11,334 research outputs found
Trade-offs between Selection Complexity and Performance when Searching the Plane without Communication
We consider the ANTS problem [Feinerman et al.] in which a group of agents
collaboratively search for a target in a two-dimensional plane. Because this
problem is inspired by the behavior of biological species, we argue that in
addition to studying the {\em time complexity} of solutions it is also
important to study the {\em selection complexity}, a measure of how likely a
given algorithmic strategy is to arise in nature due to selective pressures. In
more detail, we propose a new selection complexity metric , defined for
algorithm such that , where is
the number of memory bits used by each agent and bounds the fineness of
available probabilities (agents use probabilities of at least ). In
this paper, we study the trade-off between the standard performance metric of
speed-up, which measures how the expected time to find the target improves with
, and our new selection metric.
In particular, consider agents searching for a treasure located at
(unknown) distance from the origin (where is sub-exponential in ).
For this problem, we identify as a crucial threshold for our
selection complexity metric. We first prove a new upper bound that achieves a
near-optimal speed-up of for . In particular, for , the speed-up is
asymptotically optimal. By comparison, the existing results for this problem
[Feinerman et al.] that achieve similar speed-up require . We then show that this threshold is tight by describing a
lower bound showing that if , then
with high probability the target is not found within moves per
agent. Hence, there is a sizable gap to the straightforward
lower bound in this setting.Comment: appears in PODC 201
Multicriteria global optimization for biocircuit design
One of the challenges in Synthetic Biology is to design circuits with
increasing levels of complexity. While circuits in Biology are complex and
subject to natural tradeoffs, most synthetic circuits are simple in terms of
the number of regulatory regions, and have been designed to meet a single
design criterion. In this contribution we introduce a multiobjective
formulation for the design of biocircuits. We set up the basis for an advanced
optimization tool for the modular and systematic design of biocircuits capable
of handling high levels of complexity and multiple design criteria. Our
methodology combines the efficiency of global Mixed Integer Nonlinear
Programming solvers with multiobjective optimization techniques. Through a
number of examples we show the capability of the method to generate non
intuitive designs with a desired functionality setting up a priori the desired
level of complexity. The presence of more than one competing objective provides
a realistic design setting where every design solution represents a trade-off
between different criteria. The tool can be useful to explore and identify
different design principles for synthetic gene circuits
Lower Bounds for Shoreline Searching With 2 or More Robots
Searching for a line on the plane with unit speed robots is a classic
online problem that dates back to the 50's, and for which competitive ratio
upper bounds are known for every . In this work we improve the best
lower bound known for robots from 1.5993 to 3. Moreover we prove that the
competitive ratio is at least for robots, and at least
for robots. Our lower bounds match the best upper
bounds known for , hence resolving these cases. To the best of our
knowledge, these are the first lower bounds proven for the cases of
this several decades old problem.Comment: This is an updated version of the paper with the same title which
will appear in the proceedings of the 23rd International Conference on
Principles of Distributed Systems (OPODIS 2019) Neuchatel, Switzerland, July
17-19, 201
Quantifying the Evolutionary Self Structuring of Embodied Cognitive Networks
We outline a possible theoretical framework for the quantitative modeling of
networked embodied cognitive systems. We notice that: 1) information self
structuring through sensory-motor coordination does not deterministically occur
in Rn vector space, a generic multivariable space, but in SE(3), the group
structure of the possible motions of a body in space; 2) it happens in a
stochastic open ended environment. These observations may simplify, at the
price of a certain abstraction, the modeling and the design of self
organization processes based on the maximization of some informational
measures, such as mutual information. Furthermore, by providing closed form or
computationally lighter algorithms, it may significantly reduce the
computational burden of their implementation. We propose a modeling framework
which aims to give new tools for the design of networks of new artificial self
organizing, embodied and intelligent agents and the reverse engineering of
natural ones. At this point, it represents much a theoretical conjecture and it
has still to be experimentally verified whether this model will be useful in
practice.
MAC Aspects of Millimeter-Wave Cellular Networks
The current demands for extremely high data rate wireless services and the spectrum scarcity at the sub-6 GHz bands are forcefully motivating the use of the millimeter-wave (mmWave) frequencies. MmWave communications are characterized by severe attenuation, sparse-scattering environment, large bandwidth, high penetration loss, beamforming with massive antenna arrays, and possible noise-limited operation. These characteristics imply a major difference with respect to legacy communication technologies, primarily designed for the sub-6 GHz bands, and are posing major design challenges on medium access control (MAC) layer. This book chapter discusses key MAC layer issues at the initial access and mobility management (e.g., synchronization, random access, and handover) as well as resource allocation (interference management, scheduling, and association). The chapter provides an integrated view on MAC layer issues for cellular networks and reviews the main challenges and trade-offs and the state-of-the-art proposals to address them
Initial Access in 5G mm-Wave Cellular Networks
The massive amounts of bandwidth available at millimeter-wave frequencies
(roughly above 10 GHz) have the potential to greatly increase the capacity of
fifth generation cellular wireless systems. However, to overcome the high
isotropic pathloss experienced at these frequencies, high directionality will
be required at both the base station and the mobile user equipment to establish
sufficient link budget in wide area networks. This reliance on directionality
has important implications for control layer procedures. Initial access in
particular can be significantly delayed due to the need for the base station
and the user to find the proper alignment for directional transmission and
reception. This paper provides a survey of several recently proposed techniques
for this purpose. A coverage and delay analysis is performed to compare various
techniques including exhaustive and iterative search, and Context Information
based algorithms. We show that the best strategy depends on the target SNR
regime, and provide guidelines to characterize the optimal choice as a function
of the system parameters.Comment: 6 pages, 3 figures, 3 tables, 15 references, submitted to IEEE COMMAG
201
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