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Underwater Direction of Arrival Estimation using Wideband Arrays of Opportunity
Get PDFWe present a scheme to estimate the direction of arrival of acoustic signals reflected by underwater targets using wideband hydrophone arrays of opportunity. Such arrays may be obtained by arranging together multiple smaller sub-arrays that were originally designed to work independently. The array of opportunity that results may be subject to practical mount- ing limitations, hence the typical constraint that closest array elements should not be spaced more than one half-wavelength may not be upheld. In these conditions, the array is affected by spatial ambiguity.
Our proposed scheme solves this issue by fusing direction- of-arrival information with side information on the estimated target location (obtained via multilateration). This makes it possible to eliminate most of the ambiguity, and yields accurate direction-of-arrival estimates. Our simulation results show that our scheme achieves satisfactory direction of arrival estimation and localization results. Moreover, even by relying on arrays of opportunity, we can outperform classical direction-of-arrival algorithms applied to larger arrays with half-wavelength spacing design.TRUEpu
Research in Visible Light Communication Systems with OpenVLC1.3
Get PDFIn this paper, we present the design and implementation of our latest OpenVLC1.3 platform to perform research in Visible Light Communication Systems. We retain the advantages of the previous versions such as TCP/IP layers support, software programmability and low-cost front-end. We re-design the transceiver to support higher modulation rates and sensitivity. This allows us to reach a throughput of 400 kb/s (a factor of 4 with respect to the previous version) and increase the distance by a factor of 3.5. We further improve the software robustness of the system and reduce the form factor at similar hardware cost.TRUEpu
Highlights of SIGCOMM 2018
No full textThe Association for Computing Machinery’s Special Interest Group on Data Communication (ACM SIGCOMM) is a leading venue for research in architectures, protocols, technologies, and applications of computer networking and data communication. The ACM SIGCOMM annual conference spans all aspects of networks and networked systems, including packet processing, hardware and software, virtualization, routing, mobility, sensors, energy consumption, novel applications of artificial intelligence to networking, and usability of underlying communication technologies. Its participants include distinguished academics, brilliant students, and representatives of major multinational companies. Centered on its highly selective main conference, SIGCOMM published many landmark works in networking and communications. The conference also involves workshops, tutorials, presentation of demos, posters, industrial demos, student research competition, topic previews, and mentoring sessions. SIGCOMM 2018 met in Budapest on August 20-25. The first visit of ACM SIGCOMM to Eastern Europe became an unqualified success. Encompassing a variety of traditional and newly introduced events, the six-day conference program attracted around 750 attendees overall, with about 700 people registered for the 3-day main conference. This talk reviews the technical main-conference program, highlighting interesting ideas in its papers and identifying emerging research trends.FALSEpu
Robust and Reliable Millimeter Wave Wireless Networks
Get PDFMillimeter wave (mmWave) technology is one of the main pillars of the next generation Wireless Local Area Network (WLAN) and 5G mobile networks. The main reason lies in the quantum leap of capacity it provides with respect to wireless networks operating in the sub-6-GHz band. Nevertheless, efficient and reliable communication in the mmWave band demands novel techniques to tackle all the barriers associated with wireless propagation in this band. For example, material penetration and diffraction in the mmWave band are much weaker than the ones experienced in the sub-6-GHz band. As a result, wireless propagation in the mmWave band has a quasi-optical behavior in which the Line-of-sight component contributes to the majority of the received signal power. For these reasons, mmWave devices rely on either horn antennas or electronically steerable phased antenna arrays to establish directional beams and focus the energy towards a specific direction in space. Although directional communication compensates for the high power attenuation, it creates a new problem that is uncharted for wireless networks operating in the sub-6-GHz band. It makes mmWave wireless links susceptible to blockage, human mobility, and device rotation. Solving these issues requires developing algorithms to quickly find alternative paths for communication upon link interruption.
The IEEE 802.11ad protocol is the first WLAN standard that supports wireless networking in the unlicensed 60 GHz band. IEEE 802.11ad tackles the aforementioned problems by introducing new mechanisms at the medium access control (MAC) and physical (PHY) layers such as beamforming training and beam tracking, hybrid channel access scheme, relay operation mode, multi-band operation, etc. The performance of 60 GHz networks is the result of the interaction of all layers of the protocol stack with the wireless medium. To understand this interaction, it is fundamental to consider 60 GHz networks as a whole. Nevertheless, real-world experimentation with mmWave communication is not always feasible due to the significant amount of resources required and its associated costs. For these reasons, we develop in this thesis a high fidelity system-level model to simulate the IEEE 802.11ad standard. This allows us to study large-scale wireless networks operating in the 60 GHz band, taking into account all of the essential features supported by the standard. We investigate the networking aspects of various mmWave wireless network deployments and provide solutions to boost their performance. Additionally, since most of the mmWave devices are anticipated to adopt the carrier sense multiple access with collision avoidance as the primary channel access scheme, we propose two frame-aggregation policies that significantly improve network throughput and reduce end-to-end delay.
To complement our insights from the simulations, we analyze in-depth the performance of Commercial off-the-shelf devices that implement the full 802.11ad protocol stack. Fortunately, a growing number of 60 GHz devices supporting the IEEE 802.11ad standard have become recently available. However, the standard does not specify implementation-dependent characteristics that have a significant impact on device performance. For example, this includes the periodicity of beamforming training, which directly affects ongoing communication and performance under mobility. Also, the placement of the 60 GHz antenna in the device plays a fundamental role regarding self-shadowing, which in turn affects how the device shall be deployed to maximize coverage and improve spatial reuse. Understanding such implementation-dependent issues is crucial to correctly draw the aforementioned system-level insights. In this thesis, we characterize and compare commercial 60 GHz devices which are widely used for research purposes. Particularly, we look at different networking aspects, including spatial sharing, beam patterns synthesis, frame aggregation, and the interactions between carrier sense multiple access with collision avoidance (CSMA/CA) and Transmission Control Protocol (TCP) protocols within dense network settings. In summary, we find significant discrepancies in terms of behavior and performance between these devices and what theory suggests. Additionally, achieving a gigabit of throughput and maintaining low-latency require adopting cross-layer solutions operating between the MAC layer and the transport layer.
The firmware running on these devices provide some experimental capabilities based on the operation of the IEEE 802.11ad protocol. These capabilities include reporting the Channel State Information (CSI) per antenna element for the connected antenna array. This CSI information contains valuable information about the spatial environment. Additionally, this information is sensitive to any minor changes in the environment. This inspires us to build a collaborative scheme consisting of spatially distributed APs that sense the environment and pinpoint the location of an obstacle without involving the end users.
In this thesis, we first delve into the operation of the IEEE 802.11ad protocol and analyze its performance both in simulations and practice. Second, we propose a set of solutions and recommendations to boost its efficiency. Finally, we extend its scope beyond typical wireless communication and utilize it to build a passive localization system.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
A Framework for Analyzing Spectrum Characteristics in Large Spatio-temporal Scales
Get PDFUnderstanding spectrum characteristics with little prior knowledge requires fine-grained spectrum data in the frequency, spatial, and temporal domains; gathering such a diverse set of measurements results in a large data volume. Analysis of the resulting dataset poses unique challenges; methods in the status quo are tailored for specific spectrum-related applications (apps), and are ill equipped to process data of this magnitude. In this paper, we design BigSpec, a general-purpose framework that allows for fast processing of apps. The key idea is to reduce computation costs by performing computation extensively on compressed data that preserves signal features. Adhering to this guideline, we build solutions for three apps, i.e., energy detection, spatio-temporal spectrum estimation, and anomaly detection. These apps were chosen to highlight BigSpec’s efficiency, scalability, and extensibility. To evaluate BigSpec’s performance, we collect more than 1 terabyte of spectrum data spanning a year, across 300MHz-4GHz, covering 400 km2. Compared with baselines and prior works, we achieve 17× run time efficiency, sublinear rather than linear run time scalability, and extend the definition of anomaly to different domains (frequency & spatio-temporal). We also obtain high-level insights from the data to provide valuable advice on future spectrum measurement and data analysis.TRUEpu
Modeling Mobile Edge Computing Deployments for Low Latency Multimedia Services
Get PDFMulti-access Edge Computing (MEC) technologies bring important improvements in terms of network bandwidth, latency and use of context information, critical for services like multimedia streaming, augmented and virtual reality. In future deployments, operators will need to decide how many MEC Points of Presence (PoPs) are needed and where to deploy them, also considering the number of base stations needed to support the expected traffic. This article presents an application of in homogeneous Poisson point processes with hard-core repulsion to model feasible MEC infrastructure deployments. With the presented methodology a mobile network operator knows where to locate the MEC PoPs and associated base stations to support a given set of services. We evaluate our model with simulations in realistic scenarios, namely Madrid city center, an industrial area, and a rural area.pu
Dynamic Windows Scheduling for Virtual Machine Placement
Get PDFWe consider applying Windows Scheduling (WS) to Virtual
Machine(VM) placement in cloud computing. In brief, the problem is to schedule the use of Physical Machines(PM) in terms of mips, processing elements, ram, storage and/or bandwidth to clients. Each client is characterized by an active cycle and a broker which is acting on behalf of that client. The broker hides virtual machine management, as VM
creation, submission of cloudlets to VM and destruction of VMs. During the period of time that any given client is active, there must be transmissions from the broker to the cloud resource provider, for example, a Data Center, for VM creation and destruction. The goal of the Data Center Virtual Machine Allocation Policy is to minimize the number
of PMs used for VM placement. With this online model, decisions are dynamic, we assume that VMs may be reallocated at some cost. We assume that such cost is a constant amount paid per reallocation. That is, we also aim to minimize the number of reallocations. We will present several online reallocation algorithms for VM placement. We will eval-
uate experimentally these policies showing that, in practice, all achieve constant amortized reallocations with close to optimal PM usage. Our simulations will also expose interesting trade-offs between reallocations and PM usage. We are developing the simulation model termed Virtual-
MachinePlacementSim (VMPSim) based on CloudSim to perform the
experiments.TRUEpu
Optimizing Network Slicing via Virtual Resource Pool Partitioning
Get PDFDOI: https://doi.org/10.23919/WiOPT47501.2019.9144143This paper focuses on optimizing resource allocation amongst a set of tenants, network slices, supporting dynamic customer loads over a set of distributed resources, e.g., base stations. The aim is to reap the benefits of statistical multiplexing resulting from flexible sharing of `pooled' resources, while enabling tenants to differentiate and protect their performance from one another's load fluctuations. To that end we consider a setting where resources are grouped into Virtual Resource Pools (VRPs) wherein resource allocation is jointly and dynamically managed. Specifically for each VRP we adopt a Share-Constrained Proportionally Fair (SCPF) allocation scheme where each tenant is allocated a fixed share (budget). This budget is to be distributed equally amongst its active customers which in turn are granted fractions of their associated VRP resources in proportion to customer shares. For a VRP with a single resource, this translates to the well known Generalized Processor Sharing (GPS) policy. For VRPs with multiple resources SCPF provides a flexible means to achieve load elastic allocations across tenants sharing the pool. Given tenants' per resource shares and expected loads, this paper formulates the problem of determining optimal VRP partitions which maximize the overall expected shared weighted utility while ensuring protection guarantees. For a high load/capacity setting we exhibit this network utility function explicitly, quantifying the benefits and penalties of any VRP partition, in terms of network slices' ability to achieve performance differentiation, load balancing, and statistical multiplexing. Although the problem is shown to be NP-Hard, a simple greedy heuristic is shown to be effective. Analysis and simulations confirm that the selection of optimal VRP partitions provide a practical avenue towards improving network utility in network slicing scenarios with dynamic loads.TRUEpu
Transport-Layer Limitations for NFV Orchestration in Resource-Constrained Aerial Networks
Get PDFIn this paper, we identify the main challenges and problems related with the management and orchestration of Virtualized Network Functions (VNFs) over aerial networks built with Small Unmanned Aerial Vehicles (SUAVs). Our analysis starts from a reference scenario, where several SUAVs are deployed over a delimited geographic area, and provide a mobile cloud environment that supports the deployment of functions and services using Network Functions Virtualization (NFV) technologies. After analyzing the main challenges to NFV orchestration in this reference scenario from a theoretical perspective, we undertake the study of one specific but relevant aspect following a practical perspective, i.e., the limitations of existing transport-layer solutions to support the dissemination of NFV management and orchestration information in the considered scenario. While in traditional cloud computing environments this traffic is delivered using TCP, our simulation results suggest that using this protocol over an aerial network of SUAVs presents certain limitations. Finally, based on the lessons learned from our practical analysis, the paper outlines different alternatives that could be followed to address these challengespu
Smartphone Positioning with Radio Measurements from a Single WiFi Access Point
Get PDFDespite the large literature on localization, there is no solution
yet to localize a commercial off-the-shelf smartphone device using
radio measurements from a single WiFi AP. We present SPRING,
Smartphone Positioning with Radio measurements from a sINGle
wifi access point. SPRING exploits Fine Time Measurements (FTM)
and Angle of Arrival (AOA) extracted from commercial chipsets exploiting
the specifications of the recent 802.11-2016 and the 802.11ac
amendment to combine distance and direction from the AP to the
client for positioning. Our system has the potential to bring indoor
positioning to homes and small businesses which typically have a
single access point. We exploit physical layer (PHY) information to
detect the number of paths and their directions. We use this information
to derive a new method for filtering ranging measurements
obtained with the FTM protocol. We achieve sub-meter distance
estimation accuracy eliminating the adverse effect of multipath
in FTM using calibrated inputs from Channel State Information
(CSI). Our evaluation in indoor scenarios in multipath rich environments
demonstrates that the combination of AOA estimation and
the proposed FTM refinement approach can locate a Google Pixel 3
smartphone with a median positioning error of 0.9-2.15 m through
an area comparable to typical flat sizes.TRUEpu