  In molecular communication via diffusion (MCvD), the inter-symbol
interference (ISI) is a well known severe problem that deteriorates both data
rates and link reliability. ISI mainly occurs due to the slow and highly random
propagation of the messenger molecules, which causes the emitted molecules from
the previous symbols to interfere with molecules from the current symbol. An
effective way to mitigate the ISI is using enzymes to degrade undesired
molecules. Prior work on ISI mitigation by enzymes has assumed an infinite
amount of enzymes randomly distributed around the molecular channel. Taking a
different approach, this paper assumes an MCvD channel with a limited amount of
enzymes. The main question this paper addresses is how to deploy these enzymes
in an effective structure so that ISI mitigation is maximized. To find an
effective MCvD channel environment, this study considers optimization of the
shape of the transmitter node, the deployment location and structure, the size
of the enzyme deployed area, and the half-lives of the enzymes. It also
analyzes the dependence of the optimum size of the enzyme area on the distance
and half-life.
