IMDEA Networks Institute Digital Repository
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1915 research outputs found
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From PLATO to Platoons
Get PDFGrouping vehicles into platoons promises to improve road capacity, driver safety, and fuel consumption. However, when platoons have to allow for cross traffic maneuvers, the ability to control single large platoons is not sufficient, and chaining smaller platoons becomes necessary. To this aim we define PLATO, an edge-assisted multi-platoon control architecture and, by delving into the dichotomy of unity and plurality of platooning, we analyze costs and benefits of multi-platooning. We investigate on the feasibility and formulate the utility of multi-platoons by analyzing the underlying edge computing and broadband cellular connectivity requirements. Using a detailed simulator, we show that, in realistic environments, multi-platoons can be effectively controlled with PLATO, as long as the latency between individual platoon managers and the multi-platoon manager is kept below a few tens of milliseconds. Surprisingly, the latency between vehicles and managers is one order of magnitude less critical.TRUEpu
Resolving the Feedback Bottleneck of Multi-Antenna Coded Caching
Get PDFMulti-antenna cache-aided wireless networks were thought to suffer from a severe feedback bottleneck, since achieving the maximal Degrees-of-Freedom (DoF) performance required feedback from all served users for the known transmission schemes. These feedback costs match the caching gains and thus scale with the number of users. In the context of the L-antenna Multiple-Input Single Output broadcast channel with K receivers, each having normalized cache size γ, we pair a fundamentally novel algorithm together with a new information-theoretic converse and identify the optimal tradeoff between feedback costs and DoF performance, by showing that having channel state information from only C < L served users implies an optimal one-shot linear DoF of C+Kγ. As a side consequence of this, we also now understand that the well known DoF performance L + Kγ is in fact exactly optimal. In practice, the above means that we are able to disentangle caching gains from feedback costs, thus achieving unbounded caching gains at the mere feedback cost of the multiplexing gain. This further solidifies the role of caching in boosting multi-antenna systems; caching now can provide unbounded DoF gains over multi-antenna downlink systems, at no additional feedback costs. The above results are extended to also include the corresponding multiple transmitter scenario with caches at both ends.TRUEpu
Outlier Detection for Functional Data with R Package fdaoutlier
Get PDFOutlier detection is one of the standard exploratory analysis tasks in functional data
analysis. We present the R package fdaoutlier which contains implementations of some
of the latest techniques for detecting functional outliers. The package makes it easy to
detect different types of outliers (magnitude, shape, and amplitude) in functional data,
and some of the implemented methods can be applied to both univariate and multivariate
functional data. We illustrate the main functionality of the R package with common
functional datasets in the literature
LED-to-LED based VLC Systems: developments and open problems
Get PDFVisible light communication (VLC) is an emerging short-range wireless communication technology using the unlicensed light spectrum. Light Emitting Diode (LED) is used as VLC transmitter, while photodiodes or image sensors are used as receiver, depending on the applications and hardware constraints. However, LEDs can be used not only as a transmitter, but also as a receiver in applications where cost is of primary concern. LED as a receiver is sensitive to a narrow band of wavelengths, it is robust to sunlight interference and widely available as compared to other light detectors. This paper surveys the potential and limitations of LED-to-LED communication. It also contributes to identifying the challenges and potential research directions in this rising area of interest.TRUEpu
Traffic-Driven Sounding Reference Signal Resource Allocation in (Beyond) 5G Networks
Get PDFBeyond 5G mobile networks have to support a wide range of performance requirements and unprecedented levels of flexibility. To this end, massive MIMO is a critical technology to improve spectral efficiency and thus scale up network capacity, by increasing the number of antenna elements. This also increases the overhead of Channel State Information (CSI) estimation and obtaining accurate CSI is a fundamental problem in massive MIMO systems. In this paper, we focus on scheduling uplink Sounding Reference Signals (SRSs) that carry pilot symbols for CSI estimation. Under the large number of users and high load that are expected to characterize beyond 5G systems, the limited amount of resources available for SRSs makes the legacy 3GPP periodic allocation scheme largely inefficient. We design TRADER, an SRS resource allocation framework that minimizes the age of channel estimates by taking advantage of machine learning-based short-term traffic forecasts at the base station level. By anticipating traffic bursts, TRADER schedules SRS resources so as to obtain CSI for each user right before the corresponding traffic arrives. Experiments with extensive real-world mobile network traces show that our solution is efficient and robust in high load scenarios: with respect to a round robin schedule of aperiodic SRS, TRADER provides more often CSI within the coherence time (up to 5× for given scenarios), leading to channel gains of up to 2 dB.TRUEpu
Robust adjusted discriminant analysis based on shrinkage with application to geochemical and environmental fields
Get PDFA novel discriminant analysis (DA) method is proposed, based on the robust reweighted shrinkage estimators and a robust Mahalanobis distance with an adjusted quantile as threshold. A simulation study is done to evaluate the performance of the proposed approach in comparison with the classical DA and the other robust alternatives from the literature. The approach is also illustrated using real dataset examples: a geochemical and environmental dataset known as the Kola Project and a second data containing the spectra of different cultivars of a fruit. The results show the appropriateness of the method while being computationally efficient at the same time. Additional simulations are included to show the additional benefits in outlier detection.TRUEpu
Chirotonía: Scalable and Secure e-Voting Framework based on Blockchains and Linkable Ring Signatures
Get PDFChirotonía is a comprehensive and scalable framework to build secure-by-design e-voting systems. Transparency, determinism, and untamperability of votes are granted by dedicated smart contracts on a blockchain, while voter authenticity and anonymity are achieved through (provable secure) linkable ring signatures. We carefully designed and implemented each required component, and we deployed it for elections of university officers. We think that presenting our design and all the choices we made to make available such a system to a wide non-technical base of users/voters is interesting for the scientific community due to the impact that such a system can have for e-voting.TRUEpu
Characterizing RNTI Allocation and Management in Mobile Networks
Get PDFThe characterization of user behavior is key to perform traffic analysis, modeling and optimization of network components and protocols. This is especially true for 5G and beyond networks that will heavily rely on machine learning for network optimization.
In Base Station (BS) traffic traces, users are uniquely identified by a Radio Network Temporary Identifier (RNTI) assigned to them.RNTIs are not bound to a user but are reused upon expiration of an inactivity timer, whose duration is operator dependent. This implies that, over time, multiple users can be mapped to the same RNTI ID in diverse ways. Hence, when using real-world radio access measurement traces for traffic analysis, distinguishing individual users within the RNTI space is a non-trivial task. In this paper, we provide the first in-depth study of the RNTI allocation process and shed light not only on the setting of the inactivity timer, but also on the relationship of the RNTI allocation scheme and the user characteristics. For this, we collect a large dataset of mobile traffic from multiple BSs of several mobile network operators. The analysis of the decoded control messages of the BS unveils that the RNTI allocation process changes over time depending on the BSs observed load and time of day. We also observe that the RNTI expiration threshold is on the order of minutes, and demonstrate how using thresholds around 10~s that are reported in the vast majority of the literature can bias subsequent analyses. Overall, our work provides an important step towards dependable mobile network trace analysis, and lays more solid foundations to research relying on traffic traces for data-driven analysis and simulation.Juan de la Cierva grant from the Spanish Ministry of Science and Innovation (IJC2019-039885-I)Atracción de Talento Investigador (2019-T1/TIC-16037 NetSense)TAPIR-CM program (S2018/TCS-4496)TRUEinpres
Multi-cell Deployment for Experimental Research in Visible Light Communication-based Internet of Things
Get PDFVisible Light Communication (VLC) provides both illumination and communication thanks to the usage of Light-Emitting Diodes (LEDs). In order to support the research in the field, the study of possible infrastructures to enable constant illumination and reliable communication becomes a necessity to pair up the evolution of both fields. Leveraging the fact that LEDs are getting more densely deployed to provide uniform illumination, in this work we present the design of a multi-cell deployment that uses several LEDs as VLC Access Points (APs) for Internet of Things (IoT) applications. We characterize the light emitted by the selected LED and show how this deployment complies with the illumination standards, as well as providing a reliable communication network. We present our design choices for controlling and communicating to the network of VLC APs, and show the required functionalities that must be fulfilled such as power monitoring, power management, and communication management.TRUEpu
A Performance Comparison of Virtualization Techniques to Deploy a 5G Monitoring Platform
Get PDFThe constant search for solutions to improve performance and resource efficiency in Cloud platforms has led to the introduction of new virtualization technologies and deployment paradigms. From container-based virtualization to micro virtual machines, new virtualization solutions claim to offer a performance close to bare-metal, with quick deployment and startup times. Furthermore, serverless computing has recently emerged as an alternative deployment model for Cloud workloads, providing scalability and cost reduction without requiring any additional configuration overhead from developers. In this work, we present a performance comparison of well-known virtualization technologies, e.g., virtual machines or containers, together with new, serverless-oriented virtualization solutions, all of them applied to deploy a real monitoring architecture for multi-site 5G platforms. The analysis shows that serverless technologies do not achieve the same performance than well-known virtualization technologies, evaluating as a result the suitability of these new virtualization technologies for production environments, extracting useful conclusions to lay the ground for future work related to this novel paradigm.TRUEpu