The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Young-ho Jung - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Subchannel and bit allocation in multiuser MIMO/OFDMA systems
2004 IEEE 59th Vehicular Technology Conference. VTC 2004-Spring (IEEE Cat. No.04CH37514), 2004Co-Authors: In-soon Park, Young-ho JungAbstract:An adaptive Subchannel allocation and modulation scheme is developed for multiuser multiple-input multiple-output (MIMO)/orthogonal frequency division multiple access (OFDMA) systems through some modification of the approach for OFDMA systems. In the multiuser MIMO/OFDMA system, there are SDMA Subchannels, in which each user occupies a single-user MIMO Subchannel, for each OFDM subcarrier. An optimal procedure for allocating the SDMA Subchannels to users and loading bits to single-user MIMO Subchannels is formulated as an integer programming (IP) problem. Then, a suboptimal algorithm that separately performs Subchannel allocation and bit loading is proposed. Computer simulation results indicate that the performance of the suboptimal algorithm is reasonably close to that of the optimal IP.
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dynamic Subchannel and bit allocation in multiuser mimo ofdma systems
Vehicular Technology Conference, 2004Co-Authors: In-soon Park, Young-ho JungAbstract:An adaptive Subchannel allocation and modulation scheme is developed for multiuser multiple-input multiple-output (MIMO)/orthogonal frequency division multiple access (OFDMA) systems through some modification of the approach for OFDMA systems. In the multiuser MIMO/OFDMA system, there are SDMA Subchannels, in which each user occupies a single-user MIMO Subchannel, for each OFDM subcarrier. An optimal procedure for allocating the SDMA Subchannels to users and loading bits to single-user MIMO Subchannels is formulated as an integer programming (IP) problem. Then, a suboptimal algorithm that separately performs Subchannel allocation and bit loading is proposed. Computer simulation results indicate that the performance of the suboptimal algorithm is reasonably close to that of the optimal IP.
Suman Khakurel - One of the best experts on this subject based on the ideXlab platform.
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Joint Subchannel Assignment and Power Allocation for OFDMA Femtocell Networks
IEEE Transactions on Wireless Communications, 2014Co-Authors: Suman Khakurel, Tho Le-ngocAbstract:In this paper, we propose a joint Subchannel and power allocation algorithm for the downlink of an orthogonal frequency-division multiple access (OFDMA) mixed femtocell/macrocell network deployment. Specifically, the total throughput of all femtocell user equipments (FUEs) is maximized while the network capacity of an existing macrocell is always protected. Towards this end, we employ an iterative approach in which OFDM Subchannels and transmit powers of base stations (BS) are alternatively assigned and optimized at every step. For a fixed power allocation, we prove that the optimal policy in each cell is to give each Subchannel to the user with the highest signal-to-interference-plus-noise ratio (SINR) on that Subchannel. For a given Subchannel assignment, we adopt the successive convex approximation (SCA) approach and transform the highly nonconvex power allocation problem into a sequence of convex subproblems. In the arithmetic-geometric mean (AGM) approximation, we apply geometric programming to find optimal solutions after condensing a posynomial into a monomial. On the other hand, logarithmic and \underline{d}ifference-of-two-\underline{c}oncave-functions (D.C.) approximations lead us to solving a series of convex relaxation programs. With the three proposed SCA-based power optimization solutions, we show that the overall joint Subchannel and power allocation algorithm converges to some local maximum of the original design problem. While a central processing unit is required to implement the AGM approximation-based solution, each BS locally computes the optimal Subchannel and power allocation for its own servicing cell in the logarithmic and D.C. approximation-based solutions. Numerical examples confirm the merits of the proposed algorithm.
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distributed Subchannel and power allocation for ofdma based femtocell networks
Vehicular Technology Conference, 2013Co-Authors: Suman Khakurel, Tho LengocAbstract:This paper proposes a distributed joint Subchannel and power allocation algorithm for the downlink of an orthogonal frequency-division multiple access (OFDMA) mixed femtocell/macrocell network deployment. Specifically, the total throughput of all femtocell user equipments (FUEs) is maximized while the network capacity of an existing macrocell is always protected. To this end, we employ an iterative process in which Subchannels and transmit powers of base stations (BS) are alternatively assigned and optimized at every step. For a fixed power allocation, we prove that the optimal policy is to give each Subchannel to the user with the highest data rate, or equivalently the highest signal-to-interference-plus-noise ratio (SINR), on that Subchannel. For any given Subchannel assignment, we apply the difference-of-concave- functions (d.c.) approach and transform the highly nonconvex program into a sequence of convex power allocation subproblems. We show that the developed iterative scheme converges to an optimal point. Importantly, we implement the devised solution by a decentralized algorithm, wherein each BS computes the optimal Subchannel and power allocation for its own servicing cell. Numerical results confirm the merits of our proposed approach.
Aiping Huang - One of the best experts on this subject based on the ideXlab platform.
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optimal distributed Subchannel rate and power allocation algorithm in ofdm based two tier femtocell networks
Vehicular Technology Conference, 2010Co-Authors: Jianmin Zhang, Zhaoyang Zhang, Kedi Wu, Aiping HuangAbstract:In this paper, we address the problem of Subchannel, rate and power allocation in OFDM-based two-tier femtocell networks, which comprise a conventional macrocell and multiple femtocells. Our objective is maximizing the multiple femtocell users' weighted rate sum by jointly adjusting their Subchannel, rate and power allocation, under the constraints of cross-tier interference (CTI) between macrocell and multiple femtocells. Then we propose an optimal distributed resource allocation algorithm based on Lagrangian dual method, and interpret it from economics angle. In order to illustrate the benefit of allowing femtocells to share the Subchannels occupied by macrocell, we compare our system with another one (macrocell guard system), in which the femtocells can only use the Subchannels unoccupied by macrocell. Simulation results validate the proposed algorithm, and show that our system can obtain better performance than the macrocell guard system.
Tho Le-ngoc - One of the best experts on this subject based on the ideXlab platform.
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Joint Power and Subchannel Allocation in Heterogeneous OFDMA Small-Cell Networks
Architectures of Small-Cell Networks and Interference Management, 2020Co-Authors: Tho Le-ngocAbstract:This chapter proposes a joint Subchannel and power allocation algorithm for the downlink of an orthogonal frequency-division multiple access (OFDMA) small-cell network. The total throughput of all femtocell user equipments is maximized while the network capacity of an existing macrocell is protected. We employ an iterative approach in which Subchannels and transmit powers of base stations are alternatively assigned and optimized at every step. For a fixed power allocation, we prove that the optimal policy in each cell is to give each Subchannel to the user with the highest signal-to-interference-plus-noise ratio on that Subchannel. For a given Subchannel assignment, we adopt the successive convex approximation approach and transform the highly nonconvex power allocation problem into a sequence of convex subproblems. We show that the overall joint Subchannel and power allocation algorithm converges to some local maximum of the original design problem.
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Joint Subchannel Assignment and Power Allocation for OFDMA Femtocell Networks
IEEE Transactions on Wireless Communications, 2014Co-Authors: Suman Khakurel, Tho Le-ngocAbstract:In this paper, we propose a joint Subchannel and power allocation algorithm for the downlink of an orthogonal frequency-division multiple access (OFDMA) mixed femtocell/macrocell network deployment. Specifically, the total throughput of all femtocell user equipments (FUEs) is maximized while the network capacity of an existing macrocell is always protected. Towards this end, we employ an iterative approach in which OFDM Subchannels and transmit powers of base stations (BS) are alternatively assigned and optimized at every step. For a fixed power allocation, we prove that the optimal policy in each cell is to give each Subchannel to the user with the highest signal-to-interference-plus-noise ratio (SINR) on that Subchannel. For a given Subchannel assignment, we adopt the successive convex approximation (SCA) approach and transform the highly nonconvex power allocation problem into a sequence of convex subproblems. In the arithmetic-geometric mean (AGM) approximation, we apply geometric programming to find optimal solutions after condensing a posynomial into a monomial. On the other hand, logarithmic and \underline{d}ifference-of-two-\underline{c}oncave-functions (D.C.) approximations lead us to solving a series of convex relaxation programs. With the three proposed SCA-based power optimization solutions, we show that the overall joint Subchannel and power allocation algorithm converges to some local maximum of the original design problem. While a central processing unit is required to implement the AGM approximation-based solution, each BS locally computes the optimal Subchannel and power allocation for its own servicing cell in the logarithmic and D.C. approximation-based solutions. Numerical examples confirm the merits of the proposed algorithm.
Tommi Heikkinen - One of the best experts on this subject based on the ideXlab platform.
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Distributed Subchannel assignment in a two-hop network
Computer Networks, 2020Co-Authors: Tommi Heikkinen, Ari HottinenAbstract:This paper studies distributed Subchannel allocation in a two-hop network comprising multiple source nodes, one multi-channel relay node and one destination node. The underlying Subchannel allocation problem in a relay network, when posed as a centralized allocation problem, is formulated as a three-dimensional assignment problem. Distributed Subchannel allocation is studied using noncooperative game theory. A sequential game model is formulated where in first stage source nodes opportunistically select their transmission resources after which in second stage a channel-aware relay node assigns the resources in a way that maximizes the sum of utilities at the destination node. The Subchannel allocation game is a potential game, possessing an implicit joint objective (potential) of the players. Numerical examples illustrate the performance of opportunistic channel allocation in an OFDMA system. Using the sequential scheme, noncooperative allocation in first link implies performance similar to that obtained by solving two consecutive assignment problems, first optimizing the allocation of Subchannels in source-relay link and second in relay-destination link. Auction-based solutions to noncooperative Subchannel allocation, both with fixed and variable transmit power, are presented to obtain approximate solutions to the underlying centralized resource optimization problems.
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VALUETOOLS - Distributed Subchannel assignment in an OFDMA relay
Proceedings of the 2nd International ICST Conference on Performance Evaluation Methodologies and Tools, 2007Co-Authors: Ari Hottinen, Tommi HeikkinenAbstract:The paper studies a distributed OFDMA system in which the transmitting nodes (source and relay) have access to channel information and to some interference-related information. Distributed Subchannel allocation is modelled as a noncooperative game where the players are the source nodes. Channel-aware source nodes opportunistically select their Subchannels while a channel-aware relay node assigns the input Subchannels at relay to appropriate output Subchannels in a way that maximizes the sum of utilities in terms of signal-to-noise ratio. Numerical examples illustrate the performance of distributed Subchannel assignment; opportunistic channel allocation implies a trade-off between the average capacity and fairness.
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Optimal Subchannel assignment in a two-hop OFDM relay
2007 IEEE 8th Workshop on Signal Processing Advances in Wireless Communications, 2007Co-Authors: Ari Hottinen, Tommi HeikkinenAbstract:The paper studies Subchannel assignment in a two-hop OFDM relay system in which the transmitting nodes (source and relay) have access to channel information and interference-related information. We show that with L-superadditive relay (performance) functions a simple ranking of Subchannels leads to the optimal assignment with a very low computational complexity. Numerical results quantify the benefit of Subchannel assignment in a frequency-selective channel.
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Distributed Subchannel assignment in an OFDMA relay
VALUETOOLS 2007 - 2nd International ICST Conference on Performance Evaluation Methodologies and Tools, 2007Co-Authors: Ari Hottinen, Tommi HeikkinenAbstract:The paper studies a distributed OFDMA system in which the transmitting nodes (source and relay) have access to channel information and to some interference-related information. Distributed Subchannel allocation is modelled as a noncooperative game where the players are the source nodes. Channel-aware source nodes opportunistically select their Subchannels while a channel-aware relay node assigns the input Subchannels at relay to appropriate output Subchannels in a way that maximizes the sum of utilities in terms of signal-to-noise ratio. Numerical examples illustrate the performance of distributed Subchannel assignment; opportunistic channel allocation implies a trade-off between the average capacity and fairness. Copyright 2007 ICST.
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Subchannel assignment in OFDM relay nodes
2006 40th Annual Conference on Information Sciences and Systems, 2006Co-Authors: Ari Hottinen, Tommi HeikkinenAbstract:The paper considers a source-relay-destination link in which the relay node is allowed to reassign the input Subchannels to different output Subchannels. In particular, we consider a channel-aware relay node and compute the Subchannel reassignment that optimizes a selected performance criterion. The numerical results suggest that optimized Subchannel reassignment is particularly beneficial in frequency-selective channels and in channels where interference information is available at transmitter.
