23,426 research outputs found
On Greedy Routing in Dynamic UAV Networks
Unmanned aerial vehicles (UAVs), commonly known as drones, are becoming
increasingly popular for various applications. Freely flying drones create
highly dynamic environments, where conventional routing algorithms which rely
on stationary network contact graphs fail to perform efficiently. Also, link
establishment through exploring optimal paths using hello messages (as is used
in AODV algorithm) deems extremely inefficient and costly for rapidly changing
network topologies.
In this paper, we present a distance-based greedy routing algorithm for UAV
networks solely based on UAVs' local observations of their surrounding
subnetwork. Thereby, neither a central decision maker nor a time-consuming
route setup and maintenance mechanism are required. To evaluate the proposed
method, we derive an analytical bound for the expected number of hops that a
packet traverses. Also, we find the expected end-to-end distance traveled by
each packet as well as the probability of successful delivery. The simulation
results verify the accuracy of the developed analytical expressions and show
considerable improvement compared to centralized shortest path routing
algorithms.Comment: 7 pages, 5 figures, accepted in IEEE International Conference on
Sensing, Communication and Networking (SECON), Workshop on Communications,
Data Processing and Control for Unmanned Autonomous Systems (CPC-UAV
Understanding object-oriented source code from the behavioural perspective
Comprehension is a key activity that underpins a variety of software maintenance and engineering tasks. The task of understanding object-oriented systems is hampered by the fact that the code segments that are related to a user-level function tend to be distributed across the system. We introduce a tool-supported code extraction technique that addresses this issue. Given a minimal amount of information about a behavioural element of the system that is of interest (such as a use-case), it extracts a trail of the methods (and method invocations) through the system that are needed in order to achieve an understanding of the implementation of the element of interest. We demonstrate the feasibility of our approach by implementing it as part of a code extraction tool, presenting a case study and evaluating the approach and tool against a set of established criteria for program comprehension tools
ConSUS: A light-weight program conditioner
Program conditioning consists of identifying and removing a set of statements which cannot be executed when a condition of interest holds at some point in a program. It has been applied to problems in maintenance, testing, re-use and re-engineering. All current approaches to program conditioning rely upon both symbolic execution and reasoning about symbolic predicates. The reasoning can be performed by a ‘heavy duty’ theorem prover but this may impose unrealistic performance constraints.
This paper reports on a lightweight approach to theorem proving using the FermaT Simplify decision procedure. This is used as a component to ConSUS, a program conditioning system for the Wide Spectrum Language WSL. The paper describes the symbolic execution algorithm used by ConSUS, which prunes as it conditions.
The paper also provides empirical evidence that conditioning produces a significant reduction in program size and, although exponential in the worst case, the conditioning system has low degree polynomial behaviour in many cases, thereby making it scalable to unit level applications of program conditioning
ConSIT: A conditioned program slicer
Conditioned slicing is a powerful generalisation of static and dynamic slicing which has applications to many problems in software maintenance and evolution, including reuse, reengineering and program comprehension. However there has been relatively little work on the implementation of conditioned slicing. Algorithms for implementing conditioned slicing necessarily involve reasoning about the values of program predicates in certain sets of states derived from the conditioned slicing criterion, making implementation particularly demanding. The paper introduces ConSIT, a conditioned slicing system which is based upon conventional static slicing, symbolic execution and theorem proving. ConSIT is the first fully automated implementation of conditioned slicing. An implementation of ConSIT is available for experimentation at &http://www.mcs.gold.ac.uk/tilde/~mas01sd/consit.htm
On the Cost of Participating in a Peer-to-Peer Network
In this paper, we model the cost incurred by each peer participating in a
peer-to-peer network. Such a cost model allows to gauge potential disincentives
for peers to collaborate, and provides a measure of the ``total cost'' of a
network, which is a possible benchmark to distinguish between proposals. We
characterize the cost imposed on a node as a function of the experienced load
and the node connectivity, and show how our model applies to a few proposed
routing geometries for distributed hash tables (DHTs). We further outline a
number of open questions this research has raised.Comment: 17 pages, 4 figures. Short version to be published in the Proceedings
of the Third International Workshop on Peer-to-Peer Systems (IPTPS'04). San
Diego, CA. February 200
Small-world networks, distributed hash tables and the e-resource discovery problem
Resource discovery is one of the most important underpinning problems behind producing a scalable,
robust and efficient global infrastructure for e-Science. A number of approaches to the resource discovery
and management problem have been made in various computational grid environments and prototypes
over the last decade. Computational resources and services in modern grid and cloud environments can be
modelled as an overlay network superposed on the physical network structure of the Internet and World
Wide Web. We discuss some of the main approaches to resource discovery in the context of the general
properties of such an overlay network. We present some performance data and predicted properties based
on algorithmic approaches such as distributed hash table resource discovery and management. We describe
a prototype system and use its model to explore some of the known key graph aspects of the global
resource overlay network - including small-world and scale-free properties
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