| 1. |
- Rohner, Christian, et al.
(författare)
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Interactions between TCP, UDP and Routing Protocols in Wireless Multi-hop Ad hoc Networks
- 2005
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Ingår i: Proceedings of the 1st IEEE ICPS Workshop on Multi-hop Ad hoc Networks: from theory to reality (REALMAN 2005).
-
Konferensbidrag (refereegranskat)abstract
- The achieved throughput in an ad hoc network is affected by many factors, including radio interference between hops, the ability of the routing protocol to react on topology changes and a complex interaction between the application and underlying protocols. This paper studies experimentally the impact of these factors on UDP and TCP throughput. Furthermore, when both TCP and UDP share some hops in an ad hoc network there is a complex interaction between the transport protocols as well as with the routing protocol. Our results show that this interaction results in significant UDP jitter, instable routes and significantly lower TCP throughput. We use a controlled real testbed for the experiments and a graphical tool that captures the interactions.
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| 2. |
- Achtzehn, Andreas, et al.
(författare)
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ARPD : Asynchronous random key predistribution in the LEAP framework for Wireless Sensor Networks
- 2007
-
Ingår i: 3rd IEEE International Workshop on Wireless and Sensor Networks Security (IEEE WSNS 2007).
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Konferensbidrag (refereegranskat)abstract
- In the LEAP framework for wireless sensor networks a set of keys is used to secure communication. LEAP distinguishes between unicast (pairwise) communication, group (cluster) communication and global (broadcast) communication. The keys used in pairwise communication are derived from an initial key KI that nodes are equipped with prior to deployment and that is deleted after link setup. Further keys are distributed encrypted with these pairwise keys. If the initial key is ever disclosed, the whole network is compromised. To lower the threat of KI disclosure, we present a novel KI -less scheme for key predistribution. Our scheme is based on random key redistribution, and proves to perform better in medium sized networks than previous proposals. It is resilient against node capture attacks and allows node to node authentication. Attacks against overlying protocols in the network are more difficult with this scheme. We have conducted computations to show the feasibility of our scheme for networks up to a size of 1000 nodes. By introducing a key reuse system we are able to increase the probability of a successful link setup. We have included a security analysis that discusses our scheme’s resistance against commonly known attacks.
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| 3. |
- Achtzehn, Andreas, et al.
(författare)
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Implementing Agreement Protocols in Sensor
- 2006
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Ingår i: The Second International Workshop on Wireless and Sensor Networks Security (WSNS'06).
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Konferensbidrag (refereegranskat)abstract
- We investigate application of agreement protocols tolerating malicious failures in sensor networks. We identify several scenarios where agreement can be used, and report on our experience with implementing an agreement protocol.
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| 4. |
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| 5. |
- Bastani, Saeed, et al.
(författare)
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A social node model for realising information dissemination strategies in delay tolerant networks
- 2012
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Ingår i: Proceedings of the 15th ACM international conference on Modeling, analysis and simulation of wireless and mobile systems. - New york : ACM Press. ; , s. 79-88, s. 78-79
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Konferensbidrag (refereegranskat)abstract
- In Delay Tolerant Networks (DTNs) as an emerging content dissemination platform, mobile nodes opportunistically exchange content as they meet, with the intent of disseminating content among nodes that share common interests. During a meeting, nodes can exchange both content of direct interest to themselves as well as content that is of interest to a larger set of nodes that may be encountered in the future. The utility of DTN is governed by the content exchange opportunity (the amount of content that can be exchanged during a meeting) as well as the selection of content to be exchanged in order to maximise the interest nodes will have in information they are exposed to. Considering that there is a cost associated with the content exchange (e.g. battery usage, buffer occupancy or consumed transmission opportunity) the aim for nodes participating in content dissemination should be to maximise their payoff. In this paper, we contribute a generic framework for describing the characteristics of content exchange among participating nodes in a network. We incorporate a distributed information popularity measurement and the pairwise interaction of nodes modelled as a bargaining problem. The outcome of this process is the fair split up of dwelling time as a network resource and the selection of which content objects to exchange in order to maximise the nodes’ payoff. The framework is generally intended to be used as a capstone for investigation of content dissemination properties and various content exchange strategies in a DTN, a topic addressed in this paper and experiments conducted to validate the function and correctness of the proposed framework.
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| 6. |
- Beneson, Zinaida, et al.
(författare)
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Verifiable Agreement: Limits of Non-Repudiation in Mobile Peer-to-Peer Ad Hoc Networks
- 2006
-
Ingår i: Third European Workshop on Security and Privacy in Ad hoc and Sensor Networks.
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Konferensbidrag (refereegranskat)abstract
- We introduce verifiable agreement as a fundamental service for securing mobile peer-to-peer ad hoc networks, and investigate its solvability. Verifiability of a protocol result means that the participants can prove that the protocol reached a particular result to any third party (the verifier) which was not present in the network at the time of the protocol execution.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Bjurefors, Fredrik
(författare)
-
Measurements in opportunistic networks
- 2012
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Opportunistic networks are a subset of delay tolerant networks where the contacts are unscheduled. Such networks can be formed ad hoc by wireless devices, such as mobile phones and laptops. In this work we use a data-centric architecture for opportunistic networks to evaluate data dissemination overhead, congestion in nodes' buffer, and the impact of transfer ordering. Dissemination brings an overhead since data is replicated to be spread in the network and overhead leads to congestion, i.e., overloaded buffers.We develop and implement an emulation testbed to experimentally evaluate properties of opportunistic networks. We evaluate the repeatability of experiments in the emulated testbed that is based on virtual computers. We show that the timing variations are on the order of milliseconds.The testbed was used to investigate overhead in data dissemination, congestion avoidance, and transfer ordering in opportunistic networks. We show that the overhead can be reduced by informing other nodes in the network about what data a node is carrying. Congestion avoidance was evaluated in terms of buffer management, since that is the available tool in an opportunistic network, to handle congestion. It was shown that replication information of data objects in the buffer yields the best results. We show that in a data-centric architecture were each data item is valued differently, transfer ordering is important to achieve delivery of the most valued data.
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| 11. |
- Bjurefors, Fredrik, 1978-
(författare)
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Opportunistic Networking : Congestion, Transfer Ordering and Resilience
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Opportunistic networks are constructed by devices carried by people and vehicles. The devices use short range radio to communicate. Since the network is mobile and often sparse in terms of node contacts, nodes store messages in their buffers, carrying them, and forwarding them upon node encounters. This form of communication leads to a set of challenging issues that we investigate: congestion, transfer ordering, and resilience.Congestion occurs in opportunistic networks when a node's buffers becomes full. To be able to receive new messages, old messages have to be evicted. We show that buffer eviction strategies based on replication statistics perform better than strategies that evict messages based on the content of the message.We show that transfer ordering has a significant impact on the dissemination of messages during time limited contacts. We find that transfer strategies satisfying global requests yield a higher delivery ratio but a longer delay for the most requested data compared to satisfying the neighboring node's requests.Finally, we assess the resilience of opportunistic networks by simulating different types of attacks. Instead of enumerating all possible attack combinations, which would lead to exhaustive evaluations, we introduce a method that use heuristics to approximate the extreme outcomes an attack can have. The method yields a lower and upper bound for the evaluated metric over the different realizations of the attack. We show that some types of attacks are harder to predict the outcome of and other attacks may vary in the impact of the attack due to the properties of the attack, the forwarding protocol, and the mobility pattern.
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| 12. |
- Bjurefors, Fredrik, et al.
(författare)
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Resilience and Opportunistic Forwarding : Beyond Average Value Analysis
- 2014
-
Ingår i: Computer Communications. - : Elsevier BV. - 0140-3664 .- 1873-703X. ; 48:SI, s. 111-120
-
Tidskriftsartikel (refereegranskat)abstract
- Opportunistic networks are systems with highly distributed operation, relying on the altruistic cooperation of highly heterogeneous, and not always software and hardware-compatible, user nodes. Moreover, the absence of central coordination and control makes them vulnerable to malicious attacks. In this paper, we study the resilience of popular forwarding protocols to a representative set of challenges to their normal operation. These include jamming locally disturbing message transfer between nodes, hardware/software failures and incompatibility among nodes rendering contact opportunities useless, and free-riding phenomena. We first formulate and promote the metric envelope concept as a tool for assessing the resilience of opportunistic forwarding schemes. Metric envelopes depart from the standard practice of average value analysis and explicitly account for the differentiated challenge impact due to node heterogeneity (device capabilities, mobility) and attackers’ intelligence. We then propose heuristics to generate worst- and best-case challenge realization scenarios and approximate the lower and upper bounds of the metric envelopes. Finally, we demonstrate the methodology in assessing the resilience of three popular forwarding protocols in the presence of the three challenges, and under a comprehensive range of mobility patterns. The metric envelope approach provides better insights into the level of protection path diversity and message replication provide against different challenges, and enables more informed choices in opportunistic forwarding when network resilience becomes important.
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| 13. |
- Bjurefors, Fredrik, et al.
(författare)
-
Resilience and Opportunistic Forwarding: Beyond Average Value Analysis
- 2013
-
Ingår i: CHANTS '13 Proceedings of the 8th ACM MobiCom workshop on Challenged networks.
-
Konferensbidrag (refereegranskat)abstract
- Opportunistic networks are systems with highly distributed operation, relying on the altruistic cooperation of heterogeneous, and not always software- and hardware-compatible user nodes. Moreover, the absence of central control makes them vulnerable to malicious attacks. In this paper, we take a fresh look at the resilience of opportunistic forwarding to these challenges. In particular, we introduce and promote the use of metric envelopes as a resilience assessment tool. Metric envelopes depart from the standard practice of average value analysis and explicitly account for the differentiated impact that a challenge may have on the forwarding performance due to node heterogeneity (device capabilities, mobility) and attackers’ intelligence. The use of metric envelopes is demonstrated in the case of three challenges: jamming, hardware/software failures and incompatibilities, and free-riding phenomena. For each challenge, we first devise heuristics to generate worst- and best-case realization scenarios that can approximate the metric envelopes. Then we derive the envelopes of common performance metrics for three popular forwarding protocols under a comprehensive range of mobility patterns. The metric envelope approach enables more informed choices in opportunistic forwarding whenever network resilience considerations become important.
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| 14. |
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| 15. |
- Borgström, Gustaf, PhD Student, 1984-, et al.
(författare)
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Faster Functional Warming with Cache Merging
- 2022
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Smarts-like sampled hardware simulation techniques achieve good accuracy by simulating many small portions of an application in detail. However, while this reduces the detailed simulation time, it results in extensive cache warming times, as each of the many simulation points requires warming the whole memory hierarchy. Adaptive Cache Warming reduces this time by iteratively increasing warming until achieving sufficient accuracy. Unfortunately, each time the warming increases, the previous warming must be redone, nearly doubling the required warming. We address re-warming by developing a technique to merge the cache states from the previous and additional warming iterations.We address re-warming by developing a technique to merge the cache states from the previous and additional warming iterations. We demonstrate our merging approach on multi-level LRU cache hierarchy and evaluate and address the introduced errors. By removing warming redundancy, we expect an ideal 2× warming speedup when using our Cache Merging solution together with Adaptive Cache Warming. Experiments show that Cache Merging delivers an average speedup of 1.44×, 1.84×, and 1.87× for 128kB, 2MB, and 8MB L2 caches, respectively, with 95-percentile absolute IPC errors of only 0.029, 0.015, and 0.006, respectively. These results demonstrate that Cache Merging yields significantly higher simulation speed with minimal losses.
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| 16. |
- Borgström, Gustaf, PhD Student, 1984-, et al.
(författare)
-
Faster FunctionalWarming with Cache Merging
- 2023
-
Ingår i: PROCEEDINGS OF SYSTEM ENGINEERING FOR CONSTRAINED EMBEDDED SYSTEMS, DRONESE AND RAPIDO 2023. - : Association for Computing Machinery (ACM). - 9798400700453 ; , s. 39-47
-
Konferensbidrag (refereegranskat)abstract
- Smarts-like sampled hardware simulation techniques achieve good accuracy by simulating many small portions of an application in detail. However, while this reduces the simulation time, it results in extensive cache warming times, as each of the many simulation points requires warming the whole memory hierarchy. Adaptive Cache Warming reduces this time by iteratively increasing warming to achieve sufficient accuracy. Unfortunately, each increases requires that the previous warming be redone, nearly doubling the total warming. We address re-warming by developing a technique to merge the cache states from the previous and additional warming iterations. We demonstrate our merging approach on multi-level LRU cache hierarchy and evaluate and address the introduced errors. Our experiments show that Cache Merging delivers an average speedup of 1.44x, 1.84x, and 1.87x for 128kB, 2MB, and 8MB L2 caches, respectively, (vs. a 2x theoretical maximum speedup) with 95-percentile absolute IPC errors of only 0.029, 0.015, and 0.006, respectively. These results demonstrate that Cache Merging yields significantly higher simulation speed with minimal losses.
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| 17. |
- Borgström, Gustaf
(författare)
-
Making Sampled Simulations Faster by Minimizing Warming Time
- 2022
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A computer system simulator is a fundamental tool for computer architects to try out brand new ideas or explore the system’s response to different configurations when executing different program codes. However, even simulating the CPU core in detail is time-consuming as the execution rate slows down by several orders of magnitude compared to native execution. To solve this problem, previous work, namely SMARTS, demonstrates a statistical sampling methodology that records measurements only from tiny samples throughout the simulation. It spends only a fraction of the full simulation time on these sample measurements. In-between detailed sample simulations, SMARTS fast-forwards in the simulation using a greatly simplified and much faster simulation model (compared to full detail), which maintains only necessary parts of the architecture, such as cache memory. This maintenance process is called warming. While warming is mandatory to keep the simulation accuracy high, caches may be sufficiently warm for an accurate simulation long before reaching the sample. In other words, much time may be wasted on warming in SMARTS.In this work, we show that caches can be kept in an accurate state with much less time spent on warming. The first paper presents Adaptive Cache Warming, a methodology for identifying the minimum amount of warming in an iterative process for every SMARTS sample. The rest of the simulation time, previously spent on warming, can be skipped by fast-forwarding between samples using native hardware execution of the code. Doing so will thus result in significantly faster statistically sampled simulation while maintaining accuracy. The second paper presents Cache Merging, which mitigates the redundant warmings introduced in Adaptive Cache Warming. We solve this issue by going back in time and merging the existing warming with a cache warming session that comes chronologically before the existing warming. By removing the redundant warming, we yield even more speedup. Together, Adaptive Cache Warming and Cache Merging is a powerful boost for statistically sampled simulations.
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| 18. |
- Cambazoglu, Volkan
(författare)
-
Protocol, mobility and adversary models for the verification of security
- 2016
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing heterogeneity of communicating devices, ranging from resource constrained battery driven sensor nodes to multi-core processor computers, challenges protocol design. We examine security and privacy protocols with respect to exterior factors such as users, adversaries, and computing and communication resources; and also interior factors such as the operations, the interactions and the parameters of a protocol.Users and adversaries interact with security and privacy protocols, and even affect the outcome of the protocols. We propose user mobility and adversary models to examine how the location privacy of users is affected when they move relative to each other in specific patterns while adversaries with varying strengths try to identify the users based on their historical locations. The location privacy of the users are simulated with the support of the K-Anonymity protection mechanism, the Distortion-based metric, and our models of users' mobility patterns and adversaries' knowledge about users.Security and privacy protocols need to operate on various computing and communication resources. Some of these protocols can be adjusted for different situations by changing parameters. A common example is to use longer secret keys in encryption for stronger security. We experiment with the trade-off between the security and the performance of the Fiat–Shamir identification protocol. We pipeline the protocol to increase its utilisation as the communication delay outweighs the computation.A mathematical specification based on a formal method leads to a strong proof of security. We use three formal languages with their tool supports in order to model and verify the Secure Hierarchical In-Network Aggregation (SHIA) protocol for Wireless Sensor Networks (WSNs). The three formal languages specialise on cryptographic operations, distributed systems and mobile processes. Finding an appropriate level of abstraction to represent the essential features of the protocol in three formal languages was central.
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| 19. |
- Cambazoglu, Volkan, et al.
(författare)
-
The impact of trace and adversary models on location privacy provided by K-anonymity
- 2012
-
Ingår i: Proc. 1st Workshop on Measurement, Privacy, and Mobility. - New York : ACM Press. - 9781450311632
-
Konferensbidrag (refereegranskat)abstract
- Privacy preserving mechanisms help users of location-based services to balance their location privacy while still getting useful results from the service. The provided location privacy depends on the users' behavior and an adversary's knowledge used to locate the users. The aim of this paper is to investigate how users' mobility patterns and adversaries' knowledge affect the location privacy of users querying a location-based service. We consider three mobility trace models in order to generate user traces that cross each other, are parallel to each other and form a circular shape. Furthermore, we consider four adversary models, which are distinguished according to their level of knowledge of users. We simulate the trace and the adversary models by using Distortion-based Metric and K-anonymity. The results show that the location privacy provided by K-anonymity decreases, as users are located closer to each other in the trace models. The impact of the adversary on location privacy is reduced as more users are cloaked together.
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| 20. |
- Cambazoglu, Volkan, et al.
(författare)
-
Towards adaptive zero-knowledge protocols : A case study with Fiat–Shamir identification protocol
- 2013
-
Ingår i: Proc. 9th Swedish National Computer Networking Workshop. ; , s. 67-70
-
Konferensbidrag (refereegranskat)abstract
- Interactive zero-knowledge protocols are used as identification protocols. The protocols are executed in rounds, with security being increased with every round. This allows for a trade-off between security and performance to adapt the protocol to the requirements of the scenario. We experimentally investigate the Fiat–Shamir identification protocol on machines and networks with different performance characteristics. We find that the delay of the protocol highly depends on network latency and upload bandwidth. Computation time becomes more visible, when the protocol transmits little amount of data via a low latency network. We also experience that the impact of the sizes of the variables on the delay of the protocol is less than the number of rounds', which are interior factors in the protocol.
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| 21. |
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| 22. |
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| 23. |
- Corneo, Lorenzo, et al.
(författare)
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Age of Information-Aware Scheduling for Timely and Scalable Internet of Things Applications
- 2019
-
Ingår i: IEEE Conference On Computer Communications (IEEE INFOCOM 2019). - 9781728105154 ; , s. 2476-2484
-
Konferensbidrag (refereegranskat)abstract
- We consider large scale Internet of Things applications requesting data from physical devices. We study the problem of timely dissemination of sensor data towards applications with freshness requirements by means of a cache. We aim to minimize direct access to the possibly battery powered physical devices, yet improving Age of Information as a data freshness metric. We propose an Age of Information-aware scheduling policy for the physical device to push sensor updates to the caches located in cloud data centers. Such policy groups application requests based on freshness thresholds, thereby reduces the number of requests and threshold misses, and accounts for delay variation. The policy is incrementally introduced as we study its behavior over ideal and more realistic communication links with delay variation. We numerically evaluate the proposed policy against a simple yet widely used periodic schedule. We show that our informed schedule outperforms the periodic schedule even under high delay variations.
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| 24. |
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| 25. |
- Corneo, Lorenzo, et al.
(författare)
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(How Much) Can Edge Computing Change Network Latency?
- 2021
-
Ingår i: 2021 IFIP Networking Conference (IFIP Networking). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665445016 - 9783903176393 ; , s. 1-9
-
Konferensbidrag (refereegranskat)abstract
- Edge computing aims to enable applications with stringent latency requirements, e.g., augmented reality, and tame the overwhelming data streams generated by IoT devices. A core principle of this paradigm is to bring the computation from a distant cloud closer to service consumers and data producers. Consequentially, the issue of edge computing facilities’ placement arises. We present a comprehensive analysis suggesting where to place general-purpose edge computing resources on an Internet-wide scale. We base our conclusions on extensive real-world network measurements. We perform extensive traceroute measurements from RIPE Atlas to datacenters in the US, resulting in a graph of 11K routers. We identify the affiliations of the routers to determine the network providers that can act as edge providers. We devise several edge placement strategies and show that they can improve cloud access latency by up to 30%.
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| 26. |
- Corneo, Lorenzo
(författare)
-
Networked Latency Sensitive Applications - Performance Issues between Cloud and Edge
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing demand for industrial automation has motivated the development of applications with strict latency requirements, namely, latency-sensitive applications. Such latency requirements can be satisfied by offloading computationally intensive tasks to powerful computing devices over a network at the cost of additional communication latency. Two major computing paradigms are considered for this: (i) cloud computing and (ii) edge computing. Cloud computing provides computation at remote datacenters, at the cost of longer communication latency. Edge computing aims at reducing communication latency by bringing computation closer to the users. This doctoral dissertation mainly investigates relevant issues regarding communication latency trade-offs between the aforementioned paradigms in the context of latency-sensitive applications.This work advances the state of the art with three major contributions. First, we design a suite of scheduling algorithms which are performed on an edge device interposed between a co-located sensor network and remote applications running in cloud datacenters. These algorithms guarantee the fulfillment of latency-sensitive applications' requirements while maximizing the battery life of sensing devices. Second, we estimate under what conditions latency-sensitive applications can be executed in cloud environments. From a broader perspective, we quantify round-trip times needed to access cloud datacenters all around the world. From a narrower perspective, we collect latency measurements to cloud datacenters in metropolitan areas where over 70% of the world's population lives. This Internet-wide large-scale measurements campaign allows us to draw statistically relevant conclusions concerning the readiness of the cloud environments to host latency-sensitive applications. Finally, we devise a method to quantify latency improvements that hypothetical edge server deployments could bring to users within a network. This is achieved with a thorough analysis of round-trip times and paths characterization resulting in the design of novel edge server placement algorithms. We show trade-offs between number of edge servers deployed and latency improvements experienced by users.This dissertation contributes to the understanding of the communication latency in terms of temporal and spacial distributions, its sources and implications on latency-sensitive applications.
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| 27. |
- Elsts, Atis, et al.
(författare)
-
IEEE 802.15.4 Channel Diversity in an Outdoor Environment
- 2015. - 12
-
Ingår i: Proceedings of the 6th ACM Workshop on Real World Wireless Sensor Networks (RealWSN '15). - New York, NY, USA : ACM. - 9781450338400 ; , s. 11-14
-
Konferensbidrag (refereegranskat)abstract
- Low-power wireless link quality is known to be frequency- dependent because of multipath fading and other factors. We present a performance study of IEEE 802.15.4 radio links that quantifies and analyzes this frequency-specific performance in a clear-field outdoor environment. Using data from 16 channels on 240 links, we show that effect from channel selection on the average link is up to 4.89 dB, comparable with the effect from 38.7 C change in temperature. These results provide a performance baseline for other environments, as the diversity can be expected to further increase in environments with more obstacles and external interference.
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| 28. |
- Engstrand, Johan, et al.
(författare)
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End-to-End Transmission of Physiological Data from Implanted Devices to a Cloud-Enabled Aggregator Using Fat Intra-Body Communication in a Live Porcine Model
- 2022
-
Ingår i: 2022 16TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP). - : Institute of Electrical and Electronics Engineers (IEEE). - 9788831299046 - 9781665416047
-
Konferensbidrag (refereegranskat)abstract
- This article presents, for the first time, the end-to-end transmission of physiological data from implanted antennas mimicking sensors to a cloud-enabled aggregator device using fat intra-body communication (fat-IBC). The experiment was performed on a live porcine model in full accordance with ethical standards. Measurement data from two different sensors were collected and sent through a fat-IBC network. The fat-IBC network consisted of three nodes, of which two used antennas implanted in the fat tissue of a live porcine model and one used an on-body antenna placed on the skin. The sensor data was forwarded via Bluetooth Low Energy to an Intel Health Application Platform device, which in turn forwarded the encrypted data to a web server. The experimental results demonstrate that the fat channel can be used in an end-to-end communication scheme, which could involve relaying of sensor data from an implanted device to an external web server.
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| 29. |
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| 30. |
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| 31. |
- Feeney, Laura Marie, et al.
(författare)
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How do the dynamics of battery discharge affect sensor lifetime?
- 2014. - 6
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Ingår i: 2014 11th Annual Conference on Wireless On-demand Network Systems and Services (WONS). - Piscataway, NJ : IEEE. - 9781479949373 ; , s. 49-56
-
Konferensbidrag (refereegranskat)abstract
- Evaluation of energy consumption and device lifetime in battery-powered wireless sensor networks (WSN) is almost exclusively based on measurements or simulations of the total charge (i.e. total mA-h) consumed by the device. In reality, batteries are complex electro-chemical systems and their discharge behavior depends heavily on the timing and intensity of the applied load. However, there is very little empirical data or reliable models available for the kinds of batteries and loads that are typically used in WSNs. The effect of battery dynamics on sensor lifetime is therefore not well understood. We characterize CR2032 Li coin cells using carefully controlled synthetic loads and a wide range of WSN-typical load parameters. Our results are the first to quantify in-depth the discharge behavior of primary batteries in the WSN context. We report that in some common cases, observed lifetimes can differ from predicted ones by almost a factor of three. Furthermore, loads with similar average currents -- which would be expected to have similar lifetimes -- can vary significantly in the amount of capacity they can utilize, with short duration loads generally faring better. The results show that energy evaluation based on ``total mA-h consumed'' has significant limitations. This has important implications for the design and evaluation of WSN applications, as well as for important practical problems in network dimensioning and lifetime estimation.
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| 32. |
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| 33. |
- Feeney, Laura Marie, et al.
(författare)
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Leveraging a power save protocol to improve performance in ad hoc networks
- 2007
-
Ingår i: ACM SIGMOBILE Mobile Computing and Communications Review. - : Association for Computing Machinery (ACM). - 1559-1662 .- 1931-1222. ; 11:2, s. 51-52
-
Tidskriftsartikel (refereegranskat)abstract
- Power save protocols reduce energy consumption in ad hoc and sensor networks by allowing nodes to put their network interface into a low power consumption sleep state. The power save protocol must allow neighboring nodes to establish intervals during which they are mutually awake and available to exchange traffic. Many such protocols are based on a coordinated election of a covering set that is responsible for buffering traffic for sleeping nodes, but uncoordinated (i.e. asynchronous) protocols have also proven an attractive option.
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| 34. |
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| 35. |
- Feeney, Laura Marie, et al.
(författare)
-
Modeling Capacity in Ad Hoc Networks : Extended Poster Abstract
- 2006
-
Konferensbidrag (refereegranskat)abstract
- We describe a simple network model for efficiently simulating the CBR flow capacity of a multi-hop wireless network. The model is particularly intended for studying the behavior of asynchronous protocols, particularly power save protocols, where it is useful to examine many scheduling variations as well as many topologies and network configurations.We describe our experience using the model in some experiments in which we examine how the network performance is sensitive to the timing to scheduling variations induced by the operation of a simple power save protocol. We note that the model also seems seems suitable for combinatoric and probabilistic analysis, which is on-going work.
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| 36. |
- Feeney, Laura Marie, et al.
(författare)
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Poster abstract: The feasibility of leveraging a power save protocol to improve performance in ad hoc networks
- 2006
-
Ingår i: The Twelfth Annual International Conference on Mobile Computing and Networking (Mobicom2006).
-
Konferensbidrag (refereegranskat)abstract
- We discuss how the operation of an asynchronous power save protocol affects the scheduling of transmissions in an ad hoc network. We present simulation results that show that network capacity is sensitive to the random distribution of wakeup schedules. Finally, we discuss the implications of this result with respect to improving performance and speculate about potential new cross-layer architectures.
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| 37. |
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| 38. |
- Feeney, Laura Marie, et al.
(författare)
-
The impact of wakeup schedule distribution in synchronous power save protocols on the performance of multihop wireless networks
- 2007. - 3
-
Konferensbidrag (refereegranskat)abstract
- By definition, the operation of an asynchronous power save protocol permits an arbitrary distribution of nodes' wakeup schedules. This wakeup schedule distribution creates an uncoordinated pattern of times at which nodes will attempt to transmit. Intuitively, we would expect that some patterns will be more (or less) favorable than others for a given traffic pattern. We investigate the impact of this wakeup pattern on network capacity and present simulation data showing that the capacity associated with the best wakeup patterns is significantly larger than that of the worst. This result not only gives insight to the behavior of such protocols, but also acts as a feasibility study showing the potential benefit of mechanisms by which nodes adapt their wakeup schedules to obtain improved performance.
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| 39. |
- Feeney, Laura Marie, et al.
(författare)
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Timing is everything: the impact of wakeup schedule distribution on asynchronous power save protocols
- 2005. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Asynchronous power save protocols have been proposed for use in ad hoc networks. In many protocols, nodes independently follow a common periodic wakeup schedule, each with some unknown offset relative to its neighbors. The schedule is defined to ensure deterministic intervals of overlap between nodes, regardless of the distribution of the nodes' wakeup schedules. This paper studies the sensitivity of a simple asynchronous power save protocol to the actual distribution of the nodes' wakeup schedules. In practical terms: For given topology and traffic load, are there particularly "good" or "bad" distributions? We define a simplified model of network operation that allows us to study this question in simulation. The results show that the performance variation has a narrow probability distribution, but with long tails. The variation is shown to derive largely from timing dependencies rather than overall capacity of the system. The result suggests the feasibility of manipulating the wakeup schedule distribution to improve performance. Although the best wakeup distributions often mitigate the performance penalty imposed by the power save protocol, their relative rarity implies that randomized strategies will not be sufficient to obtain maximum advantage.
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| 40. |
- Feeney, Laura Marie, et al.
(författare)
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Towards realistic lifetime estimation in battery-powered IoT devices
- 2017
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Ingår i: Proceedings of the 15th ACM Conference on Embedded Network Sensor Systems Article No. 67. - New York, NY, USA : Association for Computing Machinery (ACM).
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Konferensbidrag (refereegranskat)abstract
- We describe a testbed for studying battery discharge behavior andthe lifetime of wireless devices under controlled temperature conditions and present preliminary measurement results.
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| 41. |
- Guerreiro, João, et al.
(författare)
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Privacy-aware probabilistic sampling for data collection in wireless sensor networks
- 2011
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Ingår i: Proc. 7th International Wireless Communications and Mobile Computing Conference. - Piscataway, NJ : IEEE conference proceedings. - 9781424495399 ; , s. 314-319
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Konferensbidrag (refereegranskat)abstract
- The rising popularity of web services and their applications to sensor networks enables real-time data collection and queries by users. Unlike traditional periodic data collection, the traffic patterns generated from real-time data collection may expose the interests of users or the locations of unusual events to the attackers. To provide privacy in data collection, we propose a novel probabilistic sampling mechanism that can hide user queries and unusual events in the network, while supporting both routine and on-demand data reporting. Our goal is to prevent attackers from locating the unusual events and identifying interests of users by eavesdropping and analyzing the network traffic. In our probabilistic sampling scheme, the data are carefully reported at random times in order to mask the unusual events and user queries. In the meantime, our scheme can provide users with high data accuracy at minimized communication overheads. Extensive simulations have been conducted to evaluate the security strength, data accuracy and communication overheads of the proposed scheme.
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| 42. |
- Hartung, Robert, et al.
(författare)
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A Platform for Experiments with Energy Storage Devices for Low-power Wireless Networks
- 2018
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Ingår i: Proc. 12th International Workshop on Wireless Network Testbeds, Experimental Evaluation & Characterization. - New York : ACM Press. ; , s. 68-76
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Konferensbidrag (refereegranskat)abstract
- We present a hardware platform for performing experimental studies of energy storage devices for low power wireless networks. It is based on a low-cost custom card that can apply fine-grain synthetic loads ? both charge and discharge ? to a set of batteries or capacitors and measure their response in detail. Loads can be defined from a "live" trace of a running wireless device, from a recorded trace, or programmatically via a script. This approach makes it practical to run well controlled, large scale, long running experiments and to obtain high precision and accuracy. We describe two proof-of-concept experiments using rechargeable Li coin cells and capacitors to demonstrate the capabilities of our platform.
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| 43. |
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| 44. |
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| 45. |
- Hermans, Frederik, et al.
(författare)
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FOCUS : Robust Visual Codes for Everyone
- 2016. - 28
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Ingår i: Proceedings of the 14th Annual International Conference on Mobile Systems, Applications, and Services (MobiSys 2016). - New York, NY, USA : ACM. - 9781450342698 ; , s. 319-332
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Konferensbidrag (refereegranskat)abstract
- Visual codes are used to embed digital data in physical objects, or they are shown in video sequences to transfer data over screen/camera links. Existing codes either carry limited data to make them robust against a range of channel conditions (e.g., low camera quality or long distances), or they support a high data capacity but only work over a narrow range of channel conditions. We present Focus, a new code design that does not require this explicit trade-off between code capacity and the reader’s channel quality. Instead,Focus builds on concepts from OFDM to encode data at different levels of spatial detail. This enables each reader to decode as much data from a code as its channel quality allows. We build a prototype of Focus devices and evaluate it experimentally. Our results show that Focus gracefully adapts to the reader’s channel, and that it provides a significant performance improvement over recently proposed designs, including Strata and PixNet.
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| 46. |
- Hermans, Frederik, et al.
(författare)
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Poster Abstract:Supporting Heterogeneous LCD/Camera Links
- 2014. - 10
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Ingår i: Proc. 13th International Symposium on Information Processing in Sensor Networks. - Piscataway, NJ : IEEE Press. - 9781479931460 ; , s. 289-290
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Konferensbidrag (refereegranskat)abstract
- Visible light communication over LCD/camera links offers a potential complement to traditional RF communication technology such as WiFi or cellular networks. However, the heterogeneity in receivers (e.g., mobile phone cameras) presents a challenge because the receivers differ widely in resolution, distance to the transmitter (LCD), and other factors, and therefore they differ in channel quality. We are researching a communication scheme in which each receiver can decode as much data from an LCD's transmission as the receiver's channel supports. The core idea is to encode the payload into an image's frequency representation rather than directly into pixels. We have successfully transmitted data using a prototype implementation and are currently investigating appropriate channel models.
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| 47. |
- Hilmia, Abdalah, et al.
(författare)
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Poster Abstract:BouKey : Location-Based Key Sharing Using Visible LightCommunication
- 2016
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Konferensbidrag (refereegranskat)abstract
- Visible Light Communication (VLC) is an emerging communication channel serving as a complement to traditional wireless communication. Visible light has many advantages over other communication channels like its inability to penetrate opaque objects. Securely sharing secret keys is a known problem in computer security. Sharing security keys using Radio Frequency (RF) communication is prone to sniffing attacks. In this paper, we introduce a system called BouKey which uses visible light to share keys. This makes BouKey immune to through the wall sniffing attacks. BouKey divides the key and shares it using multiple transmission bulbs allowing the key to be received in a specific area only. Our initial results show that the characteristics and height of the receiver, as well as the transmission angle play a key role in determining the shape and size of this area.
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| 48. |
- Hossmann, Theus, et al.
(författare)
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Twitter in Disaster Mode : Security Architecture
- 2011
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Ingår i: Conference on emerging Networking EXperiments and Technologies (CoNEXT). - Tokyo : ACM Press. - 9781450310444
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Konferensbidrag (refereegranskat)abstract
- Recent natural disasters (earthquakes, floods, etc.) have shown that people heavily use platforms like Twitter to communicate and organize in emergencies. However, the fixed infrastructure supporting such communications may be temporarily wiped out. In such situations, the phones’ capabilities of infrastructure-less communication can fill in: By propagating data opportunistically (from phone to phone), tweets can still be spread, yet at the cost of delays. In this paper, we present Twimight and its network security extensions. Twimight is an open source Twitter client for Android phones featured with a “disaster mode”, which users enable upon losing connectivity. In the disaster mode, tweets are not sent to the Twitter server but stored on the phone, carried around as people move, and forwarded via Bluetooth when in proximity with other phones. However, switching from an online centralized application to a dis- tributed and delay-tolerant service relying on opportunistic communication requires rethinking the security architecture. We propose security extensions to offer comparable security in the disaster mode as in the normal mode to protect Twimight from basic attacks. We also propose a simple, yet efficient, anti-spam scheme to avoid users from being flooded with spam. Finally, we present a preliminary empirical performance evaluation of Twimight.
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| 49. |
- Hossmann, Theus, et al.
(författare)
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Twitter in Disaster Mode : Opportunistic Communication and Distribution of Sensor Data in Emergencies
- 2011
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Ingår i: ExtremeCom2011. - : ACM Press. - 9781450310796
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Konferensbidrag (refereegranskat)abstract
- Recent events (earthquakes, floods, etc.) have shown that users heavily rely on online social networks (OSN) to communicate and organize during disasters and in their aftermath. In this paper, we discuss what features could be added to OSN apps for smart phones – for the example of Twitter – to make them even more useful for disaster situations. In particular, we consider cases where the fixed communication infrastructure is partially or totally wiped out and propose to equip regular Twitter apps with a disaster mode. The disaster mode relies on opportunistic communication and epidemic spreading of Tweets from phone to phone. Such “disaster-ready” applications would allow to resume (although limited) communication instantaneously and help distressed people to self-organize un- til regular communication networks are functioning again, or, temporary emergency communication infrastructure is installed. We argue why we believe that Twitter with its simplicity and versatile features (e.g., retweet and hashtag) is a good platform to support a variety of different situations and present Twimight, our disaster ready Twitter application. In addition, we propose Twimight as a platform for disseminating sensor data providing information such as locations of drinkable water sources. Eventually, we propose to rely on interest matching to scale Twitter hashtag-based searches in an opportunistic environment. The combination of these features make our opportunistic Twitter the ideal emergency kit in situations of disasters. We discuss and define the main implementation and research challenges (both technical and non- technical).
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| 50. |
- Hylamia, Abdullah, et al.
(författare)
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Demo : Towards battery-free radio tomographic imaging
- 2018
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Ingår i: WiSec 2018 - Proceedings of the 11th ACM Conference on Security and Privacy in Wireless and Mobile Networks. - New York, NY, USA : ACM. - 9781450357319 ; , s. 293-295, s. 293-295
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Konferensbidrag (refereegranskat)abstract
- Radio Tomographic Imaging (RTI) enables novel radio frequency (RF) sensing applications such as intrusion detection systems by observing variations in radio links caused by human actions. RTI applications are, however, severely limited by the requirement to retrofit existing infrastructure with energy-expensive sensors. In this demonstration, we present our ongoing efforts to develop the first battery-free RTI system that operates on minuscule amounts of energy harvested from the ambient environment. Our system eliminates the energy-expensive components employed on state-of-the-art RTI systems achieving two orders of magnitude lower power consumption. Battery-free operation enables a sustainable deployment, as RTI sensors could be deployed for long periods of time with little maintenance effort. Our demonstration showcases an intrusion detection scenario enabled by our system.
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