5,280 research outputs found
On Reliability of Underwater Magnetic Induction Communications with Tri-Axis Coils
Underwater magnetic induction communications (UWMICs) provide a low-power and
high-throughput solution for autonomous underwater vehicles (AUVs), which are
envisioned to explore and monitor the underwater environment. UWMIC with
tri-axis coils increases the reliability of the wireless channel by exploring
the coil orientation diversity. However, the UWMIC channel is different from
typical fading channels and the mutual inductance information (MII) is not
always available. It is not clear the performance of the tri-axis coil MIMO
without MII. Also, its performances with multiple users have not been
investigated. In this paper, we analyze the reliability and multiplexing gain
of UWMICs with tri-axis coils by using coil selection. We optimally select the
transmit and receive coils to reduce the computation complexity and power
consumption and explore the diversity for multiple users. We find that without
using all the coils and MII, we can still achieve reliability. Also, the
multiplexing gain of UWMIC without MII is 5dB smaller than typical terrestrial
fading channels. The results of this paper provide a more power-efficient way
to use UWMICs with tri-axis coils
PrisCrawler: A Relevance Based Crawler for Automated Data Classification from Bulletin Board
Nowadays people realize that it is difficult to find information simply and
quickly on the bulletin boards. In order to solve this problem, people propose
the concept of bulletin board search engine. This paper describes the
priscrawler system, a subsystem of the bulletin board search engine, which can
automatically crawl and add the relevance to the classified attachments of the
bulletin board. Priscrawler utilizes Attachrank algorithm to generate the
relevance between webpages and attachments and then turns bulletin board into
clear classified and associated databases, making the search for attachments
greatly simplified. Moreover, it can effectively reduce the complexity of
pretreatment subsystem and retrieval subsystem and improve the search
precision. We provide experimental results to demonstrate the efficacy of the
priscrawler.Comment: published in GCIS of IEEE WRI '0
Enhancing quantum entropy in vacuum-based quantum random number generator
Information-theoretically provable unique true random numbers, which cannot
be correlated or controlled by an attacker, can be generated based on quantum
measurement of vacuum state and universal-hashing randomness extraction.
Quantum entropy in the measurements decides the quality and security of the
random number generator. At the same time, it directly determine the extraction
ratio of true randomness from the raw data, in other words, it affects quantum
random numbers generating rate obviously. In this work, considering the effects
of classical noise, the best way to enhance quantum entropy in the vacuum-based
quantum random number generator is explored in the optimum dynamical
analog-digital converter (ADC) range scenario. The influence of classical noise
excursion, which may be intrinsic to a system or deliberately induced by an
eavesdropper, on the quantum entropy is derived. We propose enhancing local
oscillator intensity rather than electrical gain for noise-independent
amplification of quadrature fluctuation of vacuum state. Abundant quantum
entropy is extractable from the raw data even when classical noise excursion is
large. Experimentally, an extraction ratio of true randomness of 85.3% is
achieved by finite enhancement of the local oscillator power when classical
noise excursions of the raw data is obvious.Comment: 12 pages,8 figure
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