509 research outputs found
On the Displacement for Covering a dimensional Cube with Randomly Placed Sensors
Consider sensors placed randomly and independently with the uniform
distribution in a dimensional unit cube (). The sensors have
identical sensing range equal to , for some . We are interested in
moving the sensors from their initial positions to new positions so as to
ensure that the dimensional unit cube is completely covered, i.e., every
point in the dimensional cube is within the range of a sensor. If the
-th sensor is displaced a distance , what is a displacement of minimum
cost? As cost measure for the displacement of the team of sensors we consider
the -total movement defined as the sum , for some
constant . We assume that and are chosen so as to allow full
coverage of the dimensional unit cube and .
The main contribution of the paper is to show the existence of a tradeoff
between the dimensional cube, sensing radius and -total movement. The
main results can be summarized as follows for the case of the dimensional
cube.
If the dimensional cube sensing radius is and
, for some , then we present an algorithm that uses
total expected movement (see Algorithm 2 and
Theorem 5).
If the dimensional cube sensing radius is greater than
and is a natural
number then the total expected movement is
(see Algorithm 3 and Theorem 7).
In addition, we simulate Algorithm 2 and discuss the results of our
simulations
Computing Majority with Triple Queries
Consider a bin containing balls colored with two colors. In a -query,
balls are selected by a questioner and the oracle's reply is related
(depending on the computation model being considered) to the distribution of
colors of the balls in this -tuple; however, the oracle never reveals the
colors of the individual balls. Following a number of queries the questioner is
said to determine the majority color if it can output a ball of the majority
color if it exists, and can prove that there is no majority if it does not
exist. We investigate two computation models (depending on the type of replies
being allowed). We give algorithms to compute the minimum number of 3-queries
which are needed so that the questioner can determine the majority color and
provide tight and almost tight upper and lower bounds on the number of queries
needed in each case.Comment: 22 pages, 1 figure, conference version to appear in proceedings of
the 17th Annual International Computing and Combinatorics Conference (COCOON
2011
Evaluation of Anonymized ONS Queries
Electronic Product Code (EPC) is the basis of a pervasive infrastructure for
the automatic identification of objects on supply chain applications (e.g.,
pharmaceutical or military applications). This infrastructure relies on the use
of the (1) Radio Frequency Identification (RFID) technology to tag objects in
motion and (2) distributed services providing information about objects via the
Internet. A lookup service, called the Object Name Service (ONS) and based on
the use of the Domain Name System (DNS), can be publicly accessed by EPC
applications looking for information associated with tagged objects. Privacy
issues may affect corporate infrastructures based on EPC technologies if their
lookup service is not properly protected. A possible solution to mitigate these
issues is the use of online anonymity. We present an evaluation experiment that
compares the of use of Tor (The second generation Onion Router) on a global
ONS/DNS setup, with respect to benefits, limitations, and latency.Comment: 14 page
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