48,948 research outputs found
Information Rates and post-FEC BER Prediction in Optical Fiber Communications
Information-theoretic metrics to analyze optical fiber communications systems
with binary and nonbinary soft-decision FEC are reviewed. The numerical
evaluation of these metrics in both simulations and experiments is also
discussed. Ready-to-use closed-form approximations are presented.Comment: Invited paper, OFC 201
Ronald Reagan, Jesse Unruh and the California Gubernatorial Race, 1970
This essay examines the 1970 gubernatorial race in California between incumbent Ronald Reagan and powerful California legislator Jesse Unruh. Most of the scholarship on this particular subject tends to revolve around Reagan\u27s first campaign for governor, but neglects his re-election campaign. Although Unruh would lose the campaign, he narrowed Reagan\u27s win significantly. This study examines the candidates themselves, the issues facing California at the time, strategies used by each camp, and possible reasons why voters strayed from Reagan to the Unruh camp, and the final outcome of the race
Fixed points of endomorphisms of complex tori
We study the asymptotic behavior of the cardinality of the fixed point set of
iterates of an endomorphism of a complex torus. We show that there are
precisely three types of behavior of this function: it is either an
exponentially growing function, a periodic function, or a product of both.Comment: Some typos corrected; the introduction was also revise
On the BICM Capacity
Optimal binary labelings, input distributions, and input alphabets are
analyzed for the so-called bit-interleaved coded modulation (BICM) capacity,
paying special attention to the low signal-to-noise ratio (SNR) regime. For
8-ary pulse amplitude modulation (PAM) and for 0.75 bit/symbol, the folded
binary code results in a higher capacity than the binary reflected gray code
(BRGC) and the natural binary code (NBC). The 1 dB gap between the additive
white Gaussian noise (AWGN) capacity and the BICM capacity with the BRGC can be
almost completely removed if the input symbol distribution is properly
selected. First-order asymptotics of the BICM capacity for arbitrary input
alphabets and distributions, dimensions, mean, variance, and binary labeling
are developed. These asymptotics are used to define first-order optimal (FOO)
constellations for BICM, i.e. constellations that make BICM achieve the Shannon
limit -1.59 \tr{dB}. It is shown that the \Eb/N_0 required for reliable
transmission at asymptotically low rates in BICM can be as high as infinity,
that for uniform input distributions and 8-PAM there are only 72 classes of
binary labelings with a different first-order asymptotic behavior, and that
this number is reduced to only 26 for 8-ary phase shift keying (PSK). A general
answer to the question of FOO constellations for BICM is also given: using the
Hadamard transform, it is found that for uniform input distributions, a
constellation for BICM is FOO if and only if it is a linear projection of a
hypercube. A constellation based on PAM or quadrature amplitude modulation
input alphabets is FOO if and only if they are labeled by the NBC; if the
constellation is based on PSK input alphabets instead, it can never be FOO if
the input alphabet has more than four points, regardless of the labeling.Comment: Submitted to the IEEE Transactions on Information Theor
Standard Model Extension with Flipped Generations
An extension of the Standard Model is presented that leads to the possible
existence of new gauge bosons with masses in the range of a few TeV. Due to the
fact that their couplings to Standard Model fermions are strongly suppressed,
it is possible for them to be hidden from current searches. The model contains
additional generations of fermions with quantum numbers resembling those of the
Standard Model fermion generations but with a twist: their charge assignments
are such that their electric charges and chiralities are flipped with respect
to those of their corresponding Standard Model counterparts. This feature
provides a way to obtain potential dark matter candidates and the interesting
possibility for a Lepton number conserving dimension-five operator for Dirac
neutrino masses. The model implications associated to electroweak precision
parameters, flavor changing neutral currents, and diphoton rate contributions
are briefly discussed. The general assumptions of this set up are also used to
sketch a couple of variants of the model with peculiar features that could
motivate further study.Comment: 8 pages, 3 figures, 2 tables. Discussion on W' boson and RH neutrinos
extended, references added, typos corrected, title changed. Matches published
version in PL
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