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INFOCOM 2008. 27th IEEE International Conference on Computer Communications, Joint Conference of the IEEE Computer and Communications Societies, 13-18 April 2008, Phoenix, AZ, USA; 01/2008
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ABSTRACT: We are concerned with maximizing the lifetime of a data-gathering wireless sensor network consisting of set of nodes directly communicating with a base-station. We model this scenario as the m-message interactive communication between multiple correlated informants (sensor nodes) and a recipient (base-station). With this framework, we show that m-message interactive communication can indeed enhance network lifetime. Both worst-case and average-case performances are considered.
Information Theory, 2007. ISIT 2007. IEEE International Symposium on; 07/2007
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Proceedings of the Global Communications Conference, 2007. GLOBECOM '07, Washington, DC, USA, 26-30 November 2007; 01/2007
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IEEE Transactions on Wireless Communications. 01/2005; 4:722-733.
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ABSTRACT: This paper jointly addresses the problem of power control and scheduling in ad hoc networks supporting multicast traffic. First, we present a distributed algorithm which, given the set of multicast transmitters and their corresponding receivers, provides an optimal solution to the power control problem, if there is any. The transmit power levels obtained by solving the optimization problem minimize the network power expenditure while meeting the requirements on the SINR at the receivers. Whenever no optimal solution can be found for the given set of multicast transmitters, we introduce a joint scheduling and power control algorithm which eliminates the strong interferers, thus allowing the other transmitters to solve the power control problem. The algorithm can be implemented in a distributed manner. Although the proposed scheme provides a suboptimal solution, simulation results show that the obtained solution is close to the global optimum, when it exists. When instead there is no optimal solution, our algorithm allows for a high number of successful multicast transmissions.
EURASIP Journal on Advances in Signal Processing. 01/2005;
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IEEE Transactions on Wireless Communications. 01/2004; 3:891-899.
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ABSTRACT: This paper addresses the problem of power control in ad hoc networks supporting multicast traffic. First, we present a distributed algorithm which, given the set of multicast transmitters and their corresponding receivers, provides an optimal solution to the power control problem, if there is any. The transmit power levels obtained by solving the optimization problem minimize the network power expenditure while meeting the requirements on the SINR at the receivers. Whenever no optimal solution can be found for the given set of multicast transmitters, we introduce a joint scheduling and power control algorithm, which eliminates the strong interferers thus allowing the other transmitters to solve the power control problem. The algorithm can be implemented in a distributed manner; however, it provides a suboptimal solution since it is based on `local' information. Simulation results show that the obtained solution is close to the global optimum, when it exists. When there is not an optimal solution, the proposed algorithm enables us to maximize the number of successful multicast transmissions.
06/2003;
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ABSTRACT: Wireless sensors have several constraints, such as a short transmission range, poor processing capabilities, and a limited available energy. Our goal is to design an energyefficient sensor network by exploiting the concept of collaborative signal processing. We consider a network composed of multiple sensor nodes, each of which corresponds to a processor. By using an appropriate collaborative computational algorithm and communication scheme, we make sensors operate as a Distributed Digital Signal Processor (DDSP) and generate the desired results. The benefit of such an approach is twofold: (i) the energy and computational limitations of the individual sensors can be overcome, and (ii) for a given level of processing complexity, the energy efficiency of the overall network can increase significantly. We apply the DDSP approach to the Fast Fourier Transform algorithm, and derive results showing the improvement in performance that can be obtained through the proposed technique. Moreover, we study the existing trade-off between energy saving, data latency and number of employed sensors.
06/2003;
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ABSTRACT: In wireless ad hoc networks, nodes communicate with far off destinations using intermediate nodes as relays. Since wireless nodes are energy constrained, it may not be in the best interest of a node to always accept relay requests. On the other hand, if all nodes decide not to expend energy in relaying, then network throughput will drop dramatically. Both these extreme scenarios (complete cooperation and complete noncooperation) are inimical to the interests of a user. In this paper we address the issue of user cooperation in ad hoc networks. We assume that nodes are rational, i.e., their actions are strictly determined by self interest, and that each node is associated with a minimum lifetime constraint. Given these lifetime constraints and the assumption of rational behavior, we are able to determine the optimal throughput that each node should receive. We define this to be the rational Pareto optimal operating point. We then propose a distributed and scalable acceptance algorithm called Generous TIT-FOR-TAT (GTFT). The acceptance algorithm is used by the nodes to decide whether to accept or reject a relay request. We show that GTFT results in a Nash equilibrium and prove that the system converges to the rational and optimal operating point.
03/2003;
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01/2003
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IEEE Transactions on Wireless Communications. 01/2003; 2:1090-1100.
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IEEE Transactions on Wireless Communications. 01/2003; 2:964-975.
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ABSTRACT: A challenging aspect of mobile communications consists in exploring ways in which the available run time of terminals can be maximized. In this paper, we present a detailed electrochemical battery model and a simple stochastic model that captures the fundamental behavior of the battery. The stochastic model is then matched to the electrochemical model and used to investigate battery management techniques that may improve the energy efficiency of radio communication devices. We consider an array of electrochemical cells. Through simple scheduling algorithms, the discharge from each cell is properly shaped to optimize the charge recovery mechanism, without introducing any additional delay in supplying the required power. Then, a battery management scheme, which exploits knowledge of the cells' state of charge, is implemented to achieve a further improvement in the battery performance. In this case, the discharge demand may be delayed. Results indicate that the proposed battery management techniques improve system performance no matter which parameters values are chosen to characterize the cells' behavior.
10/2002;
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ABSTRACT: Wireless systems operating in the ISM frequency bands and sharing the same environment are likely to interfere with each other. We address the problem of coexistence between IEEE 802.11 and IEEE 802.15 devices, and we present a mechanism that mitigates the interference between these devices when IEEE 802.15 supports voice traffic. The proposed scheme can work when 802.11 and 802.15 devices operate in non-collaborative mode, i.e., independently of one another. The performance of the proposed algorithm is compared to the results obtained through the so-called MEHTA scheme, which is a collaborative mechanism recently presented to the IEEE 802.15 Working Group. Simulation results show that the proposed algorithm gives good performance relatively to the MEHTA scheme when co-located interfering devices only are considered, while it outperforms the MEHTA scheme when non co-located interfering devices are present.
10/2002;
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ABSTRACT: In this paper we propose a routing protocol for wireless ad hoc networks whose nodes are largely battery powered. The battery capacity of the nodes is viewed as a common resource of the system and its use is to be optimized. Results from a previous study on battery management have shown that: (1) pulsed current discharge outperforms constant current discharge, (2) battery capacity can be improved by using a bursty discharge pattern due to charge recovery effects that take place during idle periods, (3) given a certain value of current drawn off the battery, higher current impulses degrade battery performance, even if the percentage of higher current impulses is relatively small. We develop a network protocol based on these findings. This protocol favors routes whose links have a low energy cost. We also distribute multihop traffic in a manner that allows all nodes a good chance to recover their battery energy reserve.
10/2002;
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ABSTRACT: Coexistence of different wireless systems that share the same frequency band is becoming one of the most challenging issue due to the wide-spread popularity of WLANs and to the rapid development of shortrange radio systems. In this paper we consider WLANs based on the IEEE 802.11 standard and a short-range radio system based on Bluetooth specifications, which operate in the 2.4 GHz ISM frequency band. We present a model of the interference that IEEE 802.11 WLANs may experience either because of a voice or a data Bluetooth link. We derive results showing that by applying simple traffic shaping techniques, interference can be significantly reduced. In the presence of Bluetooth data traffic, WLAN packet error probability can be decreased by 19% at the expense of an additional average delay in Bluetooth packet transmission equal to 10 ms, or by 29% at the expense of a Bluetooth average packet delay equal to 110 ms.
10/2002;
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ABSTRACT: We deal with energy efficiency and quality of service provisioning in multihop ad hoc wireless networks. We assume that each node generates traffic for some other node in the network and that the available routes between each source-destination pair are known. Each source randomly selects one of the possible routes and asks the intermediate nodes on the route to relay traffic. Since energy is a valuable resource, intermediate nodes may not wish to consume their energy to carry the source's traffic. However, if every node behaves `selfishly' and refuses to cooperate, network throughput may be drastically reduced. In this paper, we investigate the tradeoff that exists between energy consumption and blocking probability of a session, and study the ability of the network at guaranteeing a low energy consumption to users that want or need to be selfish. We define a parameter, called sympathy, which reflects the level of selfishness /altruism of the nodes. We propose two different strategies, which govern the node behavior, and compare their performance as sympathy is varied.
10/2002;
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ABSTRACT: In this paper we develop a novel approach to conserving energy in battery powered communication devices. There are two salient aspects to this approach. First, the battery powered devices move through multiple, progressively deeper, sleep states in a predictable manner. Nodes in deeper sleep states consume lower energy while asleep but incur a longer delay and higher energy cost to wake up. Second, the nodes are woken up on demand through a paging signal. To awaken nodes that are in deep sleep, the paging signal has to be decoded using very low power circuits such as those used in RF tags. To accommodate this need, in a manner that scales well with the number of nodes, the number of distinct paging signals has to be much less than the number of possible nodes. This is accomplished through a group based wake up scheme, that initially awakens the targeted node along with a number of other similarly disposed nodes that subsequently return to their original sleep state. Trade-offs among energy consumption, delay as well as overhead are presented; comparisons with other protocols show the potential for 16 to 50% improvement in energy consumption.
10/2002;
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ABSTRACT: Different wireless systems sharing the same frequency band and operating in the same environment are likely to interfere with each other and experience a severe decrease in throughput. In this paper, we consider IEEE 802.11 WLANs and Bluetooth-based WPANs, which operate in the 2.4 GHz ISM bands. We propose two coexistence mechanisms based on traffic scheduling techniques, which mitigate interference between the two technologies. The proposed algorithms can be applied either when 802.11 and Bluetooth are able to exchange information as well as when they operate independently of one another. Results show that through the proposed coexistence mechanisms the interference between 802.11 and Bluetooth can be reduced and the throughput of the two systems is significantly improved at the expense of a small additional delay in the transfer of data traffic.
10/2002;
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ABSTRACT: This paper presents a power management scheme that maximizes energy saving in wireless ad hoc networks while still meeting the required quality of service (QoS). We assume that battery-powered devices can be remotely activated by a waking-up signal using a simple circuit based on RF tag technology. In this way, devices that are not currently active may enter a sleep state and power up only when they have pending traffic. Radio devices select different time-out values, so called sleep pattern, to enter various sleep states depending on their battery status and quality of service. Performances of the proposed policy are derived by simulation for a simple ad hoc network scenario. Results show the achieved tradeoff between power saving and traffic delay.
10/2002;
