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Date 10-12 Oct. 2011

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Displaying Results 1 - 25 of 89
  • A WSN-driven service discovery technique for disaster recovery using mobile ad hoc networks

    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (593 KB) |  | HTML iconHTML  

    Mobile ad hoc networks (MANET) can be used quite effectively to manage resource allocation in operations such as search and rescue, military combat, and firefighting. In the event that an operations area, e.g. in case of disaster rescue operations, is large, the use of Wireless Sensor Networks (WSNs) can be crucial in locating the spots of highest need of rescue resources. We can adapt the techniques of service discovery in MANET for use in the process of searching for and allocating the most proper rescue resource for encountered emergency situations and needs. This service discovery operation can therefore be triggered by findings of the WSNs that have been deployed in several locations within the operations area. We call the emergency response personnel “service providers”. Service providers are equipped with lightweight communication devices. In this study, we devise the protocol by which this entire operation is conducted. We also experiment with the proposed technique and present some results that show its performance under different operating conditions. View full abstract»

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  • Performance of iterative decoding with imperfect MMSE DFE

    Publication Year: 2011 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB) |  | HTML iconHTML  

    The MMSE-DFE is a well established Intersymbol Interference (ISI) mitigating structure on linear, noisy, and dispersive channels. Time invariant communication channels exhibits ISI for severe frequency-selective channels. In this paper we investigate the iterative decoding with imperfect MMSE decision feedback equalizer using different modulation scheme. We assume that soft outputs from channel decoder are independent identically distributed Gaussian random variables with known mean and variance. The Imperfect MMSE DFE using different modulation outperforms other turbo equalization algorithms of similar computational complexity in terms of bit-error rate. The achieved improvement is up to 3dB for severe frequency-selective channels. View full abstract»

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  • Information dissemination in VANETs using zone based forwarding

    Publication Year: 2011 , Page(s): 1 - 3
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    Several VANET-based safety applications require information dissemination to all vehicles within a certain area for a certain time. Among the existing information dissemination protocols for VANETs, only Stored Geocast provides retention of information within a pre-determined area of the road for a duration of time. However, the overhead incurred by it is large. In this paper, we propose and evaluate ZBF, a zone based forwarding scheme for information dissemination which provides both a spatial and temporal retention of information and incurs less overhead than Stored Geocast. View full abstract»

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  • Prototyping an automatic notification scheme for traffic accidents in vehicular networks

    Publication Year: 2011 , Page(s): 1 - 5
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (605 KB) |  | HTML iconHTML  

    The new communication technologies integrated into the automotive sector offer an opportunity for better assistance to people injured in traffic accidents, reducing the response time of emergency services, and increasing the information they have about the incident. Determining more accurately the human and material resources required for each particular accident could significantly reduce the number of victims. The proposed system requires each vehicle to be endowed with an On-Board Unit responsible for detecting and reporting accident situations to an external Control unit that estimates its severity, allocating the necessary resources for its assistance. The development of a prototype based on off-the-shelf devices shows that this system could reduce notably the time needed to deploy the emergency services after an accident takes place. View full abstract»

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  • On the throughput capacity of wireless multi-hop networks with ALOHA, node coloring and CSMA

    Publication Year: 2011 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (222 KB) |  | HTML iconHTML  

    We quantify the throughput capacity of wireless multi-hop networks with several medium access schemes. We analyze pure ALOHA scheme where simultaneous transmitters are dispatched according to a uniform Poisson distribution and exclusion schemes where simultaneous transmitters are dispatched according to an exclusion rule such as node coloring and carrier sense based schemes. We consider both no-fading and standard Rayleigh fading channel models. Our results show that, under no-fading, slotted ALOHA can achieve at least one-third (or half under Rayleigh fading) of the throughput capacity of node coloring scheme whereas carrier sense based scheme can achieve almost the same throughput capacity as node coloring. View full abstract»

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  • Toward an energy reduction in mobile relays: Combining MIMO and multi-mode

    Publication Year: 2011 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    The current generation of mobile terminals can communicate on multiple modes using several antennas. However, their energy consumption remains a critical parameter. In this paper, we explore the combination of multiple communication modes and MIMO as a possible way to reduce the energy consumption of both the terminals and the network. We propose a realistic energy model for the PHY layer of a MIMO and multi-mode terminal, taking into account the MAC layer behaviour. We show that the combination of MIMO and multi-mode provides a solution to reduce global energy consumption. View full abstract»

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  • Performance evaluation of a file sharing DTN protocol with realistic mobility

    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (650 KB) |  | HTML iconHTML  

    Mobile Ad-hoc Networks (MANETs) exhibit unpredictable topology with heterogeneous node contact rates, high mobility and limited information. When dealing with such challenging environments, the mobility model has a key role in testing the performance and proving the expected behavior of routing algorithms. While synthetic mobility models have been largely used to measure quantitative aspects of routing protocols, they are not sufficient as they do not capture reliably the properties of movement in the real life scenarios. In this paper we present some experimentation done in THE_ONE simulation environment, involving our M2MShare, a peer-to-peer (P2P) delay tolerant file sharing platform for mobile networks. For testing purposes we have chosen the Working Day Movement (WDM) model which is shown to make a good approximation of human mobility patterns and provides the flexibility of configuring real life test scenarios. View full abstract»

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  • Channel capacity in cellular systems

    Publication Year: 2011 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (267 KB) |  | HTML iconHTML  

    By applying information theory to the analysis of a cellular system, it has been shown that it is a useful idea to reuse all the frequency bands in the adjacent cell (frequency reuse factor 1) and use the most robust modulation scheme at the cell boundary. This is not a surprising result since this is done in LTE and other systems like WIMAX and DTT. How this was derived by means of simple formulas is hopefully original and should provide some useful insights. The analysis has been done for the up link which is normally more critical than down link. As expected, the capacity of the cell increases as the propagation exponent increases since there is less interference between the cells using the same frequency and only the interference from other cells using the same frequency limits the capacity - not the thermal noise. The analysis presented is not limited to a particular system like LTE. View full abstract»

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  • An optimal cooperative spectrum sensing method in cognitive radio network over Rayleigh fading channel

    Publication Year: 2011 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (301 KB) |  | HTML iconHTML  

    In cognitive radios, there exist two kinds of detection errors: missed-detection errors and false-alarm errors. These errors severely degrade sensing performance. In this paper, we aim to minimize the total detection probability by considering it as a target function for the optimization of sensing parameters in a Rayleigh fading environment. With this established target function, we perform a discrete difference operation and derive the closed - form expression of the optimal fusion rule for cooperative spectrum sensing. Furthermore, we derive an algorithm to optimize the energy detection threshold for the cognitive users for any fusion rule. A second algorithm that optimizes both the energy threshold and the fusion rule is also proposed so as to minimize the total error probability. Based on this algorithm, an optimal sensing method for a cooperative cognitive radio network is suggested. View full abstract»

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  • Optimal secondary throughput over two primary channels in cooperative cognitive radio networks

    Publication Year: 2011 , Page(s): 1 - 3
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    In this paper, we investigated the throughput of a cognitive radio network where two primary frequency channels (PCs) are sensed and opportunistically accessed by N secondary users. The sharing sensing member (SSM) protocol is introduced to sense both PCs simultaneously. The throughput of the network is formulated as a convex optimization problem. The numerical investigation shows that the proposed optimal allocation improves the throughput of the SU under a misdetection constraint to protect the PCs. View full abstract»

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  • SOCS: A self-optimized coverage scheme for Femto-Enterprise deployment

    Publication Year: 2011 , Page(s): 1 - 3
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (613 KB) |  | HTML iconHTML  

    In this work, we propose a green and coordination scheme SOCS to dynamically optimize the Femto-Enterprise coverage by adjusting the Femtocell transmit pilot power in enterprise environment. The resulting evolved algorithm shows the ability to optimize the coverage well, and by consequence the resultant substantial energy consumption. Our analysis is validated through MATLAB simulations. View full abstract»

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  • On the optimal transmission scheme to maximize local capacity in wireless networks

    Publication Year: 2011 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (315 KB) |  | HTML iconHTML  

    We study the optimal transmission scheme that maximizes the local capacity In two-dimensional (2D) wireless networks. Local capacity Is defined as the average Information rate received by a node randomly located In the network. Using analysis based on analytical and numerical methods, we show that maximum local capacity can be obtained If simultaneous emitters are positioned In a grid pattern based on equilateral triangles. We also compare this maximum local capacity with the local capacity of slotted ALOHA scheme and our results show that slotted ALOHA can achieve at least half of the maximum local capacity in wireless networks. View full abstract»

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  • Location-aided power and mobility aware routing in wireless ad hoc network

    Publication Year: 2011 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (253 KB) |  | HTML iconHTML  

    For wireless ad hoc networks with nodes having limited battery capacity, we propose route selection based on maximizing the minimum node battery power and minimizing the total transmission power required to reach the destination. The lifetime of the selected routes should also be long enough to sustain the data transmission, if possible. This motivates the design of a Location-Aided Power and Mobility Aware Routing (LAPMAR) protocol that can be used on an on-demand basis. This protocol uses location information and controlled flooding for improved system performance. This is studied using simulations and its performance is compared with other power aware protocols. View full abstract»

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  • Distributed admission control in 802.11e-based MANETs: From theory to practice

    Publication Year: 2011 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (169 KB) |  | HTML iconHTML  

    Providing Quality of Service (QoS) in wireless ad-hoc networks is an extremely complex task due to issues such as mobility, channel contention, and interference. Over the past years, several algorithms have been presented with the aim of providing QoS support in these environments; specifically, a lot of work has been done in the creation of a reliable admission control mechanism since it has been proved to be a fundamental element for QoS support in ad-hoc networks. In this paper we present a real implementation of DACME, a distributed admission control system for mobile ad-hoc networks, and we test its effectiveness in an IEEE 802.11e enabled testbed. Experimental results show that the solution developed is able to achieve good QoS levels, offering sustained bandwidth and bounded delay. Also, since DACME operates on an end-to-end basis, no restrictions are imposed on intermediate nodes. View full abstract»

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  • Efficient routing of data for femtocells

    Publication Year: 2011 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    The paper proposes novel routing method for two users connected to the same femtocell communicating with each other. In conventional case, data are sent in two sequential steps. In the first step, data are transmitted from the user to the femtocell. In the second step, data have to be retransmitted to other user. We suggest transmitting user's data directly instead of two hop communications if both users are sufficiently close to each other. In addition, we propose exchange of management messages in order to implement our routing scheme in LTE-A standard. The simulation results indicate that the throughput offered by femtocells can be significantly increased. View full abstract»

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  • Multichannel access for bandwidth improvement in IEEE 802.15.4 Wireless Sensor Networks

    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (739 KB) |  | HTML iconHTML  

    In this paper, we propose a new multichannel allocation protocol for ZigBee/IEEE 802.15.4 networks. The main goal is to improve the global throughput which is basically insufficient to satisfy high bandwidth requirements for applications like monitoring or traffic control. The solution is based on the availability of multiple channels on current low-cost, low-energy radio transceivers, such as TI/Chipcon CC2420, which can be easily tuned dynamically to different frequencies. This possibility can be exploited to increase the number of simultaneous transmissions on adjacent links. The allocation of the different channels is centralized and distributed by the coordinator thanks to a function designed to compute the channel offset between two successive children routers. In the nodes, the switching process between the transmission and the reception channels is triggered starting from the PHY primitive available on the transceiver. The evaluation shows that the proposed protocol improves the global throughput by a factor between 2 and 5, depending on the scenario, compared to the single-channel solution or a random channel allocation. View full abstract»

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  • Cross-quadrature interference canceller-XQIC: A fresh view of the asymmetric equalizer

    Publication Year: 2011 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (409 KB) |  | HTML iconHTML  

    This paper develops an alternate configuration of the familiar complex-valued baseband linear adaptive equalizer which endows it with greater degrees of freedom, allowing it to equalize more general I/Q imbalances suffered by wireless signals in modern transceiver designs, in addition to equalizing the difficult propagation channel characteristics. As most spectrally-efficient wireless signals employ quadrature-amplitude modulation (QAM), it is natural to treat the data symbols as complex-valued quantities. However, some of the distortions, especially I/Q delay mismatches and frequency-dependent imbalances, do not fit the complex-valued model whereby the I and Q components are treated as the real and imaginary parts. Such complex-valued DSP blocks obviously cannot compensate for these I/Q mismatches. In this paper, the complex-valued adaptive equalizer is re-architected in a more general vector form [4] which allows it to compensate for such I/Q imbalances. Although not a new concept in itself, its development is outlined as a natural extension of the conventional complex-valued, blind (decision-directed) adaptive equalizer to a vector-valued equalizer without an increase in complexity. It is presented as a candidate for blind IQ signal separation [1] where the original I and Q components are dominant. The extension is further related to the adaptive cross-polarization interference canceller (XPIC), inspiring the name XQIC for this equalizer architecture. The developments are supported by simulation and laboratory test results on a microwave radio link employing a broadband wireless modem. View full abstract»

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  • When network coding improves the performances of clustered wireless networks

    Publication Year: 2011 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (595 KB) |  | HTML iconHTML  

    This paper introduces a network coding scheme that significantly increases the performances of clustering algorithms in wireless multi-hop networks. Knowing the promising capabilities of network coding over broadcast mediums, we propose a simple and non-invasive packet scheduling mechanism based on proactive code selection and overheard messages to optimize intra and inter-cluster communications. Our solution uses bitwise XOR operations at the packet level to combine several messages in one transmission. Simulations show an important gain in the network reliability, and a major enhancement of the throughput without any substantial computation or network overhead. View full abstract»

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  • Prediction quality of contact history in opportunistic networks

    Publication Year: 2011 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1600 KB) |  | HTML iconHTML  

    Routing in opportunistic networks heavily relies on past behavior of the mobile devices it is formed of to predict their future and thus making routing decisions. While almost every protocol relies on this history, its prediction quality has never been studied in a realistic setting. Using extensive simulations on real traces, we are able to describe for the first time how well predictions can be. Unlike oracle-based prediction comparisons, we do not try to predict a contact, but compare the expected user result, namely message delivery probabilities. The analysis also provides guidance on the importance of multi-path routing and the path diversity required, as well as on the impact on forward error correction on the delivery probability. Our results show that the repetitive nature of path is directly proportional to the mobility extent of the devices and, consequently, history obtained from dense opportunistic networks is reliable. View full abstract»

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  • Energy-aware QoS uplink scheduling for UGS traffic services in WiMAX

    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (510 KB) |  | HTML iconHTML  

    This paper presents new energy-aware QoS scheduling and call admission control algorithms for WiMAX IEEE 802.16e broadband wireless access standard. The scheduling algorithm works at MAC layer and is designed towards minimizing power consumption at mobile stations supporting multiple UGS connections, while meeting the QoS requirements of the connections. The scheduling algorithm uses a novel idea to fill an active OFDM frame as much as possible in order to increase the number of OFDM frames in sleep mode at mobile station. The algorithm also considers the dynamic nature of connection joining and termination, and the schedule adjusts itself on a new connection arrival. We used VoIP traffic connection models to simulate and validate our algorithms. Simulation results show that a power saving in the range of 50-75% can be easily achieved at the mobile station under low-to-moderate traffic intensities. View full abstract»

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  • Design, implementation, and optimization of a Raptor-based content delivery protocol

    Publication Year: 2011 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (463 KB) |  | HTML iconHTML  

    When attempting to deliver contents over wireless networks in an efficient manner, the different protocols involved must deal with several sources of loss such as congestion and channel errors, which can prevent an effective message reception at the destination. Therefore, content delivery protocols must deal with these problems in the most appropriate way. In this paper we focus on the design, implementation, and optimization of RCDP, a content delivery protocol for wireless network environments based on Raptor codes. We propose different architectural and design alternatives in order to find the solution that achieves the best trade-off between throughput achieved and resource requirements under both lossy and lossless conditions. Experimental results based on a real implementation of RCDP show that parallelization strategies, together with other optimizations, are able to significantly boost performance. View full abstract»

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  • On enhancement of handover decision in femtocells

    Publication Year: 2011 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (526 KB) |  | HTML iconHTML  

    Deployment of femtocells with open or hybrid access into mobile networks leads to problems with handling handover of mobile users. In this paper we discuss two important aspects that can be considered and exploited in a design of innovative handover procedure for scenario with femtocells. The first aspect is related to varying quality and limited capacity of femtocell's backbone. Further, an accuracy of determination of a time spent by users in a femtocell is analyzed in this paper with purpose to exploit it for elimination of redundant handovers. The implementation aspects of proposed enhancements in handover decision algorithm are discussed as well. View full abstract»

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  • Loose coupling approach for UMTS/WiMAX integration

    Publication Year: 2011 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (458 KB) |  | HTML iconHTML  

    Fourth generation (4G) Network integrates existing wireless technologies (GPRS/UMTS, WiMAX, WLAN, etc.) and offers access to services while on the move, at any place and any time. A multi-interface device can switch connection among available access points implementing different technologies. Integration of heterogeneous wireless networks can be performed at different levels (open coupling and tight coupling.). This paper presents a loose coupling approach to interconnect UMTS and WIMAX systems. View full abstract»

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  • Radio resource allocation for OFDMA-based cognitive systems

    Publication Year: 2011 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (285 KB) |  | HTML iconHTML  

    This paper addresses the problem of wireless resource allocation in OFDMA-based cognitive radio cooperative systems. The objective is maximizing the total throughput and minimizing the transmission power of cognitive transmissions while guaranteeing fairness between the different cognitive users queues. The proposed radio resource allocation algorithm is based on maximizing the rate to power ratio. We also investigate the conflict resolution problem by suggesting a Conflict Resolution rate-based procedure to allocate conflicted subcarriers. Moreover, to secure cognitive transmissions we propose a double reservation procedure based on rate to power ratio margin RPRM, and thus to allocate secondary subcarriers. We propose to serve urgent transmissions, based on a fairness indicator. Simulations show the performance and the efficiency of the proposed algorithm. View full abstract»

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  • Energy-aware object tracking algorithm using heterogeneous wireless sensor networks

    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (659 KB) |  | HTML iconHTML  

    Mobile target tracking consists in detecting and locating targets in a surveillance region. Wireless Multimedia Sensor Networks (WMSN) can provide more information about the moving target than classical Wireless Sensor Networks (WSN), but their process and the transmission of multimedia data are costly which reduces the network's lifetime. In this paper, we propose a low-cost new solution for tracking a mobile target called EAOT (Energy Aware Object Tracking). It consists of a distributed cooperative algorithm that runs in heterogeneous Wireless Sensor Networks composed of both scalar and multimedia sensors. The scalar sensors (MS) are equipped with a motion detector; their role is to detect the target and then activate the camera sensors (CS) through message exchanges. We conducted simulations to evaluate the performance of the proposed mechanism in terms of tracking accuracy, number of exchanged messages, energy consumption, and spatial average deviation. The results are compared to two existing solutions: one based on simple camera sensors which always run in active mode and the other one based on the optimal camera node selection (OCNS) to track the target. The obtained results show that for the same number of nodes, EAOT consumes between 2.6% and 44% less energy than OCNS depending on the distribution of MS/CS. View full abstract»

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