Nowadays nanotechnologies are developing and effecting in many areas. The presence of nanotechnology topics in communications can expand the boundaries of this science. In specific medical and industrial applications, nanoscale communications are needed. As a result, a new and interdisciplinary field is presented called Molecular Communication. Radio-based communication system models differ from molecular ones, so they cannot be used in molecular communication systems. Low achievable data rate is disadvantage of diffusion-based molecular over radio-based communication and there are not much researches on this. One solution to overcome this disadvantage is using molecular MIMO communication. In this thesis, we first discuss the differences between multi-antenna and single-antenna molecular communication systems, and introduce a formula for the first-hitting probability in molecular MIMO communication systems. Secondly, we introduce a matrix called channel matrix in these systems to examine the rank of this matrix in different scenarios. We would use diversity techniques in molecular MIMO communication if the channel matrix is full rank. In the next step, for the first time we introduce molecular spatial modulation (MSM) to increase data rate of systems. In a 1 system based on MSM to reduce bit error rate, a convex optimization problem is proposed in which the optimum number of transmitting molecules according to system structure is calculated. Then, we generalize the proposed modulation for 2 2 and 4 4 systems. In each of these systems, special detection methods are used, all of which are based on the threshold level detection method and use diversity techniques in molecular communication systems. Finally, based on BER, systems using MSM are fairly compared with the systems that have similar data rates. The results showed that the proposed modulation and detection methods not only increase the data rate, but also reduce BER. Whereas the proposed methods are very simple. Key Words: Molecular Communication, Molecular Spatial Modulation, MSM, MIMO, Diffusion, Increasing Data rate, Threshold Level Detection, Convex Optimization.
