  In this paper, we address the symbol synchronization issue in molecular
communication via diffusion (MCvD). Symbol synchronization among chemical
sensors and nanomachines is one of the critical challenges to manage complex
tasks in the nanonetworks with molecular communication (MC). As in
diffusion-based MC, most of the molecules arrive at the receptor closer to the
start of the symbol duration, the wrong estimation of the start of the symbol
interval leads to a high symbol detection error. By utilizing two types of
molecules with different diffusion coefficients we propose a synchronization
technique for MCvD. Moreover, we evaluate the symbol-error-rate performance
under the proposed symbol synchronization scheme for equal and non-equal symbol
duration in MCvD systems.
