44,709 research outputs found
A stochastic control approach for scheduling multimedia transmissions over a polled multiaccess fading channel
We develop scheduling strategies for carrying multimedia traffic over a polled multiple access wireless network with fading. We consider a slotted system with three classes of traffic (voice, streaming media and file transfers). A Markov model is used for the fading and also for modeling voice packet arrivals and streaming arrivals. The performance objectives are a loss probability for voice, mean network delay for streaming media, and time average throughput for file transfers. A central scheduler (e.g., the access point in a single cell IEEE 802.11 wireless local area network (WLAN)) is assumed to be able to keep track of all the available state information and make the scheduling decision in each slot (e.g., as would be the case for PCF mode operation of the IEEE 802.11 WLAN). The problem is modeled as a constrained Markov decision problem. By using constraint relaxations (a linear relaxation and Whittle type relaxations) an index based policy is obtained. For the file transfers the decision problem turns out to be one with partial state information. Numerical comparisons are provided with the performance obtained from some simple policies
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
- …