955 resultados para COMMUNICATION-NETWORKS


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Part 15: Performance Management Frameworks

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Part 14: Interoperability and Integration

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Wireless power transfer (WPT) and radio frequency (RF)-based energy har- vesting arouses a new wireless network paradigm termed as wireless powered com- munication network (WPCN), where some energy-constrained nodes are enabled to harvest energy from the RF signals transferred by other energy-sufficient nodes to support the communication operations in the network, which brings a promising approach for future energy-constrained wireless network design. In this paper, we focus on the optimal WPCN design. We consider a net- work composed of two communication groups, where the first group has sufficient power supply but no available bandwidth, and the second group has licensed band- width but very limited power to perform required information transmission. For such a system, we introduce the power and bandwidth cooperation between the two groups so that both group can accomplish their expected information delivering tasks. Multiple antennas are employed at the hybrid access point (H-AP) to en- hance both energy and information transfer efficiency and the cooperative relaying is employed to help the power-limited group to enhance its information transmission throughput. Compared with existing works, cooperative relaying, time assignment, power allocation, and energy beamforming are jointly designed in a single system. Firstly, we propose a cooperative transmission protocol for the considered system, where group 1 transmits some power to group 2 to help group 2 with information transmission and then group 2 gives some bandwidth to group 1 in return. Sec- ondly, to explore the information transmission performance limit of the system, we formulate two optimization problems to maximize the system weighted sum rate by jointly optimizing the time assignment, power allocation, and energy beamforming under two different power constraints, i.e., the fixed power constraint and the aver- age power constraint, respectively. In order to make the cooperation between the two groups meaningful and guarantee the quality of service (QoS) requirements of both groups, the minimal required data rates of the two groups are considered as constraints for the optimal system design. As both problems are non-convex and have no known solutions, we solve it by using proper variable substitutions and the semi-definite relaxation (SDR). We theoretically prove that our proposed solution method can guarantee to find the global optimal solution. Thirdly, consider that the WPCN has promising application potentials in future energy-constrained net- works, e.g., wireless sensor network (WSN), wireless body area network (WBAN) and Internet of Things (IoT), where the power consumption is very critical. We investigate the minimal power consumption optimal design for the considered co- operation WPCN. For this, we formulate an optimization problem to minimize the total consumed power by jointly optimizing the time assignment, power allocation, and energy beamforming under required data rate constraints. As the problem is also non-convex and has no known solutions, we solve it by using some variable substitutions and the SDR method. We also theoretically prove that our proposed solution method for the minimal power consumption design guarantees the global optimal solution. Extensive experimental results are provided to discuss the system performance behaviors, which provide some useful insights for future WPCN design. It shows that the average power constrained system achieves higher weighted sum rate than the fixed power constrained system. Besides, it also shows that in such a WPCN, relay should be placed closer to the multi-antenna H-AP to achieve higher weighted sum rate and consume lower total power.

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Part 10: Sustainability and Trust

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Part 9: Innovation Networks

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Part 8: Business Strategies Alignment

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Part 8: Business Strategies Alignment

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Part 6: Engineering and Implementation of Collaborative Networks

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Part 5: Service Orientation in Collaborative Networks

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Part 2: Behaviour and Coordination

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The EU-funded project UAN - Underwater Acoustic Network aims at conceiving, developing and testing at sea an innovative and operational concept for integrating in a unique communication system submerged, surface and aerial sensors with the objective of protecting off-shore and coastline critical infrastructures. A crucial aspect of the project consisted in the use of autonomous underwater vehicles (AUVs) as mobile nodes in the underwater acoustic communication network. In particular, AUVs have the role of adapting the network geometry to the variation of the acoustic channel. This paper reports on the project concept and vision as well as on the progress of its various development phases. The recent at-sea successes that have been demonstrated within the UAN framework are detailed and results of the final UAN project demonstration, UAN11, held in the May of 2011, are reported. The UAN network was in operation for five continuous days with up to five nodes, of which three of them were mobile nodes. © IFAC.

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Data aggregation in wireless sensor networks is employed to reduce the communication overhead and prolong the network lifetime. However, an adversary may compromise some sensor nodes, and use them to forge false values as the aggregation result. Previous secure data aggregation schemes have tackled this problem from different angles. The goal of those algorithms is to ensure that the Base Station (BS) does not accept any forged aggregation results. But none of them have tried to detect the nodes that inject into the network bogus aggregation results. Moreover, most of them usually have a communication overhead that is (at best) logarithmic per node. In this paper, we propose a secure and energy-efficient data aggregation scheme that can detect the malicious nodes with a constant per node communication overhead. In our solution, all aggregation results are signed with the private keys of the aggregators so that they cannot be altered by others. Nodes on each link additionally use their pairwise shared key for secure communications. Each node receives the aggregation results from its parent (sent by the parent of its parent) and its siblings (via its parent node), and verifies the aggregation result of the parent node. Theoretical analysis on energy consumption and communication overhead accords with our comparison based simulation study over random data aggregation trees.

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Randomly scattered sensors may cause sensing holes and redundant sensors. In carrier-based sensor relocation, mobile robots (with limited capacity to carry sensors) pick up additional or redundant sensors and relocate them at sensing holes. In the only known localized algorithm, robots randomly traverse field and act based on identified pair of spare sensor and coverage hole. We propose a Market-based Sensor Relocation (MSR) algorithm, which optimizes sensor deployment location, and introduces bidding and coordinating among neighboring robots. Sensors along the boundary of each hole elect one of them as the representative, which bids to neighboring robots for hole filling service. Each robot randomly explores by applying Least Recently Visited policy. It chooses the best bid according to Cost over Progress ratio and fetches a spare sensor nearby to cover the corresponding sensing hole. Robots within communication range share their tasks to search for better possible solutions. Simulation shows that MSR outperforms the existing competing algorithm G-R3S2 significantly on total robot traversed path and energy, and time to cover holes, slightly on number of sensors needed to cover the hole and number of sensor messages for bidding and deployment location sharing.

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One of the major challenges in healthcare wireless body area network (WBAN) applications is to control congestion. Unpredictable traffic load, many-to-one communication nature and limited bandwidth occupancy are among major reasons that can cause congestion in such applications. Congestion has negative impacts on the overall network performance such as packet losses, increasing end-to-end delay and wasting energy consumption due to a large number of retransmissions. In life-critical applications, any delay in transmitting vital signals may lead to death of a patient. Therefore, in order to enhance the network quality of service (QoS), developing a solution for congestion estimation and control is imperative. In this paper, we propose a new congestion detection and control protocol for remote monitoring of patients health status using WBANs. The proposed system is able to detect congestion by considering local information such as buffer capacity and node rate. In case of congestion, the proposed system differentiates between vital signals and assigns priorities to them based on their level of importance. As a result, the proposed approach provides a better quality of service for transmitting highly important vital signs.

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G20 outreach processes, in the form of the Think 20, Labour 20, Business 20, and Civil 20, Youth 20, and Women 20, are a formal attempt by G20 leaders to engage various social sectors with G20 policymaking. This essay contends that G20 outreach processes are best understood as transnational policy networks, which are involved in widening the field of policy communication and deliberation. The importance of these transnational policy networks rest upon their role in developing and disseminating G20 policy priorities and principles; and are an attempt to enhance the legitimacy and influence of the G20 and its policy proposals.

"We agree that, in order to strengthen its ability to build and sustain the political consensus needed to respond to challenges, the G20 must remain efficient, transparent and accountable. To achieve this, we decide to … pursue consistent and effective engagement with non-members, regional and international organisations, including the United Nations, and other actors, and we welcome their contribution to our work as appropriate. We also encourage engagement with civil society.G20 Cannes Summit Final Declaration 2011 (G20 2011)"

The difficulty in balancing the effectiveness and representativeness of the Group of Twenty (G20) has led to sustained questions about its legitimacy (Cooper 2010; Rudd 2011; Cooper and Pouliot 2015). Consequently, while leaders have long sought external advice about the agendas of Group of Seven (G7) summits since 1975, and about the G20 finance ministers and central bank governors’ meetings (G20 FM/CBG) since 1999, there has been intensification, elaboration, and institutionalization of transnational networks of policymakers with respect to the G20 in recent years. These networks are especially evident in the form of the G20 working groups and G20 outreach processes involved in the G20 FM/CBG and the G20 leaders’ forum created in 2008.

G20 working groups include transgovernmental groups of government officials and outside experts within a specific policy area who are charged with preparing material for G20 deliberations. G20 outreach processes are a recent and more formal attempt by G20 leaders to engage various social sectors with the policymaking activity of the G20 and were first considered by the G20 membership in 2010 with a more formal engagement with business interests. This led to the formal development of G20 outreach groups in 2013 in the form of the Think 20 (think tanks), Labour 20, Business 20, Civil 20 and Youth 20, which include representatives from these sectors. In 2015, a Women 20 outreach group was also added. These outreach processes are best understood as transnational policy networks which have been built to support the G20’s capacity to be effective and legitimate.

This essay focuses on G20 outreach processes and examines why and how the G20 has sought to augment its intergovernmental summitry and transgovernmental working groups with transnational policy networks, purposely involving a range of societal interests. Transnational policy networks demonstrate the existence of policymaking practices which include the policy influence of experts and advocates outside government. These networks also indicate the ways in which governments, International Governmental Organizations (IGOs) and summits like the G20 engage society, or where elements of society engage themselves with the policymaking process (Stone 2008). These networks intersect with the intergovernmental activities of leaders and key diplomats, and overlap with the transgovernmental relationships of various levels of government bureaucrats (Baker 2009). One of the principle features of transnational policy networks is the way they create and channel the communication of political ideas and priorities. However, it is important to keep in the mind the purpose and power of actors involved in the network and consider who has the discretion and motivation to create the network in the first instance. As the G20 members stated in 2012, the aspiration for outreach is founded upon an intent to strengthen the G20’s capacity “to build and sustain the political consensus”. Consequently, it is important to consider how the development of transnational policy networks in the form of G20 outreach processes are able to sustain the effectiveness and legitimacy of the G20.

This essay contends that G20 outreach processes are best understood as transnational policy networks. These networks have been built to widen the field of policy communication and deliberation. Furthermore, these outreach processes and networks are an attempt to enhance the legitimacy and influence of the G20 and its policy proposals. While there is no doubt that outreach practices are “ad hoc responses to the widespread charge that the G20 reproduces the politics of exclusion in global governance” (Cooper and Pouliot 2015, 347), these practices have the potential to improve both the effectiveness and legitimacy of the G20. The G20 possesses uncertain legitimacy and members of the G20 demonstrate an awareness of this and a corresponding willingness to actively develop various political practices to support the capacity and legitimacy of the G20.

However, G20 outreach also enables the G20 to place some limit upon the policy narratives and ideas that develop within these policy networks. The G20 is liable to be misunderstood without examining the activity of these transnational networks because the G20 is fundamentally a deliberative policy forum rather than a negotiating forum of binding regulations. Transnational policy networks have the potential to scrutinize and amplify relevant policy ideas and thereby enhance the legitimacy of the G20 and strengthen the capacity of the G20 to address an array of global economic and social problems. However, while some narrative control is important to amplify the G20 agenda, too much narrative control will undermine its legitimacy and capacity to develop broad-based responses to global problems. This essay explores the formation of these transnational policy networks by first outlining the evolution of the purpose and configuration of the G20, then it considers the ways G20 outreach processes constitute transnational policy networks and why they have been established, and lastly, analyses how these networks operate to enhance the legitimacy and effectiveness of the G20.