  Communication via diffusion (CvD) is an effective and energy efficient method
for transmitting information in nanonetworks. In this work, we focus on a
diffusion-based communication system where the reception process is an
absorption via receptors. Whenever a molecule hits to the receiver it is
removed from the environment. This kind of reception process is called first
passage process and it is more complicated compared to diffusion process only.
In 3-D environments, obtaining analytical solution for hitting time
distribution for realistic cases is complicated, hence we develop an end-to-end
simulator for he diffusion-based communication system that sends consecutive
symbols.
  In CvD, each symbol is modulated and demodulated in a time slot called symbol
duration, however the long tail distribution of hitting time is the main
challenge that affects the symbol detection error. The molecules arriving in
the following slots become an interference source when detection takes place.
End-to-end simulator enables us to analyze the effect of inter symbol
interference (ISI) without making any assumptions on the ISI. We propose an ISI
cancellation technique that utilizes decision feedback for compensating the
effect of previously demodulated symbol. Three different modulation types are
considered with pulse, square, and cosine carrier waves. In case of constraints
on transmitter or receiver node it may not be possible to use pulse as a
carrier, and peak-to-average messenger molecule metric is defined for this
purpose. Results show that, the proposed ISI mitigation technique improves the
symbol detection performance and the amplitude-based modulations are improved
more than frequency-based modulations.
