10,019 research outputs found
Meeting Real-Time Constraint of Spectrum Management in TV Black-Space Access
The TV set feedback feature standardized in the next generation TV system,
ATSC 3.0, would enable opportunistic access of active TV channels in future
Cognitive Radio Networks. This new dynamic spectrum access approach is named as
black-space access, as it is complementary of current TV white space, which
stands for inactive TV channels. TV black-space access can significantly
increase the available spectrum of Cognitive Radio Networks in populated urban
markets, where spectrum shortage is most severe while TV whitespace is very
limited. However, to enable TV black-space access, secondary user has to
evacuate a TV channel in a timely manner when TV user comes in. Such strict
real-time constraint is an unique challenge of spectrum management
infrastructure of Cognitive Radio Networks. In this paper, the real-time
performance of spectrum management with regard to the degree of centralization
of infrastructure is modeled and tested. Based on collected empirical network
latency and database response time, we analyze the average evacuation time
under four structures of spectrum management infrastructure: fully
distribution, city-wide centralization, national-wide centralization, and
semi-national centralization. The results show that national wide
centralization may not meet the real-time requirement, while semi-national
centralization that use multiple co-located independent spectrum manager can
achieve real-time performance while keep most of the operational advantage of
fully centralized structure.Comment: 9 pages, 7 figures, Technical Repor
S-Store: Streaming Meets Transaction Processing
Stream processing addresses the needs of real-time applications. Transaction
processing addresses the coordination and safety of short atomic computations.
Heretofore, these two modes of operation existed in separate, stove-piped
systems. In this work, we attempt to fuse the two computational paradigms in a
single system called S-Store. In this way, S-Store can simultaneously
accommodate OLTP and streaming applications. We present a simple transaction
model for streams that integrates seamlessly with a traditional OLTP system. We
chose to build S-Store as an extension of H-Store, an open-source, in-memory,
distributed OLTP database system. By implementing S-Store in this way, we can
make use of the transaction processing facilities that H-Store already
supports, and we can concentrate on the additional implementation features that
are needed to support streaming. Similar implementations could be done using
other main-memory OLTP platforms. We show that we can actually achieve higher
throughput for streaming workloads in S-Store than an equivalent deployment in
H-Store alone. We also show how this can be achieved within H-Store with the
addition of a modest amount of new functionality. Furthermore, we compare
S-Store to two state-of-the-art streaming systems, Spark Streaming and Storm,
and show how S-Store matches and sometimes exceeds their performance while
providing stronger transactional guarantees
Elastic Business Process Management: State of the Art and Open Challenges for BPM in the Cloud
With the advent of cloud computing, organizations are nowadays able to react
rapidly to changing demands for computational resources. Not only individual
applications can be hosted on virtual cloud infrastructures, but also complete
business processes. This allows the realization of so-called elastic processes,
i.e., processes which are carried out using elastic cloud resources. Despite
the manifold benefits of elastic processes, there is still a lack of solutions
supporting them.
In this paper, we identify the state of the art of elastic Business Process
Management with a focus on infrastructural challenges. We conceptualize an
architecture for an elastic Business Process Management System and discuss
existing work on scheduling, resource allocation, monitoring, decentralized
coordination, and state management for elastic processes. Furthermore, we
present two representative elastic Business Process Management Systems which
are intended to counter these challenges. Based on our findings, we identify
open issues and outline possible research directions for the realization of
elastic processes and elastic Business Process Management.Comment: Please cite as: S. Schulte, C. Janiesch, S. Venugopal, I. Weber, and
P. Hoenisch (2015). Elastic Business Process Management: State of the Art and
Open Challenges for BPM in the Cloud. Future Generation Computer Systems,
Volume NN, Number N, NN-NN., http://dx.doi.org/10.1016/j.future.2014.09.00
A Taxonomy of Data Grids for Distributed Data Sharing, Management and Processing
Data Grids have been adopted as the platform for scientific communities that
need to share, access, transport, process and manage large data collections
distributed worldwide. They combine high-end computing technologies with
high-performance networking and wide-area storage management techniques. In
this paper, we discuss the key concepts behind Data Grids and compare them with
other data sharing and distribution paradigms such as content delivery
networks, peer-to-peer networks and distributed databases. We then provide
comprehensive taxonomies that cover various aspects of architecture, data
transportation, data replication and resource allocation and scheduling.
Finally, we map the proposed taxonomy to various Data Grid systems not only to
validate the taxonomy but also to identify areas for future exploration.
Through this taxonomy, we aim to categorise existing systems to better
understand their goals and their methodology. This would help evaluate their
applicability for solving similar problems. This taxonomy also provides a "gap
analysis" of this area through which researchers can potentially identify new
issues for investigation. Finally, we hope that the proposed taxonomy and
mapping also helps to provide an easy way for new practitioners to understand
this complex area of research.Comment: 46 pages, 16 figures, Technical Repor
Research issues in real-time database systems
Cataloged from PDF version of article.Today's real-time systems are characterized by managing large volumes of data.
Efficient database management algorithms for accessing and manipulating data are
required to satisfy timing constraints of supported applications. Real-time database
systems involve a new research area investigating possible ways of applying database
systems technology to real-time systems. Management of real-time information through
a database system requires the integration of concepts from both real-time systems and
database systems. Some new criteria need to be developed to involve timing constraints
of real-time applications in many database systems design issues, such as
transaction/query processing, data buffering, CPU, and IO scheduling. In this paper, a
basic understanding of the issues in real-time database systems is provided and the
research efforts in this area are introduced. Different approaches to various problems of
real-time database systems are briefly described, and possible future research directions
are discussed
Model-Based Proactive Read-Validation in Transaction Processing Systems
Concurrency control protocols based on read-validation schemes allow transactions which are doomed to abort to still run until a subsequent validation check reveals them as invalid. These late aborts do not favor the reduction of wasted computation and can penalize performance. To counteract this problem, we present an analytical model that predicts the abort probability of transactions handled via read-validation schemes. Our goal is to determine what are the suited points-along a transaction lifetime-to carry out a validation check. This may lead to early aborting doomed transactions, thus saving CPU time. We show how to exploit the abort probability predictions returned by the model in combination with a threshold-based scheme to trigger read-validations. We also show how this approach can definitely improve performance-leading up to 14 % better turnaround-as demonstrated by some experiments carried out with a port of the TPC-C benchmark to Software Transactional Memory
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