11,419 research outputs found
Maximum Coverage and Maximum Connected Covering in Social Networks with Partial Topology Information
Viral marketing campaigns seek to recruit the most influential individuals to
cover the largest target audience. This can be modeled as the well-studied
maximum coverage problem. There is a related problem when the recruited nodes
are connected. It is called the maximum connected cover problem. This problem
ensures a strong coordination between the influential nodes which are the
backbone of the marketing campaign. In this work, we are interested on both of
these problems. Most of the related literature assumes knowledge about the
topology of the network. Even in that case, the problem is known to be NP-hard.
In this work, we propose heuristics to the maximum connected cover problem and
the maximum coverage problem with different knowledge levels about the topology
of the network. We quantify the difference between these heuristics and the
local and global greedy algorithms
Optimal Alignments for Designing Urban Transport Systems: Application to Seville
The achievement of some of the Sustainable Development Goals (SDGs) from the recent
2030 Agenda for Sustainable Development has drawn the attention of many countries towards
urban transport networks. Mathematical modeling constitutes an analytical tool for the formal
description of a transportation system whereby it facilitates the introduction of variables and the
definition of objectives to be optimized. One of the stages of the methodology followed in the
design of urban transit systems starts with the determination of corridors to optimize the population
covered by the system whilst taking into account the mobility patterns of potential users and the
time saved when the public network is used instead of private means of transport. Since the capture
of users occurs at stations, it seems reasonable to consider an extensive and homogeneous set of
candidate sites evaluated according to the parameters considered (such as pedestrian population
captured and destination preferences) and to select subsets of stations so that alignments can take
place. The application of optimization procedures that decide the sequence of nodes composing the
alignment can produce zigzagging corridors, which are less appropriate for the design of a single line.
The main aim of this work is to include a new criterion to avoid the zigzag effect when the alignment
is about to be determined. For this purpose, a curvature concept for polygonal lines is introduced,
and its performance is analyzed when criteria of maximizing coverage and minimizing curvature are
combined in the same design algorithm. The results show the application of the mathematical model
presented for a real case in the city of Seville in Spain.Ministerio de Economía y Competitividad MTM2015-67706-
Observer Placement for Source Localization: The Effect of Budgets and Transmission Variance
When an epidemic spreads in a network, a key question is where was its
source, i.e., the node that started the epidemic. If we know the time at which
various nodes were infected, we can attempt to use this information in order to
identify the source. However, maintaining observer nodes that can provide their
infection time may be costly, and we may have a budget on the number of
observer nodes we can maintain. Moreover, some nodes are more informative than
others due to their location in the network. Hence, a pertinent question
arises: Which nodes should we select as observers in order to maximize the
probability that we can accurately identify the source? Inspired by the simple
setting in which the node-to-node delays in the transmission of the epidemic
are deterministic, we develop a principled approach for addressing the problem
even when transmission delays are random. We show that the optimal
observer-placement differs depending on the variance of the transmission delays
and propose approaches in both low- and high-variance settings. We validate our
methods by comparing them against state-of-the-art observer-placements and show
that, in both settings, our approach identifies the source with higher
accuracy.Comment: Accepted for presentation at the 54th Annual Allerton Conference on
Communication, Control, and Computin
A Low-Complexity Approach to Distributed Cooperative Caching with Geographic Constraints
We consider caching in cellular networks in which each base station is
equipped with a cache that can store a limited number of files. The popularity
of the files is known and the goal is to place files in the caches such that
the probability that a user at an arbitrary location in the plane will find the
file that she requires in one of the covering caches is maximized.
We develop distributed asynchronous algorithms for deciding which contents to
store in which cache. Such cooperative algorithms require communication only
between caches with overlapping coverage areas and can operate in asynchronous
manner. The development of the algorithms is principally based on an
observation that the problem can be viewed as a potential game. Our basic
algorithm is derived from the best response dynamics. We demonstrate that the
complexity of each best response step is independent of the number of files,
linear in the cache capacity and linear in the maximum number of base stations
that cover a certain area. Then, we show that the overall algorithm complexity
for a discrete cache placement is polynomial in both network size and catalog
size. In practical examples, the algorithm converges in just a few iterations.
Also, in most cases of interest, the basic algorithm finds the best Nash
equilibrium corresponding to the global optimum. We provide two extensions of
our basic algorithm based on stochastic and deterministic simulated annealing
which find the global optimum.
Finally, we demonstrate the hit probability evolution on real and synthetic
networks numerically and show that our distributed caching algorithm performs
significantly better than storing the most popular content, probabilistic
content placement policy and Multi-LRU caching policies.Comment: 24 pages, 9 figures, presented at SIGMETRICS'1
Relieving the Wireless Infrastructure: When Opportunistic Networks Meet Guaranteed Delays
Major wireless operators are nowadays facing network capacity issues in
striving to meet the growing demands of mobile users. At the same time,
3G-enabled devices increasingly benefit from ad hoc radio connectivity (e.g.,
Wi-Fi). In this context of hybrid connectivity, we propose Push-and-track, a
content dissemination framework that harnesses ad hoc communication
opportunities to minimize the load on the wireless infrastructure while
guaranteeing tight delivery delays. It achieves this through a control loop
that collects user-sent acknowledgements to determine if new copies need to be
reinjected into the network through the 3G interface. Push-and-Track includes
multiple strategies to determine how many copies of the content should be
injected, when, and to whom. The short delay-tolerance of common content, such
as news or road traffic updates, make them suitable for such a system. Based on
a realistic large-scale vehicular dataset from the city of Bologna composed of
more than 10,000 vehicles, we demonstrate that Push-and-Track consistently
meets its delivery objectives while reducing the use of the 3G network by over
90%.Comment: Accepted at IEEE WoWMoM 2011 conferenc
Проект беспроводной ячеистой сети для индустриального парка «Великий Камень»
Беспроводная ячеистая сеть (WMN) все чаще становится популярным решением из-за низкой стоимости как альтернатива проводной сети для предоставления широкополосного доступа для пользователей. Беспроводная ячеистая сеть (WMN) представляет собой коммуникационные сети, состоящие из радио узлов, организованных в топологии сети. Беспроводные сети состоят из сети клиентов, сетевых маршрутизаторов и шлюзов. Клиенты сети - это часто ноутбуки, сотовые телефоны и другие беспроводные устройства, в то время как сетевые маршрутизаторы пересылают трафик и из шлюзов, которые могут, но не обязательно, быть подключены к Интернету. В статье рассматриваются разные каналы радио беспроводной связи, подключенные к точке доступа (AP) в рамках Белорусско-Китайского проекта индустриального парка «Большой Камень», который является территориальным образованием площадью около 80 кв. Км с особым правовым статусом для предоставления комфортных условий для ведения бизнеса. Парк расположен в уникальном природном комплексе в 25 км от Минска, столицы Республики Беларусь. Он находится в непосредственной близости от международного аэропорта, железнодорожных линий и транснациональной магистрали Берлин-Москва. Результат анализа показывает распределение точек доступа, обеспечивающих принципиальные функции на территории индустриального парка. При этом обеспечивается надежность и балансировка нагрузки в беспроводных ячеистых сетях связи
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