5,765 research outputs found
On the Relationship between Transmission Power and Capacity of an Underwater Acoustic Communication Channel
The underwater acoustic channel is characterized by a path loss that depends
not only on the transmission distance, but also on the signal frequency. As a
consequence, transmission bandwidth depends on the transmission distance, a
feature that distinguishes an underwater acoustic system from a terrestrial
radio system. The exact relationship between power, transmission band, distance
and capacity for the Gaussian noise scenario is a complicated one. This work
provides a closed-form approximate model for 1) power consumption, 2) band-edge
frequency and 3) bandwidth as functions of distance and capacity required for a
data link. This approximate model is obtained by numerical evaluation of
analytical results which takes into account physical models of acoustic
propagation loss and ambient noise. The closed-form approximations may become
useful tools in the design and analysis of underwater acoustic networks.Comment: 6 pages, 9 Figures, Awaiting acceptance to IEEE Oceans 08
(Conference), Kobe, Japa
Orbital Angular Momentum Waves: Generation, Detection and Emerging Applications
Orbital angular momentum (OAM) has aroused a widespread interest in many
fields, especially in telecommunications due to its potential for unleashing
new capacity in the severely congested spectrum of commercial communication
systems. Beams carrying OAM have a helical phase front and a field strength
with a singularity along the axial center, which can be used for information
transmission, imaging and particle manipulation. The number of orthogonal OAM
modes in a single beam is theoretically infinite and each mode is an element of
a complete orthogonal basis that can be employed for multiplexing different
signals, thus greatly improving the spectrum efficiency. In this paper, we
comprehensively summarize and compare the methods for generation and detection
of optical OAM, radio OAM and acoustic OAM. Then, we represent the applications
and technical challenges of OAM in communications, including free-space optical
communications, optical fiber communications, radio communications and acoustic
communications. To complete our survey, we also discuss the state of art of
particle manipulation and target imaging with OAM beams
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