The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
Hayssam Dahrouj - One of the best experts on this subject based on the ideXlab platform.
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power spectrum optimization for interference mitigation via Iterative Function evaluation
Eurasip Journal on Wireless Communications and Networking, 2012Co-Authors: Hayssam Dahrouj, Wei Yu, Taiwen TangAbstract:Power spectrum optimization is a well-known difficult nonconvex optimization problem for which only local optimality can typically be assured. This paper unifies several classes of local optimization methods and proposes efficient and new methods for power spectrum optimization by observing that methods for reaching the local optimal points can often be expressed in the form of an Iterative Function evaluation. This proposed new approach is based on the fact that the gradient of the objective Function is zero at a local optimum, and that different manipulations of the optimality condition can then lead to different power update equations. As a practical application, this paper examines the benefit of dynamic power spectrum optimization for interference mitigation in a wireless backhaul network in which remote radio units are deployed to serve mobile users in areas with high data traffic demand. The remote radio units, called remote terminals (RT), are connected to access nodes (AN) via orthogonal frequency division multiple access (OFDMA) over a fixed bandwidth with one RT active in each frequency tone. The system performance is thus limited by internode interference solely, and no intranode interference. This paper shows that Iterative Function evaluation based methods provide a significant improvement in the overall network throughput in this setting as compared to a conventional network with fixed transmit power spectrum. The proposed methods have computationally fast convergence and can be implemented in a distributed fashion assuming reasonable amount of internode information exchange. Further, some of the proposed methods can be implemented asynchronously at each AN, which makes them amenable to practical utilization.
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On power spectrum optimization by Iterative Function evaluation
2012 26th Biennial Symposium on Communications (QBSC), 2012Co-Authors: Hayssam Dahrouj, Wei Yu, Taiwen TangAbstract:The problem of optimally adjusting the power spectral density level, referred as power spectrum optimization, is a well-known and difficult nonconvex optimization problem. This paper investigates a class of local optimization methods based on a technique called Iterative Function evaluation. This idea, first proposed in our previous work, is based on the manipulation of the first order condition of the optimization problem into an algorithm. This paper shows that these manipulations are not unique, and proposes a new Iterative-Function-evaluation-based method for power spectrum optimization. In addition, this paper proposes methods based on the average channel gains for an orthogonal frequency division multiple access network. Finally, the performance of the proposed methods is evaluated in a wireless backhaul application.
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Interference mitigation via power control under the one-power-zone constraint
2012 IEEE Global Communications Conference (GLOBECOM), 2012Co-Authors: Hayssam Dahrouj, Wei Yu, Jerry Chow, Radu SeleaAbstract:Complexity and hardware constraints are two essential considerations in applying interference mitigation techniques to practical wireless systems. This paper considers a practical wireless backhaul network composed of several access nodes (AN), each serving several remote terminals (RT), and where the transmit frame structure at each AN is comprised of multiple zones, with different RTs scheduled on different zones. The objective of this paper is to design power control strategies to mitigation inter-AN interference in the downlink. Unlike prior studies, this paper adopts a practical constraint whereby every AN maintains the same power level across the different zones within one transmitted frame. The main advantage of imposing this new constraint, called the one-power-zone (OPZ) constraint in this paper, is that for a class of scheduling policies under which the number of zones assigned to each RT is fixed, the power optimization and the scheduling subproblems are decoupled under the OPZ constraint. This allows the design of efficient power control methods independent of scheduling. Further, it also simplifies the design of radio-frequency (RF) front-end. The main contribution of this paper is a set of efficient algorithms to solve this constrained power control problem based on an Iterative Function evaluation technique. The proposed algorithms have low computational complexity, and can be implemented in a distributed fashion. Some of these algorithms can be further implemented asynchronously at each AN.
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Power spectrum optimization for interference mitigation via Iterative Function evaluation
2011 IEEE GLOBECOM Workshops (GC Wkshps), 2011Co-Authors: Hayssam Dahrouj, Wei Yu, Taiwen Tang, Steve BeaudinAbstract:This paper proposes practical methods for and examines the benefit of dynamic power spectrum optimization for interference mitigation in wireless networks. The paper envisions a distributed antenna system, deployed as a means to increase the network capacity for areas with high data traffic demand. The network comprises several access nodes (AN), each serving a fixed set of remote radio units called remote terminals (RT). The RTs belonging to each AN are separated from each other using orthogonal frequency division multiple access (OFDMA) over a fixed bandwidth, where only one RT is active at each frequency tone. The system performance is thus limited by internode interference solely, and no intranode interference. This paper proposes methods for power spectrum optimization based on the idea of Iterative Function evaluation. The proposed methods provide a significant improvement of the overall network throughput, as compared to conventional wireless networks with fixed transmit power spectrum. The proposed methods are computationally feasible and fast in convergence. They can be implemented in a distributed fashion across all access nodes, with reasonable amount of internode information exchange. Some of the proposed methods can be further implemented asynchronously at each AN, which makes them amenable to practical utilization.
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Mode Selection and Power Allocation in Multi-level Cache-enabled Networks
IEEE Communications Letters, 1Co-Authors: Ahmed Douik, Hayssam Dahrouj, Osama Amin, Bayan Al Oquibi, Tareq Y. Al-naffouri, Mohamed-slim AlouiniAbstract:Moving contents proximity to the network edge and proactively caching popular contents at multiple infrastructures are promising directions for solving the backhaul congestion problem. This paper proposes and evaluates a multi-level cacheenabled network, where cache-hit users can fetch their data from the available cache at either small base-stations, unmanned aerial vehicles, or cache-enabled mobile device-to-device users. Cache-miss users, on the other hand, fetch their data from the central cloud via limited capacity backhaul links. This paper considers the problem of maximizing the network weighted-sum rate by jointly determining the users’ mode of operation and their transmit powers, subject to backhaul capacity and transmit power constraints. After showing how the association problem can be formulated as a generalized assignment problem, the paper solves the transmit power problem using an Iterative Function evaluation apprach. The resulting mode-selection and powerallocation (MSPA) Iterative algorithm is then tested through numerical simulations, which suggest that, while being easily implementable, the proposed multi-level caching can substantially relieve the backhaul congestion, especially in dense-networks, and at low-backhaul capacity regimes.
Wei Yu - One of the best experts on this subject based on the ideXlab platform.
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power spectrum optimization for interference mitigation via Iterative Function evaluation
Eurasip Journal on Wireless Communications and Networking, 2012Co-Authors: Hayssam Dahrouj, Wei Yu, Taiwen TangAbstract:Power spectrum optimization is a well-known difficult nonconvex optimization problem for which only local optimality can typically be assured. This paper unifies several classes of local optimization methods and proposes efficient and new methods for power spectrum optimization by observing that methods for reaching the local optimal points can often be expressed in the form of an Iterative Function evaluation. This proposed new approach is based on the fact that the gradient of the objective Function is zero at a local optimum, and that different manipulations of the optimality condition can then lead to different power update equations. As a practical application, this paper examines the benefit of dynamic power spectrum optimization for interference mitigation in a wireless backhaul network in which remote radio units are deployed to serve mobile users in areas with high data traffic demand. The remote radio units, called remote terminals (RT), are connected to access nodes (AN) via orthogonal frequency division multiple access (OFDMA) over a fixed bandwidth with one RT active in each frequency tone. The system performance is thus limited by internode interference solely, and no intranode interference. This paper shows that Iterative Function evaluation based methods provide a significant improvement in the overall network throughput in this setting as compared to a conventional network with fixed transmit power spectrum. The proposed methods have computationally fast convergence and can be implemented in a distributed fashion assuming reasonable amount of internode information exchange. Further, some of the proposed methods can be implemented asynchronously at each AN, which makes them amenable to practical utilization.
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On power spectrum optimization by Iterative Function evaluation
2012 26th Biennial Symposium on Communications (QBSC), 2012Co-Authors: Hayssam Dahrouj, Wei Yu, Taiwen TangAbstract:The problem of optimally adjusting the power spectral density level, referred as power spectrum optimization, is a well-known and difficult nonconvex optimization problem. This paper investigates a class of local optimization methods based on a technique called Iterative Function evaluation. This idea, first proposed in our previous work, is based on the manipulation of the first order condition of the optimization problem into an algorithm. This paper shows that these manipulations are not unique, and proposes a new Iterative-Function-evaluation-based method for power spectrum optimization. In addition, this paper proposes methods based on the average channel gains for an orthogonal frequency division multiple access network. Finally, the performance of the proposed methods is evaluated in a wireless backhaul application.
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Interference mitigation via power control under the one-power-zone constraint
2012 IEEE Global Communications Conference (GLOBECOM), 2012Co-Authors: Hayssam Dahrouj, Wei Yu, Jerry Chow, Radu SeleaAbstract:Complexity and hardware constraints are two essential considerations in applying interference mitigation techniques to practical wireless systems. This paper considers a practical wireless backhaul network composed of several access nodes (AN), each serving several remote terminals (RT), and where the transmit frame structure at each AN is comprised of multiple zones, with different RTs scheduled on different zones. The objective of this paper is to design power control strategies to mitigation inter-AN interference in the downlink. Unlike prior studies, this paper adopts a practical constraint whereby every AN maintains the same power level across the different zones within one transmitted frame. The main advantage of imposing this new constraint, called the one-power-zone (OPZ) constraint in this paper, is that for a class of scheduling policies under which the number of zones assigned to each RT is fixed, the power optimization and the scheduling subproblems are decoupled under the OPZ constraint. This allows the design of efficient power control methods independent of scheduling. Further, it also simplifies the design of radio-frequency (RF) front-end. The main contribution of this paper is a set of efficient algorithms to solve this constrained power control problem based on an Iterative Function evaluation technique. The proposed algorithms have low computational complexity, and can be implemented in a distributed fashion. Some of these algorithms can be further implemented asynchronously at each AN.
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Power spectrum optimization for interference mitigation via Iterative Function evaluation
2011 IEEE GLOBECOM Workshops (GC Wkshps), 2011Co-Authors: Hayssam Dahrouj, Wei Yu, Taiwen Tang, Steve BeaudinAbstract:This paper proposes practical methods for and examines the benefit of dynamic power spectrum optimization for interference mitigation in wireless networks. The paper envisions a distributed antenna system, deployed as a means to increase the network capacity for areas with high data traffic demand. The network comprises several access nodes (AN), each serving a fixed set of remote radio units called remote terminals (RT). The RTs belonging to each AN are separated from each other using orthogonal frequency division multiple access (OFDMA) over a fixed bandwidth, where only one RT is active at each frequency tone. The system performance is thus limited by internode interference solely, and no intranode interference. This paper proposes methods for power spectrum optimization based on the idea of Iterative Function evaluation. The proposed methods provide a significant improvement of the overall network throughput, as compared to conventional wireless networks with fixed transmit power spectrum. The proposed methods are computationally feasible and fast in convergence. They can be implemented in a distributed fashion across all access nodes, with reasonable amount of internode information exchange. Some of the proposed methods can be further implemented asynchronously at each AN, which makes them amenable to practical utilization.
D.j. Jackson - One of the best experts on this subject based on the ideXlab platform.
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A new searchless fractal image encoding method for a real-time image compression device
2004 IEEE International Symposium on Circuits and Systems (IEEE Cat. No.04CH37512), 2004Co-Authors: S. Ongwattanakul, Xianwei Wu, D.j. JacksonAbstract:In this paper, we present a new searchless Iterative Function system (SIFS) fractal encoding method that encodes image range blocks based on fixed location domain blocks. The advantage of this method is that the fractal code does not contain coordinates (x,y) of the domain-range matched pairs. Therefore, the size of the range block can be as small as 2/spl times/2 pixels and still maintain a good compression rate and image quality. A fractal image encoding device based on the new method is implemented and tested. Finally, the experimental results of the fractal encoding device are presented. The results show that the peak signal-to-noise ratio (PSNR) and the compression rate of the reconstructed image are as good as the traditional domain block search methods. An FPGA implementation is capable of encoding a 256/spl times/256 8-bit gray-scale image in 0.63 ms. This provides the basis for real-time fractal image compression.
Taiwen Tang - One of the best experts on this subject based on the ideXlab platform.
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power spectrum optimization for interference mitigation via Iterative Function evaluation
Eurasip Journal on Wireless Communications and Networking, 2012Co-Authors: Hayssam Dahrouj, Wei Yu, Taiwen TangAbstract:Power spectrum optimization is a well-known difficult nonconvex optimization problem for which only local optimality can typically be assured. This paper unifies several classes of local optimization methods and proposes efficient and new methods for power spectrum optimization by observing that methods for reaching the local optimal points can often be expressed in the form of an Iterative Function evaluation. This proposed new approach is based on the fact that the gradient of the objective Function is zero at a local optimum, and that different manipulations of the optimality condition can then lead to different power update equations. As a practical application, this paper examines the benefit of dynamic power spectrum optimization for interference mitigation in a wireless backhaul network in which remote radio units are deployed to serve mobile users in areas with high data traffic demand. The remote radio units, called remote terminals (RT), are connected to access nodes (AN) via orthogonal frequency division multiple access (OFDMA) over a fixed bandwidth with one RT active in each frequency tone. The system performance is thus limited by internode interference solely, and no intranode interference. This paper shows that Iterative Function evaluation based methods provide a significant improvement in the overall network throughput in this setting as compared to a conventional network with fixed transmit power spectrum. The proposed methods have computationally fast convergence and can be implemented in a distributed fashion assuming reasonable amount of internode information exchange. Further, some of the proposed methods can be implemented asynchronously at each AN, which makes them amenable to practical utilization.
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On power spectrum optimization by Iterative Function evaluation
2012 26th Biennial Symposium on Communications (QBSC), 2012Co-Authors: Hayssam Dahrouj, Wei Yu, Taiwen TangAbstract:The problem of optimally adjusting the power spectral density level, referred as power spectrum optimization, is a well-known and difficult nonconvex optimization problem. This paper investigates a class of local optimization methods based on a technique called Iterative Function evaluation. This idea, first proposed in our previous work, is based on the manipulation of the first order condition of the optimization problem into an algorithm. This paper shows that these manipulations are not unique, and proposes a new Iterative-Function-evaluation-based method for power spectrum optimization. In addition, this paper proposes methods based on the average channel gains for an orthogonal frequency division multiple access network. Finally, the performance of the proposed methods is evaluated in a wireless backhaul application.
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Power spectrum optimization for interference mitigation via Iterative Function evaluation
2011 IEEE GLOBECOM Workshops (GC Wkshps), 2011Co-Authors: Hayssam Dahrouj, Wei Yu, Taiwen Tang, Steve BeaudinAbstract:This paper proposes practical methods for and examines the benefit of dynamic power spectrum optimization for interference mitigation in wireless networks. The paper envisions a distributed antenna system, deployed as a means to increase the network capacity for areas with high data traffic demand. The network comprises several access nodes (AN), each serving a fixed set of remote radio units called remote terminals (RT). The RTs belonging to each AN are separated from each other using orthogonal frequency division multiple access (OFDMA) over a fixed bandwidth, where only one RT is active at each frequency tone. The system performance is thus limited by internode interference solely, and no intranode interference. This paper proposes methods for power spectrum optimization based on the idea of Iterative Function evaluation. The proposed methods provide a significant improvement of the overall network throughput, as compared to conventional wireless networks with fixed transmit power spectrum. The proposed methods are computationally feasible and fast in convergence. They can be implemented in a distributed fashion across all access nodes, with reasonable amount of internode information exchange. Some of the proposed methods can be further implemented asynchronously at each AN, which makes them amenable to practical utilization.
Radu Selea - One of the best experts on this subject based on the ideXlab platform.
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Interference mitigation via power control under the one-power-zone constraint
2012 IEEE Global Communications Conference (GLOBECOM), 2012Co-Authors: Hayssam Dahrouj, Wei Yu, Jerry Chow, Radu SeleaAbstract:Complexity and hardware constraints are two essential considerations in applying interference mitigation techniques to practical wireless systems. This paper considers a practical wireless backhaul network composed of several access nodes (AN), each serving several remote terminals (RT), and where the transmit frame structure at each AN is comprised of multiple zones, with different RTs scheduled on different zones. The objective of this paper is to design power control strategies to mitigation inter-AN interference in the downlink. Unlike prior studies, this paper adopts a practical constraint whereby every AN maintains the same power level across the different zones within one transmitted frame. The main advantage of imposing this new constraint, called the one-power-zone (OPZ) constraint in this paper, is that for a class of scheduling policies under which the number of zones assigned to each RT is fixed, the power optimization and the scheduling subproblems are decoupled under the OPZ constraint. This allows the design of efficient power control methods independent of scheduling. Further, it also simplifies the design of radio-frequency (RF) front-end. The main contribution of this paper is a set of efficient algorithms to solve this constrained power control problem based on an Iterative Function evaluation technique. The proposed algorithms have low computational complexity, and can be implemented in a distributed fashion. Some of these algorithms can be further implemented asynchronously at each AN.
