938 research outputs found
On the Impact of Optimal Modulation and FEC Overhead on Future Optical Networks
The potential of optimum selection of modulation and forward error correction
(FEC) overhead (OH) in future transparent nonlinear optical mesh networks is
studied from an information theory perspective. Different network topologies
are studied as well as both ideal soft-decision (SD) and hard-decision (HD) FEC
based on demap-and-decode (bit-wise) receivers. When compared to the de-facto
QPSK with 7% OH, our results show large gains in network throughput. When
compared to SD-FEC, HD-FEC is shown to cause network throughput losses of 12%,
15%, and 20% for a country, continental, and global network topology,
respectively. Furthermore, it is shown that most of the theoretically possible
gains can be achieved by using one modulation format and only two OHs. This is
in contrast to the infinite number of OHs required in the ideal case. The
obtained optimal OHs are between 5% and 80%, which highlights the potential
advantage of using FEC with high OHs.Comment: Some minor typos were correcte
Mindfulness Program for Student Athletes
Student athletes face challenging situations during their time at college which can cause their experience to be a negative one if they are not fully supported. This can be due to several factors; most athletes face an immense amount of pressure to succeed in the classroom as well as in their sport. Also, many athletes are moving away from home for the first time and this can be a daunting feeling. They are expected to manage all of these challenges, and if mishandled, it can lead to an overwhelming amount of negative stress resulting in an unsuccessful time as a student athlete. Furthermore, the intensity and pressure of their sport can be detrimental to other areas of their life. Many of these young athletes do not possess the leadership skills necessary to manage these tasks and remain in a healthy state of mind.
My recommendation is not to take away these challenges, but rather offer support systems which empower student athletes to be able to manage the struggles they encounter in university settings. This mindfulness program enables people to be present and aware of themselves, acknowledge what their body is saying to them, and take action in a calm focused way to move into a healthy state of mind. My program offers communication at the individual and group level, techniques to be present, manage stress, and motivate positive thoughts which create pathways for successful experiences.
Mindfulness practices are new to sports and are not currently applied to college athletics; however, the stress and challenges associated with being a student athlete are ever present. Therefore, I argue that college programs/coaches need to provide support systems which help their students be successful. This would then become a platform whereby they could succeed athletically, academically, personally, and prepare them for life outside of college
The association between cardiorespiratory fitness and cardiometabolic risk in children is mediated by abdominal adiposity: the HAPPY study
Background: It is unclear whether cardiorespiratory fitness (CRF) is independently linked to cardiometabolic risk in children. This study investigated a) the association between CRF level and presence of cardiometabolic risk disorders using health-related cut points, and b) whether these associations were mediated by abdominal adiposity in children. Methods: This was a cross-sectional design study. Anthropometry, biochemical parameters and CRF were assessed in 147 schoolchildren (75 girls) aged 10-14 years. CRF was determined using a maximal cycle ergometer test. Children were classified as ‘fit’ or ‘unfit’ according to published thresholds. Logistic regression was used to investigate the odds of having individual and clustered cardiometabolic risk factors according to CRF level and whether abdominal adiposity mediated these associations. Results: Children classified as unfit had increased odds of presenting individual and clustered cardiometabolic risk factors (p 0.05). Conclusions: This study suggests that the association between CRF and cardiometabolic risk is mediated by abdominal adiposity in 10-14 year-old children and that abdominal adiposity may be a more important determinant of adverse cardiometabolic health in this age group
Why compensating fibre nonlinearity will never meet capacity demands
Current research efforts are focussed on overcoming the apparent limits of
communication in single mode optical fibre resulting from distortion due to
fibre nonlinearity. It has been experimentally demonstrated that this Kerr
nonlinearity limit is not a fundamental limit; thus it is pertinent to review
where the fundamental limits of optical communications lie, and direct future
research on this basis. This paper details recently presented results. The work
herein briefly reviews the intrinsic limits of optical communication over
standard single mode optical fibre (SMF), and shows that the empirical limits
of silica fibre power handling and transceiver design both introduce a
practical upper bound to the capacity of communication using SMF, on the order
of 1 Pbit/s. Transmission rates exceeding 1 Pbit/s are shown to be possible,
however, with currently available optical fibres, attempts to transmit beyond
this rate by simply increasing optical power will lead to an asymptotically
zero fractional increase in capacity.Comment: 4 pages, 2 figure
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Approximating the Partially Coherent Additive White Gaussian Noise Channel in Polar Coordinates
We consider the partially coherent additive white
Gaussian noise channel (PCAWGN) in optical communications
and review the derivation of the exact channel conditional
probability model in a closed-form solution in polar coordinates.
In addition, we derive a reduced-complexity approximation
by replacing the Rician and Tikhonov distributions describing amplitude and phase components, respectively, with their
Gaussian approximation under certain assumptions of high
SNR and low phase noise or jitter. Our proposal significantly
reduces the hardware complexity by removing the modified
Bessel functions involved in the exact solution. Furthermore,
we compare the proposed approximation with a different metric
previously found in the literature and observe that for maximumlikelihood hard symbol decision, both models are in perfect
agreement with the optimal detector. However, our model not only
reduces the required number of multiplications from 12 to 8 and
additions from 9 to 3 (per computed symbol) but also reduces
the information loss by at least one and up to several orders of
magnitude with respect to the previously published metric when
used to compute the channel achievable information rate (AIR).
In all the simulation cases, we use QAM constellations of orders
4, 8, 16, and 32 as test input symbol sets
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Machine Learning based Noise Estimation in Optical Fiber Communication Networks
In this paper, we discuss a machine learning based approach to jointly estimating both linear and nonlinear noise contributions in an optical fiber communication link. We will expound the rational for utilizing machine learning for this problem, before discussing current progress and then concluding with future research directions.The authors gratefully acknowledge the donation of equipment, funding and support from Ciena. This research was performed under the auspices of a Ciena university collaborative research grant. S. J. Savory also acknowledges support from UK EPSRC (through the project INSIGHT EP/L026155/2)
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