19,609 research outputs found
A survey of performance enhancement of transmission control protocol (TCP) in wireless ad hoc networks
This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2011 Springer OpenTransmission control protocol (TCP), which provides reliable end-to-end data delivery, performs well in traditional wired network environments, while in wireless ad hoc networks, it does not perform well. Compared to wired networks, wireless ad hoc networks have some specific characteristics such as node mobility and a shared medium. Owing to these specific characteristics of wireless ad hoc networks, TCP faces particular problems with, for example, route failure, channel contention and high bit error rates. These factors are responsible for the performance degradation of TCP in wireless ad hoc networks. The research community has produced a wide range of proposals to improve the performance of TCP in wireless ad hoc networks. This article presents a survey of these proposals (approaches). A classification of TCP improvement proposals for wireless ad hoc networks is presented, which makes it easy to compare the proposals falling under the same category. Tables which summarize the approaches for quick overview are provided. Possible directions for further improvements in this area are suggested in the conclusions. The aim of the article is to enable the reader to quickly acquire an overview of the state of TCP in wireless ad hoc networks.This study is partly funded by Kohat University of Science & Technology (KUST),
Pakistan, and the Higher Education Commission, Pakistan
Agile-SD: A Linux-based TCP Congestion Control Algorithm for Supporting High-speed and Short-distance Networks
Recently, high-speed and short-distance networks are widely deployed and
their necessity is rapidly increasing everyday. This type of networks is used
in several network applications; such as Local Area Networks (LAN) and Data
Center Networks (DCN). In LANs and DCNs, high-speed and short-distance networks
are commonly deployed to connect between computing and storage elements in
order to provide rapid services. Indeed, the overall performance of such
networks is significantly influenced by the Congestion Control Algorithm (CCA)
which suffers from the problem of bandwidth under-utilization, especially if
the applied buffer regime is very small. In this paper, a novel loss-based CCA
tailored for high-speed and Short-Distance (SD) networks, namely Agile-SD, has
been proposed. The main contribution of the proposed CCA is to implement the
mechanism of agility factor. Further, intensive simulation experiments have
been carried out to evaluate the performance of Agile-SD compared to Compound
and Cubic which are the default CCAs of the most commonly used operating
systems. The results of the simulation experiments show that the proposed CCA
outperforms the compared CCAs in terms of average throughput, loss ratio and
fairness, especially when a small buffer is applied. Moreover, Agile-SD shows
lower sensitivity to the buffer size change and packet error rate variation
which increases its efficiency.Comment: 12 Page
Mining developer communication data streams
This paper explores the concepts of modelling a software development project
as a process that results in the creation of a continuous stream of data. In
terms of the Jazz repository used in this research, one aspect of that stream
of data would be developer communication. Such data can be used to create an
evolving social network characterized by a range of metrics. This paper
presents the application of data stream mining techniques to identify the most
useful metrics for predicting build outcomes. Results are presented from
applying the Hoeffding Tree classification method used in conjunction with the
Adaptive Sliding Window (ADWIN) method for detecting concept drift. The results
indicate that only a small number of the available metrics considered have any
significance for predicting the outcome of a build
Landscape of standing variation for tandem duplications in Drosophila yakuba and Drosophila simulans
We have used whole genome paired-end Illumina sequence data to identify
tandem duplications in 20 isofemale lines of D. yakuba, and 20 isofemale lines
of D. simulans and performed genome wide validation with PacBio long molecule
sequencing. We identify 1,415 tandem duplications that are segregating in D.
yakuba as well as 975 duplications in D. simulans, indicating greater variation
in D. yakuba. Additionally, we observe high rates of secondary deletions at
duplicated sites, with 8% of duplicated sites in D. simulans and 17% of sites
in D. yakuba modified with deletions. These secondary deletions are consistent
with the action of the large loop mismatch repair system acting to remove
polymorphic tandem duplication, resulting in rapid dynamics of gain and loss in
duplicated alleles and a richer substrate of genetic novelty than has been
previously reported. Most duplications are present in only single strains,
suggesting deleterious impacts are common. D. simulans shows larger numbers of
whole gene duplications in comparison to larger proportions of gene fragments
in D. yakuba. D. simulans displays an excess of high frequency variants on the
X chromosome, consistent with adaptive evolution through duplications on the D.
simulans X or demographic forces driving duplicates to high frequency. We
identify 78 chimeric genes in D. yakuba and 38 chimeric genes in D. simulans,
as well as 143 cases of recruited non-coding sequence in D. yakuba and 96 in D.
simulans, in agreement with rates of chimeric gene origination in D.
melanogaster. Together, these results suggest that tandem duplications often
result in complex variation beyond whole gene duplications that offers a rich
substrate of standing variation that is likely to contribute both to
detrimental phenotypes and disease, as well as to adaptive evolutionary change.Comment: Revised Version- Accepted at Molecular Biology and Evolutio
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