Transmit Signal Shaping for Molecular Communication

The nano size of the molecular transmitter limits it from storing or releasing a large number of molecules instantaneously. This physical constraint makes instantaneous release of molecules from the transmitter infeasible. In this letter, we model the molecule emission process more accurately using rectangular and exponential transmit signals and derive closed form expressions for the number of molecules that are absorbed by the receiver in a Diffusion-Based Molecular Communication (DBMC) system. We show that the effect of inter symbol interference (ISI) depends on the shape of the transmit signal. Also, we design an optimal transmit signal with minimum inter symbol interference effect using the least squares approach. Moreover, the bit error rate performance of the DBMC system is analyzed for different transmit signals compared to that of the ideal system with instantaneous release of molecules. The match between analytical expressions and particle-based simulations is shown.