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Optimal Packet Scheduling in an Energy Harvesting Communication System
"... We consider the optimal packet scheduling problem in a singleuser energy harvesting wireless communication system. In this system, both the data packets and the harvested energy are modeled to arrive at the source node randomly. Our goal is to adaptively change the transmission rate according to th ..."
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Cited by 126 (26 self)
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We consider the optimal packet scheduling problem in a singleuser energy harvesting wireless communication system. In this system, both the data packets and the harvested energy are modeled to arrive at the source node randomly. Our goal is to adaptively change the transmission rate according to the traffic load and available energy, such that the time by which all packets are delivered is minimized. Under a deterministic system setting, we assume that the energy harvesting times and harvested energy amounts are known before the transmission starts. For the data traffic arrivals, we consider two different scenarios. In the first scenario, we assume that all bits have arrived and are ready at the transmitter before the transmission starts. In the second scenario, we consider the case where packets arrive during the transmissions, with known arrival times and sizes. We develop optimal offline scheduling policies which minimize the time by which all packets are delivered to the destination, under causality constraints on both data and energy arrivals.
Optimum transmission policies for battery limited energy harvesting nodes,” Submitted to IEEE Transactions on Wireless Communications, available at: http://arxiv.org/PS_cache/arxiv/pdf/1010/1010.6280v1.pdf. This full text paper was peer reviewed at the di
 in the IEEE ICC 2011 proceedings
"... Abstract—Wireless networks with energy harvesting battery equipped nodes are quickly emerging as a viable option for future wireless networks with extended lifetime. Equally important to their counterpart in the design of energy harvesting radios are the design principles that this new networking pa ..."
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Cited by 122 (23 self)
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Abstract—Wireless networks with energy harvesting battery equipped nodes are quickly emerging as a viable option for future wireless networks with extended lifetime. Equally important to their counterpart in the design of energy harvesting radios are the design principles that this new networking paradigm calls for. In particular, unlike wireless networks considered to date, the energy replenishment process and the storage constraints of the rechargeable batteries need to be taken into account in designing efficient transmission strategies. In this work, such transmission policies for rechargeable nodes are considered, and optimum solutions for two related problems are identified. Specifically, the transmission policy that maximizes the short term throughput, i.e., the amount of data transmitted in a finite time horizon is found. In addition, the relation of this optimization problem to another, namely, the minimization of the transmission completion time for a given amount of data is demonstrated, which leads to the solution of the latter as well. The optimum transmission policies are identified under the constraints on energy causality, i.e., energy replenishment process, as well as the energy storage, i.e., battery capacity. For battery replenishment, a model with discrete packets of energy arrivals is considered. The necessary conditions that the throughputoptimal allocation satisfies are derived, and then the algorithm that finds the optimal transmission policy with respect to the shortterm throughput and the minimum transmission completion time is given. Numerical results are presented to confirm the analytical findings. Index Terms—Energy harvesting, optimal scheduling, wireless networks, battery limited nodes. I.
Broadcasting with an energy harvesting rechargeable transmitter
 IEEE Trans. Wireless Comm
, 2010
"... Abstract—In this paper, we investigate the transmission completion time minimization problem in an additive white Gaussian noise (AWGN) broadcast channel, where the transmitter is able to harvest energy from the nature, using a rechargeable battery. The harvested energy is modeled to arrive at the t ..."
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Cited by 76 (22 self)
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Abstract—In this paper, we investigate the transmission completion time minimization problem in an additive white Gaussian noise (AWGN) broadcast channel, where the transmitter is able to harvest energy from the nature, using a rechargeable battery. The harvested energy is modeled to arrive at the transmitter during the course of transmissions. The transmitter has a fixed number of packets to be delivered to each receiver. The objective is to minimize the time by which all of the packets are delivered to their respective destinations. To this end, we optimize the transmit powers and transmission rates in a deterministic setting. We first analyze the structural properties of the optimal transmission policy in a twouser broadcast channel via the dual problem of maximizing the departure region by a fixed time
Optimal packet scheduling in a multiple access channel with rechargeable nodes
 in Proc. IEEE ICC
, 2011
"... Abstract: In this paper, we investigate the optimal packet scheduling problem in a twouser multiple access communication system, where the transmitters are able to harvest energy from the nature. Under a deterministic system setting, we assume that the energy harvesting times and harvested energy a ..."
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Cited by 61 (16 self)
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Abstract: In this paper, we investigate the optimal packet scheduling problem in a twouser multiple access communication system, where the transmitters are able to harvest energy from the nature. Under a deterministic system setting, we assume that the energy harvesting times and harvested energy amounts are known before the transmission starts. For the packet arrivals, we assume that packets have already arrived and are ready to be transmitted at the transmitter before the transmission starts. Our goal is to minimize the time by which all packets from both users are delivered to the destination through controlling the transmission powers and transmission rates of both users. We first develop a generalized iterative backward waterfilling algorithm to characterize the maximum departure region of the transmitters for any given deadline T. Then, based on the sequence of maximum departure regions at energy arrival instants, we decompose the transmission completion time minimization problem into convex optimization problems and solve the overall problem efficiently. Index Terms: Energyharvesting communications, iterative backward waterfilling, multiaccess channel, throughput maximization.
Optimal packet scheduling on an energy harvesting broadcast link
 IEEE J. Sel. Areas Commun
, 2011
"... The minimization of transmission completion time for a given number of bits per user in an energy harvesting communication system, where energy harvesting instants are known in an offline manner is considered. An achievable rate region with structural properties satisfied by the 2user AWGN Broadcas ..."
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Cited by 53 (1 self)
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The minimization of transmission completion time for a given number of bits per user in an energy harvesting communication system, where energy harvesting instants are known in an offline manner is considered. An achievable rate region with structural properties satisfied by the 2user AWGN Broadcast Channel capacity region is assumed. It is shown that even though all data are available at the beginning, a nonnegative amount of energy from each energy harvest is deferred for later use such that the transmit power starts at its lowest value and rises as time progresses. The optimal scheduler ends the transmission to both users at the same time. Exploiting the special structure in the problem, the iterative offline algorithm, FlowRight, from earlier literature, is adapted and proved to solve this problem. The solution has polynomial complexity in the number of harvests used, and is observed to converge quickly on numerical examples. Index Terms Packet scheduling, energy harvesting, AWGN broadcast channel, flowright, energyefficient scheduling.
Optimal broadcast scheduling for an energy harvesting rechargeable transmitter with a finite capacity battery
 IEEE Trans. Wireless Commun
"... Abstract—We consider the minimization of the transmission completion time with a battery limited energy harvesting transmitter in an Muser AWGN broadcast channel where the transmitter is able to harvest energy from the nature, using a finite storage capacity rechargeable battery. The harvested ener ..."
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Cited by 40 (19 self)
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Abstract—We consider the minimization of the transmission completion time with a battery limited energy harvesting transmitter in an Muser AWGN broadcast channel where the transmitter is able to harvest energy from the nature, using a finite storage capacity rechargeable battery. The harvested energy is modeled to arrive (be harvested) at the transmitter during the course of transmissions at arbitrary time instants. The transmitter has fixed number of packets for each receiver. Due to the finite battery capacity, energy may overflow without being utilized for data transmission. We derive the optimal offline transmission policy that minimizes the time by which all of the data packets are delivered to their respective destinations. We analyze the structural properties of the optimal transmission policy using a dual problem. We find the optimal total transmit power sequence by a directional waterfilling algorithm. We prove that there exist M − 1 cutoff power levels such that user i is allocated the power between the i−1st and the ith cutoff power levels subject to the availability of the allocated total power level. Based on these properties, we propose an algorithm that gives the globally optimal offline policy. The proposed algorithm uses directional waterfilling repetitively. Finally, we illustrate the optimal policy and compare its performance with several suboptimal policies under different settings. Index Terms—Energy harvesting, rechargeable wireless networks, broadcast channels, finitecapacity battery, transmission completion time minimization, throughput maximization. I.
Achieving AWGN capacity under stochastic energy harvesting
 IEEE Trans. on Inform. Theory
"... Abstract—In energy harvesting communication systems, an exogenous recharge process supplies energy necessary for data transmission and the arriving energy can be buffered in a battery before consumption. We determine the informationtheoretic capacity of the classical additive white Gaussian noise ( ..."
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Cited by 37 (17 self)
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Abstract—In energy harvesting communication systems, an exogenous recharge process supplies energy necessary for data transmission and the arriving energy can be buffered in a battery before consumption. We determine the informationtheoretic capacity of the classical additive white Gaussian noise (AWGN) channelwithanenergyharvestingtransmitterwithanunlimited sized battery. As the energy arrives randomly and can be saved in the battery, codewords must obey cumulative stochastic energy constraints. We show that the capacity of the AWGN channel with such stochastic channel input constraints is equal to the capacity with an average power constraint equal to the average recharge rate. We provide two capacity achieving schemes: saveandtransmit and bestefforttransmit. In the saveandtransmit scheme, the transmitter collects energy in a saving phase of proper duration that guarantees that there will be no energy shortages during the transmission of code symbols. In the bestefforttransmit scheme, the transmission starts right away without an initial saving period, and the transmitter sends a code symbol if there is sufficient energy in the battery, and a zero symbol otherwise. Finally, we consider a system in which the average recharge rate is time varying in a larger time scale and derive the optimal offline power policy that maximizes the average throughput, by using majorization theory. Index Terms—Additive white Gaussian noise (AWGN) channel, energy harvesting, offline power management, Shannon capacity. I.
Optimal transmission policies for energy harvesting twohop networks
 in Proc. 2012 Conf. Inform. Sciences and Systems
, 2012
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Optimal power allocation for energy harvesting and power grid coexisting wireless communication systems
 IEEE Transactions on Communications
, 2013
"... Abstract—This paper considers the power allocation of a singlelink wireless communication with joint energy harvesting and grid power supply. We formulate the problem as minimizing the grid power consumption with random energy and data arrival in fading channel, and analyze the structure of the opt ..."
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Cited by 15 (10 self)
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Abstract—This paper considers the power allocation of a singlelink wireless communication with joint energy harvesting and grid power supply. We formulate the problem as minimizing the grid power consumption with random energy and data arrival in fading channel, and analyze the structure of the optimal power allocation policy in some special cases. For the case that all the packets are arrived before transmission, it is a dual problem of throughput maximization, and the optimal solution is found by the twostage water filling (WF) policy, which allocates the harvested energy in the first stage, and then allocates the power grid energy in the second stage. For the random data arrival case, we first assume grid energy or harvested energy supply only, and then combine the results to obtain the optimal structure of the coexisting system. Specifically, the reverse multistage WF policy is proposed to achieve the optimal power allocation when the battery capacity is infinite. Finally, some heuristic online schemes are proposed, of which the performance is evaluated by numerical simulations. Index Terms—Energy harvesting and power grid coexisting, convex optimization, twostage water filling, reverse multistage water filling. I.
Leveraging Dynamic Spare Capacity in Wireless Systems to Conserve Mobile Terminals’ Energy
 TO APPEAR IN IEEE/ACM TRANSACTIONS ON NETWORKING
, 2009
"... In this paper we study several ways in which mobile terminals can backoff on their uplink transmit power in order to extend battery lifetimes. This is particularly effective when a wireless system is underloaded as the degradation in user’s perceived quality of service can be negligible. The challen ..."
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Cited by 11 (2 self)
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In this paper we study several ways in which mobile terminals can backoff on their uplink transmit power in order to extend battery lifetimes. This is particularly effective when a wireless system is underloaded as the degradation in user’s perceived quality of service can be negligible. The challenge, however, is developing a mechanism that achieves a good tradeoff among transmit power, idling/circuit power, and the performance customers will see. We consider systems with flowlevel dynamics supporting either realtime or best effort (e.g., file transfers) sessions. The energyoptimal transmission strategy for realtime sessions is determined by solving a convex optimization. An iterative approach exhibiting superlinear convergence achieves substantial amount energy savings, e.g., more than 50 % when the session blocking probability is 0.1 % or less. The case of file transfers is more subtle because power backoff changes the system dynamics. We study energyefficient transmission strategies that realize energydelay tradeoff. The proposed mechanism achieves a 35–75 % in energy savings depending on the load and file transfer target throughput. A key insight, relative to previous work focusing on static scenarios, is that idling power has a significant impact on energyefficiency, while circuit power has limited impact as the load increases.