IMDEA Networks Institute Digital Repository
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On the Accuracy of Passive Multipath-Aided Underwater Range Estimation
Get PDFWe consider a range estimation algorithm based on the time-of-arrival differences between multipath replicas of a signal transmitted by an anchor node of known location to a silent node that needs to localize itself. We consider the geometry of the problem in the simplified case of a constant sound speed profile (SSP), and argue that the more realistic case of a non- constant SSP can be still tackled as if the SSP were constant, provided that an “effective” sound speed value is computed based on the geometry of the signal propagation.
We finally evaluate the accuracy of the latter approach in the presence of errors affecting different quantities required for the range estimation process, including the TDoA values and the bottom depth. Our results show that our approach offers improved accuracy with respect to a baseline LSE estimator.TRUEpu
Analysis, Design and Experimental Evaluation of Connectivity Management in Heterogeneous Wireless Environments
Get PDFThe future of network communications is mobile as user's demand for ubiquitous connectivity increases. Wireless has become the primary access technology, leading to an explosion in traffic demand. This challenges network providers to manage and configure new requirements without incrementing costs in the same amount. In addition to the growth in the use of mobile devices, there is a need to operate simultaneously different access technologies. As well, the great diversity of applications and the capabilities of mobile terminals make possible for us to live in a hyper-connected world and offer new scenarios. This heterogeneity poses great challenges that need to be addressed to offer better performance and seamless experience to the final user. We need to orchestrate solutions to increase flexibility and empower interoperability.
Connectivity management is handled from different angles. In the network stack, mobility can be conveniently handled by IP mobility protocols, since IP is the common layer between the different access technologies and the application diversity. From the end-user perspective, the connection manager in mobile devices is in charge of handling connectivity issues, but it is an unstandardized entity so its performance is heavily implementation-dependent.
In this thesis, we explore connectivity management and handover by taking into account the previous challenges. We study and evaluate IP mobility protocols and their combination, including an experimental evaluation of handover latency performance, as they are part of our proposed solutions. We consider heterogeneous scenarios, with several access technologies where mobile devices have also several network interfaces. To increase our understanding of the impact of the mobile terminal behavior in the mobility management, we evaluate how connectivity is handled in the three most widely-used mobile operating systems, as well as its influence in a handover. We include an experimental evaluation of performance with 3G and IEEE 802.11 as the main technologies. Third, once the mobility protocols and the end terminal have been evaluated, we propose and confirm the suitability of more efficient mobility management, based on the analysis of real traces from a cellular network operator.
Moreover, we propose and evaluate three diverse solutions for providing mobility support in different heterogeneous scenarios: vehicular networks, wireless optical broadband access networks and software-defined networks. We perform an experimental evaluation of a vehicular route optimization for network mobility, reporting on the challenges and lessons learned in the development process from the laboratory controlled environment to the working prototype on the road for such a complicated networking environment.
We propose an architecture for supporting mobility and enhance handover in a passive optical network deployment, by leveraging the architecture of a passive optical network, collocated with mobility management entities to support Proxy Mobile IPv6 and IEEE 802.21 mechanisms for a more efficient handover. In addition, we design and deploy a mechanism for mobility management based on software-defined networking, leveraging SDN mechanisms for adding flexibility and including an experimental evaluation in an initial prototype.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
Device-to-device communications with social awareness [Guest Editorial]
No full textHigh data rate applications have recently become more and more popular in cellular networks (e.g. video calls, interactive gaming, and mobile social networking). To efficiently facilitate more high data rate services among nearby users and devices, device-to-device (D2D) communication has been proposed, and has attracted significant attention in both academia and industry. Since mobile devices are typically carried by people, it is critical to study the impact of social networks on D2D communications. D2D communication with social awareness is an interesting but largely unexploited area that requires intensive research efforts.pu
Empirical Analysis of Mobile Systems: Illuminating the Dark Side
No full texthttp://niclabs.cl/ssn/2016/As a society we have come to rely upon our mobile phones for myriad daily tasks. It is striking how little insight we, as mobile users and researchers, have into the operation and performance of our devices and network, into how (or whether) they protect the information we entrust to them, and with whom they share it. The research community
(including the speaker) have energetically used a variety of
approaches to gain empirical understanding of the mobile
device/network ecosystem; however, these techniques have had to make tradeoffs that affect either the scale, scope or granularity of measurements.
This talk describes how we leverage ideas from this prior work to design and develop two tools such as Netalyzr (active analysis of mobile systems) and Lumen (passive analysis of mobile traffic). Both tools are freely available on Google Play. The talk will demonstrate their utility to researchers and average users alike by providing three case studies on mobile traffic characterization, identification of privacy and security risks caused by mobile apps, and performance measurements.FALSEpu
Procedimiento de establecimiento y borrado de caminos y de reenvío de tramas para conexiones de transporte y puente de red [METHOD FOR ESTABLISHING AND CLEARING PATHS AND FORWARDING FRAMES FOR TRANSPORT CONNECTIONS, AND NETWORK BRIDGE]
No full textThe present invention describes mechanisms that, in a network of transparent bridges, both seek and establish a specific path for each new TCP connection established between two terminals. The new path is established by the border bridge connected to the source terminal when receiving a TCP segment type SYN to establish a connection, encapsulating the said segment within a special path request packet that is resent by all network links and is responded to in unicast mode by the border bridge of the destination terminal through an acceptance package in which the SYN + ACK response segment of terminal S is encapsulated, the said packet confirming both the TCP connection as well as the chosen path between A and S. The path is automatically cleared after a certain period of time without the use of the connection or through exchanges of FIN segments in both directions of the connection.
Application number (OEPM): P201301133 (10.12.2013) | Publication number (1) (OEPM): ES2540595 A1 (10.07.2015) | Publication number (2) (OEPM): ES2540595 B2 (02.02.2016) | Patent granted (OEPM): 26.01.2016IMDEA Networkspu
Large Profits or Fast Gains: A Dilemma in Maximizing Throughput with Applications to Network Processors
Get PDFWe consider the fundamental problem of managing a bounded size queue buffer where traffic consists of packets of varying size, each packet requires several rounds of processing before it can be transmitted out, and the goal is to maximize the throughput, i.e., total size of successfully transmitted packets. Our work addresses the tension between two conflicting algorithmic approaches: favoring packets with fewer processing requirements as opposed to packets of larger size. We present a novel model for studying such systems and study the performance of online algorithms that aim to maximize throughput.pu
Multi-round Master-Worker Computing: a Repeated Game Approach
Get PDFWe consider a computing system where a master
processor assigns tasks for execution to worker processors
through the Internet. We model the workers’ decision of whether to comply (compute the task) or not (return a bogus result to save the computation cost) as a mixed extension of a strategic game among workers. That is, we assume that workers are rational in a game-theoretic sense, and that they randomize their strategic choice. Workers are assigned multiple tasks in subsequent rounds.We model the system as an infinitely repeated game of the mixed extension of the strategic game. In each round, the master decides stochastically whether to accept the answer of the majority or verify the answers received, at some cost. Incentives and/or penalties are applied to workers accordingly.
Under the above framework, we study the conditions in which
the master can reliably obtain tasks results, exploiting that the repeated game model captures the effect of long-term interaction. That is, workers take into account that their behavior in one computation will have an effect on the behavior of other workers in the future. Indeed, should a worker be found to deviate from some agreed strategic choice, the remaining workers would change their own strategy to penalize the deviator. Hence, being
rational, workers do not deviate.
We identify analytically the parameter conditions to induce
a desired worker behavior, and we evaluate experimentally the mechanisms derived from such conditions. We also compare the performance of our mechanisms with a previously known multiround mechanism based on reinforcement learning.TRUEpu
Cloud Federation and Geo-Distribution
No full texthttp://eu.wiley.com/WileyCDA/WileyTitle/productCd-1118821971,subjectCd-CS40.htmlThe cloud computing paradigm has significantly evolved beyond the simple early application scenarios such as third-party hosting of web servers. This evolution was triggered by the desire of cloud providers to serve diverse needs of customers around the globe. In particular, the term “cloud” was originally put on par with “datacenter”, yet data– and compute-clouds have evolved to complex multi-datacenter infrastructures (see Figure 1). As many cloud-based solutions start to serve customers around the globe or through new media, data may be spread across multiple sites and even cloud offerings for various reasons including low latency retrieval based on geographical proximity, legal constraints, or cost considerations. Regardless of the original motivation, federation across datacenters including especially so-called “geo-distribution” leads to many challenges around (1) the location and access of data stored and shared between datacenters, (2) the computation on such distributed data, and, in general, around (3) the communication of data across datacenters in the context of (1) and (2). This article first motivates federation and then describes the challenges in these three areas and outlines solutions to them.TRUEpu
Resource-on-Demand Schemes in 802.11 WLANs with Non-Zero Start-Up Times
Get PDFIncreasing the density of access points is one of the most effective mechanisms to cope with the growing traffic demand in wireless networks. To prevent energy wastage at low loads, a resource-on-demand (RoD) scheme is required to opportunistically (de)activate access points as network traffic varies. While previous publications have analytically modelled these schemes in the past, they have assumed that resources are immediately available when activated, an assumption that leads to inaccurate results and might result in inappropriate configurations of the RoD scheme. In this paper, we analyse a general RoD scenario with N access points and non-zero start-up times. We first present an exact analytical model that accurately predicts performance but has a high computational complexity, and then derive a simplified analysis that sacrifices some accuracy in exchange for a much lower computational cost. To illustrate the practicality of this model, we present the design of a simple configuration algorithm for RoD. Simulation results confirm the validity of the analyses, and the effectiveness of the configuration algorithm.pu
Analysis and Enhancement of CSMA/CA with Deferral in Power-Line Communications
Get PDFPower-line communications are employed in home networking to provide easy and high-throughput connectivity. The IEEE 1901, the MAC protocol for power-line networks, employs a CSMA/CA protocol similar to that of 802.11, but is substantially more complex, which probably explains why little is known about its performance. One of the key differences between the two protocols is that whereas 802.11 only reacts upon collisions, 1901 also reacts upon several consecutive transmissions and thus can potentially achieve better performance by avoiding unnecessary collisions. In this paper, we propose a model for the 1901 MAC. Our analysis reveals that the default configuration of 1901 does not fully exploit its potential and that its performance degrades with the number of stations. Based on analytical reasoning, we derive a configuration for the parameters of 1901 that drastically improves throughput and achieves optimal performance without requiring the knowledge of the number of stations in the network. In contrast, 802.11 requires knowing the number of contending stations to provide a similar performance, which is unfeasible for realistic traffic patterns. We confirm our results and enhancement with testbed measurements, by implementing the 1901 MAC protocol on WiFi hardware.pu