The Experts below are selected from a list of 1542 Experts worldwide ranked by ideXlab platform
Mohamed-slim Alouini - One of the best experts on this subject based on the ideXlab platform.
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GLOBECOM - Rate adaptive hierarchical modulation assisted two-user opportunistic scheduling
GLOBECOM '05. IEEE Global Telecommunications Conference 2005., 2020Co-Authors: Jahangir Hossain, Mohamed-slim Alouini, Vijay K. BhargavaAbstract:We propose and study a two best user opportunistic scheduling algorithm using discrete rate adaptive hierarchical constellations (known also as embedded, multi-resolution, or asymmetrical constellations). The key idea is to rely on hierarchical constellations to transmit information to the two best users opportunistically. The newly proposed scheme transmits information to single or two best users jointly considering the channel qualities of these users. We present expressions for the information transmission probability and the overall Average Spectral Efficiency [Bits/Sec/Hz] defined as the overall Average transmitted data rate per unit bandwidth for a specified number of users, Average carrier-to-noise ratio (CNR), and bit error rate (BER). Numerical results for an identical and independent (i.i.d.) fading environment, where the channel variation among the users is i.i.d., are presented. The results show that in such i.i.d. fading environment, our newly proposed discrete rate adaptive hierarchical modulation assisted two best user scheduling provides more frequent access to the information (almost double) without any Average Spectral Efficiency degradation compared to the classical single best user opportunistic scheduling.
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IWCMC - A threshold-based multiple optical signal selection scheme for WDM FSO systems
2017 13th International Wireless Communications and Mobile Computing Conference (IWCMC), 2017Co-Authors: Mohamed-slim Alouini, Young-chai KoAbstract:In this paper, we propose a threshold-based-multiple optical signal selection scheme (TMOS) for free-space optical systems based on wavelength division multiplexing. With the proposed TMOS, we can obtain higher Spectral Efficiency while reducing the potential increase in complexity of implementation caused by applying a selection-based beam selection scheme without a considerable performance loss. Here, to accurately characterize the performance of the proposed TMOS, we statistically analyze the characteristics with heterodyne detection technique over independent and identically distributed Log-normal turbulence conditions taking into considerations the impact of pointing error. Specifically, we derive exact closed-form expressions for the Average bit error rate, and the Average Spectral Efficiency by adopting an adaptive modulation. Some selected results shows that the Average Spectral Efficiency can be increased with TMOS while the system requirement is satisfied.
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Threshold-based multiple optical signal selection scheme for free-space optical wavelength division multiplexing systems
IEEE OSA Journal of Optical Communications and Networking, 2017Co-Authors: Sung Sik Nam, Mohamed-slim Alouini, Lin Zhang, Young-chai KoAbstract:We propose a threshold-based multiple optical signal selection scheme (TMOS) for free-space optical wavelength division multiplexing systems. With this scheme, we can obtain higher Spectral Efficiency while reducing the possible complexity of implementation caused by the beam-selection scheme and without a considerable performance loss. To characterize the performance of our scheme, we statistically analyze the operation characteristics under conventional detection conditions (i.e., heterodyne detection and intensity modulation/direct detection techniques) with log-normal turbulence while taking into consideration the impact of pointing error. More specifically, we derive exact closed-form expressions for the outage probability, the Average bit error rate, and the Average Spectral Efficiency while adopting an adaptive modulation. Some selected results show that TMOS increases the Average Spectral Efficiency while maintaining a minimum Average bit error rate requirement.
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Performance analysis of switch-based multiuser scheduling schemes with adaptive modulation in spectrum sharing systems
Wireless Communications and Mobile Computing, 2014Co-Authors: Marwa Qaraqe, Mohamed Abdallah, Erchin Serpedin, Mohamed-slim AlouiniAbstract:This paper focuses on the development of multiuser access schemes for spectrum sharing systems whereby secondary users are allowed to share the spectrum with primary users under the condition that the interference observed at the primary receiver is below a predetermined threshold. In particular, two scheduling schemes are proposed for selecting a user among those that satisfy the interference constraint and achieve an acceptable signal-to-noise ratio level. The first scheme focuses on optimizing the Average Spectral Efficiency by selecting the user that reports the best channel quality. In order to alleviate the relatively high feedback required by the first scheme, a second scheme based on the concept of switched diversity is proposed, where the base station BS scans the secondary users in a sequential manner until a user whose channel quality is above an acceptable predetermined threshold is found. We develop expressions for the statistics of the signal-to-interference and noise ratio as well as the Average Spectral Efficiency, Average feedback load, and the delay at the secondary BS. We then present numerical results for the effect of the number of users and the interference constraint on the optimal switching threshold and the system performance and show that our analysis results are in perfect agreement with the numerical results. Copyright © 2014 John Wiley & Sons, Ltd.
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Adaptive Discrete Rate and Power Transmission for Spectrum Sharing Systems
IEEE Transactions on Wireless Communications, 2012Co-Authors: Mohamed M. Abdallah, Ahmed H. Salem, Mohamed-slim Alouini, Khalid A. QaraqeAbstract:In this paper we develop a framework for optimizing the performance of the secondary link in terms of the Average Spectral Efficiency assuming quantized channel state information (CSI) of the secondary and the secondary-to-primary interference channels available at the secondary transmitter. We consider the problem under the constraints of maximum Average interference power levels at the primary receiver. We develop a sub-optimal computationally efficient iterative algorithm for finding the optimal CSI quantizers as well as the discrete power and rate employed at the cognitive transmitter for each quantized CSI level so as to maximize the Average Spectral Efficiency. We show via analysis and simulations that the proposed algorithm converges for Rayleigh fading channels. Our numerical results give the number of bits required to sufficiently represent the CSI to achieve almost the maximum Average Spectral Efficiency attained using full knowledge of the CSI.
George K. Karagiannidis - One of the best experts on this subject based on the ideXlab platform.
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GLOBECOM - Average Spectral Efficiency of Opportunistic QRD-Based Cyclic Prefixed Single-Carrier Cooperative Diversity Systems with Power Allocation
2010 IEEE Global Telecommunications Conference GLOBECOM 2010, 2010Co-Authors: Theodoros A. Tsiftsis, George K. KaragiannidisAbstract:Due to higher peak-to-Average power ratio and higher power backing-off in OFDM relaying systems, a cyclic prefixed single-carrier cooperative diversity system is considered in this paper. Under the transmission power constraint, the joint optimal power allocation to the source and relay node is investigated.
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Average Spectral Efficiency of opportunistic qrd based cyclic prefixed single carrier cooperative diversity systems with power allocation
Global Communications Conference, 2010Co-Authors: Theodoros A. Tsiftsis, George K. KaragiannidisAbstract:Due to higher peak-to-Average power ratio and higher power backing-off in OFDM relaying systems, a cyclic prefixed single-carrier cooperative diversity system is considered in this paper. Under the transmission power constraint, the joint optimal power allocation to the source and relay node is investigated.
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Average Spectral Efficiency of Opportunistic QRD-Based Cyclic Prefixed Single-Carrier Cooperative Diversity Systems with Power Allocation
2010 IEEE Global Telecommunications Conference GLOBECOM 2010, 2010Co-Authors: Theodoros A. Tsiftsis, George K. KaragiannidisAbstract:Due to higher peak-to-Average power ratio and higher power backing-off in OFDM relaying systems, a cyclic prefixed single-carrier cooperative diversity system is considered in this paper. Under the transmission power constraint, the joint optimal power allocation to the source and relay node is investigated. For a two-hop decode-and-forward relaying protocol, the optimal power allocation is first obtained in the considered system, and then the opportunistic destination terminal selection is applied to improve the achievable Average Spectral Efficiency (ASE). Based on the proposed QR decomposition (QRD)-based receiver in the destination terminal, closed-form expressions for the maximum achievable ASE are derived. Simulation results verify the derived closed-form analytical expressions.
Young-chai Ko - One of the best experts on this subject based on the ideXlab platform.
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IWCMC - A threshold-based multiple optical signal selection scheme for WDM FSO systems
2017 13th International Wireless Communications and Mobile Computing Conference (IWCMC), 2017Co-Authors: Mohamed-slim Alouini, Young-chai KoAbstract:In this paper, we propose a threshold-based-multiple optical signal selection scheme (TMOS) for free-space optical systems based on wavelength division multiplexing. With the proposed TMOS, we can obtain higher Spectral Efficiency while reducing the potential increase in complexity of implementation caused by applying a selection-based beam selection scheme without a considerable performance loss. Here, to accurately characterize the performance of the proposed TMOS, we statistically analyze the characteristics with heterodyne detection technique over independent and identically distributed Log-normal turbulence conditions taking into considerations the impact of pointing error. Specifically, we derive exact closed-form expressions for the Average bit error rate, and the Average Spectral Efficiency by adopting an adaptive modulation. Some selected results shows that the Average Spectral Efficiency can be increased with TMOS while the system requirement is satisfied.
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Threshold-based multiple optical signal selection scheme for free-space optical wavelength division multiplexing systems
IEEE OSA Journal of Optical Communications and Networking, 2017Co-Authors: Sung Sik Nam, Mohamed-slim Alouini, Lin Zhang, Young-chai KoAbstract:We propose a threshold-based multiple optical signal selection scheme (TMOS) for free-space optical wavelength division multiplexing systems. With this scheme, we can obtain higher Spectral Efficiency while reducing the possible complexity of implementation caused by the beam-selection scheme and without a considerable performance loss. To characterize the performance of our scheme, we statistically analyze the operation characteristics under conventional detection conditions (i.e., heterodyne detection and intensity modulation/direct detection techniques) with log-normal turbulence while taking into consideration the impact of pointing error. More specifically, we derive exact closed-form expressions for the outage probability, the Average bit error rate, and the Average Spectral Efficiency while adopting an adaptive modulation. Some selected results show that TMOS increases the Average Spectral Efficiency while maintaining a minimum Average bit error rate requirement.
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Maximum Spectral Efficiency of Amplify-and-Forward Cooperative Transmission with Multiple Relays
IEEE Transactions on Wireless Communications, 2011Co-Authors: Jae-woo Kwon, Young-chai Ko, Hong-chuan YangAbstract:In this paper, we propose a new amplify-and-forward (AF) cooperative transmission scheme with adaptive modulation to maximize overall system Spectral Efficiency. We quantify the Average Spectral Efficiency performance of the proposed scheme through statistical analysis based on an upper bound of the combiner output signal-to-noise ratio (SNR) and obtain the closed-form solutions for some practical scenarios of interest.
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Joint Adaptive M-QAM and Selection Combining in SVD-Based MIMO Systems
IEICE Transactions on Communications, 2009Co-Authors: Young-chai Ko, Taehyun JeonAbstract:In this paper, we propose a hybrid M-ary Quadrature Amplitude Modulation (M-QAM) transmission scheme that jointly uses discrete-rate adaptation and selection combining for singular value decomposition (SVD)-based multiple-input multiple-output (MIMO) systems, and derive exact closed-form expressions of the performance of the proposed scheme in terms of the Average Spectral Efficiency and the outage probability.
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Performance analysis of opportunistic incremental relaying with adaptive modulation over cooperative networks
2008 3rd International Symposium on Wireless Pervasive Computing, 2008Co-Authors: Kyu-sung Hwang, Young-chai Ko, Mohamed-slim AlouiniAbstract:Opportunistic relaying and incremental relaying over cooperative network were introduced as efficient relaying protocols to increase the system capacity and performance. In this paper, we propose an opportunistic incremental relaying scheme in conjunction with adaptive modulation, and provide its performance analysis in terms of Average Spectral Efficiency, Average bit error rate, and outage probability. For more tractable analysis, we start with an upper bound for the combined signal-to-noise ratio at the destination and derive closed-form expressions for Rayleigh fading conditions. Our analytical-based numerical results are validated by some selected computer-based simulations.
Theodoros A. Tsiftsis - One of the best experts on this subject based on the ideXlab platform.
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GLOBECOM - Average Spectral Efficiency of Opportunistic QRD-Based Cyclic Prefixed Single-Carrier Cooperative Diversity Systems with Power Allocation
2010 IEEE Global Telecommunications Conference GLOBECOM 2010, 2010Co-Authors: Theodoros A. Tsiftsis, George K. KaragiannidisAbstract:Due to higher peak-to-Average power ratio and higher power backing-off in OFDM relaying systems, a cyclic prefixed single-carrier cooperative diversity system is considered in this paper. Under the transmission power constraint, the joint optimal power allocation to the source and relay node is investigated.
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Average Spectral Efficiency of opportunistic qrd based cyclic prefixed single carrier cooperative diversity systems with power allocation
Global Communications Conference, 2010Co-Authors: Theodoros A. Tsiftsis, George K. KaragiannidisAbstract:Due to higher peak-to-Average power ratio and higher power backing-off in OFDM relaying systems, a cyclic prefixed single-carrier cooperative diversity system is considered in this paper. Under the transmission power constraint, the joint optimal power allocation to the source and relay node is investigated.
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Average Spectral Efficiency of Opportunistic QRD-Based Cyclic Prefixed Single-Carrier Cooperative Diversity Systems with Power Allocation
2010 IEEE Global Telecommunications Conference GLOBECOM 2010, 2010Co-Authors: Theodoros A. Tsiftsis, George K. KaragiannidisAbstract:Due to higher peak-to-Average power ratio and higher power backing-off in OFDM relaying systems, a cyclic prefixed single-carrier cooperative diversity system is considered in this paper. Under the transmission power constraint, the joint optimal power allocation to the source and relay node is investigated. For a two-hop decode-and-forward relaying protocol, the optimal power allocation is first obtained in the considered system, and then the opportunistic destination terminal selection is applied to improve the achievable Average Spectral Efficiency (ASE). Based on the proposed QR decomposition (QRD)-based receiver in the destination terminal, closed-form expressions for the maximum achievable ASE are derived. Simulation results verify the derived closed-form analytical expressions.
Khalid A. Qaraqe - One of the best experts on this subject based on the ideXlab platform.
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Adaptive Discrete Rate and Power Transmission for Spectrum Sharing Systems
IEEE Transactions on Wireless Communications, 2012Co-Authors: Mohamed M. Abdallah, Ahmed H. Salem, Mohamed-slim Alouini, Khalid A. QaraqeAbstract:In this paper we develop a framework for optimizing the performance of the secondary link in terms of the Average Spectral Efficiency assuming quantized channel state information (CSI) of the secondary and the secondary-to-primary interference channels available at the secondary transmitter. We consider the problem under the constraints of maximum Average interference power levels at the primary receiver. We develop a sub-optimal computationally efficient iterative algorithm for finding the optimal CSI quantizers as well as the discrete power and rate employed at the cognitive transmitter for each quantized CSI level so as to maximize the Average Spectral Efficiency. We show via analysis and simulations that the proposed algorithm converges for Rayleigh fading channels. Our numerical results give the number of bits required to sufficiently represent the CSI to achieve almost the maximum Average Spectral Efficiency attained using full knowledge of the CSI.
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Adaptive rate transmission for spectrum sharing system with quantized channel state information
2011 45th Annual Conference on Information Sciences and Systems, 2011Co-Authors: Mohamed Abdallah, Mohamed-slim Alouini, Ahmed Salem, Khalid A. QaraqeAbstract:The capacity of a secondary link in spectrum sharing systems has been recently investigated in fading environments. In particular, the secondary transmitter is allowed to adapt its power and rate to maximize its capacity subject to the constraint of maximum interference level allowed at the primary receiver. In most of the literature, it was assumed that estimates of the channel state information (CSI) of the secondary link and the interference level are made available at the secondary transmitter via an infinite-resolution feedback links between the secondary/primary receivers and the secondary transmitter. However, the assumption of having infinite resolution feedback links is not always practical as it requires an excessive amount of bandwidth. In this paper we develop a framework for optimizing the performance of the secondary link in terms of the Average Spectral Efficiency assuming quantized CSI available at the secondary transmitter. We develop a computationally efficient algorithm for optimally quantizing the CSI and finding the optimal power and rate employed at the cognitive transmitter for each quantized CSI level so as to maximize the Average Spectral Efficiency. Our results give the number of bits required to represent the CSI sufficient to achieve almost the maximum Average Spectral Efficiency attained using full knowledge of the CSI for Rayleigh fading channels.
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CISS - Adaptive rate transmission for spectrum sharing system with quantized channel state information
2011 45th Annual Conference on Information Sciences and Systems, 2011Co-Authors: Mohamed Abdallah, Mohamed-slim Alouini, Ahmed Salem, Khalid A. QaraqeAbstract:The capacity of a secondary link in spectrum sharing systems has been recently investigated in fading environments. In particular, the secondary transmitter is allowed to adapt its power and rate to maximize its capacity subject to the constraint of maximum interference level allowed at the primary receiver. In most of the literature, it was assumed that estimates of the channel state information (CSI) of the secondary link and the interference level are made available at the secondary transmitter via an infinite-resolution feedback links between the secondary/primary receivers and the secondary transmitter. However, the assumption of having infinite resolution feedback links is not always practical as it requires an excessive amount of bandwidth. In this paper we develop a framework for optimizing the performance of the secondary link in terms of the Average Spectral Efficiency assuming quantized CSI available at the secondary transmitter. We develop a computationally efficient algorithm for optimally quantizing the CSI and finding the optimal power and rate employed at the cognitive transmitter for each quantized CSI level so as to maximize the Average Spectral Efficiency. Our results give the number of bits required to represent the CSI sufficient to achieve almost the maximum Average Spectral Efficiency attained using full knowledge of the CSI for Rayleigh fading channels.
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Discrete rate and variable power adaptation for underlay cognitive networks
2010 European Wireless Conference (EW), 2010Co-Authors: Mohamed Abdallah, Mohamed-slim Alouini, Ahmed Salem, Khalid A. QaraqeAbstract:We consider the problem of maximizing the Average Spectral Efficiency of a secondary link in underlay cognitive networks. In particular, we consider the network setting whereby the secondary transmitter employs discrete rate and variable power adaptation under the constraints of maximum Average transmit power and maximum Average interference power allowed at the primary receiver due to the existence of an interference link between the secondary transmitter and the primary receiver. We first find the optimal discrete rates assuming a predetermined partitioning of the signal-to-noise ratio (SNR) of both the secondary and interference links. We then present an iterative algorithm for finding a suboptimal partitioning of the SNR of the interference link assuming a fixed partitioning of the SNR of secondary link selected for the case where no interference link exists. Our numerical results show that the Average Spectral Efficiency attained by using the iterative algorithm is close to that achieved by the computationally extensive exhaustive search method for the case of Rayleigh fading channels. In addition, our simulations show that selecting the optimal partitioning of the SNR of the secondary link assuming no interference link exists still achieves the maximum Average Spectral Efficiency for the case where the Average interference constraint is considered.
