184,171 research outputs found
Efficient memory management in VOD disk array servers usingPer-Storage-Device buffering
We present a buffering technique that reduces video-on-demand server memory requirements in more than one order of magnitude. This technique, Per-Storage-Device Buffering (PSDB), is based on the allocation of a fixed number of buffers per storage device, as opposed to existing solutions based on per-stream buffering allocation. The combination of this technique with disk array servers is studied in detail, as well as the influence of Variable Bit Streams. We also present an interleaved data placement strategy, Constant Time Length Declustering, that results in optimal performance in the service of VBR streams. PSDB is evaluated by extensive simulation of a disk array server model that incorporates a simulation based admission test.This research was supported in part by the National R&D Program of Spain, Project Number TIC97-0438.Publicad
Joint Hybrid Precoder and Combiner Design for mmWave Spatial Multiplexing Transmission
Millimeter-wave (mmWave) communications have been considered as a key
technology for future 5G wireless networks because of the orders-of-magnitude
wider bandwidth than current cellular bands. In this paper, we consider the
problem of codebook-based joint analog-digital hybrid precoder and combiner
design for spatial multiplexing transmission in a mmWave multiple-input
multiple-output (MIMO) system. We propose to jointly select analog precoder and
combiner pair for each data stream successively aiming at maximizing the
channel gain while suppressing the interference between different data streams.
After all analog precoder/combiner pairs have been determined, we can obtain
the effective baseband channel. Then, the digital precoder and combiner are
computed based on the obtained effective baseband channel to further mitigate
the interference and maximize the sum-rate. Simulation results demonstrate that
our proposed algorithm exhibits prominent advantages in combating interference
between different data streams and offer satisfactory performance improvement
compared to the existing codebook-based hybrid beamforming schemes
Using a Discriminator to Improve Compressive Sensing Efficiency
Our work defines, implements, and evaluates a modification to a spectrum-based compression scheme for data streams coming from jet aircraft health-monitoring sensors. The modification consists of the addition of a discriminator which separates data streams into similar classes. We create and justify a simulation of a jet sensor network as a source for data streams. The data streams are compressed and decompressed under the new compression scheme and also under two old ones, and the reconstructions are evaluated for quality. The discriminator-based modification to the existing compression algorithm is found to yield better quality than the other two compression algorithms, at the cost of increased runtime
Discrete event simulation and virtual reality use in industry: new opportunities and future trends
This paper reviews the area of combined discrete
event simulation (DES) and virtual reality (VR) use within industry.
While establishing a state of the art for progress in this
area, this paper makes the case for VR DES as the vehicle of choice
for complex data analysis through interactive simulation models,
highlighting both its advantages and current limitations. This paper
reviews active research topics such as VR and DES real-time
integration, communication protocols, system design considerations,
model validation, and applications of VR and DES. While
summarizing future research directions for this technology combination,
the case is made for smart factory adoption of VR DES as
a new platform for scenario testing and decision making. It is put
that in order for VR DES to fully meet the visualization requirements
of both Industry 4.0 and Industrial Internet visions of digital
manufacturing, further research is required in the areas of lower
latency image processing, DES delivery as a service, gesture recognition
for VR DES interaction, and linkage of DES to real-time data streams and Big Data sets
A survey on cost-effective context-aware distribution of social data streams over energy-efficient data centres
Social media have emerged in the last decade as a viable and ubiquitous means of communication. The ease of user content generation within these platforms, e.g. check-in information, multimedia data, etc., along with the proliferation of Global Positioning System (GPS)-enabled, always-connected capture devices lead to data streams of unprecedented amount and a radical change in information sharing. Social data streams raise a variety of practical challenges, including derivation of real-time meaningful insights from effectively gathered social information, as well as a paradigm shift for content distribution with the leverage of contextual data associated with user preferences, geographical characteristics and devices in general. In this article we present a comprehensive survey that outlines the state-of-the-art situation and organizes challenges concerning social media streams and the infrastructure of the data centres supporting the efficient access to data streams in terms of content distribution, data diffusion, data replication, energy efficiency and network infrastructure. We systematize the existing literature and proceed to identify and analyse the main research points and industrial efforts in the area as far as modelling, simulation and performance evaluation are concerned
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