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128
Dual methods for nonconvex spectrum optimization of multicarrier systems
- IEEE TRANS. COMMUN
, 2006
"... The design and optimization of multicarrier communications systems often involve a maximization of the total throughput subject to system resource constraints. The optimization problem is numerically difficult to solve when the problem does not have a convexity structure. This paper makes progress ..."
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Cited by 201 (7 self)
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The design and optimization of multicarrier communications systems often involve a maximization of the total throughput subject to system resource constraints. The optimization problem is numerically difficult to solve when the problem does not have a convexity structure. This paper makes progress toward solving optimization problems of this type by showing that under a certain condition called the time-sharing condition, the duality gap of the optimization problem is always zero, regardless of the convexity of the objective function. Further, we show that the time-sharing condition is satisfied for practical multiuser spectrum optimization problems in multicarrier systems in the limit as the number of carriers goes to infinity. This result leads to efficient numerical algorithms that solve the nonconvex problem in the dual domain. We show that the recently proposed optimal spectrum balancing algorithm for digital subscriber lines can be interpreted as a dual algorithm. This new interpretation gives rise to more efficient dual update methods. It also suggests ways in which the dual objective may be evaluated approximately, further improving the numerical efficiency of the algorithm. We propose a low-complexity iterative spectrum balancing algorithm based on these ideas, and show that the new algorithm achieves near-optimal performance in many practical situations.
Joint optimization of relay strategies and resource allocations in cooperative cellular networks
- in Proceedings of the Conference on Information Sciences and Systems (CISS
, 2006
"... Abstract — This paper considers a wireless cooperative cellular data network with a base station and many subscribers in which the subscribers have the ability to relay information for each other to improve the overall network performance. For a wireless network operating in a frequency-selective fa ..."
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Cited by 103 (2 self)
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Abstract — This paper considers a wireless cooperative cellular data network with a base station and many subscribers in which the subscribers have the ability to relay information for each other to improve the overall network performance. For a wireless network operating in a frequency-selective fading environment, the choices of relay node, relay strategy, and the allocation of power and bandwidth for each user are important design parameters. The design challenge is compounded further by the need to take user traffic demands into consideration. This paper proposes a utility maximization framework for such a network. We show that for a cellular system employing orthogonal frequency-division multiple-access (OFDMA), the optimization of physical-layer transmission strategies can be done efficiently by introducing a set of pricing variables. The proposed solution incorporates both user traffic demand and the physical channel realization in a cross-layer design that not only allocates power and bandwidth optimally for each user, but also selects the best relay node and best relay strategy (i.e. decode-and-forward vs. amplify-and-forward) for each source-destination pair. I.
Application-driven cross-layer optimization for video streaming over wireless networks
- IEEE Communications Magazine
, 2006
"... This paper proposes a cross-layer optimization framework that provides efficient allocation of wireless network resources across multiple types of applications to maximize network capacity and user satisfaction. We define a novel optimization scheme based on the Mean Opinion Score (MOS) as the unify ..."
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Cited by 47 (3 self)
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This paper proposes a cross-layer optimization framework that provides efficient allocation of wireless network resources across multiple types of applications to maximize network capacity and user satisfaction. We define a novel optimization scheme based on the Mean Opinion Score (MOS) as the unifying metric. Our experiments, applied to scenarios where users simultaneously run three types of applications, such as realtime voice, video conferencing and file download, confirm that MOS-based optimization leads to significant improvement in terms of user perceived quality when compared to throughput-based optimization.
Cross-layer optimization for energy-efficient wireless communications: a survey,” to be published
"... Abstract—Since battery technology has not progressed as rapidly as semiconductor technology, power efficiency has be-come increasingly important in wireless networking, in addition to the traditional quality and performance measures, such as bandwidth, throughput, and fairness. Energy-efficient desi ..."
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Cited by 45 (7 self)
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Abstract—Since battery technology has not progressed as rapidly as semiconductor technology, power efficiency has be-come increasingly important in wireless networking, in addition to the traditional quality and performance measures, such as bandwidth, throughput, and fairness. Energy-efficient design requires a cross layer approach as power consumption is affected by all aspects of system design, ranging from silicon to applica-tions. This article presents a comprehensive overview of recent advances in cross-layer design for energy-efficient wireless com-munications. We particularly focus on a system-based approaches towards energy optimal transmission and resource management across time, frequency, and spatial domains. Details related to energy-efficient hardware implementations are also covered. Index Terms – energy efficiency, cross-layer, wireless commu-nications, energy aware I.
Dynamic Frequency Allocation in Fractional Frequency Reused OFDMA Networks
, 2009
"... This paper proposes a dynamic fractional frequency reused cell architecture that simplifies the problem of subcarrier allocation with frequency reuse in multicell OFDMA networks. The architecture divides the cell surface into two overlapping geographical regions and orthogonally allocates subcarrie ..."
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Cited by 33 (0 self)
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This paper proposes a dynamic fractional frequency reused cell architecture that simplifies the problem of subcarrier allocation with frequency reuse in multicell OFDMA networks. The architecture divides the cell surface into two overlapping geographical regions and orthogonally allocates subcarriers, which are called super and regular group of subcarriers, to the regions. The proposed architecture allows a frequency reuse factor of 1 with reduced inter-cell interference and increased trunking gain, while satisfying minimum data rate requirements. We also propose an efficient hierarchical solution to realize the proposed architecture. The solution first allocates subcarriers to the groups so that long term performance is maximized and next opportunistically schedules subcarriers to the users. The opportunistic scheduling is performed at the base stations considering the fairness requirements of the users. Simulation results illustrate the performance improvements of the proposed solution in comparison to the traditional frequency allocation schemes.
Radio resource allocation algorithms for the downlink of multiuser OFDM communication systems
- Commun. Surveys Tuts
, 2009
"... Abstract—This article surveys different resource allocation algorithms developed for the downlink of multiuser OFDM wireless communication systems. Dynamic resource allocation algorithms are categorized into two major classes: margin adaptive (MA) and rate adaptive (RA). The objective of the first c ..."
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Cited by 25 (0 self)
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Abstract—This article surveys different resource allocation algorithms developed for the downlink of multiuser OFDM wireless communication systems. Dynamic resource allocation algorithms are categorized into two major classes: margin adaptive (MA) and rate adaptive (RA). The objective of the first class is to minimize the total transmit power with the constraint on users ’ data rates whereas in the second class, the objective is to maximize the total throughput with the constraints on the total transmit power as well as users ’ data rates. The overall performance of the algorithms are evaluated in terms of spectral efficiency and fairness. Considering the trade-off between these two features of the system, some algorithms attempt to reach the highest possible spectral efficiency while maintaining acceptable fairness in the system. Furthermore, a large number of RA algorithms considers rate proportionality among the users and hence, are categorized as RA with constrained-fairness. Following the problem formulation in each category, the discussed algo-rithms are described along with their simplifying assumptions that attempt to keep the performance close to optimum but significantly reduce the complexity of the problem. It is noted that no matter which optimization method is used, in both classes, the overall performance is improved with the increase in the number of users, due to multiuser diversity. Some on-going research areas are briefly discussed throughout the article. Index Terms—OFDM, radio resource management, adaptive subcarrier and power allocation, fairness, rate and margin adaptive algorithms. I.
Asymptotic Throughput Analysis for Channel-Aware Scheduling ∗
"... In this paper, we provide an asymptotic performance analysis of channel-aware packet scheduling based on extreme value theory. We first address the average throughput of systems with a homogeneous average signal-to-noise ratio (SNR) and obtain its asymptotic expression. Compared to the exact through ..."
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Cited by 24 (1 self)
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In this paper, we provide an asymptotic performance analysis of channel-aware packet scheduling based on extreme value theory. We first address the average throughput of systems with a homogeneous average signal-to-noise ratio (SNR) and obtain its asymptotic expression. Compared to the exact through-put expression, the asymptotic one, which is applicable to a broader range of fading channels, is more concise and easier to get insights. Furthermore, we confirm the accuracy of the asymptotic results by theoretical analysis and numerical simulation. For a system with heterogeneous SNRs, normalized-SNR-based scheduling need to be used for fairness. We also investigate the asymptotic average throughput of the normalized-SNR-based scheduling and prove that the average throughput in this case is less than that in the homogeneous case with a power constraint.
Efficient Resource Allocation with Flexible Channel Cooperation in OFDMA Cognitive Radio Networks
"... Abstract—Recently, a cooperative paradigm for single-channel cognitive radio networks has been advocated, where primary users can leverage secondary users to relay their traffic. However, it is not clear how such cooperation can be exploited in multi-channel networks effectively. Conventional cooper ..."
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Cited by 22 (1 self)
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Abstract—Recently, a cooperative paradigm for single-channel cognitive radio networks has been advocated, where primary users can leverage secondary users to relay their traffic. However, it is not clear how such cooperation can be exploited in multi-channel networks effectively. Conventional cooperation entails that data on one channel has to be relayed on exactly the same channel, which is inefficient in multi-channel networks with channel and user diversity. Moreover, the selfishness of users complicates the critical resource allocation problem, as both parties target at maximizing their own utility. This work represents the first attempt to address these challenges. We propose FLEC, a novel design of flexible channel cooperation. It allows secondary users to freely optimize the use of channels for transmitting primary data along with their own data, in order to maximize performance. Further, we formulate a unifying optimization framework based on Nash Bargaining Solutions to fairly and efficiently address resource allocation between primary and secondary networks, in both decentralized and centralized settings. We present an optimal distributed algorithm and sub-optimal centralized heuristics, and verify their effectiveness via realistic simulations.
Optimization framework and graph-based approach for relay-assisted bidirectional OFDMA cellular networks
- IEEE Trans. Wireless Commun
, 2010
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Cross-Layer Design in Wireless Mesh Networks
"... Abstract—The conventional layered-protocol architecture does not provide optimal performance for wireless mesh networks (WMNs). The method of optimization decomposition of the protocol stack can achieve optimal network performance. This method usually results in a clean-slate protocol architecture t ..."
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Cited by 21 (0 self)
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Abstract—The conventional layered-protocol architecture does not provide optimal performance for wireless mesh networks (WMNs). The method of optimization decomposition of the protocol stack can achieve optimal network performance. This method usually results in a clean-slate protocol architecture that is different from the protocol architecture of WMNs. Such a difference actually demonstrates the need for a cross-layer design. Specific features pertaining to WMNs also show the need for cross-layer optimization across different protocol layers. In this paper, motivations for cross-layer design in WMNs are stated first. Moreover, cross-layer optimization schemes and algorithms between different protocol layers are investigated with an objective of shedding light on open research problems and new approaches. Guidelines for carrying out cross-layer design in WMNs are also provided in this paper. Index Terms—Control, cross-layer design, medium access, optimization decomposition, routing, wireless mesh networks. I.
