Abstract
Molecular communication is a biologically-inspired technique to communicate in very small dimension networks. Many different modulation schemes were proposed in the literature based on different properties of molecules. In this paper, we propose to use the direction of releasing molecules as a new property to convey information and we propose Direction Shift Keying (DSK) modulation scheme. Then, we obtain a solid analytical formulation for the concentration of molecules in the 3-D diffusion environment when the transmitter employs DSK modulation. We analyze the concentration of molecules by numerical results. It is observed that the concentration of molecules becomes maximum on the receiver surface in the releasing direction and at a specific time. The derived results may be useful for designing molecular communication systems and evaluating the performance of DSK scheme in the future works.