192 research outputs found
Diffusive MIMO Molecular Communications: Channel Estimation, Equalization and Detection
In diffusion-based communication, as for molecular systems, the achievable
data rate is low due to the stochastic nature of diffusion which exhibits a
severe inter-symbol-interference (ISI). Multiple-Input Multiple-Output (MIMO)
multiplexing improves the data rate at the expense of an inter-link
interference (ILI). This paper investigates training-based channel estimation
schemes for diffusive MIMO (D-MIMO) systems and corresponding equalization
methods. Maximum likelihood and least-squares estimators of mean channel are
derived, and the training sequence is designed to minimize the mean square
error (MSE). Numerical validations in terms of MSE are compared with Cramer-Rao
bound derived herein. Equalization is based on decision feedback equalizer
(DFE) structure as this is effective in mitigating diffusive ISI/ILI.
Zero-forcing, minimum MSE and least-squares criteria have been paired to DFE,
and their performances are evaluated in terms of bit error probability. Since
D-MIMO systems are severely affected by the ILI because of short transmitters
inter-distance, D-MIMO time interleaving is exploited as countermeasure to
mitigate the ILI with remarkable performance improvements. The feasibility of a
block-type communication including training and data equalization is explored
for D-MIMO, and system-level performances are numerically derived.Comment: Accepted paper at IEEE transaction on Communicatio
A Vertical Channel Model of Molecular Communication based on Alcohol Molecules
The study of Molecular Communication(MC) is more and more prevalence, and
channel model of MC plays an important role in the MC System. Since different
propagation environment and modulation techniques produce different channel
model, most of the research about MC are in horizontal direction,but in nature
the communications between nano machines are in short range and some of the
information transportation are in the vertical direction, such as transpiration
of plants, biological pump in ocean, and blood transportation from heart to
brain. Therefore, this paper we propose a vertical channel model which
nano-machines communicate with each other in the vertical direction based on
pure diffusion. We first propose a vertical molecular communication model, we
mainly considered the gravity as the factor, though the channel model is also
affected by other main factors, such as the flow of the medium, the distance
between the transmitter and the receiver, the delay or sensitivity of the
transmitter and the receiver. Secondly, we set up a test-bed for this vertical
channel model, in order to verify the difference between the theory result and
the experiment data. At last, we use the data we get from the experiment and
the non-linear least squares method to get the parameters to make our channel
model more accurate.Comment: 5 pages,7 figures, Accepted for presentation at BICT 2015 Special
Track on Molecular Communication and Networking (MCN). arXiv admin note: text
overlap with arXiv:1311.6208 by other author
Improving Receiver Performance of Diffusive Molecular Communication with Enzymes
This paper studies the mitigation of intersymbol interference in a diffusive
molecular communication system using enzymes that freely diffuse in the
propagation environment. The enzymes form reaction intermediates with
information molecules and then degrade them so that they cannot interfere with
future transmissions. A lower bound expression on the expected number of
molecules measured at the receiver is derived. A simple binary receiver
detection scheme is proposed where the number of observed molecules is sampled
at the time when the maximum number of molecules is expected. Insight is also
provided into the selection of an appropriate bit interval. The expected bit
error probability is derived as a function of the current and all previously
transmitted bits. Simulation results show the accuracy of the bit error
probability expression and the improvement in communication performance by
having active enzymes present.Comment: 13 pages, 8 figures, 1 table. To appear in IEEE Transactions on
Nanobioscience (submitted January 22, 2013; minor revision October 16, 2013;
accepted December 4, 2013
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