixed-power variable-rate transmission per subcarrier as a function of channel variations, we propose an implementation-friendly antenna selection method which offers a reduced complexity in comparison with the optimal antenna selection scheme. More specifically, in order to solve the subcarrier imbalance across the antennas, we operate a two-step reallocation procedure to minimize the loss of spectral efficiency. We also provide an analytic lower bound on the spectral efficiency for the proposed scheme. From selected numerical results, we show that our suboptimal scheme offers almost the same spectral efficiency as the optimal one.</P>

Performance analysis of incremental opportunistic relaying over identically and non-identically distributed cooperative paths

Kyu-Sung Hwang,Young-Chai Ko,Alouini, M.-S. IEEE 2009 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.8 No.4

<P>In this paper, we consider an incremental relaying protocol based on an amplify-and-forward transmission in conjunction with the best relay selection scheme over non-identically distributed relay channels. In order to satisfy the spectral efficiency and the bit error rate (BER) requirements, adaptive modulation is applied to our proposed scheme. We derive the average spectral efficiency, average BER and outage probability for the performance analysis of our proposed scheme. For a more tractable analysis, we start with an upper bound for the combined signal-to-noise ratio at the destination and provide closed-form expressions for independent non-identically distributed Rayleigh fading conditions. Our analytical-based numerical results are validated by some computer-based simulations. These results show that our proposed scheme leads to a considerable improvement in the performance of cooperative diversity systems.</P>