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47
Theoretical Results on Base Station Movement Problem for Sensor Network
 In Proc. IEEE INFOCOM
, 2008
"... The benefits of using mobile base station to prolong sensor network lifetime have been well recognized. However, due to the complexity of the problem (timedependent network topology and traffic routing), theoretical performance limit and provably optimal algorithms remain difficult to develop. This ..."
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Cited by 46 (5 self)
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The benefits of using mobile base station to prolong sensor network lifetime have been well recognized. However, due to the complexity of the problem (timedependent network topology and traffic routing), theoretical performance limit and provably optimal algorithms remain difficult to develop. This paper fills this important gap by contributing theoretical results regarding the optimal movement of a mobile base station. Our main result hinges upon a novel transformation of the joint base station movement and flow routing problem from time domain to space domain. Based on this transformation, we first show if the base station is allowed to be present only on a set of predefined points, then we can find the optimal time duration for the base station on each of these points so that the overall network lifetime is maximized. Based on this finding, we show that when the location of the base station is unconstrained (i.e., can move to any point in the twodimensional plane), we can develop an approximation algorithm for the joint mobile base station location and flow routing problem such that the network lifetime is guaranteed to be at least of the maximum network lifetime, where can be made arbitrarily small depending on required precision.
Extending Network Lifetime for PrecisionConstrained Data Aggregation
 in Wireless Sensor Networks,” Proc. IEEE INFOCOM
, 2006
"... Abstract — This paper exploits the tradeoff between data quality and energy consumption to extend the lifetime of wireless sensor networks. We consider the applications that require some aggregate form of sensed data with precision guarantees. Our key idea is to differentiate the precisions of data ..."
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Cited by 38 (8 self)
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Abstract — This paper exploits the tradeoff between data quality and energy consumption to extend the lifetime of wireless sensor networks. We consider the applications that require some aggregate form of sensed data with precision guarantees. Our key idea is to differentiate the precisions of data collected from different sensor nodes to balance their energy consumption. This is achieved by partitioning the precision constraint of data aggregation and allocating error bounds to individual sensor nodes in a coordinated fashion. Three factors affecting the lifetime of sensor nodes are identified: (1) the changing pattern of sensor readings; (2) the residual energy of sensor nodes; and (3) the communication cost between the sensor nodes and the base station. We analyze the optimal precision allocation in terms of network lifetime and propose an adaptive precision allocation scheme that dynamically adjusts the error bounds of sensor nodes. Experimental results using real data traces show that the proposed scheme significantly improves network lifetime compared to existing methods. I.
On the Construction of a MaximumLifetime Data Gathering Tree in Sensor Networks: NPCompleteness and Approximation Algorithm
"... Energy efficiency is critical for wireless sensor networks. The data gathering process must be carefully designed to conserve energy and extend the network lifetime. For applications where each sensor continuously monitors the environment and periodically reports to a base station, a treebased top ..."
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Cited by 37 (6 self)
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Energy efficiency is critical for wireless sensor networks. The data gathering process must be carefully designed to conserve energy and extend the network lifetime. For applications where each sensor continuously monitors the environment and periodically reports to a base station, a treebased topology is often used to collect data from sensor nodes. In this work, we study the construction of a data gathering tree to maximize the network lifetime, which is defined as the time until the first node depletes its energy. The problem is shown to be NPcomplete. We design an algorithm which starts from an arbitrary tree and iteratively reduces the load on bottleneck nodes (nodes likely to soon deplete their energy due to high degree or low remaining energy). We show that the algorithm terminates in polynomial time and is provably near optimal.
Maximum Throughput and Fair Bandwidth Allocation in MultiChannel Wireless Mesh Networks
, 2006
"... Wireless mesh network is designed as an economical solution for lastmile broadband Internet access. In this paper, we study bandwidth allocation in multichannel multihop wireless mesh networks. Our optimization goals are to maximize the network throughput and, at the same time, to enhance fairnes ..."
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Cited by 35 (2 self)
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Wireless mesh network is designed as an economical solution for lastmile broadband Internet access. In this paper, we study bandwidth allocation in multichannel multihop wireless mesh networks. Our optimization goals are to maximize the network throughput and, at the same time, to enhance fairness. First, we formulate and present an Linear Programming (LP) formulation to solve the Maximum throughput Bandwidth Allocation (MBA) problem. However, simply maximizing the throughput may lead to a severe bias on bandwidth allocation among wireless mesh nodes. In order to achieve a good tradeoff between fairness and throughput, we consider a simple maxmin fairness model which leads to high throughput solutions with guaranteed maximum minimum bandwidth allocation values, and the wellknown Lexicographical MaxMin (LMM) model. Correspondingly, we formulate the Maxmin guaranteed Maximum throughput Bandwidth Allocation (MMBA) problem and the Lexicographical MaxMin Bandwidth Allocation (LMMBA) problem. For the former one, we present an LP formulation to provide optimal solutions and for the later one, we propose a polynomial time optimal algorithm.
Link scheduling with power control for throughput enhancement in multihop wireless networks
 IEEE Transactions on Vehicular Technology
, 2006
"... Abstract — Throughput is an important performance consideration for multihop wireless networks. In this paper, we study the joint link scheduling and power control problem, focusing on maximizing the network throughput. We formulate the MAximum THroughput link Scheduling with Power Control (MATHSPC ..."
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Cited by 35 (3 self)
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Abstract — Throughput is an important performance consideration for multihop wireless networks. In this paper, we study the joint link scheduling and power control problem, focusing on maximizing the network throughput. We formulate the MAximum THroughput link Scheduling with Power Control (MATHSPC) problem, and present a Mixed Integer Linear Programming (MILP) formulation to provide optimal solutions. However, simply maximizing the throughput leads to a severe bias on bandwidth allocation among all links. In order to enhance both throughput and fairness, we define a new parameter, the Demand Satisfaction Factor (DSF), to characterize the fairness of bandwidth allocation. We formulate the MAximum Throughput fAir link Scheduling with Power Control (MATASPC) problem and present an MILP formulation for this problem. We also present an effective polynomial time heuristic algorithm, namely, the Serial LP Rounding (SLPR) heuristic. Our numerical results show that bandwidth can be fairly allocated among all links/flows by solving our MATASPC formulation or using our heuristic algorithm at the cost of a minor reduction of network throughput.
Minimizing Delay and Maximizing Lifetime for Wireless Sensor Networks With Anycast
"... In this paper, we are interested in minimizing the delay and maximizing the lifetime of eventdriven wireless sensor networks, for which events occur infrequently. In such systems, most of the energy is consumed when the radios are on, waiting for a packet to arrive. Sleepwake scheduling is an effe ..."
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Cited by 27 (3 self)
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In this paper, we are interested in minimizing the delay and maximizing the lifetime of eventdriven wireless sensor networks, for which events occur infrequently. In such systems, most of the energy is consumed when the radios are on, waiting for a packet to arrive. Sleepwake scheduling is an effective mechanism to prolong the lifetime of these energyconstrained wireless sensor networks. However, sleepwake scheduling could result in substantial delays because a transmitting node needs to wait for its nexthop relay node to wake up. An interesting line of work attempts to reduce these delays by developing “anycast”based packet forwarding schemes, where each node opportunistically forwards a packet to the first neighboring node that wakes up among multiple candidate nodes. In this paper, we first study how to optimize the anycast forwarding schemes for minimizing the expected packetdelivery delays from the sensor nodes to the sink. Based on this result, we then provide a solution to the joint control problem of how to optimally control the system parameters of the sleepwake scheduling protocol and the anycast packetforwarding protocol to maximize the network lifetime, subject to a constraint on the expected endtoend packetdelivery delay. Our numerical results indicate that the proposed solution can outperform prior heuristic solutions in the literature, especially under practical scenarios where there are obstructions, e.g., a lake or a mountain, in the coverage area of the wireless sensor network.
A Utilitybased Distributed Maximum Lifetime Routing Algorithm for Wireless Networks
"... Energy efficient routing is a critical problem in multihop wireless networks due to the severe power constraint of wireless nodes. Despite its importance and many research efforts towards it, a distributed routing algorithm that maximizes network lifetime is still missing. To address this problem, ..."
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Cited by 18 (0 self)
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Energy efficient routing is a critical problem in multihop wireless networks due to the severe power constraint of wireless nodes. Despite its importance and many research efforts towards it, a distributed routing algorithm that maximizes network lifetime is still missing. To address this problem, we propose a novel utilitybased nonlinear optimization formulation to the maximum lifetime routing problem. Based on this formulation, we further present a fully distributed, localized routing algorithm, which is proved to converge to the optimal point, where the network lifetime is maximized. Solid theoretical analysis and simulation results are presented to validate our solution.
Deploying Longlived and Costeffective Hybrid Sensor Networks
 In Proceedings of the First Workshop on Broadband Advanced Sensor Networks (BaseNets 2004
, 2004
"... In this paper, we study the problem of network deployment in hybrid sensor networks, consisting of both resourcerich and resourceimpoverished sensor devices. The resourcerich devices, called microservers, are more expensive but have significantly greater bandwidth and energy capabilities compare ..."
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Cited by 18 (3 self)
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In this paper, we study the problem of network deployment in hybrid sensor networks, consisting of both resourcerich and resourceimpoverished sensor devices. The resourcerich devices, called microservers, are more expensive but have significantly greater bandwidth and energy capabilities compared to the lowcost, lowpowered sensors. Such hybrid sensor networks have the potential to support the higher bandwidth communications of broadband sensor networking applications, as well as the finegrained sensing that is made possible by smaller sensor devices. We propose several techniques to investigate some fundamental questions on hybrid sensor network deployment — for a given number of microservers, what is the maximum lifetime of a sensor network and the optimal microserver placement? What benefit can additional microservers add to the network, and how financially costeffective is it to introduce these microservers? For our investigation, we propose a cost model for energy usage in hybrid sensor networks, which is then formulated into an integer linear optimization problem and solved optimally. The integer linear problem solution does not scale with network size thus we introduce an approximation algorithm using tabusearch technique. Our studies show that network life time can be extended by more than 100 % by adding an extra microserver to the network; the network life time of optimized microservers ’ placement can be seven times longer than the worst case life time. We also propose a normalized cost model that balances the benefits with deployment costs, and show how to achieve an optimal deployment. 1
Joint spectrum allocation and scheduling for fair spectrum sharing in cognitive radio wireless networks,”Comput
 Netw. J
, 2008
"... Cognitive radio and Dynamic Spectrum Access (DSA) enable wireless users to share a wide range of available spectrums. In this paper, we study joint spectrum allocation and scheduling problems in cognitive radio wireless networks with the objectives of achieving fair spectrum sharing. A novel Multi ..."
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Cited by 14 (1 self)
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Cognitive radio and Dynamic Spectrum Access (DSA) enable wireless users to share a wide range of available spectrums. In this paper, we study joint spectrum allocation and scheduling problems in cognitive radio wireless networks with the objectives of achieving fair spectrum sharing. A novel MultiChannel Contention Graph (MCCG) is proposed to characterize the impact of interference under the protocol model in such networks. Based on the MCCG, we present an optimal algorithm to compute maximum throughput solutions. As simply maximizing throughput may result in a severe bias on resource allocation, we take fairness into consideration by presenting optimal algorithms as well as fast heuristics to compute fair solutions based on a simplified maxmin fairness model and the wellknown proportional fairness model. Numerical results show that the performance given by our heuristic algorithms is very close to that of the optimal solution, and our proportional fair algorithms achieve a good tradeoff between throughput and fairness. In addition, we extend our research to the physical interference model, and propose effective heuristics for solving the corresponding problems. Key words: Cognitive radio, dynamic spectrum access, spectrum allocation, scheduling, fairness.
Algorithm design for base station placement problems in sensor networks
 in Proc. the 3rd international
, 2006
"... Base station placement has significant impact on sensor network performance. Despite its significance, results on this problem remain limited, particularly theoretical results that can provide performance guarantee. This paper proposes a set of procedure to design �approximation algorithms for base ..."
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Cited by 11 (1 self)
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Base station placement has significant impact on sensor network performance. Despite its significance, results on this problem remain limited, particularly theoretical results that can provide performance guarantee. This paper proposes a set of procedure to design �approximation algorithms for base station placement problems under any desired small error bound��. It offers a general framework to transform infinite search space to a finiteelement search space with performance guarantee. We apply this procedure to solve two practical problems. In the first problem where the objective is to maximize network lifetime, an approximation algorithm designed through this procedure offers��complexity reduction when compared to a stateoftheart algorithm. This represents the best known result to this problem. In the second problem, we apply the design procedure to address base station placement problem for maximizing network capacity. Our �approximation algorithm is the first theoretical result on this problem. 1.