ISI mitigation techniques in molecular communication

Molecular communication via diffusion (MCvD) is a new field of communication where molecules are used to transfer information. One of the main challenges in MCvD is the intersymbol interference (ISI), which inhibits communication at high data rates. Furthermore, at 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 thesis, an analytical technique is proposed to determine the optimum threshold, whereas in the literature, these thresholds are usually calculated empirically. Since the main goal of this thesis is to build an MCvD system suitable for operating at high data rates without sacrificing quality, new modulation and filtering techniques are also proposed to decrease the effects of ISI and enhance energy efficiency. As the first transmitter-based solution, a modulation technique, molecular transition shift keying (MTSK), is proposed in order to increase the data rate by suppressing ISI. As the second transmitter-based solution, a pre-equalization method is proposed in which the transmitter utilizes two types of messenger molecules. 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 conventional decoders in the literature. Error performance of all modulation techniques are presented in a comprehensive manner. Additionally, 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.