844 research outputs found
Modular software architecture for flexible reservation mechanisms on heterogeneous resources
Management, allocation and scheduling of heterogeneous resources for complex distributed real-time applications is a chal-
lenging problem. Timing constraints of applications may be fulfilled by a proper use of real-time scheduling policies, admission
control and enforcement of timing constraints. However, it is not easy to design basic infrastructure services that allow for an easy
access to the allocation of multiple heterogeneous resources in a distributed environment.
In this paper, we present a middleware for providing distributed soft real-time applications with a uniform API for reserving
heterogeneous resources with real-time scheduling capabilities in a distributed environment. The architecture relies on standard
POSIX OS facilities, such as time management and standard TCP/IP networking services, and it is designed around CORBA, in
order to facilitate modularity, flexibility and portability of the applications using it. However, real-time scheduling is supported
by proper extensions at the kernel-level, plugged within the framework by means of dedicated resource managers. Our current implementation on Linux supports reservation of CPU, disk and network bandwidth. However, additional resource managers supporting alternative real-time schedulers for these resources, as well as additional types of resources, may be easily added.
We present experimental results gathered on both synthetic applications and a real multimedia video streaming case study, showing advantages deriving from the use of the proposed middleware. Finally, overhead figures are reported, showing sustainability of the approach for a wide class of complex, distributed, soft real-time applications
A Survey of Techniques for Improving Security of GPUs
Graphics processing unit (GPU), although a powerful performance-booster, also
has many security vulnerabilities. Due to these, the GPU can act as a
safe-haven for stealthy malware and the weakest `link' in the security `chain'.
In this paper, we present a survey of techniques for analyzing and improving
GPU security. We classify the works on key attributes to highlight their
similarities and differences. More than informing users and researchers about
GPU security techniques, this survey aims to increase their awareness about GPU
security vulnerabilities and potential countermeasures
The AXIOM software layers
AXIOM project aims at developing a heterogeneous computing board (SMP-FPGA).The Software Layers developed at the AXIOM project are explained.OmpSs provides an easy way to execute heterogeneous codes in multiple cores. People and objects will soon share the same digital network for information exchange in a world named as the age of the cyber-physical systems. The general expectation is that people and systems will interact in real-time. This poses pressure onto systems design to support increasing demands on computational power, while keeping a low power envelop. Additionally, modular scaling and easy programmability are also important to ensure these systems to become widespread. The whole set of expectations impose scientific and technological challenges that need to be properly addressed.The AXIOM project (Agile, eXtensible, fast I/O Module) will research new hardware/software architectures for cyber-physical systems to meet such expectations. The technical approach aims at solving fundamental problems to enable easy programmability of heterogeneous multi-core multi-board systems. AXIOM proposes the use of the task-based OmpSs programming model, leveraging low-level communication interfaces provided by the hardware. Modular scalability will be possible thanks to a fast interconnect embedded into each module. To this aim, an innovative ARM and FPGA-based board will be designed, with enhanced capabilities for interfacing with the physical world. Its effectiveness will be demonstrated with key scenarios such as Smart Video-Surveillance and Smart Living/Home (domotics).Peer ReviewedPostprint (author's final draft
Efficient Management of Flexible Functional Splits in 5G Second Phase Networks
The fifth mobile network generation (5G), which offers better data speeds, reduced latency,
and a huge number of network connections, promises to improve the performance of the
cellular network in practically every way available. A portion of the network operations are
deployed in a centralized unit in the 5G radio access network (RAN) partially centralized
design. By centralizing these functions, operational expenses are decreased and coordinating strategies are made possible. To link centralized units (CU) and distributed units (DU),
and the DU to remote radio units (RRU), both the midhaul and fronthaul networks must
have higher capacity. The necessary fronthaul capacity is also influenced by the fluctuating
instantaneous user traffic. Consequently, the 5G RAN must be able to dynamically change
its centralization level to the user traffic to maximize its performance. To try to relieve this
fronthaul capacity it has been considered a more flexible distribution between the base band
unit (BBU) (or CU and DU if enhanced common public radio interface (eCPRI) is considered) and the RRU. It may be challenging to provide high-speed data services in crowded
areas, particularly when there is imperfect coverage or significant interference. Because of
this, the macrocell deployment is insufficient. This problem for outdoor users could be resolved by the introduction of low-power nodes with a limited coverage area. In this context,
this MSc dissertation explores, in an urban micro cell scenario model A (UMi_A) for three
frequency bands (2.6 GHz, 3.5 GHz, and 5.62 GHz), the highest data rate achievable when a
numerology zero is used. For this, it was necessary the implementation of the UMi_A in the
5G-air-simulator. Allowing the determination of the saturation level using the results for the
packet loss ratio (PLR=2%). By assuming Open RAN (O-RAN) and functional splitting, the
performance of two schedulers in terms of quality-of-service (QoS) were also studied. The
QoS-aware modified largest weighted delay first (M-LWDF) scheduler and the QoS-unaware
proportional fair (PF) scheduler. PLR was evaluated for both schedulers, whilst analyzing
the impact of break point distance while changing the frequency band. The costs, revenues,
profit in percentage terms, and other metrics were also estimated for the PF and M-LWDF
schedulers when used video (VID) and video plus best effort (VID+BE), with or without consideration of the functional splits 7.2 and 6, for the three frequency bands. One concluded
that the profit in percentage terms with functional split option 7.2 applied is always slightly
higher than with functional split option 6. It reaches a maximum profit of 366.92% in the
case of the M-LWDF scheduler, and 305.51% in the case of the PF scheduler, at a cell radius
of 0.4 km for the 2.6 GHz frequency band, considering a price of the traffic of 0.0002 €/min.A quinta geração de redes móveis (5G), oferece ritmos de transmissão melhorados, atraso
extremo-a-extremo reduzido, e um vasto número de ligações de rede. A 5G promete melhorar o desempenho das redes celulares em praticamente todos os aspectos relevantes. Uma
parte da operação da rede é colocada numa unidade centralizada na rede de acesso de rádio
(RAN) 5G com dimensionamento parcialmente centralizado. Ao centralizar estas funções,
os custos operacionais decrescem, viabilizando-se as estratégias de coordenação. Para ligar
as unidades centralizadas e unidades distribuídas, e por sua vez, unidades distribuidas e
unidades de rádio remotas, ambos os midhaul e fronthaul devem ter uma capacidade mais
elevada. A capacidade da fronthaul necessária é também influenciada pela flutuação do
tráfego instantâneo dos utilizadores. Consequentemente, a RAN 5G deve ser capaz de alterar
dinamicamente o seu nível de centralização para o tráfego de utilizadores, com objetivo de
maximizar o seu desempenho. Para tentar aliviar o aumento da capacidade suportada pelo
fronthaul, tem sido considerada uma distribuição mais flexível entre a unidade de banda
base, BBU (ou unidade central e unidade distribuída se a interface de rádio pública comum
melhorada, eCPRI, for considerada), e a unidade de rádio remota, RRU. Em áreas densamente povoadas, pode ser um desafio fornecer serviços de dados de elevada velocidade, particularmente quando existe uma cobertura deficiente ou interferência significativa. Por este
motivo, o desenvolvimento de macrocélulas pode ser insuficiente, mas este problema para
utilizadores em ambiente de exterior pode ser mitigado com a introdução de nós de potência
reduzida com uma área de cobertura limitada. Neste contexto, esta dissertação de mestrado
explora, num cenário urbano de microcélulas caracterizado pelo modelo A (UMi_A) para
três bandas de frequência (2.6 GHz, 3.5 GHz, e 5.62 GHz), o débito binário máximo que se
pode alcançar quando se utiliza numerologia zero. Para tal, foi necessária a implementação
do UMi_A no 5G - air - simulator. Determinou-se o nivel de saturação, considerandose os resultados para a taxa de perda de pacotes (PLR=2%). Estudou-se o desempenho de
dois escalonadores de pacotes em termos de qualidade de serviço (QoS), assumindo-se o
OpenRAN (O-RAN) e as divisões funcionais (functionalsplitting). Um dos escalonadores
é ciente da QoS, e é de atraso máximo-superior ponderado primeiro (M-LWDF), enquanto
que o outro não é ciente da QoS, e é de justiça proporcional (PF). Avaliou-se o PLR para
ambos os escalonadores de pacotes, estudando-se o impacto da distância de ponto de quebra (breakpointdistance), variando-se a banda de frequências. Foram também estimados os
custos, proveitos, o lucro (em percentagem), e outras metricas, para os escalonadores PF e
M-LWDF, considerando o vídeo (VID) e vídeo mais besteffort (VID+BE) como aplicações,
com ou sem a consideração das divisões funcionais 7.2 e 6, para as três bandas de frequência.
Concluiu-se que o lucro em termos percentuais, com a escolha da opção de divisão funcional
7.2, é sempre ligeiramente mais elevado do que com a opção de divisão funcional 6. Atingese um lucro máximo de 366,92% no caso do escalonador M-LWDF, e de 305,51% no caso do
escalonador PF, para um raio de célula de 0,4 km, para a banda de frequência de 2,6 GHz,
considerando-se um preço do tráfego de 0,0002 €/min
The Sensor Network Workbench: Towards Functional Specification, Verification and Deployment of Constrained Distributed Systems
As the commoditization of sensing, actuation and communication hardware increases, so does the potential for dynamically tasked sense and respond networked systems (i.e., Sensor Networks or SNs) to replace existing disjoint and inflexible special-purpose deployments (closed-circuit security video, anti-theft sensors, etc.). While various solutions have emerged to many individual SN-centric challenges (e.g., power management, communication protocols, role assignment), perhaps the largest remaining obstacle to widespread SN deployment is that those who wish to deploy, utilize, and maintain a programmable Sensor Network lack the programming and systems expertise to do so.
The contributions of this thesis centers on the design, development and deployment of the SN Workbench (snBench). snBench embodies an accessible, modular programming platform coupled with a flexible and extensible run-time system that, together, support the entire life-cycle of distributed sensory services. As it is impossible to find a one-size-fits-all programming interface, this work advocates the use of tiered layers of abstraction that enable a variety of high-level, domain specific languages to be compiled to a common (thin-waist) tasking language; this common tasking language is statically verified and can be subsequently re-translated, if needed, for execution on a wide variety of hardware platforms.
snBench provides: (1) a common sensory tasking language (Instruction Set Architecture) powerful enough to express complex SN services, yet simple enough to be executed by highly constrained resources with soft, real-time constraints, (2) a prototype high-level language (and corresponding compiler) to illustrate the utility of the common tasking language and the tiered programming approach in this domain, (3) an execution environment and a run-time support infrastructure that abstract a collection of heterogeneous resources into a single virtual Sensor Network, tasked via this common tasking language, and (4) novel formal methods (i.e., static analysis techniques) that verify safety properties and infer implicit resource constraints to facilitate resource allocation for new services. This thesis presents these components in detail, as well as two specific case-studies: the use of snBench to integrate physical and wireless network security, and the use of snBench as the foundation for semester-long student projects in a graduate-level Software Engineering course
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