3,945 research outputs found
Forward error correction for molecular communications
Communication between nanoscale devices is an area of considerable importance as it is essential that future devices be able to form nanonetworks and realise their full potential. Molecular communication is a method based on diffusion, inspired by biological systems and useful over transmission distances in the nm to Ī¼m range. The propagation of messenger molecules via diffusion implies that there is thus a probability that they can either arrive outside of their required time slot or ultimately, not arrive at all. Therefore, in this paper, the use of a error correcting codes is considered as a method of enhancing the performance of future nanonetworks. Using a simple block code, it is shown that it is possible to deliver a coding gain of ā¼1.7 dB at transmission distances of . Nevertheless, energy is required for the coding and decoding and as such this paper also considers the code in this context. It is shown that these simple error correction codes can deliver a benefit in terms of energy usage for transmission distances of upwards of for receivers of a radius
Distributed Control of Microscopic Robots in Biomedical Applications
Current developments in molecular electronics, motors and chemical sensors
could enable constructing large numbers of devices able to sense, compute and
act in micron-scale environments. Such microscopic machines, of sizes
comparable to bacteria, could simultaneously monitor entire populations of
cells individually in vivo. This paper reviews plausible capabilities for
microscopic robots and the physical constraints due to operation in fluids at
low Reynolds number, diffusion-limited sensing and thermal noise from Brownian
motion. Simple distributed controls are then presented in the context of
prototypical biomedical tasks, which require control decisions on millisecond
time scales. The resulting behaviors illustrate trade-offs among speed,
accuracy and resource use. A specific example is monitoring for patterns of
chemicals in a flowing fluid released at chemically distinctive sites.
Information collected from a large number of such devices allows estimating
properties of cell-sized chemical sources in a macroscopic volume. The
microscopic devices moving with the fluid flow in small blood vessels can
detect chemicals released by tissues in response to localized injury or
infection. We find the devices can readily discriminate a single cell-sized
chemical source from the background chemical concentration, providing
high-resolution sensing in both time and space. By contrast, such a source
would be difficult to distinguish from background when diluted throughout the
blood volume as obtained with a blood sample
Scaling laws for molecular communication
In this paper, we investigate information-theoretic scaling laws, independent
from communication strategies, for point-to-point molecular communication,
where it sends/receives information-encoded molecules between nanomachines.
Since the Shannon capacity for this is still an open problem, we first derive
an asymptotic order in a single coordinate, i.e., i) scaling time with constant
number of molecules and ii) scaling molecules with constant time . For a
single coordinate case, we show that the asymptotic scaling is logarithmic in
either coordinate, i.e., and , respectively.
We also study asymptotic behavior of scaling in both time and molecules and
show that, if molecules and time are proportional to each other, then the
asymptotic scaling is linear, i.e., .Comment: Accepted for publication in the 2014 IEEE International Symposium on
Information Theor
Molecular communication in fluid media: The additive inverse Gaussian noise channel
We consider molecular communication, with information conveyed in the time of
release of molecules. The main contribution of this paper is the development of
a theoretical foundation for such a communication system. Specifically, we
develop the additive inverse Gaussian (IG) noise channel model: a channel in
which the information is corrupted by noise with an inverse Gaussian
distribution. We show that such a channel model is appropriate for molecular
communication in fluid media - when propagation between transmitter and
receiver is governed by Brownian motion and when there is positive drift from
transmitter to receiver. Taking advantage of the available literature on the IG
distribution, upper and lower bounds on channel capacity are developed, and a
maximum likelihood receiver is derived. Theory and simulation results are
presented which show that such a channel does not have a single quality measure
analogous to signal-to-noise ratio in the AWGN channel. It is also shown that
the use of multiple molecules leads to reduced error rate in a manner akin to
diversity order in wireless communications. Finally, we discuss some open
problems in molecular communications that arise from the IG system model.Comment: 28 pages, 8 figures. Submitted to IEEE Transactions on Information
Theory. Corrects minor typos in the first versio
A Novel A Priori Simulation Algorithm for Absorbing Receivers in Diffusion-Based Molecular Communication Systems
A novel a priori Monte Carlo (APMC) algorithm is proposed to accurately
simulate the molecules absorbed at spherical receiver(s) with low computational
complexity in diffusion-based molecular communication (MC) systems. It is
demonstrated that the APMC algorithm achieves high simulation efficiency since
by using this algorithm, the fraction of molecules absorbed for a relatively
large time step length precisely matches the analytical result. Therefore, the
APMC algorithm overcomes the shortcoming of the existing refined Monte Carlo
(RMC) algorithm which enables accurate simulation for a relatively small time
step length only. Moreover, for the RMC algorithm, an expression is proposed to
quickly predict the simulation accuracy as a function of the time step length
and system parameters, which facilitates the choice of simulation time step for
a given system. Furthermore, a rejection threshold is proposed for both the RMC
and APMC algorithms to significantly save computational complexity while
causing an extremely small loss in accuracy.Comment: 11 pages, 14 figures, submitted to IEEE Transactions on
NanoBioscience. arXiv admin note: text overlap with arXiv:1803.0463
Using Surface-Motions for Locomotion of Microscopic Robots in Viscous Fluids
Microscopic robots could perform tasks with high spatial precision, such as
acting in biological tissues on the scale of individual cells, provided they
can reach precise locations. This paper evaluates the feasibility of in vivo
locomotion for micron-size robots. Two appealing methods rely only on surface
motions: steady tangential motion and small amplitude oscillations. These
methods contrast with common microorganism propulsion based on flagella or
cilia, which are more likely to damage nearby cells if used by robots made of
stiff materials. The power potentially available to robots in tissue supports
speeds ranging from one to hundreds of microns per second, over the range of
viscosities found in biological tissue. We discuss design trade-offs among
propulsion method, speed, power, shear forces and robot shape, and relate those
choices to robot task requirements. This study shows that realizing such
locomotion requires substantial improvements in fabrication capabilities and
material properties over current technology.Comment: 14 figures and two Quicktime animations of the locomotion methods
described in the paper, each showing one period of the motion over a time of
0.5 milliseconds; version 2 has minor clarifications and corrected typo
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