1,721,048 research outputs found
End-to-End Design and Evaluation of mmWave Cellular Networks
Full text linkThe next generation of cellular networks (5G) is being designed to provide unprecedented performance in mobile scenarios, with an increase in capacity, ultra-low latency and a massive number of connections. This will require the integration of novel technologies in more advanced and complex networks. Millimeter wave (mmWave) communications are considered as a key enabler for ultra-high datarates and low latency, thanks to the massive amount of available bandwidth at such high frequencies. Nonetheless, there are a number of challenges that must be solved before this technology can be deployed, mainly related to the high propagation loss, the need for directional communications and the blockage.
This thesis provides system-level solutions to make mmWave mobile networks more reliable, robust and better performing. Notably, we consider mmWave links as a part of more complex, end-to-end networks, in which the quality of experience that the end user perceives is the result of the interaction among the variability and unreliability of the mmWave channel, the full protocol stack, and the deployment strategy of the wireless network. To this end, we develop and describe a tool for the simulation of end-to-end mmWave cellular networks that, combined with analysis and experimental results, makes it possible to consistently evaluate how these systems behave in their entirety.
The main research areas that this thesis explores are the design and evaluation of (i) architectures for mmWave systems, in terms of mobility and beam management, and wireless backhaul solutions; (ii) protocols for end-to-end connectivity over mmWave networks; and (iii) intelligent and data-driven optimizations in cellular networks. Among other results, we highlight the importance of multi connectivity for mmWave systems, in the access network and at the transport layer, discuss the tradeoffs of beam management in 3GPP NR, propose how to update protocols at the transport layer for an improved end-to-end performance, and evaluate practical approaches for the integration of intelligent techniques in 5G networks
TCP and MP-TCP in mmWave 5G Networks
No full textFuture 5G networks will likely include mmWave radio access communication links, because of their potential multi-gigabit-per-second capacity. However, these frequencies are characterized by very dynamic channel conditions which lead to wide fluctuations in the received signal quality. This article explains how the end-to-end user experience in mobile mmWave networks could be affected by a sub-optimal interaction between the most widely used transport protocol, TCP, and mmWave links. It also provides insights on the throughput-latency trade-off when Multipath TCP (MP-TCP) is used judiciously across various links (e.g., LTE and mmWave)
Multi-Sector and Multi-Panel Performance in 5G mmWave Cellular Networks
No full textThe next generation of cellular networks (5G) will exploit the mmWave spectrum to increase the available capacity. Communication at such high frequencies, however, suffers from high path loss and blockage, therefore directional transmissions using antenna arrays and dense deployments are needed. Thus, when evaluating the performance of mmWave mobile networks, it is necessary to accurately model the complex channel, the directionality of the transmission, but also the interplay that these elements can have with the whole protocol stack, both in the radio access and in the higher layers. In this paper, we improve the channel model abstraction of the mmWave module for ns-3, by introducing the support of a more realistic antenna array model, compliant with 3GPP NR requirements, and of multiple antenna arrays at the base stations and mobile handsets. We then study the end-to-end performance of a mmWave cellular network by varying the channel and antenna array configurations, and show that increasing the number of antenna arrays and, consequently, the number of sectors is beneficial for both throughput and latency
Scalable and Accurate Modeling of the Millimeter Wave Channel
No full textCommunication at millimeter wave (mmWave) frequencies is one of the main novelties introduced in the 5th generation (5G) of cellular networks. The opportunities and challenges associated with such high frequencies have stimulated a number of studies that rely on simulation for the evaluation of the proposed solutions. The accuracy of simulations largely depends on that of the channel model, but popular channel models for mmWaves, such as the Spatial Channel Models (SCMs), have high computational complexity and limit the scalability of the scenarios. This paper profiles the implementation of a widely-used SCM model for mmWave frequencies, and proposes a simplified version of the 3GPP SCM that reduces the computation time by up to 12.5 times while providing essentially the same distributions of several metrics, such as the Signal-to-Interference-plus-Noise Ratio (SINR) in large scale scenarios. We also give insights on the use cases in which using a simplified model can still yield valid results
Autonomous Driving From the Sky: Design and End-to-End Performance Evaluation
Full text linkFor autonomous vehicles to operate without human intervention, information
sharing from local sensors plays a fundamental role. This can be challenging to
handle with bandwidth-constrained communication systems, which calls for the
adoption of new wireless technologies, like in the mmwave bands, to solve
capacity issues. Another approach is to exploit uav, able to provide human
users and their cars with an aerial bird's-eye view of the scene otherwise
unavailable, thus offering broader and more centralized observations. In this
article we combine both aspects and design a novel framework in which uav,
operating at mmwave, broadcast sensory information to the ground as a means to
extend the (local) perception range of vehicles. To do so, we conduct a
full-stack end-to-end simulation campaign with ns-3 considering real UAV data
from the Stanford Drone Dataset, and study four scenarios representing
different uav-to-ground communication strategies. Our results focus on the
trade-off between centralized data processing in the sky vs. distributed local
processing on the ground, with considerations related to the throughput,
latency and reliability of the communication process
Optimizing and Managing Wireless Backhaul for Resilient Next-Generation Cellular Networks
No full textNext-generation wireless networks target high network availability, ubiquitous coverage, and extremely high data rates for mobile users. This requires exploring new frequency bands, e.g., mmWaves, moving toward ultra-dense deployments in urban locations, and providing ad hoc, resilient connectivity in rural scenarios. The design of the backhaul network plays a key role in advancing how the access part of the wireless system supports next-generation use cases. Wireless backhauling, such as the newly introduced Integrated Access and Backhaul (IAB) concept in 5G, provides a promising solution, also leveraging the mmWave technology and steerable beams to mitigate interference and scalability issues. At the same time, however, managing and optimizing a complex wireless backhaul introduces additional challenges for the operation of cellular systems. This paper presents a strategy for the optimal creation of the backhaul network considering various constraints related to network topology, robustness, and flow management. We evaluate its feasibility and efficiency using synthetic and realistic network scenarios based on 3D modeling of buildings and ray tracing. We implement and prototype our solution as a dynamic IAB control framework based on the Open Radio Access Network (RAN) architecture, and demonstrate its functionality in Colosseum, a large-scale wireless network emulator with hardware in the loop
Standalone and Non-Standalone Beam Management for 3GPP NR at mmWaves
No full textThe next generation of cellular networks will exploit mmWave frequencies to dramatically increase the network capacity. Communication at such high frequencies, however, requires directionality to compensate the increased propagation loss. Users and base stations need to align their beams during both initial access and data transmissions to ensure that the maximum gain is reached. The accuracy of beam selection, and the delay in updating the beam pair or performing initial access, impact the end-to-end performance and the quality of service. In this article we review the beam management procedures included in the 3GPP NR specifications and propose possible enhancements, based on both standalone and non-standalone architectures, to improve network control operations. We also provide a performance comparison among different schemes, along with design insights on the most important parameters related to beam management frameworks
Toward 6G Networks: Use Cases and Technologies
No full textReliable data connectivity is vital for the ever increasingly intelligent, automated, and ubiquitous digital world. Mobile networks are the data highways and, in a fully connected, intelligent digital world, will need to connect everything, including people to vehicles, sensors, data, cloud resources, and even robotic agents. Fifth generation (5G) wireless networks, which are currently being deployed, offer significant advances beyond LTE, but may be unable to meet the full connectivity demands of the future digital society. Therefore, this article discusses technologies that will evolve wireless networks toward a sixth generation (6G) and which we consider as enablers for several potential 6G use cases. We provide a fullstack, system-level perspective on 6G scenarios and requirements, and select 6G technologies that can satisfy them either by improving the 5G design or by introducing completely new communication paradigms
Accuracy vs. Complexity for mmWave Ray-Tracing: A Full Stack Perspective
No full textThe millimeter wave (mmWave) band will provide multi-gigabits-per-second connectivity in the radio access of future wireless systems. The high propagation loss in this portion of the spectrum calls for the deployment of large antenna arrays to compensate for the loss through high directional gain, thus introducing the need for a spatial dimension in the channel model to accurately represent the performance of a mmWave network. In this perspective, ray tracing can characterize the channel in terms of Multi Path Components (MPCs) to provide a highly accurate model, at the price of extreme computational complexity (e.g., for processing detailed environment information about the propagation), which may limit the scalability of the simulations. In this paper, we present possible simplifications to improve the trade-off between accuracy and complexity in ray-tracing simulations at mmWaves by reducing the total number of MPCs. The effect of such simplifications is evaluated from a full-stack perspective through end-to-end simulations, testing different configuration parameters, propagation scenarios, and higher-layer protocol implementations. We then provide guidelines on the optimal degree of simplification, for which it is possible to reduce the complexity of simulations with a minimal reduction in accuracy for different deployment scenarios
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