2,937 research outputs found
Crystallization in large wireless networks
We analyze fading interference relay networks where M single-antenna
source-destination terminal pairs communicate concurrently and in the same
frequency band through a set of K single-antenna relays using half-duplex
two-hop relaying. Assuming that the relays have channel state information
(CSI), it is shown that in the large-M limit, provided K grows fast enough as a
function of M, the network "decouples" in the sense that the individual
source-destination terminal pair capacities are strictly positive. The
corresponding required rate of growth of K as a function of M is found to be
sufficient to also make the individual source-destination fading links converge
to nonfading links. We say that the network "crystallizes" as it breaks up into
a set of effectively isolated "wires in the air". A large-deviations analysis
is performed to characterize the "crystallization" rate, i.e., the rate (as a
function of M,K) at which the decoupled links converge to nonfading links. In
the course of this analysis, we develop a new technique for characterizing the
large-deviations behavior of certain sums of dependent random variables. For
the case of no CSI at the relay level, assuming amplify-and-forward relaying,
we compute the per source-destination terminal pair capacity for M,K converging
to infinity, with K/M staying fixed, using tools from large random matrix
theory.Comment: 30 pages, 6 figures, submitted to journal IEEE Transactions on
Information Theor
Asymptotic Capacity and Optimal Precoding Strategy of Multi-Level Precode & Forward in Correlated Channels
We analyze a multi-level MIMO relaying system where a multiple-antenna
transmitter sends data to a multipleantenna receiver through several relay
levels, also equipped with multiple antennas. Assuming correlated fading in
each hop, each relay receives a faded version of the signal transmitted by the
previous level, performs precoding on the received signal and retransmits it to
the next level. Using free probability theory and assuming that the noise power
at the relay levels - but not at the receiver - is negligible, a closed-form
expression of the end-to-end asymptotic instantaneous mutual information is
derived as the number of antennas in all levels grow large with the same rate.
This asymptotic expression is shown to be independent from the channel
realizations, to only depend on the channel statistics and to also serve as the
asymptotic value of the end-to-end average mutual information. We also provide
the optimal singular vectors of the precoding matrices that maximize the
asymptotic mutual information : the optimal transmit directions represented by
the singular vectors of the precoding matrices are aligned on the eigenvectors
of the channel correlation matrices, therefore they can be determined only
using the known statistics of the channel matrices and do not depend on a
particular channel realization.Comment: 5 pages, 3 figures, to be published in proceedings of IEEE
Information Theory Workshop 200
Approximating Mexican highways with slime mould
Plasmodium of Physarum polycephalum is a single cell visible by unaided eye.
During its foraging behavior the cell spans spatially distributed sources of
nutrients with a protoplasmic network. Geometrical structure of the
protoplasmic networks allows the plasmodium to optimize transport of nutrients
between remote parts of its body. Assuming major Mexican cities are sources of
nutrients how much structure of Physarum protoplasmic network correspond to
structure of Mexican Federal highway network? To find an answer undertook a
series of laboratory experiments with living Physarum polycephalum. We
represent geographical locations of major cities by oat flakes, place a piece
of plasmodium in Mexico city area, record the plasmodium's foraging behavior
and extract topology of nutrient transport networks. Results of our experiments
show that the protoplasmic network formed by Physarum is isomorphic, subject to
limitations imposed, to a network of principle highways. Ideas and results of
the paper may contribute towards future developments in bio-inspired road
planning
Physics-inspired methods for networking and communications
Advances in statistical physics relating to our understanding of large-scale complex systems have recently been successfully applied in the context of communication networks. Statistical mechanics methods can be used to decompose global system behavior into simple local interactions. Thus, large-scale problems can be solved or approximated in a distributed manner with iterative lightweight local messaging. This survey discusses how statistical physics methodology can provide efficient solutions to hard network problems that are intractable by classical methods. We highlight three typical examples in the realm of networking and communications. In each case we show how a fundamental idea of statistical physics helps solve the problem in an efficient manner. In particular, we discuss how to perform multicast scheduling with message passing methods, how to improve coding using the crystallization process, and how to compute optimal routing by representing routes as interacting polymers
Deep Learning Reveals Underlying Physics of Light-matter Interactions in Nanophotonic Devices
In this paper, we present a deep learning-based (DL-based) algorithm, as a
purely mathematical platform, for providing intuitive understanding of the
properties of electromagnetic (EM) wave-matter interaction in nanostructures.
This approach is based on using the dimensionality reduction (DR) technique to
significantly reduce the dimensionality of a generic EM wave-matter interaction
problem without imposing significant error. Such an approach implicitly
provides useful information about the role of different features (or design
parameters such as geometry) of the nanostructure in its response
functionality. To demonstrate the practical capabilities of this DL-based
technique, we apply it to a reconfigurable optical metadevice enabling
dual-band and triple-band optical absorption in the telecommunication window.
Combination of the proposed approach with existing commercialized full-wave
simulation tools offers a powerful toolkit to extract basic mechanisms of
wave-matter interaction in complex EM devices and facilitate the design and
optimization of nanostructures for a large range of applications including
imaging, spectroscopy, and signal processing. It is worth to mention that the
demonstrated approach is general and can be used in a large range of problems
as long as enough training data can be provided
Throughput Scaling of Wireless Networks With Random Connections
This work studies the throughput scaling laws of ad hoc wireless networks in
the limit of a large number of nodes. A random connections model is assumed in
which the channel connections between the nodes are drawn independently from a
common distribution. Transmitting nodes are subject to an on-off strategy, and
receiving nodes employ conventional single-user decoding. The following results
are proven:
1) For a class of connection models with finite mean and variance, the
throughput scaling is upper-bounded by for single-hop schemes, and
for two-hop (and multihop) schemes.
2) The throughput scaling is achievable for a specific
connection model by a two-hop opportunistic relaying scheme, which employs
full, but only local channel state information (CSI) at the receivers, and
partial CSI at the transmitters.
3) By relaxing the constraints of finite mean and variance of the connection
model, linear throughput scaling is achievable with Pareto-type
fading models.Comment: 13 pages, 4 figures, To appear in IEEE Transactions on Information
Theor
Англійська мова для навчання і роботи Т. 4. Професійне іншомовне письмо
Подано всі види діяльності студентів з вивчення англійської мови, спрямовані на
розвиток мовної поведінки, необхідної для ефективного спілкування в академічному та
професійному середовищах. Містить завдання і вправи, типові для різноманітних
академічних та професійних сфер і ситуацій. Структура організації змісту – модульна,
охоплює певні мовленнєві вміння залежно від мовної поведінки.
Даний модуль має на меті розвиток у студентів умінь і навичок писемного
спілкування, що пов’язане з майбутньою професією студентів, та основ медіації і письмового
перекладу, які спрямовані на розвиток умінь писати тексти різних типів і жанрів, такі як
резюме, листи, анотації тощо. Ресурси для самостійної роботи (частина ІІ) містять завдання
та вправи для розвитку словникового запасу та розширення діапазону функціональних
зразків, необхідних для виконання певних функцій, та завдання, які спрямовані на
організацію самостійної роботи студентів. За допомогою засобів діагностики (частина ІІІ)
студенти можуть самостійно перевірити засвоєння навчального матеріалу та оцінити свої
досягнення. Граматичні явища і вправи для їх засвоєння наводяться в томі 5.
Призначений для студентів технічних університетів гірничого профілю. Може
використовуватися для викладання вибіркових курсів з англійської мови, а також для
самостійного вивчення англійської мови викладачами, фахівцями і науковцями різних
інженерних галузей
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