| 1. |
- Angelopoulos, Constantinos Marios, et al.
(författare)
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Improving sensor network performance with wireless energy transfer
- 2015
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Ingår i: International Journal of Ad Hoc and Ubiquitous Computing. - : InderScience Publishers. - 1743-8225 .- 1743-8233. ; 20:3, s. 159-171
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Tidskriftsartikel (refereegranskat)abstract
- Through recent technology advances in the field of wireless energy transmission wireless rechargeable sensor networks have emerged. In this new paradigm for wireless sensor networks a mobile entity called mobile charger (MC) traverses the network and replenishes the dissipated energy of sensors. In this work we first provide a formal definition of the charging dispatch decision problem and prove its computational hardness. We then investigate how to optimise the trade-offs of several critical aspects of the charging process. In the light of these optimisations, we study the impact of the charging process to the network lifetime for three characteristic underlying routing protocols. Finally, we propose a mobile charging protocol that locally adapts the circular trajectory of the MC to the energy dissipation rate of each sub-region of the network. We compare this protocol against several MC trajectories by a detailed experimental evaluation. The derived findings demonstrate significant performance gains.
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| 2. |
- Asplund, Mikael, et al.
(författare)
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Worst-case latency of broadcast in intermittently connected networks
- 2012
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Ingår i: International Journal of Ad Hoc and Ubiquitous Computing. - : Inderscience. - 1743-8225 .- 1743-8233. ; 11:2-3, s. 125-138
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Tidskriftsartikel (refereegranskat)abstract
- Worst-case latency is an important characteristic of information dissemination protocols. However, in sparse mobile ad hoc networks where end-to-end connectivity cannot be achieved and store-carry-forward algorithms are needed, such worst-case analyses have not been possible to perform on real mobility traces due to lack of suitable models. We propose a new metric called delay expansion that reflects connectivity and reachability properties of intermittently connected networks. Using the delay expansion, we show how bounds on worst-case latency can be derived for a general class of broadcast protocols and a wide range of real mobility patterns. The paper includes theoretical results that show how worst-case latency can be related with delay expansion for a given mobility scenario, as well as simulations to validate the theoretical model.
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| 3. |
- Balador, Ali, et al.
(författare)
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A Density-Based Contention Window Control Scheme for Unicast Communications in Vehicular Ad Hoc Networks
- 2015
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Ingår i: International Journal of Ad Hoc and Ubiquitous Computing. - 1743-8225 .- 1743-8233. ; 24, s. 65-75
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Tidskriftsartikel (refereegranskat)abstract
- Achieving a well-designed medium access control MAC protocol is a challenging issue to improve communications efficiency due to the dynamic nature of vehicular ad hoc networks VANETs. IEEE 802.11p standard was selected as the best choice for vehicular environments considering its availability, maturity, and cost. The common problem in all IEEE 802.11 based protocols is scalability, exhibiting performance degradation in highly variable network scenarios. Experimental results for the IEEE 802.11-based MAC protocol show the importance of contention window adjustment on communications performance; however the vehicular communications community has not yet addressed this issue in unicast communication environments. This paper proposes a novel contention window control scheme for VANET environments based on estimating the network density, which is then used to dynamically adapt the CW size. Analysis and simulation results show that our proposal provides better overall performance compared with previous proposals, even in high network density scenarios.
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| 4. |
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| 5. |
- Fowler, Scott, et al.
(författare)
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Ubiquitous Fair Bandwidth Allocation for Multimedia Traffic on a WiMAX Mesh Network with Multi-channels
- 2012
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Ingår i: International Journal of Ad Hoc and Ubiquitous Computing. - : InderScience Publishers. - 1743-8225 .- 1743-8233. ; 9:4, s. 224-240
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Tidskriftsartikel (refereegranskat)abstract
- The WiMAX, also known as IEEE 802.16, provides a mechanism for deploying high-speed wireless mesh network, (an ubiquitous wireless network) in metropolitan areas. WiMAX technology can be used as ``last mile ubiquitous" broadband connections to deliver streaming audio or video to clients. Thus, Quality of Service (QoS) is very important for WiMAX networks. Providing QoS in multi-hop WiMAX networks such as WiMAX mesh networks is challenging since the WiMAX mesh networks MAC is connectionless based and does not have proper support guarantees for QoS over multiple hops. As a result, multiple links can interfere with each other when they are scheduled at the same time. The scheduling function plays a crucial role in QoS support, and various algorithms have been proposed and analyzed. These analysis basically assume a backlogged situation evenly in all queues. However, multimedia traffic is bursty in nature, and the fairness of bursty traffic relative to continuous traffic has not been fully studied yet. Therefore, in this paper, we will discuss the potential unfairness that bursty traffic may be subjected to and propose a new frame-based packet scheduling algorithm. The scheduling is evaluated with multiple channels on WiMAX mesh nodes, which are operated in a distributed coordinated scheduling mode. Each wireless node has a single radio interface which is able to switch between multiple channels. We evaluated the performance of the proposed dynamic changing scheduling method by extensive simulations, and it was shown to provide fair bandwidth allocation while increasing the traffic performance by means of throughput.
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| 6. |
- Guo, Cheng, et al.
(författare)
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Designing a flexible and low-cost testbed for Wireless Sensor Networks
- 2012
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Ingår i: International Journal of Ad Hoc and Ubiquitous Computing. - : InderScience Publishers. - 1743-8225 .- 1743-8233. ; 9:2, s. 111-121
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Tidskriftsartikel (refereegranskat)abstract
- Setting up a Wireless Sensor Network (WSN) for an experiment is both time consuming and effort intensive. Many testbeds connect and manage experimental nodes using wires and gateways. It leads to extra cost, extensive setup and maintenance effort and dedicated deployment place. We propose a framework for implementing a flexible and low-cost wireless for sensor network testbed (FIST). FIST consists of only experimental nodes. Both testbed and experiment management are carried out by the nodes wirelessly without extra devices. Thus, the testbed can be easily and quickly deployed anywhere. We present our framework and also a case study using FIST.
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| 7. |
- Hajiesmaili, Mohammad H., et al.
(författare)
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Joint multipath rate control and scheduling for SVC streams in wireless mesh networks
- 2014
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Ingår i: International Journal of Ad Hoc and Ubiquitous Computing. - 1743-8225 .- 1743-8233. ; 15:4, s. 239-251
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Tidskriftsartikel (refereegranskat)abstract
- Rate adaptation of video signal for different quality-of-service scenarios through scalable video coding (SVC) standard has been considered as a key feature for multimedia transmission. This paper addresses joint multipath rate control and scheduling for SVC-encoded video transmission over wireless mesh networks (WMNs). Each video stream is assumed to use multipath routing and to possess a staircase utility function. Using the conflict graph that represents the interference-limited model, we formulate the problem as one of maximising the sum of source utilities subject to transport and link layers constraints. The multipath routing over wireless channels and staircase utilities yield a non-convex optimisation problem. To attain a convex formulation, we adopt multimodal sigmoid approximation and exploit utility-proportional fairness approach. Then, employing dual decomposition, we devise a distributed algorithm for joint multipath rate control and scheduling in WMNs. Experiments validate the effectiveness of our endeavor toward achieving cross-layer optimisation for video transmission in WMNs.
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| 8. |
- Hilletofth, Per, et al.
(författare)
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Editorial
- 2016
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Ingår i: International Journal of Ad Hoc and Ubiquitous Computing. - 1743-8225 .- 1743-8233. ; 21:4, s. 221-223
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Hilletofth, Per, et al.
(författare)
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Editorial
- 2016
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Ingår i: International Journal of Ad Hoc and Ubiquitous Computing. - : InderScience Publishers. - 1743-8225 .- 1743-8233. ; 21:4, s. 221-223
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Jordaan, Coert, et al.
(författare)
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Design of a monitoring and safety system for underground mines using wireless sensor networks
- 2019
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Ingår i: International Journal of Ad Hoc and Ubiquitous Computing. - : InderScience Publishers. - 1743-8225 .- 1743-8233. ; 32:1, s. 14-28
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a mine safety system using a wireless sensor network (WSN) is implemented. Investigations are done into design of sensors and wireless communication to profile the underground mining environment. The information is used to design and implement a robust hardware-based sensor node with standalone microcontrollers that sample data from six different sensors, namely temperature, humidity, airflow speed, noise, dust and gas level sensors, and transmit the processed data to a graphical user interface. The system reliability and accuracy is tested in a simulated mine and provided linear and accurate results over nearly a month of daily testing. It is observed that critical success factors for the wireless sensor node is its robust design, which does not easily fail or degrade in performance. The node also has strong, self-adaptive networking functionality, to recover in the case of a node failure.
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| 11. |
- Van Haute, Tom, et al.
(författare)
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Comparability of RF-based indoor localisation solutions in heterogeneous environments : An experimental study
- 2016
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Ingår i: International Journal of Ad Hoc and Ubiquitous Computing. - : Inderscience Enterprises Ltd.. - 1743-8225 .- 1743-8233. ; 23:1-2, s. 92-114
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Tidskriftsartikel (refereegranskat)abstract
- The growing popularity of indoor localisation research has resulted in a significant amount of research papers describing and evaluating innovative localisation solutions. Unfortunately, the results from most of these research papers cannot easily be compared since they are evaluated in different environments, use different evaluation criteria and typically tailor their solutions towards a single testbed environment. To evaluate how these different conditions influence the localisation performance, in this paper an exhaustive set of experiments has been performed, in which three different localisation solutions have been evaluated using multiple metrics in three different test environments: two types of office environments and an industry-like factory environment. None of the used localisation solutions was previously optimised for any of these test environments and they were all evaluated under similar conditions. The results reveal several weaknesses in the evaluation methods used in the majority of existing scientific literature of indoor localisation solutions.
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| 12. |
- Nilsson, Niklas, Assistant Professor, 1979-, et al.
(författare)
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Resistant to Change? The EU as a Normative Power and Its Troubled Relations with Russia and China
- 2018
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Ingår i: Foreign Policy Analysis. - : Oxford University Press (OUP). - 1743-8586 .- 1743-8594.
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we investigate the European Union's (EU) role as a normative foreign policy actor and its troubled relations to Russia and China. We contend that the lack of preparedness of the EU to foresee the increasingly tense relations with these countries can be explained through a role theoretical perspective. We show that the attachment of the EU to its role as a normative international actor reduced its awareness of Russia's and China's growing refusal to accept the EU's ambition to diffuse liberal norms and principles. The EU's inability to read the changing role expectations of China and Russia hampered the shaping of an appropriate foreign policy leading up the diplomatic crises with these two countries in the late 2000s and early 2010s, respectively. Theoretically, the findings contribute with a novel understanding of role conceptions in terms of reducing an actor's preparedness to acknowledge changes to its international role position caused by challenges raised by antagonistic partners.
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| 13. |
- Myrvold, Kristina, et al.
(författare)
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Miniature Qur’ans in the First World War : Religious Comforts for Indian Muslim Soldiers
- 2013
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Ingår i: Postscripts. - Sheffield : Equinox Publishing. - 1743-887X .- 1743-8888. ; 9:2-3, s. 125-151, s. 132-157
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Tidskriftsartikel (refereegranskat)abstract
- During the First World War Muslim soldiers from India made up a significant part of the British forces. Attempts to satisfy the soldiers' religious needs became a British strategy to maintain military discipline among the soldiers in Europe and to avoid public unease and discontent in colonial India. Based on archival material, this article examines how the British tried to identify the religious needs of the Indian soldiers and how letters written by Muslim soldiers emphasized the importance of the Qur'an. The article further explores how the Indian Soldiers' Fund became an important charity which procured and distributed miniature copies of the Qur'an and how prominent persons in India and Europe donated scriptures to Muslim soldiers. Although the soldiers' uses of the miniature scriptures remain uncertain, the books were given iconic functions to represent religion and identities in a time when the British national honour was threatened.
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