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Initial Access and Beam-Steering Mechanisms for mmWave Wireless Systems
Get PDFFuture millimeter-wave networks will support very high densities of devices and access points. This vastly increases the overhead required for access point selection and beam training. Due to unfavorable radio propagation, mmWave systems will exploit largescale MIMO and adaptive antenna arrays at both the transmitter and receiver to realize sufficient link margin. Beamforming is vital to overcome the high attenuation in wireless millimeter-wave networks. It enables nodes to steer their antennas in the direction of communication. Fortunately, the quasi-optical properties of millimeter-wave channels
make location-based network optimization a highly promising technique to reduce control overhead in such millimeter-wave WLANs.
In this thesis we present tools to improve mmWave systems. We start by designing
an effective lightweight sector beam-pattern design for using as a baseline for hybrid analog-digital structures. We deal with practical constraints of mmWave transceivers and propose a novel, geometric approach to synthesize multi-beamwidth beam patterns that can be leveraged for simultaneous multi-direction scanning. Then we make use of this multi-direction scanning to create a beam training protocol which effectively accelerates the link establishment by exploiting the ability of mobile users to simultaneously receive from multiple directions. We propose smart beam training and tracking strategies for
fast mm-wave link establishment and maintenance under node mobility. We leverage the ability of hybrid analog-digital transceivers to collect channel information from multiple spatial directions simultaneously and formulate a probabilistic optimization problem to model the temporal evolution of the mm-wave channel under mobility. We propose a mechanism to extract full channel state information (CSI) regarding phase and magnitude from coarse signal strength readings on off-the-shelf IEEE 802.11ad devices. Using this CSI, transmitters dynamically compute a transmit beam pattern that maximizes the signal strength at the receiver. Channel properties and antenna design at 60GHz are ideal for path angular information extraction, following an almost ideal geometric channel
model. Due to this, we present some localization method speciffically designed for the 60GHz band. We merge the ideas presented in this thesis and by extracting channel state information from off-the-shelf routers we estimate the user location to manage a location aware beam-training and device handling method. The resulting scheme can predict blockage,optimize access point association, and select the most suitable antenna
beam patterns while signifficantly reducing the beam training overhead.Signal and Communications TheoryUniversidad Carlos III de Madrid, Spainpu
Limitations and sidelink-based extensions of 3GPP cellular access protocols for very crowded environments
Get PDFAn experience common to smartphone users is the difficulty in accessing services in crowded scenarios, such as a rock concert or a football match. In these cases, to (partially) mitigate frustration, users generically claim that network congestion is occurring, and try again and again to access the network with their smartphones: the result is that user frustration and network congestion reinforce each other! This paper investigates the root causes of poor performance of cellular networks in crowded environments and shows that the commonly adopted random access procedure can prevent full utilization of wireless resources. We develop a simple yet accurate analytical model to analyze why attempting random access to wireless resources can become a problem even when access congestion avoidance is enforced, e.g., with the Access Class Barring technique. The model we propose suggests that cluster-based network ac- cess, leveraging device-to-device communications, significantly alleviates access problems. Moreover, it sheds light on scalability laws that govern network utilization and quality of experience, in terms of cell capacity, number of access channels, and cluster size.pu
A Monitoring Framework for Multi-Site 5G Platforms
Get PDFDOI: https://doi.org/10.1109/EuCNC48522.2020.9200914The fifth generation (5G) of mobile networks will have to accommodate different types of use cases, each of them with different and stringent requirements and key performance indicators (KPIs). To support this, apart from novel technologies such as network slicing or artificial intelligence, 5G will require a flexible and efficient monitoring system. The collected metrics serve to optimize the performance of the network, and to confirm the achievement of the KPIs. Furthermore, in the envisioned multi-site, multi-stakeholder scenarios, having a common monitoring system is even more critical for an efficient optimization and service provisioning. In this paper, we present a Monitoring architecture for the distribution and consumption of metrics and KPIs for 5G multi-site platforms, where different verticals from different stakeholders are implemented over a shared infrastructure. We also assess the performance of the implemented publish-subscribe paradigm, to confirm that it suits the requirements of these scenarios, and discuss how the architecture could be mapped to other 5G scenarios.TRUEpu
Leveraging online advertising platforms to measure and characterize digital inequalities
Get PDFAs the Internet is becoming a fundamental aspect of the society serving as a de facto platform for social and business activities, traditional offline activities and services have remarkably migrated to the web. The presence and interaction of users on these platforms has created a large amount of digital trace which is being effectively exploited by businesses targeting users on these platforms. One of the main players in this regard is online advertising which is the underneath business that drives the majority of the most important online services such as social media, search engines, map services, etc. This has made online advertising a crucial Internet service in its own right. While the benefit of using these digital resources has been accepted widely pushing governments and organizations to improve their Internet coverage, there are major challenges that limit the society from enjoying their benefits. Together with transparency and privacy, digital inequality is the main challenge that the society faces today.
In this thesis we propose a set of inexpensive and large scale methodologies that leverages datasets from online advertising systems to measure and characterize digital inequality on the web. Our methodologies consider various demographic, geographic and interest categories at global scale that advances the knowledge of the scientific community to better understand the challenges in the interplay between online services and users, specifically digital inequalities.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
WearFlow: Expanding Information Flow Analysis To Companion Apps in Wear OS
Get PDFSmartwatches and wearable technology have proliferated in the recent years featured by a seamless integration with a paired smartphone. Many mobile applications now come with a companion app that the mobile OS deploys on the wearable. These execution environments expand the context of mobile applications across more than one device, introducing new security and privacy issues. One such issue is that current information flow analysis techniques can not capture communication between devices. This can lead to undetected privacy leaks when developers use these channels. In this paper, we present WearFlow, a framework that uses static analysis to detect sensitive data flows across mobile and wearable companion apps in Android. WearFlow augments taint analysis capabilities to enable inter-device analysis of apps. WearFlow models proprietary libraries embedded in Google Play Services and instruments the mobile and wearable app to allow for a precise information flow analysis between them. We evaluate WearFlow on a test suite purposely designed to cover different scenarios for the communication Mobile-Wear, which we release as Wear-Bench. We also run WearFlow on 3K+ real-world apps and discover privacy violations in popular apps (10M+ downloads).TRUEpu
Optimal and approximation algorithms for joint routing and scheduling in millimeter-wave cellular networks
Get PDFMillimeter-wave (mmWave) communication is a promising technology to cope with the exponential increase in 5G data traffic. Such networks typically require a very dense deployment of base stations. A subset of those, so-called macro base stations, feature high-bandwidth connection to the core network, while relay base stations are connected wirelessly. To reduce cost and increase flexibility, wireless backhauling is needed to connect both macro to relay as well as relay to relay base stations. The characteristics of mmWave communication mandates new paradigms for routing and scheduling. The paper investigates scheduling algorithms under different interference models. To showcase the scheduling methods, we study the maximum throughput fair scheduling problem. Yet the proposed algorithms can be easily extended to other problems. For a fullduplex network under the no interference model, we propose an efficient polynomial-time scheduling method, the scheduleoriented optimization. Further, we prove that the problem is NPhard if we assume pairwise link interference model or halfduplex radios. Fractional weighted coloring based approximation algorithms are proposed for these NP-hard cases. Moreover, the approximation algorithm parallel data stream scheduling is proposed for the case of half-duplex network under the no interference model. It has better approximation ratio than the fractional weighted coloring based algorithms and even attains the optimal solution for the special case of uniform orthogonal backhaul networks.pu
Outage of Millimeter Wave Links With Randomly Located Obstructions
Get PDFAccording to current regulation, millimeter wave links can only rely on low transmission power, which calls for high gain steerable antenna arrays to generate very directional beams bringing signals of detectable power to the intended receiver. However, beam directionality, jointly with the very limited scattering and diffracting capabilities of millimeter waves, implies high sensitivity to obstructions, which can cause link outage. This article proposes new analytical models for the estimation of the outage probability of millimeter wave indoor and outdoor links, based on the derivation of the distribution of the obstruction length along the beam. To derive the models, we use stochastic geometry and assume randomly located obstructions. The proposed models are used to explore the impact on millimeter wave link performance of a number of parameters such as distance between transmitter and receiver, obstruction shape and size, density of obstructions, carrier frequency and modulated bandwidth. The models can be used to study realistic 2D and 3D scenarios, and are shown to be quite accurate by comparing analytical predictions and simulation results in numerous cases.pu
ACHO: A framework for flexible re-orchestration of virtual network functions
Get PDFNetwork Function Virtualization enables network slicing as a novel paradigm for service provisioning. With network slicing, Virtual Network Functions (VNFs) can be instantiated at different locations of the infrastructure, choosing their optimal placement based on parameters such as the requirements of the service or the resources available. One limitation of state-of-the-art technology for network slicing is the inability to re-evaluate orchestration decisions once the slice has been deployed, in case of changing service demands or network conditions.
In this paper, we present ACHO, a novel software framework that enables seamless re-orchestration of VNFs of any kind, including RAN and Core. With ACHO, VNFs and resources can be easily re-assigned to match, e.g., varying user demands or changes in the nodes’ load. ACHO uses lightweight mechanisms, such as splitting the engine of a VNF from the data it requires to perform its operation, in such a way that, when re-allocating a VNF, only the data is moved (a new engine is instantiated in the new location). We demonstrate the use of ACHO in a small scale testbed, showing that (i) the proposed re-orchestration is feasible, (ii) it results much faster than existing alternatives (especially for relocation), and (iii) the framework can be readily applied to existing VNFs after minimal changes to their implementation.pu
Towards enabled industrial verticals in 5G: a survey on MEC-based approaches to provisioning and flexibility
Get PDFThe increasing number of heterogeneous devicesconnected to the Internet, together with tight 5G requirementshave generated new challenges for designing network infras-tructures. Industrial verticals such as automotive, smart cityand eHealthcare (among others) need secure, low latency andreliable communications. To meet these stringent requirements,computing resources have to be moved closer to the user, fromthe core to the edge of the network. In this context, ETSIstandardized Multi-Access Edge Computing (MEC). However,due to the cost of resources, MEC provisioning has to be carefullydesigned and evaluated. This survey firstly overviews standards,with particular emphasis on 5G and virtualization of networkfunctions, then it addresses flexibility of MEC smart resourcedeployment and its migration capabilities. This survey exploreshow the MEC is used and how it will enable industrial vertical.pu