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Distributed energyefficient power optimization in cellular relay networks with minimum rate constraints
 in Proc. IEEE Intl. Conf. Acoustics, Speech and Signal Process. (ICASSP
, 2014
"... In this work, we derive a distributed power control algorithm for energyefficient uplink transmissions in interferencelimited cellular networks, equipped with either multiple or shared relays. The proposed solution is derived by modeling the mobile terminals as utilitydriven rational agents tha ..."
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Cited by 6 (3 self)
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In this work, we derive a distributed power control algorithm for energyefficient uplink transmissions in interferencelimited cellular networks, equipped with either multiple or shared relays. The proposed solution is derived by modeling the mobile terminals as utilitydriven rational agents that engage in a noncooperative game, under minimumrate constraints. The theoretical analysis of the game equilibrium is used to compare the performance of the two different cellular architectures. Extensive simulations show that the shared relay concept outperforms the distributed one in terms of energy efficiency in most network configurations. 1.
1Energy Efficiency Optimization in RelayAssisted MIMO Systems with Perfect and Statistical CSI
"... A framework for energyefficient resource allocation in a singleuser, amplifyandforward (AF), relayassisted, multipleinputmultipleoutput (MIMO) system is devised in this paper. Previous results in this area have focused on rate maximization or sum power minimization problems, whereas fewer re ..."
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Cited by 4 (2 self)
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A framework for energyefficient resource allocation in a singleuser, amplifyandforward (AF), relayassisted, multipleinputmultipleoutput (MIMO) system is devised in this paper. Previous results in this area have focused on rate maximization or sum power minimization problems, whereas fewer results are available when bits/Joule energy efficiency (EE) optimization is the goal. Here, the performance metric to optimize is the ratio between the system’s achievable rate and the total consumed power. The optimization is carried out with respect to the source and relay precoding matrices, subject to qualityofservice (QoS) and power constraints. Such a challenging nonconvex optimization problem is tackled by means of fractional programming and alternating maximization algorithms, for various channel state information (CSI) assumptions at the source and relay. In particular the scenarios of perfect CSI and those of statistical CSI for either the sourcerelay or the relaydestination channel are addressed. Moreover, sufficient conditions for beamforming optimality are derived, which is useful in simplifying the system design. Numerical results are provided to corroborate the validity of the theoretical findings. Index Terms Copyright (c) 2013 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purpose must be obtained from the IEEE by sending a request to pubspermissions@ieee.org.
EnergyAware Competitive Power Allocation for Heterogeneous Networks Under QoS Constraints
"... This work proposes a distributed power allocation scheme for maximizing energy efficiency in the uplink of orthogonal frequencydivision multiple access (OFDMA)based heterogeneous networks (HetNets) where a macrotier is augmented with a mix of small cell access points – broadly varying in capabili ..."
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Cited by 3 (1 self)
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This work proposes a distributed power allocation scheme for maximizing energy efficiency in the uplink of orthogonal frequencydivision multiple access (OFDMA)based heterogeneous networks (HetNets) where a macrotier is augmented with a mix of small cell access points – broadly varying in capabilities. The user equipment (UE) in the network are modeled as rational agents that engage in a noncooperative game where each UE allocates its available transmit power over the set of assigned subcarriers so as to maximize its individual utility (defined as the user’s throughput per Watt of transmit power) subject to minimumrate constraints. In this framework, the relevant solution concept is that of a Debreu equilibrium, a generalization of the concept of Nash equilibrium which accounts for the case where an agent’s set of possible actions depends on the actions of its opponents. Since the problem at hand might not be feasible, Debreu equilibria do not always exist. However, using techniques from fractional programming, we provide a characterization of equilibrial power allocation profiles for when they do exist. In particular, Debreu equilibria are found to be the fixed points of a waterfilling best response operator whose water level is a function of minimum rate constraints and circuit power. Moreover, we also describe a set of sufficient conditions for the existence and uniqueness of Debreu equilibria exploiting the contraction properties of the best response operator. This analysis provides the necessary tools to derive a power allocation scheme that steers the network to equilibrium in an iterative and distributed manner without the need for any centralized processing. Numerical simulations are then used to validate the analysis and assess the performance of the proposed algorithm as a function of the system parameters, also discussing key design tradeoffs to meet 5G requirements (e.g., obtaining more than 500 b/s/Hz/km2 area spectral efficiency) with a reasonable amount of physical resources (e.g., bandwidth and transmit power), and complexity at the receiving stations, such as minimal information requirements at the user level and number of antennas.
Green Power Control in Cognitive Wireless Networks
, 2013
"... Abstract—A decentralized network of cognitive and noncognitive transmitters where each transmitter aims at maximizing his energyefficiency is considered. The cognitive transmitters are assumed to be able to sense the transmit power of their noncognitive counterparts and the former have a cost for s ..."
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Abstract—A decentralized network of cognitive and noncognitive transmitters where each transmitter aims at maximizing his energyefficiency is considered. The cognitive transmitters are assumed to be able to sense the transmit power of their noncognitive counterparts and the former have a cost for sensing. The Stackelberg equilibrium analysis of this 2−level hierarchical game is conducted, which allows us to better understand the effects of cognition on energyefficiency. In particular, it is proven that the network energyefficiency is maximized when only a given fraction of terminals are cognitive. Then, we study a sensing game where all the transmitters are assumed to take the decision whether to sense (namely to be cognitive) or not. This game is shown to be a weighted potential game and its set of equilibria is studied. Playing the sensing game in a first phase (e.g., of a timeslot) and then playing the power control game is shown to be more efficient individually for all transmitters than playing a game where a transmitter would jointly optimize whether to sense and his power level, showing the existence of a kind of Braess paradox. The derived results are illustrated by numerical results and provide some insights on how to deploy cognitive radios in heterogeneous networks in terms of sensing capabilities. Index Terms—Power Control, Stackelberg Equilibrium, EnergyEfficiency.
Crosslayer design for green power control
 IEEE International Conference on Communications (ICC
, 2012
"... Abstract—In this work, we propose a new energy efficiency metric which allows one to optimize the performance of a wireless system through a novel power control mechanism. The proposed metric possesses two important features. First, it considers the whole power of the terminal and not just the radia ..."
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Abstract—In this work, we propose a new energy efficiency metric which allows one to optimize the performance of a wireless system through a novel power control mechanism. The proposed metric possesses two important features. First, it considers the whole power of the terminal and not just the radiated power. Second, it can account for the limited buffer memory of transmitters which store arriving packets as a queue and transmit them with a success rate that is determined by the transmit power and channel conditions. Remarkably, this metric is shown to have attractive properties such as quasiconcavity with respect to the transmit power and a unique maximum, allowing to derive an optimal power control scheme. Based on analytical and numerical results, the influence of the packet arrival rate, the size of the queue, and the constraints in terms of quality of service are studied. Simulations show that the proposed crosslayer approach of power control may lead to significant gains in terms of transmit power compared to a physical layer approach of green communications. I.
An energyefficient power allocation game with selfish channel state reporting in cellular networks
 in Performance Evaluation Methodologies and Tools (VALUETOOLS), 2012 6th International Conference on, 2012
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A crosslayer approach for distributed energyefficient power control in interference networks
 IEEE Transactions on Vehicular Technology
, 2014
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GREEN RESOURCE ALLOCATION IN RELAYASSISTED MIMO SYSTEMSWITH STATISTICAL CHANNEL STATE INFORMATION
"... Green resource allocation in an amplifyandforward (AF) relayassisted MIMO system is considered, consisting of one source, one AF relay, and one destination, in which the relaytodestination channel is only statistically known to the source and relay. The source covariance matrix and the relay AF ..."
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Green resource allocation in an amplifyandforward (AF) relayassisted MIMO system is considered, consisting of one source, one AF relay, and one destination, in which the relaytodestination channel is only statistically known to the source and relay. The source covariance matrix and the relay AF matrix are optimized so as to maximize the system energy efficiency (EE), defined as the ratio of the system ergodic achievable rate over the total consumed power. The resulting optimization problem is a challenging nonconvex problem, which is tackled employing fractional programming in conjunction with the alternating maximization algorithm. In addition, the regime of singlestream transmission is investigated and a sufficient condition for its optimality is derived.
Power Control in Networks With Heterogeneous Users: A QuasiVariational Inequality Approach
"... AbstractThis work deals with the power allocation problem in a multipointtomultipoint network, which is heterogenous in the sense that each transmit and receiver pair can arbitrarily choose whether to selfishly maximize its own rate or energy efficiency. This is achieved by modeling the transmit ..."
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AbstractThis work deals with the power allocation problem in a multipointtomultipoint network, which is heterogenous in the sense that each transmit and receiver pair can arbitrarily choose whether to selfishly maximize its own rate or energy efficiency. This is achieved by modeling the transmit and receiver pairs as rational players that engage in a noncooperative game in which the utility function changes according to each player's nature. The underlying game is reformulated as a quasi variational inequality (QVI) problem using convex fractional program theory. The equivalence between the QVI and the noncooperative game provides us with all the mathematical tools to study the uniqueness of its Nash equilibrium points and to derive novel algorithms that allow the network to converge to these points in an iterative manner, both with and without the need for a centralized processing. Numerical results are used to validate the proposed solutions in different operating conditions.
DOI: 10.1109/SPAWC.2013.6612123 Energy Efficient Design in MIMO Multicell Systems with Time Average QoS Constraints
, 2014
"... Abstract—In this work, we address the issue of energy efficient design in a MIMO multicell network consisting of N cells, Nt antennas per BS and K UTs per cell. Under this set up, we address the following question: given certain time average QoS targets for the users, what is the minimum energy exp ..."
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Abstract—In this work, we address the issue of energy efficient design in a MIMO multicell network consisting of N cells, Nt antennas per BS and K UTs per cell. Under this set up, we address the following question: given certain time average QoS targets for the users, what is the minimum energy expenditure with which they can be met? Time average QoS constraints can lead to greater energy savings as compared to instantaneous QoS constraints since it provides the flexibility to dynamically allocate resources over the fading channel states. We formulate the problem as a stochastic optimization problem whose solution is the design of the downlink beamforming vectors during each time slot. We first characterize the set of time average QoS targets which is achievable by some feasible control policy. We then use the technique of virtual queue to model the time average QoS constraints and convert the problem into a queue stabilization problem while minimizing the time average energy expenditure. We solve this problem using the approach of Lyapunov optimization and characterize its performance. Interestingly, our solution leads to a decentralized design in which the BSs only have to exchange limited side information. Our simulation results show that solving the problem with time average QoS constraints provide greater energy savings as compared to the instantaneous QoS constraints. I.