| 1. |
- van de Beek, Jan-Jaap, et al.
(författare)
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A time and frequency synchronization scheme for multiuser OFDM
- 1999
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Ingår i: IEEE Journal on Selected Areas in Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8716 .- 1558-0008. ; 17:11, s. 1900-1914
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Tidskriftsartikel (refereegranskat)abstract
- We present a multiuser synchronization scheme for tracking the mobile's uplink time and frequency offsets. It uses the redundancy introduced by the cyclic prefix and does not need additional pilots. We show performance results of an orthogonal frequency division multiplexing (OFDM)-based radio interface based on universal mobile telecommunication system (UMTS) parameters. For a UMTS-typical mobile channel environment, the performance of a coherent system employing the scheme is virtually indistinguishable from the performance of a perfectly synchronized system. In a differentially modulated system, synchronization errors decrease the system performance by about 0.7 dB compared to a perfectly synchronized system. Index Terms - Communication system, delay estimation, frequency estimation, multicarrier, multiuser system, orthogonal frequency division multiplexing (OFDM), synchronization, universal mobile telecommunication system (UMTS).
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| 2. |
- van de Beek, Jaap, et al.
(författare)
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Synchronization of a TDMA-OFDM frequency hopping system
- 1998
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Ingår i: Pathway to a global wireless revolution. - Piscataway, NJ : IEEE Communications Society. - 0780343204 ; , s. 1290-1294
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a Time Division Multiple Access-Orthogonal Frequency Division Multiplexing (TDMA-OFDM)-based radio interface proposal for the Universal Mobile Telecommunication System (UMTS). We focus on synchronization and present an implementable algorithm for the tracking of the mobiles' time and frequency offsets at the base station in the uplink. This algorithm is based on recently developed estimation methods that use redundancy introduced by the cyclic prefix. A modified Maximum Likelihood (ML) estimator for the Additive White Gaussian Noise (AWGN) channel is used to meet both implementational requirements and performance requirements for frequency-selective fading multiuser environments. Simulation results for a typical UMTS mobile channel environment show that the uncoded symbol error rate of a coherently modulated system using our synchronization scheme is virtually indistinguishable from that of a system with no time and frequency offset.
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| 3. |
- van de Beek, Jaap, et al.
(författare)
-
A conceptual study of OFDM-based multiple access schemes : Part 4: Tracking of time and frequency offset
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper is part of a conceptual study of a multiuser OFDM system. In previous reports we have examined requirements for the air interface and presented uncoded performance (in terms of bit error rate) for the uplink of such systems. In this report we adopt the user allocation structure from the previous parts of the study and examine the role of channel coding. We present performance simulations that illustrate the effects of a convolutional code exploiting channel diversity, and channel estimator performance exploiting the channel correlation.
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| 4. |
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| 5. |
- Tärneberg, William, et al.
(författare)
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The 6G Computing Continuum (6GCC) : Meeting the 6G computing challenges
- 2022
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Ingår i: 2022 1st International Conference on 6G Networking, 6GNet 2022. - : IEEE Computer Society. - 9781665467636
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Konferensbidrag (refereegranskat)abstract
- 6G systems, such as Large Intelligent Surfaces, will require distributed, complex, and coordinated decisions through-out a very heterogeneous and cell free infrastructure. This will require a fundamentally redesigned software infrastructure accompanied by massively distributed and heterogeneous computing resources, vastly different from current wireless networks. To address these challenges, in this paper, we propose and motivate the concept of a 6G Computing Continuum (6GCC) and two research testbeds, to advance the rate and quality of research. 6G Computing Continuum is an end-to-end compute and software platform for realizing large intelligent surfaces and its tenant users and applications. One for addressing the challenges or orchestrating shared computational resources in the wireless domain, implemented on a Large Intelligent Surfaces testbed. Another simulation-based testbed is intended to address scalability and global-scale orchestration challenges.
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| 6. |
- Krzywda, Jakub, et al.
(författare)
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Telco Clouds: Modelling and Simulation
- 2015
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Ingår i: Proceedings of the 5th International Conference on Cloud Computing and Services Science. - : SciTePress. - 9789897581045 ; , s. 597-609
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a telco cloud meta-model that can be used to simulate different infrastructure con- figurations and explore their consequences on the system performance and costs. To achieve this, we analyse current telecommunication and data centre infrastructure paradigms, describe the architecture of the telco cloud and detail the benefits of merging both infrastructures in a unified system. Next, we detail the dynamics of the telco cloud and identify the components that are the most relevant from the perspective of modelling performance and cost. A number of well established simulation technologies exist for most of the telco cloud components, we thus proceed with surveying existing models in an attempt to construct a suitable composite meta-model. Finally, we present a showcase scenario to demonstrate the scope of our telco cloud simulator.
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| 7. |
- Beldiceanu, Nicolas, et al.
(författare)
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Assistant: Learning and robust decision support system for agile manufacturing environments
- 2021
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Ingår i: IFAC-PapersOnLine. - : Elsevier. ; , s. 641-646
-
Konferensbidrag (refereegranskat)abstract
- The European project ASSISTANT will provide a set of AI-based digital twins that helps process engineers and production planners to operate collaborative mixed-model assembly lines based on the data collected from IoT devices and external data sources. Such a tool will help planners to design the assembly line, plan the production, operate the line, and improve process tuning. In addition, the system monitors the line in real-time, ensures that all required resources are available, and allows fast re-planning when necessary. ASSISTANT aims to make cost-effective decisions while ensuring product quality, safety and wellbeing of the workers, and managing the various sources of uncertainties. The resulting digital twin systems will be data-driven, agile, autonomous, collaborative and explainable, safe but reactive.
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| 8. |
- Domaschka, Jörg, et al.
(författare)
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Towards an Architecture for Reliable Capacity Provisioning for Distributed Clouds
- 2020
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Ingår i: Managing Distributed Cloud Applications and Infrastructure. - Cham : Palgrave Macmillan. - 9783030398620 - 9783030398637 ; , s. 1-25
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Bokkapitel (refereegranskat)abstract
- The complexity of computing along the cloud-to-edge continuum presents significant challenges to ICT operations and in particular reliable capacity planning and resource provisioning to meet unpredictable, fluctuating, and mobile demand. This chapter presents a high-level conceptual overview of RECAP—an architectural innovation to support reliable capacity provisioning for distributed clouds—and its operational modes and functional building blocks. In addition, the major design concepts informing its design—namely separation of concerns, model-centricism, modular design, and machine learning and artificial intelligence for IT operations—are also discussed.
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| 9. |
- Krzywda, Jakub, et al.
(författare)
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A Sensor-Actuator Model for Data Center Optimization
- 2015
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Ingår i: 2015 International Conference on Cloud and Autonomic Computing (ICCAC). - : IEEE Computer Society. - 9781467395663 ; , s. 192-195
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Konferensbidrag (refereegranskat)abstract
- Cloud data centers commonly use virtualization technologies to provision compute capacity with a level of indirection between virtual machines and physical resources. In this paper we explore the use of that level of indirection as a means for autonomic data center configuration optimization and propose a sensor-actuator model to capture optimization-relevant relationships between data center events, monitored metrics (sensors data), and management actions (actuators). The model characterizes a wide spectrum of actions to help identify the suitability of different actions in specific situations, and outlines what (and how often) data needs to be monitored to capture, classify, and respond to events that affect the performance of data center operations.
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| 10. |
- Krzywda, Jakub, 1989-, et al.
(författare)
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ALPACA : Application Performance Aware Server Power Capping
- 2018
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Ingår i: ICAC 2018. - : IEEE Computer Society. - 9781538651391 ; , s. 41-50
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Konferensbidrag (refereegranskat)abstract
- Server power capping limits the power consumption of a server to not exceed a specific power budget. This allows data center operators to reduce the peak power consumption at the cost of performance degradation of hosted applications. Previous work on server power capping rarely considers Quality-of-Service (QoS) requirements of consolidated services when enforcing the power budget. In this paper, we introduce ALPACA, a framework to reduce QoS violations and overall application performance degradation for consolidated services. ALPACA reduces unnecessary high power consumption when there is no performance gain, and divides the power among the running services in a way that reduces the overall QoS degradation when the power is scarce. We evaluate ALPACA using four applications: MediaWiki, SysBench, Sock Shop, and CloudSuite’s Web Search benchmark. Our experiments show that ALPACA reduces the operational costs of QoS penalties and electricity by up to 40% compared to a non optimized system.
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