Massive MIMO for Internet of Things (IoT) Connectivity

Massive MIMO is considered to be one of the key technologies in the emerging 5G systems, but also a concept applicable to other wireless systems. Exploiting the large number of degrees of freedom (DoFs) of massive MIMO essential for achieving high spectral efficiency, high data rates and extreme spatial multiplexing of densely distributed users. On the one hand, the benefits of applying massive MIMO for broadband communication are well known and there has been a large body of research on designing communication schemes to support high rates. On the other hand, using massive MIMO for Internet-of-Things (IoT) is still a developing topic, as IoT connectivity has requirements and constraints that are significantly different from the broadband connections. In this paper we investigate the applicability of massive MIMO to IoT connectivity. Specifically, we treat the two generic types of IoT connections envisioned in 5G: massive machine-type communication (mMTC) and ultra-reliable low-latency communication (URLLC). This paper fills this important gap by identifying the opportunities and challenges in exploiting massive MIMO for IoT connectivity. We provide insights into the trade-offs that emerge when massive MIMO is applied to mMTC or URLLC and present a number of suitable communication schemes. The discussion continues to the questions of network slicing of the wireless resources and the use of massive MIMO to simultaneously support IoT connections with very heterogeneous requirements. The main conclusion is that massive MIMO can bring benefits to the scenarios with IoT connectivity, but it requires tight integration of the physical-layer techniques with the protocol design.Comment: Submitted for publicatio

JANUS: an FPGA-based System for High Performance Scientific Computing

This paper describes JANUS, a modular massively parallel and reconfigurable FPGA-based computing system. Each JANUS module has a computational core and a host. The computational core is a 4x4 array of FPGA-based processing elements with nearest-neighbor data links. Processors are also directly connected to an I/O node attached to the JANUS host, a conventional PC. JANUS is tailored for, but not limited to, the requirements of a class of hard scientific applications characterized by regular code structure, unconventional data manipulation instructions and not too large data-base size. We discuss the architecture of this configurable machine, and focus on its use on Monte Carlo simulations of statistical mechanics. On this class of application JANUS achieves impressive performances: in some cases one JANUS processing element outperfoms high-end PCs by a factor ~ 1000. We also discuss the role of JANUS on other classes of scientific applications.Comment: 11 pages, 6 figures. Improved version, largely rewritten, submitted to Computing in Science & Engineerin

Massive MIMO is a Reality -- What is Next? Five Promising Research Directions for Antenna Arrays

Massive MIMO (multiple-input multiple-output) is no longer a "wild" or "promising" concept for future cellular networks - in 2018 it became a reality. Base stations (BSs) with 64 fully digital transceiver chains were commercially deployed in several countries, the key ingredients of Massive MIMO have made it into the 5G standard, the signal processing methods required to achieve unprecedented spectral efficiency have been developed, and the limitation due to pilot contamination has been resolved. Even the development of fully digital Massive MIMO arrays for mmWave frequencies - once viewed prohibitively complicated and costly - is well underway. In a few years, Massive MIMO with fully digital transceivers will be a mainstream feature at both sub-6 GHz and mmWave frequencies. In this paper, we explain how the first chapter of the Massive MIMO research saga has come to an end, while the story has just begun. The coming wide-scale deployment of BSs with massive antenna arrays opens the door to a brand new world where spatial processing capabilities are omnipresent. In addition to mobile broadband services, the antennas can be used for other communication applications, such as low-power machine-type or ultra-reliable communications, as well as non-communication applications such as radar, sensing and positioning. We outline five new Massive MIMO related research directions: Extremely large aperture arrays, Holographic Massive MIMO, Six-dimensional positioning, Large-scale MIMO radar, and Intelligent Massive MIMO.Comment: 20 pages, 9 figures, submitted to Digital Signal Processin

TrIMS: Transparent and Isolated Model Sharing for Low Latency Deep LearningInference in Function as a Service Environments

Deep neural networks (DNNs) have become core computation components within low latency Function as a Service (FaaS) prediction pipelines: including image recognition, object detection, natural language processing, speech synthesis, and personalized recommendation pipelines. Cloud computing, as the de-facto backbone of modern computing infrastructure for both enterprise and consumer applications, has to be able to handle user-defined pipelines of diverse DNN inference workloads while maintaining isolation and latency guarantees, and minimizing resource waste. The current solution for guaranteeing isolation within FaaS is suboptimal -- suffering from "cold start" latency. A major cause of such inefficiency is the need to move large amount of model data within and across servers. We propose TrIMS as a novel solution to address these issues. Our proposed solution consists of a persistent model store across the GPU, CPU, local storage, and cloud storage hierarchy, an efficient resource management layer that provides isolation, and a succinct set of application APIs and container technologies for easy and transparent integration with FaaS, Deep Learning (DL) frameworks, and user code. We demonstrate our solution by interfacing TrIMS with the Apache MXNet framework and demonstrate up to 24x speedup in latency for image classification models and up to 210x speedup for large models. We achieve up to 8x system throughput improvement.Comment: In Proceedings CLOUD 201

Distributed Implementation of eXtended Reality Technologies over 5G Networks

Mención Internacional en el título de doctorThe revolution of Extended Reality (XR) has already started and is rapidly expanding as technology advances. Announcements such as Meta’s Metaverse have boosted the general interest in XR technologies, producing novel use cases. With the advent of the fifth generation of cellular networks (5G), XR technologies are expected to improve significantly by offloading heavy computational processes from the XR Head Mounted Display (HMD) to an edge server. XR offloading can rapidly boost XR technologies by considerably reducing the burden on the XR hardware, while improving the overall user experience by enabling smoother graphics and more realistic interactions. Overall, the combination of XR and 5G has the potential to revolutionize the way we interact with technology and experience the world around us. However, XR offloading is a complex task that requires state-of-the-art tools and solutions, as well as an advanced wireless network that can meet the demanding throughput, latency, and reliability requirements of XR. The definition of these requirements strongly depends on the use case and particular XR offloading implementations. Therefore, it is crucial to perform a thorough Key Performance Indicators (KPIs) analysis to ensure a successful design of any XR offloading solution. Additionally, distributed XR implementations can be intrincated systems with multiple processes running on different devices or virtual instances. All these agents must be well-handled and synchronized to achieve XR real-time requirements and ensure the expected user experience, guaranteeing a low processing overhead. XR offloading requires a carefully designed architecture which complies with the required KPIs while efficiently synchronizing and handling multiple heterogeneous devices. Offloading XR has become an essential use case for 5G and beyond 5G technologies. However, testing distributed XR implementations requires access to advanced 5G deployments that are often unavailable to most XR application developers. Conversely, the development of 5G technologies requires constant feedback from potential applications and use cases. Unfortunately, most 5G providers, engineers, or researchers lack access to cutting-edge XR hardware or applications, which can hinder the fast implementation and improvement of 5G’s most advanced features. Both technology fields require ongoing input and continuous development from each other to fully realize their potential. As a result, XR and 5G researchers and developers must have access to the necessary tools and knowledge to ensure the rapid and satisfactory development of both technology fields. In this thesis, we focus on these challenges providing knowledge, tools and solutiond towards the implementation of advanced offloading technologies, opening the door to more immersive, comfortable and accessible XR technologies. Our contributions to the field of XR offloading include a detailed study and description of the necessary network throughput and latency KPIs for XR offloading, an architecture for low latency XR offloading and our full end to end XR offloading implementation ready for a commercial XR HMD. Besides, we also present a set of tools which can facilitate the joint development of 5G networks and XR offloading technologies: our 5G RAN real-time emulator and a multi-scenario XR IP traffic dataset. Firstly, in this thesis, we thoroughly examine and explain the KPIs that are required to achieve the expected Quality of Experience (QoE) and enhanced immersiveness in XR offloading solutions. Our analysis focuses on individual XR algorithms, rather than potential use cases. Additionally, we provide an initial description of feasible 5G deployments that could fulfill some of the proposed KPIs for different offloading scenarios. We also present our low latency muti-modal XR offloading architecture, which has already been tested on a commercial XR device and advanced 5G deployments, such as millimeter-wave (mmW) technologies. Besides, we describe our full endto- end complex XR offloading system which relies on our offloading architecture to provide low latency communication between a commercial XR device and a server running a Machine Learning (ML) algorithm. To the best of our knowledge, this is one of the first successful XR offloading implementations for complex ML algorithms in a commercial device. With the goal of providing XR developers and researchers access to complex 5G deployments and accelerating the development of future XR technologies, we present FikoRE, our 5G RAN real-time emulator. FikoRE has been specifically designed not only to model the network with sufficient accuracy but also to support the emulation of a massive number of users and actual IP throughput. As FikoRE can handle actual IP traffic above 1 Gbps, it can directly be used to test distributed XR solutions. As we describe in the thesis, its emulation capabilities make FikoRE a potential candidate to become a reference testbed for distributed XR developers and researchers. Finally, we used our XR offloading tools to generate an XR IP traffic dataset which can accelerate the development of 5G technologies by providing a straightforward manner for testing novel 5G solutions using realistic XR data. This dataset is generated for two relevant XR offloading scenarios: split rendering, in which the rendering step is moved to an edge server, and heavy ML algorithm offloading. Besides, we derive the corresponding IP traffic models from the captured data, which can be used to generate realistic XR IP traffic. We also present the validation experiments performed on the derived models and their results.This work has received funding from the European Union (EU) Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie ETN TeamUp5G, grant agreement No. 813391.Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan CarlosPresidente: Narciso García Santos.- Secretario: Fernando Díaz de María.- Vocal: Aryan Kaushi

A Very Brief Introduction to Machine Learning With Applications to Communication Systems

Given the unprecedented availability of data and computing resources, there is widespread renewed interest in applying data-driven machine learning methods to problems for which the development of conventional engineering solutions is challenged by modelling or algorithmic deficiencies. This tutorial-style paper starts by addressing the questions of why and when such techniques can be useful. It then provides a high-level introduction to the basics of supervised and unsupervised learning. For both supervised and unsupervised learning, exemplifying applications to communication networks are discussed by distinguishing tasks carried out at the edge and at the cloud segments of the network at different layers of the protocol stack