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Crosslayer design for lifetime maximization in interferencelimited wireless sensor networks
, 2006
"... We consider the joint optimal design of the physical, medium access control (MAC), and routing layers to maximize the lifetime of energyconstrained wireless sensor networks. The problem of computing lifetimeoptimal routing flow, link schedule, and link transmission powers for all active time slots ..."
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Cited by 54 (6 self)
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We consider the joint optimal design of the physical, medium access control (MAC), and routing layers to maximize the lifetime of energyconstrained wireless sensor networks. The problem of computing lifetimeoptimal routing flow, link schedule, and link transmission powers for all active time slots is formulated as a nonlinear optimization problem. We first restrict the link schedules to the class of interferencefree time division multiple access (TDMA) schedules. In this special case, we formulate the optimization problem as a mixed integerconvex program, which can be solved using standard techniques. Moreover, when the slots lengths are variable, the optimization problem is convex and can be solved efficiently and exactly using interior point methods. For general nonorthogonal link schedules, we propose an iterative algorithm that alternates between adaptive link scheduling and computation of optimal link rates and transmission powers for a fixed link schedule. The performance of this algorithm is compared to other design approaches for several network topologies. The results illustrate the advantages of load balancing, multihop routing, frequency reuse, and interference mitigation in increasing the lifetime of energyconstrained networks. We also briefly discuss computational approaches to extend this algorithm to large networks.
A gametheoretic approach to energyefficient power control in multicarrier CDMA systems
 IEEE Journal on Selected Areas in Communications (JSAC
, 2006
"... Abstract—A gametheoretic model for studying power control in multicarrier codedivision multipleaccess systems is proposed. Power control is modeled as a noncooperative game in which each user decides how much power to transmit over each carrier to maximize its own utility. The utility function co ..."
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Cited by 42 (8 self)
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Abstract—A gametheoretic model for studying power control in multicarrier codedivision multipleaccess systems is proposed. Power control is modeled as a noncooperative game in which each user decides how much power to transmit over each carrier to maximize its own utility. The utility function considered here measures the number of reliable bits transmitted over all the carriers per joule of energy consumed and is particularly suitable for networks where energy efficiency is important. The multidimensional nature of users ’ strategies and the nonquasiconcavity of the utility function make the multicarrier problem much more challenging than the singlecarrier or throughputbasedutility case. It is shown that, for all linear receivers including the matched filter, the decorrelator, and the minimummeansquareerror detector, a user’s utility is maximized when the user transmits only on its “best ” carrier. This is the carrier that requires the least amount of power to achieve a particular target signaltointerferenceplusnoise ratio at the output of the receiver. The existence and uniqueness of Nash equilibrium for the proposed power control game are studied. In particular, conditions are given that must be satisfied by the channel gains for a Nash equilibrium to exist, and the distribution of the users among the carriers at equilibrium is characterized. In addition, an iterative and distributed algorithm for reaching the equilibrium (when it exists) is presented. It is shown that the proposed approach results in significant improvements in the total utility achieved at equilibrium compared with a singlecarrier system and also to a multicarrier system in which each user maximizes its utility over each carrier independently. Index Terms—Energy efficiency, game theory, multicarrier codedivision multipleaccess (CDMA), multiuser detection, Nash equilibrium, power control, utility function. I.
PEDAMACS: Power efficient and delay aware medium access protocol for sensor networks
 IEEE Transactions on Mobile Computing
, 2002
"... Abstract—PEDAMACS is a Time Division Multiple Access (TDMA) scheme that extends the common single hop TDMA to a multihop sensor network, using a highpowered access point to synchronize the nodes and to schedule their transmissions and receptions. The protocol first enables the access point to gathe ..."
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Cited by 28 (5 self)
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Abstract—PEDAMACS is a Time Division Multiple Access (TDMA) scheme that extends the common single hop TDMA to a multihop sensor network, using a highpowered access point to synchronize the nodes and to schedule their transmissions and receptions. The protocol first enables the access point to gather topology (connectivity) information. A scheduling algorithm then determines when each node should transmit and receive data, and the access point announces the transmission schedule to the other nodes. The performance of PEDAMACS is compared to existing protocols based on simulations in TOSSIM, a simulation environment for TinyOS, the operating system for the Berkeley sensor nodes. For the traffic application we consider, the PEDAMACS network provides a lifetime of several years compared to several months and days based on random access schemes with and without sleep cycles, respectively, making sensor network technology economically viable. Index Terms—Sensor networks, energy efficiency, delay guarantee. 1
Optimal Energy Management Policies for Energy Harvesting Sensor Nodes
"... We study a sensor node with an energy harvesting source. The generated energy can be stored in a buffer. The sensor node periodically senses a random field and generates a packet. These packets are stored in a queue and transmitted using the energy available at that time. We obtain energy management ..."
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Cited by 27 (3 self)
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We study a sensor node with an energy harvesting source. The generated energy can be stored in a buffer. The sensor node periodically senses a random field and generates a packet. These packets are stored in a queue and transmitted using the energy available at that time. We obtain energy management policies that are throughput optimal, i.e., the data queue stays stable for the largest possible data rate. Next we obtain energy management policies which minimize the mean delay in the queue. We also compare performance of several easily implementable suboptimal energy management policies. A greedy policy is identified which, in low SNR regime, is throughput optimal and also minimizes mean delay.
Energyefficient cooperative relaying over fading channels with simple relay selection
 in EEE Global Telecommunications Conference (GLOBECOM
, 2006
"... We consider a cooperative wireless network where a set of nodes cooperate to relay in parallel the information from a source to a destination using a decodeandforward approach. The source broadcasts the data to the relays, some or all of which cooperatively beamform to forward the data to the dest ..."
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Cited by 24 (9 self)
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We consider a cooperative wireless network where a set of nodes cooperate to relay in parallel the information from a source to a destination using a decodeandforward approach. The source broadcasts the data to the relays, some or all of which cooperatively beamform to forward the data to the destination. We generalize the standard approaches for cooperative communications in two key respects: (i)we explicitly model and factor in the cost of acquiring channel state information (CSI), and (ii)we consider more general selection rules for the relays and compute the optimal one among them. In particular, we consider simple relay selection and outage criteria that exploit the inherent diversity of relay networks and satisfy a mandated outage constraint. These criteria include as special cases serveral relay selection criteria proposed in the literature. We obtain expressions for the total energy consumption for general relay selection and outage criteria for the nonhomogeneous case, in which different relay links have different mean channel power gains, and the homogeneous case, in which the relay links statistics are identical. We characterize the structure of the optimal transmission scheme. Numerical results show that the cost of training and feedback of CSI is significant. The optimal strategy is to use a varying subset (and number) or relay nodes to cooperatively beamform at any given time. Depending on the relative location of the relays, the source, and the destination, numerical computations show energy savings of about 16 % when an optimal relay selection rule is used. We also study the impact of shadowing correlation on the energy consumption for a cooperative relay network.
Crosslayer energy and delay optimization in smallscale sensor networks
 IEEE Trans.Wirel. Commun
"... Abstract — The general joint design of the physical, MAC, and routing layers to minimize network energy consumption is complex and hard to solve. Heuristics to compute approximate solutions and highcomplexity algorithms to compute exact solutions have been previously proposed. In this paper, we foc ..."
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Cited by 13 (1 self)
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Abstract — The general joint design of the physical, MAC, and routing layers to minimize network energy consumption is complex and hard to solve. Heuristics to compute approximate solutions and highcomplexity algorithms to compute exact solutions have been previously proposed. In this paper, we focus on synchronous smallscale networks with interferencefree link scheduling and practical MQAM link transmission schemes. We show that the crosslayer optimization problems can be closely approximated by convex optimization problems that can be efficiently solved. There are two main contributions of this paper. First of all, we minimize the total network energy that includes both transmission and circuit energy consumptions, where we explore the tradeoff between the two energy elements. Specifically, we use interferencefree TDMA as the medium access control scheme. We optimize the routing flow, TDMA slot assignment, and MQAM modulation rate and power on each link. The results demonstrate that the minimum energy transmission scheme is a combination of multihop and singlehop transmissions for general networks; including circuit energy favors transmission schemes with fewer hops. Secondly, based on the solved optimal transmission scheme, we quantify the best tradeoff curve between delay and energy consumption, where we derive a scheduling algorithm to minimize the worstcase packet delay. Index Terms — Crosslayer, energy efficiency, routing, link scheduling, link adaptation, convex programming, minimum
Energyefficient scheduling for wireless sensor networks
 IEEE TRANS. COMPUT
, 2005
"... We consider the problem of minimizing the energy needed for data fusion in a sensor network by varying the transmission times assigned to different sensor nodes. The optimal scheduling protocol is derived, based on which we develop a lowcomplexity inverselog scheduling (ILS) algorithm that achieve ..."
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Cited by 12 (0 self)
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We consider the problem of minimizing the energy needed for data fusion in a sensor network by varying the transmission times assigned to different sensor nodes. The optimal scheduling protocol is derived, based on which we develop a lowcomplexity inverselog scheduling (ILS) algorithm that achieves nearoptimal energy efficiency. To eliminate the communication overhead required by centralized scheduling protocols, we further derive a distributed inverselog protocol that is applicable to networks with a large number of nodes. Focusing on largescale networks with high total data rates, we analyze the energy consumption of the ILS. Our analysis reveals how its energy gain over traditional timedivision multiple access depends on the channel and the datalength variations among different nodes.
The energyperusefulbit metric for evaluating and optimizing sensor network physical layers
 International Workshop on Wireless Network and Sensor Networks
, 2006
"... Abstract To become truly ubiquitous, sensor network nodes must achieve ultra low power consumption. This paper proposes the EnergyperUsefulBit (EPUB) metric for evaluating and comparing sensor network physical layers. EPUB includes the energy consumption of both the transmitter and receiver, and ..."
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Cited by 12 (0 self)
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Abstract To become truly ubiquitous, sensor network nodes must achieve ultra low power consumption. This paper proposes the EnergyperUsefulBit (EPUB) metric for evaluating and comparing sensor network physical layers. EPUB includes the energy consumption of both the transmitter and receiver, and amortizes the energy consumption during the synchronization preamble over the number of data bits in the packet. Using EPUB, we compare six existing sensor network PHYs. Next, we optimize the PHY according to EPUB. We conclude that the EPUB of sensor network PHYs can be reduced by increasing data rate, lowering carrier frequency, and using simple modulation schemes such as OOK to reduce synchronization overhead. I.
A System Level Energy Model and EnergyQuality Evaluation for Integrated Transceiver FrontEnds
"... voltage and digital power consumption goes down. However, the supply voltage and power consumption of the RF frontend and analog sections do not scale in a similar fashion. In fact, in many stateoftheart communication transceivers, RF and analog sections can consume more energy compared to the d ..."
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Cited by 6 (2 self)
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voltage and digital power consumption goes down. However, the supply voltage and power consumption of the RF frontend and analog sections do not scale in a similar fashion. In fact, in many stateoftheart communication transceivers, RF and analog sections can consume more energy compared to the digital part. In this paper, first, a system level energy model for all the components in the RF and analog frontend is presented. Next, the RF and analog frontend energy consumption and communication quality of three representative systems are analyzed: a single user pointtopoint wireless data communication system, a multiuser code division multiple access (CDMA)based system and a receiveonly video distribution system. For the single user system, the effect of occupied signal bandwidth, peaktoaverage ratio (PAR), symbol rate, constellation size, and pulseshaping filter rolloff factor is analyzed; for the CDMAbased multiuser system, the effect of the number of users in the cell and multiple access interference (MAI) along with the PAR and filter rolloff factor is studied; for the receiveonly system, the effect of I noise for directconversion receiver and the effect of IF frequency for lowIF architecture on the RF frontend power consumption is analyzed. For a given communication quality specification, it is shown that the energy consumption of a wireless communication frontend can be scaled down by adjusting parameters such as the pulse shaping filter rolloff factor, constellation size, symbol rate, number of users in the cell, and signal center frequency. Index Terms—Energyefficient, energy model, peaktomean ratio (PAR), pulse shaping rolloff factor, RF frontend. I.