  Molecular communication is a new field of communication where molecules are
used to transfer information. Among the proposed methods, molecular
communication via diffusion (MCvD) is particularly effective. One of the main
challenges in MCvD is the intersymbol interference (ISI), which inhibits
communication at high data rates. Furthermore, at the nano scale, energy
efficiency becomes an essential problem. Before addressing these problems, a
pre-determined threshold for the received signal must be calculated to make a
decision. In this paper, an analytical technique is proposed to determine the
optimum threshold, whereas in the literature, these thresholds are generally
calculated empirically. Since the main goal of this paper is to build an MCvD
system suitable for operating at high data rates without sacrificing quality,
new modulation and filtering techniques are proposed to decrease the effects of
ISI and enhance energy efficiency. As a transmitter-based solution, a
modulation technique for MCvD, molecular transition shift keying (MTSK), is
proposed in order to increase the data rate via suppressing the ISI.
Furthermore, for energy efficiency, a power adjustment technique that utilizes
the residual molecules is proposed. Finally, as a receiver-based solution, a
new energy efficient decision feedback filter (DFF) is proposed as a substitute
for the decoders such as minimum mean squared error (MMSE) and decision
feedback equalizer (DFE). The error performance of DFF and MMSE equalizers are
compared in terms of bit error rates, and it is concluded that DFF may be more
advantageous when energy efficiency is concerned, due to its lower
computational complexity.
