Showing posts with label matlab. Show all posts
Showing posts with label matlab. Show all posts
Thursday, 3 January 2013
Performance Analysis of a Laser Ground-Station-to-Satellite Link With Modulated Gamma-Distributed Irradiance Fluctuations
Performance Analysis of a Laser
Ground-Station-to-Satellite Link With
Modulated Gamma-Distributed
Irradiance Fluctuations
Abstract—The performance of a ground-station-to-space
laser uplink with a Gaussian-beam wave model subject to
turbulence and beam wander effects is the topic of the
present study. The modulated gamma distribution is used to
describe the combined effect of the above two deteriorating
factors. At first, a versatile expression of the above probability
density function is deduced. We then derive novel closedform
expressions for its cumulative distribution function
and the moment-generating function. The scintillation index
and the probability of fade are hence readily evaluated. The
analysis is completed with the evaluation of the bit error
rate assuming heterodyne detection with differential phaseshift
keying. In order to attain an adequate error rate target,
we incorporate diversity at the satellite receiver. A proper
simulation scenario is adopted, and numerical results are
provided to verify the accuracy of the derived expressions.
Free-Space Optical Communication Through Atmospheric Turbulence Channels
Free-Space Optical Communication Through
Atmospheric Turbulence Channels
Abstract—In free-space optical communication links, atmospheric
turbulence causes fluctuations in both the intensity and
the phase of the received light signal, impairing link performance.
In this paper, we describe several communication techniques to
mitigate turbulence-induced intensity fluctuations, i.e., signal
fading. These techniques are applicable in the regime in which the
receiver aperture is smaller than the correlation length of fading
and the observation interval is shorter than the correlation time
of fading. We assume that the receiver has no knowledge of the
instantaneous fading state. When the receiver knows only the
marginal statistics of the fading, a symbol-by-symbol ML detector
can be used to improve detection performance. If the receiver
has knowledge of the joint temporal statistics of the fading, maximum-
likelihood sequence detection (MLSD) can be employed,
yielding a further performance improvement, but at the cost of
very high complexity. Spatial diversity reception with multiple
receivers can also be used to overcome turbulence-induced fading.
We describe the use of ML detection in spatial diversity reception
to reduce the diversity gain penalty caused by correlation between
the fading at different receivers. In a companion paper, we
describe two reduced-complexity implementations of the MLSD,
which make use of a single-step Markov chain model for the
fading correlation in conjunction with per-survivor processing.
Index Terms—Atmospheric turbulence, free-space optical
Wednesday, 2 January 2013
Performance Analysis of Decode-and-Forward Relaying in Gamma-Gamma Fading Channels
Performance Analysis of Decode-and-Forward
Relaying in Gamma-Gamma Fading Channels
Manav R. Bhatnagar, Member, IEEE
(DF) protocol in the free space optical (FSO) links following
the Gamma-Gamma distribution. The cumulative distribution
function (cdf) and probability density function (pdf) of a random
variable containing mixture of the Gamma-Gamma and Gaussian
random variables is derived. By using the derived cdf and pdf,
average bit error rate of the DF relaying is obtained.
Tuesday, 1 January 2013
IEEE papers A COHERENT FREE SPACE OPTICAL LINK FOR LONG DISTANCE CLOCK COMPARISION, NAVIGATION, AND COMMUNICATION: THE MINI-DOLL PROJECT
A COHERENT FREE SPACE OPTICAL LINK FOR LONG DISTANCE CLOCK
COMPARISON, NAVIGATION, AND COMMUNICATION:
THE MINI-DOLL PROJECT
ABSTRACT
We describe the realization of a 5 km free space coherent optical link through the turbulent atmosphere between
a telescope and a ground target. We present the phase noise of the link, limited mainly by atmospheric
turbulence and mechanical vibrations of the telescope and the target. We discuss the implications of our results
for applications, with particular emphasis on optical Doppler ranging to satellites and long distance frequency
transfer.
For full paper mail me to kamalakannanmsajce@gmail.com
IEEE Papers on fiber optical communication ATMOSPHERIC CHANNEL EFFECTS ON TERRESTRIAL FREE SPACE OPTICAL COMMUNICATION LINKS
ATMOSPHERIC CHANNEL EFFECTS ONTERRESTRIAL FREE SPACE OPTICALCOMMUNICATION LINKS
Abstract.
This paper illustrates the challenges imposed by the
atmospheric channel on the design of a terrestrial laser communication link.
The power loss due to scattering effect is described using the Kim/Kruse
scattering model while the effect and the penalty imposed by atmospheric
turbulence is highlighted by considering the bit error rate (BER) of an On-
Off Keying modulated link in an optical Poisson channel. The power loss due
to thick fog can measure over 100 dB/km while snow and rain result in much
lower attenuation. We show that non-uniformity in the atmospheric
temperature also contributes to performance deterioration due to
scintillation effect. At a BER of 10-4, for a channel with a turbulence strength
of >0.1, the penalty imposed by turbulence induced fading is over 20
photoelectron counts in order to achieve the same level of performance as a
channel with no fading. The work reported here is part of the EU COST
actions and EU projects
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