21,151 research outputs found
Effects of Rate Adaption on the Throughput of Random Ad Hoc Networks
No full textThe capacity of wireless ad hoc networks has been studied in an excellent treatise by Gupta and Kumar [1], assuming a fixed transmission rate. By contrast, in this treatise we investigate the achievable throughput improvement of rate adaptation in the context of random ad hoc networks, which have been studied in conjunction with a fixed transmission rate in [1]. Our analysis shows that rate adaptation has the potential of improving the achievable throughput compared to fixed rate transmission, since rate adaptation mitigates the effects of link quality fluctuations. However, even perfect rate control fails to change the scaling law of the per-node throughput result given in [1], regardless of the absence or presence of shadow fading. This result is confirmed in the context of specific adaptive modulation aided design examples
Bibliographics for the 983 eprints in the live archives of E-LIS : trends and status report up to 7th July 2004, based on author-self-archiving metadata
No full textThe priority for ideas and philosophy related to "Network Theory" have been traced back and documented by Braun(2004),and credit goes to Karinthy(1929).The IT has empowered to realise it, as the most practical phenomena and it is no more a humour. The OAI (Open Archives Initiatives)and ACIS (Academic Contributor Information System)are progressive in the direction ,which may lead to realise the "Collective Genius" at global level. Focus of present study is on Author-Self-Archiving (A-S-A)Metadata of the 983 Eprints in the Live Archives of the E-LIS (EPrints of Library and Information Science),which were approved till 7th July 2004.The A-S-A Metadata was used for librametric analysis. Self-explanatory bibliographics are illustrated.The highlights include: Conference papers (34%); highest approval, June 2004 (28%); published archives (76%);not refereed (52%); not in public domain (60%); highest self-archiving-author (De Robbio, Antonella).The Nos. of EPrints having single JITA domain specifications were: Theoretical and general aspects of libraries and information(27); Information use and sociology of information(80);Users,literacy and reading(13);Libraries as physical collections(30);Publishing and legal issues(57);Management(13);Industry, profession and education(36);Information sources, supports, channels(113) ; Information treatment for information services, Information functions and techniques (101); Technical services libraries, archives and museums(25); Housing technologies(1); Information technology and library technology(92); and Inter-domainery (395) i.e. having specifications of two or more than two JITA classes
Editorial: Biotechnology of plant secondary metabolites: Phytochemical biopharming as a sustainable contribution to a high-tech bioeconomy
No full textPlant cell and tissue culture has made a great contribution to the advance of knowledge in plant biotechnology (Altman 2019). Today thousands of biotech companies distributed around the world produce millions of micropropagated plants, contributing to certified seed programs of a wide spectrum of commercial varieties for the agricultural, forestry and food industries. However, the biotechnological production of secondary metabolites has lagged behind the previously mentioned advances in translational plant biotechnology. So much so that with current developments in cell biology, cell, tissue and plant cultures are considered tools that should promote the use of plant biodiversity as an essential biotechnological resource focused on the production of natural phytocompounds for a wide spectrum of applications (Pasdaran and Hamedi 2017; Ochatt et al., 2022
Quorum based geographically static data storage in ad-hoc networks
No full textLarge-scale wireless ad-hoc networks are formed automatically and allow nodes to communicate over greater distances. Every node acts as a router forming a complex network, which is simplified by the use of geodesic routing. However, a method to discover a node.s location is needed for geodesic routing. In this paper we propose two algorithms which could support location servers in ad-hoc networks and examine their performance
Link stability estimation based on link connectivity changes in mobile ad-hoc networks
No full textDear Wang,
Re: Link Stability Estimation Based on Link Connectivity Changes in Mobile Ad-hoc Networks
I have not been able to assess if this is an author version peer-reviewed or is it an author version non peer reviewed. Could you please clarify this so I can proceed to add your paper to Spiral. Spiral digital repository only accept peer-reviewed papers.
30/11/12 author has confirmed peer reviewe
Modulo and grid based channel selection in ad hoc networks
No full textIn this paper, we describe several approaches to spatial-reuse in ad-hoc networks using multiple channels. We analyse many techniques requiring only information available locally and those that do not collaborate with neighbouring nodes. Our justification for this is to avoid extra network overhead. The results we obtain show that intelligent allocation of channels can make a significant performance improvement over that of simply using all available. We propose several approaches to allocating the channels intelligently and a grid-based approach that only requires Global Positioning information
Cerebral atrophy in mild cognitive impairment and Alzheimer disease: rates and acceleration.
No full textOBJECTIVE: To quantify the regional and global cerebral atrophy rates and assess acceleration rates in healthy controls, subjects with mild cognitive impairment (MCI), and subjects with mild Alzheimer disease (AD). METHODS: Using 0-, 6-, 12-, 18-, 24-, and 36-month MRI scans of controls and subjects with MCI and AD from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, we calculated volume change of whole brain, hippocampus, and ventricles between all pairs of scans using the boundary shift integral. RESULTS: We found no evidence of acceleration in whole-brain atrophy rates in any group. There was evidence that hippocampal atrophy rates in MCI subjects accelerate by 0.22%/year2 on average (p = 0.037). There was evidence of acceleration in rates of ventricular enlargement in subjects with MCI (p = 0.001) and AD (p < 0.001), with rates estimated to increase by 0.27 mL/year2 (95% confidence interval 0.12, 0.43) and 0.88 mL/year2 (95% confidence interval 0.47, 1.29), respectively. A post hoc analysis suggested that the acceleration of hippocampal loss in MCI subjects was mainly driven by the MCI subjects that were observed to progress to clinical AD within 3 years of baseline, with this group showing hippocampal atrophy rate acceleration of 0.50%/year2 (p = 0.003). CONCLUSIONS: The small acceleration rates suggest a long period of transition to the pathologic losses seen in clinical AD. The acceleration in hippocampal atrophy rates in MCI subjects in the ADNI seems to be driven by those MCI subjects who concurrently progressed to a clinical diagnosis of AD
Design and investigation of scalable multicast recursive protocols for wired and wireless ad hoc networks
No full textThe ever-increasing demand on content distribution and media streaming over the Internet has created the need for efficient methods of delivering information. One of the most promising approaches is based on multicasting. However, multicast solutions have to cope with several constraints as well as being able to perform in different environments such as wired, wireless, and ad hoc environments. Additionally, the scale and size of the Internet introduces another dimension of difficulty. Providing scalable multicast for mobile hosts in wireless environment and in mobile ad hoc networks (MANETs) is a challenging problem. In
the past few years, several protocols have been proposed to efficient multicast solutions over the Internet, but these protocols did not give efficient solution for the scalability issue. In this thesis, scalable multicast protocols for wired, wireless and wireless ad hoc networks are
proposed and evaluated. These protocols share the idea of building up a multicast tree
gradually and recursively as join/leave of the multicast group members using a dynamic
branching node-based tree (DBT) concept. The DBT uses a pair of branching node messages
(BNMs). These messages traverse between a set of dynamically assigned branching node
routers (BNRs) to build the multicast tree. In the proposed protocols only the branching node routers (BNRs) carry the state information about their next BNRs rather than the multicast group members, which gives a fixed size of control packet header size as the multicast group size increases, i.e. a good solution to the problem of scalability. Also the process of join/leave of multicast group members is carried out locally which gives low join/leave latency.
The proposed protocols include: Scalable Recursive Multicast protocol (SReM) which is
proposed using the DBT concepts mentioned above, Mobile Scalable Recursive Multicast
protocol (MoSReM) which is an extension for SReM by taking into consideration the
mobility feature in the end hosts and performing an efficient roaming process, and finally, a Scalable Ad hoc Recursive Multicast protocol (SARM) to achieve the mobility feature for all nodes and performing an efficient solution for link recovery because of node movement. By cost analysis and an extensive simulation, the proposed protocols show many positive features like fixed size control messages, being scalable, low end to end delay, high packet rate delivery and low normalized routing overhead. The thesis concludes by discussing the
contributions of the proposed protocols on scalable multicast in the Internet society
A trust framework for peer-to-peer interaction in ad hoc networks
No full textPhDAs a wider public is increasingly adopting mobile devices with diverse applications,
the idea of who to trust while on the move becomes a crucial one. The need to find
dependable partners to interact is further exacerbated in situations where one finds
oneself out of the range of backbone structures such as wireless base stations or
cellular networks. One solution is to generate self-started networks, a variant of
which is the ad hoc network that promotes peer-to-peer networking. The work in
this thesis is aimed at defining a framework for such an ad hoc network that provides
ways for participants to distinguish and collaborate with their most trustworthy
neighbours.
In this framework, entities create the ability to generate trust information by directly
observing the behaviour of their peers. Such trust information is also shared in order
to assist those entities in situations where prior interactions with their target peers
may not have existed.
The key novelty points of the framework focus on aggregating the trust evaluation
process around the most trustworthy nodes thereby creating a hierarchy of nodes that
are distinguished by the class, defined by cluster heads, to which they belong.
Furthermore, the impact of such a framework in generating additional overheads for
the network is minimised through the use of clusters. By design, the framework also
houses a rule-based mechanism to thwart misbehaving behaviour or non-cooperation.
Key performance indicators are also defined within this work that allow a framework
to be quickly analysed through snapshot data, a concept analogous to those used
within financial circles when assessing companies. This is also a novel point that
may provide the basis for directly comparing models with different underlying
technologies.
The end result is a trust framework that fully meets the basic requirements for a
sustainable model of trust that can be developed onto an ad hoc network and that
provides enhancements in efficiency (using clustering) and trust performance
A Fair and Secure Cluster Formation Process for Ad Hoc Networks
No full textAn efficient approach for organizing large ad hoc networks is to divide the nodes
into multiple clusters and designate, for each cluster, a clusterhead which is responsible for
holding intercluster control information. The role of a clusterhead entails rights and duties.
On the one hand, it has a dominant position in front of the others because it manages the
connectivity and has access to other node¿s sensitive information. But on the other hand, the
clusterhead role also has some associated costs. Hence, in order to prevent malicious nodes
from taking control of the group in a fraudulent way and avoid selfish attacks from suitable
nodes, the clusterhead needs to be elected in a secure way. In this paper we present a novel
solution that guarantees the clusterhead is elected in a cheat-proof manner
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